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Characterizing the Bennett Batholith : implications for Early-Middle Jurassic magmatism in Southwest… Pillsbury, Joshua Nash Phillips Apr 30, 2016

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i  CHARACTERIZING THE BENNETT BATHOLITH: IMPLICATIONS FOR EARLY-MIDDLE JURASSIC MAGMATISM IN SOUTHWEST YUKON   by  JOSHUA NASH PHILLIPS PILLSBURY   A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF  THE REQUIREMENTS FOR THE DEGREE OF   BACHELOR OF SCIENCE  in   THE FACULTY OF SCIENCE  (Earth and Ocean Sciences)*         This thesis conforms to the required standard  ……………………………………… Dr. Murray Allan  THE UNIVERSITY OF BRITISH COLUMBIA  (Vancouver)  April 2016    © Joshua Nash Phillips Pillsbury, 2016   *Geology      ii  Abstract  Late Triassic to Early Jurassic magmatic belts which extend from southern British Columbia into the Yukon-Tanana Terrane of Yukon are known to collectively host the most important porphyry Cu-Au and Cu-Mo deposits in the Northern Cordillera. Late Triassic to Early Jurassic magmatism in Yukon is currently divided into four plutonic suites, which from oldest to youngest are: Stikine (228-210 Ma), Minto (204-195 Ma), Long Lake (192-180 Ma), and Bryde (178-167 Ma). In addition to hosting the Minto and Carmacks Copper deposits in Yukon, these plutonic suites also represent the northern extension of paired plutonic belts which host significant copper-gold and copper-molybdenum deposits in British Columbia. The purpose of this study is to determine the potential of Early-Middle Jurassic intrusion-related mineralization in southwest Yukon by providing a comprehensive characterization of the Bennett batholith, the largest pluton of the Bryde plutonic suite. At over 50 km in length and 15 km in width, the intrusion is a weakly foliated, coarse to medium grained, leucocratic granodiorite to quartz monzonite, characterized by large (up to 5 cm) locally aligned alkali feldspar phenocrysts. To facilitate creating a tectono-magmatic framework for the Bennett batholith, three other plutons are sampled for comparison: the Aishihik batholith of the Long Lake suite, the Fourth of July batholith from the Bryde suite, and the Mt. Bryde pluton of the Bryde suite. This characterization and comparison includes modal mineralogy using the image-processing program ImageJ, petrography, major and trace element geochemistry, uranium-lead zircon dating, and plagioclase-hornblende geothermobarometry. The Bennett batholith is an Early Jurassic (178.20 ± 0.05 Ma), medium grained, leucocratic, equigranular to megacrystic, (rarely) biotite-bearing hornblende granite to granodiorite which may have been emplaced at depths of 4.5 ± 1.5 km below the surface. In addition to having similarities in composition, texture, mineralogy and tectonic setting with rocks of the Aishihik batholith of the Long Lake plutonic suite, the Bennett batholith is at the very least 2 Ma older than the Fourth of July batholith or Mt. Bryde pluton. Preliminary constraints on age, emplacement depth, oxidation state and hydrothermal activity suggest the calc-alkaline Bennett batholith appears to have been a fertile system for copper porphyry generation.           iii  TABLE OF CONTENTS  Title Page              i Abstract              ii Table of Contents                       iii List of Figures                        v List of Tables             vi List of Appendices            vi  Acknowledgements           vii 1. Introduction                                 1                                                                                                         2. Regional Geology             8 2.1 Devonian to Paleogene Tectono-Magmatic Evolution of the Northern     Cordillera                                                                                                                     8 2.2 The Bennett Batholith                                                    10 3. Methodology                                                                                                                  12        3.1 Field Work                                                                                                    12 3.2 Potassium Feldspar Staining         12 3.3 Petrography             14 3.4 Whole Rock Geochemistry         15 3.5 Geochronology           15 3.5.1 CA-TIMS          15 3.5.2 LA-ICP-MS          17 4. Results             19 4.1 Modal Mineralogy          19 4.2 Petrography             22  4.2.1 Bennett Batholith         22  4.2.2 Aishihik Batholith         24  4.2.3 Fourth of July Batholith        25  4.2.4 Mt. Bryde Pluton         26 4.3 Whole Rock Geochemistry         27  4.3.1 Major Oxides          27 iv   4.3.2 Trace Elements         30 4.4 Geochronology           33 4.4.1 CA-TIMS          33 4.4.2 LA-ICP-MS          34 5. Discussion             38  5.1 The Nature and Timing of Bennett Batholith Magmatism     38  5.2 A Case for the Long Lake Suite        39  5.3 Metallogenic Potential of the Bennett Batholith      40 6. Summary               41 References             42 Appendices                        46                     v  List of Figures   Figure 1. Nomenclature related to Late Triassic - Early Jurassic Magmatism in Yukon    2 Figure 2. Yukon Terrane map with Bryde and Long Lake plutonic suites      3 Figure 3. Map of the Bennett batholith           4 Figure 4. Map of the Fourth of July batholith and Mt. Bryde pluton      6 Figure 5. Map of the Aishihik batholith           7 Figure 6. Early Jurassic paleogeographic reconstruction          9 Figure 7. Simplified location map of the Tally Ho shear zone         11 Figure 8. ImageJ photograph of scanned slab prior to analysis        13 Figure 9. ImageJ photograph of scanned slab post-analysis        13 Figure 10. Quartz-Alkali-feldspar-Plagioclase (QAP) diagram for all samples     20 Figure 11. Unstained and stained photograph of scanned slab 15PS-032     21 Figure 12. PPL and XPL image of 15PS-043        22 Figure 13. Unstained and stained photograph of scanned slab 15PS-128      