Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
DSpace
UBCV
Ruks, Tyler William
Doctor of Philosophy - PhD
University of British Columbia
Wrangellia is a fundamental component of the North American Cordillera and contains significant mineral deposits, including Myra Falls (Nyrstar N.V.), which is currently the largest producing volcanogenic massive sulfide (VMS) deposit in western Canada. Understanding the evolution of Wrangellia is therefore important for understanding the crustal growth and metallogenic history of the North American continent, and in doing so, facilitating the discovery of new mineral wealth. Geochronological, lithogeochemical and Nd and Pb isotopic studies of the Paleozoic Wrangellia arc (PWA), Vancouver Island have significantly revised our understanding of the terrane, suggesting that the PWA comprises a progressively rifting Late Devonian through Early Permian oceanic volcanic arc complex developed above an east dipping subduction zone (modern coordinates) with Late Devonian through middle Mississippian, and Pennsylvanian through Early Permian pulses of bimodal volcanism and associated VMS mineralization. The relatively primitive lithogeochemical and Nd isotopic signatures of PWA intrusive and volcanic rocks indicate that the PWA originated in an oceanic arc environment close enough to a continental margin to undergo slight contamination via the subduction of continent derived sediments. Recently recognized, Pennsylvanian-Early Permian aged, VMS associated bimodal volcanic rocks in the PWA have lithogeochemical and Nd isotopic signatures indicative of derivation from more primitive and significantly hotter source melts than their Late Devonian counterparts, suggesting that Late Paleozoic volcanic rocks in the terrane are prospective for VMS mineralization. Lead isotope geochemistry of newly discovered VMS style mineralization in the PWA indicates that host areas for the new mineral occurrences are prospective for Myra Falls-like VMS deposits of Late Devonian-Early Mississippian age. Lead isotope geochemistry for recently recognized Pennsylvanian-Early Permian VMS mineralization in the PWA supports lithogeochemical and Nd isotopic arguments which suggest that Late Paleozoic bimodal volcanic rocks in the PWA were derived from more primitive melts than their Late Devonian-Early Mississippian counterparts, reflective of an origin in a progressively rifting, oceanic island arc environment.
STRATIGRAPHIC AND PALEOTECTONIC STUDIES OF PALEOZOIC WRANGELLIA AND ITS CONTAINED VOLCANOGENIC MASSIVE SULFIDE (VMS) OCCURRENCES, VANCOUVER ISLAND, BRITISH COLUMBIA, CANADA by TYLER WILLIAM RUKS M.Sc., Laurentian University, 2004 B.Sc., University of Victoria, 2002 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (GEOLOGICAL SCIENCES) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) August 2015 ©Tyler William Ruks, 2015 ABSTRACT Wrangellia is a fundamental component of the North American Cordillera and contains significant mineral deposits, including Myra Falls (Nyrstar N.V.), which is currently the largest producing volcanogenic massive sulfide (VMS) deposit in western Canada. Understanding the evolution of Wrangellia is therefore important for understanding the crustal growth and metallogenic history of the North American continent, and in doing so, facilitating the discovery of new mineral wealth. Geochronological, lithogeochemical and Nd and Pb isotopic studies of the Paleozoic Wrangellia arc (PWA), Vancouver Island have significantly revised our understanding of the terrane, suggesting that the PWA comprises a progressively rifting Late Devonian through Early Permian oceanic volcanic arc complex developed above an east dipping subduction zone (modern coordinates) with Late Devonian through middle Mississippian, and Pennsylvanian through Early Permian pulses of bimodal volcanism and associated VMS mineralization. The relatively primitive lithogeochemical and Nd isotopic signatures of PWA intrusive and volcanic rocks indicate that the PWA originated in an oceanic arc environment close enough to a continental margin to undergo slight contamination via the subduction of continent derived sediments. Recently recognized, Pennsylvanian-Early Permian aged, VMS associated bimodal volcanic rocks in the PWA have lithogeochemical and Nd isotopic signatures indicative of derivation from more primitive and significantly hotter source melts than their Late Devonian counterparts, suggesting that Late Paleozoic volcanic rocks in the terrane are prospective for VMS mineralization. Lead isotope geochemistry of newly discovered VMS style mineralization in the PWA indicates that host areas for the new mineral occurrences are prospective for Myra Falls-like VMS deposits of Late Devonian-Early Mississippian age. Lead isotope geochemistry for recently recognized Pennsylvanian-Early Permian VMS mineralization in the PWA supports lithogeochemical and Nd isotopic arguments which suggest that Late Paleozoic bimodal volcanic rocks in the PWA were derived from more primitive melts than their Late Devonian-Early Mississippian counterparts, reflective of an origin in a progressively rifting, oceanic island arc environment. iiPREFACE The research program for this thesis was designed with Jim Mortensen. I was the principal investigator for field, lithogeochemical, geochronological and isotopic studies, and was the primary author for all of the chapters contained in this thesis. Chapters 3 through 6 of the thesis are intended to form the body of several manuscripts intended for publishing in international technical journals, co-authored with Jim Mortensen and Fabrice Cordey. My supervisory committee, including Jim Mortensen, Ken Hickey and Craig Hart, all provided comments and suggested edits to each of the chapters. Richard Friedman conducted U-Pb (zircon) geochronology for several samples in Chapter 3 using the chemical abrasion ID-TIMS method. Janet Gabites and Bruno Kieffer conducted Pb and Nd isotopic analyses for samples in Chapters 4 and 5, respectively. Fabrice Cordey and Mike Orchard conducted radiolarian and conodont biochronology (Chapter 3), respectively. Jim Haggart kindly provided a sample of the Chaatl batholith (Chapter 4). Richard Friedman, Janet Gabites, Bruno Kieffer, Mike Orchard and Jim Haggart will be co-authors on future publications arising from this thesis that include their respective contributions. Four articles published by project sponsor Geoscience British Columbia (GBC) are included in Appendix 4. These articles, including Ruks and Mortensen (2007, 2008) and Ruks et al. (2009, 2010) discuss preliminary results for research presented in the thesis, and were co-authored with Jim Mortensen and Fabrice Cordey. References for these articles are as follows: Ruks, T. W., and Mortensen, J. K., 2007, Geological setting of volcanogenic massive sulphide occurrences in the Middle Paleozoic Sicker Group of the southeastern Cowichan Lake uplift (NTS 092B/13), southern Vancouver Island: Geological Fieldwork 2006, Geoscience BC, Report 2007-1, p. 381-394. -, 2008, Geological setting of volcanogenic massive sulphide occurrences in the Middle Paleozoic Sicker Group of the Cowichan Lake uplift, Port Alberni area, southern Vancouver Island, British Columbia: Geoscience BC Summary of Activities 2007, Geoscience BC, Report 2008-1, p. 77-92. Ruks, T. W., Mortensen, J. K., and Cordey, F., 2009, Preliminary results of geological mapping, uranium-lead zircon dating, and micropaleontological and lead isotopic studies of volcanogenic massive sulphide–hosting stratigraphy of the Middle and Late Paleozoic Sicker and Lower Buttle Lake groups on Vancouver Island, British iiiColumbia (NTS 092B/13, 092C/16, 092E/09, /16, 092F/02, /07): Geoscience BC Summary of Activities 2008, Geoscience BC, Report 2009-1, p. 103-122. -, 2010, New results of geological mapping, micropaleontological and lead isotopic studies of volcanogenic massive sulphide–hosting stratigraphy of the middle and late Paleozoic Sicker and Buttle Lake groups on Vancouver Island, British Columbia (NTS 092B/13, 092C/16, 092E/09, /16, 092F/02, /05, /07): Geoscience BC Summary of Activities 2009, Geoscience BC, Report 2010-1, p. 149-170. ivTABLE OF CONTENTS Abstract ............................................................................................................................... ii Preface................................................................................................................................ iii Table of contents..................................................................................................................v List of tables..................................................................................................................... viii List of figures..................................................................................................................... ix Acknowledgements.......................................................................................................... xiii Chapter 1: Introduction ...................................................................................................1 1.1. INTRODUCTION .................................................................................................2 1.2. METHODOLOGY ................................................................................................4 1.3. THESIS PRESENTATION...................................................................................6 Chapter 2: Regional geology and metallogeny of Paleozoic Wrangellia ...................11 2.1. INTRODUCTION ...............................................................................................12 2.2. REGIONAL GEOLOGY AND METALLOGENY OF PALEOZOIC WRANGELLIA..........................................................................................................14 Chapter 3: The chronostratigraphy of Paleozoic Wrangellia and its contained volcanogenic massive sulphide occurrences, Vancouver Island, British Columbia..............................................................................................................25 3.1. INTRODUCTION ...............................................................................................26 3.2. NEW GEOCHRONOLOGY AND BIOCHRONOLOGY FOR PALEOZOIC WRANGELLIA..........................................................................................................26 3.2.1. Geochronology and Biochronology ..........................................................27 3.2.2. Isotopic Ages and Biochronology of the Cowichan Area .........................28 3.2.3. Isotopic Ages and Biochronology of the Alberni Area .............................29 3.2.4. Isotopic Ages and Biochronology of the Nanoose Area ...........................30 3.2.5. Isotopic Ages of the Bedingfield Area ......................................................31 3.2.6. Isotopic Ages of the Dragon Property, Gold River Area ..........................31 3.2.7. Isotopic Ages of the Dorado Property, Hesquiat Peninsula ......................32 3.2.8. Isotopic Ages of the Myra Falls Area........................................................32 3.3. REVISED CHRONOSTRATIGRAPHY FOR SOUTHERN PALEOZOIC WRANGELLIA, VANCOUVER ISLAND, B.C.......................................................32 v3.3.1. Revised Chronostratigraphy of the Cowichan Uplift ................................33 3.3.2. A Revised Chronostratigraphy of the Nanoose Uplift ..............................37 3.3.3. Revised Chronostratigraphy of the Bedingfield Uplift .............................38 3.3.4. Revised Chronostratigraphy of the Dragon Property, Gold River Area ...39 3.3.5. A Revised Chronostratigraphy of the Dorado Property, Hesquiat Peninsula ..............................................................................................39 3.3.6. Correlations with Buttle Lake Uplift Stratigraphy ....................................40 3.4. SUMMARY.........................................................................................................41 Chapter 4: The magmatic evolution of Paleozoic Wrangellia, Vancouver Island, British Columbia..............................................................................................................53 4.1. INTRODUCTION ...............................................................................................54 4.2. LITHOGEOCHEMISTRY AND ISOTOPE GEOCHEMISTRY.......................54 4.2.1. Methodology..............................................................................................54 4.2.2. Effects of Alteration, Metamorphism and Element Mobility....................58 4.2.3. Results .......................................................................................................58 4.3. SUMMARY.........................................................................................................67 Chapter 5: The lead isotopic systematics of Paleozoic Wrangellia hosted sulfide occurrences, Vancouver Island, British Columbia .......................................................99 5.1. INTRODUCTION .............................................................................................100 5.2. ANALYTICAL TECHNIQUES .......................................................................104 5.3. LEAD ISOTOPIC COMPOSITIONS OF PWA SULFIDE OCCURENCES........................................................................................................104 5.4. DISCUSSION....................................................................................................109 5.5. SUMMARY.......................................................................................................118 Chapter 6: The tectonic evolution of the southern Paleozoic Wrangellia arc and its prospectivity for hosting volcanogenic massive sulphide (VMS) deposits...........130 6.1. INTRODUCTION .............................................................................................131 6.2. A TECTONIC MODEL FOR THE EVOLUTION OF SOUTHERN PALEOZOIC WRANGELLIA ................................................................................133 6.3. THE PROSPECTIVITY OF PWA VOLCANIC ROCKS FOR HOSTING VMS DEPOSITS................................................................................................................147 6.4. SUMMARY AND CONCLUSIONS................................................................150 viChapter 7: Conclusions and directions for future research......................................160 7.1. CONTRIBUTIONS ...........................................................................................161 7.2. DELIVERABLES..............................................................................................162 7.3. FUTURE RESEARCH......................................................................................163 References.......................................................................................................................168 Appendices......................................................................................................................186 Appendix 1: U-Pb Geochronology ..........................................................................187 Appendix 2: Geochemistry ......................................................................................256 Appendix 3: Lead isotopes ......................................................................................270 Appendix 4: Fieldwork articles ................................................................................273 Appendix 5: Fieldtrip guide.....................................................................................343 viiLIST OF TABLES Table 3.1. Geochronology results and sample descriptions for Paleozoic rocks of southern Wrangellia ...................................................................................49 Table 3.2. Fossil ages for rocks collected from southern Paleozoic Wrangellia ........51 Table 4.1. Lithogeochemical data for felsic igneous rocks of the PWA (Vancouver Island)...........................................................................86 Table 4.2. Lithogeochemical data for mafic igneous rocks of the PWA (Vancouver Island and Haida Gwaii) ........................................................92 Table 4.3. Neodymium isotope data for PWA igneous rocks.....................................98 Table 5.1. Descriptions and locations of PWA hosted sulfide occurrences sampled for lead isotopic studies .............................................................128 Table 5.2. Lead isotopic compositions of sulfides from PWA hosted strata ............129 Table 6.1. Neodymium crustal index (NCI) calculations (DePaolo et al., 1992) for PWA igneous rocks............................................................................159 Table A1.1. TIMS and LA-ICP-MS U, Pb and Th isotope analytical data of dated zircon grains from samples from southern Paleozoic Wrangellia ...............................................................................200 Table A1.2. Chemical dissolution TIMS U-Pb Analytical Data for rocks of Paleozoic southern Wrangellia ..................................................235 Table A2.1. Precision and accuracy data for in-house MDRU reference materials ....257 Table A2.2. Results for duplicate samples analyzed by ICP-AES in this study and assessment of precision ................................................258 Table A2.3. Results for duplicate samples analyzed by ICP-MS in this study and assessment of precision ...........................................................261 Table A2.4. Results for duplicate samples analyzed by XRF for major elements in this study and assessment of precision .................................267 Table A2.5. Results for duplicate samples analyzed by XRF for trace elements in this study and assessment of precision .................................269 viiiLIST OF FIGURES Figure 1.1. Terranes of the Canadian-Alaska Cordillera................................................9 Figure 1.2. Distribution of Paleozoic strata of the Sicker and Buttle Lake groups on Vancouver Island and the Gulf Islands .....................................10 Figure 2.1. Stratigraphic nomenclature for the Sicker and Buttle Lake groups on Vancouver Island ......................................................................23 Figure 2.2. Schematic stratigraphic sections for Paleozoic rocks of Wrangellia on Vancouver Island, Haida Gwaii and Yukon-Alaska ..........24 Figure 3.1. Geology, geochronology, biochronology, significant VMS occurrences and iron formations of the Cowichan area, Vancouver Island .......................................................................................42 Figure 3.2. Geology, geochronology and biochronology of the Alberni area, Vancouver Island .................................................................43 Figure 3.3. Geology, geochronology and biochronology of the Nanoose area, Vancouver Island .......................................................................................44 Figure 3.4. Geology, mineral occurrences, geochronology and biochronology of the Bedingfield area, Vancouver Island ................................................45 Figure 3.5. Geology, geochronology and mineral occurrences of the Dragon property, Gold River area ..........................................................................46 Figure 3.6. Geology, geochronology and biochronology of the Dorado property area, Hesquiat Peninsula, Vancouver Island ...............................47 Figure 3.7. Stylized, time-stratigraphic columns showing temporal relations between units comprising Paleozoic Wrangellia ........................48 Figure 4.1. Variation diagrams of major elements vs. Zr for both mafic and felsic rocks of the PWA ......................................................................68 Figure 4.2. Variation diagrams of immobile elements vs. Zr for both mafic and felsic rocks of the PWA ......................................................................69 Figure 4.3. Geology, lithogeochemical affinities, and significant VMS and iron formations of the PWA, Cowichan area, Vancouver Island ..............70 ixFigure 4.4. Geology, lithogeochemical affinities, and signficant VMS and iron formations of the PWA, Alberni area, Vancouver Island ..................71 Figure 4.5. Trace element lithogeochemical characteristics of pre-Late Devonian mafic volcanic rocks of the PWA (Cowichan and Alberni areas) ...................................................................72 Figure 4.6. Trace element lithogeochemical characteristics of Late Devonian through Early Mississippian mafic volcanic rocks of the PWA (Cowichan and Alberni areas) ...................................................................73 Figure 4.7. Trace element lithogeochemical characteristics of Late Devonian through Early Mississippian felsic volcanic rocks of the PWA ................74 Figure 4.8. Trace element lithogeochemical characteristics of the Late Devonian through Early Mississippian Saltspring Intrusions....................75 Figure 4.9. Trace element lithogeochemical characteristics of Mississippian felsic volcanic rocks of the PWA (Alberni area) .......................................76 Figure 4.10. Geology and lithogeochemical affinities of the PWA, Nanoose area, VancouverIsland................................................................................77 Figure 4.11. Trace element lithogeochemical characteristics of Early Permian mafic volcanic rocks of the PWA (Alberni and Nanoose areas) .........................78 Figure 4.12. Geology, VMS occurrences, iron formations, and lithogeochemical affinities of the PWA, Dragon property, Gold River area .........................79 Figure 4.13. Geology, mineral occurrences, and lithogeochemical affinities of the PWA, Bedingfield area, Vancouver Island................................................80 Figure 4.14. Trace element lithogeochemical characteristics of Pennsylvanian through Early Permian mafic volcanic rocks of the PWA (Dragon and Bedingfield areas) .................................................................81 Figure 4.15. Trace element lithogeochemical characteristics of Pennsylvanian through Early Permian felsic volcanic rocks of the PWA (Dragon and Bedingfield areas) .................................................................82 Figure 4.16. Geochemical affinities of PWA samples, geology, and mineral occurrences of the Dorado property area, Hesquiat Peninsula, Vancouver Island .......................................................................................83 xFigure 4.17. Trace element lithogeochemical characteristics of potential Pennsylvanian through Early Permian mafic volcanic rocks of the PWA (Hesquiat area) ...........................................................................84 Figure 4.18. Trace element lithogeochemical characteristics of the Pennsylvanian Chaatl Batholith .........................................................................................85 Figure 5.1. Geology, Pb isotope sample locations, and significant VMS and iron formations of the PWA, Alberni area, Vancouver Island ................122 Figure 5.2. Geology, Pb isotope sample locations, and significant VMS and iron formations of the PWA, Cowichan area, Vancouver Island....................123 Figure 5.3. Geology, VMS occurrences, iron formations, and Pb isotope sample locations for the PWA, Dragon property, Gold River area......................124 Figure 5.4. Lead isotopic compositions for sulfide occurrences in PWA strata ........125 Figure 5.5. Lead isotopic compositions for sulfide occurrences in PWA strata ........126 Figure 5.6. Lead isotopic compositions for sulfide occurrences in PWA strata .......127 Figure 6.1. A series of cartoons illustrating the tectonic setting of the PWA throughout the mid Paleozoic ..................................................................153 Figure 6.2. A series of cartoons illustrating the tectonic setting of the PWA in the Late Paleozoic................................................................................154 Figure 6.3. ε Nd,t versus time (millions of years) for samples collected from the PWA..........................................................................................155 Figure 6.4. Ti/Sc, Nb/Ta, Nb/Th and La/Sm values can be used to ascertain the relative amounts of mantle contribution to magmas................................156 Figure 6.5. Trace element ratios and Nd isotope systematics suggest variable mantle contributions to mafic igneous rocks of the PWA .........157 Figure 6.6. Diagrams for felsic rocks associated with VMS mineralization in the PWA...............................................................................................158 Figure A1.1. Conventional U-Pb concordia plots and 206Pb/238U age plots for samples from the Cowichan area .......................................................237 Figure A1.2. Conventional U-Pb concordia plots and 206Pb/238U age plots for samples from the Alberni area ...............................................................................243 xiFigure A1.3. Relative probability plots with histograms showing detrital zircon ages for two samples from the Nanoose area (A and B). Conventional U-Pb concordia plots and 206Pb/238U age plots for one sample from the Nanoose area (C).....................................................................................................248 Figure A1.4. Conventional U-Pb concordia plots and 206Pb/238U age plots for samples from the Bedingfield area ........................................................................249 Figure A1.5. Conventional U-Pb concordia plots and 206Pb/238U age plots for samples from the Dragon property area.................................................................251 Figure A1.6. Conventional U-Pb concordia plots and 206Pb/238U age plots for samples from the Dorado property area.................................................................254 Figure A1.7. Conventional U-Pb concordia plots and 206Pb/238U age plots for a sample from the Myra Falls mine (Nyrstar N.V.) ................................................255 xiiACKNOWLEDGEMENTS This thesis would not exist were it not for the support of many different groups and individuals, to all of whom I am indebted. Firstly, I would like to thank my supervisor, Jim Mortensen, for his friendship and mentorship during the course of my studies. Jim is not only a geologist par excellence, but is an educator in the truest sense. Jim, I owe you more than a few “cold ones”! I would also like to thank Ken Hickey and Craig Hart for all of their hard work and patience as members of my supervisory committee. Their advice regarding the direction and structure of the thesis and their top notch editing skills were greatly appreciated. I would like to thank Fabrice Cordey of the University of Lyons, whose participation in this project was invaluable. Were it not for his excellent skills in biochronology, Paleozoic Wrangellia would remain far more of a mystery than it is today. The good citizens of Port Alberni would also like to thank Fabrice for his assistance in keeping their local Dairy Queen in business. Financial support for this thesis was generously provided by Geoscience BC, Bitterroot Resources Ltd., Paget Resources Corporation, Treasury Metals Inc., Westridge Resources Inc., Nystar N.V., a Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant to Dr. James Mortensen, and an NSERC postgraduate scholarship to Tyler Ruks. Numerous individuals provided valuable advice and direction regarding my PhD studies. Rick and Libby Avis of Port Alberni, B.C., provided my first introduction to Sicker Group geology, having provided a young rock hound with his first bedrock maps of the Alberni area and directions to local mineral occurrences. Rick, who knew that the rocks just beyond Horne Lake Rd. would prove to be some of the most important in my PhD studies? Sean McKinley of Eldorado Gold is thanked for providing me with early mentorship, and my first introduction to VMS mineralization at Myra Falls. To the best of my knowledge, Sean, Murray Jones and the Westmin-Boliden geological team were the first to recognize that VMS associated volcanic rocks of the Dragon property were likely not part of the Sicker Group. B.C. Geological Survey regional geologist Nick Massey (now retired) is also thanked for his support. Nick is the foremost authority on the Sicker and Buttle Lake Groups, and provided xiiiinvaluable logistical support and geological insight to this project. Steve Piercey is thanked for providing me with a geological foundation and research mindset upon which I could undertake this project. His friendship and support during the course of my PhD studies is greatly appreciated. Steve Israel is thanked for geological discussions regarding northern and southern Wrangellia, and for providing encouragement throughout the thesis. Discussions regarding Wrangellian geology and early versions of the thesis with Mo Colpron, JoAnne Nelson, Mitch Mihalynuk, Jim Logan, Dick Tosdal, Jim Ryan and Luke Beranek are also appreciated. Jim Haggart is thanked for providing a sample of the Chaatl batholith (Haida Gwaii). The late Mike Becherer is thanked for providing geological insight into the geology of the Myra Falls and Alberni areas, and for assistance in organizing financial support for the project. He is sorely missed. Special thanks go out to Lyn’ Anglin, Christa Sluggett, Mike Carr (Bitterroot Resources), Scott Jobin-Bevans, Steve Wetherup, Tim Sadlier-Brown, Peter Schulhof, John Bradford and David Volkert, all of whom played a critical role in arranging financial support for this project. Rick Sawyer and Armand Stansell of Nystar N.V. are thanked for providing geological insight, and their time and support for geochronological studies at Myra Falls. Efrem Specogna, one of our province’s most famous prospectors, is thanked for discussions regarding the geology of the Dragon and Cimadoro properties, and for generously providing sulphide samples for Pb isotopic studies. Rich Friedman, Janet Gabites and Bruno Kieffer of the Pacific Centre for Isotopic Geochemical Research (PCIGR) are thanked for providing excellent support for U-Pb geochronology, Pb isotopic and Nd isotopic studies conducted in this thesis, respectively. Mike Orchard of the Geological Survey of Canada is thanked for providing conodont biochronology. The team at Ontario Geoscience Laboratories is thanked for providing excellent lithogeochemical data with a timely turnaround. I’m indebted to my many peers at UBC-MDRU, past and present, for their friendship, support and geological discourse during my PhD studies, especially fellow Mortensen students Reza Tafti, Kirsten Rasmussen, Chris Leslie and Luke Beranek. Gareth Chalmers and Bruno Kieffer are also thanked for the many great conversations over caffeinated beverages. xiv xvLastly, I’d like to thank my family for their support throughout the course of my PhD studies, especially my wife, Bebhinn Smyth, whose love, patience and encouraging words helped me every step of the way. Chapter 1: Introduction 11.1. INTRODUCTION The North American Cordillera (NAC), well endowed with mineral deposits, is an example of a convergent margin that has been in existence since Late Devonian time (Colpron et al., 2007) and provides a natural laboratory for addressing important questions regarding convergent margin tectonic and metallogenic processes in both modern and ancient times. Owing to its long-lived history as a convergent margin, the present day NAC is a composite of numerous tectonic and stratigraphic entities (Colpron et al., 2007). Previous workers have subdivided these entities into terranes (e.g., Coney et al., 1980; Wheeler et al., 1991), which are defined as fault-bounded crustal blocks that each preserve a geological record distinct from that of adjacent terranes (Jones et al., 1983). One of the most poorly understood terranes comprising the NAC is Wrangellia (Fig. 1.1). The Wrangellia terrane, host to several major mineral deposits, represents a major component of the NAC and comprises a multi-episodic, Devonian and younger arc terrane that extends for over 2500 km in strike length, from southern Vancouver Island and Haida Gwaii to south-central Alaska (Colpron and Nelson, 2009). Many outstanding questions surround the tectonic and metallogenic evolution of Wrangellia. Until these questions are resolved, there will be large gaps in our understanding of the tectonic and metallogenic evolution of the North American Cordillera, which has long since been recognized as one of the type accretionary orogens on Earth (Colpron and Nelson, 2009). Questions addressed in this study are: 1) What is Wrangellia? Wrangellia was one of the first described and one of the most widely known of the North American Cordilleran terranes (Jones et al., 1977; Stevens, 2008). The terrane was originally described on the basis of similarities in Triassic stratigraphy (e.g., the Nikolai-Karmutsen Formation) (Jones et al., 1977). However, subsequent research has shown that northern and southern Wrangellia record somewhat different tectonic histories in Paleozoic time. This has lead several authors to question whether northern and southern Wrangellia are actually part of the same terrane, or whether they comprise different tectonic entities altogether (e.g., Katvala, 2006). In order to understand the accretionary history of the North American Cordillera and facilitate paleogeographic reconstructions through geologic time, it is imperative to understand whether Wrangellia is a composite terrane or not. 2 2) How old is Wrangellia? The oldest rocks in Wrangellia represent the evolution of a mid-Paleozoic oceanic island arc (Yorath et al., 1999), the Paleozoic Wrangellia Arc (PWA), recorded in rocks of the Sicker Group. However, there is a paucity of geochronological control for rocks of the Sicker Group, with current stratigraphic interpretations relying primarily on field observations. As a result, the development of a robust model to explain the evolution of this geologically and economically significant belt of rocks has been inhibited, and important questions addressing the age and nature of the oldest rocks in Wrangellia have gone unanswered. In addition, recent work has suggested the possibility that evolved, continental crust-like material may locally underlie the oldest rocks in Wrangellia (Sluggett, 2003). The nature and age of this potential, continental-crust like basement, however, has not been resolved. Addressing this problem is significant, because the nature of this potential, continental-like basement may lend itself to paleogeographic reconstructions for the earliest history of Wrangellia. In order to test the accuracy of Wrangellia stratigraphy, and in doing so understand the earliest history of this significant terrane, it is imperative to improve the geochronological and stratigraphic control for Paleozoic rocks of Vancouver Island. 3) Where did Wrangellia form? In order to understand the evolution of convergent margin settings (e.g., the NAC) and relative plate motions over time, it is critical to establish the relative positions of accreted terranes throughout history. Contrary to many of the Cordilleran terranes (e.g., the Intermontane terranes), the paleogeographic setting of Wrangellia during its earliest history is not constrained (Yorath et al., 1999; Colpron and Nelson, 2009). Examining Wrangellian Paleozoic rocks for evidence of cratonic influence will help to answer this question. Paleontological investigations of radiolarian and conodont assemblages in Paleozoic rocks of southern Wrangellia will also help constrain the paleogeographic setting of Wrangellia during its earliest history. 4) How many cycles of VMS mineralization exist in Paleozoic Wrangellia and what does this imply for the tectonic history and mineral potential of the terrane? 3Convergent margin settings are commonly host to significant VMS deposits, with the formation of VMS mineralization typically associated with periods of arc extension and back arc basin development (e.g., Franklin et al., 2005). However, many outstanding questions surround the origins of VMS deposits, particularly concerning the longevity of hydrothermal and magmatic systems associated with VMS mineralization, and the temporal relationships between subvolcanic intrusions, commonly interpreted as the “heat engines” responsible for VMS mineralization (e.g., Piercey et al., 2003; Franklin et al., 2005). Many significant VMS occurrences and past producing VMS deposits are present in the Sicker Group, including those of the Myra Falls camp (Nyrstar, N.V.), which currently is the largest producing VMS deposit in western Canada (Fig. 1.2). However, evidence suggests that there may be as many as four, temporally distinct cycles of VMS mineralization contained in Paleozoic rocks on Vancouver Island (e.g., Ruks et al., 2010). VMS deposits are the products of mineralizing events that tend to occur during distinct temporal intervals, and are commonly associated with periods of crustal extension (e.g., back arc basin development). Thus, resolving the age of VMS mineralization in Sicker Group rocks is critical not only for enhancing the prospectivity of Wrangellian rocks by pin-pointing specific windows in geologic time which are prospective for VMS mineralization, but also for resolving the age(s) of crustal extension and differentiating between tectonic regimes (e.g., arc versus back arc environments) in different stages of Wrangellian tectonic evolution. 1.2. METHODOLOGY To answer the above questions, a combination of field work, geochronological, biochronological, lithogeochemical and isotopic investigations have been undertaken: Field work Field work for the project was undertaken during the summers of 2006 through 2010. Areas of study were selected on the basis of their potential to allow for the testing of existing models for the stratigraphic, magmatic and metallogenic evolution of southern Paleozoic Wrangellia. Particular emphasis was placed on conducting fieldwork and sampling in areas where the activities of the forestry industry have resulted in the creation of abundant, never before studied bedrock exposures. These areas held the potential for the discovery of new mineral occurrences, and the potential to provide new information that could build upon and/or 4revise existing models for the stratigraphic, magmatic and metallogenic evolution of the terrane. Field studies involved a substantial amount of new geological mapping, in addition to detailed sampling for petrographic, lithogeochemical, geochronological and biochronological analysis. Geochronology and biochronology Geochronolgical and biochronological studies were conducted in order to constrain the age of igneous and sedimentary units comprising the PWA, and in doing so, create a new model for the stratigraphic, magmatic and metallogenic evolution of the PWA. A total of 128 samples were collected for U-Pb zircon studies from which 51 samples were dated. A total of 84 samples were collected for biochronology, from which 20 provided diagnostic faunal assemblages and ages. The samples were collected from a 160 km by 40 km study area comprising much of the southern half of Vancouver Island (Fig. 1.2). Sampling for isotopic dating and fossil ages was concentrated in areas where exposures of Paleozoic rocks had been reported by previous workers, and especially where new outcrop was available for remapping in order to provide the best possible stratigraphic constraints on the samples that were analyzed. Special emphasis was placed on geochronological and biostratigraphic sampling in the vicinity of VMS deposits and occurrences in order to constain the timing of VMS mineralization in the terrane. A detailed methodology for geochronological and biochronological studies is provided in Chapter 3. Lithogeochemistry and Nd isotope geochemistry This study, which builds on previous stratigraphic investigations of the PWA, presents a combined lithogeochemical and isotopic study of all recognized magmatic cycles that comprise southern Paleozoic Wrangellia. Results of the study help resolve the tectonic and metallogenic evolution of the southern PWA, with emphasis on characterizing its potential for hosting additional VMS deposits associated with newly recognized magmatic cycles and on understanding the relative contribution of the PWA to the crustal growth history of the North American continent. In total, 164 samples were analyzed for major, trace and rare earth element compositions during the course of this study. A subset of 25 samples with well constrained isotopic and/or fossil ages were selected for Nd isotopic analysis. A detailed methodology for lithogeochemical and Nd isotopic studies is provided in Chapter 4. 5Pb isotope geochemistry This study presents 30 new Pb isotope analyses for sulfide occurrences hosted in Paleozoic Wrangellia strata on Vancouver Island, along with analyses for two samples of VMS-like sulfide mineralization collected from undated, potential Late Palezoic strata on Haida Gwaii (the Cimadoro sulphide occurrence; Fig. 1.1; MINFILE, 2013). Many of the samples are from potential VMS occurrences, and others are from zones of stockwork sulfide mineralization which may be VMS related or epigenetic in nature. The Pb isotopic signature of these samples are used to evaluate a syngenetic versus epigenetic origin for specific sulfide occurrences, and in doing so, help inform VMS exploration in the district. In addition, several of the samples in the dataset are from VMS-like sulfide occurrences hosted in newly recognized Late Paleozoic bimodal volcanic rocks in southern Wrangellia. The Pb isotopic signature of these occurrences has not been characterized prior to. The Pb isotopic signature of these occurrences is compared to that of their Late Devonian counterparts. A Pb isotopic variation between the two populations would provide VMS explorationists in the district with a time and cost effective tool for distinguishing Late Devonian from Late Paleozoic VMS occurrences, which would be a useful contribution towards developing VMS exploration models for the terrane. Another fundamental question regarding Wrangellia is its role in the crustal growth history of the North American continent. Previous workers have demonstrated that Wrangellia was an oceanic island arc with a magmatic history involving little to no influence from continental sources (Samson et al., 1990; Yorath et al., 1999). As such, the terrane represents a significant contributor of juvenile, mantle derived crust to the North American continent. The Pb isotopic signature of Wrangellian sulfide occurrences presented in this paper will be evaluated in order to test for potential contributions of continental crust to the terrane. A detailed methodology for Pb isotopic studies is provided in Chapter 5. 1.3. THESIS PRESENTATION The thesis is presented as five main chapters that form its body (chapters 2 through 6), in addition to introductory and concluding chapters (chapters 1 and 7, respectively). Chapter 1 is the introductory chapter. This chapter provides background for the thesis, and introduces the main research questions addressed by the project. The chapter also provides a summary of methodologies used and describes the layout of the thesis. 6 Chapter 2 provides background information regarding the geology, tectonic history and metallogeny of Paleozoic Wrangellia, with a focus on exposures of the terrane on Vancouver Island. Chapter 3 presents a geochronological and biochronological study of the PWA. This chapter provides a revised chronostratigraphic framework for the the southern PWA. Emphasis is placed on describing newly recognized Late Paleozoic bimodal volcanic rocks and VMS mineralization in the southern PWA. Chapter 4 presents a lithogeochemical and Nd isotope geochemical study of the southern PWA. This chapter uses the chronostratigraphic framework developed in the preceding chapter in order to develop a new model for the magmatic evolution of the PWA. Emphasis in this chapter is placed on describing the lithogeochemical and isotopic characteristics of newly recognized Late Paleozoic bimodal volcanic rocks and VMS mineralization in the southern PWA. Chapter 5 presents a Pb isotope study of PWA sulfide occurrences. The Pb isotopic composition of sulfide occurrences, in conjunction with their respective geological settings, style of mineralization, and relationship to alteration minerals, is used to differentiate sygenetic versus epigenetic sulfide occurrences, and in doing so, evaluate the prospectivity of select, southern PWA sulfide occurrences for VMS mineralization. Emphasis is also placed on describing for the first time the Pb isotopic signatures of recently recognized Late Paleozoic VMS mineralization in the terrane.. The isotopic signature of Late Paleozoic VMS mineralization is compared to that of Late Devonian, PWA hosted VMS mineralization in order to see if sulfide Pb isotope compositions can be a cost effective tool in order to differentiate Late Paleozoic from Middle Paleozoic VMS occurrences in the terrane. Chapter 6 is a synthesis chapter, combining the geochronological, lithogeochemical and isotopic data presented in previous chapters in order to present a revised model for the tectonic and metallogenic evolution of the PWA and its prosepctivity for hosting VMS deposits. This chapter also evaluates the role of the PWA in the development of the North American continent. Chapter 7 serves as the concluding chapter of the thesis, and provides a summary of the main results and significant contributions for the study. It also provides a summary of further research that could be conducted in the PWA in order to address outstanding questions. Appendices 1 and 2 include tabulated geochronological and lithogeochemical data, in addition to sample descriptions and quality control studies. Appendix 3 contains references for Pb isotopic data utilized in geochemical modeling in Chapter 5. Appendix 4 contains four 7 articles published by Geoscience BC describing field work and preliminary results pertaining to this study. These articles were co-authored by Dr. J. Mortensen and Dr. F. Cordey, and include Ruks and Mortensen (2007, 2008), and Ruks et al. (2009, 2010). In addition, three separate field trips designed to highlight the results of this study for government geological surveys, geology students, mineral exploration professionals and the Society of Economic Geologsits were lead by the author and Dr. J. Mortensen. A guide designed for these field trips is available in Appendix 5. 8910Chapter 2: Regional geology and metallogeny of Paleozoic Wrangellia 112.1. INTRODUCTION The Wrangellia terrane, which is the focus of this study, is a significant component of the North American Cordillera (NAC). The NAC is an example of a convergent margin that has been in existence since Late Devonian time (Colpron et al., 2007) and can be subdivided into five, first-order tectonic entities (Fig. 1.1). These include: 1. Autochthonous to parautochthonous ancestral North America (Laurentia; NAm and NAb on Fig. 1.1) comprising rock units in several geographical areas including the Yukon-Tanana upland, Alaska Range, and southeastern British Columbia. These rocks comprise Proterozoic to Triassic miogeoclinal, dominantly sedimentary strata of the western Laurentian continental margin, which extend from eastern British Columbia, through Yukon, into east central Alaska; 2. The allochthonous marginal pericratonic terranes (Intermontane terranes). Located farther west of ancestral North America and underlying most of British Columbia, Yukon and Alaska, these rocks comprise Paleozoic to Mesozoic intrusive, volcanic, sedimentary, and metamorphic packages that represent magmatic arcs, microcontinents, and ocean basins which were developed in the peri-Laurentian realm and accreted to western Laurentia, beginning in Mesozoic time; 3. The allochthonous Insular and Northern Alaska terranes, which occur farther west of the Intermontane terranes in western British Columbia and southwestern Yukon and Alaska. They may have evolved in the Arctic realm in Paleozoic time and were accreted to western Laurentia in Middle Jurassic time (Nelson and Colpron, 2009) 4. Oceanic and accretionary complex terranes. These terranes evolved alongside the Intermontane and Northern Alaska–Insular terranes (indicated in red on Fig. 1.1); 5. Mesozoic and younger arc and accretionary terranes that form a western and southern fringe to the Insular and Northern Alaska terranes. These are referred to as “Late accreted terranes” in Figure 1.1. The main focus of this study is the Insular Terranes, which lie west of the Intermontane terranes (Fig. 1.1). The Insular terranes comprise Wrangellia, the Alexander terrane (Insular Superterrane; Monger et al., 1982) and the Peninsular terrane of southwest Alaska (Plafker et al., 1989; Colpron et al., 2007). Unlike the Intermontane terranes, the Insular terranes have no demonstrable ties to the Laurentian margin during their early histories. The Alexander terrane, 12which extends for over 1000 km from western British Columbia to southeastern Alaska, comprises Neoproterozoic through early Paleozoic volcanic arc and back arc assemblages in southeastern Alaska and northwestern British Columbia (Gehrels and Saleeby, 1987; Gehrels, 1990; Gehrels et al., 1996). Late Neoproterozic (Ediacaran) arc rocks in the Alexander terrane show evidence for a pre-Early Ordovician orogenic event (Colpron and Nelson, 2009). Alexander terrane also has a shared history of Ordovician to Silurian arc magmatism and Silurian-Devonian deformation with the Canadian Appalachians and the Caledonides (Bazard et al., 1995). Furthermore, detrital zircon studies of Cambro-Ordovician through Lower Devonian sedimentary rocks of the Alexander terrane show no ties to the Laurentian margin, but rather, with support from paleomagnetic, paleontological and detrial zircon studies , show similarities to Baltica (Bazard et al., 1995; Soja and Antoshkina, 1997; Beranek et al., 2013). Collectively all of this evidence argues for a closer link between the Alexander terrane and the Appalachian/Caledonian system and/or possibly Baltica than with western Laurentia (Colpron and Nelson, 2009; Beranek et al., 2013). The Wrangellia terrane represents a second major component of the Insular Superterrane and comprises a multi-episodic, Devonian and younger arc terrane that extends for over 2500 km in strike length, from southern Vancouver Island and Haida Gwaii to south-central Alaska (Colpron and Nelson, 2009). The Paleozoic geology of southern Wrangellia (Vancouver Island) is fundamentally different from that of northern Wrangellia (Alaska and southwest Yukon). The oldest rocks in Wrangellia comprise the mid-Paleozoic Sicker Group and are exposed almost exclusively on Vancouver Island. The Sicker Group has been interpreted to be a Late Devonian oceanic island arc which hosts significant volcanogenic massive sulfide (VMS) mineralization (Massey, 1995a, 1995b, 1995c; Yorath et al., 1999; Ruks and Mortensen, 2007, 2008; Ruks et al., 2009). Epiclastic sedimentary rocks and bioclastic limestone of the Mississippian through Permian Buttle Lake Group overlie this arc package (Yorath et al., 1999). In northern Wrangellia, the oldest rocks identified thus far represent a Carboniferous through Permian arc. Both northern and southern Wrangellia share voluminous and widespread Late Triassic basalts of the Nikolai-Karmutsen Formation, which are interpreted to represent the products of mantle plume related, oceanic plateau volcanism (Greene et al., 2009). Unlike the Alexander terrane, for which evidence discussed above suggests possible linkages with Baltica (e.g., Bazard et al., 1995; Colpron and Nelson, 2009), resolving the paleogeographic position of Wrangellia throughout the course of its history is more problematic. Several lines of evidence support a linkage between northern Wrangellia and Alexander terrane 13in the Paleozoic. Israel et al. (2014) argue that Wrangellia and Alexander terrane were linked by the Late Devonian, based on the presence in both terranes of Late Devonian gabbros with non-arc lithogeochemical signatures. These Late Devonian gabbros are interpreted to represent the development of a back-arc, suggesting that Alexander terrane forms the basement to northern Wrangellia . The 309 Ma Barnard Glacier pluton in eastern Alaska is interpreted to be a stitching pluton that unequivocally links the Alexander and Wrangellia terranes by Middle Pennsylvanian time (Gardner et al., 1988; Van Staal et al., 2010). Beranek et al. (2014) argue that the Alexander, Wrangellia and Peninsular terranes collided in the Early Permian, with Barnard Glacier suite magmatism forming as a result of post collisional slab break-off. Paleontological data suggest that Late Paleozoic rocks of Wrangellia developed in a cool temperate setting (Katvala and Henderson, 2002). Early Permian paleogeographic reconstructions place Wrangellia, and presumably the Alexander terrane to which it was now linked, north of the Intermontane terranes and potentially several thousand kilometers west of the Laurentian margin (Belasky et al., 2002; Stevens, 2008). There is no record of interaction between the Insular Superterrane (e.g., post-Middle Pennsylvanian combined Alexander and Wrangellia terranes) and the Laurentian margin (i.e., the peri-Laurentian terranes) until mid-Jurassic time (Colpron and Nelson, 2009). In southeastern Alaska, post-Triassic, pre-Late Jurassic structures mark the boundary between Alexander terrane and Yukon Tanana terrane, with Late Jurassic strata of the Gravina belt overlying both terranes (McClelland et al., 1992; Gehrels, 2001, 2002). Middle Jurassic intrusion, deformation and metamorphism in rocks of the Coast Mountains in British Columbia are believed to also represent interaction between the Insular Superterrane and the Laurentian margin (Van der Heyden, 1992). 2.2. REGIONAL GEOLOGY AND METALLOGENY OF PALEOZOIC WRANGELLIA The mid-Paleozoic Sicker Group on southern and central Vancouver Island (Fig. 1.2) represents the oldest rocks identified thus far in Wrangellia The oldest rocks identified in northern Wrangellia were previously interpreted to be those of the Skolai Group, comprising volcanic and sedimentary rocks deposited in a volcanic arc setting which is no older than Pennsylvanian (Smith and MacKevett, 1970; Read and Monger, 1976; Israel and Cobbett, 2008). However, recent work in northern Wrangellia by Israel et al. (2010; 2014) identified mafic volcanic rocks of Early Mississippian age as well as Late Devonian gabbros. These lithologies might represent potential correlatives to the Sicker Group on Vancouver Island. 14Other potential correlatives to Paleozoic rocks of southern Wrangellia (Vancouver Island) are also found on the San Juan Islands, USA, approximately 35 km northeast of Victoria, Vancouver Island, B.C. Here, Late Paleozoic volcanic rocks and limestone comprise the Deadman Bay terrane (Brandon et al., 1988; Yamagata, 2009). Late Paleozoic rocks of the Seven Devils Terrane in eastern Oregon and western Idaho have also been proposed as correlatives to Paleozoic Wrangellia, based largely on paleomagnetic arguments (e.g., Panuska and Stone, 1981; Harbert et al., 1988). Southern Wrangellia (Paleozoic) On Vancouver Island, Paleozoic Wrangellia is exposed in several northwest trending basement highs or uplifts that are largely the result of the accretion of Wrangellia to the North American margin in the Middle Jurassic and subsequent Eocene deformation related to the Cowican fold and thrust belt (Muller, 1980; England and Calon, 1991; Massey, 1995a, 1995b, 1995c). Structurally, these uplifts comprise upright, asymmetric folds that have been imbricated by Eocene thrust faults (Yorath et al., 1999). These thrust faults, part of the Cowichan fold and thrust belt, have been traced from southern Vancouver Island to Campbell River, and also have affected Paleozoic strata at the Myra Falls mine (England and Calon, 1991; Jones et al., 2006). Shortening related to these structures is maximum in southern Vancouver Island, and decreases to the north (England and Calon, 1991). Metamorphism in Paleozoic Wrangellia strata is typically greenschist facies, with local amphibolite facies developed near the margins of Jurassic intrusions (Juras, 1987; Yorath et al., 1999; Jones et al., 2006). The Cowichan uplift on Vancouver Island and adjacent portions of the Gulf Islands is the largest of four uplifts that expose the Sicker and overlying Late Paleozoic Buttle Lake groups (Fig. 1.2). The Sicker Group within the Cowichan uplift is presently interpreted to represent three distinct volcanic and volcaniclastic assemblages that together are thought to record the evolution of an oceanic magmatic arc known as the Sicker arc (Massey, 1995a, b, c; Yorath et al., 1999; Fig. 2.1). The lowermost Duck Lake Formation yields mainly normal mid-ocean-ridge basalt (N-MORB) geochemical signatures (Massey, 1995a), and is interpreted to represent the oceanic crust basement on which the Sicker arc was built. The upper portions of the Duck Lake Formation yield tholeiitic to calcalkaline compositions and may represent primitive arc rocks. Rare felsic volcanic rocks are also present within the Duck Lake Formation of the Port Alberni 15area. The Duck Lake Formation is overlain by the Nitinat Formation, which comprises mafic, submarine volcanic and volcaniclastic rocks with dominantly calcalkaline compositions and trace-element signatures typical of a volcanic arc setting. These rocks are interpreted to represent an early stage of arc development. The andesitic to mainly dacitic and rhyolitic McLaughlin Ridge Formation overlies the Nitinat and is believed to be correlative with the Myra Formation, which is the host rock for the Myra Falls volcanogenic massive sulfide (VMS) deposits in the Buttle Lake uplift southwest of Campbell River (Fig. 2.1). Rocks of the McLaughlin Ridge and Myra formations reflect a more evolved stage of arc activity. Eruption of Nitinat volcanic and volcaniclastic rocks appears to have occurred from several widely scattered centres, whereas the McLaughlin Ridge Formation within the Cowichan uplift is thought to represent eruption from a more centralized volcanic edifice. The abundance of proximal felsic volcaniclastic rocks, as well as voluminous comagmatic felsic intrusions in the Saltspring Island and Duncan areas (Fig. 1.2), indicate that one of these major volcanic centres was located in this area. Plant fossils indicate that at least a minor amount of McLaughlin Ridge volcanism occurred in a subaerial setting (Massey, 1995c; Yorath et al., 1999). In the Port Alberni area, the McLaughlin Ridge Formation has previously been interpreted to comprise felsic, fine-grained tuffaceous volcaniclastic and epiclastic rocks, suggesting deposition distal from a volcanic centre. Deposition of sedimentary and volcano-sedimentary rocks of the overlying Fourth Lake Formation of the Buttle Lake Group followed the cessation of Sicker arc magmatism, and scarce mafic volcanic rocks contained within the Fourth Lake Formation yield enriched tholeiitic rather than the calcalkaline compositions that characterize the McLaughlin Ridge Formation. Massey (1995a, b, c) speculated that the Buttle Lake Group may represent a marginal-basin assemblage that developed on top of the Sicker arc. Rocks of the Fourth Lake Formation form the oldest stratigraphic unit of the Buttle Lake Group, and comprise a diverse range of lithologies that vary in proportion from one locality to the next; these include siliceous argillite, shale, black chert, bioclastic limestone, intermediate volcanic sandstone, green and red ribbon chert, chert breccia, and conglomerate with an intermediate volcanic sandstone matrix (Yorath et al., 1999). Biostratigraphic data from on the Fourth Lake Formation indicates an age ranging from Mississippian through Early Permian (Orchard, 1987; Katvala and Henderson, 2002). Upper sections of the Fourth Lake Formation have been demonstrated in places to laterally interfinger with rocks of the Middle Pennsylvanian through Early Permian Mount Mark Formation (Yorath et al., 1999; Katvala and Henderson, 2002). In the Mount Whymper area in the eastern part of the Cowichan uplift, massive basalt flows of the alkalic Mount Whymper volcanic suite are 16interbedded with cherts and cherty sediments belonging to the Fourth Lake Formation (Massey, 1993c) and may represent a component of Late Paleozoic magmatism that has gone largely unrecognized in southern Wrangellia thus far. Studies of the Sicker and Buttle Lake groups on southern Saltspring Island by Sluggett (2003) and Mortensen and Sluggett (manuscript in preparation) provided new U-Pb zircon age constraints on felsic volcanic rocks of the McLaughlin Ridge Formation, granodioritic to quartz porphyritic bodies of the Saltspring Intrusive Suite, as well as felsic tuffaceous and sedimentary rocks of the Fourth Lake Formation. This work demonstrated that several pulses of felsic magmatism occurred in this portion of the Cowichan uplift. Two samples of felsic volcanic rocks assigned to the McLaughlin Ridge Formation yielded ages ranging from 364.8 +/- 1.3 Ma through 363.8 +/- 2.5 Ma. Samples of several felsic intrusions assigned to the Saltspring yielded ages ranging from 356.5 +/- 1.7 Ma through 359.1 +/- 1.4 Ma. Collectively, these new data indicate that magmatism represented by the McLaughlin Ridge Formation and associated Saltspring intrusions occurred over a time span of at least 15 Ma. There is insufficient age control available at this point to determine whether the magmatism was continuous or episodic during this time period. Lithogeochemical studies of the Saltspring Intrusions by Sluggett (2003) indicate peraluminous compositions. Peraluminous magmas are not common to ocean island arc environments, suggesting that there may be older, evolved, continental crust like basement underlying southern Wrangellia from which melts of the Saltspring Intrusions were derived (Sluggett, 2003; Mortensen and Sluggett, manuscript in preparation). In the same study, a felsic tuffaceous sandstone from rocks assigned to the Fourth Lake Formation yielded abundant, euhedral 320 Ma zircons (Sluggett, 2003). Three samples of volcanosedimentary rocks from strata assigned to the Fourth Lake Formation on Saltspring Island (Fig. 1.2) yielded abundant detrital zircons (Mortensen, pers. comm.) with an age range of 296.1 Ma through 350 Ma and age peaks at 300 Ma, 308 Ma, 313 Ma 314 Ma, 316 Ma, 317 Ma, 321 Ma, 340 Ma and 343 Ma. Collectively, these Pennsylvanian zircon ages are significant, as they represent a pulse of Wrangellian magmatism for which there are no known sources on Vancouver Island. Rocks in the Nanoose uplift (Fig. 1.2) have been tentatively correlated with both the Sicker Group and the Buttle Lake Group, and comprise fine clastic rocks, chert, diabasic to andesitic volcanic rocks and limestone (Yorath et al., 1999). Fossiliferous limestone in the Nanoose uplift provided Permian brachiopods as well as fusulinids that yielded a Middle Pennsylvanian age (Muller, 1980). However, diabasic and andesitic pillow lavas in the area have unknown stratigraphic affinities. On the Ballenas Islands (Fig. 1.2), these pillow lavas are 17associated with green and grey chert, and are interbedded with a red tuff breccia which contains both scoriaceous mafic volcanic clasts and crinoidal limestone clasts. In addition, Yorath et al. (1999) reported the presence of extensive areas of mélange in the Nanoose area. This is significant, as it may represent the only documented occurrence of a Paleozoic subduction complex in Wrangellia. A potential correlative to volcanic rocks and limestones exposed in the Nanoose uplift include the Deadman Bay Volcanics of the San Juan Islands, located approximately 35 km to the northeast of Victoria, British Columbia (Fig. 1.2). Similar to much of the Nanoose uplift, the Deadman Bay Volcanics comprise Permian basaltic rocks and limestones. Together, they are interpreted to represent a Permian seamount complex (Yamagata, 2009). Previous stratigraphic work on Paleozoic rocks in the Buttle Lake uplift (Fig. 1.2 and 2.1) has focused on the geology in and around the Myra Falls VMS deposits (e.g., Juras, 1987; Barrett and McLean, 1996). The oldest rocks of the Buttle Lake Group are basaltic andesite flows and lesser mafic volcaniclastic deposits of the Price andesite (Juras, 1987), which form the “footwall” to VMS mineralization. Lithogeochemically, rocks of the Price andesite have marked negative Nb anomalies, and trend towards transitional to mildly calc-alkaline affinities, both features of volcanic rocks generated in suprasubduction zone settings (Barrett and Sherlock, 1996). Overlying rocks of the Myra Formation comprise basaltic to rhyolitic flows and volcaniclastic rocks, with lesser epiclastic sediments, argillites, cherts, and massive suphide mineralization (Juras, 1987). Barrett and Sherlock (1996) concluded that the Price and Myra formation volcanic rocks that host the Myra Falls VMS deposits were generated in a suprasubduction setting during submarine rifting of a mature oceanic island arc, similar to that observed in modern day settings at the Valu Fu Ridge in the southern Lau Basin (Pearce, 1982; Fouquet et al., 1993) and the southern tip of the Japan arc (Ikeda and Yuasa, 1989). Lead isotopic studies conducted on VMS mineralization in the Myra Falls camp and from the Cowichan uplift (Andrew and Godwin, 1989; Godwin and Robinson, 1996) showed that massive sulfide mineralization hosted in lower levels of the mine stratigraphy at Myra Falls is somewhat more radiogenic than that hosted in upper stratigraphic levels (Godwin and Robinson, 1996). Godwin and Robinson (1996) attributed this to a potential contribution by a component of lead derived from evolved, continental detritus into massive sulfide accumulations at lower stratigraphic levels. Siliceous tuffaceous sediments, subaqueous volcaniclastic debris flows, pyroclastic deposits and mafic sills comprise the Thelwood Formation, which locally unconformably overlies the Myra Formation (Juras, 1987). Conformably overlying the 18Thelwood Formation are rocks of the Flower Ridge Formation, which include amygdaloidal basaltic lapilli tuff and volcanic breccia, minor basaltic flows and tuffs, and tuffaceous sedimentary rocks (mudstones and siltstones) (Juras, 1987). Volcanic rocks of the Flower Ridge Formation may be correlative to those of the Mount Whymper Volcanic Suite, which is locally present within the Fourth Lake Formation in the Cowichan uplift (Massey, 1993b). Geochronologic and some limited biostratigraphic work have been conducted in the Myra Falls area. Juras (1987) reported a U-Pb (zircon) age of 370 +18/-6 Ma for a rhyolite unit in the upper part of the Myra Formation. Parrish and McNichol (1992) dated a rhyolite from the lower part of the Myra Formation at 366 +/- 4 Ma. Early Mississippian radiolaria have been derived from rocks of the Thelwood Formation (Jones, 2001). No direct age constraints are available for the Flower Ridge Formation; however, it is bracketed between Early Mississippian and Pennsylvanian to Early Permian age, based on ages of the underlying Thelwood Formation and the overlying Buttle Lake Formation, respectively (Brandon et al., 1986; Juras, 1987). Potential Sicker Group rocks and VMS mineralization in the Bedingfield uplift occur north of Tofino (Fig. 1.2). The age and stratigraphic relations of this extensive belt of potential Sicker Group rocks are poorly understood. The most recent geological descriptions of the area are contained in mineral exploration assessment reports from the late 1980s by BHP-Utah Mines (e.g., Duncan and Ord, 1987) and Cominco (e.g., Freeze, 1986). VMS mineralization of the Bedingfield area comprises several sulfide occurrences with significant polymetallic grades, that are contained within a variably deformed package of waterlain, bimodal volcanic rocks and associated sedimentary rocks, all of which are intruded by gabbroic sills assumed to be correlative with the Triassic Mount Hall Gabbro. A sedimentary unit comprising argillite and chert is observed to unconformably overlie the volcanic package (Freeze et al., 1986), and may be correlative to the Fourth Lake Formation of the Buttle Lake Group. Overlying this sedimentary unit is variably fossiliferous (crinoid bearing) limestone, which is potentially correlative with the Mount Mark Formation of the Buttle Lake Group (Freeze et al. 1986). The age and stratigraphy of previously undated volcanic and sedimentary rocks underlying the Dragon and Dorado mineral claims, in the vicinity of Gold River and Hesquiat, respectively (Fig. 1.2), are poorly constrained. The Dragon property is located approximately 80 km west of Campbell River, 20 km northwest of Gold River and 65 km northwest of the Myra Falls mine of Breakwater Resources Ltd. (Fig. 1.2). Regional mapping of the Dragon property area by Muller (1977) interpreted the rocks underlying the Dragon property to be amphibolite-grade metamorphic rocks derived from the Westcoast Crystalline Complex. Muller described the 19Westcoast Crystalline Complex as amphibolite-facies metamorphic rocks belonging to the Middle Paleozoic Sicker Group, the Late Paleozoic Buttle Lake Group and the Triassic Karmutsen Formation. After the discovery of massive sulfides in stream bed float on the Dragon property by prospector E. Specogna, work by Noranda geologists culminated in the discovery of the Falls and North VMS occurrences (Kemp and Gill, 1993). Further geological mapping and diamond-drilling by Noranda and Westmin geologists indicated that these showings, with grades up to 7.33% Zn, 1.34% Pb, 173 ppm Cu, 680 ppb Au, and 19.2 g/t Ag over a 2 m thickness, are associated with the contact zone between underlying bimodal volcanic rocks and overlying sedimentary rocks and limestone (Jones, 1997). Volcanic rocks of the Dragon property that underlie massive sulfide mineralization consist of massive, flow-banded rhyolite, andesite and tuffaceous felsic and intermediate volcanic rocks. Sedimentary and carbonate rocks overlying and interlayered with massive sulfide mineralization on the Dragon property consist of chert, mudstone, calcareous mudstone, fossiliferous felsic tuff, fossiliferous wackestone and marble (e.g., Jones, 1997; Ruks et al., 2009). The Dorado property is located approximately 17 km north of the village of Hesquiat, on the west coast of Vancouver Island. Like the Dragon property, rocks underlying the Dorado property were originally interpreted by Muller (1977) as amphibolite-facies metamorphic rocks that were assigned to the Westcoast Crystalline Complex. However, geological mapping of the area by Marshall et al. (2006) has shown the region to be underlain by abundant mafic volcanic rocks of possible Sicker Group affinity, and by clastic and carbonate rocks that resemble portions of the Buttle Lake Group. Following up on reports by Marshall et al. (2006) of polymetallic VMS-like stockwork mineralization in the area, Paget Resources Corporation staked the Dorado property and soon after discovered several polymetallic massive sulfide occurrences (Ruks et al., 2008). Massive sulfide mineralization on the Dorado property is associated with the contact between massive, variably silica-altered, clinopyroxene- and feldspar-phyric andesite and overlying tuffaceous, volcano-sedimentary rocks (Ruks et al, 2009). In the Bedingfield, Dragon and Dorado areas, the juxtaposition of interbedded fossiliferous limestones, tuffs and sedimentary rocks with underlying VMS-like mineralization and volcanic rocks has not previously been observed in the Sicker Group. It raises the possibility that volcanic rocks and mineralization of the Bedingfield, Dragon and Dorado areas may represent a Late Paleozoic cycle of arc magmatism and VMS mineralization not previously recognized in Wrangellia. If limestones of the Bedingfield, Dragon and Dorado areas are correlative with limestones of the Permian Mt. Mark Formation, arc magmatism and 20mineralization contained in these areas are potentially correlative to Late Paleozoic volcanic rocks in northern Wrangellia (e.g., the Skolai Group). If this is the case, northern Wrangellia and southern Wrangellia may be much more similar in Late Paleozoic time than previously thought, and previous arguments for assigning northern and southern Wrangellia to different terranes (e.g., Katvala, 2006) may not be justified. Paleozoic Northern Wrangellia (Yukon/Alaska and Haida Gwaii) Rocks of northern Wrangellia in Yukon-Alaska and Haida Gwaii (Fig. 1.1 and 2.2) include Upper Paleozoic through Upper Triassic volcanic and sedimentary rocks (Jones et al., 1977). Upper Triassic rocks of northern Wrangellia, similar to those of southern Wrangellia, consist of dominantly mafic volcanic rocks of the Nikolai-Karmutsen Formation, which have been interpreted as a product of mantle plume-related, oceanic plateau volcanism (Richards et al., 1991; Greene et al., 2009). Upper Paleozic rocks of northern Wrangellia in Yukon-Alaska comprise the Skolai arc (MacKevett, 1971; Read and Monger, 1976; Hulbert, 1997), which consists dominantly of Pennsylvanian to Permian basalt, andesite and sedimentary rocks of the Station Creek Formation (Smith and MacKevett, 1970), and overlying sedimentary and carbonate rocks (with rare volcanic rocks) of the Early Permian Hasen Creek Formation (Smith and MacKevett, 1970; Israel and Cobbett, 2008). Recent work by Israel et al. (2010) has shown that volcanic rocks in northern Wrangellia, where they are preserved between the Denali and Duke River faults, are at least as old as 352 Ma. Israel et al. (2010) also identified 364 Ma gabbro complexes, which were intruded into crust of unknown age and affinity. These gabbros, of unknown tectonic affinity, are unconformably overlain by Permian sedimentary rocks of Wrangellia. The gabbros resemble intrusions of similar age in the Alexander terrane, where they are observed to intrude Ordovician through Devonian sedimentary rocks (Israel et al., 2010). In Yukon, Wrangellia rocks are in fault contact with adjacent portions of the Alexander terrane along the Duke River fault. Recent detrital zircon investigations of northern Wrangellian rocks of Permian age by Israel et al. (2010) also indicate that Alexander terrane and Wrangellia were amalgamated in Pennsylvanian time, with potential, additional influence from igneous rock sources in the Stikine terrane. This detrital zircon data also suggests similarities between northern Wrangellia and the Taku terrane. Similarities between Wrangellia and the Taku terrane have also been documented by previous workers (e.g., Gehrels, 2002 and references therein). 21Very little is known about Paleozoic Wrangellia of Haida Gwaii. The first documented occurrence of Paleozoic rock on Haida Gwaii was during mapping of the area as part of the Frontier Geoscience Program (FGP; Geological Survey of Canada) in the summer of 1990 (Hesthammer et al., 1991). In the western part of Moresby Island, mafic volcanic rocks were observed to be overlain by low energy marine sedimentary rocks and limestone of Permian and possibly Carboniferous age (Hesthammer et al., 1991; Indrelid and Hesthammer, 1991). Mapping in the area also revealed the presence of a large, 8 km wide, quartz diorite batholith (the Chaatl Inlet intrusion; Massey et al., 2005) that yielded an unpublished 317 Ma U-Pb (zircon) date (J. Haggart, pers. comm., 2007). In 1988, prospector E. Specogna discovered significant polymetallic VMS mineralization east of the Chaatl Inlet pluton (the Cimadoro occurrence; MINFILE 103F 052; MINFILE, 2012), hosted in a sequence of interbedded argillite, tuffaceous sedimentary rocks, chert and limestone which is interpreted to be Late Paleozoic in age. 222324Chapter 3: The chronostratigraphy of Paleozoic Wrangellia and its contained volcanogenic massive sulphide occurrences, Vancouver Island, British Columbia 253.1. INTRODUCTION Wrangellia is a fundamental and economically significant component of the Insular Superterrane. It comprises mainly Middle Paleozoic through Late Triassic rock units, and extends over 2500 km in length from southern Vancouver Island through southern Alaska. The Paleozoic geology of southern Wrangellia (Vancouver Island), however, is notably different from that of northern Wrangellia (Alaska and southwest Yukon). This has lead some researchers to question whether northern and southern Wrangellia are actually part of the same terrane, or if they comprise different tectonic entities altogether. The Late Devonian through Early Mississippian Sicker Group (SG) on Vancouver Island, one of the main components of southern Wrangellia, is interpreted to record the evolution of an oceanic island arc that represents the basement of Wrangellia. The SG hosts many significant volcanogenic massive sulphide (VMS) deposits, including those of the Myra Falls camp (Nyrstar N.V.), the largest producing VMS deposit in western Canada. This study presents the results of 51 new U-Pb zircon ages and 17 new microfossil ages that, coupled with new geological information, redefine the stratigraphy and mineral exploration potential of southern, Paleozoic Wrangellia on Vancouver Island. These new data indicate that volcanic rocks in southern Paleozoic Wrangellia are not restricted to a single Late Devonian through Early Mississippian island arc complex with associated VMS mineralization, as previously thought. Instead, southern Paleozoic Wrangellia comprises a long-lived, episodic ocean island arc, with pulses of bimodal volcanism hosting VMS mineralization beginning in the Late Devonian and continuing sporadically through the Early Permian. 3.2. NEW GEOCHRONOLOGY AND BIOCHRONOLOGY FOR PALEOZOIC WRANGELLIA Brief descriptions and location of the samples dated in this study are summarized in Table 3.1 and their locations are shown on the maps of the study areas in Figures 3.1 through 3.6. A total of 128 samples were collected for U-Pb zircon studies from which 51 samples were dated. A total of 84 samples were collected for biochronology, from which 20 provided diagnostic faunal assemblages and ages. The samples were collected from a 160 km by 40 km study area comprising much of the southern half of Vancouver Island (Fig. 1.2). Sampling for isotopic dating and fossil ages concentrated on areas where exposures of Paleozoic rocks were 26reported by previous workers. Special emphasis was placed on geochronological and biostratigraphic sampling in the vicinity of VMS deposits and occurrences in order to constain the timing of mineralization. Since geochronological and biochronological sampling as part of this study was conducted in several geographically and geologically distinct areas, the resulting isotopic and biochronological dates are discussed separately, by geographic area. 3.2.1. Geochronology and Biochronology Geochronology Isotopic ages reported herein are for both igneous and detrital zircons. All analyses have been conducted at the Pacific Centre for Isotopic and Geochemical Research (PCIGR) at the University of British Columbia in Vancouver. Select igneous zircons have been dated using either chemical abrasion isotope dilution-thermal ionization mass spectrometry (ID-TIMS) using methods described by Mortensen et al. (2008) or laser ablation inductively coupled mass spectrometry (LA-ICPMS; methods described by Tafti et al. (2009) and summarized in Appendix 1). Detrital zircons have been dated exclusively with LA-ICPMS using methods as described by Beranek et al. (2009), summarized in Appendix 1. Sample descriptions, sample locations and interpreted U-Pb ages for a total of 51 samples are summarized in Table 3.1. Measured and/or calculated 207Pb/206Pb, 207Pb/235U and 206Pb/238U ratios and ages for individual analyses analyzed by LA-ICPMS and TIMS are reported in Tables A1.1 and A1.2, respectively. Data from each igneous rock sample are plotted on conventional concordia diagrams, and on compilation plots of 206Pb/238U ages for each sample in Figures A1.1 through A1.5. The 206Pb/238U age is the most precisely determined age for relatively young (Phanerozoic) zircons and is interpreted to give the best estimate for the crystallization age of the samples. For each sample, the crystallization age was calculated based on a weighted average of 206Pb/238U ages for individual analyses. Errors are quoted at the 2 σ (95% confidence) level. Discordant analyses and analyses interpreted to be from older inherited grains, or grains that had experienced post crystallization Pb loss, were excluded from the weighted average calculations. U-Pb zircon age data for detrital zircon samples are presented in relative probability plots with stacked histograms, prepared using the Isoplot 3.0 Excel macro of Ludwig (2003). These plots contain both a relative probability curve corresponding to age peaks and a histogram (e.g., Link et al., 2005). Each detrital zircon sample comprises a single plot in 5 Ma bins to highlight 27the populations observed in the dataset. Age peaks were determined by using the Detrital Zircon Age Pick macro created by G.E. Gehrels for Microsoft Excel; this macro processes given ages and errors at the 1- sigma level and produces age groupings and peaks at the 2-sigma level. U-Pb results for individual samples are briefly discussed in Appendix 1. Biochronology Samples were collected during this study for both radiolarian and conodont biostratigraphy. Samples collected for radiolarian biostratigraphy were analyzed by Dr. Fabrice Cordey of the University of Lyon, France. Samples collected for conodont biostratigraphy were analyzed by Dr. Michael Orchard of the Geological Survey of Canada. Microfossil sampling and processing methods are described in Appendix 1. Sample descriptions, sample locations and biostratigraphic ages for radiolarian and conodont samples are summarized in Table 3.2. 3.2.2. Isotopic Ages and Biochronology of the Cowichan Area The geology of the Cowichan area, including locations of select VMS occurrences, iron formations, and isotopic and biochronological samples taken as part of this study, is shown in Fig. 3.1. A total of 17 isotopic ages and 3 biochronological ages were produced for Paleozoic rocks of the Cowichan area. Of these 17 isotopic ages, 13 are from felsic volcanic rocks spatially associated with VMS mineralization or iron formations, and 4 are from quartz-feldspar porphyries assigned to the Saltspring intrusions. Felsic volcanic rocks dated in the Cowichan area comprise crystal tuffs, lapilli tuffs, rhyolite flows and domes, and yield ages ranging from 363 ± 6.7 Ma through 353.1 ± 3.4 Ma (Fig. A1.1), whereas quartz-feldspar porphyries of the Saltspring intrusions yield ages ranging from 360.7 ± 2.4 Ma through 355.0 ± 1.5 Ma. Several samples collected from the Cowichan area for igneous zircon ages were dated via ID-TIMS. These include samples 05M393 and 05M366, comprising rhyolite tuffs from the Lara and Lenora adits, respectively (Fig. 3.1). Five zircons from 05M393 were dated, yielding two concordant ages from which a weighted average age of 362.6 ± 9.4 Ma was calculated (Fig. A1.1. G). The remaining zircons in the sample yielded discordant ages, and are interpreted to have suffered post-crystallization lead loss. Five zircons from 05M366 yielded concordant ages (Fig. A1.1. I), including a cluster of three, younger zircons, from which a weighted average age of 360.2 ± 4.3 Ma was calculated. Older zircons in the sample, yielding ages of 364.35 ± 1.50 28Ma and 371.98 ±1.01 Ma, are interpreted as xenocrysts, likely the result of a recycled volcanosedimentary component to the sample. Three cherts from the Cowichan area yielded Paleozoic fossil ages. A sample of chert (09TR079) spatially associated with the Lady D magnetite iron formation (Fig. 3.1) yielded a Late Pennsylvanian or Early Permian (Moscovian-Asselian) age. Two chert samples from sedimentary rocks of the Fourth Lake Formation, located in the western side of the Cowichan area (Fig. 3.1) yielded a Late Paleozoic (possibly Carboniferous) age, and an Early Permian (Asselian-Artinskian) age, respectively. 3.2.3. Isotopic Ages and Biochronology of the Alberni Area The geology of the Alberni area, including locations of select VMS occurrences, iron formations and isotopic and biochronological samples taken as part of this study, is shown in Fig. 3.2. A total of 14 isotopic ages and 11 biochronological ages were produced for rocks of the Alberni area. Felsic volcanic rocks dated in the Alberni area comprise dacitic flows, felsic breccias, lapilli and crystal tuffs, and comprise two age groups; the first representing episodic volcanism from 366.8 ± 2.4 Ma through 335.3 ± 2.5 Ma and the second representing a pulse of volcanism at 293.6 ± 1.8 Ma (Fig. A1.2). One sample was collected from the Alberni area for igneous zircon age dating via ID-TIMS. This sample (07TR051) collected from a dacite flow, yielded four concordant zircon ages (Fig. A1.2. B). A weighted average age of 366.58 ± 0.67 Ma was calculated from the youngest two zircons in this sample, which yielded similar, concordant ages. The older zircons in the sample are interpreted as xenocrysts. Five chert samples from the southern portion of the Alberni study area yielded Paleozoic fossil ages. One of these samples (09SI04) from near the base of the formerly undated Duck Lake Formation type section (Yorath et al., 1999), yielded a Middle to Late Devonian age. Sample 08SI27, from a package of cherts associated with the formerly undated McLaughin Ridge Formation type section, yielded a Late Devonian (Frasnian-Famennian) age. Sample 09SI08, taken from a package of cherts assigned to the Fourth Lake Formation (Yorath et al., 1999), yielded a potential Late Paleozoic age. Eight chert samples from the northern portion of the Alberni study area yielded Paleozoic fossil ages. Two chert samples near the southwestern tip of Horne Lake, samples 09SI15 and 09SI14, yielded Devonian or Carboniferous and Late Devonian or Carboniferous ages, respectively. Sample 08SI03, south of Horne Lake, yielded a Mississippian fossil age, similar to isotopic ages produced as part of this study for nearby felsic 29volcanic rocks. Four chert samples to the west of Horne Lake yielded Late Paleozoic, or potential Late Paleozoic fossil ages. Samples 08SI07 and 08SI10, located north of Lacy Lake, yielded Early Permian (possibly Artinskian) and Permian fossil ages, respectively. Sample 08SI32, located west-southwest of Lacy Lake, yielded a Carboniferous or Permian (possibly Early Permian) fossil age. Samples 08SI19 and 08SI22, located south of Lacy Lake, yielded Carboniferous or Permian and Pennsylvanian or Permian fossil ages, respectively. 3.2.4 Isotopic Ages and Biochronology of the Nanoose Area The geology of the Nanoose area, including locations of isotopic and biochronological samples taken as part of this study, is shown in Fig. 3.3. A total of 3 isotopic ages and 3 biochronological ages were produced for rocks of the Nanoose area (Fig. A1.3), including two detrital zircon samples (samples 08TR017 and 08TR019) and one sample for igneous zircon (sample 08TR020) : Sample 08TR017 (n = 26) Siltstone from the Nanoose complex contained detrital zircons ranging in age from 294.7 through 355 Ma, with age peaks at 305, 321 and 354 Ma (Fig. A1.3A). Sample 08TR019 (n = 65) Sandstone from the Nanoose complex contained detrital zircons ranging in age from 298 through 330 Ma, with a single age peak at 311 Ma (Fig. A1.3B). A sample of granodiorite from the Nanoose area (08TR020) contained a total of 18 zircons which yielded a weighted average 206Pb/238U age of 199.1 ± 1.5 Ma (Fig. A1.3C). Three samples were collected for microfossil dating from rocks of the Nanoose Complex exposed on west Ballenas Island (Fig. 3.3). Chert sample 09TR102B yielded a Late Paleozoic (possibly Carboniferous) radiolarian fossil age whereas carbonate samples 09TR123 and 09TR104 yielded conodont fossil ages of Early Permian (Asselian) and Late Carboniferous age, respectively. 30 3.2.5 Isotopic Ages of the Bedingfield Area The geology of the Bedingfield area, including locations of select VMS occurrences, and isotopic samples taken as part of this study, is shown in Fig. 3.4. A total of 5 isotopic ages were produced for rocks of the Bedingfield area (Fig. A1.4). Four felsic volcanic rocks dated in the Bedingfield area comprise rhyolite flows, lapilli, and crystal tuffs. Two samples of felsic volcanic rocks from the Herbert Inlet area, samples 09TR117 and 09TR118, yielded ages of 305.6 ± 4.1 Ma and 308.3 ± 3.2 Ma, respectively. A rhyolite flow from the Cypress Bay area (sample 09TR105) yielded an age of 312.2 ± 3.7 Ma. A rhyolitic lapilli tuff from the Cypre River area (sample 09TR110) yielded an age of 312.4 ± 3.5 Ma. A deformed quartz-feldpsar porphyry dike in the Bedwell Sound area (sample 09TR107) cross cuts felsic volcanic rocks and yielded an age of 200.1 ± 1.2 Ma. Samples taken for biochronology from the Bedingfield area did not yield microfossils. 3.2.6 Isotopic Ages of the Dragon Property, Gold River Area The geology of the Dragon property, including locations of select VMS occurrences, and isotopic samples taken as part of this study, is shown in Fig. 3.5. A total of 8 isotopic ages were produced for rocks of the Dragon property area (Fig. A1.5). Six felsic volcanic rocks dated from the property comprise rhyolite flows, tuff breccias, lapilli and crystal tuffs. These samples yielded ages ranging from 311.1 ± 0.3 Ma through 291.6 ± 2.2 Ma. A single quartz-feldspar phyric rhyolite porphyry with undetermined contact relationships was also dated on the property (sample 08TRDR056), yielding a 172 ± 2.5 Ma age. Two samples from the Dragon property were collected for igneous zircon dating using the ID-TIMS method. These samples included 08TRDR007B and 08TRDR053A, collected from an aphyric rhyolite flow, and a quartz-feldspar phyric porphyry, respectively. Of five zircons dated from sample 07TRDR007B, only one zircon yielded a concordant age, with the remaining four discordant ages interpreted to be the result of post-crystallization lead loss (Fig. A1.5. A). The single concordant age of 304.2 ± 3.1 Ma was interpreted as the age of the sample. Four zircons were dated from sample 08TRDR053A, yielding two, overlapping concordant ages. A weighted average age of 311.10 ± 0.31 Ma was calculated for this sample. Discordant ages in this sample are interpreted to be the result of post crystallization lead loss. 31Samples taken for biochronology from the Dragon area did not yield microfossils. 3.2.7 Isotopic Ages of the Dorado Property, Hesquiat Peninsula The geology of the Dorado property, including locations of potential VMS occurrences, and isotopic samples taken as part of this study, is shown in Fig. A1.2. A total of two isotopic ages were produced for rocks of the Dorado area (Fig. A1.6). Sample 07TRHS018A is from a feldspar phyric diorite porphyry, whereas 07TRHS020A is a highly altered, aphyric rhyolite dike. Both of these intrusions were observed to cross-cut altered and mineralized mafic volcanic rocks that are host to the Dorado showings. These samples yielded ages of 202.2 ± 1.3 Ma and 180.9 ± 3.2 Ma, respectively. Samples taken for biochronology from the Dorado area did not yield microfossils. 3.2.8 Isotopic Ages of the Myra Falls Area A total of 11 samples were collected for isotopic dating from felsic volcanic rocks associated with VMS mineralization at the Myra Falls deposit (Nyrstar N.V.; Fig. 1.2). Of these samples, only 4 yielded zircons and only 1 out of these 4 samples yielded zircons amenable to dating via LA-ICPMS methods. This sample was from a strongly altered and stockwork sulphide mineralized quartz-feldpsar phyric rhyolite, which is underlain by mafic volcanic rocks belonging to the Price Formation. This altered and sulphide mineralized rhyolite forms the immediate footwall to overlying VMS mineralization of the Marshall Zone. This sample (11TRMF010) represents the first pulse of felsic magmatism in the Myra Formation, and yielded an age of 361.5 ± 2.5 Ma (Fig. A1.7) 3.3. REVISED CHRONOSTRATIGRAPHY FOR SOUTHERN PALEOZOIC WRANGELLIA, VANCOUVER ISLAND, B.C New isotopic and fossil ages obtained during this study have revealed that Paleozoic Wrangellia comprises not only abundant Late Devonian through early Mississppian age bimodal volcanic rocks and associated VMS mineralization, but also a previously unrecognized cycle of Pennsylvanian through Early Permian bimodal volcanic rocks and associated VMS 32mineralization (Fig. 3.7). Late Devonian through Early Permian stratigraphy is exposed in the Cowichan and Buttle Lake uplifts, whereas rocks of the Nanoose and Bedingfield uplifts, as well as rocks of the Dragon property, expose Pennsylvanian through Permian stratigraphy (Fig. 3.7). The most representative section of Paleozoic Wrangellian stratigraphy examined as part of this study is exposed in rocks of the Cowichan uplift (Fig. 1.2), most notably in the Alberni area (Fig. 3.2). Geochronological control for Paleozoic Wrangellian stratigraphy is most complete in the Alberni area (Fig. 3.2), which also includes the type sections for Paleozoic Wrangellian stratigraphy (e.g. Yorath et al., 1999). 3.3.1 Revised Chronostratigraphy of the Cowichan Uplift The stratigraphy of Paleozoic Wrangellia and its contained VMS occurrences, as exposed in rocks of the Cowichan uplift, is shown in several schematic stratigraphic sections (Fig. 3.7). These sections depict variations in Paleozoic stratigraphy of the Cowichan uplift as observed in the Alberni and Cowichan areas. Pre Late Devonian The oldest dated rocks in southern Wrangellia are Late Devonian in age (e.g., Brandon et al., 1986; Yorath et al., 1999), and are restricted to rocks of the Saltspring Intrusive suite and McLaughlin Ridge Formation, in which felsic igneous rocks are prevalent and numerous isotopic ages are available. However, there is evidence for pre Late Devonian Wrangellian rock units in both the Cowichan and Alberni areas. In the Cowichan area (Maple Mountain), clinopyroxene phyric mafic volcanic rocks assigned to the Nitinat Formation are cross-cut by quartz-feldpar phyric rhyolite porphyry of the Saltspring Intrusive suite dated at 360.7 Ma (09TR132; Fig. 3.1). Similar cross-cutting relationships are observed in the vicinity of Big Sicker Mountain (e.g. Brandon et al., 1986) and on Saltspring Island (Sluggett, 2003), where exposures of Nitinat Formation mafic volcanic rocks are cross cut by Saltspring Intrusions ranging in age from 358 ± 1.0 Ma through 356.5 Ma (Sluggett, 2003). Saltspring Intrusions sampled on Saltspring Island and dated as part of this study (samples 09M302, 09M308 and 09M309; Fig. 3.1) yield similar ages ranging from 359.3 ± 3.1 Ma through 355.0 ± 1.5 Ma. In the Port Alberni area, Massey (1995a) interpreted mafic volcanic rocks of the Duck Lake Formation to be Late Devonian in age, and representative of the oceanic crust upon which 33the Sicker arc was built. However, no chronological data is available to support this hypothesis (Yorath et al., 1999).. Several samples of chert were collected from the base of the Duck Lake Formation type section as part of this study (sample 09SI04), and yielded radiolarian assemblages suggesting either a Middle or Late Devonian age. These cherts are part of a thick package of mafic volcanic rocks and lesser volcanosedimentary rocks that stratagraphically underlie the type section for the McLaughlin Ridge Formation (Fig. 3.2; Massey, 2005). Radiolarian biochronology conducted on cherts within the McLaughlin Ridge Formation type section as part of this study have yielded Late Devonian ages (08SI27; Fig. 3.2), suggesting that underlying mafic volcanic rocks assigned to the Nitinat and Duck Lake Formations are pre Late Devonian in age. Felsic volcanic rocks are exceedingly rare in the Duck Lake Formation; however, north of the Duck Lake Formation type section, a dacite flow is interbedded with basalt flows assigned to the Duck Lake Formation (sample 07TR051). A sample of this dacite flow yielded an age of 366.6 ± 0.7 Ma, indicating that in some areas, rocks of the Duck Lake Formation are time transgressive, overlapping in age with rocks of the McLaughlin Ridge Formation as dated elsewhere in the Cowichan uplift. Late Devonian – Early Mississippian (370 Ma to 350 Ma) Late Devonian through Early Mississippian volcanic rocks and associated volcano-sedimentary and sedimentary rocks are abundant in the Cowichan uplift. Late Devonian through Early Mississippian exposures in the Cowichan area are dominated by felsic volcanic rocks (with lesser mafic volcanic, volcano-sedimentary and sedimentary rocks) associated with numerous VMS occurrences, whereas strata of similar age in the Alberni area are dominated by mafic volcanic rocks (with associated volcano-sedimentary and sedimentary rocks), and fewer VMS occurrences. Felsic volcanic rocks of the McLaughlin Ridge Formation in the Cowichan area (Fig. 3.1) that were sampled as part of this study range in age from 363.0 ± 6.7 Ma to 353.1 ± 3.4 Ma. Quartz-feldspar porphyritic intrusions of the Saltspring Intrusive suite are also present in the Cowichan area, where they intrude variably epidote-chlorite altered mafic volcanic rocks of the Nitinat Formation. Saltspring Intrusions sampled as part of this study range in age from 360.7 ± 2.4 Ma to 355.0 ± 1.5 Ma, indicating they are broadly coeval with, and the probable subvolcanic feeders to, VMS associated felsic volcanic rocks of the McLaughlin Ridge Formation. 