Structural evolution of the Mitchell Au-Cu-Ag-Mo porphyry deposit, northwestern British Columbia by Gayle Elizabeth Febbo A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in The Faculty of Graduate and Postdoctoral Studies (Geological Sciences) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) February 2016 © Gayle Elizabeth Febbo, 2016 ii Abstract The Mitchell Au-Cu-Ag-Mo porphyry deposit, hosted by Early Jurassic volcanosedimentary and intrusive rocks in the Stikine terrane of northwestern British Columbia, is considered the largest undeveloped gold resource in Canada. As of 2015 it held a resource of 1777 Mt at 0.61 g/t Au, 0.17% Cu, 3.1 g/t Ag, and 58 ppm Mo (0.5 g/t Au eqiv. cut-off; meas+ind). The calc-alkalic deposit is genetically related to multiple diorite intrusions (Sulphurets suite) that cut volcanosedimentary strata of the Stuhini Group (Upper Triassic) and Jack Formation (basal Hazelton Group, Lower Jurassic). Phase 1 plutons (U/Pb, zircon; 196 ±2.9 Ma and 192.2±2.8 Ma) host Stage 1 potassic and propylitic alteration, veins and copper-gold mineralization. A Phase 2 plug (189.9±2.8 Ma; U/Pb zircon) is central and temporally related to a molybdenum halo (190.3±0.8 Ma; Re-Os, Mo) that is accompanied by phyllic alteration (Stage 2). Phase 3 plutonism is temporally related to diatreme breccia, intrusion breccia dikes and Stage 3 massive pyrite veins and advanced argillic alteration. High-level, gold-rich veins comprise Stage 4. Three phases of progressive deformation related to the mid-Cretaceous Skeena fold and thrust belt structurally modify the Mitchell deposit. Deformation Phase 1 is characterized by a steep, easterly striking pervasive pressure solution cleavage (S1) and steeply west-plunging buckle folds in veins (F1); fold geometry and flattening degree are a function of alteration type. In rheologically weak alteration types a pressure solution cleavage is associated with loss of silica, mechanical remobilization of chalcopyrite-molybdenite, and passive enrichment of chalcopyrite-molybdenite-pyrite along the cleavage planes. Strain intensity (i.e., S1 development) is heterogeneous and this greatly affects the shape of the orebody. In Deformation Phase 2, steeply north-plunging F2 vein folds overprint S1 and F1. The Mitchell thrust fault (Deformation Phase 3) offsets the Snowfield deposit ~ 1600 m to the east-southeast and the Mitchell Basal shear zone displaces the Mitchell deposit from its core zone, located ~1-2 km to the west at a depth of ~ 1 km. It is speculated the Mitchell deposit was emplaced into a structurally influenced, north-trending Jurassic basin and subsidiary east-west structures controlled the intrusion, vein geometry, alteration and metal pattern trends. iii Preface This thesis comprises modified versions of two papers (Chapters 2 and 3) to be submitted to refereed journals or that are in preparation for publication. Chapter 2 was submitted to Geological Fieldwork and published in January, 2015 under the title ‘Geology of the Mitchell Au-Cu-Ag-Mo porphyry deposit, northwestern British Columbia, Canada.’ My supervisor, Dr. Lori A. Kennedy, is co-author of this paper in addition to Michael Savell, Dr. Robert A. Creaser, and Dr. Richard M. Freidman. Michael Savell provided text revisions for Chapter 2, Dr. Creaser wrote the Re-Os methodology section and undertook the Re-Os analysis, and Dr. Freidman carried out the U-Pb dating. Revisions and edits for Chapter 2 were provided by Dr. Lawrence Aspler, JoAnne Nelson and Jim Logan of the British Columbia Geological Survey. Chapter 3 is in preparation for submission and is authored by myself and Dr. Kennedy. All data collection (lab and field), geology map interpretation, and figure creation were performed by me. Dr. Kennedy supervised field and petrographic research and provided extensive text revisions for both chapters. iv Table of Contents Abstract ............................................................................................................................... ii Preface ............................................................................................................................... iii Table of contents ................................................................................................................. iv List of tables ....................................................................................................................... vi List of figures.....................................................................................................................viii Acknowledgements .............................................................................................................. x Dedication ......................................................................................................................... xii 1. Introduction ................................................................................................................... 1 2. Geology of the Mitchell deposit....................................................................................... 5 2.1. Introduction ............................................................................................................ 5 2.2. Geologic Setting ..................................................................................................... 5 2.3. Sulphurets district geology....................................................................................... 8 2.3.1. Stratigraphy .................................................................................................... 8 2.3.2. Plutonism ....................................................................................................... 9 2.3.3. Structure....................................................................................................... 13 2.3.4. Mineralization .............................................................................................. 14 2.4. The Mitchell deposit.............................................................................................. 15 2.4.1. Lithologic units............................................................................................ 18 18.104.22.168. Stuhini Group (Triassic) .................................................................... 18 22.214.171.124. Hazelton Group (Late Triassic to Middle Jurassic) .............................. 18 126.96.36.199. Premier intrusive suite ....................................................................... 22 188.8.131.52. Sulphurets intrusive suite and related breccia bodies ............................ 22 2.4.2. Geochemistry of the Premier and Sulphurets intrusions ................................... 28 2.4.3. Alteration .................................................................................................... 28 184.108.40.206. Stage 1 ............................................................................................. 28 220.127.116.11. Stage 2 ............................................................................................. 31 18.104.22.168. Stage 3 ............................................................................................. 31 2.4.4. Vein paragenesis ........................................................................................... 32 2.4.5. Mineralization .............................................................................................. 33 2.4.6. Structure....................................................................................................... 36 v 2.5. Geochronology of the Mitchell deposit ................................................................... 38 2.5.1. Analytical methods: U-Pb zircon................................................................... 38 2.5.2. Analytical methods: Re-Os (molybdenite) ..................................................... 38 2.5.3. Results ......................................................................................................... 38 22.214.171.124. Sample M-11-123; Phase 1 diorite ...................................................... 38 126.96.36.199. Sample GF-13-02; Phase 1 diorite ...................................................... 41 188.8.131.52. Sample M-07-49; Phase 2 diorite........................................................ 41 184.108.40.206. Sample M-10-116; Stage 2 molybdenite vein (Re-Os) ......................... 41 220.127.116.11. Geochronologic summary .................................................................. 42 2.6. Discussion ............................................................................................................ 42 2.6.1. Evolution of the Mitchell deposit .................................................................. 42 2.6.2. The Mitchell deposit: a calc-alkalic porphyry................................................. 43 2.6.3. The relationship between the Snowfield and Mitchell deposits ........................ 44 2.7. Conclusion ........................................................................................................... 44 3. Structural geology of the Mitchell deposit ...................................................................... 46 3.1. Introduction .......................................................................................................... 46 3.2. Regional geologic setting....................................................................................... 48 3.3. The Mitchell ore deposit: stratigraphy, plutonism and mineralization........................ 52 3.4. Field Observations ................................................................................................ 55 3.4.1. Mid-Cretaceous SFTB deformation (D2)........................................................ 57 18.104.22.168. Deformation Phase 1 ......................................................................... 57 22.214.171.124. Deformation Phase 2 ......................................................................... 68 126.96.36.199. Deformation Phase 3 ......................................................................... 72 3.4.2. Dextral faults (D3) ........................................................................................ 78 3.4.3. Pre-S1 structures (D1) ................................................................................... 78 188.8.131.52. Porphyry-related veins....................................................................... 78 184.108.40.206. Sinistral shear zones .......................................................................... 81 220.127.116.11. Small-scale, strike-slip faults.............................................................. 81 3.5. Discussion ............................................................................................................ 82 3.5.1. Comparison with the Skeena fold and thrust belt ............................................ 82 3.5.2. The role of strain partitioning and post-emplacement deformation ................... 82 3.5.3. Early Jurassic structural setting ..................................................................... 84 3.6. Conclusions .......................................................................................................... 86 4. Conclusions ................................................................................................................. 89 References ......................................................................................................................... 92 vi Appendix A. List of field structure data from the Mitchell deposit and surrounding areas ...... 100 Appendix B. Descriptions of relogged core intervals from the Mitchell deposit .................... 179 Appendix C. Field station descriptions and photo locations in the Mitchell deposit and surrounding areas ............................................................................................................. 192 Appendix D. Petrographic photos and descriptions from the Mitchell and surrounding area... 229 Appendix E. Illustrated field photos from the Mitchell deposit ............................................ 279 Appendix F. X-ray diffraction spectra from the Mitchell deposit.......................................... 282 Appendix G. Scanning Electron Microscope images and spectra from the Mitchell deposit ... 292 Appendix H. Laser ablation ICP-MS analyses: images of zircons, petrographic descriptions, microphotographs, and zircon standards............................................................................. 296 Appendix I. Sample locations, descriptions, images and petrographic scans ......................... 308 Appendix J. Table of Terraspec data .................................................................................. 326 vii List of tables Table 2.1. Radiometric ages for Mitchell intrusions and molybdenite mineralization in the Sulphurets district ......................................................................................................... 10 Table 2.2. Selected geochemical data ................................................................................... 30 Table 2.3. Summary of mineralization, alteration, vein and plutonic stages and phases............ 31 viii List of figures Figure 1.1. Tectonic setting of the Kerr-Sulphurets-Mitchell (KSM) deposits and other Triassic-Jurassic porphyry and related deposits in Quesnellia and Stikinia (from Nelson and Kyba, 2014). ........................................................................................................................ 2 Figure 1.2. Western Iskut region geology ............................................................................... 3 Figure 2.1. Location of the Kerr-Sulphurets-Mitchell (KSM) deposits and other Triassic-Jurassic porphyry and related deposits in Quesnellia and Stikinia (from Nelson and Kyba, 2014) ................................................................................................................................... 6 Figure 2.2. Western Iskut region geology ............................................................................... 7 Figure 2.3. Geology of the KSM property, showing the conceptual pit boundaries for Mitchell, Sulphurets, Kerr and Iron Cap zones...................................................................... 11 Figure 2.4. Legend for Figures 2.3, 2.5, 2.7a, 2.7b, 2.8 and 2.22 ............................................ 12 Figure 2.5. Stratigraphy of the Mitchell-Snowfield area. ....................................................... 13 Figure 2.6. Mitchell zone and surrounding area rocks ........................................................... 16 Figure 2.7. Cross sections across KSM property ................................................................... 17 Figure 2.8. Geology of the Mitchell zone and surrounding area ............................................. 19 Figure 2.9. Mitchell zone Jack Formation andesite................................................................ 21 Figure 2.10. Mitchell intrusions: Premier and Sulphurets suites (Jurassic) .............................. 23 Figure 2.11. Sulphurets suite diorite breccia ......................................................................... 24 Figure 2.12. Abundance of quartz veins, molybdenite contours (>30 ppm) and contact of Phase 2 pluton ................................................................................................................... 25 Figure 2.13. Diatreme breccia and intrusion breccia dike in outcrop....................................... 27 Figure 2.14. Geochemistry of the Mitchell intrusions (Premier and Sulphurets suites) ............. 29 Figure 2.15. Alteration map of the Mitchell zone .................................................................. 32 Figure 2.16. Quartz stockwork and vein fold geometry in the Mitchell zone ........................... 34 Figure 2.17. Microtextures of chalcopyrite mineralization ..................................................... 35 Figure 2.18. Poles to S1 cleavage, F1 fold axes, and F2 fold axes ............................................ 36 Figure 2.19. Qualitative estimate of strain for altered rocks of the Mitchell zone as indicated by F1 and F2 fold morphology.............................................................................................. 37 Figure 2.20. U-Pb concordia diagrams for Sulphurets suite diorite in the Mitchell deposit ....... 39 Figure 2.21. Photomicrographs of the three dated Mitchell intrusions..................................... 40 Figure 2.22. Model for the evolution of the Mitchell deposit ................................................. 43 Figure 2.23. Au, Cu, Ag and Mo metal grades of the Mitchell and Snowfield deposits, after Savell and Threlkeld (2013) ................................................................................................ 45 Figure 3.1. Location of the Kerr-Sulphurets-Mitchell (KSM) property ................................... 47 ix Figure 3.2. Tectonic setting of the Kerr, Sulphurets, Mitchell, Iron Cap, Snowfield, Brucejack and other Triassic-Jurassic porphyry and related deposits in Quesnellia and Stikinia (from Nelson and Kyba, 2014) ............................................................................... 48 Figure 3.3. Geological compilation of the Sulphurets district ................................................. 49 Figure 3.4. Stratigraphic column for stratigraphy in northwesetern Stikinia (modified after Logan and Schiarizza, 2011) ............................................................................................... 50 Figure 3.5. Poles to cleavage in the KSM-Snowfield area...................................................... 52 Figure 3.6. Examples of F1-3 buckle folds in the Sulphurets district ........................................ 53 Figure 3.7. Geology of the Mitchell deposit and surrounding area (Febbo, this study) ............. 54 Figure 3.8. Alteration map for the Mitchell zone and associated Structural Domains .............. 57 Figure 3.9. Hand sample photographs of Structural Domains 1-4 .......................................... 59 Figure 3.10. Examples of F1 buckle folds ............................................................................. 61 Figure 3.11. Equal angle stereographic projections of Phase 1 Deformation beneath the Mitchell thrust fault ............................................................................................................ 62 Figure 3.12. Map of quartz vein abundance contours beneath the Mitchell thrust fault ............ 63 Figure 3.13. Field photographs and stereographic projections of Phase 1 Deformation shear bands ................................................................................................................................. 64 Figure 3.14. Photomicrographs of Phase 1 Deformation microstructure ................................. 65 Figure 3.15. Microphotographs illustrating pressure solution cleavage in Structural Domain 4, from a quartz vein xenolith-bearing intrusion breccia ........................................................ 67 Figure 3.16. Field photographs and stereographic projections of Phase 2 Deformation features .............................................................................................................................. 69 Figure 3.17. Qualitative estimate of strain for altered rocks of the Mitchell zone as indicated by cleavage development .................................................................................................... 70 Figure 3.18. Field photographs and stereographic projections of the Mitchell thrust fault and kinematically related structures ........................................................................................... 71 Figure 3.19. Structural cross section interpretation for section lines A-A’-A,’’ B-B,’ and C-C’ from Figure 3.3.............................................................................................................. 73 Figure 3.20. Field photos and stereographic projections of faults related to Phase 3 Deformation....................................................................................................................... 75 Figure 3.21. Field photographs and stereographic projections of Stage 1-3 veins .................... 79 Figure 3.22. Structures interpreted to be Early Jurassic ......................................................... 80 Figure 3.23. Model for the structural evolution of the Sulphurets district ................................ 87 Figure 4.1. The structural evolution of the Mitchell-Snowfield system plotted over time and temperature ........................................................................................................................ 91 x Acknowledgements This research was made possible by a generous financial contribution from Seabridge Gold Inc. to the Mineral Deposit Research Unit. In addition to this donation, the company financed field support, helicopter transportation, field assistants and countless other expenses related to the research. Words cannot express how valuable this gift was to me and how grateful I am for this research opportunity. Rudi Fronk, Bill Threlkeld and Michael Savell have been particularly supportive in campaigning to fund this research and for that I would like to express my most sincere and deepest gratitude. Much valuable geological work on the Mitchell deposit by project geologists Tim Dodd, Pete Erwich and Michael Savell formed the groundwork of this study, and I thank them for sharing their knowledge with me. I would very much like to thank Pretium Resources Inc, namely Kenneth McNaughton, for permission to collect samples and conduct mapping on their claims. This research would have incomplete without the access and insight gained from mapping the Snowfield and eastern Mitchell areas. Many illuminating days spent with Chief Geologist Dr. Warwick Board in 2010 sparked my interest in structural geology and it was his enthusiasm that motivated me to pursue a research project on the deformation history in the district. The thoughtful guidance, structural insights, and knowledge that Dr. Lori Kennedy has bequeathed to me will be the most valuable aspect of this project that will carry forward with me. For her determination to train me both in the field and in writing this manuscript I am very grateful. Her mentorship and positive encouragement throughout this research project is so much appreciated. My work with then Regional Geologist Paul Wojdak in 2008 allowed me a life altering field tour of the Mitchell and Snowfield deposits. He educated me well to appreciate the Sulphurets district as an emerging world class mineral district with untapped potential. Paul encouraged and kindly referred me to pursue graduate research with Seabridge Gold Inc. and I am so appreciative of his foresight and for correctly guiding me. Much knowledge has been shared with me through many invigorating conversations with JoAnne Nelson along the way. Her and Jeff Kyba’s fieldwork in the Sulphurets area in 2013 tremendously shaped the scale and scope of my research for which I am so thankful. She rightly encouraged me to publish in Geological Fieldwork and in doing so the manuscript was greatly improved. Much thanks to JoAnne Nelson, Jim Logan and Lawrence Aspler for their thoughtful reviews of Chapter 2. Valuable advice has been provided by my committee members Dr. Craig Hart, Dr. Lucy Poritt, and Dr. Kelly Russell that have strengthened the focus of the research. Much support from the Mineral Deposit Research Unit has been appreciated, namely conversations with Dr. Thomas Bissig and Dr. Farhad xi Bouzari and analysis and interpretation of Terraspec data by Sergio Gamonal. I’m also very grateful for Dr Mati Raudsepp and his staff’s assistance with the XRD and SEM component of the research. Thank you to Dr. Jim Mortensen and Dr. Richard Friedman for carrying out the U-Pb zircon age dating. I’m very glad to have labmates Amy Ryan and Luke Hilchie for petrographic consultation and Michelle Campbell for many beneficial conversations about my research. Thanks to my officemate Nader Mostaghimi for his excellent company and especially for accommodating my pet. Much thanks to my MDRU comrades Irene del Real and Lauren Greenlaw for many enlightening conversations. I’m also grateful for the company of cheerful field assistants Jocelyn Poirier-Hardy, Rylan Maschak, Norbert Quock and Rachael Kramer while I conducted my fieldwork. I owe much to my housemate Alicia Carptenter for enduring me, bringing me tea and comforting me with positive words of encouragement during the writing process. In addition to these friends and colleagues, I am grateful to my family for their encouragement through this journey. My husband’s support and love has allowed me the freedom to pursue my academic aspirations and it is thanks to him I have been able to complete it. I’m very glad for my mother for emphasizing the value of education, believing in me and helping me find my way here. Last but not least, I have been so very grateful for my dog Freedom who accompanied me on every field traverse and lay at my feet for each day of writing until his last days. xii Dedicated to all the many explorers who had a part in discovering and defining Canada’s largest gold deposit 1 1. Introduction The Mitchell deposit, located in northwestern British Columbia (Fig. 1.1), contains the largest mineral reserve in the Sulphurets district, the largest undeveloped gold resource in Canada (Visual Capitalist, 2013), and the largest undeveloped copper resource in Canada. According to the classification system proposed by Cooke et al. (2005), the Mitchell deposit lies in the top one percent in terms of contained metal and is considered a ‘supergiant’ copper and a ‘supergiant’ gold porphyry deposit. According to Clark’s classification system (1993), the Mitchell deposit is a ‘behemoth’ based on the contained copper content. What attributes and processes contributed towards making this a gold and copper supergiant resource? The Mitchell deposit is very well exposed as a result of glacial retreat in the last two decades. It is unique amongst other deposits in the area, the so-called ‘golden triangle’ located in northwestern Stikinia, in that it is strongly deformed and its structural fabric (oriented east-west) goes against the regional north-south fabric. The Kerr, Sulphurets, Mitchell and Iron Cap porphyry deposits are part of the Kerr-Sulphurets-Mitchell (KSM) project, currently owned by Seabridge Gold Inc. Although previous surface mapping had outlined mineralization in the Mitchell zone (e.g., Margolis, 1993), it was not drill tested until 2006. The KSM and Snowfield Cu-Au porphyry deposits and the high-grade Au-Ag deposits at Brucejack, all occur along a north-south trend termed the ‘Treaty Glacier-KSM-Brucejack-Stewart trend’ (Fig. 1.2; Nelson and Kyba, 2014). The trend lies on the western margin of the ‘golden triangle’ and includes a number of gold-rich porphyry and epithermal systems formed in an island arc setting, off-board of North America in the Early Jurassic. Recent regional geological studies by Nelson and Kyba (2014) suggest that the KSM deposits were emplaced at relatively shallow depths into an actively extending north-south striking basin. The Mitchell and neighbouring porphyry deposits are part of a prolific porphyry mineralizing epoch in Quesnellia and Stikinia that is restricted to a ~15-m.y. interval that spans the Triassic-Jurassic boundary (Logan and Mihalynuk, 2014). These deposits include the Highland Valley, Copper Mountain, Gibraltar, Kemess, Red Chris, Schaft Creek and Galore Creek deposits among many others (Fig. 1.2). To the west of the KSM area, it is postulated that a rift zone opened after porphyry emplacement, that was coeval with the formation of the Eskay Creek past-producing mine, located ~18 km to the northwest of the Mitchell deposit (Fig. 1.2). To understand the processes involved in the formation of the Mitchell deposit, detailed mapping of the geology was undertaken for this research. The focus of this research is two-fold: 1) to map and characterize the host rock lithologies, alteration, mineralization and vein type and geometry exposed at surface in the Mitchell deposit facilitated by drill core observations; and 2) to characterize the geometry, 2 Fig. 1.1. Tectonic setting of Kerr-Sulphurets-Mitchell (KSM) deposits and other Triassic-Jurassic porphyry and related deposits in Quesnellia and Stikinia (from Nelson and Kyba, 2014). kinematics and timing of ductile and brittle deformation that has structurally modified the deposit. Ultimately the primary goal is to determine the Early Jurassic structural setting during porphyry emplacement that gave rise to the generation of a copper and gold supergiant resource and to evaluate to what extent the ore body has been modified by post-emplacement deformation. The thesis is written as two stand-alone papers (Chapters 2 and 3) followed by a summary of principle conclusions (Chapter 4). Appendices A-J provide supplemental data that compliments the observations and conclusions reached in the document. Chapter 2 characterizes the surface and cross section geology, alteration, and mineralization of the Mitchell deposit. This chapter presents the geochronology of plutonic suites and the relative timing of mineralized veins and an absolute age for molybdenum mineralization. Data is presented to support the premise that the Snowfield Cu-Au deposit is the faulted offset of the Mitchell deposit. The Mitchell Basal shear zone, discovered during core logging, is interpreted to offset the Mitchell deposit and it is proposed that the down-dip continuation of the Mitchell deposit is located approximately 1-2 km to the west at depth. The Mitchell deposit is classified as a calc-alkalic deposit 3 Fig. 1.2. Western Iskut region geology. The Stewart-Sulphurets district trend extends from the Premier deposit ~60 km north to the Sulphurets district (from Nelson and Kyba, 2014). rather than alkalic as proposed previously for the Snowfield deposit, the up-dip continuation of the Mitchell deposit. Chapter 3 characterizes the geometry and kinematics of post-emplacement, mid-Cretaceous, brittle-ductile deformation of the deposit, that is related to the Skeena fold and thrust belt. Evidence for an Early Jurassic deformation event is preserved in less strained rocks, and a model is proposed for a structural control on porphyry emplacement. Detailed field maps and structural data are presented for the Mitchell zone. Three phases of post-emplacement deformation are identified and correlated with the Skeena fold and thrust belt. Structural ‘domains’ are assigned to surface exposures and estimates of flattening are provided. Based on structural data from the least deformed, competent rocks, of the Mitchell deposit, a model is presented for the porphyry emplacement to be structurally controlled. It is proposed that syn-emplacement structures were predominantly east-west striking, steeply dipping sinistral-normal faults (e.g., Glacier shear zone) within a north-south structurally controlled mineral district. The anomalous 4 east-west trends in the Mitchell zone are modelled as subsidiary antithetic, sinistral strike-slip faults to a north-south trending transtensive fault system that resulted in the formation of a basin into which the Sulphurets district deposits were emplaced. 5 2. Geology of the Mitchell deposit 2.1. Introduction The Mitchell Au-Cu-Ag-Mo porphyry deposit is in the Stikine terrane of northwestern British Columbia (Fig. 2.1). Together the Kerr-Sulphurets-Mitchell porphyry deposits (KSM), the Brucejack high-grade gold deposit, and the Snowfield porphyry deposit are hosted in volcanosedimentary rocks of the Stuhini Group (Triassic) and the unconformably overlying volcanosedimentary strata and allied plutonic rocks of the Hazelton Group (Lower Jurassic; Fig. 2.2). These deposits are part of the Sulphurets district and lie at the northern end of a 60 km long north-northwest trending Cu-Au porphyry and related mineralization trend that extends south to the town of Stewart (Fig. 2.2). The origin of the trend has been ascribed to Jurassic faults that controlled sedimentation of the Jack Formation (basal Hazelton Group; Henderson et al., 1992; Lewis, 2001; Nelson and Kyba, 2014), which partly hosts mineralization at KSM, Snowfield and Brucejack. The Mitchell deposit, delineated by extensive drilling that began in 2006, is considered the largest undeveloped gold resource in Canada (Visual Capitalist, 2013). Although porphyry-related mineralization in the Mitchell zone has been studied for over 50 years (e.g., Kirkham, 1963; Margolis, 1993; Alldrick and Britton, 1991; Lewis, 1992), detailed deposit-scale documentation has hitherto been lacking. Herein new field, petrographic, geochemical, and geochronologic data are presented to document relationships between sedimentation, plutonism, alteration, vein paragenesis, mineralization, and deformation. 2.2. Geologic setting The Quesnel and Stikine arc terranes are part of the Intermontane Belt of the Canadian Cordillera, geographically inboard of the Cost Plutonic Complex and separated from each other by primitive arc and oceanic rocks of the Cache Creek terrane (Fig. 2.1). Long-lived arc magmatism across Stikinia and Quesnellia during the Late Triassic to Early Jurassic generated paired belts of alkalic and calc-alkalic porphyry deposits that extend for 2,000 km along the axis of the Canadian Cordillera (Logan and Mihalynuk, 2014). These deposits are both alkalic (e.g., Afton-Ajax, Copper Mountain, Mount Polly and Galore Creek) and calc-alkalic (e.g., Gibraltar, Schaft Creek and Kemess). Porphyry deposits of the Sulphurets district are located along the western margin of the Stikine terrane (Fig. 2.1) with mineralization ages between 197 and 190 Ma (Bridge, 1992; Margolis, 1993; this study). Gold mineralization in the Sulphurets district spans ~12 Ma as indicated by high-grade gold-silver at Brucejack (~185 Ma) superimposed onto older porphyry mineralization (192-190 Ma; Pretium Resources, 2013). 6 Fig. 2.1. Tectonic setting of Kerr-Sulphurets-Mitchell (KSM) deposits and other Triassic-Jurassic porphyry and related deposits in Quesnellia and Stikinia (from Nelson and Kyba, 2014).7 Fig. 2.2. Western Iskut region geology. The Stewart-Sulphurets district trend extends from the Premier deposit ~60 km north to the Sulphurets district (from Nelson and Kyba, 2014). 8 The Stikine terrane comprises three unconformity-bounded island arc volcanosedimentary successions that span 200 m.y. These include the Stikine assemblage (Devonian to Mississippian; Anderson, 1989; Greig, 1992; Logan et al., 2000), the Stuhini and Takla groups (Middle to Late Triassic), and the Hazelton Group (Late Triassic to Middle Jurassic). Mesozoic plutonic suites (Figs. 2.1, 2.2) include Stikine and Copper Mountain (Late Triassic, coeval and comagmatic with the Hazelton Group; Early Jurassic), Texas Creek (coeval and comagmatic with the Hazelton Group; Early Jurassic), and the Three Sisters (Middle Jurassic). Gold-rich deposits are associated with both the Late Triassic and Early Jurassic intrusive suites in northwestern Stikinia. Between Stewart and the Sulphurets district (Fig. 2.2) these deposits coincide with a belt of 195-187 Ma Texas Creek plutons (Alldrick, 1993; Logan and Mihalynuk, 2014). The Premier intrusions are an important subset of the Texas Creek plutons named for the synmineral dike occurrences in the Premier mine area near Stewart (Alldrick, 1993). Premier suite rocks are defined in the Stewart area by the presence of potassium feldspar megacrysts and plagioclase phenocrysts (‘two-feldspar porphyry’) in a fine-grained groundmass (Alldrick, 1993). East of the Sulphurets district, the Bowser Lake Group is a molassoid sedimentary succession containing debris derived from the collision of the Intermontane terranes and the edge of ancestral North America (Evenchick et al., 2007). The area was deformed by mid-Cretaceous sinistral transpression that gave rise to the Skeena fold and thrust belt, an extensive northeast-verging zone of shortening that extends across most of the northern Intermontane Belt (Evenchick, 1991). The Sulphurets district is on the eastern limb of the McTagg anticlinorium, a north-trending mid-Cretaceous structural culmination (Fig. 2.2). The anticlinorium is bounded in part by outward-vergent thrust faults, including the east-vergent Sulphurets fault, structurally above the Mitchell deposit (Figs. 2.2, 2.3). 2.3. Sulphurets district geology 2.3.1. Stratigraphy The Sulphurets district is underlain predominantly by Stuhini Group bedded sedimentary rocks and Hazelton Group siliciclastic rocks that interfinger with massive and fragmental andesites, and comagmatic Mitchell plutons (Lewis, 2013; Figs. 2.3-2.5). Drill holes in the western Sulphurets district intersected maroon radiolarian chert from surface to depths of 200 m that are interpreted to be Stikine assemblage (Nelson, pers. comm., 2014). The chert is located in the bottom of the valley in the hinge area of the McTagg anticlinorium and represents the lowest stratigraphic level identified in the McTagg anticlinorium. Stuhini Group rocks comprise thinly bedded mudstone, graphitic mudstone, and lesser calcareous mudstone, and felsic tuff. The uppermost Stuhini Group unit immediately beneath the sub-Hazelton Group unconformity consist of felsic volcanic stratified tuffs, fragmental and coherent rocks (Fig. 2.5.). 9 The base of the Hazelton Group is marked by an angular unconformity that cuts into previously folded Stuhini Group rocks, marking a significant regional hiatus in volcanism and an episode of uplift and erosion (e.g., Nelson and Kyba, 2014). The unconformity is overlain by polymictic conglomerates with felsic intrusive and extrusive clasts and quartz-rich arkoses of the Jack Formation, a unique basal Hazelton unit that is restricted to the periphery of the McTagg anticlinorium (Nelson and Kyba, 2014). In the KSM area, the conglomerate commonly contains black mudstone intraclasts, and clasts of black chert, felsic and intermediate volcanic rock, crowded feldspar porphyry intrusive rock and bedded mudstone. In the Sulphurets district, Jack Formation strata interfinger with, and pass gradationally to, andesitic breccias, flows, and tuffs (Nelson and Kyba, 2014). Subaerial andesite and dacite volcanic and volcaniclastic strata overlie the Jack Formation in the Brucejack area. They were included in the Betty Creek Formation by Lewis (2013). A thin unit of Middle Jurassic fossiliferous mudstone, also assigned to the Betty Creek Formation, crops out east of the Iron Cap deposit. 2.3.2. Plutonism Small Early Jurassic porphyritic diorite to syenite bodies referred to as the Mitchell intrusions cut the Stuhini and Hazelton groups in the Sulphurets district and are considered part of the Texas Creek plutonic suite (Kirkham, 1963; Alldrick and Britton, 1988, 1991). Two suites are recognized: modified from Alldrick and Britton (1991) ‘one-feldspar’ Sulphurets Glacier porphyry and ‘two-feldspar’ Premier porphyry identified in the Sulphurets district (see also Alldrick, 1993). Crowded, coarse-grained Premier intrusions are cut by uncrowded, relatively fine-grained Sulphurets intrusions. The Premier suite, consisting of diorite, monzonite, granite, syenite and quartz syenite (herein referred to as syenodiorite), are crowded porphyry intrusions that are commonly medium to coarse grained and contain minor porphyry mineralization. West of the Sulphurets zone and above the Sulphurets thrust, diorite margins to monzonite plugs are interpreted to indicate that the diorite is the oldest phase of the Premier suite (Fig. 3). In the northern Mitchell valley, Premier suite syenite cuts monzonite and monzonite cuts diorite in drill core. Monzonite and syenite intrusions are cut in drill core by the Sulphurets suite diorite and related stockwork and alteration in the Iron Cap area. The Sulphurets suite, consisting of diorite to monzonite porphyry (herein referred to as monzodiorite), are fine to medium grained. The Sulphurets suite plutons are a partial host to all porphyry deposits in the district and were emplaced before, during, and after mineralization. Current geochronological data (Table 2.1) and cross cutting relationships suggest that the Premier suite magmatism preceded, and possibly overlapped with, the Sulphurets suite. 