23 Figure 14. Hand sample photograph of 15PS-090          24 Figure 15. XPL image of 15PS-089            24 Figure 16. PPL and XPL image of 15PS-002          25 Figure 17. PPL and XPL image of 15PS-002          26 Figure 18. Major oxide vs. Silica plots          28 Figure 19. Total-Alkali-Silica (TAS) plot          29 Figure 20. AFM diagram            30 Figure 21. C1-chondrite normalized REE diagram for the Bennett batholith      31 Figure 22. C1-chondrite normalized REE diagram for the Aishihik batholith      32 Figure 23. PM-normalized trace element diagram for the Bennett batholith        32 Figure 24. PM-normalized trace element diagram for the Aishihik batholith      33 Figure 25. Weighted mean CA-TIMS ages for 15PS-032, 15PS-044, 15PS-123             34 Figure 26. Cathodoluminescence (CL) zircon images from 15PS-032         35 Figure 27. Cathodoluminescence (CL) zircon images from 15PS-044      36 Figure 28. Cathodoluminescence (CL) zircon images from 15PS-123      37  vi  List of Tables   Table 1. Calculated (normalized to QAP) abundances for ImageJ modal analysis for all samples.  List of Appendices*   *Appendices 2 - 6 are also included in digital format in the back pocket of this thesis.   Appendix 1. Outcrop photos, hand sample photos, unstained and stained slab scans, plain and cross-polarized light scans, thin section descriptions for each sample.  Appendix 2. Sample location/description spreadsheet.  Appendix 3. ImageJ modal abundance calculations spreadsheet.  Appendix 4. Whole rock major and trace element geochemical data tables.  Appendix 5. U-Pb CA-TIMS data table.  Appendix 6. U-Pb LA-ICP-MS data table.  Appendix 7. Analytical data of plagioclase-hornblende from scanning electron microprobe analysis (EMPA).                vii  Aknowledgements   This thesis has been an invaluable challenge and learning experience which could not have been completed without the support of numerous individuals. Foremost I would like to express my sincere gratitude to my supervisor Dr. Murray M. Allan of the Mineral Deposit Research Unit at UBC and co-supervisor Dr. Patrick J. Sack of the Yukon Geological Survey. I am deeply grateful for the opportunity Murray gave me to work under him, and he has inspired me by showing me what a brilliant and hard-working scientist can accomplish. I would not have been able to finish this thesis without his help and expertise. There are too many things to list, but specifically in operating the scanning electron microprobe, assisting in technical writing, and his feedback on my technical presentations.  There is no way to express how much it meant to have a mentor like Patrick throughout my first field season, he showed by example that real science truly does begin in the field. There is too much to thank him for but I would not put a price on the skills of sample/data collection, preparation and organization I learned from him in the summer of 2015.  I would also like to thank Dr. Jim Crowley from Boise State University, who I had the pleasure of meeting in person during the summer of 2015 in Yukon. I am not only indebted to him for completing the uranium-lead zircon dating for my thesis, but for providing consistent feedback and being a great teacher.  I am grateful to Dr. Maurice Colpron of the Yukon Geological Survey for his valuable insight when we were in the field. Additionally, I would like to thank him for inspiring me through his own work, which I am only truly starting to appreciate now through this project.  Thank you to Dr. Mary Lou Bevier for providing constant support throughout the year and reminding me that the course of true research never did run smooth. viii   I am grateful to my previous instructors Dr. James K. Mortensen, Dr. Lori A. Kennedy, Dr. James S. Scoates and Dr. Kenneth A. Hickey for helping build the foundation of my geoscience knowledge, without which none of this would have been possible.  I cannot forget to thank my friends Chris Moll, John Tejada, Marvin Melana, Won Choi and all the executives of the G.M. Dawson club. We went through some hard times together, but we also celebrated each accomplishment together. I am grateful to have such supportive sisters, brothers-in-law, nieces and nephews, Katie, Ben, Tobias, Taliah, Holly, Gio, Emily, Brian, and Travis. Lastly, I am eternally grateful to my parents Anne and John for their unconditional support, timely encouragement and endless patience. Thank you for your love and belief in me.    1  Introduction  The northern Canadian Cordillera is made up of numerous distinct arc and peri-Laurentian terranes which were accreted to the western continental margin of ancestral North America during the Mesozoic period. Yukon-Tanana, Quesnellia and Stikinia (Monger et al. 1982) are the primary peri-Laurentian terranes of the Intermontane Superterrane, which was fully obducted onto ancestral North America by Middle Jurassic time. Late Triassic to Middle Jurassic accretionary tectonism in the northern Canadian Cordillera represents the transition from loosely connected arc and peri-cratonic terranes lying west of composite Laurentia to a single, progressively thickening transpressional/transtensional orogen (Nelson et al. 2013).    