34Late Devonian – Early Mississippian mafic volcanic rocks are abundant in the Port Alberni area, with rare exposures of pre 350 Ma felsic volcanic rocks. This is in stark contrast to stratigraphy of similar age in the Cowichan area, where felsic volcanic rocks predominate. In the southern portion of the Alberni area (Fig. 3.2; sample 09SI04), cherts interbedded with mafic volcanic rocks and a small, newly discovered, pyrite dominated VMS lens (Ruks et al., 2009, 2010) are assigned to the Duck Lake Formation and provide a radiolarian fossil age of either Middle or Late Devonian. Immediately to the east, a package of reworked mafic tuffs and interbedded sedimentary rocks (including ribbon cherts) assigned to the McLaughlin Ridge Formation yielded a Late Devonian (Frasnian or Famennian; sample 08SI27) radiolarian age. This fossil locality is proximal to the type section for the McLaughlin Ridge Formation (Yorath, 1999), for which no previous age constraints were available. To the northwest, a package of reworked mafic tuffs and interbedded sedimentary rocks (including chert and rusty argillite) contains layers of feldspar rich, crystal tuff, and is assigned to the McLaughlin Ridge Formation (Massey et al., 2005). A sample of this material (08TR031; Fig. 3.2) from an outcrop located above the Yellow Creek adit of Bitterroot Resources Corp. yielded an age of 366.8 ± 2.4 Ma. To the north, a dacite flow is interbedded with basalt flows assigned to the Duck Lake Formation. A sample of this dacite flow (07TR051; Fig. 3.2) yielded an age of 366.6 ± 0.7 Ma, indicating that again, in certain areas, rocks of the Duck Lake Formation are time transgressive, overlapping in age with rocks of the McLaughlin Ridge Formation elsewhere in the Cowichan uplift. To the east, several thin beds of rhyolitic crystal tuff are exposed near a microwave tower, interbedded with clinopyroxene phyric mafic volcanic rocks mapped near the contact between Duck Lake and Nitinat Formations (Massey et al., 2005). Four samples of these felsic tuffs (samples 05M386b, 05M386c, 08TR002 and 08TR002B; Fig. 3.2) yielded ages ranging from 366.7 ± 2.3 Ma through 360.8 ± 2.9 Ma. To the northwest, a heterolithic lapilli tuff mapped as part of the Duck Lake Formation contains rounded clasts of quartz-feldspar phyric rhyolite porphyry, and subrounded to subangular clasts of clinopyroxene phyric basalt. A felsic clast from this material (07TR043; Fig. 3.2) yielded an age of 351.1 ± 3.0 Ma, providing additional evidence that in certain locations, strata assigned to the Duck Lake Formation is time transgressive. Tournaisian to Visean (350 Ma to 330 Ma) Tournaisian to Visean stratigraphy in the Cowichan area comprises dominantly sedimentary and reworked tuffaceous volcanic rocks assigned to the Fourth Lake Formation 35(Massey, 1995 a,b,c). Similar Fourth Lake Formation strata were believed to be of Tournaisian through Visean age in the Port Alberni area (Massey, 1995 a,b,c; Yorath et al., 1999). However, new exposures flanking the ridges of Horne Lake, in an area previously mapped as mafic volcanic rocks assigned to the Nitinat Formation (Massey, 1995a; Yorath et al., 1999), reveal the presence of abundant felsic volcanic rocks ranging in age from 347.2 ± 2.3 Ma through 335.3 ± 2.5 Ma. On a ridge top southeast of Horne Lake, felsic volcanic rocks comprise rhyolitic lapilli tuffs, tuff breccias, and reworked felsic crystal tuffs (samples 08TR078, 08TR084B, and 08TR082, respectively; Fig. 3.2), ranging in age from 346.4 ± 2.7 Ma through 340.7 ± 1.7 Ma. These felsic volcanic rocks overlie a thin unit of interbedded argillite, chert and reworked tuff, from which a Mississippian radiolarian age was produced (sample 08SI03). Southwest of Horne Lake, newly recognized felsic volcanic rocks comprise rhyolite lapilli tuffs and crystal tuffs, in addition to rhyolite porphyry. Two samples of rhyolite porphyry yielded ages ranging from 338.2 Ma ± 3.5 through 335.3 ± 2.5 Ma (09TR090 and 09TR034, respectively; Fig. 3.2). A reworked rhyolite crystal tuff from the same area (07TR049) yielded an age of 347.2 ± 2.3 Ma. Notably, this sample also contains Late Devonian xenocrystic zircons, indicating that Visean volcanic centres in the Alberni area were constructed upon or proximal to pre-existing, Late Devonian volcanic centres. Visean to Early Permian (330 Ma to 295 Ma) Visean through Early Permian strata in the Cowichan and southern Alberni areas are assigned to the Fourth Lake and Mt. Mark Formations (Massey, 1995 a,b,c; Yorath et al., 1999), which comprise “laterally interfingering ramp carbonate and slope argillite deposits” (Massey, 1995a; Katvala and Henderson, 2002). A package of interbedded argillite, chert with lesser siltstone and sandstone is present in the vicinity of Mt. Whymper in the western part of the Cowichan study area (Fig. 3.1). Here, chert samples 09SI09 and 09TR058 yielded Early Permian (Asselian-Artinskian) and Late Paleozoic (possibly Carboniferous) radiolarian ages, respectively. In the Alberni area, in the vicinity of Lacy Lake (Fig. 3.2), extensive ribbon chert with interbedded cherty mudstone and intermediate crystal tuff conformably overlies a scoriaceous basalt flow breccia which contains abundant inter-clast limey mudstone. Two samples of this chert (08SI07 and 08SI10; Fig. 3.2) provided Early Permian (possibly Artinskian) and Permian radiolarian ages, respectively. Clinopyroxene phyric basaltic volcanic rocks that are texturally identical to Late Devonian through Visean mafic volcanic rocks 36elsewhere in the Alberni area, underlie these Early Permian ribbon cherts and scoriaceous basalts. Southwest of Lacy Lake, a bed of heterolithic lapilli tuff containing angular aphyric felsic and mafic clasts was dated at 293.6 ± 1.8 Ma (sample 07TR005A; Fig. 3.2). This sample was found to contain three populations of zircons (Fig. A1.2n); one comprising Early Permian grains interpreted to represent the age of the tuff (approximately 295 Ma), another containing grains ranging in age from 322.3 Ma to 309 Ma, and a third population ranging in age from 339.1 Ma to 337.8 Ma. These older populations are significant, because they show that Permian volcanic centres in the Alberni area were constructed upon or proximal to older, igneous centres of Mississippian age. This heterolithic tuff is interbedded with argillite, and is proximal to excellent exposures of clinopyroxene phyric basalt agglomerate that are texturally identical to clinopyroxene phyric mafic volcanic rocks of Late Devonian through Visean age elsewhere in the Alberni area. A noteworthy feature for the Alberni area is the presence of a conspicuous heterolithic breccia/pebble-boulder conglomerate, which invariably occurs up section from Early Permian lithologies recognized in the Horne Lake-Lacy Lake area, and stratigraphically below mafic volcanic rocks assigned to the Karmutsen Formation. This breccia is best exposed in the Lacy Lake area, just meters up section from Early Permian ribbon cherts, where it includes variably rounded to angular, locally boulder sized clasts of crinoidal limestone, and mafic volcano-sedimentary, argillite and chert clasts set in a hematite rich matrix. This breccia is equivalent to the St. Mary’s Lake Formation (Massey, 1995a), a lithologically similar unit which lies above Mt. Mark Formation carbonates and below Karmutsen Formation basalts south of Cameron Lake and east of McKinlay Peak in the Alberni area (Fig. 3.2). 3.3.2 A Revised Chronostratigraphy of the Nanoose Uplift Early Permian Rocks of the Nanoose Complex (Figures 1.2 and 3.3) comprise turbiditic sedimentary rocks, and interbedded crinoidal limestone and pillow basalts. Yorath et al. (1999) considered limestones of the Nanoose Complex to be potential correlatives of rocks of the St. Mary’s Lake and Mt. Mark formations, but were unable to resolve the stratigraphic affinities of abundant pillow basalts in the area, for which a possible correlation with pre Late Devonian mafic volcanic rocks of the Duck Lake Formation was suggested. Sampling of sedimentary rocks of the Nanoose Complex (08TR017 and 08TR017) as part of this study has shown detrital zircons 37populations ranging in age from 294.7 Ma through 355 Ma, with age peaks at 305, 311, 321 and 354 Ma (Fig. A1.3). Sampling of cherts and crinoidal limestones interbedded with abundant pillow basalts on west Ballenas Island yielded Late Paleozoic (possibly Carboniferous) and Early Permian (Asselian) fossil ages. Early Permian (Asselian) conodonts recovered from these crinoidal limestones are similar to those which characterize Asselian strata at high latitudes (Orchard, 2011). These new data indicate that rocks of the Nanoose Complex are entirely Early Permian in age, precluding any correlation with supposed pre Late Devonian mafic volcanic rocks of the Duck Lake Formation, and establishing a firm correlation with Early Permian rocks of the Fourth Lake and Mt. Mark formations. Pillow basalts of the Nanoose Complex are correlative with Early Permian basalts of the Port Alberni area, in the vicinity of Lacy Lake, a possibility previously suggested by Massey (1995a). The older zircon populations contained in sedimentary rocks of the Nanoose Complex indicate that this Early Permian volcanic centre was constructed upon or proximal to pre-existing Late Devonian through Visean igneous centres. The revised stratigraphy for the Nanoose uplift is shown in Fig. 3.7. 3.3.3 Revised Chronostratigraphy of the Bedingfield Uplift No isotopic and fossil dates existed for potential Paleozoic stratigraphy of the Bedingfield uplift prior to this study (Fig. 3.4). The oldest rocks in the Bedingfield uplift comprise a waterlain bimodal volcanic complex and associated VMS mineralization, which is overlain by a sedimentary unit including argillite and chert, and a carbonate unit comprising crinoidal limestone (Freeze et al. 1986; Ruks et al., 2010). Previous workers have interpreted volcanic rocks of the Bedingfield uplift to be an undivided package of volcanic rocks belonging to the Sicker Group (Massey et al., 2005). Overlying sedimentary and carbonate rocks may be interfingering, and correlative to Late Paleozoic rocks of the Fourth Lake and Mt. Mark formations (Freeze, 1986; Ruks et al., 2010). Sampling of felsic volcanic rocks of the Bedingfield uplift as part of this study have revealed the presence of a Late Paleozoic bimodal volcanic assemblage, with VMS associated felsic volcanic rocks of the Cypress Bay-Cypre River area yielding ages ranging from 312.2 ± 3.7 Ma through 312.4 ± 3.5 Ma, respectively. Felsic volcanic rocks of the Herbert Inlet area (Fig. 3.4) yielded ages ranging from 308.3 ± 3.2 Ma through 305.6 ± 4.1 Ma. Late Paleozoic felsic volcanic rocks dated in the Bedingfield uplift overlap in age with zircon populations observed in detrital samples from the Nanoose area (see previous discussion). This indicates that the Bedingfield volcanic centre(s) may have been 38proximal to depositional centres in the Cowichan and Nanoose uplifts prior to Early Permian time. A stratigraphic section for the Bedingfield uplift is shown in Fig. 3.7. 3.3.4 Revised Chronostratigraphy of the Dragon Property, Gold River Area As with rocks of the Bedingfield Uplift, no isotopic or fossil ages existed for VMS associated lithologies comprising the Dragon property prior to this study (Figures 1.2 and A1.1). However, geological mapping of the property by previous workers identified a package of waterlain, VMS associated felsic volcanic rocks that were apparently conformably overlain by limestone, a stratigraphic relationship not observed elsewhere in Paleozoic Wrangellia (e.g., Kemp and Gill, 1993; Jones, 1997; Ruks et al., 2009, 2010). Isotopic dating of VMS associated rocks on the Dragon property as part of this study has revealed the presence of abundant felsic volcanic rocks ranging in age from 311.1 ± 0.3 Ma through 300.0 ± 3.4 Ma, with overlying felsic tuffs interbedded with cherts and argillites yielding ages of 291.6 ± 2.2 Ma (sample 09TRDR016; Fig. A1.1). The ages of felsic volcanic rocks of the Dragon property are similar to those obtained from felsic volcanic rocks of the Bedingfield Uplift, and also to the ages of detrital zircon populations from sedimentary rocks of the Nanoose Uplift. A lapilli tuff from the Alberni area (07TR005) yielded an age of 293.6 ± 1.8 Ma, which overlaps with the youngest felsic tuff dated on the Dragon property (sample 09TRDR016; 291.6 ± 2.2 Ma). Collectively, these new dates indicate that Late Paleozoic rocks of the Cowichan, Nanoose, Bedingfield and Dragon areas have a shared history, and may have been probably proximal during the time of their formation. 3.3.5 A Revised Chronostratigraphy of the Dorado Property, Hesquiat Peninsula The stratigraphic section in the vicinity of the Dorado property (Figures 1.2 and A1.2) comprises strongly epidote-chlorite-silica altered and pyrrhotite-chalcopyrite stockwork mineralized clinopyroxene-phyric basalt, which is overlain by carbonate (Marshall, 2006; Ruks et al., 2009, 2010). Small, VMS-like occurrences exist in several areas on the property (Fig. A1.2). Extensive sampling of volcanic and carbonate rocks in the vicinity of the Dorado property were unsuccessful in producing any fossil or isotopic ages. However, two felsic dikes observed to cross-cut altered and mineralized basalts of the Dorado property yielded ages of 202.2 ± 1.3 Ma and 180.9 ± 3.2 Ma, indicating that altered and mineralized basalts of the Dorado 39property can be no younger than Late Triassic. The juxtaposition of altered and mineralized volcanic rocks with overlying carbonate on the Dorado property is also observed in Late Pennsylvanian-Early Permian stratigraphy of the Alberni, Nanoose, Bedingfield and Dragon areas, suggesting a possible correlation with Fourth Lake and Mt. Mark Formations. 3.3.6 Correlations with Buttle Lake Uplift Stratigraphy Late Devonian, VMS associated stratigraphy is abundant in rocks of the Buttle Lake Uplift (Fig. 1.2), with felsic volcanic rocks of the Myra Formation, host to the Myra Falls VMS deposits, yielding ages of 370 +18/-6 Ma (Juras, 1987) through 366 ± 4 Ma (Parrish and McNicoll, 1992). Only one sample from the Buttle Lake uplift was dated as part of this study. This sample, a strongly altered and stockwork sulphide mineralized quartz-feldpsar phyric rhyolite porphyry, occurs at the stratigraphic contact between lower mafic volcanic rocks belonging to the Price Formation, and overlying bimodal volcanic rocks of the Myra Formation. and forms the immediate footwall to overlying VMS mineralization of the Marshall Zone. This sample (11TRMF010) represents the first pulse of felsic magmatism in the Myra Formation, yielding an age of 361.5 ± 2.5 Ma (Fig. A1.7), an age similar to that of VMS associated felsic volcanic rocks dated as part of this study in the Cowichan and Alberni areas. Early Mississippian radiolaria have been reported in sedimentary rocks immediately overlying both the H-W and Battle deposits (Jones, 2001; Chong, 2005) and from largely sedimentary-volcanosedimentary rocks of the overlying Thelwood Formation (Muller, 1980). This supports correlation of the upper Myra Formation and Thelwood Formations with the lower Fourth Lake Formation of the Cowichan uplift. Mafic volcanic rocks comprising the Flower Ridge Formation in the Buttle Lake uplift have not been directly dated, but are bracketed between Early Mississippian and Pennsylvanian to Early Permian age, based on ages of the underlying Thelwood Formation, and the overlying, Early Permian Buttle Lake Formation (Brandon et al., 1986; Juras, 1987). The juxtaposition of Flower Ridge Formation mafic volcanic rocks and overlying limestone of Early Permian age is similar to that observed in the Lacy Lake and Nanoose areas of the Cowichan uplift (Figures 3.2 and 3.3), suggesting a correlation w`ith stratigraphy of the upper Fourth Lake and Mt. Mark Formations. 40 3.4. SUMMARY New isotopic and fossil ages presented in this chapter demonstrate that Paleozoic Wrangellia on Vancouver Island comprises not only abundant Late Devonian through early Mississippian Paleozoic bimodal volcanic rocks and associated VMS mineralization, but also a previously unrecognized cycle of Pennsylvanian through Early Permian bimodal volcanic rocks and associated VMS mineralization. Late Devonian through Early Permian strata are exposed in the Cowichan and Buttle Lake uplifts, whereas rocks of the Nanoose and Bedingfield uplifts, as well as rocks of the Dragon property, expose Pennsylvanian through Permian strata (Fig. 3.7). The most representative section of Paleozoic Wrangellian stratigraphy examined as part of this study is exposed in rocks of the Cowichan uplift (Fig. 1.2), most notably in the Alberni area. Geochronological control for Paleozoic Wrangellian stratigraphy is best established in the Alberni area, which also includes the locations of previously defined type sections for Paleozoic Wrangellian stratigraphy (e.g., Yorath et al., 1999). 4142434445464748rTable 3.1. Geochronology results and sample descriptions for Paleozoic rocks of southern Wrangellia.Sample numbe Description UTM Zone1 Easting1 Northing1 Method2 Age Age Error (2σ)05M366 Rhyolite lapilli tuff proximal to Lenora adit 10 442034 5412829 TIMS 360.2 4.305M386b Thinly bedded rhyolite tuff 10 376146 5461004 LA-ICPMS 360.8 2.905M386c Rhyolitic volcanic sandstone or crystal tuff 10 376146 5461004 TIMS 363.9 0.405M393 Rhyolite crystal tuff at Lara adit 10 433603 5414742 TIMS 362.6 9.407TR005A Heterolithic dacitic lapilli tuff 10 372459 5462694 LA-ICPMS 293.6 1.807TR043 Rhyolite tuff breccia 10 373264 5464269 LA-ICPMS 351.1 307TR049 Rhyolitic volcanic sandstone 10 373123 5465421 LA-ICPMS 347.2 2.307TR051B Dacite flow 10 375421 5460259 TIMS 366.6 0.707TRHS018A Epidote altered granodiorite porphyry 9 685580 5491948 LA-ICPMS 202.2 1.307TRHS020A Strongly epidote altered rhyolite dike 9 685258 5491596 LA-ICPMS 180.9 3.208TR002 Rhyolite crystal tuff 10 376136 5461003 LA-ICPMS 363.8 2.508TR002B Rhyolite crystal tuff 10 376136 5461003 LA-ICPMS 366.7 2.308TR017 Siltstone 10 414154 5460649 LA-ICPMS 314.2 3.908TR019 Sandstone 10 415815 5460307 LA-ICPMS 311.9 1.308TR020 Granodiorite 10 418106 5458798 LA-ICPMS 199.1 1.508TR031 Heterolithic lapilli tuff 10 379312 5450558 LA-ICPMS 366.8 2.408TR049A Foliated and sericitized felsic crystal tuff 10 436422 5415373 LA-ICPMS 359.7 2.408TR055A Foliated and sericitzed rhyolite porphyry 10 432659 5416605 LA-ICPMS 357.2 208TR061B Foliated felsic tuff or rhyolite flow 10 429969 5417447 LA-ICPMS 359.2 208TR078 Rhyolite lapilli tuff 10 377154 5463947 LA-ICPMS 343.4 2.208TR082 Rhyolite lapilli tuff 10 377452 5463186 LA-ICPMS 346.4 2.708TR084B Rhyolite tuff breccia 10 377045 5463647 LA-ICPMS 340.7 1.708TR101 Strongly sericitized felsic tuff 10 443809 5414036 LA-ICPMS 360.9 2.708TR107 Weakly sericitized quartz-feldspar porphyry 10 444835 5413694 LA-ICPMS 361.5 2.408TR114 Chlorite and hematite altered quartz-feldspar porphyry 10 445394 5413283 LA-ICPMS 355.8 4.408TR121 Weakly sericitized rhyolite crystal tuff 10 450236 5411581 LA-ICPMS 353.1 3.408TRDR007B Aphyric rhyolite flow 9 692704 5527315 LA-ICPMS 308.3 508TRDR007B Aphyric rhyolite flow 9 692704 5527315 TIMS 303.1 0.508TRDR042 Heterolithic tuff breccia 9 691768 5525930 LA-ICPMS 308.0 1608TRDR053A Quartz-feldspar porphyry 9 688759 5525974 TIMS 311.1 0.3208TRDR056 Rhyolite dike 9 691424 5525265 LA-ICPMS 172.3 2.509M302 Quartz-feldspar porphyry 10 469473 5405425 LA-ICPMS 355.0 1.509M308 Quartz-feldspar porphyry 10 468712 5403979 LA-ICPMS 358.7 2.51 - Datum used for the location of all samples is NAD 83; 2 - Samples collected for U-Pb (zircon) geochronology were analyzed byTIMS (Thermal Ionization Mass Spectrometry) or LA ( Laser Ablation Inductively Coupled Mass Spectrometry).49rTable 3.1. Geochronology results and sample descriptions for Paleozoic rocks of southern Wrangellia.Sample numbe Description UTM Zone1 Easting1 Northing1 Method2 Age Age Error (2σ)09M309 Quartz-feldspar porphyry 10 467293 5403326 LA-ICPMS 359.3 3.109TR034 Quartz-feldspar porphyry 10 373074 5465628 LA-ICPMS 335.3 2.509TR041 Weakly foliated rhyolite tuff 10 429876 5417115 LA-ICPMS 355.3 4.409TR042 Strong foliated and sericitized rhyolite crystal tuff 10 432751 5416851 LA-ICPMS 362.8 2.609TR063 Rhyolite flow 10 410679 5419619 LA-ICPMS 355.6 3.309TR090 Quartz-feldspar rhyolite porphyry 10 372710 5465993 LA-ICPMS 338.2 3.509TR105 Foliated and silicified rhyolite flow with sulphide stockwork 10 289679 5462352 LA-ICPMS 312.2 3.709TR107 Quartz-feldspar porphyry dike 10 293753 5461954 LA-ICPMS 200.1 1.209TR110 Quartz-feldspar rhyolite porphyry 10 292339 5463853 LA-ICPMS 312.4 3.509TR117 Rhyolite lapilli tuff 10 286622 5470693 LA-ICPMS 305.6 4.109TR118 Rhyolite flow 10 286965 5471653 LA-ICPMS 308.3 3.209TR128 Rhyolite crystal tuff 10 410915 5419457 LA-ICPMS 359.3 1.309TR132 Quartz-feldspar porphyry 10 454100 5409558 LA-ICPMS 360.7 2.409TRDR010 Rhyolite lapilli tuff 9 695787 5525220 LA-ICPMS 307.6 2.209TRDR013 Quartz-feldspar rhyolite porphyry 9 693478 5525389 LA-ICPMS 300.0 3.409TRDR016 Rhyolitic volcanic sandstone 9 694363 5524749 LA-ICPMS 291.6 2.211TRMF010 Quartz-feldspar rhyolite porphyry 10 NA NA LA-ICPMS 361.5 2.51 - Datum used for the location of all samples is NAD 83; 2 - Samples collected for U-Pb (zircon) geochronology were analyzed byTIMS (Thermal Ionization Mass Spectrometry) or LA ( Laser Ablation Inductively Coupled Mass Spectrometry).50Table 3.2. Fossil ages for rocks collected from southern Paleozoic WrangelliaSample Easting (m) Northing (m) Fossil1 Faunas Age08SI03 376843 5463540 RadiolariansScharfenbergia sp. cf. plenospongiosa ;Scharfenbergia sp. cf. turgida ;Tetragregnon sycamorensis Mississippian08SI07 372862 5463759Conodonts;Radiolarians;SpongesConodonts: Mesogondolella sp. cf. intermedius ;Radiolarians: Pseudoalbaillella sp., Hegleria mammifera ; Sponge spicules Early Permian, possibly Artinskian08SI10 372518 5464305 Radiolarians Hegleria mammifera Permian08SI19 373743 5459082Radiolarians;SpongesRecrystallized radiolarians, morphotypes possibly attributed to Latentibifistula sp.rare sponge spicules Carboniferous or Permian08SI22 373759 5459083 RadiolariansLatentifistula sp.Tormentum sp. Pennsylvanian or Permian08SI27 384171 5447140 Radiolarians? Adamas sp.Radiobisphaera domanicensisTetrentactinia barysphaera Late Devonian, Frasnian or Famenian08SI30 383412 5446409 RadiolariansCeratoikiscum sp.Entactinosphaera sp. Devonian or Carboniferous08SI32 372360 5462580 RadiolariansCopiellintra sp.Cubaxonium octaedrospongiosum Carboniferous or Permian, possibly Early Permian09SI04 380106 5446114 RadiolariansCeratoikiscum sp.Various entactinids Middle or Late Devonian09SI07 382440 5435008Radiolarians;SpongesEntactinia sp.sponge spicules Paleozoic09SI08 387012 5447539 Radiolarians ?Latentibifistula sp. possibly Late Paleozoic09SI09 417485 5421987 RadiolariansPseudoalbaillella sakmarensisPseudoalbaillella sp. cf. longicornisPseudoalbaillella sp. cf. scalprata Early Permian (Asselian-Artinskian)09SI12 384697 5446354 Radiolarians Entactinia sp., spines Paleozoic1 - Conodont fossil ages were determined by Mike Orchard of the Geological Survey of Canada; Radiolaria fossil ages were determined by Fabrice Cordeyof the University of Lyons, France.51Table 3.2. (continued)Sample Easting (m) Northing (m) Fossil Faunas Age09SI14 373069 5465617 RadiolariansEntactinia sp.Entactinosphaera sp.Scharfenbergia sp. Paleozoic, Late Devonian or Carboniferous09SI15 373037 5464967 RadiolariansEntactinia sp.Entactinosphaera sp. Paleozoic, Devonian or Carboniferous09TR058 418865 5423525 Radiolarians Scharfenbergia sp. Late Paleozoic, possibly Carboniferous09TR079 441680 5417322 Radiolarians Pseudalbaillella U-formaLate Pennsylvanian or Early Permian (Moscovian-Asselian)09TR102B 415768 5466235 Radiolarians Scharfenbergia sp. Late Paleozoic, possibly Carboniferous09TR123 416052 5466310 Conodonts Mesogondolella sp(p); Streptognathodos? sp. Early Permian (Asselian)09TR104 416061 5466354 Conodonts Idioprioniodus? sp.; Gnathodid? fragment Late Carboniferous?1 - Conodont fossil ages were determined by Mike Orchard of the Geological Survey of Canada; Radiolaria fossil ages were determined by Fabrice Cordeyof the University of Lyons, France.52Chapter 4: The magmatic evolution of Paleozoic Wrangellia, Vancouver Island, British Columbia 534.1. INTRODUCTION The results of geological mapping studies, together with extensive U-Pb (zircon) and microfossil dating outlined in Chapter 3 has redefined the stratigraphy of Paleozoic Wrangellia, a terrane not only suspected to be a significant contributor to the crustal growth history of the North American continent, but also one that is well endowed with VMS deposits, including the Myra Falls camp (Nystar N.V.), currently the largest producing VMS deposit in western Canada. This work has demonstrated that Paleozoic Wrangellia is a product of more cycles of magmatism (and associated VMS mineralization) than was previously thought. As such, combined field, lithogeochemical, geochronological and isotopic studies of the terrane are necessary in order to evaluate not only its potential for VMS mineralization, but also its contribution to the crustal growth history of the North American continent. This paper builds on recent chronostratigraphic work presented in Chapter 3, and presents a combined lithogeochemical and isotopic study of all recognized magmatic cycles comprising Paleozoic Wrangellia on Vancouver Island (Fig. 1.1). This study serves several purposes. First, it provides new constraints on the tectonic and metallogenic evolution of Paleozoic Wrangellia, with emphasis on characterizing its potential for hosting additional VMS deposits associated with newly recognized magmatic cycles. Secondly, it serves to evaluate the relative contribution of Paleozoic Wrangellia to the crustal growth history of the North American continent. 4.2. LITHOGEOCHEMISTRY AND ISOTOPE GEOCHEMISTRY 4.2.1. Methodology A combination of lithogeochemical and radiogenic isotope studies has been successful for elucidating the tectonic setting and petrogenesis of similar rock types in both ancient (Stern et al., 1995; Swinden et al., 1997; Piercey et al., 2006) and modern settings (Pearce, 1983; Pearce and Parkinson, 1993; Pearce and Peate, 1995). Trace elements are particularly useful for understanding the tectonic environment of igneous 54rocks for several reasons. Firstly, different tectonic environments are associated with different geochemical reservoirs, with resulting magmas having unique geochemical signatures (e.g., Pearce and Cann, 1973). For instance, basalts generated at mid-ocean ridges are typically depleted in trace elements relative to those generated in intraplate settings (e.g., Sun and McDonough, 1989). Secondly, during magma genesis, trace elements behave differently depending on their tectonic environment. For example, magmas generated in subduction zones typically have elevated large ion lithophile elements (LILE) due to the presence of aqueous fluids derived from the subducting slab (e.g., Tatsumi et al., 1986) . Similarily, magmas generated in subduction environments typically have low Nb contents due to the low mobility of high field strength elements in aqueous fluids; this creates the negative Nb anomaly relative to other compatible elements that is a hallmark geochemical signature of magmas generated in subduction zone settings (e.g., Arculus, 1994; Tatsumi and Eggins, 1995). Numerous workers have demonstrated the utility of lithogeochemistry in identifying volcanic rocks which are prospective for VMS mineralization (e.g., Piercey, 2011 and references therein). Key in these studies was the recognition of lithogeochemical characteristics in VMS associated felsic volcanic rocks reflective of high temperatures of melting at shallow levels in the lithosphere (Lesher et al., 1986). For example, the FI through FIII rhyolite classification scheme, developed by Lesher et al. (1986), was the product of a study of VMS associated and VMS barren felsic volcanic rocks in the Superior Province of Canada. In the study, it was discovered that VMS associated felsic volcanic rocks were enriched in HFSE and REE (FIII rhyolites), whereas VMS barren felsic volcanic rocks had markedly lower HFSE and REE contents (FI rhyolites). The greater HFSE and REE contents of VMS associated rhyolites (FIII rhyolites) were attributed to high temperatures of melting at shallow levels in the crust, whereas VMS barren rhyolites (FI rhyolites) were the products of lower temperature melting, and as a result, had lower HFSE and REE contents. Although the FI through FIII classification scheme was originally developed for felsic volcanic rocks of the Superior Province, subsequent workers have demonstrated that the scheme is also applicable to Phanerozoic VMS environments (e.g., Hart et al., 2004). Studies of mafic volcanic rock lithogeochemistry in a variety of VMS camps have demonstrated that those 55associated with VMS also contain lithogeochemical signatures representative of high temperatures of formation at shallow crustal levels in extensional geodynamic settings. (e.g., Piercey, 2011 and references therein). Lithogeochemical samples were collected during the course of regional studies of Paleozoic strata on Vancouver Island from 2005 through 2011, in order to characterize VMS associated Late Devonian through Early Permian magmatic suites present in all recognized uplifts of Paleozoic Wrangellia in this region. In total, 164 samples were analyzed for major, trace and rare earth element compositions during the course of this study. A subset of 25 samples with well constrained isotopic and/or fossil ages were selected for Nd isotopic analysis. Rock samples were defined as mafic, felsic or intermediate based on lithogeochemistry. Analytical procedures for this study are similar to those described by Piercey et al. (2008). Weathered edges were removed from samples using a diamond saw and were subsequently crushed in a steel-jaw crusher. In order to reduce contamination, crushed samples were processed using an agate mill. Rock powders were analyzed by X-ray fluorescence (XRF) for major elements (on fused discs), select trace elements (on pressed pellets: Nb, Zr, and Y), and LOI at Ontario Geoscience Laboratories, Sudbury, Ontario, Canada. The remaining trace elements and REE were analyzed by ICP-ES (Ba, Be, Cd, Co, Cr, Cu, Li, Mo, Ni, S, Sc, Sr, V, W and Zn) and ICP-MS (Nb, Ta, Zr, Hf, Y, Cs, Th, U, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) at the Ontario Geoscience Laboratories, Sudbury, Ontario, Canada using a closed-beaker multi-acid digestion prior to analysis (Tomlinson et al., 1998; Tomlinson et al., 1999; Burnham et al., 2002). Nb, Zr, and Y concentrations determined via XRF were compared to those determined via ICP-MS in order to test for complete dissolutions. In the rare cases in which Nb, Zr, and Y concentrations determined by XRF were greater than those determined via ICP-MS, results of the former technique were substituted for the latter. Precision and accuracy for trace element analyses by ICP-ES and ICP-MS at the Ontario Geoscience Laboratories (OGL) is <7% RSD for precision, and below 8% RSD for accuracy (except Nb = 9.8% RSD and Pr = 12.3% RSD; Lightfoot and Farrow, 2002). Precision for major elements determined by XRF at the OGL is 2 to 5 percent (except MgO = 7% and P2O5 = 10%; MacDonald et al., 2005). The accuracy and precision of lithogeochemical data produced 56in this study was evaluated through multiple duplicate analyses of samples and Mineral Deposit Research Unit (MDRU) in-house reference material WP-1, a dacite from Watt’s Point. Analytical data from WP-1 is displayed in Table A2.1, whereas analytical data for duplicate analyes of samples is displayed in Tables A2.2 through A2.5. Percent relative standard deviation for multiple analyses of MDRU in house reference material WP-1 are less than 7% for trace elements of interest, meeting the criteria for excellent to very good precision (Jenner, 1996). Percent relative difference for multiple analyses of MDRU in house reference material WP-1 are typically less than 10% for trace elements of interest, meeting the criteria of Jenner (1996) for good accuracy. Concentrations for Cs, Ga, Nb and Ta are notably higher in the MDRU reference values. A similar observation was made by Piercey (2001), and attributed to those elements having been analyzed using a different technique than in this study (e.g., instrumental neutron activation analysis versus ICP-MS/ES, respectively). In summary, accuracy and precision for lithogeochemical data presented herein is sufficient for this study. Major and trace element lithogeochemical data is summarized for felsic rocks in Table 4.1, and for mafic rocks in Table 4.2. Whole-rock Nd isotope analyses (Table 4.3) were conducted at the Pacific Centre for Isotope Geochemical Research (PCIGR) at the University of British Columbia, using thermal ionization mass spectrometry (TIMS). These analyses followed the analytical and dissolution methods of Pretorius et al. (2006) and Weis et al. (2006). Neodymium isotope data are listed in Table 4.3 and presented relative to the La Jolla standard, with an analytical uncertainty of 0.511855 ± .000009 (2σ). Conversion of initial 143Nd/144Nd ratios into εNd values, adjusted to the time of deposition, and depleted mantle model ages (TDM) were calculated by equations defined in DePaolo (1981). Initial εNd values were calculated using ages of 360 Ma, 317 Ma, 300 Ma, 200 Ma and 180 Ma, the approximate ages of magma suites sampled during the study. The chondritic uniform reservoir (CHUR) values used for εNd calculations were 143Nd/144Nd = 0.512638 and 147Sm/144Nd = 0.1966 (Hamilton et al., 1983). The present day 143Nd/144Nd and 147Sm/144Nd ratios used for calculations involving depleted mantle are 0.513150 and 0.2137, respectively (Goldstein et al., 1984). 574.2.2. Effects of Alteration, Metamorphism and Element Mobility Although attempts were made to collect least altered samples, field and petrographic data for the samples illustrate that they have been exposed to variable degrees of hydrothermal alteration, together with polyphase deformation and greenschist facies metamorphism (Ruks and Mortensen, 2007, 2008; Ruks et al., 2009). Given these metamorphic conditions, most major elements (e.g., SiO2, Na2O, K2O, and CaO) and low field strength elements (LFSE: Cs, Rb, Ba, Sr) may have been mobilized to varying degrees (MacLean, 1990). The major elements Al2O3, TiO2 (±P2O5), the transition elements (Cr, Ni, Sc, V), the high field strength elements (HFSE: Zr, Hf, Nb, Ta, Y), the REEs, and Th were likely immobile under these metamorphic conditions (e.g., Pearce and Cann, 1973; Wood, 1980; MacLean, 1990; Rollinson, 1993; Jenner, 1996). When plotted against the immobile element Zr (Fig. 4.1), the major elements show a large degree of scatter, suggesting that they have suffered mobility as a result of hydrothermal alteration. In contrast, the HFSE and REE show coherent trends relative to Zr (Fig. 4.2), indicating that they have been relatively immobile. Since the major elements of the sample suite have been affected by hydrothermal alteration, they are not discussed in detail in this manuscript. Instead, we have relied primarily on immobile elements and Sm-Nd isotope geochemistry in order to understand the petrogenetic history of Paleozoic Wrangellia. 4.2.3. Results New isotopic and fossil ages for the study area discussed in Chapter 3 demonstrate that Paleozoic Wrangellia on Vancouver Island comprises not only abundant Late Devonian through early Mississippian Paleozoic bimodal volcanic rocks and associated VMS mineralization, but also a previously unrecognized cycle of Pennsylvanian through Early Permian bimodal volcanic rocks and associated VMS mineralization. Late Devonian through Early Permian strata are exposed in the Cowichan and Buttle Lake uplifts, whereas rocks of the Nanoose and Bedingfield uplifts, as well as rocks of the Dragon property, expose Pennsylvanian through Permian strata 58(Fig. 3.7). The most representative section of Paleozoic Wrangellian stratigraphy examined as part of this study is exposed in rocks of the Cowichan uplift (Fig. 1.2), most notably in the Alberni area. Geochronological control for Paleozoic Wrangellian stratigraphy is best established in the Alberni area (Chapter 3), which also includes the locations of previously defined type sections for Paleozoic Wrangellian stratigraphy (e.g., Yorath et al., 1999). Pre Late Devonian magmatism Pre-Late Devonian mafic volcanic rocks comprise the oldest rocks in Wrangellia (Massey et al., 1995a, b, c; Yorath et al., 1999; Chapter 3), and are present in both the Cowichan and Alberni regions of the Cowichan uplift (Figures 1.2, 4.3 and 4.4; Chapter 3). The geochemical characteristics of these rocks show that two populations of pre-Late Devonian mafic volcanic rocks are present. The first, and most abundant population, represented by samples from both the Cowichan and Alberni areas, resembles island arc tholeiites and light rare earth element (LREE) enriched island arc tholeiites from modern settings (e.g., Stolz et al., 1990; Shinjo et al., 1999; Fig. 4.5). This population is characterized by having mainly subalkalic to alkalic Nb/Y (< 0.7 to 0.9), and mafic Zr/TiO2 (Fig. 4.5a). In addition, Zr/Y from these rocks resembles tholeiitic through transitional magma suites (Fig. 4.5b), and Ti-V systematics are similar to island arc tholeiites (IAT; 3.5c). Primitive mantle normalized trace element patterns for this population show that slight differences exist between island arc tholeiites in the Cowichan and Alberni areas. Samples from both areas are characteristic of rocks generated in a subduction zone setting, exhibiting light rare earth element (LREE) enrichment (La/Smn = 1.79 - 3.58; “n” subscript indicates normalization to chondrite using values of Sun and McDonough, 1989), and negative Nb (Nb/Thmn = 0.16 - 0.60; “mn” subscript indicates normalization to primitive mantle using values of Sun and McDonough, 1989) and Ti anomalies (Fig. 4.5d). Several samples from the Cowichan area contain slightly higher LREE enrichment, resembling LREE enriched island arc tholeiites (L-IAT) from the Ryukyus arc (e.g., Shinjo et al., 1999; Fig. 4.5d). Samples from the Alberni area have less intense negative Nb anomalies than their Cowichan 59counterparts; Nb/Thmn = 0.51 - 0.60 and Nb/Thmn = 0.16 - 0.35, respectively. A second population of basalt from the Alberni area resembles enriched, mid-ocean ridge basalts (E-MORB; e.g., Sun and McDonough, 1989). This population, which is represented by only two samples, occurs in the southern Alberni area, just south of the Duck Lake Formation type section (Yorath et al., 1999). These basalts exhibit subalkalic Nb/Y (< 0.7), mafic Zr/TiO2 (Fig. 4.5a), as well as Zr/Y resembling transitional magma suites (Fig. 4.5b) and Ti-V systematics similar to the back arc basin or mid-ocean ridge basalt (BAB-MORB). These samples also plot in the alkaline basalt field of Shervais (1982) (Fig. 4.5c). Primitive mantle normalized trace element patterns for this population resembles E-MORB (Sun and McDonough, 1989; Fig. 4.5e). Late Devonian through Early Mississippian magmatism (Cowichan uplift) Mafic volcanic rocks Late Devonian through Early Misssissippian bimodal volcanic rocks and synvolcanic intrusions are abundant in the Cowichan uplift (Figures 1.2, 4.3 and 4.4; Massey et al., 1995a, b, c; Yorath et al., 1999; Chapter 3). As with the pre-Late Devonian mafic volcanic rocks in the area, Late Devonian through Early Mississippian mafic volcanic rocks of the Cowichan uplift resemble island arc tholeiites and light rare earth element (LREE) enriched island arc tholeiites from modern settings (e.g., Stoltz et al., 1990; Shinjo et al., 1999). With the exception of a single sample, these rocks are characterized by having largely subalkalic Nb/Y (< 0.7; Fig. 4.6a). The samples also have mafic Zr/TiO2 (Fig. 4.6a), Zr/Y resembling transitional through tholeiitic magma suites (Fig. 4.6b), and Ti-V systematics similar to back arc basin/mid-ocean ridge basalts or island arc tholeiites (3.6c). Primitive mantle normalized trace element patterns for these rocks are characteristic of rocks generated in a subduction zone setting, exhibiting LREE enrichment (La/Smn = 1.14 – 3.55), and negative Nb (Nb/Thmn = 0.16 – 0.79) and Ti anomalies (Fig. 4.6d). 60Four samples of Late Devonian-Early Mississippian basalt from the Cowichan uplift have yielded εNd(t=360) values ranging from 4.3 to 5.5 (Table 4.3), less radiogenic than the depleted mantle reservoir at 360 Ma (εNd(t=360) = +9.2) (Hamilton et al., 1983). Felsic volcanic rocks Late Devonian through Early Missisppian felsic volcanic rocks of the Cowichan uplift range in age from 366.8 ± 2.4 Ma to 353.1 ± 3.4 Ma (Chapter 3) and have subalkalic Nb/Y (< 0.7; Fig. 4.7a) and Zr/Y resembling predominantly transitional through calc-alkaline magma suites (Fig. 4.7b). Their Nb-Y and Ta-Yb systematics resemble those of rocks generated in magmatic arc environments (Fig. 4.7c and d). Primitive mantle normalized trace element patterns for these rocks are characteristic of rocks generated in a subduction zone setting, exhibiting LREE enrichment (La/Smn = 1.96 – 6.53), and negative Nb (Nb/Thmn = 0.08 – 0.24) and Ti anomalies (Fig. 4.7e). Six samples of Late Devonian-Early Mississippian felsic volcanic rocks from the Cowichan uplift have yielded εNd(t=360) values ranging from 4.3 to 5.9 (Table 4.3), less radiogenic than the depleted mantle reservoir at 360 Ma (εNd(t=360) = +9.2) (Hamilton et al., 1983) and overlapping with εNd(t=360) values for similarily aged mafic volcanic rocks in the Cowichan uplift. Saltspring Intrusive Suite (SSI) Granitoids Late Devonian through Early Mississippian granitoids of the Saltspring Intrusive Suite (SSI; Fig. 4.3) are interpreted to be the subvolcanic feeders to felsic volcanic rocks in the Cowichan area. They range in age from 360.7 ± 2.4 Ma through 355.0 ± 1.5 Ma (U-Pb, zircon), and are geochemically similar to the felsic volcanic rocks (Chapter 3). These intrusions have subalkalic Nb/Y (< 0.7; Fig. 4.8a) and Zr/Y resembling transitional through calc-alkaline magma suites (Fig. 4.8b). Their Nb-Y and Ta-Yb systematics resemble those of rocks generated in magmatic arc environments (Fig. 4.8c and d). Primitive mantle normalized trace element patterns for these rocks are characteristic of rocks generated in a subduction zone setting, exhibiting LREE enrichment (La/Smn = 612.57 – 6.96), and negative Nb (Nb/Thmn = 0.50 – 0.17 ) and Ti anomalies (Fig. 4.8e). SSI granitoids have a dominantly metaluminous character (Fig. 4.8f), with 5 of 8 samples resembling intrusions in oceanic island arc environments (Maniar and Piccoli, 1989). However, 3 of 8 samples analyzed have peraluminous character, resembling granitoids associated with continental arcs (Maniar and Piccoli, 1989). Four samples of Late Devonian-Early Mississippian quartz-feldspar porphyry (Saltspring Intrusive Suite) from the Cowichan uplift yielded εNd(t=360) values ranging from 5.4 to 5.5, which is slightly less radiogenic than the depleted mantle reservoir at 360 Ma (εNd(t=360) = +9.2) (Hamilton et al., 1983) and overlaps with εNd(t=360) values for mafic and felsic volcanic rocks of similar age in the Cowichan uplift. Mississippian magmatism (Cowichan uplift) Newly recognized Mississippian intermediate-felsic volcanic rocks are present in the Horne Lake area of the Cowichan uplift, and yield ages ranging from 340.7 ± 1.7 Ma to 335.3 ± 2.5 Ma (Fig. 4.4; Chapter 3). These rocks have subalkalic Nb/Y (< 0.7; Fig. 4.7a) and Zr/Y resembling dominantly transitional through weakly calc-alkaline magma suites (Fig. 4.9b). Their Nb-Y and Ta-Yb systematics resemble those of rocks generated in magmatic arc environments (Fig. 4.9c and d). Primitive mantle normalized trace element patterns for these rocks are characteristic of rocks generated in a subduction zone setting, exhibiting LREE enrichment (La/Smn = 1.64 – 3.01), and negative Nb (Nb/Thmn = 0.11 – 0.30 ) and Ti anomalies (Fig. 4.9e). This suite of magmatism is notably less felsic, slightly less LREE enriched, and less enriched in Zr-Hf than Late Devonian-Early Mississippian felsic volcanic rocks of the Cowichan uplift. Mississippian intermediate to felsic volcanic rocks contain higher V and Sc concentrations than their Late Devonian-Early Mississippian counterparts. No samples of Mississippian volcanic rocks were analyzed for Nd isotopes. 62Early Permian magmatism (Cowichan and Nanoose uplifts) Two geochemical populations are recognized within newly identified Early Permian basalts of the Cowichan and Nanoose uplifts (Figures 4.4 and 4.10). Both of these populations are present in the Alberni area, whereas only one of the two populations occurs in the Nanoose uplift (Fig 1.2). The first geochemical population of Early Permian basalt in the Alberni area resembles island arc tholeiites from modern settings (e.g., Stolz et al., 1990; Shinjo et al., 1999), similar to pre-Late Devonian and Late Devonian-Early Mississippian mafic volcanic rocks from the Cowichan uplift. These basalts are characterized by having subalkalic Nb/Y (< 0.7; Fig. 4.11a). These samples also have mafic Zr/TiO2 (Fig. 4.11a), Zr/Y resembling tholeiitic magma suites (Fig. 4.11b), and Ti-V systematics similar to back arc basin/mid-ocean ridge basalts or island arc tholeiites (Fig. 3.11c). Primitive mantle normalized trace element patterns for these rocks are characteristic of rocks generated in a subduction zone setting, exhibiting LREE enrichment (La/Smn = 1.63 – 1.64), and negative Nb (Nb/Thmn = 0.15 – 0.29) and Ti anomalies (Fig. 4.11d). The second geochemical population of Early Permian basalt is non-arc in character, and is present in both the Alberni and Nanoose areas. In the Alberni area, these basalts resemble enriched mid-ocean ridge basalts (E-MORB) and ocean island basalts (OIB) from modern settings (e.g., Sun and McDonough, 1989). These samples have largely alkalic Nb/Y (> 0.7; Fig. 4.11a), mafic Zr/TiO2 (Fig. 4.11a), Zr/Y resembling transitional through calc-alkaline magma suites (Fig. 4.11b), and Zr-Th-Nb systematics resembling E-MORB and OIB (Fig. 4.11e). Primitive mantle normalized trace element patterns for these rocks resemble both E-MORB and OIB (Fig. 4.11d), exhibiting both LREE enrichment (La/Smn = 1.73 – 2.69), and positive Nb anomalies (Nb/Thmn = 1.80 – 1.86). Early Permian basalts in the Nanoose area most closely resemble E-MORB and OIB from modern day settings (e.g., Sun and McDonough, 1989). These samples have alkalic Nb/Y (> 0.7; Fig. 4.11a), mafic Zr/TiO2 (Fig. 4.11b), and Zr-Th-Nb systematics resembling E-MORB (Fig. 4.11e). Primitive mantle normalized trace element patterns 63for these rocks most closely resemble OIB (Fig. 4.11d), exhibiting both LREE enrichment (La/Smn = 2.71 – 3.23), and positive Nb anomalies (Nb/Thmn = 1.35 – 1.86). Nd isotopic compositions for three samples of Early Permian basalt from the Alberni and Nanoose areas are less radiogenic than the depleted mantle reservoir at 300 Ma (εNd(t=300) = +9.3) (Hamilton et al., 1983). Early Permian basalts from the Alberni with arc tholeiite and OIB composition yield εNd(t=300) values ranging from 4.3 to 5.2, respectively, overlapping with εNd(t=360) values for older volcanic rocks and synvolcanic intrusions in the Cowichan uplift. Early Permian basalt from the Nanoose area with OIB chemistry yield an εNd(t=300) value of 6.1. This value is slightly more radiogenic than εNd(t=360) for older volcanic rocks and synvolcanic intrusions in the Cowichan uplift. Pennsylvanian through Early Permian magmatism (Dragon property and Bedingfield uplift) Mafic volcanic rocks Pennsylvanian mafic volcanic rocks of the Dragon property and the Bedingfield uplift comprise several geochemical populations (Figures 4.12 and 4.13). Pennsylvanian basalts of the Dragon property comprise one of these populations, most closely resembling calc-alkaline basalts from modern settings (Stoltz et al., 1990). This population has subalkalic Nb/Y (< 0.7; Fig. 4.14a), mafic Zr/TiO2 (Fig. 4.14a), Zr/Y resembling transitional magma suites (Fig. 4.14b), and Ti-V systematics similar to back arc basin/mid-ocean ridge basalts (Fig. 4.14c). Primitive mantle normalized trace element patterns for these rocks most closely resemble calc-alkaline basalts from modern settings (Fig. 4.14d), exhibiting LREE enrichment (La/Smn = 3.38 – 4.00), and negative Nb (Nb/Thmn = 0.10 – 0.11) and Ti anomalies (Fig. 4.14d). Pennsylvanian mafic volcanic rocks of the Dragon property are more LREE enriched than other mafic volcanic rocks with arc affinities encountered in the study. Mafic volcanic rocks of Pennsylvanian age were identified in one locality in the Bedingfield area. The chemistry of a single sample from this locality resembles E-64MORB from modern settings (Sun and McDonough, 1989). This population has subalkalic Nb/Y (< 0.7; Fig. 4.14a), mafic Zr/TiO2 (Fig. 4.14a), Zr/Y resembling transitional magma suites (Fig. 4.14b), and Ti-V systematics similar to back arc basin/mid-ocean ridge basalts (Fig. 4.14c). A primitive mantle normalized trace element pattern for this unit most closely resemble E-MORB from modern settings (Fig. 4.14d), exhibiting LREE enrichment (La/Smn = 1.51). Felsic volcanic rocks Pennsylvanian through Early Permian felsic volcanic rocks of the Dragon property and Bedingfield uplift (Figures 4.12 and 4.13) have subalkalic Nb/Y (< 0.7; Fig. 4.15a) and Zr/Y resembling dominantly transitional through calc-alkaline magma suites (Fig. 4.15b). Their Nb-Y and Ta-Yb systematics resemble those of rocks generated in both magmatic arc and anomalous ocean ridge settings (Fig. 4.15c and d). Primitive mantle normalized trace element patterns for these rocks are characteristic of rocks generated in a subduction zone setting, exhibiting LREE enrichment (La/Smn = 0.87 – 3.34), and negative Nb (Nb/Thmn = 0.12 – 0.48) and Ti anomalies (Fig. 4.15e). Two samples of felsic volcanic rocks from the Dragon and Bedingfield areas have yielded εNd(t=300) values ranging from 6.8 to 6.9, less radiogenic than the depleted mantle reservoir at 300 Ma (εNd(t=300) = +9.3) (Hamilton et al., 1983), but significantly more radiogenic than εNd(t=360) and εNd(t=300) values calculated for rocks in the Cowichan and Nanoose uplifts. Potentially Pennsylvanian through Early Permian magmatism (Hesquiat area) Mafic volcanic rocks thought to be of Pennsylvanian through Early Permian age in the Hesquiat area (Fig. 4.16) most closely resemble island arc tholeiites from modern settings (e.g., Stolz et al., 1990; Shinjo et al., 1999). This population has subalkalic Nb/Y (< 0.7; Fig. 4.17a), mafic Zr/TiO2 (Fig. 4.17a), Zr/Y resembling tholeiitic magma suites (Fig. 4.17b), and Ti-V systematics similar to basalts generated in island arc and/or back arc basin settings (Fig. 4.17c). Primitive mantle normalized trace element patterns for 65these rocks most closely resemble island arc tholeiites from modern settings (Fig. 4.17d), exhibiting LREE enrichment (La/Smn = 1.06 – 1.63), and negative Nb (Nb/Thmn = 0.30 -0.46) and Ti anomalies (Fig. 4.17d). Potentially Late Paleozoic mafic volcanic rocks of the Hesquiat area have less LREE enrichment than other mafic volcanic rocks sampled during the course of this study, reflected in lower average La/Smn ratios and “flatter” trace element patterns. Three samples of potentially Pennsylvanian through Early Permian mafic volcanic rocks from the Hesquiat area yield εNd(t=300) values ranging from 5.59 through 6.25, less radiogenic than the depleted mantle reservoir at 300 Ma (εNd(t=300) = +9.3) (Hamilton et al., 1983), but overlap with or are slightly more radiogenic than εNd(t=360) and εNd(t=300) values for rocks in the Cowichan and Nanoose uplifts. Pennsylvanian magmatism (Chaatl Inlet intrusion, Haida Gwaii) Quartz diorite of the Chaatl Inlet intrusion (Massey, 2005) has yielded a U-Pb (zircon) age of 317 Ma (Haggart, pers. comm., 2007). A single sample of this intrusion was submitted for lithogeochemical and Nd isotopic analyses as part of the present study. The intrusion has subalkalic Nb/Y (< 0.7; Fig. 4.18a), mafic Zr/TiO2 (Fig. 4.18a), Zr/Y resembling tholeiitic magma suites (Fig. 4.18b) and Ti-V systematics similar to basalts generated in a back arc basin setting (Fig. 4.18c). Primitive mantle normalized trace element patterns for this sample most closely resembles island arc tholeiites from modern settings (Fig. 4.18d), exhibiting LREE enrichment (La/Smn = 1.91), and negative Nb (Nb/Thmn = 0.21). The chemistry of the Chaatl Inlet intrusion resembles that of pre-Late Devonian, Late Devonian-Early Mississippian and Permian island arc tholeiites of the Cowichan uplift. The Chaatl Inlet intrusion yielded an εNd(t=300) value of 6.1, less radiogenic than the depleted mantle reservoir at 300 Ma (εNd(t=300) = +9.3) (Hamilton et al., 1983), slightly more radiogenic than εNd(t=360) values for rocks of the Cowichan uplift, and overlapping with εNd(t=300) for a sample of basalt from the Nanoose uplift. 66 4.3. SUMMARY In general terms, the lithogeochemical and Nd isotopic results described here indicate that pre-Late Devonian through Early Permian southern Wrangellia on Vancouver Island comprised an episodically active island arc, punctuated by pulses of bimodal volcanism and associated VMS mineralization related to periods of arc rifting and back arc basin development. This interpreted model is similar to the evolution of typical oceanic arcs and associated back arc basins in modern settings (Martinez et al., 2007). Non-arc volcanic rocks do not become prevalent in southern Paleozoic Wrangellia until Early Permian time. The overwhelming majority of pre-Late Devonian through Early Permian mafic volcanic rocks analyzed during the course of this study are chemically similar to modern day island arc tholeiites (IAT; Stolz et al., 1990; Shinjo et al., 1999). Felsic volcanic rocks analyzed during the course of this study are similar to those generated in arc settings, exhibiting strong subduction zone signatures characterized by LREE enrichment, and negative Nb and Ti anomalies (Tatsumi, 2005). More typical back arc geochemical affinities for Pennsylvanian through Early Permian felsic volcanic rocks of the Dragon and Bedingfield areas are suggested by increased Y and Yb contents in several of the samples (e.g., Fig. 4.14b). Non-arc basalts are also present in the sample suite, but are not abundant throughout the study area. They are characterized by trace element profiles with flat to positive Nb anomalies (i.e., Nb/Thmn ≥ 1). Potential pre-Late Devonian to Late Devonian E-MORB is represented by two samples from the southern Alberni area (Fig. 4.5). Non-arc basalts are also present in Early Permian volcanic assemblages of the Alberni and Nanoose areas, with chemistry similar to E-MORB or OIB from modern settings (e.g., Fig. 4.11; Sun and McDonough, 1989). The appearance of similar non-arc basalts in modern backarc settings typically marks the end of backarc related magmatism in an area (e.g., Sato et al., 2002; Martinez et al., 2007) . This relationship is evident in southern Paleozoic Wrangellia, where the paucity of volcanic rocks in Early Permian strata (dominated by carbonate rocks), has been interpreted by previous workers to mark the end of Sicker arc-related magmatism (e.g., Yorath et al., 1995). 67686970717273747576777879808182838485Table 4.1. Lithogeochemical data for felsic igneous rocks of the PWA (Vancouver Island).Sample 05M-366 05M-393 08TR049B 08TR055A 08TR061A 08TR101 08TR107 08TR114 08TR121 09TR042Rock type FSLT FSXT FSTF DCPR FSTF FSVO RHPR QFPR FSVO RHXTAge LDEM LDEM LDEM LDEM LDEM LDEM LDEM LDEM LDEM LDEMRegion CW CW CW CW CW CW CW CW CW CWAffinity CA CA CA CA CA CA CA CA CA CAEasting 442034 433603 436422 432659 429969 443809 444835 445394 450236 432751Northing 5412829 5414742 5415373 5416605 5417447 5414036 5413694 5413283 5411581 5416851Al2O3 12.62 12.96 12.41 11.55 13.36 12.2 13.05 12.51 13.43 12.31CaO 0.63 1.65 0.21 1.56 1.29 0.06 0.16 0.11 0.49 4.96Fe2O3 1.99 1.9 1.58 1.94 1.64 2.12 1 5.43 1.27 2.95K2O 3.24 3.96 2.33 1.69 2.78 3.33 5.36 2.8 1.33 2.56MgO 2.29 0.56 2.06 2.02 0.49 0.2 0.18 1.26 0.98 1.07MnO 0.04 0.03 0.01 0.04 0.07 0.01 0.02 0.05 0.02 0.1Na2O 1.12 3.65 2.22 1.78 3.36 0.16 3.23 0.76 5.12 0.75P2O5 0.1 0.05 0.03 0.03 0.04 0.04 0.03 0.05 0.07 0.05SiO2 74.42 73.93 77.63 77.61 75.45 80.33 77.26 74.89 76.5 68.85TiO2 0.15 0.18 0.15 0.16 0.18 0.23 0.19 0.23 0.27 0.23LOI 2.6 1.77 2.03 2.27 2.22 2.11 0.75 2.53 1.21 7.03Total 99.19 100.64 100.67 100.63 100.88 100.78 101.21 100.58 100.69 100.86Ba 1685 886 713 734 1649 562 943 1609 801 917Sc 1 3 2 2 2 4 3 3 6 4Sr 87 159 168 176 96 18 98 14 113 67V 17 17 9 9 13 26 16 19 26 24Y 11 14 9 11 10 8 10 9 18 10Ce 18 23.2 14.15 25.66 23.37 15.54 24.52 16.08 34.33 20.72Cs 1.788 0.403 0.686 0.531 0.364 0.951 0.824 0.184 0.283 0.877Dy 1 2 0.603 1.947 1.544 1.558 1.716 1.222 3.301 1.92Er 0.69 1.31 0.45 1.266 1.119 1.133 1.222 0.89 2.206 1.337Eu 0.4210 0.5440 0.2800 0.5760 0.6380 0.4660 0.5890 0.3670 0.8050 0.6640Ga 9.97 10.17 11.18 10.64 9.82 11.52 12.48 14.6 11.92 11.91Gd 1.02 1.77 0.673 1.876 1.417 1.267 1.529 1.109 3.04 1.682Hf 3.51 3.27 2.15 1.98 2.06 2.26 2.03 2.37 3.15 2.36Ho 0.218 0.439 0.134 0.403 0.338 0.344 0.377 0.266 0.706 0.426La 10.83 12.4 8.42 16.19 13.87 8.67 14.6 8.95 17.64 11.72Lu 0.155 0.268 0.111 0.235 0.244 0.231 0.249 0.202 0.393 0.257Nb 3.36 3.32 3.306 3.181 3.478 3.524 3.283 4 5 4Nd 6.74 9.1 4.76 9.77 8.46 6.23 9.09 6.37 14.64 8.09Pr 1.96 2.38 1.378 2.767 2.458 1.713 2.58 1.759 3.861 2.244Rb 30.2 39.2 37.89 34.45 46.4 55.62 59.33 40.92 25.96 46.41Sm 1.2 1.92 0.832 1.99 1.605 1.35 1.691 1.249 3.073 1.642Ta 0.3 0.3 0.28 0.27 0.294 0.266 0.282 0.289 0.314 0.278Tb 0.168 0.304 0.102 0.296 0.23 0.221 0.256 0.181 0.49 0.279Th 4.3 4.58 3.295 5.036 5.094 3.214 4.959 2.991 4.036 3.48Tm 0.132 0.227 0.081 0.201 0.187 0.188 0.201 0.156 0.346 0.218U 1.48 1.62 2.021 1.953 1.692 1.769 1.713 2.076 2.28 1.76Yb 0.936 1.63 0.614 1.431 1.421 1.38 1.483 1.161 2.443 1.566Zr 153 149 95 88 90 99 99 110 131 104T-Zr** 895 892 847 839 841 851 851 862 879 855Note: All samples are from Universal Transverse Mercator (UTM) zone 10, except for samples from theHesquiat and Dragon areas, which are from UTM zone 9. Four letter rock type codes consist of a two letter prefix followed by a two letter suffix. Prefix codes include: FS, felsic; RH, rhyolite; DC, dacite; QF, quartz-feldspar; IN, intermediate; BS, basalt; MX, heterolithic; DI, diorite. Suffix codes include: IV, intrusvive; DI, dike; PR, porphyry;VO, volcanic; TF, tuff; XT, crystal tuff; LT, lapilli tuff; TB, tuff breccia; BX, breccia; FB, flow breccia;AB, autobreccia; PL, pillow flow; FL, flow. Age codes include: PLD, Pre-Late Devonian; LDEM, Late Devonian-EarlyMississippian; MS, Mississippian; PN, Pennsylvanian; PM, Permian. Region codes include: CW, Cowichan; AL, Alberni;NA, Nanoose; DR, Dragon; BD, Bedingfield; HS, Hesquiat; HG, Haida Gwaii. Affinity codes include: CA, calc-alkaline;TR, transitional; TH, tholeiitic.*Samples are quartz-feldspar porhyries of the Saltspring Intrusions**T-Zr = zircon saturation temperature (Watson and Harrison, 1983)86Table 4.1. (continued)Sample 09TR063 05M-345 05M-349 05M-369 05M388B 05M392 08TR052 08TR057 09TR048 09TR053Rock type RDFL FSXT FSTF FSLT FSVO FSTF FSVO FSVO RHPR RHTFAge LDEM LDEM LDEM LDEM LDEM LDEM LDEM LDEM LDEM LDEMRegion CW CW CW CW CW CW CW CW CW CWAffinity CA CA TR CA CA CA CA CA CA CAEasting 410679 461736 462412 446982 438889 433558 437086 432456 431382 432941Northing 5419619 5403669 5403230 5413082 5413763 5414829 5414136 5416858 5417408 5415759Al2O3 13.52 13.49 16.88 13.44 12.63 13.48 12.68 12.44 13.14 13.33CaO 5.41 0.19 1.68 2.43 0.15 1.72 1.83 2.29 1.28 3.11Fe2O3 3.08 1.09 5.41 2.64 1.93 1.79 2.28 1.71 1.25 2.89K2O 0.88 4.43 1.42 2.09 3.4 3.67 1.38 2.88 0.31 2.77MgO 0.94 0.12 3.48 0.97 2.58 0.94 1.91 1.02 1.15 1.88MnO 0.07 0.03 0.08 0.07 0.04 0.03 0.04 0.07 0.01 0.06Na2O 2.81 4.47 5.04 3.45 0.08 3.05 3.94 0.55 4.71 1.27P2O5 0.08 0.04 0.14 0.06 0.05 0.06 0.04 0.06 0.05 0.05SiO2 72 75.69 62.88 73.2 76.76 72.19 73.8 74.97 77.05 68.68TiO2 0.29 0.18 0.52 0.24 0.28 0.21 0.22 0.22 0.23 0.25LOI 1.5 0.79 3.16 2.03 2.94 3.29 1.78 4.43 1.86 4.93Total 100.58 100.54 100.68 100.61 100.83 100.41 99.9 100.63 101.05 99.22Ba 405 1430 585 797 1123 1337 779 916 285 855Sc 6 3 11 4 5 2 4 3 4 3Sr 462 73 377 104 8 91 194 55 264 185V 47 17 49 31 25 16 21 18 26 17Y 14 11 35 12 17 10 10 13 10 13Ce 43.91 29 38.8 22.1 18.65 27.87 21.76 25.88 18.55 22.67Cs 0.237 0.274 0.577 0.321 0.21 0.956 0.172 1.141 0.211 0.474Dy 2.852 1.9 5.7 1.7 2.22 1.762 1.63 2.232 1.78 1.929Er 1.838 1.18 3.42 1.17 1.445 1.211 1.224 1.535 1.266 1.404Eu 0.9510 0.6080 1.3780 0.5880 0.3900 0.7280 0.6010 0.7240 0.3770 0.6380Ga 12.88 10.13 13.57 10.9 12.26 11.96 11.62 11.62 8.51 12.52Gd 2.894 1.77 5.53 1.64 1.926 1.682 1.457 1.992 1.478 1.764Hf 2.8 3.83 5.42 3.47 3.12 2.37 2.25 2.26 2.32 2.52Ho 0.592 0.404 1.189 0.376 0.472 0.377 0.366 0.496 0.39 0.423La 23.74 15.74 15.67 12.22 9.17 15.96 12.36 14.01 10.65 12.85Lu 0.332 0.267 0.607 0.254 0.236 0.245 0.252 0.277 0.263 0.279Nb 8 3.32 8 4 5 5.186 4 4 3.729 4.176Nd 18.09 10.13 21.27 8.36 8.65 10.23 8.2 10.62 7.53 8.86Pr 4.849 2.8 4.78 2.25 2.171 2.897 2.302 2.843 2.112 2.395Rb 21.61 45.9 28.3 33.8 40.82 47.71 14.59 52.37 4.77 45.08Sm 3.359 1.97 5.16 1.75 1.89 1.896 1.61 2.091 1.531 1.791Ta 0.442 0.3 0.5 0.3 0.3 0.38 0.274 0.27 0.285 0.306Tb 0.444 0.308 0.903 0.278 0.334 0.273 0.241 0.332 0.258 0.292Th 6.868 4.96 5.14 3.55 2.524 4.851 3.428 3.25 3.745 3.622Tm 0.29 0.22 0.566 0.201 0.221 0.197 0.205 0.241 0.214 0.228U 2.837 1.72 2.27 2.07 1.373 2.372 2.116 1.589 1.965 1.519Yb 2.072 1.564 3.671 1.443 1.506 1.448 1.484 1.7 1.544 1.689Zr 122 187 231 163 124 109 110 106 105 123T-Zr** 871 917 940 902 874 860 861 857 857 872Note: All samples are from Universal Transverse Mercator (UTM) zone 10, except for samples from theHesquiat and Dragon areas, which are from UTM zone 9. Four letter rock type codes consist of a two letter prefix followed by a two letter suffix. Prefix codes include: FS, felsic; RH, rhyolite; DC, dacite; QF, quartz-feldspar; IN, intermediate; BS, basalt; MX, heterolithic; DI, diorite. Suffix codes include: IV, intrusvive; DI, dike; PR, porphyry;VO, volcanic; TF, tuff; XT, crystal tuff; LT, lapilli tuff; TB, tuff breccia; BX, breccia; FB, flow breccia;AB, autobreccia; PL, pillow flow; FL, flow. Age codes include: PLD, Pre-Late Devonian; LDEM, Late Devonian-EarlyMississippian; MS, Mississippian; PN, Pennsylvanian; PM, Permian. Region codes include: CW, Cowichan; AL, Alberni;NA, Nanoose; DR, Dragon; BD, Bedingfield; HS, Hesquiat; HG, Haida Gwaii. Affinity codes include: CA, calc-alkaline;TR, transitional; TH, tholeiitic.*Samples are quartz-feldspar porhyries of the Saltspring Intrusions**T-Zr = zircon saturation temperature (Watson and Harrison, 1983)87Table 4.1. (continued)Sample 09TR056 05M-363 05M-367 05M-368 05M-398b 08TR040 09M302* 09M308* 09M309* 05M-394*Rock type RHPR FSTF FSLT FSLT FSTF FSPR QFPR QFPR QFPR QFPRAge LDEM LDEM LDEM LDEM LDEM LDEM LDEM LDEM LDEM LDEMRegion CW CW CW CW CW CW CW CW CW CWAffinity CA CA CA CA CA CA CA CA TH CAEasting 433226 442424 442607 442596 465126 433913 469473 468712 467293 424063Northing 5415134 5412853 5413030 5413280 5400344 5414510 5405425 5403979 5403326 5420086Al2O3 13.91 12.81 14.06 13.06 13.77 13.36 12.29 13.36 12.79 11.36CaO 1.74 2.59 0.21 0.43 0.58 0.45 2.53 1.62 1.29 0.29Fe2O3 2.61 2.09 1.71 2.29 3 1.41 1.75 0.99 1.52 1.28K2O 0.36 2.08 2.46 2.9 2.95 4.92 2.29 0.94 3.68 3.02MgO 1.06 2.86 1.34 1.87 2.78 0.78 0.55 0.45 0.28 0.39MnO 0.06 0.04 0.03 0.02 0.05 0.03 0.09 0.02 0.04 0.03Na2O 6.22 0.52 3.41 1.33 1.66 2.16 3.04 5.98 4.01 4.08P2O5 0.07 0.05 0.08 0.05 0.06 0.04 0.03 0.04 0.02 0.03SiO2 73.1 73.36 75 76.48 71.38 75.92 73.95 76.46 76 79.41TiO2 0.27 0.20 0.28 0.21 0.31 0.19 0.15 0.17 0.15 0.11LOI 1.17 3.55 1.8 2.33 2.41 1.35 3.42 1.02 0.76 0.63Total 100.56 100.13 100.39 100.97 98.95 100.61 100.1 101.04 100.54 100.61Ba 248 592 1051 1426 >2000 698 736 355 988 1538Sc 5 4 5 2 4 3 2 3 2 2Sr 140 139 119 39 91 62 143 155 102 97V 30 26 32 24 21 12 11 12 9 10Y 11 13 18 12 24 12 10 8 16 10Ce 22.25 24 30.3 15.9 27 25.32 24.25 19.02 31.53 21.6Cs 0.113 0.772 0.423 0.367 0.568 0.271 0.237 0.123 0.264 0.334Dy 2.141 1.9 2.9 1 2.2 1.919 1.676 1.399 2.623 1.3Er 1.453 1.27 1.8 0.66 1.3 1.383 1.24 0.961 1.904 0.9Eu 0.6460 0.5810 0.7480 0.2470 0.8180 0.5430 0.4310 0.4900 0.4750 0.4800Ga 12.35 11.4 12.27 11.32 13.31 11.58 10.75 10.96 11.79 6.91Gd 1.875 1.8 2.83 1.04 2.04 1.817 1.488 1.28 2.146 1.31Hf 2.45 3.03 3.93 3.42 4.86 2.04 1.9 1.7 2.39 3.55Ho 0.46 0.426 0.636 0.223 0.451 0.427 0.373 0.301 0.573 0.299La 12.83 13.06 15.26 8.48 14 14.56 14.13 12.18 18.41 15.32Lu 0.273 0.279 0.333 0.131 0.203 0.278 0.261 0.187 0.387 0.188Nb 4 3.04 5.08 4 8 3.419 3.392 3 5.116 2.32Nd 9.35 9.51 12.79 5.9 11.46 9.55 8.65 6.64 10.96 7.86Pr 2.507 2.47 3.29 1.64 3.06 2.65 2.469 1.9 3.205 2.24Rb 4.44 35.8 38.8 32.9 34.2 49.61 40.36 14.8 69.37 32.8Sm 1.892 1.94 2.74 1.16 2.37 1.874 1.655 1.356 2.197 1.42Ta 0.273 0.2 0.3 0.3 0.4 0.277 0.287 0.221 0.559 0.2Tb 0.318 0.298 0.477 0.163 0.352 0.295 0.246 0.211 0.382 0.213Th 3.572 3.41 3.65 2.58 4.23 5.025 5.841 5.659 8.163 5.56Tm 0.232 0.227 0.299 0.117 0.207 0.231 0.213 0.156 0.317 0.156U 2.349 1.33 1.75 1.75 2.6 1.838 2.332 1.943 4.322 1.62Yb 1.655 1.612 2.014 0.773 1.395 1.673 1.538 1.137 2.312 1.12Zr 120 136 171 151 216 103 86 75 83 161T-Zr** 870 883 907 894 933 855 837 824 834 900Note: All samples are from Universal Transverse Mercator (UTM) zone 10, except for samples from theHesquiat and Dragon areas, which are from UTM zone 9. Four letter rock type codes consist of a two letter prefix followed by a two letter suffix. Prefix codes include: FS, felsic; RH, rhyolite; DC, dacite; QF, quartz-feldspar; IN, intermediate; BS, basalt; MX, heterolithic; DI, diorite. Suffix codes include: IV, intrusvive; DI, dike; PR, porphyry;VO, volcanic; TF, tuff; XT, crystal tuff; LT, lapilli tuff; TB, tuff breccia; BX, breccia; FB, flow breccia;AB, autobreccia; PL, pillow flow; FL, flow. Age codes include: PLD, Pre-Late Devonian; LDEM, Late Devonian-EarlyMississippian; MS, Mississippian; PN, Pennsylvanian; PM, Permian. Region codes include: CW, Cowichan; AL, Alberni;NA, Nanoose; DR, Dragon; BD, Bedingfield; HS, Hesquiat; HG, Haida Gwaii. Affinity codes include: CA, calc-alkaline;TR, transitional; TH, tholeiitic.*Samples are quartz-feldspar porhyries of the Saltspring Intrusions**T-Zr = zircon saturation temperature (Watson and Harrison, 1983)88Table 4.1. (continued)Sample 05M350* 05M352* 05M-353* 08TR084A 08TR087A 09TR034 09TR081 09TR088 09TR090 05M-383Rock type QFPR QFPR QFPR RHTB DCDI RHPR RHLT DCPR RHPR DCIVAge LDEM LDEM LDEM MS MS MS MS MS MS LDEMRegion CW CW CW AL AL AL AL AL AL ALAffinity TH CA CA CA TR TR TH TR CA CAEasting 453880 454100 455606 377045 377117 373074 373010 372780 372710 375408Northing 5410766 5409559 5409777 5463647 5463641 5465628 5465583 5466229 5465993 5460305Al2O3 14.26 13.05 13.71 15.7 17.19 17.19 16.79 19.62 16.8 13.02CaO 2.62 2.71 1.56 2.57 7 2.21 2.1 6.9 2.57 1.08Fe2O3 3.65 3.3 1.75 4.2 9.24 5.28 9.49 5.91 6.32 2.15K2O 0.78 0.49 0.27 1.63 2.74 1.08 0.49 2.16 0.24 2.43MgO 1.1 1.51 0.94 1.61 4.03 2.32 6.79 1.8 2.99 0.6MnO 0.07 0.07 0.03 0.09 0.16 0.17 0.2 0.13 0.09 0.04Na2O 5.01 5.04 6.71 5.16 3.19 6.51 4.63 3.99 7.27 4.63P2O5 0.11 0.07 0.06 0.24 0.34 0.26 0.07 0.42 0.26 0.11SiO2 71.62 73.19 73.82 67.13 53.7 61.41 54.36 54.48 57.09 75.23TiO2 0.37 0.28 0.23 0.50 0.91 0.47 0.50 0.68 0.58 0.41LOI 1.34 1.34 1.49 1.72 2.04 2.94 4.39 3.94 4.14 1.44Total 100.92 101.02 100.58 100.56 100.52 99.83 99.81 100.02 98.3 101.13Ba 526 436 136 528 1008 328 452 430 >2000 786Sc 7 6 5 12 24 8 33 11 13 9Sr 238 180 173 355 456 358 313 572 559 136V 35 31 26 115 224 74 262 93 133 25Y 24 14 14 11 23 17 12 24 15 28Ce 27.52 27.78 24.6 28.06 29.22 54.71 9.38 40.03 43.88 63.2Cs 0.115 0.051 0.04 1.398 2.464 0.796 1.193 0.468 0.42 0.765Dy 4.208 2.494 1.9 2.327 4.624 3.524 2.322 4.696 3.214 5.2Er 2.901 1.733 1.28 1.381 2.843 2.039 1.563 2.806 1.978 2.98Eu 1.1300 0.6570 0.5310 0.9760 1.3650 1.6750 0.6370 1.4510 1.5970 1.6130Ga 14.97 12.42 11.32 13.77 17.08 17 15.21 18.62 16.41 10.43Gd 3.709 2.289 1.84 2.59 4.547 4.418 1.98 4.887 3.665 5.66Hf 2.64 2.41 3.74 1.75 2.91 2.22 0.88 3.61 2.61 4.68Ho 0.913 0.55 0.432 0.47 0.951 0.705 0.508 0.951 0.655 1.048La 13.49 15.98 12.61 13.37 13.32 24.94 4.27 18.85 19.61 31.67Lu 0.49 0.307 0.274 0.221 0.425 0.345 0.256 0.419 0.331 0.519Nb 4.049 3.42 4.18 5.37 5 5 0.787 9.034 5 10Nd 13.83 10.97 9.79 14.09 17.99 28.96 6.08 22.46 23.38 29.28Pr 3.339 2.955 2.59 3.471 4.073 7.044 1.305 5.263 5.658 7.21Rb 12.24 5.17 3.3 37.69 57.41 24.35 11 53.44 5.32 43Sm 3.383 2.342 1.97 2.863 4.534 5.675 1.679 5.108 4.665 6.14Ta 0.309 0.268 0.3 0.397 0.281 0.298 0.054 0.475 0.309 0.5Tb 0.624 0.382 0.315 0.383 0.72 0.597 0.332 0.741 0.538 0.879Th 3.433 5.421 2.97 2.158 2.825 3.938 0.863 3.591 4.379 5.92Tm 0.452 0.274 0.23 0.209 0.415 0.314 0.239 0.416 0.304 0.482U 1.339 2.407 1.38 1.229 1.243 2.055 0.404 1.652 1.823 1.83Yb 3.133 1.932 1.561 1.392 2.751 2.158 1.623 2.755 2.065 3.219Zr 112 100 180 78 109 105 29 145 107 210T-Zr** 863 851 912 828 859 856 742 888 858 929Note: All samples are from Universal Transverse Mercator (UTM) zone 10, except for samples from theHesquiat and Dragon areas, which are from UTM zone 9. Four letter rock type codes consist of a two letter prefix followed by a two letter suffix. Prefix codes include: FS, felsic; RH, rhyolite; DC, dacite; QF, quartz-feldspar; IN, intermediate; BS, basalt; MX, heterolithic; DI, diorite. Suffix codes include: IV, intrusvive; DI, dike; PR, porphyry;VO, volcanic; TF, tuff; XT, crystal tuff; LT, lapilli tuff; TB, tuff breccia; BX, breccia; FB, flow breccia;AB, autobreccia; PL, pillow flow; FL, flow. Age codes include: PLD, Pre-Late Devonian; LDEM, Late Devonian-EarlyMississippian; MS, Mississippian; PN, Pennsylvanian; PM, Permian. Region codes include: CW, Cowichan; AL, Alberni;NA, Nanoose; DR, Dragon; BD, Bedingfield; HS, Hesquiat; HG, Haida Gwaii. Affinity codes include: CA, calc-alkaline;TR, transitional; TH, tholeiitic.*Samples are quartz-feldspar porhyries of the Saltspring Intrusions**T-Zr = zircon saturation temperature (Watson and Harrison, 1983)89Table 4.1. (continued)Sample 05M-386b 05M-386c 05M-374 07TR051A 07TR052C 09TR105 09TR106 09TR110 09TR117 09TR118Rock type FSTF FSXT FSTF DCFL DCBX RHFL FSVO RHPR FSVC RHFLAge LDEM LDEM LDEM LDEM LDEM PN PN PN PN PNRegion AL AL AL AL AL BD BD BD BD BDAffinity TH CA CA TR TR TR TR TR CA TREasting 376146 376146 386505 375421 375323 289679 293761 292339 286622 286965Northing 5461004 5461004 5442020 5460259 5460373 5462352 5461967 5463853 5470693 5471653Al2O3 15.51 18.09 17.77 11.97 10.6 17.71 14.46 13.28 15.29 11.56CaO 2.52 4.55 6.53 1.95 2.41 2.98 2.35 1.45 0.51 0.2Fe2O3 7.07 5.31 3.43 1.99 1.84 2.1 7.48 3.75 4.26 2.06K2O 0.43 1.89 2.29 2.58 0.49 0.56 1.96 1.38 2.69 2.93MgO 2.98 1.7 1.43 0.56 0.5 4.16 3.75 1.41 1.52 0.4MnO 0.11 0.07 0.06 0.04 0.02 0.02 0.27 0.08 0.1 0.07Na2O 6.01 6.09 1.97 3.81 4.97 5.35 3.03 4.98 5.57 4.66P2O5 0.34 0.24 0.08 0.1 0.13 0.07 0.15 0.08 0.12 0.02SiO2 62.28 60.09 61.14 74.63 77.19 64.2 61.58 72.78 68.49 76.59TiO2 0.86 0.53 0.32 0.38 0.52 0.60 0.63 0.46 0.55 0.17LOI 2.38 1.69 5.47 2.06 1.63 2.22 4.55 0.99 1.25 0.54Total 100.5 100.25 100.49 100.06 100.28 99.97 100.21 100.62 100.33 99.21Ba 225 608 1014 723 208 194 384 705 864 340Sc 18 11 4 8 9 19 18 10 11 6Sr 333 600 212 111 272 247 129 120 183 27V 103 102 29 25 45 84 138 44 52 2Y 34 20 23 22 25 28 20 29 35 41Ce 39.9 51.1 53 54.3 55.35 8.57 10 33.17 45.76 47.94Cs 0.097 0.107 3.595 0.811 0.153 0.257 0.461 0.495 0.32 0.09Dy 5.9 2.9 3.1 4.1 4.99 4.798 3.359 4.97 6.602 7.79Er 3.48 1.66 1.86 2.37 2.926 3.547 2.34 3.357 4.162 5.081Eu 1.7560 1.1810 0.7290 1.2720 1.5210 1.1450 1.0040 1.1040 1.3310 1.1260Ga 14.41 17.39 14.42 10.74 7.83 14.52 13.93 12.23 15.11 13.49Gd 5.85 3.19 3.32 4.7 5.513 3.295 2.762 4.547 6.135 6.782Hf 3.08 3.92 5.88 3.07 3.13 3.71 2.13 4.67 6.34 5.94Ho 1.252 0.599 0.652 0.854 0.997 1.106 0.752 1.08 1.374 1.646La 17.34 26.87 23.33 26.56 26.29 3.03 4 15.5 20.5 20.8Lu 0.563 0.305 0.366 0.398 0.409 0.592 0.393 0.564 0.674 0.797Nb 5.45 11.05 14 9 10 5.097 2.035 6 12 13.519Nd 23.14 20.63 20.2 25.62 27.04 6.61 7.1 18.21 24.92 26.74Pr 5.11 5.44 5.54 6.23 6.626 1.316 1.457 4.364 5.943 6.33Rb 6.3 27.3 49.8 49.4 11.25 10.87 38.9 23.93 44.79 39.92Sm 5.64 3.71 3.77 5.23 5.891 2.253 2.218 4.246 5.979 6.511Ta 0.3 0.6 1.1 0.5 0.491 0.389 0.131 0.4 0.878 0.926Tb 0.925 0.487 0.519 0.719 0.828 0.651 0.485 0.757 1.013 1.168Th 2.84 5.76 17.27 5.36 5.186 1.648 1.415 2.383 4.241 3.38Tm 0.554 0.265 0.329 0.37 0.419 0.54 0.373 0.517 0.632 0.775U 1.49 2.34 7.11 1.6 1.559 0.806 0.724 1.221 1.824 1.351Yb 3.535 1.802 2.226 2.527 2.73 3.704 2.493 3.527 4.27 5.178Zr 118 182 227 126 133 150 81 196 276 243T-Zr** 868 913 938 875 880 893 831 922 961 946Note: All samples are from Universal Transverse Mercator (UTM) zone 10, except for samples from theHesquiat and Dragon areas, which are from UTM zone 9. Four letter rock type codes consist of a two letter prefix followed by a two letter suffix. Prefix codes include: FS, felsic; RH, rhyolite; DC, dacite; QF, quartz-feldspar; IN, intermediate; BS, basalt; MX, heterolithic; DI, diorite. Suffix codes include: IV, intrusvive; DI, dike; PR, porphyry;VO, volcanic; TF, tuff; XT, crystal tuff; LT, lapilli tuff; TB, tuff breccia; BX, breccia; FB, flow breccia;AB, autobreccia; PL, pillow flow; FL, flow. Age codes include: PLD, Pre-Late Devonian; LDEM, Late Devonian-EarlyMississippian; MS, Mississippian; PN, Pennsylvanian; PM, Permian. Region codes include: CW, Cowichan; AL, Alberni;NA, Nanoose; DR, Dragon; BD, Bedingfield; HS, Hesquiat; HG, Haida Gwaii. Affinity codes include: CA, calc-alkaline;TR, transitional; TH, tholeiitic.*Samples are quartz-feldspar porhyries of the Saltspring Intrusions**T-Zr = zircon saturation temperature (Watson and Harrison, 1983)90Table 4.1. (continued)Sample 08TRDR036 08TRDR007A 08TRDR047A 09TRDR006A 09TRDR010 09TRDR013Rock type RHFL RHFL RHFL DCXT RHVO RHPRAge PN PN PN PN PN PNRegion DR DR DR DR DR DRAffinity CA CA CA TR TR CAEasting 692814 692704 691940 692266 684348 694897Northing 5527147 5527315 5528868 5525028 5499931 5525610Al2O3 12.91 12.63 13.32 18.23 13.17 18.8CaO 0.56 0.12 0.27 5.28 1.1 1.61Fe2O3 1.62 2.26 1.71 5.54 1.63 3.21K2O 3.34 10.67 11.51 2.86 2.79 5.26MgO 0.17 0.06 0.03 1.43 0.16 1.45MnO 0.04 0.07 0.02 0.13 0.07 0.09Na2O 4.93 0.14 0.22 3.69 4.97 4.69P2O5 0.03 0.02 0.02 0.24 0.02 0.09SiO2 76.71 73.36 72.39 61.08 76.01 63.13TiO2 0.29 0.31 0.30 0.42 0.14 0.43LOI 0.43 0.64 0.6 1.74 0.59 1.25Total 101.03 100.27 100.37 100.64 100.65 100.02Ba 1047 961 >2000 1435 782 1167Sc 7 7 7 6 5 6Sr 91 21 18 352 98 161V 2 1 <1 60 2 42Y 58 51 64 13 26 25Ce 53.31 88.43 98.01 26.97 43.76 22.27Cs 0.323 0.491 0.469 0.55 0.586 0.885Dy 10.247 10.082 12.954 2.549 4.486 4.155Er 6.945 6.335 7.911 1.563 2.993 2.891Eu 2.2990 3.1740 3.7840 0.9530 1.0060 0.7200Ga 18.81 19.38 16.88 15.87 13.4 26.87Gd 7.926 9.834 12.619 2.803 4.182 2.611Hf 10.12 10.19 10.54 1.96 3.93 4.68Ho 2.259 2.093 2.699 0.53 0.967 0.923La 23.25 41.05 47.15 13.34 22.21 11.2Lu 1.087 0.995 1.182 0.255 0.54 0.505Nb 24 25.375 24.817 5 7.179 8Nd 28.4 46.92 54.45 14.27 20.25 9.37Pr 6.879 11.481 13.155 3.398 5.292 2.562Rb 56.43 190.78 206.84 74.92 76.17 123.82Sm 7.139 10.497 12.358 3.078 4.292 2.207Ta 1.509 1.593 1.603 0.304 0.489 0.596Tb 1.473 1.601 2.063 0.417 0.693 0.559Th 7.093 7.278 7.416 2.674 5.245 7.63Tm 1.06 0.975 1.178 0.237 0.483 0.445U 3.411 2.585 2.926 1.847 2.151 3.45Yb 7.017 6.545 7.713 1.638 3.357 3.063Zr 466 456 476 81 155 224T-Zr** 1026 1023 1028 831 896 937Note: All samples are from Universal Transverse Mercator (UTM) zone 10, except for samples from theHesquiat and Dragon areas, which are from UTM zone 9. Four letter rock type codes consist of a two letter prefix followed by a two letter suffix. Prefix codes include: FS, felsic; RH, rhyolite; DC, dacite; QF, quartz-feldspar; IN, intermediate; BS, basalt; MX, heterolithic; DI, diorite. Suffix codes include: IV, intrusvive; DI, dike; PR, porphyry;VO, volcanic; TF, tuff; XT, crystal tuff; LT, lapilli tuff; TB, tuff breccia; BX, breccia; FB, flow breccia;AB, autobreccia; PL, pillow flow; FL, flow. Age codes include: PLD, Pre-Late Devonian; LDEM, Late Devonian-EarlyMississippian; MS, Mississippian; PN, Pennsylvanian; PM, Permian. Region codes include: CW, Cowichan; AL, Alberni;NA, Nanoose; DR, Dragon; BD, Bedingfield; HS, Hesquiat; HG, Haida Gwaii. Affinity codes include: CA, calc-alkaline;TR, transitional; TH, tholeiitic.*Samples are quartz-feldspar porhyries of the Saltspring Intrusions**T-Zr = zircon saturation temperature (Watson and Harrison, 1983)91Table 4.2. Lithogeochemical data for mafic igneous rocks of the PWA (Vancouver Island and Haida Gwaii).Sample 05M-355 08TR054 08TR064A 08TR069 08TR099 08TR119 08TR122 09TR037 09TR044 09TR051Rock type INXT INTF INTF MFTF INTF INTF INVO INTF INTF INTFAge LDEM LDEM LDEM LDEM LDEM LDEM LDEM LDEM LDEM LDEMRegion CW CW CW CW CW CW CW CW CW CWArc/Non-arc Arc Arc Arc Arc Arc Arc Arc Arc Arc ArcAffinity L-IAT L-IAT L-IAT IAT L-IAT L-IAT IAT L-IAT IAT L-IATEasting 442990 432799 429924 377403 443546 450234 450062 430714 433019 432235Northing 5414805 5416490 5418840 5460272 5414471 5412710 5412110 5418303 5416880 5416467Al2O3 17.71 16.75 18.37 15.94 14.69 16.81 16.85 15.28 17.01 17.14CaO 4.44 4.85 4.9 7.83 5.42 8.51 5.85 6.77 10 3.61Fe2O3 10.35 7.75 8.54 9.61 12.78 9.43 7.57 11.18 11.09 11.53K2O 0.3 1.61 2.17 2.53 0.04 0.62 0.17 1.41 0.05 2.18MgO 5.51 2.49 3.89 9.49 12.87 3.4 4.28 9.24 3.58 2.24MnO 0.19 0.16 0.14 0.17 0.15 0.21 0.23 0.17 0.26 0.13Na2O 5.1 3.85 3.57 2.12 1.5 4.3 5.32 3.11 2.07 2.53P2O5 0.28 0.34 0.46 0.22 0.28 0.2 0.11 0.46 0.12 0.22SiO2 50.88 57.45 54.45 47.97 42.36 51.07 54.31 47.5 50.26 53.67TiO2 0.76 0.79 0.73 0.75 0.79 0.66 0.59 0.87 0.93 0.91LOI 4.82 4.12 2.91 3.8 9.29 5.39 3.96 4.06 4.72 5.86Total 100.33 100.14 100.12 100.42 100.15 100.58 99.22 100.02 100.09 100.02Ba 177 626 804 589 23 458 121 735 88 1081Co 34 15 23 35 38 22 15 39 26 18Cr 11 3 27 318 123 12 48 108 249 <2Cu 109 21 68 70 <6 151 83 120 60 <6Ni 11 2 17 85 47 6 15 50 33 <2Pb 33 <15 <15 <15 <15 <15 <15 <15 <15 <15Sc 25 17 19 39 38 21 27 33 40 22Sr 331 322 880 376 168 376 302 518 664 174V 245 93 224 275 279 194 226 306 279 209Y 21 34 20 15 18 19 14 17 18 25Ce 31.5 40.8 58.61 20.56 29.24 25.06 15.24 58.37 11.13 23.33Cs 0.144 0.892 0.564 1.927 0.342 0.291 0.035 0.729 0.054 0.635Dy 3.6 6.386 4.424 3.263 3.988 3.894 2.877 4.34 3.616 4.765Er 2.11 4.139 2.479 1.895 2.2 2.424 1.876 2.354 2.284 3.015Eu 1.25 1.628 1.853 1.15 1.048 1.14 0.643 1.854 0.974 1.293Ga 15.02 17.4 16.72 14.92 15.42 17.19 16.64 16.03 15.71 17.58Gd 3.89 5.98 5.233 3.376 4.393 3.745 2.5 5.211 3.148 4.346Hf 2.15 2.63 2.29 1.35 1.4 2.07 1.42 1.97 1.48 2.08Ho 0.763 1.358 0.853 0.652 0.782 0.821 0.619 0.829 0.763 1.008La 15.32 20.25 31.99 9.66 13.32 12.18 7.05 31.3 4.56 10.85Lu 0.336 0.646 0.369 0.267 0.281 0.373 0.291 0.305 0.33 0.454Nb 3 4.43 7 3 5.109 5 2.295 15.811 1.634 3.238Nd 16.51 22.91 27.8 12.41 18 13.98 8.51 27.77 8.21 14.07Pr 3.82 5.206 7.011 2.732 3.959 3.202 1.984 6.855 1.651 3.129Rb 5.9 49.9 46.56 56.11 1.08 10.3 2.01 23.59 0.84 44.77Sm 3.82 5.576 5.9 3.174 4.485 3.499 2.213 5.683 2.574 3.799Ta <0.2 0.243 0.271 0.144 0.173 0.245 0.127 0.613 0.096 0.185Tb 0.621 0.963 0.745 0.512 0.654 0.607 0.422 0.731 0.542 0.71Th 2.16 2.924 4.467 1.289 1.92 2.11 1.215 4.084 0.609 2.269Tm 0.335 0.629 0.365 0.272 0.305 0.362 0.282 0.322 0.329 0.448U 0.98 1.363 2.012 0.43 0.82 1.302 0.889 1.565 0.259 0.716Yb 2.186 4.14 2.381 1.784 1.912 2.413 1.893 2.048 2.162 2.97Zn 89 94 93 71 60 110 94 90 80 129Zr 85 101 99 50 53 79 52 82 54 75Note: All samples are from Universal Transverse Mercator (UTM) zone 10, except for samples from theHesquiat and Dragon areas, which are from UTM zone 9, and the lone Haida Gwaii sample, which is from UTM zone 8. Rock type, age and region codes are described in Table 3.1. Affinity codes include: IAT, island arc tholeiite; L-IAT, light rareearth element enriched island arc tholeiite; CAB, calc-alkaline basalt; E-MORB, enriched mid-ocean ridge basalt; OIB, ocean island basalt.92Table 4.2. (continued)Sample 09TR054 09TR065 05M-313 05M-320 05M-326 05M-351 05M338 09TR002 09TR003 09TR014Rock type MFTF BSTB MFTB MFBX INXT MFBX BSBX BSFL BSPL BSPLAge LDEM LDEM PLD PLD PLD PLD LDEM PLD PLD PLDRegion CW CW CW CW CW CW CW AL AL ALArc/Non-arc Arc Arc Arc Arc Arc Arc Arc Non-arc Non-arc ArcAffinity IAT L-IAT L-IAT IAT L-IAT L-IAT IAT E-MORB E-MORB L-IATEasting 433226 410678 457000 448683 458107 453920 431930 381569 382023 382418Northing 5415146 5419954 5407892 5411028 5410769 5409719 5401092 5443070 5444482 5445139Al2O3 16.65 14.11 17.12 14.7 18.32 15.82 13.09 13.16 15.06 10.94CaO 1.75 5.36 12.33 9.31 6.64 11.1 9.28 13.83 8.63 12.07Fe2O3 8.52 7.84 7.98 9.07 8.32 10.68 7.5 7.19 7.95 7.84K2O 1.28 3.63 0.08 0.11 1.22 0.41 1.04 0.1 0.35 0.01MgO 7.53 9.13 5.3 6.93 4.71 6.47 8.89 5.2 4.32 8.75MnO 0.25 0.1 0.12 0.19 0.14 0.17 0.16 0.16 0.1 0.13Na2O 3.34 2.19 3.75 4.28 4.85 3.09 3.71 4.4 4.59 1.17P2O5 0.13 0.63 0.19 0.13 0.22 0.15 0.23 0.24 0.25 0.22SiO2 54.6 50.69 51.45 53.64 53.16 50.15 51.39 41.29 47.51 50.58TiO2 0.61 0.96 0.73 0.55 0.70 0.58 0.74 1.30 1.39 0.56LOI 4.71 4.98 1.54 1.64 2.02 2.12 4.55 12.77 9.7 7.47Total 99.38 99.63 100.6 100.55 100.3 100.75 100.59 99.63 99.83 99.75Ba 984 304 74 118 713 191 334 106 50 10Co 15 30 24 29 27 34 27 33 48 39Cr 13 200 133 260 21 129 386 235 147 660Cu 261 16 12 13 174 37 80 47 <6 104Ni 9 45 31 37 7 33 77 148 160 197Pb <15 <15 <15 <15 <15 <15 <15 <15 <15 <15Sc 17 32 38 35 23 34 32 23 15 32Sr 84 161 396 391 437 552 350 286 262 61V 202 151 280 237 235 269 243 174 114 179Y 17 27 19 15 21 16 14 15 16 11Ce 15.7 64.02 31.9 12.2 36.6 23 16.07 20.23 12.78 34.96Cs 0.641 2.711 0.02 0.022 0.283 0.218 0.3 0.281 0.425 0.34Dy 2.285 5.763 3.3 2.4 3.6 2.8 2.91 3.582 3.745 2.535Er 1.48 2.755 1.98 1.51 2.07 1.6 1.62 1.884 1.882 1.395Eu 0.776 2.396 0.995 0.578 1.171 0.858 0.923 1.269 1.122 0.973Ga 15.19 13.75 15.35 12.77 14.81 15.14 10.89 15.26 16.99 8.57Gd 2.106 7.55 3.32 2.03 3.49 2.65 3.033 3.823 4.164 2.934Hf 1.78 3.3 2.05 1.75 2.46 1.66 1.32 2.06 2.15 1.34Ho 0.486 1.045 0.693 0.526 0.73 0.573 0.576 0.688 0.705 0.488La 7.49 30.44 16.16 5.4 18.88 11.29 7.46 9.6 5.25 17.5Lu 0.212 0.321 0.319 0.254 0.35 0.262 0.222 0.234 0.221 0.198Nb 3.097 15 6 2.14 6 3 3 9.115 6.19 9.548Nd 8.59 34.65 15.39 6.98 17.33 11.29 9.83 12.71 10.65 16.77Pr 2.007 8.275 3.72 1.52 4.18 2.6 2.114 2.742 1.963 4.185Rb 16.97 77.41 0.8 0.9 17.2 7.4 17.21 1.2 9.84 <0.23Sm 2.051 7.862 3.41 1.81 3.73 2.66 2.694 3.586 3.708 3.381Ta 0.175 0.73 0.3 <0.2 0.3 <0.2 0.154 0.551 0.37 0.408Tb 0.341 1.044 0.524 0.351 0.564 0.435 0.466 0.589 0.637 0.427Th 1.552 3.804 2.61 0.87 4.24 2.26 1.032 1.101 0.599 2.239Tm 0.22 0.362 0.314 0.237 0.335 0.253 0.234 0.262 0.256 0.197U 0.901 1.182 0.85 0.66 2.44 1.36 0.605 0.465 0.409 0.604Yb 1.457 2.14 2.014 1.595 2.238 1.638 1.514 1.613 1.56 1.328Zn 191 83 26 47 73 42 55 63 117 59Zr 68 146 84 69 103 71 52 87 86 56Note: All samples are from Universal Transverse Mercator (UTM) zone 10, except for samples from theHesquiat and Dragon areas, which are from UTM zone 9, and the lone Haida Gwaii sample, which is from UTM zone 8. Rock type, age and region codes are described in Table 3.1. Affinity codes include: IAT, island arc tholeiite; L-IAT, light rareearth element enriched island arc tholeiite; CAB, calc-alkaline basalt; E-MORB, enriched mid-ocean ridge basalt; OIB, ocean island basalt.93Table 4.2. (continued)Sample 09TR017 07TR072A 07TR056A 07TR047A 07TR064A 07TR045A 07TR069B 07TR066A 08TR011Rock type BSPL INFL MFFL MFTB MFXT BSFL BSFL BSFL BSPLAge PLD PLD LDEM LDEM LDEM LDEM LDEM LDEM LDEMRegion AL AL AL AL AL AL AL AL ALArc/Non-arc Arc Arc Arc Arc Arc Arc Arc Arc ArcAffinity L-IAT L-IAT IAT IAT IAT L-IAT L-IAT L-IAT IATEasting 382549 380193 376490 373708 376538 373350 379062 376484 379413Northing 5442889 5446010 5454944 5465112 5455276 5464966 5448906 5455305 5446128Al2O3 10.85 16.41 19.06 15.98 14.55 16.79 17.66 19.84 11.51CaO 10.54 9.03 16.03 7.26 11.55 12.77 11.69 7.82 12.43Fe2O3 6.7 9.98 6.98 8.31 8.84 9.78 9.21 7.57 7.68K2O 0.95 0.45 0.68 0.31 0.58 1.01 0.69 0.97 0.23MgO 7.78 8.19 1.22 8.17 7.63 2.61 4.36 2.48 7.64MnO 0.11 0.15 0.15 0.19 0.15 0.19 0.16 0.13 0.14Na2O 1.44 2.31 1.97 3.94 2.08 2.37 3.18 4.43 3.98P2O5 0.19 0.24 0.4 0.26 0.25 0.51 0.39 0.5 0.12SiO2 49.57 49.33 47.24 51.74 51.08 47.3 47.02 53.16 49.35TiO2 0.46 0.79 0.89 0.73 0.72 1.10 0.87 0.99 0.51LOI 11.26 4.15 5.81 4 3.72 6.03 5.62 2.62 7.15Total 99.85 101.03 100.43 100.91 101.14 100.47 100.84 100.5 100.74Ba 248 137 133 216 174 196 276 215 80Co 40 36 20 33 33 18 28 13 41Cr 637 231 14 295 272 22 50 8 643Cu 62 136 49 50 97 6 74 49 118Ni 219 77 8 85 102 8 26 5 181Pb <15 <15 <15 <15 <15 23 <15 <15 <15Sc 27 39 22 35 32 26 26 20 31Sr 142 465 >1400 347 396 739 431 664 102V 165 303 263 245 250 328 270 239 171Y 10 18 18 16 17 26 20 23 11Ce 29.13 27.2 23.1 20.6 24.7 42.1 38.9 31.5 14.16Cs 0.761 0.318 0.53 0.651 0.268 0.974 0.231 0.571 0.074Dy 2.148 3.1 2.8 2.9 3.3 4.6 3.9 3.9 2.192Er 1.235 1.84 1.5 1.6 1.83 2.57 2.03 2.1 1.333Eu 0.761 0.988 1.078 0.927 1.149 1.841 1.503 1.394 0.719Ga 9.16 12.58 20.79 13.42 14.83 21.08 15.67 16.83 8.65Gd 2.444 3.07 3.32 3.01 3.27 5.48 4.39 4.29 2.2Hf 1.05 1.42 1.54 1.22 1.3 2.41 1.89 1.98 0.94Ho 0.426 0.645 0.554 0.6 0.669 0.953 0.757 0.764 0.446La 15.05 13.31 10.7 9.33 13.02 20.55 18.74 14.69 6.52Lu 0.17 0.286 0.215 0.237 0.277 0.372 0.307 0.311 0.198Nb 9.219 10 4.81 2.51 3 7.11 6 5.25 2.307Nd 13.48 13.96 13.74 11.6 13.12 23.43 21.14 18.15 8.22Pr 3.451 3.27 3.02 2.56 3 5.22 4.86 3.98 1.827Rb 12.61 7.6 15 5.7 10.2 24.8 10.4 21 2.24Sm 2.71 3.16 3.27 2.83 3.15 5.6 4.67 4.25 2.076Ta 0.387 0.4 0.3 <0.2 <0.2 0.4 0.3 0.3 0.139Tb 0.348 0.507 0.493 0.481 0.529 0.825 0.668 0.664 0.342Th 1.836 2.02 1.43 1.31 1.3 2.66 2.09 1.81 1.06Tm 0.175 0.282 0.234 0.248 0.28 0.391 0.309 0.319 0.194U 0.508 0.56 0.8 0.48 0.44 1.21 0.84 1.06 0.464Yb 1.134 1.853 1.398 1.562 1.856 2.523 1.996 2.054 1.283Zn 47 67 48 74 58 87 64 68 60Zr 42 53 58 45 49 92 72 75 35Note: All samples are from Universal Transverse Mercator (UTM) zone 10, except for samples from theHesquiat and Dragon areas, which are from UTM zone 9, and the lone Haida Gwaii sample, which is from UTM zone 8. Rock type, age and region codes are described in Table 3.1. Affinity codes include: IAT, island arc tholeiite; L-IAT, light rareearth element enriched island arc tholeiite; CAB, calc-alkaline basalt; E-MORB, enriched mid-ocean ridge basalt; OIB, ocean island basalt.94Table 4.2. (continued)Sample 07TR060B 05M382 05M-384 05M-386a 07TR026B 07TR011B 07TR023 07TR039 09TR091Rock type MFBX BSFL BSFL BSFL MFXT BSBX BSAB BSFB BSFBAge LDEM LDEM LDEM LDEM PM PM PM PM PMRegion AL AL AL AL AL AL AL AL ALArc/Non-arc Arc Arc Arc Arc Arc Arc Non-arc Non-arc Non-arcAffinity IAT IAT IAT L-IAT IAT IAT OIB E-MORB E-MORBEasting 376894 375328 375464 376146 372786 372566 372849 372881 372990Northing 5454957 5460197 5461778 5461004 5463991 5462895 5463776 5464145 5464098Al2O3 13.28 16.72 13.2 17.9 17.96 16.67 12 13.32 15.84CaO 9.62 4.14 14.32 6.6 3.81 6.18 7.61 6.94 8.52Fe2O3 9.17 7.82 9.66 7.34 10.15 10.04 10.66 10.52 12.47K2O 1 2.19 0.15 4.87 1.44 2.03 2.05 1.06 0.17MgO 11.51 4.56 9.2 6.82 7.52 7.45 6.52 7.18 8.89MnO 0.19 0.09 0.19 0.13 0.17 0.16 0.3 0.23 0.21Na2O 2.25 3.44 1.54 2.02 4.19 4.06 1.37 3.09 2.72P2O5 0.16 0.37 0.13 0.45 0.19 0.31 0.36 1.33 0.4SiO2 49.84 55.27 48.32 50.05 49.37 49.79 47 46.81 42.18TiO2 0.63 1.36 0.75 1.00 0.81 1.03 2.15 1.78 2.05LOI 3.5 4.4 3.31 3.67 5.29 3.11 9.47 7.61 6.83Total 101.14 100.36 100.75 100.86 100.9 100.83 99.47 99.86 100.24Ba 266 194 67 >2000 404 607 398 182 69Co 44 21 41 28 31 32 35 39 53Cr 649 18 460 167 167 134 267 215 479Cu 72 90 62 42 458 97 30 35 20Ni 174 20 54 82 61 42 134 83 191Pb <15 <15 20 <15 <15 <15 <15 <15 <15Sc 40 21 44 26 35 39 25 28 34Sr 167 279 804 533 433 444 148 131 94V 240 183 256 211 283 278 99 182 334Y 14 21 14 20 17 18 18 24 30Ce 14.8 26.11 9.4 46.4 18.4 22.5 66.02 39.53 37.87Cs 0.926 0.759 0.053 1.485 1.501 0.658 1.231 0.333 0.111Dy 2.6 4.302 2.3 3.7 3.1 3.4 4.431 5.334 5.86Er 1.52 2.368 1.38 1.83 1.74 1.8 2.017 2.807 3.366Eu 0.837 1.511 0.682 1.687 1.05 1.296 2.224 1.865 1.932Ga 10.95 15.69 12.93 15.27 17.12 14.37 14.71 13.54 18.89Gd 2.62 4.667 2.2 4.38 3.03 3.76 6.026 5.751 6.024Hf 1.05 2.47 1.25 2.54 1.62 1.45 3.64 3.19 3.77Ho 0.558 0.84 0.504 0.703 0.643 0.676 0.788 1.021 1.176La 6.49 11.38 3.83 22.55 7.56 9.47 28.51 14.94 17.71Lu 0.24 0.308 0.202 0.269 0.274 0.276 0.219 0.341 0.431Nb 2 9.04 1.56 14 3 2.21 38.714 17.696 19Nd 9.33 16.34 6.51 22.81 11.75 14.59 33.07 23.62 23Pr 1.99 3.507 1.29 5.47 2.46 3.04 7.95 5.232 5.225Rb 21 39.81 1.8 102.8 32 25.6 36.44 16.28 1.56Sm 2.44 4.387 1.86 4.85 2.97 3.76 6.835 5.584 5.571Ta <0.2 0.55 <0.2 0.7 0.2 0.2 2.286 1.057 1.188Tb 0.424 0.707 0.36 0.654 0.494 0.558 0.801 0.864 0.936Th 0.91 1.361 0.45 2.88 1.23 1.79 2.488 1.17 1.232Tm 0.239 0.329 0.204 0.281 0.281 0.276 0.262 0.391 0.46U 0.29 1.261 0.23 0.89 0.38 0.76 0.568 0.514 0.481Yb 1.506 2.075 1.303 1.793 1.795 1.798 1.553 2.385 2.86Zn 60 81 61 48 69 85 81 84 81Zr 37 105 51 107 56 49 157 150 178Note: All samples are from Universal Transverse Mercator (UTM) zone 10, except for samples from theHesquiat and Dragon areas, which are from UTM zone 9, and the lone Haida Gwaii sample, which is from UTM zone 8. Rock type, age and region codes are described in Table 3.1. Affinity codes include: IAT, island arc tholeiite; L-IAT, light rareearth element enriched island arc tholeiite; CAB, calc-alkaline basalt; E-MORB, enriched mid-ocean ridge basalt; OIB, ocean island basalt.95Table 4.2. (continued)Sample 09TR099 09TR102a 09TR125 09TR126 09TR111 11TRDR007A 11TRDR007B 07TRHS008ARock type BSFB BSPL BSPL BSPL MFTF BSAB BSAB BSFLAge PM PM PM PM PN PN PN PNRegion NA NA NA NA BD DR DR HSArc/Non-arc Non-arc Non-arc Non-arc Non-arc Non-arc Arc Arc ArcAffinity OIB OIB OIB OIB E-MORB CAB CAB IATEasting 415679 415767 416106 416817 290998 695836 695836 684069Northing 5466306 5466234 5466378 5460572 5463372 5526010 5526010 5490506Al2O3 17.55 17.06 18.87 19.99 15.39 17.77 17.56 14.34CaO 5.13 4.07 6.64 6.61 8.13 4.74 4.75 6.53Fe2O3 7.45 10.24 8.24 11.13 11.21 7.34 7.29 12.74K2O 2.73 0.8 4.28 2.11 2.19 1.46 1.55 0.69MgO 3.01 2.26 3.48 4.11 5.65 2.45 2.31 3.92MnO 0.12 0.16 0.11 0.15 0.23 0.11 0.11 0.26Na2O 5.06 7.53 3.54 4.51 3.09 1.48 1.5 3.62P2O5 0.69 1.04 0.6 0.75 0.24 0.28 0.29 0.43SiO2 52.28 53.18 46.93 47.97 51.15 61.84 62.62 54.11TiO2 1.75 2.08 2.36 2.61 1.41 0.83 0.83 1.91LOI 4.32 1.94 4.5 0.37 1.55 1.79 1.69 1.73Total 100.07 100.35 99.55 100.25 100.22 100.1 100.49 100.28Ba 262 143 539 172 704 804 835 496Co 13 14 23 26 35 12 12 33Cr 10 <2 19 51 96 14 19 16Cu <6 <6 <6 28 35 6 6 224Ni 6 2 9 20 25 2 2 11Pb <15 <15 <15 <15 <15 15 15 <15Sc 9 10 16 19 35 18 18 34Sr 410 623 732 585 282 234 234 244V 97 83 184 231 276 115 116 354Y 35 41 22 29 20 22 23 44Ce 97.39 112.07 56.36 73.75 21.01 67.69 56.68 31.4Cs 1.07 0.535 3.685 1.032 0.523 2.967 3.205 0.514Dy 7.588 8.945 5.044 6.492 4.021 3.881 4.007 7.8Er 4.202 4.726 2.611 3.408 2.366 2.19 2.282 4.84Eu 2.867 3.362 2.146 2.593 1.436 1.6831 1.5342 1.777Ga 21.73 17.53 20.91 22.58 17.11 16.14 15.76 16.95Gd 8.481 10.527 5.885 7.529 4.126 4.6 4.523 7.01Hf 8.51 8.53 4.63 6.11 2.22 3.94 3.89 4.51Ho 1.463 1.722 0.967 1.238 0.818 0.7652 0.8089 1.725La 45.58 52.43 26.23 34.84 8.8 31.53 25.41 12.26Lu 0.561 0.585 0.322 0.419 0.315 0.3013 0.3271 0.746Nb 48.632 46.287 22.594 32.043 7 6 6 5.16Nd 45.25 54.91 28.78 37.56 13.97 25.53 22.73 22.47Pr 11.438 13.507 6.979 9.222 3.005 6.445 5.679 4.56Rb 33.81 11.06 60.04 22.54 39.26 37.8 37.22 13.8Sm 9.103 11.154 6.243 7.947 3.762 5.086 4.848 6.26Ta 3.124 3.01 1.511 2.137 0.41 0.36 0.358 0.3Tb 1.251 1.533 0.865 1.107 0.646 0.6369 0.6578 1.196Th 4.71 4.427 2.272 2.824 0.632 6.995 6.686 2.04Tm 0.588 0.644 0.352 0.466 0.332 0.3131 0.3359 0.755U 1.306 1.584 1.331 0.893 0.27 1.911 1.892 1.04Yb 3.74 4.021 2.202 2.881 2.099 2.044 2.184 4.857Zn 86 125 70 85 93 99 95 90Zr 443 435 232 307 98 148 148 165Note: All samples are from Universal Transverse Mercator (UTM) zone 10, except for samples from theHesquiat and Dragon areas, which are from UTM zone 9, and the lone Haida Gwaii sample, which is from UTM zone 8. Rock type, age and region codes are described in Table 3.1. Affinity codes include: IAT, island arc tholeiite; L-IAT, light rareearth element enriched island arc tholeiite; CAB, calc-alkaline basalt; E-MORB, enriched mid-ocean ridge basalt; OIB, ocean island basalt.96Table 4.2. (continued)Sample 07TRHS008B 07TRHS022B07TRHS016C HFB-94-02Rock type MFPR MFPR MFPR DIIVAge PN PN PN PNRegion HS HS HS HGArc/Non-arc Arc Arc Arc ArcAffinity IAT IAT IAT IATEasting 684271 685179 684748Northing 5490711 5491473 5490738Al2O3 16.93 16.48 16.43 17.13CaO 7.1 7.66 11.39 7.89Fe2O3 10.13 8.19 8.33 8.69K2O 1.54 0.71 0.16 1.42MgO 3.21 4.65 5.47 4.03MnO 0.17 0.16 0.16 0.16Na2O 3.45 3.51 1.73 2.8P2O5 0.37 0.17 0.07 0.19SiO2 54.08 57.63 55.51 55.8TiO2 1.33 0.62 0.58 0.82LOI 2.04 1.14 1.32 1.57Total 100.35 100.92 101.16 100.51Ba 503 363 100 456Co 24 22 27 21Cr 17 73 112 51Cu 99 62 69 85Ni 4 23 40 12Pb <15 <15 <15 <15Sc 25 27 35 24Sr 401 409 330 384V 247 216 269 211Y 32 16 11 14Ce 31.1 13.6 5 18.43Cs 1.019 1.236 0.309 1.059Dy 5.7 2.6 1.8 2.969Er 3.29 1.62 1.07 1.76Eu 1.479 0.77 0.488 1.038Ga 16.66 14.28 13.73 16.67Gd 5.48 2.46 1.42 3.069Hf 3.11 1.4 0.52 1.42Ho 1.209 0.554 0.368 0.61La 13.12 5.64 1.96 8.6Lu 0.504 0.262 0.165 0.257Nb 5.28 3 0.88 2.459Nd 20.58 8.72 3.61 11.33Pr 4.32 1.83 0.69 2.513Rb 35.4 18.2 2.6 33.4Sm 5.21 2.32 1.19 2.906Ta 0.3 0.2 <0.2 0.158Tb 0.886 0.413 0.253 0.474Th 1.82 0.99 0.23 1.386Tm 0.503 0.252 0.159 0.258U 0.98 0.81 0.35 0.613Yb 3.242 1.69 1.043 1.699Zn 84 46 58 71Zr 122 50 17 46Note: All samples are from Universal Transverse Mercator (UTM) zone 10, except for samples from theHesquiat and Dragon areas, which are from UTM zone 9, and the lone Haida Gwaii sample, which is from UTM zone 8. Rock type, age and region codes are described in Table 3.1. Affinity codes include: IAT, island arc tholeiite; L-IAT, light rareearth element enriched island arc tholeiite; CAB, calc-alkaline basalt; E-MORB, enriched mid-ocean ridge basalt; OIB, ocean island basalt.97Table 4.3. Neodymium isotope data for PWA igneous rocksSample Region Age Rock type 143Nd/144Nd 147Sm/144Nd εNd(t=360)a εNd(t=317)a εNd(t=300)a εNd(t=200)a εNd(t=180)a TDMb Sm(ppm) Nd(ppm)07TRHS020B HS 180 FSIV 0.512840 0.154904 - - - - 4.9 803.71 2.26 9.1907TRHS018B HS 200 GRIV 0.512865 0.141633 - - - 5.8 - 602.57 3.04 13.5209TR110 BD 300 RHPR 0.512894 0.146872 - - 6.9 - - 585.17 4.25 18.2108TRDR007A DR 300 RHFL 0.512879 0.140921 - - 6.8 - - 568.39 10.50 46.9207TRHS008B HS 300 MFPR 0.512885 0.159463 - - 6.3 - - 744.01 5.21 20.5807TRHS022B HS 300 MFPR 0.512879 0.167587 - - 5.8 - - 895.88 2.32 8.7207TRHS016C HS 300 MFPR 0.512946 0.207639 - - 5.6 - - - 1.19 3.6107TR023 AL 300 BSAB 0.512774 0.130189 - - 5.2 - - 687.75 6.84 33.0707TR011B AL 300 BSBX 0.512790 0.162331 - - 4.3 - - 1068.23 3.76 14.5909TR125 NA 300 BSPL 0.512831 0.136638 - - 6.1 - - 631.42 6.24 28.78HFB-94-02 HG 317 DIIV 0.512876 0.161560 - 6.1 - - - 800.38 2.91 11.3307TR051A AL 360 DCFL 0.512718 0.128585 4.7 - - - - 774.24 5.23 25.6207TR060B AL 360 MFBX 0.512847 0.164731 5.5 - - - - 944.70 2.44 9.3307TR069B AL 360 BSFL 0.512747 0.139149 4.8 - - - - 823.77 4.67 21.1407TR072A AL 360 INFL 0.512757 0.142584 4.8 - - - - 841.91 3.16 13.9605M-386a AL 360 BSFL 0.512710 0.133932 4.3 - - - - 841.53 4.85 22.8105M-386b AL 360 FSLT 0.512757 0.153527 4.3 - - - - 996.59 5.64 23.1405M-366 CW 360 FSLT 0.512720 0.112148 5.5 - - - - 645.39 1.20 6.7405M-393 CW 360 FSXT 0.512768 0.132901 5.5 - - - - 720.34 1.92 9.1005M-394 CW 360 QFPR 0.512721 0.113798 5.4 - - - - 654.56 1.42 7.8605M-369 CW 360 FSLT 0.512727 0.131856 4.7 - - - - 788.29 1.75 8.3605M-356 CW 360 FSLT 0.512814 0.141870 5.9 - - - - 714.60 7.41 32.9009M309* CW 360 QFPR 0.512751 0.126266 5.5 - - - - 695.41 2.20 10.9609M302* CW 360 QFPR 0.512739 0.120518 5.5 - - - - 672.81 1.66 8.6505M352* CW 360 QFPR 0.512774 0.134477 5.5 - - - - 723.61 2.34 10.97Note: All samples are from Universal Transverse Mercator (UTM) zone 10, except for samples from the Hesquiat and Dragon areas, which are from UTM zone 9. Four letter rock type codes consist of a two letter prefix followed by a two letter suffix. Prefix codes include: FS, felsic; RH, rhyolite; DC, dacite; QF, quartz-feldspar; IN, intermediate; BS, basalt; MX, heterolithic; DI, diorite. Suffix codes include: IV, intrusvive; DI, dike; PR, porphyry; VO, volcanic; TF, tuff; XT, crystal tuff; LT, lapilli tuff; TB, tuff breccia; BX, breccia; FB, flow breccia; AB, autobreccia; PL, pillow flow; FL, flow. Age codes include: PLD, Pre-Late Devonian; LDEM, Late Devonian-Early Mississippian; MS, Mississippian; PN, Pennsylvanian; PM, Permian. Region codes include: CW, Cowichan; AL, Alberni; NA, Nanoose; DR, Dragon; BD, Bedingfield; HS, Hesquiat; HG, Haida Gwaii. Affinity codes include: CA, calc-alkaline; TR, transitional; TH, tholeiitic.