10 Table 2.1. Radiometric ages for Mitchell intrusions and molybdenite mineralization in the Sulphurets district (1 laser ablation, 2 TIMS). Sub-district: location Stage Suite Unit Sample Method Age + - Reference Brucejack: Bridge zone - - hornblende porphyritic diorite 93-PL-185 U-Pb zircon2 182.1 4.8 14.2 Lewis et al., 2001 Brucejack: Bridge zone - - post-mineral mafic dike - U-Pb zircon1 182.7 1 1 Pretium Resources, 2013 Brucejack: south of Hanging glacier - - k-feldspar megacrystic dike KQ-90-152 U-Pb zircon2 188 0.5 0.5 McNicoll and Kirkham, in Kirkham and Margolis, 1995 Snowfield: east of Snowfield deposit post-3 - k-feldspar megacrystic plagioclase-hornblende porphyry S238 U-Pb zircon2 189.6 2.2 2.2 Margolis, 1993 Mitchell: 423312E, 6265278N 2 Sulphurets hornblende-plagioclase diorite porphyry GF-13-02 U-Pb zircon1 189.9 2.8 2.8 this study Brucejack: Bridge zone - n/a molybdenite in vein - Re-Os 190.2 0.8 0.8 Pretium Resources, 2013 Mitchell: DDH M-10-116, 214.6 m 2 n/a molybdenite in vein M-10-116 Re-Os 190.3 0.8 0.8 this study Sulphurets: west of Hanging glacier - Sulphurets albite-hornblende porphyry KQ-90-154C Pb-Pb 191.4 5.3 5.3 Mortensen and Kirkham, in Kirkham and Margolis, 1995 Brucejack: Bridge zone, DDH SU-151 - n/a molybdenite in vein - Re-Os 191.5 0.8 0.8 Pretium Resources, 2013 Sulphurets: Main Copper/Montgomery - Premier Feldspar porphyry, monzonite to syenite - U-Pb zircon2 191.8 6.5 1 Macdonald, in Kirkham and Margolis, 1995 Mitchell: DDH M-07-49, 320 m 2 Sulphurets hornblende-plagioclase diorite porphyry M-07-49 U-Pb zircon1 192.2 2.8 2.8 this study Mitchell: southwest side of Mitchell glacier pre-1 Premier quartz syenite S462 U-Pb zircon2 192.7 5.4 3.6 Margolis, 1993 Mitchell: north of Mitchell glacier pre-1 Premier trachytoid syenite to aplitic granite porphyry KQ-89- 890/90A U-Pb zircon2 193.9 0.5 0.5 Mortensen and Kirkham, in Kirkham and Margolis, 1995 Brucejack: south of Hanging glacier - Sulphurets altered plagioclase-hornblende porphyry KQ-90-151A U-Pb zircon2 194 1 1 McNicoll and Kirkham, published in Kirkham and Margolis, 1995 Brucejack: west of West zone - - K-feldspar megacrystic porphyry 93-PL-187 U-Pb zircon2 194 3.7 0.6 Lewis et al., 2001 Kerr: eastern deposit - k-feldspar megacrystic, plagioclase-hornblende porphyry, late synmineral 00-Iskut U-Pb zircon2 195 1.5 1.5 Bridge, 1993 Mitchell: DDH M-11-123, 621 m 1 Sulphurets diorite porphyry M-11-123 U-Pb zircon1 196 2.9 2.9 this study Sulphurets: Raewyn - Premier altered quartz monzonite - U-Pb zircon2 196 17 32 Macdonald, in Kirkham and Margolis, 1995 Kerr: western deposit - - syenodiorite, synmineral Iskut-lapp U-Pb zircon2 197 3 3 Bridge, 1993 11 Fig. 2.3. Geology of the KSM property, showing the conceptual pit boundaries for Mitchell, Sulphurets, Kerr and Iron Cap zones. For section A-A’ refer to Figure 2.7a, for section B-B’ refer to Figure 2.7b and for section C-C’ refer to Figure 2.23. For lithology legend refer to Figure 2.4. 12 Fig. 2.4. Legend for Figures 2.3, 2.5, 2.7a, 2.7b, 2.8 and 2.22. 13 Fig. 2.5. Stratigraphy of the Mitchell-Snowfield area. For lithology refer to Figure 2.4. 2.3.3. Structure The Kerr, Sulphurets, Snowfield, and Iron Cap porphyry deposits are located in the footwall of the Sulphurets fault (Fig. 2.3), an east-vergent thrust that marks the eastern margin of the McTagg anticlinorium (Fig. 2.2). Both of these regional structures are interpreted to be kinematically linked to the Skeena fold and thrust belt (Kirkham and Margolis, 1995). The Mitchell thrust fault is a prominent splay of the Sulphurets thrust that separates the Snowfield and Iron Cap zones in its hanging wall from the Mitchell zone in its footwall (e.g., Savell and Threlkeld, 2013; Nelson and Kyba, 2014). Rocks in the 14 Sulphurets area have been affected by folding, faulting, penetrative cleavage formation, and low-grade regional metamorphism (Kirkham, 1963; Henderson et al., 1992; Margolis, 1993). Beds in the district are generally north striking with moderate to steep dips and have been deformed into upright buckle folds, also related to Skeena fold and thrust belt deformation (Kirkham and Margolis, 1995). Two fold geometries are documented in the district: 1) north-northwest-plunging buckle folds with a related axial planar cleavage (Bridge, 1992; Kramer, 2014); and 2) west-plunging buckle folds, with a variably developed steep, north-dipping pressure solution cleavage (Kirkham, 1963; Margolis, 1993; this study; see Appendix A). Although Margolis (1993) suggested that east-west striking cleavage in the Mitchell-Snowfield area may have developed as a post-emplacement fabric in the Jurassic, orthogonal fold trends in the Brucejack area may record progressive mid-Cretaceous deformation (C. Greig, pers. comm., 2014). Altered rocks at Kerr, Mitchell, Snowfield and Brucejack in particular are characterized by a strong pervasive pressure solution cleavage, folded veins, and 5-70% flattening compared to Sulphurets and Iron Cap, which have poorly developed deformation fabrics. Kirkham (1963) directly correlated cleavage development, degree of alteration, and abundance of micaceous minerals. 2.3.4. Mineralization The Sulphurets district contains five undeveloped porphyry deposits (Kerr, Sulphurets, Snowfield, Mitchell and Iron Cap) and the high-grade epithermal Brucejack deposit (Fig. 2.2) with compliant estimates of mineral reserves and resources. Seabridge Gold Inc. claims cover the KSM property (Kerr, Sulphurets, Mitchell, and Iron Cap); Pretium Reosurces Inc. claims cover the Snowfield and Brucejack deposits. At surface, the Kerr deposit is hosted by Stuhini Group volcanosedimentary rocks, Jack Formation sandstone, and Sulphurets plutons; at depths of 0.5-1km, it is intrusion hosted. The Sulphurets deposit is a tabular-shaped, northwest dipping ore body hosted in Jack Formation sandstone, andesite volcanic rocks, and subordinate Sulphurets suite monzodiorite dikes and sills. The Iron Cap and Snowfield deposits are hosted by Jack Formation sandstone, interfingering andesite volcaniclastic rocks, and Sulphurets suite monzodiorite intrusions. The Mitchell deposit is largely hosted in Sulphurets suite diorite stocks. It lies in the footwall of the Mitchell thrust, and is considered equivalent to the Snowfield deposit. The Snowfield deposit is interpreted to lie in the hanging wall of the Mitchell thrust and to be offset ~ 1.6 km to the southeast of the Mitchell deposit (Savell and Threlkeld, 2013). The KSM deposits have a measured and indicated resource of 2.78 billion tonnes at 0.55 g/t Au, 0.21% Cu, 2.9 g/t Ag and 55 ppm Mo (0.5 g/t gold equivalent cut off; Seabridge Gold, 2015). The Snowfield deposit hosts an additional measured and indicated resource of 1.37 billion tonnes at 0.59 g/t Au, 1.72 g/t Ag, 0.10% Cu and 85.5 ppm Mo (0.3 g/t gold equivalent cut off; Pretium Resources, 2011). The high-grade Valley of the Kings deposit (Brucejack 15 project) contains a measured and indicated resource of 15.3 million tonnes at 17.6 g/t gold and 14.3 g/t Ag (5 g/t gold equivalent cut off; Pretium Resources, 2014). The Snowfield deposit is underlain by andesite flow breccias and interbedded volcaniclastic arenite (Margolis, 1993) that host most of the mineralization. These rocks are intruded by pre-mineralization Sulphurets suite diorite and Premier suite quartz-syenite (192.7 +5.4 -3.5 Ma; U-Pb, zircon; Margolis, 1993). Mineralization at Snowfield is divided into four stages (Margolis, 1993): Stage 1) deep, chalcopyrite-bearing potassic alteration flanked by propylitic alteration and Cu-Au enriched quartz-stockwork; Stage 2) high-level quartz-sericite-pyrite-chlorite-molybdenite-tourmaline; Stage 3) high-level advanced argillic alteration and deeper massive pyrite veins containing Bi-Te-Sn; and Stage 4) predominantly high-level, gold-rich vein and disseminated mineralization enriched in Ag-Pb-Zn-Ba-Sb-Hg-Cd-Te. Herein we adopt the Margolis (1993) scheme of four Stages of alteration, veins, and mineralization for the Mitchell deposit. Nelson and Kyba (2014) assigned quartz-rich arenites in the Snowfield area to the Jack Formation. Polymictic Jack Formation conglomerate outcrops west of the Snowfield alteration zone (Nelson and Kyba, 2014). Argillic-altered sandstones in the upper part of the Jack Formation in the Snowfield area contain pebbles of banded quartz-pyrite vein fragments (Fig. 2.8a), indicating predepositional mineralization. Sulphurets suite porphyry plugs (Nelson and Kyba, 2014) contain Jack Formation sandstone xenoliths indicating that intrusion followed sedimentation. However, the Sulphurets suite porphyry is overprinted by alteration and mineralization (Margolis, 1993) and also contains clasts of chalcopyrite-bearing quartz veins (Margolis, 1993). In short, the mineralizing system appears to have been active before, during, and after deposition of the Jack Formation. 2.4. The Mitchell deposit The Mitchell deposit is centred around a dense cluster of Mitchell porphyry diorites that cut the Stuhini Group and basal Hazelton Group (Jack Formation, Figs. 2.5, 2.6). Three pulses of Sulphurets suite diorite form a crudely elliptical 2 x 1 km outcrop with sills and dikes extending to the east. Multiple stocks of uniform medium-grained hornblende-plagioclase porphyritic diorite grade into coarse-grained porphyritic K-feldspar-hormblende-plagioclase diorite at depth (Figs. 2.7a, b). The deposit is characterized by episodic intrusion, stockwork and cannibalization of previously emplaced diorite and stockwork into later-stage intrusion breccias and diatremes. Deeper-level potassic and transitional potassic alteration in the western part of the map area grade into higher-level intermediate argillic and chloritic alteration in the central part which, in turn, grades to phyllic and clay alteration farther east. This alteration pattern is flanked by propylitic and albitic alteration that together with core alteration assemblages define a >4 km diameter alteration halo that is truncated by the Sulphurets thrust to the west and by the Brucejack fault to the east (see Appendix C for field station descriptions). 16 Fig. 2.6. Mitchell zone and surrounding area rocks. a) Jack Formation conglomeratic sandstone in the Snowfield zone with andesite and quartz-pyrite vein clasts. S1 foliation and veins folded by F2, 424583 E, 6264244 N. b) Pale Stuhini Group felsic ash tuff interbedded with siltstone (drill core, M-07-42, 348.7 m). c) Jack Formation conglomerate contains felsic flow breccia clasts derived from subjacent Stuhini Group, 421431 E, 6266817 N. d) Phyllic- and clay-altered Jack Formation feldspathic sandstone of the Mitchell zone, 424861 E, 6265572 N. e) Elliptical concretionary structure in Jack Formation sandstone with concentric banding defined by albite-chlorite-chalcopyrite-pyrite, 424475 E, 6266436 N. 17 Fig. 2.7. Cross sections across KSM property (see Figure 2.3 for locations): a) A-A’ east-west, b) B-B’ north-south. For lithology legend, refer to Figure 2.4. See Appendix B for descriptions of relogged core intervals. 18 2.4.1. Lithologic units 18.104.22.168. Stuhini Group (Triassic) The Stuhini Group is the oldest unit exposed in the Mitchell area (Fig. 2.6). The most abundant lithologies are cm-scale bedded siltstone, graphitic shales and less common calcareous mudstones intersected in drill core. Lesser amounts of dolostone and limestone are identified in drill core in the Mitchell mineralized zone (Hansley, 2008) and are of unknown thickness and extent. A unit of rhythmically bedded felsic tuff and siltstone assigned to Stuhini Group was intersected in drill core (Fig. 2.6b) in the western part of the map area, beneath the Mitchell thrust. Similar rocks outcrop north and south of the Mitchell zone above the Mitchell thrust fault (Fig. 2.7b), and the unit appears to be > 200m thick. In the northwestern Mitchell valley, Jack Formation conglomerates contain clasts of a quartz-feldspar porphyritic flow breccia that were likely derived from an identical breccia body immediately beneath the unconformity (Fig. 2.6c). Ubiquitous felsic clasts in the Jack Formation were likely derived from similar rocks (J. Nelson, pers. comm., 2014). 22.214.171.124. Hazelton Group (Late Triassic to Middle Jurassic) Beneath the Mitchell thrust fault east of the Mitchell deposit (Fig. 2.8), the Jack Formation is represented by a unit of massive feldspathic sandstone (Fig. 2.6d). The sandstone contains 10-45% quartz and 50-70% feldspar and is typically very fine grained to fine grained, but with rare granule fragments. The unit is 300 m to 1 km thick and has gradational contacts with conglomerate and andesite lapilli tuff. Rarely, the sandstones contain lenses of conglomerate up to 10 m thick with felsic volcanic, black chert and intermediate volcanic clasts in a sandstone matrix. In the northeastern Mitchell zone, bedding in the lower part of the sandstone unit is locally defined by high concentrations of concretionary structures with concentric bands of chalcopyrite-pyrite-chlorite-albite (Fig. 2.6e). Some concretions contain small amounts of carbonate. The intensity of hydrothermal minerals in concretionary structures relates to intensity of pervasive and mottled chalcopyrite-pyrite-chlorite-albite in sandstone and to the proximity to Sulphurets dikes. If the concretionary structures are a product of diagenesis that contained carbonate cement, then mineralization post-dates both sandstone deposition and diagenesis. Jack Formation sandstone is intruded by pre- to post-mineral Sulphurets diorite and is intensely altered to albite, quartz-sericite-pyrite and muscovite-illite in all outcrops beneath the Mitchell thrust fault. Alteration is characterized by partial to complete replacement of feldspar and interstitial carbonate by hydrothermal minerals. Quartz grains in altered sandstone are subrounded to angular and fractures in grains are commonly filled with pyrite and chalcopyrite. 19 Fig. 2.8. Geology of the Mitchell zone and surrounding area. Geochronologic sample GF-12-02 from outcrop, M-10-116 from drill core. For legend refer to Figure 2.4.20 Andesite volcanic rocks in the Mitchell zone outcrop beneath the Mitchell thrust fault east of the Mitchell intrusions (Fig. 2.8). They comprise three general types that are broadly laterally equivalent: 1) lapilli-sized breccia; 2) tuff-breccia; and 3) feldspar-phyric flows. The breccia are well sorted, massive, and contain abundant (60-85%) 1-2 cm porphyritic juvenile clasts with aspect rations that range from 1:1 to 2:1 (Fig. 2.9a). Clast sizes tend to be uniform within individual layers, and many of the clasts have concavo-convex shapes and margins with flame-like projections. The breccias interfinger with sandstone layers and locally contain a sandstone matrix. The deposits are interpreted to record subaqueous phreatomagmatic volcanic eruptions, as indicated by the porphyritic textures and irregular clast boundaries, coeval with sandstone sedimentation. Andesite tuff breccia deposits contain poorly sorted, 50-80%, angular, porphyritic clasts that range from ~1 cm to more than 1 m in a massive tuffaceous matrix (Fig. 2.9b). They display local stratification and rare sigmoidal shaped fiamme fragments. Fragments typically have aspect ratios of 1:1 to 5:1. Sections with >1 m clast sizes are interpreted to be near-vent deposits. The deposits are interpreted to be block and ash flows due to their poor sorting, tuffaceous matrix and the angular, large monolithic andesite clasts. Andesite flows and flow breccias outcrop in the most easterly Mitchell zone beneath the Mitchell thrust and west of the Brucejack fault (Fig. 2.8), where they probably represent the highest parts of the section. Fine-grained plagioclase-hornblende-phyric flows near the sandstone contact grade into overlying crowded, coarse-grained (up to 1 cm), feldspar-phyric flows. A lava tube, ~2 m in diameter, crops out in the transition between fine- and coarse-grained intermediate flow sequences. The tube is defined by concentric flow banding that is truncated by a subhorizontal erosional surface and overlain locally by a coherent andesite flow and flow breccia (Fig. 2.9c). The andesites host stockwork and disseminated mineralization and are cut by Sulphurets suite diorite intrusions. The andesites are interpreted to be coeval with the Premier suite intrusions because: 1) of their stratigraphic position within the basal Hazelton Group; 2) of their spatial association with Premier intrusions; and 3) at Snowfield they contain hypabyssal syenite clasts with a pink K-feldspar matrix (J. Nelson, pers. comm., 2013). Above the Mitchell thrust, offset equivalents of the andesite strata of the Mitchell zone are locally cut by Premier suite syenite and monzonite in drill core and Sulphurets suite diorite in outcrop (Fig. 2.8). 21 Fig. 2.9. Mitchell zone Jack Formation andesite. a) Chlorite and quartz altered andesite lapilli tuff, 424000 E, 6265584 N. b) Andesite block breccia, 424950 E, 6265755 N. c) Lava tube with concentric bands cut by overlying andesite flow breccia, 424874 E, 6266646 N. 22 126.96.36.199. Premier intrusive suite Premier suite syenodiorite intrusions outcrop in the immediate hanging wall of the Mitchell thrust fault (Figs. 2.8, 2.7b). Premier suite plutons are characteristically phaneritic with crowded oscillatory zoned plagioclase and common pink or maroon K-feldspar phenocrysts (Figs. 2.10a, b). Dioritic varieties are crowded biotite-pyroxene-hornblende-plagioclase phyric, medium- to coarse-grained porphyries that outcrop in the southwestern Mitchell valley above the Sulphurets thrust fault (Fig. 2.3). Monzonite varieties are commonly coarse grained, crowded with oscillatory zoned plagioclase, pink K-feldspar phenocrysts up to 2 cm, hornblende up to 1 cm, biotite and trace quartz phenocrysts (Fig. 2.10a). Syenitic varieties (Fig. 2.10b) are commonly maroon to red, contain from 40-65% perthitic K-feldspar phenocrysts, oscillatory zoned plagioclase phenocrysts, local quartz phenocrysts, and lack mafic primary minerals (Kirkham, 1963; Simpson, 1983; see Appendix D for petrographic descriptions). 188.8.131.52. Sulphurets intrusive suite and related breccia bodies Sulphurets suite plutons in the Mitchell deposit are diorite in composition. Compared to the Premier suite diorite, they are more uniform in texture and composition, and are notably finer grained and less crowded (Figs. 2.10c-d). Based on field observations, we distinguish three phases of diorite. Phase 1 includes diorite in contact with country rock and Phase 2 is a plug that crosscuts Phase 1 rocks and contains quartz-pyrite-chalcopyrite veins as xenoliths. A breccia body and small breccia dikes cut Phase 2 rocks but are cut by a small Phase 3 plug (see Appendix D for petrographic descriptions). Phase 1: Phase 1 diorite is the most voluminous of the three Sulphurets intrusions. It cuts bedded sedimentary rocks of the Stuhini Group and both cuts and interfingers with Jack Formation sandstone and andesite breccia (Fig. 2.8). The margins of the diorite contain xenoliths of sedimentary rocks. The country rock adjacent to the intrusions has albite alteration and local skarn alteration mineralogy (see below). Phase 1 diorite is a partial host to the high quartz zone (Fig. 2.8) near the southern contact area and is interpreted to have been emplaced prior to or possibly synchronous with the high quartz zone that is cut by Phase 2 diorite (Fig. 2.8). Phase 1 diorite is remarkably homogeneous in composition and texture and is characterized by partial to complete hydrothermal replacement of plagioclase and replacement of hornblende phenocrysts (Figs. 2.10c, e, f). A narrow diorite sill intersected in drill core along the western margin of the Mitchell zone is relatively unaltered and provides primary texture information (Fig. 2.10d). This sill contains 20-30% plagioclase (An10-An20) phenocrysts (up to 3 mm) 1-10% K-feldspar (up to 1 mm), 5% hornblende phenocrysts (up to 3 mm), trace biotite (~1 mm) and trace apatite. At depth, diorite contains up to 1% K-feldspar oikiocrysts 1-1.5 cm in diameter in local coarser intervals (Fig. 2.10e). Inclusions in the K-feldspar oikiocryst include 20% anorthite, 5% hornblende, 1% clinopyroxene and 23 trace garnet. Where Phase 1 diorite is cut by veins with relatively sharp boundaries, we infer emplacement before mineralization. Where mineralized veins in the diorite are disarticulated, fluidal shaped, and irregular, which suggests incomplete diorite crystallization, we infer synmineralization emplacement. Fig. 2.10. Mitchell intrusions; Premier and Sulphurets suites (Jurassic). a) Premier suite; coarse-grained, crowded monzonite porphyry. Hb-hornblende; Plag-plagioclase; Kf- K-feldspar. Drill core M-06-23, 54 m. b) Premier suite; red hematite dusted coarse-grained, syenite. Plag-plagioclase; Kf- K-feldspar. Drill core M-12-129, 895 m. c) Sulphurets suite; Phase 1 diorite with chloritized hornblende and plagioclase phenocrysts. Drill core M-07-58, 690.5m. d) Sulphurets suite; Phase 1 medium-grained diorite; Hb- hornblende; Plag- plagioclase. Drill core M-07-42, 50 m. e) Sulphurets suite; Phase 1 bimodal porphyry diorite contains 1% coarse-grained K-feldspar (Kf) phenocrysts in a hornblende-plagioclase, medium-grained diorite porphyry. Drill core M-07-25, 456.6m. f) Phase 1 diorite with k-feldspar-altered groundmass and chlorite-altered mafic phenocrysts. Drill core M-11-126, 336.5 m. 24 Phase 2: The Phase 2 intramineral diorite plug contains quartz vein xenoliths, cuts Phase 1 diorite and the high quartz zone (Fig. 2.11a) and occupies the core of the deposit (Fig. 2.8). It is distinguished on surface by a contact breccia, sparser (10-20%) quartz veins than Phase 1, and uniformly high concentrations of quartz vein xenoliths (Fig. 2.11b). Contacts between Phase 1 and Phase 2 are most clearly identified where Phase 2 rocks cut the high quartz zone, with quartz zone xenoliths in the contact breccia (Fig. 2.11a) and by internally stockworked Phase 1 diorite xenoliths (Fig. 2.11c). Elsewhere, contacts are inferred by transitions from higher to lower quartz stockworks coupled with an increase in quartz vein xenoliths (Fig. 2.12). Fig. 2.11. Sulphurets suite diorite breccia. a) Contact between Phase 2 phyllic altered diorite and high quartz zone, 423353 E, 6265193 N. b) Angular quartz (qtz) vein xenoliths in Phase 2 diorite, 422958 E, 6265505 N. c) Xenolith of Phase 1 diorite (with internal quartz stockwork veins abruptly truncated at clast boundary) in Phase 2 diorite, 423300 E, 6265575 N. d) Clast of diatreme breccia in Phase 3 diorite, 423391 E, 6265661 N. 25 Fig. 2.12. Abundance of quartz veins, molybdenite contours (> 30 ppm) and contact of Phase 2 pluton. Molybdenite traces from Savell (2009). 26 Diatreme breccia: A ~100 x 300 m, northeast-trending complex breccia body interpreted to be the root zone of a diatreme breccia, outcrops in the northeastern Mitchell zone (Fig. 2.8). It cuts Phase 2 diorite on its southern margin and cuts sandstone and andesite on its southeastern margin, but is cut by Phase 3 diorite at its western margin where indistinct boundaries to xenoliths of the diatreme within Phase 3 diorite are interpreted to indicate an unlithified breccia at the time of Phase 3 magmatism (Fig. 2.11d). On the west, clast sizes are up to 20 cm in diameter, on the east clasts are generally < 2 cm across. Clasts include: 1) andesite volcanic fragments that are 1-2 cm in diameter, fine-grained, porphyritic, and angular (Figs. 2.13a, b); 2) quartz-rich sandstones that are subrounded and < 3 mm in diameter; 3) porphyritic diorite (?), that display amoeboid shapes and 2-6 cm in diameter; 4) quartz-pyrite±chalcopyrite veins, 0.5 – 3 cm in diameter (Fig. 2.13b); and 5) mineralized quartz stockworked diorite (Fig. 2.13a) that are subrounded and 2-20 cm in diameter. Concentrations of quartz stockworked diorite clasts can make up ~80% of the rock in the western ‘bone breccia’ outcrop (Fig. 2.13a; see also Figure 20 in Kyba and Nelson, 2014) but decrease eastward. Clasts of andesite or diorite are flattened to form a local banding that is at an angle to the overprinting pervasive foliation (Fig. 2.13b). The breccia is overprinted by 1-5% quartz-chalcopyrite-molybdenite stockwork. Late quartz-pyrite stringers with tourmaline alteration halos are common, and tourmaline is locally in the groundmass. The groundmass displays weak chlorite and sericitic alteration, but subtle porphyritic textures in thin section suggest a magmatic origin. The breccia is interpreted to have formed as a subvertical diatreme pipe that now plunges steeply to the west, and that the eastward decrease in clast sizes reflects increasing distance from source rocks. Cross-cutting relationships suggest that the pipe was emplaced during the waning stages of Phase 2 plutonism, and/or the early stages of Phase 3 plutonism. Emplacement of the diatreme pipe coincided with the waning of latest molybdenite-rich, porphyry-type mineralization and cessation of stockwork veining. The quartz stockwork dense ‘bone breccia’ outcrop is interpreted to be an intact root zone to the diatreme breccia that is penetrated by intrusion breccia dikes (see also Nelson and Kyba, 2014). Intrusion breccia dikes: Small (20-50 cm wide; 2-20 m long) intrusion breccia dikes cut sandstone, Phase 1 and 2 diorite and the diatreme are cut by Phase 3 diorite. The dikes are distributed about the margins of and emanate from, Phase 3 diorite. Boundaries are commonly sharp and irregular, and dike traces anastomose. Where dikes cut sandstone, clasts of chert, rounded siliceous pebbles and angular mineralized quartz veins are in a tourmalinized porphyritic groundmass (Fig. 2.13c). Where dikes cut the diorite, clasts are predominantly quartz vein fragments and quartz stockworked diorite fragments. Where dikes cut the diatreme breccia, they contain clasts of quartz stockworked diorite, angular diorite (?) porphyry, and quartz veins in a 27 Fig. 2.13. Diatreme breccia and intrusion breccia dike in outcrop. a) Dense internally stockworked diorite clasts, quartz vein and andesite fragments 423469 E, 6265628 N. b) Irregular flow banding in the diatreme breccia is locally at a high angle to steeply dipping main cleavage (S1), 423511 E, 6265640 N. c) Intrusion breccia dike with tourmalinized groundmass, containing quartz-chalcopyrite-pyrite vein clasts, 423575 E, 6265533 N. 28 tourmalinized groundmass. The clast compositions in these three examples appear to directly reflect cannibalization of the host lithologies. Breccia dikes are cut by pyrite-quartz veins with tourmaline halos and tourmaline is commonly observed in the groundmass of the dikes (Fig. 2.13c). A particularly notable 3 m thick breccia dike that intrudes the diatreme breccia is cut by Phase 3 diorite. The breccia dikes are interpreted to have been emplaced during the early stages of Phase 3 diorite intrusion as they emanate from the Phase 3 plug and are locally cut by it. Phase 3: A small (50 x 125 m) plug of Phase 3 diorite cuts the western end of the diatreme breccia (Fig. 2.8) and intrusion breccia dikes, and is overprinted only by minor quartz-pyrite-tourmaline stringers. The plug is most easily distinguished by a near lack (< 1%) of quartz veins, by abundant clasts of quartz stockworked diorite (up to 20 cm), clasts of diatreme breccia (> 1 m, Fig. 2.11c) and clasts of breccia dikes. The plug is assigned intermineral status because it post-dates Stage 2 stockwork and pre-dates Stage 3 pyrite stringers described below. 2.4.2. Geochemistry of the Premier and Sulphurets intrusions On plots of immobile elements (Fig. 2.14a), most intrusions of the Mitchell deposit plot in the andesite (diorite) field, although some plugs border the dacite (monzonite) field. Compositions of the Premier and Sulphurets suites are comparable, although the younger phases of Premier magmatism trend toward the trachyte (syenite) fields. Kirkham (1963) attributed this compositional differentiation to fractional crystallization, with composite intrusions resulting from progressive crystallization from diorite to monzonite to syenite over time. The Premier and Sulphurets suites display separate trend lines on a Co versus Th plot (Fig. 2.14b), which shows the Premier to be more alkaline. Overlapping crystallization ages of the Premier and Sulphurets suites (Table 2.1) suggest that they may have been emplaced in separate but kindred crustal chambers. 2.4.3. Alteration Margolis (1993) simplified the hydrothermal evolution of the Mitchell and Snowfield areas into four general Stages. Because of the simplicity and thoroughness of Margolis’ (1993) classification scheme I have adopted this scheme for alteration, vein paragenesis, and mineralization (Table 2.3). 184.108.40.206 Stage 1 Stage 1 potassic alteration is characterized by equigranular textures and a simpler, less dense quartz vein stockwork in the western Mitchell zone (Fig. 2.15) and in the central, deeper regions of the drilled extents 29 Fig. 2.14. Geochemistry of the Mitchell intrusions (Premier and Sulphurets suites). a) Zr/Ti vs Nb/Y diagram (Winchester and Floyd, 1977) and b) Th vs Co diagram (Hastie et al., 2007). For geochemical data, refer to Table 2.2.30 Table 2.2. Representative geochemical data. Abbrevations: SP1: Sulphurets suite, Phase 1; SP2: Sulphurets suite, Phase 2; PS: Premier suite. Sample Depth/UTM Unit Weight SiO2 Al2O3 Fe2O3 MgO CaO Na2O K2O TiO2 P2O5 MnO LOI Total (Kg) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) 0.01 0.01 0.04 0.01 0.01 0.01 0.01 0.01 0.01 0.01 -5.1 0.01 M-11-123 608-621m SP1 1.89 64.5 11.95 10.13 2.55 0.9 0.1 5.19 0.36 0.26 0.11 3.4 99.41 M-07-49 341-368 m SP2 2.32 61.11 14.12 5.93 2.37 3.99 0.77 5.02 0.49 0.23 0.17 5.2 99.39 GF-13-02 423312E, 6265278N SP1 2.1 61.85 16.09 8.85 2.19 0.32 0.11 4.46 0.55 0.24 0.05 4.8 99.55 GF-13-29 423549E, 6265515N SP1 1.6 61.17 15.04 7.34 2.63 1.11 0.22 4.22 0.39 0.29 0.29 6.8 99.5 GF-13-38 422382E, 6265428N SP1 1.85 61.11 16.96 6.89 2.47 0.45 0.14 5.14 0.44 0.33 0.05 5.4 99.38 M-08-67 932 m PS 0.8 56 16.9 6.74 2.61 3.11 1.13 6.31 0.49 0.29 0.11 5.7 99.43 GC-1 423275E, 6265548N SP2 2.25 60.22 15.98 6.4 2.1 2.95 3.35 2.71 0.56 0.25 0.12 4.8 99.39 M-07-36 43.8m SP1 1.1 62.35 15.56 6.62 1.32 1.88 3 5.38 0.53 0.23 0.11 2.5 99.46 M-06-23 56m PS 0.82 57.93 17.26 4.64 1 3.03 4.33 6.66 0.35 0.23 0.08 3.9 99.46 M-07-58 526.5m SP1 0.79 54.2 15.94 8.97 3.37 3.63 0.07 5.76 0.55 0.26 0.26 6.3 99.32 M-10-128 124m PS 5.66 69.32 15.08 1.55 0.12 0.99 4.26 7.32 0.07 0.03 0.02 1 99.79 Ti Co Th Zr Y Nb Mo Cu Ag Au (cont.) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppb) 0.2 0.2 0.1 0.1 0.1 0.1 0.1 M-11-123 2157.59 11.4 3 43.6 10.3 4.9 22.6 1925.4 2.6 629 M-07-49 2936.73 8.3 4.6 78.5 14.5 6.6 14.7 1351.1 1.5 503.2 GF-13-02 3296.33 9.4 4.7 87 12.8 7.3 13.1 1205.3 1.3 928 GF-13-29 2337.39 12.2 2.3 35 9.6 4.8 56.8 499.2 2.9 497.7 GF-13-38 2637.06 16.3 3.3 55.9 13.3 7.2 9.7 894.8 1.4 110.2 M-08-67 2936.73 18.2 4.3 65.2 12.1 6.3 0.7 100.1 1.8 58.4 GC-1 3356.26 8.3 3.7 81.1 14.8 7 92.4 1150.6 1.3 688.7 M-07-36 3176.46 7.5 4.3 91 14.5 7 51.4 1017.5 1.9 211.3 M-06-23 2097.66 6.8 5.2 76.6 12.8 9.5 0.6 53 0.4 9.5 M-07-58 3296.33 8.8 4.4 86.3 15.3 6.3 12.7 1260.7 3.8 503.7 M-10-128 419.53 1.1 11.7 104.9 3.8 10.2 2.6 305.6 0.7 9.7 31 of the Mitchell intrusion. Secondary biotite, K-feldspar (Fig. 2.10f), magnetite, albite, anhydrite, chlorite, phengite are commonly preserved. The potassic assemblage transitions laterally and upwards (into stratified wall rocks) to transitional potassic, a calcite-epidote-chlorite distal propylitic (Fig. 2.6b) and hornfels alteration that contains epidote, albite, cordierite and carbonates, and quartz veins diminish in volume. The transitional potassic alteration (Fig. 2.15), characterized by quartz, chlorite, anhydrite, magnetite, biotite and several episodes of quartz stockwork veins, is outboard of the core potassic alteration zone and inboard of the propylitic zone. Here, fine, shreddy textures and rutile inclusions commonly observed in chlorite suggest that chlorite replaces some of the secondary biotite. Local zones of skarn mineral assemblages, including magnetite, diopside, zoisite, garnet and epidote occur, farther outboard in the hornfelsed host rocks (see Appendix F for X-ray diffraction spectra and Appendix J for Terraspec data for alteration minerals). 220.127.116.11. Stage 2 Secondary phyllic alteration overprints the primary alteration (Fig. 2.15) and consists of quartz, sericite, illite, and chlorite accompanied by quartz stockwork veins (Figs. 2.11a, 2.9b). The degree of overprint ranges from spaced, meter scale, fracture-controlled replacement in deeper regions of the porphyry (observed in drill core), to pervasive overprint in the eastern and upper levels of the deposit. Intense phyllic alteration in the eastern Mitchell zone is defined by bleached to pale grey or yellow rocks entirely lacking in mafic minerals and magnetite (Fig. 2.6d). 18.104.22.168. Stage 3 Stage 3 advanced argillic alteration includes kaolinite, pyrophyllite and rutile in southeastern Mitchell zone. High pyrite concentrations are spatially associated with this alteration type, but lack significant gold and copper mineralization. Stage Plutonism Alteration Mineralization Veins ~ Age 1 Phase 1 potassic, transitional potassic, propyllitic, albitic Cu-Au core zone 5-95% by volume quartz-pyrite-chalcopyrite veining, sheeted high quartz zone 196-192 Ma 2 Phase 2 Phyllic Mo envelope, additional Cu-Au <10% by volume quartz-pyrite-chalcopyrite-molybdenite veining 192-190 Ma 3 Phase 3 advanced argillic n/a massive pyrite veins <190 Ma 4 n/a n/a high grade Au-Ag-Cu-Pb-Zn epithermal ?185 Ma Table 2.3. Summary of mineralization, alteration, vein and plutonic Stages and Phases. 32 Fig. 2.15. Alteration map of the Mitchell zone. Alteration above the Mitchell thrust fault is not plotted. 2.4.4. Vein paragenesis Adopting the vein paragenesis scheme developed for the Snowfield deposit by Margolis (1993), Stage 1 veins comprise mm- to cm-scale stockwork to sheeted veins (Figs. 2.16a-c) that make up 5-95% of the host rock and are composed of chalcopyrite-pyrite-quartz±magnetite±K-feldspar±chlorite (see Appendix E for additional field photos of veins). The high quartz zone, formed during Stage 1, is characterized by ~1-2 cm thick, sheeted quartz veins that strike east-northeast and dip steeply to the north (Fig. 2.16b). The high quartz zone is tabular in shape and grades into lower quartz vein abundance stockwork to the west. To the north, the high quartz zone is cut by Phase 2 diorite. In general, Stage 1 veins have uniform mineralogy, lack alteration halos (Fig. 2.16c) and are part of a protracted stockwork event that overlapped with emplacement of Phase 1 diorite. At deeper levels Stage 1 stockworks dispay diffuse boundaries and contain more magnetite and K-feldspar but are interpreted to be part of the same progressive stockwork event that is responsible for the vast majority of veins in the deposit. Stage 1 veins are temporally associated with early potassic and propylitic alterations (Margolis, 1993). Stage 2 veins are molybdenite-rich stockworks distributed in a halo about the core copper-gold mineralized zone and are composed of quartz-pyrite-molybdenite±chalcopyrite±chlorite±sericite± fluorite±anhydrite. The veins are more typically stockwork-style and are not sheeted in the Mitchell zone. Molybdenite-bearing veins (Fig. 2.16d) are generally associated with smaller volumes of quartz veins compared to Stage 1 veins. Stage 2 veins are spatially distributed with phyllic alteration assemblages 33 (Fig. 2.15). A bornite-bearing hydrothermal stockwork and breccia body intersected in drill core (Fig. 2.7b) is interpreted as Stage 2. The breccia body overprints Stage 1 stockwork and is cut by Stage 3 pyrite veins and a late, narrow diorite sill interpreted as Phase 3. The bornite breccia is interpreted to be up to ~100 m thick tabular to pipe-like body that plunges steeply to the north. Contact margins of the breccia contain clasts of Phase 1 quartz stockwork and diorite, and the core areas contain banded, stockwork and breccia textures with clasts and matrix composed of hydrothermal gangue and sulphide minerals. Clasts in the breccia are commonly lenticular and irregular and are interpreted to have been coeval with the matrix because the mineralogy of both is comparable. X-ray diffraction determinations of gangue and sulphide mineralogy in the breccia indicates: quartz, anhydrite, fluorite, calcite, gypsum, muscovite, illite, apatite, anatase, albite and chlorite together with pyrite, chalcopyrite, bornite, molybdenite, tennantite, enargite, sphalerite and traces of magnetite. The bornite breccia body preserves all four stages of mineralization with Stage 1 stockwork preceding breccia emplacement, and Stage 3 and Stage 4-related veins and breccias cutting the body. Bornite and molybdenite disseminations in the same veins suggest that the bornite breccia is temporally associated with Stage 2 molybdenite mineralization. Anhydrite-fluorite-bornite-chalcopyrite assemblages in the bornite body also resemble the Stage 2 molybdenite veins peripheral to the core zone, which contain anhydrite and fluorite. Stage 3 massive pyrite veins cut all phases of diorite, Stage 2 molybdenite veins, the high quartz zone (Fig. 2.16b) and the bornite breccia. Massive pyrite veins in the Mitchell zone are 1 mm to 3 cm wide and contain ~60-95% medium- to coarse-pyrite grains. Gangue minerals are commonly quartz and muscovite that, together with disseminated pyrite, extend into the country rock as a halo to the vein. Pyrite contains small inclusions of sphalerite, galena, chalcopyrite and tennantite. Margolis (1993) interpreted massive pyrite veins to be related to acid-sulphate style advanced-argillic alteration in the eastern Mitchell zone and the Snowfield gold zone. The late timing of our Stage 3 veins is consistent with this interpretation. Stage 4 high-grade gold veins contain quartz, barite, calcite, and manganoan calcite gangue minerals, with banded sulphides that include galena, sphalerite, tetrahedrite, electrum and tennantite. Stage 4 veins cut sandstone in the eastern part of the deposit, the bornite breccia and Stage 3 massive pyrite veins. Veins display sharp margins and euhedral to banded textures consistent with an epithermal origin. Minor bornite mineralization in Stage 4 veins that cut the bornite body is interpreted to have been remobilized during veining. 2.4.5. Mineralization Most of the disseminated and vein-controlled copper and gold mineralization is related to Stage 1 alteration and Phase 1 diorite plutonism. Chalcopyrite rims and replaces pyrite, occurs as inclusions in 34 Fig. 2.16. Quartz stockwork and vein fold geometry in the Mitchell zone. a) Planar Stage 1 quartz-K-feldspar-magnetite-chalcopyrite veins in potassic altered diorite, 422532 E, 6265370 N. b) Sheeted Stage 1 veins of the high quartz zone parallel main cleavage (S1) with cross cutting Stage 3 related pyrite vein, 423150 E, 6265155 N. c) Open F1 folded quartz veins in chlorite-quartz altered sandstone formed during the first phase of deformation, 423493 E, 6265539 N. d) Tight to isoclinal folded molybdenite-quartz veins and related pervasive cleavage formed in intense phyllic altered rocks during the first phase of deformation (F1, S1), 423832 E, 6265290 N. pyrite and as inclusions in and replacements of magnetite (Fig. 2.17a). Chalcopyrite and pyrite are inversely related; chalcopyrite to pyrite ratios generally decrease from the core outwards. Gold is microscopic and typically occurs as inclusions in sulphides or at sulphide grain boundaries. Copper and gold values are positively correlated and are notably homogeneous in their relative grade. Gold grades in general are proportional to the volume percent of quartz veins. A molybdenum-rich shell envelopes the copper-gold core (Fig. 2.12) and is interpreted to have formed with Stage 2 phyllic alteration assemblages (Margolis, 1993) and Phase 2 diorite. The molybdenite to copper ratio increases from the core of the deposit outward. In the eastern, shallow levels of the system, molybdenite veins lack chalcopyrite. Although Stage 2 stockwork and mineralization are devoid of chalcopyrite at Snowfield (Margolis, 1993), we observed chalcopyrite and molybdenite-bearing veins in the transition zone between the core copper-gold and the molybdenite-rich shell at Mitchell (Fig. 2.17b). 