The term magmatic episode (or magmatic epoch) is commonly encountered within the literature of Northern Cordilleran geology (Tempelman-Kluit 1974; 1976; Hart 1990; Hart 1997; Mihalynuk 1999). Hart (1997) stated that: “Magmatic episodes can be determined on the basis of clusters or peaks of similar isotopic age dates, reflecting the crystallization of various igneous rocks, that are separated by periods of obvious magmatic abeyance.” Exclusively using age data to a) define whether or not a pluton belongs to a specific magmatic episode is prone to error due to overlapping age ranges of protracted magmatic episodes and/or b) use of K-Ar or Rb-Sr age determinations which are susceptible to partial resetting (Hart 1997). Despite being prone to error, the classification of magmatic episodes remains a useful mechanism for systematically grouping plutonic suites in the Northern Cordillera. Late Triassic to Early-Middle Jurassic magmatism in Yukon, previously generalized as the Klotassin magmatic episode (Tempelman-Kluit 1974, 1976; Hart 1997) or Aishihik magmatic epoch (Mihalynuk 1999), comprises four plutonic suites. Hart (1997) stated, “Individual plutonic suites are defined by similarities in tectonic setting, composition, mineralogical, textural, geochemical and isotopic characteristics of constituent plutons”. From oldest to youngest, these plutonic suites are: Stikine (228-210 Ma), Minto (204-195 Ma), Long Lake (192-180 Ma), and Bryde (178-167 Ma). Previously the Klotassin magmatic episode (or Aishihik magmatic epoch) included an Aishihik plutonic suite (Hart 1997; Mihalynuk 1999), but it was subsequently divided into the Minto and Long Lake suites (Figure 1). Additionally, 2  previous literature on this magmatic episode/epoch included the Bennett and Fourth of July suites (Mihalynuk 1999), which were later merged to form the Bryde plutonic suite (Figure 1). The plutonic rocks of interest for this thesis lie within the Early Jurassic Long Lake and Middle Jurassic Bryde suites (Figures 1 and 2).  Figure 1. Timeline describing the nomenclature used for Late Triassic to Early-Middle Jurassic Magmatism in Yukon. Modified from (Mihalynuk 1999). 3   Figure 2. Yukon terrane map with the Bryde and Long Lake plutonic suites, representing the Bennett, Aishihik, Fourth of July batholiths and the Mt. Bryde pluton. Modified from Yukon Geological Survey (2015). 4  Late Triassic to Early-Middle Jurassic magmatic belts which extend from southern British Columbia into the Yukon Tanana terrane of Yukon are known to collectively host the most important porphyry Cu-Au and Cu-Mo deposits in the Northern Cordillera (Nelson et al. 2013). Operating mines within these Late Triassic to Early-Middle Jurassic plutonic rocks of British Columbia and Yukon include Highland Valley, Gibraltar, Copper Mountain, Brenda, Afton and Minto. In addition, numerous mines remain in development such as Red Chris, Mt. Milligan, Kerr-Sulpurets-Mitchell (KSM) and Brucejack. Taking into account operating, developing, and probable future mines, the host intrusions range from 210 Ma (Galore, Highland Valley) to 178 Ma (Lorraine), with the most common ages being 205 to 202 Ma (Nelson et al. 2013). The purpose of this study is to determine the potential of Early-Middle Jurassic intrusion-related mineralization in southwest Yukon by providing a comprehensive characterization of the Bennett batholith (Figure 3).  Figure 3. Map of the Bennett batholith. Samples are marked with corresponding sample numbers for reference. The southern margin of the map represents the Yukon/BC border. Modified from Yukon Geological Survey (2015). 5  The 600 km2 Bennett batholith (Figure 3), currently the largest pluton of the Bryde plutonic suite, was initially established as Late Triassic in age (Morrison et al. 1979; Hart and Radloff 1990). Variable Late Triassic estimates for the Bennett batholith were due to recalculated K-Ar hornblende dates from Bultman (1979), an unpublished date of 209 Ma from M. G. Mihalynuk, and a 220 Ma U-Pb zircon date (Hart 1997). The validity of the Doherty and Hart (1988) 220 Ma date was questioned due to evidence of Pb-loss and Proterozoic inheritance in Currie and Parrish (1993). An unpublished (Mortensen and Hart) date from of another sample of the Bennett batholith yielded an age of 177 Ma (Hart 1997). Due to the lack of reliable published age data for the Bennett batholith and the recent re-classification of plutonic suites within the Klotassin episode, further dating must be completed to accurately confirm in which suite(s) it belongs. Other plutons within the Bryde suite that have been dated include the Mt. Bryde pluton (Figure 3) (173 ± 3 Ma, Ar40-Ar39 hornblende; 169 ± 2, Ar40-Ar39 biotite) (Gordey and Stevens 1994) and the Fourth of July pluton (Figure 3) (171.7 ± 3, U-Pb zircon) (Mihalynuk et al. 1992), both of which have been sampled to allow comparison with the Bennett Batholith. Field observations, whole rock major and trace element geochemistry, petrographic data, feldspar staining, plagioclase-hornblende geothermobarometry and U-Pb zircon dating analyses were done on various plutons (Figures 3, 4, 5) within the Long Lake and Bryde suites to provide context for the characterization of the Bennett Batholith and its place within Late Triassic to Middle Jurassic magmatism in Yukon.  This research is part of the Yukon-Alaska Metallogeny Project and was funded by the Yukon Geological Survey (YGS), University of British Columbia’s (UBC) Mineral Deposit Research Unit (MDRU) and an undergraduate thesis scholarship provided by the Society of Economic Geology (SEG). The study will contribute to a comprehensive characterization of Late Triassic to Middle Jurassic plutonic suites in Yukon by Dr. Maurice Colpron and Dr. Patrick Sack of the YGS.    6        Figure 4. Map of the Fourth of July batholith and Mt. Bryde pluton. Samples are marked with corresponding sample numbers for reference. The bottom of the map represents the Yukon/BC border. Modified from Yukon Geological Survey (2015). 7      Figure 5. Map of the Aishihik batholith. Samples are marked with corresponding sample numbers for reference. Modified from Yukon Geological Survey (2015). 8  Regional Geology  2.1 Devonian to Paleogene Tectono-Magmatic Evolution of the Northern Cordillera During the Devonian, a transition occurred along the western margin of ancestral North America from dominantly extensional tectonic processes to subduction and compressional-related processes. Eastward-dipping subduction of oceanic crust beneath the western continental margin in the Middle to Late Devonian resulted in emplacement of magmatic arcs along the North American Cordillera. The affinity and age of this subduction-related magmatism has been recorded within the Yukon-Tanana, Stikine and Quesnel terranes (Piercey et al. 2006). The continuation of subduction during latest Devonian to Early Mississipian time resulted in back-arc extension, formation of the Slide Mountain Ocean and the separation of the frontal (western) portion of the arc and its peri-cratonic basement, the Yukon-Tanana terrane (Colpron et al. 2007a). As a result of the opening of the Slide Mountain Ocean, magmatism on its eastern flank had completely ceased by the Middle-Mississippian and remnants of the magmatic arc, such as the Kootenay terrane, were preserved within the Laurentian continent (Nelson et al. 2006).  