*Samples are quartz-feldspar porhyries of the Saltspring Intrusions. aCalculated using 143Nd/144Nd of chondrite uniform reservoir (CHUR) = 0.512638 and 147Sm/144Nd = 0.1966 (Hamilton et al., 1983). bCalculated using the values of 143Nd/144Nd = 0.513163 and 147Sm/144Nd = 0.2137 for the DM reservoir (Goldstein et al., 1984) .98Chapter 5: The lead isotopic systematics of Paleozoic Wrangellia hosted sulfide occurrences, Vancouver Island, British Columbia 995.1. INTRODUCTION Volcanogenic massive sulfide (VMS) deposits are globally significant sources of copper, lead, zinc, gold and silver (Franklin et al., 2005). Wrangellia, comprising an assemblage of Late Devonian through Middle Jurassic oceanic arcs and Middle Triassic flood basalts (Samson et al., 1990; Yorath et al., 1999; Greene et al., 2009), is particularly well endowed with VMS deposits and occurrences (Fig. 1.1). The most notable of these is Myra Falls (Nyrstar N.V.), which is currently the largest producing VMS mine in western Canada, with combined production and proven and probable reserves in excess of 40 million tonnes of Zn-Cu-Au-Ag sulfides (Fig. 1.2; Chong, 2005). Felsic volcanic host rocks to VMS mineralization at Myra Falls and in the Cowichan area have been demonstrated by previous workers to be Late Devonian in age (Brandon et al., 1986; Juras, 1987). Geochronological investigations of the timing of VMS mineralization in Wrangellia (Chapter 3) indicates that quartz-feldspar phyric rhyolite which forms the footwall to VMS mineralization at Myra Falls (Marshall Zone) has an age of 361.5 ± 2.5 Ma, and that VMS associated felsic volcanic rocks in the Cowichan area range in age from 366.8 ± 2.4 Ma to 353.1 ± 3.4 Ma. Geological investigations presented in Chapter 3 have also demonstrated that large areas of Vancouver Island previously mapped as Late Devonian bimodal volcanic rocks of the Sicker Group are actually products of a previously unrecognized Late Paleozoic cycle of arc magmatism. These volcanic rocks are associated with several VMS and VMS-like occurrences (Dragon and Bedingfield areas; Fig. 1.2; Freeze, 1986), and range in age from 312.4 ± 3.5 Ma through 291.6 ± 2.2 Ma (Chapter 3). Various workers have demonstrated that VMS deposits commonly form during rifting events, commonly resulting in the formation of sulfide deposits of similar age along the axis of the rift (e.g., Piercey, 2011). Examples of this in the North American Cordillera are found in the Yukon-Tanana terrane, Kootenay terrane, and in strata of the ancient North American Margin (Fig. 1.1), where VMS, sedimentary exhalative (SEDEX) and Mississippi Valley Type (MVT) sulfide deposits of Late Devonian age formed in rifts created in response to the initiation of east dipping (modern coordinates) subduction underneath the ancient North American margin (Nelson et al., 2006). As 100such, understanding the timing of VMS mineralization in a district is critical for facilitating exploration, as it will help the explorationist to identify similarly aged strata that formed in VMS prospective, extensional tectonic environments. Lead isotope studies of syngenetic deposits have proven useful for understanding both the timing of mineralization and the nature of metal sources within different mining districts (e.g., Tosdal et al., 1999; Mortensen et al., 2006). The applicability of Pb isotope studies to addressing these questions in VMS environments arises from the nature of hydrothermal systems that form VMS deposits and the process through which the metals in VMS deposits are derived (Mortensen et al., 2006). In VMS environments, the heat engines for hydrothermal activity are generally interpreted to be shallow, subvolcanic intrusions (e.g., Galley et al., 2007). Heat derived from these intrusions facilitates the circulation of hydrothermal fluids, which comprise a mixture of downwelling seawater and magmatic fluids expelled from a subvolcanic intrusive “heat engine” (e.g., Franklin et al., 2005, and references therein). Circulating hydrothermal fluids in VMS environments can leach metals from surrounding country rock up to depths of 2 km. As such, depending on the tectonic setting of the hydrothermal system, an variety of metal source rocks of varying ages can interact with hydrothermal fluids, including mixtures of felsic and mafic volcanic rocks, reworked and mechanically homogenized volcanic rocks, sedimentary rocks, and if close to a craton, sedimentary rocks sourced from a continental margin (Franklin et al., 2005; Mortensen et al., 2006; Piercey, 2011). The resulting hydrothermal fluid vents to the seafloor and deposits its entrained metal at or near the seawater-seafloor interface in the form of a massive sulfide lens. Due to the interaction of the parent hydrothermal fluid with a variety of different rock types, the Pb contained in the massive sulfide lens will therefore be a mixture of Pb derived from different metal source rocks (Mortensen et al., 2006). Since mantle and upper crustal derived lithologies have different Pb isotopic fingerprints (e.g., Fouquet and Marcoux, 1995), the Pb isotopic signature of a VMS deposit can provide clues as to the nature of metal sources and the tectonic setting of a VMS deposits (e.g., did the VMS mineralization form close to a continental margin or in an oceanic setting?). The utility of Pb isotope studies in understanding the timing and nature of metal sources in a VMS district is important for identifying strata of VMS prospective 101age (i.e., strata similar in age to known, district scale, VMS producing rift events), and for understanding the type(s) of VMS deposit that might exist in the area. For example, in studies of Vancouver Island VMS occurrences, Andrew and Godwin (1989c) and Godwin and Robinson (1996) showed that although variations in Pb isotopic signatures from one lens to another within a specific deposit do exist (e.g., Myra Falls), Pb isotopic compositions of Late Devonian VMS deposits in Wrangellia, in relative terms, form a tight cluster, distinguishing them from the more radiogenic Pb isotopic signatures of non-VMS related sulfide occurrences related to younger magmatism within the same terrane. Similarly, although VMS deposits comprising a single district in the Abitibi Greenstone belt typically have similar lead isotope systematics (i.e., deposits of the Noranda district have similar lead isotopic compositions), the average, lead isotopic signature among separate VMS districts in the region can be variable (i.e., lead isotopic compositions of Noranda district VMS differ from those of the Matagami district) (Franklin et al., 2005). These differences were interpreted to result from variability in basement and/or mantle melt source composition from one district to another (Franklin et al., 2005). Importantly, the similarity in lead isotopic compositions for VMS occurrences within a single district provides the explorationist with a cost and time effective method for distinguishing VMS related sulfide occurrences from younger, epigenetic sulfide occurrences in an area. This is especially important in districts which contain several overprinting episodes of sulfide mineralization as a result of multiple metallogenic events. For example, in a district that contains VMS mineralization that has been overprinted by younger, less prospective sulfide veins related to the emplacement of younger intrusions, how does one distinguish prospective zones of VMS related stockwork sulfide veining from zones of non-VMS related sulfide veining? Lead isotope geochemistry has proven useful in addressing this problem, as younger sulfide veins can have significantly different Pb isotopic compositions than older, VMS related sulfides (e.g., Mortensen et al., 2006; e.g., Mortensen et al., 2008). This paper presents 30 new Pb isotope analyses for sulfide occurrences hosted in Paleozoic Wrangellia strata on Vancouver Island, along with analyses for two samples of “VMS-like” sulfide mineralization (i.e., mineralization showing physical and or mineralogical characteristics similar to VMS deposits) contained within undated, but 102potentially Late Palezoic strata on Haida Gwaii (the Cimadoro sulphide occurrence; Fig. 1.1; MINFILE, 2013). Many of the samples are from VMS-like occurrences, and others are from zones of stockwork-style sulfide mineralization which could be either VMS-related or younger and epigenetic in nature. Several samples in the suite are likely epigenetic in nature, based on cross cutting relationships observed in the field. An extensive Pb isotopic dataset already exists for VMS occurrences in southern Wrangellia (e.g., Godwin et al., 1988; e.g., Andrew and Godwin, 1989c; Godwin and Robinson, 1996). Sample collection during the course of this study was done opportunistically during regional mapping studies, with a focus on collecting samples from recently discovered sulfide occurrences (some of which were discovered during the course of this study). The Pb isotopic signature of the samples are used to test a syngenetic versus epigenetic origin for the specific occurrences, and thereby facilitate VMS exploration in the region. In addition, several of the samples in the dataset are from VMS-like sulfide occurrences that are hosted in newly recognized Late Paleozoic bimodal volcanic rocks in southern Wrangellia. The Pb isotopic signature of these occurrences has not been characterized prior to this study. The Pb isotopic signature of these occurrences is compared to that of their Late Devonian counterparts. A consistent difference in Pb isotopic signature between these two populations would provide VMS explorationists in the district with a time- and cost-effective tool for distinguishing Late Devonian from Late Paleozoic VMS occurrences, a useful contribution towards developing VMS exploration models for the terrane. Previous workers have demonstrated that Wrangellia was an oceanic island arc with a magmatic history involving little or no influence from continental sources (Samson et al., 1990; Yorath et al., 1999). As such, the terrane represents a significant contributor of juvenile, mantle derived crust to the North American continent. The Pb isotopic signature of Wrangellian sulfide occurrences presented in this paper are used to evaluate potential contributions of continental crust to the terrane. 1035.2. ANALYTICAL TECHNIQUES Lead isotope compositions were determined for samples from various sulfide occurrences throughout the PWA. Sample names, locations and descriptions are provided in Table 5.1. Sample locations are shown in figures 5.1, 5.2 and 5.3. Sample preparation, geochemical separations, and isotopic measurements were done at the Pacific Centre for Isotopic Geochemical Research (PCIGR) at the University of British Columbia, using methods as described in Mortensen et al. (2010). Approximately 10 to 50 mg of sulfides were handpicked from samples suspected to contain trace lead. Samples were subsequently decontaminated via leaching in dilute hydrochloric acid and were then dissolved in dilute nitric acid. Galena samples were directly dissolved in hydrochloric acid. Using a phosphoric acid-silia gel emitter, rhenium filaments were loaded with 100 to 250 ng of Pb in chloride form subsequent to ion exchange chemistry. A modified VG54R thermal ionization mass spectrometer in peak-switching mode on a Faraday detector was used to determine isotopic ratios..Measured isotopic ratios were corrected for instrumental mass fractionation of 0.12%/amu, based on replicate analyses of the NBS 981 standard and the absolute values recommended by Thirwall (2000). Errors were numerically propagated throughout all calculations and are reported at the 2σ level (Table 5.2). 5.3. LEAD ISOTOPIC COMPOSITIONS OF PWA SULFIDE OCCURENCES A total of 32 sulfide samples were collected from VMS, VMS-like, and probably epigenetic mineral occurrences hosted in PWA strata on Vancouver Island (Fig. 5.1, 5.2 and 5.3) and were analyzed for their Pb isotopic compositions. A single sample from Haida Gwaii (Cimadoro; Table 5.1; Fig. 1.1) was also analyzed. Lead isotopic compositions for samples analyzed during the course of this study are plotted on uranogenic and thorogenic diagrams in Figures 5.4 and 5.5, respectively and on a 208Pb/206Pb versus 207Pb/206Pb diagram in Figure 5.6. In all figures, several model Pb isotopic growth curves are included for reference, including the average upper crustal growth curve of Stacey and Kramer (1975), and the upper crustal and mantle growth 104curves of Zartman and Doe (1981) . Uranogenic and thorogenic diagrams include fields defining the Pb isotopic composition of several modern day, intra-oceanic island arcs, including the Mariana (Meijer, 1976; McDermott and Hawkesworth, 1991) and Aleutian arcs (Kay et al., 1978) and a field defining the Pb isotopic composition of modern day, Pacific mid-ocean ridge basalt. A list of references for the compiled Pb isotopic composition of modern day, Pacific mid-ocean ridge basalt is available in the Appendix 3. Many of these references were compiled from the GEOROC database (http://georoc.mpchmainz.gwdg.de/georoc/ ) Previous workers have demonstrated that the Pb isotopic signatures of Late Devonian VMS (LDVMS) occurrences in Wrangellia form a relatively tight cluster (e.g., Godwin et al., 1988; Andrew and Godwin, 1989c; Godwin and Robinson, 1996). A field defining these data is also included for reference in uranogenic, thorogenic and 208Pb/206Pb versus 207Pb/206Pb diagrams. Generally speaking, Pb isotopic compositions for PWA sulfide samples define four distinct populations, including samples with compositions that are: 1) less radiogenic than the LDVMS field; 2) similar to the LDVMS field; 3) somewhat more radiogenic than the LDVMS field, and; 4) samples with Pb isotopic compositions significantly more radiogenic than the LDVMS field (Fig. 5.4, 5.5 and 5.6) The majority of PWA samples have Pb isotopic compositions similar to the modern day Mariana and Aleutian arc fields and a significant overlaps exists with the Pb isotopic composition of modern day MORB (Fig. 5.4 and 5.5). Population 1 Sulfide samples with Pb isotopic compositions less radiogenic than the Late Devonian VMS field are exclusively from the Port Alberni area (Fig. 5.1). These include samples from recently discovered, VMS-like showings in the Rift Creek (sample 09TR021) and Horne Lake areas (sample 09TR085), in addition to samples from the Thistle, Regina, and Railway (sample 08TR004A) MINFILE occurrences (Fig. 5.1; MINFILE, 2013). Samples from the Rift Creek area (sample 09TR021; Fig. 5.1) are from a thin lens of massive, fine grained pyrite interbedded with chert and volcano-sedimentary rocks of 105likely pre-Late Devonian or Late Devonian age, assigned to the Duck Lake Formation (Chapter 3). A sample from the Thistle occurrence (Fig. 5.1) comprises massive pyrite collected from the surface dump near historic workings. Cu-Au-Ag mineralization at the past producing Thistle mine comprises disseminated to massive pyrite and chalcopyrite hosted in quartz-sericite-pyrite schists and chloritized mafic volcanic rocks assigned to Late Devonian strata of the McLaughin Ridge Formation, leading previous workers to interpret the mineralization as VMS in nature. However, the presence of skarn-like mineralization in limestones proximal to the Thistle workings causes some uncertainty concerning a VMS origin for the Thistle occurrence. A sample from surface dumps for the nearby Regina workings (MINFILE, 2013) comprises quartz-pyrite-chalcopyrite-galena vein material (Fig. 5.1) In situ mineralization in the Regina workings is reportedly of a similar nature, and is hosted in pre-Late Devonian to Late Devonian mafic volcanic rocks assigned to the Duck Lake Formation (Chapter 3). Sample 08TR004A from the Railway showing is a quartz-pyrite vein hosted in a diabase intrusion assigned to the Upper Triassic Mt. Hall gabbros (Fig. 5.1; MINFILE, 2013). This intrusion, although undated at this locality, cross cuts ribbon cherts of Pennsylvanian or Permian age assigned to the Fourth Lake Formation (Chapter 3). A recently discovered showing in the Horne Lake area (sample 09TR085) comprises small pods of massive pyrite hosted in red ribbon chert of probable Early Permian age and Fourth Lake Formation affinity (Fig. 5.1; Chapter 3). Population 2 Volcanogenic massive sulfide and vein hosted sulfide occurrences with Pb isotopic compositions that generally overlap with those in the LDVMS field occur in PWA strata of various ages throughout Vancouver Island and in strata of probable Late Paleozoic age in Haida Gwaii (Fig. 5.4, 5.5, and 5.6). Sulfide samples that exhibit the most significant overlap with the LDVMS field include those from the Lara (sample 08TR041), China Creek (sample 08TR016), Dragon and Cimadoro VMS occurrences, and sample 08TR095, a vein hosted sulfide occurrence. The Lara sulfide occurrence in the Cowichan area (sample 08TR041; Fig. 5.2) comprises polymetallic VMS 106mineralization hosted in felsic, crystal tuff. Felsic volcanic host rocks to VMS mineralization of the Lara occurrence (MINFILE, 2013) have recently been dated at 358.1 ± 7.7 Ma (U-Pb, zircon; Chapter 3). Several samples of VMS-like, massive, fine grained pyrite mineralization from the China Creek area (Alberni region; Fig. 5.1) have Pb isotopic compositions that fall very close to the LDVMS field, albeit slightly more radiogenic. This sulfide occurrence (sample 08TR016) is interbedded with chert, argillite and mafic volcanosedimentary rocks of potential pre-Late Devonian to Late Devonian age (Chapter 3). The Dragon occurrence, located near the community of Gold River in northern Vancouver Island (Fig. 1.2 and 5.3), comprises polymetallic VMS mineralization hosted in felsic volcanic rocks that have been recently dated at 303.1 ± 0.5 Ma (Chapter 3). The Cimadoro occurrence, located on Moresby Island, Haida Gwaii (Fig. 1.1), comprises polymetallic VMS mineralization hosted in an undated sequence of interbedded argillite, tuffaceous sedimentary rocks, chert and limestone (MINFILE, 2013). Host rocks to the Cimadoro are thought to be Late Paleozoic in age due to their proximity to Early Permian and possibly Carboniferous strata of similar geological character and setting on the west side of Moresby Island (Hesthammer et al., 1991; Indrelid and Hesthammer, 1991). Unlike the other samples that make up this isotopic population, sample 08TR095, which is located in the Alberni area (Fig. 5.1), also yields isotopic compositions similar to the LDVMS deposits but is clearly not derived from VMS-type mineralization. The occurrence comprises pyrite stringers that cross cut a diabase which is mapped as part of the Late Triassic Mount Hall gabbro (Massey et al., 2005). Population 3 Several sulfide samples with similar Pb isotopic compositions plot close to the LDVMS field, but are slightly more radiogenic in nature (Fig. 5.4, 5.5 and 5.6). These samples are from localities in Cowichan, Alberni and Dragon areas (Fig. 1.2). Samples from the Cowichan area include VMS-like mineralization of the Breen Lake and Fortuna occurrences (MINFILE, 2013). Newly discovered, chalcopyrite rich VMS mineralization of the Breen Lake occurrence (sample 08TR001; Fig. 5.2) is hosted in sericite-chlorite 107altered ash tuff. Sample 08TR115 is located to the northwest of the Breen Lake occurrence (Fig. 5.2), and is derived from pyrite veins which cross cut strongly silica-sericite-pyrite altered felsic tuff. A felsic volcanic rock in the vicinity of the Breen Lake occurrence has recently been dated at 353.1 ± 3.4 Ma (Chapter 3). Sample 10TRWR024 is located to the southwest of the Breen Lake area, and comprises massive pyrite pods within strongly sericite-pyrite altered quartz-feldspar phyric rhyolite porphyry proximal to the Fortuna VMS occurrence (Fig. 5.2; MINFILE, 2013). A nearby sample of altered rhyolite porphyry has recently been dated at 355.8 ± 4.4 Ma (Chapter 3). In the Alberni area, two samples from the Horne Lake area also form part of this isotopic population. Sample 07TR052B (Fig. 5.1) is from disseminated to blebby pyrite-chalcopyrite mineralization hosted in variably silica-pyrite altered, heterolithic tuff breccia. To the south, sample 08TR008 (Fig. 5.1) is derived from pyrite stringers hosted in intensely sericitized mafic volcanic rocks. The host rocks for samples 07TR052B and 08TR008 are likely Late Devonian in age, given their proximity to a nearby dacite flow that has been dated at 366.6 ± 0.7 Ma (Chapter 3). A single sample from the Dragon property belonging to this isotopic population (08TRDR057) is taken from pyrite veins which cross cut silica-pyrite altered felsic volcanic rocks. Nearby felsic volcanic rocks have been dated at 303.1 ± 0.5 Ma (Chapter 3). Population 4 The last isotopic population in the dataset comprises those samples with compositions significantly more radiogenic than the Late Devonian VMS field (Fig. 5.4, 5.5 and 5.6). This population includes samples from the Cowichan, Alberni, Gold River and Hesquiat areas (Fig. 1.2). Sample 08TR066B comprises disseminated pyrite extracted from the Lady A iron formation (MINFILE, 2013) in the Cowichan area (Fig. 5.2). This iron formation has not been directly dated, but is believed to be Late Devonian-Early Mississippian in age, based on its position stratigraphically above VMS mineralization of the Lara-Coronation occurrence (Fig. 5.2; MINFILE, 2013). Sample 07TR072, from the Alberni area, comprises pyrite from Au-Ag bearing quartz-carbonate veins of the 900 Zone, which are spatially associated with similar mineralization of 108Debbie occurrence (Fig. 5.1; MINFILE, 2013). Quartz-carbonate veins of the 900 zone cross cut mafic volcanic rocks assigned to the Duck Lake Formation. These host rocks are likely Late Devonian in age, based on their proximity to nearby microfossil and U-Pb (zircon) age localities (Chapter 3). Sample 08TRDR045, from the Dragon property, comprises pyrrhotite from stringer veins which cross-cut granitic rocks of probable Early to Middle Jurassic age (Fig. 5.3; Massey, 2005). Lastly, sample 07TRHS007B comprises pyrrhotite extracted from lenses of fine grained, massive pyrrhotite and chalcopyrite hosted in strongly chlorite-epidote-quartz altered mafic volcanic rocks of the Dorado occurrence (Fig. 1.2). The host volcanic rocks to the Dorado sulfide occurrence have not been directly dated, but are believed to be Late Paleozoic in age based on cross-cutting relationships and lithogeochemical arguments (Chapter 3). Four additional samples with very highly radiogenic lead isotopic compositions relative to population 4 samples are not shown on the uranogenic, thorogenic and 208Pb/206Pb versus 207Pb/206Pb diagrams. Three of the four samples comprising this population are from the Cowichan region, and the fourth sample is from the Dragon property. Sample 08TR113, from near the Fortuna sulfide occurrence in the Cowichan area (Fig. 5.2; MINFILE, 2013), comprises pyrite from pyrite-chalcopyrite stringers which cut quartz-feldspar phyric porphyry dated at 355.8 ± 4.4 Ma (Chapter 3). Rhyolite along the margins of the veins is chlorite altered. These pyrite-chalcopyrite stringers are reminiscent of stockwork style mineralization found in the footwall of VMS deposits (e.g., Franklin et al., 2005). Sample 08TR114 is from the same area, and comprises disseminated pyrite from the core of a magnetite-hematite vein which cuts chlorite altered, quartz-feldspar phyric rhyolite porphyry dated at 355.8 ± 4.4 Ma (Chapter 3). A third sample from the Cowichan area which yields highly radiogenic isotopic compositions is 08TR118, which was from pyrite stringers cutting a diabase sill mapped as Late Triassic Mt. Hall gabbro (Fig. 5.2; Massey, 2005). 5.4. DISCUSSION Lead isotopic compositions for PWA sulfide samples collected during the course of this study define four sample populations which range from somewhat less radiogenic to substantially more radiogenic than the LDVMS field. Here we attempt to explain the 109Pb isotopic compositions of sulfide occurrences sampled in this study through comparison with Pb isotopic compositional fields defined for metallogenic events on Vancouver Island by previous workers. Samples belonging to population 1 (Pb isotopic compositions less radiogenic than the LDVMS field) are restricted to the Alberni area in the northwestern part of the Cowichan uplift. These less radiogenic compositions could be explained if population 1 sulfide occurrences were significantly older than the LDVMS. However, recent microfossil and U-Pb geochronology (Chapter 3) in the Alberni area have not revealed the presence of strata significantly older than Late Devonian in the area, suggesting that this interpretation is not valid. Furthermore, several of the sulfide occurrences in population 1 are hosted by rocks significantly younger than the LDVMS, including sample 09TR085, which comprises small lenses of massive pyrite hosted in ribbon chert of Early Permian age, and sample 08TR004A, which comprises quartz-pyrite veins which crosscut a diabase sill of potential Late Triassic age. Sample 08TR004A is likely epigenetic in nature, based on crosscutting relationships observed in the field. However, 09TR085 might be VMS related, potentially coeval with other Pennsvylvanian-Early Permian VMS occurrences that have recently been recognized elsewhere in the terrane (e.g., Dragon occurrence; MINFILE, 2013). A possible explanation for the less radiogenic signature of 09TR085 involves interaction of its source fluids with more juvenile lithologies in the area. Potential candidates include mid-ocean ridge basalt (MORB) or ocean island basalt, which likely forms basement to the Late Devonian arc assemblage. In some modern settings, MORB basalts have been found to yield lead isotopic compositions less radiogenic than that of modern day, oceanic volcanic arcs (e.g., Andrew and Godwin, 1989c). MORB has previously been documented in the Alberni area by Massey (1995a), in the general vicinity of the Duck Lake type section (Yorath et al., 1999) and samples 09TR021, Regina and Thistle (Fig. 5.1). Lithogeochemical investigations of this area (Chapter 4), however, failed to identify any MORB. The only non-arc basalts of likely pre-Late Devonian to Late Devonian age that have thus far been identified in the PWA are located in the vicinity of the Duck Lake type section (Chapter 4). These samples resemble E-MORB from modern day environments, and may have less radiogenic Pb isotopic compositions than other volcanic rocks in the 110area. If samples 09TR021, Regina and Thistle represent syngenetic sulfide occurrences, their less radiogenic Pb isotopic compositions may result from the interaction of their source hydrothermal fluid with lithologies bearing less radiogenic Pb isotopic compositions. A similar mechanism might explain the more primitive lead isotopic composition of sample 09TR085, which is hosted by strata that is likely Early Permian in age, and is found in an area where abundant Early Permian mafic volcanic rocks resembling E-MORB and OIB have been documented (Fig. 5.1; Chapters 3 and 4). Samples belonging to population 2 and 3 have lead isotopic compositions resembling those of the LDVMS field (see discussion above). Population 2 lead isotopic compositions directly overlap with the LDVMS field, whereas population 3 compositions are slightly more radiogenic in nature. The most straight forward explanation for the similarity in lead isotopic compositions between the two sample populations and the LDVMS field is that both sample populations are Late Devonian in age, and are syngenetic in nature. This is most likely the case for samples 08TR041 and 10TRWR024, which are from the Cowichan area, and are spatially associated with known, Late Devonian VMS showings, including the Lara and Fortuna occurrences, respectively (Fig. 5.2). Although VMS occurrences are not as common in the Alberni area as they are in the eastern Cowichan uplift, a Late Devonian, syngenetic origin is also likely the case for Alberni-area samples 08TR016, 08TR008, and 07TR052B (Fig. 5.1), which display characteristics in the field suggestive of VMS-style mineralization (see discussion above). However, a Late Devonian, syngenetic origin is not possible for VMS-like sulfide samples from the Dragon or Cimadoro showings (Fig. 1.1 and 5.3). These occurrences, several of which have lead isotopic compositions which directly overlap the LDVMS field, display characteristics in the field suggestive of a VMS origin. Sulfide occurrences from the Dragon property are hosted by altered and sulfide mineralized volcanic rocks ranging in age from 311.1 Ma through 291.6 Ma (Chapter 3). Similarly, a Late Paleozoic age is suspected for host rocks to the Cimadoro occurrence based on regional geological correlations (see discussion above). This indicates that the Dragon and Cimadoro sulfide occurrences are significantly younger than the samples comprising the LDVMS field. In order to explain the similarities in lead isotopic signature, a Dragon and Cimadoro metal source with Pb isotopic compositions less 111radiogenic than that for the LDVMS is required. Lithogeochemical and isotopic studies of the PWA (Chapter 4) indicate that younger rocks in the arc were derived from increasingly primitive, more mantle rich source melts, with potentially less radiogenic Pb isotopic compositions. It is possible that Late Paleozoic host rocks to the Dragon and Cimadoro sulfide occurrences have less radiogenic Pb isotopic compositions than their LDVMS counterparts, and that this difference in original Pb isotopic compositions is responsible for their overlap with the LDVMS, despite an approximately 60 million year difference in time of formation. Population 4 comprises those samples with Pb isotopic compositions significantly greater than the LDVMS field. This population includes samples from all of the study areas. The simplest explanation for the more radiogenic Pb isotopic compositions of population 4 is that samples comprising the group are significantly younger than the LDVMS. While this could hold true for much of the dataset, field relationships and style of mineralization suggest that this may not be the case for all of the samples in the group. For instance, samples 08TR001 and 08TR015, from the Cowichan area, have the least radiogenic Pb isotopic compositions of population 4, and are from sulfide showings proximal to the Jane VMS occurrence (Fig. 5.2; MINFILE, 2013). Both of the samples are from occurrences which strongly resemble VMS-related sulfide mineralization in the field. A felsic volcanic rock in the vicinity of both samples has been dated at 353.1 ± 3.4 Ma (Chapter 3), making host rocks to the sulfide occurrences age equivalent to other VMS deposits in the Cowichan area. It is possible that the more radiogenic Pb isotopic compositions of these samples is due to the potential presence of localized, continent derived sedimentary rocks interbedded with volcanic rocks of the Breen Lake area. Hydrothermal fluids responsible for the formation of 08TR001 and 08TR015 may have leached highly radiogenic Pb from these continent derived sediments, resulting in their more radiogenic signatures relative to the LDVMS field. Two other samples from the Cowichan uplift are part of population 4, including sample 08TR066B and 07TR072. Sample 08TR066B was taken from pyrite stringers which cut magnetite iron formation of the Lady A occurrence (Fig. 5.2; MINFILE, 2013). Iron formation of the Lady A occurrence is believed to be Late Devonian-Early Mississippian in age, and is interpreted to represent oxide facies, exhalative 112mineralization related to underlying VMS mineralization in the Cowichan district. Iron formations of the Cowichan area are regionally extensive, and are believed to be similar to iron formations which overlie VMS mineralization in other districts (e.g., the Bathurst district; Galley et al., 2007). It was originally thought that pyrite stringers cross cutting the Lady A iron formation may have been roughly syngenetic in nature. However, the relatively radiogenic Pb isotopic composition of 08TR066B suggests that this is not the case, and that the pyrite stringers are likely derived from a younger, more radiogenic source. A large intrusion of Middle to Late Jurassic granodiorite is present to the north of the Lady A iron formation, and a probable apophysis of this intrusion is present just to the west of the Lady A (Fig. 5.2). It is possible that pyrite stringers cross-cutting the Lady A iron formation are related to the emplacement of these intrusions. Sample 07TR072, from the Alberni area, comprises pyrite from Au-Ag bearing quartz-carbonate veins of the 900 Zone. It is spatially associated with similar mineralization of the Debbie occurrence and is likely epigenetic in nature (Fig. 5.1; MINFILE, 2013). Au-Ag bearing quartz-carbonate veins of the Debbie area are spatially associated with the Mineral Creek fault system, a large, steeply dipping, north striking structure that cross cuts Late Devonian through Cretaceous strata in the Alberni area (Massey, 2005). Intrusions of Jurassic and Eocene age are located proximal to the Mineral Creek fault system, in the vicinity of the Debbie Au-Ag vein occurrences (Fig. 5.1; Massey, 2005). Fluids expelled during the emplacement of these intrusions, especially those of the Eocene suite (e.g., Andrew and Godwin, 1989b) would be enriched in radiogenic Pb, and may be responsible for the relatively radiogenic Pb isotopic composition of 07TR072. Two samples from the Dragon property are included in population 4. These include a sample of massive sulfide from the Dragon occurrence (MINFILE, 2013) and 08TRDR045, a sample from pyrrhotite stringers which cross cut granitic rock of probable Early to Middle Jurassic age. Most samples of massive sulfide mineralization from the Dragon occurrence have Pb isotopic compositions which overlap those of the LDVMS (see discussion above). However, undated granodiorite intrusions assigned to the Early to Middle Jurassic Island plutonic suite are abundant on the property, and are mapped just to the west of massive sulfide occurrences (Fig. 5.3). These intrusions might have Pb 113isotopic compositions more radiogenic than those of the LDVMS field. It is possible that sulfide veins related to the emplacement of these intrusions cross cut massive sulfide mineralization of the Dragon occurrence, and that some of this material was inadvertently sampled during processing for Pb isotopic analysis, resulting in the more radiogenic Pb isotopic composition of the sample. Sample 08TRDR045 is derived from sulfide veins that cross cut granodioritic intrusive rock, and its more radiogenic Pb isotopic composition is also likely related to the emplacement of nearby Early to Middle Jurassic or younger intrusions. The final sample in population 4 is 07TRHS004B, which is from massive pyrrhotite-chalcopyrite mineralization in the Hesquiat area (Dorado property; Fig. 1.2). This occurrence is believed to be hosted in Late Paleozoic strata that are potentially correlative to those that host the Dragon occurrence. The Dorado was originally suspected to be VMS related, as it is hosted near the contact between strongly silica-epidote altered basalt flows and overlying carbonate rocks (Ruks et al., 2010). However, the highly radiogenic Pb isotopic composition of the sample suggests that this is not the case. Geochronological investigations of the area (Chapter 3.) have shown that highly altered felsic dykes of Early Jurassic age occur in the general vicinity of the Dorado occurrence. In addition, strongly silica-sulfide altered diorite porphyry of unknown age is spatially related to the Dorado sulfide occurrence, and hosts similar mineralization within the intrusion. It is possible that massive pyrrhotite-chalcopyrite mineralization of the Dorado occurrence is genetically related to the emplacement of this diorite porphyry. Economic implications The economically most significant style of mineralization hosted by PWA strata on Vancouver Island is VMS, and a significant amount of exploration dollars have been spent by numerous operators in exploring for Myra Falls-like VMS deposits on Vancouver Island. As such, the primary focus of this study was to utilize the Pb isotopic compositions of PWA hosted sulfide occurrences (many of them recently discovered) in order to understand whether they were the result of syngenetic (i.e, VMS related) or 114epigenetic processes, and on that basis, characterize their prospectivity for Myra Falls-like VMS mineralization. Aside from the Buttle Lake uplift, which hosts the Myra Falls VMS deposit, Late Devonian VMS occurrences are most abundant in the Cowichan uplift, particularly in the Cowichan area, where they are spatially associated with Late Devonian-Early Mississippian bimodal volcanic rocks of the McLaughlin Ridge Formation (Brandon et al., 1986; Massey, 1995b) Most VMS-like sulfide occurrences from the Cowichan area analyzed during the course of this study have Pb isotopic compositions that plot within, or very close to, the Pb isotopic compositions defining the LDVMS field. However, two occurrences in the Breen Lake area (Fig. 5.2) display characteristics in the field strongly suggestive of a VMS origin (Ruks et al., 2010), but have Pb isotopic compositions more radiogenic than those of the LDVMS field. It remains unclear whether the Breen Lake area occurrences are indeed VMS in nature, suggesting that the field defining LDVMS Pb isotopic compositions must be expanded to encompass these occurrences, or are actually younger and epigenetic in nature. Volcanogenic massive sulfide occurrences are present in the Alberni area, although they appear to be less common in the Cowichan area. This coincides with a relative paucity of Late Devonian-Early Mississippian felsic volcanic rock in the Alberni area (Massey, 1995a), which might indicate that less rifting has occurred in that area, and it would therefore be less conducive to the development of VMS mineralization. However, a group of sulfide occurrences in the Alberni area displays field characteristics that are suggestive of a LDVMS origin, but yield Pb isotopic compositions significantly less radiogenic than the LDVMS field (see discussion above). These occurrences are mostly concentrated in the southern part of the study area (09TR021, Thistle and Regina sample areas; Fig. 5.1), where local areas of non-arc mafic volcanic rocks have been documented (Chapter 4), and some mafic volcanic rocks present may be older than Late Devonian (Chapter 3). This suggests that the LDVMS Pb isotopic composition field, which is defined based on the isotopic composition of VMS mineralization in more proximal, felsic volcanic dominated settings, is not entirely applicable for evaluating all VMS occurrences in the PWA. However, the China Creek VMS occurrence (08TR016) is also present in the same area, and has Pb isotopic compositions which overlap those of 115the LDVMS. Sulfide occurrences in the northern part of the Alberni study area (Horne Lake area; Fig. 5.1) display field characteristics suggestive of a VMS affinity, but have Pb isotopic compositions slightly more radiogenic than the main LDVMS field. Several of these occurrences (07TR051B and 08TR008) are proximal to a recently identified, Late Devonian felsic volcanic centre (Chapter 3), which contains numerous characteristics suggestive of VMS mineralization, including hydrothermal alteration, and jasper-magnetite iron formations similar to those that overlie VMS mineralization in the Cowichan area and other VMS districts. Collectively, this suggests that the northern part of the Alberni study area is prospective for felsic volcanic rock associated LDVMS mineralization similar to that found in the Cowichan area and Buttle Lake uplifts. Significant sulfide mineralization that appears to be epigenetic in character is present in the Alberni area, particularly in the vicinity of the Mineral Creek fault (e.g., sample 07TR072; Fig. 5.1). However, VMS-like occurrences are also present in the general vicinity of this structure (see discussion above). If 07TR072 is reflective of other sulfide occurrences associated with the Mineral Creek fault, it suggests that Pb isotopes can provide a useful tool for distinguishing epigenetic sulfide occurrences related to the Mineral Creek fault from VMS-like occurrences in the Alberni area. Volcanogenic massive sulfide occurrences of the Dragon and Cimadoro areas have Pb isotopic compositions that overlap with those of the LDVMS. This is especially interesting given that host rocks for the Dragon VMS occurrences are roughly 60 million years younger than the LDVMS. Host rocks to the Cimadoro occurrence (Haida Gwaii; Fig. 1.1) are undated, but are suspected to be similar in age to those of the Dragon based on the presence of Late Paleozoic strata in the region (Hesthammer et al., 1991; Indrelid and Hesthammer, 1991). The overlapping range of Dragon-Cimadoro and LDVMS Pb isotopic compositions indicates that Pb isotopes do not always provide a useful tool for differentiating between the mainly Late Devonian and the Late Paleozoic sulfide occurrences, rendering Pb isotopes less useful for understanding the timing of VMS mineralization regjonally within the PWA. This overlap in Pb isotopic compositions suggests that VMS occurrences of the Dragon and Cimadoro are derived from fluids that interacted with volcanic rocks with a more primitive Pb isotopic signature than those associated with the LDVMS (see discussion above). Results of lithogeochemical studies 116described in Chapter 4 demonstrated that younger rocks in the PWA were derived from progressively more primitive melt sources, with lithogeochemical and Nd isotopic arguments suggesting that host rocks to the Dragon and Bedingfield VMS occurrences are the most primitive, highest temperature felsic volcanic rocks identified thus far in the PWA on Vancouver Island. The more primitive Pb isotopic compositions of the Dragon-Cimadoro VMS occurrences also suggest that Late Paleozoic volcanic rocks in the PWA may contain a larger mantle component than their Late Devonian-Early Mississippian counterparts. Various workers have shown that felsic volcanic rocks derived from primitive sources are typically high temperature in nature, and are indicative of zones of rifting and mantle upwelling (Lesher et al., 1986; Barrie, 1995; Piercey, 2011). These high temperature magmas create large, effective hydrothermal cells, and can result in the formation of large VMS deposits. The identification of primitive, high temperature felsic volcanic rocks in the Dragon and Bedingfield areas suggest that Late Paleozoic strata of the PWA are some of the most prospective strata in southern Wrangellia for VMS mineralization. Previous exploration for VMS mineralization in the PWA (Vancouver Island) has concentrated on Late Devonian-Early Mississippian strata, with newly recognized Late Paleozoic bimodal volcanic rocks and associated VMS mineralization having seen less attention. Massive sulfide mineralization of the Hesquiat area (Dorado property; Fig. 1.2) was previously interpreted to be VMS in nature. However, its significantly more radiogenic Pb isotopic composition relative to the LDVMS and is proximity to Jurassic (or younger) intrusions suggests it should be re-evaluated as a potential target for porphyry copper or skarn related mineralization. Crustal contamination A fundamental question surrounding the PWA regards its paleogeography, and whether or not the terrane originated proximal to a continental landmass. Results of isotopic studies of LDVMS and host rocks in the PWA by previous workers (Andrew and Godwin, 1989c; Samson et al., 1990; Godwin and Robinson, 1996) suggested at least some amount of contamination of the PWA by continental crust, likely through the 117process of continent derived sediments being subducted and incorporated into PWA magmas. Lithogeochemical and Nd isotopic studies of the PWA (Chapter 4) reached a similar conclusion, strengthening the argument that the PWA must have formed within sediment transport distance of a continental margin during its lifetime. Lead isotopic compositions of PWA sulfide occurrences investigated during this study generally fall between growth curves for the mantle and upper crustal model growth curves of Zartman and Doe (1981) (Fig. 5.4, 5.5 and 5.6), suggesting that they comprise mixtures of Pb derived from mantle and upper crustal sources. However, the majority of sulfide samples in this study also have Pb isotopic compositions which overlap those of modern day intraoceanic volcanic arcs and Pacific MORB (Fig. 5.4, 5.5 and 5.6 and references therein), indicating that contamination by continental crust is not necessary to explain their Pb isotopic compositions. A similar mechanism was proposed by Samson et al. (1990) in order to explain the Pb isotopic composition of LDVMS reported by Andrew and Godwin (1989c). 5.5. SUMMARY The Pb isotopic composition of Late Devonian VMS (LDVMS) occurrences on Vancouver Island are relatively uniform (e.g., Godwin et al., 1988; e.g., Andrew and Godwin, 1989c; Godwin and Robinson, 1996), a phenomenon observed in other VMS districts worldwide (e.g., Franklin et al., 2005, and references therein). The Pb isotopic compositions of 30 sulfide occurrences from exposures of Paleozoic rocks on Vancouver Island have been measured, revealing the presence of four isotopic populations: 1) those samples with Pb isotopic compositions less radiogenic than those defining the LDVMS; 2) those samples with Pb isotopic compositions similar to those defining the LDVMS; 3) those samples with Pb isotopic compositions slightly more radiogenic than the LDVMS, and; 4) those samples with Pb isotopic compositions significantly more radiogenic than those defining the LDVMS. Volcanogenic massive sulfide-like occurrences with Pb isotopic compositions less radiogenic than those of the LDVMS (population 1) are restricted to the southern part of the Alberni study area, and include samples from the Rift Creek area, and the Thistle and 118Regina occurrences. Strata appreciably older than Late Devonian have not yet been identified in this area; the less radiogenic Pb isotopic compositions of these occurrences are attributed to metal derivation from more primitive MORB or OIB-like source rocks stratigraphically below the occurrences. Volcanogenic massive sulfide-like sulfide occurrences with Pb isotopic compositions similar to those of the LDVMS are found in the Cowichan, Alberni, Dragon and Cimadoro (Haida Gwaii) areas. These sulfide occurrences in the Cowichan area are proximal to known, felsic volcanic associated VMS occurrences of Late Devonian-Early Mississippian age, and include those from the Fortuna and Lara occurrences. Two sulfide occurrences in the Breen Lake area exhibit characteristics in the field strongly suggestive of a Late Devonian-Early Mississippian VMS origin, but yield Pb isotopic compositions that are notably more radiogenic than those of the LDVMS field. This suggests that the field defining the Pb isotopic composition of LDVMS on Vancouver Island should be expanded to include those occurrences with more radiogenic Pb isotopic compositions. An alternative interpretation is that the Breen Lake occurrences are not VMS-related, and that more work is required to understand their age and origin.. Several VMS-like occurrences with Pb isotopic signatures overlapping those of the LDVMS are present in the Alberni area. Most notable are those in the northern part of the Alberni study area (samples 07TR052B and 08TR008). These samples are spatially related to a Late Devonian felsic volcanic centre, altered and sulfide mineralized volcanic rocks, and jasper-magnetite iron formations similar to those which overlie VMS deposits in the Cowichan area and other, better known VMS districts. Newly discovered VMS-like mineralization with Pb isotopic compositions overlapping those of the LDVMS is also present in the China Creek region of the Alberni study area (sample 08TR016). Lead isotopic compositions of VMS-like mineralization of the Dragon and Cimadoro occurrences also overlap those of the LDVMS field, despite being much younger in age. Felsic volcanic host rocks to the Dragon VMS occurrence range in age from 311.1 Ma through 291.6 Ma (Chapter 3), and host rocks to the Cimadoro (Haida Gwaii) are interpreted to be similar in age, based on the presence of Late Paleozoic strata in the area (Hesthammer et al., 1991; Indrelid and Hesthammer, 1991). The anomalous 119Pb isotopic compositions of Dragon and Cimadoro VMS occurrences is interpreted to be the result of metal derivation from more primitive source rocks with less radiogenic Pb isotopic compositions. Volcanic rocks containing a greater mantle component than those associated with the LDVMS have been documented in the Dragon and Bedingfield areas as a result of lithogeochemical and Nd isotopic studies (Chapters 3 and 4). It is possible that the less radiogenic Pb isotopic compositions of Dragon and Cimadoro VMS occurrences are a result of the interaction of hydrothermal fluids with these more primitive source rocks in Late Paleozoic time. Sulfide occurrences with Pb isotopic compositions significantly more radiogenic than those of the LDVMS have been found in all uplifts of Paleozoic rocks on Vancouver Island. These occurrences are likely the result of hydrothermal processes associated with the emplacement of intrusions of Mesozoic or Tertiary age (e.g., Andrew and Godwin, 1989a1989b). Some of these sulfide occurrences are associated with mineral deposits that have undergone significant exploration. The Debbie occurrence in the Alberni area is one of these. Here, Au-Ag bearing quartz-carbonate veins are spatially related to the Mineral Creek fault, which cuts Paleozoic through Cretaceous strata in the area. Tertiary intrusions of the Mt. Washington Plutonic suite occur in the vicinity of this structure. The radiogenic Pb isotopic compositions of the Debbie occurrence (sample 07TR072) may be related to fluids derived from these intrusions during their emplacement. Massive pyrrhotite-chalcopyrite mineralization of the Dorado occurrence (sample 07TRHS004B), Hesquiat area, was previously suspected of being VMS related, as it is hosted by strongly altered and sulfide mineralized mafic volcanic rocks of suspected Late Paleozoic age (Chapter 3). However, the relatively radiogenic Pb isotopic composition of the occurrence suggests it is related to fluids derived from the emplacement of younger, altered and sulfide mineralized porphyritic intrusions that are found in the general area. As such, sulfide mineralization of the Dorado occurrence should be re-evaluated as a target for intrusion related mineralization. Although the Pb isotopic signatures of PWA hosted sulfide occurrences plot in between growth curves for the mantle and upper crust (Zartman and Doe, 1981), suggesting they are the product of a degree of crustal contamination, they also broadly overlap with the Pb isotopic compositions of modern day, intraoceanic volcanic arcs and 120 Pacific MORB. As such, significant contamination through the subduction of continental derived sediment need not be invoked to explain their Pb isotopic signatures. 121122123124125126127Table 5.1. Descriptions and locations of PWA hosted sulfide occurrences sampled for lead isotopic studiesSample Mineral1 Occurrence Host Rock Host Rock UTM Easting Northing Age Zone (mE) (mE)08TR041 sl VMS - Lara occurrence FSXT LDEM 10 433490 541484108TR113 py VMS stockwork pyrite veins - Fortuna occurrence RHPR LDEM 10 445369 541332208TR114 py VMS stockwork pyrite-magnetite veins - Fortuna occurrence RHPR LDEM 10 445394 541328310TRWR024 py VMS stockwork semi-massive pyrite veins - Fortuna occurrence RHPR LDEM 10 444735 541338708TR001 py VMS - Breen Lake occurrence FSTF LDEM 10 449960 541209508TR115 py VMS stockwork pyrite veins - Breen Lake FSTF LDEM 10 448667 541290508TR066B py Massive magnetite-pyrite - Lady A occurrence FEMS LDEM? 10 430206 541943408TR118 py Vein - pyrite - Breen Lake area DBIV TK 10 450869 541225208TR016 py VMS - China creek occurrence MFVO PLD-LDEM? 10 380187 544650109TR021 py VMS - Rift Creek occurrence MFVS PLD-LDEM? 10 382598 543478107TR052B py Disseminated pyrite - Alberni area DCBX LDEM 10 375323 5460373Thistle py VMS stockwork pyrite veins - Thistle occurrence MFVO LDEM? 10 380527 544057308TR008 py VMS stockwork pyrite veins - Alberni MFVO LDEM 10 376246 545888107TR072 py Vein - pyrite in quartz-carbonate veins - Debbie occurrence MFTF LDEM 10 378362 5447624Regina gl VMS stockwork pyrite-galena-chalcopyrite vein - Regina occurrence MFVO PLD-LDEM? 10 378572 544574408TR095 py Vein - pyrite - Alberni area DBIV TK? 10 378969 544435508TR004A py Vein - pyrite - Railway occurrence DBIV TK? 10 374015 545892209TR085 py VMS (?) - lenses of semi-massive pyrite - Alberni area SDCH PM 10 372565 5466128Dragon cpy or gl VMS - Dragon FSVO PN-PM 9 692436 552792608TRDR057 py Vein - pyrite - Dragon FSVO PN-PM 9 691843 552559508TRDR045 po Vein - pyrrhotite - Dragon GRIV JK? 9 691559 552579508TRDR059 po Vein - pyrrhotite - Dragon FSTF PN-PM 9 690798 552487707TRHS004b po Massive sulphide - Hesquiat MFVO PN-PM? 9 685044 5490977Cimadoro py VMS - Cimadoro occurrence MFVS PN-PM? 8 684185 58848591Minerals: sl = sphalerite; py = pyrite; gl = galena; cp = chalcopyrite; po = pyrrhotiteFour letter rock type codes consist of a two letter prefix followed by a two letter suffix. Prefix codes include: SD, sedimentary; FS, felsic; GR, granite; RH, rhyolite;DC, dacite; QF, quartz-feldspar; IN, intermediate; BS, basalt; MX, heterolithic; DI, diorite; DB, diabase; MF, mafic; FE, iron exhalite. Suffix codes include: IV, intrusive; DI, dike; PR, porphyry; VS, volcanosedimentary; CH, chert; VO, volcanic; TF, tuff; XT, crystal tuff; LT, lapilli tuff;TB, tuff breccia; BX, breccia; FB, flow breccia AB, autobreccia; PL, pillow flow; FL, flow; MS, massive. Age codes include: PLD, Pre-Late Devonian; LDEM, Late Devonian-Early Mississippian; MS, Mississippian; PN, Pennsylvanian; PM, Permian; TK, Triassic; JK, Jurassic.128Table 5.2. Lead isotopic compositions of sulfides from PWA hosted strataSample Mineral1 206Pb/204Pb Error (%)2 207Pb/204Pb Error (%)2 208Pb/204Pb Error (%)2 207Pb/206Pb Error (%)2 208Pb/206Pb Error (%)208TR041 sl 18.5141 0.02 15.5375 0.02 38.0686 0.02 0.8392 0.010 2.0562 0.01108TR113 py 20.3146 0.02 15.6738 0.02 38.8923 0.03 0.7716 0.007 1.9145 0.00808TR114 py 19.6332 0.08 15.8040 0.08 39.0113 0.08 0.8050 0.010 1.9870 0.00910TRWR024 py 18.6236 0.07 15.5778 0.07 38.2603 0.08 0.8365 0.014 2.0544 0.01408TR001 py 18.6618 0.03 15.6144 0.02 38.3318 0.03 0.8367 0.010 2.0540 0.01308TR001 py 18.6857 0.09 15.6074 0.06 38.2361 0.10 0.8353 0.074 2.0463 0.03908TR115 py 18.7083 0.05 15.6242 0.05 38.3718 0.05 0.835 0.006 2.051 0.00308TR066B py 18.8568 0.02 15.6215 0.02 38.4289 0.02 0.828 0.010 2.038 0.01508TR118 py 19.4247 0.04 16.0260 0.04 39.4744 0.05 0.8250 0.014 2.0322 0.01208TR016 py 18.6025 0.02 15.5877 0.02 38.2577 0.03 0.8379 0.008 2.0566 0.00608TR016 py 18.5963 0.02 15.5715 0.01 38.2346 0.02 0.8373 0.009 2.0560 0.00809TR021 py 18.3576 0.03 15.5544 0.02 38.0709 0.03 0.8473 0.015 2.0738 0.01009TR021 py 18.3766 0.04 15.5822 0.04 38.1777 0.04 0.8479 0.005 2.0775 0.00707TR052B py 18.6036 0.04 15.5430 0.03 38.2240 0.05 0.8355 0.027 2.0547 0.013Thistle py 18.0510 0.04 15.5310 0.04 37.6619 0.04 0.8604 0.005 2.0864 0.005Thistle py 18.0118 0.03 15.4969 0.03 37.5543 0.03 0.8604 0.002 2.0850 0.00408TR008 py 18.5846 0.09 15.5348 0.09 38.2703 0.09 0.8359 0.014 2.0592 0.01207TR072 py 18.9214 0.04 15.6391 0.03 38.4336 0.05 0.8265 0.033 2.0312 0.023Regina gl 18.3079 0.01 15.5582 0.01 38.0391 0.01 0.8498 0.004 2.0777 0.00408TR095 py 18.4874 0.03 15.5504 0.02 38.1088 0.03 0.8411 0.013 2.0613 0.01808TR004A py 17.9198 0.02 15.5165 0.02 37.6298 0.02 0.866 0.005 2.100 0.00309TR085 py 18.3834 0.07 15.4746 0.07 37.8656 0.08 0.8418 0.008 2.0598 0.010Dragon cp 18.5462 0.01 15.5716 0.01 38.1861 0.01 0.840 0.004 2.059 0.004Dragon cp 18.7367 0.05 15.5871 0.05 38.2480 0.05 0.832 0.012 2.041 0.010Dragon gl 18.5355 0.01 15.5626 0.01 38.1522 0.01 0.8396 0.004 2.0583 0.005Dragon gl 18.5346 0.02 15.5635 0.02 38.1817 0.03 0.8397 0.009 2.0600 0.01508TRDR057 py 18.6112 0.04 15.5573 0.04 38.2111 0.04 0.836 0.011 2.053 0.00808TRDR045 po 19.0213 0.02 15.6162 0.02 38.5550 0.02 0.821 0.002 2.027 0.00308TRDR059 po 19.5269 0.01 15.6259 0.01 38.7722 0.01 0.800 0.003 1.986 0.00407TRHS004b po 19.0341 0.09 15.6726 0.09 38.6229 0.10 0.8234 0.020 2.0291 0.015Cimadoro py 18.5580 0.06 15.5569 0.05 38.2656 0.08 0.838 0.036 2.062 0.046Cimadoro py 18.5637 0.07 15.6111 0.04 38.3023 0.09 0.841 0.054 2.063 0.0571Minerals: sl = sphalerite; py = pyrite; gl = galena; cp = chalcopyrite; po = pyrrhotite2Errors given at the 2σ level129Chapter 6: The tectonic evolution of the southern Paleozoic Wrangellia arc and its prospectivity for hosting volcanogenic massive sulphide (VMS) deposits 1306.1. INTRODUCTION Chronostratigraphic, lithogeochemical and isotopic studies have been used to understand the tectonic evolution of terranes comprising the North American Cordillera (e.g., Samson et al., 1990; Mortensen, 1992; Ghosh and Lambert, 1995; Piercey et al., 2006a) . These studies provides insight into the convergent margin systems and the evolution of continents over time (Colpron et al., 2006). These studies also provide insight into the potential for terranes to host mineral deposits (e.g., Piercey, 2010). Chapters 3, 4 and 5 have provided a chronostratigraphic, lithogeochemical and isotopic framework upon which the evolution of Paleozoic Wrangellia, its relative contribution to North American crustal growth and its prospectivity for hosting VMS deposits can be evaluated. One of the most fundamental questions concerning the PWA is the nature of its basement and its paleogeography throughout the Paleozoic. Previous workers have suggested that the PWA comprises an oceanic island arc that was located at high latitudes offshore of northern Pangaea during Early Permian time (Yorath et al., 1999; Belasky et al., 2002; Katvala and Henderson, 2002). However, the paleogeographic position of the PWA during its earliest, Late Devonian history is unknown. Furthermore, in contrast to the pericratonic terranes of the northern Cordillera, the position of the PWA relative to continental landmasses, particularly Laurentia, during the course of its history is also unknown. Previous workers have suggested that the PWA may have existed close to a continent in Late Devonian time, based on the relatively radiogenic Pb isotopic signatures of Late Devonian sulphides of the Myra Falls camp (e.g., Godwin and Robinson, 1996). Studies of the Late Devonian-Early Mississippian SSI have shown that some of these intrusions have peraluminous compositions (Sluggett, 2003; this study), suggesting the possible presence of evolved, continental-like crust at least locally underlying the PWA. Identifying the nature of the crust upon which the PWA was built may provide important clues regarding the paleogeographic position of the PWA through the course of its history. It may also help determine which lithogeochemical toolsets can be used to evaluate the prospectivity of volcanic rocks in the terrane for hosting VMS deposits. For instance, the prospectivity of felsic volcanic rocks to host VMS mineralization has 131commonly been evaluated using the FI through FIII rhyolite classification of Lesher et al. (1986), later modified by Hart et al., (2004). This classification scheme was developed using rhyolites from VMS associated and VMS barren Archean stata developed on basaltic substrate. In this scheme, most VMS deposits are spatially associated with FIII rhyolites, with FII and FI rhyolites being the least prospective. Piercey et al. (2008) demonstrated that in continental margin environments, such as the Finlayson Lake VMS district in Yukon Territory, host rhyolites to VMS deposits commonly have FII and FI geochemical signatures, owing to contamination by continental crust in the area of melt generation, and resulting HFSE and REE enrichment. In the case of the Finlayson Lake VMS district, utilization of the FIII through FI classification scheme would lead to the classification of the most prospective felsic volcanic rocks as unprospective for VMS mineralization. On this basis, it can be concluded that the nature of the substrate of a volcanic belt must be elucidated prior to utilizing the FI through FIII rhyolite classification scheme (i.e., is the area of interest underlain by continental or juvenile crust?). If the area of interest is underlain by continental crust, the most prospective felsic volcanic rocks for hosting VMS mineralization have enrichment in HFSE and REE, and are not identified using the FI through FIII rhyolite criteria (e.g., Piercey et al., 2008). This chapter will combine these datasets to understand the tectonic and metallogenic evolution of southern Paleozoic Wrangellia, and answer questions concerning the nature of Wrangellia basement (i.e., is Wrangellia underlain by continental crust?), the relationship between Wrangellia and adjacent terranes comprising the North American Cordillera (i.e., where did Wrangellia form?), and questions concerning the prospectivity of newly identified magmatic cycles in the terrane for hosting VMS deposits. 1326.2 A TECTONIC MODEL FOR THE EVOLUTION OF SOUTHERN PALEOZOIC WRANGELLIA The magmatic evolution of Paleozoic Wrangellia, Vancouver Island Southern Paleozoic Wrangellia on Vancouver Island records the development of a Late Devonian through Early Permian island arc and arc-back arc complex. Bimodal volcanic sequences containing VMS mineralization are found in the Cowichan, Buttle Lake and Bedingfield uplifts, and on the Dragon property. Together, these rock units mark areas of incipient back arc rifting. Early Permian E-MORB-OIB in the Cowichan uplift reflect cessation of backarc related Paleozoic magmatism in southern Wrangellia. Cartoons illustrating the tectonic evolution of the PWA are included in Figures 6.1 and 6.2. The oldest rocks recognized in southern Wrangellia comprise pre-Late Devonian mafic volcanic rocks of the Duck Lake and Nitinat formations. With the exception of two non-arc samples, these mafic volcanic rocks resemble IAT and L-IAT from modern settings (Fig. 4.5), indicating that arc volcanism was occurring in southern Wrangellia in pre-Late Devonian time (Fig. 6.1a). Two non-arc samples in the south Alberni area (Fig. 4.5) resemble E-MORB, and their probable cogenetic relationship to nearby IAT is puzzling, as the differing basalt types suggest origins in different tectonic regimes. However, contemporaneously erupted basalts of variable geochemical affinities been observed proximal to one another in modern arc and back arc settings. For example, OIB and IAT have been documented in proximal volcanic centres of similar age in the Ryuku arc (e.g., Shinjo et al., 2000). In addition, contemporaneous basalts of the northern Fiji Basin exhibit a range of compositions, from those with a strong subduction related component (i.e., a negative Nb anomaly and high loss on ignition), to those resembling N-MORB and E-MORB (Eissen et al., 1994). These settings represent a potential analogue for the Cowichan uplift in pre-Late Devonian time. The prevalence of IAT among pre-Late Devonian mafic volcanic rocks of the Cowichan uplift suggests a closer affinity with the Ryukyu arc example. 133 Late Devonian through Early Mississippian, bimodal volcanic rocks containing VMS mineralization are abundant in the Cowichan uplift (Massey, 1995a, 1995b, 1995c; Ruks et al., 2010), and are interpreted to represent the initial phases of back arc rifting in the Sicker arc (Fig. 6.1b). The eruption of felsic lavas commonly characterizes early back-arc formation in modern settings (e.g., Clift, 1995; Marsaglia, 1995; e.g., Gribble et al., 1998). Late Devonian-Early Mississippian mafic volcanic rocks, mapped as Duck Lake and Nitinat formations, are geochemically similar to pre-Late Devonian examples, resembling island arc tholeiites and light rare earth element (LREE) enriched island arc tholeiites from modern settings (Fig. 4.6; e.g., Stoltz et al., 1990; Shinjo et al., 1999). Previous workers theorized that mafic volcanic rocks at the base of the Duck Lake formation represented the oceanic crust upon which the Sicker arc was built (e.g., Massey, 1995a; e.g., Yorath et al., 1999). However, geochemical analyses completed on these rocks during the course of this study have failed to identify the presence of volcanic strata with MORB affinities. Instead, these rocks resemble IAT, suggesting that the oceanic crust which formed the basement of the Sicker arc is either not exposed, or has yet to be identified. Probable Late Devonian mafic volcanic rocks of the Buttle Lake uplift include those of the Price Formation, which form the footwall to VMS mineralization of the Myra Falls camp. A strongly sericitized and stockwork sulphide mineralized quartz-feldspar phyric rhyolite porphyry, dated at 361.5 ± 2.5 Ma (Chapter 3), overlies Price Formation mafic volcanic rocks, and forms the footwall to VMS mineralization of the Marshall Zone. As with Late Devonian-Early Mississippian mafic volcanic rocks of the Cowichan uplift, mafic volcanic rocks of the Price Formation have marked negative Nb anomalies, and tend towards transitional to mildly calc-alkaline affinities, both features typical of volcanic rocks generated in suprasubduction zone settings (Barrett and Sherlock, 1996). Late Devonian-Early Mississippian felsic volcanic rocks range in age from 366.8 ± 2.4 Ma to 353.1 ± 3.4 Ma (U-Pb, zircon; Chapter 3), and exhibit strong subduction zone signatures, including LREE enrichment, and negative Ti and Nb anomalies (Fig. 4.7). Felsic volcanic rocks of Late Devonian-Early Mississippian age assigned to the McLaughlin Ridge Formation are abundant in the Cowichan uplift where they are commonly interlayered with mafic volcanic rocks. However, felsic volcanic rocks of this 134suite are far more abundant in the Cowichan area than the Alberni area (Figures 4.3 and 4.4). In addition, the Saltspring Intrusions, which are interpreted to be subvolcanic feeders to felsic volcanic rocks of the McLaughlin Ridge Formation, are also only present in the Cowichan area (e.g., Massey, 1995b, Yorath et al., 1999). Recent geochronological investigations of the Saltspring Intrusions (SSI; Chapter 3) have yielded U-Pb (zircon) ages ranging from 360.7 ± 2.4 Ma through 355.0 ± 1.5 Ma, approximately overlapping in age with VMS associated felsic volcanic rocks of the McLaughlin Ridge Formation. Lithogeochemically, The SSI are also similar to felsic volcanic rocks of the McLaughlin Ridge Formation. Both the SSI and McLaughlin Ridge Formation felsic volcanic rocks display geochemical signatures indicative of having been generated in a subduction zone setting, including LREE enrichment, and negative Ti and Nb anomalies (e.g., Figures 4.8 and 4.7, respectively). McLaughlin Ridge Formation igneous rocks in the Cowichan area are strikingly similar to Myra Formation volcanic rocks that host VMS mineralization in the Buttle Lake uplift, in terms of rock types present, age and lithogeochemistry (e.g., Massey, 1995b; e.g., Barrett and Sherlock, 1996; Ruks et al., 2010). Felsic volcanic rocks from both areas exhibit subduction modified lithogeochemical signatures, including LREE enrichment and negative Nb anomalies. The abundance of felsic volcanic rocks and felsic, subvolcanic intrusions in the Cowichan area suggests that it represents a locus of back arc rifting during Late Devonian-Early Mississippian time. This was likely also the tectonic setting for Late Devonian strata of the Buttle Lake uplift. Barrett and Sherlock (1996) concluded that volcanic rocks of the Price and Myra Formations in the Buttle Lake uplift that host the Myra Falls VMS deposits were generated in a suprasubduction setting during submarine rifting of the mature phase of an oceanic island arc, similar to that observed in modern day settings at the Valu Fu Ridge in the southern Lau Basin (Pearce, 1982; Fouquet et al., 1993) and the south tip of the Japan arc (Ikeda and Yuasa, 1989). In contrast, the apparent absence bimodal magmatism of Late Devonian-Early Mississippian age in the Alberni area of the Cowichan uplift suggests that back arc rifting was not occurring in the Alberni area at this time. Rather, Late Devonian-Early Mississippian strata of the Alberni area (Horne Lake area; Fig. 4.6) mainly comprises IAT, suggesting that the area 135was a locus of continued arc volcanism during the Late Devonian through Early Mississippian. By Visean time (i.e., after 343 Ma, the youngest volcanic rock dated in the Cowichan area in this study), volcanism in the Cowichan area waned (Fig. 6.1c). Deposition in the area was characterized by the accumulation of reworked volcanic rocks and low energy marine sedimentary rocks (cherts and mudstones) of the Fourth Lake Formation (e.g., Massey, 1995b; Yorath et al., 1999), possibly suggesting a transition to a back arc spreading regime. A similar transition is recorded in strata of the Buttle Lake uplift, where Late Devonian, VMS associated bimodal volcanic rocks of the Myra Formation are overlain by siliceous tuffaceous sediments, subaqueous volcaniclastic debris flows, pyroclastic deposits and mafic sills of the Thelwood Formation. Juras (1987) interpreted this transition to reflect a shift to a Guaymas Basin-like extensional environment. Primary (i.e., unreworked) volcanic rocks of Visean age are largely absent in the Cowichan area. However, strata of this age have now been recognized in the Alberni area (Chapter 3). These rocks comprise bimodal volcanic rocks in the vicinity of Horne Lake (Figure 3.2; Chapter 3). Felsic volcanic rocks in this suite range in age from 335.3 ± 2.5 Ma through 340.7 ± 1.7 Ma (U-Pb, zircon; Chapter 3) and have no known VMS association. Lithogeochemically, this suite of magmatism is notably less felsic, slightly less LREE enriched, and less enriched in Zr-Hf than Late Devonian-Early Mississippian felsic volcanic rocks of the Cowichan uplift (Fig. 4.9). This suite also contains higher Sc concentrations than its Late Devonian-Early Mississippian counterparts, potentially reflecting a more mafic melt source. This suite of bimodal volcanic rocks suggests that by Visean time the arc infrastructure in the Alberni area was beginning to rift. Late Visean through Late Pennsylvanian strata of the Buttle Lake uplift are present in the Thelwood Formation (Juras, 1987; Yorath et al., 1999). Strata of the Thelwood Formation also contain undated penecontemporaneous mafic sills, which according to Juras (1987), bear geochemical similarities to back arc basin basalts of the Marianas Basin. Collectively, this evidence indicates that from Late Visean through Late Pennsylvanian time, southern Wrangellia was evolving into an extensional back arc basin setting. 136Late Pennsylvanian through Early Permian strata of southern Wrangellia reflect a more complex tectonic scenario, characterized by the presence of contemporaneous magmatism of variable tectonic affinities in different geographic areas (Fig. 6.2). In the Cowichan uplift (Fig. 6.2a), Early Permian strata is mainly characterized by laterally interfingering shallow water chert (spiculites) and limestone of the upper Fourth Lake and Mt. Mark formations (Yorath et al., 1999; Katvala and Henderson, 2002). Previous workers have interpreted these strata to reflect development of a carbonate platform on the PWA (Yorath et al., 1999). However, in the vicinity of Lacy Lake in the Alberni area of the Cowichan uplift (Fig. 4.4), Massey (1995a) identified a package of mafic volcanic rocks of probable Late Paleozoic age. These basalts are spatially associated with carbonate and chert of the Mt. Mark Formation, and have been recently dated (Chapter 3) as Early Permian, based on proximal microfossil and U-Pb (zircon) ages. These Early Permian basalts in the Lacy Lake area comprise several geochemically distinct suites, including IAT, E-MORB and OIB (Fig. 4.11). Early Permian basalts with similar E-MORB and OIB-like chemistry are present in the Nanoose uplift (Fig. 4.11). In addition, basalt sills intrude cherts and mudstones of the Fourth Lake Formation in vicinity of Mt. Whymper in the Cowichan area (Massey, 1995b). These sills, which are considered to be part of the Mount Whymper volcanic suite, also resemble ocean island basalts (Massey, 1995b) and are of probable Early Permian age based on the presence of a nearby microfossil age (Chapter 3). In the Cowichan and Nanoose uplifts, these Early Permian, dominantly non-arc basalts mark the end of PWA magmatism, with successive strata comprising chert and carbonate of the Mt. Mark Formation. The appearance in modern settings of similar non-arc basalts with within plate signatures (e.g., the Shikoku basin) typically marks the end of back-arc related magmatism (e.g., Sato et al., 2002; Martinez et al., 2007). Although Early Permian strata of the Cowichan and Nanoose uplifts is mainly characterized by non-arc magmatism, continued arc/back-arc magmatism is invoked for strata of similar age at the Dragon property, and in the Buttle Lake and Bedingfield uplifts (Fig. 6.2b). In the Buttle Lake uplift, basalt sills of probable Pennsylvanian-Early Permian age intrude volcano-sedimentary rocks of the Thelwood Formation, and are interpreted to be subvolcanic feeders for overlying basalts of the Flower Ridge Formation 137(Juras, 1987). Although these mafic volcanic rocks occupy a similar stratigraphic position to E-MORB and OIB-like Early Permian basalt sills and flows of the Cowichan and Nanoose uplifts, they have lithogechemical characteristics that, according to Juras (1987), more closely resemble modern day back arc basin basalts (BABB). This indicates that by the Pennsylvanian-Early Permian, the Buttle Lake area had evolved into a more mature back arc environment. In contrast, Pennsylvanian through Early Permian strata of the Dragon property and Bedingfield uplift comprise largely VMS associated, bimodal volcanic rocks with subduction modified lithogeochemical signatures (see discussion above), indicative of a rifted island arc setting. Undated mafic volcanic rocks of the Hesquiat area (Fig. 4.16) are of potential Early Permian age (see discussion above), and have lithogeochemical signatures similar to modern day island arc tholeiites (Fig. 4.17), suggesting an origin in an island arc setting. What killed the PWA? A common stratigraphic thread between all of the exposures of Paleozoic Wrangellian rocks on Vancouver Island, and those comprising northern Wrangellia (i.e., Haida Gwaii and Yukon-Alaska), is the presence of Early Permian carbonate, and the recognition that PWA volcanism appears to have ceased after the Early Permian (e.g., Yorath et al., 1999). Many workers (e.g., McGeary et al., 1985, and references therein) have attributed cessation of arc volcanism to the collision of the arc with another landmass, potentially a continent (e.g., Asia and Taiwan; ), another arc (e.g., Panama and Columbia), or an oceanic plateau (e.g., Caroline Ridge and the Marianas arc). Potential evidence for a post-Early Permian, pre-Middle Triassic collision of southern Wrangellia with another landmass is present in the PWA in conglomerates of the St. Mary’s Lake Formation (Massey, 1995a). In the Alberni area, these conglomerates overlie Early Permian cherts (Chapter 3) which are in turn overlain by undated pillow basalts assigned to the Karmutsen Formation (Massey et al., 2005). Detrital zircon systematics for Early Permian sedimentary rocks of the PWA (Chapter 3) show no evidence for a continental landmass outboard of the PWA in the late Paleozoic. However, the post-Early Permian age of this potential tectonism suggests that additional detrital geochronology of post-138Early Permian lithologies in the PWA is required in order to test for the presence of such a landmass. A potential candidate for a post-Early Permian indentor is the Alexander terrane. However, studies of Alexander terrane and Wrangellia interactions by previous workers suggest that northern Wrangellia and Alexander terrane have been evolving as a singular entity since 309 Ma (Gardner et al., 1988) and possibly since as early as Late Devonian time (Israel, 2010), thereby ruling out a later collision between the two terranes in Late Paleozoic time. Although there is no strong evidence to suggest that Wrangellia was proximal to the North American margin in Paleozoic time, there are some striking similarities between the stratigraphy, magmatic history and paleontology of the southern PWA and that of Paleozoic Stikine terrane in the Iskut River area (Belasky et al., 2002; Logan, 2004; Gunning et al., 2006). Although Paleozoic Stikine terrane in the Iskut is as old as Early Devonian, both terranes share Late Devonian-Early Mississippian felsic intrusions associated with bimodal volcanic rocks and VMS mineralization. The Late Devonian through Early Permian of both terranes are also similar, characterized predominantly by the presence of island arc mafic volcanic rocks and local felsic volcanic rocks dated at approximately 340 Ma and 312 Ma. Notably, Early Permian strata for both terranes are similar, comprising non-arc mafic volcanic rocks (E-MORB and OIB) overlain by Early Permian limestones. Limestones from both terranes contain the conodont Gondolelloides, a cool water endemic species suggesting that Paleozoic Stikinia and Wrangellia were both proximal to the northern margin of Pangea at high latitudes in Early Permian time (Belasky et al., 2002; Katvala and Henderson, 2002). Paleozoic Stikinia is believed to have been constructed, in part, upon a terrane with strong pericratonic affinities; probably the Yukon-Tanana terrane (Nelson et al., 2006). Recent work by Beranek and Mortensen (2011) suggests that the YTT collided with the North American margin between 260 and 252.5 Ma, raising the possibility that post-Early Permian, pre-Middle Triassic conglomerates of the St. Mary’s Lake formation in the southern PWA may be the result of far field stress related uplift due to this collisional event. Lastly, another clue to the demise of the PWA might lie in Middle Triassic basalts of the Karmutsen Group. Undated basalts assigned to the Karmutsen Group overlie conglomerates of the St. Mary’s Lake Formation. These basalts, and their 139northern Wrangellia correlatives, the Nikolai Group, are interpreted to represent a large igneous province (LIP) that formed as the result of mantle plume related magmatism (Greene et al., 2009). It is conceivable that post-Early Permian, pre-Middle Triassic conglomerates of the St. Mary’s Lake Formation on Vancouver Island reflect initial stages of uplift related to the impingement of the Karmutsen-Nikolai plume head on Wrangellia basement. The phenomenon of uplift preceding mantle plume related magmatism has been documented in LIPs worldwide (Saunders et al., 2007). Niu et al. (2003) propose that a collision of the Hawaiian plume with the Cretaceous-Eocene Okhotsk-Chukotka arc halted subduction of the Pacific plate at 43 Ma. Similarly, perhaps a post Early Permian collision with the Karmutsen-Nikolai plume resulted in uplift of the PWA, deposition of St. Mary’s Lake formation conglomerates, and ultimately played a role in the termination of PWA, subduction related magmatism. The polarity of the Paleozoic Wrangellia Arc (PWA) A fundamental question surrounding the PWA is the polarity of the arc that was active in middle and late Paleozoic time. In the pericratonic northern Cordilleran terranes, the distribution of mélange, blueschist, eclogite, arc and back arc related strata gives clues about the polarity of their associated, ancient arcs (e.g., Nelson et al., 2006). Understanding the polarity of the PWA, however, has been difficult given the absence of many of these key geological elements within the terrane. Yorath et al. (1999) proposed east dipping subduction (modern coordinates) being responsible for the PWA magmatism, based on the identification by Massey (1995b) of generally deeper water facies in Paleozoic strata in the western regions of the Cowichan uplift. Stratigraphic and geochemical work conducted as part of this study also supports the existence of an east dipping subduction zone (modern coordinates) in Late Devonian through Early Permian time associated with formaton of the PWA. Evidence for east dipping subduction at this time is given by the distribution of arc versus back arc volcanic facies within the Cowichan uplift. Here, VMS associated bimodal volcanic rocks located east of Cowichan Lake represent the locus of PWA rifting in Late Devonian-Early Mississippian time. These rock units are now truncated on the west by the east dipping, Fulford thrust 140of Eocene age (Massey, 1995b). This relationship suggests that prior to the Eocene thrust faulting, Late Devonian-Early Mississippian bimodal volcanic rocks of the Cowichan area were even farther to the east of their present location. In contrast, Late Devonian-Early Mississippian strata of the Alberni (Horne Lake) area are characterized mainly by mafic volcanic rocks with IAT affinities, and thus represent the arc infrastructure of the PWA. These rocks are situated to the west-northwest of bimodal, back-arc like rocks of the Cowichan area. The relative positions of arc versus backarc in this situation could be explained by the presence of an east dipping subduction zone that was located to the west of the PWA in Late Devonian-Early Mississippian time (Fig. 6.1). East dipping subduction is also inferred for Pennsylvanian through Permian strata of the PWA, based on the relative positions of incipient back arc versus evolved back arc regimes in the Bedingfield-Dragon-Hesquiat and Buttle Lake uplifts, respectively (Fig. 6.2). Strata of the Bedingfield uplift and Dragon property comprise Pennsylvanian through Early Permian bimodal volcanic rocks. As with Late Devonian-Early Mississippian strata east of Cowichan Lake, these rock units are interpreted to represent incipient back arc basin formation in an arc environment. Mafic volcanic rocks of the Hesquiat area are of potential Early Permian age, display IAT-like lithogeochemical compositions, and are interpreted to have formed in an island arc setting. In contrast, mafic volcanic rocks of the Flower Ridge Formation (Buttle Lake uplift) are located to the east of the Bedingfield-Dragon-Hesquiat areas, and are of probable Pennsylvanian-Early Permian age based on the presence of overlying Early Permian carbonates of the Buttle Lake Formation (Muller, 1977; Brandon et al., 1986; Juras, 1987). The presence of arc/incipient back arc strata (e.g., bimodal volcanic rocks of the Bedingfield-Dragon areas and IAT basalts of the Hesquiat area) to the west of mature, back arc basin strata (e.g., back arc basin basalts of the Flower Ridge Formation, Buttle Lake uplift) can be explained by the presence of an east dipping subduction zone (modern coordinates; Fig. 6.2) associated with the PWA during Pennsylvanian-Early Permian time. These interpretations suggest that strata associated with the PWA record at least 60 million years of evolution associated with an east dipping (modern coordinates) subduction zone. Comparable longevities have been documented for modern day oceanic 141subduction zones, including the Mariana Arc, which is believed to have been in existence for at least 40 million years (e.g., Lee et al., 1995). Was the PWA built on continental crust? Some fundamental questions concerning the PWA are the nature of its basement and its paleogeography throughout the Paleozoic. Furthermore, in order to evaluate the prospectivity of PWA strata for hosting VMS deposits using lithogeochemical tools (e.g., Piercey, 2010), the nature of PWA basement must first be characterized. Previous workers have suggested that the PWA comprises an oceanic island arc that was located at high latitudes offshore of northern Pangaea during Early Permian time (Yorath et al., 1999; Belasky et al., 2002; Katvala and Henderson, 2002). Others have postulated that the PWA, locally, may be underlain by continental crust (e.g., Sluggett, 2003) or originated proximal to a continental landmass (e.g., Godwin and Robinson, 1996) The lithogeochemical characteristics of the majority of Late Devonian through Early Permian volcanic rocks sampled during the course of this study are typical of rocks generated in subduction zone settings. These characteristics include LREE enrichment, and negative Nb and Ti anomalies (Tatsumi, 2005). However, contamination of non-arc magmas by continental crust can produce similar signatures (e.g., Piercey et al., 2002a). Therefore, in order to understand the true tectonic setting of the PWA, and to evaluate the prospectivity of felsic volcanic rocks in the terrane for hosting VMS deposits, it is imperative to resolve the nature of the basement to the PWA. Trace element and Nd isotope systematics have been used to understand the nature of the basement underlying Cordilleran terranes and its evolution over time (e.g., Ghosh, 1995; Piercey et al., 2003). The Nd isotope systematics Late Devonian through Early Permian felsic and mafic rocks of the PWA suggest derivation from a radiogenic, mantle-like source, with εNd,t values ranging between 4.3 and 6.9 (Fig. 6.3). The εNd(t=360) value for depleted mantle is 9.5 (Goldstein et al., 1984; Peucat et al., 1988), suggesting that crustal contamination has played a role in the genesis of PWA rocks. Younger volcanic rocks in the PWA are characterized by changing geochemical and isotopic 142characteristics reflective of an increasing mantle contribution during the evolution of the PWA. For example, younger rocks in the PWA exhibit increasing εNd,t values (Chapter 4), and associated sulfide occurrences exhibit less radiogenic Pb isotopic signatures (Chapter 5); both characteristics that are suggestive of an increasing mantle contribution during the evolution of the PWA. Trace element ratios for PWA felsic and mafic rocks also exhibit this trend. For example, Ti/Sc ratios for Late Devonian through Early Permian PWA felsic rocks decrease over time, reflecting an increasing mantle contribution as the PWA evolves (Fig. 6.4a). Increased Nb/Ta ratios are also interpreted to reflect greater mantle contribution over time (Piercey et al., 2008), and this trend is generally observed for Late Devonian through Mississippian felsic rocks in the Cowichan uplift (Fig. 6.4b). Upper continental crust normalized Nb/Th ratios (values from Taylor and McLennan, 1995) for Late Devonian-Early Mississippian felsic rocks of the PWA are typically approximately equal to 1, suggesting potential derivation from an upper continental crust like source (Fig. 6.4c). However, these ratios rise in progressively younger rocks, reflecting an increasing mantle contribution as the PWA evolves. Similarly, Late Devonian-Early Mississippian PWA felsic rocks have upper continental crust normalized La/Sm ratios (values from Taylor and McLennan, 1995) approximately equal to 1, indicating potential derivation from upper continental crust (Fig. 6.4d). However, these values decrease in progressively younger felsic rocks, again reflecting an increasing mantle contribution during the evolution of the PWA. Mafic rocks of the PWA commonly exhibit both Th enrichment and negative Nb anomalies on normalized diagrams (see discussion above), two features which can be explained by contamination of a mantle derived magma with continental crust, inheritance of a subduction modified signature via magma genesis in an arc environment, or both of these processes working in tandem (Pearce, 1983; Pearce and Peate, 1995; Piercey et al., 2004). Th/Yb ratios generally decrease with increasing εNd,t (Fig. 6.5a and b) in Late Devonian through Early Permian PWA mafic rocks, suggesting that contamination by continental crust is responsible in part for their enhanced Th contents. In contrast, the largest negative Nb anomalies in Late Devonian through Early Permian PWA mafic rocks, reflected by the lowest Nb/Thmn ratios (values from Sun and McDonough, 1989), are associated with the the greatest εNd,t values (Fig. 6.5c). This 143suggests that negative Nb anomalies in PWA mafic rocks might be the product of subduction related processes, and not contamination by continental crust. Collectively, trace element , Nd and Pb isotope systematics indicate a progressively increasing mantle component to mafic and felsic rocks during the evolution of the PWA, supporting a model for the PWA as a rifting, oceanic island arc system. This model has been used to explain similar geochemical and isotopic trends observed in other Cordilleran terranes (e.g., the Yukon-Tanana Terrane; Piercey et al., 2004). However, in contrast to other Cordilleran terranes, especially those of the pericratonic realm, where the presence of abundant inherited, Precambrian zircon, negative εNd,t values and radiogenic Sr isotope systematics indicate their interaction with continental crust over time (e.g., Colpron et al., 2006; Piercey et al., 2006b), evidence for interaction between the PWA and evolved, continental crust is much less pronounced. For example, extensive geochronological investigations of the PWA in Chapter 3 did not reveal the presence of any inherited zircons. All zircons dated during the course of the study could be explained by local sources related to the PWA. Previous Nd isotopic studies of Wrangellia igneous rocks by Samson et al. (1990), including samples of the SSI, indicated that Wrangellian magmas were derived from a mantle source, with little or no contamination by continental crust. The Nd isotopic systematics of PWA samples collected as part of this study (including several samples of Jurassic diorites) are similar to those reported by Samson et al. (1990). As with the Samson et al. (1990) study, the Nd isotopic characteristics of PWA samples determined during this study are less radiogenic than depleted mantle, possibly suggesting some degree of contamination by continental crust in their genesis. The Neodymium Crustal Index (NCI) of DePaolo et al. (1992) provides a method for estimating the amount of crustal involvement in magma source regions, using the following formula NCI = [εNdrock – εNdMC] / [εNdCC – εNdMC] where εNdrock is the εNd of the sample, εNdMC is the εNd of the mantle component, and εNdCC is the εNd of the crustal component. The NCI assumes that PWA samples of this study are the result of mantle-crust mixing. For the calculations, the mantle end member is the 144depleted mantle (DM) reservoir (Goldstein et al., 1984) calculated to the age of PWA samples (i.e., 360 Ma, 317 Ma, 300 Ma, 200 Ma, and 180 Ma). The NCI assumes that PWA samples are a mix of mantle-crust mixing. Crustal Nd reservoirs for the PWA samples are taken to be an average of Devonian through Jurassic miogeoclinal rocks of the Canadian Cordillera (Boghossian et al., 1996). Results of these calculations (Table 4.1) indicate that PWA samples contain 14% to 30% crustal Nd, and that on average, Late Devonian-Early Mississippian samples contain more crustal Nd (25%) than Pennsylvanian-Permian samples (20%). In addition, Late Devonian-Early Mississippian samples from the Alberni area have higher average NCI than their Cowichan counterparts. Jurassic intrusions sampled during the course of this study contain an average of 22% crustal Nd, similar to PWA samples, suggesting that the nature of Wrangellian basement did not change significantly in between Late Devonian and Early Jurassic time. A similar conclusion was reached in the Nd isotopic study by Samson et al. (1990). The lack of inherited zircon in PWA samples (Chapter 3) suggests that the PWA is not directly underlain by a fragment of older, evolved continental crust. This requires an alternative explanation in order to explain the presence of continental derived Nd in PWA source magmas. A possible mechanism for this is the incorporation of continent derived sediments into the PWA subduction zone, a mechanism previously invoked by Samson (1990) to explain low εNd values observed in Sicker Group volcanic rocks. The contamination of arc magmas by subducted sediments of continental origin has been well documented in arc systems worldwide (e.g., Davidson, 1996). In the case of the PWA, continent derived sediments may have been sourced from the Devonian through Jurassic migeocline of the Canadian Cordillera (Boghossian et al., 1996). Previous workers have argued for an Early Permian paleogeographic position for Wrangellia potentially several thousand kilometers west of the Laurentian margin and north of the Intermontane terranes, based on paleontologic data (Belasky et al., 2002; Stevens, 2008). However, the potential contamination of PWA source magmas by continent derived sediment, when combined with the results of sediment transport studies suggests that the PWA was located within 1500 km of a continental margin during most of its history (e.g., Barron and Whitman, 1981; McLennan et al., 1990; Patchett and Gehrels, 1998). 145Depleted mantle model ages (TDM) for the PWA might offer clues as to the potential source of subducted, continent derived sediment involved in the PWA melt source region, and on the paleogeographic position of the PWA in the Paleozoic. However, the significance of PWA depleted mantle model ages in tracing a subducted sediment component to source is highly debatable, especially given the nature of Nd isotopic systematics in marine sediments and continent derived, sediment source components of mixed mantle extraction ages (Arndt and Goldstein, 1987). For example, Arndt and Goldstein (1987), discuss how Nd isotopic systematics of marine sediments can be highly variable due to mixing between continental derived sediments, and chemical sediments precipitated from the water column, the latter of which inherit a fractionated, and in some cases, strongly variable Nd isotopic signature. These two sources, when evaluated on an individual basis, can yield radically different depleted mantle model ages (Arndt and Goldstein, 1987). When mixed, the resulting sediment yields an average depleted mantle model age of debatable significance. Nevertheless, depleted mantle model ages for PWA samples span the entirety of the Neoproterozoic, ranging from 568 Ma through 996 Ma. These ages are similar to depleted mantle model ages calculated for Wrangellia samples reported in Samson et al. (1990), which range from 451 Ma through 1031 Ma. Depleted mantle model ages calculated for rocks collected from Stikine and Alexander terranes using data reported in Samson et al. (1989; 1990) range from 546 Ma through 1433 Ma, and 475 Ma through 1286 Ma, respectively. Collectively, TDM values for PWA, Stikine and Alexander terranes are dominantly Neoproterozoic in age. This is in stark contrast to TDM ages from the pericratonic Cordilleran terranes (e.g., the Yukon-Tanana and Kootenay terranes), which are much older, ranging mainly from Mesoproterozoic to Paleoproterozoic in age (Patchett and Gehrels, 1998; Piercey et al., 2003). This difference can be attributed to the Wrangellia, Alexander and Stikine terranes having developed upon crust of a more juvenile nature (i.e., an intraoceanic setting), removed from the North American margin (Patchett and Gehrels, 1998). 146 6.3 THE PROSPECTIVY OF PWA VOLCANIC ROCKS FOR HOSTING VMS DEPOSITS Numerous workers have shown the utility of lithogeochemistry in identifying volcanic rocks which are prospective for VMS mineralization (e.g., Piercey, 2011 and references therein). Key in these studies was the recognition of lithogeochemical characteristics in VMS associated felsic volcanic rocks reflective of high temperatures of melting at shallow levels in the lithosphere (Lesher et al., 1986). For example, the FI through FIII rhyolite classification scheme, developed by Lesher et al. (1986), was the product of a study of VMS associated and VMS barren felsic volcanic rocks in the Superior Province of Canada. In the study, it was discovered that VMS associated felsic volcanic rocks were enriched in HFSE and REE, whereas VMS barren felsic volcanic rocks had markedly lower HFSE and REE contents. The greater HFSE and REE contents of VMS associated rhyolites were attributed to high temperatures of melting at shallow levels in the crust, whereas VMS barren rhyolites were the products of lower temperature melting, and as a result, had lower HFSE and REE contents. Although the FI through FIII classification scheme was originally developed for felsic volcanic rocks of the Superior Province, subsequent workers have demonstrated that the scheme is also applicable to Phanerozoic VMS environments (e.g., Hart et al., 2004). Studies of mafic volcanic rock lithogeochemistry in a variety of VMS camps have demonstrated that those associated with VMS also contain lithogeochemical signatures representative of high temperatures of formation at shallow crustal levels in extensional geodynamic settings. (e.g., Piercey, 2011 and references therein). The vast majority of PWA felsic volcanic rocks, including those that host the world class Myra Falls deposit, are similar to FII rhyolites (Fig. 6.6a and b), and those that host the Kuroko and Mt. Windsor VMS deposits in Japan and eastern Australia, respectively (Fig. 6.6c). However, VMS associated rhyolites of Pennsylvanian-Permian age on the Dragon property are more similar to the more prospective FIII rhyolite designation (Fig. 6.6a and b), and those hosting the Tobique and Avoca VMS deposits (Fig. 6.6c). 147Various workers have shown that calculated zircon saturation temperatures of felsic volcanic rocks in known VMS districts can be useful for distinguishing those that are VMS associated from those that are VMS barren (Barrie, 1995; Piercey et al., 2008), with VMS associated rhyolites typically returning significantly higher zircon saturation temperatures than their VMS barren counterparts. Zircon saturation temperatures are calculated using the following equation (Watson and Harrison, 1983): ln DZr, zirc° n/melt = [–3.8 – [0.85(M – 1)]] + 12,900/T where DZr, zirc° n/melt is the concentration ratio of Zr in the stoichiometric zircon to that in the melt, T is the absolute temperature, and M is the cation ratio (or alumina saturation factor) for the rock [M = (Na + K + 2 · Ca)/(Al · Si)] Several variables can affect the reliability of zircon saturation temperatures. Firstly, zircon saturation temperatures for rocks containing inherited zircon provide only maximum estimates for the temperature of formation (Barrie, 1995; Miller et al., 2003; Piercey et al., 2008). Secondly, alkali element mobility related to hydrothermal alteration can also influence calculated zircon saturation temperatures (Barrie, 1995; Piercey et al., 2008). The absence of inherited zircon in rocks of the PWA makes them ideal candidates for zircon saturation thermometry. However, the presence of hydrothermally altered samples within the sample suite means that zircon saturation temperatures calculated for the sample suite must be used with caution. Zircon saturation temperatures (ZST) calculated for PWA felsic rocks (Table 4.1) exhibit a general trend whereby increasing temperatures are associated with increasingly young samples (Fig. 4.6d). Average trace element compositions for PWA magma suites exhibit a similar trend, with increasingly young samples have greater REE and HFSE concentrations (Fig. 6.6e). ZST calculated for PWA felsic rocks are proportional to Nb concentrations (Fig. 6.6d), with Pennsvylvanian-Permian, VMS associated rhyolites of the Dragon property yielding the greatest calculated temperatures and Nb concentrations by a significant margin. Late Devonian-Early Mississippian, VMS associated felsic rocks of the Cowichan uplift have calculated temperatures similar to those of felsic 148volcanic rocks which host the Myra Falls deposit, calculated from lithogeochemical data collected by Barrett and Sherlock (1996). A similar relationship between zircon saturation temperatures, HFSE-REE contents and VMS prospectivity in increasingly younging rocks has been documented in the Finlayson Lake district in Yukon, Canada, by Piercey et al. (2003; 2008). Here, VMS associated felsic rocks are notably enriched with HFSE and REE relative to their VMS barren counterparts. In addition, Piercey et al. (2008) noted that progressively younger felsic sills spatially associated with the Wolverine VMS deposit yielded both higher zircon saturation temperatures and greater HFSE and REE concentrations. These were attributed to increased mantle contributions as a result of increasing extension during the life of the Wolverine magmatic-hydrothermal system. Felsic rocks with greater mantle contributions were associated with higher temperatures of melting. This allowed for greater dissolution of HFSE-REE bearing accessory minerals in the melt source region, and as a result, the production of melts with enhanced HFSE-REE concentrations (Watson and Harrison, 1983; Watson, 1996; Bea, 1996a, 1996b; Piercey et al., 2003; Piercey et al., 2008). These HFSE-REE enriched melts formed hotter subvolcanic intrusions, leading to a source of sustained, high heat flow at shallow levels in the lithosphere, and ultimately, significant VMS mineralization. A similar model might explain the elevated HFSE-REE contents observed in increasingly young rocks of the southern PWA (Chapter 4). Interestingly, felsic rocks of the Cowichan uplift have very similar ZST and HFSE concentrations to VMS associated felsic rocks which host the world class Myra Falls VMS deposit. The similarities between felsic volcanic rocks of the Cowichan and Myra Falls areas in terms of geological setting and style of mineralization are well documented, and the potential for the discovery of Myra Falls caliber VMS deposits in the Cowichan area has long been recognized (Muller, 1980; Brandon et al., 1986; Massey, 1995b; Yorath et al., 1999). However, the recognition that VMS associated felsic rocks of the Cowichan and Myra Falls areas have similar zircon saturation temperatures and HFSE contents adds further strength to this argument. Despite the presence of altered samples in the dataset, the high temperatures inferred for rhyolites of Pennsylvanian-Early Permian age on the Dragon property on the 149basis of zircon saturation temperature calculations (the highest temperatures in the entire dataset) are also supported by other geochemical arguments, most notably in terms of isotopic and trace element geochemical compositions that argue for a strong juvenile component, and therefore a higher temperature of formation in their melt source region (see discussion above). Rhyolites of the Dragon property are also spatially associated with the Falls and North VMS occurrences (MINFILE, 2013), and are geochemically similar to prospective rhyolites of the FIII designation (Fig. 6.6a and b). Collectively, this data suggests that felsic volcanic rocks of the Dragon property, and other, correlative belts of Pennsylvanian-Early Permian felsic volcanic rocks in the area (e.g., VMS associated felsic volcanic rocks of the Bedingfield uplift), are strongly prospective for VMS. The spatial association of Dragon-Bedingfield felsic volcanic hosted VMS and conformably overlying carbonate rocks suggests that the Dragon-Bedingfield areas might also be prospective for shallow water, precious metal enriched VMS similar to the Eskay Creek, Horne and LaRonde Penna VMS deposits. 6.4 SUMMARY AND CONCLUSIONS The PWA represents the remnants of an intraoceanic arc that existed from Late Devonian through Early Permian time. Stratigraphic, lithogeochemical and isotopic studies of the PWA have shed light on its evolution, which can be summarized as follows: 1. The earliest magmatism in the PWA is potentially pre-Late Devonian age, and comprises dominantly IAT with rare E-MORB in the Cowichan uplift (Alberni area). The juxtaposition of similar basalt types in modern day settings has been documented in the Ryuku arc (Shinjo et al., 2000); 2. The Late Devonian through Early Mississippian evolution of the PWA is characterized by VMS associated, subduction related bimodal magmatism in the Cowichan Lake and Buttle Lake uplifts, with more arc like magmatism (IAT) occurring in the Alberni area (Cowichan Lake uplift). Bimodal magmatism in the Cowichan and Buttle Lake uplifts ranges in age from 366.8 ± 2.4 Ma to 353.1 ± 3.4 Ma and is 150interpreted to represent the initial rifting of a mature, oceanic arc. The juxtaposition of bimodal, back arc associated magmatism in the Cowichan area with more arc like magmatism in the Alberni area suggests the presence of an east dipping subduction zone (modern coordinates). 