35 Fig. 2.17. Microtextures of chalcopyrite mineralization. a) Stage 1 cp: chalcopyrite with mt: magnetite and chl: chlorite replaces pyrite, reflected and plane polarized light, M-07-55, 255 m. b) Stage 2 mo: molybdenite and cp: chalcopyrite in quartz vein, reflected and cross polarized light M-08-70, 329 m. c) bn: bornite and cp: chalcopyrite replace py: pyrite and are spatially associated with anhy: anhydrite and fl: fluorite in the bornite breccia body, reflected and plane polarized light, M-08-67, 251.3 m. d) Early py: pyrite is partially replaced by cp:chalcopyrite-sph:sphalerite-tn:tennantite in Stage 4 barite-quartz vein, reflected light, M-07-26, 212.6 m. 36 Higher than average grades of copper and gold are intersected in the bornite breccia body and are interpreted to be the result of progressive upgrading during Stages1 through 4 hydrothermal activity. Elevated copper grades correspond to high bornite to chalcopyrite ratios and are interpreted to have been introduced with anhydrite-fluorite-quartz (Fig. 2.17c). High-grade Au-Ag-Pb-Zn-Cu mineralization associated with Stage 4 low sulphidation-type veins are superposed onto earlier (Stage 1-3) porphyry system stockworks and breccia bodies. Unlike porphyry-related mineralization, veins related to Stage 4 tend to have much higher tennantite to chalcopyrite ratios (Fig. 2.17d), higher gold and silver values, and visible sphalerite, galena and electrum grains. The veins are interpreted to be genetically related to porphyry emplacement and their timing may correlate with porphyry-related epithermal mineralization at Brucejack (~185 Ma; Pretium Resources, 2013). Epithermal veins cutting earlier stockwork zones suggest that uplift occurred between Stages 3 and 4. The Stage 4 veins lack significant mineralization in the drilled resource area but offer potential in the eastern Mitchell area (see Appendix D for petrographic descriptions and photos of mineralization Stages and Appendix G for SEM photos of key minerals). 2.4.6. Structure Three phases of progressive deformation related to mid-Cretaceous transpression and the formation of the Skeena fold and thrust belt, structurally modify the Mitchell deposit. Deformation Phase 1 is defined by a pervasive east-trending, near-vertical S1 foliation, defined by aligned chlorite and muscovite. Below the Mitchell thrust, the S1 foliation (Fig. 2.18a) is subparallel to the sheeted Stage 1 quartz veins. Quartz veins other than the high quartz zone are commonly folded into F1 folds (Fig. 2.18b) that plunge steeply to the west, similar to the overall plunge of the orebody. S1 foliation, in particular the limbs of F1 folds, are locally overprinted by steep north-northwest plunging, gentle-open F2 folds (Deformation Phase 2; Fig. 2.18c; see Appendix A for complete structure data). Fig. 2.18. a) Poles to S1 cleavage, b) F1 fold axes, and c) F2 fold axes. 37 Fold geometry is a function of alteration type (Fig. 2.19). Isoclinal F1 folds in quartz veins are in intensely phyllic altered rocks; close folds are in chlorite and intermediate argillic altered rocks, and folds are not present in potassic altered rocks. Veins that comprise the high quartz zone are sheeted and preferentially develop F2 folds due to their east-west striking trends. Foliation is very well developed in the predominantly phyllic altered southeastern parts of the Mitchell zone and is poorly developed to non-existent in the western, potassic and transitional potassic areas (Fig. 2.15). The Mitchell thrust fault (Deformation Phase 3; 110.2 ± 2.3 Ma; Ar-Ar sericite; Margolis, 1993) is curviplanar, dips shallowly to the northwest and offsets the steeply plunging deposit ~1600 m to the southeast. The Mitchell thrust is in the footwall of the Sulphurets thrust and is interpreted as a younger, in-sequence, foreland-propagating fault. The Mitchell thrust clearly truncates the east-west striking sheeted quartz veins and the subparallel east-west striking S1 cleavage. The ore deposit is further imbricated by smaller thrust and reverse faults (Fig. 2.8) that are likely kinematically linked with the Mitchell thrust. West-northwest to west-southwest striking, steeply dipping predominantly sinistral strike Fig. 2.19. Qualitative estimate of strain for altered rocks of the Mitchell zone as indicated by F1 and F2 fold morphology. 38 slip faults (Fig. 2.8) are interpreted to have formed during Deformation Phase 3. Mineralization in the Mitchell deposit is offset at ~900 m depth by a 20 m thick deformation zone named here as the Mitchell Basal shear zone observed in holes M-08-62 and M-08-67 (Figs. 2.7a, b). 2.5. Geochronology of the Mitchell deposit Two Phase 1 and one Phase 2 medium-grained dioritic samples from the Sulphurets suite were collected for U-Pb zircon geochronology. One vein sample of molybdenite from the Mitchell deposit was collected from drill core for Re-Os geochronology (see Appendix H and Appendix I for additional information). 2.5.1. Analytical methods: U-Pb zircon Zircon analysis was by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) at the University of British Columbia’s Pacific Centre for Isotopic and Geochemical Research; detailed methods are described by Tafti et al. (2009). 2.5.2. Analytical methods: Re-Os (molybdenite) A molybdenite mineral separate was produced by metal-free crushing followed by gravity and magnetic concentration methods. Methods used for molybdenite analysis are described in detail by Selby and Creaser (2004) and Markey et al. (2007). The 187Re and 187Os concentrations in molybdenite were determined by isotope dilution mass spectrometry using Carius-tube, solvent extraction, anion chromatography and negative thermal ionization mass spectrometry techniques. A mixed double spike containing known amounts of isotopically enriched 185Re, 190Os, and 188Os analysis is used. Isotopic analysis is made using a ThermoScientific Triton mass spectrometer by Faraday collector. Total procedural blanks for Re and Os are less than <3 picograms and 2 picograms, respectively, which are insignificant for the Re and Os concentrations in molybdenite. The Chinese molybdenite powder HLP-5 (Markey et al., 1998), is analyzed as a standard. For this control sample over a period of two years, an average Re-Os date of 221.56 ± 0.40 Ma (1SD uncertainty, n=10) is obtained. This Re-Os age date is identical to that reported by Markey et al. (1998) of 221.0 ± 1.0 Ma. The age uncertainty is quoted at 2 level, and includes all known analytical uncertainty, including uncertainty in the decay constant of 187Re. 2.5.3. Results 22.214.171.124. Sample M-11-123; Phase 1 diorite A medium-grained, potassic altered, Phase 1 diorite (sample M-11-123; Fig 2.20a) sampled from a depth of 621 m yielded an age 196±2.9 Ma (Fig. 2.20a). The intrusion is interpreted to be intramineral as it is host to Stage 1 related veins that are irregularly shaped, have diffuse boundaries, and are disarticulated. 39 Fig. 2.20. U-Pb concordia diagrams for Sulphurets suite diorite in the Mitchell deposit. a) Sample M-11-123, b) sample M-07-49 and c) sample GF-12-02. See Figs. 2.7a, b for sample locations. 40 Fig. 2.21. Photomicrographs of the three dated Mitchell intrusions. a) Primary plag: plagioclase altered to cal: calcite, kf: K-feldspar replacement of groundmass and plagioclase, secondary bt: biotite replaced to chl: chlorite, sample M-11-123. b) Plagioclase ghosts are defined by sericite domains (plag->ser) and groundmass consists of quartz altered domains (gdms->qtz), sample GF-13-02. c) Phenocrysts and groundmass completely replaced by sericite-quartz (ser-qtz gdms), quartz vein clasts (high quartz zone) and pyrite-chalcopyrite-magnetite (py-cp-mt) accompanies alteration, sample M-07-49. 41 The sampled intrusion is diorite in composition from whole rock geochemistry (Fig. 2.13a). The porphyry contains 35% sericitized anorthitic plagioclase (0.5 - 2 mm in diameter), 7% K-feldspar (1-5 mm in diameter) with inclusions of hornblende in an altered, fine-grained groundmass (Fig. 2.21a). The sampled area is overprinted by pervasive and vein-controlled secondary K-feldspar, quartz, biotite, chlorite, magnetite, pyrite and chalcopyrite. 126.96.36.199. Sample GF-13-02; Phase 1 diorite A medium-grained, chlorite and phyllic altered, Phase 1 diorite that outcrops adjacent to the high quartz zone (sample GF-13-02; 423312 E, 6265278 N; Fig. 6) yielded an age of 192.2±2.8 Ma (Fig. 2.20b). The diorite is interpreted as a host rock to the high quartz zone in this location because there are no clasts of sheeted quartz veins in the intrusion and it appears to grade into the high quartz zone. The sampled intrusion is diorite in composition from whole rock geochemistry (Fig. 2.13a). The porphyry contains 35% sericitized laths interpreted to be replaced plagioclase (1-2 mm in diameter), 8% chlorite rhombohedral aggregates interpreted to be replaced hornblende (0.5-1 mm in diameter) and 5% equant anhedral K-feldspar partially replaced to sericite (2-3 mm diameter) in an altered, fine-grained groundmass (Fig. 2.21b). The intrusion is overprinted by Stage 2 sericite-chlorite-pyrite alteration with disseminations of secondary magnetite, trace chalcopyrite, 2% pyrite and ~10% quartz-chalcopyrite-pyrite veins by volume. 188.8.131.52. Sample M-07-49; Phase 2 diorite A sample (M-07-49, 320m; Fig. 2.7a) of fine-grained, Phase 2 diorite plug that cuts the high quartz zone and is overprinted by Stage 2 phyllic alteration yields an age of 189.9±2.8 Ma (Fig. 2.20c). The high quartz zone that is cut by the plug contains 60-90% quartz-pyrite-chalcopyrite veins in the contact area. The sampled intrusion is diorite in composition from whole rock geochemistry (Fig. 2.13a) and contains 1-10% quartz vein xenoliths that are most abundant in the contact areas. The porphyry contains 30% sericitized laths (~1 mm long) interpreted to be replaced plagioclase, 5% chlorite aggregates interpreted to be replaced hornblende, and 5% anhedral inclusion-rich K-feldspar in a fine-grained groundmass (Fig. 2.21c). The intrusion is overprinted by Stage 2 sericite-chlorite-pyrite alteration with 1% secondary magnetite, trace chalcopyrite and stringers of anhydrite and calcite. Sample M-10-116, Stage 2 molybdenite vein (Re-Os) Molybdenite in a sample (M-10-116, 214.6 m; Fig. 2.8) from a Stage 2 quartz-pyrite vein with yellow sericite alteration haloes in intensely sericite-pyrite-chlorite altered andesite breccia yielded an Re-Os age of 190.3±0.8 Ma. The vein host rock contains juvenile porphyritic angular andesite fragments 60% clasts 1 cm in diameter with < 1% subrounded granule-sized felsic clasts. The host rock is intensely altered to 42 sericite-pyrite-chlorite and is well foliated. The molybdenite-bearing vein is 3-4 mm wide with wavy margins, is parallel to foliation and contains a thin (1mm) selvage of white and yellow sericite alteration. The vein contains 75% grey-white microcrystalline quartz, 15% blue-grey elongate molybdenite disseminations, 8% brass-yellow anhedral to subhedral pyrite disseminations ( <0.2; mm) and 2% sericite. Geochronologic summary Phase 1 plutonism and Stage 1 alteration and copper-gold mineralization are bracketed between 198.9-189.5 Ma and 195-193.1 Ma. Crystallization ages of Phase 2 rocks are 192.7-187.1 Ma, close to the age of molybdenite mineralization (190.3 Ma), which we consider records Stage 2 alteration and mineralization. Advanced argillic, Stage 3 and Phase 3 plutonism are interpreted to be ~189.9 Ma and younger. 2.6. Discussion 2.6.1. Evolution of the Mitchell deposit The most significant mineralization and alteration event (Stage 1) was coeval with Phase 1 Sulphurets diorite intrusion, potassic and propylitic alteration, and the formation of a copper-gold core zone (Fig. 2.22 a; Table 2.3). An east-striking, steeply dipping sheeted high quartz zone (>60% volume of quartz) is developed in the contact area between Phase 1 diorite and Stuhini Group rocks or overlying Jack Formation (Fig. 2.22a). A Stage 2 molybdenite shell envelopes a Phase 2 Sulphurets diorite plug in the core region of the deposit (Fig. 2.12) related to overprinting phyllic and intermediate argillic alteration. The alteration developed laterally in Jack Formation sandstone and penetrated along fractured stockwork zones at deeper levels (Fig. 2.22b; Table 2.3). The molybdenite shell is contiguous with the core zone copper-gold stockwork emplaced during Stage 1 and Stage 2 events. Poorly mineralized massive Stage 3 pyrite veins are temporally related to a small Phase 3 Sulphurets diorite plug, advanced argillic alteration in the southeastern Mitchell zone and widespread advanced argillic alteration in the Snowfield zone (Fig. 2.22c; Table 2.3). Stage 3 alteration lacks significant mineralization. Epithermal textures in Stage 4 veins suggest uplift during a hiatus of hydrothermal activity between Stages 3 and 4. In the mid-Cretaceous, three phases of progressive deformation modified the deposit. Pervasive east-west striking S1 cleavage and associated steeply west-plunging F1 folds are overprinted by steeply north-plunging F2 fold trends similar to the McTagg Anticlinorium, and the Mitchell thrust fault separated the Snowfield and Mitchell zones (Fig. 2.22d). 43 Fig. 2.22. Model for the evolution of the Mitchell deposit. a) Stage 1 alteration and mineralization is related to the emplacement of Phase 1diorite and the high quartz after the emplacement of Premier diorite and monzonite; b) Stage 2 phyllic alteration is related to a molybdenite-rich envelope, Phase 2 diorite and the bornite breccia; c) Stage 3 advanced argillic alteration in shallow levels is related to massive pyrite veins, Phase 3 diorite and the diatreme breccia; d) mid-Cretaceous deformation related to Skeena fold and thrust belt; S1 pervasive cleavage F1, F2 folds and D3 Mitchell thrust, Mitchell Basal shear zone and the Sulphurets thrust. 2.6.2. The Mitchell deposit: a calc-alkalic porphyry The shallower porphyry deposits of the Sulphurets district have been variously classified as alkalic and calc-alkalic. For example, Logan and Mihalynuk (2014) referred to the Kerr deposit as calc-alkalic whereas Bissig and Cooke (2014) designated the KSM deposits as a whole as silica-saturated alkalic. At Sulphurets, quartz veins and molybdenum content are considered characteristic of calc-alkaline magmatism whereas the composition of the intrusions and alteration types are more typical of alkalic systems (Fowler and Wells, 1995). Ditson and Wells (1995) suggested the core chlorite with phyllic alteration halo at Kerr is atypical of British Columbia porphyry deposits and does not fit either alkalic or calc-alkalic models. Margolis (1993) interpreted early Cu-Au mineralization at Snowfield as a result of alkaline magmatism and related molybdenum and sericitic alteration (uncommon to alkaline systems) to a younger overprint. Pretium Resources (2013) considers epithermal high grade gold veins at Brucejack to be genetically related to alkaline Cu-Au porphyry mineralization at KSM. 44 Although the Mitchell deposit shares characteristics with alkalic porphyry systems, such as relatively high gold grades and magnetite in alteration assemblages (Bissig and Cooke, 2014), we consider the Mitchell a calc-alkalic porphryry deposit because: 1) the Sulphurets suite is subalkaline; 2) phyllic and clay alteration assemblages are abundant, 3) alteration assemblages contain high pyrite concentrations throughout; 4) alteration is extensive (> 4 km wide; Fig. 2.14); 5) silica contents in the ore zone are high (5-95% volume quartz veins); 6) it contains economically significant molybdenum mineralization; and 7) of the scale of the deposit (>4.5 billion tonnes of inferred resources combining the Mitchell and Snowfield; Pretium Resources, 2011; Seabridge Gold, 2015). 2.6.3. The relationship between the Snowfield and Mitchell deposits The Snowfield deposit occupies the hanging wall of the Mitchell thrust fault ~1.6 km east-southeast of the Mitchell deposit and is interpreted to be the shallower continuation of the Mitchell deposit (Fig. 2.22). This interpretation is based on the following: 1) metal zonation patterns indicate a core zone of elevated copper and gold with a shell of molybdenum-rich ore common to both deposits separated by the Mitchell thrust (Fig. 2.23; Savell and Threlkeld, 2013); 2) the Snowfield mineralization is hosted in Mitchell intrusions and Jack Formation quartz-bearing sandstone and conglomerate that are also in the highest stratigraphic levels of the Mitchell zone; and 3) the Snowfield deposit is composed predominantly of phyllic and argillic alteration assemblages whereas in the Mitchell deposit phyllic alteration is limited to shallow and easterly regions and penetrations at depth suggesting continuity of alteration assemblages between the two deposits. Margolis (1993) considered the advanced argillic alteration intensity in the Snowfield stockwork as evidence that it is a shallower system than the Mitchell stockwork. The Mitchell-Snowfield system is interpreted as a west-plunging, fault-dissected ore body that grades from Jack Formation sandstone hosted stockwork on surface in the Snowfield deposit to intrusion-hosted stockwork at depth in the Mitchell deposit. 2.7. Conclusion The calc-alkalic Mitchell deposit formed during emplacement of Sulphurets suite dioritic magmatism and is interpreted to be the deeper level of a once contiguous, gigantic porphyry deposit that included the structurally offset Snowfield deposit. The Mitchell-Snowfield mineral system was likely active for at least 2 million years. Mineralization is related to Sulphurets suite plagioclase-hornblende intrusions that cut and overprint earlier Premier suite monzonite and syenite intrusions. Three new U-Pb zircon ages for the Sulphurets suite diorite and a Re-Os molybdenite age indicate that magmatic-hydrothermal mineralizing processes started after 198.9 Ma and ended before 189.9 Ma. 45 Figure 2.23. Au, Cu, Ag and Mo metal grades of the Mitchell and Snowfield deposits, after Savell and Threlkeld (2013). 46 3. Structural geology of the Mitchell deposit and surrounding area 3.1. Introduction The Early Jurassic Mitchell Au-Cu-Ag-Mo porphyry deposit is part of the Sulphurets mineral district, located in northwestern British Columbia (Fig. 3.1). The district comprises Early Jurassic Cu-Au-Mo-Ag porphyry mineralization and epithermal Au-Ag deposits, that lie at the northern extent of a discontinuous, ~ 60 km long, narrow, north trending corridor of mineralized rocks. Undeveloped porphyry deposits within the Sulphurets district include the ‘KSM’ (Kerr-Sulphurets-Mitchell) deposits (that also includes the Iron Cap, Lower Iron Cap and Deep Kerr deposits), the Snowfield deposit, and high-grade Au-Ag veins in the Brucejack area (e.g., Valley of the Kings and West zone deposits). All of these deposits are hosted in Early Jurassic Sulphurets Suite plutonic rocks and volcanosedimentary strata of both Upper Triassic Stuhini and Lower Hazelton groups (Figs. 3.1, 3.2; Nelson and Kyba, 2014). In contrast to many porphyry systems, the Mitchell deposit underwent post-emplacement ductile and brittle deformation related to horizontal shortening and sinistral transpression associated with the mid-Cretaceous Skeena fold and thrust belt (Evenchick, 1991a; Margolis, 1993; Lewis, 2013). This deformation significantly altered the geometry of the porphyry system; however, because of the variability in the intensity of phyllic alteration associated with mineralization, the distribution of strain is very heterogeneous within the deposit. The primary thrust fault in the district is the Sulphurets thrust, which is part of the northeast-directed Skeena fold and thrust belt (SFTB). The SFTB is characterized by thin-skinned deformation of sub horizontal Bowser Basin sedimentary rocks that crop out ~8 km to the northeast of the study area (Fig. 3.2). The sedimentary strata underwent shortening associated with sinistral transpression that resulted in the formation of northwest and northeast trending, shallowly plunging folds and minor thrusting (Evenchick, 1991a, 1991b, 1999, 2001, 2007). The geometry of the structures is fairly typical of shortening in upper crustal sedimentary rocks. The Mitchell deposit rocks form the basement of the SFTB as a result of preferential uplift and erosion, the Mitchell deposit basement rocks are exposed at surface just west of the Bowser Basin rocks. The distribution of strain developed in Early Jurassic and Upper Triassic basement rocks within the Sulphurets district is distinctly heterogeneous because of the abundance of plutonic and volcanic rocks. Hydrothermally altered intrusive rocks and the presence of early Jurassic structures affect the way in which strain is accommodated during shortening. In the Sulphurets district all folds are steeply plunging and the intensity and orientation of an axial planar cleavage (Kirkham, 1963; Bridge, 1992; Margolis, 1993; Kramer, 2014; Febbo et al., 2015) is seemingly controlled by the orientation and density of veins and hydrothermal alteration of the porphyry systems. Hence, rocks in the porphyry systems are locally penetratively strained whereas, outside the mineralized 47 Fig. 3.1. Location of the Kerr-Sulphurets-Mitchell (KSM) property. Modified from Colpron and Nelson (2011). system, deformation was accommodated by open folds, localized, brittle faults and a poorly developed spaced disjunctive cleavage. I show that strain partitioning plays a key role in the post-emplacement structural modification of the Mitchell deposit and the distribution of ore grade. All deposits within the Sulphurets district lie in the footwall or immediate hanging wall of the Sulphurets thrust fault (Fig. 3.3) and all porphyry-related mineralization and plutonism are intimately associated with the Jack Formation, a regional marker horizon that lies above a regional Late Triassic-Early Jurassic angular unconformity, and demarcates the beginning of a basin-filling episode. Nelson and Kyba (2014) proposed that the Sulphurets thrust fault is a reactivated Early Jurassic, western basin-bounding fault (the ‘proto-Sulphurets’ fault) located between a topographic high to the west (expressed now as the McTagg anticlinorium; Fig. 3.3) and basin sedimentation (i.e., Jack Formation) to the east (Fig. 3.3). Nelson and Kyba (2014) also consider the proto-Sulphurets fault to be a first order structural control on the localization of the porphyry system. 48 Fig. 3.2. Tectonic setting of Kerr, Sulphurets, Mitchell, Iron Cap, Snowfield, Brucejack and other Triassic-Jurassic porphyry and related deposits in Quesnellia and Stikinia (from Nelson and Kyba, 2014). Here, I describe the geometry and kinematics of structures that offset the Mitchell deposit. The variation in foliation development is described and the role of hydrothermal alteration and strain partitioning on the resultant shape of the ore body are discussed. An older, Jurassic (?) deformation event that is preserved in the more competent and less strained rocks is documented. From these observations, the Mitchell deposit is placed into a regional tectonic framework, that is consistent with the deposit having been emplaced within a Jurassic basin environment; and a model for the structural evolution of the Sulphurets district is constructed. 3.2. Regional Geologic setting The Mitchell deposit is located near the western margin of the Bowser Basin and is a part of the Stikine terrane of the Intermontane Belt of the Canadian Cordillera (Fig. 3.1). The Stikine terrane comprises three unconformity-bounded island arc volcanosedimentary successions that span 200 m.y. These include the 49 Fig. 3.3. Geological compilation of the Sulphurets district. Data is compiled from Febbo et al. (2014) for the Seabridge Gold claims (western map area); modified from Margolis (1993) and Febbo et al. (2014) for the Snowfield area, and; modified from Greig and Greig (2013) and Febbo (2010) for the Brucejack area in the southeastern map. New stratigraphic designations (e.g., Jack Formation) derived from Nelson and Kyba (2014). Stikine assemblage (Devonian to Mississippian; Anderson, 1989; Greig, 1992; Logan et al., 2000), the Stuhini and Takla groups (Middle to Late Triassic), and the Hazelton Group (Late Triassic to Middle Jurassic; Fig. 3.2). Mesozoic plutonic suites include Stikine and Copper Mountain (Late Triassic, coeval and comagmatic with Stuhini Group), Texas Creek (coeval and comagmatic with the Hazelton Group; Early Jurassic), and Three Sisters (Middle Jurassic; Fig. 3.2). Gold-rich deposits are associated with both the Late Triassic and Early Jurassic intrusive suites in northwestern Stikinia. East of the Sulphurets district, the Bowser Lake Group (mid-Jurassic to mid-Cretaceous) is a molassoid sedimentary succession containing debris derived from the collision of the Intermontane terranes and the edge of ancestral North America (Evenchick et al., 2007; Figs.3.2, 3.4). Strata of the Stuhini, Hazelton and Bowser Lake groups were deformed as part of the SFTB which is inferred to result from sinistral plate convergence early in the history of the fold belt. In the Bowser Basin, western domains of northeast-trending folds and eastern domains of northwest-trending folds 50 Fig. 3.4. Stratigraphic column for stratigraphy in northwestern Stikinia (modified after Logan and Schiarizza, 2011). characterize the fold belt with local areas of interference and dome-and-basin style folding. The relative age of the two fold sets has not been resolved (Evenchick, 2001). West of the Bowser Basin, folds in the lower Hazelton and Stuhini groups plunge north-northwest in the Stewart area (Alldrick, 1993) and north to northeast in the southern Iskut area, producing local culminations such as the McTagg anticlinorium, a north-trending, Cretaceous structural culmination bounded by thrust faults that verge away from its hinge, particularly the east-vergent Sulphurets fault (Evenchick, 1991a; Lewis, 2013; Nelson and Kyba, 2014; Fig. 3.2). The Sulphurets thrust is a foreland propagating thrust on the east limb of the McTagg anticlinorium that is situated structurally above, and spatially correlated with all of the porphyry deposits in the Sulphurets district. Structurally below the Sulphurets thrust, the Mitchell thrust is an east-vergent splay of the Sulphurets thrust that separates the Snowfield deposit in its hanging wall from the Mitchell deposit in its footwall and has an estimated 1600 m of displacement (Savell and Threlkeld, 2013; Febbo 51 et al., 2015). The youngest movement along the Mitchell thrust is 110.2±2.3 Ma (Ar-Ar, sericite; Margolis, 1993). District-scale folds in the Sulphurets district include a north-plunging synform west of the Sulphurets thrust fault that folds unmineralized Jack Formation sedimentary rocks, and a north-plunging synform that folds hydrothermally-altered Jack Formation volcanosedimentary rocks east of the Brucejack fault (Fig. 3.3.). The mineral deposits of the Sulphurets district are proposed to be controlled by basin-bounding growth faults (Fig. 3.3). For example, the north-south striking ‘proto-Brucejack’ fault (Pretium Resources, 2013; Nelson and Kyba, 2014) and the north-south striking proto-Sulphurets thrust (Nelson and Kyba, 2014) both lie parallel to a ~10 km linear trend of altered and mineralized rocks (Kirkham and Margolis, 1995; Febbo et al., 2015) and have been interpreted as syn-depositional basin-margin growth faults that overlapped temporally with both porphyry and epithermal mineralization in the district (Pretium Resources, 2013; Nelson and Kyba, 2014; Febbo et al., 2015) and have subsequently been reactivated. The Sulphurets district contains five undeveloped porphyry deposits (Kerr, Sulphurets, Snowfield, Mitchell and Iron Cap) and the high-grade epithermal Brucejack deposit (Fig.3.3). Porphyry deposits in the Sulphurets district are related to Early Jurassic Mitchell intrusions that are partial host to all porphyry deposits in the district. Here, the Mitchell and Snowfield are considered the same porphyry system, with the Snowfield deposit representing the offset, shallower portion of the Mitchell deposit (Febbo et al., 2015). The KSM, Snowfield and Brucejack deposits are interpreted to have been formed from the same mineralizing system (Pretium Resources, 2013; Febbo et al., 2015). Rocks in the Sulphurets district have been affected by subgreenschist regional metamorphism that occurred at or by 110 Ma (Kirkham, 1963; Henderson et al., 1992; Margolis, 1993). Most rocks in the Sulphurets area contain a post-mineral, steeply dipping cleavage of variable orientation and intensity (Kirkham, 1963; Margolis, 1993; Bridge, 1993; Kramer, 2014; Fig. 3.5). In the Northern Sulphurets panel and the North Mitchell areas (Fig. 3.5), foliation strikes moderately to steeply southwest. A pervasive (S1) steeply dipping cleavage is heterogeneously developed in the Iron Cap area (Fig. 3.5.) that strikes east-west and a non-pervasive, steeply dipping cleavage is present that strikes south and southwest. The Kerr area cleavage (S1) is folded forming F2 folds with an axial planar cleavage that strikes northwest and dips steeply west (S2; Fig. 3.5). In the Mitchell and Snowfield areas (Fig. 3.5), the cleavage strikes easterly and dips steeply north. Margolis (1993) proposed that the east-striking cleavage, which is axial planar to cm-scale, steeply plunging folds (F1; Fig. 3.5), developed in the Jurassic. F1 folds in the Sulphurets district are mostly restricted to folded hydrothermal veins that have a subvertical westerly to northerly plunge in the Iron Cap area (Fig. 3.6a), are predominantly westerly plunging in the Mitchell and Snowfield areas (Figs. 3.5, 3.6b, c), plunge northerly in the Kerr area (Figs. 3.5, 3.6d), and are subvertical in the Brucejack area (Fig. 3.6e). In this study, S1 is axial planar to F1 folds, F2 folds overprint 52 Fig. 3.5. Poles to cleavage in the KSM-Snowfield area. The mean of the attitude of F2 fold axes for Kerr from Kramer (2013) and Febbo et al. (2014); the mean of the attitude for F1 and F2 in the Mitchell and Snowfield subdistricts also plotted (this study); cleavage data other than Mitchell and Snowfield from Febbo et al. (2014). Undifferentiated cleavage not plotted at Kerr. and fold S1, and a third generation (F3) asymmetric folds are associated with east-vergent thrusting (Fig. 3.6f). 3.3. The Mitchell ore deposit: stratigraphy, plutonism and mineralization The Mitchell deposit is centred amongst a dense cluster of Mitchell diorites, part of the Sulphurets plutonic suite (Fig. 3.7). Within the Mitchell deposit, multiple stocks of uniform medium-grained hornblende-plagioclase porphyritic Sulphurets suite diorite grade into coarse-grained porphyritic K-feldspar-hornblende-plagioclase diorite at depth. Three pulses of Sulphurets suite diorite (Phase 1-3) form a crudely elliptical 2x1 km outcrop with sills and dikes extending to the east (Fig. 3.7). Phase 1 plutonism is dated as 196±2.9 Ma and 192.2±2.8 Ma (U/Pb zircon); Phase 2 plutonism is dated as 189±2.8 Ma (U/Pb zircon; Febbo et al., 2015). The mineralized veins are hosted within and immediately peripheral to Phase 1 and 2 plutons. 53 Fig. 3.6. Examples of F1-3 buckle folds in the Sulphurets district. a) Gentle folds (F1) in banded quartz-pyrite-chalcopyrite vein with a pervasive axial planar cleavage (S1). Note that veins oriented west-north-west are not folded, Iron Cap deposit, 424569 E, 6267446 N. b) Isoclinal fold train of F1 buckle folds in quartz-pyrite-chalcopyrite vein. Folds have a pervasive axial planar cleavage, Mitchell deposit, 423190 E, 6265643 N. c) Intense, pervasive S1 cleavage is axial planar to tight fold in thin quartz-pyrite vein with gentle, north-plunging F2 fold of vein and S1 in north limb of F1, Snowfield deposit, 424325 E, 6264203 N. d) North-northwest-plunging ptygmatic to isoclinal fold (F2) in a quartz-pyrite banded vein and associated transposed foliation (ST) of S1 and S2, axial planar to F2, Kerr deposit, 421782 E, 6258847 N. e) Close folds in quartz-pyrite veins plunge west (F1), with well-developed axial planar cleavage S1, gentle F2 folds in veins plunge north, 426982 E, 6258179 N. f) Asymmetric, open to isoclinal buckle folds (F3) in calcareous mudstone of Stuhini Group that formed during movement along the Sulphurets thrust, 425044 E, 6268079 N. 54 Fig. 3.7. Geology of the Mitchell deposit and surrounding area. 55 The plutonic rocks are emplaced into thinly bedded sedimentary strata and overlying felsic volcanic rocks of the Stuhini Group (Triassic) that outcrop west of the Sulphurets plutons (Fig. 3.7) and into basal Hazelton Group (Jurassic) sandstone, conglomerate and andesitic rocks of the Jack Formation (Early Jurassic) that outcrop east of the Sulphurets plutons (Fig. 3.7). Mineralization, veins and alteration in the Mitchell deposit are divided into four Stages (Margolis, 1993; Febbo et al., 2015). 1) Stage 1: Cu-Au porphyry stockwork and tabular veins in the high quartz zone (Fig. 3.7) are coeval with Phase 1 plutonism, and associated with potassic alteration (K-feldpsar-magnetite-biotite-quartz-chlorite), transitional potassic alteration (magnetite-quartz-chlorite-biotite), albitic alteration (albite-quartz-chlorite) and propylitic alteration (epidote-chlorite-quartz-calcite), 2) Stage 2: Cu-Mo stockwork coeval is with Phase 2 plutonism and accompanied by chlorite alteration (chlorite-quartz), intermediate argillic alteration (chlorite-muscovite-quartz) and phyllic alteration (quartz-muscovite-illite), 3) Stage 3: massive pyrite veins with no significant mineralization are coeval with Phase 3 plutonism and associated with advanced argillic alteration (pyrophyllite-kaolinite-rutile) and 4) Stage 4: epithermal high grade Au-Ag-Cu-Pb-Zn veins that may be related temporally to similar epithermal mineralization at the Brucejack deposit ~185 Ma (U-Pb zircon; Pretium Resources, 2013; Febbo et al., 2015). Copper mineralization occurs primarily as chalcopyrite both within quartz veins and disseminated within the plutons and country rocks, with minor copper in bornite that is restricted to a bornite breccia body located at depth; and minor copper within tennantite. Molybdenum mineralization is hosted as molybdenite disseminations within, and as halos to, quartz veins that are spatially associated with phyllic alteration. Gold occurs as disseminated electrum in chalcopyrite and pyrite grains found in quartz veins, and in plutonic rocks and immediately adjacent country rocks (Febbo et al., 2015). 3.4. Field observations The Mitchell deposit was structurally modified by a progressive deformation attributed to sinistral transpression associated with the mid-Cretaceous SFTB. The structures that formed during this progressive deformation are separated into Deformation Phases 1, 2 and 3. The Mitchell deposit was mapped in detail (1:1000 scale) and most of the observations presented below were obtained from the Mitchell deposit. The Mitchell deposit is located in the immediate footwall of Mitchell thrust fault (Fig. 3.7) The Snowfield deposit is interpreted as the thrust-offset, shallower portion of the Mitchell deposit (Febbo et al., 2015), and observations taken from the Snowfield deposit (i.e., structurally above the Mitchell thrust) are also presented. Stages of mineralization, veins and alteration as well as Deformation Phases are equivalent in both deposits. The intensity of strain within the deposit is directly correlated with the intensity and type of porphyry alteration associated with the mineralizing events (e.g., Kirkham, 1963; Bridge, 1992; and 56 Margolis,1993). Strain is partitioned into portions of the deposit containing significant amounts of mechanically ‘soft’ hydrothermal muscovite, pyrophyllite, illite, and chlorite that resulted in the development of a locally, penetrative foliation. The intensity of foliation development is spatially irregular and entirely dependent on the geometry of the porphyry hydrothermal and mineralizing system. In addition, hydrothermal quartz veins are extensively folded as a result of the competence (strength) contrast between the altered (weak) matrix and the relatively strong hydrothermal veins. In areas where the matrix material is relatively strong (e.g. high K-feldspar content) the competence contrast is small and veins do not buckle (fold). The map area is divided into Structural Domains1-4 (Fig. 3.8) based on the relative intensity of strain recorded (i.e., foliation and fold development) in the map area, with Structural Domain 1 comprising the least deformed areas and Structural Domain 4 the most deformed. For all Structural Domains, fold geometry and orientation are a result of the initial orientation of the veins with respect to the flattening direction, the thickness of the veins, and the vein composition. Structural Domains are designated based on alteration not lithology because the diorite and the surrounding volcanosedimentary strata behave similarly due to comparable mineralogy (i.e., high feldspar to quartz ratios) and homogeneous textures. Structural Domain 1 rocks are massive to poorly foliated and veins are not folded, except in local outcrops with high chlorite:K-feldspar ratios (Figs. 3.9a, b). The rocks have undergone potassic, transitional potassic, albite and propylitic alteration (Fig. 3.8). Rocks assigned to Structural Domain 1 include Stuhini Group sedimentary rocks (Triassic) and the Mitchell intrusions (Early Jurassic). Structurally above the Mitchell thrust, unaltered rocks are also assigned to Structural Domain 1 (e.g. Fig. 3.9a). Structural Domain 2 rocks contain abundant chlorite alteration accompanied by quartz-magnetite±sericite. An east-west striking foliation is well developed and all porphyry-related veins are folded, and plunge westerly (Figs. 3.9c, d). Structural Domain 2 is developed in Phases 1-3 diorite (Fig. 3.9d) and Jack Formation volcaniclastic strata (Fig. 3.9c). Structural Domain 3 is located directly below the Mitchell thrust, in the high quartz zone where veins have a sheeted geometry (Figs. 3.8, 3.9e). Structural Domain 3 rocks are strongly sericitized and contain a well-developed foliation. Steeply plunging folds are common and ptygmatic folds are locally common in areas with high wall rock: vein ratios (Fig. 3.9f). Structural Domain 4 comprises the least competent and most highly strained rocks in the deposit (Figs. 3.9g-j). Rocks are typically intensely foliated and porphyry-related veins are tightly to isoclinally folded. Phyllic and intermediate argillic alteration assemblages that characterize Structural Domain 4 occur in Jack Formation sandstone (Fig. 3.9j), conglomerate (Fig. 3.9.i), and andesite breccia and Phase 1 and 2 diorite (Fig. 3.9g). 57 3.4.1. Mid-Cretaceous SFTB-related deformation (D2) Structures associated with mid-Cretaceous shortening are the most prominent in the field area. In particular, the main foliation (S1) and associated folds are the most prevalent structures. Older structures have been discerned (D1) and are described after this section. Below, all structures that are interpreted to have formed in the mid-Cretaceous are described from the oldest to youngest: Deformation Phase 1, Deformation Phase 2 and Deformation Phase 3. 