As the Slide Mountain ocean continued to open during the Pennsylvanian to Middle Permian, arc-related magmatism due to east dipping subduction led to the emplacement of plutonic suites within the offshore terranes of Yukon-Tanana, Stikinia and Quesnellia (Nelson et al. 2006). Belansky and Stevens (2006) suggested that these terranes likely lay 2,000 to 3,000 km offshore of North America by Early Permian time based on statistical faunal analyses. A switch in arc-polarity during Middle to Late Permian time replaced the long-lived east-dipping subduction zone along the western margin of the Yukon-Tanana terrane. Evidence for this switch in arc polarity is preserved within the Klondike assemblage, a suite of continental arc affinity rocks that overlies and intrudes Mississippian and older rocks of the Yukon-Tanana terrane (Beranek and Mortensen 2011). Continued west-dipping subduction under the eastern margin of the Yukon-Tanana and Quesnel terranes led to the closing of the Slide Mountain ocean by the end of the Triassic. Current models suggest the re-accretion of the inner margin of Yukon-Tanana and Quesnellia at their final stages of collision with North America was accompanied by counter-clockwise 9  oroclinal spinning of northeastern Stikinia (Figure 6), closing the Cache Creek ocean and obducting it onto Stiknia via south-west verging faults (Nelson et al. 2013). As a result, the Cache Creek terrane became enclosed between Quesnellia and Stikinia (Mihalynuk et al. 1994). Associated with the closing of the Slide Mountain and Cache Creek oceans was Late Triassic to Early-Middle Jurassic magmatism which emplaced the continental arc-affinity plutonic suites studied herein into Quesnellia, Stikinia and Yukon-Tanana (Nelson et al. 2013). The Fourth of July pluton represents one of the oldest post-kinematic intrusions in the Northern Cordillera at 171.7 ± 3 Ma, providing evidence that Stikinia had been fully accreted by this time (Nelson et al. 2013).     Figure 6. Early Jurassic paleogeographic construction with fossil constraints from Smith et al. (2001). AA = Arctic Alaska, AX = Alexander, FW = Farewell, Ku = Kutcho, OM = Omulevka, PN = Peninsular, QN = Quesnellia, RB = Ruby, ST = Stikinia, WR = Wrangellia (Nelson et al. 2013). 10  In southwest Yukon, Late Triassic to Early-Middle Jurassic plutonism in Quesnellia and Stikinia accompanied rapid exhumation of adjacent metamorphic basement rocks (Nelson et al. 2013). This exhumation, estimated at 15 km (Nelson et al. 2013), is recorded in the sedimentary succession of the Whitehorse Trough’s (Figure 6) Early to Middle Jurassic Laberge Group. The Laberge Group contains abundant Late Triassic to Early Jurassic detrital zircons (Colpron et al., 2007b) which reflect the local erosion of exposed plutonic suites (such as those of the Klotassin Magmatic Episode). Synchronous with the emplacement of Late-Triassic to Middle Jurassic plutonic suites in Yukon was overall subduction-related compressional tectonism which caused crustal thickening, folding and reverse faulting of the Quesnellia, Stikinia and Yukon-Tanana terranes (Nelson et al. 2013). Finally, the Coast Plutonic Complex, a group of poorly understood plutons and orthogneiss equivalents intruded the western margin of the Intermontane Superterrane from the mid-Cretaceous to Eocene (Hart 1997).  2.2 The Bennett Batholith Located within the Coast Mountains, the field area lies 20 km west of the town of Carcross trending northwest from the west arm of Bennett Lake. The physiography is characterized by high relief mountains which commonly reach elevations greater than 2000 m. The effects of glaciation are evidenced by pronounced physical topography, abundant glaciofluvial deposits at lower elevations and massive boulders (meter scale) at elevations as high as 1500 m.  As previously mentioned, the Bennett Batholith is the largest pluton of the Bryde plutonic suite (although it contains small portions of Long Lake suite rocks), trending northwest in map view over a distance of approximately 50 km. Previous mapping determined the intrusion was composed primarily of coarse to medium grained, non-foliated, potassium-feldspar phyric hornblende granodiorite to monzogranite (Hart and Radloff 1990). More rarely, both biotite and hornblende were present, with hornblende being the dominant mafic mineral. Prospecting in the region dates back to the late 1800’s and led to discoveries of gold-bearing veins near Carcross and the Wheaton River by miners on their way to the Klondike in 1896 (Hart and Radloff 1990). Overall, the region has yielded over 12 tonnes of gold, 125 tonnes of silver and 123,000 tonnes of copper with trace amounts of lead, zinc and cadmium (Hart and Radloff 1990).  11    The eastern side of the Bennett batholith is in intrusive and fault contact with highly strained to mylonitic volcanic and volcaniclastic rocks in the Tally Ho shear zone (THSZ) (Figure 7). The THSZ hosts allochthonous ultramafic to gabbroic rocks which were thrusted and then folded to their present position by Early Jurassic time (Tizzard and Johnston 2005). Since the un-deformed Bennett batholith intrudes the THSZ, the timing of complete deformation has been constrained based on the assumption that the Bennett batholith is Early Jurassic in age (Tizzard and Johnston 2005). The nature and timing of Bennett batholith magmatism, which this thesis aims to characterize, has important implications for age interpretations of the Tally Ho shear zone.  