3. The evolution of the PWA during the Visean through Late Pennsylvanian is characterized predominantly by the deposition of low energy marine sediments and reworked volcanic rocks in the Cowichan and Buttle Lake areas. Pyroclastic rocks as well as penecontemporaneous mafic sills with back-arc basin-like chemistry are interbedded with these strata in the Buttle Lake uplift. Collectively, these strata have been interpreted to represent a transition to a Guaymas basin or back arc-basin like spreading environment (e.g., Juras, 1987). In contrast, Visean strata of the Alberni area are characterized by bimodal volcanic rocks, indicating that the locus of PWA rifting had migrated to the Alberni area by this time. 4. The evolution of the PWA from the Late Pennsylvanian through Early Permian was more complicated. Non arc magmatism, characterized by the eruption of alkalic basalt was abundant in the Cowichan and Nanoose areas, whereas bimodal, arc related magmatism and associated VMS mineralization was present in the Dragon and Bedingfield areas. The juxtaposition of bimodal arc magmatism in the Dragon-Bedingfield areas with non-arc, back arc basin-like magmatism in the Buttle Lake uplift suggests the presence of an east dipping subduction zone (modern coordinates). 5. By the end of the Early Permian, PWA magmatism had ceased, and carbonate reef development predominated. The presence of a post Early Permian, pre Middle Triassic unconformity throughout much of the PWA argues for a bout of similarly aged regional uplift affecting the terrane. This uplift might be attributable to the collision of the PWA with another landmass, or alternatively, to the impingement of the Karmutsen-Nikolai mantle plume head upon the base of the PWA. 6. Isotopic and lithogeochemical data support a model for the PWA as a progressively rifting, oceanic island arc, where progressively younger igneous rocks show evidence for an increasing mantle component in their genesis. This is indicated in PWA igneous rocks and contained sulfide occurrences by increasing εNd,t values and less radiogenic Pb isotopic signatures over time, respectively. Trace element lithogeochemistry for PWA 151 felsic rocks also reflects an increasing mantle contribution to PWA magmas over time, reflected in increasing Nb/Ta and upper continental crust normalized Nb/Th ratios, and in decreasing Ti/Sc, and upper continental crust normalized La/Sm ratios. Progressively younger PWA rocks have increasing zircon saturation temperatures, which are interpreted to be a manifestation of greater partial melting temperatures in their respective melt source regions due to enhanced mantle contributions. These enhanced mantle contributions caused more efficient dissolution of HFSE-REE bearing mineral phases into the partial melt, and enhanced HFSE-REE concentrations as a result. 7. The vast majority of PWA felsic volcanic rocks, including those that host the world class Myra Falls VMS deposit, are similar to FII rhyolites, and those that host the Kuroku and Mt. Windsor VMS deposits. Late Devonian-Early Mississippian felsic volcanic rocks of the Cowichan uplift have similar lithogeochemical characteristics to those that host the Myra Falls deposit, adding further evidence to the hypothesis that the Cowichan area is prospective for Myra Falls sized VMS deposits. Interestingly, Pennsylvanian-Permian aged VMS associated rhyolites of the Dragon property are similar to the more prospective FIII rhyolite designation, and those hosting the Tobique and Avoca VMS deposits. Conformably overlying carbonate rocks suggest that these VMS associated rhyolites might have been erupted in a shallow marine setting, and as such, might be prospective for shallow water, precious metal enriched VMS mineralization similar to that associated with the famous Eskay Creek, Horne and LaRonde Penna VMS deposits. 8. Lastly, geological mapping, geochronological, isotopic and lithogeochemical investigations of the PWA indicate that it comprises an ancient oceanic island arc with little evidence for significant interaction with evolved continental crust throughout the course of its history. A small amount of subducted sediment of continental derivation may be responsible for the somewhat less radiogenic, but still dominantly juvenile Nd isotope systematics for PWA igneous rocks. This interpretation is similar to that proposed by previous workers in the terrane (Samson et al., 1990). 152153154155156157158Table 6.1. Neodymium crustal index (NCI) calculations (DePaolo et al., 1992)for PWA igneous rocksSample Region Age Rock Type DJMG07TRHS020B HS 180 FSIV 0.2507TRHS018B HS 200 GRIV 0.2009TR110 BD 300 RHPR 0.1408TRDR007A DR 300 RHFL 0.1407TRHS008B HS 300 MFPR 0.1807TRHS022B HS 300 MFPR 0.2007TRHS016C HS 300 MFPR 0.2207TR023 AL 300 BSAB 0.2407TR011B AL 300 BSBX 0.2909TR125 NA 300 BSPL 0.19HFB-94-02 HG 317 DIIV 0.1907TR051A AL 360 DCFL 0.2707TR060B AL 360 MFBX 0.2207TR069B AL 360 BSFL 0.2707TR072A AL 360 INFL 0.2605M-386a AL 360 BSFL 0.3005M-386b AL 360 FSLT 0.3005M-366 CW 360 FSLT 0.2205M-393 CW 360 FSXT 0.2205M-394 CW 360 QFPR 0.2305M-369 CW 360 FSLT 0.2705M-356 CW 360 FSLT 0.2009M309* CW 360 QFPR 0.2309M302* CW 360 QFPR 0.2205M352* CW 360 QFPR 0.22Note: The calculations are based on a mantle end member (MC) with a composition similar to the DM reservoir (εNd(t=360)= +9.2, εNd(t=317)= +9.30, εNd(t=300)= +9.33,εNd(t=200)= +9.56, εNd(t=180)= +9.60) and crustal end members (CC) using the values for the DJMG (εNd(t=360)= -7.40, εNd(t=317)= -7.85, εNd(t=300)= -8.03, εNd(t=200)= -9.07, εNd(t=180) = -9.28) sedimentary rocks (Boghossian et al., 1996). DJMG = Devonian-Jurassic miogeocline (Boghossian et al., 1996). See text for discussion of results.Four letter rock type codes consist of a two letter prefix followed by a two letter suffix. Prefix codes include: FS, felsic; RH, rhyolite; DC, dacite; QF, quartz-feldspar; IN, intermediate; BS, basalt; MX, heterolithic; DI, diorite. Suffix codes include: IV, intrusvive; DI, dike; PR, porphyry; VO, volcanic; TF, tuff; XT, crystal tuff; LT, lapilli tuff; TB, tuff breccia; BX, breccia; FB, flow breccia; AB, autobreccia; PL, pillow flow; FL, flow. Age codes include: PLD, Pre-Late Devonian; LDEM, Late Devonian-Early Mississippian; MS, Mississippian; PN, Pennsylvanian; PM, Permian. Region codes include: CW, Cowichan; AL, Alberni; NA, Nanoose; DR, Dragon; BD, Bedingfield; HS, Hesquiat; HG, Haida Gwaii. Affinity codes include: CA, calc-alkaline; TR, transitional; TH, tholeiitic.159Chapter 7: Conclusions and directions for future research 1607.1. CONTRIBUTIONS Through the development of a new model for the tectonic, magmatic and metallogenic evolution of Paleozoic Wrangellia, this study represents a significant contribution towards our understanding of the crustal growth history and metallogeny of the North American continent. This study was successful in addressing several research questions highlighted in Chapter 1, including the following: What is Wrangellia? Our understanding of Wrangellia has been hampered by the absence of a robust chronostratigraphy for its Paleozoic history. Previous workers interpreted Paleozoic Wrangellia as a Late Devonian-Early Mississippian arc-back arc complex, which foundered in the Late Paleozoic, leading to the formation of Pennsylvanian-Permian fringing carbonate reefs (e.g., Massey et al., 1995a, b, c; Yorath et al., 1999). The results of this study demonstrates that the Paleozoic history of Wrangellia on Vancouver Island is far more complex than previously thought, with the revised model for the PWA comprising a multi-episodic, Late Devonian through Early Permian arc-back arc complex, associated with vast tracts of previously unrecognized, Pennsylvanian-Early Permian bimodal magmatism and associated VMS mineralization. How old is Wrangellia? Prior to this study, the oldest dated rocks in Wrangellia were Late Devonian-Early Mississippian felsic volcanic rocks and associated subvolcanic intrusions in the Cowichan and Buttle Lake upifts, underlain by presumably older mafic volcanic rocks of the Duck Lake Formation (Alberni area) (e.g., Brandon et al., 1986; Massey et al., 1995a, b, c; Yorath et al., 1999). Chronostratigraphic work conducted as part of this study (Chapter 3) indicates that tuffaceous sedimentary rocks in the vicinity of McLaughlin Ridge (Alberni area) are Late Devonian in age, and that thick sections of underlying mafic volcanic rocks and associated sedimentary rocks assigned to the Duck Lake and Nitinat formations are Late Devonian or older (Chapter 3). 161Where did Wrangellia form? Geological, chonostratigraphic and isotopic studies of Paleozoic Wrangellia by previous workers suggest that the terrane was located at northern latitudes in Late Paleozoic time, within sediment transport distance from the western margin of Laurentia (modern coordinates; e.g., Samson et al., 1990; Yorath et al., 1999). Similar work conducted as part of this study supports this hypothesis (Chapters 3, 4 and 5). Detrital zircon studies described in Chapter 3 did not reveal the presence of pre Late Devonian, continent derived zircons that would have linked the PWA to continental landmasses in Late Devonian time. How many cycles of VMS mineralization exist in Paleozoic Wrangellia and what does this imply for the tectonic history and mineral potential of the terrane? Previous workers interpreted PWA hosted VMS mineralization on Vancouver Island to be associated with Late Devonian-Early Mississippian bimodal volcanic rocks; the result of rifting of the Sicker arc (e.g., Brandon et al., 1986; Massey et al., 1995a, b, c; Barrett and Sherlock, 1996; Yorath et al., 1999). Chronostratigraphic work conducted during the course of this study (Chapter 3), however, indicates that vast tracts of bimodal volcanic rocks and associated VMS-like occurrences in central and western Vancouver Island (Dragon and Bedingfield areas, respectively) are Middle Pennsylvanian to Early Permian in age, indicating that the PWA underwent multiple bouts of arc rifting, with associated pulses of bimodal volcanism and VMS mineralization. VMS exploration models for Wrangellia must be revised in order to properly explore these newly recognized, prospective belts of Late Paleozoic strata for VMS mineralization. 7.2 DELIVERABLES The following products were generated as a result of work conducted in four field seasons and subsequent laboratory-based investigations: 1) four reports published by Geoscience British Columbia (GBC) describing the results of field work and the initial results of related analytical studies (Appendix 4; Ruks and Mortensen, 2007, 2008; Ruks et al., 2009, 2010); 2) fifty-one new U-Pb (zircon) age datasets for igneous and sedimentary rocks; 3) twenty-one new biochronological ages; 4) one hundred sixty four new lithogeochemical 162analyses; 5) twenty-five new Sm-Nd isotope geochemical analyses; 6) thirty new Pb isotope geochemical analyses, 7) five poster and five oral presentations at academic and professional conferences in the United States and Canada; and 8) three field trips (Appendix 5) that highlighted the results of the research project for Canadian and American government geological surveys (EDGES field trip on behalf of the Geological Survey of Canada’s Geo Mapping for Minerals program (2010), field trip for mineral explorationists and geology students on behalf of the University of British Columbia Society of Economic Geologists Student Chapter (2011); and field trip for international economic geologists as part of the Society of Economic Geologists Annual Meeting (2013). 7.3 FUTURE RESEARCH Southern Paleozoic Wrangellia, Vancouver Island: Correlative with Northern, Paleozoic Wrangellia, Northern, Paleozoic Stikine Terrane, or both? One of the largest contributions of this study is a revised model for the tectonic, magmatic and metallogenic evolution of southern Paleozoic Wrangellia (Vancouver Island). This revised model is strikingly similar to that proposed for Paleozoic Stikine terrane in northwestern British Columbia (e.g., Logan, 2004; e.g., Gunning et al., 2006). Furthermore, recent work by Israel et al. (2010, 2014) has demonstrated fundamental differences between northern Paleozoic Wrangellia (Yukon and Alaska) and southern Paleozoic Wrangellia (Vancouver Island), calling into question proposed correlations between the two areas. A striking difference between southern and northern Paleozoic Wrangellia includes a relative lack of Late Devonian strata in northern Wrangellia, whereas Late Devonian-Early Missisippian strata are abundant in southern Wrangellia. In addition, Early Mississippian mafic volcanic rocks in northern Wrangellia have back-arc basin basalt chemistry, whereas mafic volcanic rocks of similar age in southern Wrangellia have predominantly island arc tholeiite chemistry. Another important difference between northern and southern Paleozoic Wrangellia includes the presence in Early Permian strata (northern Wrangellia) of detrital zircon populations presumably sourced from the Alexander and/or Stikine terranes. Detrital zircon studies of the southern PWA (Chapter 3) did not reveal the presence of zircon populations that were derived from non-Wrangellian sources. These significant differences between northern and southern Paleozoic Wrangellia suggest that more work should be conducted in order to further test proposed 163correlations between the two areas. Similarly, more work should be conducted in northern Paleozoic Stikine terrane (northwestern British Columbia) to better evaluate potential correlations with southern Paleozoic Wrangellia (Vancouver Island). For example, a detrital zircon study of Paleozoic Stikine terrane (northwestern B.C.) would be useful in understanding its potential relationship to the Insular terranes, and in doing so, furthering our understanding of the tectonic evolution of the North American Cordillera. Using in-situ Hf isotopic studies and Ti in zircon thermometry to understand the nature of crustal contamination and the VMS “fertility” of Paleozoic Wrangellia volcanic and intrusive rocks, Vancouver Island In the process of developing a new model for the tectonic, magmatic and metallogenic evolution of Paleozoic Wrangellia, Vancouver Island (this study), a large suite of samples were processed for LA-ICP-MS U-Pb (zircon) geochronology by the author. As such, a large sample set of mounted and dated zircons are available for further in situ microanalytical studies. Such studies could involve using Hf isotopic analyses of zircon (e.g., Siebel and Chen, 2010) to further evaluate the geochemical evolution of Paleozoic Wrangellia source magmas over time and test for crustal contamination. Although several studies have been conducted to address this question (e.g., Andrew and Godwin, 1989; e.g., Samson et al., 1990; this study), whole rock Pb, Nd, Sr and sulfide Pb isotopic studies were utilized in these efforts. Whole rock isotopic analyses provide only an average isotopic signature for a given sample, wheras in situ Hf isotope studies of individual zircon grains would provide a more accurate assessment of the nature of Paleozoic Wrangellia source magmas and their evolution over time. The present study utilized zircon saturation temperatures, combined with whole rock lithogeochemical and Nd isotopic studies, to understand the nature and evolution of Paleozoic Wrangellia source magmas over time and their “fertility” for producing VMS deposits. Since all of these parameters are the result of whole rock studies, use of the Ti in zircon thermometer, which relies on in situ microanalytical methods (e.g., Fu et al., 2008), would provide a more accurate assessment of the temperatures of Paleozoic Wrangellia magmas, and thus provide a more accurate assessment of their relationship to, and prospectivity for associated VMS mineralization. 164The geology of the Hesquiat area, Vancouver Island Despite the efforts of recent workers, a stratigraphic framework for the geology of the Hesquiat area has not been established. This is largely due to a paucity of geochronological control for the area. In particular, the age of abundant stratified rocks in the area has not been established. This information would be critical not only for improving our understanding of Wrangellian geology, but it is also for facilitating mineral exploration in the area. Providing geochronological control for stratified rocks in the Hesquiat area (including extensive tracts of strongly altered mafic volcanic rocks) will facilitate VMS exploration by providing insight into whether or not the area is prospective for Late Devonian, Myra Falls style VMS mineralization, or Late Paleozoic VMS mineralization similar to that of the Dragon prospect in the Gold River area. A large suite of samples has already been collected for this purpose but have not yet been analyzed. Lead isotope geochemistry of VMS-like mineralization of the Bedingfield area, Vancouver Island Logistical problems encountered during the course of this study prevented the author from sampling VMS-like mineralization of the Bay Creek occurrence, in the Bedingfield uplift, for Pb isotope geochemistry (MINFILE 092F 343; MINFILE, 2013). Silica-pyrite altered rhyolites in that area are spatially related to this mineral occurrence, and have been dated as part of this study at 312.2 ± 3.7 Ma, suggesting that VMS-like mineralization of the Bedingfield area is coeval with Late Paleozoic VMS mineralization of the Dragon property (Gold River area). Despite the VMS-like nature of the Bay Creek occurrence (MINFILE, 2013), however, its proximity to a nearby porphyry Cu-Mo deposit of Tertiary age (the Catface deposit; Imperial Metals Corp.) suggests that an origin as distal precious metal enriched sulfide mineralization related to a porphyry Cu-Mo deposit (e.g., high sulphidation epithermal mineralization) cannot be ruled out. Lead isotope geochemistry of the Bay Creek occurrence could help resolve this question, thereby improving our understanding regarding the VMS potential of the Bedingfield uplift. 165Age and geological setting of Paleozoic strata and VMS-like mineralization, Haida Gwaii Paleozoic strata have only recently been recognized on Haida Gwaii (Hesthammer et al., 1991; Indrelid and Hesthammer, 1991), and significant potential exists to expand their “footprint” in the area. Little research has been conducted on these rocks since their discovery, and as a result, their geological setting and relationship to Paleozoic strata elsewhere in Wrangellia remains poorly understood. VMS-like mineralization of the Cimadoro occurrence (MINFILE, 2013) is likely hosted by this newly recognized belt of Paleozoic strata based on their proximity, although volcanic and sedimentary rocks that host the sulfide occurrence have not yet been directly dated. Geochronological, lithogeochemical and isotopic investigations of the Cimadoro occurrence and surrounding area are required in order to further our understanding of Wrangellian geology on Haida Gwaii, and facilitate VMS exploration in the area. Undated mafic volcanic rocks assigned to the Karmutsen Formation on southern Vancouver Island Abundant Early Permian mafic volcanic rocks with non-arc lithogeochemical affinities have been identified in the Alberni and Nanoose areas as the result of this study. Large thicknesses of mafic volcanic rocks interpreted as a Permian seamount complex have also been recently identified on Orcas Island (Deadman Bay volcanics; Yamagata, 2009), south of Vancouver Island. Interestingly, recently identified Early Permian mafic volcanic rocks of the Alberni area are in immediate proximity to large tracts of undated mafic volcanic rocks that have been assigned to the Middle Triassic Karmutsen Formation (Massey et al., 2005). It is possible that some or all of these basalts in the Alberni area are actually Early Permian in age, and correlative with similar, nearby mafic volcanic rocks of the Alberni and Nanoose areas. Resolving the age(s) of these undated mafic volcanic rocks has important implications for understanding the origin of the Nikolai-Karmutsen Formation, which has been interpreted by many workers as a mantle plume related, large igneous province of Middle Triassic age, and one of the defining stratigraphic features of Wrangellia. If a significant amount of so-called Karmutsen Formation in the Alberni area is not Middle Triassic in age, the Nilkolai-Karmutsen Formation might not be as voluminous as previously thought. 166The nature and timing of oxide facies exhalative iron formation mineralization in the Cowichan uplift Magnetite iron formations are regionally significant stratigraphic units in the Cowichan area, where they stratigraphically overlie VMS occurrences in the area (Massey, 1995b; Ruks and Mortensen, 2007, 2008; Ruks et al., 2009, 2010). They are interpreted to be similar in nature to oxide facies exhalite iron formations which overlie and are interbedded with VMS mineralization in other districts (e.g., the Bathurst district; Galley et al., 2007), and in cases, might provide a means of “vectoring” towards VMS mineralization (e.g., Spry et al., 2000; Peter, 2003; Galley et al., 2007). Several attempts were made during the course of this study to constrain the timing of iron formation mineralization in the Cowichan district using both U-Pb (zircon) geochronology on adjacent tuffaceous volcanic rocks and microfossil biochronology on nearby chert-bearing strata. Unfortunately, no zircons were recovered in this process, and only one chert sample yielded a fossil age. This sample, located 600 m south, and along strike, from the Lady D iron formation (MINFILE, 2013), yielded a Late Pennsylvanian–Early Permian radiolarian fossil age. Although structural complexity exists in this area, this single fossil age suggests that nearby mineralization of the Lady D iron formation is Late Paleozoic in age, approximately coeval with newly recognized, Late Paleozoic VMS mineralization elsewhere in the terrane (e.g., the Dragon and Cimadoro occurrences; MINFILE, 2013). Importantly, a Late Paleozoic age for the Lady D iron formation suggests that iron formations in the Cowichan area might not all be genetically related to Late Devonian VMS occurrences in the district, as was previously thought. This is an important distinction, as iron formations in the Cowichan area have been drill tested in the past for underlying, Late Devonian, Myra Falls-like VMS deposits. Furthermore, the presence of Late Paleozoic exhalative iron formations in the Cowichan area suggests that the district might also be prospective for Late Paleozoic VMS mineralization similar to that found elsewhere in the terrane (e.g., the Dragon and Cimadoro occurrences, MINFILE, 2013). The most significant iron formation in the Cowichan area, notably the Lady A occurrence (MINFILE, 2013), occurs stratigraphically above VMS mineralization of the Anita occurrence (MINFILE, 2013), and locally attains thicknesses of up to 9 m. 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D., 1999, LITHOPROBE, southern Vancouver Island, British Columbia: geology: Geological Survey of Canada Bulletin, v. 498, p. 145. Zartman, R. E., and Doe, B. R., 1981, Plumbotectonics - the model: Tectonophysics, v. 75, p. 135-162. 185Appendices 186Appendix 1: U-Pb Geochronology 187Analytical Methods for U-Pb Geochronology Uranium-lead ages for zircons from volcanic rocks and intrusive phases collected from uplifts of Paleozoic rocks on Vancouver Island were obtained using a combination of laser ablation ICP-MS and ID-TIMS methods. Laser ablation ICP-MS The following methods for U-Pb dating of zircon using laser ablation ICP-MS are from Tafti et al. (2009): U-Pb zircon dates were obtained by laser ablation ICP-MS methods at the Pacific Centre for Isotopic and Geochemical Research (PCIGR) at the University of British Columbia. Zircons from each sample were mounted in thermal-setting epoxy pucks together with several grains of the Plešovice reference zircon standard (338 ±1 Ma; Sláma et al. 2008). The mount was loaded into a New Wave “Supercell” ablation cell and analyzed using a New Wave 213nm Nd-YAG laser coupled to a Thermo Finnigan Element2 high resolution ICP-MS. A 25-30 micron spot with 60% laser power was used; employing line scans rather than spot analyses to minimize within-run elemental fractionation. 238U and 232Th data were acquired in analog mode, whereas 208Pb, 207Pb, 206Pb, 204Pb and 202Hg were acquired using ion counting mode. Data were reduced using GLITTER software (GEMOC, Macquarie University, Australia; van Achterberg et al., 1999). Time-resolved data were carefully examined to identify and avoid portions of the signal that reflected Pb-loss and/or the presence of older inherited cores or altered zones in the zircon being analyzed. Final interpretation and plotting of the analytical results employed the ISOPLOT v. 3.09 software of Ludwig (2003). The 206Pb/238U age is the most precisely determined age for relatively young (Phanerozoic) zircons and is interpreted as the best estimate for the crystallization age of the samples. Assigned ages are based on a weighted average of overlapping, concordant 206Pb/238U ages of individual analyses for each sample. Errors are quoted at the 2σ level. 188CA-TIMS The following methods for U-Pb dating of zircon using CA-TIMS are from Scoates and Friedman (2008): Zircon was separated from 5- to 20-kg samples using conventional crushing, grinding, Wilfley table, heavy liquids, and Frantz magnetic separator techniques. The zircon grains selected for CA-TIMS analysis were annealed in quartz glass crucibles in a muffle furnace at 850ºC for 48 h. They were transferred into 10 mL Pyrex® beakers, agitated in ultrapure 3 N HNO3 in an ultrasonic cleaner for 15 min, warmed to 60º ± 10ºC for 30 min, and rinsed with ultrapure acetone and water. The zircon grains were then transferred to 3.5 mL PFA screwtop beakers, ultrapure HF (50%, 500 μL) and HNO3 (14 N, 50 μL) were added, and caps were closed finger-tight. Following this, the beakers were placed in 125 mL PTFE Teflon® liners (up to four per liner) and about 2 mL HF and 0.2 mL concentrated HNO3 was added to the liners. The liners were slid into stainless steel jackets of Parr® high-pressure dissolution devices, which were sealed and brought up to 200ºC for 16 h. After cooling, the beakers were removed from the liners and the remaining zircon grains were separated from the leachate. The grains were pipetted into clean 3.5 mL PFA Teflon® beakers and rinsed with ultrapure water. They were then transferred into clean 10 mL Pyrex® beakers, one grain per beaker, and 2 mL of ultrapure 6 N HCl was added to each beaker. Each beaker was agitated in an ultrasonic cleaner for 15 min, warmed to 60 ± 10ºC for 30 min, and rinsed with ultrapure acetone and water. The annealed, leached, and rinsed grains were then weighed, each transferred into 300 μL PFA microcapsules, and 50 μL of 50 percent HF and 5 μL of 14 N HNO3 were added. Each single zircon in its microcapsule was spiked with a 233–235U-205Pb isotopic tracer, capped and placed in a Parr® liner (8-13 microcapsules per liner). HF and nitric acids in a 10:1 ratio, respectively, were added to the liner, which was then placed in the jacket, sealed, and brought up to 240ºC for 40 h for complete dissolution. The resulting solutions were dried on a hotplate at 130ºC. The fluorides were dissolved in 3.1 N HCl in the high-pressure devices for 12 h at 210°C. Separation and purification of Pb and U employed ion exchange column techniques modified slightly from those described by Parrish et al. (1987), where Pb and U were sequentially eluted into a single beaker. Leachates were also spiked and processed in this manner along with the single annealed and leached zircon grains; following chemistry they were transferred into clean 7 mL PFA beakers and dried after adding 2 μL of 0.5 N H3PO4. 189 All zircon samples, including zircon leachates, were loaded onto single zone-refined Re filaments with 5 μL of silicic acid activator (Gerstenberger and Haase, 1997). Isotopic ratios were measured using a modified single collector VG-54R thermal ionization mass spectrometer equipped with a Daly photomultiplier housed at the Pacific Centre for Isotopic and Geochemical Research. Measurements were done in peak-switching mode on the Daly detector. U and Pb total procedural blanks were 1.0 pg and 4 to 9 pg for zircon.. U fractionation was determined directly on individual runs using the 233–235U tracer. Pb isotope ratios were corrected for a fractionation of 0.23 to 0.32%/amu based on replicate analyses of the NBS-981 and NBS-982 Pb reference materials and the values recommended by Thirwall (2000). The UBC 233–235U-205Pb isotopic tracer was calibrated in 2003 against mixed reference solutions prepared in-house from standard reference lead (NBS 981) and uranium (CRM 112-A; natural composition U metal, formerly NBS 960). Calibration results for two reference solutions of different U/Pb ratios yielded indistinguishable results. During 2005, the original calibration was checked against three mixed U-Pb gravimetric reference solutions from MIT, UC Santa Barbara, and NIGL (UK) made available through the EARTHTIME initiative (http://www.earth-time.org) and gave a U/Pb ratio that agreed within 0.1% of the 2003 value. All analytical errors were numerically propagated through the entire age calculation using the technique of Roddick (1987). Standard Concordia diagrams were constructed and U-Pb Concordia ages calculated with Isoplot 3.00 (Ludwig, 2000); all errors are quoted at the 2σ level. U-Pb Zircon Geochronology: Interpretation of the Results Uranium-lead ages for zircons from volcanic rocks and intrusive phases collected from uplifts of Paleozoic rocks on Vancouver Island were obtained using a combination of laser ablation ICP-MS and ID-TIMS methods. Crystallization ages for the samples are based on the 206/Pb/238U age, which is considered the most precisely determined age for Phanerozoic zircon. Assigned ages are based on a weighted average of overlapping, concordant 206Pb/238U ages of individual analyses for each sample. Interpretations of the results for the samples are summarized below. 09TR063. A total of 20 zircon grains were analyzed by LA-ICP-MS from this sample of rhyolite flow, located approximately 600 m north of the Sherk Lake iron formation (Fig. 2.12; MINFILE 092C 026; MINFILE, 2012). Twenty analyses are concordant and yielded 206Pb/238U 190ages between 344.7 Ma and 367.2 Ma (Fig. 2.5A). Twenty analyses yielded a weighted average 206Pb/238U age of 355.6 ± 3.3 Ma. 09TR128. A total of 64 grains were analyzed by LA-ICP-MS from this sample of rhyolite crystal tuff, located approximately 300 m west of the Sherk Lake iron formation (Fig. 2.12; MINFILE 092C 026; MINFILE, 2012). Sixty-three analyses are concordant and yielded 206Pb/238U ages between 349 Ma and 372.1 Ma (Fig. 2.5B). Analyses 13 and 9 are discordant. Analyses 13 (349 Ma) and 52 (372.1 Ma) were rejected by Isoplot. Sixty-two analyses yielded a weighted average 206Pb/238U age of 359.3 ± 1.3 Ma. 09TR041. A total of 12 grains were analyzed by LA-ICP-MS from this sample of weakly foliated rhyolite tuff, located approximately 500 m south of the Anita VMS occurrence (Fig. 2.12; MINFILE 092B 037; MINFILE, 2012). Eleven analyses are concordant and yielded 206Pb/238U ages between 343.1 Ma and 364 Ma (Fig. 2.5C). Analysis 8 is discordant. Eleven analyses yielded a weighted average 206Pb/238U age of 355.3 ± 4.4 Ma. 08TR061B. A total of 20 grains were analyzed by LA-ICP-MS from this sample of foliated rhyolite tuff, located approximately 150 m southeast of the Anita VMS occurrence (Fig. 2.12; MINFILE 092B 037; MINFILE, 2012). A total of 19 analyses are concordant and yielded 206Pb/238U ages between 353.1 Ma and 365.9 Ma (Fig. 2.5D). Analysis 8 is slightly discordant. Nineteen analyses yielded a weighted average 206Pb/238U age of 359.2 ± 2.0 Ma. 08TR055A. A total 20 grains were analyzed by LA-ICP-MS from this sample of foliated and sericitized rhyolite porphyry, located approximately 2100 m northwest of the Lara VMS occurrence (Fig. 2.12; MINFILE 092B 129; MINFILE, 2012). Nineteen analyses are concordant and yielded 206Pb/238U ages between 350 Ma and 365.3 Ma (Fig. 2.5E). Analysis 7 is discordant. Nineteen analyses yielded a weighted average 206Pb/238U age of 357.2 ± 2.0 Ma. 09TR042. A total of 20 zircon grains were analyzed by LA-ICP-MS from this sample of strongly foliated and sericitized rhyolite crystal tuff, located approximately 250 m northwest of the Randy North VMS occurrence (Fig. 2.12; MINFILE 092B 128; MINFILE, 2012). Eighteen analyses are concordant and yielded 206Pb/238U ages between 350.5 Ma and 370 Ma (Fig. 2.5F). Analyses 19 and 20 are slightly discordant. Analysis 11 (350.5 Ma) was rejected by Isoplot. Eighteen analyses yielded a weighted average 206Pb/238U age of 362.8 ± 2.6 Ma. 05M393. A total of 5 zircon grains were analyzed by ID-TIMS from this sample of rhyolite crystal tuff, located approximately 70 m southwest of the Lara VMS occurrence (Fig. 2.12; MINFILE 092B 129; MINFILE, 2012). Four analyses are concordant and yielded 191206Pb/238U ages between 353 Ma and 363 Ma (Fig. 2.5G). Analysis C is slightly discordant. Four analyses yielded a weighted average 206Pb/238U age of 358.1 ± 7.7 Ma. 08TR049A. A total of 20 zircon grains were analyzed by LA-ICP-MS from this sample of foliated and sericitized felsic crystal tuff, located approximately 2.8 km northeast of the Lara VMS occurrence (Fig. 2.12; MINFILE 092B 129; MINFILE, 2012). Eighteen analyses are concordant and yielded 206Pb/238U ages between 349.8 Ma and 368.7 Ma (Fig. 2.5H). Analyses 10 and 16 are discordant. Eighteen analyses yielded a weighted average 206Pb/238U age of 359.7 ± 2.4 Ma. 05M366. A total of 5 zircon grains were analyzed by ID-TIMS from this sample of rhyolite lapilli tuff, located next to the Lenora VMS occurrence (Fig. 2.12; MINFILE 092B 001; MINFILE, 2012). Five analyses are concordant and yielded 206Pb/238U ages between 360.19 Ma and 371.98 Ma (Fig. 2.5I). Five analyses yielded a weighted average 206Pb/238U age of 363.0 ± 6.7 Ma. 08TR101. A total of 13 zircon grains were analyzed by LA-ICP-MS from this sample of strongly sericitized felsic tuff, located approximately 2 km northeast of the Lenora VMS occurrence (Fig. 2.12; MINFILE 092B 001; MINFILE, 2012). A total of thirteen analyses are concordant and yielded 206Pb/238U ages between 355.8 Ma and 372.4 Ma (Fig. 2.5J) . Analysis 3 (372.4 Ma) was rejected by Isoplot. Twelve analyses yielded a weighted average 206Pb/238U age of 360.9 ± 2.7 Ma. 08TR107A. A total of 20 zircon grains were analyzed by ID-TIMS from this sample of weakly sericitized quartz-feldspar porphyry, located 2.8 km northeast of the Lenora VMS occurrence (Fig. 2.12; MINFILE 092B 001; MINFILE, 2012). Twenty analyses are concordant and yielded 206Pb/238U ages between 350.1 Ma and 370.3 Ma (Fig. 2.5K). Analysis 19 (350.1) was rejected by Isoplot. Nineteen analyses yielded a weighted average 206Pb/238U age of 361.5 ± 2.4 Ma. 08TR114. A total of 13 zircon grains were analyzed by LA-ICP-MS from this sample of chlorite and hematite altered quartz-feldspar porphyry, located approximately 3.3 km northeast of the Lenora VMS occurrence (Fig. 2.12; MINFILE 092B 001; MINFILE, 2012). Eleven analyses are concordant and yielded 206Pb/238U ages between 350.9 Ma and 371.5 Ma (Fig. 2.5L). Analyses 2 and 13 are discordant. Thirteen samples yielded a weighted average 206Pb/238U age of 355.8 ± 4.4 Ma. 08TR121. A total of 7 zircon grains were analyzed by LA-ICP-MS from this sample of weakly sericitized rhyolite crystal tuff, located approximately 800 m east of the Jane VMS 192occurrence (Fig. 2.12; MINFILE 092B 084; MINFILE, 2012). Seven analyses are concordant and yielded 206Pb/238U ages between 345.3 Ma and 361.6 Ma (Fig. 2.5M). Seven analyses yielded a weighted average 206Pb/238U age of 353.1 ± 3.4 Ma. 09TR132. A total of 20 zircon grains were analyzed by LA-ICP-MS from this sample of quartz-feldspar porphyry, located approximately 4.4 km southeast of the Jane VMS occurrence (Fig. 2.12; MINFILE 092B 084; MINFILE, 2012). Seventeen analyses are concordant and yielded 206Pb/238U ages between 347 Ma and 370.1 Ma (Fig. 2.5N). Analyses 1, 8 and 19 are slightly discordant. Analysis 16 (347 Ma) was rejected by Isoplot. Sixteen analyses yielded a weighted average 206Pb/238U age of 360.7 ± 2.4 Ma. 09M309. A total of 20 zircon grains were analyzed by LA-ICP-MS from this sample of quartz-feldspar porphyry, located approximately 1.7 km north of Fulford Harbour (Fig. 2.12). Twenty analyses are concordant and yielded 206Pb/238U ages between 347.4 Ma and 372.2 Ma (Fig. 2.5O). Twenty analyses yielded a weighted average 206Pb/238U age of 359.3 ± 3.1 Ma. 09M308. A total of 20 zircon grains were analyzed by LA-ICP-MS from this sample of quartz-feldspar porphyry, located approximately 3 km northeast of Fulford Harbour (Fig. 2.12). A total of 13 analyses are concordant and yielded 206Pb/238U ages between 353.8 Ma and 365.3 Ma (Fig. 2.5P). Analyses 6, 8, 10, 11, 16, 17, and 19 are discordant. Thirteen analyses yielded a weighted average 206Pb/238U age of 358.7 ± 2.5 Ma. 09M302. A total of 20 zircon grains were analyzed by LA-ICP-MS from this sample of quartz-feldspar porphyry, located approximately 4.5 km northeast of Fulford Harbour (Fig. 2.12). Nineteen analyses are concordant and yielded 206Pb/238U ages between 350.3 Ma and 365.4 Ma (Fig. 2.5Q). Analysis 19 is discordant. Nineteen analyses yielded a weighted average 206Pb/238U age of 355.0 ± 1.5 Ma. 08TR031. A total of 20 zircon grains were analyzed by LA-ICP-MS from this sample of heterolithic lapilli tuff, located 11 km south of Cameron Lake (Fig. 2.13). Twenty analyses are concordant and yielded 206Pb/238U ages between 356 Ma and 384.9 Ma (Fig. 2.6A). Analysis 18 (384.9 Ma) was rejected by Isoplot. Nineteen analyses yielded a weighted average 206Pb/238U age of 366.8 ± 2.4 Ma 07TR051B. A total of 4 zircon grains were analyzed by LA-ICP-MS from this sample of dacite flow, located 4 km west of Cameron Lake (Fig. 2.13). Four analyses are concordant, and yielded 206Pb/238U ages between 366.45 Ma and 372.02 Ma (Fig. 2.6B). Analyses A (371.18 Ma) and D (372.02 Ma) were rejected. Two analyses yielded a weighted average 206Pb/238U age of 366.58 ± 0.67 Ma. 193 08TR002B. A total of 64 zircon grains were analyzed by LA-ICP-MS from this sample of rhyolite crystal tuff, located 4 km west of Cameron Lake (Fig. 2.13). A total of 58 analyses are concordant, and yielded 206Pb/238U ages between 350.6 Ma and 389.2 Ma (Fig. 2.6C). Analyses 14, 23, 31, and 39 are discordant. Analyses 15 (389.2 Ma) and 62 (387.6 Ma) were rejected by Isoplot. A total of 56 analyses yielded a weighted average 206Pb/238U age of 366.7 ± 2.3 Ma. 08TR002. A total of 62 zircon grains were analyzed by LA-ICP-MS from this sample of rhyolite crystal tuff, located 4 km west of Cameron Lake (Fig. 2.13). A total of 51 analyses are concordant, and yielded 206Pb/238U ages between 350.8 Ma and 383.3 Ma (Fig. 2.6D). Analyses 6, 11, 31, and 36 are discordant. A total of 51 analyses yielded a weighted average 206Pb/238U age of 363.8 ± 2.5 Ma. 05M386b. A total of 12 zircon grains were analyzed by LA-ICP-MS from this sample of thinly bedded rhyolite tuff, located 3 km west of Cameron Lake (Fig. 2.13). A total of 11 analyses are concordant, and yielded 206Pb/238U ages between 342.4 Ma and 366.7 Ma (Fig. 2.6E). Analysis 7 is discordant. Analysis 9 (342.4 Ma) was rejected by Isoplot. A total of 10 analyses yielded a weighted average 206Pb/238U age of 360.8 ± 2.9 Ma. 05M386c. A total of 5 zircon grains were analyzed by LA-ICP-MS from this sample of rhyolite crystal tuff, located 3 km west of Cameron Lake (Fig. 2.13). A total of 5 analyses are concordant, and yielded 206Pb/238U ages between 363.51 Ma and 363.95 Ma (Fig, 2.6F). A total of 5 analyses yielded a weighted average 206Pb/238U age of 363.86 ± 0.40 Ma. 08TR082. A total of 18 zircon grains were analyzed by LA-ICP-MS from this sample of rhyolite lapilli tuff, located 2.4 km northwest of Cameron Lake (Fig. 2.13). A total of 16 analyses are concordant, and yielded 206Pb/238U ages between 336.6 Ma and 355.6 Ma (Fig. 2.6G). Analyses 4 and 6 are weakly discordant. A total of 16 analyses yielded a weighted average 206Pb/238U age of 346.4 ± 2.7 Ma. 08TR084B. A total of 20 zircon grains were analyzed by LA-ICP-MS from this sample of rhyolite tuff breccia, located 3 km northwest of Cameron Lake (Fig. 2.13). A total of 18 analyses are concordant, and yielded 206Pb/238U ages between 333.9 Ma and 349.4 Ma (Fig. 2.6H). Analyses 13 and 20 are discordant. Analysis 17 (349.4 Ma) was rejected by Isoplot. A total of 17 analyses yielded a weighted average 206Pb/238U age of 340.7 ± 1.7 Ma. 08TR078. A total of 20 zircon grains were analyzed by LA-ICP-MS from this sample of rhyolite lapilli tuff, located 3.2 km northwest of Cameron Lake (Fig. 2.13). A total of 18 analyses are concordant, and yielded 206Pb/238U ages between 337.6 Ma and 371.6 Ma (Fig. 1942.6I). Analyses 8 and 19 are discordant. Analysis 11 (371.6 Ma) was rejected by Isoplot. A total of 17 analyses yielded a weighted average 206Pb/238U age of 343.4 ± 2.2 Ma. 07TR043. A total of 20 zircon grains were analyzed by LA-ICP-MS from this sample of rhyolite tuff breccia, located 1.5 km south of Horne Lake (Fig. 2.13). A total of 19 analyses are concordant, and yielded 206Pb/238U ages between 339 Ma and 363.2 Ma (Fig. 2.6J). Analysis 7 is discordant. A total of 19 analyses yielded a weighted average 206Pb/238U age of 351.1 ± 3.0 Ma. 07TR049. A total of 15 zircon grains were analyzed by LA-ICP-MS from this sample of rhyolitic volcanic sandstone, located approximately 600 m south of Horne Lake (Fig. 2.13). A total of 14 analyses are concordant, and yielded 206Pb/238U ages between 341.6 Ma and 377 Ma (Fig. 2.6K). Analysis 8 is weakly discordant. Analysis 11 (377.0 Ma) was rejected by Isoplot. A total of 13 analyses yielded a weighted average 206Pb/238U age of 347.2 ± 2.3 Ma. 09TR034. A total of 20 zircon grains were analyzed by LA-ICP-MS from this sample of quartz-feldspar porphyry, located approximately 400 m southwest of Horne Lake (Fig. 2.13). A total of 20 analyses are concordant, and yielded 206Pb/238U ages between 321.8 Ma and 345.5 Ma (Fig. 2.6L). Analysis 9 (321.8 Ma) was rejected by Isoplot. A total of 19 analyses yielded a weighted average 206Pb/238U age of 335.3 ± 2.5 Ma. 09TR090. A total of 20 zircon grains were analyzed by LA-ICP-MS from this sample of quartz-feldspar rhyolite porphyry, located approximately 700 m west of Horne Lake (Fig. 2.13). A total of 20 analyses are concordant, and yielded 206Pb/238U ages between 322.7 Ma and 352.8 Ma (Fig. 2.6M). A total of 20 analyses yielded a weighted average 206Pb/238U age of 338.3 ± 3.5 Ma. 07TR005A. A total of 19 zircon grains were analyzed by LA-ICP-MS from this sample of heterolithic dacite clast bearing lapilli tuff, located 400 m west of Lacy Lake (Fig. 2.13). All analyses from this sample are concordant, and three zircon populations are present (Fig. 2.6N). The first and oldest population yielded 206Pb/238U ages between 337.8 Ma and 339.1 Ma. The second population yielded 206Pb/238U ages between 309 Ma and 322.3 Ma. The third, and youngest population yielded 206Pb/238U ages between 289.9 Ma and 298.4 Ma. A total of 11 analyses from the youngest zircon population yielded a weighted average 206Pb/238U age of 293.6 ± 1.8 Ma. 08TR017. A total of 28 zircons were analyzed by LA-ICP-MS from this sample of siltstone from the Nanoose area (Fig. 2.14). A total of 26 analyses are concordant, and yielded 206Pb/238U ages between 294.7 Ma and 355 Ma (Fig. 2.7A). Analyses 9 and 18 are discordant. Three age peaks are present in this sample, at 305 Ma, 321 Ma, and 354 Ma. 19508TR019. A total of 65 zircons were analyzed by LA-ICP-MS from this sample of sandstone from the Nanoose area (Fig. 2.14). A total of 65 analyses yielded 206Pb/238U ages between 297.8 Ma and 330.2 Ma (Fig. 2.7B). A single age peak is present in this sample, at 311 Ma. 08TR020. A total of 19 zircons were analyzed by LA-ICP-MS from this sample of granodiorite from the Nanoose area (Fig. 2.14). A total of 18 analyses are concordant and yielded 206Pb/238U ages between 193.8 Ma and 205.7 Ma (Fig. 2.7C). Analysis 1 is discordant. A total of 18 zircons yielded a weighted average 206Pb/238U age of 199.1 ± 1.5 Ma. 09TR118. A total of 19 zircons were analyzed by LA-ICP-MS from this sample of rhyolite flow from the Herbert Inlet area (Fig. 2.15). A total of 18 analyses are concordant, and yielded 206Pb/238U ages between 290.4 Ma and 322.2 Ma (Fig. 2.8A). Analysis 19 is weakly discordant. Analysis 8 (290.4 Ma) was rejected by Isoplot. A total of 17 analyses yielded a weighted average 206Pb/238U age of 308.0 ± 3.2 Ma. 09TR117. A total of 20 zircons were analyzed by LA-ICP-MS from this sample of rhyolite lapilli tuff from the Herbert Inlet area (Fig. 2.15). A total of 20 analyses are concordant, and yielded 206Pb/238U ages between 285.1 Ma and 323.8 Ma (Fig. 2.8B). Analysis 1 (285.1 Ma) was rejected by Isoplot. A total of 19 analyses yielded a weighted average 206Pb/238U age of 305.6 ± 4.1 Ma. 09TR105. A total of 19 zircons were analyzed by LA-ICP-MS from this sample of foliated, silicified and stockwork sulphide mineralized rhyolite flow from the Cypress Bay area (Fig. 2.15). A total of 19 analyses are concordant, and yielded 206Pb/238U ages between 296.8 Ma and 329.3 Ma (Fig. 2.8C). Analysis 18 (329.3 Ma) was rejected by Isoplot. A total of 18 analyses yielded a weighted average 206Pb/238U age of 312.2 ± 3.7 Ma. 09TR110. A total of 20 zircons were analyzed by LA-ICP-MS from this sample of quartz-feldspar rhyolite porphyry, located 2.6 km northwest of the Claim Post stockwork chalcopyrite occurrence (Fig. 2.15; MINFILE 092F 290; MINFILE, 2012). A total of 19 analyses are concordant, and yielded 206Pb/238U ages between 299.9 Ma and 324.7 Ma (Fig. 2.8D). Analysis 3 is discordant. A total of 19 analyses yielded a weighted average 206Pb/238U age of 312.4 ± 3.5 Ma. 09TR107. A total of 20 zircons were analyzed by LA-ICP-MS from this sample of quartz-feldspar porphyry dike, located adjacent to the Claim Post stockwork chalcopyrite occurrence (Fig. 2.15; MINFILE 092F 290; MINFILE, 2012). A total of 19 analyses are concordant, and yielded 206Pb/238U ages between 190.3 Ma and 205.6 Ma (Fig. 2.8E). Analysis 19612 is discordant. Analysis 1 (190.3 Ma) was rejected by Isoplot. A total of 18 analyses yielded a weighted average 206Pb/238U age of 200.1 ± 1.2 Ma. 08TRDR007B. A total of 4 zircons were analyzed by ID-TIMS from this sample of aphyric rhyolite flow, located 700 m south of the Falls and North VMS occurrences (Fig. 2.16; MINFILE 092E 072; MINFILE, 2012). One of four analyses is concordant, yielding a 206Pb/238U age of 303.09 ± 0.53 Ma (Fig. 2.9A). Analyses C, D and E are discordant. All four analyses define a discordia curve, with an upper intercept yielding a 206Pb/238U age of 304.2 ± 3.1 Ma, and a lower intercept yielding a 206Pb/238U age of 19 ± 40 Ma (Fig. 2.9A). The single concordant analysis (B), yielding a 206Pb/238U age of 303.09 ± 0.53 Ma, is interpreted as the age of the sample. 08TRDR007B. A total of 20 zircons were analyzed by LA-ICP-MS from this sample of aphyric rhyolite flow, located 700 m south of the Falls and North VMS occurrences (Fig. 2.16; MINFILE 092E 072; MINFILE, 2012). A total of 14 analyses are concordant, and yielded 206Pb/238U ages between 295.2 Ma and 325.1 Ma (Fig. 2.9B). Analyses 3, 6, 7, 8 and 19 are discordant. A total of 14 analyses yielded a weighted average 206Pb/238U age of 308.3 ± 5.0 Ma. 08TRDR053A. A total of 4 zircons were analyzed by ID-TIMS from this sample of quartz-feldspar porphyry located 4.2 km southwest of the Falls and North VMS occurrences (Fig. 2.16; MINFILE 092E 072; MINFILE, 2012). A total of two analyses are concordant, and yielded 206Pb/238U ages between 311.02 Ma and 311.21 Ma (Fig. 2.9C). Analyses A and B are discordant. A total of 2 analyses yielded a weighted average 206Pb/238U age of 311.10 ± 0.31 Ma. 08TRDR042. A total of 3 zircons were analyzed by LA-ICP-MS from this sample of heterolithic tuff breccia, located approximately 2.1 km south of the Falls and North VMS occurrences (Fig. 2.16; MINFILE 092E 072; MINFILE, 2012). A total of 3 analyses are concordant, and yielded 206Pb/238U ages between 301.2 Ma and 314.1 Ma (Fig. 2.9D). A total of 3 analyses yielded a weighted average 206Pb/238U age of 308 ± 16 Ma. 08TRDR056. A total of 6 zircons were analyzed by LA-ICP-MS from this sample of rhyolite dike, located approximately 2.8 km southwest of the Falls and North VMS occurrences Fig. 2.16; MINFILE 092E 072; MINFILE, 2012). A total of 5 analyses are concordant, and yielded 206Pb/238U ages between 168.9 Ma and 175.1 Ma (Fig. 2.9E). Analysis 2 is discordant. A total of 5 analyses yielded a weighted average 206Pb/238U age of 172.3 ± 2.5 Ma. 09TRDR013. A total of 20 zircons were analyzed by LA-ICP-MS from this sample of quartz-feldspar rhyolite porphyry, located approximately 2.8 km southeast of the Falls and North VMS occurrences (Fig. 2.16; MINFILE 092E 072; MINFILE, 2012). A total of 20 analyses are 197concordant, and yielded 206Pb/238U ages between 284.5 Ma and 360.2 Ma (Fig. 2.9F). Analysis 6 (360.2 Ma) is likely xenocrystic zircon, and is not included in the weighted average age calculation for this sample. A total of 19 analyses yielded a weighted average 206Pb/238U age of 300 ± 3.4 Ma. 09TRDR016. A total of 65 zircons were analyzed by LA-ICP-MS from this sample of rhyolitic volcanic sandstone, located approximately 3.7 km southeast of the Falls and North VMS occurrences (Fig. 2.16; MINFILE 092E 072; MINFILE, 2012). A total of 47 analyses are within a ± 10% discordance threshold, and yielded 206Pb/238U ages between 275.3 Ma and 324 Ma (Fig. 2.9G). Analyses 3 through 8, 11, 14, 21, 25 through 27, 35, 36, 47, 54, 55, and 63 fall outside a ± 10% discordance threshold and are not included in the weighted average age calculation for the sample. Analyses 13 (275.3 Ma), 24 (324 Ma) and 64 (318.6 Ma) were rejected by Isoplot. A total of 44 analyses yielded a weighted average 206Pb/238U age of 291.6 ± 2.2 Ma. 09TRDR010. A total of 29 zircons were analyzed by LA-ICP-MS from this sample of rhyolite lapilli tuff, located 4.3 km southeast of the Falls and North VMS occurrences (Fig. 2.16; MINFILE 092E 072; MINFILE, 2012). A total of 19 analyses are concordant, and yielded 206Pb/238U ages between 294.2 Ma and 313.3 Ma (Fig. 2.9H). Analysis 14 (294.2 Ma) was rejected by Isoplot. A total of 18 analyses yielded a weighted average 206Pb/238U age of 307.6 ± 2.2 Ma. 07TRHS018A. A total of 20 zircons were analyzed by LA-ICP-MS from this sample of epidote altered granodiorite porphyry, located in the Hesquiat Peninsula area, just to the north of an unnamed lake (Fig. 2.17). A total of 19 analyses are concordant, and yielded 206Pb/238U ages between 199 Ma and 211.1 Ma (Fig. 2.10A). Analysis 11 is discordant. Analysis 15 (211.1 Ma) was rejected by Isoplot. A total of 18 analyses yielded a weighted average 206Pb/238U age of 202.2 ± 1.3 Ma. 07TRHS020A. A total of 20 zircons were analyzed by LA-ICP-MS from this sample of strongly epidote altered rhyolite dike, located in the Hesquiat Peninsula area, just to the west of an unnamed lake (Fig. 2.17). A total of 7 analyses are concordant, and yielded 206Pb/238U ages between 174.3 Ma and 184.6 Ma (Fig. 2.10B). Analyses 8 through 20 are discordant. A total of 7 analyses yielded a weighted average 206Pb/238U age of 180.9 ± 3.2 Ma. 11TRMF010. A total of 20 zircons were analyzed by LA-ICP-MS from this sample of quartz-feldspar rhyolite porphyry, which immediately underlies the Marshall Zone of the Myra Falls VMS deposit (Fig. 2.2). A total of 20 analyses are concordant, and yielded 206Pb/238U ages 198 between 353.7 Ma and 380.6 Ma (Fig. 2.11). Analysis 12 (380.6 Ma) was rejected by Isoplot. A total of 19 analyses yielded a weighted average 206Pb/238U age of 361.5 Ma. 199Table A1.1. TIMS and LA-ICP-MS U, Pb and Th isotope analytical data of dated zircon grains from samples from southern Paleozoic WrangelliaIsotopic Ratios Calculated AgesRun # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs05M386b: Thinly bedded rhyolite tuff 1 0.05466 0.00050 0.9 0.43103 0.00435 1.0 0.05762 0.00021 0.4 0.36 398.5 20.06 363.9 3.08 361.2 1.252 0.05375 0.00057 1.1 0.42320 0.00501 1.2 0.05732 0.00024 0.4 0.35 360.7 23.85 358.3 3.57 359.3 1.463 0.05397 0.00061 1.1 0.43687 0.00544 1.2 0.05829 0.00025 0.4 0.34 369.6 25.22 368.0 3.84 365.2 1.534 0.05321 0.00067 1.3 0.41907 0.00582 1.4 0.05732 0.00028 0.5 0.35 337.8 28.05 355.4 4.17 359.3 1.705 0.05336 0.00078 1.5 0.42341 0.00686 1.6 0.05774 0.00032 0.6 0.34 344.3 32.62 358.5 4.90 361.9 1.976 0.05255 0.00091 1.7 0.41656 0.00805 1.9 0.05766 0.00039 0.7 0.35 309.2 39.11 353.6 5.77 361.4 2.357 0.05090 0.00076 1.5 0.40136 0.00666 1.7 0.05705 0.00032 0.6 0.34 236.2 34.28 342.6 4.83 357.7 1.988 0.05228 0.00094 1.8 0.40640 0.00812 2.0 0.05560 0.00039 0.7 0.35 297.6 40.29 346.3 5.86 348.8 2.399 0.05429 0.00091 1.7 0.40571 0.00761 1.9 0.05456 0.00036 0.7 0.35 383.1 37.21 345.8 5.49 342.4 2.2310 0.05385 0.00106 2.0 0.43102 0.00952 2.2 0.05768 0.00045 0.8 0.35 364.8 43.77 363.9 6.76 361.5 2.7511 0.05323 0.00097 1.8 0.42607 0.00878 2.1 0.05853 0.00043 0.7 0.36 338.4 40.66 360.4 6.25 366.7 2.6112 0.05236 0.00121 2.3 0.41563 0.01086 2.6 0.05737 0.00053 0.9 0.35 301.3 51.74 352.9 7.79 359.6 3.2207TR005A: Heterolithic dacitic lapilli tuff1 0.05271 0.00183 3.5 0.35299 0.01281 3.6 0.04911 0.00059 1.2 0.33 316.3 77.00 307.0 9.62 309.0 3.602 0.05302 0.00199 3.8 0.37073 0.01463 3.9 0.04951 0.00065 1.3 0.33 329.7 83.05 320.2 10.83 311.5 4.003 0.05435 0.00149 2.7 0.35872 0.01031 2.9 0.04704 0.00047 1.0 0.35 385.5 60.09 311.3 7.70 296.3 2.894 0.05277 0.00051 1.0 0.34017 0.00351 1.0 0.04672 0.00020 0.4 0.41 319.0 21.86 297.3 2.66 294.4 1.225 0.05123 0.00083 1.6 0.33145 0.00569 1.7 0.04738 0.00030 0.6 0.37 251.0 36.99 290.7 4.34 298.4 1.866 0.05400 0.00096 1.8 0.34370 0.00644 1.9 0.04610 0.00032 0.7 0.37 371.1 39.61 300.0 4.86 290.5 1.987 0.05345 0.00077 1.4 0.39506 0.00612 1.5 0.05401 0.00032 0.6 0.38 348.0 32.23 338.1 4.45 339.1 1.948 0.05192 0.00159 3.1 0.37996 0.01230 3.2 0.05127 0.00055 1.1 0.33 281.9 68.55 327.0 9.05 322.3 3.379 0.05263 0.00104 2.0 0.36576 0.00769 2.1 0.05019 0.00038 0.8 0.36 312.9 44.47 316.5 5.72 315.7 2.3110 0.05236 0.00123 2.3 0.33831 0.00832 2.5 0.04680 0.00040 0.9 0.35 301.1 52.47 295.9 6.31 294.8 2.4911 0.05131 0.00061 1.2 0.32428 0.00410 1.3 0.04600 0.00023 0.5 0.40 254.6 27.27 285.2 3.15 289.9 1.4012 0.05777 0.00210 3.6 0.38454 0.01460 3.8 0.04974 0.00062 1.2 0.33 520.9 78.10 330.4 10.71 312.9 3.8213 0.05342 0.00073 1.4 0.39509 0.00576 1.5 0.05380 0.00030 0.6 0.38 346.7 30.37 338.1 4.19 337.8 1.8314 0.05343 0.00104 1.9 0.34097 0.00695 2.0 0.04683 0.00034 0.7 0.36 346.9 43.41 297.9 5.26 295.0 2.0715 0.05057 0.00106 2.1 0.32884 0.00724 2.2 0.04715 0.00036 0.8 0.35 221.2 47.90 288.7 5.53 297.0 2.1916 0.05270 0.00075 1.4 0.33438 0.00504 1.5 0.04623 0.00026 0.6 0.37 315.9 32.05 292.9 3.83 291.3 1.6317 0.05294 0.00095 1.8 0.33693 0.00641 1.9 0.04639 0.00032 0.7 0.36 326.0 40.34 294.8 4.86 292.3 1.9918 0.05304 0.00072 1.4 0.36621 0.00533 1.5 0.05042 0.00028 0.6 0.38 330.5 30.61 316.8 3.96 317.1 1.70200Table A1.1. (continued)Isotopic Ratios Calculated AgesRun # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs07TR005A: Heterolithic dacitic lapilli tuff (continued)19 0.05263 0.00071 0.33555 0.00483 1.4 0.04679 0.00026 0.6 0.39 312.9 30.58 293.8 3.67 294.8 1.5807TR043: Rhyolite tuff breccia 1 0.05474 0.00184 3.4 0.41922 0.01521 3.6 0.05492 0.00071 1.3 0.36 401.5 73.03 355.5 10.89 344.7 4.332 0.05432 0.00204 3.8 0.40981 0.01653 4.0 0.05688 0.00081 1.4 0.35 384.2 81.56 348.7 11.91 356.6 4.963 0.05175 0.00159 3.1 0.42116 0.01402 3.3 0.05617 0.00066 1.2 0.35 274.6 68.87 356.9 10.02 352.3 4.004 0.05196 0.00177 3.4 0.39097 0.01428 3.7 0.05462 0.00070 1.3 0.35 283.6 75.96 335.1 10.42 342.8 4.285 0.05617 0.00210 3.7 0.43252 0.01746 4.0 0.05510 0.00079 1.4 0.36 458.6 80.63 365.0 12.37 345.7 4.816 0.05468 0.00227 4.2 0.39480 0.01753 4.4 0.05399 0.00084 1.6 0.35 400.1 89.00 337.9 12.76 339.0 5.147 0.04964 0.00162 3.3 0.38716 0.01356 3.5 0.05874 0.00071 1.2 0.35 178.1 74.30 332.3 9.93 368.0 4.298 0.05316 0.00180 3.4 0.40178 0.01465 3.6 0.05584 0.00073 1.3 0.36 335.4 74.88 342.9 10.61 350.3 4.459 0.05625 0.00164 2.9 0.42792 0.01346 3.1 0.05650 0.00064 1.1 0.36 461.6 63.90 361.7 9.57 354.3 3.8910 0.05406 0.00207 3.8 0.42041 0.01731 4.1 0.05739 0.00081 1.4 0.34 373.4 83.95 356.3 12.38 359.7 4.9311 0.05504 0.00256 4.7 0.41464 0.02070 5.0 0.05519 0.00093 1.7 0.34 413.8 100.66 352.2 14.86 346.3 5.7112 0.05448 0.00178 3.3 0.42338 0.01485 3.5 0.05631 0.00069 1.2 0.35 390.9 70.78 358.5 10.59 353.1 4.2213 0.05210 0.00173 3.3 0.40851 0.01460 3.6 0.05775 0.00072 1.2 0.35 289.9 73.92 347.8 10.53 361.9 4.4114 0.05275 0.00197 3.7 0.40604 0.01625 4.0 0.05632 0.00077 1.4 0.34 318.1 81.99 346.0 11.74 353.2 4.7115 0.05245 0.00171 3.3 0.40965 0.01438 3.5 0.05594 0.00069 1.2 0.35 305.2 72.57 348.6 10.36 350.9 4.2116 0.05328 0.00241 4.5 0.40719 0.01971 4.8 0.05532 0.00092 1.7 0.34 340.9 98.91 346.9 14.23 347.1 5.5917 0.05217 0.00193 3.7 0.40426 0.01607 4.0 0.05514 0.00076 1.4 0.35 292.8 82.12 344.7 11.62 346.0 4.6618 0.05383 0.00219 4.1 0.41399 0.01805 4.4 0.05796 0.00087 1.5 0.34 363.9 88.98 351.7 12.96 363.2 5.3019 0.05401 0.00227 4.2 0.41273 0.01855 4.5 0.05604 0.00086 1.5 0.34 371.4 91.20 350.8 13.33 351.5 5.2620 0.05269 0.00256 4.9 0.41547 0.02179 5.2 0.05595 0.00102 1.8 0.35 315.6 106.67 352.8 15.63 351.0 6.2507TR049: Rhyolitic volcanic sandstone1 0.05229 0.00123 2.4 0.39365 0.00981 2.5 0.05548 0.00047 0.8 0.34 297.9 52.79 337.0 7.15 348.1 2.862 0.05501 0.00112 2.0 0.42491 0.00928 2.2 0.05536 0.00044 0.8 0.36 412.5 44.64 359.6 6.61 347.3 2.663 0.05058 0.00163 3.2 0.38507 0.01307 3.4 0.05528 0.00060 1.1 0.32 221.7 72.74 330.8 9.58 346.9 3.694 0.05245 0.00123 2.3 0.39774 0.00989 2.5 0.05510 0.00047 0.9 0.34 305.0 52.50 340.0 7.19 345.8 2.855 0.05458 0.00136 2.5 0.42027 0.01114 2.7 0.05596 0.00051 0.9 0.34 394.9 54.58 356.2 7.96 351.0 3.106 0.05217 0.00173 3.3 0.38543 0.01350 3.5 0.05562 0.00067 1.2 0.34 293.0 73.77 331.0 9.89 348.9 4.077 0.05409 0.00258 4.8 0.42061 0.02138 5.1 0.05673 0.00099 1.7 0.34 374.8 103.27 356.5 15.28 355.7 6.02201Table A1.1. (continued)Isotopic Ratios Calculated AgesRun # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs07TR049: Rhyolitic volcanic sandstone (continued)8 0.05628 0.00120 2.1 0.44221 0.01018 2.3 0.05640 0.00048 0.9 0.37 462.5 47.04 371.8 7.17 353.7 2.939 0.05545 0.00151 2.7 0.42731 0.01243 2.9 0.05568 0.00058 1.0 0.36 430.3 59.14 361.3 8.84 349.3 3.5210 0.05377 0.00095 1.8 0.42100 0.00800 1.9 0.05636 0.00038 0.7 0.35 361.4 39.70 356.8 5.72 353.5 2.3511 0.05475 0.00138 2.5 0.45412 0.01240 2.7 0.06022 0.00059 1.0 0.36 401.9 55.25 380.2 8.66 377.0 3.5812 0.05338 0.00136 2.5 0.40040 0.01072 2.7 0.05562 0.00049 0.9 0.33 344.8 56.70 341.9 7.78 348.9 2.9913 0.05393 0.00071 1.3 0.40456 0.00575 1.4 0.05443 0.00030 0.6 0.39 368.1 29.65 344.9 4.15 341.6 1.8214 0.05431 0.00080 1.5 0.40883 0.00642 1.6 0.05505 0.00032 0.6 0.37 384.0 32.64 348.0 4.63 345.4 1.9815 0.05445 0.00146 2.7 0.41341 0.01174 2.8 0.05543 0.00052 0.9 0.33 389.8 58.93 351.3 8.44 347.8 3.1907TRHS018A: Epidote altered granodiorite porphyry1 0.04848 0.00173 3.6 0.20939 0.00752 3.6 0.032 0.00036 1.1 0.31 123 81.74 193 6.31 203 2.242 0.05024 0.00173 3.4 0.21434 0.00745 3.5 0.03182 0.00035 1.1 0.32 206 78.03 197.2 6.23 201.9 2.183 0.05042 0.00096 1.9 0.21561 0.00417 1.9 0.0314 0.00022 0.7 0.36 214.6 43.54 198.2 3.48 199.3 1.374 0.04602 0.00153 3.3 0.20868 0.00702 3.4 0.03227 0.00033 1.0 0.3 0.1 75.97 192.4 5.89 204.7 2.075 0.05045 0.00171 3.4 0.22157 0.00758 3.4 0.03213 0.00035 1.1 0.32 215.9 76.57 203.2 6.3 203.9 2.176 0.05051 0.00218 4.3 0.21471 0.00934 4.4 0.03143 0.00041 1.3 0.3 218.5 97.06 197.5 7.81 199.5 2.547 0.04998 0.00243 4.9 0.22662 0.01113 4.9 0.03239 0.00047 1.5 0.3 193.9 109.3 207.4 9.22 205.5 2.958 0.04923 0.0017 3.5 0.22138 0.00771 3.5 0.03143 0.00034 1.1 0.31 158.9 78.65 203.1 6.41 199.5 2.139 0.05062 0.00286 5.6 0.22768 0.01297 5.7 0.03235 0.00052 1.6 0.28 223.6 125.71 208.3 10.73 205.2 3.2310 0.05181 0.00126 2.4 0.23029 0.00569 2.5 0.03167 0.00026 0.8 0.33 276.8 54.83 210.4 4.7 201 1.6511 0.05775 0.00241 4.2 0.24657 0.01038 4.2 0.03092 0.00043 1.4 0.33 520.1 89.29 223.8 8.45 196.3 2.6812 0.05033 0.00169 3.4 0.21692 0.00736 3.4 0.03136 0.00036 1.1 0.34 210.1 76.07 199.3 6.14 199 2.2213 0.04699 0.00138 2.9 0.20781 0.00616 3.0 0.03181 0.00029 0.9 0.31 48.5 68.88 191.7 5.18 201.9 1.8414 0.05242 0.00178 3.4 0.22537 0.0077 3.4 0.03145 0.00034 1.1 0.32 303.6 75.29 206.4 6.38 199.6 2.1515 0.05037 0.00203 4.0 0.23261 0.00949 4.1 0.0333 0.00042 1.3 0.31 212.1 90.98 212.3 7.82 211.1 2.5916 0.049 0.00155 3.2 0.21787 0.00698 3.2 0.03239 0.00034 1.0 0.33 147.9 72.54 200.1 5.82 205.5 2.1317 0.05339 0.00164 3.1 0.23546 0.00731 3.1 0.03208 0.00034 1.1 0.34 345.3 67.93 214.7 6 203.6 2.1418 0.04659 0.00222 4.8 0.20407 0.00978 4.8 0.03176 0.00042 1.3 0.28 27.9 110.48 188.6 8.25 201.5 2.6319 0.05268 0.002 3.8 0.23058 0.00881 3.8 0.03276 0.00037 1.1 0.3 314.8 84.06 210.7 7.27 207.8 2.320 0.05062 0.00162 3.2 0.22276 0.0072 3.2 0.03227 0.00034 1.1 0.33 223.7 72.29 204.2 5.98 204.8 2.11202Table A1.1. (continued)20 0.05122 0.00043 0.8 0.2013 0.00173 0.9 0.02873 0.00011 0.4 0.45 250.9 19.05 186.2 1.46 182.6 0.6810 0.05697 0.00251 4.4 0.43182 0.02063 4.8 0.0567 0.00146 2.6 0.54 489.7 94.9 364.5 14.63 355.5 8.88Run # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ absIsotopi1 σ %c Ratios206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ absCalculated A207Pb/235Uges1 σ abs 206Pb/238U 1 σ abs07TRHS020A: Strongly epidote altered rhyolite dike1 0.04925 0.00048 1.0 0.19783 0.00199 1.0 0.02906 0.00012 0.4 0.41 159.7 22.81 183.3 1.69 184.6 0.762 0.0505 0.00038 0.8 0.19929 0.00157 0.8 0.02886 0.0001 0.3 0.44 217.9 17.51 184.5 1.33 183.4 0.643 0.05151 0.00054 1.0 0.19163 0.00204 1.1 0.02741 0.00012 0.4 0.41 263.8 23.82 178 1.74 174.3 0.764 0.05027 0.00053 1.1 0.20069 0.00217 1.1 0.02896 0.00013 0.4 0.42 207.5 24.35 185.7 1.84 184 0.815 0.05111 0.00043 0.8 0.19899 0.00173 0.9 0.02854 0.00011 0.4 0.44 245.9 19.32 184.3 1.47 181.4 0.686 0.05058 0.00041 0.8 0.19526 0.00164 0.8 0.02833 0.0001 0.4 0.42 221.6 18.63 181.1 1.39 180.1 0.667 0.05119 0.00053 1.0 0.19659 0.00207 1.1 0.02804 0.00012 0.4 0.41 249.4 23.44 182.2 1.75 178.3 0.768 0.05131 0.00059 1.1 0.19444 0.00228 1.2 0.02755 0.00013 0.5 0.4 254.9 26.22 180.4 1.94 175.2 0.829 0.05409 0.00071 1.3 0.20076 0.00266 1.3 0.02728 0.00015 0.5 0.41 374.6 29.3 185.8 2.25 173.5 0.9210 0.05483 0.00057 1.0 0.21189 0.00226 1.1 0.02806 0.00013 0.5 0.43 405.3 22.98 195.1 1.89 178.4 0.7911 0.05242 0.00053 1.0 0.19464 0.002 1.0 0.0274 0.00012 0.4 0.43 303.7 22.79 180.6 1.7 174.2 0.7512 0.05217 0.00058 1.1 0.21113 0.00241 1.1 0.02979 0.00014 0.5 0.41 292.7 25.31 194.5 2.02 189.2 0.8713 0.0517 0.00058 1.1 0.20214 0.00231 1.1 0.02818 0.00013 0.5 0.4 272.2 25.44 186.9 1.95 179.2 0.8314 0.05087 0.00039 0.8 0.20112 0.00161 0.8 0.02877 0.0001 0.3 0.43 234.9 17.68 186.1 1.36 182.8 0.6515 0.06143 0.00078 1.3 0.23968 0.00309 1.3 0.02856 0.00015 0.5 0.41 654.5 26.93 218.2 2.53 181.6 0.9716 0.05164 0.00051 1.0 0.21103 0.00216 1.0 0.02902 0.00012 0.4 0.4 269.6 22.66 194.4 1.81 184.4 0.7717 0.05161 0.00049 0.9 0.20671 0.00202 1.0 0.02894 0.00012 0.4 0.42 268.2 21.71 190.8 1.7 183.9 0.7518 0.05187 0.00044 0.8 0.20165 0.00176 0.9 0.02817 0.00011 0.4 0.45 279.6 19.21 186.5 1.49 179.1 0.6719 0.05472 0.00045 0.8 0.21403 0.0018 0.8 0.02815 0.00011 0.4 0.46 400.1 18.51 196.9 1.5 179 0.6708TR002: Rhyolite crystal tuff1 0.05361 0.00124 2.3 0.42391 0.01074 2.5 0.05746 0.00125 2.2 0.86 354.5 51.54 358.8 7.66 360.1 7.622 0.0504 0.00219 4.3 0.42064 0.01992 4.7 0.0585 0.00147 2.5 0.53 213.4 97.51 356.5 14.24 366.5 8.963 0.05618 0.00242 4.3 0.46028 0.02182 4.7 0.05983 0.00154 2.6 0.54 458.6 93.71 384.5 15.17 374.6 9.354 0.05424 0.00288 5.3 0.46238 0.02682 5.8 0.06127 0.00167 2.7 0.47 380.7 114.62 385.9 18.62 383.3 10.145 0.05658 0.00191 3.4 0.44985 0.01661 3.7 0.06034 0.00142 2.4 0.64 474.4 73.76 377.2 11.63 377.7 8.656 0.0486 0.00308 6.3 0.38899 0.02652 6.8 0.06103 0.00177 2.9 0.43 128.6 142.72 333.6 19.39 381.9 10.747 0.0502 0.00233 4.6 0.39776 0.01995 5.0 0.05786 0.00148 2.6 0.51 204.4 104.15 340 14.5 362.6 9.038 0.0567 0.00222 3.9 0.44461 0.01903 4.3 0.05765 0.00142 2.5 0.58 479.3 85.09 373.5 13.38 361.3 8.679 0.05205 0.00267 5.1 0.39976 0.02207 5.5 0.05593 0.00147 2.6 0.48 287.4 112.71 341.5 16.01 350.8 9203Table A1.1. (continued)Run # Pb/ Pb 1 σ abs 1 σ % Pb/ U 1 σ abs 1 σ % Pb/ U 1 σ abs 1 σ % rho Pb/ Pb 1 σ abs Pb/ U 1 σ abs Pb/ U 1 σ abs42 0.0486 0.00255 5.2 0.38457 0.02162 5.6 0.05732 0.00146 2.5 0.45 128.5 119 330.4 15.85 359.3 8.91207 206 207 235Isotopic Ratios206 238 1 207 206Calculated A207 235ges206 23808TR002: Rhyolite crystal tuff (continued)11 0.05075 0.00336 6.6 0.38096 0.02703 7.1 0.06127 0.00181 3.0 0.42 229.6 146.17 327.7 19.87 383.3 10.9912 0.05461 0.00281 5.1 0.41628 0.02304 5.5 0.05837 0.00157 2.7 0.49 396.3 110.86 353.4 16.52 365.7 9.5713 0.05737 0.00307 5.4 0.46306 0.02705 5.8 0.05752 0.00161 2.8 0.48 505.4 113.98 386.4 18.77 360.5 9.7914 0.05503 0.00223 4.1 0.43034 0.01898 4.4 0.05904 0.00146 2.5 0.56 413.3 87.66 363.4 13.48 369.8 8.8815 0.04789 0.0058 12.1 0.38509 0.04896 12.7 0.05743 0.00227 4.0 0.31 92.7 265.25 330.8 35.89 360 13.8216 0.05387 0.00236 4.4 0.41429 0.01962 4.7 0.058 0.00145 2.5 0.53 365.5 95.21 352 14.09 363.4 8.8517 0.05678 0.0059 10.4 0.45455 0.05016 11.0 0.06052 0.00225 3.7 0.34 482.2 214.94 380.5 35.02 378.8 13.718 0.05361 0.00289 5.4 0.4135 0.02399 5.8 0.05943 0.00161 2.7 0.47 354.8 116.85 351.4 17.23 372.2 9.7819 0.05755 0.003 5.2 0.41959 0.02371 5.7 0.057 0.00159 2.8 0.49 512.4 110.85 355.8 16.96 357.3 9.6920 0.05602 0.00238 4.2 0.43913 0.02043 4.7 0.05931 0.00149 2.5 0.54 452.8 91.85 369.6 14.42 371.5 9.0821 0.05248 0.003 5.7 0.41467 0.02582 6.2 0.05843 0.00166 2.8 0.46 306.5 125.08 352.2 18.53 366 10.122 0.05128 0.00158 3.1 0.39919 0.01331 3.3 0.05684 0.00128 2.3 0.68 253.5 69.28 341.1 9.66 356.4 7.7923 0.05271 0.00266 5.0 0.42072 0.02318 5.5 0.05809 0.00156 2.7 0.49 316.4 110.73 356.6 16.57 364 9.524 0.056 0.00329 5.9 0.41027 0.02582 6.3 0.05762 0.00163 2.8 0.45 452.2 125.74 349.1 18.59 361.1 9.9625 0.05586 0.00392 7.0 0.41727 0.03154 7.6 0.05701 0.0018 3.2 0.42 446.5 148.56 354.1 22.59 357.4 10.9826 0.05222 0.00148 2.8 0.43029 0.01337 3.1 0.0604 0.00134 2.2 0.71 295 63.44 363.4 9.49 378 8.1327 0.05009 0.00166 3.3 0.39694 0.0143 3.6 0.05778 0.00132 2.3 0.63 199.2 75.31 339.4 10.4 362.1 8.0428 0.0517 0.00282 5.5 0.39572 0.0231 5.8 0.05736 0.00153 2.7 0.46 271.9 120.38 338.5 16.8 359.6 9.3529 0.05647 0.00216 3.8 0.42844 0.01778 4.1 0.05821 0.0014 2.4 0.58 470.1 83.07 362.1 12.64 364.7 8.5430 0.05049 0.00187 3.7 0.41149 0.01656 4.0 0.05896 0.00138 2.3 0.58 217.5 83.71 349.9 11.91 369.3 8.431 0.04391 0.00309 7.0 0.35706 0.02658 7.4 0.05862 0.00162 2.8 0.37 0.1 48.79 310 19.89 367.2 9.8632 0.05358 0.00199 3.7 0.43434 0.01749 4.0 0.05953 0.00139 2.3 0.58 353.4 81.48 366.3 12.38 372.7 8.4433 0.0531 0.00248 4.7 0.40332 0.02023 5.0 0.05598 0.0014 2.5 0.5 332.8 102.38 344.1 14.63 351.1 8.5634 0.0519 0.00282 5.4 0.41077 0.02407 5.9 0.05957 0.00158 2.7 0.45 281.2 118.95 349.4 17.32 373 9.5935 0.0555 0.0059 10.6 0.42667 0.04863 11.4 0.05827 0.00237 4.1 0.36 432.3 221.29 360.8 34.61 365.1 14.4136 0.05121 0.00333 6.5 0.39736 0.02777 7.0 0.0616 0.00181 2.9 0.42 250.4 143.13 339.7 20.18 385.3 10.9637 0.05416 0.00218 4.0 0.41856 0.01824 4.4 0.05654 0.00136 2.4 0.55 377.5 87.36 355 13.05 354.5 8.3138 0.0526 0.00241 4.6 0.42332 0.02104 5.0 0.05744 0.00144 2.5 0.5 311.8 100.95 358.4 15.01 360.1 8.7839 0.05056 0.00222 4.4 0.40521 0.01934 4.8 0.0579 0.00143 2.5 0.52 220.8 98.68 345.4 13.98 362.8 8.7340 0.05336 0.00158 3.0 0.41589 0.01336 3.2 0.05785 0.00127 2.2 0.68 344.1 65.69 353.1 9.58 362.6 7.7441 0.05269 0.00217 4.1 0.42672 0.01913 4.5 0.05835 0.00141 2.4 0.54 315.5 91.03 360.8 13.62 365.6 8.56204Table A1.1. (continued)Run # Pb/ Pb 1 σ abs 1 σ % Pb/ U 1 σ abs 1 σ % Pb/ U 1 σ abs 1 σ % rho Pb/ Pb 1 σ abs Pb/ U 1 σ abs Pb/ U 1 σ abs55 0.05382 0.00191 3.5 0.42847 0.01645 3.8 0.0578 0.00131 2.3 0.59 363.6 77.75 362.1 11.69 362.2 8.01207 206 207 235Isotopic Ratios206 238 1 207 206Calculated A207 235ges206 23808TR002: Rhyolite crystal tuff (continued)43 0.05215 0.00289 5.5 0.42883 0.02582 6.0 0.05849 0.00157 2.7 0.45 292.1 121.83 362.3 18.35 366.4 9.5744 0.0549 0.00215 3.9 0.41562 0.01753 4.2 0.05711 0.00134 2.3 0.56 408.2 84.76 352.9 12.57 358 8.1845 0.05508 0.00136 2.5 0.43944 0.01179 2.7 0.05973 0.00126 2.1 0.79 415.4 53.79 369.9 8.31 374 7.6646 0.05495 0.00232 4.2 0.41208 0.01876 4.6 0.05764 0.00139 2.4 0.53 410 91.35 350.4 13.49 361.3 8.4947 0.05465 0.00182 3.3 0.42317 0.01532 3.6 0.0572 0.00129 2.3 0.62 398.1 72.28 358.3 10.93 358.6 7.8948 0.05388 0.00338 6.3 0.42263 0.02873 6.8 0.05738 0.00166 2.9 0.43 365.8 135.06 357.9 20.51 359.7 10.1449 0.05266 0.00168 3.2 0.42034 0.01454 3.5 0.05812 0.00129 2.2 0.64 314.3 71.04 356.3 10.4 364.2 7.8550 0.0507 0.00209 4.1 0.39841 0.01767 4.4 0.05831 0.00138 2.4 0.53 227.2 92.51 340.5 12.83 365.3 8.4251 0.055 0.00258 4.7 0.44745 0.02285 5.1 0.05812 0.00146 2.5 0.49 412 101.49 375.5 16.03 364.2 8.8852 0.05391 0.0039 7.2 0.41745 0.03264 7.8 0.0566 0.00176 3.1 0.4 367 155.15 354.2 23.38 354.9 10.7153 0.05417 0.00251 4.6 0.43841 0.02207 5.0 0.05862 0.00147 2.5 0.5 377.8 100.4 369.1 15.58 367.3 8.9554 0.05297 0.00189 3.6 0.41651 0.01614 3.9 0.05638 0.00129 2.3 0.59 327.7 79.18 353.6 11.57 353.6 7.8508TR002B: Rhyolite crystal tuff1 0.06033 0.00561 9.3 0.49021 0.04764 9.7 0.06054 0.00139 2.3 0.24 615.4 189.1 405.1 32.46 378.9 8.442 0.05601 0.00213 3.8 0.44225 0.01835 4.1 0.05835 0.00076 1.3 0.31 452.3 81.99 371.8 12.92 365.6 4.623 0.0455 0.00284 6.2 0.37314 0.0243 6.5 0.05849 0.00086 1.5 0.23 0.1 115.52 322 17.97 366.5 5.234 0.0515 0.00137 2.7 0.42531 0.01233 2.9 0.06027 0.00053 0.9 0.3 263.2 59.94 359.8 8.79 377.3 3.245 0.0528 0.00133 2.5 0.43823 0.01201 2.7 0.05864 0.0005 0.9 0.31 320.3 55.97 369 8.48 367.4 3.026 0.0516 0.00135 2.6 0.4197 0.01189 2.8 0.05888 0.0005 0.8 0.3 267.8 58.89 355.8 8.51 368.8 3.047 0.05301 0.00118 2.2 0.42268 0.01022 2.4 0.05835 0.00044 0.8 0.31 329.1 49.43 358 7.29 365.6 2.718 0.05237 0.00136 2.6 0.42586 0.01206 2.8 0.06084 0.00053 0.9 0.31 301.8 58.14 360.2 8.59 380.7 3.219 0.0496 0.00182 3.7 0.3969 0.01575 4.0 0.05687 0.00066 1.2 0.29 176.5 83.28 339.4 11.45 356.5 4.0410 0.0501 0.00239 4.8 0.40044 0.02055 5.1 0.05831 0.00083 1.4 0.28 199.8 107.37 342 14.9 365.3 5.0711 0.05347 0.00228 4.3 0.40805 0.01855 4.5 0.05589 0.00071 1.3 0.28 348.8 93.23 347.5 13.38 350.6 4.3612 0.0553 0.00171 3.1 0.4415 0.01487 3.4 0.05784 0.00059 1.0 0.3 424.2 67.32 371.3 10.48 362.5 3.613 0.05354 0.00187 3.5 0.4128 0.01554 3.8 0.05699 0.00064 1.1 0.3 351.5 76.74 350.9 11.17 357.3 3.9114 0.04988 0.00331 6.6 0.3789 0.02642 7.0 0.05769 0.00101 1.8 0.25 189.3 147.53 326.2 19.45 361.6 6.1815 0.05383 0.00236 4.4 0.44071 0.02074 4.7 0.06224 0.00082 1.3 0.28 363.9 95.23 370.8 14.62 389.2 4.9816 0.05326 0.00398 7.5 0.42795 0.03369 7.9 0.05646 0.00112 2.0 0.25 339.9 160.6 361.7 23.96 354.1 6.84205Table A1.1. (continued)Run # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ absIsotopic Ratios Calculated Ages08TR002B: Rhyolite crystal tuff (continued)18 0.05647 0.00303 5.4 0.42056 0.02394 5.7 0.05589 0.00089 1.6 0.28 470 115.27 356.5 17.11 350.6 5.4319 0.0526 0.00169 3.2 0.42479 0.0148 3.5 0.05956 0.00062 1.0 0.3 311.6 71.27 359.5 10.55 372.9 3.7820 0.05363 0.00158 2.9 0.42068 0.0134 3.2 0.05715 0.00055 1.0 0.3 355.5 65.07 356.5 9.58 358.3 3.3221 0.05325 0.00227 4.3 0.40689 0.01836 4.5 0.05703 0.00069 1.2 0.27 339.4 93.48 346.6 13.25 357.6 4.2222 0.0595 0.00344 5.8 0.45912 0.02838 6.2 0.05855 0.00104 1.8 0.29 585.5 120.64 383.6 19.75 366.8 6.3223 0.04593 0.00308 6.7 0.36771 0.02556 7.0 0.05824 0.00085 1.5 0.21 0.1 148.09 318 18.97 364.9 5.224 0.05748 0.00246 4.3 0.43135 0.0197 4.6 0.05686 0.00076 1.3 0.29 509.6 91.63 364.1 13.98 356.5 4.6525 0.05428 0.00321 5.9 0.41927 0.02622 6.3 0.05709 0.00094 1.6 0.26 382.5 127.33 355.5 18.76 357.9 5.7326 0.05661 0.00331 5.8 0.43185 0.02645 6.1 0.05899 0.00091 1.5 0.25 475.5 124.96 364.5 18.76 369.5 5.5727 0.05347 0.00229 4.3 0.42602 0.01946 4.6 0.05659 0.00071 1.3 0.27 348.8 93.75 360.3 13.86 354.8 4.3328 0.05241 0.00202 3.9 0.43736 0.01813 4.1 0.05899 0.00068 1.2 0.28 303.2 85.61 368.4 12.81 369.5 4.1329 0.05425 0.00387 7.1 0.4373 0.03351 7.7 0.05786 0.00124 2.1 0.28 381.3 152.49 368.3 23.68 362.6 7.5730 0.05564 0.00198 3.6 0.43432 0.01678 3.9 0.05706 0.00066 1.2 0.3 437.8 77.47 366.2 11.88 357.7 4.0531 0.04937 0.00345 7.0 0.38352 0.02824 7.4 0.06113 0.00113 1.8 0.25 165.5 155.54 329.6 20.73 382.5 6.8832 0.05328 0.00251 4.7 0.43217 0.02185 5.1 0.05859 0.00083 1.4 0.28 340.6 102.96 364.7 15.49 367 5.0333 0.05478 0.00276 5.0 0.45705 0.02501 5.5 0.05988 0.00095 1.6 0.29 403.4 108.81 382.2 17.43 374.9 5.834 0.05196 0.00302 5.8 0.39165 0.02403 6.1 0.05802 0.00093 1.6 0.26 283.9 127.78 335.6 17.54 363.5 5.6935 0.05171 0.00162 3.1 0.40596 0.01375 3.4 0.05923 0.0006 1.0 0.3 272.5 70.32 346 9.93 370.9 3.6236 0.05498 0.00145 2.6 0.45166 0.01291 2.9 0.06116 0.00054 0.9 0.31 411.4 57.08 378.4 9.03 382.7 3.2637 0.05181 0.00266 5.1 0.41217 0.02259 5.5 0.05828 0.00088 1.5 0.28 277.2 113.32 350.4 16.24 365.2 5.3538 0.05211 0.00179 3.4 0.42313 0.01558 3.7 0.06018 0.00063 1.0 0.28 290.3 76.4 358.3 11.12 376.7 3.8339 0.0507 0.00293 5.8 0.37955 0.02334 6.1 0.05722 0.00095 1.7 0.27 227.1 128.43 326.7 17.18 358.7 5.8140 0.05402 0.0018 3.3 0.44039 0.01583 3.6 0.05829 0.00061 1.0 0.29 371.7 73.19 370.5 11.16 365.2 3.7141 0.05585 0.00455 8.1 0.4654 0.03946 8.5 0.05814 0.0011 1.9 0.22 446.2 171.73 388 27.34 364.3 6.7242 0.05513 0.00327 5.9 0.41836 0.02629 6.3 0.05835 0.00099 1.7 0.27 417.4 127.29 354.9 18.82 365.6 6.0543 0.05866 0.00356 6.1 0.43178 0.02754 6.4 0.05773 0.00098 1.7 0.27 554.6 127.17 364.4 19.53 361.8 5.9644 0.05481 0.0033 6.0 0.42664 0.02716 6.4 0.05833 0.00097 1.7 0.26 404.4 128.93 360.8 19.33 365.5 5.9145 0.05394 0.00207 3.8 0.43091 0.01763 4.1 0.05823 0.00066 1.1 0.28 368.5 83.98 363.8 12.51 364.9 446 0.04958 0.00209 4.2 0.41867 0.01913 4.6 0.05841 0.00076 1.3 0.28 175.1 95.7 355.1 13.7 366 4.6147 0.04955 0.00474 9.6 0.40945 0.04044 9.9 0.06129 0.00124 2.0 0.2 173.9 208.94 348.5 29.13 383.5 7.5448 0.05781 0.00298 5.2 0.4416 0.02429 5.5 0.05709 0.00087 1.5 0.28 522.4 109.58 371.4 17.11 357.9 5.32206Table A1.1. (continued)Run # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs64 0.05477 0.00233 4.3 0.42726 0.01931 4.5 0.05767 0.00072 1.2 0.28 402.8 91.98 361.2 13.74 361.5 4.37Isotopic Ratios Calculated Ages08TR002B: Rhyolite crystal tuff (continued)50 0.05243 0.00265 5.1 0.42752 0.02304 5.4 0.06005 0.00087 1.4 0.27 304 110.99 361.4 16.39 376 5.2851 0.05918 0.00229 3.9 0.46985 0.01965 4.2 0.06016 0.00075 1.2 0.3 573.6 82.02 391.1 13.57 376.6 4.5752 0.05621 0.00453 8.1 0.4571 0.03889 8.5 0.06069 0.00129 2.1 0.25 460 170.01 382.2 27.1 379.8 7.8453 0.05374 0.00241 4.5 0.43144 0.02049 4.7 0.05979 0.00074 1.2 0.26 360 98.09 364.2 14.54 374.3 4.4954 0.05322 0.00512 9.6 0.41811 0.04198 10.0 0.06008 0.00139 2.3 0.23 338.1 203.55 354.7 30.06 376.1 8.4455 0.05635 0.00272 4.8 0.44737 0.02298 5.1 0.05977 0.00083 1.4 0.27 465.3 104.33 375.4 16.12 374.2 5.0356 0.05512 0.00244 4.4 0.44109 0.02088 4.7 0.05959 0.00078 1.3 0.28 417 95.9 371 14.71 373.1 4.7657 0.05637 0.0027 4.8 0.44457 0.02254 5.1 0.06002 0.00081 1.3 0.27 466.1 103.51 373.5 15.84 375.8 4.9458 0.05895 0.00335 5.7 0.44184 0.02649 6.0 0.05634 0.00089 1.6 0.26 565.1 119.16 371.5 18.65 353.3 5.4259 0.05337 0.00266 5.0 0.4294 0.02293 5.3 0.06028 0.0009 1.5 0.28 344.5 108.64 362.7 16.29 377.3 5.4960 0.04121 0.0021 5.1 0.34549 0.01854 5.4 0.05955 0.00076 1.3 0.24 0.1 0 301.3 13.99 372.9 4.6461 0.05384 0.00252 4.7 0.42687 0.02121 5.0 0.05864 0.00078 1.3 0.27 364.3 101.68 361 15.09 367.4 4.7462 0.05478 0.00333 6.1 0.42646 0.02729 6.4 0.06197 0.00099 1.6 0.25 403.4 130.27 360.7 19.43 387.6 5.9863 0.05348 0.00181 3.4 0.44929 0.01646 3.7 0.06058 0.00066 1.1 0.3 349.3 74.71 376.8 11.53 379.1 4.0108TR017: Siltstone1 0.05095 0.00474 9.3 0.35485 0.03379 9.5 0.0495 0.00099 2.0 0.21 238.4 201.14 308.4 25.32 311.5 6.062 0.05158 0.00232 4.5 0.3673 0.01755 4.8 0.05027 0.00065 1.3 0.27 266.7 100.08 317.6 13.03 316.2 3.973 0.05326 0.00687 12.9 0.38435 0.05067 13.2 0.05224 0.00136 2.6 0.2 339.8 268.34 330.2 37.17 328.3 8.324 0.05372 0.00181 3.4 0.42502 0.01561 3.7 0.05661 0.00062 1.1 0.3 359.1 74.11 359.6 11.12 355 3.775 0.05255 0.00204 3.9 0.36939 0.01545 4.2 0.05107 0.00064 1.3 0.3 309.6 86.12 319.2 11.45 321.1 3.916 0.05304 0.00437 8.2 0.36383 0.03101 8.5 0.05146 0.00098 1.9 0.22 330.6 176.44 315.1 23.09 323.5 6.017 0.05508 0.0021 3.8 0.42443 0.01759 4.1 0.05638 0.0007 1.2 0.3 415.2 82.6 359.2 12.54 353.6 4.288 0.04978 0.00751 15.1 0.3511 0.0539 15.4 0.04911 0.00136 2.8 0.18 184.8 317.29 305.5 40.51 309 8.379 0.04685 0.00747 15.9 0.32979 0.05335 16.2 0.05085 0.00134 2.6 0.16 41.4 342.95 289.4 40.74 319.8 8.2510 0.05043 0.00451 8.9 0.33598 0.03151 9.4 0.04678 0.00112 2.4 0.26 214.8 195.08 294.1 23.95 294.7 6.9211 0.05301 0.00264 5.0 0.39421 0.02107 5.3 0.05588 0.00086 1.5 0.29 329.3 108.9 337.4 15.34 350.5 5.2312 0.05319 0.0016 3.0 0.35491 0.0113 3.2 0.04843 0.00054 1.1 0.35 336.8 66.72 308.4 8.47 304.9 3.3313 0.04523 0.0036 8.0 0.29006 0.02386 8.2 0.04857 0.00108 2.2 0.27 0.1 139.64 258.6 18.78 305.7 6.6714 0.05112 0.00254 5.0 0.35451 0.01837 5.2 0.04901 0.00075 1.5 0.3 246.2 110.3 308.1 13.77 308.5 4.61207Table A1.1. (continued)Run # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs28 0.05221 0.00276 5.3 0.36983 0.02043 5.5 0.05052 0.00082 1.6 0.29 294.8 116.29 319.5 15.15 317.7 5.04Isotopic Ratios Calculated Ages08TR017: Siltstone (continued)16 0.05799 0.00364 6.3 0.37435 0.02472 6.6 0.04772 0.00106 2.2 0.34 529 132.17 322.9 18.26 300.5 6.5217 0.06224 0.00789 12.7 0.42477 0.05755 13.5 0.05301 0.00267 5.0 0.37 682.5 249.66 359.5 41.01 333 16.3218 0.06003 0.00371 6.2 0.41328 0.0271 6.6 0.04963 0.00114 2.3 0.35 604.7 128.19 351.2 19.47 312.2 719 0.05025 0.00341 6.8 0.34525 0.02426 7.0 0.04929 0.00092 1.9 0.27 206.4 150.16 301.1 18.31 310.1 5.6820 0.05493 0.00246 4.5 0.36364 0.01712 4.7 0.04756 0.00073 1.5 0.33 409.5 96.88 314.9 12.75 299.5 4.4721 0.04662 0.00463 9.9 0.32504 0.03304 10.2 0.05161 0.00116 2.2 0.22 29.7 222.53 285.8 25.32 324.4 7.1222 0.05311 0.00396 7.5 0.36944 0.02906 7.9 0.05167 0.00129 2.5 0.32 333.6 160.36 319.2 21.55 324.8 7.9123 0.05213 0.0009 1.7 0.37002 0.00685 1.9 0.05128 0.00037 0.7 0.39 291.1 38.76 319.7 5.07 322.3 2.2824 0.05317 0.00171 3.2 0.36641 0.01253 3.4 0.05079 0.00061 1.2 0.35 336.2 71.14 317 9.31 319.4 3.7625 0.04818 0.00232 4.8 0.33658 0.01702 5.1 0.04755 0.00075 1.6 0.31 108.1 109.79 294.6 12.93 299.5 4.626 0.05093 0.00285 5.6 0.3538 0.02086 5.9 0.05089 0.00095 1.9 0.32 237.9 124.17 307.6 15.64 320 5.8327 0.04888 0.00331 6.8 0.34693 0.02437 7.0 0.04948 0.00098 2.0 0.28 141.9 151.61 302.4 18.37 311.3 608TR019: Sandstone1 0.05221 0.00133 2.5 0.342 0.00926 2.7 0.04816 0.00047 1.0 0.36 294.7 56.86 298.7 7.01 303.2 2.92 0.05483 0.00099 1.8 0.368 0.00718 2.0 0.04939 0.00038 0.8 0.39 405.1 39.71 318.2 5.33 310.8 2.353 0.05308 0.00128 2.4 0.36634 0.00951 2.6 0.05067 0.00049 1.0 0.37 332.1 53.78 316.9 7.07 318.7 2.984 0.05449 0.0021 3.9 0.37441 0.01547 4.1 0.04948 0.00071 1.4 0.35 391.3 83.52 322.9 11.43 311.3 4.365 0.05139 0.00202 3.9 0.3549 0.01491 4.2 0.0499 0.00069 1.4 0.33 258.5 87.94 308.4 11.17 313.9 4.216 0.04772 0.00228 4.8 0.32569 0.01646 5.1 0.04975 0.00078 1.6 0.31 84.3 110.47 286.3 12.61 313 4.787 0.05208 0.00138 2.6 0.36491 0.01043 2.9 0.05179 0.00054 1.0 0.36 289.1 59.42 315.9 7.76 325.5 3.298 0.05201 0.00203 3.9 0.34959 0.01456 4.2 0.04895 0.0007 1.4 0.34 285.8 86.76 304.4 10.95 308.1 4.289 0.05237 0.00146 2.8 0.34861 0.01037 3.0 0.04818 0.00051 1.1 0.36 301.4 62.08 303.7 7.81 303.3 3.1410 0.04927 0.00146 3.0 0.33611 0.01059 3.2 0.05002 0.00054 1.1 0.34 160.5 67.73 294.2 8.05 314.6 3.3111 0.05369 0.00126 2.3 0.37965 0.00968 2.5 0.0502 0.00048 1.0 0.38 357.8 52.38 326.8 7.12 315.7 2.9412 0.04855 0.00207 4.3 0.33748 0.01538 4.6 0.05012 0.00076 1.5 0.33 126.1 97.44 295.3 11.68 315.2 4.6513 0.05225 0.001 1.9 0.35943 0.00739 2.1 0.05057 0.0004 0.8 0.38 296.2 42.93 311.8 5.52 318 2.4714 0.05723 0.0022 3.8 0.36517 0.01495 4.1 0.04827 0.00071 1.5 0.36 500 82.88 316.1 11.12 303.9 4.415 0.05584 0.00172 3.1 0.37088 0.01225 3.3 0.04936 0.00058 1.2 0.36 445.5 67.14 320.3 9.07 310.6 3.5916 0.05362 0.00097 1.8 0.36011 0.00705 2.0 0.04842 0.00038 0.8 0.4 355 40.58 312.3 5.27 304.8 2.31208Table A1.1. (continued)Run # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs48 0.05382 0.00168 3.1 0.35882 0.01204 3.4 0.04909 0.0006 1.2 0.36 363.4 68.79 311.3 9 308.9 3.67Isotopic Ratios Calculated Ages08TR019: Sandstone (continued)18 0.05449 0.00163 3.0 0.35963 0.01153 3.2 0.04872 0.00056 1.1 0.36 391.2 65.62 311.9 8.61 306.7 3.4319 0.05135 0.00191 3.7 0.36054 0.01444 4.0 0.05075 0.0007 1.4 0.34 256.4 83.42 312.6 10.78 319.1 4.320 0.0504 0.00218 4.3 0.36072 0.01669 4.6 0.05207 0.00078 1.5 0.32 213.5 97.26 312.8 12.46 327.2 4.7721 0.0549 0.00269 4.9 0.40112 0.02104 5.2 0.04996 0.00085 1.7 0.32 408.3 105.57 342.5 15.25 314.3 5.2122 0.05164 0.00249 4.8 0.35425 0.01822 5.1 0.05172 0.00089 1.7 0.33 269.3 106.69 307.9 13.66 325.1 5.4723 0.0504 0.00214 4.2 0.34633 0.01565 4.5 0.04896 0.00072 1.5 0.33 213.3 95.63 302 11.8 308.1 4.4324 0.05218 0.00165 3.2 0.3572 0.01212 3.4 0.05034 0.00061 1.2 0.36 293.2 70.42 310.1 9.07 316.6 3.7625 0.05459 0.00152 2.8 0.37328 0.01123 3.0 0.04992 0.00055 1.1 0.37 395.2 61.12 322.1 8.3 314 3.3626 0.05157 0.00159 3.1 0.35323 0.01171 3.3 0.05029 0.00059 1.2 0.35 266.3 69.29 307.1 8.78 316.3 3.6327 0.04905 0.00222 4.5 0.33504 0.01621 4.8 0.05114 0.00084 1.6 0.34 150.1 102.74 293.4 12.33 321.5 5.1228 0.05529 0.00138 2.5 0.39072 0.01059 2.7 0.0513 0.00052 1.0 0.37 423.6 54.23 334.9 7.73 322.5 3.2129 0.05178 0.00119 2.3 0.35168 0.0087 2.5 0.0496 0.00045 0.9 0.37 275.8 51.89 306 6.53 312 2.7830 0.05378 0.00141 2.6 0.35938 0.01011 2.8 0.0491 0.00051 1.0 0.37 361.7 57.99 311.8 7.55 309 3.1231 0.05073 0.00141 2.8 0.35326 0.01055 3.0 0.05051 0.00053 1.0 0.35 228.8 63.06 307.2 7.92 317.6 3.2732 0.05195 0.00138 2.7 0.35359 0.01007 2.8 0.04857 0.0005 1.0 0.36 283.1 59.53 307.4 7.55 305.8 3.0533 0.0548 0.00165 3.0 0.37462 0.01217 3.2 0.04872 0.00057 1.2 0.36 404.3 65.4 323.1 8.99 306.7 3.534 0.04899 0.0019 3.9 0.34878 0.01447 4.1 0.05036 0.00069 1.4 0.33 147.4 88.55 303.8 10.9 316.7 4.2535 0.04848 0.00185 3.8 0.32094 0.01298 4.0 0.05031 0.00068 1.4 0.33 122.9 87.34 282.6 9.98 316.4 4.1836 0.05268 0.00106 2.0 0.37219 0.00811 2.2 0.05057 0.00042 0.8 0.38 315.2 45.08 321.3 6 318 2.5837 0.05304 0.00162 3.1 0.35374 0.01157 3.3 0.04934 0.00057 1.2 0.35 330.4 67.89 307.5 8.68 310.5 3.5338 0.05384 0.00149 2.8 0.36917 0.01098 3.0 0.04958 0.00054 1.1 0.37 364.1 61.05 319 8.14 312 3.2939 0.05705 0.00185 3.2 0.37912 0.01322 3.5 0.04945 0.00064 1.3 0.37 493 70.38 326.4 9.74 311.1 3.940 0.05283 0.0018 3.4 0.36225 0.01327 3.7 0.04888 0.00063 1.3 0.35 321.4 75.76 313.9 9.89 307.6 3.8641 0.0511 0.00171 3.3 0.33859 0.01209 3.6 0.04896 0.00061 1.2 0.35 245.2 75.27 296.1 9.17 308.2 3.7342 0.04929 0.00147 3.0 0.34579 0.01105 3.2 0.04946 0.00054 1.1 0.34 161.5 68.3 301.6 8.34 311.2 3.3343 0.05597 0.00196 3.5 0.38379 0.01451 3.8 0.05003 0.00069 1.4 0.36 450.8 75.84 329.8 10.64 314.7 4.2244 0.05403 0.0017 3.1 0.36914 0.01247 3.4 0.04992 0.0006 1.2 0.36 372.2 69.14 319 9.25 314.1 3.6945 0.05238 0.00137 2.6 0.36292 0.01027 2.8 0.0503 0.00052 1.0 0.37 301.8 58.64 314.4 7.65 316.4 3.1946 0.05398 0.00127 2.4 0.3748 0.00953 2.5 0.04955 0.00047 0.9 0.37 370.2 52.02 323.2 7.04 311.7 2.947 0.05227 0.00089 1.7 0.37518 0.00694 1.8 0.05256 0.00039 0.7 0.4 297.2 38.38 323.5 5.12 330.2 2.36209207Pb/206Pb 207Pb/235U 206Pb/238U rho1 207Pb/206Pb 207Pb/235U 206Pb/238U64 0.0514 0.00168 3.3 0.35758 0.01258 3.5 0.04982 0.00062 1.2 0.35 258.9 73.33 310.4 9.41 313.4 3.7813 0.05098 0.00116 2.3 0.22552 0.00523 2.3 0.03215 0.00027 0.8 0.36 239.9 51.54 206.5 4.34 204 1.71Table A1.1. (continued)Isotopic Ratios Calculated AgesRun # 1 σ abs 1 σ % 1 σ abs 1 σ % 1 σ abs 1 σ % 1 σ abs 1 σ abs 1 σ abs08TR019: Sandstone (continued)50 0.05166 0.00181 3.5 0.35054 0.01318 3.8 0.04841 0.00062 1.3 0.34 270.2 78.55 305.1 9.91 304.8 3.8451 0.05322 0.00166 3.1 0.35787 0.01196 3.3 0.04943 0.00059 1.2 0.36 338 69 310.6 8.94 311 3.6252 0.05231 0.00145 2.8 0.36444 0.01088 3.0 0.04915 0.00053 1.1 0.36 299 61.86 315.5 8.1 309.3 3.2553 0.05349 0.00189 3.5 0.36269 0.01376 3.8 0.05039 0.00067 1.3 0.35 349.7 77.78 314.2 10.25 316.9 4.1354 0.05221 0.00134 2.6 0.35437 0.00976 2.8 0.04903 0.00049 1.0 0.36 294.5 57.4 308 7.32 308.5 3.0255 0.05123 0.00168 3.3 0.33725 0.01185 3.5 0.04728 0.00058 1.2 0.35 251.3 73.91 295.1 9 297.8 3.5856 0.05377 0.00144 2.7 0.36426 0.01054 2.9 0.04868 0.00051 1.0 0.36 361.3 59.46 315.4 7.84 306.4 3.1657 0.05034 0.00195 3.9 0.35666 0.01487 4.2 0.05014 0.00072 1.4 0.34 210.6 87.47 309.7 11.13 315.4 4.4158 0.05327 0.0013 2.4 0.36414 0.00964 2.6 0.04851 0.00048 1.0 0.37 340.1 54.53 315.3 7.17 305.4 2.9459 0.05151 0.00159 3.1 0.35886 0.01189 3.3 0.04965 0.00058 1.2 0.35 263.8 69.22 311.4 8.88 312.4 3.5560 0.05341 0.0016 3.0 0.36429 0.01171 3.2 0.04835 0.00055 1.1 0.35 346.2 66.29 315.4 8.72 304.4 3.3961 0.04978 0.00154 3.1 0.3514 0.01167 3.3 0.04873 0.00056 1.1 0.35 184.7 70.32 305.8 8.77 306.7 3.4762 0.05349 0.00165 3.1 0.36737 0.01217 3.3 0.05004 0.00059 1.2 0.36 349.4 68.11 317.7 9.04 314.8 3.663 0.04942 0.00151 3.1 0.34132 0.01122 3.3 0.04972 0.00057 1.1 0.35 167.8 70 298.2 8.49 312.8 3.565 0.0528 0.00128 2.4 0.37588 0.00988 2.6 0.05115 0.0005 1.0 0.37 320.2 54.01 324 7.29 321.6 3.0608TR020: Granodiorite1 0.05204 0.00099 1.9 0.21233 0.00412 1.9 0.02944 0.00022 0.7 0.39 287.3 42.99 195.5 3.45 187 1.392 0.0497 0.00094 1.9 0.21671 0.00417 1.9 0.03143 0.00023 0.7 0.38 181 43.38 199.2 3.48 199.5 1.433 0.05013 0.0009 1.8 0.21999 0.00405 1.8 0.03134 0.00022 0.7 0.38 201.1 41.37 201.9 3.37 198.9 1.364 0.04991 0.00094 1.9 0.21306 0.00408 1.9 0.03083 0.00023 0.7 0.39 190.9 43.11 196.1 3.42 195.8 1.415 0.04814 0.00077 1.6 0.21077 0.00345 1.6 0.0318 0.0002 0.6 0.38 106.1 37.36 194.2 2.89 201.8 1.256 0.05094 0.00084 1.6 0.21708 0.00367 1.7 0.03113 0.00021 0.7 0.4 238.3 37.76 199.5 3.07 197.6 1.297 0.05021 0.00074 1.5 0.21782 0.0033 1.5 0.03159 0.00019 0.6 0.4 204.5 33.93 200.1 2.75 200.5 1.198 0.0517 0.00106 2.1 0.22084 0.00461 2.1 0.03097 0.00025 0.8 0.39 272.1 46.25 202.6 3.84 196.6 1.559 0.05072 0.00075 1.5 0.21386 0.00324 1.5 0.03087 0.00019 0.6 0.41 228.1 33.81 196.8 2.71 196 1.1710 0.0491 0.0013 2.6 0.215 0.00582 2.7 0.0312 0.00031 1.0 0.37 152.8 61.09 197.7 4.87 198.1 1.9111 0.04996 0.00133 2.7 0.21867 0.00594 2.7 0.03145 0.00031 1.0 0.36 193.3 60.9 200.8 4.95 199.6 1.9112 0.05088 0.00088 1.7 0.21637 0.00384 1.8 0.03102 0.00021 0.7 0.38 235.3 39.52 198.9 3.21 196.9 1.34210207 206 207 235 206 238 1 207 206 207 235 206 23818 0.05123 0.00097 1.9 0.22333 0.00433 1.9 0.03192 0.00024 0.8 0.39 251.4 42.78 204.7 3.59 202.6 1.4919 0.05416 0.00111 2.0 0.44142 0.00997 2.3 0.06007 0.00044 0.7 0.32 377.7 45.44 371.3 7.02 376.1 2.6620 0.05377 0.00144 2.7 0.43309 0.01278 3.0 0.0575 0.00054 0.9 0.32 361.2 59.35 365.4 9.06 360.4 3.29Table A1.1. (continued)Isotopic Ratios Calculated AgesRun # Pb/ Pb 1 σ abs 1 σ % Pb/ U 1 σ abs 1 σ % Pb/ U 1 σ abs 1 σ % rho Pb/ Pb 1 σ abs Pb/ U 1 σ abs Pb/ U 1 σ abs08TR020: Granodiorite (continued)15 0.04948 0.00103 2.1 0.20969 0.00446 2.1 0.03052 0.00025 0.8 0.39 170.6 47.9 193.3 3.75 193.8 1.5316 0.05016 0.00087 1.7 0.2165 0.00389 1.8 0.03151 0.00022 0.7 0.39 202.4 39.97 199 3.24 200 1.3717 0.05011 0.00086 1.7 0.21504 0.00379 1.8 0.03108 0.00021 0.7 0.38 200.2 39.23 197.8 3.17 197.3 1.3319 0.04964 0.00086 1.7 0.21462 0.00384 1.8 0.03193 0.00022 0.7 0.39 178.2 39.96 197.4 3.21 202.6 1.3708TR031: Heterolithic lapilli tuff1 0.05373 0.00202 3.8 0.42338 0.01694 4.0 0.05677 0.0006 1.1 0.26 359.6 82.58 358.5 12.08 356 3.662 0.05458 0.00146 2.7 0.43365 0.01257 2.9 0.0589 0.00051 0.9 0.3 395.1 58.59 365.8 8.9 368.9 3.13 0.05528 0.00209 3.8 0.45794 0.01868 4.1 0.05897 0.00067 1.1 0.28 423.3 82.1 382.8 13.01 369.4 4.14 0.05367 0.00242 4.5 0.44479 0.02126 4.8 0.05991 0.00074 1.2 0.26 357.1 98.52 373.6 14.94 375.1 4.485 0.0549 0.00222 4.0 0.42912 0.01834 4.3 0.05776 0.00064 1.1 0.26 408.1 87.56 362.6 13.03 362 3.886 0.0541 0.00075 1.4 0.43611 0.00674 1.5 0.0592 0.00031 0.5 0.34 375.1 31.16 367.5 4.77 370.7 1.917 0.05029 0.00276 5.5 0.41804 0.02429 5.8 0.05904 0.00086 1.5 0.25 208.2 122.3 354.6 17.39 369.8 5.258 0.05144 0.00199 3.9 0.40692 0.01675 4.1 0.05796 0.00064 1.1 0.27 260.5 86.41 346.7 12.09 363.2 3.899 0.05368 0.00101 1.9 0.41165 0.00846 2.1 0.0576 0.00038 0.7 0.32 357.6 42.52 350.1 6.08 361 2.3210 0.05491 0.00146 2.7 0.44198 0.01267 2.9 0.0581 0.00049 0.8 0.29 408.4 57.51 371.6 8.92 364 311 0.05349 0.00259 4.8 0.42774 0.02225 5.2 0.05835 0.00084 1.4 0.28 349.4 105.8 361.6 15.82 365.6 5.1412 0.05353 0.00172 3.2 0.42205 0.01455 3.4 0.05858 0.00058 1.0 0.29 351.3 70.98 357.5 10.39 367 3.5313 0.05338 0.00147 2.8 0.42395 0.0127 3.0 0.05835 0.00053 0.9 0.3 344.8 61.29 358.9 9.06 365.6 3.2114 0.05433 0.00113 2.1 0.43349 0.00986 2.3 0.05878 0.00042 0.7 0.31 384.5 46.1 365.6 6.99 368.2 2.5415 0.05189 0.00231 4.5 0.42346 0.02021 4.8 0.05756 0.00075 1.3 0.27 280.7 98.81 358.5 14.42 360.8 4.5716 0.05243 0.00186 3.5 0.41925 0.01612 3.8 0.05875 0.00067 1.1 0.3 304.1 78.85 355.5 11.54 368 4.0617 0.05365 0.0013 2.4 0.4375 0.01154 2.6 0.05874 0.00047 0.8 0.3 356.3 53.86 368.5 8.15 368 2.8718 0.05545 0.00174 3.1 0.46369 0.01586 3.4 0.06152 0.00063 1.0 0.3 430 68.09 386.8 11 384.9 3.83211Isotopic Ratios Calculated Ages207 206 207 235 206 238 1 207 206 207 235 206 23819 0.05448 0.00209 3.8 0.43364 0.01803 4.2 0.05704 0.00084 1.5 0.35 390.8 83.02 365.8 12.77 357.6 5.13Table A1.1. (continued)Run # Pb/ Pb 1 σ abs 1 σ % Pb/ U 1 σ abs 1 σ % Pb/ U 1 σ abs 1 σ % rho Pb/ Pb 1 σ abs Pb/ U 1 σ abs Pb/ U 1 σ abs08TR049A: Foliated and sericitized felsic crystal tuff1 0.05361 0.00104 1.9 0.41133 0.00863 2.1 0.05702 0.00044 0.8 0.37 354.4 43.42 349.8 6.21 357.5 2.712 0.05351 0.00123 2.3 0.41985 0.01046 2.5 0.05799 0.00053 0.9 0.37 350.2 51.3 355.9 7.48 363.4 3.223 0.05343 0.00108 2.0 0.42974 0.00946 2.2 0.05807 0.00047 0.8 0.37 347.2 45.28 363 6.72 363.9 2.864 0.05398 0.0009 1.7 0.42444 0.00763 1.8 0.05743 0.00039 0.7 0.38 370.1 37.06 359.2 5.44 360 2.45 0.05497 0.00098 1.8 0.43618 0.00843 1.9 0.05826 0.00042 0.7 0.37 410.9 39.1 367.6 5.96 365.1 2.576 0.05394 0.00127 2.4 0.42871 0.01098 2.6 0.05809 0.00054 0.9 0.36 368.2 52.26 362.3 7.8 364 3.317 0.05544 0.00103 1.9 0.43108 0.00868 2.0 0.05721 0.00043 0.8 0.37 429.8 40.47 363.9 6.16 358.6 2.638 0.05461 0.00118 2.2 0.4322 0.01011 2.3 0.05721 0.00049 0.9 0.37 396.3 47.4 364.7 7.17 358.6 2.999 0.05339 0.00103 1.9 0.43447 0.00908 2.1 0.05885 0.00045 0.8 0.37 345.4 43.02 366.3 6.43 368.7 2.7510 0.05633 0.00133 2.4 0.46479 0.01196 2.6 0.05783 0.00054 0.9 0.36 464.7 51.93 387.6 8.29 362.4 3.3111 0.05368 0.00114 2.1 0.41069 0.00939 2.3 0.0568 0.00048 0.8 0.37 357.5 47.22 349.4 6.76 356.1 2.9212 0.05658 0.0017 3.0 0.45225 0.0148 3.3 0.05663 0.00067 1.2 0.36 474.5 65.25 378.9 10.35 355.1 4.113 0.05555 0.00119 2.1 0.43703 0.01016 2.3 0.05743 0.00049 0.9 0.37 434.2 46.66 368.2 7.18 360 3.0114 0.05356 0.00098 1.8 0.42077 0.0083 2.0 0.05701 0.00041 0.7 0.36 352.5 40.82 356.6 5.93 357.4 2.5315 0.051 0.0012 2.4 0.40441 0.01023 2.5 0.05664 0.0005 0.9 0.35 240.8 53.2 344.8 7.4 355.1 3.0816 0.05693 0.00147 2.6 0.45598 0.01277 2.8 0.05643 0.00058 1.0 0.37 488.3 56.45 381.5 8.91 353.8 3.5317 0.05382 0.00102 1.9 0.43788 0.00901 2.1 0.05815 0.00044 0.8 0.37 363.5 42.34 368.8 6.36 364.3 2.6818 0.0534 0.00121 2.3 0.42391 0.01042 2.5 0.05621 0.0005 0.9 0.36 345.7 50.68 358.8 7.43 352.5 3.0320 0.05392 0.00123 2.3 0.41234 0.01012 2.5 0.05577 0.00049 0.9 0.36 367.6 50.66 350.6 7.28 349.8 2.9908TR055A: Foliated and sericitized rhyolite porphyry1 0.05288 0.00105 2.0 0.41589 0.00923 2.2 0.05758 0.00045 0.8 0.35 323.8 44.5 353.1 6.62 360.9 2.772 0.05634 0.00122 2.2 0.43532 0.01055 2.4 0.05663 0.00049 0.9 0.36 464.9 47.72 366.9 7.46 355.1 3.013 0.05404 0.00095 1.8 0.41719 0.00813 1.9 0.05637 0.0004 0.7 0.36 372.7 39.15 354 5.83 353.5 2.454 0.05209 0.00104 2.0 0.41303 0.00919 2.2 0.05678 0.00045 0.8 0.36 289.1 45 351.1 6.61 356 2.725 0.05387 0.0016 3.0 0.4189 0.01391 3.3 0.05802 0.00067 1.2 0.35 365.4 65.49 355.3 9.95 363.6 4.096 0.05294 0.00131 2.5 0.40901 0.01129 2.8 0.05688 0.00055 1.0 0.35 326.3 55.26 348.2 8.13 356.6 3.347 0.05693 0.0013 2.3 0.44896 0.01153 2.6 0.05612 0.00052 0.9 0.36 488.3 49.76 376.5 8.08 352 3.148 0.05404 0.00099 1.8 0.41149 0.0084 2.0 0.05609 0.00042 0.7 0.37 372.4 40.95 349.9 6.05 351.8 2.54212Isotopic Ratios Calculated Ages19 0.05286 0.00112 2.1 0.40932 0.00964 2.4 0.05695 0.00047 0.8 0.35 322.7 47.43 348.4 6.94 357.1 2.89Table A1.1. (continued)Run # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs08TR055A: Foliated and sericitized rhyolite porphyry (continued)11 0.05547 0.00127 2.3 0.43636 0.01109 2.5 0.05612 0.0005 0.9 0.35 430.8 49.66 367.7 7.84 352 3.0612 0.05251 0.00114 2.2 0.41967 0.01021 2.4 0.05678 0.00049 0.9 0.35 307.6 48.78 355.8 7.3 356 2.9613 0.05247 0.00115 2.2 0.4126 0.01003 2.4 0.05741 0.00048 0.8 0.34 305.9 49.05 350.7 7.21 359.9 2.9514 0.05291 0.00134 2.5 0.42791 0.01207 2.8 0.05788 0.00056 1.0 0.34 324.7 56.3 361.7 8.58 362.7 3.415 0.05571 0.00148 2.7 0.45016 0.01332 3.0 0.0583 0.0006 1.0 0.35 440.6 57.64 377.4 9.33 365.3 3.6316 0.05281 0.00167 3.2 0.42274 0.01484 3.5 0.05785 0.00068 1.2 0.33 320.6 70.28 358 10.59 362.5 4.1217 0.05594 0.00219 3.9 0.41078 0.01775 4.3 0.05735 0.00085 1.5 0.34 449.6 84.45 349.4 12.77 359.5 5.218 0.05569 0.0015 2.7 0.41517 0.01245 3.0 0.05579 0.00059 1.1 0.35 439.7 58.73 352.6 8.93 350 3.620 0.05326 0.00099 1.9 0.42026 0.00874 2.1 0.05759 0.00044 0.8 0.37 339.7 41.55 356.2 6.25 361 2.6508TR061B: Foliated felsic tuff or rhyolite flow1 0.05367 0.0007 1.3 0.42251 0.00597 1.4 0.05668 0.0003 0.5 0.37 357.2 29.42 357.8 4.26 355.4 1.852 0.05329 0.00086 1.6 0.42745 0.00745 1.7 0.05787 0.00037 0.6 0.37 341.2 36.14 361.4 5.3 362.6 2.233 0.05419 0.00084 1.6 0.43485 0.00726 1.7 0.05705 0.00035 0.6 0.37 378.7 34.6 366.6 5.14 357.7 2.134 0.05302 0.0007 1.3 0.41843 0.00597 1.4 0.05753 0.00031 0.5 0.38 329.6 29.68 354.9 4.27 360.6 1.95 0.05333 0.00072 1.4 0.42795 0.00622 1.5 0.0584 0.00032 0.5 0.38 342.9 30.13 361.7 4.42 365.9 1.956 0.0532 0.00088 1.7 0.41552 0.00739 1.8 0.05692 0.00036 0.6 0.36 337.3 37.1 352.8 5.3 356.9 2.227 0.05306 0.00065 1.2 0.42312 0.00556 1.3 0.0584 0.00029 0.5 0.38 331.4 27.36 358.3 3.97 365.9 1.798 0.05407 0.00097 1.8 0.43202 0.00831 1.9 0.05629 0.0004 0.7 0.37 373.9 39.79 364.6 5.89 353 2.439 0.05312 0.00069 1.3 0.42446 0.00591 1.4 0.05771 0.0003 0.5 0.37 334 28.93 359.2 4.21 361.7 1.8510 0.05366 0.00089 1.7 0.43203 0.00769 1.8 0.05801 0.00038 0.7 0.37 356.9 36.98 364.6 5.45 363.5 2.2911 0.05401 0.00064 1.2 0.42201 0.00542 1.3 0.05652 0.00028 0.5 0.39 371.4 26.73 357.5 3.87 354.5 1.7212 0.0525 0.00061 1.2 0.40949 0.0051 1.2 0.05679 0.00027 0.5 0.38 307.4 26.07 348.5 3.67 356.1 1.6713 0.05535 0.00079 1.4 0.43463 0.00669 1.5 0.05683 0.00033 0.6 0.38 426 31.44 366.5 4.73 356.3 2.0114 0.05361 0.0008 1.5 0.43119 0.00698 1.6 0.05738 0.00035 0.6 0.38 354.6 33.6 364 4.95 359.7 2.1115 0.05526 0.00086 1.6 0.43951 0.00736 1.7 0.05749 0.00036 0.6 0.37 422.4 34.11 369.9 5.19 360.4 2.216 0.05322 0.00077 1.4 0.42136 0.00653 1.5 0.05779 0.00033 0.6 0.37 338 32.3 357 4.67 362.1 217 0.05295 0.00072 1.4 0.42219 0.00619 1.5 0.058 0.00032 0.6 0.38 326.5 30.52 357.6 4.42 363.5 1.9418 0.0552 0.00085 1.5 0.43547 0.00718 1.6 0.0565 0.00035 0.6 0.38 420.1 33.66 367.1 5.08 354.3 2.13213Isotopic Ratios Calculated Ages19 0.05036 0.00081 1.6 0.38845 0.0067 1.7 0.05631 0.00035 0.6 0.36 211.6 36.73 333.2 4.9 353.2 2.15Table A1.1. (continued)Run # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs08TR078: Rhyolite lapilli tuff1 0.05386 0.00076 1.4 0.40428 0.00612 1.5 0.05389 0.00031 0.6 0.38 365.1 31.5 344.7 4.42 338.4 1.92 0.05423 0.00082 1.5 0.41215 0.00671 1.6 0.05601 0.00034 0.6 0.37 380.5 33.63 350.4 4.82 351.3 2.13 0.05448 0.00108 2.0 0.412 0.00877 2.1 0.05552 0.00043 0.8 0.36 390.8 43.46 350.3 6.3 348.3 2.644 0.05458 0.00101 1.9 0.41298 0.00826 2.0 0.05534 0.00041 0.7 0.37 395 40.82 351 5.94 347.2 2.485 0.05542 0.00069 1.2 0.40692 0.0055 1.4 0.05414 0.00029 0.5 0.4 428.8 27.62 346.7 3.97 339.9 1.766 0.05366 0.00068 1.3 0.4064 0.00557 1.4 0.05466 0.00029 0.5 0.39 356.6 28.45 346.3 4.02 343.1 1.777 0.05288 0.00135 2.6 0.4026 0.01098 2.7 0.05516 0.00052 0.9 0.35 323.6 56.77 343.5 7.95 346.1 3.168 0.05495 0.00091 1.7 0.40878 0.00728 1.8 0.05333 0.00036 0.7 0.38 410 36.28 348 5.25 334.9 2.189 0.05264 0.00062 1.2 0.39292 0.00501 1.3 0.05467 0.00027 0.5 0.39 313.2 26.67 336.5 3.65 343.1 1.6710 0.05385 0.00106 2.0 0.40796 0.00867 2.1 0.05528 0.00043 0.8 0.37 364.7 43.95 347.4 6.25 346.9 2.611 0.05343 0.00104 1.9 0.43705 0.00924 2.1 0.05934 0.00045 0.8 0.36 347.1 43.53 368.2 6.53 371.6 2.7512 0.05361 0.0009 1.7 0.40246 0.00725 1.8 0.05457 0.00036 0.7 0.37 354.4 37.45 343.4 5.25 342.5 2.2213 0.05373 0.00084 1.6 0.41082 0.00693 1.7 0.05552 0.00035 0.6 0.37 359.8 34.99 349.5 4.99 348.3 2.1514 0.05442 0.00081 1.5 0.40281 0.00645 1.6 0.05451 0.00033 0.6 0.38 388.4 32.98 343.7 4.67 342.1 215 0.05272 0.00087 1.7 0.40316 0.00719 1.8 0.05506 0.00036 0.7 0.37 316.6 37.11 343.9 5.2 345.5 2.2216 0.05544 0.00083 1.5 0.40631 0.00653 1.6 0.05406 0.00033 0.6 0.38 429.9 32.49 346.2 4.72 339.4 2.0217 0.0529 0.00057 1.1 0.39972 0.00461 1.2 0.0541 0.00025 0.5 0.4 324.5 24.06 341.4 3.35 339.7 1.5318 0.05261 0.00094 1.8 0.39468 0.00756 1.9 0.05377 0.00038 0.7 0.37 312.2 39.98 337.8 5.5 337.6 2.320 0.05496 0.00089 1.6 0.41831 0.00734 1.8 0.05588 0.00037 0.7 0.38 410.7 35.63 354.8 5.25 350.5 2.2508TR082: Rhyolite lapilli tuff1 0.05415 0.00083 1.5 0.4214 0.00701 1.7 0.05672 0.00035 0.6 0.37 377.3 34.31 357 5.01 355.6 2.162 0.05423 0.00093 1.7 0.40847 0.00758 1.9 0.05595 0.00038 0.7 0.37 380.6 38.24 347.8 5.46 351 2.353 0.05349 0.00086 1.6 0.41837 0.00724 1.7 0.05548 0.00035 0.6 0.36 349.3 35.77 354.9 5.18 348.1 2.164 0.05645 0.00125 2.2 0.43832 0.01051 2.4 0.05662 0.0005 0.9 0.37 469.3 48.76 369.1 7.42 355.1 3.035 0.05299 0.00102 1.9 0.40933 0.00851 2.1 0.05578 0.00042 0.8 0.36 328.4 43.01 348.4 6.13 349.9 2.576 0.05623 0.00111 2.0 0.42469 0.00901 2.1 0.05452 0.00042 0.8 0.36 460.5 43.39 359.4 6.42 342.2 2.597 0.05412 0.00103 1.9 0.40763 0.00837 2.1 0.0536 0.0004 0.7 0.36 375.7 42.35 347.2 6.04 336.6 2.478 0.05435 0.00077 1.4 0.41475 0.00635 1.5 0.05529 0.00032 0.6 0.38 385.4 31.46 352.3 4.55 346.9 1.97214Isotopic Ratios Calculated Ages17 0.05411 0.00108 2.0 0.39694 0.00851 2.1 0.0539 0.00042 0.8 0.36 375.3 44.34 339.4 6.19 338.4 2.5718 0.0522 0.00066 1.3 0.39534 0.00548 1.4 0.05489 0.00031 0.6 0.41 294.3 28.77 338.3 3.99 344.5 1.8719 0.05457 0.00089 1.6 0.40215 0.00712 1.8 0.05404 0.00037 0.7 0.39 394.7 36.05 343.2 5.16 339.3 2.2620 0.05311 0.0008 1.5 0.40899 0.00672 1.6 0.05656 0.00036 0.6 0.39 333.5 33.76 348.1 4.84 354.7 2.2Table A1.1. (continued)Run # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs08TR082: Rhyolite lapilli tuff (continued)11 0.05294 0.00081 1.5 0.40071 0.00658 1.6 0.0544 0.00034 0.6 0.38 326.2 34.1 342.2 4.77 