184.108.40.206. Deformation Phase 1 Field observations: A pervasive, variably developed, axial planar, pressure solution cleavage (S1) is defined by hydrothermal chlorite, muscovite, illite, pyrophyllite and other phyllosilicate minerals (see section below; Figs. 3.9c-j; see Appendix A for complete structure data). The foliation strikes ~270° and dips steeply to the north (Fig. 3.8). The foliation is axial planar to west-plunging buckle folds in porphyry-related, quartz veins described below. The limbs of isoclinally folded, hydrothermal veins are generally sub-parallel to S1. The foliation is weakly developed in Structural Domain 1 (Figs. 3.9a, b), well-developed in Structural Domain 2 (Figs. 3.9c, d) and intensely developed in Structural Domain 3 (Figs. 3.9e, f) and Structural Domain 4 (Figs. 3.9g, j; Fig. 3.8). In Structural Domain 3 (the high quartz zone), S1 is subparallel to the west-northwest strike of a thick package (up to 250 meters) of sheeted quartz veins (Fig. 3.8). The foliation is best described as a flattening foliation (Figs. 3.10a-d) formed during shortening: there is little to no evidence for extensive non-coaxial shear associated with the foliation. For example, vein folds associated with the cleavage can exhibit S, M and Z fold geometries consistent with coaxial flattening (Fig. 3.10c). The easterly striking S1 cleavage is observed throughout the Mitchell valley from the Snowfield area to the Iron Cap area, both west and east of the Brucejack fault (Fig. 3.5). Strata containing an easterly striking cleavage in the Mitchell valley includes: Stuhini Group sedimentary strata (Triassic), Jack Formation volcanosedimentary strata (Early Jurassic; basal Hazelton), Treaty Ridge member (Early Jurassic Betty Creek Formation; Lower Hazelton), and Upper Hazelton Bruce Glacier Member felsic volcanic rocks (Early Jurassic Salmon River Formation; Upper Hazelton). Pumice and lithic-bearing, felsic, pyroclastic lapilli tuff, east of the Brucejack fault that contains an easterly striking, penetrative S1 fabric, is regionally constrained in age to 178-172 Ma (Lewis, 1992, 2013; Bruce Glacier Member). The S1 cleavage overprints fossils from the Treaty Ridge Member of the Betty Creek Formation east of the Iron Cap deposit. Regionally the Treaty Ridge Member has been constrained in age to older than 170.3 Ma (Lewis, 1992, 2013). Margolis (1993) concludes that metamorphic heating and related S1 cleavage growth occurred at or before 110.2 ± 2.3 Ma (Ar-Ar plateau; sericite in pressure shadow). 58 Fig. 3.8. Alteration map for the Mitchell zone and associated Structural Domains. Alteration above the Mitchell thrust fault not plotted.59 Fig. 3.9. Hand sample photographs of Structural Domains 1- 4. Structural Domain 1: a) unaltered Jack Formation conglomerate from the Iron Cap area, above the Mitchell thrust, 424975 E, 6267960 N; b) 60 Sulphurets suite Phase 1 diorite porphyry altered to K-feldspar-quartz-magnetite-phengite (drill hole M-11-123, 628 m). Structural Domain 2: c) foliated diatreme breccia with quartz vein clast (Qz) altered to chlorite-quartz-muscovite-pyrite, 423682 E, 6265473 N; d) foliated Phase 2 diorite altered to chlorite-quartz-magnetite, 426160 E, 6265160 N. Structural Domain 3: e) sheeted quartz veins and pyrite-replaced selvages, S1 subparallel to veins, 423029 E, 6265248 N; f) sheeted quartz veins and sericite-replaced wall rock selvages with ptygmatic vein folds, S1 subparallel to veins, 423029 E, 6265248 N. Structural Domain 4: g) penetrative cleavage defined by muscovite and illite in intensely altered Sulphurets suite diorite, 423684 E, 6265293 N; h) penetrative cleavage defined by paragonite-illite in intensely altered feldspathic sandstone, a thin molybdenite (Mo) vein is oblique to S1, 423623 E, 6265350 N; i) Jack Formation conglomerate with chert clasts with a matrix replaced to sericite that defines a well-developed foliation, 423648 E, 6265491 N; j) penetrative cleavage in Jack Formation feldspathic sandstone altered to sericite, 423657 E, 6265318 N. S1 is bracketed between ~170 and ~110 Ma. To date there is no documentation of a deformation event that occurs between 170 and 110 Ma other than the SFTB. Bridge (1993) dated a foliated monzonite dike in the Kerr area at 124 ± 4 Ma (K-Ar) and interpreted this to represent the age of the end of ductile deformation in the rock. The S1 cleavage in the Mitchell area is demonstrably the oldest deformation fabric caused by shortening associated with the SFTB. Therefore, we interpret that S1 formed at the onset of SFTB deformation that spans ~120-110 Ma (Evenchick, 2007). F1 folds are isoclinal to gentle in geometry, and typically occur as buckle folds in quartz veins that are heterogeneously distributed throughout the Mitchell deposit. Folds generally plunge steeply towards the west-northwest. Fold geometry and abundance are controlled by vein orientation, thickness and competence contrast between the quartz veins and host rock. Veins that strike north-south are tightly folded (Fig. 10b) whereas veins that strike east-west are more commonly boudinaged parallel to S1. Fold intensity is a direct function of vein thickness; where two veins of the same orientation are folded, the thinner vein will develop higher amplitude and shorter wavelength fold trains. F1 folds in Structural Domain 2 are gentle to closed in geometry (Fig. 3.10c) with moderate to steep westerly plunges. Fold amplitudes in Structural Domain 2 range 1-100 mm and fold trains are common in north striking veins with wavelengths between 2 cm (in thinnest veins) to 20 cm (in thicker veins). In Structural Domain 3, the high quartz zone, the rock is composed of 60-100% veins which are predominantly oriented parallel to the foliation and, hence, are not folded. In areas of relatively fewer quartz veins in Structural Domain 3 (e.g., 60-70%), and where veins are not oriented parallel to foliation, F1 folds are gentle to closed in geometry, have small amplitudes (< 2 cm) and plunge steeply along a range of trends, that is dependent on the original vein orientation. In Structural Domain 4, F1 folds are abundant in the rheologically weak rocks. Most of Structural Domain 4 is characterized by low quartz vein abundance (e.g., 5-40%), and the veins have several different orientations. The resulting competence contrast generated well-developed and widespread F1folds. The folded veins plunge steeply to the west, are open to isoclinal (Fig. 3.10d) and are the most non-cylindrical as a result of interference with well-developed F2 folds (described below). In 61 Fig. 3.10. Examples of F1 buckle folds: a) erosional exposure of nearly cylindrical hinge lines to F1 folds in Structural Domain 2, 423412 E, 6265488 N; b) north-south striking veins preferentially folded (F1), east-west striking veins are not folded, Structural Domain 2, 422991 E, 6265592 N; c) s, m and z folds in quartz-pyrite vein in Structural Domain 2, 424030 E, 6265547 N; d) tight F1 fold train in Structural Domain 4, 421982 E, 6258792 N. areas with high quartz vein abundance (e.g., 40-60%), where the veins are sheeted and strike east-west (i.e., parallel to S1), F1 fold geometries are not favoured. Within the most competent rocks of Structural Domain 1, veins are generally not folded or are weakly folded. The overall shape of the Mitchell ore body mimics the geometry of the F1 folds: the ore body plunges steeply to the west. The steep dip and steep plunge of the F1 folds (Figs. 3.11b-d) is not the anticipated orientation for folds that were formed during subhorizontal shortening; typically such folds would have a shallow plunge. The steep dip of the hydrothermal veins and the steep plunge to the folds are interpreted to reflect the original orientation of the veins before deformation. That is, the veins are interpreted to have been steeply dipping when emplaced during the related hydrothermal event. To test this, quartz vein abundance was contoured from surface and drill core estimates (Fig. 3.12). In competent Structural Domain 1, west of the high quartz zone, quartz-vein-abundance contours trend northerly in areas that veins generally strike easterly. In contrast, in the incompetent Structural Domain 4, east of the high quartz zone, quartz-vein-abundance 62 Fig. 3.11. Equal area stereographic projections of Deformation Phase 1 beneath the Mitchell thrust fault: a) contoured poles to S1 pressure solution cleavage in Structural Domain 1; b) contoured poles to S1 pressure solution cleavage and F1 fold axes in Structural Domain 2; c) F1 fold axes and poles to S1 pressure solution cleavage in Structural Domain 3; d) contoured poles to S1 pressure solution cleavage F1 fold axes in Structural Domain 4; and e) contoured poles to S1 pressure solution cleavage in the Snowfield slide area (Structural Domain 4) are anomalously north-dipping as a result of rotation. contours are tighter, and trend easterly and veins also strike easterly; this relationship is interpreted to reflect a higher degree of transposition between the veins and the foliation in the weaker rocks. This is interpreted to indicate that the veins were likely originally steeply dipping and were subsequently folded into steeply plunging folds. S1 is locally offset by conjugate sets of northwest-striking dextral-reverse, and southwest-striking sinistral-reverse ductile shear bands, that range in strike length from millimeter- (Fig. 3.13a) to meter-scale (Fig. 3.13b), and are mostly spatially restricted to Structural Domains 3 and 4. Crenulation folds within the shear bands plunge moderately north within dextral- and sinistral-reverse shear bands and plunge shallowly towards the east in reverse shear bands (Fig. 3.13c). As some of these shear-related folds coincide in geometry and orientation with Deformation Phase 2 folds (F2), it is unclear whether the shear bands cut F2 or are overprinted by it. The acute bisectrix of the conjugate shear band dips 51° 63 Fig. 3.12. Map of quartz-vein-abundance contours beneath the Mitchell thrust fault. 64 Fig. 3.13. Field photographs and stereographic projections of Deformation Phase 1 shear bands. a) Conjugate dextral-sinistral pair of shear bands in Structural Domain 3, view looking down foliation, 423186 E, 6265193 N; b) millimeter-spaced dextral (green) and sinistral (blue) shear bands cut S1 at a low angle in Structural Domain 4 (Snowfield slide), view looking down foliation, 423623 E, 6265350 N; c) reverse shear bands in Structural Domain 3 with crenulation folds, view toward southeast on cliff 423029 E, 6265248 N; and d) stereographic projections of poles to predominantly dextral (green), sinistral (blue) and reverse (black), the location of σ1 calculated from the average of the sinistral-reverse and dextral-reverse clusters. toward 122°, which provides an estimate of 25° toward 190° for σ1 (Fig. 3.13d). The orientation of σ 1 consistent with north-south compression and the ductile nature of the shear bands is consistent with the interpretation that these shear bands formed as late stage features during the same shortening that formed the S1 fabrics. Microscopic observations: The least deformed rocks, Structural Domain 1, have undergone minor brittle fracturing of quartz grains, and quartz has weak undulose extinction; phyllosilicate minerals (e.g., biotite, chlorite and sericite) can define a very weak fabric (Fig. 3.14a). There is no evidence for pressure solution (e.g., pressure 65 Fig. 3.14. Photomicrographs of Deformation Phase 1 microstructure. a) Structural Domain 1: Potassic-altered diorite contains a potassium feldspar (kf) vein with evidence of grain boundary mobility, secondary, equant kf replacements of groundmass, primary plagioclase (plag) phenocrysts overprinted by foliated, narrow, discontinuous, sericite S1 wisps, drill core- M-11-123, 621.6 m. b) Structural Domain 2: quartz vein in diorite contains deformation lamellae, evidence for bulge (blg) recrystallization and dynamically recrystallized quartz grains (dyn), M-07-26, 212.6 m. c) Structural Domain 2: foliation (S1) in chlorite-quartz altered diorite defined by chlorite (chl) located in groundmass and also in pressure shadows to pyrite (py) and chalcopyrite (cpy), M-07-26, 252.3 m. d) Structural Domain 3 is characterized by sheeted quartz veins (‘Q’ domains) with undulose extinction, bulge recrystallization (blg), and Mode I fractures in pyrite that are perpendicular to S1 cleavage; boundary between vein and sericitized wall rock (ser; ‘S’ domains) are straight to embayed; wall rock contains pyrite (py) grains with recrystallized pressure shadows (shad) of quartz, sample GF-12-16A, 423223 E, 6265144 N. e) Phyllic-altered feldspathic arenite (Jack Formation, Structural Domain 4) with relict quartzose clasts (qz), pressure solution cleavage (S1) defined by sericite, note post-S1 extensional, dextral shear band, sample D3-3, 424856 E, 6265635 N. 66 shadows), these rocks are weakly strained. The distribution of disseminated metals (e.g., chalcopyrite and molybdenite) is generally homogeneous. In Structural Domain 2, the S1 cleavage is moderately developed, defined by a platy alignment of hydrothermal chlorite, muscovite, and biotite. Most microstructures indicate that solution transfer processes accommodated some strain. Pressure shadows are weakly developed and are composed of quartz, muscovite, chlorite, calcite and anhydrite. Quartz exhibits straight grain boundaries against phyllosilicates, indicating dissolution at grain contacts. Quartz has extensive undulose extinction and deformation lamellae, and has limited bulge recrystallization (Fig. 3.14b). Quartz grains in porphyry-related veins show limited dynamic recrystallization (Fig 3.14b) and are generally equant in shape with seriated grain boundaries. Brittle fracture and boudinage are common in both disseminated and vein-hosted pyrite. Chalcopyrite grains range in shape from equant to slightly elongate, where they are oriented sub-parallel to phyllosilicate minerals that define S1 (Fig. 3.14c). In addition, the chalcopyrite (and pyrite) can be concentrated in the phyllosilicate seams (or ‘P domains’), and probably represents the insoluble residue that was left behind during the solution transfer processes. Structural Domain 2 demarcates the initiation of segregation of the metals as a result of the solution transfer process. Based on the deformation microstructure, the temperature of deformation is interpreted as > 300°C and possibly as high as 350°C (e.g., Stipp et al, 2002; Passchier and Trouw, 2005). In Structural Domain 3 (the high quartz zone), there is a well-developed pressure solution cleavage (S1) defined by aligned sericite or chlorite layers (or ‘P domains’). Quartz textures record intracrystalline deformation (e.g., undulose extinction and deformation lamellae; as well as some evidence for dynamic recrystallization via grain boundary mobility (e.g., bulge recrystallization). Fibrous pressure shadows about pyrite are common, and the fibres are always oriented parallel to the S1, not oblique to the foliation. This observation is consistent with the interpretation that the main foliation formed from flattening and not from shearing during a non-coaxial strain. Quartz commonly has abundant fluid inclusions and straight to cuspate boundaries where in contact with P domains (Fig. 3.14d), which indicates dissolution of quartz and probably subsequent precipitation in pressure shadows. Pyrite and chalcopyrite are disseminated as coarse, equant grains with Mode I (i.e., extension) fractures perpendicular to S1 in Q domains and as finer disseminations with relatively large pressure shadows in P domains. Abundant lenses of pyrite-chalcopyrite in quartz veins (Q domains) do not have well-developed pressure shadows and may reflect that sulphides filled fractures at the time of emplacement rather than a flattening-related concentration of minerals. In Structural Domain 4, an anastomosing pressure solution cleavage (Fig. 3.14e) is well developed throughout, pressure shadows are ubiquitous about disseminated pyrite, and layer parallel compositional 67 Fig. 3.15. Microphotographs illustrating pressure solution cleavage in Structural Domain 4, from a quartz vein xenolith-bearing intrusion breccia. Drill hole M-08-67, 738 m: a) full thin section scan showing location of photographs c, d, e, and f, cross polarized light; b) sketch of quartz (Q) and phyllosilicate (P) domains with traces of pressure solution cleavage seams (PS); c) clays and other insoluble minerals (i.e. , pyrite (py) and chalcopyrite (cp)) are concentrated in pressure solution seams; plane polarized and reflected light; d) quartz (qz) grains display blunt boundaries due to dissolution in contact with pressure solution (PS) cleavage, chalcopyrite (cp) and pyrite (py) proximal to cleavage seam; e) fibrous quartz (qz)growth in pressure shadow to pyrite (py) grains. Note that tennantite (tn) and chalcopyrite (cp) precipitate in a Mode I fracture that is orthogonal to c-axis of quartz grains; cross polarized and reflected light; f) A few pyrite (py) and chalcopyrite (cp) grains are elongated subparallel to cleavage and pressure solution seams. Pyrite also contains Mode 1 extension fractures oriented perpendicular to the pressure solution cleavage orientation; plane polarized and reflected light. 68 banding is common. In a few easterly samples, extensional, sinistral shear bands cut S1 at a low angle (Fig. 3.14e). The S1 fabric is defined by mica-rich bands with lattice preferred orientation and pressure solution seams lined with sulphide minerals (Figs. 3.15a, b). In plane-polarized light, the pressure solution cleavages are defined by brown to black, less soluble minerals including pyrite and chalcopyrite and oxide and clay minerals (Fig. 3.15c). Pressure shadows are common and contain fibrous quartz, calcite, anhydrite, chlorite and muscovite; all are oriented parallel to the main fabric (Fig. 3.15e). Solution transfer is the dominant mechanism in Structural Domain 4, resulting in tightly spaced pressure solution seams (Fig. 3.15d). Chalcopyrite and tennantite grains are commonly stretched in an east-west orientation and concentrated in pressure solution seams. Pyrite is predominantly deformed by brittle microfracture and is extended parallel to the foliation; local polygonal texture is observed proximal to well-developed pressure solution seams only. Chalcopyrite is commonly lenticular in shape near the pressure solution seams (Fig. 3.15c, f). Tabular molybdenite grains in quartz veins can be crenulated and grains commonly have cleavage-parallel, elongate to lenticular geometry where they are disseminate in the wall rock. Porphyry-related veins are commonly extended by microcracks perpendicular to S1 that are infilled by calcite, quartz and anhydrite. The original geometric and textural distribution of metals in Structural Domain 4 is changed as a function of strain. The metals are clearly segregated by solution transfer processes. Dynamic recrystallization is prevalent within quartz-rich domains and temperatures of deformation were likely in the order of 300-350°C. The microstructures documented all suggest that solution transfer was the dominant mechanism that accommodated the development of the S1 cleavage with brittle fracture of more competent minerals and intracrystalline deformation playing subsidiary roles. The fine grain size of the phyllosilicates indicates limited grain growth. In addition, the lack of microstructure indicative of dislocation creep in quartz indicates that temperatures during deformation likely did not exceed 350°C. Pyrite was deformed during deformation within Structural Domains 2, 3 and 4, as indicated by brittle elongation parallel to S1 and was insoluble during solution transfer as suggested by its location generally within the phyllosilicate P domains. Chalcopyrite was also deformed during deformation within Structural Domains 2, 3 and 4, as indicated by mechanical reshaping of the grains into lenticular, S1 parallel geometries coupled with boudinage along the P domains and it was insoluble as suggested by its concentration in the P domains. Similarly molybdenite is mechanically reshaped into lenticular grains concentrated in the P domains and is observed predominantly in Structural Domain 4. 220.127.116.11. Deformation Phase 2 F2 folds are developed in limbs of F1 folds (Figs. 3.16a, d) and fold the S1 foliation. Folds are best developed in veins that strike east-west (which is estimated to be approximately orthogonal to the flattening direction for Deformation Phase 2; Figs. 3.16b, c). F2 folds plunge 60 - 80° towards 300 - 015°. 69 Fig. 3.16. Field photographs and stereographic projections of Deformation Phase 2 features. a) Tight to isoclinal F1 folds in veins plunge steeply west and gentle F2 folds defined by veins and S1 foliation plunge northwest. b) F2 vein folds in Structural Domain 3 are defined by gentle folds of sheeted quartz veins and subparallel S1 cleavage, 423209 E, 6265198 N. c) F2 fold in Structural Domain 4 is defined by folded S1 cleavage and Stage 2 veins, 423832 E, 6265290 N. d) S1 cleavage is axial planar to F1 folds and S2 spaced cleavage is axial planar to F2 folds, 423394 E, 6265352 N. Stereographic projections of: e) F2 fold axes of folds in Structural Domain 2 (triangles) and in Structural Domain 3 (circles) plunge steeply north to northwest; f) F2 fold axes of folds in Structural Domain 4 plunge steeply north to northwest; and g) axial planar cleavage to F2 (S2) defined by brittle fractures (fracture cleavage) in quartz veins strikes north to northwest. 70 Fig. 3.17. Qualitative estimate of strain for altered rocks of the Mitchell zone as indicated by cleavage development. a) Structural Domain 4 - phyllic tight-isoclinal F1 folds of Stage 2 veins, 423832 E, 6265290 N; b) Structural Domain 4 open F1 folds and gentle F2 folds in intermediate argillic altered andesite lapilli tuff, 423630 E, 6265501 N; c) Structural Domain 3gentle F1 folds in sheeted veins, 423151 E, 6265163 N; d) Structural Domain 2 open F1 and gentle F2 folds in vein chlorite-quartz altered, 423493 E, 6265525 N; e) sheeted quartz veins in diorite intrusion are not folded, 423213 E, 6265195 N; f) Structural Domain 1:unfoliated potassic-altered diorite cut by sheeted quartz veins that are not folded, 422532 E, 6265370 N. Structural Domain 2 hosts rare, gentle F2 folds predominantly in thin veins (< 5 mm thick; Fig. 3.16e). In Structural Domain 3, F2 folds are well developed, are open to gentle in geometry, with amplitudes < 2 cm and wavelengths range 5-15 cm (Figs. 3.16c, e). Structural Domain 4 contains gentle to open folds of both thick, and thin quartz veins (up to 5 cm; Figs. 3.16b, f) and has gentle folds of S1 cleavage. A locally poorly to moderately developed axial planar fracture cleavage (S2) strikes north to northwest and dips steeply to the west (Fig. 3.16g). These folds have the same fold trend as the McTagg anticlinorium (Fig. 3.2) and are interpreted to be kinematically linked to this structure. Qualitative estimates of F1 and F2 fold 71 Fig. 3.18. Field photographs and stereographic projections of the Mitchell thrust fault and kinematically related structures. a) Cross sectional view of the Sulphurets and the bifurcated Mitchell thrust. Also shown are the Iron Cap and Snowfield reverse faults and the dextral-oblique Brucejack fault, the relative dip-slip movement indicated by up (U) and down (D). b) Fault traces observed in the southern valley wall of the Mitchell valley. Refer to Figure 3.7 for fault legend. c) Photograph of the Mitchell thrust fault in outcrop with unaltered andesite in hanging wall and the high quartz zone in the footwall, 423129 E, 6265129 N; stereographic projection of poles to the Mitchell thrust fault. d) Photograph of the fault rocks composed of sericite-pyrite-quartz within the Mitchell thrust fault; in Riedel shear geometry ‘Y’ slip plane indicates top-to-the-east-southeast, ‘S’ deflected foliation, R1(‘R’) slip planes, and sigmoidal quartz (Qz) vein fragments, view toward southwest on cliff, 423129 E, 6265129 N. 72 geometries and estimated flattening amounts are presented for alteration assemblages of each Structural Domain (Fig. 3.17). 18.104.22.168. Deformation Phase 3 The Mitchell thrust fault, imbricate thrusts associated with Mitchell thrust fault, and strike slip faults, cross cut Deformation Phase 1 and 2 fabrics and are interpreted to have formed at shallower crustal levels than Deformation Phase 1 and 2 structures. The Mitchell thrust fault (Figs. 3.18a, b) is a prominent splay of the Sulphurets thrust that exposes the Mitchell deposit through an erosional window in the Mitchell valley. The thrust fault offsets Premier plutons and Stuhini Group volcanosedimentary strata in the northern trace of the fault, cuts Premier plutons and basal Hazelton Formation massive andesite in the southern trace of the fault, and is interpreted to cut Sulphurets plutons and Basal Hazelton Formation sandstone in the eastern extents of the interpreted fault trace beneath till (Fig. 3.7). The fault clearly crosscuts the steeply dipping S1 cleavage and sheeted quartz veins (Fig. 3.18c) of the deposit located in the footwall of the thrust. The Mitchell fault is located at a rheological break between competent Structural Domains 1 and 2 and the incompetent Structural Domain 4 (Fig. 3.19a). The Mitchell thrust fault is curviplanar with moderate southerly, westerly and northerly dips recorded as well as shallow northwesterly to southwesterly dips (Fig. 3.18c). The thrust fault extends throughout the Mitchell valley and is interpreted to be down-dropped at the Brucejack fault (Figs. 3.19a, b) where the surface trace of the fault terminates. The fault contains a well-developed, foliated cataclasite that is ~ 3 – 15 cm thick and a total deformation zone of 1-2 m characterized by brittle fracture and a fault-parallel foliation (Fig. 3.18d). The fault fabric contains good shear sense indicators including a shape foliation, (‘S’ in the Reidel shear geometry terminology; Fig. 3.18d), sigmoidal quartz vein clasts (Qz; Fig.3.18d), shear planes (‘Y’; Fig. 3.18d), and Reidel extensional faults (‘R’; Fig. 3.18d), all of which indicate a top to the east-southeast shear sense. Quartz fragments in the fault are likely sourced from the high quartz zone in the footwall of the fault (quartz-pyrite-chalcopyrite veins). Calcite veins and compositionally banded quartz-chlorite-calcite veins were emplaced during thrusting. Beneath the Mitchell thrust, a fault-parallel cleavage is developed (S3): the intersection of this S3 with the steeply north-dipping S1 cleavage in the footwall sheeted veins area creates a shallowly west-plunging pencil lineation (see also Margolis, 1993). Microstructurally, the Mitchell thrust cataclasite is composed of fractured pyrite grains (~5%; < 50 µm diameter) in a matrix of quartz, feldspar, calcite hematite and clays (10-30 µm diameter). Quartz grains have undergone grain size reduction by cataclasis and are highly variable in grain size. Sutured grain 73 Fig. 3.19. Structural cross section interpretations for section lines A-A’-A,’’ B-B,’ and C-C’ from Figure 3.3. a) Section A-A’-A’’: Cross section through the Snowfield deposit, the eastern margin of the Mitchell zone beneath the Mitchell glacier, and the Iron Cap deposit. Structural Domains for the Snowfield deposit are inferred from surface mapping and modified from Armstrong et al. (2011), e.g., ‘hydrothermal silica 74 replacement’ is correlated with the high quartz zone or Structural Domain 3. Iron Cap area lithology and Structural Domains are modified from Febbo et al. (2014). b) Section B-B’: Cross section through the Snowfield and Mitchell deposits are in the Mitchell thrust fault kinematic plane. The estimated location of the down-dip continuation (core zone) of the Mitchell-Snowfield porphyry system is projected along the Mitchell Basal shear zone. The location of the intrusion to the east of Pretium-Seabridge claim boundary is projected from surface mapping (this study). c) Section C-C’: cross section through the Mitchell deposit, showing the locations of Structural Domains, and locations of the Snowfield and Mitchell faults. boundaries in quartz indicate limited dynamic recrystallization. Calcite veins also show limited evidence for dislocation creep and dynamic recrystallization. Solution transfer is evident by the presence of spaced Y surface-parallel shear bands with locally higher concentrations of pyrite interpreted to be a result of dissolution of quartz and other minerals. Based on the microstructural observations, the Mitchell thrust is interpreted to have formed at a maximum of 300°C (e.g., Passchier and Trouw, 2005). Displacement along the Mitchell thrust is estimated to be ~1600 m (~1500 m up dip movement and ~600 m strike-slip movement). Metal zonation patterns between the Mitchell and the Snowfield deposit match remarkably well, suggesting that the Snowfield deposit is offset from the Mitchell deposit along the Mitchell thrust fault (Savell and Threlkeld, 2013). This interpretation requires ~1600 m east-southeast-directed separation along the thrust fault, with the thrust sheet carrying the Snowfield deposit (Savell and Threlkeld, 2013). Three field observations are compatible with Savell and Threlkeld’s model: 1) sigmoidal quartz fragments within fault rocks developed during thrusting, indicate east-southeast vergent thrusting; 2) the Late Triassic-Early Jurassic unconformity, mapped in this study, intersects the Mitchell thrust fault in the footwall ~ 3 km west of where it intersects the thrust fault in the hanging wall, consistent with an interpretation of easterly displacement along the thrust (Fig. 3.7); and 3) the southern trace of the Mitchell thrust fault juxtaposes intensely altered and mineralized rocks in the footwall against rocks that are poorly altered in the immediate hanging wall; such an offset requires a minimum of 1 km displacement along the thrust based on the lateral extent of alteration in the footwall (Fig. 3.7). Hence, Mitchell area field data support an interpretation of east-southeast vergent movement and bracket the easterly displacement in the range of 1-3 km along the fault, consistent with Savell and Threlkeld’s (2013) proposed 1600 m. The Mitchell thrust fault extends throughout the Mitchell valley and is interpreted to be down-dropped at the Brucejack fault (Figs. 19a, b), where the surface trace of the fault terminates. The Mitchell thrust has a ramp-flat geometry, with a floor and a roof thrust. The flats dip ~ 10° to the west and the ramps dip ~40-50° to the west. The fault has two ramps (Campbell, 2011; Febbo et al., 2014): one located near the Snowfield fault and another located near the toe of the Mitchell glacier (Fig. 3.19a). Only one fault trace is mapped in the southern Mitchell valley (Fig. 3.19b) that accommodates significant displacement and is interpreted to correlate with the roof thrust in the northern Mitchell valley wall. 75 Fig. 3.20. Field photos and stereographic projections of faults related to Deformation Phase 3. a) Tectonic quartz vein in conjugate geometry with east-vergent, reverse fault zone, 423145 E, 625538 N; b) east-vergent thrust imbricate places the high quartz zone structurally above diorite with ~30% quartz stockwork, note the duplex structure formed in the thrust sheet, 424384 E, 6265269 N; and c) east-vergent, brittle, reverse imbricate thrust with tectonic shear veins with Riedel shear geometry (‘Y’ and ‘R1’ slip planes), 423555 E, 6265636 N. d) Stereographic projection of poles to reverse thrust imbricate faults. e) Fault rock developed during sinistral shear showing Y and R1 shears (using Riedel shear geometry), view is looking down dip, 423310 E, 6265475 N. f) Stereographic projection of poles to dextral (green), sinistral (circles), and ambiguous (dots) strike-slip faults. 76 The footwall of the Mitchell thrust (i.e., the Mitchell deposit) contains several imbricate thrust faults that dip moderately westerly and strike south-southwest to north-northwest (Figs. 3.7, 20a-d). These faults generally contain a 20-50 cm wide foliated cataclasite with sigmoidal fragmented quartz veins, Riedel shears and deflection of S1 that define a top-to-the-southeast sense of shear. Locally, fault duplex structures are observed with lensoidal ‘horses’ within < 1 m deformation zone (Fig. 3.20b). Thrust-related quartz-chlorite-calcite veins in the hanging wall in a Riedel shear orientation, indicate top-to-the east (Fig. 3.20c). The Mitchell Basal shear zone is located approximately 1 km below the Mitchell thrust fault and is identified only in two of the deeper drill holes that are separated by 200 m in an east-west direction (M-08-62 and M-08-67; Fig 3.19b). The shear zone does not intersect the shallower, neighbouring drill holes (Fig. 3.19b) and therefore its orientation must be subhorizontal (+/- 20 degrees) and is interpreted to have thrust fault kinematics. The shear zone is located within the mineralized Mitchell intrusion (diorite). Below the Mitchell Basal shear zone, the Premier suite diorite in the footwall contains poorly disseminated chalcopyrite and pyrite and low intensity chlorite-sericite alteration. In drill hole M-08-62, assays of drill core collected from 30 m above the thrust averages 0.22 g/t Au and 0.12%, in the 12 m below the thrust, the grade averages 0.05 g/t Au and 0.0056% Cu. In drill hole M-08-67, the 29.7 m above the thrust fault average 0.33 g/t Au and 0.18% Cu, in the 8.25 m below the thrust the grade averages 0.01 g/t Au and 0.015% Cu. Considering the overall homogeneous grade of gold and copper within the Mitchell deposit, the sharp drop of gold and copper grades across the shear zone suggests considerable (> 1 km) displacement along the fault. Further, the weak alteration and mineralization of the footwall rocks suggests that these rocks are part of the periphery of the hydrothermal system (i.e., the displacement along the fault is less than the ~4 km diameter of the alteration system; Fig. 3.8). The Mitchell Basal shear zone is ~20 m thick and characterized by mm-scale banded muscovite-chlorite and quartz that is crenulated by a second compression event. The shear zone contains folded extension veins, abundant anhydrite located in dilation sites, and drag folds of the shear zone fabric. Microstructural observations show that muscovite defines the foliations and is medium grained, much coarser than in the Mitchell thrust or those that define S1 throughout the deposit. Pressure shadows of quartz are very common, highlighting the role of fluids during thrusting. Quartz has undergone limited dynamic recrystallization. Based on the grain size and the microstructures, the temperature during movement is estimated to be ~350°C. Estimating the displacement along the Mitchell Basal shear zone is difficult. The shear zone juxtaposes mineralized Sulphurets suite diorite in its hanging wall against Premier suite diorite in its footwall (Fig. 3.19b) that contains low intensity alteration and trace chalcopyrite disseminations. The fault is interpreted 77 to be kinematically linked to the Sulphurets and Mitchell thrusts (i.e., top-to-the-east-and top-to-the-east-southeast thrusting respectively). The Sulphurets plutons that host the Mitchell deposit have a surface expression of ~ 2 km by 1 km. Based upon this information, an offset of ~ 1 km is likely required along the Mitchell Basal shear zone in order to juxtapose the Suphurets diorite against the Premier Suite pluton. In addition, the Mitchell deposit alteration halo (expressed at surface) is ~ 4 km in diameter (Fig. 3.8). Extrapolating this halo dimension to the depth of the shear zone, an offset of ~ 2 km is required to juxtapose altered Suphurets suite diorite against unaltered rocks in the footwall. If the shear displaced its hanging wall 1-2 km to the east, then the downward continuation of the Mitchell-Snowfield mineral system would be located ~ 1-2 km to the west of the existing Mitchell deposit at a depth of ~1 km below the surface. Several strike-slip and oblique fault zones define linear gullies that are traceable over 250 m. The fault zones strike west-northwest to west-southwest and dip steeply north, and appear to be conjugate faults, similar in orientation to the conjugate shear bands described above. The strike-slip faults are characterized by 50-200 cm wide foliated cataclasites (Fig. 3.20e). Within the faults, sigmoidal shaped clasts of fragmented quartz-pyrite-chalcopyrite veins, and Riedel shears provide good shear sense indicators (Fig. 3.20e). In general, the strike-slip faults with shallower dips display a tendency toward dextral strike-slip movement; the steeper dips toward sinistral shear sense (Fig. 3.20e). Some of these faults have a dip-slip component; both reverse and normal kinematics were observed. The cataclasites are composed primarily of illite and do not have chlorite even where chlorite is abundant in the wall rock. The orientation of the acute bisectrix of the sinistral, west-northwest striking and dextral west-southwest striking, conjugate faults (Fig. 3.7), dips 74° towards 002° (Fig. 3.20e). If these are truly conjugate faults, then this trend provides an estimate of 10° towards 089° for 1. These conjugate strike slip are inferred to be coeval with the Mitchell thrust. A high angle, north-northeast striking sinistral-reverse fault (herein named the Snowfield fault) extends from the Mitchell thrust, and was previously interpreted to be the trace of the Mitchell thrust, despite its steep dip (Margolis, 1993). The Snowfield fault has a known strike length of 8 km (Febbo et al., 2014). Here, the Snowfield fault length is extrapolated to include several other reverse faults: a reverse fault located in the northern Mitchell valley that terminates at the Iron Cap reverse fault (the Coulson fault; Campbell, 2011), the Snowfield sinistral-reverse fault located west of the Snowfield deposit (Margolis, 1993; Kirkham and Margolis, 1995), the Ridge reverse fault located east of the Sulphurets deposit (which has a purported ~ 50-100 m of west side up displacement; Fig. 3.3; Kirkham and Margolis, 1995) and a reverse fault mapped east of the Kerr deposit (Fig. 3.3). These reverse faults are interpreted as segments along a continuous reverse fault based on the map distribution and the coincidence of their projection using structure contours. The Snowfield sinistral reverse fault does not extend beyond the porphyry trend 78 and demonstrates a strong spatial relationship with the alteration and mineralization trend and is interpreted here to be to be a significant, district-scale structure. We speculate in the discussion that the Snowfield fault may have an earlier, Jurassic movement history. 3.4.2. Dextral faults (D3) The subvertical Brucejack fault strikes north and extends the length of the Sulphurets district (e.g. ~1 km; Fig. 3.3). In the Brucejack area, the fault has a demonstrated ~100 m dextral strike-slip movement (Kirkham and Margolis, 1993). The Brucejack fault, near the Iron Cap deposit, has >500 m east-side-down dip-slip displacement (Kirkham and Margolis, 1995) that drops Bowser Lake Group sedimentary rocks down to the same structural level as Jack Formation sedimentary rocks (lower Hazelton Group; Lewis, 2013; Nelson and Kyba, 2014). The Brucejack fault clearly cuts the Iron Cap reverse fault and the Mitchell roof thrust fault (Fig. 3.3). The Brucejack fault and similar, smaller-scale dextral north-south striking faults have not been dated, but are inferred to be Eocene in age (Kirkham and Margolis, 1995). 3.4.3. Pre-S1 structures (D1) Structures that are interpreted to pre-date S1 and to have formed in the Early Jurassic, coeval with the emplacement of the Mitchell intrusions, are described below. These include porphyry-related veins with east-west strikes, strike-slip faults that are deformed by S1, the Glacier shear zone that is cross cut by porphyry-related veins that are not offset, and small scale faults that are interpreted to have formed late in the porphyry system. Generally, pre-S1 structures are observed only in the competent, less strained rocks assigned to Structural Domain 1. It is inferred that the structures survived the mid-Cretaceous deformation because they were developed in relatively unaltered and therefore strong rocks. 