The 3-km-wide and 40-km-long THSZ separates the Stikine terrane to the east from the Yukon Tanana terrane to the west (Tizzard and Johnston 2005). The northern, western, and southern flanks of the Bennett batholith are primarily intruded by hornblende granodiorite to gabbro phases of the Late Cretaceous Whitehorse plutonic suite (112–108 Ma), and more rarely phases of the Paleogene Ruby Range plutonic suite (58-54 Ma).    Figure 7. Simplified tectonic boundaries of southern Yukon showing location of the Tally Ho shear zone (THSZ) with respect to the Yukon-Tanana, Stikinia and Cache Creek Terranes. LFZ = Lllewellyn fault zone, CLF = Craig Lake fault, NF = Nahlin fault. The contact between the Bennett granite and the THSZ is highlighted as the study area (Tizzard and Johnston 2004). 12  Methodology  3.1 Field Work  During the summer of 2015, approximately forty days of field work were conducted with Dr. Patrick Sack of the Yukon Geological Survey in southwest and central Yukon as part of a metallogenic study of Late Triassic to Early Jurassic plutonic rocks. Of these forty days of field work, approximately 10 pertained to this thesis’ research. All granitoid samples were collected for the possibility of geochronological, whole-rock geochemical, mineralogical and petrographic analysis, and commonly weighed 4 kg or more. Collection in the field was for the least altered/weathered/veined sample which best represented the lithology of the outcrop. If the outcrop observed was too altered/veined/weathered to be a candidate for analyses, a representative sample was collected which weighed 1 kg or less. When non-granitoid outcrops were encountered in the field they were noted but not sampled.   3.2 Potassium Feldspar Staining  All twenty samples were prepared for potassium feldspar staining by being cut into approximate 10x10x1 cm slabs at the Yukon Geological Survey in Whitehorse. Prior to being sent out for staining, the side of each slab to be stained was made wet and scanned in high resolution (600 ppi). The process was completed using a sodium cobaltinitrite solution at Vancouver Petrographics Ltd. which stains potassium feldspar yellow. Stained slabs were then scanned in high-resolution to allow for image processing. The freeware program ImageJ 1.49 was used to determine the modal abundance of quartz, plagioclase, potassium feldspar and mafic minerals. Using the program, an approximately 4 mm2 portion of the slab was selected for each mineral as a template color (Figure 8), processing determined the percentage of the scanned photo which matches this color (Figure 9). Due to analytical error from measuring the abundance of 4 phases in each sample individually, the total abundance of minerals commonly ranged from 95-105%.  13    Figure 8. High resolution scanned JPEG image of a potassium-feldspar stained slab (15PS-032) in ImageJ. The arrow is pointing to an approximately 4 mm2 stained portion of potassium feldspar. The sample selection button is visible in the bottom right corner. Figure 9. High resolution scanned JPEG image of a potassium-feldspar stained slab (15PS-032) in ImageJ. This is directly after the sample button has been selected in Figure 7. The circled portion of this figure indicates how much percentage area the potassium feldspar occupies within the image. 14  3.3 Petrography  Twenty granitoid samples were selected for this thesis under the direction of Dr. Patrick Sack of the Yukon Geological Survey and Dr. Murray Allan of the Mineral Deposit Research Unit at UBC in 2015. The twenty samples represent different intrusive units of the Bennett, Aishihik, Fourth of July and Mt. Bryde batholiths. All twenty samples were cut at the Yukon Geological Survey in Whitehorse and sent to Vancouver Petrographics Ltd. for polished thin section preparation. Thin sections were examined using an Eclipse E600 POL polarizing microscope to determine mineral abundances, distributions, textures, sizes, contact relationships, degrees of alteration and crystal habits. Plagioclase was abundant in all twenty samples and when possible the Michael-Levy method was used to determine anorthite percentage. Rarely the samples were too sericitically altered to obtain an accurate anorthite percentage, in which case no plagioclase composition was obtained. The Michael-Levy method was used with at minimum, 5 euhedral plagioclase grains. The range and mean of these 5 measurements is recorded in the thin section description for each corresponding sample (Appendix 1). Corresponding outcrop and hand sample photos are paired with their respective thin section descriptions. High resolution scans of all twenty thin sections were obtained in the MDRU lab for both plane-polatized and cross-polarized light. Mineralogically-based rock names for each sample were determined from mineral modalities, determined from a combination of stained slab results, thin section petrography and field/hand sample observations.  In addition to the detailed mineralogical and textural descriptions for each sample, petrography was also the primary method to determine if samples were eligible for plagioclase-hornblende geothermobarometry, based on the well-documented (but temperature-sensitive) relationship between Al content of hornblende and crystallization pressure. Suitable samples must contain a nine phase equilibrium assemblage to be in accordance with the method of Anderson and Smith (1995). This assemblage is: quartz, plagioclase, orthoclase, biotite, hornblende, titanite, magnetite, melt and water. Hornblende and plagioclase rims must be unaltered so point compositional analysis (electron microprobe) can obtain accurate mineral compositions at the time of crystallization. Contacts between hornblende and plagioclase must indicate that they were co-precipitated. As a result, euhedral hornblende grains are not suitable for this method because they crystallized prior to the remainder of the rock mass (and therefore 15  plagioclase). Finally, the mole fraction of anorthite in plagioclase must lie between 25-35% to be eligible for Anderson and Smith’s (1995) geothermobarometer.  