341.5 2.0612 0.05203 0.00112 2.2 0.40358 0.00932 2.3 0.05574 0.00046 0.8 0.36 286.8 48.28 344.2 6.75 349.7 2.7813 0.0523 0.00128 2.4 0.38348 0.01004 2.6 0.0549 0.00051 0.9 0.35 298.4 54.83 329.6 7.37 344.5 3.114 0.05434 0.00101 1.9 0.41363 0.00827 2.0 0.05512 0.00041 0.7 0.37 384.9 40.95 351.5 5.94 345.9 2.4815 0.0529 0.00108 2.0 0.40329 0.00889 2.2 0.05528 0.00043 0.8 0.35 324.5 45.77 344 6.43 346.9 2.6416 0.05512 0.00121 2.2 0.4014 0.00948 2.4 0.05408 0.00047 0.9 0.37 417.1 47.73 342.7 6.87 339.5 2.8818 0.05357 0.00105 2.0 0.41563 0.00878 2.1 0.056 0.00043 0.8 0.36 353 43.67 352.9 6.3 351.3 2.6208TR084B: Rhyolite tuff breccia1 0.05446 0.00102 1.9 0.40878 0.00825 2.0 0.05467 0.00041 0.7 0.37 389.9 41.23 348 5.94 343.1 2.52 0.05291 0.00082 1.5 0.39582 0.00659 1.7 0.05375 0.00034 0.6 0.38 324.8 34.64 338.6 4.79 337.5 2.083 0.053 0.00072 1.4 0.40128 0.00591 1.5 0.055 0.00032 0.6 0.4 328.6 30.58 342.6 4.28 345.1 1.944 0.05353 0.00101 1.9 0.39331 0.00795 2.0 0.05338 0.0004 0.7 0.37 351 42.06 336.8 5.79 335.2 2.445 0.05342 0.00065 1.2 0.39392 0.00518 1.3 0.05402 0.00029 0.5 0.41 346.5 27.26 337.2 3.77 339.2 1.766 0.05326 0.00062 1.2 0.39318 0.00497 1.3 0.054 0.00028 0.5 0.41 340 26.21 336.7 3.62 339 1.717 0.05362 0.00061 1.1 0.39706 0.00486 1.2 0.05316 0.00027 0.5 0.41 355.1 25.32 339.5 3.53 333.9 1.658 0.05388 0.00066 1.2 0.40251 0.00536 1.3 0.05416 0.00029 0.5 0.4 365.9 27.66 343.5 3.88 340 1.799 0.05475 0.00065 1.2 0.41047 0.00527 1.3 0.05493 0.00029 0.5 0.41 402.2 26.09 349.2 3.8 344.7 1.7710 0.05368 0.00069 1.3 0.40047 0.00556 1.4 0.05409 0.0003 0.6 0.4 357.5 28.77 342 4.03 339.6 1.8511 0.05308 0.00066 1.2 0.40008 0.00539 1.3 0.05473 0.0003 0.5 0.41 332.3 27.93 341.7 3.91 343.5 1.8212 0.05464 0.00083 1.5 0.4065 0.00668 1.6 0.05413 0.00035 0.6 0.39 397.5 33.45 346.4 4.82 339.8 2.1213 0.0511 0.0008 1.6 0.37569 0.00635 1.7 0.05393 0.00035 0.6 0.38 245.4 35.78 323.9 4.69 338.6 2.1314 0.05325 0.00071 1.3 0.40337 0.00585 1.5 0.05463 0.00032 0.6 0.4 339.5 29.89 344.1 4.23 342.9 1.9315 0.05404 0.00068 1.3 0.41056 0.00565 1.4 0.05465 0.0003 0.5 0.4 372.6 28.43 349.3 4.07 343 1.8516 0.05271 0.00085 1.6 0.39501 0.00693 1.8 0.05463 0.00037 0.7 0.39 316.3 36.41 338 5.04 342.9 2.2517 0.05266 0.00064 1.2 0.40429 0.00536 1.3 0.0557 0.0003 0.5 0.41 314.3 27.42 344.8 3.88 349.4 1.83215Isotopic Ratios Calculated Ages11 0.05285 0.00087 1.6 0.4256 0.0077 1.8 0.05732 0.00041 0.7 0.4 322.4 36.97 360 5.48 359.3 2.5315 0.05263 0.00102 1.9 0.42347 0.0088 2.1 0.05895 0.00042 0.7 0.34 312.9 43.51 358.5 6.27 369.2 2.55Table A1.1. (continued)Run # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs08TR101: Strongly sericitized felsic tuff1 0.05353 0.00129 2.4 0.42675 0.01128 2.6 0.05738 0.00055 1.0 0.36 351.1 53.74 360.9 8.02 359.6 3.352 0.05252 0.00143 2.7 0.43391 0.01297 3.0 0.0585 0.00062 1.1 0.35 307.9 60.73 366 9.19 366.5 3.793 0.05597 0.00116 2.1 0.46307 0.01063 2.3 0.05947 0.00052 0.9 0.38 451 45.34 386.4 7.38 372.4 3.154 0.0532 0.00138 2.6 0.4269 0.01211 2.8 0.05744 0.00058 1.0 0.36 337.1 57.76 361 8.61 360 3.565 0.05246 0.00101 1.9 0.42565 0.009 2.1 0.05703 0.00046 0.8 0.38 305.7 43.33 360.1 6.41 357.6 2.86 0.05517 0.00107 1.9 0.44298 0.00942 2.1 0.05787 0.00048 0.8 0.39 419 41.99 372.4 6.63 362.6 2.97 0.05471 0.00149 2.7 0.42884 0.01278 3.0 0.05674 0.00061 1.1 0.36 400.1 59.58 362.4 9.08 355.8 3.748 0.05523 0.00144 2.6 0.43314 0.01235 2.9 0.05709 0.0006 1.1 0.37 421.3 56.54 365.4 8.75 357.9 3.669 0.05798 0.0019 3.3 0.46115 0.01659 3.6 0.05858 0.00076 1.3 0.36 528.6 70.72 385.1 11.53 367 4.610 0.05766 0.0025 4.3 0.45916 0.02186 4.8 0.05734 0.00095 1.7 0.35 516.7 92.91 383.7 15.21 359.4 5.8112 0.05342 0.00108 2.0 0.43584 0.00967 2.2 0.05894 0.0005 0.8 0.38 346.4 45.04 367.3 6.84 369.2 3.0313 0.05471 0.00141 2.6 0.41807 0.0118 2.8 0.05696 0.0006 1.1 0.37 400.1 56.84 354.7 8.45 357.1 3.6508TR107: Weakly sericitized quartz-feldspar porphyry1 0.05404 0.00083 1.5 0.42357 0.00697 1.6 0.05779 0.00035 0.6 0.37 372.6 34.19 358.6 4.97 362.2 2.152 0.05511 0.00073 1.3 0.44121 0.00632 1.4 0.05825 0.00032 0.5 0.38 416.6 29.09 371.1 4.45 365 1.933 0.05481 0.00081 1.5 0.44122 0.00704 1.6 0.05913 0.00035 0.6 0.37 404.5 32.51 371.1 4.96 370.3 2.124 0.05351 0.00074 1.4 0.42231 0.00628 1.5 0.05695 0.00032 0.6 0.38 350.4 30.91 357.7 4.48 357 1.925 0.05423 0.00078 1.4 0.4297 0.00664 1.5 0.05764 0.00033 0.6 0.37 380.4 32.09 363 4.71 361.3 26 0.05499 0.00069 1.3 0.42582 0.00572 1.3 0.05669 0.00029 0.5 0.38 411.8 27.39 360.2 4.08 355.5 1.797 0.05277 0.0009 1.7 0.42458 0.00781 1.8 0.05891 0.00039 0.7 0.36 318.7 38.31 359.3 5.57 369 2.388 0.0539 0.00102 1.9 0.41826 0.00851 2.0 0.05731 0.00043 0.8 0.37 366.7 42.18 354.8 6.09 359.3 2.69 0.05442 0.00062 1.1 0.43445 0.00536 1.2 0.05745 0.00028 0.5 0.4 388.5 25.39 366.3 3.79 360.1 1.6810 0.05363 0.00085 1.6 0.42917 0.00734 1.7 0.05781 0.00036 0.6 0.36 355.6 35.64 362.6 5.21 362.3 2.1711 0.05379 0.00082 1.5 0.43605 0.00713 1.6 0.05866 0.00035 0.6 0.36 362 33.98 367.5 5.04 367.5 2.1212 0.05403 0.00079 1.5 0.43193 0.00684 1.6 0.05766 0.00034 0.6 0.37 371.9 32.81 364.5 4.85 361.4 2.0813 0.05473 0.00073 1.3 0.43327 0.00627 1.4 0.05733 0.00031 0.5 0.37 401.4 29.48 365.5 4.44 359.4 1.9214 0.05301 0.00081 1.5 0.41836 0.00683 1.6 0.05818 0.00035 0.6 0.37 329.1 34.02 354.9 4.89 364.5 2.13216Isotopic Ratios Calculated Ages18 0.05381 0.00078 1.4 0.42922 0.00673 1.6 0.05776 0.00033 0.6 0.36 363.1 32.65 362.6 4.78 362 2.0311 0.05439 0.0021 3.9 0.43231 0.01879 4.3 0.05639 0.00082 1.5 0.33 387.3 83.63 364.8 13.32 353.6 5.035 0.05444 0.00267 4.9 0.39919 0.0209 5.2 0.05502 0.00098 1.8 0.34 389.1 106.1 341.1 15.17 345.3 66 0.05605 0.00143 2.6 0.42657 0.01171 2.7 0.05571 0.00056 1.0 0.37 453.9 55.57 360.7 8.33 349.5 3.417 0.05329 0.0021 3.9 0.41023 0.01739 4.2 0.05654 0.00083 1.5 0.35 341.2 86.79 349 12.52 354.6 5.06Table A1.1. (continued)207Pb/206Pb 207Pb/235U 206Pb/238U rho1 207Pb/206Pb 207Pb/235U 206Pb/238URun # 1 σ abs 1 σ % 1 σ abs 1 σ % 1 σ abs 1 σ % 1 σ abs 1 σ abs 1 σ abs08TR107: Weakly sericitized quartz-feldspar porphyry (continued)19 0.05455 0.0008 1.5 0.41609 0.00655 1.6 0.0558 0.00033 0.6 0.38 393.7 32.45 353.3 4.7 350.1 1.9920 0.05425 0.00077 1.4 0.41928 0.00636 1.5 0.05611 0.00032 0.6 0.38 381.4 31.63 355.5 4.55 351.9 1.9308TR114: Chlorite and hematite altered quartz-feldspar porphyry1 0.05266 0.00529 10.0 0.44434 0.0491 11.1 0.05932 0.00177 3.0 0.27 314 213.32 373.3 34.52 371.5 10.772 0.03889 0.00701 18.0 0.30373 0.05776 19.0 0.05863 0.00254 4.3 0.23 0.1 0 269.3 44.98 367.3 15.443 0.05301 0.00391 7.4 0.42161 0.03428 8.1 0.05697 0.00136 2.4 0.29 329.4 158.55 357.2 24.48 357.2 8.284 0.04819 0.00393 8.2 0.38361 0.03467 9.0 0.05733 0.00159 2.8 0.31 108.6 182.03 329.7 25.44 359.4 9.715 0.05973 0.00275 4.6 0.4423 0.023 5.2 0.05595 0.00102 1.8 0.35 594 96.81 371.9 16.19 350.9 6.26 0.05147 0.00261 5.1 0.40647 0.02303 5.7 0.05599 0.00101 1.8 0.32 261.8 112.26 346.3 16.62 351.2 6.197 0.0572 0.0045 7.9 0.47969 0.04226 8.8 0.05817 0.00157 2.7 0.31 498.7 165.14 397.9 29 364.5 9.588 0.05602 0.00283 5.1 0.45334 0.02571 5.7 0.05623 0.00103 1.8 0.32 452.7 108.63 379.6 17.96 352.7 6.289 0.05518 0.00482 8.7 0.44302 0.04355 9.8 0.05778 0.00177 3.1 0.31 419.5 184.04 372.4 30.65 362.1 10.7910 0.05687 0.00337 5.9 0.42972 0.02818 6.6 0.05692 0.00118 2.1 0.32 485.8 126.42 363 20.01 356.9 7.1812 0.0567 0.00496 8.7 0.44778 0.0442 9.9 0.0576 0.00186 3.2 0.33 479.1 183.29 375.7 31 361 11.3313 0.04282 0.00441 0.32493 0.03565 11.0 0.05887 0.00161 2.7 0.25 0.1 60.37 285.7 27.32 368.8 9.7808TR121: Weakly sericitized rhyolite crystal tuff1 0.05727 0.00297 5.2 0.46653 0.02611 5.6 0.0577 0.00108 1.9 0.33 501.5 110.83 388.8 18.08 361.6 6.62 0.05456 0.00209 3.8 0.41271 0.01701 4.1 0.05723 0.00084 1.5 0.36 394 82.84 350.8 12.22 358.8 5.13 0.05548 0.00214 3.9 0.4305 0.01788 4.2 0.05699 0.00082 1.4 0.35 431.4 83.65 363.5 12.69 357.3 5.024 0.05415 0.00146 2.7 0.40743 0.01179 2.9 0.0561 0.00058 1.0 0.36 377.2 59.37 347 8.51 351.8 3.56217Table A1.1. (continued)18 0.05275 0.00064 1.2 0.36457 0.00479 1.3 0.05003 0.00025 0.5 0.38 318.2 27.5 315.6 3.57 314.7 1.551 0.05328 0.00176 3.3 0.34341 0.01185 3.5 0.04783 0.00054 1.1 0.33 340.7 72.91 299.8 8.96 301.2 3.3Isotopic Ratios Calculated Ages207 206 207 235 206 238 1 207 206 207 235 206 238Run # Pb/ Pb 1 σ abs 1 σ % Pb/ U 1 σ abs 1 σ % Pb/ U 1 σ abs 1 σ % rho Pb/ Pb 1 σ abs Pb/ U 1 σ abs Pb/ U 1 σ abs08TRDR007B: Aphyric rhyolite flow1 0.05391 0.00062 1.2 0.3797 0.00468 1.2 0.05172 0.00025 0.5 0.39 367 25.78 326.8 3.44 325.1 1.532 0.05403 0.00081 1.5 0.34724 0.00552 1.6 0.04775 0.00029 0.6 0.38 372.1 33.52 302.6 4.16 300.7 1.773 0.05181 0.0005 1.0 0.35011 0.00359 1.0 0.05008 0.00021 0.4 0.41 277.1 21.78 304.8 2.7 315 1.284 0.05292 0.00054 1.0 0.35414 0.00384 1.1 0.04911 0.00021 0.4 0.39 325.1 22.78 307.8 2.88 309 1.315 0.05143 0.00059 1.1 0.33158 0.00402 1.2 0.04714 0.00022 0.5 0.38 260.1 25.93 290.8 3.06 296.9 1.376 0.05471 0.00059 1.1 0.3573 0.00412 1.2 0.04776 0.00022 0.5 0.4 400.1 23.87 310.2 3.08 300.7 1.357 0.05184 0.00057 1.1 0.35475 0.0042 1.2 0.05035 0.00023 0.5 0.39 278.3 25.09 308.3 3.14 316.7 1.438 0.05922 0.00082 1.4 0.36444 0.00537 1.5 0.0445 0.00026 0.6 0.4 575.4 29.83 315.5 4 280.7 1.599 0.0527 0.00088 1.7 0.34438 0.0061 1.8 0.04818 0.00032 0.7 0.37 316 37.38 300.5 4.61 303.4 1.9510 0.05305 0.00056 1.1 0.35083 0.00396 1.1 0.04852 0.00022 0.5 0.4 330.9 23.67 305.3 2.98 305.4 1.3411 0.05247 0.00052 1.0 0.35179 0.00376 1.1 0.04892 0.00021 0.4 0.4 305.8 22.47 306.1 2.83 307.9 1.2912 0.05282 0.00057 1.1 0.3403 0.00392 1.2 0.04766 0.00022 0.5 0.4 320.9 24.21 297.4 2.97 300.1 1.3313 0.0527 0.0006 1.1 0.35003 0.00426 1.2 0.04872 0.00023 0.5 0.39 315.8 25.59 304.7 3.2 306.7 1.4214 0.05276 0.00061 1.2 0.34041 0.0042 1.2 0.04685 0.00023 0.5 0.4 318.4 25.96 297.5 3.18 295.2 1.3915 0.05371 0.00059 1.1 0.362 0.00428 1.2 0.04878 0.00023 0.5 0.4 359 24.62 313.7 3.19 307 1.3916 0.05354 0.00054 1.0 0.37062 0.00404 1.1 0.05077 0.00022 0.4 0.4 351.5 22.59 320.1 2.99 319.3 1.3617 0.05309 0.00059 1.1 0.36315 0.00438 1.2 0.0507 0.00024 0.5 0.39 332.8 25.12 314.6 3.26 318.8 1.4719 0.0543 0.00066 1.2 0.36574 0.0048 1.3 0.04857 0.00025 0.5 0.39 383.3 27.24 316.5 3.57 305.8 1.5120 0.05314 0.00064 0.36618 0.00478 1.3 0.04974 0.00025 0.5 0.39 334.8 27.15 316.8 3.55 312.9 1.5308TRDR042: Heterolithic tuff breccia2 0.05027 0.0016 3.2 0.33915 0.01137 3.4 0.04874 0.00055 1.1 0.34 207.3 72.19 296.5 8.62 306.8 3.363 0.05266 0.00149 2.8 0.35005 0.01038 3.0 0.04994 0.00049 1.0 0.33 314.4 62.81 304.8 7.81 314.1 3.0308TRDR056: Rhyolite dike1 0.04965 0.0035 7.0 0.18252 0.01289 7.1 0.02655 0.00049 1.8 0.26 178.7 156.57 170.2 11.07 168.9 3.052 0.04208 0.00271 6.4 0.15723 0.01016 6.5 0.02726 0.00044 1.6 0.25 0.1 0 148.3 8.92 173.4 2.79218Table A1.1. (continued)18 0.05348 0.00076 1.4 0.42523 0.00677 1.6 0.05686 0.00032 0.6 0.35 349.2 31.7 359.8 4.82 356.5 1.96Isotopic Ratios Calculated AgesRun # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs08TRDR056: Rhyolite dike (continued)6 0.04915 0.00237 4.8 0.18703 0.00908 4.9 0.02754 0.00043 1.6 0.32 155.1 109.34 174.1 7.77 175.1 2.6809M302: Quartz-feldspar porphyry1 0.05426 0.00071 1.3 0.43824 0.00645 1.5 0.05832 0.00031 0.5 0.36 381.8 29.23 369 4.56 365.4 1.892 0.05493 0.00093 1.7 0.42594 0.0081 1.9 0.05585 0.00037 0.7 0.35 409.4 37.29 360.3 5.77 350.3 2.283 0.05327 0.00066 1.2 0.42349 0.0059 1.4 0.05675 0.00029 0.5 0.37 340.1 27.81 358.5 4.21 355.8 1.754 0.05392 0.00067 1.2 0.42078 0.00581 1.4 0.05602 0.00028 0.5 0.36 367.7 27.73 356.6 4.16 351.4 1.735 0.05374 0.0007 1.3 0.42024 0.00611 1.5 0.05591 0.00029 0.5 0.36 360 29.13 356.2 4.37 350.7 1.796 0.05283 0.00067 1.3 0.41919 0.00596 1.4 0.05629 0.00029 0.5 0.36 321.5 28.55 355.5 4.26 353 1.767 0.05276 0.00069 1.3 0.41832 0.00613 1.5 0.05642 0.00029 0.5 0.35 318.4 29.46 354.8 4.39 353.8 1.88 0.05323 0.00072 1.4 0.42508 0.00648 1.5 0.05647 0.00031 0.5 0.36 338.4 30.43 359.7 4.62 354.1 1.879 0.05329 0.00072 1.4 0.42426 0.0064 1.5 0.05692 0.0003 0.5 0.35 341.2 30.15 359.1 4.56 356.8 1.8610 0.0522 0.00073 1.4 0.43296 0.00683 1.6 0.05715 0.00031 0.5 0.34 294.2 31.68 365.3 4.84 358.2 1.9211 0.05252 0.00074 1.4 0.41972 0.00665 1.6 0.05714 0.00032 0.6 0.35 307.9 31.9 355.9 4.75 358.2 1.9312 0.053 0.00071 1.3 0.42241 0.00632 1.5 0.05681 0.0003 0.5 0.35 328.8 30 357.8 4.51 356.2 1.8513 0.0516 0.00064 1.2 0.40725 0.00565 1.4 0.05623 0.00028 0.5 0.36 267.5 28.29 346.9 4.08 352.6 1.7114 0.05395 0.00067 1.2 0.42489 0.00594 1.4 0.0575 0.00029 0.5 0.36 368.7 28.04 359.5 4.23 360.4 1.7815 0.05243 0.00059 1.1 0.4147 0.00522 1.3 0.05633 0.00026 0.5 0.37 304.1 25.5 352.3 3.75 353.3 1.5916 0.05289 0.00067 1.3 0.40879 0.00577 1.4 0.05614 0.00029 0.5 0.37 323.9 28.47 348 4.16 352.1 1.7417 0.05375 0.00066 1.2 0.43233 0.00598 1.4 0.05738 0.00029 0.5 0.37 360.4 27.72 364.8 4.24 359.7 1.7519 0.05519 0.00074 1.3 0.43753 0.00656 1.5 0.0558 0.0003 0.5 0.36 419.6 29.39 368.5 4.63 350.1 1.8420 0.05389 0.0008 1.5 0.43101 0.0072 1.7 0.05712 0.00034 0.6 0.36 366.4 33.75 363.9 5.11 358.1 2.0509M308: Quartz-feldspar porphyry1 0.05595 0.00046 0.8 0.44005 0.00401 0.9 0.0583 0.00021 0.4 0.4 450.2 17.61 370.3 2.83 365.3 1.312 0.05311 0.00045 0.8 0.41604 0.00392 0.9 0.05692 0.00021 0.4 0.39 333.6 19.04 353.2 2.81 356.9 1.293 0.05413 0.0004 0.7 0.42561 0.00352 0.8 0.05697 0.00019 0.3 0.4 376.2 16.78 360.1 2.5 357.2 1.194 0.05412 0.00046 0.8 0.42856 0.00405 0.9 0.05784 0.00022 0.4 0.4 375.8 19.06 362.2 2.88 362.5 1.32219Table A1.1. (continued)18 0.0537 0.0005 0.9 0.41725 0.00433 1.0 0.05652 0.00023 0.4 0.39 358.3 20.82 354.1 3.1 354.4 1.38Isotopic Ratios Calculated AgesRun # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs09M308: Quartz-feldspar porphyry (continued)8 0.05524 0.00053 1.0 0.43928 0.00474 1.1 0.05734 0.00024 0.4 0.39 421.6 21.21 369.7 3.34 359.4 1.459 0.05416 0.00056 1.0 0.42072 0.00484 1.2 0.05645 0.00024 0.4 0.37 377.4 22.72 356.6 3.46 354 1.4910 0.05702 0.00048 0.8 0.44372 0.00413 0.9 0.05634 0.00021 0.4 0.4 491.8 18.5 372.9 2.9 353.3 1.2811 0.05429 0.00043 0.8 0.42062 0.00367 0.9 0.05554 0.0002 0.4 0.41 383.1 17.01 356.5 2.63 348.5 1.212 0.05344 0.00049 0.9 0.42261 0.00433 1.0 0.05676 0.00022 0.4 0.38 347.5 20.58 357.9 3.09 355.9 1.3713 0.05313 0.00043 0.8 0.42243 0.00385 0.9 0.05818 0.00021 0.4 0.4 334.4 18.4 357.8 2.75 364.6 1.2914 0.05411 0.00045 0.8 0.42666 0.00397 0.9 0.05789 0.00021 0.4 0.39 375.6 18.8 360.8 2.82 362.8 1.315 0.05446 0.00049 0.9 0.42874 0.00428 1.0 0.05699 0.00022 0.4 0.39 390.1 19.96 362.3 3.04 357.3 1.3516 0.05461 0.00054 1.0 0.42205 0.00466 1.1 0.05552 0.00023 0.4 0.38 396.5 21.89 357.5 3.33 348.3 1.4317 0.05465 0.00054 1.0 0.43499 0.00484 1.1 0.0567 0.00024 0.4 0.38 397.7 21.99 366.7 3.43 355.5 1.4619 0.05484 0.00046 0.8 0.43058 0.00398 0.9 0.05634 0.00021 0.4 0.4 405.6 18.31 363.6 2.82 353.3 1.2620 0.05386 0.00057 1.1 0.42197 0.00502 1.2 0.05642 0.00025 0.4 0.37 365.2 23.9 357.5 3.58 353.8 1.5309M309: Quartz-feldspar porphyry1 0.0546 0.00089 1.6 0.43938 0.00796 1.8 0.05812 0.00037 0.6 0.35 395.9 35.85 369.8 5.61 364.2 2.282 0.05483 0.00103 1.9 0.43514 0.00899 2.1 0.05766 0.00041 0.7 0.34 405.5 41.02 366.8 6.36 361.4 2.493 0.05417 0.00101 1.9 0.43713 0.00907 2.1 0.05944 0.00043 0.7 0.35 378.1 41.32 368.2 6.41 372.2 2.644 0.05332 0.00147 2.8 0.42948 0.01317 3.1 0.0583 0.00059 1.0 0.33 342.4 61.43 362.8 9.35 365.3 3.65 0.05466 0.00138 2.5 0.42413 0.01181 2.8 0.05714 0.00053 0.9 0.33 398.5 55.42 359 8.42 358.2 3.236 0.05437 0.00109 2.0 0.42798 0.00959 2.2 0.05763 0.00045 0.8 0.35 386.4 44.39 361.7 6.82 361.2 2.757 0.05318 0.00098 1.8 0.43567 0.00886 2.0 0.0586 0.0004 0.7 0.34 336.4 41 367.2 6.26 367.1 2.468 0.05457 0.00097 1.8 0.43546 0.00856 2.0 0.05658 0.00038 0.7 0.34 394.7 39.02 367 6.06 354.8 2.359 0.05358 0.00158 2.9 0.41214 0.01344 3.3 0.05696 0.00063 1.1 0.34 353.2 65.05 350.4 9.66 357.1 3.8310 0.05386 0.00126 2.3 0.43129 0.01123 2.6 0.05891 0.00053 0.9 0.35 365.2 51.7 364.1 7.97 369 3.2111 0.05344 0.00122 2.3 0.42962 0.01085 2.5 0.05718 0.00048 0.8 0.33 347.3 50.93 362.9 7.7 358.4 2.912 0.05489 0.0016 2.9 0.44114 0.01418 3.2 0.05657 0.00059 1.0 0.32 407.8 63.28 371.1 9.99 354.7 3.6313 0.05576 0.00163 2.9 0.44617 0.01438 3.2 0.05612 0.0006 1.1 0.33 442.3 63.51 374.6 10.09 352 3.6314 0.05516 0.0012 2.2 0.42828 0.01036 2.4 0.05537 0.00046 0.8 0.34 418.7 47.3 362 7.37 347.4 2.81220Table A1.1. (continued)18 0.0545 0.00115 2.1 0.43346 0.01017 2.3 0.05804 0.00046 0.8 0.34 391.6 46.55 365.6 7.2 363.7 2.8318 0.05207 0.00112 2.2 0.38289 0.00913 2.4 0.05407 0.00047 0.9 0.36 288.4 48.21 329.2 6.7 339.5 2.85Isotopic Ratios Calculated AgesRun # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs09M309: Quartz-feldspar porphyry (continued)19 0.05578 0.00119 2.1 0.43951 0.01041 2.4 0.05795 0.00048 0.8 0.35 443.2 46.26 369.9 7.34 363.2 2.9120 0.05392 0.00108 2.0 0.41609 0.0092 2.2 0.05603 0.00043 0.8 0.35 367.6 44.51 353.3 6.6 351.5 2.6109TR034: Quartz-feldspar porphyry1 0.05277 0.00097 1.8 0.40684 0.00837 2.1 0.05506 0.00041 0.7 0.36 318.7 41.22 346.6 6.04 345.5 2.522 0.05388 0.00099 1.8 0.39781 0.0081 2.0 0.05369 0.0004 0.7 0.37 365.9 40.92 340.1 5.88 337.1 2.433 0.05189 0.00068 1.3 0.38703 0.00563 1.5 0.05299 0.0003 0.6 0.39 280.6 29.71 332.2 4.12 332.8 1.854 0.0544 0.00123 2.3 0.39269 0.00982 2.5 0.05257 0.00047 0.9 0.36 387.6 49.58 336.3 7.16 330.3 2.895 0.0519 0.00146 2.8 0.38564 0.01195 3.1 0.05367 0.00056 1.0 0.34 281.2 63.09 331.2 8.76 337 3.416 0.05309 0.00085 1.6 0.38686 0.00688 1.8 0.05282 0.00035 0.7 0.37 332.6 35.89 332.1 5.04 331.8 2.167 0.05188 0.00094 1.8 0.37794 0.00759 2.0 0.05326 0.00039 0.7 0.36 280 41.03 325.5 5.6 334.5 2.398 0.05373 0.0012 2.2 0.40481 0.01005 2.5 0.05438 0.00048 0.9 0.36 359.7 49.74 345.1 7.27 341.4 2.929 0.05337 0.00174 3.3 0.37935 0.0136 3.6 0.05119 0.00063 1.2 0.34 344.4 72.14 326.6 10.01 321.8 3.8410 0.05435 0.00088 1.6 0.38828 0.00698 1.8 0.05247 0.00036 0.7 0.38 385.7 35.89 333.1 5.1 329.7 2.211 0.05476 0.00101 1.8 0.39509 0.00806 2.0 0.05245 0.0004 0.8 0.37 402.3 40.31 338.1 5.87 329.5 2.4412 0.05292 0.00115 2.2 0.38923 0.00935 2.4 0.05168 0.00045 0.9 0.36 325.4 48.3 333.8 6.83 324.8 2.7313 0.05466 0.00112 2.0 0.40397 0.00915 2.3 0.05319 0.00044 0.8 0.37 398.4 44.8 344.5 6.62 334.1 2.6714 0.05254 0.0012 2.3 0.38758 0.00986 2.5 0.05383 0.00049 0.9 0.36 309.2 51.28 332.6 7.22 338 2.9915 0.05298 0.00088 1.7 0.39375 0.00734 1.9 0.05408 0.00038 0.7 0.38 327.8 37.38 337.1 5.35 339.5 2.3216 0.05259 0.00098 1.9 0.38834 0.00807 2.1 0.05366 0.00041 0.8 0.37 311.3 41.88 333.2 5.9 336.9 2.517 0.05228 0.00146 2.8 0.3958 0.01218 3.1 0.0545 0.00057 1.0 0.34 297.6 62.27 338.6 8.86 342.1 3.4619 0.05215 0.00089 1.7 0.39253 0.00753 1.9 0.0531 0.00038 0.7 0.37 291.8 38.54 336.2 5.49 333.5 2.3420 0.05406 0.0011 2.0 0.40649 0.00927 2.3 0.0547 0.00046 0.8 0.37 373.2 45.21 346.3 6.69 343.3 2.7909TR041: Weakly foliated rhyolite tuff1 0.05286 0.00149 2.8 0.41676 0.01302 3.1 0.05466 0.00057 1.0 0.33 322.9 62.69 353.7 9.33 343.1 3.492 0.05453 0.00088 1.6 0.44399 0.00808 1.8 0.05808 0.00039 0.7 0.37 392.9 35.59 373.1 5.68 364 2.37221Table A1.1. (continued)9 0.05342 0.00194 3.6 0.43132 0.01738 4.0 0.05669 0.00073 1.3 0.32 346.5 80.06 364.1 12.33 355.4 4.4717 0.05309 0.00223 4.2 0.4196 0.01861 4.4 0.05708 0.00066 1.2 0.26 332.7 92.44 355.8 13.31 357.9 418 0.05256 0.00169 3.2 0.42044 0.01455 3.5 0.05702 0.00059 1.0 0.3 309.9 71.29 356.4 10.4 357.5 3.5919 0.0599 0.00178 3.0 0.47702 0.01547 3.2 0.05835 0.00061 1.0 0.32 599.9 63.04 396 10.64 365.6 3.6920 0.05589 0.00138 2.5 0.45629 0.01226 2.7 0.05759 0.00049 0.9 0.32 447.8 53.63 381.7 8.55 360.9 2.98Isotopic Ratios Calculated AgesRun # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs09TR041: Weakly foliated rhyolite tuff (continued)6 0.05335 0.0016 3.0 0.42204 0.01411 3.3 0.05732 0.00064 1.1 0.33 343.8 66.55 357.5 10.08 359.3 3.937 0.05215 0.00131 2.5 0.40543 0.0113 2.8 0.05616 0.00053 0.9 0.34 291.8 56.23 345.6 8.16 352.2 3.258 0.056 0.00125 2.2 0.45427 0.01144 2.5 0.05668 0.00051 0.9 0.36 452 48.56 380.3 7.99 355.4 3.0910 0.05608 0.00243 4.3 0.4505 0.02197 4.9 0.05652 0.00091 1.6 0.33 455 93.88 377.6 15.38 354.4 5.5411 0.05352 0.00178 3.3 0.41128 0.01511 3.7 0.05665 0.00068 1.2 0.33 350.8 73.21 349.8 10.87 355.2 4.1712 0.05469 0.00219 4.0 0.43889 0.0197 4.5 0.0565 0.00084 1.5 0.33 400.1 86.09 369.5 13.9 354.3 5.1509TR042: Strongly foliated and sericitized rhyolite crystal tuff1 0.05396 0.00188 3.5 0.41725 0.01531 3.7 0.05661 0.00055 1.0 0.26 369.3 76.37 354.1 10.97 355 3.362 0.05327 0.00141 2.6 0.43162 0.01233 2.9 0.05908 0.00049 0.8 0.29 340.1 59.08 364.3 8.74 370 2.993 0.05607 0.00239 4.3 0.44369 0.02013 4.5 0.05886 0.00077 1.3 0.29 454.8 92.15 372.9 14.16 368.7 4.684 0.05707 0.00235 4.1 0.46644 0.0206 4.4 0.05816 0.00075 1.3 0.29 493.8 88.73 388.7 14.27 364.4 4.555 0.0551 0.00118 2.1 0.43331 0.01012 2.3 0.05893 0.00045 0.8 0.33 416.2 46.39 365.5 7.17 369.1 2.746 0.05451 0.00169 3.1 0.44131 0.01487 3.4 0.05869 0.0006 1.0 0.3 392.3 67.45 371.2 10.47 367.6 3.677 0.05458 0.00154 2.8 0.43489 0.01332 3.1 0.05855 0.00055 0.9 0.31 395.1 61.82 366.6 9.42 366.8 3.368 0.05172 0.00136 2.6 0.41283 0.01167 2.8 0.05711 0.00048 0.8 0.3 272.8 59.08 350.9 8.39 358 2.99 0.0539 0.00184 3.4 0.41984 0.01525 3.6 0.05792 0.00059 1.0 0.28 366.5 74.86 355.9 10.91 363 3.610 0.05481 0.00329 6.0 0.41186 0.02632 6.4 0.05687 0.00103 1.8 0.28 404.4 128.63 350.2 18.93 356.6 6.2811 0.05323 0.00142 2.7 0.39478 0.01133 2.9 0.05588 0.0005 0.9 0.31 338.6 59.47 337.9 8.25 350.5 3.0312 0.05447 0.00157 2.9 0.43389 0.01341 3.1 0.05717 0.00052 0.9 0.29 390.7 63.03 365.9 9.5 358.4 3.1513 0.05359 0.00154 2.9 0.43531 0.01349 3.1 0.05751 0.00053 0.9 0.3 353.6 63.45 366.9 9.54 360.5 3.2514 0.05788 0.00245 4.2 0.46088 0.02105 4.6 0.05813 0.0008 1.4 0.3 524.9 90.56 384.9 14.63 364.3 4.8615 0.05562 0.00184 3.3 0.44834 0.0159 3.5 0.05762 0.00059 1.0 0.29 437 71.91 376.1 11.15 361.1 3.6116 0.05227 0.00204 3.9 0.42427 0.01758 4.1 0.05818 0.00064 1.1 0.27 297.3 86.64 359.1 12.53 364.5 3.89222Table A1.1. (continued)17 0.05374 0.00073 1.4 0.42286 0.00646 1.5 0.0571 0.00034 0.6 0.39 359.9 30.62 358.1 4.61 358 2.057 0.05335 0.00116 2.2 0.38672 0.00922 2.4 0.05306 0.00046 0.9 0.36 343.5 48.4 332 6.75 333.3 2.8Isotopic Ratios Calculated Ages207Pb/206Pb 207Pb/235U 206Pb/238U rho1 207Pb/206Pb 207Pb/235U 206Pb/238URun # 1 σ abs 1 σ % 1 σ abs 1 σ % 1 σ abs 1 σ % 1 σ abs 1 σ abs 1 σ abs09TR063: Rhyolite flow1 0.05351 0.00077 1.4 0.42096 0.00675 1.6 0.05618 0.00034 0.6 0.38 350.2 32.1 356.7 4.82 352.3 2.072 0.05462 0.00069 1.3 0.4084 0.00575 1.4 0.05493 0.00031 0.6 0.4 396.7 27.97 347.7 4.14 344.7 1.863 0.0522 0.00087 1.7 0.40716 0.00753 1.8 0.05618 0.00038 0.7 0.37 294.1 37.46 346.8 5.43 352.3 2.314 0.05405 0.00064 1.2 0.41584 0.00551 1.3 0.05558 0.00029 0.5 0.39 372.8 27.27 353.1 3.95 348.7 1.85 0.05509 0.0008 1.5 0.41589 0.00668 1.6 0.05622 0.00034 0.6 0.38 415.7 31.72 353.1 4.79 352.6 2.116 0.05405 0.00095 1.8 0.41631 0.00818 2.0 0.05629 0.00041 0.7 0.37 373.1 39.32 353.4 5.87 353 2.487 0.05501 0.00083 1.5 0.41216 0.00693 1.7 0.05497 0.00035 0.6 0.38 412.8 33.15 350.4 4.98 344.9 2.158 0.05228 0.00129 2.5 0.40567 0.0111 2.7 0.05603 0.00053 0.9 0.35 297.7 55.08 345.8 8.02 351.4 3.259 0.05496 0.00132 2.4 0.43509 0.01171 2.7 0.05705 0.00054 0.9 0.35 410.5 52.18 366.8 8.28 357.6 3.310 0.0535 0.00131 2.4 0.41877 0.01135 2.7 0.05705 0.00053 0.9 0.34 349.8 54.43 355.2 8.12 357.6 3.2311 0.05293 0.00121 2.3 0.43247 0.01102 2.5 0.05852 0.00051 0.9 0.34 325.8 50.88 364.9 7.81 366.6 3.1312 0.05328 0.0012 2.3 0.41598 0.01039 2.5 0.05727 0.0005 0.9 0.35 340.6 50.09 353.2 7.45 359 3.0613 0.05372 0.00095 1.8 0.44432 0.0088 2.0 0.05862 0.00042 0.7 0.36 359 39.38 373.3 6.19 367.2 2.5714 0.05455 0.00063 1.2 0.42695 0.00552 1.3 0.05735 0.0003 0.5 0.4 393.6 25.66 361 3.93 359.5 1.8315 0.05399 0.00122 2.3 0.4256 0.01067 2.5 0.05728 0.0005 0.9 0.35 370.4 49.98 360 7.6 359.1 3.0516 0.05307 0.00063 1.2 0.42928 0.00569 1.3 0.0586 0.00031 0.5 0.4 331.9 26.6 362.7 4.04 367.1 1.8918 0.05494 0.00075 1.4 0.42457 0.0065 1.5 0.05703 0.00034 0.6 0.39 409.9 30.12 359.3 4.63 357.5 2.0619 0.05249 0.00161 3.1 0.42757 0.01463 3.4 0.05686 0.00066 1.2 0.34 306.7 68.07 361.5 10.4 356.5 4.0420 0.05267 0.0008 0.4157 0.00709 0.05767 0.00037 0.6 0.38 314.5 34.3 353 5.09 361.4 2.2509TR090: Quartz-feldspar rhyolite porphyry1 0.05335 0.00105 2.0 0.38138 0.00824 2.2 0.05157 0.00041 0.8 0.37 343.6 43.96 328.1 6.06 324.1 2.532 0.05384 0.00065 1.2 0.39071 0.00518 1.3 0.05328 0.0003 0.6 0.42 364.4 27.07 334.9 3.78 334.6 1.813 0.05492 0.00087 1.6 0.41053 0.00718 1.7 0.05464 0.00037 0.7 0.39 408.9 34.73 349.3 5.17 342.9 2.264 0.05447 0.00112 2.1 0.3987 0.00903 2.3 0.05374 0.00045 0.8 0.37 390.4 45.28 340.7 6.56 337.5 2.745 0.05369 0.00107 2.0 0.38447 0.00841 2.2 0.05364 0.00043 0.8 0.37 358.1 44.53 330.3 6.17 336.8 2.646 0.05251 0.00126 2.4 0.38348 0.01004 2.6 0.05334 0.00049 0.9 0.35 307.8 53.59 329.6 7.37 335 2.97223Table A1.1. (continued)17 0.05167 0.00117 2.3 0.39225 0.00975 2.5 0.05463 0.00048 0.9 0.35 270.8 51 336 7.11 342.9 2.9316 0.05453 0.00239 4.4 0.36356 0.01663 4.6 0.04866 0.00061 1.3 0.27 393 94.67 314.9 12.38 306.3 3.77Isotopic Ratios Calculated Ages207 206 207 235 206 238 1 207 206 207 235 206 238Run # Pb/ Pb 1 σ abs 1 σ % Pb/ U 1 σ abs 1 σ % Pb/ U 1 σ abs 1 σ % rho Pb/ Pb 1 σ abs Pb/ U 1 σ abs Pb/ U 1 σ abs09TR090: Quartz-feldspar rhyolite porphyry (continued)11 0.05276 0.00094 1.8 0.39408 0.00776 2.0 0.05511 0.0004 0.7 0.37 318.6 40.05 337.3 5.65 345.8 2.4712 0.05308 0.00107 2.0 0.3933 0.00876 2.2 0.05528 0.00045 0.8 0.37 332.3 45.11 336.8 6.38 346.8 2.7513 0.05206 0.00192 3.7 0.39019 0.01581 4.1 0.05404 0.00073 1.4 0.33 287.9 82.13 334.5 11.54 339.3 4.4714 0.05403 0.0012 2.2 0.41605 0.01021 2.5 0.05625 0.0005 0.9 0.36 372.2 49.1 353.2 7.32 352.8 3.0515 0.05235 0.00214 4.1 0.38688 0.01724 4.5 0.05481 0.0008 1.5 0.33 300.9 90.52 332.1 12.62 344 4.8716 0.05366 0.00103 1.9 0.40835 0.00871 2.1 0.05371 0.00042 0.8 0.37 356.9 43.22 347.7 6.28 337.2 2.618 0.05278 0.00094 1.8 0.39716 0.00777 2.0 0.05364 0.00039 0.7 0.37 319.4 39.71 339.6 5.64 336.8 2.419 0.05381 0.00109 2.0 0.40988 0.00917 2.2 0.05595 0.00046 0.8 0.37 363.2 45.05 348.8 6.61 351 2.820 0.05264 0.00099 1.9 0.39127 0.00812 2.1 0.05382 0.00041 0.8 0.37 313.1 42.18 335.3 5.93 337.9 2.5309TR105: Foliated and silicified rhyolite flow with sulphide stockwork1 0.05368 0.00222 4.1 0.36863 0.01607 4.4 0.04987 0.00062 1.2 0.29 357.6 90.69 318.6 11.92 313.7 3.782 0.04803 0.00286 6.0 0.32681 0.01999 6.1 0.05093 0.0007 1.4 0.22 100.8 134.98 287.1 15.3 320.2 4.283 0.0523 0.00386 7.4 0.33941 0.02566 7.6 0.04795 0.00079 1.6 0.22 298.4 159.87 296.7 19.45 301.9 4.854 0.05586 0.00237 4.2 0.37062 0.01644 4.4 0.04843 0.00059 1.2 0.27 446.4 91.42 320.1 12.18 304.9 3.625 0.05746 0.00517 9.0 0.40646 0.03735 9.2 0.05034 0.00097 1.9 0.21 508.7 186.74 346.3 26.96 316.6 5.966 0.05218 0.00147 2.8 0.3676 0.01106 3.0 0.0516 0.00048 0.9 0.31 293.4 62.76 317.9 8.21 324.3 2.917 0.05597 0.00304 5.4 0.38303 0.02164 5.6 0.04904 0.00074 1.5 0.27 451 116.46 329.3 15.89 308.6 4.548 0.0552 0.00256 4.6 0.36382 0.01778 4.9 0.05 0.0007 1.4 0.29 420.1 100.39 315.1 13.24 314.5 4.39 0.05002 0.00598 12.0 0.3375 0.04122 12.2 0.05115 0.00127 2.5 0.2 196.1 256.02 295.3 31.29 321.6 7.7910 0.05213 0.00405 7.8 0.35903 0.0292 8.1 0.04948 0.00106 2.1 0.26 291 167.75 311.5 21.82 311.3 6.5411 0.04377 0.00503 11.5 0.29108 0.03385 11.6 0.04939 0.00095 1.9 0.17 0.1 137.85 259.4 26.62 310.8 5.8312 0.05199 0.00393 7.6 0.33937 0.02657 7.8 0.04712 0.0009 1.9 0.24 285 163.96 296.7 20.14 296.8 5.5513 0.05347 0.00444 8.3 0.37078 0.03169 8.5 0.05017 0.00096 1.9 0.22 348.9 177.35 320.2 23.47 315.5 5.9114 0.05828 0.0041 7.0 0.39188 0.02847 7.3 0.04908 0.00089 1.8 0.25 539.6 147.62 335.7 20.77 308.9 5.4515 0.04591 0.01883 41.0 0.33827 0.13943 41.2 0.0492 0.00273 5.5 0.13 0.1 765.55 295.9 105.79 309.6 16.7722417 0.05017 0.0007 1.4 0.21966 0.00325 1.5 0.03137 0.00018 0.6 0.39 203.1 31.87 201.6 2.71 199.1 1.14Table A1.1. (continued)207 206 207 235Isotopic Ratios206 238 1 207 206Calculated A207 235ges206 238Run # Pb/ Pb 1 σ abs 1 σ % Pb/ U 1 σ abs 1 σ % Pb/ U 1 σ abs 1 σ % rho Pb/ Pb 1 σ abs Pb/ U 1 σ abs Pb/ U 1 σ abs09TR107: Quartz-feldspar porphyry dike1 0.05085 0.00142 2.8 0.21644 0.00625 2.9 0.02995 0.00031 1.0 0.36 233.8 63.06 198.9 5.22 190.3 1.932 0.05121 0.00064 1.2 0.22508 0.00296 1.3 0.03145 0.00017 0.5 0.41 250.3 28.55 206.1 2.46 199.6 1.053 0.05161 0.00057 1.1 0.22108 0.00257 1.2 0.03139 0.00015 0.5 0.41 268.2 25.04 202.8 2.13 199.3 0.964 0.05035 0.00048 1.0 0.21643 0.00218 1.0 0.03152 0.00014 0.4 0.44 211.3 21.81 198.9 1.82 200.1 0.885 0.05204 0.00066 1.3 0.22333 0.00296 1.3 0.03152 0.00017 0.5 0.41 287.1 28.52 204.7 2.46 200.1 1.066 0.05013 0.00146 2.9 0.21516 0.00648 3.0 0.03104 0.00032 1.0 0.34 200.9 66.06 197.9 5.41 197 2.027 0.05009 0.0007 1.4 0.21887 0.0032 1.5 0.03169 0.00018 0.6 0.39 199.1 31.92 201 2.66 201.1 1.148 0.0511 0.0006 1.2 0.2193 0.00275 1.3 0.03112 0.00016 0.5 0.41 245.5 27.04 201.3 2.29 197.6 1.019 0.04984 0.00059 1.2 0.22091 0.00277 1.3 0.03177 0.00016 0.5 0.4 187.7 27.21 202.7 2.3 201.6 1.0210 0.04998 0.00057 1.1 0.22012 0.00267 1.2 0.03182 0.00016 0.5 0.41 194.2 26.21 202 2.22 201.9 111 0.05026 0.00067 1.3 0.22174 0.00315 1.4 0.0323 0.00018 0.6 0.39 207.1 30.83 203.4 2.62 204.9 1.1412 0.04908 0.00062 1.3 0.21987 0.00293 1.3 0.033 0.00018 0.5 0.41 151.5 29.13 201.8 2.44 209.3 1.113 0.05033 0.0007 1.4 0.21776 0.00322 1.5 0.03163 0.00018 0.6 0.38 210.3 32.05 200 2.69 200.7 1.1514 0.05238 0.0006 1.1 0.22459 0.00276 1.2 0.03133 0.00016 0.5 0.42 302 25.85 205.7 2.29 198.8 115 0.05083 0.00058 1.1 0.22408 0.00275 1.2 0.03241 0.00016 0.5 0.4 232.9 26.14 205.3 2.28 205.6 1.0216 0.05018 0.00068 1.4 0.21892 0.00316 1.4 0.03147 0.00018 0.6 0.4 203.3 31.11 201 2.63 199.7 1.1218 0.05031 0.00057 1.1 0.21382 0.00261 1.2 0.03075 0.00015 0.5 0.4 209.4 25.91 196.8 2.19 195.2 0.9719 0.05025 0.00075 1.5 0.21756 0.00345 1.6 0.03142 0.00019 0.6 0.38 206.4 34.11 199.9 2.87 199.4 1.220 0.05147 0.00063 1.2 0.21938 0.00292 1.3 0.03144 0.00017 0.5 0.41 261.8 28.04 201.4 2.43 199.5 1.0509TR110: Quartz-feldspar porphyry1 0.05319 0.0021 3.9 0.36645 0.01573 4.3 0.0488 0.00065 1.3 0.31 336.9 86.9 317 11.69 307.2 4.022 0.05087 0.002 3.9 0.34765 0.01482 4.3 0.04996 0.00065 1.3 0.31 235.1 88.41 302.9 11.17 314.3 3.973 0.05623 0.00129 2.3 0.39152 0.00999 2.6 0.04982 0.00045 0.9 0.35 460.6 50.32 335.5 7.29 313.4 2.744 0.05403 0.00085 1.6 0.37307 0.00648 1.7 0.05086 0.00031 0.6 0.35 372 34.99 321.9 4.79 319.8 1.925 0.05171 0.00178 3.4 0.38247 0.01464 3.8 0.05166 0.00065 1.3 0.33 272.5 76.87 328.9 10.75 324.7 3.966 0.05295 0.00106 2.0 0.37655 0.00841 2.2 0.05052 0.00039 0.8 0.35 326.4 44.88 324.5 6.21 317.7 2.3822517 0.05493 0.00237 4.3 0.39404 0.01885 4.8 0.04912 0.00078 1.6 0.33 409.2 93.3 337.3 13.73 309.1 4.77Table A1.1. (continued)Isotopic Ratios Calculated AgesRun # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs09TR110: Quartz-feldspar porphyry (continued)11 0.05203 0.00211 4.1 0.35877 0.01585 4.4 0.04942 0.00068 1.4 0.31 286.5 89.94 311.3 11.85 311 4.1812 0.05279 0.00129 2.4 0.36128 0.00978 2.7 0.04865 0.00045 0.9 0.34 319.8 54.48 313.2 7.29 306.2 2.7613 0.04843 0.00444 9.2 0.35424 0.03479 9.8 0.05047 0.0013 2.6 0.26 120.5 202.64 307.9 26.09 317.4 8.0114 0.0528 0.0018 3.4 0.36479 0.01362 3.7 0.04842 0.00058 1.2 0.32 320.3 75.52 315.8 10.14 304.8 3.615 0.04991 0.00233 4.7 0.36072 0.01849 5.1 0.0499 0.00081 1.6 0.32 191 105.03 312.8 13.8 313.9 4.9616 0.05795 0.00234 4.0 0.37915 0.01676 4.4 0.04853 0.00071 1.5 0.33 527.4 86.6 326.4 12.34 305.5 4.3718 0.05519 0.00114 2.1 0.37098 0.00853 2.3 0.04867 0.00039 0.8 0.35 419.8 44.95 320.4 6.32 306.4 2.3919 0.05446 0.00235 4.3 0.37818 0.01803 4.8 0.05091 0.00081 1.6 0.33 390.2 93.55 325.7 13.28 320.1 4.9520 0.05109 0.00262 5.1 0.3338 0.01839 0.04762 0.0008 1.7 0.3 244.9 113.83 292.5 14 299.9 4.9509TR117: Rhyolite lapilli tuff1 0.05226 0.00387 7.4 0.31005 0.02458 7.9 0.04522 0.00112 2.5 0.31 296.8 160.55 274.2 19.05 285.1 6.882 0.05335 0.00281 5.3 0.33993 0.01949 5.7 0.04747 0.00088 1.9 0.32 343.7 114.75 297.1 14.77 299 5.423 0.04865 0.0026 5.3 0.3267 0.01902 5.8 0.04916 0.00088 1.8 0.31 131.1 121.03 287 14.56 309.4 5.434 0.05915 0.00373 6.3 0.35999 0.02466 6.9 0.04693 0.00109 2.3 0.34 572.6 131.5 312.2 18.41 295.6 6.695 0.05369 0.00276 5.1 0.35151 0.01966 5.6 0.04681 0.00085 1.8 0.32 357.8 111.58 305.9 14.77 294.9 5.246 0.05313 0.00284 5.3 0.36457 0.02146 5.9 0.0493 0.00093 1.9 0.32 334.2 116.42 315.6 15.97 310.2 5.77 0.05839 0.00618 10.6 0.39948 0.04551 11.4 0.04702 0.00149 3.2 0.28 544.4 215.91 341.3 33.02 296.2 9.168 0.05323 0.00461 8.7 0.33459 0.03077 9.2 0.04724 0.00123 2.6 0.28 338.7 184.9 293.1 23.41 297.5 7.559 0.05314 0.00299 5.6 0.38748 0.02398 6.2 0.04823 0.00095 2.0 0.32 334.7 122.4 332.5 17.55 303.7 5.8310 0.04816 0.00576 12.0 0.38281 0.04995 13.0 0.04808 0.00172 3.6 0.27 107.2 260.27 329.1 36.68 302.8 10.5811 0.05627 0.00327 5.8 0.37858 0.024 6.3 0.04835 0.00097 2.0 0.32 462.2 124.66 326 17.68 304.4 5.9812 0.05128 0.00363 7.1 0.37554 0.02898 7.7 0.05098 0.00118 2.3 0.3 253.2 155.26 323.7 21.39 320.5 7.2613 0.05131 0.00303 5.9 0.34026 0.02188 6.4 0.04924 0.00098 2.0 0.31 254.9 130.43 297.4 16.58 309.9 6.0514 0.05298 0.00341 6.4 0.37578 0.02658 7.1 0.05107 0.00116 2.3 0.32 327.8 138.93 323.9 19.62 321.1 7.1215 0.05235 0.00282 5.4 0.36109 0.02133 5.9 0.04945 0.00093 1.9 0.32 300.9 118.31 313 15.91 311.1 5.7216 0.04866 0.00414 8.5 0.31788 0.02905 9.1 0.04847 0.00132 2.7 0.3 131.4 188.82 280.3 22.38 305.1 8.0922616 0.05093 0.00222 4.4 0.35539 0.01723 4.8 0.05055 0.00082 1.6 0.33 237.5 97.69 308.8 12.91 317.9 5.01Table A1.1. (continued)Isotopic Ratios Calculated AgesRun # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs09TR118: Rhyolite flow1 0.05392 0.00279 5.2 0.40148 0.0226 5.6 0.05104 0.00083 1.6 0.29 367.4 112.04 342.7 16.38 320.9 5.062 0.05151 0.0017 3.3 0.33946 0.01218 3.6 0.04905 0.00056 1.1 0.32 263.5 73.93 296.8 9.23 308.7 3.443 0.0523 0.00145 2.8 0.33133 0.01008 3.0 0.04817 0.0005 1.0 0.34 298.5 62.03 290.6 7.68 303.3 3.094 0.05214 0.00237 4.5 0.35925 0.01795 5.0 0.0491 0.0008 1.6 0.33 291.6 100.5 311.7 13.41 309 4.925 0.05073 0.00255 5.0 0.33055 0.01814 5.5 0.04799 0.00086 1.8 0.33 228.4 112.11 290 13.84 302.2 5.326 0.05213 0.00495 9.5 0.371 0.03776 10.2 0.05124 0.0014 2.7 0.27 291.3 202.91 320.4 27.97 322.2 8.567 0.05486 0.00174 3.2 0.37008 0.01295 3.5 0.0483 0.00056 1.2 0.33 406.5 68.96 319.7 9.59 304.1 3.468 0.05121 0.00242 4.7 0.32331 0.01646 5.1 0.04609 0.00074 1.6 0.32 250.3 105.06 284.4 12.63 290.4 4.549 0.05221 0.00166 3.2 0.34345 0.01195 3.5 0.04809 0.00054 1.1 0.32 294.4 70.87 299.8 9.04 302.8 3.3410 0.05225 0.00209 4.0 0.3623 0.01594 4.4 0.04953 0.00071 1.4 0.33 296.5 88.72 313.9 11.88 311.6 4.3611 0.05368 0.00332 6.2 0.35616 0.0239 6.7 0.04898 0.00102 2.1 0.31 357.6 133.28 309.3 17.89 308.3 6.2912 0.0615 0.00375 6.1 0.40347 0.02707 6.7 0.04781 0.00107 2.2 0.33 656.6 125.67 344.2 19.58 301.1 6.5613 0.05215 0.00474 9.1 0.32384 0.03096 9.6 0.05041 0.00137 2.7 0.28 291.9 194.74 284.9 23.75 317 8.3814 0.05817 0.00815 14.0 0.44117 0.06584 14.9 0.05078 0.00191 3.8 0.25 535.6 280.89 371.1 46.39 319.3 11.7315 0.05342 0.00294 5.5 0.348 0.02078 6.0 0.04873 0.00093 1.9 0.32 346.5 119.26 303.2 15.65 306.7 5.7217 0.05254 0.00169 3.2 0.34594 0.0122 3.5 0.04837 0.00057 1.2 0.33 309.2 71.54 301.7 9.21 304.5 3.5118 0.05275 0.00255 4.8 0.35135 0.01855 5.3 0.05053 0.00086 1.7 0.32 317.8 106.22 305.7 13.94 317.8 5.2619 0.04234 0.00353 8.3 0.28958 0.02557 8.8 0.05097 0.00111 2.2 0.25 0.1 0 258.2 20.14 320.5 6.8109TR128: Rhyolite crystal tuff1 0.05301 0.00157 3.0 0.43118 0.01362 3.2 0.05862 0.00047 0.8 0.25 329 65.82 364 9.66 367.2 2.832 0.05289 0.00106 2.0 0.41907 0.00909 2.2 0.05806 0.00036 0.6 0.29 323.8 44.63 355.4 6.5 363.8 2.183 0.05346 0.00043 0.8 0.42623 0.00385 0.9 0.05789 0.00019 0.3 0.36 348.4 18.17 360.5 2.74 362.8 1.164 0.0528 0.00097 1.8 0.4048 0.00803 2.0 0.05618 0.00032 0.6 0.29 320.1 41.06 345.1 5.81 352.4 1.955 0.05387 0.00076 1.4 0.42684 0.00672 1.6 0.05757 0.00029 0.5 0.32 365.5 31.69 360.9 4.78 360.8 1.796 0.05283 0.00085 1.6 0.4075 0.00714 1.8 0.05718 0.0003 0.5 0.3 321.6 35.89 347.1 5.15 358.4 1.867 0.05389 0.00066 1.2 0.42853 0.00582 1.4 0.05704 0.00025 0.4 0.32 366.3 27.42 362.1 4.13 357.6 1.5522739 0.05208 0.00073 1.4 0.41354 0.00643 1.6 0.0569 0.00028 0.5 0.32 288.9 31.8 351.4 4.62 356.7 1.73Table A1.1. (continued)Isotopic Ratios Calculated AgesRun # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs09TR128: Rhyolite crystal tuff (continued)12 0.05262 0.00082 1.6 0.41518 0.0072 1.7 0.05704 0.00031 0.5 0.31 312.4 35.16 352.6 5.17 357.6 1.9213 0.05427 0.00047 0.9 0.42413 0.00407 1.0 0.05563 0.00019 0.3 0.36 382 19.37 359 2.9 349 1.1814 0.05333 0.00086 1.6 0.4218 0.00747 1.8 0.0574 0.00031 0.5 0.3 342.9 36.04 357.3 5.33 359.8 1.8915 0.05373 0.00102 1.9 0.41518 0.0086 2.1 0.05669 0.00035 0.6 0.3 359.7 42.59 352.6 6.17 355.5 2.1116 0.05283 0.00092 1.7 0.40249 0.0077 1.9 0.05699 0.00034 0.6 0.31 321.3 38.92 343.5 5.58 357.3 2.0817 0.05339 0.00068 1.3 0.42546 0.00599 1.4 0.05731 0.00026 0.5 0.32 345.2 28.29 359.9 4.27 359.3 1.6118 0.05469 0.00068 1.2 0.42485 0.00587 1.4 0.05661 0.00026 0.5 0.33 400.1 26.64 359.5 4.18 354.9 1.619 0.05264 0.00055 1.0 0.41451 0.00477 1.2 0.0566 0.00022 0.4 0.34 313.2 23.4 352.1 3.42 354.9 1.3520 0.05452 0.00063 1.2 0.43658 0.00565 1.3 0.05842 0.00025 0.4 0.33 392.3 25.77 367.8 3.99 366 1.5421 0.05466 0.00084 1.5 0.43152 0.00729 1.7 0.05807 0.00031 0.5 0.32 398.4 33.68 364.3 5.17 363.9 1.8922 0.05327 0.00101 1.9 0.42724 0.00899 2.1 0.05757 0.00037 0.6 0.31 340.3 42.41 361.2 6.4 360.8 2.2723 0.05324 0.00097 1.8 0.43365 0.00872 2.0 0.05831 0.00036 0.6 0.31 338.8 40.51 365.8 6.18 365.4 2.2124 0.0534 0.00072 1.3 0.42399 0.00634 1.5 0.05732 0.00028 0.5 0.33 345.8 30.06 358.9 4.52 359.3 1.7125 0.05393 0.00086 1.6 0.43505 0.00777 1.8 0.05859 0.00033 0.6 0.32 368.1 35.87 366.8 5.5 367.1 2.0326 0.05242 0.00069 1.3 0.41001 0.00591 1.4 0.05645 0.00026 0.5 0.32 303.7 29.52 348.9 4.26 354 1.627 0.05287 0.00061 1.2 0.41797 0.00533 1.3 0.05652 0.00024 0.4 0.33 323.4 25.96 354.6 3.82 354.4 1.4528 0.05372 0.00045 0.8 0.42404 0.00396 0.9 0.05771 0.0002 0.3 0.37 359.1 18.71 358.9 2.83 361.7 1.229 0.05295 0.00096 1.8 0.42011 0.00835 2.0 0.05702 0.00035 0.6 0.31 326.7 40.4 356.1 5.97 357.5 2.1330 0.05307 0.00063 1.2 0.41175 0.00545 1.3 0.05617 0.00025 0.4 0.34 331.8 26.74 350.1 3.92 352.3 1.5231 0.05206 0.00135 2.6 0.42304 0.0119 2.8 0.05758 0.00045 0.8 0.28 287.9 58.12 358.2 8.49 360.9 2.7632 0.05403 0.00074 1.4 0.42397 0.00644 1.5 0.05613 0.00028 0.5 0.33 372.1 30.72 358.9 4.59 352 1.6933 0.05287 0.00066 1.2 0.41849 0.00582 1.4 0.05823 0.00027 0.5 0.33 323.2 28.06 355 4.16 364.9 1.6534 0.05406 0.00151 2.8 0.42844 0.01299 3.0 0.05662 0.00049 0.9 0.29 373.5 61.48 362.1 9.24 355.1 3.0135 0.05323 0.00094 1.8 0.41565 0.00808 1.9 0.05633 0.00034 0.6 0.31 338.7 39.54 352.9 5.8 353.3 2.0536 0.05375 0.00059 1.1 0.42713 0.00519 1.2 0.05722 0.00024 0.4 0.35 360.6 24.45 361.1 3.69 358.7 1.4537 0.05395 0.00072 1.3 0.43086 0.00641 1.5 0.05762 0.00028 0.5 0.33 368.7 30.04 363.8 4.55 361.2 1.7238 0.05287 0.00059 1.1 0.42677 0.00535 1.3 0.05802 0.00025 0.4 0.34 323.1 25.29 360.9 3.81 363.6 1.522860 0.05183 0.00072 1.4 0.42276 0.00655 1.5 0.05906 0.0003 0.5 0.33 277.9 31.42 358 4.67 369.9 1.835 0.0535 0.00099 1.9 0.43165 0.00892 2.1 0.05843 0.00044 0.8 0.36 349.9 41.26 364.3 6.33 366.1 2.66Table A1.1. (continued)Isotopic Ratios Calculated AgesRun # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs09TR128: Rhyolite crystal tuff (continued)44 0.05248 0.00114 2.2 0.39445 0.00938 2.4 0.05677 0.00041 0.7 0.3 306.4 48.8 337.6 6.83 356 2.5145 0.05253 0.00079 1.5 0.43325 0.00726 1.7 0.05877 0.00031 0.5 0.31 308.5 34.04 365.5 5.14 368.2 1.946 0.05317 0.0009 1.7 0.41237 0.00767 1.9 0.05667 0.00033 0.6 0.31 336.2 37.88 350.6 5.51 355.4 2.0147 0.05287 0.00145 2.7 0.42737 0.01266 3.0 0.05831 0.00048 0.8 0.28 323.4 60.98 361.3 9.01 365.4 2.9248 0.05308 0.00067 1.3 0.4156 0.0059 1.4 0.05586 0.00027 0.5 0.34 332 28.36 352.9 4.23 350.4 1.6649 0.05216 0.00128 2.5 0.40881 0.01085 2.7 0.05712 0.00043 0.8 0.28 292.5 55.11 348 7.82 358.1 2.6150 0.05357 0.00153 2.9 0.42605 0.01308 3.1 0.05868 0.00049 0.8 0.27 352.9 63.39 360.4 9.32 367.6 2.9851 0.05486 0.0012 2.2 0.43677 0.01049 2.4 0.05793 0.00042 0.7 0.3 406.4 47.91 368 7.41 363 2.5952 0.05306 0.00099 1.9 0.43993 0.00918 2.1 0.05942 0.00039 0.7 0.31 331.1 41.82 370.2 6.47 372.1 2.3853 0.0517 0.0009 1.7 0.40982 0.00776 1.9 0.05829 0.00033 0.6 0.3 272 39.26 348.7 5.59 365.2 2.0354 0.05305 0.00066 1.2 0.42899 0.00598 1.4 0.05817 0.00027 0.5 0.33 331 28.06 362.5 4.25 364.5 1.6455 0.05345 0.00117 2.2 0.42303 0.01023 2.4 0.05705 0.00042 0.7 0.3 347.8 48.94 358.2 7.3 357.7 2.5856 0.05285 0.00086 1.6 0.41869 0.00753 1.8 0.05781 0.00033 0.6 0.32 322.4 36.47 355.1 5.39 362.3 2.0157 0.05399 0.00108 2.0 0.43908 0.00977 2.2 0.05689 0.0004 0.7 0.32 370.6 44.49 369.6 6.89 356.7 2.4458 0.05284 0.00066 1.2 0.43178 0.00606 1.4 0.05841 0.00028 0.5 0.34 321.7 28.07 364.4 4.3 365.9 1.6959 0.05253 0.00065 1.2 0.4307 0.00599 1.4 0.05839 0.00028 0.5 0.34 308.4 27.87 363.7 4.25 365.8 1.6861 0.05307 0.00092 1.7 0.43214 0.00827 1.9 0.05897 0.00035 0.6 0.31 331.9 38.66 364.7 5.86 369.4 2.1562 0.05471 0.00126 2.3 0.42241 0.01061 2.5 0.05565 0.00043 0.8 0.31 400.1 50.49 357.8 7.58 349.1 2.6363 0.05388 0.00059 1.1 0.42149 0.00521 1.2 0.05639 0.00024 0.4 0.34 366 24.6 357.1 3.72 353.6 1.4964 0.05193 0.00089 0.43033 0.0082 0.05824 0.00034 0.31 282.5 38.91 363.4 5.82 364.9 2.0809TR132: Quartz-feldpsar porphyry1 0.05574 0.00134 2.4 0.4546 0.01226 2.7 0.05744 0.00054 0.9 0.35 441.9 52.46 380.5 8.56 360 3.272 0.05425 0.00094 1.7 0.42726 0.00828 1.9 0.05702 0.0004 0.7 0.36 381.3 38.55 361.2 5.89 357.5 2.473 0.05225 0.00095 1.8 0.41483 0.00846 2.0 0.05669 0.00042 0.7 0.36 296.2 41.11 352.3 6.07 355.5 2.544 0.0523 0.00127 2.4 0.4189 0.01137 2.7 0.05746 0.00054 0.9 0.35 298.5 54.42 355.3 8.14 360.2 3.322916 0.05408 0.00105 1.9 0.42019 0.00913 2.2 0.0553 0.00043 0.8 0.36 374.3 43.33 356.2 6.53 347 2.65Table A1.1. (continued)Isotopic Ratios Calculated Ages207 206 207 235 206 238 1 207 206 207 235 206 238Run # Pb/ Pb 1 σ abs 1 σ % Pb/ U 1 σ abs 1 σ % Pb/ U 1 σ abs 1 σ % rho Pb/ Pb 1 σ abs Pb/ U 1 σ abs Pb/ U 1 σ abs09TR132: Quartz-feldpsar porphyry (continued)10 0.05558 0.00125 2.2 0.43832 0.01105 2.5 0.05734 0.00051 0.9 0.35 435.5 49.06 369.1 7.8 359.4 3.1311 0.05627 0.00352 6.3 0.47057 0.03228 6.9 0.05828 0.00121 2.1 0.3 462.1 133.04 391.6 22.29 365.2 7.3512 0.05481 0.00329 6.0 0.45163 0.02999 6.6 0.05695 0.00116 2.0 0.31 404.6 128.64 378.4 20.98 357.1 7.113 0.05457 0.0012 2.2 0.44616 0.01104 2.5 0.05684 0.00049 0.9 0.35 394.5 48.46 374.6 7.75 356.4 3.0114 0.05405 0.00112 2.1 0.44429 0.01033 2.3 0.05875 0.00048 0.8 0.35 373 46.03 373.3 7.26 368 2.9415 0.05352 0.00164 3.1 0.42558 0.01438 3.4 0.0569 0.00064 1.1 0.33 350.8 67.59 360 10.24 356.7 3.8717 0.05518 0.00143 2.6 0.4424 0.0128 2.9 0.05802 0.00059 1.0 0.35 419.5 56.15 371.9 9.01 363.6 3.5718 0.05351 0.00102 1.9 0.4252 0.00905 2.1 0.05764 0.00044 0.8 0.36 350.3 42.7 359.8 6.45 361.3 2.6719 0.05579 0.00115 2.1 0.44103 0.01018 2.3 0.05631 0.00047 0.8 0.36 443.8 44.98 371 7.17 353.2 2.8420 0.05391 0.0013 2.4 0.44555 0.012 2.7 0.05829 0.00054 0.9 0.34 367.1 53.26 374.2 8.43 365.2 3.3109TRDR010: Rhyolite lapilli tuff1 0.05412 0.00214 4.0 0.3573 0.01533 4.3 0.04873 0.00073 1.5 0.35 375.7 86.16 310.2 11.47 306.7 4.492 0.05234 0.00175 3.3 0.35873 0.01302 3.6 0.04822 0.00061 1.3 0.35 300.3 74.23 311.3 9.73 303.6 3.733 0.05274 0.00149 2.8 0.35811 0.01101 3.1 0.04797 0.00052 1.1 0.35 317.7 62.79 310.8 8.23 302 3.224 0.05299 0.00088 1.7 0.35927 0.0065 1.8 0.0491 0.00034 0.7 0.38 328.2 37.11 311.7 4.85 309 2.15 0.05259 0.00152 2.9 0.37202 0.01182 3.2 0.04976 0.00056 1.1 0.35 311.1 64.5 321.2 8.75 313 3.446 0.05348 0.00139 2.6 0.37049 0.01056 2.9 0.0498 0.00051 1.0 0.36 349.1 57.88 320 7.82 313.3 3.137 0.05437 0.00091 1.7 0.36112 0.00659 1.8 0.04847 0.00034 0.7 0.38 386.4 37.04 313.1 4.92 305.1 2.118 0.05285 0.0011 2.1 0.3552 0.00807 2.3 0.0492 0.00041 0.8 0.37 322.3 46.7 308.6 6.05 309.6 2.519 0.05331 0.00087 1.6 0.36279 0.00648 1.8 0.04942 0.00034 0.7 0.39 341.8 36.51 314.3 4.83 310.9 2.110 0.05307 0.00089 1.7 0.35763 0.00653 1.8 0.04862 0.00034 0.7 0.38 331.8 37.5 310.4 4.89 306.1 2.0911 0.05372 0.00118 2.2 0.37031 0.00893 2.4 0.04935 0.00043 0.9 0.36 359 49.06 319.9 6.61 310.5 2.6612 0.05258 0.00161 3.1 0.36559 0.01219 3.3 0.04954 0.00057 1.2 0.35 310.7 67.94 316.4 9.06 311.7 3.5313 0.05158 0.00156 3.0 0.36601 0.01205 3.3 0.0497 0.00055 1.1 0.34 267 67.93 316.7 8.96 312.7 3.4114 0.05218 0.00187 3.6 0.34233 0.01326 3.9 0.04669 0.00061 1.3 0.34 293.1 79.84 298.9 10.03 294.2 3.7523016 0.05596 0.00317 5.7 0.39673 0.02514 6.3 0.04758 0.00099 2.1 0.33 450.5 121.39 339.3 18.28 299.6 6.1Table A1.1. (continued)207 206 207 235Isotopic Ratios206 238 1 207 206Calculated A207 235ges206 238Run # Pb/ Pb 1 σ abs 1 σ % Pb/ U 1 σ abs 1 σ % Pb/ U 1 σ abs 1 σ % rho Pb/ Pb 1 σ abs Pb/ U 1 σ abs Pb/ U 1 σ abs09TRDR013: Quartz-feldspar rhyolite porphyry1 0.05855 0.00329 5.6 0.34407 0.02091 6.1 0.04513 0.00091 2.0 0.33 550.4 118.04 300.2 15.8 284.5 5.62 0.05166 0.00305 5.9 0.32798 0.02083 6.4 0.04865 0.00092 1.9 0.3 270.4 129.72 288 15.92 306.2 5.663 0.05427 0.00381 7.0 0.32973 0.025 7.6 0.04582 0.00112 2.4 0.32 382.1 150.31 289.4 19.09 288.8 6.94 0.05131 0.00668 13.0 0.3337 0.04623 13.9 0.04843 0.0018 3.7 0.27 254.5 274.45 292.4 35.2 304.9 11.15 0.05035 0.00642 12.8 0.31865 0.04309 13.5 0.04881 0.00173 3.5 0.26 211 270.68 280.9 33.18 307.2 10.616 0.05033 0.00892 17.7 0.31273 0.05828 18.6 0.05747 0.00265 4.6 0.25 210.5 366.09 276.3 45.08 360.2 16.157 0.04923 0.00797 16.2 0.30955 0.05227 16.9 0.0501 0.00202 4.0 0.24 158.9 339.8 273.8 40.53 315.1 12.388 0.06186 0.00723 11.7 0.39676 0.05116 12.9 0.04715 0.00208 4.4 0.34 669.1 232.3 339.3 37.19 297 12.789 0.05491 0.00362 6.6 0.37923 0.02785 7.3 0.04701 0.00115 2.4 0.33 408.4 141.3 326.5 20.5 296.1 7.0810 0.05067 0.00275 5.4 0.3319 0.01948 5.9 0.04839 0.00087 1.8 0.31 225.6 120.77 291 14.85 304.6 5.3611 0.05216 0.00287 5.5 0.3467 0.02085 6.0 0.04855 0.00093 1.9 0.32 292.2 121.1 302.2 15.72 305.6 5.7112 0.05386 0.00739 13.7 0.33309 0.04795 14.4 0.0468 0.00173 3.7 0.26 365 282.88 291.9 36.52 294.8 10.6713 0.05895 0.00411 7.0 0.36817 0.02797 7.6 0.0471 0.00117 2.5 0.33 565.1 145.05 318.3 20.76 296.7 7.1814 0.04545 0.01182 26.0 0.28895 0.07783 26.9 0.04794 0.00263 5.5 0.2 0.1 501.33 257.7 61.31 301.9 16.1515 0.0523 0.00377 7.2 0.32881 0.0256 7.8 0.04798 0.00119 2.5 0.32 298.7 156.14 288.7 19.56 302.1 7.3517 0.05517 0.00436 7.9 0.36709 0.03111 8.5 0.0489 0.00121 2.5 0.29 418.8 167.73 317.5 23.1 307.8 7.4218 0.0583 0.00647 11.1 0.36017 0.04301 11.9 0.04678 0.00184 3.9 0.33 540.2 226.44 312.3 32.11 294.7 11.319 0.06015 0.00427 7.1 0.40648 0.03164 7.8 0.0482 0.00123 2.6 0.33 608.9 146.64 346.3 22.84 303.5 7.5920 0.05346 0.00506 9.5 0.33132 0.03325 0.04769 0.00134 2.8 0.28 348.5 200.79 290.6 25.36 300.3 8.2709TRDR016: Rhyolitic volcanic sandstone1 0.05285 0.00205 3.9 0.35405 0.01516 4.3 0.04758 0.00069 1.5 0.34 322.2 85.85 307.8 11.37 299.6 4.262 0.05307 0.00436 8.2 0.34483 0.03092 9.0 0.04543 0.00134 2.9 0.33 331.9 175.81 300.8 23.34 286.4 8.273 0.05184 0.00576 11.1 0.29376 0.03463 11.8 0.04589 0.00156 3.4 0.29 278.5 236.03 261.5 27.18 289.2 9.624 0.0572 0.00388 6.8 0.377 0.02794 7.4 0.04484 0.00109 2.4 0.33 498.8 143.23 324.8 20.6 282.8 6.75 0.04722 0.00253 5.4 0.27679 0.01582 5.7 0.04428 0.00078 1.8 0.31 59.8 123.28 248.1 12.58 279.3 4.84231Table A1.1. (continued)Isotopic Ratios Calculated AgesRun # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs09TRDR016: Rhyolitic volcanic sandstone (continued)11 0.06033 0.00496 8.2 0.36882 0.03274 8.9 0.04461 0.00128 2.9 0.32 615.6 168.18 318.8 24.28 281.4 7.912 0.0571 0.00603 10.6 0.35309 0.03999 11.3 0.04816 0.00159 3.3 0.29 494.7 217.82 307 30.01 303.2 9.7913 0.05479 0.0034 6.2 0.31188 0.02068 6.6 0.04364 0.00094 2.2 0.32 403.6 132.55 275.6 16.01 275.3 5.8114 0.04584 0.00412 9.0 0.25919 0.02447 9.4 0.0442 0.00121 2.7 0.29 0.1 193 234 19.73 278.8 7.4815 0.04768 0.00703 14.7 0.33252 0.05261 15.8 0.04805 0.00199 4.1 0.26 82.7 317.39 291.5 40.09 302.5 12.2216 0.05226 0.00403 7.7 0.32091 0.02665 8.3 0.04572 0.00122 2.7 0.32 296.8 166.43 282.6 20.49 288.2 7.5117 0.05177 0.00097 1.9 0.32368 0.00665 2.1 0.04599 0.00033 0.7 0.35 275.1 42.43 284.7 5.1 289.9 2.0218 0.06612 0.00747 11.3 0.37968 0.0467 12.3 0.04876 0.00206 4.2 0.34 810.3 220 326.8 34.37 306.9 12.6819 0.05821 0.00673 11.6 0.33298 0.04097 12.3 0.04764 0.00178 3.7 0.3 537 235.28 291.8 31.21 300 10.9720 0.05128 0.00388 7.6 0.29814 0.0241 8.1 0.0461 0.00118 2.6 0.32 253.3 165.04 264.9 18.85 290.5 7.2921 0.04425 0.00593 13.4 0.26794 0.03813 14.2 0.04716 0.0019 4.0 0.28 0.1 203 241 30.53 297.1 11.7122 0.06954 0.01168 16.8 0.35986 0.06383 17.7 0.04498 0.00268 6.0 0.34 914.9 311.91 312.1 47.66 283.6 16.5123 0.05306 0.03478 65.5 0.18693 0.12394 66.3 0.04826 0.00843 17.5 0.26 331.5 1047.5 174 106.03 303.8 51.8424 0.065 0.00823 12.7 0.38303 0.05211 13.6 0.05154 0.00232 4.5 0.33 774.4 246.09 329.3 38.26 324 14.2525 0.03604 0.00953 26.4 0.26781 0.07578 28.3 0.04805 0.00303 6.3 0.22 0.1 0 240.9 60.69 302.5 18.6526 0.04799 0.00533 11.1 0.28603 0.03326 11.6 0.04723 0.00147 3.1 0.27 97.4 244.72 255.4 26.26 297.5 9.0227 0.0487 0.00656 13.5 0.28667 0.04006 14.0 0.04813 0.00166 3.4 0.25 133.6 288.94 255.9 31.62 303 10.228 0.05071 0.00615 12.1 0.31824 0.04114 12.9 0.04412 0.00162 3.7 0.28 227.8 257.93 280.6 31.69 278.3 9.9929 0.04962 0.01047 21.1 0.3227 0.07121 22.1 0.04501 0.00242 5.4 0.24 177.3 429.45 284 54.66 283.8 14.9230 0.05753 0.0114 19.8 0.34458 0.07286 21.1 0.04472 0.00234 5.2 0.25 511.4 385.06 300.6 55.02 282 14.4131 0.05455 0.00983 18.0 0.34439 0.06461 18.8 0.04875 0.00218 4.5 0.24 393.6 360.23 300.5 48.8 306.8 13.4132 0.05547 0.00673 12.1 0.32017 0.04064 12.7 0.04522 0.00151 3.3 0.26 430.8 249.92 282 31.26 285.1 9.3233 0.05194 0.00237 4.6 0.34091 0.01692 5.0 0.0478 0.00077 1.6 0.32 282.8 100.94 297.9 12.82 301 4.7134 0.04939 0.00265 5.4 0.31996 0.0185 5.8 0.0453 0.00082 1.8 0.31 166.3 120.73 281.9 14.23 285.6 5.0435 0.05723 0.00634 11.1 0.36209 0.04271 11.8 0.04486 0.00155 3.5 0.29 499.7 227.49 313.8 31.84 282.9 9.5536 0.04149 0.00554 13.4 0.29274 0.04129 14.1 0.0512 0.00179 3.5 0.25 0.1 50.3 260.7 32.43 321.9 10.9637 0.04933 0.00426 8.6 0.30921 0.02876 9.3 0.04673 0.00137 2.9 0.32 163.7 190.01 273.6 22.31 294.4 8.4723261 0.04592 0.00538 11.7 0.30668 0.03816 12.4 0.04713 0.00145 3.1 0.25 0.1 254.13 271.6 29.66 296.9 8.95Table A1.1. (continued)Isotopic Ratios Calculated AgesRun # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs09TRDR016: Rhyolitic volcanic sandstone (continued)43 0.0596 0.00587 9.8 0.35271 0.03731 10.6 0.04705 0.0016 3.4 0.32 588.9 200.35 306.8 28.01 296.4 9.8444 0.04852 0.00318 6.6 0.32034 0.02273 7.1 0.0476 0.00104 2.2 0.31 124.7 147.34 282.2 17.48 299.8 6.4145 0.04934 0.00249 5.0 0.29807 0.01619 5.4 0.04584 0.0008 1.7 0.32 164.1 113.97 264.9 12.66 288.9 4.9246 0.05297 0.00536 10.1 0.31139 0.03299 10.6 0.0455 0.00138 3.0 0.29 327.6 214 275.3 25.54 286.8 8.547 0.04636 0.01385 29.9 0.25423 0.07698 30.3 0.04375 0.00231 5.3 0.17 16.3 594.78 230 62.32 276 14.2448 0.05591 0.00571 10.2 0.33607 0.03639 10.8 0.04593 0.00153 3.3 0.31 448.4 212.63 294.2 27.65 289.5 9.4149 0.05156 0.00256 5.0 0.32915 0.01778 5.4 0.04676 0.00081 1.7 0.32 266 110.15 288.9 13.58 294.6 5.0150 0.05145 0.01068 20.8 0.35465 0.07737 21.8 0.0491 0.00262 5.3 0.24 261 417.73 308.2 57.99 309 16.0751 0.05139 0.00434 8.4 0.3143 0.02821 9.0 0.0446 0.00117 2.6 0.29 258.4 182.89 277.5 21.79 281.3 7.2152 0.05279 0.0077 14.6 0.33226 0.05113 15.4 0.04597 0.00198 4.3 0.28 319.8 301.23 291.3 38.97 289.7 12.2253 0.04755 0.00661 13.9 0.3233 0.04781 14.8 0.04462 0.00181 4.1 0.27 76.2 301.53 284.4 36.68 281.4 11.1654 0.03694 0.00891 24.1 0.25542 0.06416 25.1 0.04609 0.00263 5.7 0.23 0.1 0 231 51.9 290.5 16.255 0.05399 0.00998 18.5 0.41014 0.08183 20.0 0.04734 0.00247 5.2 0.26 370.4 370.06 349 58.92 298.2 15.2156 0.05178 0.00212 4.1 0.31323 0.01392 4.4 0.04457 0.00067 1.5 0.34 275.9 90.86 276.7 10.77 281.1 4.1157 0.05316 0.00239 4.5 0.35083 0.01738 5.0 0.04769 0.0008 1.7 0.34 335.4 98.69 305.3 13.06 300.3 4.9158 0.05212 0.00574 11.0 0.32245 0.03754 11.6 0.04732 0.00158 3.3 0.29 290.6 233.62 283.8 28.82 298.1 9.7559 0.05473 0.00535 9.8 0.35073 0.03715 10.6 0.04872 0.00158 3.2 0.31 401.2 205.14 305.3 27.93 306.7 9.7460 0.05037 0.00225 4.5 0.32298 0.01574 4.9 0.04761 0.00075 1.6 0.32 212.2 100.3 284.2 12.08 299.8 4.6462 0.05278 0.00377 7.1 0.34334 0.02645 7.7 0.04602 0.00108 2.3 0.3 319.2 153.87 299.7 19.99 290 6.6563 0.06143 0.00505 8.2 0.43329 0.03901 9.0 0.04848 0.00138 2.8 0.32 654.2 167.33 365.5 27.64 305.2 8.4664 0.05517 0.00517 9.4 0.35741 0.03605 10.1 0.05066 0.00158 3.1 0.31 419 196.71 310.3 26.97 318.6 9.7265 0.04829 0.00644 13.3 0.31248 0.04377 14.0 0.04645 0.00163 3.5 0.25 113.6 287.82 276.1 33.86 292.7 10.0211TRMF010: Quartz-feldspar rhyolite porphyry1 0.05236 0.00129 2.5 0.41983 0.01115 2.7 0.05941 0.00047 0.8 0.3 301 55.22 355.9 7.98 372 2.852 0.0547 0.00393 7.2 0.43648 0.03251 7.4 0.05806 0.00101 1.7 0.23 400.1 153.41 367.8 22.98 363.8 6.13233Table A1.1. (continued)Isotopic Ratios Calculated AgesRun # 207Pb/206Pb 1 σ abs 1 σ % 207Pb/235U 1 σ abs 1 σ % 206Pb/238U 1 σ abs 1 σ % rho1 207Pb/206Pb 1 σ abs 207Pb/235U 1 σ abs 206Pb/238U 1 σ abs11TRMF010: Quartz-feldspar rhyolite porphyry (continued)8 0.05579 0.00249 4.5 0.43159 0.02042 4.7 0.05708 0.00074 1.3 0.27 443.5 96.05 364.3 14.48 357.8 4.529 0.04945 0.00139 2.8 0.39089 0.01179 3.0 0.05719 0.00049 0.9 0.28 169.2 64.51 335 8.6 358.5 3.0210 0.05145 0.00188 3.7 0.40838 0.01593 3.9 0.05845 0.00064 1.1 0.28 261.1 81.86 347.7 11.48 366.2 3.911 0.05571 0.00195 3.5 0.4509 0.01697 3.8 0.05719 0.00063 1.1 0.29 440.5 75.96 377.9 11.87 358.5 3.8612 0.05884 0.00156 2.7 0.47874 0.01393 2.9 0.06082 0.00058 1.0 0.33 561 56.67 397.2 9.56 380.6 3.513 0.05371 0.00188 3.5 0.41555 0.01557 3.7 0.0583 0.00063 1.1 0.29 358.9 77.06 352.9 11.17 365.3 3.8314 0.05301 0.00096 1.8 0.40612 0.00801 2.0 0.05685 0.00037 0.7 0.33 329.2 40.45 346.1 5.79 356.4 2.2415 0.05448 0.00173 3.2 0.41964 0.01436 3.4 0.05776 0.0006 1.0 0.3 390.9 69.1 355.8 10.27 362 3.66234Table A1.2. Chemical dissolution TIMS U-Pb Analytical Data for rocks of Paleozoic Southern WrangelliaWt. U Th Pb 206Pb* mol % Pb* Pbc206Pb 208Pb 207Pb 207Pb 206Pb corr. 207Pb 207Pb 206PbSample mg ppm U ppm x10-13 mol206Pb* Pbc (pg) 204Pb 206Pb 206Pb % err 235U % err 238U % err coef. 206Pb ± 235U ± 238U ± (a) (b) (c) (d) (c) (e) (e) (e) (e) (f) (g) (g) (h) (g) (h) (g) (h) (i) (h) (i) (h) (i) (h)05M366: Rhyolite lapilli tuff proximal to Lenora aditA 0.004 83 0.277 5.7 0.8074 94.42% 4.80 3.96 326 0.088 0.054186 1.034 0.434433 1.161 0.058148 0.424 0.466 378.78 23.25 366.32 3.57 364.35 1.50B 0.004 189 0.337 10.9 1.8000 99.66% 86.88 0.50 5506 0.106 0.053614 0.342 0.421839 0.504 0.057065 0.331 0.739 354.87 7.72 357.37 1.52 357.75 1.15C 0.004 226 0.412 13.8 2.2398 99.76% 125.90 0.43 7809 0.130 0.053933 0.470 0.441719 0.586 0.059400 0.280 0.613 368.26 10.59 371.46 1.82 371.98 1.01D 0.004 158 0.365 9.2 1.5117 99.65% 83.99 0.43 5284 0.115 0.053543 0.945 0.424229 1.062 0.057464 0.324 0.493 351.87 21.36 359.07 3.21 360.19 1.13E 0.004 163 0.376 9.6 1.5652 99.59% 71.39 0.53 4482 0.118 0.053411 0.668 0.424526 0.752 0.057647 0.214 0.512 346.28 15.11 359.28 2.27 361.30 0.7505M386C: Rhyolitic volcanic sandstone or crystal tuffA 0.004 150 0.672 9.8 1.4503 98.70% 24.01 1.58 1414 0.210 0.053445 0.728 0.427976 0.818 0.058078 0.221 0.518 347.75 16.47 361.74 2.49 363.92 0.78B 0.004 180 0.731 12.1 1.7452 98.58% 22.27 2.08 1290 0.230 0.053659 0.391 0.429180 0.493 0.058009 0.224 0.636 356.77 8.83 362.59 1.50 363.51 0.79C 0.004 200 0.632 12.8 1.9395 99.42% 54.38 0.92 3217 0.199 0.053844 0.291 0.431923 0.472 0.058179 0.338 0.790 364.53 6.57 364.54 1.45 364.54 1.20D 0.003 146 0.713 9.5 1.0582 99.17% 38.20 0.73 2222 0.224 0.053593 0.522 0.428857 0.662 0.058037 0.343 0.622 353.98 11.80 362.36 2.02 363.68 1.21E 0.003 166 0.690 10.8 1.2095 99.39% 52.12 0.61 3040 0.217 0.053853 0.605 0.431279 0.700 0.058083 0.243 0.538 364.91 13.63 364.08 2.14 363.95 0.8605M393: Rhyolite crystal tuff at Lara aditA 0.004 389 0.381 22.5 3.6508 99.49% 57.63 1.53 3626 0.120 0.053676 0.166 0.416600 0.269 0.056291 0.149 0.834 357.47 3.76 353.62 0.80 353.03 0.51B 0.004 295 0.327 17.2 2.8409 99.54% 62.67 1.08 4010 0.103 0.053865 0.176 0.428427 0.309 0.057686 0.206 0.840 365.40 3.96 362.06 0.94 361.54 0.72C 0.004 228 0.332 13.4 2.1657 99.03% 29.60 1.75 1894 0.105 0.053897 0.254 0.423405 0.376 0.056976 0.218 0.759 366.74 5.72 358.48 1.14 357.21 0.76D 0.003 327 0.358 19.8 2.3711 98.78% 23.59 2.42 1501 0.113 0.053809 0.251 0.429883 0.340 0.057942 0.146 0.744 363.06 5.65 363.09 1.04 363.10 0.52E 0.003 237 0.379 14.8 1.6880 97.58% 11.77 3.47 752 0.120 0.053865 0.330 0.422187 0.419 0.056845 0.155 0.698 365.43 7.44 357.61 1.26 356.41 0.54(a) A, B etc. are labels for fractions composed of single zircon grains or fragments; all fractions annealed and chemically abraded after Mattinson (2005).(b) Nominal fraction weights estimated from photomicrographic grain dimensions, adjusted for partial dissolution during chemical abrasion.(c) Nominal U and total Pb concentrations subject to uncertainty in photomicrographic estimation of weight and partial dissolution during chemical abrasion.(d) Model Th/U ratio calculated from radiogenic 208Pb/206Pb ratio and 207Pb/235U age.(e) Pb* and Pbc represent radiogenic and common Pb, respectively; mol % 206Pb* with respect to radiogenic, blank and initial common Pb.(f) Measured ratio corrected for spike and fractionation only. Daly analyses, based on analysis of NBS-982.(g) Corrected for fractionation, spike, and common Pb; up to 0.5 pg of common Pb was assumed to be procedural blank: 206Pb/204Pb = 18.50 ± 1.0%; 207Pb/204Pb = 15.50 ± 1.0%; 208Pb/204Pb = 38.40 ± 1.0% (all uncertainties 1-sigma). Excess over blank was assigned to initial common Pb.(h) Errors are 2-sigma, propagated using the algorithms of Schmitz and Schoene (2007) and Crowley et al. (2007).(i) Calculations are based on the decay constants of Jaffey et al. (1971). 206Pb/238U and 207Pb/206Pb ages corrected for initial disequilibrium in 230Th/238U using Th/U [magma] = 3.(j) Corrected for fractionation, spike, and blank Pb only.Compositional Parameters Radiogenic Isotope Ratios Isotopic Ages235Table A1.2. (continued)Wt. U Th Pb 206Pb* mol % Pb* Pbc206Pb 208Pb 207Pb 207Pb 206Pb corr. 207Pb 207Pb 206PbSample mg ppm U ppm x10-13 mol206Pb* Pbc (pg) 204Pb 206Pb 206Pb % err 235U % err 238U % err coef. 206Pb ± 235U ± 238U ± (a) (b) (c) (d) (c) (e) (e) (e) (e) (f) (g) (g) (h) (g) (h) (g) (h) (i) (h) (i) (h) (i) (h)07TR051B: Dacite flowA 0.003 84 0.706 6.6 0.6259 94.13% 5.14 3.21 315 0.223 0.054105 1.994 0.442152 2.163 0.059269 0.460 0.460 375.44 44.87 371.77 6.73 371.18 1.66B 0.003 198 1.019 15.4 1.4503 95.97% 8.22 5.01 459 0.321 0.053902 1.309 0.434713 1.418 0.058492 0.252 0.505 366.95 29.50 366.52 4.36 366.45 0.90C 0.003 125 1.124 11.0 0.9164 92.11% 4.12 6.46 234 0.353 0.053700 2.756 0.433475 2.936 0.058545 0.299 0.635 358.49 62.19 365.64 9.01 366.77 1.07D 0.003 124 1.031 10.5 0.9229 93.35% 4.85 5.41 278 0.323 0.053639 2.367 0.439357 2.527 0.059407 0.285 0.600 355.90 53.45 369.80 7.83 372.02 1.0308TRDR007B: Aphyric rhyolite flowB 0.005 274 0.476 14.0 2.7491 99.30% 42.53 1.60 2613 0.151 0.052422 0.183 0.347952 0.299 0.048140 0.180 0.822 303.87 4.16 303.18 0.78 303.09 0.53C 0.005 934 1.174 53.3 9.0073 99.84% 225.52 1.18 11621 0.373 0.052428 0.122 0.334246 0.225 0.046239 0.131 0.898 304.11 2.78 292.80 0.57 291.39 0.37D 0.005 343 0.839 17.1 3.1075 99.69% 105.89 0.80 5911 0.268 0.052362 0.152 0.313961 0.269 0.043487 0.170 0.853 301.26 3.47 277.25 0.65 274.41 0.46E 0.005 124 0.161 4.7 0.9879 98.80% 22.62 0.99 1524 0.052 0.052396 0.506 0.275767 0.638 0.038172 0.325 0.618 302.73 11.54 247.29 1.40 241.49 0.7708TRDR053A: Quartz-feldspar porphyryA 0.004 558 0.570 29.1 4.5558 99.83% 180.72 0.64 10802 0.181 0.052683 0.129 0.355808 0.217 0.048983 0.109 0.898 315.15 2.93 309.08 0.58 308.28 0.33B 0.002 118 0.522 6.2 0.4728 98.71% 23.50 0.51 1438 0.167 0.053215 0.645 0.351231 0.705 0.047869 0.163 0.467 337.98 14.62 305.65 1.86 301.43 0.48C 0.002 448 0.568 23.8 1.8452 99.59% 75.47 0.62 4525 0.180 0.052787 0.322 0.359766 0.375 0.049430 0.136 0.546 319.64 7.31 312.04 1.01 311.02 0.41E 0.002 493 0.673 31.5 2.0344 94.51% 5.43 9.79 332 0.213 0.052738 0.451 0.359653 0.539 0.049461 0.167 0.641 317.54 10.25 311.96 1.45 311.21 0.51(a) A, B etc. are labels for fractions composed of single zircon grains or fragments; all fractions annealed and chemically abraded after Mattinson (2005).(b) Nominal fraction weights estimated from photomicrographic grain dimensions, adjusted for partial dissolution during chemical abrasion.(c) Nominal U and total Pb concentrations subject to uncertainty in photomicrographic estimation of weight and partial dissolution during chemical abrasion.(d) Model Th/U ratio calculated from radiogenic 208Pb/206Pb ratio and 207Pb/235U age.(e) Pb* and Pbc represent radiogenic and common Pb, respectively; mol % 206Pb* with respect to radiogenic, blank and initial common Pb.(f) Measured ratio corrected for spike and fractionation only. Daly analyses, based on analysis of NBS-982.(g) Corrected for fractionation, spike, and common Pb; up to 0.5 pg of common Pb was assumed to be procedural blank: 206Pb/204Pb = 18.50 ± 1.0%; 207Pb/204Pb = 15.50 ± 1.0%; 208Pb/204Pb = 38.40 ± 1.0% (all uncertainties 1-sigma). Excess over blank was assigned to initial common Pb.(h) Errors are 2-sigma, propagated using the algorithms of Schmitz and Schoene (2007) and Crowley et al. (2007).(i) Calculations are based on the decay constants of Jaffey et al. (1971). 206Pb/238U and 207Pb/206Pb ages corrected for initial disequilibrium in 230Th/238U using Th/U [magma] = 3.(j) Corrected for fractionation, spike, and blank Pb only.Compositional Parameters Radiogenic Isotope Ratios Isotopic Ages236237238239240241242243244245246247248249250251252253254255Appendix 2: Geochemistry 256Table A2.1. Precision and accuracy data for in-house MDRU reference materialsSample WP-1a WP-1b WP-1c WP-1d WP-1e WP-1f Mean 1σ %RSD MDRU %RDMajor elements (wt. %)Al2O3 16.31 16.41 16.42 16.47 16.48 16.57 16.42 0.087 0.53 16.51 -0.14CaO 5.08 5.1 5.08 5.1 5.11 5.11 5.09 0.01 0.27 5.12 -0.13Fe2O3 4.47 4.48 4.48 4.5 4.47 4.48 4.48 0.01 0.24K2O 1.62 1.63 1.63 1.65 1.66 1.63 1.64 0.015 0.92 1.59 0.74MgO 2.62 2.62 2.63 2.64 2.64 2.64 2.63 0.01 0.37 2.64 -0.09MnO 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.00 0.00 0.09 -2.94Na2O 4.6 4.46 4.43 4.48 4.45 4.53 4.48 0.063 1.41 4.4 0.47P2O5 0.18 0.18 0.18 0.18 0.18 0.18 0.18 0.00 0.00 0.18 0.00SiO2 65.13 65.07 65.31 65.4 65.14 65.51 65.21 0.17 0.27 64.04 0.45TiO2 0.49 0.49 0.49 0.49 0.49 0.48 0.49 0.00 0.83 0.52 -1.49LOI 0.16 0.21 0.2 0.13 0.23 0.14 0.19 0.04 21.88Total 100.74 100.74 100.93 101.12 100.92 101.37 100.89 0.24 0.24Trace elements (ppm)Ba 535 541 540 522 523 514 532 11.05 2.08 607 -3.28Sc 9 9 9 8 8 8 9 0.55 6.37 9.26 -1.85Sr 660 670 670 644 683 692 665 16.90 2.54 737 -2.55V 74 76 74 73 74 75 74 1.03 1.39 83 -2.80Y 11 11 11 11 11 11 11 0.00 0.00 8.67 5.92Y* 11 11 11 11 11 11 11 0.00 0.00Ce 28.64 28.29 29.39 28.41 26.53 26.5 28.25 1.18 4.19 28.37 -0.10Cs 0.442 0.445 0.453 0.454 0.439 0.433 0.447 0.008 1.82 0.81 -14.46Dy 2.50 2.45 2.51 2.41 2.32 2.28 2.44 0.10 3.96Er 1.415 1.401 1.419 1.37 1.299 1.273 1.381 0.062 4.53Eu 0.9780 0.9570 0.9930 0.9730 0.9300 0.9130 0.9662 0.0305 3.16 0.9500 0.42Ga 18.84 18.82 18.46 18.46 18.27 18.18 18.57 0.27 1.48 29 -10.96Gd 2.867 2.798 2.835 2.835 2.652 2.608 2.797 0.108 3.87Hf 3.24 3.22 3.22 3.17 3.18 3.15 3.21 0.04 1.09 3.14 0.52Ho 0.483 0.484 0.489 0.478 0.45 0.448 0.477 0.018 3.81La 13.57 13.37 13.85 13.49 12.69 12.59 13.39 0.51 3.78 13.83 -0.80Lu 0.213 0.212 0.216 0.208 0.197 0.191 0.209 0.010 4.76 0.2 1.12Nb 3.663 3.63 3.715 3.679 3.581 3.586 3.654 0.053 1.46 6.56 -14.23Nb* 4 4 4 4 4 4 4 0.00 0.00Nd 15.38 15.21 15.61 15.4 14.13 14.01 15.15 0.70 4.62 13.72 2.47Pr 3.745 3.71 3.809 3.684 3.467 3.418 3.683 0.16 4.30Rb 23.65 23.41 23.03 23.11 22.96 22.64 23.23 0.35 1.53 22 1.36Sm 3.195 3.168 3.267 3.173 2.977 2.944 3.156 0.13 4.10 2.84 2.64Ta 0.222 0.221 0.222 0.22 0.212 0.214 0.219 0.00 1.99 0.5 -19.50Tb 0.425 0.408 0.417 0.41 0.391 0.382 0.410 0.02 3.93 0.29 8.58Th 2.05 2.05 2.08 2.02 1.94 1.87 2.03 0.08 4.00 1.91 1.50Tm 0.208 0.204 0.21 0.201 0.193 0.189 0.203 0.008 4.10U 0.83 0.84 0.83 0.82 0.83 0.82 0.829 0.008 0.95 0.85 -0.61Yb 1.353 1.346 1.365 1.344 1.277 1.262 1.337 0.043 3.25 1.27 1.29Zr 130 132 130 129 129 126 130 1.97 1.51 136 -1.13Zr* 131 130 131 131 131 131 131 0.41 0.31SDV (1σ) = standard deviation; RSD = relative standard deviation = SDV/Mean;RD = relative difference = |(Mean-MDRU)/(Mean+MDRU)|/2.* analysis by XRF257Table A2.2. Results for duplicate samples analyzed by ICP-AES in this study and assessment of precision.Sample 05M-113c 05M-113c* %RD 05M-353 05M-353* %RD 05M-364 05M-364* %RDTrace elements (ppm)Al 68716 67717 0.37 63959 66377 -0.93 46864 46381 0.26Ba 357 350 0.50 136 143 -1.25 453 446 0.39Be 3 3 0.00 1 2 -16.67 3 3 0.00Ca 19956 19668 0.36 10351 10594 -0.58 7111 7011 0.35Co 5 6 -4.55 2 3 -10.00 16 16 0.00Cr 10 6 12.50 5 5 0.00 21 20 1.22Cu 6 5 4.55 6 1 35.71 95 94 0.26Fe 28496 28203 0.26 12310 12745 -0.87 42600 41918 0.40K 1095 1082 0.30 1993 2084 -1.12 14936 14752 0.31Li 17 16 1.52 1 1 0.00 12 12 0.00Mg 8798 8687 0.32 5477 5693 -0.97 21769 21434 0.39Mn 468 463 0.27 189 197 -1.04 604 593 0.46Na 31000 42457 -7.80 31000 45087 -9.26 2403 2403 0.00Ni 2 0 50.00 2 2 0.00 7 7 0.00P 861 861 0.00 245 252 -0.70 899 879 0.56Pb 15 -1 57.14 15 6 21.43 15 14 1.72S 1006 1046 -0.97 60 6 40.91 60 131 -18.59Sc 13 13 0.00 5 5 0.00 20 20 0.00Sr 232 228 0.43 173 181 -1.13 24 24 0.00Ti 3899 3891 0.05 1407 1472 -1.13 4306 4232 0.43V 49 49 0.00 26 27 -0.94 221 217 0.46Y 27 27 0.00 12 13 -2.00 13 13 0.00Zn 23 23 0.00 12 11 2.17 50 50 0.00Sample 05M-386c 05M-386c* %RD 07TR064A 07TR064A* %RD 07TR066A 07TR066A* %RDAl 88837 88793 0.01 72919 73713 -0.27 96060 93653 0.63Ba 608 612 -0.16 174 181 -0.99 215 213 0.23Be 3 3 0.00 4 4 0.00 5 5 0.00Ca 30542 30525 0.01 72635 79549 -2.27 51813 48048 1.89Co 10 10 0.00 33 35 -1.47 13 14 -1.85Cr 48 46 1.06 272 291 -1.69 8 8 0.00Cu 6 5 4.55 97 101 -1.01 49 50 -0.51Fe 37730 37345 0.26 60317 60720 -0.17 52460 51505 0.46K 14730 14644 0.15 4424 4741 -1.73 7652 7527 0.41Li 4 4 0.00 8 9 -2.94 7 7 0.00Mg 9677 9654 0.06 41479 42001 -0.31 13140 13367 -0.43Mn 547 547 0.00 1077 1077 0.00 934 919 0.40Na 31000 42846 -8.02 16031 17162 -1.70 31000 32621 -1.27Ni 12 13 -2.00 102 102 0.00 5 3 12.50P 971 966 0.13 1066 980 2.10 1985 1943 0.53Pb 15 2 38.24 15 4 28.95 15 12 5.56S 4199 3927 1.67 66 25 22.53 60 61 -0.41Sc 11 11 0.00 32 31 0.79 20 19 1.28Sr 600 600 0.00 396 388 0.51 664 647 0.65Ti 3177 3168 0.07 4072 4158 -0.52 5632 5568 0.29V 102 103 -0.24 250 242 0.81 239 236 0.32Y 17 17 0.00 16 15 1.61 20 19 1.28Zn 59 59 0.00 72 74 -0.68 84 82 0.60Sample names followed by an asterix are duplicate samplesRD = relative difference = |(A-A*)/(A+A*)|/2.258Table A2.2. (continued)Sample 09TR125 09TR125* %RD 09TRHS025 09TRHS025* %RD 08TRDR007A 08TRDR007A* %RDTrace elements (ppm)Al 96065 92934 0.83 87823 89031 -0.34 59656 58147 0.64Ba 539 524 0.71 178 181 -0.42 961 938 0.61Be 3 3 0.00 1 1 0.00 2 2 0.00Ca 42763 40819 1.16 54909 55487 -0.26 713 702 0.39Co 23 22 1.11 25 24 1.02 1 0 50.00Cr 19 18 1.35 62 62 0.00 5 5 0.00Cu 6 1 35.71 32 34 -1.52 6 1 35.71Fe 55432 54164 0.58 63948 64526 -0.22 15160 14749 0.69K 33666 32919 0.56 4398 4463 -0.37 45000 71808 -11.48Li 36 35 0.70 6 6 0.00 4 4 0.00Mg 18794 18396 0.54 24255 24649 -0.40 273 270 0.28Mn 729 714 0.52 1636 1656 -0.30 485 476 0.47Na 26111 25441 0.65 31000 34431 -2.62 1626 1604 0.34Ni 9 9 0.00 20 22 -2.38 2 0 50.00P 2108 2043 0.78 771 797 -0.83 65 54 4.62Pb 15 2 38.24 15 -3 75.00 15 6 21.43S 214 213 0.12 1467 1591 -2.03 1320 1295 0.48Sc 16 15 1.61 29 29 0.00 7 7 0.00Sr 732 711 0.73 609 618 -0.37 21 20 1.22Ti 13279 12959 0.61 4245 4317 -0.42 1708 1682 0.38V 184 181 0.41 217 218 -0.11 1 1 0.00Y 22 21 1.16 16 16 0.00 47 45 1.09Zn 66 66 0.00 78 79 -0.32 74 71 1.03Sample 05M350 05M350* %RD 08TR054 08TR054* %RD 08TR087A 08TR087A* %RDAl 71139 70834 0.11 84649 84393 0.08 87266 86387 0.25Ba 526 527 -0.05 626 625 0.04 1008 996 0.30Be 1 1 0.00 2 1 16.67 1 1 0.00Ca 17967 17788 0.25 32335 32285 0.04 45661 45475 0.10Co 3 3 0.00 15 15 0.00 22 22 0.00Cr 6 5 4.55 3 3 0.00 14 13 1.85Cu 6 4 10.00 21 20 1.22 62 67 -1.94Fe 26637 26085 0.52 53888 53333 0.26 62834 64057 -0.48K 6001 5995 0.03 12209 12179 0.06 21518 20874 0.76Li 3 3 0.00 12 11 2.17 9 8 2.94Mg 6014 5916 0.41 13452 13308 0.27 22010 22180 -0.19Mn 523 513 0.48 1119 1114 0.11 1120 1130 -0.22Na 31000 32184 -0.94 26067 25869 0.19 22673 22443 0.25Ni 2 0 50.00 2 1 16.67 7 7 0.00P 389 374 0.98 1271 1249 0.44 1258 1242 0.32Pb 15 -2 65.38 15 5 25.00 15 -1 57.14S 60 -30 150.00 1123 1104 0.43 1560 1744 -2.78Sc 7 7 0.00 17 17 0.00 24 24 0.00Sr 238 236 0.21 322 323 -0.08 456 452 0.22Ti 1901 1904 -0.04 4054 4033 0.13 4833 4794 0.20V 35 34 0.72 93 92 0.27 224 226 -0.22Y 23 22 1.11 31 32 -0.79 21 21 0.00Zn 35 27 6.45 91 90 0.28 77 78 -0.32Sample names followed by an asterix are duplicate samplesRD = relative difference = |(A-A*)/(A+A*)|/2.259Table A2.2. (continued)Sample 08TR121 08TR121* %RD 09TR044 09TR044* %RD 09TR060 09TR060* %RDTrace elements (ppm)Al 64139 66653 -0.96 84714 87624 -0.84 74119 73421 0.24Ba 801 839 -1.16 88 91 -0.84 2000 7107 -28.04Be 1 1 0.00 1 1 0.00 3 3 0.00Ca 3259 3384 -0.94 63488 66058 -0.99 16340 16082 0.40Co 1 0 50.00 26 27 -0.94 2 2 0.00Cr 3 3 0.00 249 246 0.30 4 1 30.00Cu 6 1 35.71 60 74 -5.22 6 1 35.71Fe 8944 9267 -0.89 74608 77301 -0.89 29613 29231 0.32K 9810 10228 -1.04 359 367 -0.55 16364 16204 0.25Li 4 4 0.00 9 9 0.00 21 22 -1.16Mg 5220 5456 -1.11 18814 19520 -0.92 5894 5979 -0.36Mn 166 173 -1.03 1773 1836 -0.87 1163 1131 0.70Na 30913 31956 -0.83 15004 15525 -0.85 11587 11428 0.35Ni 2 0 50.00 33 36 -2.17 4 2 16.67P 227 227 0.00 416 444 -1.63 105 103 0.48Pb 15 -8 164.29 15 4 28.95 15 13 3.57S 87 -20 79.85 225 245 -2.13 102 73 8.29Sc 6 6 0.00 40 41 -0.62 1 1 0.00Sr 113 117 -0.87 664 686 -0.81 220 219 0.11Ti 1435 1517 -1.39 4642 4795 -0.81 577 571 0.26V 26 26 0.00 279 289 -0.88 1 -1 -Y 17 17 0.00 16 17 -1.52 82 80 0.62Zn 12 12 0.00 82 85 -0.90 102 104 -0.49Sample 09M305 09M305* %RD 09TR099 09TR099* %RD 11TRDR008 11TRDR008* %RDAl 79108 79870 -0.24 91409 89845 0.43 406 397 0.56Ba 286 292 -0.52 262 258 0.38 4 6 -10.00Be 1 1 0.00 4 4 0.00 1 0 50.00Ca 41001 41332 -0.20 35149 34698 0.32 320 303 1.36Co 27 28 -0.91 13 13 0.00 1 0 50.00Cr 280 278 0.18 10 10 0.00 23 19 4.76Cu 6 5 4.55 6 2 25.00 6 1 35.71Fe 76213 77168 -0.31 53652 52707 0.44 9484 9631 -0.38K 6804 6841 -0.14 21397 21119 0.33 70 68 0.72Li 83 83 0.00 33 32 0.77 1 1 0.00Mg 39824 40122 -0.19 16858 16551 0.46 40 37 1.95Mn 990 1002 -0.30 880 864 0.46 11 10 2.38Na 11527 11688 -0.35 31000 34154 -2.42 500 165 25.19Ni 59 57 0.86 6 6 0.00 2 0 50.00P 945 946 -0.03 2579 2558 0.20 55 59 -1.75Pb 15 2 38.24 15 9 12.50 15 0 50.00S 103 90 3.37 79 68 3.74 60 6 40.91Sc 38 38 0.00 9 9 0.00 1 0 50.00Sr 279 283 -0.36 410 404 0.37 2 25 -42.59Ti 4737 4780 -0.23 9887 9797 0.23 9 6 10.00V 288 289 -0.09 97 95 0.52 8 8 0.00Y 14 14 0.00 33 33 0.00 1 0 50.00Zn 156 157 -0.16 88 84 1.16 5 3 12.50Sample names followed by an asterix are duplicate samplesRD = relative difference = |(A-A*)/(A+A*)|/2.260Table A2.3. Results for duplicate samples analyzed by ICP-MS in this study and assessment of precision.Sample 05M-113c 05M-113c* %RD 05M-353 05M-353* %RD 05M-364 05M-364* %RDTrace elements (ppm)Ba 356.3 353.2 0.22 136.1 139.1 -0.55 475 483 -0.42Be 0.65 0.67 -0.76 0.89 0.8 2.66 0.81 0.83 -0.61Bi 0.033 0.059 -14.13 0.03 0.03 0.00 0.08 0.111 -8.12Cd 0.05 0.06 -4.55 0.03 0.04 -7.14 0.06 0.06 0.00Ce 31 30.8 0.16 24.6 24.9 -0.30 12.1 12.9 -1.60Co 6.4 6.4 0.00 4 4.1 -0.62 17.1 17.1 0.00Cr 24 7 27.42 24 6 30.00 24 22 2.17Cs 0.161 0.165 -0.61 0.04 0.039 0.63 0.74 0.758 -0.60Cu 8 9 -2.94 5 5 0.00 97 97 0.00Dy 4.9 4.8 0.52 1.9 2 -1.28 2.6 2.7 -0.94Er 2.89 2.89 0.00 1.28 1.28 0.00 1.58 1.64 -0.93Eu 1.366 1.312 1.01 0.531 0.54 -0.42 0.75 0.782 -1.04Ga 14.68 14.28 0.69 11.32 11.39 -0.15 11.71 11.57 0.30Gd 4.73 4.75 -0.11 1.84 1.83 0.14 2.63 2.69 -0.56Hf 4.95 5.05 -0.50 3.74 3.83 -0.59 2.03 2.09 -0.73Ho 1.047 1.005 1.02 0.432 0.431 0.06 0.56 0.577 -0.75La 12.88 12.69 0.37 12.61 13.06 -0.88 4.68 4.92 -1.25Li 19 18 1.35 1.4 1.4 0.00 14.6 14.4 0.34Lu 0.479 0.489 -0.52 0.274 0.26 1.31 0.252 0.265 -1.26Mo 0.42 0.39 1.85 0.31 0.29 1.67 0.16 0.21 -6.76Nb 3.26 3.24 0.15 4.18 4.24 -0.36 2.3 2.3 0.00Nd 19.49 19.19 0.39 9.79 9.91 -0.30 8.44 8.85 -1.19Ni 3 3 0.00 3 1 25.00 12 12 0.00Pb 1.3 1.4 -1.85 2 2.1 -1.22 3.4 3.4 0.00Pr 4.14 4.14 0.00 2.59 2.6 -0.10 1.68 1.77 -1.30Rb 3.9 3.7 1.32 3.3 3.1 1.56 40.9 40.1 0.49Sb 0.14 0.13 1.85 0.06 0.05 4.55 0.05 0.05 0.00Sc 14 13.3 1.28 5.3 5.4 -0.47 22.8 23.6 -0.86Sm 4.73 4.69 0.21 1.97 2 -0.38 2.31 2.46 -1.57Sn 1.37 1.63 -4.33 0.64 0.65 -0.39 0.68 0.66 0.75Sr 231 223 0.88 171 174 -0.43 30 30 0.00Ta 0.2 0.2 0.00 0.3 0.3 0.00 0.2 0.1 16.67Tb 0.774 0.78 -0.19 0.315 0.309 0.48 0.415 0.423 -0.48Th 1.81 1.83 -0.27 2.97 3.08 -0.91 1.27 1.31 -0.78Ti 3412 3350 0.46 1180 1257 -1.58 4018 4125 -0.66Tl 0.056 0.06 -1.72 0.012 0.011 2.17 0.243 0.243 0.00Tm 0.449 0.464 -0.82 0.23 0.213 1.92 0.249 0.26 -1.08U 0.71 0.74 -1.03 1.38 1.48 -1.75 0.53 0.55 -0.93V 45 44 0.56 23 24 -1.06 221 221 0.00W 0.5 0.3 12.50 0.5 0.4 5.56 0.5 0.3 12.50Y 30.65 29.98 0.55 14.2 13.58 1.12 16.12 16.11 0.02Yb 2.958 3.067 -0.90 1.561 1.568 -0.11 1.588 1.652 -0.99Zn 22 21 1.16 10 10 0.00 45 46 -0.55Zr 205 204 0.12 163 163 0.00 86 87 -0.29Sample names followed by an asterix are duplicate samplesRD = relative difference = |(A-A*)/(A+A*)|/2.261Table A2.3. (continued)Sample 05M-386c 05M-386c* %RD 07TR064A 07TR064A* %RD 07TR066A 07TR066A* %RDTrace elements (ppm)Ba 586.9 604.8 -0.75 175.6 179 -0.48 209.5 201.6 0.96Be 1.4 1.3 1.85 0.8 0.87 -2.10 1.82 1.82 0.00Bi 0.082 0.101 -5.19 0.072 0.031 19.90 0.043 0.076 -13.87Cd 0.09 0.09 0.00 0.05 0.06 -4.55 0.06 0.06 0.00Ce 51.1 53.7 -1.24 24.7 20 5.26 31.5 26.2 4.59Co 10 9.6 1.02 33.2 34.6 -1.03 12.4 12.9 -0.99Cr 47 44 1.65 277 304 -2.32 24 9 22.73Cs 0.107 0.116 -2.02 0.268 0.297 -2.57 0.571 0.564 0.31Cu 9 10 -2.63 89 93 -1.10 48 50 -1.02Dy 2.9 3 -0.85 3.3 2.9 3.23 3.9 3.2 4.93Er 1.66 1.75 -1.32 1.83 1.68 2.14 2.1 1.69 5.41Eu 1.181 1.288 -2.17 1.149 0.969 4.25 1.394 1.156 4.67Ga 17.39 17.19 0.29 14.83 14.39 0.75 16.83 16.97 -0.21Gd 3.19 3.46 -2.03 3.27 2.97 2.40 4.29 3.44 5.50Hf 3.92 3.95 -0.19 1.3 1.37 -1.31 1.98 2 -0.25Ho 0.599 0.611 -0.50 0.669 0.614 2.14 0.764 0.635 4.61La 26.87 28.45 -1.43 13.02 9.23 8.52 14.69 12.27 4.49Li 3.5 3.5 0.00 8.9 9.8 -2.41 6.9 5.9 3.91Lu 0.305 0.309 -0.33 0.277 0.257 1.87 0.311 0.258 4.66Mo 2.62 2.72 -0.94 0.33 0.25 6.90 0.37 0.36 0.68Nb 11.05 11.19 -0.31 2.7 2.76 -0.55 5.25 5.26 -0.05Nd 20.63 21.55 -1.09 13.12 11.41 3.49 18.15 14.77 5.13Ni 16 15 1.61 112 110 0.45 9 9 0.00Pb 6.6 6.6 0.00 3.2 3 1.61 5.4 4 7.45Pr 5.44 5.71 -1.21 3 2.53 4.25 3.98 3.28 4.82Rb 27.3 27.1 0.18 10.2 11.2 -2.34 21 21 0.00Sb 0.58 0.58 0.00 1.07 0.98 2.20 2.75 2.67 0.74Sc 10.2 10.5 -0.72 32.3 32.7 -0.31 19.2 16.5 3.78Sm 3.71 3.87 -1.06 3.15 2.88 2.24 4.25 3.52 4.70Sn 0.85 0.89 -1.15 0.64 0.61 1.20 0.91 0.89 0.56Sr 580 578 0.09 391 382 0.58 637 622 0.60Ta 0.6 0.6 0.00 0.2 0.2 0.00 0.3 0.3 0.00Tb 0.487 0.52 -1.64 0.529 0.465 3.22 0.664 0.528 5.70Th 5.76 6.12 -1.52 1.3 1.31 -0.19 1.81 1.62 2.77Ti 2720 2704 0.15 3695 3862 -1.10 4961 5026 -0.33Tl 0.156 0.158 -0.32 0.049 0.051 -1.00 0.08 0.081 -0.31Tm 0.265 0.291 -2.34 0.28 0.259 1.95 0.319 0.263 4.81U 2.34 2.38 -0.42 0.44 0.44 0.00 1.06 1.02 0.96V 94 96 -0.53 253 253 0.00 224 222 0.22W 0.5 0.3 12.50 0.5 0.2 21.43 0.5 0.3 12.50Y 17.53 18.49 -1.33 19.24 17.5 2.37 22.05 18.39 4.53Yb 1.802 1.963 -2.14 1.856 1.717 1.95 2.054 1.681 4.99Zn 47 47 0.00 58 61 -1.26 68 68 0.00Zr 175 178 -0.42 48 49 -0.52 74 74 0.00Sample names followed by an asterix are duplicate samplesRD = relative difference = |(A-A*)/(A+A*)|/2.262Table A2.3. (continued)Sample 05M350 05M350* %RD 08TR054 08TR054* %RD 08TR087A 08TR087A* %RDTrace elements (ppm)Ba 599.6 602 -0.10 758.2 750 0.27 1215.8 1190.9 0.52Be 0.9 0.88 0.56 1.21 1.15 1.27 0.77 0.83 -1.88Bi 0.15 0.06 21.43 0.15 0.06 21.43 0.15 0.03 33.33Cd 0.048 0.038 5.81 0.276 0.204 7.50 0.126 0.14 -2.63Ce 27.52 29.71 -1.91 40.8 40.81 -0.01 29.22 28.82 0.34Co 3.74 3.64 0.68 17.54 17.86 -0.45 24.74 24.88 -0.14Cr 8 7 3.33 8 6 7.14 21 20 1.22Cs 0.115 0.109 1.34 0.892 0.893 -0.03 2.464 2.41 0.55Cu 7 7 0.00 26.4 26.4 0.00 75.6 81.1 -1.75Dy 4.208 4.252 -0.26 6.386 6.412 -0.10 4.624 4.55 0.40Er 2.901 2.915 -0.12 4.139 4.181 -0.25 2.843 2.739 0.93Eu 1.13 1.146 -0.35 1.628 1.65 -0.34 1.365 1.336 0.54Ga 14.97 15.16 -0.32 17.4 17.12 0.41 17.08 17.24 -0.23Gd 3.709 3.749 -0.27 5.98 6.044 -0.27 4.547 4.492 0.30Hf 2.64 2.63 0.09 2.63 2.61 0.19 2.91 2.83 0.70Ho 0.913 0.924 -0.30 1.358 1.37 -0.22 0.951 0.93 0.56In 0.044 0.043 0.57 0.073 0.072 0.34 0.065 0.064 0.39La 13.49 14.9 -2.48 20.25 20.13 0.15 13.32 13.24 0.15Li 3 3.2 -1.61 12.2 12 0.41 7.9 8 -0.31Lu 0.49 0.502 -0.60 0.646 0.646 0.00 0.425 0.413 0.72Mo 0.38 0.41 -1.90 0.15 0.15 0.00 1.53 1.62 -1.43Nb 4.049 4.062 -0.08 4.43 4.424 0.03 4.963 4.857 0.54Nd 13.83 14.73 -1.58 22.91 22.79 0.13 17.99 17.84 0.21Ni 1.7 1.7 0.00 5.6 5.6 0.00 12 12.7 -1.42Pb 2.8 2.5 2.83 6.9 6.8 0.36 3.2 3.1 0.79Pr 3.339 3.524 -1.35 5.206 5.218 -0.06 4.073 4 0.45Rb 12.24 12.52 -0.57 49.9 49.08 0.41 57.41 56.58 0.36Sb 0.25 0.24 1.02 0.31 0.31 0.00 0.2 0.19 1.28Sc 9 9.1 -0.28 21.7 21.1 0.70 29.1 29.3 -0.17Sm 3.383 3.501 -0.86 5.576 5.573 0.01 4.534 4.396 0.77Sn 1.14 1.13 0.22 1.14 1.16 -0.43 0.87 0.96 -2.46Sr 258.1 260.3 -0.21 365.8 359.7 0.42 506.5 506.3 0.01Ta 0.309 0.3 0.74 0.243 0.241 0.21 0.281 0.272 0.81Tb 0.624 0.629 -0.20 0.963 0.972 -0.23 0.72 0.7 0.70Th 3.433 3.518 -0.61 2.924 2.904 0.17 2.825 2.73 0.86Ti 2119 2119 0.00 4736 4640 0.51 5456 5461 -0.02Tl 0.042 0.042 0.00 0.183 0.179 0.55 0.174 0.17 0.58Tm 0.452 0.458 -0.33 0.629 0.633 -0.16 0.415 0.412 0.18U 1.339 1.381 -0.77 1.363 1.367 -0.07 1.243 1.189 1.11V 39.2 41.4 -1.36 115.5 111.1 0.97 261.3 266.4 -0.48W 0.27 0.27 0.00 0.33 0.34 -0.75 0.36 0.34 1.43Y 26.35 26.75 -0.38 39.17 39.06 0.07 26.06 25.58 0.46Yb 3.133 3.161 -0.22 4.14 4.136 0.02 2.751 2.692 0.54Zn 26 27 -0.94 94 93 0.27 78 79 -0.32Zr 83 86 -0.89 101 99 0.50 109 106 0.70Sample names followed by an asterix are duplicate samplesRD = relative difference = |(A-A*)/(A+A*)|/2.263Table A2.3. (continued)Sample 08TR121 08TR121* %RD 09TR044 09TR044* %RD 09TR060 09TR060* %RDTrace elements (ppm)Ba 941.6 974.2 -0.85 106.4 104.9 0.35 1740 8828.2 -33.54Be 0.8 0.92 -3.49 0.51 0.46 2.58 2.78 2.74 0.36Bi 0.15 0.06 21.43 0.15 0.11 7.69 0.15 0.11 7.69Cd 0.035 0.023 10.34 0.054 0.048 2.94 0.273 0.285 -1.08Ce 34.33 37.44 -2.17 11.13 11.01 0.27 95.7 98.73 -0.78Co 0.87 0.87 0.00 31.16 31.03 0.10 1.39 1.27 2.26Cr 5 5 0.00 302 288 1.19 7 3 20.00Cs 0.283 0.292 -0.78 0.054 0.052 0.94 3.16 3.165 -0.04Cu 1.9 2 -1.28 75.3 88.1 -3.92 1.9 2.1 -2.50Dy 3.301 3.34 -0.29 3.616 3.676 -0.41 15.696 15.598 0.16Er 2.206 2.263 -0.64 2.284 2.299 -0.16 11.902 11.914 -0.03Eu 0.805 0.849 -1.33 0.974 0.955 0.49 2.994 3.03 -0.30Ga 11.92 12.34 -0.87 15.71 15.48 0.37 24.43 24.4 0.03Gd 3.04 3.133 -0.75 3.148 3.145 0.02 11.335 11.331 0.01Hf 3.15 3.19 -0.32 1.48 1.48 0.00 12.63 12.59 0.08Ho 0.706 0.721 -0.53 0.763 0.773 -0.33 3.59 3.584 0.04In 0.024 0.025 -1.02 0.07 0.07 0.00 0.105 0.107 -0.47La 17.64 19.43 -2.41 4.56 4.64 -0.43 49.55 52.04 -1.23Li 3.3 3.6 -2.17 10 9.7 0.76 17.8 19.8 -2.66Lu 0.393 0.393 0.00 0.33 0.322 0.61 2.218 2.22 -0.02Mo 0.35 0.37 -1.39 0.13 0.13 0.00 7.33 8.34 -3.22Nb 4.864 5.068 -1.03 1.634 1.551 1.30 65.947 66.234 -0.11Nd 14.64 15.89 -2.05 8.21 8.28 -0.21 41.76 42.88 -0.66Ni 2.7 0.9 25.00 47.1 46.7 0.21 7.1 4.5 11.21Pb 1.2 1.3 -2.00 3.9 3.9 0.00 7.3 7.3 0.00Pr 3.861 4.249 -2.39 1.651 1.635 0.24 10.856 11.211 -0.80Rb 25.96 26.69 -0.69 0.84 0.8 1.22 43.05 53.27 -5.31Sb 0.09 0.09 0.00 0.42 0.41 0.60 0.58 0.55 1.33Sc 7.5 7.6 -0.33 50.5 50 0.25 1.4 1.5 -1.72Sm 3.073 3.321 -1.94 2.574 2.557 0.17 9.548 9.661 -0.29Sn 1.38 1.42 -0.71 0.46 0.45 0.55 4 4.16 -0.98Sr 128.8 134 -0.99 766.2 763 0.10 262.8 267.5 -0.44Ta 0.314 0.327 -1.01 0.096 0.095 0.26 3.892 3.868 0.15Tb 0.49 0.51 -1.00 0.542 0.545 -0.14 2.144 2.158 -0.16Th 4.036 4.052 -0.10 0.609 0.616 -0.29 7.011 7.162 -0.53Ti 1628 1721 -1.39 5382 5427 -0.21 684 691 -0.25Tl 0.096 0.102 -1.52 0.005 0.003 12.50 0.231 0.22 1.22Tm 0.346 0.36 -0.99 0.329 0.335 -0.45 1.951 1.934 0.22U 2.28 2.312 -0.35 0.259 0.267 -0.76 2.913 2.878 0.30V 30.8 32.1 -1.03 340.8 338.9 0.14 0.8 0.8 0.00W 0.56 0.61 -2.14 0.08 0.07 3.33 0.68 0.72 -1.43Y 20.44 20.83 -0.47 20.52 20.66 -0.17 103.48 103.88 -0.10Yb 2.443 2.488 -0.46 2.162 2.168 -0.07 13.747 13.727 0.04Zn 13 13 0.00 80 80 0.00 109 113 -0.90Zr 123 126 -0.60 53 53 0.00 599 599 0.00Sample names followed by an asterix are duplicate samplesRD = relative difference = |(A-A*)/(A+A*)|/2.264Table A2.3. (continued)Sample 09M305 09M305* %RD 09TR099 09TR099* %RD 09TR125 09TR125* %RDTrace elements (ppm)Ba 348.3 358.8 -0.74 302.9 302.3 0.05 616.4 613.9 0.10Be 0.9 1.07 -4.31 3.28 3.07 1.65 2.13 1.88 3.12Bi 0.15 0.01 43.75 0.15 0.01 43.75 0.15 0.02 38.24Cd 0.149 0.134 2.65 0.245 0.196 5.56 0.16 0.165 -0.77Ce 12.52 12.82 -0.59 97.39 96.94 0.12 56.36 55.45 0.41Co 32.47 33.18 -0.54 13.57 13.43 0.26 23.19 23.51 -0.34Cr 335 338 -0.22 13 13 0.00 21 21 0.00Cs 1.357 1.412 -0.99 1.07 1.067 0.07 3.685 3.72 -0.24Cu 9.4 10.1 -1.79 5.4 5.9 -2.21 9.8 7.6 6.32Dy 3.323 3.421 -0.73 7.588 7.612 -0.08 5.044 4.883 0.81Er 1.965 2.027 -0.78 4.202 4.174 0.17 2.611 2.551 0.58Eu 0.852 0.856 -0.12 2.867 2.847 0.18 2.146 2.11 0.42Ga 15.43 15.99 -0.89 21.73 21.54 0.22 20.91 21.19 -0.33Gd 3.262 3.283 -0.16 8.481 8.429 0.15 5.885 5.731 0.66Hf 0.92 0.96 -1.06 8.51 8.53 -0.06 4.63 4.66 -0.16Ho 0.682 0.696 -0.51 1.463 1.482 -0.32 0.967 0.938 0.76In 0.056 0.058 -0.88 0.086 0.084 0.59 0.071 0.072 -0.35La 5.34 5.52 -0.83 45.58 45.17 0.23 26.23 25.59 0.62Li 91 98.6 -2.00 33.8 33.8 0.00 34.9 34.5 0.29Lu 0.265 0.274 -0.83 0.561 0.565 -0.18 0.322 0.315 0.55Mo 0.08 0.48 -35.71 0.8 0.79 0.31 0.72 0.68 1.43Nb 1.837 1.863 -0.35 48.632 49.148 -0.26 22.594 22.889 -0.32Nd 9.59 9.77 -0.46 45.25 45.67 -0.23 28.78 28.13 0.57Ni 74.1 75.6 -0.50 10.5 10.5 0.00 14.8 14.7 0.17Pb 2.1 2.1 0.00 4.1 4.1 0.00 2 2.1 -1.22Pr 1.866 1.945 -1.04 11.438 11.455 -0.04 6.979 6.832 0.53Rb 21.71 22.16 -0.51 33.81 33.5 0.23 60.04 58.84 0.50Sb 0.11 0.28 -21.79 0.21 0.2 1.22 0.71 0.6 4.20Sc 48.2 48.9 -0.36 10.7 10.8 -0.23 19 18.6 0.53Sm 2.843 2.987 -1.23 9.103 9.259 -0.42 6.243 6.023 0.90Sn 0.74 0.73 0.34 3.17 3.02 1.21 1.76 1.69 1.01Sr 314.9 326.1 -0.87 445.7 445.4 0.02 765.8 767 -0.04Ta 0.106 0.106 0.00 3.124 3.172 -0.38 1.511 1.519 -0.13Tb 0.518 0.524 -0.29 1.251 1.27 -0.38 0.865 0.841 0.70Th 0.675 0.688 -0.48 4.71 4.696 0.07 2.272 2.24 0.35Ti 5495 5584 -0.40 10468 10421 0.11 13914 14035 -0.22Tl 0.059 0.063 -1.64 0.12 0.119 0.21 0.137 0.137 0.00Tm 0.281 0.289 -0.70 0.588 0.599 -0.46 0.352 0.348 0.29U 0.318 0.324 -0.47 1.306 1.315 -0.17 1.331 1.333 -0.04V 347.8 354.4 -0.47 111.8 111.3 0.11 211.7 215.3 -0.42W 0.4 0.87 -18.50 0.24 0.24 0.00 0.34 0.27 5.74Y 17.93 18.53 -0.82 39.09 39.15 -0.04 25.09 24.37 0.73Yb 1.786 1.854 -0.93 3.74 3.771 -0.21 2.202 2.148 0.62Zn 161 166 -0.76 86 85 0.29 70 71 -0.35Zr 32 33 -0.77 443 442 0.06 232 230 0.22Sample names followed by an asterix are duplicate samplesRD = relative difference = |(A-A*)/(A+A*)|/2.265Table A2.3. (continued)Sample 09TRHS025 09TRHS025* %RD 08TRDR007A 08TRDR007A* %RD 11TRDR008 11TRDR008* %RDTrace elements (ppm)Ba 207.3 207.5 -0.02 1119.8 1109.4 0.23 5 6.6 -6.90Be 0.69 0.73 -1.41 1.5 1.49 0.17 0.11 0.1 2.38Bi 0.15 0.02 38.24 0.15 0.07 18.18 0.15 0.03 33.33Cd 0.123 0.107 3.48 0.237 0.21 3.02 0.013 0.007 15.00Ce 18.78 18.84 -0.08 88.43 85.62 0.81 0.61 0.64 -1.20Co 28.01 27.88 0.12 0.15 0.13 3.57 0.23 0.21 2.27Cr 73 71 0.69 8 7 3.33 22 19 3.66Cs 0.545 0.542 0.14 0.491 0.491 0.00 0.023 0.024 -1.06Cu 41.7 43.4 -1.00 1.9 1.8 1.35 2.7 2.9 -1.79Dy 3.437 3.458 -0.15 10.082 9.934 0.37 0.048 0.052 -2.00Er 2.096 2.142 -0.54 6.335 6.288 0.19 0.036 0.034 1.43Eu 1.127 1.138 -0.24 3.174 3.114 0.48 0.0122 0.0113 1.91Ga 15.26 15.16 0.16 19.38 19.15 0.30 0.28 0.27 0.91Gd 3.376 3.384 -0.06 9.834 9.56 0.71 0.045 0.043 1.14Hf 1.77 1.77 0.00 10.19 10.23 -0.10 0.14 0.03 32.35Ho 0.71 0.71 0.00 2.093 2.052 0.49 0.0117 0.0118 -0.21In 0.054 0.054 0.00 0.09 0.087 0.85 0.0018 0.0007 22.00La 8.63 8.73 -0.29 41.05 39.37 1.04 0.37 0.4 -1.95Li 6.1 6.1 0.00 4.1 4 0.62 0.4 0.5 -5.56Lu 0.31 0.314 -0.32 0.995 1.006 -0.27 0.0077 0.0075 0.66Mo 0.73 0.69 1.41 0.88 0.82 1.76 1.55 1.37 3.08Nb 3.312 3.315 -0.02 25.375 25.435 -0.06 0.049 0.042 3.85Nd 12.23 11.98 0.52 46.92 45.55 0.74 0.24 0.28 -3.85Ni 30.8 30.7 0.08 1.6 0.6 22.73 1.6 1 11.54Pb 3.4 3.4 0.00 10.5 10.5 0.00 0.6 0.5 4.55Pr 2.647 2.613 0.32 11.481 10.996 1.08 0.067 0.073 -2.14Rb 8.62 8.42 0.59 190.78 188.84 0.26 0.41 0.38 1.90Sb 0.61 0.57 1.69 0.38 0.43 -3.09 1.12 1.2 -1.72Sc 35.1 33.9 0.87 8.8 8.7 0.29 1.1 0.5 18.75Sm 3.176 3.206 -0.24 10.497 10.136 0.87 0.048 0.052 -2.00Sn 0.75 0.72 1.02 3.43 3.46 -0.22 0.16 0.05 26.19Sr 663 654 0.34 28.7 28.1 0.53 3.9 27.2 -37.46Ta 0.191 0.19 0.13 1.593 1.62 -0.42 0.023 -0.01 126.92Tb 0.543 0.538 0.23 1.601 1.565 0.57 0.0072 0.0075 -1.02Th 1.529 1.541 -0.20 7.278 7.256 0.08 0.035 0.034 0.72Ti 4658 4599 0.32 1838 1830 0.11 13 11 4.17Tl 0.041 0.042 -0.60 1.044 1.038 0.14 0.005 0.003 12.50Tm 0.312 0.309 0.24 0.975 0.962 0.34 0.0062 0.006 0.82U 1.025 1.026 -0.02 2.585 2.581 0.04 0.414 0.426 -0.71V 260.1 254.4 0.55 2.3 2 3.49 8.4 8.6 -0.59W 0.29 0.29 0.00 1.31 1.27 0.78 1.32 1.37 -0.93Y 19.39 19.28 0.14 56.34 54.89 0.65 0.33 0.35 -1.47Yb 2.033 2.047 -0.17 6.545 6.541 0.02 0.046 0.048 -1.06Zn 80 80 0.00 83 80 0.92 7 6 3.85Zr 68 67 0.37 455 450 0.28 6 1 35.71Sample names followed by an asterix are duplicate samplesRD = relative difference = |(A-A*)/(A+A*)|/2.266Table A2.4. Results for duplicate samples analyzed by XRF for major elements in this study and assessment of precision.Sample 05M-326 05M-326* %RD 05M-328 05M-328* %RD 05M-383 05M-383* %RDMajor elements (wt. %)Al2O3 18.32 18.26 0.08 17.57 17.54 0.04 13.02 12.73 0.56CaO 6.64 6.66 -0.08 6.89 6.96 -0.25 1.08 1.08 0.00Fe2O3 8.32 8.33 -0.03 7.9 7.99 -0.28 2.15 2.1 0.59K2O 1.22 1.21 0.21 0.88 0.87 0.29 2.43 2.4 0.31LOI 2.02 2.34 -3.67 6.92 6.93 -0.04 1.44 1.46 -0.34MgO 4.71 4.81 -0.53 2.96 2.99 -0.25 0.6 0.61 -0.41MnO 0.14 0.14 0.00 0.17 0.18 -1.43 0.04 0.04 0.00Na2O 4.85 4.78 0.36 6.09 6.13 -0.16 4.63 4.58 0.27P2O5 0.22 0.23 -1.11 0.2 0.2 0.00 0.11 0.11 0.00SiO2 53.16 53.2 -0.02 49.08 49.25 -0.09 75.23 73.69 0.52TiO2 0.7 0.69 0.36 0.7 0.69 0.36 0.41 0.43 -1.19Total 100.3 100.64 -0.08 99.36 99.73 -0.09 101.13 99.23 0.47Sample 05M-403 05M-403* %RD 07TR045A 07TR045A* %RD 07TR024A 07TR024A* %RDMajor elements (wt. %)Al2O3 16.05 16.05 0.00 16.79 16.85 -0.09 5.06 5.04 0.10CaO 1.93 1.95 -0.26 12.77 12.73 0.08 0.81 0.82 -0.31Fe2O3 10.6 10.61 -0.02 9.78 9.77 0.03 3.25 3.29 -0.31K2O 1.3 1.33 -0.57 1.01 1.02 -0.25 1.3 1.31 -0.19LOI 3.71 3.71 0.00 6.03 6.25 -0.90 1.99 2.04 -0.62MgO 3.19 3.17 0.16 2.61 2.59 0.19 0.89 0.91 -0.56MnO 0.06 0.06 0.00 0.19 0.19 0.00 0.86 0.87 -0.29Na2O 1.78 1.83 -0.69 2.37 2.38 -0.11 0.71 0.73 -0.69P2O5 0.85 0.86 -0.29 0.51 0.52 -0.49 0.12 0.12 0.00SiO2 59.45 59.81 -0.15 47.3 47.43 -0.07 85.98 85.95 0.01TiO2 0.81 0.81 0.00 1.1 1.1 0.00 0.35 0.34 0.72Total 99.73 100.19 -0.12 100.47 100.83 -0.09 101.32 101.41 -0.02Sample 09M307 09M307* %RD 09TR127 09TR127* %RD 08TR027 08TR027* %RDMajor elements (wt. %)Al2O3 15.09 15.21 -0.20 3.45 3.47 -0.14 14.92 14.95 -0.05CaO 1.92 1.95 -0.39 0.05 0.04 5.56 4.76 4.76 0.00Fe2O3 5.01 5.03 -0.10 2.1 2.1 0.00 9.57 9.53 0.10K2O 2.15 2.17 -0.23 0.96 0.97 -0.26 0.19 0.19 0.00LOI 2.31 2.31 0.00 1.02 1.14 -2.78 5.92 5.93 -0.04MgO 2.68 2.69 -0.09 0.23 0.23 0.00 6.51 6.55 -0.15MnO 0.07 0.07 0.00 0.01 0.01 0.00 0.14 0.14 0.00Na2O 3.38 3.32 0.45 0.01 -0.08 -64.29 4.99 4.98 0.05P2O5 0.14 0.14 0.00 0.02 0.02 0.00 0.33 0.33 0.00SiO2 66.48 67 -0.19 92.68 93.12 -0.12 50.56 50.79 -0.11TiO2 0.6 0.59 0.42 0.17 0.17 0.00 2.03 2.01 0.25Total 99.83 100.48 -0.16 100.62 101.19 -0.14 99.92 100.17 -0.06Sample names followed by an asterix are duplicate samplesRD = relative difference = |(A-A*)/(A+A*)|/2.267Table A2.4. (continued)Sample 08TR114 08TR114* %RD 09TR048 09TR048* %RD 11TRDR006 11TRDR006* %RDMajor elements (wt. %)Al2O3 12.51 12.42 0.18 13.14 13.17 -0.06 1.08 1.1 -0.46CaO 0.11 0.12 -2.17 1.28 1.3 -0.39 0.11 0.11 0.00Fe2O3 5.43 5.46 -0.14 1.25 1.27 -0.40 3.95 3.98 -0.19K2O 2.8 2.8 0.00 0.31 0.32 -0.79 0.21 0.22 -1.16LOI 2.53 2.54 -0.10 1.86 1.86 0.00 0.58 0.58 0.00MgO 1.26 1.26 0.00 1.15 1.17 -0.43 0.19 0.19 0.00MnO 0.05 0.05 0.00 0.01 0.01 0.00 0.01 0.01 0.00Na2O 0.76 0.93 -5.03 4.71 4.69 0.11 0.01 -0.08 -64.29P2O5 0.05 0.05 0.00 0.05 0.05 0.00 0.01 0.01 0.00SiO2 74.89 74.89 0.00 77.05 76.81 0.08 94.29 94.34 -0.01TiO2 0.2 0.2 0.00 0.23 0.23 0.00 0.01 0 50.00Total 100.58 100.73 -0.04 101.05 100.88 0.04 100.36 100.46 -0.02Sample names followed by an asterix are duplicate samplesRD = relative difference = |(A-A*)/(A+A*)|/2.268Table 2.5. Results for duplicate samples analyzed by XRF for trace elements in this study and assessment of precision.Sample 05M-322 05M-322* %RD 05M-356 05M-356* %RD 05M-378 05M-378* %RDTrace elements (ppm)Nb 2 2 0.00 7 7 0.00 2 2 0.00Y 16 16 0.00 48 48 0.00 16 15 1.61Zr 64 64 0.00 239 239 0.00 71 70 0.35Sample 05M-398b 05M-398b* %RD 07TR064A 07TR064A* %RD 07TR011B 07TR011B* %RDTrace elements (ppm)Nb 8 8 0.00 3 2 10.00 2 2 0.00Y 24 25 -1.02 17 16 1.52 18 18 0.00Zr 210 211 -0.12 49 49 0.00 49 49 0.00Sample 08TR015 08TR015* %RD 08TR057 08TR057* %RD 08TR107 08TR107* %RDTrace elements (ppm)Nb <2 0 4 4 0.00 3 4 -7.14Y 1 1 0.00 13 12 2.00 10 10 0.00Zr 2 1 16.67 106 105 0.24 99 96 0.77Sample 09TR044 09TR044* %RD 09M306c 09M306c* %RD 09TR127 09TR127* %RDTrace elements (ppm)Nb <2 1 11 10 2.38 4 4 0.00Y 18 17 1.43 11 12 -2.17 7 7 0.00Zr 54 55 -0.46 88 87 0.29 51 51 0.00Sample 11TRDR008 11TRDR008* %RDTrace elements (ppm)Nb <2 0Y 2 2 0.00Zr 3 3 0.00Sample names followed by an asterix are duplicate samplesRD = relative difference = |(A-A*)/(A+A*)|/2.269Appendix 3: Lead isotopes 270References for the modern day lead isotopic composition of Pacific Ocean mid-ocean ridge basalt used in Figures 5.4, 5.5 and 5.6: Note: This is not a separate references section. These references are also included in the main references section of the thesis Bach, W., Hegner, E., Erzinger, J., and Satir, M., 1994, Chemical and isotopic variations along the superfast spreading East Pacific Rise from 6 degree to 30 degrees S: Contribution to Mineralogy and Petrology, v. 116, p. 365 - 380. Brevart, O., Dupre, B., and Allegre, C. J., 1981, Metallogenesis at spreading centers: Lead isotope systematics for sulfides, manganese-rich crusts, basalts and sediments from the Cyamex and Alvin areas (East Pacific Rise): Economic Geology, v. 76, p. 1205 - 1210. Castillo, P. R., Natland, J. H., Niu, Y., and Lonsdale, P. F., 1998, Sr, Nd, and Pb isotopic variation along the Pacific-Antarctic risecrest, 53-57 degree S: Implications for the composition and dynamics of the South Pacific upper mantle: Earth and Planetary Science Letters, v. 154, p. 109 - 125. Church, S. E., and Tatsumoto, M., 1975, Lead isotope relations in oceanic ridge basalts from the Juan de Fuca-Gorda Ridge area, NE Pacific Ocean: Contribution to Mineralogy and Petrology, v. 53, p. 253-279. Cohen, R. S., Evenson, N. M., Hamilton, P. J., and O'Nions, R. K., 1980, U-Pb, Sm-Nd, and Rb-Sr systematics of mid-ocean ridge basalt glasses: Nature, v. 283, p. 149 - 153. Cohen, R. S., and O'Nions, R. K., 1982, The lead, neodymium and strontium isotopic structure of ocean ridge basalts: Journal of Petrology, v. 23, p. 299-324. Davis, A. S., Clague, D. A., and White, W. M., 1998, Geochemistry of basalt from Escanaba Trough: Evidence for sediment contamination: Journal of Petrology, v. 39, p. 841 - 858. Davis, A. S., Clague, D. A., Cousens, B. L., Keaten, R., and Paduan, J. B., 2008, Geochemistry of basalt from the North Gorda segment of the Gorda Ridge: Evolution toward ultraslow spreading ridge lavas due to decreasing magma supply: Geochemistry, Geophysics, Geosystems, v. 9. Goss, A. R., Perfit, M. R., Ridley, W. I., Rubin, K. H., Kamenov, G. D., Soule, S. A., Fundis, A., and Fornari, D. J., 2010, Geochemistry of lavas from the 2005-2006 eruption at the East Pacific Rise, 9°46′N–9°56′N: Implications for ridge crest plumbing and decadal changes in magma chamber compositions: Geochemistry, Geophysics, Geosystems, v. 11. Hamelin, B., Dupre, B., and Allegre, C. J., 1984, Lead-strontium isotopic variations along the East Pacific Rise and the Mid-Atlantic Ridge: A comparative study: Earth and Planetary Science Letters, v. 67, no. 340-350. Harpp, K. S., 1995, Geochemical variations in a single basaltic flow at 9 deg 30 N on the East Pacific rise: Proceedings of the Ocean Drilling Program, Scientific Results, v. 142, p. 9-22. Hegner, E., and Tatsumoto, M., 1987, Pb, Sr, and Nd isotopes in basalts and sulfides from the Juan de Fuca Ridge: Journal of Geophysical Research, v. 92, p. 11380 - 11386. 271-, 1989, Pb, Sr, and Nd isotopes in seamount basalts from the Juan de Fuca Ridge and Kodiak-Bowie seamount chain, Northeast Pacific: Journal of Geophysical Research, v. 94, p. 17839 - 17846. Mahoney, J. J., Sinton, J. M., Kurz, M. D., MacDougall, J. D., Spencer, K. J., and Lugmair, G. W., 1993, Isotope and trace element characteristics of a super-fast spreading ridge: East Pacific Rise 13-23 degree S: Earth and Planetary Science Letters, v. 121, p. 171-191. Newsom, H. E., White, W. M., Jochum, K. P., and Hoffmann, A. W., 1986, Siderophile and chalcophile element abundances in oceanic basalts, Pb isotope evolution and growth of the earth's core: Earth and Planetary Science Letters, v. 80, p. 299-313 Niu, Y., Waggoner, D. G., Sinton, J. M., and Mahoney, J. J., 1996, Mantle source heterogeneity and melting processes beneath seafloor spreading centres: the East Pacific Rise, 18o-19o S: Journal of Geophysical Research, v. 101, no. 12, p. 27711-27733. Pollock, M. A., Klein, E. M., Karson, J. A., and Coleman, D. S., 2009, Compositions of dikes and lavas from the Pito Deep rift: Implications for crustal accretion at superfast spreading centers: Journal of Geophysical Research, v. 114. Prinzhofer, A., Lewin, E., and Allègre, C. J., 1989, Stochastic melting of the marble cake mantle: evidence from local study on the East Pacific Rise at 12o50' N: Earth and Planetary Science Letters, v. 92, p. 189-206. Regelous, M., Niu, Y., Wendt, I. J., Batiza, R., Greig, A., and Collerson, K. D., 1999, Variations in the geochemistry of magmatism on the East Pacific rise at 10 Deg 30 N since 800 Ka: Earth and Planetary Science Letters, v. 168, p. 45-63. Sims, K. W. W., Goldstein, S. J., J., B.-T., Donnellan, N. C. B., Perfit, M. R., Kelemen, P., Fornari, D. J., Michael, P. J., Murrell, M. T., Hart, S. R., DePaolo, D. J., Layne, G., Ball, L., Jull, M., and Bender, J. F., 2002, Chemical and isotopic constraints on the generation and transport of magma beneath the East Pacific Rise: Geochemica et Cosmochimica Acta, v. 66, p. 3481 - 3504. Sims, K. W. W., Blichert-Toft, J., Fornari, D. J., Perfit, M. R., Goldstein, S. L., Johnson, P., DePaolo, D. J., HARt, S. R., Murrell, M. T., Michael, P. J., Layne, G., and Ball, L., 2003, Aberrant youth: Chemical and isotopic constraints on the orign of off-axis lavas from the East Pacific Rise, 9-10 deg N: Geochemistry, Geophysics, Geosystems, v. 4. Sun, S. S., 1980, Lead isotope studies of young volcanic rocks from mid-ocean ridges, ocean islands and island arcs: Philosophical Transactions of the Royal Society of London, v. A297, p. 409-445. Tatsumoto, M., 1966, Genetic relations of oceanic basalts as indicated by lead isotopes: Science, v. 153, p. 1094 - 1101. -, 1978, Isotopic composition of lead in oceanic basalt and its implication to mantle evolution: Earth and Planetary Science Letters, v. 38, p. 63-87 Vidal, P., and Clauer, N., 1981, Pb and Sr isotopic systematics of some basalts and sulfides from the East Pacific Rise at 21 N (project RITA): Earth and Planetary Science Letters, v. 55, p. 237-246. Wanless, V. D., Perfit, M. R., Ridley, W. I., and Klein, E. M., 2010, Dacite petrogenesis on mid-ocean ridges: Evidence for oceanic crustal melting and assimilation: 51, p. 2377-2410. 272Appendix 4: Fieldwork articles 273Geological Setting of Volcanogenic Massive Sulphide Occurrences in theMiddle Paleozoic Sicker Group of the Southeastern Cowichan Lake Uplift(NTS 092B/13), Southern Vancouver Island1by T. Ruks2 and J.K. Mortensen2KEYWORDS: Sicker Group, Pa leo zoic, Van cou ver Is land,Cowichan Lake up lift, VMS de posit, stra tig ra phy, U-Pbzir con geo chron ol ogy, lithogeochemistryINTRODUCTIONVolcanogenic strata of the mid-Pa leo zoic SickerGroup on Van cou ver Is land (Fig 1) host the world-classMyra Falls volcanogenic mas sive sul phide (VMS) de posit(com bined pro duc tion and proven and prob a ble re serves inex cess of 30 mil lion tonnes of Zn-Cu-(Au-Ag) ore), as wellas nu mer ous other VMS de pos its and oc cur rences, es pe -cially in the Big Sicker Moun tain area in the south east ernpart of the Cowichan Lake up lift (Fig 1). Three of these de -pos its, the Lenora, Tyee and Rich ard III (MINFILE oc cur -rences 092B 001, 002, 003) have seen lim ited his tor i calpro duc tion, and the Lara de posit (MINFILE oc cur rence092B 129), far ther to the north west, also con tains a sig nif i -cant drill-in di cated re source. Geo log i cal map ping (Masseyand Fri day, 1987) sug gests that the Big Sicker Moun tainarea is un der lain mainly by de formed mafic to fel sic vol ca -nic and volcaniclastic rocks of the Nitinat and McLaughlinRidge for ma tions and high level in tru sions of theSaltspring in tru sive suite, as well as abun dant gabbroicdikes and sills of the Tri as sic Mount Hall gab bro. Log gingac tiv ity in the Big Sicker Moun tain area over the past de -cade has pro vided abun dant new out crops and prompted are-ex am i na tion of the geo log i cal set ting of VMS min er al -iza tion and of the po ten tial for new dis cov er ies in this area.This re port pres ents a pre lim i nary ver sion of a re vised geo -log i cal map of the Big Sicker Moun tain area, as well as newlithogeochemical and U-Pb zir con geo chron ol ogy re sultsthat bear on the geo log i cal set ting of VMS min er al iza tionin the south east ern Cowichan Lake uplift, as well as thepotential for new discoveries in the area.Re con nais sance sam pling for lithogeochemistry, U-Pb zir con dat ing and Pb iso to pic stud ies in the Big SickerMoun tain area was car ried out in 2005 (Mortensen, 2005),and a to tal of two weeks of geo log i cal map ping was done inOctober 2006.REGIONAL GEOLOGY OF THE SICKERGROUPThe mid-Pa leo zoic Sicker Group on south ern and cen -tral Van cou ver Is land rep re sents the stratigraphically low -est por tion of the Wrangellia Terrane. Equiv a lents of theSicker Group are not pres ent else where in Wrangellia far -ther to the north in north west ern Brit ish Co lum bia, south -west ern Yu kon and south ern Alaska, where the old est rockunits are the Skolai Group, which is no older than Penn syl -va nian (e.g., Katvala, 2006). This and other dif fer ences be -tween the Wrangellian stra tig ra phy on Van cou ver Is landand that in more north erly ex po sures em pha sizes the lack of un der stand ing re gard ing much of Wrangellia (e.g.,Katvala, 2006) and the need for stud ies such as this. TheCowichan Lake up lift on Van cou ver Is land and ad ja centpor tions of the Gulf Is lands, which is the fo cus of this study, is the larg est of four struc tural up lifts that ex pose the Sickerand overlying late Paleozoic Buttle Lake groups (Fig 1).Pre vi ous de tailed stud ies of the Sicker Group have fo -cused mainly on the strati graphic set ting of VMS min er al -iza tion at the Myra Falls de pos its in the Buttle Lake up lift(Fig 1; e.g., Juras, 1987; Barrett and Sherlock, 1996). Re -gional map ping of the Cowichan Lake up lift by Massey and Fri day (1987, 1989) and Yorath et al. (1999) led to an in ter -Geo log i cal Field work 2006, Pa per 2007-1 3811 Geoscience BC con tri bu tion GBC0352 Mineral Deposit Research Unit, Department of Earth andOcean Sciences, University of British Columbia, VancouverBC V6T 1Z4 (tyler_ruks@hotmail.com)This publication is also available, free of charge, as colourdigital files in Adobe Acrobat® PDF format from the BCMinistry of Energy, Mines and Petroleum Resources website athttp://www.em.gov.bc.ca/Mining/Geolsurv/Publications/catalog/cat_fldwk.htmkm0 25 50 VictoriaTofinoPortAlberniNanaimoSidneyTexadaIslandCowichan LkButtleLakeCampbell RiverCourtenayButtle LakeupliftBedingfieldupliftCowichan LakeupliftSaltspringIslandMyra Falls depositMt Sicker andLara depositsNanoose upliftButtle Lake GroupSicker Group50°49°126° 124°:this studyFig ure 1. Dis tri bu tion of Pa leo zoic strata of the Sicker and ButtleLake groups on Van cou ver Is land and the Gulf Is lands.274preted strati graphic frame work that may be ap pli ca ble tothe en tire Sicker Group (Fig. 2). This strati graphic frame -work, how ever, is based on map ping in only one of the fourmain up lifts of Sicker Group rocks, and is sup ported by avery lim ited amount of biostratigraphic and iso to pic agedata (e.g., Brandon et al., 1986). Ma jor along and across-strike fa cies changes and geo chem i cal vari a tions are to beex pected in sub ma rine vol ca nic se quences such as the onethat forms the Sicker Group; hence, the re gional ap pli ca bil -ity of the pro posed strati graphic frame work of Yorath et al.