22.214.171.124. Porphyry-related veins Densely sheeted quartz veins located in the footwall of the Mitchell thrust fault, define the tabular shaped high quartz zone (Figs. 3.13, 3.21a) that is composed of more than 60% by volume, quartz veins (Stage 1) that strike roughly west-northwest, dip steeply north, and are laterally continuous for ~1.5 km (Fig. 3.10d). Sheeted veins within the high quartz zone grade into less densely sheeted veined rock with the same vein orientation (Stage 1 veins in Structural Domain 1). As described in section 126.96.36.199 above, even in the relatively undeformed areas of Structural Domain 1, hydrothermal veins strike east-west, suggesting that this orientation is primary and not a result of rotation during deformation. In addition, sheeted veins are not tightly folded, and this would be anticipated if the veins were reoriented to the ~ east-west orientation as a result of transposition. Furthermore, the correlation between the strike of the sheeted veins and the S1 fabric in Structural Domain 1 is only moderate, and the rocks are demonstrably the weakest rocks in the Mitchell area. It is within these incompetent Structural Domain 4 rocks that 79 Fig. 3.21. Field photographs and stereographic projections of Stage 1-3 veins. a) Sheeted quartz veins strike east-northeast (Structural Domain 3, Stage 1), 423114 E, 6265124 N; b) quartz stockwork veins in quartz-chlorite altered diorite strike southwest to northwest and have steep northerly dips (Structural Domain 1, Stage 1), 423120 E, 6265136 N; c) molybdenite-quartz vein stockwork hosted in intensely phyllic altered rock (Structural Domain 3, Stage 2), 423805 E, 6265365 N; and d) orthogonal vein trends cut Phase 2 diorite (Structural Domain 2, Stage 2), 423033 E, 6265514 N. Stereographic projection of poles to e) Stage 1 sheeted quartz veins in Structural Domain 3 (quartz vein abundance is >60%) strike west-northwest and dip steeply to the north; f) Stage 1 quartz veins where quartz abundance <60% (i.e., Stage 1 veins excluding the high quartz zone) strike northwest to southwesterly with steep northerly dips; g) Stage 2 veins strike west-northwest and dip steeply north; and h) Stage 3 veins strike southwest to northwest with steep northerly dips. 80 Fig. 3.22. Structures interpreted to be Early Jurassic. a) Dextral and sinistral faults (Structural Domain 1) lined with hydrothermal silica in K-feldspar-magnetite-chlorite-quartz altered diorite are overprinted by SFTB-related tectonic veins (not photographed), 422532 E, 6265370 N; b) a series of dextral offsets of quartz vein (Structural Domain 2) overprinted by S1 that is oblique to offset planes, 423184 E, 6265457 N; c) S1 flattening overprints sinistral offset (phyllosilicate-rich Structural Domain 2), 423145 E, 625538 N; and d) stereographic projection of poles small scale strike-slip faults. f) Glacier shear zone mylonite with ‘S’ schistosity and ‘C’ cisaillement (slip) plane indicating sinistral kinematics, 424833 E, 6265631 N; and f) nearby porphyry-related quartz-pyrite vein cuts Glacier shear zone C-S mylonite and is not offset along C planes. g) Photo of sinistral sigmoidal tectonic quartz-ankerite-vermicular chlorite veins west of Snowfield deposit (Structural Domain 1), veins folded by S1 along strike in the same fault, stereographic projection of poles to cataclasites west of Snowfield, 423981 E, 6263965 N. 81 transposition of veins would be anticipated if the present orientation of the sheeted veins was caused by isoclinal folding and elongation of the porphyry-related veins. The abundant sheeted veins that are oriented ~ east-west are interpreted to have been emplaced within an east-west oriented tectonic extensional field, not simply from a pluton-induced mechanism of emplacement (Cloose and Sapiie, 2013). The high quartz zone is interpreted to have formed incrementally over more than 1.5 km in strike length, under a differential stress that existed during pluton emplacement in the Early Jurassic. 188.8.131.52. Sinistral shear zones A shear zone east of the Mitchell deposit area (herein termed the Glacier shear zone; Figs. 3.7, 3.18b) and several smaller cataclastic fault zones west of the Snowfield fault are interpreted as pre-S1, Jurassic-aged faults. The Glacier shear zone strikes 245 and dips 82° north crops out east of the Mitchell deposit and was not exposed in the deposit. The shear zone is about 10 meters wide and is characterized by sinistral S-C fabrics that are preserved in andesite breccia (Fig. 3.22f). The shear zone is cross cut by an undeformed porphyry-related Stage 3 or 4 quartz-pyrite vein. The shear zone deforms Stage 2 chlorite-sericite alteration, suggesting that the shear zone was active during or after the main two stages of porphyry mineralization (~190 – 189 Ma) and movement along the fault waned during the latest stages of mineralization. Steeply dipping east- to east-northeast striking cataclastic fault zones are offset by the Snowfield fault. The faults are defined by narrow (< 10 cm wide) cataclasites that extend up to 40 m in strike length and contain sigmoidal tension gashes, and sigmoidal shape fabrics within the fault gouge consistent with a sinistral shear sense (Fig. 3.22g). The sigmoidal veins are locally folded by S1 in phyllosilicate-bearing rocks. One anomalous north-south striking, steeply dipping dextral fault was also identified (Fig. 3.22g). 184.108.40.206. Small-scale, strike-slip faults Several small-scale faults, with strike lengths of 1-5 m, offset Stage 1-3 veins (Figs. 3.22a-d). The small faults are subvertical, strike north-south and east-west (Fig. 3.22e), are discontinuous and are preserved only in Structural Domain 1 and 2 rocks. The slip planes have sinistral (predominant) and dextral strike-slip offsets (1- 30 cm displacement; Figs. 3.23d, e) some of which also have a small dip-slip component < 30 cm where measured in offset quartz veins. The faults offset most veins and are rarely lined with trace pyrite or silica associated with Stage 3 or 4 hydrothermal alteration (Fig. 3.23a). In local incompetent, phyllosilicate-rich regions of Structural Domain 2, the north-south striking faults are folded by S1, forming an F1 fold defined by the folded fault surface (Fig. 3.23b). Additional evidence that the slip planes are pre-SFTB (i.e., Early Jurassic) is that they are cut by: 1) quartz-ankerite tension gashes that are folded by S1 and 2) discontinuous tectonic veins composed of fibrous quartz that cut S1 and the quartz-ankerite vein. 82 3.5. Discussion 3.5.1. Comparison with the Skeena fold and thrust belt The Skeena fold and thrust belt (SFTB) is well expressed in rocks that form the Bowser Basin, located ~8 km east of the Mitchell deposit. The Bowser Basin consists of Middle Jurassic to latest Cretaceous clastic successions that overlie Paleozoic and Mesozoic strata of the Stikine Terrane (Evenchick, 2001). Evenchick (1991b) estimates that the total stratigraphic thickness in the late Cretaceous reached a minimum of 4 km. At the onset of deformation, the 4 km thickness of Bowser Basin sedimentary rocks are inferred to overlie the Hazelton Group stratigraphy into which the Mitchell deposit intrudes. Given a geothermal gradient of 25°C/km, and a lithostatic gradient of 25 MPa/km, this translates into a minimum 100°C and 100 MPa during deformation. The Bowser Basin was deformed during docking of the Insular Terrane to the Intermontane Terrane, starting in the Early Cretaceous (Evenchick, 2007). Deformation within the Boswer Lake Group was accommodated by the widespread development of tight, early formed, northeast trending folds, followed by northwest-trending folds, and variably developed cleavage (Evenchick, 2001). Dome and basin fold interference patterns have been observed (Evenchick, 2001). Evenchick (1991) proposed that large scale sinistral transpression along the boundary of the Bowser Basin resulted in the formation of the two fold orientations. There are commonalities and discrepancies between structures developed within Bowser Basin area and those in the Mitchell deposit. The F1 and F2 fold trends are mutually orthogonal both in the Bowser Basin and in the Mitchell deposit: however, folds are rotated ~ 45° counterclockwise in the Mitchell deposit with respect to folds in the Bowser Basin. In addition, fold axes are steeply plunging in the Mitchell deposit whereas they are shallowly plunging in the Bowser Basin. Deformation Phase 2 folds in the Mitchell deposit have the same trend as the McTagg anticlinorium, synforms in the Sulphurets district, and other SFTB-related folds in the Stewart area. The anomalous steeply plunging fold axes in the Mitchell deposit is attributed to folding the pre-existing steeply dipping sheeted veins. The counter clockwise rotation of the fold axes is attributable to the east-west orientation of the Mitchell deposit veins, alteration trends and fault zones. I propose that the pre-existing geometry of structures (e.g., veins) in the area dictated the present orientation of fold axes. 3.5.2. The role of strain partitioning and post-emplacement deformation. Strain partitioning is an important process in the Sulphurets district where phyllosilicate-bearing alteration types are widespread, especially for the Kerr, Mitchell, Snowfield and Brucejack areas. Unlike the laterally continuous, shallowly dipping sediments of the Bowser Lake Group rocks, Hazelton Group rocks are more laterally heterogeneous, host plutonic rocks and contain pre-existing structural features. In 83 the Mitchell deposit, which is hosted in plutonic rocks that intrude the basal Hazelton strata, strain is heterogeneously distributed, with shortening accommodated by intense cleavage development in highly altered rocks and by the formation of thrust faults. Deformation in the Mitchell zone is a function of alteration type: rheologically soft rocks are folded and flattened; rheologically hard alteration types and Hazelton Group strata outside of the Mitchell deposit accommodate deformation by the formation of broad scale folds and contraction along gently dipping faults. Because the strain recorded in the rocks is heterogeneously distributed as a function of porphyry alteration, cleavage and fold development can be erratic in their distribution. This heterogeneous accommodation of strain in deformed porphyries may have implications for the geometry of the deposits both at surface and at depth. For example, at the Mitchell deposit, the top of the deposit is highly flattened in an east-west direction and this intensity of flattening decreases with depth as the phyllic alteration decreases in abundance. Globally, most copper porphyry deposits are relatively young and have not undergone deformation similar to the Mitchell deposit; peak periods of porphyry development are Jurassic, Cretaceous, Eocene, and Miocene (Sinclair, 2007). Exceptions to this include the Gibraltar copper-molybdenum porphyry deposit in southern British Columbia (Mostaghimi and Kennedy, 2015). In the Gibraltar deposit, deformation is localized in the sericitic-altered rocks and so strain is localized as a function of alteration type. Outside of the altered areas of Gibraltar, only a poorly developed cleavage exists, similar to the Sulphurets porphyry deposits. High strain zones are also correlated with rheologically soft alteration types at the Messgay deposit gold-molybdenum porphyry in Quebec (Jebrak and Doucet, 2002) and the Coppin Gap deposit in Australia (Williams and Collins, 1990). Locally, the adjacent Kerr deposit underwent similar deformation as the Mitchell deposit and strain is localized in phyllic altered rocks (Kramer, 2014). Within the phyllic altered rocks at Kerr, second generation folds are defined by tight folds of a pre-existing pervasively developed cleavage and complex dome and basin folding of the pervasive cleavage is also observed (Febbo et al., 2014). Away from the phyllic altered, complexly deformed rocks, deformation occurs as a spaced fracture cleavage (Febbo et al., 2014). Hence, the rheologically soft alteration types accommodate significant strain during deformation and record two post-S1 deformation phases that are otherwise not developed. In the Mitchell deposit, alteration types are directly correlated with the amount of flattening and qualitatively correlated to fold geometry. Each Structural Domain is a window into a phase of deformation (Fig. 3.18): in Structural Domain 1, D1 (Early Jurassic) structures are preferentially preserved; in Structural Domain 2, D2 Deformation Phase 1 (SFTB) is preserved and is not complicated by interference of later phases of deformation; in Structural Domains 3 and 4, D2 Deformation Phase 2 is well developed. 84 Strain partitioning also occurs at the microscopic scale and has implications for the distribution of metals in deformed porphyry deposits (i.e., the geometallurgy). In rheologically weak alteration types, a penetrative pressure solution cleavage is associated with loss of silica, mechanical remobilization of chalcopyrite and molybdenite, and passive enrichment of chalcopyrite, molybdenite and pyrite along the cleavage planes. Ore in high strain zones is subject to solid state mechanical mobilization where strain is preferentially partitioned into easily deformable sulphide minerals (e.g., chalcopyrite, Roscoe, 1975; molybdenite, Thompkins et al., 2004). Pyrite is grain size reduced via brittle microfracture and boudinage. Loss of quartz along pressure solution seams passively enriches pyrite, chalcopyrite molybdenite (i.e., copper and molybdenum) along the cleavage planes. As gold resides as electrum inclusions in pyrite and chalcopyrite (Febbo et al., 2015), it is considered to be similarly passively enriched. Lianxing and McClay (1992) also documented enrichment of sulphides that are less susceptible to dissolution in massive sulphide ores. In the Mitchell deposit, the pressure solution seams are associated with the dissolution (loss) of quartz and passive enrichment of sericite and sulphide minerals. This passive enrichment of sulphide minerals as a result of quartz dissolution is considered to be a significant remobilization mechanism for Structural Domains 2-4 where flattening estimates suggest significant loss of quartz (between 10 and 70% flattening). Hence, areas of high strain can be enriched in sulphide mineralogy through grain scale processes of solution transfer. 3.5.3. Early Jurassic structural setting Nelson and Kyba (2014) propose that the Sulphurets thrust is a reactivated basin-bounding fault located on the east side of the McTagg anticlinorium and they suggest that the McTagg anticlinorium was a topographic high during Early Jurassic sedimentation of the Jack Formation. Paleocurrent indicators in the KSM area record an east-directed flow, suggesting that the sediments were derived from the McTagg topographic high (Nelson and Kyba, 2014; Fig 3.2). Early Jurassic basin sedimentation, represented by the Jack Formation in the field area, is extensive in the KSM area (Febbo et al., 2015). Outcrops of the Jack Formation form an elongate pattern on the eastern margin of the McTagg anticlinorium. The KSM deposits are presently located in the immediate footwall of the Sulphurets thrust fault and the deposits both intrude and are overlain by the Jack Formation, suggesting that porphyry formation and basin sedimentation were coeval. Based on these observations, and that the deposits are all located within the footwall of the Sulphurets thrust faults, Nelson and Kyba (2014) speculate that in the Early Jurassic, the Sulphurets fault was a steeply dipping normal fault, that formed the western margin of a west-tilted half graben, along which the porphyry plutons were emplaced. The fault was subsequently rotated and reactivated as a thrust fault in the mid-Cretaceous. The observations recorded in the Mitchell deposit can support this model. 85 From south to north, the Kerr, Sulphurets, Mitchell-Snowfield and Iron Cap deposits are aligned on a district-scale, ~12 km north-south oriented lineament. This lineament is also parallel to several faults in the district including: the Sulphurets fault, located structurally west and above the porphyry deposits; the Snowfield fault, located east of Kerr and Sulphurets deposits and west of Snowfield-Mitchell and Iron Cap deposits; and the Brucejack fault, spatially associated with mineralization in the Brucejack area and east of the porphyry deposits (Fig. 3.3). Cloos (2013) observes that in general anywhere that three or more porphyry centres line up, a ‘fault control’ is usually inferred. Here we suggest that these three district-scale faults were active in the Jurassic (i.e., as basin growth faults) and present a model for their Jurassic locations and subsequent reactivation kinematics. In the Brucejack area, Early Jurassic structures are oriented predominantly north-south with subsidiary faults oriented east-west, that are interpreted to be active during deposition (Pretium Resources, 2013; Nelson and Kyba, 2014). The prominent Brucejack fault extends over 11 km through the alteration and mineralization associated with the Brucejack deposit, and was active as late as the Eocene (Kirkham and Margolis, 1995). Its position within and parallel to the zone of alteration and mineralization led Nelson and Kyba (2014) to infer that the Brucejack fault was also active in the Early Jurassic as a normal fault (Nelson and Kyba, 2014) and was responsible for a north-south structural control of the deposits. The Snowfield fault may also have been active during basin formation in the Early Jurassic as a steep, north striking dextral-normal Early Jurassic fault. Kirkham and Margolis (1995) suggest that one strand of the fault (i.e., the‘Ridge fault’) was active during porphyry emplacement, based on the close association of hydrothermal sericitic and chloritic alteration with the fault. Fault outcrops record sinistral strike-slip movement (Margolis, 1993) and postmineral sills belonging to the Mitchell intrusions (<189 Ma) east of the Sulphurets deposit record 50-100 m reverse offset along the Snowfield fault (Kirkham and Margolis, 1995; Febbo et al., 2014), which is kinematically comparable to other SFTB structures. The fault mimics the strike and dip of the tabular Kerr deposit and traces the western margin of the Snowfield and Iron Cap deposits. The amount of total displacement along the Snowfield fault prior to 189 Ma is unknown, but it is speculated that the fault was active during Early Jurassic hydrothermal activity because of its close spatial relationship to the structurally controlled KSM and Snowfield porphyry deposits and because it has a comparable strike and extent as the Brucejack and Sulphurets faults, interpreted by other workers to be Jurassic basin-bounding faults. In contrast to the general north-south trend of the Sulphurets district porphyry deposits, the Mitchell deposit, and the foliations, trend ~ east-west in orientation. Field observations suggest that at least some of the east-west structures were likely formed in the Early Jurassic. For example, 1) the sheeted veins trend ~ east-west; 2) east-west striking small scale faults, interpreted to have formed during porphyry emplacement, record predominantly sinistral kinematics, and 3) S-C fabrics record sinistral movement in 86 the Glacier shear zone, and the fabrics are cross cut by a porphyry-related vein with no visible offset. In addition to these observations from the Mitchell deposit, several pre-S1 east-west striking cataclastic fault zones west of the Snowfield deposit record sinistral kinematics. It is proposed that these east-west oriented structures played a role in the localization of the Mitchell-Snowfield porphyry system in the Early Jurassic. Based on the above observations, interpretations and speculations, the Mitchell deposit is proposed to have formed in a graben that is bounded to the north by the Iron Cap fault, to the south by the Glacier shear zone, to the west by the Snowfield fault and to the east by the Brucejack fault (Fig. 3.23a). The Sulphurets, Snowfield and Brucejack faults are modelled as Early Jurassic oblique slip faults with normal and dextral motion: the east-west striking Glacier shear zone is a sinistral strike-slip fault that is antithetic to the north-south striking basin bounding faults. The Iron Cap fault dips steeply north, strikes, east-west and is offset by the Sulphurets thrust fault. The Iron Cap fault is interpreted as a Jurassic transfer fault (Fig. 3.23a). Such strike-slip pull-apart fault regimes as modelled here would be an ideal place to form steeply dipping pathways that tap magma plumbing systems where they intersect crustal-scale inverted extensional faults at depth (Corbett, 1994; Cloos, 2013). Strike-slip faulting localized intrusion and mineralization at other supergiant deposits including Chuquicamata Cu-Mo porphyry in Chile and the Grasberg Cu-Au porphyry in Indonesia, two of greatest copper ore bodies discovered on Earth (Cloos and Sapiie, 2013). Cloos and Sapiie (2013) conclude that porphyry copper ore deposits form where strike-slip movements are concurrent with the early stages of deep-seated bubbling along the walls of a rapidly cooling stock of magma and that supergiant deposits form where the bubbling front extends into the top of a parent batholith. Similar to the model for Grasberg (Cloos and Sapiie, 2013), I envision that the incremental movement along strike-slip faults like the Glacier shear zone acted as a throttle that prevented explosive detonation of a bubbling magma chamber and was a significant process that contributed to the formation of a supergiant copper deposit. 3.6. Conclusions Three phases of progressive deformation related to the mid-Cretaceous thin-skinned SFTB structurally modify the Mitchell deposit. Deformation Phase 1 is characterized by: pervasive S1 pressure solution cleavage defined by chlorite-sericite that strikes west and dips 80° to the north, and by F1 folds developed in quartz veins that plunge steeply to the west; similar to the overall plunge of the orebody (Fig. 3.23b). Fold geometry and degree of flattening varies as a function of alteration type. In rheologically weak alteration types, a penetrative pressure solution cleavage is associated with loss of silica, mechanical remobilization of chalcopyrite and molybdenite, and passive enrichment of chalcopyrite, molybdenite and pyrite along the cleavage planes. F1 folds are overprinted by steep north-northwest plunging, open-gentle F2 folds (Deformation Phase 2; Fig. 3.23c). The Mitchell thrust fault (Deformation Phase 3; 110.2 ± 2.3 87 88 Fig. 3.23. Model for the structural evolution of the Sulphurets district. a) Early Jurassic (D1) structural setting: the proto-Sulphurets fault is modelled as a steeply west-dipping dextral-normal fault that defines the western boundary of the basin, the proto-Snowfield fault is modelled as a steeply west-dipping dextral-normal fault that segments the basin; the proto-Brucejack fault is modelled as a steeply west-dipping, dextral-normal fault that defines the eastern margin of the basin and Jack Formation sedimentation; subsidiary east-west striking, normal faults like the Iron Cap and Glacier faults are basin growth faults that localize plutonism, volcanism and hydrothermal alteration and mineralization and are associated with the formation of horsts and grabens. b) Mid-Cretaceous, Deformation Phase 1 (D2): sinistral transpression and a switch in kinematics along the fault zones (i.e., from dextral transtensive step-over to sinistral transpressive step-over); first order faults are reactivated as sinistral-reverse faults (e.g. Sulphurets, Snowfield and Brucejack faults); second order faults are reactivated as reverse faults (i.e., pop-up structures); and S1 foliation forms parallel to second order structures. c) Mid-Cretaceous, Deformation Phase 2 (D2): folds pre-existing foliation (S1) into gentle to isoclinal steeply north-plunging folds and folds Hazelton Group strata into broad-scale anticline-synclines. d) Mid-Cretaceous, Deformation Phase 3 (D2): the Sulphurets fault is reactivated as an east-vergent thrust fault placing mixed Stuhini and Hazelton group strata over altered and mineralized rocks in its footwall; the Snowfield fault is reactivated as a steeply west-dipping reverse fault; the Brucejack fault is reactivated in the Eocene and so is not illustrated, its current location is west of the proto-Brucejack fault location; the east-southeast vergent Mitchell thrust offsets the Snowfield and Mitchell deposits; the Mitchell Basal shear zone offsets the Mitchell deposit from its core zone. Ma) is curviplanar, dips gently to the west and offsets the Snowfield deposit ~1600 m to the southeast; both deposits are slightly west-plunging. The Mitchell deposit is further imbricated by smaller thrust faults with mineralization terminating at ~ 900 m depth due to displacement along the Mitchell Basal shear zone (Fig. 3.23d). It is speculated that the Mitchell porphyry system was emplaced into a structurally controlled, Early Jurassic pull-apart basin in a graben that is bounded to the north by the Iron Cap fault and to the south by the Glacier shear zone (Fig. 3.23a). Plutonism, vein geometry, alteration and metal patterns reflect a strong east-west trend attributed to subsidiary east-west striking faults, like the Glacier shear zone, along the larger scale north-south trend (Fig. 3.23a). 89 4. Conclusions This research completed two principle objectives: 1) map, date and classify the Mitchell deposit, and 2) determine the relative timing and nature of post-emplacement flattening (S1). In addition, a correlation is made between strain intensity and the degree and type of hydrothermal alteration. Research presented in Chapter 2 demonstrates that the Mitchell deposit is a calc-alkalic porphyry associated with the emplacement of subalkaline Sulphurets suite dioritic magmatism, not the alkaline Premier suite plutons as previously interpreted. The deposit is correlated with the structurally offset Snowfield deposit based on lithology and metal zonation patterns. Four general stages of mineralization, alteration and veins are identified (Stage 1-4; Fig. 4.1); the first three relate temporally to three phases of dioritic plutonism (Phase 1-3). The Mitchell-Snowfield system was emplaced into a basinal setting where siliciclastic sedimentation and subaqueous volcanism (Jack Formation) was ongoing (i.e., preceded Stage 1 mineralization and post-dated Stage 3 mineralization). Three new U-Pb zircon ages for the Sulphurets suite diorite and one Re-Os molybenite age indicate that magmatic-hydrothermal mineralizing process started after 198.9 and ended before 189.9 Ma (Fig. 4.1). In Chapter 3, my research demonstrates that the S1 cleavage post-dates porphyry emplacement and is related to the earliest phase of deformation related to the SFTB (Fig. 4.1). Three phases of progressive deformation related to the mid-Cretaceous SFTB are identified: Deformation Phase 1) development of a widespread pressure solution cleavage (S1) and associated steeply west-plunging folded veins (F1), Deformation Phase 2) development of steeply, north-plunging folds, and Phase 3) development of thrust and imbricate faults (Fig. 4.1). Porphyry alteration types control strain distribution: the flattening intensity, fold geometry and S1 cleavage intensity and geometry are directly related to host rock alteration. A newly identified fault, the Mitchell basal thrust, is identified at depth in the Mitchell deposit, and it offsets the Mitchell deposit from its core zone to the west. Early Jurassic vein orientations and alteration trends, in addition to pre-S1 (Early Jurassic ? ) fault geometries, are predominantly east-west striking, an orientation that is orthogonal to the north-south mineral trend in the Sulphurets district. Chapter 3 concludes by presenting a model for the syn-emplacement structural setting of the Mitchell deposit (D1). Here it is proposed that the Mitchell-Snowfield deposit was emplaced into a structurally controlled, Early Jurassic pull-apart basin (Fig. 4.1) within a district-scale transtensive step-over between the Sulphurets and Brucejack faults. Mineralization, veins and alteration in the Mitchell deposit are controlled by second order east-west striking subsidiary structures throughout the life of the mineral system. 90 Fig. 4.1. The structural evolution of the Mitchell-Snowfield system plotted over time and temperature. Contoured stereographic projections are of poles to planes except for F1 and F2, average planes are plotted in white. Temperature determinations and estimates inferred from the Snowfield deposit (O-isotope; Margolis, 1993). 91 References Alldrick, D.J., 1993. Geology and metallogeny of the Stewart mining camp, northwestern B.C. British Columbia Ministry of Energy, Mines and Petroleum Resources, British Columbia Geological Survey Bulletin 85, 105 p. Alldrick, D.J., and Britton, J.M., 1988. Geology and mineral deposits of the Sulphurets area. British Columbia Ministry of Energy, Mines and Petroleum Resources, British Columbia Geological Survey Open File 1988-04: scale 1:50,000. 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List of field structure data from the Mitchell deposit and surrounding areas 100 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423534 6265140 210 0 Fold D2 P3 Vein and foliation folded into gentle fold train provides thrust kinematics 3 2014-07-08 423529 6265056 314 60 Normal Fault D3 2 cm spaced fabric nearby normal fault with reidel indicating west side down 1 2014-07-08 423682 6265108 2 40 S1 D2 P1 local fabric, rest of outcrop lacks cleavage 2 2014-07-08 423624 6265141 154 44 Thrust Fault D2 P3 sigmoidal fabric indicates, photo view east 3 2014-07-08 423612 6265135 158 32 Thrust Fault D2 P3 sigmoidal fabric indicates, photo view east 3 2014-07-08 423614 6265135 110 37 Lineation Intersection D2 P3 intersection lineation between y plane of thrust and fault fabric , perpendicular line on fault is movement direction 3 2014-07-08 423609 6265136 185 75 S1 D2 P1 irregular here, maybe not rotated 3 2014-07-08 423613 6265151 295 28 Lineation Intersection D2 P3 2 2014-07-08 423463 6265525 186 84 Dyke D1 boundary of ibx dyke 2 2014-07-09 425605 6265811 325 65 S1 D2 P1 pervasive subtle fabric defined by chl 1 2014-07-12 425608 6265813 315 90 S2 D2 P2 mm spacing to fracture cleavage cuts S1 1 2014-07-12 425638 6265774 0 35 Slickensides D3 mulions, qz fabric lineated define lastmovement 1 2014-07-12 425564 6265792 120 40 Fault No Kinematics D2 P3 minor shear faultlets,2 m spaced 1 2014-07-12 425454 6265777 0 70 S1 D2 P1 pervasive subtle fabric defined by chlorite, consistent with mitchell S1 fabrics 1 2014-07-12 425445 6265767 285 52 Reverse Fault D2 P3 distributed fracture cleavage with top to the east, 8 m wide deformation zone 1 2014-07-12 425440 6265765 270 66 Reverse Fault D2 P3 distributed fracture cleavage with top to the east, 8 m wide deformation zone 1 2014-07-12 424939 6265692 17 85 S1 D2 P1 intense s1 pervasive fabric (sample), red pencil 2 2014-07-12 424941 6265693 328 75 S2 D2 P2 semi pervasive fabric cuts S1, green pencil 2 2014-07-12 424941 6265690 40 77 S2 D2 P2 semi pervasive fabric cuts S1, purple pencil 2 2014-07-12 424943 6265694 293 80 Vein Fold D2 P1 tight classic vein fold, 80->293 2 2014-07-12 424918 6265665 350 76 S1 D2 P1 strong 4 2014-07-12 424928 6265671 9 81 S1 D2 P1 purple 4 2014-07-12 424927 6265674 360 80 S2 D2 P2 yellow, sinistral 4 2014-07-12 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 101 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 424930 6265670 25 81 S2 D2 P2 green, dextral 4 2014-07-12 424834 6265632 355 74 S1 D2 P1 pervasive intense fabric cut 4 2014-07-12 424839 6265631 335 82 Spaced Cleavage D2 P2 pervasive coaxal flattening localized into non coaxial , unknown timing but cuts S1, C-S fabrics! locally mylonitic 4 2014-07-12 424861 6265573 10 78 S1 D2 P1 intense foliation 4 2014-07-12 424858 6265654 343 66 S1 D2 P1 intense, some sinistral shear 4 2014-07-12 424857 6265635 345 72 S1 D2 P1 sample location of enigmatic C-S fabric and possible mylonite lacks vein offset 4 2014-07-12 424944 6265748 355 80 S1 D2 P1 ser, perv 2 2014-07-12 424948 6265758 280 77 Bedding D1 exceptional planar clasts provide eutaxitic fabric of volcanic pile, nearly perpendicular to fabric! 2 2014-07-12 424955 6265753 280 84 Vein D1 narrow qtz-py vein -many appear to follow beds 2 2014-07-12 424951 6265767 295 65 S2 D2 P2 spaced cleavage very subtle 2 2014-07-12 424951 6265763 93 0 Fold D2 P1 vein fold open, 82-> 93 2 2014-07-12 423814 6265155 203 53 Thrust Fault D2 P3 Y-plane of Mitchell thrust fault or nearby splay to the thrust, excellent top-to-the-southeast kinematics 2014-07-14 423791 6265154 213 43 Thrust Fault D2 P3 Y-plane of Mitchell thrust or splay, top to the East 2014-07-14 423795 6265155 210 48 Reverse Fault D2 P3 Measurement of Y-plane of thrust splay/reverse fault that traces into the fault itself 2014-07-14 423807 6265155 205 85 S1 D2 P1 Main foliation 2014-07-14 423811 6265155 300 34 Lineation Pencil Cleavage D2 P3 Pencil lineation just below fault 2014-07-14 423824 6265181 16 76 Vein D1 Quartz veins are subparallel, boudined and up to 5 cm wide, 2 2014-07-17 423822 6265178 21 77 S1 D2 P1 4 2014-07-17 423825 6265178 305 24 Fold D2 P3 Gentle fold define dy foliation 4 2014-07-17 423820 6265178 218 34 Dextral fault Shearband dextral (34->218) 4 2014-07-17 423298 6264578 256 90 Joint D3 1 2014-07-18 423322 6264555 345 90 Spaced Cleavage D3 interpreted as tectonic cleavage, local cm spacing, some up to m 1 2014-07-18 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 102 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423320 6264550 57 83 Joint D3 1 2014-07-18 423318 6264546 199 89 Joint D3 1 2014-07-18 423317 6264542 15 70 Spaced Cleavage D2 P1 locally pervasive sericite foliated corridor 1 2014-07-18 423302 6264521 275 69 Bedding D1 cm scale spacing to folded fractures appesarto be subtlety folded tuff/sed beds, 1 2014-07-18 423305 6264517 317 80 Joint D3 2014-07-18 423297 6264505 262 72 Joint D3 1 2014-07-18 423283 6264508 182 70 Joint D3 1 2014-07-18 423270 6264485 219 85 Joint D3 1 2014-07-18 423268 6264475 18 17 Joint D3 1 2014-07-18 423222 6264357 266 71 Joint D3 1 2014-07-18 423213 6264345 45 82 Vein D1 1cm wide milky white quartz vein sharp boundaeries 1 2014-07-18 423088 6264054 38 83 Vein D1 hairline fractures infilled by dark chlorite 1 2014-07-18 423087 6264041 345 35 Bedding D1 colour bands in aphanitic dacite, interpreted to be stratification 1 2014-07-18 423116 6264042 177 80 Vein D1 qz-ankerite 1 2014-07-18 423453 6264111 357 55 S1 D2 P1 local fabric pervasive dfined by sericite 1 2014-07-18 423507 6264110 32 73 S1 D2 P1 pervasive sericite only in phyllic altered patch of outcrop 2 2014-07-18 423506 6264129 60 86 Vein D1 thick py-only vein transposed into foliation 2 2014-07-18 423934 6264833 14 50 S1 D2 P1 pervasive corridor of foliated ser 1 2014-07-18 423851 6264238 35 88 S1 D2 P1 patchy penetrative cleavage in patchy sericite altered regions 2 2014-07-19 423860 6264207 128 77 Vein Tectonic D2 P3 discontinuous qz tension gashes en echelon indicate sinistral 1 2014-07-19 423858 6264205 189 65 Sinistral fault D2 P3 enveloping surfce to en echelon sinistral shear, related to STF? 1 2014-07-19 423859 6264229 172 70 Spaced Cleavage D2 P1 1 cm spacing 1 2014-07-19 423869 6264117 224 87 S1 D2 P1 weakly developed penetrative foliation defined by chl 1 2014-07-19 423898 6264137 14 76 S1 D2 P1 weakly developed penetrative foliation defined by chl 1 2014-07-19 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 103 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423915 6264150 352 60 S1 D2 P1 weakly developed penetrative foliation defined by chl 1 2014-07-19 423905 6264145 304 69 Lineation D1 subtle clast lineation, photo view to south 1 2014-07-19 423943 6264119 4 82 S1 D2 P1 pervasive weak foliation defined by chlorite, view west 1 2014-07-19 423895 6264053 4 53 S1 D2 P1 pervasive weak foliation defined by chlorite, view east 1 2014-07-19 423881 6263992 19 70 Bedding D1 porphyritic hypabyssal clasts define ?volc layering 1 2014-07-19 423880 6264012 21 90 Sinistral fault D2 P3 sigmoidal tension gashes sinistral, reading of slip surface 1 2014-07-19 423873 6264010 9 80 S1 D2 P1 pervasive weak foliation defined by chlorite 1 2014-07-19 423870 6264002 112 38 Vein Tectonic D2 P1 en echelon tension gashes milky white qtz(up to 10cm, several); interpreted to be D1 flattening as they are weakly folded by F1 and cut foliation, some subtle sinistral sigmoids 1 2014-07-19 423872 6263999 192 90 Sinistral fault D2 P1 small offset of tectonic vein; photo view east, sinistral flattening 1 2014-07-19 423810 6263993 6 63 S1 D2 P1 locally sericitic patch 1 2014-07-19 423767 6263971 246 70 Spaced Cleavage competent host rock lacks clear S1, dominated by fracture cleage 1 2014-07-19 423769 6263957 223 83 Spaced Cleavage D2 P1 very subtle chl-defined foliation 1 2014-07-19 423788 6264012 26 82 S1 D2 P1 very subtle chl-defined foliation 1 2014-07-19 423759 6264013 212 60 Sinistral fault D2 P1 Excellent syntaxial qtz coarsens towards centre, sinistral offsets of fault-related veins, photo view SE hammer=fault 1 2014-07-19 423756 6264015 84 65 Vein Tectonic D2 P1 Excellent syntaxial qtz coarsens towards centre, sinistral offsets of fault-related veins 1 2014-07-19 423690 6264003 31 78 Sinistral fault D1 stepover on small sinistral fault 1 2014-07-19 423685 6264006 35 80 Bedding D1 eutaxitic fabric defined by flattened fluidal monz-syen clasts 1 2014-07-19 423326 6265061 254 62 Joint D3 1 2014-07-21 423309 6265077 12 42 S1 D2 P1 locally pervasive 1 2014-07-21 423367 6265062 210 58 Reverse Fault D2 P3 thin minor fault -deformation zone of MTA 1 2014-07-21 423350 6265107 246 49 Reverse Fault D2 P3 thin brittle fault, reidels give reverse 1 2014-07-21 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 104 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423339 6265082 197 46 Reverse Fault D2 P3 thin fault top to the east, reidel shears common 85->149 1 2014-07-21 423343 6265076 145 61 Vein Tectonic D2 P3 tension gashes in reidel geometry 1 2014-07-21 423441 6265049 298 62 Joint D3 1 2014-07-21 423431 6265047 70 70 Joint D3 1 2014-07-21 423251 6265057 268 75 Vein D1 pink-white qtz-kp veins stockwork most subparallel 1 2014-07-21 423286 6265066 175 82 Vein D1 pink-white qtz-kp veins stockwork most subparallel 1 2014-07-21 423205 6265073 326 80 Vein D1 sheeted ~1cm veins locally hosted in wall rock cut byred10 cm crowded porphyry 1 2014-07-21 423156 6265093 346 55 Joint D3 strong fracture sets, maybe young normal faults 1 2014-07-21 423045 6264951 50 79 Joint D3 1 2014-07-21 423130 6264949 261 66 Joint D3 strong jointing subparallel 1 2014-07-21 423126 6264948 188 65 Joint D3 1 2014-07-21 423134 6264949 304 73 Joint D3 1 2014-07-21 423588 6264117 51 88 Joint D3 spaced joints 1 2014-07-22 423592 6264118 329 70 Joint D3 1 2014-07-22 423631 6264148 322 56 S1 D2 P1 pervasive foliation very locally in sericitic corridor of alteration 2 2014-07-22 423629 6264151 70 73 Reverse Fault D2 P1 sigmoidal tension gashes indicate reverse - dextral movement- D1? 1 2014-07-22 423630 6264151 136 74 Vein Tectonic D2 P1 sigmoidal tension gashes indicate reverse - dextral movement- D1? 1 2014-07-22 423638 6264226 217 60 Joint D3 this area lacks prominent jointing, massive competent rock 1 2014-07-22 423640 6264229 2 85 Joint D3 1 2014-07-22 423623 6264233 245 90 Dextral fault 10 cm wide foliated cataclasite with sigmoidal dextral qz clasts 1 2014-07-22 423664 6264181 46 86 S1 subtle fabric defined by chl flow banding 1 2014-07-22 423736 6264165 214 88 Joint D3 1 2014-07-22 423739 6264167 113 55 Vein Tectonic D2 P1 3 cm wide tension gashes lck shear, view east 1 2014-07-22 423744 6264165 30 67 S1 D2 P1 subtle fabric <1mm spacing. photo view NE 1 2014-07-22 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 105 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423733 6264134 237 70 S1 D2 P1 corridor of ser altered rock pervasive foliation locally 1 2014-07-22 423743 6264147 214 82 S1 D2 P1 mixed pervasive and spaced foliation- D1? 1 2014-07-22 423761 6264162 224 83 Spaced Cleavage D2 P1 very strong fracture cleavage 1 2014-07-22 423781 6264176 1 68 S1 D2 P1 localized strain in slightly more chloritic domains 1 2014-07-22 423782 6264181 3 21 Joint D3 1 2014-07-22 423798 6264194 13 75 S1 D2 P1 subtle pervasive cleavage defined by chl and tr ser 1 2014-07-22 423841 6264218 23 83 S1 D2 P1 subtle pervasive cleavage defined by chl and tr ser 1 2014-07-22 423768 6264234 57 88 S1 D2 P1 intense pervasive foliation defined by ser 4 2014-07-22 423769 6264238 113 79 Vein D1 qtz and tr sulphide 4 2014-07-22 423767 6264239 110 77 Vein Fold D2 P1 gentle fold of qtz vn axial planar to fabric 4 2014-07-22 423769 6264242 30 70 Lineation Crenulation D2 P2 subtle crenulation of S1 4 2014-07-22 424101 6264099 66 6 S1 D2 P1 intensely foliated defined by sericitized 4 2014-07-23 424097 6264096 317 78 Vein D1 ~1cm wide boudined py>qtz 4 2014-07-23 424080 6264091 4 85 S1 D2 P1 intensely foliated defined by sericitized 4 2014-07-23 424030 6264057 19 79 S1 D2 P1 intensely foliated defined by sericitized 4 2014-07-23 424048 6264041 356 90 Vein Tectonic D2 P3 20 cm wide, cal-qtz-blue-green chl (resembles vermicular D3-associated chl from mitchell area), sharp boundaries- boudined? 