3.4 Whole Rock Geochemistry All twenty samples were prepared for whole rock geochemistry by being cut into 250 gram blocks at the Yukon Geological Survey in Whitehorse. Samples were trimmed to avoid any altered, weathered or veined portions. Samples were then packaged and shipped to Acme Labs for whole rock geochemical analyses via fusion inductively coupled plasma mass spectrometry.   3.5 Geochronology  U-Pb dates were obtained by a combination of chemical abrasion isotope dilution thermal ionization mass spectrometry (CA-TIMS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) by Dr. James Crowley at Boise State University. 3.5.1 CA-TIMS U-Pb dates were obtained by the chemical abrasion isotope dilution thermal ionization mass spectrometry (CA-TIMS) method from analyses composed of single zircon grains. Zircon was separated from rocks using standard techniques and mounted in epoxy and polished until the centers of the grains were exposed. Cathodoluminescence (CL) images were obtained with a JEOL JSM-1300 scanning electron microscope and Gatan MiniCL. Zircon was removed from the epoxy mounts and subjected to a modified version of the chemical abrasion method of Mattinson (2005), reflecting analysis of single grains or fragments of grains. Grains were selected for dating based on CL images.  Zircon was placed in a muffle furnace at 900°C for 60 hours in quartz beakers. Single grains were then transferred to 3 ml Teflon PFA beakers and loaded into 300 µl Teflon PFA microcapsules. Fifteen microcapsules were placed in a large-capacity Parr vessel and the grains partially dissolved in 120 µl of 29 M HF for 12 hours at 180°C. The contents of the microcapsules were returned to 3 ml Teflon PFA beakers, HF removed, and the residual grains immersed in 3.5 M HNO3, ultrasonically cleaned for an hour, and fluxed on a hotplate at 80°C 16  for an hour. The HNO3 was removed and grains were rinsed twice in ultrapure H2O before being reloaded into the 300 µl Teflon PFA microcapsules (rinsed and fluxed in 6 M HCl during sonication and washing of the grains) and spiked with the Boise State University mixed 233U-235U-205Pb tracer solution. Zircon was dissolved in Parr vessels in 120 µl of 29 M HF with a trace of 3.5 M HNO3 at 220°C for 48 hours, dried to fluorides, and re-dissolved in 6 M HCl at 180°C overnight. U and Pb were separated from the zircon matrix using an HCl-based anion-exchange chromatographic procedure (Krogh, 1973), eluted together and dried with 2 µl of 0.05 N H3PO4. Pb and U were loaded on a single outgassed Re filament in 5 µl of a silica-gel/phosphoric acid mixture (Gerstenberger and Haase, 1997), and U and Pb isotopic measurements made on a GV Isoprobe-T multicollector thermal ionization mass spectrometer equipped with an ion-counting Daly detector. Pb isotopes were measured by peak-jumping all isotopes on the Daly detector for 100 to 160 cycles, and corrected for 0.16 ± 0.03%/a.m.u. (1 sigma error) mass fractionation. Transitory isobaric interferences due to high-molecular weight organics, particularly on 204Pb and 207Pb, disappeared within approximately 30 cycles, while ionization efficiency averaged 104 cps/pg of each Pb isotope. Linearity (to ≥1.4 x 106 cps) and the associated deadtime correction of the Daly detector were monitored by repeated analyses of NBS982, and have been constant since installation. Uranium was analyzed as UO2+ ions in static Faraday mode on 1012 ohm resistors for 200-300 cycles, and corrected for isobaric interference of 233U18O16O on 235U16O16O with an 18O/16O of 0.00206. Ionization efficiency averaged 20 mV/ng of each U isotope. U mass fractionation was corrected using the known 233U/235U ratio of the Boise State University tracer solution.  U-Pb dates and uncertainties were calculated using the algorithms of Schmitz and Schoene (2007), 235U/205Pb of 77.93 and 233U/235U of 1.007066 for the Boise State University tracer solution, and U decay constants recommended by Jaffey et al. (1971). 206Pb/238U ratios and dates were corrected for initial 230Th disequilibrium using a Th/U[magma] = 3.0 ± 0.3 using the algorithms of Crowley et al. (2007), resulting in an increase in the 206Pb/238U dates of ~0.09 Ma. All common Pb in analyses was attributed to laboratory blank and subtracted based on the measured laboratory Pb isotopic composition and associated uncertainty. U blanks are difficult to precisely measure, but are estimated at 0.07 pg. 17  Weighted mean 206Pb/238U dates were calculated from equivalent dates using Isoplot 3.0 (Ludwig, 2003). Errors on the weighted mean dates are given as ± x / y / z, where x is the internal error based on analytical uncertainties only, including counting statistics, subtraction of tracer solution, and blank and initial common Pb subtraction, y includes the tracer calibration uncertainty propagated in quadrature, and z includes the 238U decay constant uncertainty propagated in quadrature. Internal errors should be considered when comparing our dates with 206Pb/238U dates from other laboratories that used the same Boise State University tracer solution or a tracer solution that was cross-calibrated using EARTHTIME gravimetric standards. Errors including the uncertainty in the tracer calibration should be considered when comparing our dates with those derived from other geochronological methods using the U-Pb decay scheme (e.g., laser ablation ICPMS). Errors including uncertainties in the tracer calibration and 238U decay constant (Jaffey et al., 1971) should be considered when comparing our dates with those derived from other decay schemes (e.g., 40Ar/39Ar, 187Re-187Os). Errors for weighted mean dates and dates from individual grains are given at 2σ.  3.5.2 LA-ICPMS Zircon grains were separated from rocks using standard techniques and annealed at 900oC for 60 hours in a muffle furnace. They were mounted in epoxy and polished until their centers were exposed. Cathodoluminescence (CL) images were obtained with a JEOL JSM-1300 scanning electron microscope and Gatan MiniCL. Zircon was analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) using