(1999) must be tested with de tailed map ping andlithogeochemical and U-Pb dat ing stud ies. This is crit i calfor re gional ex plo ra tion for VMS de pos its within theSicker Group. For ex am ple, the ques tion of whether VMSde pos its and oc cur rences in the Cowichan Lake up lift areall of the same age, and how their hostrocks are di rectly cor -re la tive with those that host the Myra Falls de posit, are ofob vi ous im por tance.The Sicker Group within the Cowichan Lake up lift ispres ently in ter preted to rep re sent three dis tinct and re gion -ally mappable vol ca nic and volcaniclastic as sem blages that to gether are thought to re cord the evo lu tion of an oce anicmag matic arc (Massey, 1995a, b, c; Yorath et al., 1999).The Duck Lake For ma tion, at the base of the sec tion, con -sists of dom i nantly tholeiitic ba salt, which passes up wardinto calcalkaline lava. The low er most Duck Lake For ma -tion yields mainly nor mal mid-ocean-ridge ba salt (N-MORB) geo chem i cal sig na tures (Massey, 1995a) and is in -ter preted to rep re sent the oce anic crust base ment on whichthe Sicker arc was built. The up per por tions of the DuckLake For ma tion yield tholeiitic to calcalkaline com po si -tions and may rep re sent prim i tive arc rocks. The Duck Lake For ma tion is over lain by the Nitinat For ma tion, whichcom prises mafic, sub ma rine, vol ca nic and volcaniclasticrocks with dom i nantly calcalkaline com po si tions and traceel e ment sig na tures typ i cal of vol ca nic arc set tings. Theserocks are in ter preted to rep re sent an early stage of arc de -vel op ment. The andesitic to mainly dacitic and rhyoliticMcLaughlin Ridge For ma tion that over lies the Nitinat andhosts the Myra Falls de posit re flects a more evolved stageof arc ac tiv ity. Erup tion of Nitinat vol ca nic andvolcaniclastic rocks ap pears to have oc curred from sev eralwidely scat tered cen tres, whereas the McLaughlin RidgeFor ma tion within the Cowichan Lake up lift is thought torep re sent erup tion from one or more ma jor vol ca nic ed i -fices. The abun dance of prox i mal fel sic volcaniclasticrocks and the pres ence of vo lu mi nous comagmatic fel sicin tru sions (Saltspring in tru sions) in the Saltspring Is landand Duncan area (Fig 1) in di cates that one of these ma jorvol ca nic cen tres was lo cated in this area. Plant ma te rial andtrace fos sils in di cate that at least a mi nor amount of theMcLaughlin Ridge vol ca nism oc curred in a subaerial set -ting. De po si tion of the over ly ing Fourth Lake For ma tion ofthe Buttle Lake Group fol lowed the ces sa tion of Sicker arcmagmatism, and scarce mafic vol ca nic rocks con tainedwithin the Fourth Lake For ma tion yield en riched tholeiiticrather than the calcalkaline com po si tions that char ac ter izethe McLaughlin Ridge. Massey (1995a) speculated that theButtle Lake Group may represent a marginal-basinassemblage that developed on top of the Sicker arc.Stud ies of the Sicker and Buttle Lake groups on south -ern Saltspring Is land at the south east ern end of theCowichan Lake up lift by Sluggett (2003) and Sluggett andMortensen (2003) pro vided new U-Pb zir con age con -straints on both fel sic vol ca nic rocks of the McLaughlinRidge For ma tion and sev eral bod ies of Saltspring in tru -sions. This work dem on strates that two dis tinct ep i sodes offel sic magmatism oc curred in this por tion of the CowichanLake up lift. One sam ple of fel sic vol ca nic rocks from theMcLaughlin Ridge For ma tion and three sam ples ofSaltspring in tru sions yielded U-Pb ages in the range356.5 to 359.1 Ma. A some what older U-Pb age of369.7 Ma was ob tained from a sep a rate body of theSaltspring in tru sions at Burgoyne Bay on the south westside of Saltspring Is land, in di cat ing that magmatism rep re -sented by the McLaughlin Ridge For ma tion and as so ci atedSaltspring in tru sions oc curred over a time span of at least15 m.y. There is in suf fi cient age con trol avail able at thispoint to de ter mine whether the magmatism was con tin u ousor ep i sodic dur ing this time pe riod. Lithogeochemical datare ported by Sluggett (2003) for sam ples of the McLaughlinRidge and Nitinat for ma tions on Saltspring Is land, to gether with data pre vi ously re ported by Massey (1995a, b, c), pro -vide a geo chem i cal frame work with which to compare thenew results from the Big Sicker Mountain study area.RESULTS OF NEW MAPPING IN THEBIG SICKER MOUNTAIN AREAField GeologyPre lim i nary map ping of an area of Big Sicker Moun -tain cov er ing ap prox i mately 25 km2 was con ducted over 12 days in Oc to ber 2006 (Fig 3). The map ping con cen tratedpri mar ily in the area of the past-pro duc ing Lenora, Rich ardIII and Tyee VMS de pos its, and nearby MINFILE (2006)oc cur rences. Bed rock out crop on Big Sicker Moun tain isgen er ally poor and is mainly re stricted to log ging-road cutsand slashes. As a re sult, con tact lo ca tions be tween ma jorrock types are mostly inferred.The old est rocks in the Big Sicker Moun tain area aremafic vol ca nic rocks as signed to the Nitinat For ma tion(Massey and Fri day, 1987). Dur ing the course of 2006 map -ping, rocks of the Nitinat For ma tion were en coun tered only in a small area along the west ern flanks of Lit tle SickerMoun tain (Fig 3). They con sist of dark green, dom i nantlyaphyric ba salt with abun dant ovoid epidote-quartz al ter -ation patches up to 4 to 5 cm in di am e ter (Fig 4a). Sul phidemin er al iza tion is ob served in one out crop of Nitinat For ma -tion, and con sists of py rite string ers up to 5 cm in widthhosted in a ver ti cally dip ping fault zone ap prox i mately 2 m382 Geoscience BC, Re port 2007-1Fig ure 2. Strati graphic no men cla ture for the Sicker and Buttle Lake groups on Van cou ver Is land.275in width (Fig 4b). This out crop ap pears to have beentrenched for mineral exploration purposes.Rocks of the McLaughlin Ridge For ma tion sitstratigraphically above those of the Nitinat For ma tion(Massey and Fri day, 1987) and con sist of in ter me di atevolcanosedimentary rocks , fe l s ic vol ca n ic andvolcaniclastic rocks, and, to a lesser de gree, mudstone,chert and mag ne tite iron for ma tion. Mafic to in ter me di atevolcanosedimentary rocks are most prev a lent along thenorth ern to north east ern bound ary of the map area. Theserocks con sist of thinly bed ded to lam i nated, dark green,vari ably chlorite, seri cite and sil ica-al tered siltstone to finesand stone, and more mas sive, me dium-grained, feld spar-bear ing sand stone or sandy tuff (Fig 5). Fel sic rocks of theMcLaughlin Ridge For ma tion in clude pre dom i nantlyrhyolitic to dacitic ash, quartz-feld spar crys tal tuff, aphyricflows, quartz-feld spar por phyry and, to a lesser extent, tuff-breccia (Fig 6).Seri cite and quartz al ter ation is com monly very strongin the fel sic vol ca nic rocks. This, to gether with a well-de -vel oped fo li a tion, makes it dif fi cult to dis tin guish be tweenthose that formed from lavas (i.e., a por phyry or flow) ver -sus those that are crys tal-bear ing volcaniclastic rocks (i.e.,a crys tal tuff). Dark grey to black, vari ably gra phiticmudstone has only been ob served lo cally within the vi cin -ity of the main de pos its (Fig 7a). Chert is not abun dant andhas been iden ti fied thus far only in a re stricted area in thenorth ern and south-southwesternmost parts of the studyarea (Fig 7b). In the south west ern part of the field area, lam -i nated chert is as so ci ated with dacitic tuff, jas per and a lo -cal ized magnetite iron formation (Fig 7c).Tri as sic gab bro and diabase in trude rocks of the SickerGroup (Fig 8), are very prev a lent through out the field area(Fig 3), and are of vari able thick ness. Drillhole MTS-81(Wells, 1990), lo cated ap prox i mately 1 km south east of theRich ard III shaft in the vi cin ity of the BC Tel com mu ni ca -tion tow ers, en coun tered a gab bro thick ness of >100 m be -fore in ter sect ing rocks of the Sicker Group at depth. How -ever, the Rich ard III and Tyee shafts are sunk in gab bro, and are as sumed to in ter sect rocks of the Sicker Group at a shal -lower depth, sug gest ing a west ward thin ning of these in tru -sions. The in tru sive tex tures are quite vari able from out -crop to out crop, most likely due to lo cal ized shear ing;how ever, the most com mon li thol ogy is holocrystallinehornblende and plagioclase gab bro (Fig 8), con sist ing ofvari ably chlorite-al tered cu mu lus hornblende pheno crysts,up to 4 mm in size, in a matrix of intercumulus plagioclase.Up per Cre ta ceous rocks of the Nanaimo Group lie un -con form ably on those of the Sicker Group (Massey and Fri -day, 1987) and crop out solely in the south ern most part ofthe field area. How ever, in the field area, the con tact be -tween the Sicker Group and Nanaimo Group marks the po -Geo log i cal Field work 2006, Pa per 2007-1 383Fig ure 3. Pre lim i nary re vised ge ol ogy of the Big Sicker Moun tain area, based on field work con ducted for this study.276si tion of the Fulford fault and as so ci ated splays. In the fieldarea, Nanaimo Group rocks con sist largely of mudstone,shale, arkosic me dium-grained sand stone and boul der con -glom er ate. The lat ter rock type con tains abun dant vol ca nicand gabbroic rock clasts that ap pear to have been de rivedfrom un der ly ing Sicker Group and Triassic gabbro.StructureThe most prom i nent fab ric in the Big Sicker Moun tainarea is, on av er age, east to south east-strik ing with a near-ver ti cal dip, and rep re sents both bed ding and a bed ding-par al lel fo li a tion herein termed S1 (Fig 9a). As men tionedbe fore, due to ex ten sive al ter ation in rocks of theMcLaughlin Ridge For ma tion, it is com monly dif fi cult todif fer en ti ate be tween those that orig i nated as bed dedvolcaniclastic rocks and those that were orig i nally mas siveflows or sills. Hence, some of the fab rics re corded asfoliations may be bed ding mea sure ments. Small-scale(sub-metre wave length), steeply plung ing S and Z-shapedf o l d s d e f o r m t h e p r i m a r y l a y e r i n g i n t h evolcanosedimentary pack age through out the map area andare prob a bly par a sitic folds re lated to a larger F1 struc ture(Fig 9b). Sec ond phase (D2) kink ing of D1 struc tures oc -curs in sev eral lo cal i ties. Third phase (D3) struc tures con -sist of small-scale, shal lowly plung ing folds (2–3 cm wave -length) that were only ob served in one lo cal ity (Fig 9a). The most prom i nent faults in the area are dom i nantly east strik -ing, with near-ver ti cal dips. In one such lo cal ity, shear-sense in di ca tors in faulted dacite tuff of the McLaughlinRidge Formation suggest a strong component of north-side-up motion (Fig 9c).384 Geoscience BC, Re port 2007-1Fig ure 4. In ter me di ate to mafic vol ca nic rocks of the Nitinat For ma -tion: A) aphyric ba saltic an de site with ovoid quartz-epidotepatches; B) py rite-stringer-bear ing fault in ba saltic an de site flow(?); note ham mer for scale in lower cen tral part of photo.Fig ure 5. In ter me di ate volcanosedimentary rocks of theMcLaughlin Ridge For ma tion (?) from the north ern (A) and north -east ern (B) parts of the field area.277MINERALIZATIONSul phide min er al iza tion is wide spread through out thefield area, and con sists mainly of py rite±chal co py ritestring ers and small pods/lenses as so ci ated with ar eas of in -tense seri cite+sil ica al ter ation. Many of these sul phide oc -cur rences are close to MINFILE (2006) oc cur rences, butsome are not. For ex am ple, sev eral zones of sul phide min -er al iza tion, con sist ing of py rite±chal co py rite string ers andpatches up to 15 cm wide, oc cur in si lici fied and sericitizedfel sic vol ca nic rocks (tuff and quartz-feld spar por phyry)ap prox i mately 3 to 3.5 km east, along strike, from theknown deposits (Fig 10).Geo log i cal Field work 2006, Pa per 2007-1 385Fig ure 6. Fel sic rocks of the McLaughlin Ridge For ma tion in cludeA) rhyodacite por phyry, B) heterolithic tuff-brec cia, and C)rhyodacite crys tal tuff.Fig ure 7. Rocks of the McLaughlin Ridge For ma tion: A) lam i natedmudstone interbedded with dacitic tuff; B) lam i nated chert; C) mag -ne tite iron for ma tion that forms a re stricted layer (ap prox i mately0.5–1 m thick) interbedded with lam i nated chert and dacitic to in ter -me di ate (?) tuff.278Also in the north east ern part of the map area (Fig 3),ap prox i mately 1.6 km north east of the Lenora-Tyee de pos -its and ap prox i mately 900 m north east of the Queen BeeMINFILE oc cur rence, abun dant py rite string ers up to 2 to3 cm thick are as so ci ated with zones of in tense sili ci fi ca tion and sericitization of in ter me di ate volcanosedimentaryrocks. These oc cur rences are not doc u mented in MINFILE, and do not show signs of sig nif i cant ex plo ra tion ac tiv ity.Min er al iza tion as so ci ated with the main work ings is bestdoc u mented in the vi cin ity of the Lenora de posit, wherepolymetallic mas sive sul phide min er al iza tion was ac cessed via an adit trending 163o. This adit was ex ca vated in highlysi lici fied and sericitized fel sic vol ca nic rocks with abun -dant si lici fied mudstone and/or chert (Fig 11). Here, sul -phide min er al iza tion con sists of ex ten sive fo li a tion/bed -ding-par al lel py rite±chal co py rite stringers and patches upto 15 cm wide, often associated with malachite staining.Min er al iza tion was not ob served at the Rich ard III andTyee work ings, as the shafts used to ac cess these de pos itsare sunk in gab bro. How ever, this sug gests that the thick -ness of postmineral Tri as sic gab bro in many lo ca tionsthrough out the field area is not sub stan tial enough to ne gate the po ten tial for large VMS deposits.U-PB GEOCHRONOLOGYUra nium-lead dat ing of zir cons by la ser-ab la tion in -duc tively cou pled plasma mass spec trom e try (ICP-MS) isbe ing used to con strain ages of erup tion and/or in tru sion of386 Geoscience BC, Re port 2007-1Fig ure 8. Tri as sic gab bros of the Big Sicker Moun tain area: A)hornblende and plagioclase-bear ing gab bro; B) gab bro cross cut -ting al tered and gos sa nous volcanosedimentary rocks of theMcLaughlin Ridge For ma tionFig ure 9. Struc tural ge ol ogy of the Big Sicker Moun tain area: A)east-strik ing S1 fab ric in dacitic tuff is de formed by F2 kink folds;both of these struc tures are de formed by shal lowly plung ing F3folds; B) steeply plung ing F1 ‘M’ folds in seri cite and sil ica-al teredrhyodacite tuff; C) north-side-up dis place ment in fault zone, in di -cated by drag fold ing in faulted dacitic tuff.279ig ne ous rock units and to con struct a chrono -stratigraphic frame work for magmatism in theSicker Group. This pa per in cludes pre lim i naryU-Pb zir con ages for six vol ca nic units in thesouth east ern Cowichan Lake up lift. Zir conswere re cov ered from sam ples weigh ing ap prox -i mately 10 kg us ing con ven tional crush ing,grind ing, wet shak ing ta ble, heavy liq uids andmag netic meth ods. Se lected grains weremounted in ther mal-set ting ep oxy; the grainmounts were care fully ground down un til the in -te rior of the in di vid ual grains were ex posed. The ground sur faces were then brought to a high pol -ish us ing se quen tially finer di a mond pastes. Thesur faces of the mounts were then washed withdi lute ni tric acid for ten min utes and rinsed withultrapure wa ter. Anal y ses were done in the Pa -cific Cen tre for Iso to pic and Geo chem i cal Re -search (PCIGR) fa cil ity at the Uni ver sity ofBrit ish Co lum bia (UBC), us ing a New Wave™213 nm Nd-YAG la ser cou pled to a ThermoFinnigan™ Element2 high-res o lu tion ICP-MS.Ab la tion took place within a New Wave‘Supercell’ ab la tion cham ber that is de signed toachieve very high ef fi ciency en train ment of aero sols intothe car rier gas. He lium was used as the car rier gas for all ex -per i ments, and gas flow rates, to gether with other pa ram e -ters such as torch po si tion, were op ti mized prior to be gin -ning a se ries of anal y ses. A 25 µm spot with 60% la serpower was used, mak ing line scans rather than spot anal y -ses in or der to avoid within-run el e men tal frac tion. Eachanal y sis con sists of a 7 sec ond back ground mea sure ment(la ser off), fol lowed by an ap prox i mately 28 sec ond dataac qui si tion pe riod with the la ser fir ing. A typ i cal an a lyt i calses sion con sists of four anal y ses of the stan dard zir con, fol -lowed by four anal y ses of un known zir cons, two stan dardanal y ses, four un known anal y ses, etc., and fi nally fourstan dard anal y ses. Data were re duced us ing the GLITTERsoft ware, mar keted by the Geo chem i cal Evo lu tion andMetallogeny of Con ti nents (GEMOC) group at Macquarrie Uni ver sity, which au to mat i cally subtracts back groundmea sure ments, prop a gates all an a lyt i cal er rors and cal cu -lates iso to pic ra tios and ages. Fi nal ages for rel a tivelyyoung (Phanerozoic) zir cons are typ i cally based on aweighted av er age of the cal cu lated 206Pb/238U ages for 10 to20 individual analyses. Final interpretation and plotting ofthe analytical results employed the Isoplot software writtenby K.R. Ludwig.Zir cons re cov ered from all of the Sicker Group vol ca -nic rocks form stubby, subhedral to euhedral pink ish prisms with vague in ter nal growth zon ing but no vis i ble in her itedcores. Ap prox i mately 25 grains were mounted from eachsam ple and 12 to 20 in di vid ual anal y ses were car ried outfor each sam ple. The re sults are plot ted in Fig ure 12, whichshows a com pi la tion of the cal cu lated 206Pb/238U ages forin di vid ual anal y ses with a calculated weighted-averageage.Sam ple 05M-366 is from strongly fo li ated, sparselyquartz-phyric lapilli tuff col lected 5 m north of the Lenoraadit. Six teen in di vid ual anal y ses were done and there iscon sid er able scat ter in the data (Fig 12a). One of the anal y -ses gives a 206Pb/238U age of 403 Ma and is re jected as prob -a bly a xenocrystic grain in cor po rated into the tuff. AGeo log i cal Field work 2006, Pa per 2007-1 387Fig ure 10. Se lected new sul phide oc cur rences: A) 1 to 2% py -rite±chal co py rite string ers (up to 15 cm wide) hosted in quartz-feld -spar por phyry, east ern part of map area; B) strongly sil ica+seri cite-al tered volcanosedimentary rock with up to 3% dis sem i nated andstringer py rite, north east ern part of map area.Fig ure 11. Ge ol ogy of the Lenora adit area. Lithological units in clude A)rhyodacite crys tal tuff (?) with abun dant mal a chite stain ing and py rite+chal co py -rite string ers up to 10 cm in size; B) vari ably sil ica-al tered, black gra phiticmudstone; and C) strongly seri cite+sil ica-al tered tuff (?) with abun dant py ritestring ers.280weighted av er age of the re main ing 15 anal y ses is 369.1±6.5 Ma. Note that the high mean stan dard weighted de vi -ate (MSWD) of 10.7 re flects the large amount of scat ter inthe data. The cal cu lated weighted av er age is con sid ered togive an ap prox i mate age for erup tion of the lapilli tuff unitthat partly hosts the Lenora VMS deposit.Sam ple 05M-393 is a strongly welded quartz and feld -spar-phyric lapilli tuff at the main adit on the Lara prop erty.388 Geoscience BC, Re port 2007-104080120160200240280320360400Sample 05M-369 (felsic lapilli tuff; Hidden Hills subdivision):349.5 ± 5.5 Ma (MSWD = 1.7; probability = 0.068)310330350370390Sample 05M-393 (felsic lapilli tuff, Lara adit):353.7 ± 4.9 Ma (MSWD = 2.3, probability = 0.007)290310330350370390410Sample 05M-394 (massive qfp; C-7 road towards RheinhartLakes): 344.2 ± 5.3 Ma; MSWD = 1.9, probability = 0.022310320330340350360370Sample 05M-356 (felsic tuff; Mt. Sicker road):339.3 ± 4.3 Ma; MSWD = 2.3, probability = 0.003240280320360400440480Sample 05M-389 (pyritic felsic crystal tuff; Sharon occurrence):345.3 ± 8.2 Ma; MSWD = 2.3, probability = 0.003340360380400420Sample 05M-366 (felsic lapilli tuff, Lenora adit):369.1 ± 6.5 Ma; MSWD = 10.7, probability = 0.000A BC DE FFig ure 12. Cal cu lated 206Pb/238U (zir con) ages for fel sic vol ca nic rocks of the Sicker Group col lected from the Cowichan Lake up lift dur ingthe course of this study.281Twelve of a to tal of six teen in di vid ual anal y ses give aweighted av er age 206Pb/238U age of 353.7 ±4.9 Ma (Fig12b), which is in ter preted as the crys tal li za tion age for thisfel sic unit. The four re main ing anal y ses ap pear to re flectmi nor postcrystallization Pb loss.Sam ple 05M-369 is a mod er ately to strongly fo li ated,py ritic, quartz-phyric fel sic lapilli tuff from a road ex po -sure in the Hid den Hills sub di vi sion, im me di ately east ofthe study area. Eleven of twelve in di vid ual anal y ses(Fig 12c) give a weighted av er age 206Pb/238U age of 349.5±5.5 Ma, which is in ter preted as the crys tal li za tion age forthis unit. One anal y sis gives a much youn ger 206Pb/238U ageand is in ter preted to have suf fered postcrystallization Pbloss.Sam ple 05M-389 is a strongly fo li ated, py ritic quartz-mus co vite schist with scat tered quartz eyes from theSharon oc cur rence that is in ter preted to be a de formedquartz-phyric crys tal tuff. A weighted av er age 206Pb/238Uage of 345.3 ±8.2 Ma for this sam ple, based on six teen in di -vid ual anal y ses (no re jects; Fig 12d), is in ter preted as thecrys tal li za tion age of the hostrocks for the Sharonmineralization.Sam ple 05M-394 is a mas sive quartz-feld spar por -phyry ex posed along the C-7 road to wards Rheinhart Lake,north west of the Lara de posit. A weighted av er age206Pb/238U age of 344.2 ±5.3 Ma was ob tained for this sam -ple, based on six teen in di vid ual anal y ses (no re jects;Fig 12e), and is in ter preted as the crys tal li za tion age for theporphyry body.Sam ple 05M-356 was col lected from a roadcut on thesouth side of the Mount Sicker road. It is a weakly tostrongly fo li ated, quartz-phyric lapilli tuff. Six teen in di vid -ual anal y ses (no re jects) give a weighted av er age 206Pb/238U age of 339.3 ±4.3 Ma, which is in ter preted as the crys tal li -za tion age of this unit.The range of ages ob tained for fel sic ex tru sive rocksand high-level fel sic in tru sions in this part of the CowichanLake up lift was un ex pected. Only one other well-con -strained age is pres ently avail able for any of the SickerGroup units in the Big Sicker Moun tain area: a U-Pb zir conage of 362 ±2 Ma re ported by Parrish and McNicoll (1992)for a quartz-feld spar por phyry body of the Saltspring in tru -sive suite along the Is land High way on the east side of BigSicker Moun tain. The pre lim i nary age of 369.1 ±6.5 Ma re -ported here for fel sic lapilli tuff that partly hosts the LenoraVMS orebody (sam ple 05M-366 above) is within un cer -tainty of both the por phyry body dated by Parrish andMcNicoll (1992) and a sep a rate body of Saltspring in tru -sions in the Burgoyne Bay area on west ern Saltspring Is -land that was dated at 369.7 ±1.9 Ma (Sluggett, 2003;Sluggett and Mortensen, work in prog ress). Two other sam -ples of Saltspring in tru sions from near Ers kine Point andLake Stowell on Saltspring Is land, which were dated bySluggett (2003) and Sluggett and Mortensen (work in prog -ress), gave U-Pb ages of 359.1 ±1.4 and 356.5 ±1.7 Ma, re -spec tively, and a sam ple of fel sic tuff of the McLaughlinRidge For ma tion near Isabella Point in the south west partof Saltspring Is land gave a U-Pb age of 354.1 ±1.2 Ma.Pre vi ous work had there fore al ready dem on strated asig nif i cant age range for McLaughlin Ridge and Saltspringintrusive suite magmatism. The new data from this study,how ever, in di cate that fel sic magmatism lasted from ca.370 Ma un til at least as young as 339 Ma. More im por tantly, these data sug gest that VMS min er al iza tion of at least twosep a rate ages is pres ent in the south east ern part of theCowichan Lake up lift. Min er al iza tion at the Lenora de posit is hosted by fel sic tuff (and interlayered sed i mentary rocks) with a depositional age of ca. 369 Ma, whereas hostrocksfor the Lara de posit give an age of 353.7 Ma. Fel sic tuff thathosts bands of stratabound, pos si bly syngenetic sul phidemin erals at the Sharon oc cur rence and in the vi cin ity of theHid den Hills sub di vi sion on the east side of Big SickerMoun tain are even youn ger, at 345.3 and 349.5 Ma, re spec -tively. There are as yet no re li able crys tal li za tion ages forfel sic vol ca nic rocks that host VMS min er al iza tion at theMyra Falls de posit in the Buttle Lake up lift. Sam pling ofthe Myra Falls hostrocks for U-Pb dat ing to fa cil i tate com -par i son with the ages of VMS min er al iza tion in the south -east ern Cowichan Lake up lift is planned for the fall of2006.LITHOGEOCHEMISTRY OF IGNEOUSROCKS IN THE BIG SICKER MOUNTAINAREASix teen sam ples of Sicker Group ig ne ous rocks fromthe south east ern part of the Cowichan Lake up lift (fromRheinhart Lake on the north west to south ern Saltspring Is -land on the south east) were an a lyzed for ma jor, trace andrare earth el e ments in or der to better char ac ter ize the pet ro -chem is try of the var i ous ig ne ous units in the area. Theseanal y ses were con ducted at ALS Chemex, us ing a com bi -na tion of x-ray flu o res cence (XRF) and ICP-MS meth ods.Data are pre sented in a se ries of plots in Fig ure 13, alongwith data from an ad di tional 11 sam ples of Sicker Grouprock units on Saltspring Is land that were re ported bySluggett (2003). The two data sets com pare very closelyand the fol low ing observations are based on the combineddataset.On a Zr/TiO2 ver sus Nb/Y plot (Fig 13a; Winchesterand Floyd, 1977), vol ca nic and volcaniclastic rocks of theNitinat For ma tion fall in the subalkaline ba salt and ba saltican de site fields. On a V ver sus Ti plot (Fig 13b; Shervais,1982), the sam ples lie in the is land arc tholeiite field. Sam -ples of the Saltspring in tru sive suite plot as subalkaline andrhyodacite/dacite to rhy o lite in com po si tion on a Zr/TiO2ver sus Nb/Y plot (Fig 13a; Winchester and Floyd, 1977),and are of vol ca nic arc af fin ity on a Nb ver sus Y tec tonicdis crim i na tion di a gram (Fig 13c; Pearce et al., 1984). On aZr/TiO2 ver sus Nb/Y plot (Fig 13a; Winchester and Floyd,1977), McLaughlin Ridge sam ples span the subalkalinerhyodacite/dacite to rhy o lite compositional fields (ex ceptfor one andesitic sam ple), and are of vol ca nic arc af fin ity on a Nb ver sus Y tec tonic dis crim i na tion di a gram (Fig 13c;Pearce et al., 1984). A sam ple of dark green, chlorite-richvolcanosedimentary rock from the north end of the maparea (05M-355) plots as subalkaline an de site on a Zr/TiO2ver sus Nb/Y di a gram (Fig 13a; Winchester and Floyd,1977), and as an is land arc tholeiite on a V ver sus Ti di a -gram (Fig 13b; Shervais, 1982). A prim i tive man tle nor -mal ized multi-el e ment di a gram (Fig 13d; Sun andMcDonough, 1989) for all sam ples shows weak to mod er -ate light rare earth el e ment (LREE) en rich ment and neg a -tive Nb and Ti anomalies, typical for rocks generated in avolcanic arc setting.Al though sam ples from the McLaughlin Ridge For ma -tion par tially over lap with the roughly co eval and prob a blycomagmatic Saltspring in tru sive suite (Fig 13), they showGeo log i cal Field work 2006, Pa per 2007-1 389282con sid er ably more scat ter and in clude one andesitic out lier. This out lier may be the re sult of a volcaniclastic or i gin in -volv ing a mafic epiclastic com po nent re worked from un -der ly ing Nitinat For ma tion, or a pulse of in ter me di ate vol -ca nism in the McLaughlin Ridge For ma tion. This sce narioalso ap plies to the in ter me di ate tuff col lected from the north end of the prop erty (05M-355). Al though this unit lacks theclinopyroxene pheno crysts that are char ac ter is tic of Nitinat For ma tion mafic units, the com po si tion of this sin gle sam -ple is very sim i lar to that of Nitinat units. If this unit is ac tu -ally Nitinat rather than McLaughlin Ridge For ma tion, itwould help con strain where the lo cal base of theMcLaughlin Ridge is and hence pro vide a use fulstratigraphic marker in the vicinity of the known VMSdeposits.VOLCANOGENIC MASSIVE SULPHIDEMINERALIZATION IN THE BIG SICKERMOUNTAIN AREAThe south east ern por tion of the Cowichan Lake up liftis one of two ex po sures of the Sicker Group wherevolcanogenic mas sive sul phide (VMS) min er al iza tion isknown to oc cur, the other be ing the Myra Falls area in theButtle Lake up lift (Fig 1). Most known VMS oc cur rencesin the Sicker Group are of the Kuroko type (or ‘bi modal fel -sic type’, as de fined by Frank lin et al., 2005) and are hostedby fel sic vol ca nic and volcaniclastic rocks of theMcLaughlin Ridge For ma tion or equiv a lents. How ever,ex am ples of manganiferous and/or py ritic chert ho ri zonsthat may be exhalitive in or i gin are also lo cally pres ent in390 Geoscience BC, Re port 2007-1LegendMcLaughlin Ridge Fm felsic volcanic and volcanic rocksMcLaughlin Ridge Fm (?) Intermediate tuffSaltspring Island Intrusive SuiteNitinat Fm volcanic and volcaniclastic rocks.11101001000Th Nb La Ce Nd Zr Sm Eu Gd Ti Dy Y Er Yb LuDRock/Primitive MantleA.01 .1 1 10.001.01.11Zr/TiO2Nb/YSubAlkaline BasaltAndesite/BasaltAndesiteRhyodacite/DaciteRhyoliteAlk-BasTrachyAndCom/PantPhonoliteTrachyteBsn/Nph1 10 100 10001101001000NbYsyn-collisionalvolcnaic arcwithin plateocean ridgeCwithin plate/anomalous ocean ridge0 5 10 15 20 250100200300400500600VTi/1000Low-Ti IATBON IATMORBBAB MORBOIBTi/V = 10BTi/V = 20Ti/V = 50Ti/V = 100Fig ure 13. Lithogeochemical plots for Sicker Group ig ne ous rock units in the south east ern part of the Cowichan Lake up lift. Solid sym bolsare from this study; open sym bols are from Sluggett (2003). Pet ro chem i cal fields de fined from the fol low ing sources: A) Zr/TiO2 ver sus Nb/Y plot (Winchester and Floyd, 1977); B) V ver sus Ti (Shervais, 1982); C) Nb ver sus Y tec tonic dis crim i na tion di a gram (Pearce et al., 1984); D)multi-el e ment di a gram nor mal ized to prim i tive man tle (Sun and McDonough, 1989). Ab bre vi a tions: BAB, back-arc ba sin; IAT, is land-arctholeiite; BON, boninite; MORB, mid-ocean-ridge ba salt; OIB, ocean-is land ba salt.283the up per Duck Lake For ma tion and the low er most FourthLake For ma tion (e.g., Massey and Fri day, 1989; thisstudy). Three VMS de pos its have been mined his tor i callyin the Big Sicker Moun tain area: the Lenora, Tyee andRich ard III (MINFILE oc cur rences 092B 001–003, re spec -tively; Fig 1). Pro duc tion data re ported in the MINFILE(2006) min eral in ven tory in di cate that, be tween 1898 and1909, a to tal of 229 221 t of ore were mined from these three de pos its, with re cov ered grades of 4.0% Cu, 4.8 g/t Au and100 g/t Ag. The three de pos its were mined as a sin gle op er -a tion (the Twin J mine) be tween 1942 and 1952; dur ing thatpe riod, a to tal of 48 082 t of ore with a re cov ered grade of7.6% Cu, 3.4% Pb, 1.0 g/t Au and 41.7 g/t Au were mined.Ex plo ra tion of the Big Sicker Moun tain area has been car -ried out spo rad i cally since the early 1960s. The most re centes ti mate of ex ist ing re sources, based on work be tween1967 and 1970, is 317 485 tonnes grad ing 1.6% Cu, 0.7%Pb, 6.6% Zn, 4.1 g/t Au and 140.5 g/t Ag (The North ernMiner, 1969). Ex plo ra tion by Minnova In cor po rated in thelate 1990s (Wells, 1990) in cluded some di a mond-drill ingin the vi cin ity of the old mines but did not lead to a re visedre source es ti mate. Stratiform and stratabound min er al iza -tion in the Lenora, Tyee and Rich ard III de pos its is hostedmainly in cherty fel sic tuff and fine-grained car bo na ceousclastic rocks. Two main ore types are pres ent: 1)polymetallic baritic ore with vari able amounts of fine-grained py rite, sphalerite, chal co py rite and ga lena, and 2)quartz-r ich ore con s ist ing mainly of quartz andchalcopyrite. Ore at the Lenora deposit forms twolenticular orebodies that are contained within foldedsedimentary strata.Sev eral other min eral oc cur rences that are in ter pretedto be syngenetic in or i gin have also been ex plored his tor i -cally through adits, trench ing and lim ited drill ing in the BigSicker Moun tain area. These in clude the Key City(MINFILE oc cur rence 092B 087), im me di ately north-north west of the Lenora adit; the Queen Bee (MINFILE oc -cur rence 092B 088), ap prox i mately 1 km north of theLenora adit; and the North east Cop per (MINFILE oc cur -rence 092B 099), ap prox i mately 2 km east-north east of theLenora adit (Fig 2). Sul phide min er al iza tion in these oc cur -rences com prises mainly dis sem i nated py rite (±pyrrhotite), chal co py rite and lo cally sphalerite in schis tose andesitic torhyolitic vol ca nic rocks and/or as so ci ated car bo na ceoussedimentary rocks, or in bands of cherty tuff.The Lara de posit (MINFILE oc cur rence 092B-129) isa polymetallic VMS de posit hosted within the same pack -age of Sicker Group stra tig ra phy and lo cated ap prox i -mately 10 km along strike to the north west from Big SickerMoun tain. The main hostrocks are steeply dip ping, in ter -me di ate to fel sic vol ca nic and volcaniclastic strata of theMcLaughlin Ridge For ma tion. A re source of ap prox i -mately 500 000 t av er ag ing 1.0% Cu, 1.2% Pb, 5.9% Zn,4.3 g/t Au and 90 g/t Ag in two sep a rate min er al ized bod ieshas been re ported (George Cross News Let ter Ltd., 1992;Lara mide Re sources Ltd., 2006). Three dis tinct styles ofmin er al iza tion are rec og nized at the Lara: a mas sive sul -phide fa cies, a banded and lam i nated fa cies and a stringerfa cies. Min er al iza tion oc curs in three main bod ies, and hasbeen traced for a to tal strike length of at least 2 km and adown-dip extent of at least 440 m.The Sharon oc cur rence (MINFILE oc cur rence 092B040), lo cated ap prox i mately 3.5 km north west of BigSicker Moun tain (be tween the Mount Sicker and Lara de -pos its), has also been tested by three short adits as well asdrill ing and trench ing. Hostrocks in the area com prise py -ritic quartz-mus co vite and chlorite-mus co vite schists thatlo cally pre serve tex tures in di cat ing a mainly lapilli tuffprotolith. Small bod ies of weakly fo li ated quartz-feld sparpor phyry are also pres ent. The Sharon is mainly a cop peroc cur rence, with zones of dis sem i nated to semimassiverecrystallized py rite and mi nor chal co py rite in bands ofstrongly fo li ated and transposed metavolcanic rocks.The au thors are us ing Pb iso to pic anal y ses of sul phidemin er als from var i ous de pos its and show ings within theSicker Group in the Cowichan Lake up lift to dif fer en ti atebe tween syngenetic min er al iza tion and youn ger epigeneticmin er al iza tion. Pre vi ous stud ies by Godwin et al. (1988)and An drew and Godwin (1989) pro vide an ex cel lentcompositional da ta base for both VMS and epigenetic oc -cur rences hosted by Sicker Group strata on south ern andcen tral Van cou ver Is land, in clud ing data from the MountSicker and Lara de pos its (Fig 3). Lead iso tope anal y ses arepres ently be ing car ry ing out on sul phide min er als from asuite of min er al ized sam ples from through out the south -east ern Cowichan Lake up lift, in clud ing banded sul phidemin er als at the Sharon oc cur rence (MINFILE oc cur rence092B 040), py rite from thin con form able bands of py rite(with mi nor base metal en rich ment; A. Fran cis, pers comm, 2005) within quartz-feld spar-phyric lapilli tuff in the Hid -den Hills sub di vi sion, and sev eral new, pos si bly syngenetic oc cur rences that were dis cov ered dur ing the 2006 fieldwork. The aim of this part of the study is to eval u ate the to tal ex tent of syngenetic min er al iza tion in the Big SickerMoun tain area and to dis tin guish which, if any, of the oc -cur rences are youn ger and un re lated to sub ma rine VMSpro cesses. These new data will make it pos si ble to fit all ofthe def i nite syngenetic oc cur rences in the Big SickerMoun tain area into their cor rect strati graphic con text andeval u ate the true lat eral and ver ti cal ex tent of VMS min er -al iza tion in the area. This approach will subsequently beextended to cover the entire Cowichan Lake uplift.IMPLICATIONS FOR VMS POTENTIAL IN THE BIG SICKER MOUNTAIN AREAEval u at ing the re main ing po ten tial within the vi cin ityof the ex ist ing Lenora, Tyee and Rich ard III mines, and po -ten tial for new, as yet un dis cov ered min er al iza tion else -where in the Big Sicker Moun tain area, is com pli cated bythe dif fi culty in cor re lat ing stra tig ra phy from one area toan other due to the lack of good marker ho ri zons, and alsoby com plex ity im posed by postmineral fold ing and fault -ing. In ad di tion, the three-di men sional ex tent of the Tri as -sic gab bro bod ies must be as cer tained in or der to de ter minethe vol ume of pro spec tive McLaughlin Ridge For ma tionthat ex ists in the subsurface. Fur ther more, the pres ence ofnu mer ous proven or prob a ble syngenetic min eral oc cur -rences scat tered through out the study area, in clud ing theKey City, Queen Bee and North east Cop per oc cur rences(MINFILE oc cur rences 092B 087, 088 and 099, re spec -tively), to gether with un named stratiform sul phide min er -als in the Hid den Hills sub di vi sion and newly dis cov eredoc cur rences in the north ern and east ern parts of the maparea, dem on strate that VMS min er al iza tion is widely de vel -oped within this pack age of Sicker Group strata. The au -thors have not yet been able to es tab lish de fin i tively the di -rec tion of strati graphic younging within the McLaughlinRidge For ma tion in the Big Sicker Moun tain area. This iscrit i cal, be cause some of the styles of min er al iza tion, es pe -Geo log i cal Field work 2006, Pa per 2007-1 391284cially the quartz-cop per ores, could be interpreted torepresent stringer or vent zone mineralization beneath asyet undiscovered stratiform ore lenses.PLANNED FUTURE WORKWork planned for the 2007 field sea son in the im me di -ate Big Sicker Moun tain area will fo cus on un rav el ling thestruc tural and strati graphic com plex ity through on go ingsur face map ping, as well as in te gra tion of all avail able sur -face and subsurface in for ma tion from pre vi ous ex plo ra tionand min ing ac tiv ity in that area into a de tailed three-di men -sional model for the area. In par tic u lar, an at tempt will bemade to place all known stratiform and/or stratabound min -er al iza tion in the area into a volcanological frame work forthis part of the Cowichan Lake up lift. Stud ies will also beex tended far ther to the north west in the Cowichan Lake up -lift, as far as Rheinhart Lake, to en com pass the other mainar eas of known VMS min er al iza tion. In par al lel with thegeo log i cal map ping and syn the sis work, the au thors willalso carry out ad di tional lithogeochemical stud ies and U-Pb dat ing, as well as fo cused geological mapping in keyareas elsewhere in the Cowichan Lake uplift.ACKNOWLEDGMENTSThis pro ject is funded by a Geoscience BC grant, aswell as a Nat u ral Sci ences and En gi neer ing Re searchCoun cil of Can ada (NSERC) Dis cov ery Grant to the ju niorau thor. We thank Nick Massey for dis cus sions and in sightsinto the ge ol ogy of the Sicker Group, and Dick Tosdal forhav ing pro vided a crit i cal re view of this manu script. Wealso thank sev eral pros pec tors , con sul tants andexplorationists work ing on Van cou ver Is land, es pe ciallyAllen Fran cis, Jacques Houle, Herb McMaster and SyTresierra, for shar ing their time and knowl edge of Sickergeology and mineralization with us.REFERENCESAn drew, A. and Godwin, C.I. (1989): Lead- and stron tium-iso topegeo chem is try of Pa leo zoic Sicker Group and Ju ras sic Bo -nanza Group vol ca nic rocks and Is land in tru sions, Van cou -ver Is land, Brit ish Co lum bia; Ca na dian Jour nal of EarthSci ences, vol ume 26, pages 894–907.Barrett, T.J. and Sherlock, R.L. (1996): Vol ca nic stra tig ra phy,lithogeochemistry and seafloor set ting of the H-W mas sivesul fide de posit, Myra Falls, Van cou ver Is land, Brit ish Co -lum bia; Ex plo ra tion and Min ing Ge ol ogy, vol ume 5, pages421–458.Brandon, M.T., Or chard, M.J., Parrish, R.R., Suther land Brown,A. and Yorath, C.J. (1986): Fos sil ages and iso to pic datesfrom the Pa leo zoic Sicker Group and as so ci ated in tru siverocks, Van cou ver Is land, Brit ish Co lum bia; in Cur rent Re -search, Part A, Geo log i cal Sur vey of Can ada, Pa per 86-1A,pages 683–696.Frank lin, J.M., Gib son, H.L., Jonasson, I.R. and Gal ley, A.G.(2005): Volcanogenic mas sive sul phide de pos its; in Eco -nomic Ge ol ogy 100th An ni ver sary Vol ume, Hedenquist,J.W., Thomp son, J.F.H., Goldfarb, R.J. and Rich ards, J.P.,Ed i tors, Eco nomic Ge ol ogy, pages 523–560.George Cross News Let ter Ltd. (1992): [ti tle un known]; GeorgeCross News Let ter, num ber 188, Sep tem ber 29, 1992.Godwin, C.I., Gabites, J.E. and An drew, A. (1988): Leadtable: aga lena lead iso tope da ta base for the Ca na dian Cor dil lera;BC Min is try of En ergy, Mines and Pe tro leum Re sources, Pa -per 1988-4, 214 pages.Juras, S.J. (1987): Ge ol ogy of the polymetallic volcanogenicButtle Lake Camp, with em pha sis on the Price Hill side, cen -tral Van cou ver Is land, Brit ish Co lum bia, Can ada; un pub -lished PhD the sis, Uni ver sity of Brit ish Co lum bia,Van cou ver, BC, 279 pages.Katvala, E.C. (2006): Re ex am in ing the strati graphic andpaleontologic def i ni tion of Wrangellia; Geo log i cal So ci etyof Amer ica, Ab stracts with Pro gram, vol ume 38, page 24.Lara mide Re sources Ltd. (2006): Lara Pro ject: Van cou ver Is land,Brit ish Co lum bia; Lara mide Re sources Ltd., pro ject de -scrip tion, URL <http://www.lara mide.com/proj_lara.html>[No vem ber 2006].Massey, N.W.D. (1995a): Ge ol ogy and min eral re sources of theDuncan sheet, Van cou ver Is land, 92B/13; BC Min is try ofEn ergy, Mines and Pe tro leum Re sources, Pa per 1992-4.Massey, N.W.D. (1995b): Ge ol ogy and min eral re sources of theAlberni-Nanaimo Lakes sheet, Van cou ver Is land, 92F/1W,92F/2E and part of 92F/7E; BC Min is try of En ergy, Minesand Pe tro leum Re sources, Pa per 1992-2.Massey, N.W.D. (1995c): Ge ol ogy and min eral re sources of theCowichan Lake sheet, Van cou ver Is land, 92C/16; BC Min is -try of En ergy, Mines and Pe tro leum Re sources, Pa per 1992-3.Massey, N.W.D. and Fri day, S.J. (1987): Ge ol ogy of theChemainus River – Duncan area, Van cou ver Is land (92C/16, 92B/13); BC Min is try of En ergy, Mines and Pe tro leum Re -sources, Pa per 1988-1, pages 81–91.Massey, N.W.D. and Fri day, S.J. (1989): Ge ol ogy of the Alberni-Nanaimo Lakes area, Van cou ver Is land (92F/1W, 92F/2Eand part of 92F/7); BC Min is try of En ergy, Mines and Pe tro -leum Re sources, Open File 1987-2.MINFILE (2006): MINFILE BC min eral de pos its da ta base; BCMin is try of En ergy, Mines and Pe tro leum Re sources, URL<http://www.em.gov.bc.ca/Min ing/Geolsurv/Minfile/>[No vem ber 2006].Mortensen, J.K. (2005): Strati graphic and paleotectonic studies ofthe Mid dle Pa leo zoic Sicker Group and contained VMSoccurrences, Van cou ver Is land, Brit ish Co lum bia; in Geo -log i cal Field work 2005, BC Min is try of En ergy, Mines andPe tro leum Re sources, Pa per 2006-1, pages 331–336.Mul ler, J.E. (1977): Evo lu tion of the Pa cific mar gin, Van cou ver Is -land and ad ja cent re gions; Ca na dian Jour nal of Earth Sci -ences, vol ume 14, pages 2062–2085.The North ern Miner Ltd. (1969): [ti tle un known]; The North ernMiner, Sep tem ber 25, 1969.Parrish, R.R. and McNicoll, V.J. (1992): U-Pb age de ter mi na tionsfrom the south ern Van cou ver Is land area, Brit ish Co lum bia;in Ra dio genic Age and Iso to pic Stud ies: Re port 5, Geo log i -cal Sur vey of Can ada, Pa per 91-2, pages 79–86.Pearce, J.A., Har ris, N.B.W. and Tindle, A.G. (1984): Trace el e -ment dis crim i na tion di a grams for the tec tonic in ter pre ta tionof gra nitic rocks; Jour nal of Pe trol ogy, vol ume 25, pages956–983.Shervais, J. W. (1982): Ti-V plots and the petro gen esis of mod ernand ophiolitic lavas; Earth and Plan e tary Sci ence Let ters,vol ume 59, pages 101–118.Sluggett, C.L. (2003): Ura nium-lead age and geo chem i cal con -straints on Pa leo zoic and Early Me so zoic magmatism inWrangellia Terrane, Saltspring Is land, Brit ish Co lum bia;un pub lished BSc the sis, Uni ver sity of Brit ish Co lum bia,Van cou ver, BC, 56 pages.Sluggett, C.L. and Mortensen, J.K. (2003): U-Pb age and geo -chem i cal con straints on the paleotectonic evo lu tion of thePa leo zoic Sicker Group on Saltspring Is land, south west ernBrit ish Co lum bia; Geo log i cal As so ci a tion of Can ada – Min -392 Geoscience BC, Re port 2007-1285er al og i cal As so ci a tion of Can ada, Joint An nual Meet ing,Pro gram with Ab stracts, vol ume 28.Sun, S.S. and McDonough, W.F. (1989): Chem i cal and iso to picsys tem at ics of oce anic bas alts: im pli ca tions for man tle com -po si tion and pro cesses; in Magmatism in Ocean Bas ins,Saunders, A.D. and Norry, M.J., Ed i tors, Geo log i cal So ci ety of Lon don, pages 313–345.Wells, G.S. (1990): Di a mond drill ing re port, Mount Sicker prop -erty; BC Min is try of En ergy, Mines and Pe tro leum Re -sources, As sess ment Re port 19754, 15 pages.Winchester, J.A. and Floyd, P.A. (1977): Geo chem i cal dis crim i na -tion of dif fer ent magma se ries and their dif fer en ti a tion prod -ucts us ing im mo bile el e ments; Chem i cal Ge ol ogy, vol ume20, pages 325–343.Yorath, C.J., Suther land Brown, A. and Massey, N.W.D. (1999):LITHOPROBE, south ern Van cou ver Is land, Brit ish Co lum -bia: ge ol ogy; Geo log i cal Sur vey of Can ada, Bul le tin 498,145 pages.Geo log i cal Field work 2006, Pa per 2007-1 393286Geological Setting of Volcanogenic Massive Sulphide Occurrences in the MiddlePaleozoic Sicker Group of the Cowichan Lake Uplift, Port Alberni Area,Southern Vancouver Island, British Columbia (NTS 092F/02, /07)T. Ruks, Mineral Deposit Research Unit, Department of Earth and Ocean Sciences, University of BritishColumbia, Vancouver BC, tyler_ruks@hotmail.comJ.K. Mortensen, Mineral Deposit Research Unit, Department of Earth and Ocean Sciences, University of British Columbia, Vancouver BCRuks, T. and Mortensen, J.K. (2008): Geo log i cal set ting of volcanogenic mas sive sul phide oc cur rences in the Mid dle Pa leo zoic SickerGroup of the Cowichan Lake up lift, Port Alberni area (NTS 092F/02, /07), south ern Van cou ver Is land, Brit ish Co lum bia; in GeoscienceBC Sum mary of Ac tiv i ties 2007, Geoscience BC, Re port 2008-1, p. 77–92.IntroductionVolcanogenic strata of the mid-Pa leo zoic Sicker Group onVan cou ver Is land (Fig ure 1) oc cur in sev eral dis tinct base -ment highs (re ferred to as ‘up lifts’ herein). These rocks host the world-class Myra Falls volcanogenic mas sive sul phide(VMS) de posit (com bined pro duc tion and proven andprob a ble re serves in ex cess of 30 mil lion tonnes of Zn-Cu-(Au-Ag) ore), as well as nu mer ous other VMS de pos its andoc cur rences, es pe cially in the Big Sicker Moun tain area inthe south east ern part of the Cowichan Lake up lift (Fig -ure 1). Three of these de pos its, the Lenora, Tyee and Rich -ard III (MINFILE oc cur rences 092B 001, 002, 003) haveseen lim ited his tor i cal pro duc tion, and the Lara de posit(MINFILE oc cur rence 092B 129), far ther to the north west,also con tains a sig nif i cant drill-in di cated re source. Geo log -i cal map ping (Massey and Fri day, 1987; Mortensen, 2005;Ruks and Mortensen, 2006) sug gests that the ge ol ogy of the Mount Sicker area con sists mainly of de formed mafic tofel sic vol ca nic and volcaniclastic rocks of the Nitinat andMcLaughlin Ridge for ma tions, and high-level in tru sions of the Saltspring in tru sive suite, as well as abundant gabbroicdikes and sills of the Triassic Mount Hall gabbro.Geo log i cal map ping in the Cowichan Lake up lift of thePort Alberni area (Massey and Fri day, 1989) in di cates thatthis area is largely un der lain by ba salt to ba saltic-an de sitevol ca nic rocks of the Duck Lake and Nitinat for ma tions, re -spec tively, in ad di tion to fel sic tuffaceous volcaniclasticrocks be long ing to the McLaughlin Ridge For ma tion. Thena ture of the McLaughlin Ridge For ma tion rocks in thePort Alberni area is in ter preted to rep re sent de po si tion dis -tal from a vol ca nic cen tre, which is thought to be rep re -sented in the Saltspring Is land–Cowichan Lake area by fel -sic in tru sive rocks of the Saltspring intrusive suite (Masseyand Friday, 1989).The Deb bie 3 VMS oc cur rence is hosted by Sicker Grouprocks of the Port Alberni area (MINFILE oc cur rence092F 445) but, un like the ma jor ity of VMS oc cur rences inthe Sicker Group, is not as so ci ated with fel sic vol ca nicrocks of the McLaughlin Ridge For ma tion. In stead, the oc -cur rence is in ter preted to be hosted by mafic vol ca nic rocksof the un der ly ing Duck Lake and Nitinat for ma tions andmay there fore rep re sent the old est known VMS min er al iza -tion in the Sicker Group.Abun dant iron for ma tions that may be exhalitive in or i ginare also pres ent in Sicker Group rocks of the Port Alberniarea (e.g., the Lacy Lake and Esary Lake show ings;MINFILE oc cur rences 092F 245 and 244, re spec tively).These iron for ma tions are sim i lar to those oc cur ring inGeoscience BC Re port 2008-1 77Keywords: Sicker Group, Pa leo zoic, Van cou ver Is land, CowichanLake up lift, VMS de posit, stra tig ra phy, U-Pb zir con geo chron ol -ogy, lithogeochemistryThis pub li ca tion is also avail able, free of charge, as col our dig i talfiles in Adobe Ac ro bat® PDF for mat from the Geoscience BCwebsite: http://www.geosciencebc.com/s/DataReleases.asp.Fig ure 1. Dis tri bu tion of Pa leo zoic strata of the Sicker and ButtleLake groups on Van cou ver Is land and the Gulf Is lands.287rocks that are stratigraphically above VMS min er al iza tionat the Myra Falls, Lara, Lenora, Tyee and Rich ard III oc cur -rences, and are be lieved to rep re sent ox ide-fa cies iron min -er al iza tion re lated to hy dro ther mal min er al iz ing sys temssim i lar to those that formed the un der ly ing VMS de pos its.As with the Deb bie 3 VMS oc cur rence, how ever, the ironfor ma tions of the Port Alberni area are un der lain by maficvolcanic rocks of the Duck Lake or Nitinat formations.If the Deb bie 3 VMS oc cur rence is in deed the same age asthe po ten tial VMS-re lated exhalitive iron for ma tions in thesame gen eral area, this makes the Port Alberni area, spe cif i -cally where it is un der lain by rocks of the Nitinat and DuckLake for ma tions, sig nif i cantly more pro spec tive for VMSmin er al iza tion than was pre vi ously ap pre ci ated. Log gingac tiv ity in the area over the past de cade has pro vided abun -dant new out crops and greatly im proved ac cess, and hasprompted a re-ex am i na tion of the geo log i cal set ting ofVMS min er al iza tion and of the potential for newdiscoveries in this area.Both re con nais sance and de tailed geo log i cal map ping, to -gether with sam pling for lithogeochemistry, U-Pb zir condat ing, and Nd, Hf and Pb iso to pic stud ies, were con ductedover a 20-day pe riod in the Port Alberni area in Oc to ber2007. This work was con cen trated in the vi cin ity of theDeb bie 3 VMS oc cur rence and the area of po ten tially cor re -la tive exhalitive iron for ma tions to the west. This re portpres ents a pre lim i nary ver sion of re vised geo log i cal map -ping in this area, with em pha sis on un der stand ing the ge ol -ogy in the vi cin ity of the Deb bie 3 VMS oc cur rence and thepo ten tially cor re la tive Lacy and Esary Lake exhalitive ironformations.Regional Geology of the Sicker GroupThe mid-Pa leo zoic Sicker Group on south ern and cen tralVan cou ver Is land rep re sents the stratigraphically low estpor tion of the Wrangellia Terrane. Equiv a lents of theSicker Group are not pres ent in Wrangellia in north west ernBrit ish Co lum bia, south west ern Yu kon and south ernAlaska, where the old est rock units are the Skolai Group,which is no older than Penn syl va nian (e.g., Katvala, 2006).This, and other dif fer ences be tween the Wrangellian stra -tig ra phy on Van cou ver Is land and that in more north erly ex -po sures, em pha sizes the lack of un der stand ing re gard ingmuch of Wrangellia (e.g., Katvala, 2006) and the need forfur ther stud ies. The Cowichan Lake up lift on Van cou ver Is -land and ad ja cent por tions of the Gulf Is lands, which is themain fo cus of this study, is the larg est of four up lifts that ex -pose the Sicker and overlying late Paleozoic Buttle Lakegroups (Figure 1).Pre vi ous de tailed stud ies of the Sicker Group have fo cusedmainly on the strati graphic set ting of VMS min er al iza tionat the Myra Falls de pos its in the Buttle Lake up lift (Fig -ure 1; e.g., Juras, 1987; Barrett and Sherlock, 1996). Re -gional map ping of the Cowichan Lake up lift by Massey and Fri day (1987, 1989) and Yorath et al. (1999) led to an in ter -preted strati graphic frame work that may be ap pli ca ble tothe en tire Sicker Group (Fig ure 2). This strati graphicframe work, how ever, is based on map ping in only one ofthe four main up lifts of Sicker Group rocks, and is sup -ported by a very lim ited amount of biostratigraphic and iso -to pic age data (e.g., Brandon et al., 1986). Ma jor along- and across-strike fa cies changes and geo chem i cal vari a tionsare to be ex pected in sub ma rine vol ca nic se quences such asthe one that forms the Sicker Group; hence, the re gional ap -pli ca bil ity of the pro posed strati graphic frame work ofYorath et al. (1999) must be tested with de tailed map pingand sub se quent lithogeochemical and U-Pb dat ing stud ies.This is crit i cal for re gional ex plo ra tion for VMS de pos itswithin the Sicker Group. For ex am ple, the ques tions ofwhether VMS de pos its and oc cur rences in the CowichanLake up lift are all of the same age, and whether theirhostrocks are di rectly cor re la tive with those that host theMyra Falls deposit, are of obvious importance.The Sicker Group within the Cowichan Lake up lift is pres -ently in ter preted to rep re sent three dis tinct and re gion allymappable vol ca nic and volcaniclastic as sem blages that to -gether are thought to re cord the evo lu tion of an oce anicmag matic arc (Massey, 1995; Yorath et al., 1999). The low -er most Duck Lake For ma tion yields mainly nor mal mid-ocean-ridge ba salt (N-MORB) geo chem i cal sig na tures(Massey, 1995) and is in ter preted to rep re sent the oce aniccrust base ment on which the Sicker arc was built. The up per por tions of the Duck Lake For ma tion yield tholeiitic tocalcalkaline com po si tions and may rep re sent prim i tive arcrocks. The Duck Lake For ma tion is over lain by the NitinatFor ma tion, which com prises mafic, sub ma rine, vol ca nicand volcaniclastic rocks with dom i nantly calcalkaline com -po si tions and trace-el e ment sig na tures typ i cal of vol ca nicarc set tings. These rocks are in ter preted as an early stage ofarc de vel op ment. The andesitic to mainly dacitic andrhyolitic McLaughlin Ridge For ma tion that over lies the78 Geoscience BC Sum mary of Ac tiv i ties 2007Fig ure 2. Strati graphic no men cla ture for the Sicker and ButtleLake groups on Van cou ver Is land (Yorath et al., 1999).288Nitinat and hosts the Myra Falls de posit re flects a moreevolved stage of arc ac tiv ity. Erup tion of Nitinat vol ca nicand volcaniclastic rocks ap pears to have oc curred fromsev eral widely scat tered cen tres, whereas the McLaughlinRidge For ma tion within the Cowichan Lake up lift isthought to rep re sent erup tion from one or more ma jor vol -ca nic ed i fices. The abun dance of prox i mal fel sicvolcaniclastic rocks and the pres ence of vo lu mi nouscomagmatic fel sic in tru sions (Saltspring in tru sions) in theSaltspring Is land and Duncan ar eas (Fig ure 1) in di catesthat one of these ma jor vol ca nic cen tres was lo cated in thisarea. Plant ma te rial and trace fos sils in di cate that at least ami nor amount of the McLaughlin Ridge vol ca nism oc -curred in a subaerial set ting. In the Port Alberni area, theMcLaughlin Ridge For ma tion com prises fel sic, fine-grained tuffaceous volcaniclastic and epiclastic rocks, in di -cat ing de po si tion dis tal from a vol ca nic cen tre. De po si tionof sed i men tary and vol cano-sed i men tary rocks of the over -ly ing Fourth Lake For ma tion of the Buttle Lake Group fol -lowed the ces sa tion of Sicker arc magmatism, and scarcemafic vol ca nic rocks con tained within the Fourth Lake For -ma tion yield en riched tholeiitic rather than the calcalkalinecom po si tions that characterize the McLaughlin Ridge.Massey (1995) speculated that the Buttle Lake Group mayrepresent a marginal-basin assemblage that developed ontop of the Sicker arc.Stud ies of the Sicker and Buttle Lake groups on south ernSaltspring Is land at the south east ern end of the CowichanLake up lift by Sluggett (2003) and Sluggett and Mortensen(2003) pro vided new U-Pb zir con age con straints on bothfel sic vol ca nic rocks of the McLaughlin Ridge For ma tionand sev eral bod ies of Saltspring in tru sions. This work dem -on strates that two dis tinct ep i sodes of fel sic magmatism oc -curred in this por tion of the Cowichan Lake up lift. Onesam ple of fel sic vol ca nic rocks from the McLaughlin Ridge For ma tion and three sam ples of Saltspring in tru sionsyielded U-Pb ages in the range 359.1–356.5 Ma. A some -what older U-Pb age of 369.7 Ma was ob tained from a sep a -rate body of the Saltspring in tru sions at Burgoyne Bay onthe south west side of Saltspring Is land, in di cat ing thatmagmatism rep re sented by the McLaughlin Ridge For ma -tion and as so ci ated Saltspring in tru sions oc curred over atime span of at least 15 mil lion years. There is in suf fi cientage con trol avail able at this point to de ter mine whether themagmatism was continuous or episodic during this timeperiod.Results of New Mapping in the Port AlberniAreaMap ping of Sicker Group bed rock ge ol ogy and sam plingfor lithogeochemistry, U-Pb zir con and Ar-Ar hornblendegeo chron ol ogy, and Pb, Nd and Hf iso tope tracer stud ieswas con ducted in the Port Alberni area (Fig ure 3). Thiswork was con cen trated in three main ar eas: 1) in the vi cin -ity of the Lacy Lake and Esary Lake iron for ma tions, lo -cated be tween Lacy and Horne lakes; 2) in the vi cin ity of apre vi ously mapped dacite unit to the north of the PortAlberni high way; and 3), in the vi cin ity of the Deb bie 3VMS oc cur rence, lo cated to the south of the Port Albernihigh way (Fig ure 3). Map ping was con ducted us ing ESRI’sArcpad™ 7 on an HP IPaq HX4700 Pocket PC hard wiredto a Garmin 76CS GPS. The Brit ish Co lum bia Geo log i calSur vey’s re gional ge ol ogy com pi la tion for UTM zone 10,south west ern Brit ish Co lum bia was used (Massey et al.,2005). Bed rock out crop in both ar eas is mod er ate, with thebest ex po sures con tained in log ging-road cuts. Off-roadex po sures are typ i cally cov ered with thick lay ers of mossand or ganic de tri tus, of ten in for ested, low-light con di -tions.Lacy Lake–Horne Lake AreaStratified RocksThe old est rocks in the Lacy Lake–Horne Lake area are as -signed to the Duck Lake For ma tion (Fig ure 4; Massey andFri day, 1989). These con sist largely of mas sive, dom i -nantly aphyric to weakly plagioclase-phyric, vari ably he -ma tite-al tered ba salt flows, flow brec cias, lapilli tuffs, andtuff brec cias (Fig ure 5). In the vi cin ity of the Lacy Lakeiron for ma tion, weakly to strongly he ma tite-al tered, com -monly highly ve sic u lar ba salt flow autobreccias, lapillituffs, and tuff brec cias are abun dant (Fig ure 5a). Car bon ateal ter ation is lo cally abun dant in these vol ca nic rocks aspink an ker ite veins up to 7 cm wide, and as car bon ateamygdules up to 3 mm in size (Fig ure 5b). An ker ite vein ingis most prev a lent in ba saltic rocks with the stron gest he ma -tite al ter ation. Duck Lake For ma tion lapilli and tuff brec -cias in this area are com monly rich in strongly he ma tite-al -tered, ve sic u lar, variably carbonate amygdule–bearingbasalt clasts (Figure 5c).Jasperoid iron for ma tion of the Lacy Lake show ing(MINFILE 092F 245) is interbedded with green- to cream-col oured chert and is in very sharp con tact with un der ly inghe ma tite- and car bon ate-al tered autobreccia as signed to the Duck Lake For ma tion (Fig ures 5a and 6). The iron for ma -tion it self is dark red and sil ica rich. The Lacy Lake iron for -ma tion show ing is ap prox i mately 21 m thick and passesgradationally up wards into a pack age of interbedded greenchert– and sil ica-rich mudstone and siltstone. Far therupsection, interbedded green chert– and sil ica-richmudstone grade into a pack age of mod er ately to well-sorted, green-grey, in ter me di ate vol ca nic crys tal tuff, sand -stone and siltstone. These units dis play ex cel lent nor malgraded bed ding, in di cat ing they are up right (Fig ure 7). Stillfar ther upsection, a dom i nantly ma trix-sup ported,hematitic heterolithic brec cia to boul der con glom er ate be -comes prev a lent. This unit is strongly heterolithic and var -ies from ma trix to clast sup ported, with clasts up to boul dersize con sist ing of an gu lar, in ter me di ate vol ca nic sand -Geoscience BC Re port 2008-1 7928980 Geoscience BC Sum mary of Ac tiv i ties 2007Fig ure 3. Re gional ge ol ogy (af ter Massey et al., 2005) of the Port Alberni area, with ar eas of study out lined in red.290Geoscience BC Re port 2008-1 81Fig ure 4. New geo log i cal map ping in the Lacy Lake–Horne Lake area, Port Alberni area. Re gional ge ol ogy af ter Massey et al. (2005).291stone; dark red, an gu lar, jasperoid iron for ma tion clasts;dark green, ve sic u lar ba salt clasts; and cream to white,subangular to rounded, variably crinoidal limestoneboulders (Figure 8).In a sec ond out crop, ap prox i mately 450 m to the north westof the Lacy Lake iron for ma tion show ing, jasperoid ironfor ma tion with in creas ing el e va tion grades into he ma tite-bear ing, in ter me di ate vol ca nic sand stone, which be comespro gres sively more clast rich and coarse grained un til it ul -82 Geoscience BC Sum mary of Ac tiv i ties 2007Fig ure 5. Ba saltic vol ca nic rocks of the Duck Lake For ma tion in theLacy Lake–Horne Lake area: a) he ma ti te-al tered ba saltautobreccia with car bon ate ma trix; b) car bon ate amyg dule–bear -ing ba salt with pink car bon ate (an ker ite) veins; c) ba salt tuff-brec -cia con tain ing ve sic u lar, he ma tite-al tered clasts.Fig ure 6. a) Sharp con tact be tween un der ly ing ba salt andjasperoid iron for ma tion and green chert of the Lacy Lake oc cur -rence (MINFILE 092F 245). b) Jasperoid iron for ma tion of the LacyLake MINFILE oc cur rence is ap prox i mately 21 m in thick ness.Fig ure 7. Mod er ately to well-sorted, green-grey, in ter me di ate vol -ca nic crys tal tuff, sand stone and siltstone ex hib it ing nor mal grad -ing.292ti mately be comes hematitic crinoidal lime stone-bear ingheterolithic brec cia (Fig ures 9 and 10). The pres ence ofcrinoidal lime stone as clasts within the heterolithic brec ciathat sits ap par ently con form ably above the Lacy Lake ironfor ma tion sug gests that these iron for ma tions and the ac -com pa ny ing sed i men tary rocks may not be part of the Duck Lake For ma tion, as pre vi ously in ter preted, but in stead maybe part of the Fourth Lake For ma tion, which is be lieved tobe, in part, tem po rally equiv a lent to cri noid-bear ing lime -stone of the Mt. Mark For ma tion (Buttle Lake Group;Yorath et al., 1999). Float boul ders of dacite tuff-brec ciawere also ob served prox i mal to an out crop of crinoidallime stone–bear ing heterolithic brec cia (Fig ure 11a). Theseboul ders are highly an gu lar in shape, sug gest ing lo cal sour -cing, and con tain abun dant feld spar-phyric dacite clasts,with mi nor, rounded, he ma tite-al tered ba saltic-an de siteclasts, (Fig ure 11b). In ad di tion, a small road bed out crop ofgrey-green, peb ble to boul der con glom er ate with abun dantsubrounded peb ble- to boul der-size quartz-feld spar–phyric rhy o lite clasts is pres ent near the con tact be tween rocksassigned to the Duck Lake Formation and those assigned tothe Nitinat Formation, to the north (Figure 12).Geoscience BC Re port 2008-1 83Fig ure 8. a) and b) Ma trix- to clast-sup ported heterolithic brec cia,with clasts up to boul der size con sist ing of an gu lar, in ter me di atevol ca nic sand stone; dark red, an gu lar, jasperoid iron for ma tionclasts; dark green, ve sic u lar ba salt clasts; and cream to white,subangular to rounded, vari ably crinoidal lime stone boul ders.Fig ure 9. Interbedded jasperoid iron for ma tion and chloriticsiltstone, ap prox i mately 450 m north west of the Lacy Lake oc cur -rence (MINFILE 092F 245).Fig ure 10. Jasperoid iron for ma tion with in creas ing el e va tiongrades into he ma tite-bear ing, in ter me di ate vol ca nic sand stone,which be comes pro gres sively more clast rich and coarse grainedun til it ul ti mately be comes hematitic crinoidal lime stone–bear ingheterolithic brec cia.293The pres ence of fel sic vol cano-sed i men tary rocks sug geststhat the sed i men tary rocks in this area are part of theMcLaughlin Ridge For ma tion or pos si bly the Fourth LakeFor ma tion. Fur ther more, if the Lacy Lake iron for ma tionsare in deed hosted by the Fourth Lake or up per mostMcLaughlin Ridge For ma tion, this sug gests that un der ly -ing mafic vol ca nic rocks in this area, which are in sharpcon tact with the iron for ma tions, may rep re sent a com po -nent of mafic vol ca nism be long ing to the McLaughlinRidge or Nitinat For ma tion. Exhalitive iron for ma tions areabun dant else where in the Sicker Group, hosted in rocks as -signed to the Fourth Lake and Thelwood for ma tions of sim -i lar age, which stratigraphically over lie VMS min er al iza -tion hosted by the McLaughlin Ridge For ma tion in theeast ern Cowichan Lake and Buttle Lake ar eas, re spec tively. To con strain the age of the Lacy Lake iron for ma tions,abun dant sam ples of iron for ma tion and as so ci ated chertwere taken for possible radiolarian biostratigraphic studies.Rocks as signed to the Nitinat For ma tion were ob served intwo main ar eas. First, strongly pyroxene-phyric ba saltic-an de site ag glom er ate was ob served on the south side of84 Geoscience BC Sum mary of Ac tiv i ties 2007Fig ure 11. a) Float boul ders of dacite tuff-brec cia lo cated prox i malto an out crop of crinoidal lime stone–bear ing heterolithic brec cia.b) Close-up of dacite tuff-brec cia boul ders that shows them to behighly an gu lar, sug gest ing lo cal sour cing, and to con tain abun dantsubangular to subrounded feld spar-phyric dacite clasts, with mi -nor, rounded, he ma tite-al tered ba saltic-an de site clasts.Fig ure 12. Clasts of peb ble- to boul der-size quartz-feld spar–phyric rhy o lite clasts are found in a small road bed out crop of grey-green, peb ble to boul der con glom er ate near the con tact be tweenrocks as signed to the Duck Lake For ma tion and those as signed tothe Nitinat For ma tion, to the north.Fig ure 13. a) Pyroxene-phyric ba saltic-an de site ag glom er ate ofthe Nitinat For ma tion. b) Pyroxene pheno crysts in ba saltic-an de -site clast; in places, the pyroxene pheno crysts can reach 1 cm insize.294Lacy Lake, with the best ex am ples found di rectly be neath apower line (Fig ure 13a). Here, euhedral, green pyroxenepheno crysts con sti tute up to 5% of the rock and reach up to1 cm in size (Fig ure 13b). Nitinat For ma tion vol ca nic rocksin this lo ca tion ap pear to be in fault con tact along theirnorth ern mar gin on the west side of Lacy Lake with a belt of Mt. Mark For ma tion crinoidal lime stone. The south ernmar gin of this out crop of Nitinat For ma tion vol ca nic rocksap pears to be in con tact with fel sic tuffaceous rocks be long -ing to the McLaughlin Ridge Formation.The sec ond main area of Nitinat For ma tion ob served in thisstudy oc curs along the south ern shore of Horne Lake andex tends ap prox i mately 1500 m to the south, where it is incon tact with mafic vol ca nic rocks of the Duck Lake For ma -tion. Nitinat For ma tion along the south ern edge of HorneLake com prises mostly pyroxene-phyric ag glom er ate, tuffbrec cia and lesser lapilli tuff. Map ping dur ing this studyhas iden ti fied a zone of Nitinat For ma tion ba saltic-andesitic vol ca nic rocks ex tend ing well into an area pre vi -ously mapped as Duck Lake For ma tion ba salt. To ac com -mo date this new zone, the con tact be tween the Nitinat andDuck Lake for ma tions south of Horne Lake has been ex -tended an additional 600 m to the south (Figure 4).Fel sic vol ca nic rocks as signed to the McLaughlin RidgeFor ma tion in this study were en coun tered in two ar eas (Fig -ure 4). The south ern most ex po sure of this for ma tion in thestudy area is lo cated south of Lacy Lake. It com prisesmainly light green-grey, dacitic ash tuff with small feld sparcrys tals; me dium-grained, dacitic vol ca nic sand stone; andheterolithic, dacitic lapilli tuff, con sist ing of chert clasts upto 4 mm in size, dark green, highly chlorite-al tered an de siteclasts up to 4 mm in size, and me dium to light green,strongly seri cite-al tered dacite clasts up to 5 mm in size setin a ma trix that may con tain fine-grained feld spar andquartz crys tals (Fig ure 14a). The north ern most ex po sure ofMcLaughlin Ridge For ma tion in the study area com priseslargely well-sorted, me dium-grained arkosic sand stone,and thinly bed ded to lam i nated mudstone, siltstone andbuff- to creamy-weath er ing chert, with po ten tial fel sic ashtuff com po nents (Fig ure 14b, c). Finer grained McLaughlin Ridge sed i men tary rocks in this area ex hibit nor mal gradedbedding, indicating an upright orientation (Figure 14a).Rocks be long ing to the Fourth Lake For ma tion (Yorath etal., 1999) were rec og nized to the south of Lacy Lake. Thissmall ex po sure, heavily in un dated with ba saltic dikes be -long ing to the Karmutsen For ma tion, con sists of thinlybed ded, cream-col oured chert; black mudstone; greysiltstone; and grey to buff, well-sorted, fine-grained sand -stone (Figure 15).A sig nif i cant zone of crinoidal lime stone and as so ci atedsed i men tary rocks be long ing to the Mt. Mark For ma tion ofthe Buttle Lake Group has been rec og nized along the west -ern shore of Lacy Lake, in ar eas pre vi ously mapped asNitinat and McLaughlin Ridge for ma tions. These car bon -ate rocks are typ i cally me dium grey to buff, me dium-grained, sandy-tex tured crinoidal packstone with up to 4%by vol ume of cri noid os si cles up to 4 mm in di am e ter (Fig -ure 16a). Lesser amounts of darker grey wackstone andGeoscience BC Re port 2008-1 85Fig ure 14. Fel sic vol cano-sed i men tary rocks of the McLaughlinRidge For ma tion: a) dacitic heterolithic lapilli tuff; b) well-sorted,me dium-grained arkosic sand stone, siltstone and thinly bed ded tolam i nated mudstone; c) white-weath er ing, lam i nated chert orcherty tuff.295white-weath er ing radiolarian chert are also pres ent (Fig ure16b). The west ern lim its of this zone were not de ter mineddur ing this study. This pack age of Mt. Mark For ma tion car -bon ate and sed i men tary rocks was traced approximately500 m to the northwest of Lacy Lake.Intrusive RocksBa saltic to diabasic vol ca nic rocks be long ing to theKarmutsen For ma tion are abun dant in the field area, typ i -cally oc cur ring as large dikes (Fig ure 17a). They are typ i -cally dark green to black, mod er ately mag netic and dom i -nantly equigranular, with acicular hornblende andplagioclase pheno crysts av er ag ing 1 mm in length.Hornblende granodiorite in tru sions as signed to the MountWash ing ton in tru sive suite are pres ent in the field area, butare less abun dant than ba saltic dikes of the Karmutsen For -ma tion. These rocks are typ i cally por phy ritic, with up to30% me dium-grained feld spar pheno crysts and 1–2%hornblende pheno crysts. In places, hornblende pheno -crysts can be up to 2 cm in length. These rocks tend to formdikes and small in tru sions rang ing from 10 to 500 m inlength, of ten with ex cel lent chilled mar gins at their contacts (Figure 17b).Structural Geology of the Lacy Lake–Horne LakeAreaBed ding of sed i men tary and vol cano-sed i men tary rocks inthe Lacy Lake–Horne Lake area is dom i nantly north weststrik ing, with mod er ate dips to the north east (Fig ure 4).Rare dis rup tions to this fab ric were ob served ap prox i -mately 350 m north west of the Lacy Lake iron for ma tion,and may in di cate the hinge area of a lo cal ized, tight, par a -sitic, iso cli nal antiformal struc ture re lated to re gional F1folding.Felsic Volcanic Rocks of the Duck LakeFormationA mi nor amount of geo log i cal map ping and sam pling wasfo cused in the im me di ate vi cin ity of a quartz-feld spar–phyric dacite flow-dome hosted in Duck Lake For ma tionba saltic vol ca nic rocks to the south of the BC Tel mi cro -wave tower, north of the Port Alberni high way (Fig ure 3).86 Geoscience BC Sum mary of Ac tiv i ties 2007Fig ure 15. Sed i men tary rocks of the Fourth Lake For ma tion: a)thinly bed ded chert, siltstone and mudstone; b) lam i nated chertand mudstone.Fig ure 16. Car bon ate and sed i men tary rocks of the Mt. Mark For -ma tion: a) grey to buff, me dium-grained, sandy-tex tured crinoidalpackstone with up to 4% cri noid os si cles up to 4 mm in di am e ter; b)white-weath er ing radiolarian chert.296The goal of this map ping was to elu ci date whether or notthis unit was an in tru sion of McLaughlin Ridge For ma tionage or a pre vi ously un rec og nized fel sic vol ca nic com po -nent of the dom i nantly ba saltic Duck Lake For ma tion thatwould be datable by U-Pb zircon geochronology.Pre vi ous work ers have in ter preted this quartz-feld spar–phyric dacite as a flow, and have traced it for ap prox i mately 1.5 km along strike (Laanela et al., 1987). Dur ing thecourse of this study, both mas sive dacite por phyry anddacite brec cia were ob served in roadcut out crops. Mas sivedacite por phyry in this area is char ac ter ized by large, buff-to creamy-weath er ing out crops with 0.5% feld spar andquartz pheno crysts up to 1 mm in size (Fig ure 18a). Feld -spar is the dom i nant phenocryst phase, with quartz pheno -crysts rare to ab sent in hand sam ple. Fresh sur faces aregrey-green in col our. Chlorite-al tered pheno crysts (pos si -bly bi o tite) that form 0.25–0.5% of the rock are also pres -ent. Weak to mod er ate seri cite al ter ation is pres ent lo cally,as are car bon ate veinlets and rare dis sem i nated py rite. Rarechal co py rite is also lo cally pres ent. Dacite brec cia was rec -og nized ap prox i mately 150 m to the north west of the maindacite body, and con sists of abun dant, vari ably feld spar-phyric, vari ably sil ica-al tered, an gu lar dacite clasts up to10 cm in size, com monly with autobrecciated mar gins (Fig -Geoscience BC Re port 2008-1 87Fig ure 17. a) Karmutsen For ma tion ba saltic dike cuts sed i men taryrocks as signed to the Duck Lake For ma tion. b) In tru sion ofhornblende granodiorite cuts ba saltic-an de site rocks of the NitinatFor ma tion.Fig ure 18. a) Mas sive feld spar+quartz–phyric dacite flow in ba saltas signed to the Duck Lake For ma tion. b) Dacite brec cia withstrongly sil ica+seri cite–al tered clasts, of ten con tain ing sul phidemin er al iza tion; cross cut ting quartz-car bon ate veinlets con taintrace chal co py rite and bornite. c) Autobrecciated dacite clasts andin tensely sil ica+seri cite–al tered clasts with py rite±chal co py ritemin er al iza tion.297ure 18b). The most in tensely sil ica-al tered clasts com monly con tain fine-grained dis sem i nated sul phide (py rite±chal -co py rite) min er al iza tion (Fig ure 18c). Sul phide blebs andpos si ble sul phide clasts up to 4 cm in size are also pres ent in the brec cia. The dacite brec cia is crosscut by quartz-carbonate veinlets, some of which contain tracechalcopyrite and bornite.Debbie 3 Volcanogenic Massive SulphideOccurrenceThe Deb bie 3 volcanogenic mas sive sul phide oc cur -rence (MINFILE oc cur rence 092F 445), cur rently ownedby Bitterroot Re sources Ltd., oc curs in mafic vol ca nic andvol cano-sed i men tary rocks as signed to the Duck Lake andNitinat for ma tions, and is lo cated along the Cameron Mainlog ging road, close to the in ter sec tion with the Mt.Arrowsmith ski road. The show ing con sists of fourstratiform lenses of banded mas sive sphalerite, with mi norchal co py rite and ga lena, each band rang ing be tween 5 and20 cm in thick ness. The best grade ob tained from sam plingof this min er al iza tion by pre vi ous work ers in cludes 14.1%Zn, 0.87% Pb and 0.12% Cu over a 20 cm thick ness(MINFILE, 2007). The min er al iza tion is hosted in fine-grained chloritic schist with vari able carbonate, sericite and silica alteration.Map ping of the Deb bie 3 area has iden ti fied al ter nat ingzones of mas sive ba saltic and ba saltic-an de site vol ca nicrocks, with vari ably chlorite-, seri cite- and sil ica-al teredmafic schist (Fig ure 19). Mafic vol ca nic rocks in this areatend to oc cur as ro bust, mas sive out crops with lit tle to nofo li a tion. In the north ern por tion of the map area, these out -crops com prise dom i nantly mas sive, grey-green,pyroxene-phyric ba salt flows and ag glom er ate. Pyroxenepheno crysts can reach abun dances of 0.5–1.5% and sizesup to 3–4 mm. Feld spar-phyric ba salt flows with abun dantchlorite amygdules be come more abun dant to wards thewest. Here, vari ably epidote-al tered plagioclase pheno -crysts with dif fuse mar gins av er age 1.5 mm size, andchlorite amygdules reach abun dances up to 3.5% and sizesup to 1–2 mm. Epidote al ter ation patches up to 5–10 cm inwidth are also pres ent. In the south ern por tion of the maparea, mas sive, largely unfoliated mafic vol ca nic rocks com -prise mainly chlorite amyg dule–bear ing ba salt flows,pyroxene-phyric ba saltic-an de site ag glom er ate and maficlapilli tuff with abun dant flat tened, chlorite-al tered pum iceclasts. Mafic schist in both the north ern and south ern por -tions of the map area com prises strongly fo li ated, stronglychlorite-al tered mafic tuff with vari able car bon ate, seri citeand sil ica al ter ation (Fig ure 20a). Min er al iza tion is ob -served in this mafic schist only in the south ern part of thearea, and is pres ent as stratiform bands of mas sivesphalerite with mi nor chal co py rite and ga lena that reach upto 20 cm in thick ness (Fig ure 20b). Strong car bon ate andseri cite al ter ation of the mafic schist is pres ent in the im me -di ate vi cin ity of sul phide min er al iza tion. Ap prox i mately320 m west of the show ing, a zone of in tensely sil ica+seri -cite+car bon ate–al tered mafic schist is as so ci ated withquartz-car bon ate and blue-green gyp sum veins (Fig -ure 21). In this zone, quartz-car bon ate veins carry blebs ofchal co py rite. The pres ence of this stockwork-style sul -phide min er al iza tion to the west of the stratiform sul phidemin er al iza tion of the Deb bie 3 VMS occurrence suggeststhat rocks to the west of the main showing may reflectdeeper stratigraphic levels, and the stratigraphic packagemay young to the east.Debbie 3 Structural GeologyStruc tures in the area are best ob served in fine-grainedmafic vol ca nic rocks in the vi cin ity of the Deb bie 3 oc cur -rence (Fig ure 19). These rocks, typ i cally chloritic schist,dis play a prom i nent north west strike, with mod er ate tosteep dips to the north east. Fold ing of this fab ric was ob -served only in two ar eas. In the north west ern part of themap area, chloritic schist was ob served to strike north eastfor a lim ited ex tent, with weak dips to the south east. Thismay rep re sent F2 kink fold ing. Ad di tional kink fold ing wasob served in chloritic schist ap prox i mately 415 m west ofthe Deb bie 3 oc cur rence. Here, warp ing of the main fab ricis rep re sented by small, out crop-scale, F2 kink folds withhinges plunging steeply towards the northeast.New Sulphide Mineralization and Implicationsfor VMS Exploration in the Alberni AreaTwo new oc cur rences of sig nif i cant sul phide min er al iza -tion were dis cov ered dur ing the course of this map ping.The first, along the power line over look ing the south side of Lacy Lake (Fig ure 4), oc curs near the con tact be tweenpyroxene-phyric ba saltic-an de site ag glom er ate of theNitinat For ma tion and over ly ing fel sic tuffaceous rocks be -long ing to the McLaughlin Ridge For ma tion. Here, a 20 mlong float train con sists of bleached, highly seri cite-, sil ica-and fuch site-al tered subangular boul ders up to 40–50 cm insize that con tain up to 4% py rite, oc cur ring as dis sem i na -tions, string ers and blebs up to 2 cm in size (Fig ure 22). This float train was traced into a small ex po sure of he ma -tite+chlorite–al tered ba salt. Trench ing of this out crop ex -posed bleached, strongly seri cite+sil ica–al tered, py rite-min er al ized rock sim i lar to that ob served in the nearby min -er al ized float. This sul phide oc cur rence is sig nif i cant inthat it oc curs at the con tact be tween mafic to in ter me di atevol ca nic rocks of the Nitinat For ma tion and over ly ing fel -sic tuffaceous vol ca nic rocks of the McLaughlin Ridge For -ma tion. In the Buttle Lake up lift, this con tact is as so ci atedwith the gi ant HW de posit, which has a pre-min ing in ven -tory of 16.5 mil lion tonnes of ore with an av er age grade of2.2 g/t Au, 39.6 g/t Ag, 1.7% Cu, 0.4% Pb and 4.3% Zn(Rob in son, 1992). In the Port Alberni area, this con tact may be es pe cially sig nif i cant, as the lack of over ly ing fel sic vol -ca nic rocks in ti mately as so ci ated with high-en ergy erup -tive activity (i.e., rhyolite flows, felsic tuff-breccia, etc.)88 Geoscience BC Sum mary of Ac tiv i ties 2007298would provide ample time for the accumulation of VMSmineralization.The sec ond sig nif i cant new sul phide oc cur rence dis cov -ered dur ing the course of this map ping is as so ci ated withthe dacite flow-dome within ba salt as signed to the DuckLake For ma tion that was de scribed above (Fig ure 3;Massey and Fri day, 1989). Here, dis sem i nated to bleb-sized py rite±chal co py rite min er al iza tion is as so ci ated withstrongly sil ica-al tered clasts in a dacite brec cia oc cur ringalong the flanks of a mas sive, feld spar+quartz–phyricdacite dome (Fig ure 18c). In ad di tion, both the mas siveGeoscience BC Re port 2008-1 89Fig ure 19. Ge ol ogy of the Deb bie 3 VMS oc cur rence, Port Alberni area.299dacite and the dacite brec cia are cross cut by quartz-car bon ate veins con tain ing trace chal co py rite and bornitemin er al iza tion. This dacite unit may rep re sent a lo cus ofhy dro ther mal ac tiv ity re lated to po ten tial volcanogenicmassive sulphide mineralization in the area.Lastly, the as so ci a tion of polymetallic mas sive sul phidemin er al iza tion of the Deb bie 3 oc cur rence with fine-grained, chloritic mafic tuff as signed to ei ther the Nitinat orthe Duck Lake For ma tion in di cates that sig nif i cant hi a tuses in mafic vol ca nism ex ist in the for ma tions where VMSmin er al iza tion could de velop. This sug gests that fur therVMS ex plo ra tion in mafic vol ca nic rocks be long ing to theDuck Lake and Nitinat for ma tions is war ranted. This workshould con cen trate on iden ti fy ing zones of sig nif i cantinterflow sed i men ta tion, sim i lar to that hosting VMSmineralization of the Debbie 3 occurrence.Future WorkField work planned for the win ter of 2007 will in clude log -ging and sam pling of re cent drillcore from the Deb bie prop -erty (Bitterroot Re sources Ltd.). This work has sev eralgoals, in clud ing iden ti fy ing and sam pling marker ho ri zonswithin mafic vol ca nic rocks of the Duck Lake and Nitinatfor ma tions, with the ul ti mate goal of con strain ing the age of these for ma tions, which are cur rently un der stood to be theold est rocks in the Wrangellia Terrane. It will aid in de ter -min ing the age and strati graphic po si tion of VMS-pro spec -tive ho ri zons within the Nitinat and Duck Lake for ma tions,and will as sist in con strain ing rel a tive mo tions along faultsys tems, which are host to sig nif i cant epi ther mal gold min -er al iza tion at the Deb bie oc cur rence (MINFILE oc cur rence 092F 079). In ad di tion, sam pling of sul phide min er al iza -tion from the Deb bie prop erty for Pb-iso tope stud ies willpro vide a frame work through which epigenetic sul phideoc cur rences as so ci ated with gold min er al iza tion on the90 Geoscience BC Sum mary of Ac tiv i ties 2007Fig ure 20. a) Strongly fo li ated mafic tuff with vari able chlorite, car -bon ate, seri cite and sil ica al ter ation. b) Stratiform bands of mas -sive sphalerite with mi nor chal co py rite and ga lena, hosted instrongly fo li ated, seri cite+chlorite+car bon ate–al tered mafic ashtuff.Fig ure 21. In tensely sil ica+seri cite+car bon ate–al tered maficschist with quartz-car bon ate and blue-green gyp sum veins; inplaces, quartz-car bon ate veins con tain blebs of chal co py rite.Fig ure 22. Bleached, highly seri cite+sil ica+fuch site–al tered mafic vol ca nic rock with up to 4% py rite min er al iza tion as dis sem i na -tions, string ers and blebs up to 2 cm in size.300prop erty (e.g., the Deb bie oc cur rence) can be dis tin guishedfrom those associated with VMS mineralization (e.g., theDebbie 3 VMS occurrence).Field work planned for 2008 will be con cen trated in theCowichan and Port Alberni ar eas, with ad di tional work inpo ten tial out crops of Sicker Group rocks in the Bedingfield Bay and Muchalat In let ar eas. In the Cowichan area, con -tin ued work will fo cus on un der stand ing the strati graphicand volcanological set ting of VMS oc cur rences hosted bythe Sicker Group, par tic u larly those of the Lara/Cor o na -tion, Randy and Anita zones, north and west of Big SickerMoun tain (MINFILE oc cur rences 092B 129, 128 and 037,re spec tively), and other po ten tial VMS oc cur rences in theim me di ate vi cin ity and west of Cowichan Lake. Ad di tionalre gional work in the Alberni area will fo cus on iden ti fy ingstrati graphic marker ho ri zons within the Sicker Group thatcan be used to con strain the age of lithological units in thearea, par tic u larly those belonging to the Duck Lake andNitinat formations.In the Bedingfield Bay and Muchalat In let ar eas, sim i lar re -gional and fo cused out crop-scale map ping and sam plingwill be con ducted to un der stand the stra tig ra phy andvolcanological set ting of po ten tial Sicker Group rocks andVMS oc cur rences, most no ta bly in the vi cin ity of the RantPoint and Dragon (Paget Re sources Corp.) VMS oc cur -rences (MINFILE oc cur rences 092F 494 and 092E 072, re -spec tively). In par al lel with the geo log i cal map ping andsyn the sis work, the au thors will also carry out ad di tional U-Pb dat ing, lithogeochemical, and Nd, Hf and Pb iso to picstud ies in or der to con strain the age and mag matic evo lu -tion of Sicker Group vol ca nic rocks, and to de velop aframe work through which VMS oc cur rences hosted by theSicker Group can be dis tin guished from younger,epigenetic sulphide occurrences.AcknowledgmentsThis pro ject is jointly funded by a Geoscience BC grant,Bitterroot Re sources Ltd., Paget Re sources Corp. and aNat u ral Sci ences and En gi neer ing Re search Coun cil ofCan ada (NSERC) Dis cov ery Grant to Mortensen. The au -thors thank N. Massey for dis cus sions and in sights into thege ol ogy of the Sicker Group, and K. Hickey for hav ing pro -vided a crit i cal re view of this manu script. They also thanksev eral pros pec tors, con sul tants and explorationists work -ing on Van cou ver Is land, es pe cially M. Becherer of Min -eral Creek Ven tures Inc., M. Carr of Bitterroot Re sourcesLtd., J. Brad ford of Paget Re sources Corp., E. Specogna ofSpecogna Min er als Corp., A. Fran cis, J. Houle, H.McMaster and S. Tresierra, for shar ing their time andknowl edge of Sicker Group geology and mineralization.ReferencesBarrett, T.J. and Sherlock, R.L. (1996): Vol ca nic stra tig ra phy,lithogeochemistry and seafloor set ting of the H-W mas sivesul fide de posit, Myra Falls, Van cou ver Is land, Brit ish Co -lum bia; Ex plo ra tion and Min ing Ge ol ogy, v. 5, p. 421–458.Brandon, M.T., Or chard, M.J., Parrish, R.R., Suther land Brown,A. and Yorath, C.J. (1986): Fos sil ages and iso to pic datesfrom the Pa leo zoic Sicker Group and as so ci ated in tru siverocks, Van cou ver Is land, Brit ish Co lum bia; in Cur rent Re -search, Part A, Geo log i cal Sur vey of Can ada, Pa per 86-1A,p. 683–696.Juras, S.J. (1987): Ge ol ogy of the polymetallic volcanogenicButtle Lake Camp, with em pha sis on the Price Hill side, cen -tral Van cou ver Is land, Brit ish Co lum bia, Can ada; Ph.D. the -sis, Uni ver sity of Brit ish Co lum bia, Van cou ver, BC, 279 p.Katvala, E.C. (2006): Re ex am in ing the strati graphic andpaleontologic def i ni tion of Wrangellia; Geo log i cal So ci etyof Amer ica, Ab stracts with Pro gram, v. 38, p. 24.Laanela, H. (1987): As sess ment re port on geo log i cal, geo chem i -cal, and geo phys i cal sur veys on the Lacy and Stokes claimgroups in the Alberni and Nanaimo min ing di vi sions, BC;BC Min is try of En ergy, Mines and Pe tro leum Re sources,As sess ment Re port 16138, 93 p.Massey, N.W.D. (1995): Ge ol ogy and min eral re sources of theDuncan sheet, Van cou ver Is land, 92B/13; BC Min is try ofEn ergy, Mines and Pe tro leum Re sources, Pa per 1992-4.Massey, N.W.D. and Fri day, S.J. (1987): Ge ol ogy of theChemainus River–Duncan area, Van cou ver Is land (92C/16;92B/13); BC Min is try of En ergy, Mines and Pe tro leum Re -sources, Pa per 1988-1, p. 81–91.Massey, N.W.D. and Fri day, S.J. (1989): Ge ol ogy of the Alberni–Nanaimo Lakes area, Van cou ver Is land (92F/1W, 92F/2Eand part of 92F/7); BC Min is try of En ergy, Mines and Pe tro -leum Re sources, Open File 1987-2.Massey, N.W.D., Mac In tyre, D.G., Desjardins, P.J., and Cooney,R.T., (2005): Dig i tal map of Brit ish Co lum bia: Tile NM10South west BC; BC Min is try of En ergy, Mines and Pe tro -leum Re sources, GeoFile 2005-3.MINFILE (2007): MINFILE BC min eral de pos its da ta base; BCMin is try of En ergy, Mines and Pe tro leum Re sources, URL<http://www.em.gov.bc.ca/Min ing/Geolsurv/Minfile/>[No vem ber 2007].Mortensen, J.K. (2005): Strati graphic and paleotectonic stud ies ofthe Mid dle Pa leo zoic Sicker Group and con tained VMS oc -cur rences, Van cou ver Is land, Brit ish Co lum bia; in Geo log i -cal Field work 2005, BC Min is try of En ergy, Mines andPe tro leum Re sources, Pa per 2006-1, p. 331–336.Rob in son, M. (1992): Ge ol ogy, min er al iza tion and al ter ation ofthe Bat tle zone, Buttle Lake camp, cen tral Van cou ver Is land, south west ern Brit ish Co lum bia; M.Sc. the sis, Uni ver sity ofBrit ish Co lum bia, Van cou ver, BC, 268 pages.Ruks, T.R. and Mortensen, J.K. (2006): Geo log i cal set ting ofvolcanogenic mas sive sul phide oc cur rences in the Mid dlePa leo zoic Sicker Group of the south east ern Cowichan Lakeup lift (NTS 092B/13), south ern Van cou ver Is land; in Geo -log i cal Field work 2006, BC Min is try of En ergy, Mines andPe tro leum Re sources, Paper 2007-1, p. 381–394.Sluggett, C.L. (2003): Ura nium-lead age and geo chem i cal con -straints on Pa leo zoic and Early Me so zoic magmatism inWrangellia Terrane, Saltspring Is land, Brit ish Co lum bia;Geoscience BC Re port 2008-1 91301B.Sc. the sis, Uni ver sity of Brit ish Co lum bia, Van cou ver,BC, 56 p.Sluggett, C.L. and Mortensen, J.K. (2003): U-Pb age and geo -chem i cal con straints on the paleotectonic evo lu tion of thePa leo zoic Sicker Group on Saltspring Is land, south west ernBrit ish Co lum bia; Geo log i cal As so ci a tion of Can ada–Min -er al og i cal As so ci a tion of Can ada, Joint An nual Meet ing,Pro gram with Ab stracts, v. 28.Yorath, C.J., Suther land Brown, A. and Massey, N.W.D. (1999):LITHOPROBE, south ern Van cou ver Is land, Brit ish Co lum -bia: ge ol ogy; Geo log i cal Sur vey of Can ada, Bul le tin 498,145 p.92 Geoscience BC Sum mary of Ac tiv i ties 2007302Preliminary Results of Geological Mapping, Uranium-Lead Zircon Dating, andMicropaleontological and Lead Isotopic Studies of Volcanogenic Massive Sulphide–Hosting Stratigraphy of the Middle and Late Paleozoic Sicker and Lower ButtleLake Groups on Vancouver Island, British Columbia(NTS 092B/13, 092C/16, 092E/09, /16, 092F/02, /07)T. Ruks, Mineral Deposit Research Unit, Department of Earth and Ocean Sciences, University of BritishColumbia, Vancouver, BC, tyler_ruks@hotmail.comJ.K. Mortensen, Mineral Deposit Research Unit, Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, BCF. Cordey, CNRS UMR 5125, Université Claude Bernard Lyon 1, 69622, Villeurbanne Cedex, FranceRuks, T., Mortensen, J.K. and Cordey, F. (2008): Pre lim i nary re sults of geo log i cal map ping, ura nium-lead zir con dat ing, andmicropaleontological and lead iso to pic stud ies of volcanogenic mas sive sul phide–host ing stra tig ra phy of the Mid dle and Late Pa leo zoicSicker and Lower Buttle Lake groups on Van cou ver Is land, Brit ish Co lum bia (NTS 092B/13, 092C/16, 092E/09, /16, 092F/02, /07); inGeoscience BC Sum mary of Ac tiv i ties 2008, Geoscience BC, Report 2009-1, p. 103–122.IntroductionVolcanogenic strata of the mid-Pa leo zoic Sicker Group onVan cou ver Is land (Fig ure 1) oc cur in sev eral dis tinct base -ment highs (re ferred to herein as ‘up lifts’). These rockshost the world-class Myra Falls volcanogenic mas sive sul -phide (VMS) de posit (com bined pro duc tion and provenand prob a ble re serves in ex cess of 40 mil lion tonnes of Zn-Cu-Au-Ag sulphides), as well as nu mer ous other VMS de -pos its and oc cur rences, in clud ing those in the Big SickerMoun tain area in the south east ern part of the CowichanLake up lift (Fig ure 1). Three of these de pos its in theCowichan Lake up lift, the Lenora, Tyee and Rich ard III(MINFILE oc cur rences 092B 001, 092B 002, 092B 003;MINFILE, 2008) have seen lim ited his tor i cal pro duc tion.The Lara de posit (MINFILE oc cur rence 092B 129), far -ther to the north west, also con tains a sig nif i cant drill-in di -cated re source of 1 146 700 tonnes grad ing 3.01% Zn,1.05% Cu, 0.58% Pb, 32.97 g/t Ag and 1.97 g/t Au (Kelso et al., 2007). Geo log i cal map ping (Massey and Fri day, 1987;Mortensen, 2005; Ruks and Mortensen, 2006) sug gests that the the Big Sicker Moun tain area con sists mainly of de -formed mafic to fel sic vol ca nic and volcaniclastic rocks ofthe Nitinat and McLaughlin Ridge for ma tions, and high-level in tru sions of the Saltspring in tru sive suite, as well asabun dant gabbroic dikes and sills of the Tri as sic MountHall gab bro (Fig ure 2). Re cent geo log i cal map ping in theCowichan Lake up lift (this study) has been a con tin u a tionof our ef forts to de velop a strati graphic frame work forSicker arc de vel op ment and VMS min er al iza tion in theSicker Group. Work con ducted on Cowichan Lake up liftmin eral ten ure owned by pro ject spon sors Trea sury Met alsInc. and Westridge Re sources Inc. con cen trated on re solv -ing the geo log i cal set ting and age of the Lara VMS de positand other VMS oc cur rences in the area, as well as ex am in -ing new bed rock ex po sure cre ated by re cent log ging ac tiv -ity. Re con nais sance field work on new bed rock ex po sureowned by Westridge Re sources Inc. cul mi nated in the dis -cov ery of a new, polymetallic VMS oc cur rence. Map pingin the Mount Brenton area by Trea sury Met als Inc. hasiden ti fied a pro spec tive zone where in tensely seri cite-al -Geoscience BC Re port 2009-1 103Keywords: Sicker Group, Pa leo zoic, Van cou ver Is land, CowichanLake up lift, volcanogenic mas sive sul phide, stra tig ra phy, ura -nium-lead zir con geo chron ol ogy, lithogeochemistryThis pub li ca tion is also avail able, free of charge, as col our dig i talfiles in Adobe Ac ro bat® PDF for mat from the Geoscience BCwebsite: http://www.geosciencebc.com/s/DataReleases.asp.Fig ure 1. Dis tri bu tion of Pa leo zoic strata of the Sicker and ButtleLake groups on Van cou ver Is land and the Gulf Is lands.303tered and py rite-min er al ized fel sic ash tuff is over lain, inturn, by si lici fied argillite and a chlorite-al tered ash tuff ofin ter me di ate com po si tion. A sim i lar geo log i cal set ting isas so ci ated with mas sive sul phide min er al iza tion at theLenora de posit (Ruks and Mortensen, 2006). Geo log i calmap ping and sam pling were also fo cused in the vi cin ity ofthe Lady A iron for ma tion (Trea sury Met als Inc.; MINFILE 092B 033). The Lady A is sim i lar to other iron for ma tionsoc cur ring in rocks that are stratigraphically above VMSmin er al iza tion at the Lenora, Tyee and Rich ard III oc cur -rences, and is be lieved to rep re sent ox ide-fa cies iron min er -al iza tion re lated to hy dro ther mal min er al iz ing sys temssim i lar to those that formed the un der ly ing VMS de pos its.Re solv ing the tim ing of iron for ma tion min er al iza tion inthe Sicker Group is crit i cal for es tab lish ing the du ra tion ofVMS-re lated hydrothermal activity.Geo log i cal map ping in the Cowichan Lake up lift of thePort Alberni area (Massey and Fri day, 1989) in di cates thatthis area is largely un der lain by ba salt to ba saltic an de sitevol ca nic rocks of the Duck Lake and Nitinat for ma tions, re -spec tively, in ad di tion to fel sic tuffaceous volcaniclasticrocks be long ing to the McLaughlin Ridge For ma tion.McLaughlin Ridge For ma tion rocks in the Port Alberniarea are in ter preted to rep re sent de po si tion dis tal from avol ca nic cen tre, which is thought to be rep re sented in theSaltspring Is land–Cowichan Lake area by fel sic in tru siverocks of the Saltspring in tru sive suite (Massey and Fri day,1989). How ever, geo log i cal map ping of new ex po sures inthe Port Alberni area (this study) in di cates that fel sic vol ca -nic rocks of po ten tial McLaughlin Ridge For ma tion age are pres ent in sig nif i cant quan ti ties, ne ces si tat ing a re in ter pre -ta tion of the nature of the Sicker Group and its VMSpotential in the Port Alberni area.Sed i men tary, mafic vol ca nic and car bon ate rocks of theNanoose up lift have been ten ta tively cor re lated with