1 2014-07-23 424049 6264038 343 90 Vein Tectonic D2 P3 70 cm wide, cal-qtz-blue-green chl (resembles vermicular D3-associated chl from mitchell area), sharp boundaries: stronly sigmodal older vein suggests top to SE 4 2014-07-23 424049 6264040 308 18 Thrust Fault D2 P3 shallow <1mm thick fault plane offsets tec vns to SE: 1 2014-07-23 424049 6264040 333 14 Slickensides D2 P3 on fault plane 1 2014-07-23 424045 6264046 330 90 Vein Tectonic D2 P3 20cm cal-qtz-blue-green chl (resembles vermicular D3-associated chl from mitchell area), sharp boundaries 1 2014-07-23 424044 6264056 30 90 Bedding D1 platy alignment of clasts 1 2014-07-23 424045 6264076 31 78 Bedding D1 platy alignment of clasts 1 2014-07-23 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 106 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 424001 6264029 10 48 S1 D2 P1 2 2014-07-23 424037 6264050 175 90 Sinistral fault D2 P1 fault 1cm thick sinistral offset of sigmoidal tension gashes; d1? photo view east 1 2014-07-23 424026 6263996 303 61 Reverse Fault D2 P3 20cm wide foliated cataclasite, sigmoidal quartz sows top to south, photo view west 2 2014-07-23 424010 6263968 186 67 Bedding D1 cm scale stratification of andesite crystal tuff overlain by block ash flow -dextral offset of beds 1 2014-07-23 423982 6263965 202 40 Sinistral fault D2 P1 up to 50cm wide sigmoidal tension gashes, 10cm wide fault zone, d? photo view south. 1 2014-07-23 423979 6263960 226 73 S1 D2 P1 1 2014-07-23 423980 6263959 196 90 S2 D2 P2 subtle sinistral slip? cuts s1. photo views east 1 2014-07-23 423932 6263929 271 85 Vein Fold D2 P1 qtz-ank 2cm wide d1 vein folded by s1, view west 2 2014-07-23 424882 6266647 326 71 Vein D1 several subparallel qtz-py-cpy veins and bxs, potential for au-pb-zn 1 2014-07-25 424807 6266612 146 90 Vein D1 70 cm wide py-dominated vein minor silver sulphidesgal-sph? 1 2014-07-25 424486 6266485 0 75 Vein D1 anastamosing breccia and veins up to 10 cm:qtz, fleshy pink adularia, calcite, py, cpy, medium grained galena, sulphosalts low sulphidation peripheral to mitchell, open space growth textures, view west 1 2014-07-26 424526 6266473 122 90 Bedding D1 clast imbrication -subtle beds 1 2014-07-26 424529 6266484 91 80 Bedding D1 subtle bedding of sandstone defined by grain size change and sulphide replacement, near unconformity 1 2014-07-26 424547 6266485 292 78 Bedding D1 subtle bedding of sandstone defined by grain size change and sulphide replacement, near unconformity 1 2014-07-26 424635 6266543 30 90 Bedding D1 subtle subvertical clast imbrication:appears to be vcl 1 2014-07-26 424538 6266467 96 84 Bedding D1 stratiform bedding, stratiform alb-chl 1 2014-07-26 424492 6266445 112 90 Bedding D1 5 cm wide finer sand defines bed 1 2014-07-26 424475 6266436 290 85 Bedding D1 band of alb-chl-qtz-py diseased texture defines crude beddingof replaced concretions 1 2014-07-26 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 107 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 424437 6266425 323 25 Thrust Fault D2 P3 very thin fault plane subtle reidels indicate top 1 2014-07-26 424438 6266423 45 90 Spaced Cleavage D2 P3 fracture cleavage appears to be parallel to transport direction, no pervasive fabric here 1 2014-07-26 424337 6266431 312 88 Sinistral fault D2 P1 brittle 2 mm wide sinistral excellent reidel: 86->259 R plane 1 2014-07-26 423249 6265900 110 10 Thrust Fault D2 P3 very thin fault zone, thin cataclased gauge no kinematics, curviplanar, reactivated?, view N 1 2014-07-28 423235 6265897 149 14 Thrust Fault D2 P3 very thin fault zone, thin cataclased gauge no kinematics, curviplanar, reactivated?, view N 1 2014-07-28 423235 6265898 63 88 Spaced Cleavage D2 P3 strong cleavages in hanging wall appear to be related to thrusting?, possibly an earlier deformation? perpendicular to thrust 1 2014-07-28 423142 6265915 238 62 Spaced Cleavage D2 P3 subparallel fractures parallel reverse faults 1 2014-07-28 423163 6265920 240 47 Reverse Fault D2 P3 broken 10 cm wide fault zone, reverse shear indicated by clasts 1 2014-07-28 423190 6265966 215 53 Spaced Cleavage D2 P3 strong subparalell fractures mimic reverse faulrs 1 2014-07-28 423180 6265965 278 45 Reverse Fault D2 P3 10 cm wide cataclasite foliated, reverse 1 2014-07-28 423253 6265956 105 40 Thrust Fault D2 P3 prominent flat fault, subtle kinematics top to the NE (potential ramp area resulting in anomalous movement, view SW 1 2014-07-28 423249 6265957 277 60 Spaced Cleavage D2 P3 strong fractures appear to be related to thrust 1 2014-07-28 423253 6265961 316 70 Spaced Cleavage D2 P3 subtle fractures possibly reidels near thrust 1 2014-07-28 423319 6266108 340 62 Spaced Cleavage D2 P3 1 2014-07-28 423326 6266109 284 58 Joint D3 1 2014-07-28 423269 6265954 219 82 Vein D1 qtz-mt-kp veins subparallel 1 2014-07-28 423218 6265874 244 11 Reverse Fault D2 P3 curviplanar shallow fault reactivated during thrusting, reverse N-Sdirected compression folded by D3, photo view east 1 2014-07-28 423291 6265897 276 82 Spaced Cleavage D2 P3 1 2014-07-28 423291 6265894 43 71 Vein Tectonic D2 P2 tectonic vein cut by d3 cleavage 1 2014-07-28 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 108 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423294 6265880 236 20 Fault No Kinematics D2 P3 1 2014-07-28 423363 6265873 300 80 Spaced Cleavage D2 P3 1 2014-07-28 423382 6265890 95 24 Fault No Kinematics D2 P3 very curviplanar fault surface, ramps up to west (back thrust? older fault reactivated as triangle zone, photo view NE 1 2014-07-28 423375 6265860 123 20 Fault No Kinematics D2 P3 folded curviplanar fault not possible to trace through cliff 1 2014-07-28 423415 6265901 220 20 Fault No Kinematics D2 P3 folded curviplanar fault not possible to trace through cliff 1 2014-07-28 424179 6266473 169 84 Spaced Cleavage D2 P1 1 2014-08-17 424229 6266481 323 80 Spaced Cleavage D2 P3 1 2014-08-17 424184 6266433 350 78 Vein D1 green/white stratiform py-cp replacement, very effervescent, away froom vein is aph fels?olc 1 2014-08-17 424165 6266414 20 83 S1 D2 P1 1 2014-08-17 424153 6266401 326 59 Reverse Fault D2 P3 5 cm rev fault top tp SE 1 2014-08-17 424134 6266398 334 31 Reverse Fault D2 P3 1 2014-08-17 424135 6266397 60 58 Bedding D1 green-white colour banded fels tuffs? 1 2014-08-17 424137 6266383 314 56 Reverse Fault D2 P3 eroded fault gauge, prominent slip plane correlates best with offset, microdiorite FW and bedded fels tuff HW 1 2014-08-17 423673 6265280 226 62 S1 D2 P1 4 2014-08-26 423684 6265294 192 62 S1 D2 P1 4 2014-08-26 423694 6265304 210 20 S1 D2 P1 4 2014-08-26 423698 6265319 192 50 S1 D2 P1 4 2014-08-26 423690 6265318 165 57 S1 D2 P1 4 2014-08-26 423686 6265322 242 48 S1 D2 P1 4 2014-08-26 423672 6265322 220 48 S1 D2 P1 4 2014-08-26 423658 6265318 48 63 S1 D2 P1 4 2014-08-26 423648 6265323 34 55 S1 D2 P1 4 2014-08-26 423640 6265321 176 50 S1 D2 P1 4 2014-08-26 423640 6265321 176 69 Lineation Crenulation D2 P2 4 2014-08-26 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 109 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423624 6265322 220 80 S1 D2 P1 4 2014-08-26 423615 6265326 205 82 S1 D2 P1 4 2014-08-26 423595 6265330 205 50 S1 D2 P1 4 2014-08-26 423581 6265334 210 80 S1 D2 P1 4 2014-08-26 423592 6265353 30 52 S1 D2 P1 4 2014-08-26 423611 6265365 20 80 Spaced Cleavage D2 P1 4 2014-08-26 423640 6265360 176 84 S1 D2 P1 4 2014-08-26 423648 6265333 209 59 S1 D2 P1 4 2014-08-26 423684 6265328 175 55 S1 D2 P1 4 2014-08-26 423687 6265335 210 65 Vein Fold D2 P1 green open 4 2014-08-26 423686 6265334 245 50 Vein Fold D2 P1 green open 4 2014-08-26 423686 6265334 172 40 Vein Fold D2 P2 yellow gentle 4 2014-08-26 423698 6265326 153 59 S1 D2 P1 4 2014-08-26 423700 6265326 188 30 Vein Fold D2 P1 4 2014-08-26 423701 6265326 210 35 Vein Fold D2 P1 4 2014-08-26 423702 6265327 167 32 Vein Fold D2 P2 4 2014-08-26 423703 6265326 161 42 Vein Fold D2 P2 4 2014-08-26 423716 6265325 165 35 S1 D2 P1 4 2014-08-26 423724 6265335 220 26 Vein Fold D2 P1 open vein folds 4 2014-08-26 423725 6265330 212 53 S1 D2 P1 photo view S, rotated s1 cleavage 4 2014-08-26 423762 6265347 250 35 S1 D2 P1 4 2014-08-26 423780 6265355 208 70 S1 D2 P1 4 2014-08-26 423790 6265346 212 55 S1 D2 P1 4 2014-08-26 423795 6265368 210 59 S1 D2 P1 view south 4 2014-08-26 423800 6265384 195 46 S1 D2 P1 view south 4 2014-08-26 423805 6265366 222 64 Vein D1 4 2014-08-26 423767 6265366 196 63 S1 D2 P1 4 2014-08-26 423774 6265375 188 50 S1 D2 P1 4 2014-08-26 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 110 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423815 6265380 260 75 S1 photo view s, transposed S1? F1 argues is very large very rotsted subcrop 4 2014-08-26 423818 6265376 222 27 S1 D2 P1 2 2014-08-26 423840 6265365 215 32 S1 D2 P2 4 2014-08-26 423841 6265364 216 67 S1 D2 P1 4 2014-08-26 423844 6265360 172 55 Vein D1 thin qtz-py-to vein associated with disseminated tourmaline 4 2014-08-26 423837 6265351 206 58 S1 D2 P1 4 2014-08-26 423844 6265353 161 76 Vein Fold D2 P1 4 2014-08-26 423853 6265352 230 70 S1 D2 P1 4 2014-08-26 423862 6265334 205 63 S1 D2 P1 4 2014-08-26 423875 6265341 201 44 S1 D2 P1 view SW 4 2014-08-26 423849 6265368 198 82 S1 D2 P1 4 2014-08-26 423841 6265386 215 76 S1 D2 P1 4 2014-08-26 423813 6265396 250 85 S1 D2 P1 4 2014-08-26 423790 6265399 195 37 S1 D2 P1 4 2014-08-26 423768 6265405 147 62 S1 D2 P1 4 2014-08-26 423703 6265425 180 70 S1 D2 P1 4 2014-08-26 423695 6265444 343 70 S1 D2 P1 4 2014-08-26 423714 6265448 0 69 S1 D2 P1 4 2014-08-26 423707 6265460 340 66 S1 D2 P1 4 2014-08-26 423726 6265465 85 88 S1 D2 P1 4 2014-08-26 423738 6265491 165 59 S1 D2 P1 4 2014-08-26 423748 6265504 333 56 S1 D2 P1 4 2014-08-26 423915 6265523 4 60 S1 D2 P1 4 2014-08-26 423969 6265525 345 46 S1 D2 P1 4 2014-08-26 423987 6265564 333 63 S1 D2 P1 4 2014-08-26 424020 6265562 12 45 S1 D2 P1 4 2014-08-26 424046 6265589 348 59 S1 D2 P1 2 2014-08-26 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 111 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 424053 6265567 335 71 S1 D2 P1 2 2014-08-26 424066 6265503 170 80 S1 D2 P1 2 2014-08-26 424447 6265605 175 87 S1 D2 P1 intense pressure solution cleavage 4 2014-08-27 424445 6265606 265 50 Vein Fold D2 P3 open to tight fold train 50% flattening or more 4 2014-08-27 424445 6265606 255 41 Vein Fold D2 P1 open to tight fold train 50% flattening or more 4 2014-08-27 424422 6265600 168 78 S1 D2 P1 4 2014-08-27 424422 6265599 152 45 Vein Fold D2 P2 4 2014-08-27 424438 6265579 187 39 Reverse Fault D2 P3 10 cm fault zone suggests top to the east but is rotated 4 2014-08-27 424440 6265582 165 67 S1 D2 P3 4 2014-08-27 424442 6265557 213 53 S1 D2 P1 4 2014-08-27 424421 6265549 149 41 S1 D2 P1 4 2014-08-27 424380 6265528 160 43 S1 D2 P1 4 2014-08-27 424372 6265527 228 35 S1 D2 P1 4 2014-08-27 424370 6265525 219 35 Vein Fold D2 P1 4 2014-08-27 424350 6265519 190 56 S1 D2 P1 4 2014-08-27 424320 6265478 212 20 S1 D2 P1 4 2014-08-27 424259 6265467 185 52 S1 D2 P1 4 2014-08-27 424229 6265462 184 53 S1 D2 P1 4 2014-08-27 424240 6265487 175 60 S1 D2 P1 4 2014-08-27 424241 6265484 305 64 Vein Fold D2 P1 4 2014-08-27 424247 6265510 217 58 S1 D2 P1 4 2014-08-27 424259 6265596 3 68 S1 D2 P1 4 2014-08-27 424271 6265607 8 80 S1 D2 P1 4 2014-08-27 424263 6265604 355 58 S1 D2 P1 4 2014-08-27 424273 6265609 8 82 Vein Fold D2 P2 4 2014-08-27 424264 6265596 349 46 S1 D2 P1 4 2014-08-27 424257 6265588 30 90 Vein Fold D2 P2 4 2014-08-27 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 112 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 424221 6265555 5 71 S1 D2 P1 4 2014-08-27 424224 6265563 30 89 Vein Fold D2 P2 4 2014-08-27 424212 6265549 53 88 Vein Fold D2 P2 4 2014-08-27 424251 6265595 140 58 Vein Fold D2 P1 open 4 2014-08-27 424250 6265595 8 59 Vein Fold D2 P2 open 4 2014-08-27 424263 6265610 350 55 S1 D2 P1 4 2014-08-27 424186 6265598 29 36 S1 D2 P1 4 2014-08-27 424186 6265609 85 65 Vein Fold D2 P1 folded jurassic sinistral? tension gashes similar to south mitchell sinistral sigmoids 4 2014-08-27 424186 6265610 12 62 S1 D2 P1 4 2014-08-27 424186 6265610 10 60 Vein Fold D2 P2 4 2014-08-27 424183 6265637 15 52 S1 D2 P1 4 2014-08-27 424177 6265650 5 65 S1 D2 P1 2 2014-08-27 424142 6265634 4 40 S1 D2 P1 2 2014-08-27 424129 6265629 356 44 Spaced Cleavage D2 P1 2 2014-08-27 424110 6265636 355 40 S1 D2 P1 2 2014-08-27 424079 6265621 357 55 S1 D2 P1 2 2014-08-27 424053 6265620 5 42 S1 D2 P1 sil-ser-chl intense 2 2014-08-27 424025 6265619 355 68 S1 D2 P1 sil-chl 2 2014-08-27 424024 6265639 352 74 S1 D2 P1 sil-chl 2 2014-08-27 424008 6265649 354 75 S1 D2 P1 2 2014-08-27 423993 6265658 8 67 S1 D2 P1 2 2014-08-27 423989 6265615 340 65 S1 D2 P1 2 2014-08-27 423968 6265610 355 62 S1 D2 P1 2 2014-08-27 423952 6265607 356 56 S1 D2 P1 2 2014-08-27 423942 6265631 353 78 S1 D2 P1 2 2014-08-27 423942 6265633 301 86 Vein Fold D2 P2 2 2014-08-27 423927 6265635 352 70 S1 D2 P1 2 2014-08-27 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 113 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423909 6265640 345 75 S1 D2 P1 2 2014-08-27 423902 6265640 340 60 Vein Fold D2 P2 2 2014-08-27 423930 6265614 346 60 S1 D2 P1 2 2014-08-27 423930 6265614 30 57 Vein Fold D2 P1 2 2014-08-27 423944 6265597 345 52 S1 D2 P1 2 2014-08-27 423720 6265679 5 58 S1 D2 P1 2 2014-08-27 423735 6265684 321 60 Vein Fold D2 P2 yellow=f1, green=f2 (green pointa N) 2 2014-08-27 423735 6265685 66 77 Vein Fold D2 P1 yellow=f1, green=f2 2 2014-08-27 423685 6265695 345 62 Vein Fold D2 P1 2 2014-08-27 423366 6265286 30 90 Vein Fold 350/90, 1/m sparse quartz wormy, trace py, chloritic fine-grained tuffs 2012-07-06 423366 6265286 40 70 Vein Fold 2012-07-06 422958 6265505 270 20 Mineral Alignment Primary D1 4% Qz-Py veins most <1cm wide, 3 stwk angles Major: 220/70 and Minor: 200/54 and 278/47, all have py+/-Cp (Tr) and dip N overall 278 vein shows most compression 2012-07-06 423366 6265286 130 50 Vein Tectonic contains no clear foliation and veins that cut it are sparse, 6/m, <3mm wide qz and wormy in strangely any direction, one vein actually cuts a xenolith clast, clas 2012-07-06 423043 6265547 190 20 S1 D2 P1 2012-07-06 423177 6265299 220 72 Vein D1 Lith: strong quartz veins parallel at 252/72, ductile shear bands indicate centimetric movement to the south, motion is subhorizontal 2012-07-06 423551 6265557 290 54 Vein D1 2012-07-06 423551 6265557 310 70 Vein D1 5% Quartz veins, deformed >90% in major axis 225/58, secondary veins orthogonal/perpendiuclar cooling cracks? 2012-07-06 423507 6265536 315 58 Vein D1 some foliation parallel and perpendicular veins (Py-glassy lim-qz), FOLIATION AND MOST VEINS 296/90, SMALL SUBSETS INTRA-QZ VEINS AT 10/80, <1 2012-07-06 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 114 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423404 6265298 342 72 Vein D1 foliation and narrow quartz veins at 100/20, very large clast of qz-cp xenolith across gully ?fault veins, foliation are near perpendicular at 330/90 (very ball park), fine-grained chloritic rock - many small clasts 2012-07-06 423177 6265299 350 80 Vein D1 1/m 180/52 veins 2-3 cm, wormy mo-py-cp, numerous qz wormy veins <1cm 5/m, very weak foliation here difficult to distinguish from stria 2012-07-06 423551 6265557 8 47 Vein D1 2012-07-06 423507 6265536 10 74 Vein D1 2012-07-06 423488 6265362 12 78 S1 D2 P1 15m wide zone at least weak 270->20 lineatiuon but strangely no foliation a few stringer veins cut the unit 2012-07-06 423236 6265304 26 90 S1 D2 P1 40/50 4cm wide vuggy epithermal Qz-only vein, clearly cuts deformed veins (photo) Lith: VU, strong deformed quartz veins, one clast of stockworked quartz set in rock, a shear band showing sinistral shear (photo) is truncated by Qz vuggy vein, shear i 2012-07-06 423236 6265304 26 90 Vein D1 unstratified, homogeneous, very fine-grained, massive tuff/flow or microdiorite STC:L moderate folding of veins, primary trend 220/50 2012-07-06 423366 6265286 30 90 S1 D2 P1 very strong foliation and all vein parallel veining, 10-15% Qz veins all with foliation 282/78 2012-07-06 423102 6265523 80 90 Vein D1 260/80 larger quartz veins 1-2 cm, another set of veins 130/72 most <1cm quartz veins and stringers at 10 deg azimuth 2012-07-06 423672 6265665 220 50 Vein Fold L moderate folding of veins, primary trend 220/50 2012-07-10 424093 6265562 226 72 Mineral Alignment Primary D1 ~1-2cm elongate and foliated groundmass is silica -?sericite/IARG, texture very consistent over outcrop 5x5m, weak lineation to clasts 226->72 2012-07-10 423295 6265468 130 80 Joint a distinct set of joints, 58/70 and 40/80 and 160/91 2012-07-10 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 115 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423538 6265699 132 82 Vein D1 contains no clear foliation and veins that cut it are sparse, 6/m, <3mm wide qz and wormy in strangely any direction, one vein actually cuts a xenolith clast, clas 2012-07-10 423295 6265468 148 70 Joint green, fine-grained andesite, gossanous hump to south and to north more green and less siliceous- a distinct set of joints, 58/70 and 40/80 and 160/92 2012-07-10 423647 6265395 185 41 Vein D1 subcrop and talus slopes of sericite schist, most blocks are rotated, unsure of orientation, abundant mo in qz veins, wavy and banded textures, rock is white and yellow 2012-07-10 423538 6265699 232 72 Vein D1 no clear foliation and veins that cut it are sparse, 6/m, <3mm wide qz and wormy in strangely any direction, one vein actually cuts a xenolith clast, clas 2012-07-10 423295 6265468 250 90 Joint a distinct set of joints, 58/70 and 40/80 and 160/93 2012-07-10 423673 6265606 270 52 Vein D1 1/m 180/52 veins 2-3 cm, wormy mo-py-cp, numerous qz wormy veins <1cm 5/m, very weak foliation here difficult to distinguish from stria 2012-07-10 423601 6265625 290 58 Vein D1 strong wormy veins, V2-style, dominant is 200/59 2012-07-10 423514 6265628 298 54 Vein D1 208/54, 95/41 vein sets, both fairly wormy weak vein folding, some offsets 2012-07-10 423593 6265157 346 12 Axial Surface/Planar Cleavage (Folds) ser schist, yellow, strong V5, 50-60% quartz 265/60 foliation, pencil cleavage 256->12 showing ribs in quartz 2012-07-10 423561 6265417 354 92 S1 D2 P1 green, fine-grained andesite tuff, good foliation developed at 264/92, qz veins 290/80 fairly wormy, marked alteration change from uphill outcrop fault 2012-07-10 423593 6265157 355 60 S1 D2 P1 ser schist, yellow, strong V5, 50-60% quartz 265/60 foliation, pencil cleavage 256->12 showing ribs in quartz 2012-07-10 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 116 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423621 6265141 2 85 S1 D2 P1 Mitchell thrust fault, 10cm of offset shear puts undeformed rock against intensely deformed QSP with qz 76/32 to thrust fault, foliation right underneath is 272/85 foliation, apparent movement is to the north …? 3 2012-07-10 423561 6265417 20 80 Vein Tectonic green, fine-grained andesite tuff, good foliation developed at 264/92, qz veins 290/80 fairly wormy, marked alteration change from uphill outcrop fault 2012-07-10 422847 6265686 260 68 Vein Fold strong foliation at 276/60, green soft IARG alteration, VU, no clear primary texture, VO veins, some offset veins 260/68, 10/m, qz-py, <1cm most 2012-07-11 423142 6265656 150 70 Vein D1 2012-07-11 422782 6265716 170 40 Joint an apparent throughgoing fracture networks possibly represent cooling - main angle appears to parallel strata at 80/40 implying an unconformity of 40deg between footwall seds, perpendicular set at 370/90 2012-07-11 422804 6264702 208 80 Vein D1 2012-07-11 423315 6265721 350 50 Vein D1 260/50, green, homogeneous, very fine-grained, subparallel veining at 260/50 veining qz-py, 8/m, shear banded offsets infilled with qz-chl (HT activity concurrent with deformation) altn: locally chlorite, t 3 2012-07-11 423142 6265656 354 60 S1 D2 P1 qz veins quite wormy V1-V2, foliation 264 2012-07-11 422943 6265700 354 60 S1 D2 P1 foliation 264/60, VU ser-chl IARG, V0, some offsets no clear folding, as previous 10/m foliation parallel qz-py veins 2012-07-11 422993 6265714 354 45 S1 D2 P1 less ser, more chl, V0 veins, 12/m, <1cm most qz-py, foliation parallel, foliation runs 264/45, apparent increase in pyrite 2012-07-11 423134 6265718 4 32 Bedding D1 rock is fissile, ?primary at 274/32, shallow dip could be due to rotation or prima 2012-07-11 422847 6265686 6 60 S1 D2 P1 2012-07-11 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 117 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423304 6265767 30 35 S1 D2 P1 very little texture good foliation at 300/35, weak qz-ankerite veins appear to mostly follow foliation, foliation is strong along edge of cliff and resistent ridge appears unfoliated from this angle, altn: chl 2012-07-11 422753 6265727 52 50 Vein Tectonic no stockworking, manganoan carbonate pods and local breccia show no preferential angle - possibly imply magmatic origin 2012-07-11 422804 6264702 54 50 Vein D1 crystals aligned in foliation plane, qz-cb veins cut 5/m, one 10cm wide at 324/50, one py-chl vein at 118/80 vein shows chl alteration halo - this must be wallrock 2012-07-11 422772 6265725 80 70 Vein Tectonic Cb vein 350/70, discontinuous, shear band?, very sparse veins 1/10m, 1cm wide, marks contact into fine-grained hb porphyry "microdiorite" appears to follow the base of the first outcrop on this slope leaving a siliceous resistent knob overlying, app 2012-07-11 422782 6265716 100 90 Joint 2012-07-11 423101 6265091 116 40 Joint Lith: Mitchell thrust fault, an overhang, brown soil in fault, grey above, yellow QSP below, hangingwall looks like andesite tuff, hangingwall shows joints not seen below 26/40, 186/52, weak chlorite hangingwall (photo 5888) 2012-07-12 423292 6265143 122 62 Vein D1 32/62 qz veins, 0.5-1/m, 50-10cm wide, very vuggy growth with large vuggy quartz crystals, sheeted sets, rock is greyish gritty very fine-grained tuff (possibly implies tuff in FW north side, weak chloritic with sericite patches related to veins (?), 3 2012-07-12 423434 6265159 150 40 Vein Tectonic 3 2012-07-12 423250 6265144 186 62 S1 D2 P1 Deep red knob, appears 95% qz sulphides foliated at 96/62, not seeing distinct veins just ribboned sulphides and sericite 3 2012-07-12 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 118 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423202 6265187 190 75 S1 D2 P1 100/75 penetrative foliation in sericite, strong banded texture not as stockworked as higher quartz zones, here we see decrease in quartz causing foliation parallel veins, quartz ~60% by volume, photo 5883 3 2012-07-12 423101 6265091 276 52 Joint 2012-07-12 423150 6265155 344 80 S1 D2 P1 yellow, strongly foliated with nearly all quartz veins intruding parallel to foliation, both at 254/80, ~50% quartz, rest is strongly foliated sericite, one zone shows a sheath fold, fold axis parallel to foliation plane (photo 5885), weak N-S 3 2012-07-12 422937 6265038 0 80 S1 D2 P1 Lith: 70% quartz in quartz stockwork zone, wavy veins, veins and foliation 270/80, photo 5889 3 2012-07-12 422925 6264987 0 65 Vein D1 2012-07-12 423375 6265187 0 40 Vein D1 yellow-white, high quartz stockwork, quartz 85% of rock showing differential erosion, apparently lacking wormy textures, stockwork is somewhat chaotic and subparallel to foliation but no strong evidence for folding or extensions of veins, many 3 2012-07-12 423328 6265206 4 75 S1 D2 P1 85% Qz Stwk (as previous), noticeable wormy veins, below this point isn't really mappable, 274/75 foliation and veins, photo 5875-5876 3 2012-07-12 423328 6265206 4 75 Vein D1 3 2012-07-12 423434 6265159 8 60 S1 D2 P1 95% massive quartz, foliation defined by a small amount of ser banded with strong py+/-Cp, wavy foliation at 278/60, late unmineralized quartz veins perpendicular to foliation (extension) 60/40, phot 3 2012-07-12 423114 6265124 12 82 S1 D2 P1 50% Qz, virtually all foliation parallel with strong Py-Ser infilling, veins and foliation 282/82, minor small veins inbetween Qz, V5 texture - not wormy, 7% Py -very strong here, strong differential erosion (photo 5887) 3 2012-07-12 423114 6265124 12 82 Vein D1 3 2012-07-12 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 119 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423315 6265190 14 85 S1 D2 P1 strongly weathered Py-Ser leaving protruding Qz Stwk ribs, a good outcrop surface able to see some worminess in smaller qz veins, weathered pods ser-py, Goe and Jar remianing, 284/85 veins and foliation, 85% Qz, photo 5873-74 3 2012-07-12 423315 6265190 14 85 Vein D1 3 2012-07-12 423065 6265077 30 66 S1 D2 P1 quartz stockwork zone, massive quartz, less banded, ribbed texture due t oincreased qz, stockwork not observed, quartz, foliation and quartz band at 300/66, 80% Qz 3 2012-07-12 422925 6264987 45 62 Vein D1 very fine-grained, dark, chloritic, high qz stockwork, 50% qz veins V2 deformed and wormy, primary 315/62 (narrower veins) and 270/65 slightly larger, most veins 5mm-1cm, many up to 10cm, rock is imcrodiorite or tuff - one possible xenolith, ph 2012-07-12 423150 6265155 54 65 Vein D1 3 2012-07-12 423408 6265620 20 0 Lineation Primary Clast D1 2012-08-12 423281 6265622 40 76 Vein Fold 2012-08-12 423581 6265655 200 82 Vein Fold 2012-08-12 423349 6265674 200 68 Vein Fold Unknown timing -vein fold. 2012-08-12 423581 6265655 226 0 Lineation Primary Clast D1 object lineation 226->?, 30x30m knob, sharp erosion contrast with homogeneous porphyries surrounding, mtx: pale green and siliceous, vein 2012-08-12 423368 6265625 240 0 Lineation Primary Clast D1 fine-grained diorite with several clastic lenses (chloritic) trending 240deg but many irregular clasts composed of chl-sil, most clasts show deformed qz stwk with smaller clasts most ly <2cm qz fragments, one clast 25cm diameter PHOTO: 2769-71, 2012-08-12 423541 6265645 242 0 Lineation Primary Clast D1 clasts are in a sorted band trending 242, clast composition: V(0) fragments, green vcl frags, containing V(0) stockwork 2012-08-12 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 120 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423281 6265622 310 38 Vein Fold 2012-08-12 423349 6265674 180 40 S1 D2 P1 foliated 90/40, qz-py 2mm wide vein with halo 2cm wide of qz-to, folded veins in both directions, irregular trend 200/68 subtle fold axis trace 280->70 (To vein), photo: 2788 2012-08-12 423575 6265525 184 90 Vein D1 2012-08-12 423428 6265620 220 72 Vein D1 strongly buckled qz-py-mo in vein 130/72, sinistral offset by qz-py vein w/ 1cm pale ser altn halo, 202/84 fltn wraps around truncated veins. 2012-08-12 423541 6265645 250 10 Vein D1 Qz-chl vein 2012-08-12 423391 6265661 250 60 Vein D1 qz-py vein 2012-08-12 423428 6265620 292 84 S1 D2 P1 2012-08-12 423581 6265655 312 74 S1 D2 P1 2012-08-12 423581 6265655 316 56 Vein D1 2012-08-12 423541 6265645 320 80 Vein D1 2012-08-12 423541 6265645 324 64 S1 D2 P1 2012-08-12 423575 6265525 342 72 Vein D1 2012-08-12 423575 6265525 346 62 S1 D2 P1 penetrative foliation of chl 256/62 vns folded all directions especially N-S veins, numerous vein orientations, larger veins prefer 94/ 2012-08-12 423482 6265624 346 86 S1 D2 P1 dark chlorite diffuse clast <1cm not lineatedsubrounded clotty irregular distribution, late planar py veins 2012-08-12 423281 6265622 350 70 S1 D2 P1 Grey, oxidized shear zone 1-2m wide, characterized by topo lineament, no through-going veins, appears to be the contact between clastic rocks and diorite, lineament trends 250, sparcely qz-bearing SZ with foliation at 260/70, note: 2 samples of 2012-08-12 423391 6265661 350 70 S1 D2 P1 foliated at 260/70, sparce qz vein fragments and qz-ser stockwork fragments rounded, qz-py vein 2cm To-Sil alteration halo, 160/60, note: 15m east clastic qsp-stwk, 2793-94 2012-08-12 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 121 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423290 6265652 0 86 Vein D1 2012-08-12 423290 6265652 2 56 S1 D2 P1 2012-08-12 423290 6265652 50 80 Vein D1 py-qz vein 320/80 with 1.5cm alteration halo, qz-?To, dextral offset of vein by py stringer 270/86, near 1 m wide shear zone, foliation 272/56, no clasts observed in area , 2782-83 2012-08-12 423530 6265660 268 90 Dyke D1 Qz eye porphyry dyke 10cm wide striking 178/90, photo: 2865 2012-08-15 423101 6265601 4 62 S1 D2 P1 Strong ser foliation 274/62, nearby IARG to north…FZ? 2012-08-15 423471 6265471 350 88 S1 D2 P1 2012-08-18 423218 6265603 95 40 Lineation Primary Clast D1 N-S lineations to phenos, opposite 2013-06-22 423235 6265580 268 86 Vein D1 pyrite vein 178/86W and Qz-sulphide 88/60S 2013-06-22 423192 6265189 105 32 Axial Surface/Planar Cleavage (Folds) 3 2013-07-01 423120 6265136 0 62 Vein Fold Tight (Z?) fold, veinlet 3 2013-07-15 423114 6265119 6 65 Vein Fold plan view profile plane, open fold 3 2013-07-15 423120 6265136 10 64 Vein Fold Tight (Z?) fold, veinlet 3 2013-07-15 423114 6265119 20 72 Vein Fold 90% qz stwk, intense foliation parallel veins, vein folds open (D2.5) 3 2013-07-15 423124 6265132 26 71 Vein Fold Plan view, open fold 3 2013-07-15 423124 6265132 28 73 Vein Fold Plan view, open fold 3 2013-07-15 423126 6265132 28 78 Vein Fold D2 P2 Fold axis to a subtle overprint of F1 3 2013-07-15 423124 6265132 30 60 Vein Fold Plan view, open fold 3 2013-07-15 423124 6265132 30 87 Vein Fold Plan view, open fold 3 2013-07-15 423121 6265130 64 50 Vein Fold Z-fold, tight Qz vein 3 2013-07-15 423121 6265130 82 42 Vein Fold Open folds 3 2013-07-15 423120 6265136 85 60 Vein Fold Tight, 1cm wide vein 3 2013-07-15 423171 6265199 94 48 Vein Fold Open folds in narrow Qz vns <1cm, cross section 3 2013-07-15 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 122 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423171 6265199 101 50 Vein Fold Open folds in narrow Qz vns <1cm, cross section 3 2013-07-15 423121 6265130 110 26 Vein Fold Open folds 3 2013-07-15 423152 6265216 113 44 Vein Fold open fold, <1cm Qz vn 3 2013-07-15 423114 6265119 116 40 Vein Fold x-section view profile plane, open fold 3 2013-07-15 423121 6265130 126 22 Vein Fold Open folds 3 2013-07-15 423109 6265144 126 34 Vein Fold Tight fold Qz vn S FA (view SE) 3 2013-07-15 423109 6265144 126 ## Vein Fold Milky mode one veins (D 2.5) 3 2013-07-15 423096 6265160 130 48 Vein Fold Open fold, plan view 'S' 3 2013-07-15 423125 6265129 140 19 Vein Fold thin box fold open, interval showing chaotic-looking folds - appears D1 3 2013-07-15 423125 6265129 148 45 Vein Fold Tight vein fold, appear disharmonic (view SW) 3 2013-07-15 423125 6265129 150 70 Vein Fold Adjacent to chl-qz pand? Is intensely fragmental, open, multi-vein fold 3 2013-07-15 423124 6265135 153 65 Vein Fold S fold, tihgt 10-20 deg intralimb angle (view SE) 3 2013-07-15 423096 6265160 172 75 Vein Fold Open fold, no vergence, plan view 3 2013-07-15 423120 6265136 208 58 Vein Fold open fold 3 2013-07-15 423120 6265136 268 60 Vein Fold Ptygmatic, smaller qz-sulphide 3 2013-07-15 423124 6265132 280 72 Vein Fold tight S fold in Qz cored by py (view NW) 3 2013-07-15 423124 6265131 300 62 Vein Fold Py banded vein, Z fold tight (view NW) 3 2013-07-15 423124 6265132 318 50 Vein Fold X-section view, open fold 3 2013-07-15 423126 6265132 320 0 Lineation Axial trace to tight fold (40deg limb angle), several veins entrained (plunge of 0 inserted for plotting) 3 2013-07-15 423124 6265132 326 52 Vein Fold Xsection, open fold 3 2013-07-15 423121 6265130 125 25 Vein D1 Mode I (view SW), meandering vein 3 2013-07-15 423106 6265179 174 50 Sinistral fault D_3 SFTB Sinistral crenulation/shear band 3 2013-07-15 423120 6265136 180 60 Vein D1 >1cm qz-sulphide vein 3 2013-07-15 423120 6265136 182 68 Vein D1 >1cm qz-sulphide vein 3 2013-07-15 423124 6265132 184 74 Sinistral fault D_3 SFTB Crenulation, pressure solution, sinistral (photo view SSE) 3 2013-07-15 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 123 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423171 6265199 190 87 S1 D2 P1 Major veins and foliation, FA 3 2013-07-15 423120 6265136 201 70 Vein D1 Qz-Cp-Py, larger >1cm veins, lithology is aphanitic chlorite -mafics, mm-scale clasts of Qz veins suggest maybe intrusive 3 2013-07-15 423132 6265150 204 85 S1 D2 P1 Intense Qz and Ser foliation parallel 3 2013-07-15 423168 6265230 310 68 Sinistral fault D_3 SFTB Sinistral crenulation adjacent to dextral 3 2013-07-15 423126 6265132 320 72 Spaced Cleavage D_3 SFTB Brittle cleavage, fractures, discrete and brittle in chlorite, parallel synchronous (?) crenulations in QsP nearby subtle offset 3 2013-07-15 423124 6265131 331 70 Vein D1 Banded Qz-Py late vein, folded S-D (approx) 3 2013-07-15 423126 6265131 332 80 Dextral fault D_3 SFTB Dextral crenulations 3 2013-07-15 423124 6265132 340 25 Dextral fault D_3 SFTB Dextral crenulation cuts veins and major fltn 3 2013-07-15 423120 6265136 346 64 Vein D1 Ptygmatic, smaller qz-sulphide 3 2013-07-15 423152 6265216 6 80 S1 D2 P1 Wavy pervasive foliation, 80% Qz 3 2013-07-15 423121 6265130 10 72 S1 D2 P1 Major fltn and qz veining (fp) 3 2013-07-15 423148 6265153 18 80 S1 D2 P1 Veins and foliation all parallel 3 2013-07-15 423124 6265132 20 85 Axial Surface/Planar Cleavage (Folds) Axial surface to previous S folds 3 2013-07-15 423136 6265172 20 70 S1 D2 P1 Foliation and veins (foliation parallel), 65% Qz 3 2013-07-15 423106 6265179 20 75 S1 D2 P1 Major fltn (veins and ser) 3 2013-07-15 423168 6265230 21 85 S1 D2 P1 foliation and veins 3 2013-07-15 423124 6265132 22 72 S1 D2 P1 wavy between veins, 80% qz 3 2013-07-15 423114 6265119 24 18 S1 D2 P1 Major fltn and vein orientation 3 2013-07-15 423126 6265131 34 82 Vein D1 Vein reading on oriented sample (thin section?), hammer directed north 3 2013-07-15 423126 6265132 35 66 Vein D1 Right limb defined by several qz veins 3 2013-07-15 423124 6265135 48 60 S1 D2 P1 Good but wavy, flnt in ser and qz veins parallel 3 2013-07-15 423148 6265153 50 62 Fault No Kinematics Cataclasite, broken vein fragments (photo up = east) 3 2013-07-15 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 124 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423168 6265230 52 50 Dextral fault D_3 SFTB Dextral crenulations, maybe barely offsets sinistral crenulation, also appears to have accomodated more movement, photo East, sinistral foreground and dextral background 3 2013-07-15 423136 6265172 52 68 Vein Shear band Py late stringer, dextral (D2) 3 2013-07-15 423126 6265132 60 68 Vein D1 Left limb defined by several qz veins 3 2013-07-15 423107 6265142 64 58 Dextral fault D_3 SFTB Dextral shear band (crenulation) 3 2013-07-15 423136 6265172 74 62 Vein Tectonic milky mode I veins (D2.5) 3 2013-07-15 423132 6265150 80 74 Dextral fault D_3 SFTB 90% Qz, nice developed crenulation dextral 3 2013-07-15 423201 6265362 45 30 Mineral Alignment Primary D1 Mineral lineation in phenos 2013-07-16 423210 6265356 50 ## Vein Fold 2013-07-16 423210 6265356 120 65 Vein Fold 2013-07-16 423162 6265309 150 75 Vein Fold A more major fold in PAND, maybe indicates large-scale syncline, locally fold defined by multiple layers of Qz90Ser10 in tight fold (<10deg intralimb angle), small lense on pand 2013-07-16 423202 6265362 170 54 Vein Fold Fold axis of vein, photo view south, FA just below it a folded vein of apparently the same event, suggests vein fragmentation ->quartz stockwork -> deformation +/- axial planar foliation 3 2013-07-16 423256 6265314 200 60 Vein Fold NW, fairly tight fold in vein striking NW, geology of interval is dominated by clasts of qz-chl stwk, >5cm 2013-07-16 423190 6265322 240 15 Vein Fold Fold axis of qz vein 2013-07-16 423210 6265356 240 65 Vein Fold 2013-07-16 423210 6265356 245 45 Vein Fold 2013-07-16 423169 6265296 250 48 Vein Fold FA to very open fold in PAND ~1cm qz vein, pen points west, no clast 2013-07-16 423184 6265390 258 60 Vein Fold Open fold in 5 cm Qz-sulphide vein, wavy vein 2013-07-16 423201 6265362 260 48 Vein Fold Fold axis of vein 2013-07-16 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 125 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423256 6265314 270 0 Lineation Primary Clast D1 Trend of bubble rock fragments (plunge of 0 inserted for plotting) 2013-07-16 423256 6265312 280 0 Lineation Primary Clast D1 Bubble rock trend of clasts (plunge of 0 inserted for plotting) 2013-07-16 423210 6265356 280 0 Lineation Primary Clast D1 (plunge of 0 inserted for plotting) 2013-07-16 423190 6265322 280 40 Vein Fold Tight folds in Qz-py vein, up=south 2013-07-16 423223 6265396 280 70 Vein Fold Minor clasts cut by ptygmatic veining, tight fold (view top=south), photo contains <1cm sparse quartz clasts in PAND 2013-07-16 423222 6265299 290 0 Lineation Primary Clast D1 Bubble rock, large equant to rectangular angular clasts cut >5cm, Qz 5% (plunge of 0 inserted for plotting) 2013-07-16 423256 6265314 290 55 Vein Fold NE striking vein folded, open 2013-07-16 423267 6265289 295 0 Lineation Primary Clast D1 Weak lineation of Qz clasts (plunge of 0 inserted for plotting) 3 2013-07-16 423267 6265289 198 75 S1 D2 P1 In bubble rock, chl-defined foliation weaves about clasts, local 60% clasts 3 2013-07-16 423201 6265362 200 40 Spaced Cleavage Pressure solution cleaveage 2013-07-16 423251 6265308 200 78 Vein D1 Qz vein 2013-07-16 423269 6265302 205 ## Vein D1 Planar qz vein 2013-07-16 423193 6265296 210 78 Vein D1 Cuts porphyritic pand, now the foliation is weakly developed and cut by 5% qz veins 2013-07-16 423251 6265308 210 67 Vein D1 Qz vein 2013-07-16 423190 6265322 210 68 Vein D1 Major vein orientation 2013-07-16 423201 6265362 230 62 Vein D1 2013-07-16 423210 6265356 246 25 Vein D1 Lense of quartz clasts within porphyritic intrusion clearly cut porphyry and are both cut by qz stringer, trend of the breccia is 280 deg, rock is mm-scale grains of altered feldspar + chlorite-replaced mafics, veins 2013-07-16 423184 6265390 272 75 Vein D1 qz vein 2013-07-16 423164 6265325 280 65 Sinistral fault offset of previous vein, sinsitral 2013-07-16 423201 6265362 280 41 Vein D1 2013-07-16 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 126 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423164 6265333 330 70 Sinistral fault D_3 SFTB 25% qz in phyllonite, most aligned with sericite 2013-07-16 423201 6265362 330 31 Vein D1 2013-07-16 423224 6265319 346 63 Fault No Kinematics cataclasite, average 50cm wide cataclasite zone, R fabrics indicate sinistral movement (the sketch looks dextral..?), photo up=south 2013-07-16 423184 6265390 351 71 S1 D2 P1 Major fltn in chlorite 2013-07-16 423210 6265356 357 62 S1 D2 P1 2013-07-16 423210 6265356 357 63 Fault No Kinematics Cataclasite 2013-07-16 423210 6265356 0 55 S1 D2 P1 2013-07-16 423201 6265362 0 52 S1 D2 P1 subtle pheno mineral alignment 2013-07-16 423269 6265302 3 76 Vein D1 qz vein 2013-07-16 423256 6265314 5 79 Vein D1 Meandering qz vn 2013-07-16 423222 6265299 6 80 Vein D1 Cuts the bubble rock texture (not observed) 2013-07-16 423193 6265296 10 85 S1 D2 P1 Major foliation weakly defined by chlorite 2013-07-16 423224 6265319 10 65 Joint R' in shear zone, resembles BJ thrust, up=south 2013-07-16 423222 6265299 10 80 Vein D1 2013-07-16 423251 6265308 10 55 Vein D1 Major vein orientation, >1cm wide qz-sulphide vein and finer qz subparallel veins, photo up=south of qz clast appears to truncate adjacent veins with one showing fragmentation adjacent to clastic lense (argues ibx) 2013-07-16 423190 6265322 15 49 Vein D1 Minor vein orientation 2013-07-16 423172 6265297 20 86 Vein D1 planar vein ~1cm 2013-07-16 423222 6265299 20 65 Vein D1 2013-07-16 423269 6265302 20 75 Vein D1 Fairly brittle/planar set of veins, large qz clast cut by qz py vein so fragmentation pre brittle, photo view south 2013-07-16 423164 6265325 21 85 S1 D2 P1 Major foliation in chlorite 2013-07-16 423222 6265299 23 75 S1 D2 P1 Major fltn 2013-07-16 423164 6265325 23 60 Vein D1 10 cm wide qz vein sinistral offset, view up=E 2013-07-16 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 127 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423340 6265293 24 72 S1 D2 P1 Phyllonite major foliation 2013-07-16 423340 6265293 24 90 Fault No Kinematics Cataclasite, qz frags show subtle sinistral sense, adjacent crenulations were possibly linked to SZ foliation (as in MTF) 2013-07-16 423164 6265333 25 86 S1 D2 P1 25% qz in phyllonite, most aligned with sericite 2013-07-16 423190 6265322 25 85 Fault No Kinematics Cataclasite 2013-07-16 423256 6265314 25 80 Vein D1 Planar qz vein 2013-07-16 423172 6265297 30 89 S1 D2 P1 Major foliation weakly defined by chlorite, no FA seen very good, veins too planar, up=soluth 2013-07-16 423201 6265362 30 78 Vein D1 2013-07-16 423340 6265293 40 40 S2 D2 P2 2013-07-16 423340 6265293 50 60 S2 D2 P2 Crenulation cuts S major, subtle dextral sense, locally 1-2 cm spacing, view SE, Qz 15% 2013-07-16 423169 6265296 69 86 Dextral fault D_3 SFTB Band of sericite, dextral crenulation shear band, up=SE 2013-07-16 423259 6265416 20 49 Vein Fold Tight fold, view NW 2013-07-17 423232 6265461 75 ## Mineral Alignment Primary D1 White laths of ?Fd in IARG island amid bubble rock 2013-07-17 423185 6265467 90 84 Vein Fold Open fold in 2 cm vein 2013-07-17 423224 6265417 218 78 Vein Fold Microfault related to cataclasites, sinistral, wraps into larger dextral fault, photo up=north, major movement accomodated here 2013-07-17 423263 6265456 255 41 Vein Fold Fold axis to open fold in below vein, minor <1cm Qz clasts 3 2013-07-17 423240 6265425 262 48 Vein Fold D2 P1 FA to qz vein, tight fold S-fold 2013-07-17 423310 6265475 270 60 Vein Fold D2 P1 Cataclasite, riedels show sinistral so sinistral overal 2013-07-17 423225 6265425 288 0 Lineation Primary Clast D1 Stranded veins and fragments cut by Qz-Cal-Ank veins 2013-07-17 423236 6265484 288 0 Lineation Primary Clast D1 Clast trend, clasts 7% Qz, photo shows local clast fragmentation (?) 