a ThermoElectron X-Series II quadrupole ICPMS and New Wave Research UP-213 Nd:YAG UV (213 nm) laser ablation system. In-house analytical protocols, standard materials, and data reduction software were used for acquisition and calibration of U-Pb dates and a suite of high field strength elements (HFSE) and rare earth elements (REE). Zircon was ablated with a laser spot of 25 µm wide using fluence and pulse rates of 5 J/cm2 and 10 Hz, respectively, during a 45 second analysis (15 sec gas blank, 30 sec ablation) that excavated a pit ~25 µm deep. Ablated material was carried by a 1.2 L/min He gas stream to the nebulizer flow of the plasma. Dwell times were 5 ms for Si and Zr, 200 ms for 49Ti and 207Pb, 80 ms for 206Pb, 40 ms for 202Hg, 204Pb, 208Pb, 232Th, and 238U and 10 ms for all other HFSE and REE. Background count rates for each analyte were obtained prior to each 18  spot analysis and subtracted from the raw count rate for each analyte. Ablations pits that appear to have intersected glass or mineral inclusions were identified based on Ti and P. U-Pb dates from these analyses are considered valid if the U-Pb ratios appear to have been unaffected by the inclusions. Analyses that appear contaminated by common Pb were rejected based on mass 204 being above baseline. For concentration calculations, background-subtracted count rates for each analyte were internally normalized to 29Si and calibrated with respect to NIST SRM-610 and -612 glasses as the primary standards. Temperature was calculated from the Ti-in-zircon thermometer (Watson et al., 2006). Because there are no constraints on the activity of TiO2, an average value in crustal rocks of 0.8 was used. Data were collected in one experiment in January 2016. For U-Pb and 207Pb/206Pb dates, instrumental fractionation of the background-subtracted ratios was corrected and dates were calibrated with respect to interspersed measurements of zircon standards and reference materials. The primary standard Plešovice zircon (Sláma et al., 2008) was used to monitor time-dependent instrumental fractionation based on two analyses for every 10 analyses of unknown zircon. A secondary correction to the 206Pb/238U dates was made based on results from the zircon standards Seiland (530 Ma, unpublished data, Boise State University) and Zirconia (327 Ma, unpublished data, Boise State University), which were treated as unknowns and measured once for every 10 analyses of unknown zircon. These results showed a linear age bias of 1.1-1.4% that is related to the 206Pb count rate. The secondary correction is thought to mitigate matrix-dependent variations due to contrasting compositions and ablation characteristics between the Plešovice zircon and other standards (and unknowns).  Radiogenic isotope ratio and age error propagation for all analyses includes uncertainty contributions from counting statistics and background subtraction. For groups of analyses that are collectively interpreted from a weighted mean date (i.e., igneous zircon analyses), a weighted mean date is first calculated using Isoplot 3.0 (Ludwig, 2003) using errors on individual dates that do not include a standard calibration uncertainty, and then a standard calibration uncertainty is propagated into the error on the weighted mean date. This uncertainty is the local standard deviation of the polynomial fit to the interspersed primary standard measurements versus time for the time-dependent U/Pb fractionation factor. This uncertainty is 0.8% (2σ) for 206Pb/238U. Age interpretations are based on 206Pb/238U. Errors on the 206Pb/238U weighted mean dates are given at 2σ.  19  Results  4.1 Modal Mineralogy  With the exception of samples from the Fourth of July batholith, all the samples collected contained significant amounts of potassium feldspar and the majority plotted within the monzogranite to granodiorite fields of the Quartz-Alkali-feldspar-Plagioclase (QAP) ternary plot (Figure 10). The Fourth of July batholith samples were similar to each other, with only minor differences in the normalized proportions of quartz and potassium feldspar, plotting within the diorite and quartz-diorite fields. The Fourth of July batholith (Bryde plutonic suite) samples (15PS-002 and 15PS-003) contained a much larger proportion of mafic minerals (> 35% biotite and hornblende) when compared to the other eighteen samples, of which seventeen had less than 20% mafic mineral content.  Nine of the twelve Bennett batholith (Bryde and Long Lake plutonic suites) samples plot within the monzogranite field with the majority of samples having 10-20% mafic mineral abundance. Additionally, all nine of these samples have lower normalized proportions of plagioclase than any of the Aishihik batholith (Long Lake plutonic suite) samples (Figure 10, Table 1). One Bennett batholith sample has an anomalous amount of mafic minerals totalling 33% (15PS-132), while the next largest proportion of mafics in any other Bennett batholith sample is 19% (15PS-046). Bennett batholith samples vary from porphyritic (7 samples) to equigranular (5 samples) but there is no correlation between the texture of the samples and the abundance of potassium feldspar, although the porphyritic samples are invariably potassium feldspar-phyric. Feldspar within the groundmass or present as phenocrysts within the Bennett batholith vary from pale pink to milky white which made it difficult to differentiate from plagioclase in the field. Figure 11 (15PS-043) is an example of a sample in which plagioclase and potassium feldspar are very similar in color. In addition to plotting dominantly within the granodiorite field, the Aishihik batholith samples are much more leucocratic than any of the other samples, with a maximum mafic abundance of 8%. Finally, the sample from the Mt. Bryde pluton (Bryde plutonic suite) is compositionally similar to the Bennett batholith samples in both where it plotted within the QAP and the abundance of mafic minerals (18%).  