boththe Sicker and Buttle Lake groups (Yorath et al., 1999).How ever, no geo chron ol ogi cal or biostratigraphic sam -pling has dem on strated an age that fa cil i tates com par i sonswith the Sicker Group. To re solve out stand ing strati graphic prob lems in the Nanoose up lift, re con nais sance field workin the area this sum mer fo cused on sam pling pro spec tiverock types for geo chron ol ogy and biostratigraphy. Of par -tic u lar im por tance is re solv ing the age of mafic volcanicrocks in the area.Map ping in the Hesquiat and Gold River ar eas, on the Do -rado and Dragon prop er ties (Paget Re sources Cor po ra tion;Fig ure 1), has iden ti fied sev eral new VMS oc cur renceshosted in po ten tial Sicker Group rocks. Geo log i cal map -ping and sam pling on the Dragon prop erty by pre vi ouswork ers in di cates the pres ence of sev eral polymetallic mas -sive sul phide lenses with grades up to 7.33% Zn, 1.34% Pb,173 ppm Cu, 680 ppb Au and 19.2 g/t Ag over a 2 m thick -ness (Jones, 1997). Geo log i cal map ping of the Do rado andDragon prop er ties in di cates that mafic and fel sic vol ca nicrocks and con tained VMS min er al iza tion are over lain byvol cano-sed i men tary and car bon ate rocks, in clud ing cal -car e ous tuffaceous sed i men tary rocks and fossiliferouslime stone, re spec tively. No where else in the Sicker Groupare car bon ate rocks ob served to di rectly, and ap par entlycon form ably, over lie fel sic vol ca nic rocks and VMS min er -al iza tion. This re la tion ship in di cates that rad i cal strati -graphic dif fer ences ex ist be tween rocks of the Dragonprop erty and better stud ied ex po sures of the Sicker Groupin the Cowichan Lake and Myra Falls ar eas. These strati -graphic dif fer ences may be ex plained by large changes invol ca nic and sedimentological fa cies or the presence of anunrecognized cycle of arc magmatism and VMSmineralization on Vancouver Island.The 2008 field work in the Sicker Group com menced inearly Au gust and fin ished in mid-Oc to ber 2008. In for ma -tion per tain ing to the Do rado prop erty of Paget Re sourcesCor po ra tion is based on field work con ducted in 2007. Bothre con nais sance and de tailed geo log i cal map ping, to getherwith sam pling for lithogeochemistry, U-Pb zir con dat ing,and Nd, Hf and Pb iso to pic stud ies, were con ducted in theCowichan Lake, Port Alberni, Nanoose, Gold River andHesquiat ar eas over this pe riod. This re port pres ents a sum -mary of this field work, with em pha sis on key strati graphicre la tion ships and areas of economic importance.Regional Geology of the Sicker GroupThe mid-Pa leo zoic Sicker Group on south ern and cen tralVan cou ver Is land rep re sents the old est rocks in theWrangellia Terrane. Equiv a lents of the Sicker Group arenot pres ent in Wrangellia in north west ern Brit ish Co lum -bia, south west ern Yu kon and south ern Alaska, where theold est rock units are the Skolai Group, which is no olderthan Penn syl va nian (e.g., Katvala, 2006). This, and otherdif fer ences be tween the Wrangellian stra tig ra phy on Van -cou ver Is land and that in more north erly ex po sures, em pha -104 Geoscience BC Sum mary of Ac tiv i ties 2008Fig ure 2. Strati graphic no men cla ture for the Sicker and ButtleLake groups on Van cou ver Is land (Yorath et al., 1999).304size the lack of un der stand ing re gard ing much ofWrangellia (e.g., Katvala, 2006) and the need for fur therstud ies. The Cowichan Lake up lift on Van cou ver Is landand ad ja cent por tions of the Gulf Is lands is the larg est offour up lifts that ex pose the Sicker and overlying latePaleozoic Buttle Lake groups (Figure 1).Pre vi ous de tailed stud ies of the Sicker Group have fo cusedmainly on the strati graphic set ting of VMS min er al iza tionat the Myra Falls de pos its in the Buttle Lake up lift (Fig -ure 1; e.g., Juras, 1987; Barrett and Sherlock, 1996). Re -gional map ping of the Cowichan Lake up lift by Massey and Fri day (1987, 1989) and Yorath et al. (1999) led to a strati -graphic frame work that may be ap pli ca ble to the en tireSicker Group (Fig ure 2). This frame work, how ever, isbased on map ping in only one of the four main up lifts ofSicker Group rocks, and is sup ported by a lim ited amountof biostratigraphic and iso to pic age data (e.g., Brandon etal., 1986). Ma jor along- and across-strike fa cies changesand geo chem i cal vari a tions are to be ex pected in sub ma rine vol ca nic se quences such as the one that forms the SickerGroup; hence, the re gional ap pli ca bil ity of the strati graphic frame work of Yorath et al. (1999) must be tested with de -tailed map ping and sub se quent lithogeochemical and U-Pbdat ing stud ies. This is crit i cal for re gional ex plo ra tion forVMS de pos its within the Sicker Group. For ex am ple, theques tions of whether VMS de pos its and oc cur rences in theCowichan Lake up lift are all of the same age, and whethertheir hostrocks are di rectly cor re la tive with those that hostthe Myra Falls deposit, are of obvious importance.The Sicker Group within the Cowichan Lake up lift is pres -ently in ter preted to rep re sent three dis tinct vol ca nic andvolcaniclastic as sem blages that to gether are thought to re -cord the evo lu tion of an oce anic mag matic arc (Massey,1995; Yorath et al., 1999). The low er most Duck Lake For -ma tion yields mainly nor mal mid-ocean-ridge ba salt (N-MORB) geo chem i cal sig na tures (Massey, 1995) and is in -ter preted to rep re sent the oce anic-crust base ment on whichthe Sicker arc was built. The up per por tions of the DuckLake For ma tion yield tholeiitic to calcalkaline com po si -tions and may rep re sent prim i tive arc rocks. The Duck Lake For ma tion is over lain by the Nitinat For ma tion, whichcom prises mafic, sub ma rine vol ca nic and volcaniclasticrocks with dom i nantly calcalkaline com po si tions andtrace-el e ment sig na tures typ i cal of vol ca nic arc set tings.These rocks are in ter preted as an early stage of arc de vel op -ment. The andesitic to mainly dacitic and rhyoliticMcLaughlin Ridge For ma tion over lies the Nitinat and isbe lieved to be cor re la tive with the Myra For ma tion, thehostrocks for the Myra Falls de pos its (Fig ure 2). Rocks ofthe McLaughlin Ridge and Myra for ma tions re flect a moreevolved stage of arc ac tiv ity. Erup tion of Nitinat vol ca nicand volcaniclastic rocks ap pears to have oc curred fromsev eral widely scat tered cen tres, whereas the McLaughlinRidge For ma tion within the Cowichan Lake up lift isthought to rep re sent erup tion from one or more ma jor vol -ca nic ed i fices. The abun dance of prox i mal fel sicvolcaniclastic rocks and the pres ence of vo lu mi nouscomagmatic fel sic in tru sions in the Saltspring Is land andDuncan ar eas (Fig ure 1) in di cate that one of these ma jorvol ca nic cen tres was lo cated in this area. Plant fos sils in di -cate that at least a mi nor amount of the McLaughlin Ridgevol ca nism oc curred in a subaerial set ting. In the PortAlberni area, the McLaughlin Ridge For ma tion has pre vi -ously been in ter preted to com prise fel sic, fine-grainedtuffaceous volcaniclastic and epiclastic rocks, sug gest ingde po si tion dis tal from a vol ca nic cen tre. The iden ti fi ca tionof sig nif i cant quan ti ties of prox i mal fel sic vol ca nic rocks in the Alberni area this year sug gests that an ad di tional fel sicvol ca nic cen tre may be lo cated in the Port Alberni area. De -po si tion of sed i men tary and vol cano-sed i men tary rocks ofthe over ly ing Fourth Lake For ma tion of the Buttle LakeGroup fol lowed the ces sa tion of Sicker arc magmatism, and scarce mafic vol ca nic rocks con tained within the FourthLake For ma tion yield en riched tholeiitic rather than thecalcalkal ine composi t ions that character ize theMcLaughlin Ridge. Massey (1995) speculated that theButtle Lake Group may represent a marginal-basinassemblage that developed on top of the Sicker arc.Stud ies of the Sicker and Buttle Lake groups on south ernSaltspring Is land by Sluggett (2003) and Sluggett andMortensen (2003) pro vided new U-Pb zir con age con -straints on both fel sic vol ca nic rocks of the McLaughlinRidge For ma tion and sev eral bod ies of Saltspring in tru -sions. This work dem on strates that two dis tinct ep i sodes offel sic magmatism oc curred in this por tion of the CowichanLake up lift. One sam ple of fel sic vol ca nic rocks from theMcLaughlin Ridge For ma tion and three sam ples ofSaltspring in tru sions yielded U-Pb ages in the range 356.5–359.1 Ma. A some what older U-Pb age of 369.7 Ma was ob -tained from a sep a rate body of the Saltspring in tru sions atBurgoyne Bay on the south west side of Saltspring Is land,in di cat ing that magmatism rep re sented by the McLaughlinRidge For ma tion and as so ci ated Saltspring in tru sions oc -curred over a time span of at least 15 Ma. There is in suf fi -cient age con trol avail able at this point to de ter minewhether the magmatism was continuous or episodic duringthis time period.Rocks in the Nanoose up lift (Fig ure 1) have been ten ta -tively cor re lated with both the Sicker Group and the ButtleLake Group, and com prise fine clastic rocks, chert,diabasic to andesitic vol ca nic rocks and lime stone (Yorathet al., 1999). A fos sil sam ple from crinoidal lime stone in the Nanoose up lift pro vided brachi o pods that yielded a Perm -ian age and fusulinids that yielded a Mid dle Penn syl va nianage (Mul ler, 1980). How ever, diabasic and andesitic pil low lavas in the area have un known strati graphic af fin i ties. Onthe Ballenas Is lands, how ever, these pil low lavas are as so -ci ated with green and grey chert, and are interbedded with aGeoscience BC Re port 2009-1 105305red tuff brec cia which con tains both scoriaceous mafic vol -ca nic clasts and crinoidal lime stone clasts. The as so ci a tionbe tween mafic flows, chert and a con spic u ous brec cia unitcon tain ing crinoidal lime stone clasts is strik ingly sim i lar togeo log i cal re la tion ships ob served in the Lacy Lake–HorneLake re gion (Ruks and Mortensen, 2007), suggesting apotential correlation between the two areas.The age and stra tig ra phy of rocks un der ly ing the Dragonand Do rado prop er ties, in the vi cin ity of Gold River andHesquiat, re spec tively, is poorly con strained. The Dragonprop erty is lo cated ap prox i mately 80 km west of Camp bellRiver, 20 km north west of Gold River and 65 km north westof the Myra Falls mine of Break wa ter Re sources Ltd. (Fig -ure 1). Re gional map ping of the Dragon prop erty area byMul ler (1977) in ter preted the rocks un der ly ing the Dragonprop erty as am phi bo lite-grade meta mor phic rocks be long -ing to the Westcoast Crys tal line Com plex. Mul ler de -scribed the Westcoast Crys tal line Com plex as am phi bo lite-faces meta mor phic rocks be long ing to the Mid dle Pa leo -zoic Sicker Group, the Late Pa leo zoic Buttle Lake Groupand the Tri as sic Karmutsen For ma tion. Af ter the dis cov eryof mas sive sulphides in float on the Dragon prop erty bypros pec tor E. Specogna, work by Noran da ge ol o gists cul -mi nated in the dis cov ery of the Falls and North VMS oc cur -rences (Kemp and Gill, 1993). Fur ther geo log i cal map pingand di a mond-drill ing by Noran da and Westmin ge ol o gistsin di cated that these show ings, with grades up to 7.33% Zn,1.34% Pb, 173 ppm Cu, 680 ppb Au and 19.2 g/t Ag over a2 m thick ness, are as so ci ated with the con tact zone be tween un der ly ing bi modal vol ca nic rocks and over ly ing sed i men -tary rocks and lime stone (Jones, 1997). Vol ca nic rocks ofthe Dragon prop erty that un der lie mas sive sul phide min er -al iza tion con sist of mas sive, flow-banded rhy o lite, an de site and tuffaceous fel sic and in ter me di ate vol ca nic rocks. Sed -i men tary and car bon ate rocks over ly ing and interlayeredwith mas sive sul phide min er al iza tion on the Dragonproperty consist of chert, mudstone, calcareous mudstone,fossiliferous felsic tuff, fossiliferous wackestone andmarble.The Do rado prop erty is lo cated ap prox i mately 17 km northof the vil lage of Hesquiat, on the west coast of Van cou verIs land. Like the Dragon prop erty, rocks un der ly ing the Do -rado prop erty were orig i nally in ter preted by Mul ler (1977)as am phi bo lite-fa cies meta mor phic rocks as signed to theWestcoast Crys tal line Com plex. How ever, geo log i calmap ping of the area by Mar shall et al. (2006) has shown there gion to be un der lain by abun dant mafic vol ca nic rocks ofpo ten tial Sicker Group af fin ity, and by sed i men tary andcar bon ate rocks of po ten tial Buttle Lake Group af fin ity.Fol low ing up on re ports by Mar shall et al. (2006) ofpolymetallic VMS-style stockwork min er al iza tion in thearea, Paget Re sources Cor po ra tion staked the Do rado prop -erty and soon af ter dis cov ered sev eral polymetallic mas sive sul phide oc cur rences. Mas sive sul phide min er al iza tion onthe Do rado prop erty is as so ci ated with the con tact be tweenmas sive, vari ably sil ica-al tered, clinopyroxene- and feld -spar-phyric andesite and overlying tuffaceous, volcano-sedimentary rocks.Results of New Fieldwork in the CowichanLake AreaMap ping for 2008 field work was con ducted us ing ESRI’sArcPad™ 7 on a Hewlett-Packard IPaq HX4700 Pocket PC wirelessly con nected to a GlobalSat® BT-359W BluetoothGPS re ceiver. The BC Geo log i cal Sur vey’s re gional ge ol -ogy com pi la tion for UTM Zone 10, south west ern BC, aswell as nu mer ous geo log i cal maps de rived from min eralex plo ra tion as sess ment re ports, were used for reference(Massey et al., 2005).Westridge Resources Inc.Due to fire-sea son ac cess re stric tions dur ing this field sea -son, only 1 day has been spent on Westridge Re sources Inc.ground thus far. As a re sult, ad di tional work on theWestridge Re sources min eral ten ure is planned for late No -vem ber of 2008. Work car ried out thus far has con cen tratedon re solv ing the geo log i cal set ting of the Breen Lake mas -sive sul phide oc cur rences (MINFILE 092B 090; Figure 3).The Breen Lake area is un der lain by east-strik ing, steeplydip ping, andesitic and rhyolitic vol ca nic rocks that havebeen in truded by gab bro. The most pro spec tive mas sivesul phide min er al iza tion dis cov ered to date in the BreenLake area is the Jane show ing. This show ing con sists of two adits re ported to in ter sect sev eral mas sive sul phide lenses(pyrrhotite-sphalerite-chal co py rite) up to 0.46 m wide and1.52 m long, of which a 0.91 m sam ple as sayed 16.1% Zn(Fyles, 1950; Pattison and Money, 1988). The adits of theJane show ing were lo cated dur ing the 2008 site visit, but nosul phide min er al iza tion could be found due to infill of theadits with over bur den. The adits are col lared in a zone ofstrongly fo li ated fel sic ash tuff, which is pre sumed to be thehost to the min er al iza tion. Ap prox i mately 500 m to the eastof the Jane adit, a new mas sive sul phide show ing was dis -cov ered in new ex po sure cre ated by re cent log ging-roadcon struc tion at the north end of Breen Lake. This show ingcon sists of a 10–20 cm wide band of mas sive py rite, chal co -py rite and trace sphalerite min er al iza tion hosted in a seri -cite- and chlorite-al tered, in ter me di ate to dacitic ash tuff(Fig ure 4). Much of the show ing is cov ered by road-build -ing ma te rial and over bur den, so the true size of the min er al -iza tion re mains to be es tab lished. Ad di tional work to becon ducted on Westridge Re sources ground this win ter willfo cus on eval u at ing the geo log i cal set ting of this new dis -cov ery, as well as that of other min eral oc cur rences in thevi cin ity. Par tic u lar at ten tion will be given to mapping newexposures of Sicker Group stratigraphy created by recentlogging-road construction in the area.106 Geoscience BC Sum mary of Ac tiv i ties 2008306Geoscience BC Re port 2009-1107 Fig ure 3. Re gional ge ol ogy, se lected min eral oc cur rences and ar eas of study for 2008 field work in the Cowichan Lake area (mod i fied from Massey et al., 2005).307Treasury Metals Inc.Work con ducted on Trea sury Met als Inc. ground this fieldsea son (the ‘Lara prop erty’) fo cused on vis it ing knownmin eral oc cur rences with the goal of es tab lish ing their geo -log i cal set ting and age, as well as on con duct ing field workin ar eas of new ex po sure cre ated by log ging-road con struc -tion. Un for tu nately, due to a de pressed for estry mar ket dur -ing the past few years, very lim ited log ging has been con -ducted on the Lara prop erty and, as a re sult, there has beenlit tle new ex po sure cre ated since the last main phase of ex -plo ra tion on the prop erty in the 1980s by Lara mide Re -sources Inc., Abermin Re sources Corp. and Minnova Inc.How ever, for estry com pa nies have re cently marked muchof the Lara prop erty for log ging, so there is a good chancethat new bed rock exposures will be created there in the near future.The Lara prop erty hosts many VMS oc cur rences, the mostno ta ble of which is the Lara VMS de posit or Cor o na tiontrend (Fig ure 3). It con sists of two main zones, the Cor o na -tion and Cor o na tion Ex ten sion zones, col lec tively re ferredto as the Cor o na tion trend, that com bine for an in di cated re -source at a 1% Zn cut-off of 1 146 700 tonnes at 3.01% Zn,1.05% Cu, 0.58% Pb, 32.97 g/t Ag and 1.97 g/t Au (Kelso et al., 2007). Sul phide min er al iza tion of the Cor o na tion andCor o na tion Ex ten sion zones is hosted by strongly si lici -fied, coarse-grained rhy o lite crys tal tuff and ash tuff (Kelsoet al., 2007). Sur face map ping and sam pling of two Cor o -na tion zone trenches was con ducted dur ing this study. Thewes tern most trench mapped in the Cor o na tion zone (UTMZone 10, 433489E, 5414841N, NAD83) is a flooded pitwith sparse bed rock ex po sure at its north end (Fig ure 5a).Here, dark grey to black, me dium-grained mas sivesulphides, con sist ing of 95% black sphalerite and 5% chal -co py rite, are in sharp con tact with an in tensely sil ica- andseri cite-al tered fel sic ash tuff con tain ing trace to 0.5%quartz and feld spar crys tals up to 3 mm in size (Fig ure 5a).Bed ding in this al tered tuff dips steeply to the north. Mas -sive sul phide min er al iza tion in this pit con tains elon gatedblebs of car bon ate up to 2 cm wide and 10 cm long. Theeast ern most trench mapped in the Cor o na tion zone (UTMZone 10, 433558E, 5414824N) con tains sim i lar, me dium-grained, mas sive sul phide min er al iza tion com pris ingabun dant black sphalerite with lesser chal co py rite and py -rite (Fig ure 5b). This min er al iza tion is hosted within astrongly si lici fied fel sic crys tal tuff with 2% quartz crys talsup to 2 mm in size and abun dant bull-quartz vein ing (up to30 cm in width). Sig nif i cant struc tural com plex ity is ex -posed in this trench, with fel sic tuff on the east side of themas sive sulphides be ing ob served to fold into the plane ofthe min er al iza tion (Fig ure 5b). No fold ing was ob served inar eas of the trench west of the mas sive sul phide min er al iza -tion, sug gest ing the po ten tial for sinistral drag fold ingalong the plane of mas sive sul phide min er al iza tion. The ab -sence of fault gouge as so ci ated with po ten tial fault mo tionin this area may be ex plained by strain ac com mo da tion viamas sive sul phide recrystallization. Abun dant concordantbull-quartz veining in felsic crystal tuff immediately east ofthe massive sulphide mineralization is probably the resultof space filling during folding (Figure 5b).The Randy North show ing (MINFILE 092B 128), lo catedap prox i mately 2 km to the north of the Cor o na tion zone(Fig ure 3), con sists of sev eral zones of anom a louspolymetallic min er al iza tion hosted in strongly seri cite-al -tered fel sic volcaniclastic rocks (Kelso et al., 2007). Ex po -sures in the vi cin ity of the Randy North show ing are of tencov ered by thick moss, mak ing geo log i cal map ping of thearea prob lem atic. In this area, mod er ately to strongly seri -cite-al tered and highly fo li ated fel sic crys tal tuff, with 1–3% quartz crys tals up to 5 mm size, hosts zones of in tensepy rite stockwork min er al iza tion. A small out crop of me -dium-grained, sandy in ter me di ate tuff was ob served ap -prox i mately 400 m to the south west of this area(downsection?). Mod er ately seri cite-al tered, quartz–108 Geoscience BC Sum mary of Ac tiv i ties 2008Fig ure 4. New mas sive sul phide min er al iza tion dis cov ered on theWestridge Re sources Inc. min eral ten ure in the Breen Lake area:A) me dium- to coarse-grained mas sive py rite with in ter sti tial chal -co py rite and trace sphalerite; B) close-up of mas sive sul phide min -er al iza tion.308potassic-feld spar por phyry be comes dom i nant to the westof the area, ex tend ing for at least 400 m along strike. Thisunit con tains up to 20% potassic feld spar and quartz pheno -crysts up to 5 mm in size, and may rep re sent thesubvolcanic heat source for the Randy North mineralizingsystem.The Hope show ing (MINFILE 092B 110) is sit u ated alongthe south ern flanks of Mount Brenton and ap prox i mately3.5 km south east of the Cor o na tion zone (Fig ure 3). Theshow ing com prises a small road side out crop of si lici fiedfel sic crys tal tuff with 1% quartz crys tals up to 2 mm in size. This tuff is in truded by gab bro, with in tense sili ci fi ca tion atthe con tact. Min er al iza tion ob served at the show ing con -sists largely of dis sem i nated py rite with trace chal co py riteveinlets and mal a chite stain ing. Sam pling of the Hopeshow ing by pre vi ous work ers has yielded re sults up to0.2% Cu, 0.85% Pb, 2.95 g/t Au and 25.03 g/t Ag, with bar -ium con tents av er ag ing about 2% (Belik, 1983). Sam plingof Hope show ing min er al iza tion for Pb iso tope anal y sis has been con ducted in or der to de ter mine if it is syngenetic with felsic volcanic rocks in the area.Ap prox i mately 1.7 km north of the Hope show ing, a po ten -tially new pro spec tive zone for VMS min er al iza tion hasbeen iden ti fied (Fig ure 3). Al though much of this zone ispoorly ex posed in road bed out crop, key strati graphic re la -tion ships are still vis i ble. Here, an in tensely seri cite-al teredfel sic ash tuff, with 1–2% dis sem i nated py rite and tracequartz crys tals, is over lain by a si lici fied argillite. Over ly -ing the si lici fied argillite is a chlorite schist with 15–20%an ker ite augen up to 5 mm in size. Col lec tively, this pack -age dips steeply to the north east. Mas sive sul phide min er al -iza tion at the Lenora adit, lo cated ap prox i mately 6 km tothe south east (Fig ure 3), is as so ci ated with the con tact be -tween a sim i lar, in tensely seri cite-al tered fel sic ash tuff andsi lici fied argillite (Ruks and Mortensen, 2006). The strati -graphic pack age that hosts anom a lous polymetallic min er -al iza tion of the Randy North zone is also capped by argillite (Kelso et al., 2007).The Anita zone (MINFILE 092B 037), lo cated ap prox i -mately 4.7 km north west of the Cor o na tion zone (Fig ure 3), con sists of polymetallic sul phide min er al iza tion sit u atedclose to the con tact be tween mafic tuffaceous rocks and fel -sic volcaniclastic rocks. The best drill in ter sec tion of theAnita ho ri zon to date is di a mond-drill hole 87-37, which in -ter sected 2.5 m of 2.37% Cu, 0.73% Pb, 2.73% Zn, 46 g/tAg and 0.72 g/t Au hosted in a py ritic fel sic tuff. An otherhole, 88-49, in cluded a 4.9 m in ter val of 2.3% Cu, 0.49%Pb, 3.66% Zn, 73.9 g/t Ag and 1.9 g/t Au. The li thol ogy thathosts the min er al iza tion in the Anita zone is not known, asthis in for ma tion is not avail able in as sess ment re ports.Map ping in the Anita zone (this study) has lo cated sev eralex po sures of mod er ately to in tensely seri cite-al tered fel sicash and crys tal tuff, with up to 1% quartz crys tals up to4 mm in size. Sam pling of fel sic vol ca nic rocks as so ci atedwith the Anita zone for U-Pb (zir con) geo chron ol ogy wascon ducted in or der to de ter mine if it is part of the sameGeoscience BC Re port 2009-1 109Fig ure 5. A) Mas sive sul phide min er al iza tion in con tact with si lici -fied fel sic ash tuff at the north west pit, Cor o na tion zone, Lara prop -erty of Trea sury Met als Inc. B) Mas sive sul phide min er al iza tionhosted by sil ica- and seri cite-al tered fel sic ash and crys tal tuff,north east pit, Cor o na tion zone; rocks on the east side of the mas -sive sul phide min er al iza tion are folded into the min er al iza tion, sug -gest ing the pres ence of drag fold ing. C) Fine- to me dium-grainedmas sive mag ne tite of the Lady B iron for ma tion of Trea sury Met alsInc. (MINFILE 092B 33).309strati graphic pack age that hosts the Cor o na tion trend or theBig Sicker Moun tain VMS de pos its. Field work this sum -mer also in di cated that the MINFILE lo ca tion for the Anitashow ing is in cor rect, with the Anita shaft lo cated at UTMco-or di nates Zone 10, 429862E, 5417127N (NAD83),approximately 450 m south of the MINFILE position.The Lady B iron for ma tion (MINFILE 092B 033) is sim i lar to other iron for ma tions oc cur ring in rocks that arestratigraphically above VMS min er al iza tion at the MyraFalls, Lenora, Tyee and Rich ard III oc cur rences, and is be -lieved to rep re sent ox ide-fa cies iron min er al iza tion re latedto hy dro ther mal min er al iz ing sys tems sim i lar to those thatformed the un der ly ing VMS de pos its. Re solv ing the tim ing of iron for ma tion min er al iza tion in the Sicker Group is crit -i cal for es tab lish ing the du ra tion of VMS-re lated hy dro -ther mal ac tiv ity. The Lady B iron for ma tion is lo cated be -neath a ma jor power line, and is ac ces si ble from the southvia a de ac ti vated log ging road in the vi cin ity of the Anitazone (Fig ure 3). The show ing con sists of a 15 m by 3 m out -crop of fine- to me dium-grained, mas sive black mag ne tite(Fig ure 5c). The mas sive mag ne tite con tains rusty py riticzones up to 30–40 cm in size and trace blebs of chal co py rite up to 2 mm in size. Abun dant dacitic to in ter me di ate vol ca -nic rocks are lo cated to the south of show ing. These vol ca -nic rocks are less fel sic than those as so ci ated with VMS oc -cur rences to the south (downsection?), and com prise lightgrey-green, dacitic to in ter me di ate tuff with abun dant feld -spar crys tals and weakly seri cite-al tered, flat tened pum iceclasts. Crys tal-poor, ash-rich lay ers of sim i lar col our arealso abun dant, many of which con tain chlorite-al tered, flat -tened pum ice clasts. In cer tain lo ca tions, ash-rich zonespick up a strong fab ric, be com ing phyllitic in tex ture andpo ten tially rep re sent ing zones of shear ing. Vol ca nic rocksmost prox i mal to the Lady B iron for ma tion were sam pledfor U-Pb (zir con) geo chron ol ogy in or der to re solve the ageof iron formation mineralization and constrain a minimumage for VMS-related hydrothermal activity in Sicker Group rocks of the Cowichan Lake area.Results of New Mapping in the Port AlberniAreaMap ping of Sicker Group bed rock ge ol ogy and sam -pling for lithogeochemistry, U-Pb zir con and Ar/Arhornblende geo chron ol ogy, and Pb, Nd and Hf iso topetracer stud ies was con ducted in the Port Alberni area. Thiswork was con cen trated 1) in the vi cin ity of re cent log gingac tiv ity south east of Horne Lake; 2) on min eral ten ureowned by Bitterroot Re sources Ltd. and Min eral CreekVen tures Inc.; and 3), in the McLaughlin Ridge area, in thevi cin ity of Kammat and Peak lakes (Fig ures 1, 6). Bed rockex po sure in all ar eas is mod er ate, with the best ex po suresoc cur ring in log ging-road cuts. Off-road ex po sures are typ -i cally cov ered with thick lay ers of moss and or ganic de tri -tus, often in forested, low-light conditions.Horne Lake AreaThe old est rocks en coun tered in re cent map ping south eastof Horne Lake (Fig ure 6, re gion A) are as signed to theNitinat For ma tion (Massey and Fri day, 1989). These con -sist largely of dark green, of ten clinopyroxene-phyricandesitic sandy tuff, lapilli tuff, tuff brec cia and ag glom er -ate. An de site clasts are dom i nantly subangular tosubrounded, vari ably he ma tite or sil ica al tered, vari ablyclinopyroxene phyric, and at tain sizes up to 15 cm.Clinopyroxene crys tals reach sizes up to 1 cm and are typ i -cally euhedral. Chlorite and epidote amygdules are of tenpres ent, reaching sizes up to 5 mm.Andesitic vol ca nic rocks pass up wards into a pack age oflow-en ergy ma rine sed i men tary rocks, con sist ing ofargillite, radiolarian chert and silty to sandy in ter me di atetuff. This re la tion ship is strik ingly sim i lar to that ob servedin the Lacy Lake–Horne Lake area, where chert, argilliteand in ter me di ate tuff also over lie mafic vol ca nic rocks(Ruks and Mortensen, 2007).Fel sic vol ca nic rocks pre dom i nate far ther upsection. Thesecon sist pri mar ily of dacite and rhyodacite lapilli tuff, tuffbrec cia and dacite in tru sions. Fel sic volcaniclastic rocks inthis area con tain potassic feld spar and bi o tite, as well asquartz-phyric dacite and rhyodacite clasts rang ing from<1 to 30 cm in size and from subrounded to subangular inshape (Fig ure 7a). Ma trix ma te rial in fel sic volcaniclasticrocks of this area con sists largely of feld spar, with morerare ex am ples con tain ing a mix ture of feld spar andeuhedral clinopyroxene. The pres ence of euhedralclinopyroxene crys tals in the ma trix of dacite-rhyodacitelapilli tuff and tuff brec cia is sig nif i cant, as it in di cates theco ex is tence of mafic and fel sic vol ca nism, or the re work ing of un der ly ing mafic vol ca nic ma te rial. In one lo cal ity, afeld spar- and bi o tite-phyric dacite plug is ob served to in -trude fel sic sandy tuff (Fig ure 7b). Feld spar and bi o titepheno crysts reach sizes of 5–7 mm. Trace quartz pheno -crysts were also ob served. Po ten tial peperitic in ter ac tionzones were ob served along the mar gin of the in tru sion. Inthese zones, mar gins of the dacitic plug were brecciating insandy tuff, with subangular to angular clasts of daciteporphyry ranging from <1 to 10 cm in size.Bitterroot Resources Ltd. and Mineral CreekVentures Inc.Work con tin ued on the Bitterroot Re sources Ltd. min eralten ure in the Port Alberni area this year (the ‘Deb bie prop -erty’), with the fo cus of re solv ing the age of Sicker Groupstra tig ra phy and con tained min eral oc cur rences in the area(Fig ure 6, re gions B and C). Much of the bed rock un der ly -ing the Bitterroot Re sources and Min eral Creek Ven turesmin eral ten ure is in ter preted to com prise rocks of the DuckLake and Nitinat For ma tions (Massey and Fri day, 1989).The Duck Lake For ma tion con sists of pil low ba salt, pil low110 Geoscience BC Sum mary of Ac tiv i ties 2008310Geoscience BC Re port 2009-1 111Fig ure 6. Re gional ge ol ogy (mod i fied from Massey, 2005), se lected min eral oc cur rences and ar eas of study for 2008 field work in the PortAlberni area.311brec cia and interflow mafic tuffaceous sed i men tary rocks,and is be lieved to rep re sent the oce anic crust upon whichthe Sicker arc was built (Massey and Fri day, 1989). Assuch, Duck Lake For ma tion rocks are in ter preted as theold est in the Sicker Group and, by de fault, the old est inWrangellia (Massey and Fri day, 1989). The VMS min er al -iza tion of the Deb bie 3 oc cur rence (MINFILE 092F 445),owned by Bitterroot Re sources and Min eral Creek Ven -tures, con sists of four stratiform lenses of banded mas sivesphalerite with mi nor chal co py rite and ga lena, each bandrang ing be tween 5 and 20 cm in thick ness. The best gradeob tained from sam pling of this min er al iza tion by pre vi ouswork ers in cludes 14.1% Zn, 0.87% Pb and 0.12% Cu over a 20 cm thick ness. The min er al iza tion is hosted in fine-grained chloritic schist with vari able car bon ate, seri cite and sil ica al ter ation (Ruks and Mortensen, 2007). The chloriticschist host ing Deb bie 3 min er al iza tion is spa tially as so ci -ated with clinopyroxene-phyric andesitic vol ca nic rocksas signed to the Nitinat For ma tion. The Deb bie 3 VMS oc -cur rence is there fore be lieved to rep re sent the old est VMSmin er al iza tion in the Sicker Group. Since most ex plo ra tionfor VMS min er al iza tion in the Sicker Group has fo cused on bi modal vol ca nic rocks be long ing to the McLaughlinRidge and Myra formations, the relatively unexploredDuck Lake and Nitinat formations represent attractivetargets for this style of mineralization.Due to the ab sence of rocks in the Nitinat and Duck Lakefor ma tions that are ame na ble to ra dio met ric dat ing, muchof the work con ducted on the Bitterroot Re sources andMin eral Creek Ven tures min eral ten ure this sea son fo cusedon lo ca t ing and sam p l ing rad io la r ian cher t fo rbiochronology. Sam ples of chert as so ci ated with mafic toin ter me di ate tuff as signed to the Nitinat For ma tion werecol lected from var i ous lo ca tions on the prop erty, most no ta -bly from chert interbedded with in ter me di ate tuff in the vi -cin ity of the Deb bie ex plo ra tion tun nel (Fig ure 6) andworkings in the immediate vicinity.In the Duck Lake area (Fig ure 6, re gion C), map ping andsam pling were con ducted on the Duck Lake For ma tiontype sec tion (Massey and Fri day, 1989), as well as in the vi -cin ity of the Re gina Cu-Au vein oc cur rence. Along theDuck Lake For ma tion type sec tion, mas sive pil low-ba saltflows al ter nate with interflow sandy to silty mafic tuff con -tain ing rare chert beds. Sev eral sam ples of sandy mafic toin ter me di ate tuff were col lected for U-Pb (zir con) geo -chron ol ogy. Pil low-ba salt flows were sam pled for geo -c h e m i c a l a n d i s o t o p e - t r a c e r s t u d i e s . W h e r erecrystallization was not too strong, chert was collected forradiolarians.A new min eral oc cur rence was dis cov ered on the BitterrootRe sources and Min eral Creek Ven tures min eral ten ure dur -ing this field work. This new min eral oc cur rence is lo catedap prox i mately 130 m south west of Duck Lake (Fig ure 6,re gion C). Here, a unit of mas sive diabase as signed to theTri as sic Karmutsen For ma tion is cross cut by sev eral gos sa -nous zones up to 30 cm in width (Fig ure 8b). These zonesare filled with 3–4% coarse py rite and up to 0.5% coarse-grained to blebby chal co py rite. In tense sili ci fi ca tion of thediabase is as so ci ated with these gos sa nous zones. A bed offine-grained mas sive sul phide (dom i nantly py rite) was dis -cov ered in a new ex po sure along China Creek Main (Fig -ure 6, re gion C). The bed is ap prox i mately 20 cm wide andinterbedded with si li ceous argillite (Fig ure 8a). Maficsandy tuff and scoriaceous mafic vol ca nic rocks are alsofound in the im me di ate vi cin ity of the min er al iza tion. Si li -ceous interbeds within the mas sive sulphide mineralizationwere sampled for radiolarian biostratigraphy.McLaughlin Ridge: Peak and Kammat LakesAreaThe type sec tion for the McLaughlin Ridge For ma tion(Yorath et al., 1999) is lo cated on McLaughlin Ridge, ap -prox i mately 18 km south east of Port Alberni and 1 km112 Geoscience BC Sum mary of Ac tiv i ties 2008Fig ure 7. Newly dis cov ered fel sic vol ca nic rocks in the Horne Lake area: A) rhyodacite lapilli tuff; B) feld spar-quartz–phyric dacite por -phyry in trud ing fel sic lapilli and sandy tuff; clasts of dacite por phyryare found in the tuff near the con tact zone with the in tru sion, sug -gest ing po ten tial peperitic in ter ac tion.312south west of Peak Lake (Fig ure 6, re gion D). TheMcLaughlin Ridge For ma tion in this area con sists ofvolcaniclastic strata, lesser greenstone and mi nor chert.Volcaniclastic rocks in the McLaughlin Ridge For ma tiontype-sec tion area are be lieved to rep re sent andesitic vol ca -nic rocks that have been re worked from the un der ly ingNitinat For ma tion. Yorath et al. (1999) cor re lated rocks ofthe McLaughlin Ridge For ma tion type-sec tion area withfel sic vol ca nic rocks and con tained VMS min er al iza tionfound in the Cowichan Lake and Buttle Lake up lifts (e.g.,the Big Sicker Moun tain/Lara and Myra Falls de pos its, re -spec tively). How ever, there are no ra dio met ric orbiostratigraphic ages to support any of these correlations. Re con nais sance field work this sum mer was con ducted inthe Peak and Kammat Lakes area (Fig ure 6, re gion D), inthe im me di ate vi cin ity of the McLaughlin Ridge For ma tion type sec tion (Yorath et al, 1999). Here, abun dant buff-weath er ing, of ten chev ron-folded, red and greenradiolarian chert is interbedded with green, in ter me di ate,silty to sandy tuff. The tuff is well sorted, with coarser frac -tions con tain ing abun dant feld spar crys tals. Radiolarianchert was sam pled in sev eral lo cal i ties. In one lo cal ity, lam -i nated radiolarian chert was ob served to have its bed dingde flected by an aphyric clast of un known li thol ogy (Fig -ure 9). This clast might be a coarse clast trans ported viaturbidite flow, or it may be a vol ca nic bomb. The lat ter pos -si bil ity is sig nif i cant as it would in di cate the co ex is tence ofvol ca nism dur ing chert de po si tion and would aid in cor re -la tions be tween stra tig ra phy in the McLaughlin Ridge areaand that of other Sicker Group localities.Rocks en coun tered in the Peak and Kammat Lakes area aredom i nated by radiolarian chert interbedded with in ter me di -ate tuff, but the chert be comes interlayered with ba salticsills to the south west. Ba saltic sills in trud ing the chertpack age of ten con tain abun dant spheru lites and quartzamygdules up to 4 mm in size; acicular feld spar pheno -crysts up to 1 mm in size; and subhedral, chlorite-al teredmafic pheno crysts up to 1.5 mm in size. Chert lay ers ap -Geoscience BC Re port 2009-1 113Fig ure 8. Newly dis cov ered min er al iza tion in the Port Alberni area: A) stratiform mas sive py rite in a new ex po sure along Duck LakeMain; the min er al iza tion is interbedded with si li ceous argillite,chert and mafic sandy to lapilli tuff; B) gos sa nous and sil ica-al tered zones within a mas sive diabase are as so ci ated with quartz-vein–hosted py rite and chal co py rite min er al iza tion; the dashed yel lowline is the trace of the min er al ized zone.Fig ure 9. A) Bed ding in radiolarian chert is de flected by a fine-grained, pur ple, rounded clast of un known li thol ogy. B) Highlyquartz-ve sic u lar and of ten spherulitic ba salt si lls in truderadiolarian chert; recrystallization of radiolarian chert is of ten ob -served in ar eas where ba salt sills are abun dant.313pear, in places, to have been mildly brecciated andrecrystallized by the sills. A large gabbroic in tru sion hasbeen mapped to the south west of these sills, and there is ahigh prob a bil ity that these ba saltic sills may be apophysesde rived from this larger in tru sion. Geo chem i cal sam plingof these sills has been con ducted in or der to de ter mine theiraf fin i ties. A lo cal ized chlorite- and ser pen tine-al tered zonewithin the gab bro was ob served to con tain trace mal a chitestain ing. Mal a chite stain ing in this zone is as so ci ated with a small pyrite-bearing pod approximately 20 cm in size.The abun dant chert, in ter me di ate tuff and gab bro ob servedin new bed rock ex po sures in the Peak and Kammat lakesarea dur ing this study all oc cur in ar eas pre vi ously mappedas McLaughlin Ridge, Nitinat and Duck Lake for ma tions(Yorath et al., 1999). Since these new ex po sures ofinterbedded chert and in ter me di ate tuff are not typ i cal unitsob served in the Nitinat and Duck Lake for ma tions, this sug -gests that there are sig nif i cant prob lems with ex ist ing geo -log i cal maps for the area that can only be resolved withadditional mapping.Results of Reconnaissance GeologicalFieldwork in the Nanoose Uplift AreaOne day of re con nais sance geo log i cal field work was con -ducted in the Nanoose up lift area (Fig ure 1). This work fo -cused on sam pling for U-Pb (zir con) geo chron ol ogy andradiolarian biostratigraphy. Sed i men tary rocks were mostcom mon and com prise interbedded argillite, grey-blacksiltstone, fine to coarse sand stone and green chert. Sand -stone in the area ranges from mod er ately to poorly sortedarenite and lithic arenite. This sand stone con tains an abun -dant feldspathic com po nent and, in places, abun dantsubrounded chert clasts. Sam ples for U-Pb (zir con) de tri talgeo chron ol ogy were taken from sev eral lo cal i ties. Sub -stan tial out crops of green chert were also ob served, es pe -cially in the im me di ate vi cin ity of the De part ment of Na -tional De fence na val base. This chert is typ i cally highlyfrac tured and, in places, was ob served to con tain po ten tialradiolarian fos sils. A large body of granodiorite ofunknown age was also observed and sampled forgeochronology.Results of Geological Mapping on theDorado and Dragon Properties (PagetResources Corporation), Hesquiat–GoldRiver AreaDorado PropertyGeo log i cal map ping at 1:5000 scale of a por tion of theprop erty (Paget Re sources Cor po ra tion; Fig ures 1, 10) wascon ducted over six days in 2007. The first visit was de -signed to fol low up on the dis cov ery by Mar shall et al.(2006) of polymetallic VMS-style stockwork min er al iza -tion hosted in mafic vol ca nic rocks. Re con nais sance geo -log i cal map ping in the vi cin ity of Mar shall’s show ing byPaget Re sources Cor po ra tion ge ol o gists led to the dis cov -ery of polymetallic mas sive sul phide min er al iza tion (Fig -ure 10, re gions A and B). Mas sive sul phide min er al iza tionhas so far been dis cov ered in two lo ca tions on the Do radoprop erty, and is as so ci ated with the con tact be tween maficvolcanic rocks and overlying tuffaceous sedimentaryrocks.The first mas sive sul phide min er al iza tion dis cov ered on the Do rado prop erty is lo cated in a shot-rock blast pit, near thecon tact be tween a vari ably sil ica-al tered, chlorite amyg -dule–bear ing, feld spar-phyric ba saltic flow and over ly ingin ter me di ate tuffaceous sand stone (Fig ure 10, re gion A).Here, a mas sive sul phide pod, mea sur ing 1.5 m by 3 m andcon sist ing of fine-grained pyrrhotite with trace chal co py -rite, is hosted within the ba salt. Sul phide string ers up to1 cm wide are abun dant near the mas sive sul phide min er al -iza tion. Nu mer ous mas sive sul phide boul ders of sim i larcom po si tion are found in close prox im ity to the show ing;some of them ap pear to have been used as sub strate for abridge cross ing a creek that drains im me di ately to the eastof the pit. The most si lici fied zones within the host ba saltare as so ci ated with abun dant quartz and epidote veinlets.Some zones of autobreccia are pres ent in the ba salt host.These zones con tain abun dant grey, glassy, an gu lar si lici -fied clasts up to 2 cm in size. Ap prox i mately 430 m south -west of this zone is a sec ond zone of mas sive sul phide min -er al iza tion (Fig ure 10, re gion B). Here, boul ders of fine- tome dium-grained mas sive pyrrhotite+chal co py rite, up to50 cm in size, oc cur as float be neath a large, gos sa nous out -crop of highly sil ica-al tered, feld spar-clinopyroxene–phyric an de site por phyry (Fig ure 11). Pyrrhotite min er al -iza tion is abun dant, as both string ers and dis sem i na tions.Euhedral feld spar and clinopyroxene pheno crysts form ap -prox i mately 25% of the rock. Plagioclase feld spar con sti -tutes ap prox i mately 85% of the phenocryst as sem blage and reaches sizes up to 3 mm. Clinopyroxene pheno crysts arevari ably chlorite al tered, form 15% of the phenocryst as -sem blage and reach sizes up to 1 cm. This al tered and min -er al ized por phyry was traced in the map area for ap prox i -mately 350 m to the south west along an over grown log gingskidder road. Less al tered, vari ably sul phide-min er al izedex am ples of feld spar- and clinopyroxene-phyric an de siteare abun dant in the map area (Fig ure 10, re gion C) and aremost likely rep re sen ta tive of mas sive in ter me di ate flows.These mafic vol ca nic rocks are mas sive and less por phy -ritic to nearly aphyric in na ture. They of ten con tain abun -dant epidote al ter ation in the form of ovoid patches up to10 cm in width. Fine-grained sul phide minerals are oftenfound in the cores of these patches. In places, pyrrhotite and chalcopyrite stringers are present, typically with strongsilica alteration along their margins.Over ly ing al tered and min er al ized mafic vol ca nic rocks are in ter ca lated tuff and mas sive in ter me di ate vol ca nic rocks114 Geoscience BC Sum mary of Ac tiv i ties 2008314Geoscience BC Re port 2009-1 115Fig ure 10. Re gional ge ol ogy, se lected min eral oc cur rences and ar eas of study for 2007 field work on the Do rado prop erty of Paget Re -sources Cor po ra tion (mod i fied from Mar shall et al., 2006).315(Fig ure 10, re gion D). Volcaniclastic rocks com priseheterolithic lapilli tuff with mafic vol ca nic and chert clastsin a feld spar-crys tal ma trix. Sandy in ter me di ate tuff, con -tain ing abun dant feld spar crys tals and vari able con cen tra -tions clinopyroxene crys tals, is also abun dant. Mas sivefeld spar-phyric por phyry of in ter me di ate com po si tion isas so ci ated with tuffaceous zones, but whether it representsintrusions or flows is undetermined.Dragon PropertyThe Dragon prop erty is lo cated ap prox i mately 80 km westof Camp bell River, 20 km north west of Gold River and65 km north west of the Myra Falls mine of Break wa ter Re -sources Ltd. (Fig ure 1). A com bi na tion of re con nais sanceand 1:5000 scale map ping was con ducted on the Dragonprop erty over 10 days. This work fo cused on es tab lish ingthe geo log i cal set ting for known min eral oc cur rences onthe prop erty, and for un der stand ing the stra tig ra phy of theprop erty ge ol ogy in gen eral. The work was suc cess ful iniden ti fy ing sev eral pro spec tive new zones of min er al iza -tion, in clud ing a new polymetallic massive sulphidediscovery (Figure 12).Mas sive sul phide min er al iza tion of the Dragon prop ertytyp i cally con sists of vary ing pro por tions of fine- to me -dium-grained mas sive pyrrhotite, chal co py rite andsphalerite at the con tact be tween fel sic vol ca nic rocks andover ly ing vol cano-sed i men tary and car bon ate rocks. Thispro spec tive ho ri zon has been traced over a strike length of4.4 km, and shows signs of VMS-style al ter ation and min -er al iza tion throughout (Figure 12).The orig i nal mas sive sul phide dis cov er ies on the Dragonprop erty in clude the Falls and North show ings, which com -prise three mas sive sul phide lenses with grades up to 7.33% Zn, 1.34% Pb, 173 ppm Cu, 680 ppb Au and 19.2 g/t Agover 2 m (Jones, 1997; Fig ure 12). This mas sive sul phidemin er al iza tion is interlayered with lam i nated chert,mudstone and cal car e ous mudstone that strikes south west -erly and dips steeply to the north west. Bi valve (?) fos silshave been ob served in cherty tuff over ly ing the Falls andNorth showings.Dur ing the course of this sum mer’s field work on theDragon prop erty, a new mas sive sul phide show ing was dis -cov ered ap prox i mately 1 km south of the Falls and Northshow ings (Fig ure 12, re gion A). This show ing con sists ofsev eral fine- to me dium-grained, pyrrhotite+chal co py rite–bear ing mas sive sul phide boul ders, up to 1.5 m by 1 m insize, found in float (Fig ure 13a). One of the boul ders con -tains mas sive sul phide min er al iza tion in con tact withstrongly sil ica-al tered aphyric rhy o lite, in di cat ing arhyolitic host for the min er al iza tion. These boul ders weredis cov ered at the top of a large set of cliffs con sist ing ofaphyric, flow-banded mas sive rhy o lite, and are lo catedprox i mal to the con tact zone be tween fel sic vol ca nic rocksand over ly ing sed i men tary and car bon ate rocks. This con -tact zone is ex posed in out crop ap prox i mately 50 m to thewest. Here, strongly sil ica-al tered and stockwork-sul -phide–min er al ized rhy o lite with lo cal ized zones of flowbrec cia is over lain by argillite, chert, siltstone, cal car e ousargillite and lime stone. Rhy o lite brec cia in this area con -tains an gu lar, jig saw-fit clasts, up to 6 cm in size, in a dark-col oured ma trix of fine-grained dis sem i nated gar net andbi o tite clots up to 1 cm in size. Chert beds in this con tactzone of ten con tain 0.5–1% dis sem i nated pyrrhotite, andargillite beds contain abundant pyrrhotite veinlets.Calcareous wackestone beds contain abundant coralfossils.An other new zone of min er al iza tion was dis cov ered ap -prox i mately 1 km north of the Falls and North show ings(Fig ure 12, re gion B). Here, sim i lar to the geo log i cal set -ting of the new mas sive sul phide dis cov ery south of theFalls and North show ings, in tensely sil ica-al tered andstockwork-sul phide (pyrrhotite and chal co py rite)–min er -al ized aphyric rhy o lite is con form ably over lain by fel sictuff, chert, argillite and car bon ate, which dip steeply to thewest-north west (Fig ure 13b). In tensely sil ica-al tered rhy o -116 Geoscience BC Sum mary of Ac tiv i ties 2008Fig ure 11. A) Mas sive pyrrhotite and chal co py rite min er al iza tionfrom re gion B of the Do rado prop erty of Paget Re sources Cor po ra -tion; B) Strongly sil ica-al tered and stockwork-sul phide–min er al -ized, clinopyroxene- and feld spar-phyric an de site por phyry fromre gion B of the Do rado prop erty.316Geoscience BC Re port 2009-1117 Fig ure 12. Re gional ge ol ogy (mod i fied from Massey, 2005; Jones, 1997), se lected min eral oc cur rences and ar eas of study for 2008 field work on the Dragon prop erty of Paget Re sources Cor -po ra tion.317lite in this area is highly gos sa nous and hosts abun dantpyrrhotite and chal co py rite string ers up to 2 cm thick. Dis -sem i nated sulphides con sist largely of pyrrhotite and reachcon cen tra tions up to 2%. Greater con cen tra tions of dis sem -i nated sulphides are as so ci ated with ar eas of strong sil icaal ter ation. Green chert con tain ing bands of fine-grainedgar net im me di ately over lie al tered and min er al ized rhy o -lite. Fossiliferous fel sic ash tuff over lies the chert and con -tains cri noid and coral fos sils. Car bon ate in creases in con -cen tra tion upsection and con sists of cal car e ous mudstone,and me dium- to coarse-grained mar ble that is interbeddedwith chert and silicified argillite (Figure 13b). Chertcontains up to 1% pyrrhotite blebs up to 2 mm in size.The ridge east of Leighton Peak hosts sub stan tial thick -nesses of mas sive, flow-banded, largely aphyric rhy o lite(Fig ure 12, re gion C). Flow band ing is very abun dant in fel -sic vol ca nic rocks, and its ori en ta tion gen er ally mim ics thatof re gional fab rics, which dip mod er ately to steeply to thewest-north west. Fold ing in the flow band ing is abun dant,and tends to oc cur as out crop-scale isoclines (Fig ure 13c).Since no prom i nent foliations were ob served in the vi cin ityof these tight folds or in the field area, it is prob a ble that thefold ing is not tec tonic but rather re lated to fold ing of therhy o lite due to vis cous drag dur ing erup tion. In places, thinsed i men tary ho ri zons can be ob served be tween flows.These are typ i cally black gra phitic argillite, of ten con tain -ing an gu lar clasts of aphyric rhy o lite up to 1 cm in size. Fel -sic vol ca nic rocks are also very abun dant in the NorgateCreek area, lo cated ap prox i mately 2 km south-south west of the Falls and North show ings (Fig ure 12, re gion D). Theserocks typ i cally com prise mas sive, weakly quartz-phyricrhy o lite that is vari ably sil ica al tered and min er al ized withsul phide string ers (pyrrhotite, sphalerite and chal co py rite). Near the top of a re cent log ging slash in the Norgate area, astrongly meta mor phosed heterolithic tuff brec cia was ob -served prox i mal to the con tact with over ly ing sed i men taryand car bon ate rocks. Here, meta mor phosed vol ca nic clastsup to 10 cm in size are vari ably stretched, an gu lar and of tenjig saw fit. Eighty per cent of the clasts con tain abun dantwhite sug ary mus co vite, and may rep re sent meta mor -phosed fel sic vol ca nic clasts. Fif teen per cent of clasts arerep re sented by a light grey va ri ety con tain ing 3% bi o titeporphyroblasts, and might rep re sent meta mor phosed in ter -me di ate vol ca nic rocks. Five per cent of the clasts con tainnearly 100% me dium- to coarse-grained bi o tite, and mayrep re sent meta mor phosed mafic vol ca nic rocks. The ma -trix of this brec cia con tains abun dant bi o tite porphyroblasts up to 3 mm in size. In places, this brec cia ac quires a fab ricre flected in strongly stretched meta vol can ic clasts in a bi o -tite-rich ma trix. Min er al iza tion in the Norgate Creek areacon sists of pyrrhotite and sphalerite string ers in felsicvolcanic rocks, and occurs both at the contact zone withoverlying carbonate sedimentary rocks and nearly 1 kmeast of this contact, within the felsic volcanic pile.In the Conuma River area, ap prox i mately 4 km to the south -west of the Falls and North show ings, fel sic vol ca nic rockscon sist of heterolithic tuff brec cia, graded beds oftuffaceous sed i men tary rocks and quartz-feld spar por phyry 118 Geoscience BC Sum mary of Ac tiv i ties 2008Fig ure 13. A) New mas sive sul phide min er al iza tion dis cov eredthis sum mer on the Dragon prop erty of Paget Re sources Cor po ra -tion. B) Con tact zone be tween mas sive, sil ica-al tered andstockwork-sul phide–min er al ized rhy o lite and over ly ing chert, fel -sic tuff and car bon ate rock; this con tact hosts all known mas sivesul phide oc cur rences on the Dragon prop erty. C) Folded, flow-banded rhy o lite on the ridge to the east of Leighton Peak.318sills (Fig ure 12, re gion E). In one out crop, a heterolithiclapilli tuff with white, aphyric, fel sic vol ca nic clasts andgrey siltstone clasts up to 2 cm in size nor mally grades intosandy tuff, silty tuff and mudstone. These rocks are in ter -preted to rep re sent turbidites. In the same out crop, thesevol cano-sed i men tary rocks are in truded by a quartz-feld -spar–phyric rhyodacite sill. This sill has ir reg u lar con tactswith the vol cano-sed i men tary rocks and, in many places, isob served to con tain en gulfed clasts of vol cano-sed i men -tary rocks. Fine-grained gar nets are pres ent as dis sem i na -tions within all rock types in the out crop but are found inlarger con cen tra tions within grey siltstone clasts. In the im -me di ate vi cin ity of this out crop is a heterolithic tuff brec ciacon tain ing large, subrounded clasts of quartz-feld spar por -phyry and grey siltstone up to 10 cm in size. These clasts are set in a ma trix con sist ing largely of feld spar crys tals. Gar -net and bi o tite porphyroblasts are pres ent in both the ma trix and the siltstone clasts. Strat i fied rocks in the ConumaRiver area have been ob served to dip both mod er ately andsteeply to the south west and north east, re spec tively, whichis sig nif i cantly dif fer ent from the prom i nent west-north -west dip ob served in strat i fied rocks to the north of NorgateCreek and east of Leighton Peak. More bed rock map ping isre quired in this area to con strain the lo ca tion of the con tactbe tween fel sic vol ca nic rocks and over ly ing sed i men taryand car bon ate rocks. Not only is this con tact highly pro -spec tive for VMS min er al iza tion, but it also serves as astratigraphic marker horizon that can help resolvedifferences in structural style throughout the property.Map ping on the Dragon prop erty this sum mer has shownthat po ten tial Sicker Group fel sic vol ca nic rocks are muchmore ex ten sive than is shown on ex ist ing geo log i cal mapsof the area (e.g., Fig ure 12, re gions B and E). More map -ping needs to be con ducted in the area to fur ther con strainthe ex tent of po ten tial Sicker Group bedrock geology.SummaryField work in 2008 has con tin ued with the fo cus of re solv -ing the stra tig ra phy and tec tonic his tory of the SickerGroup and its con tained min eral oc cur rences via a com bi -na tion of bed rock map ping and sam pling for geo chron ol -ogy (U-Pb, Ar/Ar), biostratigraphy (macrofossils, radio lar -ians and cono donts), geo chem is try (ma jor and traceel e ments) and iso to pic anal y ses (Nd and Pb; whole rockand sulphides, re spec tively). In the Cowichan Lake up lift,the goal of the field work has been to re solve the geo log i caland strati graphic set ting of VMS min er al iza tion, par tic u -larly for those VMS de pos its and oc cur rences on min eralten ure owned by Trea sury Met als Inc. and Westridge Re -sources Inc. Dur ing this sum mer, a new polymetallic mas -sive sul phide show ing was found on Westridge Re sourcesground, and a pro spec tive zone for VMS min er al iza tionwas iden ti fied on Trea sury Met als ground. Sam pling for U-Pb (zir con) geo chron ol ogy in the im me di ate vi cin ity of theLady B iron for ma tion (Trea sury Met als Inc.) was con -ducted to con strain the longevity of the VMS mineralizinghydrothermal system in the Cowichan Lake area.Field work in the Port Alberni area fo cused on ex am in ingnew bed rock ex po sures south east of Horne Lake, as well ascon tin u ing ex am i na tions of bed rock and min er al iza tionhosted by rocks of the Nitinat and Duck Lake for ma tions on ground owned by Bitterroot Re sources Ltd. Ex am i na tionsof new ex po sures in the Kammat and Peak lakes area werealso con ducted. South east of Horne Lake, re cent log gingac tiv ity has re sulted in the dis cov ery of a large area un der -lain by prox i mal fel sic vol ca nic rocks. This find ing ishighly sig nif i cant, as Sicker Group rocks of the PortAlberni area have pre vi ously been in ter preted to rep re senta depositional area dis tal from fel sic mag matic cen tres(Yorath et al., 1999). Not only does this new dis cov ery in di -cate the pres ence of a new cen tre of fel sic magmatism in theSicker Group, but it has large pos i tive im pli ca tions for theVMS po ten tial of Sicker Group rocks in the Port Alberniarea. Re con nais sance field work in new ex po sures of Sicker Group rocks of the Peak-Kammat lakes area has shown thatsig nif i cant re vi sions are nec es sary to the ex ist ing geo log i -cal map for the area. Sam pling of abun dant radiolarianchert in this area was con ducted to de ter mine an age forrocks of the McLaughlin Ridge For ma tion type sec tion(Yorath et al., 1999). Abun dant sam pling for geo chron ol -ogy and radiolarian biostratigraphy was con ducted onground owned by Bitterroot Re sources Ltd., to de ter minethe age of mafic vol ca nic rocks of the Nitinat and DuckLake for ma tions. Re solv ing the ages of these units is crit i -cal for un der stand ing the tem po ral evo lu tion of the Sickerarc, and the ear li est his tory of the Wrangellia Terrane. Twonew min eral oc cur rences were dis cov ered on the BitterrootRe sources min eral ten ure: stratiform mas sive sul phidemin er al iza tion interlayered with mafic vol ca nic rocks andsilicified argillite; and pyrite-chalcopyrite mineralizationassociated with strongly silica-altered zones in massivediabase.Re con nais sance field work in the Nanoose area fo cused onre solv ing the age of sed i men tary, car bon ate and vol ca nicrocks that have pre vi ously been in ter preted as po ten tialcor re la tives to the Buttle Lake and Sicker groups. Abun -dant sam pling for U-Pb (zir con) de tri tal geo chron ol ogyand radiolarian biostratigraphy was conducted.In the Gold River and Hesquiat ar eas, geo log i cal field workwas car ried out on po ten tial Sicker Group rocks un der ly ingthe Dragon and Do rado prop er ties, re spec tively (Paget Re -sources Corp.), where new polymetallic mas sive sul phideoc cur rences were dis cov ered. On the Do rado prop erty,mas sive sul phide min er al iza tion was dis cov ered by PagetRe sources Cor po ra tion ge ol o gists in sev eral lo cal i ties,both prox i mal to the con tact zone be tween clinopyroxene-phyric, vari ably sil ica-al tered and stockwork sul phide–Geoscience BC Re port 2009-1 119319min er al ized mafic vol ca nic rocks and over ly ing tuffaceoussed i men tary rocks. A new polymetallic mas sive sul phideoc cur rence and a new highly pro spec tive zone for VMSmin er al iza tion were dis cov ered on the Dragon prop erty.Mas sive sul phide min er al iza tion on the Dragon prop erty islo cated prox i mal to the con tact be tween mas sive, vari ablysil ica-al tered and stockwork sul phide–min er al ized fel sicvol ca nic rocks (dom i nantly rhy o lite flows) and over ly ingvol cano-sed i men tary rocks, chert and car bon ate rocks. The jux ta po si tion of fossiliferous car bon ate rocks and fel sictuff with un der ly ing VMS min er al iza tion and fel sic vol ca -nic rocks is ob served no where else in the Sicker Group Itraises the pos si bil ity that vol ca nic rocks and min er al iza tionon the Dragon property may represent a cycle of arcmagmatism and VMS mineralization not previouslyrecognized on Vancouver Island.Future WorkField work in 2009 will be pur sued in the Cowichan Lakeand Port Alberni ar eas, with ad di tional work planned in po -ten tial out crops of Sicker Group rocks in the BedingfieldBay and Muchalat In let (Gold River–Hesquiat) ar eas. Inthe Cowichan Lake area, work will fo cus on un der stand ingthe strati graphic and volcanological set ting of VMS oc cur -rences hosted by the Sicker Group, par tic u larly those of theLara/Cor o na tion, Randy and Anita zones, north and west of Big Sicker Moun tain (MINFILE oc cur rences 092B 129,092B 128 and 092B 037, re spec tively). Par tic u lar em pha -sis will be placed on un der stand ing the strati graphic andvolcanological set ting of other po ten tial VMS oc cur rencesin the im me di ate vi cin ity of, and west of, Cowichan Lake.Ad di tional re gional work in the Alberni area will fo cus oniden ti fy ing strati graphic marker ho ri zons within the SickerGroup that can be used to con strain the age of lithologicalunits in the area, par tic u larly those belonging to the DuckLake and Nitinat formations.In the Bedingfield Bay and Muchalat In let ar eas, sim i lar re -gional and fo cused out crop-scale map ping and sam plingwill be con ducted to better un der stand the stra tig ra phy andvolcanological set ting of po ten tial Sicker Group rocks andVMS oc cur rences, most no ta bly in the vi cin ity of the RantPoint oc cur rence (MINFILE oc cur rence 092F 494) and the Do rado and Dragon prop er ties (Paget Re sources Cor po ra -tion). In par al lel with the geo log i cal map ping and syn the siswork, the au thors will also carry out ad di tional U-Pb dat -ing, lithogeochemical, and Nd, Hf and Pb iso to pic stud iesto con strain the age and mag matic evo lu tion of SickerGroup vol ca nic rocks and to de velop a frame work throughwhich VMS oc cur rences hosted by the Sicker Group can be dis t in guished from younger, epigenetic sulphideoccurrences.AcknowledgmentsThis pro ject is jointly funded by a Geoscience BC grant,Bitterroot Re sources Ltd., Paget Re sources Cor po ra tion,Trea sury Met als Ltd., Westridge Re sources Inc., a Nat u ralSci ences and En gi neer ing Re search Coun cil of Can ada(NSERC) Dis cov ery Grant to JKM and an NSERC post -grad u ate schol ar ship to TR. The au thors thank N. Masseyfor dis cus sions and in sights into the ge ol ogy of the SickerGroup and S. Mc Kin ley for hav ing pro vided a crit i cal re -view of this manu script. The au thors thank C. Amy andW. Ruks for as sis tance in the field and Is land Tim ber landsfor land ac cess as sis tance. They also thank sev eral pros pec -tors, con sul tants and explorationists work ing on Van cou ver Is land, es pe cially M. Becherer of Min eral Creek Ven turesInc., M. Carr of Bitterroot Re sources Ltd., J. Brad ford ofPaget Re sources Cor po ra tion, E. Specogna of SpecognaMin er als Corp., T. Sadlier-Brown of Westridge Re sourcesInc., S. Mc Kin ley of Cam bria Geosciences, S. Tresierra,J. Houle, H. McMaster and the late A. Fran cis, for shar ingtheir time and knowledge of Sicker Group geology andmineralization.ReferencesBarrett, T.J. and Sherlock, R.L. (1996): Vol ca nic stra tig ra phy,lithogeochemistry and seafloor set ting of the H-W mas sivesul fide de posit, Myra Falls, Van cou ver Is land, Brit ish Co -lum bia; Ex plo ra tion and Min ing Ge ol ogy, v. 5, p. 421–458.Belik, G.D. (1983): Trench ing, geo phys i cal and geo log i cal re porton the Lara prop erty, Vic to ria Min ing Di vi sion, Brit ish Co -lum bia, 48°53′N, 123°52′W, NTS 92B/13W; BC Min is tryof En ergy, Mines and Pe tro leum Re sources, As sess mentReport 11123, 71 p.Brandon, M.T., Or chard, M.J., Parrish, R.R., Suther land Brown,A. and Yorath, C.J. (1986): Fos sil ages and iso to pic datesfrom the Pa leo zoic Sicker Group and as so ci ated in tru siverocks, Van cou ver Is land, Brit ish Co lum bia; in Cur rent Re -search, Part A, Geo log i cal Sur vey of Can ada, Pa per 86-1A,p. 683–696.Fyles, J.T. (1950): Jane, Sally and Sally No. 2; in Min is ter ofMines An nual Re port, 1949, BC Min is try of En ergy, Minesand Pe tro leum Re sources, p. A224–A225.Jones, M.I. (1997): 1996 as sess ment re port, Dragon prop erty, di a -mond drill ing, Alberni and Nanaimo Min ing Di vi sions,NTS map a r eas 92E/16E, 92L/1E, 49°55 ′00″N,126°20′00″W; BC Min is try of En ergy, Mines and Pe tro leum Re sources, As sess ment Re port 24895, 189 p.Juras, S.J. (1987): Ge ol ogy of the polymetallic volcanogenicButtle Lake camp, with em pha sis on the Price hill side, cen -tral Van cou ver Is land, Brit ish Co lum bia, Can ada; un pub -lished Ph.D. the sis, Uni ver sity of Brit ish Co lum bia,Van cou ver, BC, 279 p.Katvala, E.C. (2006): Re-ex am in ing the strati graphic andpaleontologic def i ni tion of Wrangellia; Geo log i cal So ci etyof Amer ica, Ab stracts with Pro gram, v. 38, p. 24.Kelso, I., Wetherup, S. and Takats, P. (2007): In de pend ent tech ni -cal re port and min eral re source es t i ma t ion, Larapolymetallic prop erty, Brit ish Co lum bia, Can ada; un pub -120 Geoscience BC Sum mary of Ac tiv i ties 2008320lished com pany re port pre pared by Caracle Creek In ter na -tional Con sult ing for Lara mide Re sources Ltd.Kemp, R. and Gill, G. (1993): Geo log i cal, geo chem i cal and di a -mond drill ing re port on the Specogna-Muchalat prop erty,NTS 92E/16, Alberni Min ing Di vi sion; BC Min is try of En -ergy, Mines and Pe tro leum Re sources, As sess ment Report23125, 48 p.Mar shall, D., Lesiczka, M., Xue, G., Close, S. and Fecova, K.(2006): Up date on the min eral de posit po ten tial of theNootka Sound re gion (NTS 092E), west coast of Van cou verIs land, Brit ish Co lum bia; in Geo log i cal Field work 2005,Geoscience BC, Re port 2006-1, p. 323–330.Massey, N.W.D. (1995): Ge ol ogy and min eral re sources of theDuncan sheet, Van cou ver Is land, 92B/13; BC Min is try ofEn ergy, Mines and Pe tro leum Re sources, Pa per 1992-4.Massey, N.W.D. and Fri day, S.J. (1987): Ge ol ogy of theChemainus River–Duncan area, Van cou ver Is land (92C/16,92B/13); BC Min is try of En ergy, Mines and Pe tro leum Re -sources, Pa per 1988-1, p. 81–91.Massey, N.W.D. and Fri day, S.J. (1989): Ge ol ogy of the Alberni–Nanaimo Lakes area, Van cou ver Is land (92F/1W, 92F/2Eand part of 92F/7); BC Min is try of En ergy, Mines and Pe tro -leum Re sources, Open File 1987-2.Massey, N.W.D., Mac In tyre, D.G., Desjardins, P.J. and Cooney,R.T., (2005): Dig i tal map of Brit ish Co lum bia: Tile NM10South west BC; BC Min is try of En ergy, Mines and Pe tro -leum Re sources, GeoFile 2005-3.MINFILE (2008): MINFILE BC min eral de pos its da ta base; BCMin is try of En ergy, Mines and Pe tro leum Re sources, URL<http://www.empr.gov.bc.ca/Mining/Geoscience/MINFILE/Pages/default.aspx> [No vem ber 2008].Mortensen, J.K. (2005): Strati graphic and paleotectonic stud ies ofthe Mid dle Pa leo zoic Sicker Group and con tained VMS oc -cur rences, Van cou ver Is land, Brit ish Co lum bia; in Geo log i -cal Field work 2005, BC Min is try of En ergy, Mines andPe tro leum Re sources, Pa per 2006-1, p. 331–336.Mul ler, J.E. (1977): Ge ol ogy of Van cou ver Is land; Geo log i calSur vey of Can ada, Open File 463, 1:250 000 scale.Mul ler, J.E. (1980): The Pa leo zoic Sicker Group of Van cou ver Is -land, Brit ish Co lum bia; Geo log i cal Sur vey of Can ada, Pa -per 79-30, 23 p.Pattison, J.M. and Money, D.P. (1988): 1987 drill ing re port on theWest claims; Pro ject # 094/107, sit u ated 1 km west ofCrofton, BC in the Vic to ria Min ing Di vi sion; BC Min is tryof En ergy, Mines and Pe tro leum Re sources, As sess ment Re -port 17007, 252 p.Ruks, T.R. and Mortensen, J.K. (2006): Geo log i cal set ting ofvolcanogenic mas sive sul phide oc cur rences in the Mid dlePa leo zoic Sicker Group of the south east ern Cowichan Lakeup lift (NTS 092B/13), south ern Van cou ver Is land; in Geo -log i cal Field work 2006, Geoscience BC, Re port 2007-1, p.381–394.Ruks, T. and Mortensen, J.K. (2007): Geo log i cal set ting ofvolcanogenic mas sive sul phide oc cur rences in the Mid dlePa leo zoic Sicker Group of the Cowichan Lake up lift, PortAlberni area, south ern Van cou ver Is land, Brit ish Co lum bia;in Geoscience BC Sum mary of Ac tiv i ties 2007, GeoscienceBC, Re port 2008-1, p. 77–92.Sluggett, C.L. (2003): Ura nium-lead age and geo chem i cal con -straints on Pa leo zoic and Early Me so zoic magmatism inWrangellia Terrane, Saltspring Is land, Brit ish Co lum bia;un pub lished B.Sc. the sis, Uni ver sity of Brit ish Co lum bia,Van cou ver, BC, 56 p.Sluggett, C.L. and Mortensen, J.K. (2003): U-Pb age and geo -chem i cal con straints on the paleotectonic evo lu tion of thePa leo zoic Sicker Group on Saltspring Is land, south west ernBrit ish Co lum bia; Geo log i cal As so ci a tion of Can ada–Min -er al og i cal As so ci a tion of Can ada, Joint An nual Meet ing,Pro gram with Ab stracts, v. 28.Yorath, C.J., Suther land Brown, A. and Massey, N.W.D. (1999):LITHOPROBE, south ern Van cou ver Is land, Brit ish Co lum -bia: ge ol ogy; Geo log i cal Sur vey of Can ada, Bul le tin 498,145 p.Geoscience BC Re port 2009-1 121321New Results of Geological Mapping and Micropaleontological and Lead IsotopicStudies of Volcanogenic Massive Sulphide–Hosting Stratigraphy of the Middle andLate Paleozoic Sicker and Buttle Lake Groups on Vancouver Island, BritishColumbia (NTS 092B/13, 092C/16, 092E/09, /16, 092F/02, /05, /07)T. Ruks, Mineral Deposit Research Unit, Department of Earth and Ocean Sciences, University of BritishColumbia, Vancouver BC; tyler_ruks@hotmail.comJ.K. Mortensen, Mineral Deposit Research Unit, Department of Earth and Ocean Sciences, University of British Columbia, Vancouver BCF. Cordey, CNRS UMR 5125, Université Claude Bernard Lyon 1, 69622, Villeurbanne Cedex, FranceRuks, T., Mortensen, J.K. and Cordey, F. (2010): New re sults of geo log i cal map ping, micropaleontological and lead iso to pic stud ies ofvolcanogenic mas sive sul phide–host ing stra tig ra phy of the mid dle and late Pa leo zoic Sicker and Buttle Lake groups on Van cou ver Is land,Brit ish Co lum bia (NTS 092B/13, 092C/16, 092E/09, /16, 092F/02, /05, /07); in Geoscience BC Sum mary of Ac tiv i ties 2009, GeoscienceBC, Report 2010-1, p. 149–170.IntroductionVolcanogenic strata of the mid-Pa leo zoic Sicker Group onVan cou ver Is land (Fig ure 1) oc cur in sev eral dis tinct base -ment highs (re ferred to herein as ‘up lifts’). These rockshost the world-class Myra Falls volcanogenic mas sive sul -phide (VMS) de posit (com bined pro duc tion and provenand prob a ble re serves in ex cess of 40 mil lion tonnes of Zn-Cu-Au-Ag sulphides), as well as nu mer ous other VMS de -pos its and oc cur rences, in clud ing those in the Big SickerMoun tain area in the south east ern part of the CowichanLake up lift (Fig ure 1). Three of these de pos its in theCowichan Lake up lift, the Lenora, Tyee and Rich ard III(MINFILE oc cur rences 092B 001, 092B 002, 092B 003;MINFILE, 2010), have seen lim ited his tor i cal pro duc tion.The Lara de posit (MINFILE oc cur rence 092B 129), far -ther to the north west, also con tains a sig nif i cant drill-in di -cated re source of 1 146 700 tonnes grad ing 3.01% Zn,1.05% Cu, 0.58% Pb, 32.97 g/t Ag and 1.97 g/t Au (Kelso et al., 2007).Geo log i cal map ping (Massey and Fri day, 1987; Ruks andMortensen, 2007) in di cates that the Big Sicker Moun tainarea con sists mainly of de formed mafic to fel sic vol ca nicand volcaniclastic rocks of the Nitinat and McLaughlinRidge for ma tions, and high-level in tru sions of theSaltspring in tru sive suite, as well as abun dant gabbroicdikes and sills of the Tri as sic Mount Hall gab bro (Fig ure 2). Re cent geo log i cal map ping in the Cowichan Lake up lift(Ruks et al., 2009a; this study) has been a con tin u a tion ofthe au thors’ ef forts to de velop a strati graphic frame workfor the Sicker Group and con tained VMS min er al iza tion.Work con ducted on min eral ten ure owned by pro ject spon -sors Trea sury Met als Inc. and Westridge Re sources Inc. inthe Cowichan Lake up lift con cen trated on re solv ing thegeo log i cal set ting and age of the Lara VMS de posit andother VMS oc cur rences in the area, as well as ex am in ingnew ex po sures cre ated by re cent log ging ac tiv ity. In 2008,re con nais sance field work on new bed rock ex po sure owned by Westridge Re sources Inc. cul mi nated in the dis cov ery of a new VMS oc cur rence (Ruks et al., 2009a). Map ping in2008 in the Mount Brenton area on min eral ten ures ownedby Trea sury Met als Inc. iden ti fied a pro spec tive zoneGeoscience BC Re port 2010-1 149Keywords: Van cou ver Is land, Pa leo zoic, Sicker Group, ButtleLake Group, Cowichan Lake up lift, volcanogenic mas sive sul -p h i d e , s t r a t i g r a p h y, U - P b z i r c o n g e o c h ro n o l o g y,lithogeochemistryThis pub li ca tion is also avail able, free of charge, as col our dig i talfiles in Adobe Ac ro bat® PDF for mat from the Geoscience BCwebsite: http://www.geosciencebc.com/s/DataReleases.asp.Fig ure 1. Dis tri bu tion of Pa leo zoic strata of the Sicker and ButtleLake groups on Van cou ver Is land and the Gulf Is lands.322where in tensely seri cite-al tered and py rite-min er al ized fel -sic ash tuff is over lain by si lici fied argillite and a chlorite-al tered ash tuff of in ter me di ate com po si tion (Ruks et al.,2009a). A sim i lar geo log i cal set ting is rec og nized in the vi -cin ity of VMS min er al iza tion at the Lenora de posit north ofthe Chemainus River (Ruks and Mortensen, 2007). Geo -log i cal map ping and sam pling were also fo cused in the vi -cin ity of the Lady A, Lady C and Lady D iron for ma tions(MINFILE oc cur rences 092B 029, 092B 033 and092B 076, re spec tively; Ruks et al., 2009a). These iron for -ma tions are sim i lar to other iron for ma tions oc cur ring inrocks that are in ter preted to lie stratigraphically aboveVMS min er al iza tion at the Lenora, Tyee and Rich ard III oc -cur rences, and are be lieved to rep re sent ox ide-fa cies ironmin er al iza tion re lated to hy dro ther mal min er al iz ing sys -tems sim i lar to those that formed the underlying VMS de -pos its. Resolving the timing of iron formation min er al iza -tion in the Sicker Group is critical for establishing theduration of VMS-related hydrothermal activity.Geo log i cal map ping in the Cowichan Lake up lift of thePort Alberni area (Massey and Fri day, 1989) in di cates thatthis area is largely un der lain by ba salt to ba saltic an de site of the Duck Lake and Nitinat for ma tions, re spec tively, in ad -di tion to fel sic tuffaceous volcaniclastic rocks be long ing tothe McLaughlin Ridge For ma tion. McLaughlin Ridge For -ma tion rocks in the Port Alberni area are in ter preted to rep -re sent de po si tion dis tal from a vol ca nic cen tre, which isthought to be rep re sented in the Saltspring Is land–Cowi -chan Lake area by fel sic in tru sive rocks of the Saltspring in -tru sive suite (Massey and Fri day, 1989). How ever, geo log i -cal map ping and geo chron ol ogy of new ex po sures in thePort Alberni area (Ruks et al., 2009a; this study) in di catethat sig nif i cant quan ti ties of fel sic vol ca nic rocks ofMcLaughlin Ridge For ma tion age or youn ger are pres ent in this area. In ad di tion, mafic vol ca nic rocks in the Lacy Lake area that were pre vi ously as signed to the pre–Late De vo -nian Duck Lake For ma tion have been dem on strated to bePerm ian in age, based on microfossil dat ing (Ruks et al.,2009a). These strati graphic re vi sions ne ces si tate a re in ter -pre ta tion of the nature of the Sicker Group and its VMSpotential in the Port Alberni area.Sed i men tary, mafic vol ca nic and car bon ate rocks of theNanoose up lift have been ten ta tively cor re lated with boththe Sicker and Buttle Lake groups (Yorath et al., 1999).How ever, no geo chron ol ogi cal or biostratigraphic con -straints are cur rently avail able from this area; hence, cor re -la tion with the Sicker Group is un proven. Re con nais sancefield work in the Nanoose up lift in 2009 fo cused on sam -pling pro spec tive rock types for geo chron ol ogy andbiostratigraphy in or der to re solve the re la tion ship be tweenvol ca nic and sed i men tary rock units in the Nanoose up liftand the Sicker and younger strata elsewhere on VancouverIsland. A large ex panse of vol ca nic and sed i men tary rocks and as -so ci ated VMS min er al iza tion, in ferred to be of Pa leo zoicage, has been mapped by pre vi ous work ers in the Beding -field up lift, near the en trance to Bedwell Sound, north ofTofino (e.g., Mul ler, 1977; Gatchalian, 1985; Fig ure 1).These units have been ten ta tively cor re lated with the Sicker Group; how ever, no iso to pic or fos sil ages are pres entlyavail able for this area. Field work in this area in 2009 con -cen trated on re solv ing the age of VMS min er al iza tion andits host stratigraphy.Map ping in the Hesquiat and Gold River ar eas, on the Do -rado and Dragon prop er ties, re spec tively (Paget Re sourcesCor po ra tion; Fig ure 1), has iden ti fied sev eral new VMS oc -cur rences hosted in rocks that have been ten ta tively cor re -lated with the Sicker Group (Ruks et al., 2009a). Geo log i -cal map ping and sam pling on the Dragon prop erty bypre vi ous work ers iden ti fied sev eral polymetallic mas sivesul phide lenses with grades up to 7.33% Zn, 1.34% Pb,173 ppm Cu, 680 ppb Au and 19.2 g/t Ag over thick nessesof up to 2 m (Jones, 1997). Geo log i cal map ping of theDragon prop erty in di cates that mafic and fel sic vol ca nicrocks and con tained VMS min er al iza tion are over lain byvol cano-sed i men tary and car bon ate rocks, in clud ing cal -car e ous tuffaceous sed i men tary rocks and fossiliferouslime stone, re spec tively (Jones, 1997; Ruks et al., 2009a;this study). No where else in the Sicker Group are car bon aterocks ob served to di rectly, and ap par ently con form ably,over lie fel sic vol ca nic rocks and VMS min er al iza tion. Thisre la tion ship in di cates that rad i cal strati graphic dif fer encesex ist be tween rocks of the Dragon prop erty and better stud -ied ex po sures of the Sicker Group in the Cowichan Lakeand Myra Falls ar eas. These strati graphic dif fer ences maybe ex plained by re gional changes in vol ca nic andsedimentological fa cies or, al ter na tively, the presence of anunrecognized cycle of Paleozoic arc magmatism and VMSmineralization on Vancouver Island.150 Geoscience BC Sum mary of Ac tiv i ties 2009Fig ure 2. Strati graphic no men cla ture for the Sicker and ButtleLake groups on Van cou ver Is land (mod i fied from Yorath et al.,1999).323Field work in the Sicker Group in 2009 com menced in lateJuly and fin ished in mid-Oc to ber. Both re con nais sance andde tailed geo log i cal map ping, to gether with sam pling forlithogeochemistry, U-Pb zir con dat ing, and Nd, Hf and Pbiso to pic stud ies, were con ducted in the Cowichan Lake,Port Alberni, Nanoose, Bedingfield, Gold River and Hes -quiat ar eas dur ing this pe riod. This pa per pres ents a sum -mary of this field work, with em pha sis on key strati graphicre la tion ships and areas of economic importance.Regional Geology of the Sicker GroupThe mid-Pa leo zoic Sicker Group on south ern and cen tralVan cou ver Is land rep re sents the old est rocks in Wrangellia. Equiv a lents of the Sicker Group are not pres ent in Wran -gellia in north west ern Brit ish Co lum bia, south west ern Yu -kon and south ern Alaska, where the old est rock units arethe Skolai Group, which is no older than Penn syl va nian(e.g., Katvala, 2006). This, and other dif fer ences be tweenthe Wrangellian stra tig ra phy on Van cou ver Is land and thatin more north erly ex po sures, em pha size the lack of un der -stand ing re gard ing much of Wrangellia (e.g., Katvala,2006) and the need for fur ther stud ies. The Cowichan Lakeup lift on Van cou ver Is land and ad ja cent por tions of theGulf Is lands is the larg est of four up lifts that ex pose theSicker Group and the overlying late Paleozoic Buttle LakeGroup (Figure 1).Pre vi ous de tailed stud ies of the Sicker Group have fo cusedmainly on the strati graphic set ting of VMS min er al iza tionat the Myra Falls de pos its in the Buttle Lake up lift (Fig -ure 1; e.g., Juras, 1987; Barrett and Sherlock, 1996). Re -gional map ping of the Cowichan Lake up lift by Massey and Fri day (1987, 1989) and Yorath et al. (1999) led to a strati -graphic frame work that may be ap pli ca ble to the en tireSicker Group (Fig ure 2). This frame work, how ever, isbased on map ping in only one of the four main up lifts ofSicker Group rocks, and is sup ported by a lim ited amountof biostratigraphic and iso to pic age data (e.g., Brandon etal., 1986). Ma jor along- and across-strike fa cies changesand geo chem i cal vari a tions are to be ex pected in sub ma rine vol ca nic se quences such as the one that forms the SickerGroup; hence, the re gional ap pli ca bil ity of the strati graphic frame work of Yorath et al. (1999) must be tested with de -tailed map ping and sub se quent lithogeochemical and U-Pbdat ing stud ies. This is crit i cal for re gional ex plo ra tion forVMS de pos its within the Sicker Group. For ex am ple, theques tions of whether VMS de pos its and oc cur rences in theCowichan Lake up lift are all of the same age, and whethertheir hostrocks are di rectly cor re la tive with those that hostthe Myra Falls deposit, are of obvious importance.The most re cent re gional map ping and strati graphic workwithin Sicker Group rocks of the Cowichan Lake up lift hasbeen con ducted by Massey (1995) and Yorath et al. (1999).The fol low ing in for ma tion re gard ing Sicker Group ge ol -ogy and stra tig ra phy in the Cowichan Lake up lift is de rivedfrom these ac counts. The Sicker Group within theCowichan Lake up lift is pres ently in ter preted to rep re sentthree dis tinct vol ca nic and volcaniclastic as sem blages thatto gether are thought to re cord the evo lu tion of an oce anicmag matic arc (Massey, 1995; Yorath et al., 1999). The low -er most Duck Lake For ma tion yields mainly nor mal mid-ocean-ridge ba salt (N-MORB) geo chem i cal sig na tures(Massey, 1995) and is in ter preted to rep re sent the oce anic-crust base ment on which the Sicker arc was built. The up per por tions of the Duck Lake For ma tion yield tholeiitic tocalcalkaline com po si tions and may rep re sent prim i tive arcrocks. The Duck Lake For ma tion is over lain by the NitinatFor ma tion, which com prises mafic, sub ma rine vol ca nicand volcaniclastic rocks with dom i nantly calcalkaline com -po si tions and trace-el e ment sig na tures typ i cal of vol ca nicarc set tings. These rocks are in ter preted as an early stage ofarc de vel op ment. The andesitic to mainly dacitic andrhyolitic McLaughlin Ridge For ma tion over lies the Nitinatand is be lieved to be cor re la tive with the Myra For ma tion,the hostrocks for the Myra Falls de pos its (Fig ure 2). Rocksof the McLaughlin Ridge and Myra For ma tions re flect amore evolved stage of arc ac tiv ity. Erup tion of Nitinat vol -ca nic and volcaniclastic rocks ap pears to have oc curredfrom sev eral widely scat tered cen tres, whereas theMcLaughlin Ridge For ma tion within the Cowichan Lakeup lift is thought to rep re sent erup tion from one or more ma -jor vol ca nic ed i fices. The abun dance of prox i mal fel sicvolcaniclastic rocks and the pres ence of vo lu mi nouscomagmatic fel sic in tru sions in the Saltspring Is land andDuncan ar eas (Fig ure 1) in di cate that one of these ma jorvol ca nic cen tres was lo cated in this area. Plant fos sils in di -cate that at least a mi nor amount of the McLaughlin Ridgevol ca nism oc curred in a subaerial set ting. In the PortAlberni area, the McLaughlin Ridge For ma tion has pre vi -ously been in ter preted to com prise fel sic, fine-grainedtuffaceous volcaniclastic and epiclastic rocks, sug gest ingde po si tion dis tal from a vol ca nic cen tre (Yorath et al.,1999). The iden ti fi ca tion of sig nif i cant quan ti ties of prox i -mal fel sic vol ca nic rocks in the Alberni area in 2009 sug -gests that an ad di tional fel sic vol ca nic cen tre may be in thePort Alberni area. De po si tion of sed i men tary and vol cano-sed i men tary rocks of the over ly ing Fourth Lake For ma tionof the Buttle Lake Group fol lowed the ces sa tion of Sickerarc magmatism, and scarce mafic vol ca nic rocks con tainedwithin the Fourth Lake For ma tion yield en riched tholeiiticrather than the calcalkaline compositions that characterizethe McLaughlin Ridge. Massey (1995) speculated that theButtle Lake Group may represent a marginal-basinassemblage that developed on top of the Sicker arc.Stud ies of the Sicker and Buttle Lake groups on south ernSaltspring Is land by Sluggett (2003) and Sluggett andMortensen (2003) pro vided new U-Pb zir con age con -straints on both fel sic vol ca nic rocks of the McLaughlinGeoscience BC Re port 2010-1 151324Ridge For ma tion and sev eral bod ies of Saltspring in tru -sions. This work dem on strated that two dis tinct ep i sodes offel sic magmatism oc curred in this por tion of the CowichanLake up lift. One sam ple of fel sic vol ca nic rocks from theMcLaughlin Ridge For ma tion and three sam ples ofSaltspring in tru sions yielded U-Pb ages in the range 356.5–359.1 Ma. A some what older U-Pb age of 369.7 Ma was ob -tained from a sep a rate body of the Saltspring in tru sions atBurgoyne Bay on the south west side of Saltspring Is land,in di cat ing that magmatism rep re sented by the McLaughlinRidge For ma tion and as so ci ated Saltspring in tru sions oc -curred over a time span of at least 15 m.y. There is in suf fi -cient age con trol avail able at this point to de ter minewhether the magmatism was continuous or episodic duringthis time period.Rocks in the Nanoose up lift (Fig ure 1) have been ten ta -tively cor re lated with both the Sicker Group and the ButtleLake Group, and com prise fine clastic rocks, chert,diabasic to andesitic vol ca nic rocks and lime stone (Yorathet al., 1999). A fos sil sam ple from crinoidal lime stone in the Nanoose up lift pro vided brachi o pods that yielded a Perm -ian age and fusulinids that yielded a Mid dle Penn syl va nianage (Mul ler, 1980). How ever, diabasic and andesitic pil low lavas in the area have un known strati graphic af fin i ties. Onthe Ballenas Is lands, how ever, these pil low lavas are as so -ci ated with green and grey chert, and are interbedded with ared tuff brec cia that con tains both scoriaceous mafic vol ca -nic clasts and crinoidal lime stone clasts. The as so ci a tionbe tween mafic flows, chert and a con spic u ous brec cia unitcon tain ing crinoidal lime stone clasts is strik ingly sim i lar togeo log i cal re la tion ships ob served in the Lacy Lake–HorneLake re gion (Ruks and Mortensen, 2008), suggesting apotential correlation between the two areas.Rocks and VMS min er al iza tion in the Bedingfield up lift(Fig ure 1), prox i mal to the en trance to Bedwell Sound,have his tor i cally been cor re lated with those of the SickerGroup, al though no geo chron ol ogi cal or biostratigraphicdata ex ist to sup port this claim. Fel sic vol ca nic rocks, com -pris ing wa ter-laid rhy o lite flows and tuffs, rep re sent theold est rocks in the area. These have been cor re lated by pre -vi ous work ers with the McLaughlin Ridge For ma tion.Lime stone as signed to the Buttle Lake Group is in ter pretedto un con form ably over lie fel sic vol ca nic rocks through outthe field area (Blackwell and Lajoie, 1986), but no de scrip -tion of the na ture of this un con formity is pro vided.Polymetallic VMS min er al iza tion oc curs in sev eral show -ings through out the field area, most no ta bly at the BayCreek, Rant Point and Claim Post MINFILE oc cur rences(MINFILE 092F 343, 092F 494 and 092F 290, re spec -tively). Volcanogenic mas sive sul phide min er al iza tion inthe area is hosted by vari ably sil ica-seri cite–al tered fel sicvol ca nic rocks, with the most no ta ble grades re ported fromthe Bay Creek show ing, where a 4 m thick lens of mas sivesul phide min er al iza tion is re ported to grade 228.00 g/t Ag,0.41 g/t Au, 0.62% Pb, 0.061% Cu and 0.017% Zn (Gat -chalian, 1985).The age and stra tig ra phy of rocks un der ly ing the Dragonand Do rado prop er ties, in the vi cin ity of Gold River andHesquiat, re spec tively, is poorly con strained. The Dragonprop erty is lo cated ap prox i mately 80 km west of Camp bellRiver, 20 km north west of Gold River and 65 km north westof the Myra Falls mine of Break wa ter Re sources Ltd. (Fig -ure 1). Re gional map ping of the Dragon prop erty area byMul ler (1977) led to an in ter pre ta tion of the rocks un der ly -ing the prop erty as am phi bo lite-grade meta mor phic rocksbe long ing to the Westcoast Crys tal line Com plex. Mul lerde scribed the Westcoast Crys tal line Com plex as am phi bo -lite-faces meta mor phic rocks be long ing to the mid dle Pa -leo zoic Sicker Group, the late Pa leo zoic Buttle Lake Groupand the Tri as sic Karmutsen For ma tion. Af ter the dis cov eryof mas sive sulphides in float on the Dragon prop erty bypros pec tor E. Specogna, work by Noran da Ex plo ra tion Co.Ltd. cul mi nated in the dis cov ery of the Falls and NorthVMS oc cur rences (Kemp and Gill, 1993). Fur ther geo log i -cal map ping and di a mond-drill ing by Noran da andWestmin Re sources Ltd. in di cated that these show ings,with grades up to 7.33% Zn, 1.34% Pb, 173 ppm Cu,680 ppb Au, and 19.2 g/t Ag over a 2 m thick ness, are as so -ci ated with the con tact zone be tween un der ly ing bi modalvol ca nic rocks and over ly ing sed i men tary rocks and lime -stone (Jones, 1997). Vol ca nic rocks of the Dragon prop ertythat un der lie mas sive sul phide min er al iza tion con sist ofmas sive, flow-banded rhy o lite, an de site and tuffaceous fel -sic and in ter me di ate vol ca nic rocks. Sed i men tary and car -bon ate rocks over ly ing and interlayered with mas sive sul -phide min er al iza tion on the Dragon property consist ofchert, mudstone, calcareous mudstone, fossiliferous felsictuff, fossiliferous wackestone and marble.The Do rado prop erty is lo cated ap prox i mately 17 km northof the vil lage of Hesquiat, on the west coast of Van cou verIs land. Like the Dragon prop erty, rocks un der ly ing the Do -rado prop erty were orig i nally in ter preted by Mul ler (1977)as am phi bo lite-fa cies meta mor phic rocks as signed to theWestcoast Crys tal line Com plex. How ever, geo log i calmap ping of the area by Mar shall et al. (2006) has shown there gion to be un der lain by abun dant mafic vol ca nic rocks ofpo ten tial Sicker Group af fin ity, and by sed i men tary andcar bon ate rocks of po ten tial Buttle Lake Group af fin ity.Fol low ing up on re ports by Mar shall et al. (2006) ofpolymetallic VMS-style stockwork min er al iza tion in thearea, Paget Re sources Cor po ra tion staked the Do rado prop -erty and soon af ter dis cov ered sev eral polymetallic mas sive sul phide oc cur rences (Ruks et al., 2009a). Mas sive sul -phide min er al iza tion on the Do rado prop erty is as so ci atedwith the con tact be tween mas sive, vari ably silica-altered,clinopyroxene- and feldspar-phyric basalt and calcareoussedimentary rocks.152 Geoscience BC Sum mary of Ac tiv i ties 2009325Results of New Fieldwork in the CowichanLake AreaMap ping for 2009 field work was con ducted us ing ESRI’sArcPad™ 7 on a Hewlett-Packard IPaq HX4700 Pocket PC wirelessly con nected to a GlobalSat® BT-359W BluetoothGPS re ceiver. The BC Geo log i cal Sur vey’s re gional ge ol -ogy com pi la tion for UTM Zones 9 and 10, south west ernBC, as well as nu mer ous geo log i cal maps (Massey et al.,2005) de rived from min eral ex plo ra tion as sess ment re -ports, were used for reference.Westridge Resources Inc.Field work on min eral ten ure owned by Westridge Re -sources Inc. fo cused on new ex po sures of pro spec tive bed -rock on the north side of Big Sicker Moun tain and in theBreen lake1 area (Fig ure 3). In the Breen lake area, the mostsig nif i cant VMS show ing is the Jane oc cur rence(MINFILE 092B 084), which con sists of two adits re -ported to in ter sect sev eral mas sive sul phide lenses(pyrrhotite-sphalerite-chal co py rite) up to 0.46 m wide and1.52 m long, from which a 0.91 m sam ple as sayed 16.1%Zn (Fyles, 1950; Pattison and Money, 1988). In 2008, a new VMS oc cur rence was dis cov ered by the au thors in theBreen lake area, lo cated ap prox i mately 1 km east of theJane show ing. This new show ing com prises mas sive py -rite±chal co py rite and is hosted by a dark green, sil -ica+chlorite–al tered, stockwork py rite–min er al ized, sandy in ter me di ate (?) tuff (Fig ure 4A, B). Mas sive sul phide min -er al iza tion is con cor dant with the pre dom i nant fab ric in thehost li thol ogy (bed ding or fo li a tion?), which dips steeply to the north east. Due to over bur den cover, the true di men sions of this VMS min er al iza tion could not be es tab lished. Ex -posed VMS min er al iza tion can be traced for ap prox i mately 3 m along strike, with a thick ness of at least 1 m. Re con nais -sance-scale map ping in the Breen lake area in di cates thatVMS show ings are hosted pre dom i nantly in fel sic vol ca nicrocks. Reworked, intermediate tuffaceous rocks becomepredominant to the north, presumably upsection.Sev eral new show ings that are thought to be syngenetic inna ture were dis cov ered in the Big Sicker Moun tain area.Ap prox i mately 700 m north west of the North east Cop perzone (MINFILE 092B 099; Fig ure 3), in tensely sil ica-seri -cite–al tered fel sic crys tal tuff con tains up to sev eral per cent dis sem i nated sulphides (py rite±chal co py rite) with abun -dant mal a chite stain ing in places. This min er al izedtuffaceous ho ri zon is interbedded with gra phitic argilliteand in ter me di ate sandy to silty tuff. As in the Breen lakearea, re worked in ter me di ate tuffaceous rocks pre dom i nateupsection of fel sic vol ca nic rocks (to the north). Ap prox i -mately 1 km east of the North east Cop per zone on new ex -po sure cre ated by re cent log ging road con struc tion, a newdis cov ery of mas sive mag ne tite min er al iza tion was lo catedwithin a vari ably sil ica-seri cite-chlorite–al tered quartz-feld spar por phyry. Here, veins and pods of mas sive mag ne -tite up to 1 m thick cut vari ably al tered quartz-feld spar por -phyry (Fig ure 4C). Mag ne tite veins com monly have coresof semimassive py rite. Flank ing the area of mas sive mag -ne tite min er al iza tion to the west, strongly sericitizedquartz-feld spar por phyry is cut by abun dant string ers of py -rite and chal co py rite. Strong chlorite al ter ation is lo cal izedalong the mar gins of these string ers. Far ther to the west,quartz-feld spar por phyry be comes in tensely si lici fied andcon tains up to 30% dis sem i nated py rite±trace chal co py ritemin er al iza tion. String ers of pyrite and chalcopyrite alsooccur in this zone, with sulphide vein margins often flanked by zones of chlorite alteration.Treasury Metals Inc.Field work on min eral ten ure owned by Trea sury Met alsCorp. north of the Chemainus River con tin ued to fo cus ones tab lish ing the tim ing and geo log i cal set ting of VMS oc -cur rences on the prop erty, as well as con strain ing the lon -gev ity of VMS min er al iz ing sys tems in the area through es -tab l i sh ing the age of ex ha la t ive i ron for ma t ionmin er al iza tion. The Lara prop erty is host to many VMS oc -cur rences, the most no ta ble of which is the Lara VMS de -posit or ‘Cor o na tion Trend’ (Fig ure 3), which con sists oftwo main zones, the Cor o na tion and Cor o na tion Ex ten sion. The in di cated re source for the Cor o na tion and Cor o na tionEx ten sion zones (at a 1% Zn cut-off) is 1 146 700 tonnes at3.01% Zn, 1.05% Cu, 0.58% Pb, 32.97 g/t Ag and 1.97 g/tAu (Kelso et al., 2007). Sul phide min er al iza tion of the Cor -o na tion and Cor o na tion Ex ten sion zones is hosted bystrongly si lici fied, coarse-grained rhyolite crystal tuff andash tuff (Kelso et al., 2007; Ruks et al., 2009a). The Randy North show ing (MINFILE 092B 128), lo catedap prox i mately 2 km north of the Cor o na tion zone (Fig -ure 3), con sists of sev eral zones of anom a lous polymetallicmin er al iza tion hosted in strongly seri cite-al tered fel sicvolcaniclastic rocks (Kelso et al., 2007). Re cent map ping(2008 field work) of the Randy North zone shows that in -tense py rite stockwork min er al iza tion is hosted by mod er -ately to strongly seri cite-al tered and highly fo li ated fel siccrys tal tuff, with 1–3% quartz crys tals up to 5 mm in size(Ruks et al. , 2009a). The Anita zone (MINFILE092B 037), lo cated ap prox i mately 4.7 km north west of theCor o na tion zone (Fig ure 3), con sists of polymetallic sul -phide min er al iza tion sit u ated close to the con tact be tweenmafic tuffaceous rocks and fel sic volcaniclastic rocks. Thebest drill in ter sec tion of the Anita ho ri zon to date is di a -mond-drill hole 87-37, which in ter sected 2.5 m of 2.37%Cu, 0.73% Pb, 2.73% Zn, 46 g/t Ag and 0.72 g/t Au hostedin a py ritic fel sic tuff. An other hole, 88-49, in cluded a 4.9 m interval of 2.3% Cu, 0.49% Pb, 3.66% Zn, 73.9 g/t Ag and1.9 g/t Au. Geoscience BC Re port 2010-1 1531 unofficial place name326154Geoscience BC Sum mary of Ac tiv i ties 2009Fig ure 3. Re gional ge ol ogy, se lected min eral oc cur rences and ar eas of study for 2009 field work in the Cowichan Lake area, south ern Van cou ver Is land (mod i fied fromMassey et al., 2005).327Re ha bil i ta tion of ex ist ing log ging roads in the vi cin ity ofthe Lara and Randy North ar eas (MINFILE oc cur rences092B 129 and 092B 128, re spec tively) since 2008 field -work cre ated abun dant new bed rock ex po sure. Mixed re -con nais sance and 1:2000 scale geo log i cal map ping of thisarea, com bined with data col lected dur ing 2008 field work(Ruks et al., 2009a), in di cate that stra tig ra phy host ing theLara and Randy North VMS oc cur rences com prises largely fel sic vol ca nic rocks, in clud ing crys tal tuff, ash tuff andflows. A per va sive fo li a tion cou pled with vari able quartz-seri cite al ter ation makes protolith iden ti fi ca tion dif fi cult inplaces. Al though fel sic vol ca nic units dom i nate the area,they are punc tu ated by thin zones of argillite and fine-grained in ter me di ate tuff, in di cat ing pe ri ods of qui es cencebe tween fel sic vol ca nic events, and pro spec tive stra tig ra -phy for VMS min er al iza tion. Ex po sures near the Anitashaft con sist of quartz-seri cite–al tered fel sic volcaniclasticrock with vari able con cen tra tions of sul phide min er al iza -tion. In the im me di ate vi cin ity of the Anita shaft, in tenselyquartz-seri cite–al tered fel sic