2013-07-17 423185 6265511 298 75 Vein Fold Vn fold axis 2013-07-17 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 128 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423185 6265511 310 78 Vein Fold Good open fold in 1.5cm qz-sulphide vein, vein that is folded parallels large one but buckles due to size, compression starts to pick up in IARG unlike mostly planar veins in chl-sil, strangely pyrite vein appears axial planar to fold, view W 2013-07-17 423222 6265471 350 65 Mineral Alignment Primary D1 Pheno alignment of sericitized hornblende-feldspar (?) 2013-07-17 423227 6265461 130 70 Sinistral fault D1 Qz-ankerite sinistral, foliation too weak to affect it contact between porphyritic texture and fine-grained, also marked by change in alteration ti IARG and planar vein deform ductily 2013-07-17 423244 6265423 136 25 Vein Tectonic Vein sets of Qz-ank 2013-07-17 423225 6265425 139 65 Vein Tectonic Tension crack, discontinuous sets of Qz-ankerite veins - folded! 2013-07-17 423227 6265461 140 70 Sinistral fault D1 Sinistral faultlet offsets Vo, possible conjugate shear to vein formation - qz ankerite lines it 2013-07-17 423244 6265423 140 83 Vein D1 Meandering 2013-07-17 423232 6265461 140 44 Vein Tectonic Milky Qz-sulphide stringer cuts Vo and offset, is deformed 2013-07-17 423240 6265425 142 ## Vein D1 Meandering qz vn 2013-07-17 423237 6265412 146 34 Vein Tectonic Ankerite vein 2013-07-17 423237 6265412 149 32 Vein Tectonic Ankerite-qz vein, corresponds to FA reading 2013-07-17 423240 6265425 162 ## Vein D1 Meandering qz vn 2013-07-17 423185 6265467 165 60 Dextral fault D1 Large, folded vein, banded Qz-py-cp offset dextrally here 2013-07-17 423217 6265420 180 75 Sinistral fault Cataclastic sinistral fault zone, 0.5 m wide, subset to major fault zone, just adjacent is gorgeous clast of quartz chl stockwork 2013-07-17 423206 6265424 182 80 Vein D1 A large number of offsets that appear to be nearly coplanar to foliation, are marked by ankerite fluid introduction, sinistral movement of Vo, decimetric spacing of offset planes, subsequent foliation flattening unit causing overlapping clasts and bu 2013-07-17 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 129 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423206 6265424 183 78 Sinistral fault D1 Sinistral offset of Vo 2013-07-17 423232 6265461 185 75 Dextral fault D1 Clear offset dextral of last vein (cut by milky white vein 2013-07-17 423245 6265460 190 74 Dextral fault D1 Dextrall offset of Vo, plane of faultlet of previous reading 2013-07-17 423222 6265471 199 90 Sinistral fault D1 Good offset plane cut by folded vein showing much less offset cut by discontinuous Py cored vein (view S) 2013-07-17 423206 6265424 200 81 Sinistral fault D1 Sinistral offset of Vo 2013-07-17 423217 6265424 209 60 Vein Tectonic ~1m wide ankerite-quartz vein showing sinistral shear at margins, implies cataclastic movement post dates cataclasite also some of these ankerite veins are folded (view south) 2013-07-17 423245 6265460 226 60 Vein D1 1cm vein, dextral offset 2013-07-17 423227 6265461 230 70 Vein D1 Parallel sets qz vein 2013-07-17 423227 6265461 234 66 Vein D1 Qz vein, planar 2013-07-17 423237 6265412 238 57 Vein Tectonic Quartz-ankerite vein 2013-07-17 423227 6265461 240 79 Vein D1 1cm parallel, planar sets 2013-07-17 423134 6265415 245 80 Vein D1 5cm weakly folded vein 2013-07-17 423232 6265461 254 61 Vein D1 1cm wide Qz-sulphide vien cut by milky white late vein 2013-07-17 423245 6265460 255 44 Vein D1 2cm major vein orientation 2013-07-17 423134 6265415 260 80 Vein D1 0.5cm vein: large vein apperas to have offset sinistral small vein here (view south) 2013-07-17 423134 6265415 280 40 Vein D1 Planar vein 1cm 2013-07-17 423185 6265467 288 80 Vein D1 Vein 6cm that is offset, also shows folding (view South) 2013-07-17 423263 6265456 290 40 Vein D1 Folded vein 3 2013-07-17 423245 6265460 298 82 Vein D1 Very planar offset of previous vein, suspect this is brittle and cuts foliation (saw some sets at BJ in Py eipthermal viens like this) 2013-07-17 423147 6265405 306 68 Vein D1 Meandering/wavy vein, vein conjugates in Fd-Hb speckled igneous rock, view up=south, appear like orthogonal cooling cracks or conjugate sets with sigma 1 N-S 2013-07-17 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 130 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423185 6265511 310 79 Vein D1 Qz(70)Py(30) vein 4cm wide slightly wavy (many sets) 2013-07-17 423134 6265415 335 72 Vein D1 4 cm vein, sinistral offset with pyrite parallel foliation (280/78, 2) 2013-07-17 423134 6265415 340 80 Sinistral fault Y plane in cataclasite, sinistral cataclasite, reading is for trend of cataclasite, broken Qz grains, apparent sinistral movement, pencil pionts NE 2013-07-17 423310 6265475 340 60 Joint Ridiel ® sinistral to cataclasite zone - appears discontinuous 2013-07-17 423259 6265416 350 72 S1 D2 P1 Weakly defined foliation 2013-07-17 423263 6265456 355 71 S1 D2 P1 Major foliation, defined by weak chlorite, slightly IARG 3 2013-07-17 423134 6265415 0 70 S1 D2 P1 weakly defined foliation by chlorite 2013-07-17 423206 6265424 0 75 S1 D2 P1 major foliation 2013-07-17 423222 6265407 0 89 Dextral fault Dextral major fault zone - cataclasite 2013-07-17 423200 6265420 5 76 Fault No Kinematics Fissile, sericite bands follow FZ cataclasite, view N, scratcher = R plane 2013-07-17 423227 6265461 8 78 S1 D2 P1 Weakly defined 2013-07-17 423185 6265511 10 70 S1 D2 P1 In ser-chl, subtle 2013-07-17 423254 6265485 14 70 S1 D2 P1 Poorly defined foliation, same qz clasts here ~5% 2013-07-17 423207 6265420 14 78 Sinistral fault Reflects geometry of sinistral cataclasite 2013-07-17 423221 6265413 20 76 S1 D2 P1 Foliation in chlorite 2013-07-17 423204 6265419 20 69 Dextral fault Foliation thought to represent Y-plane fabric, dextral movement 2013-07-17 423227 6265461 20 85 Vein D1 Parallel sets qz vein 2013-07-17 423200 6265420 30 68 Joint At angle to Y plane, maybe suggests dextral movement 2013-07-17 423259 6265416 40 84 Vein D1 2cm wide Qz-sulphide vein wavy 2013-07-17 423207 6265420 52 80 Dextral fault Reflects geometry of dextral cataclasite, two cleaveages result in interference pattern, appear geometrically linked to two ctaclasite fault zones sitting on either side of outcrop 2013-07-17 423185 6265467 55 80 Vein D1 2cm vein orientation 2013-07-17 423267 6265639 11 44 Vein Fold D2 P1 Good FA, tight fold (parasitic) 3 2013-07-18 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 131 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423267 6265639 14 49 Vein Fold D2 P1 Very good FA, 0.5cm vein width, open fold 3 2013-07-18 423268 6265639 32 44 Vein Fold D2 P1 Chaotic veins amid planar, earliest fold event appears to be related to D1 (possibly magmatic-related), vein 0.4cm wide 2013-07-18 423268 6265639 33 48 Vein Fold D2 P1 Chaotic veins amid planar, earliest fold event appears to be related to D1 (possibly magmatic-related) 2013-07-18 423188 6265640 48 3 Vein Fold 1.5 cm Qz-Cp vein folded open fold 2013-07-18 423206 6265597 55 72 Vein Fold Fold axis of above vein 2013-07-18 423240 6265627 106 10 Slickensides Slickenslides in folded Qz-chl vein, multiple orientations and some variation due to folding 2013-07-18 423274 6265643 264 65 Vein Fold 2013-07-18 423210 6265600 267 64 Vein Fold fold axis of qz vein 2013-07-18 423240 6265627 273 60 Vein Fold Open fold in narrow qz sulphide vien 2013-07-18 423200 6265641 287 65 Vein Fold 4cm vein 2013-07-18 423190 6265643 294 66 Vein Fold 5cm Qz-sulphide vein, tight fold, skinny "pressure solution" veinlets appear to radiate out from fold - possibly suggest magmatic process at work here (FA of some vein -2 folds) 2013-07-18 423190 6265643 341 58 Vein Fold Tight fold axis 2013-07-18 423274 6265643 354 65 Slickensides Vein cuts the Qz with FA 65->264, and approx orientation of 240/68 wavy, offset is dextral but strong dip-slip, also offset plane is lined by strong Qz-Chl slickenslides 2013-07-18 423180 6265564 110 44 Vein Tectonic 2cm Qz-Ank-py, minor chlorite (view SW) 2013-07-18 423180 6265564 119 43 Vein Tectonic 20cm as above, scale N-S (view SW) 2013-07-18 423218 6265612 130 78 Vein D1 Refer to sketch, Py-only 2013-07-18 423180 6265564 132 66 Vein Tectonic 70cm Qz-sulphide (view SW) 2013-07-18 423180 6265564 134 60 Vein Tectonic 12cm Qz-Ank-Py-Chl (view SW) 2013-07-18 423240 6265627 164 50 Vein D1 0.5cm planar secondary 2013-07-18 423240 6265627 168 80 Vein D1 Late pyrite>>Qz cuts milky Qz>py veins ,weak folding, also descent Fd porphyritic textures here 2013-07-18 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 132 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423240 6265627 180 60 Vein D1 1cm wavy secondary 2013-07-18 423240 6265627 188 62 Vein D1 3cm planar qz-sulphide minor 2013-07-18 423219 6265604 213 59 Vein D1 Qz-chl-cp vein, wavy 2013-07-18 423218 6265612 226 90 Vein D1 Refer to sketch Vn 2013-07-18 423240 6265627 231 70 Vein D1 0.5cm wavy qz-cp-chl major 2013-07-18 423221 6265601 236 85 Vein Tectonic Qz-Cb (ankerite?), planar ankerite cored 2013-07-18 423240 6265627 252 62 Vein D1 0.5cm wavy Qz-Cb-Chl major 2013-07-18 423218 6265612 255 88 Dextral fault D1 Dextral offset, appears more dip-slip 2013-07-18 423280 6265613 270 50 Vein D1 Strong dex offset of vein 2013-07-18 423240 6265627 300 52 Vein D1 2.5cm wavy Qz-Cp-Chl second 2013-07-18 423267 6265639 321 70 Sinistral fault D1 Discrete sinistral offset cuts both veins and offsets foliation wrapping it into the shear 3 2013-07-18 423274 6265643 322 61 Dextral fault D1 Dextral 2013-07-18 423216 6265607 324 65 Joint R plane shows subtle sinistral movement locally (view N) 2013-07-18 423216 6265607 334 90 Fault No Kinematics Trend of fault zone running through gully (assumed subvertical) 2013-07-18 423218 6265612 334 85 Vein D1 Refer to sketch Vn 2013-07-18 423240 6265627 342 70 Reverse Fault D_3 SFTB Mini reverse fault, top down dropped (view south) 2013-07-18 423216 6265607 348 60 Fault No Kinematics Spaced cleavages interpreted to be 'Y' plane within cataclasite 2013-07-18 423280 6265613 350 70 S1 D2 P1 Chl fltn in intrusion, one clast in intrusion 2013-07-18 423229 6265622 352 59 S1 D2 P1 Chl defined fabric 2013-07-18 423221 6265602 356 61 S1 D2 P1 2013-07-18 423280 6265613 0 44 Dextral fault D1 Dextral offset of Vo, brittle, right inbetween conjugate cataclasite 2013-07-18 423267 6265639 2 64 Vein D1 Planar vein 3 2013-07-18 423274 6265643 4 69 S1 D2 P1 Led with ?Fd or Hb replaced by ser, very minor chlorite Weak silica, the unit does not appear to deform easily but has a more marked fltn than chl alt'd unit, milky white 2013-07-18 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 133 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423267 6265639 5 64 S1 D2 P1 Major foliation parallels vein orientation that is strongly folded implying an older folding event (possibly N-S axial planar cleavage or simply magmatic-related) 3 2013-07-18 423216 6265607 10 70 S1 D2 P1 Major foliation within FZ makes diamond shaped interference patterns with Y-plan within fault 2013-07-18 423209 6265593 10 78 Vein D1 Very planar Vn 3 2013-07-18 423188 6265640 16 76 Vein D1 1 cm thick Qz-Cp-Chl 2013-07-18 423233 6265639 21 92 S1 D2 P1 Slightly more sericitic defined foliation 2013-07-18 423190 6265643 22 65 S1 D2 P1 major foliation 2013-07-18 423267 6265639 24 45 Vein D1 Overall vein orientation to above folds (vein is ptygmatic, irregular nad interpreted to have formed from magmatic processes), a very unusual occurance of ptygmatic, apparently a unique FA orientation maybe evidence for magmatic, also a vein adjacent 3 2013-07-18 423280 6265613 36 55 Dextral fault D1 Dextral offset of Vo, brittle, right inbetween conjugate cataclasite 2013-07-18 423274 6265643 43 68 Vein D1 3cm wide Qz, black To/Qz(?) vein, host rock is speckled with ?Fd or Hb replaced by sericite, very minor chlorite and weak silica, the unit does not appear to deform easily but has a more marked foliation than chlorite altered unit, milky white vein c 2013-07-18 423206 6265597 56 72 Vein D1 Qz-Cp-Chl wavy vein 2013-07-18 423200 6265641 62 81 Vein D1 Broad orientation to vein, 4cm, folded up=south 2013-07-18 423316 6265632 122 70 Vein Fold D2 P1 View N, stranded veins and no foliation parallel alignment, numerous FA orientations in PPFP, tight fold 2013-08-06 423260 6265640 170 80 Vein Fold Correlates with So possibly (cuts all veins) and an offset, open fold 2013-08-06 423316 6265632 220 38 Vein Fold D2 P1 Tight fold axis 2013-08-06 423359 6265608 265 55 Vein Fold 2.5cm vein QzCp>Py, appears Sm is axial planar to foliation (open fold) view W 2013-08-06 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 134 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423352 6265621 270 66 Vein Fold D2 P1 Tight fold in 3mm wide (below) 2013-08-06 423316 6265632 284 48 Vein Fold D2 P1 open fold axis 2013-08-06 423287 6265648 286 80 Vein Fold A box fold in QzChl vein (related to dex shear) 2013-08-06 423387 6265606 288 0 Lineation Primary Clast D1 Clast trend of angular, large clasts (boarders onto chl altn), a nearby example of angular, mineralized clast (clst up to 10cm here) clast points to north, several other frags Qz-only, the large clast causes interference in Sm flow pattern, looks lik 2013-08-06 423260 6265640 290 60 Vein Fold D2 P1 Correlates with Sm, open fold 2013-08-06 423260 6265643 296 60 Vein Fold Open fold in 0.5cm vein, major fltn appears axial planar 2013-08-06 423301 6265656 310 44 Vein Fold D2 P1 Magmatic related folding (?), tight fold 2013-08-06 423301 6265644 328 70 Mineral Alignment Primary D1 Planar vein corresponds to offset of bx (dextral) and of To haloed vein cored by Qz-Py, fragments are 1-10cm Qz-sulphide veins (most Qz-Py), Py fragments and clasts - most are angular (highly!), one 1cm angular clast of Py contains pressure shadows o 2013-08-06 423362 6265622 114 70 Axial Surface/Planar Cleavage (Folds) Fold axis in a clast, foliation penetrates clast matrix, also wraps about the clast, view south 2013-08-06 423301 6265644 172 30 Vein D1 Planar Qz-Chl-Py relates to dextral shearing, might correlate to cataclasites (synchronous growth with foliation) 2013-08-06 423260 6265643 190 80 Dextral fault D1 Five dex offsets, some defined by Qz-Py veinlets, a sixth offset 2013-08-06 423260 6265643 190 80 Dextral fault D1 Shows major movement, the continuation shows more folds where offsets are lacking, folding increases, locally 5cm overlap of 30cm vein stretch (15% shortening here) 2013-08-06 423260 6265640 215 85 S1 D2 P1 One foliation that is parallel to significant offset, also is axial planar to minor folds (post-dates dextral offsets and Qz-To veins) 2013-08-06 423260 6265640 250 70 Vein D1 0.5 cm wide, ~5m long Qz-Py banded vein 2013-08-06 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 135 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423287 6265648 265 74 Vein D1 To haloes, planar Qz-Py (foliation perpendicular but not folded 2013-08-06 423352 6265621 269 90 Vein D1 3mm wide very folded Qz-Py vein perpendicular to foliation, yet several veins nearby are planar and perpendicular to foliation, the vein does not cut dense clastic lense but other planar ones do! The vein does cut a rock hosting stragler clasts 2013-08-06 423287 6265648 286 90 Dextral fault D1 Minor dextral shear zone, photo view west 2013-08-06 423260 6265643 316 85 Vein D1 folded, offset and flattened vein 0.5cm wide 2013-08-06 423287 6265648 318 74 Vein Tectonic Banded Qz-Chl defines dextral offset planes, one of these veins shows a clear jog confirming syn dex en echalon development (no clast locally -?Vu), view south 2013-08-06 423301 6265656 332 73 Vein D1 Tightly folded vein cut by planar vein - suggests a magmatic - related folding (?), locally trace fragments of Qz vein material thus PAND interpretation 2013-08-06 423260 6265640 344 75 Vein Tectonic 2mm wide, ~2m long Qz-Py associated with dextral 2013-08-06 423387 6265606 355 90 S1 D2 P1 major foliation 2013-08-06 423260 6265640 1 68 Vein Tectonic 2mm wide, Qz-Py post-dating previous vein 2013-08-06 423359 6265608 2 65 S1 D2 P1 Weakly defined by chl>ser, good alteration contact can be seen in photo view E 2013-08-06 423301 6265656 5 69 S1 D2 P1 Major foliation not consistent with folding! 2013-08-06 423362 6265622 8 76 S1 D2 P1 Well defined, a 5m trend of clasts ranging from near subrounded <1cm grains to 30cm diamter, Qz stwk clast weakly folded, most clasts contain sharp subrounded boundaries, many loose fragments but most confined to a narrow lense of clast-supported (>9 2013-08-06 423260 6265640 9 50 S1 D2 P1 Major foliation, old foliation appears to wrap into this one 2013-08-06 423260 6265643 10 80 S1 D2 P1 Scrunches up into arm pit of fold (pinched) axial planar (?) 2013-08-06 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 136 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423287 6265648 17 82 Axial Surface/Planar Cleavage (Folds) D2 P1 Axial planar foliation drug from previous reading into fold (Qz-chl), this implies that offsets, Qz-Chl precede Sm and are possibly synchronous with the cataclasites, all of which would then be cut by Sm, photo view west 2013-08-06 423301 6265656 30 80 Vein D1 Fine-grained QSP alt'd PAND, vein 3mm wide planar cuts below readign bolded vein, South 2013-08-06 423362 6265622 83 90 Vein D1 Slightly wavy Qz>Py vein cuts clastic unit and is perpendicular to Sm, could suggest folds in clast are magmatic in nature and that they preded the fragmentation event itself, view south 2013-08-06 423357 6265291 239 62 Vein Fold D2 P1 3cm thick vein fragmented by Do (magma) and folded Dm, tight 2013-08-07 423357 6265291 279 70 Vein Fold D2 P1 3cm thick vein fragmented by Do (magma) and folded Dm, open 2013-08-07 423357 6265291 280 45 Vein Fold D2 P1 3cm thick vein fragmented by Do (magma) and folded Dm, open 2013-08-07 423394 6265348 283 65 Vein Fold D2 P1 2mm Qz vein with Mo selvages 2013-08-07 423365 6265375 320 67 Vein Fold adjacent to cataclasite the foliation is subtly folded and nearby Qz veins show orientations consistent with skeena (NNW), good clastic, angular quartz here, sinistral reidels indicate dextral movement on the structure, vein is qz-mo-cp 2013-08-07 423359 6265372 350 73 Vein Fold 0.5cm py-qz vein, folding appears associated with a K cataclasite 2013-08-07 423372 6265355 354 75 Vein Fold open fold, cataclasite is less clastic here 2013-08-07 423358 6265373 354 62 Vein Fold Poorlyl defined Qz sulphide vein 0.5cm discontinuous 2013-08-07 423365 6265375 356 57 Vein Fold Cretaceous related fold in vein qz-mo-cp 2013-08-07 423372 6265355 358 82 Vein Fold Tight fold in cataclasite (less clast here) 2013-08-07 423357 6265291 126 22 Vein Tectonic Milky qz>>cb veins with sparse euhedral qz growth strongly resemble both qz-ank veins near cataclasite and seem to show again the relationship between these cataclasites (shallow) and epithermal qz growth related 2013-08-07 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 137 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date to these events, good evidence to sho 423357 6265291 128 88 Vein Tectonic 2013-08-07 423357 6265291 170 80 Vein Tectonic Banded qz-cb related to TF-related strucutres (hah), offset by veins described below and offsets them also, proof that they are close in timing, chl related to deformation, milky open space 2013-08-07 423357 6265291 180 90 S1 D2 P1 Very fissile dominant foliation, making platy schistosity mm-scale cleavage/foliation causing scallops beatle sized, the orientation is equivalent to milky veins in pand, the foliations do not appear to be associated with offset so this might not be 2013-08-07 423394 6265348 316 88 S2 D2 P2 subtle cleavage cuts Sm (maybe subtle sinistral? Conjugate) 2013-08-07 423357 6265291 340 85 Vein Tectonic 2013-08-07 423357 6265291 345 88 S2 D2 P2 Crenulation consistent with K deformation cuts Sm 2013-08-07 423394 6265348 0 85 S1 D2 P1 Schistose pervasive foliation 2013-08-07 423372 6265355 12 90 Sinistral fault Y-surface in cataclasite, the major cataclasite juxtaposing alteration once again, the shear zone broadens to ~3m wide, very good sinistral shape fabric and interference of a major foliation (Y or Sm?) and a second (R I think), a clear scallopy erros 2013-08-07 423394 6265348 35 72 S2 D2 P2 Micro shear band (?) subtle dextral sense 2013-08-07 423258 6265209 166 44 Vein Fold unusual FA, maybe not real, looks like Vmq axial planar (?) 3 2013-08-09 423213 6265195 210 70 Vein Fold 0.5cm wide vein, open fold (F1?), photo view south 3 2013-08-09 423198 6265220 230 60 Vein Fold D2 P1 FA is in clast but is consistent with FA1 3 2013-08-09 423198 6265220 248 62 Vein Fold D2 P1 FA is in clast but consistent with F1 3 2013-08-09 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 138 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423213 6265195 271 80 Vein Fold D2 P1 Tight fold in 3mm vein related to flattening (axial planar to foliation) 3 2013-08-09 423318 6265188 296 40 Vein Fold D2 P1 Very poor reading 3 2013-08-09 423318 6265188 314 40 Vein Fold D2 P2 open 1cm wide vein 3 2013-08-09 423318 6265189 317 47 Vein Fold D2 P2 1cm wide open 3 2013-08-09 423318 6265189 318 62 Vein Fold D2 P2 1cm wide open 3 2013-08-09 423318 6265189 322 60 Vein Fold D2 P2 3 2013-08-09 423318 6265189 336 45 Vein Fold D2 P2 1cm wide, open 3 2013-08-09 423209 6265198 352 68 Vein Fold D2 P2 NNW trend folds gentle and common, china marker points to FA 3 2013-08-09 423258 6265209 124 68 Vein Tectonic 1cm discontinuous, cuts Vpy 3 2013-08-09 423318 6265189 125 37 Vein Tectonic milky qz vein ~2cm wide, discontinuous and mostly planar 3 2013-08-09 423318 6265191 129 60 Vein D1 also major foliation 3 2013-08-09 423318 6265191 129 60 Vein Tectonic planar, 1cm wide, perpendicular to veins, milky - no clear offset with Cd and Cs, it seems to me that some are folded and some are not, syn to post FA2? 3 2013-08-09 423258 6265209 136 60 Vein Tectonic 1cm discontinuous, cuts Vpy 3 2013-08-09 423198 6265220 182 78 S1 D2 P1 Fragmental textures, Qz-Chl clasts, clastic textures in QSP 3 2013-08-09 423213 6265195 205 88 Vein D1 50% qz stwk, major vein orientation, >90% of all veins, many veins almost planar, major change in orientation of Vmj relative of to blood lake, view south 3 2013-08-09 423258 6265209 224 76 Vein D1 wavy, folded 3 2013-08-09 423258 6265209 251 90 Vein D1 1-2cm, boudined, related to D1? 3 2013-08-09 423318 6265189 263 65 Axial Surface/Planar Cleavage (Folds) D2 P2 2 veins and foliation 3 2013-08-09 423318 6265188 273 55 Axial Surface/Planar Cleavage (Folds) D2 P2 4 qz veins and foliation 3 2013-08-09 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 139 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423318 6265189 275 46 Axial Surface/Planar Cleavage (Folds) D2 P2 4 veins and foliation 3 2013-08-09 423318 6265188 282 54 Axial Surface/Planar Cleavage (Folds) D2 P2 Appears to be axial planar cleavage, narrow discontinuous fracture 3 2013-08-09 423209 6265198 282 68 Axial Surface/Planar Cleavage (Folds) D2 P2 Axial surface to second fold event, of previous FA reading, 3 vein folds and foliation entrained in folds 3 2013-08-09 423318 6265189 293 60 Axial Surface/Planar Cleavage (Folds) D2 P2 3 veins and foliation 3 2013-08-09 423318 6265189 295 60 Sinistral fault D_3 SFTB shear band cuts milky vein, cut (and deflect) foliation, cut veins and folds 3 2013-08-09 423318 6265189 298 46 Sinistral fault D_3 SFTB shear band cuts milky vein, cut (and deflect) foliation, cut veins and folds 3 2013-08-09 423252 6265168 326 70 Sinistral fault D_3 SFTB Shear band sinsitral 3 2013-08-09 423318 6265191 327 75 Sinistral fault D_3 SFTB minor offset: shear band 3 2013-08-09 423209 6265198 350 78 Sinistral fault D_3 SFTB Sinistral shear band cuts F2 3 2013-08-09 423151 6265163 6 72 Axial Surface/Planar Cleavage (Folds) D2 P1 Tight, multivein, fold, axial surface mimics Sm 3 2013-08-09 423209 6265198 6 83 Vein D1 foliation and major vein orientation (wavy but consistent) 3 2013-08-09 423252 6265172 18 76 S1 D2 P1 Cataclasite associated with locus of dextral shear bands -shows mechanism for creation of cataclasites, proves conjugate sets could exist as in Cd and Cs 3 2013-08-09 423252 6265168 22 70 Vein D1 Veins and foliation 3 2013-08-09 423258 6265209 39 34 Dextral fault D_3 SFTB truncates Vpy 3 2013-08-09 423252 6265172 55 60 Fault No Kinematics cataclasite, view NE 3 2013-08-09 423318 6265191 59 47 Dextral fault D_3 SFTB minor offset 3 2013-08-09 423252 6265172 66 60 Dextral fault D_3 SFTB view NE 3 2013-08-09 423285 6265333 196 62 Lineation D2 P1 dilation planes infilled by calcite 2013-08-10 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 140 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423271 6265307 258 83 Vein Fold D2 P1 foliation axial planar, 1cm wide vein, open 2013-08-10 423271 6265307 266 75 Vein Fold D2 P1 open fold, py>>qz (previous), view west 2013-08-10 423285 6265410 268 62 Vein Fold D2 P1 3cm vein, open 2013-08-10 423259 6265417 270 44 Vein Fold D2 P1 tight, vein 3mm 2013-08-10 423270 6265334 277 60 Vein Fold D2 P1 in 2mm wide qz vein cut by Vmj set, little 2mm laths, sericitized composed matrix proving intrusive texture, view south 2013-08-10 423271 6265307 284 38 Vein Fold D2 P1 3mm qz-sulphide vein very folded - open, nice eroded exposure, view west 2013-08-10 423285 6265333 303 20 Lineation Primary Clast D1 fairly clear lineation of clasts, view south 2013-08-10 423281 6265333 172 88 Sinistral fault D_3 SFTB minor discontinuous shear bands, subtle shear sense 2013-08-10 423311 6265407 180 70 Vein Tectonic Ankerite vein, discontinuous, 80cm wide, sinistral deflection of Sm, easy sample - good helipad, what are these accomodating? View west 2013-08-10 423304 6265352 184 70 Dextral fault D1 dextral offset, Slip surface possibly predates Sm 2013-08-10 423342 6265299 192 80 Vein D1 1cm wide, not folded 2013-08-10 423281 6265333 201 75 Sinistral fault D_3 SFTB minor discontinuous shear bands, subtle shear sense, photo view south 2013-08-10 423304 6265352 204 60 Dextral fault D1 Slip surface possibly predates Sm dextral offset 2013-08-10 423304 6265352 210 72 S2 D2 P2 Subtle interference pattern with Sm - a second foliation event? 2013-08-10 423349 6265274 212 25 Vein Tectonic Milky vein (chl-py cuts cataclasite and is offset by Sk (S2)! An excellent constraint for these elusive veins! Juxtaposes Qz90% and chloritic PAND, likely defines this low lying band lacking outcrop, view west 2013-08-10 423304 6265352 229 69 Vein D1 1cm wide, offset dextrally 2013-08-10 423349 6265274 230 62 S2 D2 P2 Cataclasite-related cleavage, view west 2013-08-10 423281 6265333 245 78 Dextral fault D_3 SFTB Major dextral, Sm deflection, view south 2013-08-10 423281 6265333 245 78 Sinistral fault D_3 SFTB minor discontinuous shear bands, subtle shear sense 2013-08-10 423271 6265307 285 82 Vein D1 Folded, 1cm 2013-08-10 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 141 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423342 6265299 315 83 Vein D1 1cm wide, planar and discontinuous 2013-08-10 423259 6265417 320 80 Vein Tectonic 10cm qz-sulphide vein, wavy 2013-08-10 423342 6265299 338 79 Vein D1 1cm wide, not folded 2013-08-10 423316 6265348 355 80 S1 D2 P1 2013-08-10 423271 6265307 357 78 S1 D2 P1 defined by chlorite 2013-08-10 423281 6265333 359 85 S1 D2 P1 in QSP side of contact 2013-08-10 423304 6265352 7 73 S1 D2 P1 Qz>ser, well defined fltn 2013-08-10 423271 6265307 10 90 Axial Surface/Planar Cleavage (Folds) D2 P1 of previous open fold 2013-08-10 423349 6265274 10 82 S1 D2 P1 intense cataclased contact juxtaposes PAND and Qz high STW, view west 2013-08-10 423270 6265334 20 74 Vein D1 1cm wide, 20cm spacing, view south 2013-08-10 423271 6265307 64 90 Vein D1 Patchy veins ~1cm, this one planar 2013-08-10 424030 6265547 66 58 Vein Fold Z fold D1 2013-08-11 423978 6265537 112 90 Vein Fold D2 P1 Open fold in 3 mm wide vein (fault might be tertiary) 2013-08-11 424030 6265547 251 90 Vein Fold D2 P1 Fold axis to 'S' fold 2013-08-11 424030 6265547 262 88 Vein Fold D2 P1 M fold, D1: 1cm wide banded qtz pyrite vein 2013-08-11 423974 6265538 266 72 Vein Fold D2 P1 foliation appears axial planar 2013-08-11 424051 6265563 301 70 Vein Fold D2 P1 of previous, view west 2013-08-11 424030 6265547 312 71 Vein Fold D2 P2 1cm wide open fold, foliation wraps around it 2013-08-11 424039 6265525 317 75 Vein Fold D2 P2 2mm vein, open fold 2013-08-11 423974 6265538 322 80 Vein Fold D2 P2 3mm vein open fold 2013-08-11 424030 6265547 323 76 Vein Fold D2 P2 Open of previous vein 2013-08-11 423978 6265537 360 58 Vein Fold D2 P2 Very good angular clast texture here 2013-08-11 423974 6265538 125 54 Vein Tectonic D2 P1 Extension fractures in previous vein, carbonate infilled either related to Sm or are axial planar fracutres (stereo net!), ?both! 2013-08-11 424109 6265487 160 58 S2 D2 P2 Subtle, < mm scale pervasive foliation 2013-08-11 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 142 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423978 6265537 166 90 Vein Tectonic 1cm wide 2013-08-11 424055 6265482 167 81 S2 D2 P2 Subtle; cuts S1 2013-08-11 424047 6265452 168 56 S2 D2 P2 BMR card, 5% qz, no clasts 2013-08-11 424044 6265530 170 75 Vein D1 Pram vein orientation - 1 cm 2013-08-11 424109 6265487 172 64 S1 D2 P1 Marked (near waterfall) 2013-08-11 424060 6265508 175 85 S1 D2 P1 Reading good but block looks rotated, view south 2013-08-11 424030 6265547 177 77 Vein Tectonic 1cm wide part of conjugates 2013-08-11 424055 6265482 179 85 S1 D2 P1 Good S1 and S2 interference, S1 subparallel to scale (view south) 2013-08-11 424047 6265452 185 50 S2 D2 P2 Ser schist, good interference but maybe rotated (view south) 2013-08-11 424060 6265508 215 68 S2 D2 P2 mm-scal cleavages interference with S1 2013-08-11 424047 6265579 224 52 Thrust Fault D_3 SFTB 2 cm schistose brittle plane, ?subset to TF (view south) 2013-08-11 423978 6265537 312 62 Vein D1 3mm wide conjugate with next (good offset problem) 2013-08-11 423976 6265537 323 55 S1 D2 P1 Heterogeneous flattening suggests dextrally sheared clasts could represent local fiamme, nearby intense ameboid and equant shaped clasts supports this - suggests flattening not related to Sm, inspired this sketch 2013-08-11 424030 6265547 323 88 Vein Tectonic 3mm wide 2013-08-11 424039 6265525 350 90 S2 D2 P2 Many arcuate clasts here suggest cognate process (scratcher = N) 2013-08-11 424051 6265563 356 60 Vein D1 1cm wide, py+cp 2013-08-11 423974 6265538 358 77 Vein D1 3cm wide vein, fairly strong trend in this orientation, view NE 2013-08-11 424030 6265547 0 84 S1 D2 P1 poorly defined and patchy 2013-08-11 423974 6265538 1 88 S1 D2 P1 Very weak - mostly localized in clasts (this area F2>>F1) 2013-08-11 423976 6265537 16 65 Sinistral fault D1 50cm offset, very local 1cm clastic qz texture and foliation 2013-08-11 424044 6265530 25 85 S2 D2 P2 Appears axial planar to F2 (F1?) 2013-08-11 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 143 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423976 6265537 78 80 Vein D1 10cm wide, mainly planar vein, no boudin along Sm, could be evidence that Sm dependent on heating mechanism 2013-08-11 423974 6265538 90 55 Vein Tectonic D2 P1 Carbonate fractures in previous vein, cut F1 and F2 suggest tied to F2 2013-08-11 423765 6265504 16 80 Vein Fold D2 P1 open 2013-08-12 423765 6265504 25 50 Vein Fold D2 P1 tight 2013-08-12 423765 6265504 50 64 Vein Fold D2 P1 A number of folds in ~1cm wide vein, off of F1, open, view north 2013-08-12 423765 6265504 65 65 Vein Fold D2 P1 Tight 2013-08-12 423679 6265483 80 66 Vein Fold D2 P1 tight 2013-08-12 423703 6265425 86 ## Vein Fold D2 P2 open fold in ser schist, vein 1 cm, china points N to FA 2013-08-12 423765 6265504 92 71 Vein Fold D2 P1 Tight 2013-08-12 423679 6265483 227 70 Vein Fold D2 P1 tight 2013-08-12 423605 6265451 260 87 Vein Fold D2 P1 3 mm wide vein, open fold, view west 2013-08-12 423679 6265483 260 78 Vein Fold D2 P1 open 2013-08-12 423679 6265483 269 76 Vein Fold D2 P1 tight (numerous limb readings in book) 2013-08-12 423679 6265483 271 70 Vein Fold D2 P1 open 2013-08-12 423679 6265483 272 69 Vein Fold D2 P1 tight 2013-08-12 423786 6265521 281 63 Vein Fold D2 P1 open folds, several eroded define good reading, vein ~1cm, view north 2013-08-12 423793 6265527 288 70 Vein Fold D2 P1 Open folds in 3 mm wide vein, view to north 2013-08-12 423765 6265504 302 86 Vein Fold D2 P2 open 2013-08-12 423679 6265483 307 68 Vein Fold D2 P2 open fold 2013-08-12 423765 6265504 310 86 Vein Fold D2 P2 open 2013-08-12 423679 6265483 312 70 Vein Fold D2 P2 open fold 2013-08-12 423679 6265483 315 79 Vein Fold D2 P2 open fold 2013-08-12 423679 6265483 320 74 Vein Fold D2 P2 open fold (several limbs to fold readings in notebook), photo view west 2013-08-12 423765 6265504 321 85 Vein Fold D2 P2 open 2013-08-12 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 144 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423679 6265483 328 73 Vein Fold D2 P2 open fold 2013-08-12 423794 6265525 338 67 Vein Fold D2 P2 Open fold, vein 1 cm wide, view north 2013-08-12 423765 6265504 360 67 Vein Fold D2 P1 open 2013-08-12 423703 6265425 136 83 S2 D2 P2 Cleavage 2 mm periodicity 2013-08-12 423703 6265425 175 80 S1 D2 P1 Hillside slufing causing rotation of foliation (or K influence) 2013-08-12 423679 6265483 220 70 S1 D2 P1 5 mm spacing cleavage, appears axial planar (retake photo?) 2013-08-12 423870 6265519 227 80 Sinistral fault D1 Offsets previous veins 2013-08-12 423870 6265519 320 64 Vein D1 1 cm wide 2013-08-12 423786 6265521 322 60 Vein Tectonic open folds, several eroded define good reading, vein ~1cm, view north 2013-08-12 423605 6265451 334 72 S1 D2 P1 Sericite replaced clasts 2013-08-12 423679 6265483 342 70 S1 D2 P1 Well defined foliation 2013-08-12 423870 6265519 345 86 Vein D1 Transition between IARG and QSP, 3cm wide 2013-08-12 423605 6265451 20 89 Sinistral fault D1 Small quartz vein offset 5 cm cleavage sets cut foliation (K?), not a clear F2 here possibly due to distance from tuff 2013-08-12 423765 6265504 27 88 S2 D2 P2 foliation 2013-08-12 423870 6265519 36 80 Vein D1 Conjugate to previous, 0.5cm, view south 2013-08-12 423765 6265504 92 85 S1 D2 P1 foliation 2013-08-12 423489 6265170 246 65 Vein Fold gentle vein fold with mo 3 2013-08-13 423489 6265170 249 60 Vein Fold gentle, multiple veins 3 2013-08-13 423489 6265170 257 45 Vein Fold A variety of folds, not a super clear association with deformation, open fold 3 2013-08-13 423458 6265251 270 72 Vein Fold D2 P1 gentle fold, small island of chl, cataclased boundary 2013-08-13 423246 6265116 120 69 Vein Tectonic " 2013-08-13 423246 6265116 131 66 Vein Tectonic extension veins, sigmoidal, quartz milky 2013-08-13 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 145 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423334 6265193 300 60 Vein Tectonic 1 cm wide ext vein is apparently folded suggesting that it is pre-D2 and linked to waning of D1, scratcher points to Famq, orientation doesn't make it look D2 but cross-cutting relationship suggests that it is 3 2013-08-13 423478 6265222 301 85 Vein D1 late py cuts all, microprobe this 2013-08-13 423450 6265190 88 78 Dextral fault D_3 SFTB good deflect, multiple and significant 3 2013-08-13 423548 6265488 238 89 Vein Fold D2 P1 Z, open 5 mm wide 2013-08-14 423538 6265577 264 79 Vein Fold D2 P1 open vein fold 2013-08-14 423609 6265574 266 80 Vein Fold D2 P1 Prominent fold in photo 2013-08-14 423581 6265581 271 60 Vein Fold D2 P1 First nice anticline to right of planar vein, open 2013-08-14 423538 6265577 280 69 Vein Fold D2 P1 Gentle fold result of vein orientation 2013-08-14 423581 6265581 289 55 Vein Fold D2 P1 To left of planar vein, open-almost box 2013-08-14 423548 6265488 291 84 Vein Fold S fold 5 mm wide vein, open 2013-08-14 423548 6265488 302 0 Lineation D2 P1 Trend to S folds (plunge of 0 inserted for plotting) 2013-08-14 423548 6265488 314 0 Lineation D2 P1 Trend of ~8 Z folds, vergence (plunge of 0 inserted for plotting) 2013-08-14 423548 6265488 329 80 Vein Fold S gentle, 1 cm wide vein 2013-08-14 423548 6265488 329 83 Vein Fold D2 P1 Z fold, 5mm wide vein, open 2013-08-14 423538 6265577 232 82 Vein D1 South limb 2013-08-14 423538 6265577 260 75 Vein D1 South limb, 1 cm quartz sulphide, view S 2013-08-14 423581 6265581 302 81 Vein D1 Defined by numerous smaller veins 2013-08-14 423538 6265577 310 86 Vein D1 North limb 2013-08-14 423548 6265488 312 80 Vein D1 Minor, weakly folded 2013-08-14 423538 6265577 318 89 Vein D1 North limb, view W 2013-08-14 423540 6265583 323 80 Vein D1 Very prominent vein orientation (65% veins), Hb microporphyry, view west 2013-08-14 423581 6265581 346 87 Vein D1 Defined by fewer, large veins 2013-08-14 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 146 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423540 6265583 347 85 Vein D1 Another strong set (20% veins), good sample of HB microdiorite and matrix (whole rock here), hb microdiorite (polish slab), local canibalism, fragmentation of quartz related to microdiorite lense 2013-08-14 423618 6265535 348 75 S1 D2 P1 CHL-SER define foliation 2013-08-14 423581 6265581 352 78 S1 D2 P1 Significance of orientation and lack of D1 folding, S1 is axial planar to fold 2013-08-14 423618 6265535 0 90 Vein D1 10cm wide vein, representative 2013-08-14 423548 6265488 11 78 S1 D2 P1 2013-08-14 423548 6265488 23 83 Vein D1 Major vein stockwork orientation (all folded) 2013-08-14 423548 6265488 30 83 S2 D2 P2 Overprinting Sm, patchy 2013-08-14 423581 6265581 60 0 Vein D1 Folded vein trend 2013-08-14 423475 6265271 160 0 Lineation Primary Clast D1 Clast trend to highly angular quartz fragments - suggests near source as with pebble dyke (plunge of 0 inserted for plotting) 2013-08-15 423464 6265366 260 69 Vein Fold D2 P1 2013-08-15 423464 6265366 270 77 Vein Fold D2 P2 Appears to be an overprint but looks close to F1 2013-08-15 423391 6265341 304 77 Vein Fold D2 P2 2013-08-15 423506 6265385 313 68 Vein Fold D2 P2 gentle fold well defined 2013-08-15 423431 6265355 360 84 Vein Fold D2 P2 gentle fold 2013-08-15 423455 6265291 134 72 Vein Tectonic Giant (>1m wide) late milky qz (no ankerite seen), pinches out, extension vein 2013-08-15 423623 6265350 162 72 Sinistral fault D_3 SFTB 3mm spacing, good shear sense to shear band 2013-08-15 423623 6265350 175 86 S1 D2 P1 GF-13-01, maybe related blocks here 2013-08-15 423623 6265350 198 86 Dextral fault D_3 SFTB Subtle, 2-3 mm spacing subtle shear sense 2013-08-15 423506 6265385 235 76 Axial Surface/Planar Cleavage (Folds) D2 P2 axial planar cleavage 2013-08-15 423506 6265385 235 76 Axial Surface/Planar Cleavage D2 P2 axial planar cleavage 2013-08-15 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 147 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date (Folds) 423506 6265385 240 83 Axial Surface/Planar Cleavage (Folds) D2 P2 axial planar cleavage 2013-08-15 423475 6265271 240 75 Spaced Cleavage 2mm spaced cleavage 2013-08-15 423506 6265385 246 80 Axial Surface/Planar Cleavage (Folds) D2 P2 axial planar cleavage 2013-08-15 423464 6265366 247 84 Axial Surface/Planar Cleavage (Folds) D2 P1 Axial surface to D1 vein fold 2013-08-15 423475 6265271 247 70 Dextral fault D_3 SFTB Shearbands change angle into PAND (maybe not) 1/10-50 cm 2013-08-15 423464 6265366 260 79 Axial Surface/Planar Cleavage (Folds) D2 P2 3 veins <1cm, gentle fold 2013-08-15 423431 6265355 299 88 Vein D1 limb a gentle fold (sketch) 2013-08-15 423506 6265385 304 82 Sinistral fault D_3 SFTB well developed, seems to mimic limbs (?) 2013-08-15 423506 6265385 333 89 Vein D1 limb to gentle fold 2013-08-15 423464 6265366 350 85 Vein D1 Finer vein sets -80% of veins 2013-08-15 423506 6265385 352 84 S1 D2 P1 7% Qz veins, phyllonite, one large clast rounded 2013-08-15 423506 6265385 355 89 Vein D1 limb to gentle fold 2013-08-15 423506 6265385 356 90 Dextral fault D_3 SFTB Poorly developed, maybe no shear sense 2013-08-15 423455 6265291 0 72 S1 D2 P1 good 2013-08-15 423464 6265366 6 87 S1 D2 P1 Intense qsp 2013-08-15 423431 6265355 6 85 Vein D1 limb b gentle fold 2013-08-15 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 148 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423391 6265341 10 87 Axial Surface/Planar Cleavage (Folds) D2 P2 Qz stockwork clast, angular quartz frags, quartz not dismembered implying intrusive breccia interpretation, note Mo veins occur as V0, and Cu poor veins comprise V02 (defined only in that it post-dates V01 which I know by its occurrence in PAND or IB 2013-08-15 423431 6265355 24 90 Axial Surface/Planar Cleavage (Folds) D2 P2 1-3 cm spaced clavage, not dilational, one orientation only 2013-08-15 423464 6265366 44 90 Vein D1 larger vein sets (~20% of veins) 2013-08-15 423310 6265407 64 64 Vein Fold D1 open 2013-08-16 423310 6265407 84 68 Vein Fold D1 isoclinal 2013-08-16 423310 6265407 91 71 Vein Fold D1 gentle, could be F1 affects 2013-08-16 423394 6265352 113 80 Vein Fold D2 P1 Tight fold in 2cm vein, good axial planar cleavage for D1 and D2 2013-08-16 423394 6265352 147 80 Vein Fold D2 P2 Weakly developed, very gentle 2013-08-16 423310 6265407 170 64 Vein Fold D1 tight 2013-08-16 423310 6265407 200 0 Lineation Primary Clast D1 Mineral trend: near numerous clasts, one 30cm diameter, magmatic vein shows numerous ptygmatric folds near subplanar vein, rock is fine-grained mafic-phyric. 12 fold axis readings taken here -refer to sketch. 2013-08-16 423310 6265407 215 68 Vein Fold D1 parallel<isoclinal 2013-08-16 423310 6265407 240 86 Vein Fold D2 P1 gentle 2013-08-16 423310 6265407 249 81 Vein Fold D2 P1 gentle 2013-08-16 423310 6265407 254 80 Vein Fold D2 P1 open 2013-08-16 423310 6265407 255 75 Vein Fold D1 gentle, could be F1 affects 2013-08-16 423310 6265407 272 82 Vein Fold D2 P1 open 2013-08-16 423375 6265396 276 57 Vein Fold D2 P1 Excellent outcrop of thisk, open fold, view SW 3 2013-08-16 423310 6265407 316 78 Vein Fold D1 isoclinal 2013-08-16 423310 6265407 342 69 Vein Fold D1 open 2013-08-16 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 149 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423394 6265352 178 75 Vein D1 limb b to vein fold 2013-08-16 423312 6265278 357 77 S1 D2 P1 Crowded, white feldspar porphyry at ser-chl contact, possibly at selvage of main intrusion representing an older, mo-rich porphyry, an up dip piece of PMFP (?), sample GF-13-02 (thin section/whole rock) 2013-08-16 423394 6265352 4 87 Axial Surface/Planar Cleavage (Folds) D2 P1 ~1 cm spacing to axial planar cleavage D1 2013-08-16 423381 6265333 5 85 S1 D2 P1 Intrusive protolith suspected, nearby we see clastic texture with stockwork, ~30% QSTW, look at cleavages or just hand sample: GF-13-04 2013-08-16 423447 6265348 5 84 S1 D2 P1 45% stwk, look for axial cleavage here (maybe Cs and Cd) GF-12-03, intrusive protolith? 2013-08-16 423310 6265407 5 90 S1 D2 P1 2013-08-16 423394 6265352 6 86 Axial Surface/Planar Cleavage (Folds) D2 P1 ~1cm spacing to axial planar cleavage D1 (?) 2013-08-16 423394 6265352 6 84 S1 D2 P1 Meandering a little 2013-08-16 423370 6265417 6 72 S1 D2 P1 Finally convinced myself that either 1. PPFP isn't real or that 2. the wall rock is older intrusion or that 3. pand has many faces. Hb still visible but ser brings out feldspar phenos more, GF-13-05 sample to look at changes in deformation with resp 2013-08-16 423375 6265394 7 86 S1 D2 P1 3 2013-08-16 423308 6265407 19 89 Axial Surface/Planar Cleavage (Folds) D2 P2 Large (previously mapped) quartz-ankerite vein shows pronounced axial planar cleavage , marked in quartz and diffuses in ankerite, vein is weakly sheared and within vein is blocky quartz growth appears open space, blocky texture cut by cleavage, shea 2013-08-16 423394 6265352 69 84 Axial Surface/Planar Cleavage (Folds) D2 P2 ~2cm spacing 2013-08-16 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 150 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423394 6265352 76 81 Axial Surface/Planar Cleavage (Folds) D2 P2 ~2cm spacing 2013-08-16 423375 6265394 78 75 Dyke D1 10cm wide, clast dense, brecciation of intrusive breccia, clasts uncommonly high in quartz. Maybe not locally derived, pinches out, rock hosts aphanitic, angular clast (hornfels ash tuff), unlike other pebble dyke this one is cut by veins but also tr 3 2013-08-16 423394 6265352 78 75 Vein D1 limb to vein fold 2013-08-16 423282 6265821 105 78 Vein Fold D2 P1 A tight fold in local stockwork QSP, 2mm wide vein 2013-08-20 423379 6265773 213 0 Lineation Primary Clast D1 13x6 clast of hornfels seds/ash tuff, fairly angular -suggest we are near to wall rock here , Py-Cb vein in photo <1% qstw, photo view west 2013-08-20 423587 6265865 267 29 Mineral Alignment Primary D1 Mineral lineation: 20%, well-formed Hb>Fd phenos, resembles Hb porphyry in Iron Cap (48) at top, view north 2013-08-20 423384 6265795 115 83 Vein Tectonic 1cm wide milky quartz growth in well defined, discontinuous, enechalon sets appear to related to MTF in timing and similar orientation as Vank wedge veins, view north 2013-08-20 423384 6265795 119 87 Vein Tectonic 2013-08-20 423553 6265824 146 90 Sinistral fault D1 Sinistral faultlet 2013-08-20 423392 6265862 165 68 Fault No Kinematics Feather fracture to sinistral 2013-08-20 423284 6265820 190 88 Sinistral fault D_3 SFTB Dominant shear band at low angle to S1, view east 2013-08-20 423553 6265824 225 85 Vein D1 1% qz stockwork, no clasts, quartz-pyrite vein sets offset 2013-08-20 423392 6265862 249 72 Dextral fault D1 dextral movement in hanging wall to MTF 2013-08-20 423392 6265862 249 72 Sinistral fault D1 Sinistral sense to brittle fault 2013-08-20 423587 6265865 259 60 Vein D1 Qz-Mo-Cp veinlet, 2% quartz stockwork, no clasts 2013-08-20 423229 6265815 280 75 Vein Tectonic D_3 SFTB MTF hanging wall features (feather fractures 2013-08-20 423433 6265814 308 78 S1 D2 P1 <1% quartz 2013-08-20 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 151 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423501 6265856 311 25 Thrust Fault D_3 SFTB Appears to be mitchell thrust fault, marked grooves measures, hanging wall hornblende porphyry, view west 2013-08-20 423513 6265813 320 80 Vein D1 25% hb porphyry, phenos chl-replaced, matrix weakly altered massive intrusion, 2% qz stwk, no clasts observed, brittle py-only vein, ser alteration halos to veins suggest we are peripheral or possible in wall rock tuff 2013-08-20 423392 6265862 321 82 Fault No Kinematics Feather fracture to dextral fault 2013-08-20 423282 6265821 340 ## Vein Tectonic Mitchell thrust fault: ankerite tension veins near thrust fault, offset by small sinsitral faults, view southwest 2013-08-20 423229 6265815 342 41 S1 D2 P1 A prominent fabric within fault seams consistent with S1, view northeast 2013-08-20 423411 6265783 342 86 Vein D1 2013-08-20 423282 6265821 350 45 Vein Tectonic Mitchell thrust fault: ankerite tension veins near thrust fault, offset by small sinsitral faults, view south 2013-08-20 423282 6265821 355 45 Thrust Fault D_3 SFTB approximate appearance of MTF orientation, <10cm thick, footwall zone shows foliation is QSP 2013-08-20 423229 6265815 356 42 Thrust Fault D_3 SFTB Y plane in mitchell thrust fault 2013-08-20 423282 6265821 12 42 S1 D2 P1 foliation in FW 2013-08-20 423384 6265795 13 72 S1 D2 P1 2013-08-20 423411 6265783 20 80 Vein D1 Xenolith in Hb porphyry, <1% quartz (most veins py), no folds here, xenolith is of hornblende porphyry (autolith), view north 2013-08-20 423364 6265804 32 80 S1 D2 P1 10m wide trend to QSP, foliated 2013-08-20 423284 6265820 43 45 Dextral fault D_3 SFTB Subordinate shear band 2013-08-20 423759 6265309 203 51 Vein Fold D2 P2 Open fold, 3 mm vein 2013-08-21 423759 6265309 261 49 Vein Fold D2 P1 Overturned 2013-08-21 423511 6265437 109 53 Vein Tectonic As prev, (3cm, main on in photo) 2013-08-21 423473 6265420 111 67 Vein Tectonic 0.5cm wide milky quartz vein, view SW 2013-08-21 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 152 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423832 6265290 113 77 Axial Surface/Planar Cleavage (Folds) Unsure of rotation here…looks to have rotated S1 about its own plane 2013-08-21 423838 6265317 166 68 S1 D2 P1 Bubble rock, veins parallel S1, good gentle Ks here 2013-08-21 423832 6265290 190 88 S1 D2 P1 Multivein D1 fold, gentle, foliation also entrained 2013-08-21 423759 6265309 194 52 S1 D2 P1 True bubble rock! Proof of intrusive contact zone, sample GF-13-08, view north 2013-08-21 423473 6265420 200 62 Vein Tectonic Anomalous orientation subhorizontal of milky quartz -just like at brucejack, view east 2013-08-21 423473 6265420 201 41 Vein Tectonic Note: 8982 MTF I might find an aerial photo 2013-08-21 423729 6265307 210 72 S1 D2 P1 Folded Mo veins, foliation strangely folded (major rotation of S1), view west 2013-08-21 423511 6265437 217 48 Fault No Kinematics Folition plane appears to parallel minor fault - no movement, view SW 2013-08-21 423811 6265261 250 85 S1 D2 P1 Anomalous S1, amazing fold outcrop 2013-08-21 423513 6265486 308 72 Vein D1 20% of veins in this oreintation 2013-08-21 423513 6265486 332 78 Vein D1 80% of veins in this orientation 2013-08-21 423526 6265453 350 85 Vein D1 Apparent thrust imbricate, this fracture may not be movement plane, almost appears to be dead end into sericite [note:MTF imbricate looks to strik NW and dip 60 deg], view SW 2013-08-21 423508 6265512 26 90 Dyke D1 Meandering breccia dyke, sharp clasts, cuts all veins, appears to be associated with chaotic heat- related folds, but up against a vein - locally assimilating wall rock locally derived material, view west 2013-08-21 423513 6265486 41 80 Vein D1 nearby late pyrite shows same trend as ibx 2013-08-21 423513 6265486 49 88 Dyke D1 10-15cm wide intrusive breccia reactivates Vpy orientation, ibx cuts late pyrite vein, view north 2013-08-21 423511 6265437 72 60 Vein Tectonic Milky quartz veins, same en echalon contain minor pyrite and weathered carbonate (2 cm to right) 2013-08-21 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 153 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423318 6265285 100 30 Vein Fold Good sinistral offset of a decoulement: links up with my wedge veins here - map this out 3 2013-08-22 423231 6265422 154 60 Vein Fold D2 P2 Foliation "flows" around these quartz-ankerite veins implying that S1 was ongoing after their emplacement, the material pinches up into the folds implying strong rheology contrast, 3% clst 2013-08-22 423838 6265317 112 70 Reverse Fault D_3 SFTB Imbricate 2013-08-22 423263 6265260 115 68 Vein Tectonic 3 2013-08-22 423264 6265255 127 50 Vein Tectonic Good outcrop of thrust fault imbricate juxtaposing lithology, sample GF-13-10 milky quartz, no thin section of this sample, these post date F2 (so does TF) 3 2013-08-22 423838 6265317 136 ## Vein Tectonic Quartz extension vein to thrust fault 2013-08-22 423231 6265425 136 70 Vein Tectonic Sample of 1m thick Vank, flow of S1 around its buckles sample is for Ar-Ar, 46/70 (1), wall rock fragment in the Vank 2013-08-22 423204 6265536 171 82 Fault No Kinematics D1 Good offset looks to have Qz-Ank, this could be brittle onset of the main flattening event with minor subsequent flattening post offset, competency preserves proto D1 deformation 2013-08-22 423838 6265317 172 25 Vein Tectonic 2013-08-22 423838 6265317 190 79 Reverse Fault D_3 SFTB Back thrust plane 2013-08-22 423184 6265557 202 62 Reverse Fault D_3 SFTB Lobster thrust, good kinematics top up reverse fault, lobster vein is perpendicular and parallel to it 2013-08-22 423384 6265269 291 60 Reverse Fault D_3 SFTB Thrust fault imbricate: excellent shape fabric and drag folds pulling S1 into it, cuts overlying, hanging wall is 95% quartz stockwork, footwall is 12%, creates a little clip (-08/-09), Sample GF-13-11 2013-08-22 423838 6265317 294 80 Thrust Fault D_3 SFTB Apparent thrust fault plane 2013-08-22 423263 6265260 330 29 Reverse Fault D_3 SFTB View west and shows good slip movement, ibx strong and contains megaclasts, Y slip surfaces show hanging wall up 3 2013-08-22 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 154 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423349 6265282 340 80 S1 D2 P1 Thrust fault duplex: major slip surface, 0.5 m wide, horse texture with shape fabric 2013-08-22 423365 6265240 15 77 S1 D2 P1 10% Qz stockwork in pand, no clasts observed [no details about what structure reading this is - S1] 2013-08-22 423090 6265595 65 45 Vein Fold D2 P2 8% quartz stockwork, strong lineament could be inferred , 1% quartz clasts, WQSP entirely. Open fold 1.5 cm wide vein. 2013-08-23 423090 6265595 286 77 Vein Fold D2 P1 2 mm wide vein 2013-08-23 423079 6265577 326 55 Mineral Alignment Primary D1 Pand with small white feldspar laths and chlorite 2013-08-23 423033 6265514 262 81 Vein D1 Note: another thicker set inbetween these orientations 2013-08-23 423079 6265577 276 80 Vein D1 9% quartz stockwork, strong orientation, 90% of veins parallel this 2013-08-23 423033 6265514 330 82 Vein D1 Orthogonal vein sets, very well developed chl pand, 10% quartz stockwork 2013-08-23 423013 6265478 2 85 Dextral fault D1 Fault zone, quartz 12%, clasts 1%, chl 3 2013-08-23 422992 6265496 7 80 S1 D2 P1 2% clasts in chl pand, >10cm, 7% quartz stockwork, view east, very weak chl defined foliation 2013-08-23 423028 6265560 7 68 Dextral fault D1 20 m long lineament links to lineament to west, 8% quartz, no clasts 2013-08-23 423357 6265631 16 60 Dextral fault Cataclasite: strike-slip gives you dextral, vein association is folded fibrous quartz-chlorite, dip-slip has drag fold giving reverse normal fault 2013-08-23 423079 6265577 20 78 S1 D2 P1 2013-08-23 422804 6265260 19 70 Vein Fold D2 P2 F2=gentle, multivein fold 2013-08-24 422802 6265322 78 78 Vein Fold 2013-08-24 422802 6265322 120 74 Vein Fold 2013-08-24 422802 6265322 148 72 Vein Fold 2013-08-24 422802 6265322 184 54 Vein Fold 2013-08-24 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 155 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 422802 6265322 193 64 Vein Fold 30% quartz, no clasts visible, lots of meandering veins, potential F1 orientations but most of those look like Fo, very disharmonic folding, gentle angles especially in veins <1cm, less of a strong vein orientation here and locally more folds observe 2013-08-24 422802 6265322 212 84 Vein Fold 2013-08-24 422724 6265288 246 60 Mineral Alignment Primary D1 Hb pheno alignment 2013-08-24 422805 6265258 250 83 Vein Fold D2 P1 2013-08-24 422756 6265420 263 60 Mineral Alignment Primary D1 Random phenocryst orientations with subtle alignment locally 2013-08-24 422804 6265260 267 84 Vein Fold D2 P1 F1=isoclinal, 2 mm thick 2013-08-24 422770 6265210 278 75 Vein Fold D2 P1 Weak, gentle fold train in 2 mm Vo vein 2013-08-24 422805 6265258 281 81 Vein Fold D2 P1 Two suspicious minor folds, open, 2 m apart suggest I am in F1 nose. This complicates QSTW interpretation ->waviness in plan view could be F1 since parallelism appears to be Do. Photo view south. 2013-08-24 422792 6265204 175 90 Vein D1 2013-08-24 422741 6265204 183 80 Vein D1 Quartz 30%, no clasts observed, most 1-2cm thick, 80% subparallel to Vmj, 10% to Vmn, view SE 2013-08-24 422804 6265260 203 80 Vein D1 Minor folds in this - appears to be band of chlorite - altered 45% quartz, no clast with mixed sericite patches - looks to behave very resistantly with minor F1 and minor F2, I'm convinced that Quartz high stockwork was injected into parallelism prio 2013-08-24 422791 6265287 205 88 Vein D1 55% quartz, no clast locally, small pods of chlorite remain but sericite introduction strong here. Hammer= north 2013-08-24 422805 6265258 293 90 Axial Surface/Planar Cleavage (Folds) D2 P1 2013-08-24 422741 6265204 315 76 Vein D1 D1 virtually absent here 2013-08-24 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 156 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 422742 6265422 322 86 Sinistral fault D1 Very brittle movement on fractures, no subsequent brittle overprint, some dip-slip motion 2013-08-24 422756 6265420 327 61 Fault No Kinematics D1 20% quartz stockwork, trace clasts, somewhat ambiguous here, this fracture is mid photo and looks like brittle, mostly dip-slip, maybe tied to S1 event (no S1 here!), photo view NW 2013-08-24 422686 6265171 327 85 Vein D1 Quartz 20%, no clasts observed, no D1 to measure, except very weak S1. View west. 2013-08-24 422804 6265258 346 90 Vein D1 2013-08-24 422807 6265211 349 89 S1 D2 P1 2013-08-24 422724 6265288 352 75 S1 D2 P1 Very poorly defined foliation by microfissility 2013-08-24 422747 6265152 357 75 S1 D2 P1 Weakly defined by chl 2013-08-24 422701 6265195 357 70 S1 D2 P1 Quartz 20%, weak hornblende phenocrysts are now noticeable, less veins means easier S1 reading 2013-08-24 422724 6265288 357 80 Vein D1 30% quartz, no clasts observed, very weak foliation and maybe subtle fold in vein, good hornblende phenocrysts visible, photo view north 2013-08-24 422686 6265171 0 75 S1 D2 P1 Weakly defined by chl 2013-08-24 422747 6265152 0 73 Vein D1 outcrop 20m above can be mapped as this, 20% quartz, no D1, good hornblende laths here 2013-08-24 422807 6265211 0 87 Vein D1 40% quartz, clast not observed, weak foliation, thin section location to look at potential F1 and F2 events and the working model that these veins were aligned into parallelism prior to D1: sample GF-13-13, could use thin section to see if S1 is para 2013-08-24 422770 6265210 1 76 S1 D2 P1 Very poorly developed 2013-08-24 422680 6265197 5 85 Vein D1 Quartz 15% locally, only trace D1, faint hornblende phenos (small o/c) 2013-08-24 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 157 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 422752 6265313 5 85 Vein D1 35% Qtz, no clasts observed, no identifiable folds - only meandering veins, patchy sericite altered pods appear to be spared from D2 and only weakly altered by D1 showing weak foliation development but lacking folding, foliation lacks Cs and Cd devel 2013-08-24 422760 6265302 8 86 Vein D1 Quartz 35%, clasts not observed, silica alteration results in weak deformation overprint of foliation alignment of silica, 60% of veins in Vmj orientation, foliation very subtle. Photo view north 2013-08-24 422770 6265210 10 78 Vein D1 Quartz 35%, no clasts, appears to be nearly orthogonal vein sets with strong Vmj, photo view south. 2013-08-24 422760 6265302 14 85 S1 D2 P1 2013-08-24 422804 6265260 24 90 S1 D2 P1 2013-08-24 422791 6265287 25 88 S1 D2 P1 Foliation here is appears very slightly off of Vmj - if S1 is axial planar and Vmj is bedding there could be a large-scale fold of Vmj, foliation perpendicular veins are not strongly folded here 2013-08-24 422756 6265420 26 90 Vein D1 Strong orientation to veins: sharp boundaries, most 1-2 cm wide, 70% of veins in this orientation, brittle, anastamosing, no identifiable folds 2013-08-24 422805 6265258 31 90 Axial Surface/Planar Cleavage (Folds) D2 P1 2013-08-24 422792 6265204 39 85 Vein D1 Quartz 35%, no clasts observed, weak deformation, Vmj >90% of veins 2013-08-24 422807 6265211 39 90 Vein D1 2013-08-24 422742 6265422 46 76 Vein D1 Strong brittle sets, meandering not folded veins imply hot intrusion during emplacement. Dog=north. 2013-08-24 422804 6265258 56 78 Vein D1 As previous - orthogonal sets of overprinting parallel veins - very weak D1 only. Photo view south 2013-08-24 422770 6265210 79 62 Vein D1 Subparallel to S1 2013-08-24 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 158 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 422811 6265277 97 45 Vein Tectonic 45% quartz, no clasts locally 0.5-2 cm wide fibrous quartz-chlorite veins in chlorite alteration and simply milky quartz in sericite alteration - host rock dependent. Photo view west. 2013-08-24 422811 6265277 100 23 Vein Tectonic Simply milky quartz in sericite alteration - host rock dependent 2013-08-24 423100 6265132 4 65 Vein Fold 3 2013-08-25 423058 6265159 7 79 Vein Fold D2 P2 Gentle fold at contact 3 2013-08-25 422994 6265128 40 25 Vein Fold Numerous veins entrained 3 2013-08-25 423013 6265151 42 30 Vein Fold Gentle fold, multiple veins entrained 3 2013-08-25 423616 6265153 90 40 Vein Fold D2 P2 2013-08-25 423100 6265132 112 72 Vein Fold 90% quartz 3 2013-08-25 422959 6265125 122 33 Vein Fold Unsure Fo (?), open fold of S1 and 3 veins. View SE. 3 2013-08-25 423122 6265141 130 85 Vein Fold D2 P1 Gentle fold of late pyrite vein appears axial planar =S1 3 2013-08-25 423122 6265141 135 74 Vein Fold D2 P1 Gentle fold of late pyrite vein appears axial planar =S1 3 2013-08-25 423267 6265247 190 75 Vein Fold D2 P2 Peak to peak of gentle fold ~10cm, amplitude ~1 cm 3 2013-08-25 423616 6265153 253 40 Vein Fold D2 P2 2013-08-25 423491 6265139 275 90 Vein Fold Normal fault placing hanging wall fine-grained andesite against 95% quartz stockwork, Y fabrics developed near contact only, no kinematics in plan view suggest subvertical fault movement - potentially in bizarre expression of MTF 2013-08-25 423100 6265132 355 70 Vein Fold 3 2013-08-25 423058 6265159 355 83 Vein Fold D2 P2 Gentle fold at contact 3 2013-08-25 423058 6265159 355 80 Vein Fold D2 P2 Open fold at contact 3 2013-08-25 422959 6265125 90 60 Dextral fault D_3 SFTB One cm wide shear band, good dextral sense, curvilinear in this case and discontinuous, view east 3 2013-08-25 423013 6265151 95 50 Vein Tectonic Two orientations of milky quartz apparently linked to shear bands (?), most are moderately dipping with subordinate set flatter lying. View southwest. 3 2013-08-25 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 159 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423032 6265166 95 20 Vein Tectonic 1cm wide 3 2013-08-25 423266 6265247 100 42 Vein Tectonic 1-2 cm white en echalon sets, appear fairly planar - no good folds in thin 3 2013-08-25 422981 6265116 110 24 Vein Tectonic 3 2013-08-25 423536 6265132 113 54 Vein Tectonic Normal fault reactivation (?), milky veins resemble those at MTF, good contact, 95% quartz (thrust fault down dropped by E-W fault) 3 2013-08-25 422994 6265128 130 42 Axial Surface/Planar Cleavage (Folds) Related to nearby fault (mitchell thrust fault) 3 2013-08-25 423013 6265151 140 18 Vein Tectonic 3 2013-08-25 422994 6265099 150 35 Axial Surface/Planar Cleavage (Folds) (as below) 3 2013-08-25 423122 6265141 160 80 Vein D1 Undulating vein at angle to main veins but folded in D1 3 2013-08-25 422924 6265080 160 45 Vein Tectonic 1cm wide, not folded 3 2013-08-25 422924 6265080 162 43 Vein Tectonic 1cm wide, not folded 3 2013-08-25 422994 6265099 167 81 Sinistral fault D_3 SFTB shear band 3 2013-08-25 422994 6265099 175 32 Axial Surface/Planar Cleavage (Folds) This fold entrained several veins and foliation but appears anomalous, gentle 3 2013-08-25 422994 6265099 200 83 Vein D1 Quartz 85%, view east 3 2013-08-25 423032 6265166 200 70 Vein D1 90% quartz, below this no outcrop just cliff, DDRT 1 m shows strong reverse shear sense. Photo view west. 3 2013-08-25 423266 6265247 200 70 Vein D1 3 2013-08-25 423094 6265149 220 70 Vein D1 1 cm wide late pyrite vein appears to be in orientation that is weakly affected by D1 and D2, new interpretation: these are injected into cool rocks and evade deformation (90% Quartz). View SW 3 2013-08-25 423362 6265223 274 25 Thrust Fault D_3 SFTB Good reverse movement on this 2013-08-25 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 160 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423349 6265213 291 42 Thrust Fault D_3 SFTB 10% quartz, appears to be faulting at rheology contrast - unknown significance, hanging wall to south from shape fabric 2013-08-25 423322 6265257 330 90 Vein D1 10% quartz, no clasts observed, some veins but very planar 2013-08-25 422959 6265125 340 70 S1 D2 P1 Defined by strong sericite yellow 3 2013-08-25 422994 6265128 342 88 Vein D1 90% quartz, subtle folds could be tied to shear band development or thrust fault, ?drag fold 3 2013-08-25 422959 6265125 345 70 Vein D1 70% quartz, strong sericite fabric, no clasts observed 3 2013-08-25 423013 6265151 352 85 Vein D1 3 2013-08-25 422924 6265080 355 51 Vein D1 50% quartz, no clast, strong sericite, unknown protolith, strong parallelism but true stockwork, view south 3 2013-08-25 423058 6265159 357 70 S1 D2 P1 0.5cm spaced foliation is folded with 3 2013-08-25 422924 6265080 0 68 S1 D2 P1 Still visible appearing to have 3 2013-08-25 423722 6265225 0 86 S1 D2 P1 ~5% quartz stockwork, 2% clasts of quartz stockwork, same clasts >10 cm 2013-08-25 423058 6265159 0 86 Dyke D1 Trend of 5m outcrop of DDRT 3 2013-08-25 423504 6265194 5 80 Vein D1 3 2013-08-25 422994 6265099 10 85 S1 D2 P1 3 2013-08-25 423616 6265153 10 87 S1 D2 P1 This marks contact marks a lineament trending N-S on map, QSTW to west and lower STWK and clastics to right Qz 12%, Clast ~1% (megaclastic) 2013-08-25 423502 6265150 12 81 S1 D2 P1 Strong, eroded ibx contact with strong foliation parallel veining overprinting it 3 2013-08-25 423504 6265194 13 85 S1 D2 P1 60% qstw 3 2013-08-25 423353 6265193 13 64 Vein D1 3 2013-08-25 423058 6265159 14 80 Vein D1 3 2013-08-25 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 161 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423353 6265193 15 70 S1 D2 P1 Intrusive breccia contact, clasts up to 20cm, highly angular shapes, the more rounding is associated with assimilation and smaller clasts, locally clasts are 95% quartz because they are locally sourced, 15% clasts highly varied size distribution, con 3 2013-08-25 423353 6265193 15 75 Vein D1 3 2013-08-25 423100 6265132 20 82 Dyke D1 25m strike length, ~15m wide dyke, possibly boudined or just eroded, four descent folds along strike length, 1-3 m wavelength in this example. View South. 3 2013-08-25 423122 6265141 30 75 S1 D2 P1 70% quartz, locally lower (beside ~5m northwest pod of chlorite ~5% quartz). Photo view west 3 2013-08-25 423353 6265193 35 85 Vein D1 3 2013-08-25 422994 6265128 55 35 Vein Tectonic Numerous sets in this outcrop 3 2013-08-25 423058 6265159 55 50 Vein Tectonic 90% quartz 3 2013-08-25 423032 6265144 70 69 Dextral fault D1 Fantastic strike-slip fault post-dates foliation, cataclased, strong deflection of S1 showing dextral (still 90%, quartz, no clasts), ~50cm wide, traces south from here ~20m only 3 2013-08-25 422981 6265116 85 48 Dextral fault D_3 SFTB 2mm wide shear band (lower in photo), reverse sense, wrapping foliation, view east 3 2013-08-25 423100 6265132 90 60 Dyke D1 3 2013-08-25 423646 6265689 69 61 Vein Fold D2 P1 ~3% clasts, 5% stwk, alteration blurs potential vcl clast, angular to rounded clasts up to 3cm. View south. 2013-08-26 423469 6265628 100 60 Vein Fold D2 P2 2013-08-26 423469 6265628 257 77 Vein Fold D2 P1 2013-08-26 423697 6265707 260 70 Vein Fold D2 P1 2mm wide vein, tight fold. View south. 2013-08-26 423627 6265674 270 85 Vein Fold D2 P1 Locally ~40% volcanic clasts observed, sericitized phenocrysts, irregular, whispy, shapes, 5 mm long quartz fragment with cognate clasts (accessory), tight fold in quartz vein ~0.5 cm wide 2013-08-26 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 162 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423509 6265681 273 75 Vein Fold D2 P1 Quartz-sulphide fragments subrounded, average 0.5-1 cm diameter, cognate fragments highly angular also average 0.5 - 1cm diameter 2013-08-26 423646 6265689 289 83 Vein Fold D2 P2 Open fold gentle, 3 mm wide vein, also folds foliation 2013-08-26 423555 6265636 301 16 Slickensides D3 slickenslides on surface 2013-08-26 423697 6265707 305 73 Vein Fold D2 P2 2mm wide vein, open fold 2013-08-26 423576 6265678 313 68 Vein Fold D2 P2 Open fold in 5 mm wide vein 2013-08-26 423555 6265636 139 42 Vein Tectonic suggest an association with MTF 2013-08-26 423620 6265646 210 62 Vein D1 2013-08-26 423642 6265640 215 72 Dyke D1 Diorite, clasts are quartz veins 5 mm -7cm, disarticulated quartz fragments, quartz stockwork with chloritic aphanitic groundmass, ibx cuts some veins and is cut by others (like 212/81). View south. 2013-08-26 423555 6265636 243 44 Thrust Fault D_3 SFTB Strong quartz-chlorite vein array with three kinematic indicators giving hanging wall up, slickenslides, quartz veins, stepovers all indicate the same sense of movement, chlorite is deep green, quartz is milky and coarse chalcopyrite growth - same a 2013-08-26 423609 6265671 245 49 Thrust Fault D_3 SFTB R1 shears in 10cm brittle structure indicate it is reverse/TF movement, ~7% Quartz, 2% Quartz ?vcl. View west. 2013-08-26 423555 6265636 250 20 Vein Tectonic Fibrous late vein 2013-08-26 423465 6265629 259 79 Dyke D1 Dyke anastamoses but has very sharp contacts, cement appears clastic, fine-grained 2013-08-26 423511 6265640 284 90 Bedding D1 Irregular flow banding appears to be result of melting clasts - interpreted as volcanic-magmatic interface, suspiciously pops up at boundary into river breccia, could also be an ignimbrite of some sort, either way - a fluidized andesite flow. 9219-92 2013-08-26 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 163 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423563 6265676 300 58 Bedding D1 Flowbanded eruptive pile, some large quartz stockwork clasts up to 20 cm chlorite matrix, andesite clasts finer-grained and ~30%, some sorting into bands but large clasts do what they want, Quartz 5%, clasts, stockwork ~3%. View southwest. 2013-08-26 423443 6265607 302 88 Vein D1 Quartz 7%, clast 3% local clast trains of chlorite quartz stockwork not mappable, good hornblende ~1 mm. View south. 2013-08-26 423642 6265640 302 81 Vein D1 Highly angular intrusive breccia dyke, cement is composed of flow aligned Hb-phyriec diorite, clasts are quartz veins 5mm - 7cm, disarticulated quartz fragments, quartz stockwork 2013-08-26 423620 6265646 306 85 Vein D1 Good porphyritic, clastless texture here, near orthogonal veins suggest some formation under roegh only, quartz clasts up to ~7cm, good Hb>Fd phenocrysts. View South. 2013-08-26 423665 6265696 318 88 Vein D1 2-3% quartz grains, subrounded, vcl clasts local and very altered, near orthogonal vein sets. View west. 2013-08-26 423469 6265628 332 68 S1 D2 P1 2013-08-26 423469 6265628 340 75 S1 D2 P1 Dense clast cluster with no apparent trend, 80% quartz, quartz stockwork (most chlorite), 5% irregular volcanic fragments =hybrid mixing pipe, good folds mostly observed where clasts are dense and subparallel veining is oriented parallel to to sigma 2013-08-26 423451 6265625 340 70 Vein D1 D' veins, good alteration halos to veins (chl), ~15cm clast quartz stockwork, nearby perfect angular quartz vein fragment, excellent hornblende texture here ~2mm laths ~15%, ~5% feldspar <1 mm 2013-08-26 423646 6265689 343 78 S1 D2 P1 2013-08-26 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 164 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423576 6265678 348 78 S1 D2 P1 Good visible rounded quartz fragments with angular flattened clasts ~ chloritic, Quartz vein ~5%, Quartz clasts ~1% 2013-08-26 423508 6265649 357 72 S1 D2 P1 Andesite breccia: ~60% cognate clasts, ~3% <2cm quartz clasts, GF-13-17 ready to pluck away orientation assumed. View southwest. 2013-08-26 423500 6265645 5 76 Dyke D1 Host rock is 65% andesite fragments, ~2% quartz accessories, 3% quartz veins, intrusive breccia dyke contains sharp contacts and within dyke ~20% of clastic are cognate, ameboid. View south 2013-08-26 423665 6265696 12 86 Vein D1 ~20% qstw, in this orientation, note qz grains dominently subrounded and <1cmView south. 2013-08-26 423577 6265661 17 65 S1 D2 P1 Traceable brittle fault bifurcates here, wrapping fabric suggests reverse motion 2013-08-26 423609 6265671 71 17 Vein Tectonic 2013-08-26 423697 6265707 79 70 S1 D2 P1 Altered and subtle andesite cognate clasts ~70% rounded quartz fragments ~1%. View south. 2013-08-26 423440 6265658 66 80 Lineation Primary Clast D1 A messy, multi-episodic intrusion of shattered xenoliths, micro-intrusive breccia dykes cut VBX unit hosting minor 1% Qz general trend 66/80, numerous stepovers and subparallel features 2013-08-27 423433 6265659 267 69 Vein Fold D2 P1 60x35 cm xenolith of quartz stockwork shows very sharp boundaries and "tail" to west contains fine clastic material as an almost pressure shadow (flow to east), fold hosted in 5mm wide quartz vein within clast. View south. 2013-08-27 423408 6265672 299 60 Vein Fold D2 P1 2013-08-27 423467 6265670 140 80 Dyke D1 5 m long, 1 m wide intrusive breccia dyke, contacts are sharp and anastamosing, dyke is more silicious than wall rock (~40% fiamme, 1% quartz <2 cm diameter, dyke is 60% clasts, 10% volcanic fragments, appears somewhat igneous matrix. View west. 2013-08-27 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 165 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 423431 6265581 199 79 Reverse Fault D_3 SFTB Good exposure, clear dip-slip movement = reverse, changes angle somewhat. View South 2013-08-27 423461 6265566 233 31 Thrust Fault D_3 SFTB Very strong fault: large continuous veins formed in hanging wall, unclear kinematics, fibrous quartz-chlorite shows dip-slip motion (?late), no strong strike-slip. View SE 2013-08-27 423394 6265631 292 80 S1 D2 P1 Broad and largely irregular clast dense bodies vary from having sharp boundaries to being assimilated, host rock contains numerous large xenoliths of quartz stockwork and is interpreted to be an intrusion. Some of those appear to have intruded the i 2013-08-27 423404 6265638 347 80 S1 D2 P1 Sample GF-13-18: in the heart of a clast train just getting into the intrusion 2013-08-27 423408 6265672 12 70 S1 D2 P1 Low clast content, fine-grained intrusion - resembles north mitchell hanging wall rocks ,4% quartz stockwork 2013-08-27 423382 6265588 50 46 Vein Tectonic D_3 SFTB Planar quartz-ankerite milky vein appears to be >20 m long and link into thrust fault 2013-08-27 423461 6265566 55 30 Vein Tectonic Irregular to folded vein mostly dominated by ankerite with epidote, maybe 2 generations of movement on this. Sample cluster: GF-13-17 TF sample (poor) 2013-08-27 423461 6265566 73 45 Vein Tectonic 1-2cm wide very continuous milky vein terminates in thrust fault gully, no north quartz-ankerite veins have formed and look folded, maybe reactivated or just old. View South. 2013-08-27 423029 6265248 110 10 Vein Fold D2 P2 3 2013-08-28 423085 6265300 230 55 Vein Fold Footwall zone of fault is strangely clastic but shows no shear sense just flattening, numerous quartz clasts excede 10cm, proximity to fault and the absense of through-going veins suggests that it is potentially related to fault movement. Fault 230/5 2013-08-28 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 166 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 422849 6265108 250 35 Vein Fold D2 P1 Folded quartz-chalcopyrite-chlorite Mode I with local euhedral quartz crystals growing open space/epithermal, Qz70Chl10Cp20Spec(?)tr, chlorite is deep green, Sample GF-13-22: microprobe on chalcopyrite and chlorite (or just characterize as anomalous 2013-08-28 422666 6265101 340 80 Mineral Alignment Primary D1 Defined by 2 mm long, 12% subhedral hornblende laths, with a marked lineation interpreted to be primary trachytic texture, remarkably no alteration or foliation observed in this rock! Possibly a very subtle one defined by trace amounts of sericite i 2013-08-28 422561 6265035 341 36 Mineral Alignment Primary D1 Green Hb porphyry, trachytic texture of 15% chlorite-replaced hornblende, most ~1x3-5 mm in size, matrix appears to be dominated by feldspar. Photo view south 2013-08-28 422549 6265052 362 48 Mineral Alignment Primary D1 Mineral lineation 2013-08-28 422571 6265006 120 80 Vein Tectonic Weakly chloritized post mineral dyke is cut by milky Qz-Chl-Cb vein ~20 cm wide with very sharp boundaries and discontinuous tips (Mode I). Sample GF-13-24: Cathode luminesence and polished binocular microscope study (GF-13-24B: wall rock DDRT, bin 2013-08-28 422849 6265106 131 83 Vein Tectonic 2013-08-28 422849 6265108 135 38 Vein Tectonic View south 2013-08-28 422549 6265052 172 86 Vein D1 2013-08-28 422970 6265155 190 81 Vein D1 3 2013-08-28 422576 6264998 212 84 Joint 2013-08-28 422575 6264995 229 78 Vein D1 Magmatic-related deformation characterized by non-throughgoing vein offsets, boudins with brittle vein ends, and stranded veins, these veins are clearly intruded into hot melt, pinch, swell and get stranded, Cp>>Py ~"A veins" 2013-08-28 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 167 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 422575 6264995 308 90 Vein D1 2013-08-28 422571 6265006 345 81 S1 D2 P1 Very subtle pervasive fabric 2013-08-28 422569 6265014 353 68 S1 D2 P1 Aphanitic, sharp contact DDRT, carbonate amygdaloidal, very subtle fabric S1 suggests an older interpretation with strong cooling joints. Photo view SE 2013-08-28 423121 6265268 353 45 Reverse Fault D_3 SFTB Another example of thrust fault movement adjacent to an intrusive contact, clasts are small subangular to subrounded randomly distributed in the groundmass, marked gully here denotes reverse fault movement, 3% quartz fragments. View south. 3 2013-08-28 423110 6265302 357 73 S1 D2 P1 Entire traverse from last thrust fault to next one is mixed chlorite-sericite pods, ~15% quartz 2013-08-28 422849 6265106 4 87 Vein D1 Strong vein parallelism but weak overprint only by D1. Chlorite strong, no clasts. View northeast. 2013-08-28 422666 6265101 5 76 Vein D1 Good planar 5 mm wide quartz-pyrite (trace) vein seems to suggest a preferred orientation to veins prior to D1 that is subparallel to plane of flattening. GF-13-23: oriented with respect to assumed foliation plane (chose fracture consistent with reg 2013-08-28 422666 6265101 7 84 S1 D2 P1 2013-08-28 422949 6265175 12 86 Vein D1 Folded but clearly at high angle to quartz stockwork, 9271 photo view south, 9271 of sample, Sample GF013021 to look at microprobe composition of this late pyrite event, grains are coarse, euhedral, dilated, ~85% of vein material, Vmj=290/90 (2), int 3 2013-08-28 422987 6265187 12 86 Vein D1 95% qz, Sample GF-13-20, large pyrite aggregate in tectonic-related mode I vein, could be a good candidate for probe work on pyrite - I could compare this to late pyrite veins from quartz stockwork zone and pyrite in quartz-ankerite veins. Photo view 3 2013-08-28 Appendix A (cont.). List of field structure data from the Mitchell deposit and surrounding areas 168 Easting UTM NAD83 Northing UTM NAD83 Dip Direction Dip Angle Structure Deformation event (D) and phase (P) Comments Domain Date 422949 6265175 20 90 S1 D2 P1 3 2013-08-28 423029 6265248 30 8 Axial Surface/Planar Cleavage (Folds) These very shallow dipping axial surfaces could be the result of primary anastamosing of fluids into a primary subplanar alignment. Sample GF-13-19 to look at whether these gentle folds are deformtion related (Vmj for orientation) 3 2013-08-28 423014 6265208 30 79 S1 D2 P1 Clasts ~4% most <1cm, quartz 30%, strong contact zone with early synmineral intrusion 3 2013-08-28 423029 6265248 30 78 Vein D1 3 2013-08-28 422549 6265052 55 50 Vein D1 8cm wide, unfolded quartz-pyrite-chalcopyrite-mo vein is locally canibalized and fragmented b
UBC Theses and Dissertations
Structural evolution of the Mitchell Au-Cu-Ag-Mo porphyry deposit, northwestern British Columbia Febbo, Gayle Elizabeth 2016
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