vol ca nic rock with less than1% quartz pheno crysts con tains up to 1% chal co py riteveinlets, of ten as so ci ated with zones of strong sili ci fi ca tion(Fig ure 5A). Sim i lar to the Breen lake and Big SickerMoun tain ar eas, fine-grained, vari ably he ma tite-al tered in -ter me di ate tuffaceous rocks and argillite predominateupsection of the Coronation, Randy North and Anita VMSoccurrences (to the north; Figure 5B). Ex ha la tive mag ne tite iron for ma tion of the Lady A(A zone) and Lady A (C zone) oc cur rences (MINFILE092B 029 and 092B 033, re spec tively; Fig ure 3), lo catedap prox i mately 5 km north west of the Lara VMS de posit, isas so ci ated with this unit. The con tact be tween fine-grained, re worked, in ter me di ate tuffaceous rocks, argillite and un -der ly ing vari ably al tered and sul phide-min er al ized fel sicvol ca nic stra tig ra phy rep re sents a re gion ally and eco nom i -cally sig nif i cant fea ture co in ci dent with the ces sa tion ofSicker Group vol ca nism. Sig nif i cant VMS min er al iza tionis as so ci ated with sim i lar con tacts at large VMS de pos itsworld wide, in clud ing Noran da (Frank lin et al., 2005) andAnyox (Mac don ald et al., 1996). At the gi ant Bathurstcamp, VMS min er al iza tion is over lain by a dis trict-wideex ha la tive chert-mag ne tite iron formation, similar to that of the Lady A occurrences (Galley et al., 2007).Results of New Fieldwork in the PortAlberni Area: Bitterroot Resources Ltd.Map ping of Sicker Group bed rock ge ol ogy and sam plingfor lithogeochemistry, U-Pb zir con geo chron ol ogy, and Pb, Nd and Hf iso tope tracer stud ies was con ducted in the PortGeoscience BC Re port 2010-1 155Fig ure 4. Min er al iza tion in the Cowichan Lake area, south ern Van -cou ver Is land: A) mas sive py rite+chal co py rite min er al iza tion, dis -cov ered dur ing 2008 field work (Ruks et al., 2009a), hosted in a sil -ica-al tered in ter me di ate tuff and lo cated ap prox i mately 1 km eastof the Jane show ing (MINFILE 092B 084) on Westridge Re sourcesInc. min eral ten ure (UTM Zone 10, 449958E, 5412112N, NAD83);B) close-up of mas sive py rite and chal co py rite VMS min er al iza tiondis cov ered on Westridge Re sources Inc. min eral ten ure dur ing2008 field work (Ruks et al., 2009a); C) new dis cov ery of mas sivemag ne tite min er al iza tion within a vari ably sil ica-seri cite-chlorite–al tered quartz-feld spar por phyry, ap prox i mately 1 km east of theNorth east Cop per zone (MINFILE 092 099) on Westridge Re -sources Inc. min eral ten ure (UTM Zone 10, 445393E, 5413282N).328Alberni area, much of which is cov ered by min eral ten ureowned by pro ject spon sor Bitterroot Re sources Ltd. (Fig -ure 1). This work was con cen trated in 1) the vi cin ity of re -cent log ging ac tiv ity west of Horne Lake (Fig ure 6, studyarea A); 2) the vi cin ity of re cent log ging in the Duck Lakeand China Creek ar eas (Fig ure 6, study ar eas B and C, re -spec tively); and 3) the Rift Creek area, east of MountSpencer (Fig ure 6, study area D). Bed rock ex po sure in allar eas is mod er ate, with the best ex po sures oc cur ring in log -ging-road cuts. Off-road ex po sures are typ i cally cov eredwith thick lay ers of moss and or ganic de tri tus, com monly in for ested, low-light conditions that greatly hampergeological mapping.Re cent log ging ac tiv ity west of Horne Lake (Fig ure 6,study area A) has cre ated sig nif i cant new bed rock ex po -sure. Ex am i na tion of these new ex po sures has re vealed thepres ence of a strati graphic sec tion with im por tant im pli ca -tions for late Pa leo zoic magmatism in south ern Wrangellia. At the base of this sec tion, close to the shore of Horne Lake,clinopyroxene-phyric ba saltic-an de site vol ca nic and vol -caniclastic rocks of prob a ble Late De vo nian age dom i nate.This unit is as sumed to be cor re la tive with sim i larclinopyroxene-phyric mafic vol ca nic rocks in the vi cin ityof a mi cro wave tower, ap prox i mately 6 km to the south east(Fig ure 6). At the mi cro wave tower, mafic vol ca nic rocksare interbedded with fel sic ash tuff, which has yielded aLate Devonian U-Pb zircon age. Over ly ing the mafic vol ca nic rocks on the west side ofHorne Lake is a pack age of sed i men tary rocks, in clud ing,in up wards strati graphic or der, me dium-grained sand stone(arkosic?), chert, interbedded fel sic crys tal tuff and chert,and a pack age of fel sic volcaniclastic rocks. Fel sic vol -caniclastic rocks in this area are sim i lar in na ture and strati -graphic po si tion to those ob served to the south of HorneLake (Ruks et al., 2009a), and com prise rhyolitic torhyodacitic crys tal tuff, lapilli tuff and tuff breccia(Figure 7A). Fel sic vol ca nic rocks are over lain by a thin unit of fine-grained, in ter me di ate tuffaceous rock and argillite, whichare in turn over lain by rib bon chert and crinoidal lime stone.This rib bon chert and lime stone are in ter preted to be cor re -la tive with a sim i lar pack age in the Lacy Lake area, whichhas yielded radiolarian biostratigraphic ages rang ing fromEarly to Mid dle Perm ian (Ruks et al., 2009b). Rib bon chertex po sures west of Horne Lake are, in places, rid dled withthick string ers and pods of fine-grained py rite, up to 5 cm in thick ness, and is over lain by a chert peb ble-boul der con -glom er ate. This con glom er ate is in turn over lain by mas -sive pil low bas alts that are prob a bly cor re la tive with theMid dle Tri as sic Karmutsen For ma tion. The pres ence ofprob a ble Perm ian chert and lime stone prox i mally un der -lain by a pack age of fel sic vol ca nic rock sug gests a late Pa -leo zoic age for fel sic vol ca nic rocks in the Horne Lake area. This age is in stark con trast to his toric in ter pre ta tions forthe bed rock ge ol ogy of the area, which as signed this com -plete strati graphic pack age to the pre–Late DevonianNitinat Formation and the Late Devonian McLaughlinRidge Formation.Rocks of the China Creek–Duck Lake area (Fig ure 6, studyarea B) were the fo cus of con tin ued ef forts to re solve theage of Duck Lake For ma tion mafic vol ca nic rocks and as -so ci ated VMS min er al iza tion. Much of the bed rock un der -ly ing the Bitterroot Re sources min eral ten ure in the ChinaCreek–Duck Lake area is in ter preted to com prise rocks ofthe Duck Lake and Nitinat for ma tions (Massey and Fri day,1989). The Duck Lake For ma tion con sists of pil low ba salt,pil low brec cia and interflow mafic tuffaceous sed i men taryrocks, and is be lieved to rep re sent the oce anic crust upon156 Geoscience BC Sum mary of Ac tiv i ties 2009Fig ure 5. Min er al iza tion on Trea sury Met als Inc. min eral ten ure,Cowichan Lake area, south ern Van cou ver Is land: A) in the im me di -ate vi cin ity of the Anita shaft (MINFILE 092B 037), in tenselyquartz-seri cite–al tered fel sic vol ca nic rock with less than 1%quartz pheno crysts con tains up to 1% chal co py rite veinlets, of tenas so ci ated with zones of strong sili ci fi ca tion (UTM Zone 10,429869E, 5417127N); B) sim i lar to the Breen lake and Big SickerMoun tain ar eas, fine-grained, vari ably he ma tite-al tered in ter me di -ate tuffaceous rocks and argillite pre dom i nate upsection of theCor o na tion, Randy North, and Anita VMS oc cur rences (to thenorth).329Geoscience BC Re port 2010-1 157Fig ure 6. Re gional ge ol ogy (mod i fied from Massey, 2005), se lected min eral oc cur rences and ar eas of study for 2008 field work in the PortAlberni area, south ern Van cou ver Is land.330which the Sicker arc was built (Massey and Fri day, 1989).As such, Duck Lake For ma tion rocks are in ter preted as theold est in the Sicker Group and, by de fault, the old est inWrangellia (Massey and Fri day, 1989). The VMS min er al -iza tion of the Deb bie 3 oc cur rence (MINFILE 092F 445),owned by Bitterroot Re sources, con sists of four stratiformlenses of banded mas sive sphalerite with mi nor chal co py -rite and ga lena, each band rang ing be tween 5 and 20 cm inthick ness. The best grade ob tained from sam pling of thismin er al iza tion by pre vi ous work ers was 14.1% Zn, 0.87%Pb and 0.12% Cu over a 20 cm thick ness. The min er al iza -tion is hosted in fine-grained chloritic schist with vari ablecar bon ate, seri cite and sil ica al ter ation (Ruks andMortensen, 2008). The chloritic schist host ing Deb bie 3min er al iza tion is spa tially as so ci ated with clinopyroxene-phyric andesitic vol ca nic rocks as signed to the Nitinat For -ma tion. The Deb bie 3 VMS oc cur rence is there fore be -lieved to rep re sent the old est VMS min er al iza tion in theSicker Group. Since most ex plo ra tion for VMS min er al iza -tion in the Sicker Group has fo cused on bi modal vol ca nicrocks be long ing to the McLaughlin Ridge and Myra for ma -tions, the relatively unexplored Duck Lake and Nitinatformations represent attractive targets for this style of min -er al iza tion. Field work in 2008 in the China Creek–Duck Lake area dis -cov ered ad di tional mas sive sul phide min er al iza tion nearthe base of the Duck Lake type sec tion (Yorath et al., 1999;Ruks et al., 2009a). Here, a bed of fine-grained mas sive sul -phide (dom i nantly py rite) was dis cov ered in a new ex po -sure along China Creek main line (Fig ure 6, study area B),ap prox i mately 1.8 km north east of the Re gina oc cur rence(MINFILE 092F 078), where polymetallic VMS-stylemin er al iza tion has also been re ported. The bed is ap prox i -mately 20 cm wide and interbedded with si li ceous argillite.Mafic sandy tuff and scoriaceous mafic vol ca nic rocks arealso found in the im me di ate vi cin ity of the min er al iza tion.Si li ceous interbeds within the mas sive sul phide min er al -iza tion were sam pled for radiolarian biostratigraphy in2008. Poorly pre served radio lar ians were re cov ered fromsi li ceous interbeds within the mas sive sul phide min er al iza -tion, and ad di tional sam pling of these horizons in 2009 wascarried out to provide a biostratigraphic age. Re con nais sance geo log i cal map ping of new ex po sure cre -ated by re cent log ging road con struc tion ap prox i mately3.4 km east of Duck Lake (Fig ure 6, study area C) re veals athick sec tion of pil low ba salt and as so ci ated ba salticvolcaniclastic rocks (Duck Lake For ma tion) over lain by ased i men tary suc ces sion com pris ing interbedded chert,argillite, siltstone and sand stone (McLaughlin Ridge For -ma tion?). A new min eral oc cur rence was dis cov ered in gra -phitic argillite of this sed i men tary pack age, con sist ing of en échelon quartz-py rite veins with strong sil ica-py rite al ter -ation ha loes (Fig ure 7B). This sed i men tary suc ces sion issim i lar in na ture to that iden ti fied in the Peak and Kammat158 Geoscience BC Sum mary of Ac tiv i ties 2009Fig ure 7. Rocks and min er al iza tion in the Port Alberni area, south -ern Van cou ver Is land: A) po ten tial late Pa leo zoic rhy o lite lapilli tuff, west of Horne Lake; B) newly dis cov ered en échelon quartz-py riteveins with strong sil ica-py rite al ter ation ha loes hosted in gra phiticargillite, lo cated ap prox i mately 3.4 km east of Duck Lake (UTMZone 10, 382588E, 5442746N); C) newly dis cov ered, 10–15 cmwide stratiform band of mas sive fine-grained py rite with trace chal -co py rite, interbedded with grey-green rib bon chert, lo cated in theRift Creek area, east of Mount Spencer (UTM Zone 10, 382597E,5434781N).331lakes area dur ing 2008 field work, from which Late De vo -nian radio lar ians were re cov ered (Ruks et al., 2009a, b),and is po ten tially cor re la tive. Sam pling of least-de formedpil low ba salt rims from this sec tion for U-Pb geo chron ol -ogy on mi cro bial ti tan ite (e.g., Banerjee et al., 2007) wascar ried out in an attempt to constrain the age of Duck LakeFormation mafic volcanic rocks in the area.In the Rift Creek area east of Mount Spencer (Fig ure 6,study area D), re con nais sance geo log i cal map ping re sultedin the dis cov ery of a new mas sive sul phide oc cur rence.This oc cur rence, pre sum ably hosted in rocks of the DuckLake For ma tion, con sists of a 10–15 cm wide stratiformband of mas sive, fine-grained py rite with trace chal co py -rite, interbedded with grey-green rib bon chert (Fig ure 7C).The chert unit that hosts the mas sive sul phide min er al iza -tion sits on top of a pack age of mafic tuffaceous turbidites,which are spa tially as so ci ated with ba salt flow brec cia. Themin er al ogy and geo log i cal set ting of this new VMS oc cur -rence is sim i lar to VMS min er al iza tion dis cov ered in theChina Creek area during 2008 fieldwork (Ruks et al.,2009a).Results of New Fieldwork in the NanooseAreaField work in the Nanoose up lift (Fig ure 1) con cen trated onre solv ing the age and geo log i cal set ting of abun dant Pa leo -zoic mafic vol ca nic rocks in the area, which have un cer tainstrati graphic re la tion ships to the Sicker Group (Yorath etal., 1999). A large body of granodiorite of the Early to Mid -dle Ju ras sic Is land in tru sions on Nanoose Pen in sula hascaused strong con tact meta mor phism of the mafic vol ca nicand interlayered clastic, chert and lime stone in large partsof the Nanoose up lift. As a re sult, radio lar ians arerecrystallized and no age de ter mi na tions are pos si ble. In or -der to find better pre served microfossils for biostrat -igraphic pur poses and fa cil i tate dat ing of this enig maticpack age of rocks, field work in the Nanoose up lift in 2009was con cen trated on north ern Ballenas Is land, where youn -ger in tru sions are ab sent (Yorath et al., 1999). Here, abun -dant ba saltic vol ca nic rocks are interbedded with and over -lie a sed i men tary pack age com pris ing interbeddedcrinoidal lime stone, argillite, chert and siltstone. Ba salticvol ca nic rocks con tain abun dant pil low flows (Fig ure 8A),with as so ci ated zones of ba saltic pil low brec cia, tuff brec -cia and finer grained tuffaceous rocks. Pil low ba salt flowsare vari ably plagioclase phyric, with pheno crysts of tenreach ing sizes of 5 mm or greater and con cen tra tions of upto 40–50%. Crinoidal lime stone lo cally forms the ma trix tobrecciated mafic vol ca nic rocks, in di cat ing de po si tion in acar bon ate-rich en vi ron ment (Fig ure 8B). Intraflow ba saltic volcaniclastic rocks are of ten interbedded with mul ti plelay ers of stratiform, he ma tite-rich sed i men tary rocks re -sem bling ex ha la tive iron for ma tions, with in di vid ual bedsreach ing thick nesses of 30 cm or more (Fig ure 8C). Sam -Geoscience BC Re port 2010-1 159Fig ure 8. Rocks in the Nanoose area, south ern Van cou ver Is land:A) pil low ba salt on north ern Ballenas Is land; B) ba salt tuff brec ciawith crinoidal lime stone ma trix (white zones), in di cat ing vol ca nismin a car bon ate-rich en vi ron ment; C) stratiform, he ma tite-rich sed i -men tary rocks re sem bling ex ha la tive iron for ma tions oc cur ring invol cano-sed i men tary rocks be tween ba salt flows.332ples of chert and car bon ate were col lected for both radio -larian and cono dont biostratigraphy. Samples of maficvolcanic rocks were collected for U-Pb geochronology andlithogeochemistry on pillow basalt microbial titanite.Results of New Fieldwork in the BedingfieldUpliftField work in the Bedingfield up lift (Fig ure 1) con cen tratedon re solv ing the age and geo log i cal set ting of pro posedSicker Group stra tig ra phy and VMS oc cur rences in thearea. Re con nais sance field work in the Bedingfield areawas con ducted over the course of four days in Sep tem ber.All-ter rain ve hi cles and a 4 m (14 ft.) alu mi num boat werebarged to a land ing at Cy press Bay, with ac com mo da tionlo cated at the Tran quil Tim ber Ltd. float ing barge campnear Whitepine Cove.Volcanogenic mas sive sul phide min er al iza tion of the BayCreek, Claim Post and Rant Point oc cur rences (MINFILE092F 343, 092F 290 and 092F 494, re spec tively; Fig ure 9)are lo cated on shore line near the en trance to BedwellSound, and are ac cessed by boat. Stockwork-style VMSmin er al iza tion of the Bay Creek show ing (Fig ure 9) con -sists of 1–2% py rite, chal co py rite and sphalerite string ersand blebs hosted in gos sa nous aphyric to quartz-phyric rhy -o lite flows (Fig ure 10A). Chlorite veins and blebs are abun -dant. Host fel sic vol ca nic rocks are fo li ated, with quartzpheno crysts of ten ex hib it ing subgrain de vel op ment andstretch ing par al lel to a south west-dip ping fo li a tion. Min er -al iza tion in the vi cin ity of the Claim Post (MINFILE092F 290) show ing (Fig ure 10B) con sists of bands of mal -a chite-stained, semimassive py rite and chal co py rite up to5 cm in thick ness, hosted by strongly quartz-seri cite–al -tered, gos sa nous fel sic ash and crys tal tuff. De formedquartz-feld spar–phyric rhy o lite por phyry plugs, which aretex tur ally sim i lar to the Saltspring in tru sions (Fig ure 10C),are pres ent in the vi cin ity of the show ing. Min er al iza tion inthe area of the Rant Point show ing (MINFILE 092F 494)con sists of a shore line gos san com pris ing mas sive, foliatedrhyolite crystal tuff with up to 15–20% disseminated pyriteand trace chalcopyrite.Work in the Her bert In let and Cypre River ar eas (Fig ure 9,study ar eas A and B, re spec tively) fo cused on ex am in ingthe na ture of the con tact be tween pro posed car bon ate rocksas signed to the Buttle Lake Group (Mount Mark For ma -tion) and un der ly ing rocks as signed to the Sicker Group, aswell as on lo cat ing new ar eas pro spec tive for VMS min er -al iza tion. Al though no con tin u ous strati graphic sec tionwas ob served, mas sive recrystallized lime stone with vary -ing pro por tions of interbedded chert and argillite was ob -served jux ta posed with abun dant rhy o lite flows and tuffs insev eral lo ca tions. Pre vi ous work ers in the Bedingfield areahave sug gested that Buttle Lake Group rocks are ob servedto sit un con form ably on fel sic vol ca nic rocks (e.g.,Blackwell and Lajoie, 1986), but they have not doc u mented the na ture of this un con formity. The jux ta po si tion of car -bon ate rocks and un der ly ing fel sic vol ca nic rocks in theBedingfield area is strik ingly sim i lar to strati graphic re la -tion ships ob served at the Dragon prop erty, north of GoldRiver, where car bon ate rocks are ob served to con form ablyover lie fel sic vol ca nic rocks, with VMS min er al iza tion be -tween them (e.g., Ruks et al., 2009a). In the Cypre Riverarea, a lo cal ized gos sa nous zone, con sist ing of 5–10%pyrrhotite+py rite+chal co py rite string ers and blebs, is ob -served prox i mal to the contact between a volcano-sedimentary unit (comprising siltstone, mudstone andfelsic lapilli tuff) and gabbro.Results of Geological Mapping on theDorado and Dragon Properties (PagetResources Corporation), Hesquiat–GoldRiver AreaDorado PropertyField work on the Do rado prop erty and Hesquiat Pen in sulawas con ducted over six days in Oc to ber 2009 (Fig ure 1).This field work was de signed to re solve the age and geo log -i cal set ting of the Do rado VMS oc cur rences and po ten tialPa leo zoic host stra tig ra phy in the area (e.g., Mar shall et al.,2006; Ruks et al., 2009a). A truck and ATV were bargedfrom Gold River into Mooyah Bay, where ac com mo da tionwas lo cated in a float ing barge camp op er ated by PortNeville Log ging Co. Ltd. Polymetallic VMS-like stock -work min er al iza tion was first dis cov ered on the HesquiatPen in sula by Mar shall et al. (2006). Fol low-up re con nais -sance geo log i cal map ping in the vi cin ity of Mar shall’sshow ing by Paget Re sources Cor po ra tion led to the dis cov -ery of polymetallic mas sive sul phide min er al iza tion andad di tional polymetallic, VMS-style, stockwork sul phideoc cur rences (Ruks et al., 2009a). Mas sive sul phide min er -al iza tion has so far been dis cov ered in two lo ca tions on theDo rado prop erty, as so ci ated with the con tact be tweenmafic vol ca nic rocks and cal car e ous sed i men tary rocks(Fig ure 11). The first mas sive sul phide min er al iza tion dis -cov ered on the Do rado prop erty is lo cated in a shot-rockblast pit near the con tact be tween a vari ably sil ica-al tered,chlorite amyg dule–bear ing, feld spar-phyric ba saltic flowand in ter me di ate tuffaceous sand stone. Here, a mas sivesul phide pod, mea sur ing 1.5 m by 3 m and con sist ing offine-grained pyrrhotite with trace chal co py rite, is hostedwithin the ba salt (Fig ure 12A). Sul phide string ers up to1 cm wide are abun dant near the mas sive sul phide min er al -iza tion. Nu mer ous mas sive sul phide boul ders of sim i larcom po si tion are found close to the show ing; some of themhave been used as sub strate for a bridge cross ing a creekthat drains im me di ately east of the pit. The most si lici fiedzones within the host ba salt are as so ci ated with abun dantquartz and epidote veinlets. Some zones of autobreccia arepres ent in the ba salt host. These zones con tain abun dant160 Geoscience BC Sum mary of Ac tiv i ties 2009333Geoscience BC Re port 2010-1 161Fig ure 9. Ge ol ogy of the Bedingfield area (af ter Massey et al., 2005), cen tral Van cou ver Is land, show ing lo ca tions of 2009 field work.334grey, glassy, an gu lar si lici fied clasts up to 2 cm in size. Ap -prox i mately 430 m south west of this zone is a sec ond zoneof mas sive sul phide min er al iza tion. Here, boul ders of fine-to me dium-grained mas sive pyrrhotite+chal co py rite, up to50 cm in size, oc cur as float be neath a large gos sa nous out -crop of highly sil ica-al tered, feld spar-clinopyroxene–phyric ba salt por phyry. Pyrrhotite min er al iza tion is abun -dant, as both string ers and dis sem i na tions. This al tered andmin er al ized por phyry was traced in the map area for ap -prox i mately 350 m to the south west along an over grownlog ging skidder road. Vari ably al tered, vari ably sul phide-min er al ized ex am ples of feld spar- and clinopyroxene-phyric ba salt are abun dant to the north of the mas sive sul -phide oc cur rences and are most likely rep re sen ta tive ofmas sive in ter me di ate flows. These mafic vol ca nic rocksare mas sive, and less por phy ritic to nearly aphyric in na -ture. They of ten con tain abun dant epidote al ter ation in theform of ovoid patches up to 10 cm in width. Fine-grainedsulphide minerals are often found in the cores of thesepatches. In places, pyrrhotite and chalcopyrite stringers arepresent, typically with strong silica alteration along theirmargins. Sed i men tary rocks spa tially re lated to the Do rado blast-pitsul phide oc cur rence first ap pear ap prox i mately 100 m tothe south. These com prise a mod er ately east-dip ping out -crop of recrystallized, interbedded mar ble and cherty car -bon ate. Ap prox i mately 50 m far ther south, vari ably al teredclinopyroxene- and feld spar-phyric ba salt, sim i lar to Do -rado VMS hostrock, in trudes a sed i men tary pack age(Mooyah For ma tion?) com pris ing recrystallized car bon -ate, chert, siltstone and fine sand stone (Fig ure 12B). Sim i -lar to Do rado VMS hostrocks, al ter ation is in tense, withmuch of the ba salt be ing re duced to as sem blages of epidoteand quartz, es pe cially in areas proximal to contacts withsedimentary rocks.Re con nais sance ge ol ogy through out the north ern por tionof the Hesquiat Pen in sula con cen trated on sam pling ex po -sures of po ten tial Pa leo zoic stra tig ra phy (Mooyah For ma -tion; Mar shall et al., 2006) for geo chron ol ogy andbiostratigraphy, as no Pa leo zoic ages ex ist for the area.How ever, due to the pres ence of sig nif i cant ex panses ofgra nitic in tru sive rocks of prob a ble Ju ras sic age (e.g., Mar -shall et al., 2006), ex po sures of po ten tial Pa leo zoic stra tig -ra phy are very sparse. Where ob served in this study, theMooyah For ma tion typ i cally com prises a mix ture of gra -phitic argillite, recrystallized car bon ate and chert, andlesser amounts of siltstone and sand stone (Fig ure 12C).Car bon ate hostrocks to the Silverado skarn oc cur rence(MINFILE 092E 017), lo cated only 6 km east of theMooyah For ma tion type sec tion in Mooyah Bay, yield Tri -as sic pre lim i nary cono dont ages (Mar shall et al., 2006).This sug gests that a potential Triassic age for the MooyahFormation should also be considered.162 Geoscience BC Sum mary of Ac tiv i ties 2009Fig ure 10. Rocks and min er al iza tion in the Bedingfield up lift area,cen tral Van cou ver Is land: A) stockwork-style VMS min er al iza tionof the Bay Creek show ing (MINFILE 092F 343), con sist ing of 1–2% py rite, chal co py rite and sphalerite string ers and blebs hostedin gos sa nous aphyric to quartz-phyric rhy o lite flows; B) Claim Postshow ing (MINFILE 092F 290), con sist ing of bands of mal a chite-stained, semimassive py rite and chal co py rite up to 5 cm in thick -ness, hosted in strongly quartz-seri cite–al tered, gos sa nous fel sicash and crys tal tuff; C) de formed quartz-feld spar rhy o lite por phyrynear the Claim Post show ing, rem i nis cent of the Saltspring in tru -sions.335Geoscience BC Re port 2010-1 163Fig ure 11. Ge ol ogy of the Hesquiat Pen in sula area (mod i fied from Mar shall et al., 2006), cen tral Van cou ver Is land, show ing lo ca tions of2009 field work and VMS min eral oc cur rences of note.336Dragon PropertyThe Dragon prop erty is lo cated ap prox i mately 80 km westof Camp bell River, 20 km north west of Gold River and65 km north west of the Myra Falls mine of Break wa ter Re -sources Ltd. (Fig ure 1). Field work in 2009 con tin ued ef -forts to es tab lish the geo log i cal set ting for known min eraloc cur rences on the prop erty, and for un der stand ing the stra -tig ra phy of the prop erty ge ol ogy in gen eral. The work wassuc cess ful in iden ti fy ing sev eral new prospective zones ofmineralization.Mas sive sul phide min er al iza tion on the Dragon prop ertytyp i cally con sists of vary ing pro por tions of fine- to me -dium-grained mas sive pyrrhotite, chal co py rite andsphalerite at the con tact be tween fel sic vol ca nic rocks andover ly ing vol cano-sed i men tary and car bon ate rocks. Field -work in 2009 has been suc cess ful in trac ing this pro spec -tive ho ri zon over a strike length of 8 km, where it showssigns of VMS-style al ter ation and mineralization through -out (Figure 13).The orig i nal mas sive sul phide dis cov er ies on the Dragonprop erty in clude the Falls and North show ings, which com -prise three mas sive sul phide lenses with grades up to 7.33% Zn, 1.34% Pb, 173 ppm Cu, 680 ppb Au and 19.2 g/t Agover 2 m (Jones, 1997; Fig ure 13; Fig ure 14A). This mas -sive sul phide min er al iza tion is interlayered with lam i natedchert, mudstone and cal car e ous mudstone that strike south -west erly and dip steeply to the north west. Bi valve (?) fos -sils have been ob served in cherty tuff over ly ing the Fallsand North show ings. Sev eral new VMS show ings were dis -cov ered on the Dragon prop erty dur ing the course of 2008field work. Mas sive sul phide min er al iza tion was dis cov -ered ap prox i mately 1 km south of the Falls and Northshow ings, and abun dant VMS stockwork sul phide min er -al iza tion was dis cov ered ap prox i mately 1 km north of these two show ings (Ruks et al., 2009a). In both new dis cov er ies, VMS min er al iza tion is as so ci ated with the con tact be tweenvari ably al tered and sul phide-min er al ized fel sic volcanicrocks (often rhyolite flows) and overlying calcareous sed i -men tary rocks.Field work was car ried out in the east ern por tion of theprop erty to iden tify po ten tial deeper and older Pa leo zoicstra tig ra phy (Fig ure 13, study area A). How ever, only more fel sic vol ca nic rocks were en coun tered, com pris ing rhy o -lite flows and as so ci ated volcaniclastic and tuffaceousrocks. In places, fel sic vol ca nic rocks are in truded bygabbroic sills of prob a ble Mid dle Tri as sic Karmutsen For -ma tion (Mount Hall gab bro) af fin ity. The pres ence of fel sicvol ca nic rocks to wards the east ern edge of the Dragonprop erty is at trib uted to a pro gres sive flat ten ing of dip an -gles as one moves east ward on the prop erty. Work in thesouth ern and south east ern por tions of the prop erty (Fig -ure 13) has re vealed ad di tional lo ca tions where vari ably164 Geoscience BC Sum mary of Ac tiv i ties 2009Fig ure 12. Rocks and min er al iza tion of the Hesquiat Pen in sulaarea, cen tral Van cou ver Is land: A) pyrrhotite+chal co py rite mas -sive sul phide min er al iza tion, mea sur ing 1.5 m by 3 m, is hostedwithin strongly epidote-quartz–al tered ba salt (UTM Zone 9,685043E, 5490975N); B) vari ably al tered clinopyroxene- and feld -spar-phyric ba salt, sim i lar to the Do rado VMS hostrock, in trudes ased i men tary pack age (Mooyah For ma t ion?) com pris ingrecrystallized car bon ate, chert, siltstone and fine sand stone; C)interbedded gra phitic argillite and chert of the Mooyah For ma tion.337Geoscience BC Re port 2010-1165 Fig ure 13. Re gional ge ol ogy of the Dragon prop erty of Paget Re sources Cor po ra tion (mod i fied from Massey, 2005; Jones, 1997), cen tral Van cou ver Is land, show ing se -lected min eral oc cur rences and ar eas of study for 2009 field work.338sil ica-seri cite–al tered and sul phide-min er al ized fel sic vol -ca nic rocks (dom i nantly rhy o lite flows) are over lain by amix ture of gra phitic argillite, chert and mas sive car bon ate.Sim i lar to east ern por tions of the prop erty, a sig nif i cantflat ten ing of bed ding ex ists. Sev eral new min eral oc cur -rences were dis cov ered through out the field area dur ing the course of 2009 work. In study area A (Fig ure 13), gabbroicsills of prob a ble Karmutsen For ma tion af fin ity were foundon sev eral oc ca sions to con tain chal co py rite veins up to1 cm width and pods of mas sive chal co py rite up to 5–7 cmin width (Fig ure 14B). East of this oc cur rence, a dacitic unit was found to con tain gos sa nous zones with stockwork-style chal co py rite min er al iza tion (Fig ure 14C). Sev eralzones of stockwork-style VMS min er al iza tion were en -coun tered in study area B (Figure 13), comprising largelylocalized zones of pyritic stockwork-style mineralizationassociated with silicified felsic volcanic rocks.SummaryField work in 2009 has con tin ued to fo cus on re solv ing thestra tig ra phy and tec tonic his tory of the Sicker Group and its con tained min eral oc cur rences in the Cowichan Lake, PortAlberni, Nanoose, Bedingfield, Gold River and Hesquiatar eas. This is be ing ac com plished us ing a com bi na tion ofbed rock map ping and sam pling for geo chron ol ogy (U-Pb,Ar/Ar), biostratigraphy (macrofossils, radio lar ians andcono donts), geo chem is try (ma jor and trace el e ments) andiso to pic anal y ses (Nd and Pb; whole rock and sulphides, re -spec tively). Work in the Cowichan area was di rected to -ward es tab lish ing the strati graphic po si tion and geo log i calset ting of VMS oc cur rences on min eral ten ure owned bypro ject spon sors Trea sury Met als Inc. and Westridge Re -sources Inc. In ad di tion, field work and sam pling were alsocon cen trated on var i ous ex ha la tive iron for ma tions to con -strain the lon gev ity of the VMS min er al iz ing hy dro ther malsys tem(s) in the Cowichan Lake area. Field work in the PortAlberni area, spon sored by Bitterroot Re sources Ltd., fo -cused on re solv ing the age and geo log i cal set ting of maficvol ca nic rocks and as so ci ated VMS oc cur rences within theNitinat and Duck Lake for ma tions. Re solv ing the ages ofthese units is crit i cal for un der stand ing the temporal andmetallogenic evolution of the Sicker arc, and the earliesthis tory of Wrangellia.Field work in the Horne Lake area, in rocks pre vi ously as -signed to the Nitinat and McLaughlin Ridge for ma tions,has iden ti fied a strati graphic sec tion con tain ing abun dant,po ten tial late Pa leo zoic vol ca nic rocks. This new sec tion,cou pled with re cent dat ing stud ies done as part of this pro -ject, in di cates that rocks in this area are prob a bly no olderthan Late De vo nian. Abun dant mafic and newly iden ti fiedfel sic vol ca nic rocks at the top of the sec tion are spa tiallyas so ci ated with re cently dated Early to Late Perm ian chert,sug gest ing the pres ence of a sig nif i cant cy cle of late Pa leo -zoic magmatism in the area (Ruks et al., 2009b). New min -er al iza tion was dis cov ered at the top of this strati graphicsec tion, where abun dant stockwork py rite min er al iza tion is hosted by ribbon chert of probable Permian age.166 Geoscience BC Sum mary of Ac tiv i ties 2009Fig ure 14. Min er al iza tion on the Dragon prop erty of Paget Re -sources Cor po ra tion, cen tral Van cou ver Is land: A) mas sive sul -phide min er al iza tion of the Falls show ing, interlayered with lam i -nated chert, mudstone and cal car e ous mudstone (UTM Zone 9,692434E, 5527815N); B) mas sive chal co py rite min er al iza tion as -so c i ated wi th Karmutsen For ma t ion gab bro (691798E,5524865N); C) stockwork-style chal co py rite stringer min er al iza -tion in al tered dacite (692265E, 5525028N).339Ap prox i mately 30 km south of the Horne Lake area, re con -nais sance field work east of Mount Spencer (Fig ure 6, study area D) re sulted in the dis cov ery of a new VMS oc cur rencehosted in stra tig ra phy of the Duck Lake For ma tion. Thismin er al iza tion con sists of a 10–15 cm wide stratiform bandof mas sive, fine-grained py rite with trace chal co py rite,interbedded with grey-green rib bon chert, which sits upon a pack age of mafic vol ca nic and as so ci ated volcaniclasticrocks.Field work in the Nanoose area con cen trated on re solv ingthe strati graphic po si tion and geo log i cal set ting of maficvol ca nic rocks in the area. Pil low bas alts and as so ci ated ba -salt volcaniclastic rocks of north ern Ballenas Is land over lie and are interbedded with crinoidal lime stone and chert. The spa tial re la tion ship of ba salt, chert and crinoidal lime stonein the Nanoose area is sim i lar to that ob served in the LacyLake area (e.g., Ruks et al., 2009a), where re cent radio -larian biostratigraphy by F. Cordey has con firmed an Earlyto Late Perm ian age. Sam pling of chert and car bon ate unitsin the Nanoose area for cono dont and radiolarianbiostratigraphy was car ried out to resolve the age of thisstratigraphy. Field work on the Do rado prop erty (Paget Re sources Cor -po ra tion) in the Hesquiat Pen in sula area has con firmed thatthe old est rocks in the area are prob a bly sed i men tary rocksas signed to the Mooyah For ma tion (Mar shall et al., 2006),which is un dated and has un known strati graphic af fin i ties.Mooyah For ma tion rocks com prise vary ing pro por tions ofgra phitic argillite, siltstone, sand stone, recrystallized car -bon ate and chert. In the vi cin ity of the Do rado VMS oc cur -rences, they are in truded by strongly sil ica-epidote–al teredclinopyroxene and feld spar-phyric ba salt subvolcanicrocks, which host VMS min er al iza tion. Vari ably al tered ba -salt flows over lie ba salt subvolcanic rocks and, in places,con tain stockwork-style VMS min er al iza tion (Mar shall etal., 2006; Ruks et al., 2009a), sug gest ing the po ten tial formul ti ple strati graphic lenses of VMS min er al iza tion on theDo rado prop erty. Volcanogenic mas sive sul phide–style al -ter ation and min er al iza tion in the con tact ar eas be tween ba -salt subvolcanic rocks and host sed i men tary rocks sug gestthat both rock types are of sim i lar age. Sig nif i cant sam pling for geo chron ol ogy and biostratigraphy was car ried out onMooyah For ma tion rocks in the Hesquiat area to ascertainpotential stratigraphic affinities with Paleozoic rocks ofWrangellia. Field work on the Dragon prop erty, north of Gold River(Paget Re sources Cor po ra tion) has iden ti fied ad di tional lo -cal i ties where vari ably al tered and sul phide-min er al izedfel sic vol ca nic rocks are over lain by a pack age of gra phiticargillite, chert and car bon ate. This eco nom i cally sig nif i -cant con tact hosts VMS min er al iza tion at the Falls andNorth oc cur rences (Ruks et al., 2009a), and has now beentraced for a length of 8 km, ex hib it ing sig nif i cant po ten tialfor VMS min er al iza tion through out. Field work in the east -ern part of the prop erty was con ducted to eval u ate thepo ten tial for deeper stra tig ra phy and as so ci ated VMS min -er al iza tion. Here, ad di tional stockwork-style VMS min er -al iza tion was doc u mented, and sam pling of fel sic vol ca nichostrocks for geo chron ol ogy was carried out to ascertainthe age and geological setting of mineralization. Field work in pro posed Sicker Group rocks and VMS min -er al iza tion of the Bedingfield area has shown that nu mer -ous VMS oc cur rences, in clud ing the Bay Creek, ClaimPost and Rant Point oc cur rences (MINFILE 092F 343,092F 290 and 092F 494) are hosted in wa ter-laid fel sic vol -ca nic rocks, com pris ing rhy o lite flows and as so ci ated fel sic volcaniclastic and tuffaceous rocks. Field work in the Cypre River and Her bert In let ar eas in di cates that fel sic vol ca nicrocks are spa tially as so ci ated with car bon ate rocks, sug -gest ing a po ten tial strati graphic sce nario sim i lar to that ob -served at the Dragon prop erty north of Gold River, wherecar bon ate rocks are ob served to con form ably over lie VMSmin er al iza tion and fel sic vol ca nic rocks. If car bon ate rocksof the Bedingfield and Dragon ar eas are Perm ian in age,this places them in a sim i lar age range to wide spread car -bon ate rocks of the Mount Mark For ma tion. This wouldsug gest the pres ence on Van cou ver Is land of a wide spreadcy cle of pre vi ously un doc u mented late Pa leo zoic bi modalmagmatism and VMS min er al iza tion pos si bly cor re la tivewith Pa leo zoic rocks of the Queen Char lotte Is lands(Hesthammer et al., 1991) and south west ern Yu kon Ter ri -tory–south east ern Alaska (Is rael and Cobbett, 2008). Sucha cor re la tion would suggest that Wrangellia is a long-lived,metallogenically well-endowed terrane of large geographic extent.Future WorkField work in 2009 con sti tutes the fi nal field work for thispro ject. Ura nium-lead zir con dat ing, to gether with litho -geochemical and Nd and Pb iso to pic stud ies of sam ples col -lected dur ing the past field sea son, are now in prog ress andwill be com pleted dur ing the next six months. Re sults ofthis work will con strain the age and mag matic evo lu tion ofPa leo zoic Wrangellia and help de velop a frame workthrough which VMS oc cur rences hosted by this stra tig ra -phy can be dis tin guished from youn ger, epigeneticsulphide occurrences.AcknowledgmentsThis pro ject is jointly funded by a Geoscience BC grant,Bitterroot Re sources Ltd., Paget Re sources Cor po ra tion,Trea sury Met als Inc., Westridge Re sources Inc., a Nat u ralSci ences and En gi neer ing Re search Coun cil of Can ada(NSERC) Dis cov ery Grant to JKM, and an NSERC post -grad u ate schol ar ship to TR. The au thors thank N. Masseyfor dis cus sions and in sights into the ge ol ogy of the SickerGeoscience BC Re port 2010-1 167340Group and S. Mc Kin ley of Cam bria Geosciences Inc. forhav ing pro vided a crit i cal re view of this manu script. Theau thors thank W. Ruks and B. Smyth for ca pa ble as sis tancein the field, and Is land Tim ber lands and the Dis trict ofNorth Cowichan for land ac cess as sis tance in the Cowichan area. For lo gis ti cal sup port and ac com mo da tions whilework ing in the Bedingfield and Hesquiat ar eas, the au thorsthank D. Drake and B. Tay lor of Iisaak For est Re sourcesLtd., Coulson For est Prod ucts Ltd., D. Lorney of Tran quilTim ber Ltd. and D. Scott of Port Neville Log ging Co. Ltd.For ex cel lent trans por ta tion ser vices in the ClayoquotSound and Nootka Sound ar eas, the au thors thankG. Boddey and Nootka Sound Ser vice Ltd. Thanks also goto sev eral pros pec tors, con sul tants and explorationistswork ing on Van cou ver Is land, es pe cially M. Becherer ofMin eral Creek Ven tures Inc., M. Carr of Bitterroot Re -sources Ltd., J. Brad ford of Paget Re sources Cor po ra tion,E. Specogna of Specogna Min er als Corp., T. Sadlier-Brown of Westridge Re sources Inc., S. Mc Kin ley of Cam -bria Geosciences, J. Miller-Tait and P. Gray of Selkirk Met -als Corp., J. Houle, H. McMaster, the late S. Tresierra andthe late A. Francis, for sharing their time and knowledge ofSicker Group geology and mineralization.ReferencesBanerjee, N.R., Simonetti, A., Furnes, H., Muehlenbachs, K.,Staudigel, H., Heaman, L. and Van Kranendonk, M.J.(2007): Di rect dat ing of Archean mi cro bial ichnofossils;Ge ol ogy, v. 35, no. 6, p. 487–490.Barrett, T.J. and Sherlock, R.L. (1996): Vol ca nic stra tig ra phy,lithogeochemistry and seafloor set ting of the H-W mas sivesul fide de posit, Myra Falls, Van cou ver Is land, Brit ish Co -lum bia; Ex plo ra tion and Min ing Ge ol ogy, v. 5, p. 421–458.Blackwell, J.D. and Lajoie, J.J. (1986): Ge ol ogy and geo phys ics of the Bedingfield 1–15, Cypre 1 min eral claims, Alberni Min -ing Di vi sion, Tofino area, Brit ish Co lum bia; BC Min is try ofEn ergy, Mines and Pe tro leum Re sources, As sess ment Re -port 15152, 111 p., URL <http://aris.empr.gov.bc.ca/search.asp?mode=repsum&rep_no=15152> [November2009].Brandon, M.T., Or chard, M.J., Parrish, R.R., Suther land Brown,A. and Yorath, C.J. (1986): Fos sil ages and iso to pic datesfrom the Pa leo zoic Sicker Group and as so ci ated in tru siverocks, Van cou ver Is land, Brit ish Co lum bia; in Cur rent Re -search, Part A, Geo log i cal Sur vey of Can ada, Pa per 86-1A,p. 683–696.Frank lin, J.M., Gib son, H.L., Jonasson, I.R. and Gal ley, A.G.(2005): Volcanogenic mas sive sul fide de pos its; Eco nomicGe ol ogy 100th An ni ver sary Vol ume, p. 523–560.Fyles, J.T. (1950): Jane, Sally and Sally No. 2; in Min is ter ofMines An nual Re port, 1949, BC Min is try of En ergy, Minesand Pe tro leum Re sources, p. 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Kluane Ranges bed rock ge ol ogy, White River area (parts of NTS 115F/9, 15 and 16; 115G/12and 115K/1, 2); in Yu kon Ex plo ra tion and Ge ol ogy 2007,D.S. Emond, L.R. Blackburn, R.P. Hill and L.H. Weston(ed.), Yu kon Geo log i cal Sur vey, p. 153–167.Jones, M.I. (1997): 1996 as sess ment re port, Dragon prop erty, di a -mond drill ing, Alberni and Nanaimo Min ing Di vi sions,NTS map ar eas 92E/16E, 92L/1E, lat i tude 49°55′00″N, lon -gi tude 126°20′00″W; BC Min is try of En ergy, Mines and Pe -tro leum Re sources, As sess ment Re port 24895, 189 p., URL<http://aris.empr.gov.bc.ca/search.asp?mode=repsum&rep_no=24895> [November 2009].Juras, S.J. (1987): Ge ol ogy of the polymetallic volcanogenicButtle Lake camp, with em pha sis on the Price hill side, cen -tral Van cou ver Is land, Brit ish Co lum bia, Can ada; Ph.D. the -sis, Uni ver sity of Brit ish Co lum bia, 279 p.Katvala, E.C. (2006): Re-ex am in ing the strati graphic andpaleontologic def i ni tion of Wrangellia; Geo log i cal So ci etyof Amer ica, Ab stracts with Pro gram, v. 38, p. 24.Kelso, I., Wetherup, S. and Takats, P. (2007): In de pend ent tech ni -cal re port and min eral re source es t i ma t ion, Larapolymetallic prop erty, Brit ish Co lum bia, Can ada; un pub -lished com pany re port pre pared by Caracle Creek In ter na -tional Con sult ing for Lara mide Re sources Ltd.Kemp, R. and Gill, G. (1993): Geo log i cal, geo chem i cal and di a -mond drill ing re port on the Specogna-Muchalat prop erty,NTS 92E/16, Alberni Min ing Di vi sion; BC Min is try of En -ergy, Mines and Pe tro leum Re sources, As sess ment Re port23125, 48 p . , URL <ht tp : / /a r i s .empr.gov.bc .ca /search.asp?mode=repsum&rep_no=23125> [No vem ber2009].Mac don ald, R.W.J., Barrett, T.J., and Sherlock, R.L. (1996): Ge ol -ogy and lithogeochemistry at the Hid den Creek mas sive sul -phide de posit, Anyox, west-cen tral Brit ish Co lum bia;Ex plo ra tion and Min ing Ge ol ogy, v. 5, p. 369–398.Mar shall, D., Lesiczka, M., Xue, G., Close, S. and Fecova, K.(2006): Up date on the min eral de posit po ten tial of theNootka Sound re gion (NTS 092E), west coast of Van cou verIs land, Brit ish Co lum bia; in Geo log i cal Field work 2005, BC Min is try of En ergy, Mines and Pe tro leum Re sources, Pa per2006-1 and Geoscience BC, Re port 2006-1, p. 323–330,URL <http://www.em.gov.bc.ca/mining/Geolsurv/Publications/Fieldwork/2005/toc.htm#GeoscienceBC>[No vem ber 2009].Massey, N.W.D. (1995): Ge ol ogy and min eral re sources of theDuncan sheet, Van cou ver Is land, 92B/13; BC Min is try ofEn ergy, Mines and Pe tro leum Re sources, Pa per 1992-4,URL <http://www.empr.gov.bc.ca/Mining/Geoscience/PublicationsCatalogue/Papers/Pages/1992-4.aspx> [No -vem ber 2009].Massey, N.W.D. and Fri day, S.J. (1988): Ge ol ogy of theChemainus River–Duncan area, Van cou ver Is land (92C/16,92B/13); in Geo log i cal Field work 1987, BC Min is try of En -168 Geoscience BC Sum mary of Ac tiv i ties 2009341ergy, Mines and Pe tro leum Re sources, Pa per 1988-1, p. 81–91, URL <http://www.empr.gov.bc.ca/Mining/Geoscience/PublicationsCatalogue/Fieldwork/Pages/GeologicalFieldwork1987.aspx> [No vem ber 2009].Massey, N.W.D. and Fri day, S.J. (1989): Ge ol ogy of the Alberni–Nanaimo Lakes area, Van cou ver Is land (92F/1W, 92F/2Eand part of 92F/7); BC Min is try of En ergy, Mines and Pe tro -leum Re sources, Open File 1987-2, URL <http://www.empr.gov.bc.ca/Mining/Geoscience/PublicationsCatalogue/OpenFiles/1987/Pages/1987-2.aspx> [No vem ber2009].Massey, N.W.D., Mac In tyre, D.G., Desjardins, P.J. and Cooney,R.T. (2005): Dig i tal map of Brit ish Co lum bia: Tile NM10South west BC; BC Min is try of En ergy, Mines and Pe tro -leum Re sources , GeoFi le 2005-3 , URL <ht tp : / /www.empr.gov.bc.ca/Mining/Geoscience/PublicationsCatalogue/GeoFiles/Pages/2005-3.aspx> [No vem ber 2009].MINFILE (2010): MINFILE BC min eral de pos its da ta base; BCMin is try of En ergy, Mines and Pe tro leum Re sources, URL<http://www.minfile.ca> [No vem ber 2010].Mul ler, J.E. (1977): Ge ol ogy of Van cou ver Is land; Geo log i calSur vey of Can ada, Open File 463, 1:250 000 scale.Mul ler, J.E. (1980): The Pa leo zoic Sicker Group of Van cou ver Is -land, Brit ish Co lum bia; Geo log i cal Sur vey of Can ada, Pa -per 79-30, 23 p.Pattison, J.M. and Money, D.P. (1988): 1987 drill ing re port on theWest claims, pro ject # 094/107, sit u ated 1 km west ofCrofton, BC in the Vic to ria Min ing Di vi sion; BC Min is tryof En ergy, Mines and Pe tro leum Re sources, As sess ment Re -port 17007, 252 p., URL <http://aris.empr.gov.bc.ca/search.asp?mode=repsum&rep_no=17007> [November2009].Ruks, T.R. and Mortensen, J.K. (2007): Geo log i cal set ting ofvolcanogenic mas sive sul phide oc cur rences in the Mid dlePa leo zoic Sicker Group of the south east ern Cowichan Lakeup lift (NTS 092B/13), south ern Van cou ver Is land; in Geo -log i cal Field work 2006, BC Min is try of En ergy, Mines andPe tro leum Re sources, Pa per 2007-1 and Geoscience BC,R e p o r t 2 0 0 7 - 1 , p . 3 8 1 – 3 9 4 , U R L < h t t p : / /www.em.gov.bc.ca/mining/Geolsurv/Publications/Fieldwork/2006/toc.htm#GeoscienceBC> [No vem ber 2009].Ruks, T. and Mortensen, J.K. (2008): Geo log i cal set ting ofvolcanogenic mas sive sul phide oc cur rences in the Mid dlePa leo zoic Sicker Group of the Cowichan Lake up lift, PortAlberni area, south ern Van cou ver Is land, Brit ish Co lum bia;in Geoscience BC Sum mary of Ac tiv i ties 2007, GeoscienceB C , R e p o r t 2 0 0 8 - 1 , p . 7 7 – 9 2 , U R L < h t t p : / /www.geosciencebc.com/s/SummaryofActivities.asp?ReportID=358405> [No vem ber 2009].Ruks, T., Mortensen, J.K. and Cordey, F (2009a): Pre lim i nary re -sults of geo log i cal map ping, ura nium-lead zir con dat ing,and micropaleontological and lead iso to pic stud ies ofvolcanogenic mas sive sul phide–host ing stra tig ra phy of theMid dle and Late Pa leo zoic Sicker and Lower Buttle Lakegroups on Van cou ver Is land, Brit ish Co lum bia (NTS092B/13, 092C/16, 092E/09, /16, 092F/02, /07); inGeoscience BC Sum mary of Ac tiv i ties 2008, GeoscienceBC, Re po r t 2009 -1 , p . 103–122 , URL < h t t p : / /www.geosciencebc.com/s/SummaryofActivities.asp?ReportID=358404> [No vem ber 2009].Ruks, T., Mortensen, J.K. and Cordey, F. (2009b): Strati graphicand paleotectonic stud ies of the Mid dle Pa leo zoic SickerGroup and con tained volcanogenic mas sive sul phide (VMS) oc cur rences, Van cou ver Is land, Brit ish Co lum bia (ab stract); Geo log i cal So ci ety of Amer ica An nual Meet ing,Cordilleran Sec tion, May 7–9, 2009, GSA Ab stracts withPro grams, Pa per 7-3.Sluggett, C.L. (2003): Ura nium-lead age and geo chem i cal con -straints on Pa leo zoic and Early Me so zoic magmatism inWrangellia Terrane, Saltspring Is land, Brit ish Co lum bia;B.Sc. the sis, Uni ver sity of Brit ish Co lum bia, 56 p.Sluggett, C.L. and Mortensen, J.K. (2003): U-Pb age and geo -chem i cal con straints on the paleotectonic evo lu tion of thePa leo zoic Sicker Group on Saltspring Is land, south west ernBrit ish Co lum bia (ab stract); Geo log i cal As so ci a tion of Can -ada–Min er al og i cal As so ci a tion of Can ada, Joint An nualMeet ing, Pro gram with Ab stracts, v. 28.Yorath, C.J., Suther land Brown, A. and Massey, N.W.D. (1999):LITHOPROBE, south ern Van cou ver Is land, Brit ish Co lum -bia: ge ol ogy; Geo log i cal Sur vey of Can ada, Bul le tin 498,145 p.Geoscience BC Re port 2010-1 169342Appendix 5: Fieldtrip guide 343Paleozoic Wrangellia and its Contained Volcanogenic Massive Sulphide Occurrences Society of Economic Geologists 2013 Annual Meeting Field Trip Sept. 21st through Sept. 24th, 2013 Trip Leader: Tyler Ruks Introduction Wrangellia comprises a multi-episodic, Devonian and younger arc terrane that extends for over 2500 km in length, from southern Vancouver Island and the Queen Charlotte Islands to south-central Alaska. The Paleozoic geology of southern Wrangellia, on Vancouver Island, appears to differ significantly from that of northern Wrangellia in Alaska and southwest Yukon. The oldest rocks in Wrangellia comprise the mid Paleozoic Sicker Group and are only found on Vancouver Island. The Sicker Group is interpreted to represent the development of a Late Devonian oceanic island arc which is associated with several cycles of economically significant volcanogenic massive sulphide (VMS) mineralization (Massey et al., 1995a, b, c; Yorath et al., 1999; Ruks and Mortensen, 2007, 2008; Ruks et al., 2009). Epiclastic sedimentary rocks and bioclastic limestone of Mississippian through Permian Buttle Lake Group overlie this arc package (Yorath et al., 1999). In northern Wrangellia, the oldest rocks recognized thus far represent a Pennsylvanian through Permian arc. This Late Paleozoic arc was not believed to manifest itself in southern Wrangellia rocks (Yorath et al., 1999; Colpron and Nelson, 2009). A geological, geochemical and geochronological study of the Sicker Group was initiated by Mortensen in 2005, with financial support from Geoscience BC and the Natural Sciences and Engineering Research Council of Canada. This project had several objectives, including: 1) to develop a physical volcanological model explaining the eruptive history of the Sicker Group; 2) to resolve the paleotectonic evolution of southern Wrangellia; and 3) to elucidate the style and stratigraphic positions of VMS occurrences in the Sicker Group. Fieldwork for the project was carried out by Mortensen in the fall of 2005. Ruks joined the project part time as a PhD candidate in September of 2006 and commenced full time studies in January of 2007. Subsequent fieldwork has been conducted for the project in 2007, 2008, and 2009 field seasons, the results of which are reported in Geoscience BC Fieldwork articles (e.g. Mortensen, 2005; Ruks and Mortensen, 2007; Ruks and Mortensen, 2008; Ruks et al., 2009; Ruks et al., 2010). Initial fieldwork focused on exposures of Sicker Group geology. However, it was recognized early in the project that large parts of the Port Alberni and Gold River regions that had been interpreted by previous workers to be Middle Paleozoic rocks of the Sicker Group were not components of the Sicker Group, and instead, were part of a previously unrecognized cycle of Late Paleozoic magmatism in southern Wrangellia. This, combined with the presence of abundant new bedrock exposures in these areas as the result of logging activity, necessitated a larger component of geological mapping than was previously anticipated at the start of the project. In addition, the scope of the original study was expanded to include investigations of Late Paleozoic stratigraphy and metallogeny in southern Wrangellia. On the basis of our initial results, the project generated a substantial interest from mineral exploration companies exploring for VMS mineralization in southern Wrangellia. As a result, several mineral exploration companies became involved with the project as corporate sponsers, with emphasis on addressing the fundamental questions related to the project on their respective mineral titles. Corporate sponsers for the project include Bitterroot Resources Ltd., Paget Resources Corporation, 344Treasury Metals Ltd., and Westridge Resources. Additional funding for subsequent work on the project was requested from GBC in the fall of 2007. This funding, a 100% match to corporate financial contributions to the project, was granted by GBC in 2008. In order to utilize biostratigraphy as a tool for resolving Paleozoic stratigraphy in southern Wrangellia (Vancouver Island), Dr. Fabrice Cordey (University of Lyon, France) joined the project as a co-researcher in 2008. Previous Studies of Paleozoic Rocks in Southern Wrangellia Strata of the Sicker Group and the Karmutsen Formation were first described as the ‘Vancouver Series’ by Selwyn (1872) and Dawson (1887). Clapp (1912) described these rocks separately as the Mount Sicker Series, after a type area on Big Sicker Mountain, north of the town of Duncan, Vancouver Island, but incorrectly assigned them to the Triassic Vancouver Group (Fyles, 1955). Clapp and Cook (1917) subdivided the Sicker Group into a lower volcanic unit and an overlying sequence of sediments, including limestone. Based on reconnaissance field studies in the Buttle Lake area (Gunning, 1931), a sequence of volcanic rocks underlying a thick limestone of Paleozoic age were assigned the name ‘Buttle Lake Group’. Fyles (1955) recognized the widespread presence of Paleozoic limestone throughout Vancouver Island, based on discovery of Paleozoic fossils in the Horne Lake area (Richardson, 1873), and geological fieldwork in the Bedwell Sound and Alberni areas by Sargent (1941) and Stevenson (1945), respectively. Based on this observation, Fyles (1955) established the name ‘Sicker Group’ to the entire Paleozoic succession in the Cowichan Lake area. Yole (1963, 1965, 1969) proposed correlation between the Cowichan and Buttle Lake areas; he also re-assigned the Buttle Lake Group to formation status, and proposed the name ‘Youbou Formation’ for the underlying volcanic rocks. Regional mapping of Vancouver Island by Muller (Muller and Carson, 1969; Muller et al., 1974; Muller, 1980) divided Paleozoic volcanic rocks into two formations, a lower Nitinat and an upper Myra Formation, and described an informal ‘sediment-sill’ unit which occurs beneath the Buttle Lake Formation. Further regional geologic mapping of Paleozoic rocks on Vancouver Island in the Cowichan area was conducted by Massey et al. from 1986 through 1990 (Massey, 1995a, 1995b, 1995c). This work resulted in recognition of a previously unrecognized lithological unit at the lowest stratigraphic level in the Sicker Group, the Duck Lake Formation. Also, Myra Formation rocks of the Alberni area were reassigned to the McLaughlin Ridge Formation, to account for substantial lithological differences between the two areas. Lastly, the Buttle Lake Group was divided into three formations, which are, from base to top, the Fourth Lake, Mount Mark and St. Mary’s Lake formations. In the Buttle Lake area, Juras (1987) revised the Sicker Group stratigraphy into four units, which are, from base to tope, the Price, Myra, Thelwood and Flower Ridge formations. Work by Barrett and Sherlock (1996) at the Myra Falls VMS deposit refined VMS associated volcanic strata and lithogeochemistry. Lead isotope studies have been conducted on massive sulphide mineralization of the Myra Falls and Cowichan VMS deposits by Andrews and Godwin (1989) and Godwin and Robinson (1996). Outcrops of Sicker Group and overlying Buttle Lake Group rocks on Vancouver Island have now been identified as occurring in several distinct uplifts, including the Cowichan, Nanoose, Buttle Lake and Bedingfield uplifts (Fig. 1). 345 Figure 1. Areas of exposure of Paleozoic strata on Vancouver Island and locations of significant VMS mineralization The current stratigraphic framework for Sicker Group rocks (Fig. 2) is based on mapping in only two of the four main uplifts of Sicker Group rocks (the Cowichan and Buttle Lake uplifts), and is supported by a limited amount of biostratigraphic and isotopic age data (e.g., Brandon et al., 1986; Sluggett, 2003; Sluggett and Mortensen, 2003). Major along- and across-strike facies changes and geochemical variations are to be expected in submarine volcanic sequences such as the one that forms the Sicker Group; hence, the regional applicability of the stratigraphic framework of Yorath et al. (1999) is currently being tested with detailed mapping and subsequent lithogeochemical and U-Pb dating studies. This is critical for regional exploration for VMS deposits within the Sicker Group. For example, the questions of whether VMS deposits and occurrences in the Cowichan Lake uplift are all of the same age, and whether their host rocks are directly correlative with those that host the Myra Falls deposit, are of obvious importance. Geology The mid-Paleozoic Sicker Group on southern and central Vancouver Island represents the oldest rocks in the Wrangellia Terrane. Equivalents of the Sicker Group are not present in Wrangellia in northwestern British Columbia, southwestern Yukon and southern Alaska, where the oldest rock units are the Skolai Group, volcanic and sedimentary rocks deposited in a volcanic arc setting which is no older than Pennsylvanian (Smith and MacKevitt, 1970; Read and 346Monger, 1976; Israel and Cobbett, 2008). Potential correlatives to Paleozoic rocks of southern Wrangellia are found on the San Juan Islands, USA, approximately 35 km northeast of Victoria, Vancouver Island, B.C. These potential correlatives comprise the Turtleback and Deadman Bay terranes (Brandon et al., 1988). The Turtleback terrane comprises a Late Devonian plutonic suite called the Turtleback Complex and an upper Paleozoic arc-volcanic sequence known as the East Sound Group (Brandon et al., 1988; E. Brown, 2008, pers. comm..). Late Paleozoic volcanic rocks and limestone comprise the Deadman Bay terrane (Yamagata, 2009). The significant differences between Wrangellian strata on Vancouver Island and that in more northerly and southerly exposures, emphasize the lack of understanding regarding much of Wrangellia (e.g., Katvala, 2006) and the need for further studies in order to define this extensive, and economically significant terrane. Figure 2. Stratigraphic nomenclature for the Sicker and Buttle Lake groups on Vancouver Island (from Yorath et al., 1999). The Cowichan Lake uplift on Vancouver Island and adjacent portions of the Gulf Islands is the largest of four uplifts that expose the Sicker and overlying late Paleozoic Buttle Lake groups (Fig. 1). The Sicker Group within the Cowichan Lake uplift is presently interpreted to represent three distinct volcanic and volcaniclastic assemblages that together are thought to record the evolution of an oceanic magmatic arc (Massey, 1995a, b, c; Yorath et al., 1999). The lowermost Duck Lake Formation yields mainly normal mid-ocean-ridge basalt (N-MORB) geochemical signatures (Massey, 1995a) and is interpreted to represent the oceanic crust basement on which the Sicker arc was built. The upper portions of the Duck Lake Formation yield tholeiitic to calcalkaline compositions and may represent primitive arc rocks. Rare felsic volcanic rocks are present in the Duck Lake Formation of the Alberni area, including a dacite flow. This unit was previously interpreted to be a felsic sill of potential McLaughlin Ridge Formation age (Yorath et al., 1999), but has since been identified by the author as a flow-dome, with associated carapace breccias, that was erupted coincident with Duck Lake Formation basalts. The Duck Lake Formation is overlain by the Nitinat Formation, which comprises mafic, 347submarine volcanic and volcaniclastic rocks with dominantly calcalkaline compositions and trace-element signatures typical of volcanic arc settings. These rocks are interpreted as an early stage of arc development. The andesitic to mainly dacitic and rhyolitic McLaughlin Ridge Formation overlies the Nitinat and is believed to be correlative with the Myra Formation, the host rocks for the Myra Falls deposits (Fig. 1). Rocks of the McLaughlin Ridge and Myra formations reflect a more evolved stage of arc activity. Eruption of Nitinat volcanic and volcaniclastic rocks appears to have occurred from several widely scattered centres, whereas the McLaughlin Ridge Formation within the Cowichan Lake uplift is thought to represent eruption from one or more major volcanic edifices. The abundance of proximal felsic volcaniclastic rocks and the presence of voluminous comagmatic felsic intrusions in the Saltspring Island and Duncan areas (Fig. 1) indicate that one of these major volcanic centres was located in this area. Plant fossils indicate that at least a minor amount of McLaughlin Ridge volcanism occurred in a subaerial setting. In the Port Alberni area, the McLaughlin Ridge Formation has previously been interpreted to comprise felsic, fine-grained tuffaceous volcaniclastic and epiclastic rocks, suggesting deposition distal from a volcanic centre. Deposition of sedimentary and volcano-sedimentary rocks of the overlying Fourth Lake Formation of the Buttle Lake Group followed the cessation of Sicker arc magmatism, and scarce mafic volcanic rocks contained within the Fourth Lake Formation yield enriched tholeiitic rather than the calcalkaline compositions that characterize the McLaughlin Ridge. Massey (1995a, b, c) speculated that the Buttle Lake Group may represent a marginal-basin assemblage that developed on top of the Sicker arc. Rocks of the Fourth Lake Formation form the oldest stratigraphic unit of the Buttle Lake Group, and comprise a diverse range of lithologies that vary in proportion from one locality to the next; these include siliceous argillite, shale, black chert, bioclastic limestone, intermediate volcanic sandstone, green and red ribbon chert, chert breccia, and conglomerate with an intermediate volcanic sandstone matrix (Yorath et al., 1999). Biostratigraphic work on the Fourth Lake Formation indicates an age ranging from Mississippian (Orchard, 1987; Katvala and Henderson, 2002) through Lower Permian (Katvala and Henderson, 2002). Upper sections of the Fourth Lake Formation have been demonstrated in places to laterally interfinger with rocks of the Middle Pennsylvanian through Early Permian Mount Mark Formation (Yorath et al., 1999; Katvala and Henderson, 2002). In the Mount Whymper area, massive basalt flows of the alkalic Mount Whymper volcanic suite are interbedded with cherts and cherty sediments belonging to the Fourth Lake Formation (Massey, 1993c) and may represent a component of Late Paleozoic magmatism that has gone largely unrecognized in southern Wrangellia thus far. Studies of the Sicker and Buttle Lake groups on southern Saltspring Island by Sluggett (2003) and Sluggett and Mortensen (2003) provided new U-Pb zircon age constraints on both felsic volcanic rocks of the McLaughlin Ridge Formation and several bodies of Saltspring intrusions. This work demonstrates that two distinct episodes of felsic magmatism occurred in this portion of the Cowichan Lake uplift. One sample of felsic volcanic rocks from the McLaughlin Ridge Formation and three samples of Saltspring intrusions yielded U-Pb ages in the range 356.5–359.1 Ma. A somewhat older U-Pb age of 369.7 Ma was obtained from a separate body of the Saltspring intrusions at Burgoyne Bay on the southwest side of Saltspring Island, indicating that magmatism represented by the McLaughlin Ridge Formation and associated Saltspring intrusions occurred over a time span of at least 15 Ma. There is insufficient age control available at this point to determine whether the magmatism was continuous or episodic during this time period. Lithogeochemical studies of the Saltspring Intrusions by Sluggett (2003) indicate peraluminous compositions. Peraluminous magmas are not common to 348ocean island arc environments, suggesting that there may be older, evolved, continental crust like basement underlying southern Wrangellia from which melts of the Saltspring Intrusions were derived (Sluggett, 2003; Sluggett and Mortensen, 2003). In the same study, a felsic tuffaceous sandstone from rocks assigned to the Fourth Lake Formation yielded abundant, euhedral 324 Ma zircons (Sluggett and Mortensen, 2003) for which there are no known sources on Vancouver Island. Rocks in the Nanoose uplift (Fig. 1) have been tentatively correlated with both the Sicker Group and the Buttle Lake Group, and comprise fine clastic rocks, chert, diabasic to andesitic volcanic rocks and limestone (Yorath et al., 1999). A fossil sample from crinoidal limestone in the Nanoose uplift provided brachiopods that yielded a Permian age and fusulinids that yielded a Middle Pennsylvanian age (Muller, 1980). However, diabasic and andesitic pillow lavas in the area have unknown stratigraphic affinities. On the Ballenas Islands, these pillow lavas are associated with green and grey chert, and are interbedded with a red tuff breccia which contains both scoriaceous mafic volcanic clasts and crinoidal limestone clasts. In addition, Yorath et al. (1999) reported the presence of extensive mélange in the Nanoose area. This is significant, as it may represent the only documented occurrence of a Paleozoic subduction complex in Wrangellia. A potential correlative of volcanic rocks exposed in the Nanoose uplift includes the Deadman Bay Volcanics of the San Juan Islands, located approximately 35 km to the northeast of Victoria, British Columbia. The Deadman Bay Volcanics comprise Permian basaltic rocks and limestones. Together, they are interpreted to represent a Permian seamount complex (Yamagata, 2009). Stratigraphic work on Paleozoic rocks in the Buttle Lake uplift (Fig. 1) has focused on geology in and around the Myra Falls VMS deposits (e.g., Juras, 1987; Barrett and Sherlock, 1996). The oldest rocks of the Buttle Lake Group are basaltic andesite flows and lesser mafic volcaniclastic deposits of the Price andesite (Juras, 1987), which form the “footwall” to VMS mineralization. Lithogeochemically, rocks of the Price andesite have marked negative Nb anomalies, and tend towards transitional to mildly calc-alkaline affinities, both features of volcanic rocks generated in suprasubduction zone settings (Barrett and Sherlock, 1996). Overlying rocks of the Myra Formation comprise basaltic to rhyolitic flows and volcaniclastic rocks, with lesser epiclastic sediments, argillites, cherts, and massive suphide mineralization (Juras, 1987). Barrett and Sherlock (1996) concluded that the Price and Myra Formation volcanic rocks that host the Myra Falls VMS deposits were generated in a suprasubduction setting during submarine rifting of the mature phase of an oceanic island arc, similar to that observed in modern day settings at the Valu Fu Ridge in the southern Lau Basin (Pearce et al., 1982; Fouquet et al., 1993) and the south tip of the Japan arc (Ikeda and Yuasa, 1989). Lead isotope studies conducted on massive sulphide mineralization of the Myra Falls and Cowichan VMS deposits (Andrews and Godwin, 1989; Godwin and Robinson, 1996) concluded that massive sulphide mineralization hosted in lower levels of the mine strata at Myra Falls were found to be more radiogenic than those hosted in upper stratigraphic levels (Godwin and Robinson, 1996). Godwin and Robinson (1996) attributed this to a potential contribution of lead derived from evolved, continental detritus to massive sulphides associated with lower stratigraphic levels. Siliceous tuffaceous sediments, subaqueous volcaniclastic debris flows, pyroclastic deposits and mafic sills comprise the Thelwood Formation, which, in places, unconformably overlies the Myra Formation (Juras, 1987). Conformably overlying the Thelwood Formation are rocks of the Flower Ridge Formation, which include amygdaloidal basaltic lapilli tuff and volcanic breccia, minor basaltic flows and tuffs, and tuffaceous 349sedimentary rocks (mudstones and siltstones) (Juras, 1987). Volcanic rocks of the Flower Ridge Formation may be correlative to those of the Mount Whymper Volcanic Suite, hosted in rocks of the Fourth Lake Formation in the Cowichan uplift (Massey, 1993b). Geochronology and some limited biostratigraphic work have been conducted in the Myra Falls area. Juras (1987) conducted U-Pb (zircon) dating of a rhyolite unit in the upper part of the Myra Formation, determining an age of 370 +18/-6 Ma. Parrish and McNichol (1992) dated a rhyolite from the lower part of the Myra Formation at 366 +/- 4 Ma. Early Mississippian radiolaria have been derived from rocks of the Thelwood Formation. The Flower Ridge Formation has no age constraints, but is bracketed between Early Mississippian and Pennsylvanian to Early Permian age, based on ages of the underlying Thelwood Formation, and the overlying Buttle Lake Formation, respectively (Brandon et al., 1986; Juras, 1987). Potential Sicker Group rocks and VMS mineralization of the Bedingfield uplift are located north of Tofino (Fig. 1). The age and stratigraphy of this extensive belt of potential Sicker Group rocks is poorly understood. The most recent geological descriptions of the area are contained in mineral exploration assessment reports from the late 1980s by BHP-Utah Mines and Cominco (e.g., Duncan and Ord, 1987, and Freeze, 1986, respectively). VMS mineralization of the Bedingfield area comprises several showings with significant polymetallic grades, associated with a variably deformed package of waterlain bimodal volcanic rocks and associated sedimentary rocks, which are intruded by gabbroic sills assumed to be correlative with the Triassic Mount Hall Gabbro. A sedimentary unit comprising argillite and chert is observed to unconformably overlie the volcanic package (Freeze et al., 1986), and may be correlative to the Fourth Lake Formation of the Buttle Lake Group. Overlying this sedimentary unit is variably fossiliferous (crinoid bearing) limestone, potentially correlative with the Mount Mark Formation of the Buttle Lake Group (Freeze et al. 1986). There is a complete absence of geochronological and biostratigraphic control for potential Paleozoic strata of the Bedingfield area. The age and stratigraphy of rocks underlying the Dragon and Dorado properties (Fig. 1), in the vicinity of Gold River and Hesquiat, respectively, are poorly constrained. The Dragon property is located approximately 80 km west of Campbell River, 20 km northwest of Gold River and 65 km northwest of the Myra Falls mine of Breakwater Resources Ltd. (Fig. 1). Regional mapping of the Dragon property area by Muller (1977) interpreted the rocks underlying the Dragon property as amphibolite-grade metamorphic rocks derived from the Westcoast Crystalline Complex. Muller described the Westcoast Crystalline Complex as amphibolite-faces metamorphic rocks belonging to the Middle Paleozoic Sicker Group, the Late Paleozoic Buttle Lake Group and the Triassic Karmutsen Formation. After the discovery of massive sulphides in float on the Dragon property by prospector E. Specogna, work by Noranda geologists culminated in the discovery of the Falls and North VMS occurrences (Kemp and Gill, 1993). Further geological mapping and diamond-drilling by Noranda and Westmin geologists indicated that these showings, with grades up to 7.33% Zn, 1.34% Pb, 173 ppm Cu, 680 ppb Au, and 19.2 g/t Ag over a 2 m thickness, are associated with the contact zone between underlying bimodal volcanic rocks and overlying sedimentary rocks and limestone (Jones, 1997). Volcanic rocks of the Dragon property that underlie massive sulphide mineralization consist of massive, flow-banded rhyolite, andesite and tuffaceous felsic and intermediate volcanic rocks. Sedimentary and carbonate rocks overlying and interlayered with massive sulphide mineralization on the Dragon property consist of chert, mudstone, calcareous mudstone, fossiliferous felsic tuff, fossiliferous wackestone and marble (e.g., Jones, 1997; Ruks et al., 2009). 350The Dorado property is located approximately 17 km north of the village of Hesquiat, on the west coast of Vancouver Island. Like the Dragon property, rocks underlying the Dorado property were originally interpreted by Muller (1977) as amphibolite-facies metamorphic rocks assigned to the Westcoast Crystalline Complex. However, geological mapping of the area by Marshall et al. (2006) has shown the region to be underlain by abundant mafic volcanic rocks of potential Sicker Group affinity, and by sedimentary and carbonate rocks of potential Buttle Lake Group affinity. Following up on reports by Marshall et al. (2006) of polymetallic VMS-style stockwork mineralization in the area, Paget Resources Corporation staked the Dorado property and soon after discovered several polymetallic massive sulphide occurrences. Massive sulphide mineralization on the Dorado property is associated with the contact between massive, variably silica-altered, clinopyroxene- and feldspar-phyric andesite and overlying tuffaceous, volcano-sedimentary rocks (Ruks et al, 2009). The juxtaposition of interbedded fossiliferous limestones, tuffs and sedimentary rocks with underlying VMS mineralization and volcanic rocks that occurs on the Dragon and Dorado properties is not observed anywhere else in the Sicker Group. It raises the possibility that volcanic rocks and mineralization of the Dragon and Dorado properties might represent a Late Paleozoic cycle of arc magmatism and VMS mineralization not previously recognized on Vancouver Island. If limestones of the Dragon and Dorado property are correlative to limestones of the Permian Mt. Mark Formation, arc magmatism and mineralization of the Dragon and Dorado properties might be correlative to Late Paleozoic volcanic rocks in northern Wrangellia (e.g., the Skolai Group). If this is the case, northern Wrangellia and southern Wrangellia will be much more similar than previously thought, and previous calls for assigning northern and southern Wrangellia to different terranes (e.g., Katvala, 2006) are not justified. References Barrett, T.J. and Sherlock, R.L. (1996): Volcanic stratigraphy, lithogeochemistry and seafloor setting of the H-W massive sulfide deposit, Myra Falls, Vancouver Island, British Columbia; Exploration and Mining Geology, v. 5, p. 421–458. Brandon, M.T., Orchard, M.J., Parrish, R.R., Sutherland Brown, A. and Yorath, C.J. (1986): Fossil ages and isotopic dates from the Paleozoic Sicker Group and associated intrusive rocks, Vancouver Island, British Columbia; in Current Research, Part A, Geological Survey of Canada, Paper 86-1A, p. 683–696. Brandon, M.T., Cowan, D.S., and Vance, J.A. (1988): The Late Cretaceous San Juan Thrus System, San Juan Islands, Washington: Geological Society of America Special Paper 221. Clapp, C.H., and Cook, H.C., 1917, Sooke and Duncan map-areas, Vancouver Island, Geological Survey of Canada, Memoir 96, 445 p. Colpron, M. and Nelson, J.L., 2009. A Palaeozoic Northwest Passage: Incursion of Caledonian, Baltican and Siberian terranes into eastern Panthalassa, and the early evolution of the North American Cordillera. In: Accretionary Orogens through Space and Time, P.A. Cawood and A. Kroner (eds.), Geological Society of London, Special Publication. Cowley, P., 1979, Correlation of rhodonite deposits on Vancouver Island and Saltspring Island, British Columbia; Unpublished B.Sc. thesis, University of British Columbia, 54 p. Dawson, G.M.,1887, Report on a geological examination of the northern part of Vancouver Island and adjacent coasts, Geological Survey of Canada, Annual Report, New Series, Vol. 2, p. 1B-107B. Duncan, D.N., and Ord, R.S., 1987, Geological, geochemical, geophysical and diamond drilling work conducted on the Cypress claims, Bedingfield Range, Vancouver Island, British Columbia; BC Ministry of Energy, Mines and Petroleum Resources, Assessment Report 16 742. Franklin, J.M., Gibson, H.L., Jonasson, I.R. and Galley, A.G. (2005): Volcanogenic massive sulfide deposits; Economic Geology 100th Anniversary Volume, p. 523–560. 351Freeze, A.C., 1986, Assessment report geology of the Bedingfield 1-15, Cypre 1 Mineral Claims, Alberni Mining Division, Tofino Area, British Columbia, BC Ministry of Energy, Mines and Petroleum Resources, Assessment Report 14 500. Fyles, J.T., 1955, Geology of the Cowichan Lake Area, Vancouver Island, BritishColumbia, British Columbia Department of Mines, Bulletin 37, 79 p. Gunning, H.C., 1931, Buttle Lake map-area, Vancouver Island, British Columbia, Geological Survey of Canada, Summary Report 1930, Part A, p. 56-78. Henderson, C.M., and Katvala, E.C., 2000; Conodont Sequence Biostratigraphy and Paleogeography of the Pennsylvanian-Permian Mount Mark Formation, Wrangellia Terrane, Southern Vancouver Island, Geological Society of America, Abstracts with Programs, Cordilleran Section, 32(6): A-19. Israel, S. and Cobbett, R., 2008. Kluane Ranges bedrock geology, White River area (Parts of NTS 115F/9, 15 and 16; 115G/12 and 115K/1, 2). In: Yukon Exploration and Geology 2007, D.S. Emond, L.R. Blackburn, R.P. Hill and L.H. Weston (eds.), Yukon Geological Survey, p. 153-167. Juras, S.J. (1987): Geology of the polymetallic volcanogenic Buttle Lake camp, with emphasis on the Price hillside, central Vancouver Island, British Columbia, Canada; Ph.D. thesis, University of British Columbia, Vancouver, BC, 279 p. Jones, M.I. (1997): 1996 assessment report, Dragon property, diamond drilling, Alberni and Nanaimo Mining Divisions, NTS map areas 92E/16E, 92L/1E, Latitude 49°55′00″N, 126°20′00″W; BC Ministry of Energy, Mines and Petroleum Resources, Assessment Report 24895, 189 p. Katvala, E., 2006, Reexamining the stratigraphic and paleontologic definition of Wrangellia, Geological Society of America Abstracts with Programs, Vol. 38, No. 5, p. 24. Katvala, E. C. & Henderson, C. M. 2002. Conodont sequence biostratigraphy and paleogeography of the Pennsylvanian-Permian Mount Mark and Fourth Lake formations, southern Vancouver Island. In: Hills, L. V., Henderson, C. M. & Bamber, E. W. (eds) Carboniferous and Permian of the World. Canadian Society of Petroleum Geologists, Memoir, 19, 461-478. Kelso, I., Wetherup, S. and Takats, P. (2007): Independent technical report and mineral resource estimation, Lara polymetallic property, British Columbia, Canada; unpublished company report prepared by Caracle Creek International Consulting for Laramide Resources Ltd. Kemp, R. and Gill, G. (1993): Geological, geochemical and diamond drilling report on the Specogna-Muchalat property, NTS: 92E/16, Alberni Mining Division; BC Ministry of Energy, Mines and Petroleum Resources, Assessment Report 23125, 48 p. Marshall, D., Lesiczka, M., Xue, G., Close, S. and Fecova, K. (2006): Update on the mineral deposit potential of the Nootka Sound region (NTS 092E), west coast of Vancouver Island, British Columbia; in Geological Fieldwork 2005, Geoscience BC, Report 2006-1, p. 323–330. Massey, N.W.D., MacIntyre, D.G., Desjardins, P.J. and Cooney, R.T., (2005): Digital map of British Columbia: Tile NM10 Southwest BC; BC Ministry of Energy, Mines and Petroleum Resources, GeoFile 2005-3. Massey, N.W.D. (1995a): Geology and mineral resources of the Alberni-Nanaimo Lakes sheet, Vancouver Island, 92 F/1W, 92 F/2E and part of 92 F/7E; BC Ministry of Energy, Mines and Petroleum Resources, Paper 1992-2. Massey, N.W.D. (1995b): Geology and mineral resources of the Cowichan Lake sheet, Vancouver Island, 92C/16; BC Ministry of Energy, Mines and Petroleum Resources, Paper 1992-3. Massey, N.W.D. (1995c): Geology and mineral resources of the Duncan sheet, Vancouver Island, 92B/13; BC Ministry of Energy, Mines and Petroleum Resources, Paper 1992-4. MINFILE (2009): MINFILE BC mineral deposits database; BC Ministry of Energy, Mines and Petroleum Resources, URL http://www.em.gov.bc.ca/Mining/Geolsurv/Minfile/> [June, 2009]. Mortensen, J.K. (2005): Stratigraphic and paleotectonic studies of the Middle Paleozoic Sicker Group and contained VMS occurrences, Vancouver Island, British Columbia; in Geological Fieldwork 2005, BC Ministry of Energy, Mines and Petroleum Resources, Paper 2006-1, p. 331–336. Muller, J.E., Carson, D.J.T., 1969; Geology and mineral deposits of the Alberni map area, British Columbia (92F); Geological Survey of Canada, Paper 68-50, 52 p. Muller, J.E., Northcote, K.E., and Carlisle, D., 1974, Geology and mineral deposits of Alert-Cape Scott map-area, Vancouver Island, British Columbia; Geological Survey of Canada, Paper 74-8, 77 p. Muller, J.E. (1977): Geology of Vancouver Island; Geological Survey of Canada, Open File 463, 1:250 000 scale. Muller, J.E. (1980): The Paleozoic Sicker Group of Vancouver Island, British Columbia; Geological Survey of Canada, Paper 79-30, 23 p. 352Parrish, R.R. and McNicoll, V.J., 1992; U-Pb age determinations from the southern Vancouver Island, area, British Columbia; in Radiogenic Age and Isotope Studies: Report 5; Geological Survey of Canada, Paper 91-2, p. 79-86. Rennie, C.C., 2003; Lady Iron Deposit and VMS Potential, Summary Report, Geology and Magnetic Reconnaissance: BC Ministry of Energy and Mines Assessment Report 27259. Ruks, T.R. and Mortensen, J.K. (2007): Geological setting of volcanogenic massive sulphide occurrences in the Middle Paleozoic Sicker Group of the southeastern Cowichan Lake uplift (NTS 092B/13), southern Vancouver Island; in Geological Fieldwork 2006, Geoscience BC, Report 2007-1, p. 381–394. Ruks, T. and Mortensen, J.K. (2008): Geological setting of volcanogenic massive sulphide occurrences in the Middle Paleozoic Sicker Group of the Cowichan Lake uplift, Port Alberni area, southern Vancouver Island, British Columbia; in Geoscience BC Summary of Activities 2007, Geoscience BC, Report 2008-1, p. 77–92. Ruks, T., Mortensen, J.K. and Cordey, F. (2009): Preliminary results of geological mapping, uranium-lead zircon dating, and micropaleontological and lead isotopic studies of volcanogenic massive sulphide–hosting stratigraphy of the Middle and Late Paleozoic Sicker and Lower Buttle Lake groups on Vancouver Island, British Columbia (NTS 092B/13, 092C/16, 092E/09, /16, 092F/02, /07); in Geoscience BC Summary of Activities 2008, Geoscience BC, Report 2009-1, p. 103–122. Ruks, T., Mortensen, J.K. and Cordey, F. (2010): New results of geological mapping, micropaleontological and lead isotopic studies of volcanogenic massive sulphide–hosting stratigraphy of the middle and late Paleozoic Sicker and Buttle Lake groups on Vancouver Island, British Columbia (NTS 092B/13, 092C/16, 092E/09, /16, 092F/02, /05, /07); in Geoscience BC Sum mary of Activities 2009, Geoscience BC, Report 2010-1, p. 149–170. Sargent, H., 1941, Supplementary report on Bedwell River area, Vancouver Island, British Columbia, British Columbia Department of Mines, Bulletin 13, 97 p. Selwyn, A.R.C., 1872, Preliminary explorations in British Columbia, Geological Survey of Canada, Report of Progress 1871-1872, p. 52, 53, 63. Sluggett, C.L. (2003): Uranium-lead age and geochemical constraints on Paleozoic and Early Mesozoic magmatism in Wrangellia Terrane, Saltspring Island, British Columbia; B.Sc. thesis, University of British Columbia, Vancouver, BC, 56 p. Smith, J.G. and MacKevett, E.M., 1970. The Skolai Group in the McCarthy B-4, C-4 and C-5 quandrangles, Wrangell Mountains, Alaska. U.S. Geological Survey, Bulletin 1274-Q, 26 p. Stevenson, J.S., 1945, Geology and ore deposits of the China Creek area, Vancouver Island, British Columbia, Minister of Mines, British Columbia, Annual Report, p. A1437-A161. Yamagata, T., 2009, The accretionary processes of the Permian and Triassic seamounts in the Deadman Bay Terrane, The San Juan Islands, Washington State, USA: 2009 Portland GSA Annual Meeting, Geological Society of America Abstracts with Programs, Vol. 41, No. 7, p. 294. Yole, R.W., 1963, An Early Permian fauna from Vancouver Island, British Columbia, Bulletin of Canadian Petroleum Geology, V. 11, p. 138-149. Yole, R.W., 1965, A faunal and stratigraphic study of upper Paleozoic rocks of Vancouver Island, British Columbia; Ph.D. thesis, University of British Columbia, Vancouver, British Columbia. Yole, R.W., 1969, Upper Paleozoic stratigraphy of Vancouver Island, British Columbia; Proceedings of the Geological Association of Canada, v. 20, p. 30-40. Yorath, C.J., Sutherland Brown, A. and Massey, N.W.D. (1999): LITHOPROBE, southern Vancouver Island, British Columbia: geology; Geological Survey of Canada, Bulletin 498, 145 p. 353FIELD TRIP ITINERARY Day 1 (Saturday, Sept. 21st): Day 1 will concentrate on examining stratigraphic relationships and VMS mineralization of the McLaughlin Ridge formation in the Cowichan area, with several stops in the vicinity of the past producing Lenora/Twin J/Richard III VMS deposits on Big Sicker Mountain, and the Lara-Coronation zone (Treasury Metals Inc.). A bedrock geology map of the area showing the location of various field trip stops is shown in Figure 3. Stop 1.1 (Northeast Copper/Fortuna Area): The Fortuna Copper area is accessed by driving south/southwest on Mt. Sicker road, and then driving east along gated logging roads traversing the northern flank of Big Sicker Mountain (Fig. 3). The Big Sicker Mountain area is host to several past producing deposits including the Lenora and Twin J mines, which contain ore reserves estimated at 317,485 tonnes grading 1.6 per cent copper, 4.11 grams per tonne gold, 140.54 grams per tonne silver, 0.65 per cent lead and 6.6 per cent zinc (MINFILE, 2010). Approximately 1 km east of the Northeast Copper/Fortuna zone on new exposure created by recent logging road construction, a new discovery of massive magnetite mineralization was located within a variably silica-sericite-chlorite–altered quartz-feldspar porphyry. Here, veins and pods of massive magnetite up to 1 m thick cut variably altered quartz-feldspar porphyry. Magnetite veins commonly have cores of semimassive pyrite. Flanking the area of massive magnetite mineralization to the west, strongly sericitized quartz-feldspar porphyry is cut by abundant stringers of pyrite and chalcopyrite. Strong chlorite alteration is localized along the margins of these stringers. Farther to the west, quartz-feldspar porphyry becomes intensely silicified and contains up to 30% disseminated pyrite ± trace chalcopyrite mineralization. Stringers of pyrite and chalcopyrite also occur in this zone, with sulphide vein margins often flanked by zones of chlorite alteration. Recent LA-ICP-MS U-Pb geochronology (zircon) of quartz-feldspar porphyry in this area has yielded an age of 363.0 ± 1.6 Ma (Ruks and Mortensen, unpublished), similar to ages reported for the felsic volcanic host rocks to VMS of the Myra Falls deposit (Brandon et al., 1986). CA-TIMS U-Pb (zircon) geochronology of felsic volcanic host rocks to the past producing Lenora/Twin J VMS deposit yield an age of 363.0 ± 6.7 Ma (Ruks and Mortensen, unpublished). Stop 1.2 (Northeast Copper/Fortuna Area): Approximately 700 m northwest of the Northeast Copper zone (MINFILE 092B 099; Fig. 3), intensely silica-sericite–altered felsic crystal tuff contains up to several percent disseminated sulphides (pyrite±chalcopyrite) with abundant malachite staining in places. This mineralized tuffaceous horizon is interbedded with graphitic argillite and intermediate sandy to silty tuff. Stop 1.3 (Intermediate Tuff): Moving north from stop 2 towards the flanks of Big Sicker Mountain and the paved section of Mt. Sicker road , felsic volcanic rocks are observed to transition into predominantly intermediate tuffaceous volcanic rocks (Fig. 3). Elsewhere in the Cowichan area, intermediate tuffaceous volcanic rocks are host to exhalative iron formations, 354and are interpreted to represent the upper stratigraphy of the McLaughlin Ridge formation, presumably upsection of VMS mineralization. Stop 1.4 (Lara-Coronation VMS): After driving northwest along the highway, turn left on Copper Canyon Mainline. The Lara-Coronation VMS deposit is accessed via the second Mt. Brenton forest service road that switch-backs to the north along the power-line. The deposit is a short hike along roads past a gated area (Fig. 3). The Lara VMS deposit or ‘Coronation Trend’ consists of two main zones, the Coronation and Coronation Extension, comprising an indicated resource of 1 146 700 tonnes at 3.01% Zn, 1.05% Cu, 0.58% Pb, 32.97 g/t Ag and 1.97 g/t Au (1% Zn cut off rate; Kelso et al., 2007). Sulphide mineralization of the Coronation and Coronation Extension zones is hosted by strongly silicified, coarse-grained rhyolite crystal tuff and ash tuff (Kelso et al., 2007; Ruks et al., 2009). CA-TIMS U-Pb (zircon) geochronology of the rhyolite tuff host to the Coronation zone yields an age of 365.2 ± 5.2 Ma (Ruks and Mortensen, unpublished), similar to reported ages for the VMS host rocks of the Myra Falls deposit. Mineralization of the Coronation zone is observed in two locations. The westernmost trench mapped in the Coronation zone (UTM 433489E, 5414841N, Zone 10, NAD83) is a flooded pit with sparse bedrock exposure at its north end. Here, dark grey to black, medium-grained massive sulphides, consisting of 95% black sphalerite and 5% chalcopyrite, are in sharp contact with an intensely silica- and sericite-altered felsic ash tuff containing trace to 0.5% quartz and feldspar crystals up to 3 mm in size. Bedding in this altered tuff dips steeply to the north. Massive sulphide mineralization in this pit contains elongated blebs of carbonate up to 2 cm wide and 10 cm long. The easternmost trench mapped in the Coronation zone (UTM 433558E, 5414824N, Zone 10) contains similar, medium–grained, massive sulphide mineralization comprising abundant black sphalerite with lesser chalcopyrite and pyrite. This mineralization is hosted within a strongly silicified felsic crystal tuff with 2% quartz crystals up to 2 mm in size and abundant bull-quartz veining (up to 30 cm in width). Significant structural complexity is exposed in this trench, with felsic tuff on the east side of the massive sulphides being observed to fold into the plane of the mineralization. No folding is observed in areas of the trench west of the massive sulphide mineralization, suggesting the potential for sinistral drag folding along the plane of massive sulphide mineralization. The absence of fault gouge associated with potential fault motion in this area may be explained by strain accommodation via massive sulphide recrystallization. Abundant concordant bull-quartz veining in felsic crystal tuff immediately east of the massive sulphide mineralization is probably the result of space filling during folding. Stop 1.5 (Exhalative Iron Formations): Return to the Copper Canyon Mainline from the Lara-Coronation zone and drive west. Turn north on Boulder Mainline and stay to your right. A short hike along a deactivated logging road parallel to Chipman Creek takes you to the power line and the Lady B iron formation, which is located in a B.C. Hydro clearing below the power line (Fig. 3) The Lady B iron formation (MINFILE 092B 033) is similar to other iron formations occurring in rocks that are stratigraphically above VMS mineralization at numerous VMS camps worldwide, including those of the Bathurst district (e.g. Franklin et al., 2005). These iron formations are believed to represent oxide-facies iron mineralization related to hydrothermal 355mineralizing systems similar to those that formed the underlying VMS deposits. Resolving the timing of iron formation mineralization in the Sicker Group is critical for establishing the duration of VMS-related hydrothermal activity. The Lady B iron formation is located beneath a major power line, and is accessible from the south via a deactivated logging road in the vicinity of the Anita zone (Figure 3). The showing consists of a 15 m by 3 m outcrop of fine- to medium-grained massive black magnetite. Diamond drilling of the Lady iron formations by previous workers indicates variable thicknesses ranging from 10 m to 30 m (Rennie, 2003). The massive magnetite contains rusty pyritic zones up to 30–40 cm in size and trace blebs of chalcopyrite up to 2 mm in size. Abundant intermediate volcanic rocks are located to the south of showing. These volcanic rocks are less felsic than those associated with VMS occurrences to the south (downsection?), and comprise light grey-green dacitic to intermediate tuff with abundant feldspar crystals and weakly sericite-altered, flattened pumice clasts. Crystal-poor, ash-rich layers of similar colour are also abundant, many of which contain chlorite-altered, flattened pumice clasts. In certain locations, ash-rich zones pick up a strong fabric, becoming phyllitic in texture and potentially representing zones of shearing. Volcanic rocks most proximal to the Lady B iron formation were sampled for U-Pb (zircon) geochronology in order to resolve the age of iron formation mineralization and constrain a minimum age for VMS-related hydrothermal activity in Sicker Group rocks of the Cowichan Lake area. Day 2 (Sunday, Sept. 22nd: Alberni Area: Paleozoic strata of the Alberni area includes the oldest rocks in southern Wrangellia, and as such, is a critical area for understanding the origins of the terrane. Today will concentrate on examining Paleozoic stratigraphy of the Alberni area, starting with the oldest known rocks in the area and investigating progressively younger stratigraphy as the day commences. The day will complete with the examination of recently identified Late Paleozoic volcanic rocks, which are interpreted to represent potential correlatives to the Late Paleozoic Skolai Group of northern Wrangellia. Stop 2.1 (Dacite Flow): Drive east of Port Alberni along the highway. Turn left onto Loon Lake Mainline and drive to the north. A rare dacite flow and associated silica altered and sulphide mineralized flow breccia is found to occur in an area dominated by basaltic flows assigned to the Duck Lake Formation (Fig. 4). Recent CA-TIMS U-Pb (zircon) geochronology conducted on this flow has yielded an age of 371.8 ± 0.9 Ma (Ruks and Mortensen, unpublished), making this unit the oldest felsic volcanic rock in southern Wrangellia. Stop 2.2 (Microwave Tower Felsic Tuff): Continue driving north along Loon Lake Mainline. Turn right on the road to the microwave tower, and park below the gate. A short hike up the road will lead to the microwave tower and the next stop of interest, located just outside the microwave tower fencing (Fig. 4). In the immediate vicinity of a microwave tower, Massey et al. (1989) reported the occurrence of several thin beds of felsic tuff hosted in mafic volcaniclastic rocks located at the transition zone between stratigraphy assigned to the pre-Late Devonian Duck Lake and Nitinat formations. 356Recent U-Pb (zircon) dating of this tuff via CA-TIMS has yielded an age of 363.9 +/- 0.9 Ma (Ruks and Mortensen, unpublished), similar to the age of VMS associated strata in the Cowichan area and at Myra Falls. This result suggests that in the Alberni area, strata of the Duck Lake and Nitinat formations is time transgressive, and that in Late Devonian time, the area was a centre of mafic volcanism. Stop 2.3 (Early to Middle Mississippian Felsic Volcanic Rocks): Continue driving to the north/northeast, towards Mt. Horne. Turn left onto the logging road that traverses the western flank of Mt. Horne, and switch backs towards the summit. To the north of the microwave tower, new logging roads in the Mt. Horne area have exposed a section consisting of mafic volcaniclastic rocks, which grade upsection into chert and argillite, and finally into felsic volcaniclastic rocks (ash tuff, lapill tuff, and tuff breccia). Recent LA-ICP-MS U-Pb (zircon) geochronology of these felsic volcanic rocks indicate an age of approximately 340 Ma (Ruks and Mortensen, unpublished). Stop 2.4 (Permian Felsic and Mafic Volcanic Rocks): Drive back to the highway from Loon Lake Mainline. Turn right on the highway and drive west towards Port Alberni. Turn right on Cherry Creek road and drive to the Cherry Creek gravel pit and power line. Follow the switchbacks up the power line. All of the stops of interest in this area will be in the vicinity of Lacy Lake. At the summit of the power line, just before dropping down to the north towards Lacy Lake, an exposure of dacitic lapilli tuff assigned to the Late Devonian McLaughlin Ridge Formation is located directly underneath the power line, close to the footings for a support tower. This dacitic tuff yields abundant 295 Ma zircons, as well as 315, 330, and 336 Ma grains (Ruks and Mortensen, unpublished). 130 m to the northeast, a large outcrop of clinopyroxene-phryic basaltic agglomerate occurs at the foot of a support tower overlooking Lacy Lake. The presence of Early Permian felsic and mafic volcanic rocks in the Alberni area represents a cycle of magmatism never before documented in southern Wrangellia, but one which may be correlative with portions of the Late Paleozoic Skolai arc in northern Wrangellia (e.g. Smith and MacKevett, 1970; Israel and Cobbett, 2008). Stop 2.5 (Permian Chert and Mafic Volcanic Rocks): Continue driving north of Lacy Lake along the power line until you get to a gate. Turn left at the gate, and proceed to the west for the final stops of interest for the fieldtrip. Here, chert assigned to the pre Late Devonian Duck Lake formation (Yorath et al., 1999) is observed to conformably overlie a basaltic tuff breccia with abundant calcite cement. Boulders and outcrop of basaltic flow breccia with abundant interclast carbonate are abundant in the area. Radiolarians recovered from this chert have yielded Early to Middle Permian ages (Ruks, Mortensen and Cordey, unpublished), indicating the presence of significant volumes of Late Paleozoic volcanic rock in the Alberni area. Stop 2.6 (Heterolithic Breccia): Continue driving west approximately 500 m. 357 15 Here, a conspicuous heterolithic breccia of uncertain nature occurs in outcrop. The breccia includes clasts of vesicular basalt, crinoidal limestone, radiolarian chert, and mafic tuff. Looking north, one is able to see Mt. Mark, located on the north side of Horne Lake. Here, Permian carbonate of the Mt. Mark Formation (Buttle Lake Group) is intruded by Triassic gabbro sills. Stop 2.7 (Radiolarian Chert and Breccia): Continue driving 200 m to the west. Here, at the final stop of the field trip, ribbon chert grades into hematite-bearing, intermediate volcanic sandstone, which becomes progressively more clast rich and coarse grained upsection (?) until becoming hematitic crinoidal limestone–bearing heterolithic breccia as per Stop 3.6. 358359360
Thesis/Dissertation
eng
Geological Sciences
Vancouver : University of British Columbia Library
Attribution-NonCommercial-NoDerivs 2.5 Canada
Graduate
Stratigraphic and paleotectonic studies of Paleozoic Wrangellia and its contained volcanogenic massive sulfide (VMS) occurrences, Vancouver Island, British Columbia, Canada
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