20     Figure 10. International Union of Geological Sciences (IUGS) Quartz-Alkali-feldspar-Plagioclase ternary diagram for normalized modal abundances of samples from the Bennett, AIshihik, Fourth of July batholiths and Mt. Bryde pluton.  21   Table 1. Calculated (normalized to QAP) abundances from ImageJ modal analysis used to plot Figure 10. Figure 11. Two versions of the same image. Unstained slab for sample 15PS-043 (left) and potassium-feldspar stained slab (right). The left image highlights the similar colour of potassium-feldspar phenocrysts to plagioclase in the groundmass, while the right image displays the difference in mineralogy. Scale bar is in the bottom left corner of each image. 22  4.2 Petrography Detailed thin section descriptions of all twenty samples can be found in Appendix 1.   4.2.1 Bennett Batholith Samples collected from the Bennett batholith, as described in 4.1, are all monzogranites with the exception of one sample of granodiorite (15PS-132) and one quartz monzonite (15PS-128). Samples are texturally medium to coarse grained, porphyritic (rarely megacrystic) and equigranular, non-foliated to minorly foliated, poikilitic, hypidiomorphic and holocrystalline. Porphyritic samples (15PS-015, -021, -032, -043, -045, -046, -128) display good mineral alignment of potassium feldspar phenocrysts and mafic minerals. Easterly samples (15PS-015, -043, -128) exhibit myrmekitic intergrowth textures of quartz and plagioclase along potassium feldspar phenocryst-groundmass contacts. They are most pronounced in 15PS-043 (Figure 12). Myrmekite commonly occurs along the rims of potassium feldspar crystals during progressive deformation in mylonitic ductile shear zones (Simpson and Wintsch 1989). These observations found in thin section agree with the northwest-southeast trending orientation of these samples and the fact they are most proximal to the (northwest-southeast trending) Tally-Ho shear zone immediately to the east. Additionally, 15PS-128 is unique within the batholith, as it displays a proto-mylonitic fabric with potassium feldspar augen (Figure 13).   Figure 12. Plane-polarized light image of 15PS-043 (top) and cross-polarized light image (bottom). Scale bar is in the bottom left corner of each image. 23   With the exception of 15PS-015 and 15PS-033, hornblende is the dominant mafic mineral in all samples, occurring primarily as strongly pleochroic, euhedral, rhombus to hexagonally shaped crystals which were commonly inter-grown with biotite and simply twinned. The dominant mafic phase in 15PS-015 and 15PS-033 is chlorite (15%), an alteration product of hornblende grains, which display a distinctly hexagonal ghost habit. Epidote alteration, paragenetically associated with the chloritization of hornblende, is also pervasive in 15PS-015. Overall, four of the twelve samples collected from the Bennett batholith contain biotite (15PS-028, -033, -044, -130), all of which are potassium-feldspar phyric hornblende monzogranites. Biotite abundance doesn’t exceed 5% in any of these samples. Opaque minerals are present in all Bennett batholith samples, ranging from <1% to 2% in abundance and very strongly associated with hornblende, occurring as sub-millimeter amorphous blebs either along contacts or disseminated as inclusions. Magnetic susceptibility measurements range from 5.05 (15PS-045) to 37.2 (15PS-046), suggesting that opaques are dominantly magnetite.  Other common accessory minerals present in thin section are sphene, apatite and primary epidote.   Figure 13. Two versions of the same image. Unstained slab for sample 15PS-128 (left) and potassium-feldspar stained slab (right). No scale bar is provided, but potassium-feldspar grains range from 1-2 cm along the long axis. The potassium-feldpsar stained image highlights the augen shape of recrystallized phenocrysts. 24  4.2.2 Aishihik Batholith Samples collected from the Aishihik batholith, as described in Section 4.1, are all granodiorite with the exception of one monzogranite (15PS-087). Samples are texturally medium grained, equigranular to porphyritic, non-foliated and allotriomorphic to hypidiomorphic. Porphyritic samples (15PS-087, -089, -090) display minor to moderate mineral alignment of potassium feldspar phenocrysts, most distinctly in 15PS-090 (Figure 14). As shown in Figure 15 potassium feldspar phenocrysts are very rarely euhedral and contacts between the phenocrysts and the groundmass are highly curvilinear. This indicates there was resorption at the edges of potassium feldspar phenocrysts prior to complete crystallization of the groundmass. Contrasting with samples of the Bennett batholith, all Aishihik batholith samples contain biotite as a mafic phase with the exception of 15PS-089, which only contains hornblende and chlorite. Additionally, biotite is the dominant mafic phase in all samples in which it occurred. Opaque minerals are present in all samples and strongly associated with biotite either as inclusions or present along grain rims and ranged from sub-mm to 2 mm in size. Overall, the abundance of mafic minerals observed in thin section is significantly lower than any other plutons, ranging from 5-10% (or 4.1-7.6% as described in section 4.1). Despite having lower abundances of mafic minerals, magnetic susceptibility measurements show no significant difference from samples of  Figure 14. Hand sample scale photograph of 15PS-090.  Figure 15. Cross-polarized light image of 15PS-089 exhibitting irregular potassium feldspar phenocryst contacts with groundmass. Scale bar is provided in bottom left corner. 25  the Bennett batholith, indicating higher concentrations of magnetite within the mafic minerals that are present. This is consistent with the size of anhedral opaque minerals, which are commonly millimeter in scale, whereas the Bennett batholith oxides are rarely ever larger than 1 millimeter.  4.2.3 Fourth of July Batholith Samples collected from the Fourth of July batholith, as described in 4.1, are of dioritic to quartz dioritic composition. Both samples 15PS-002 (Figure 16) and 15PS-003 are texturally medium grained, equigranular, non-foliated and hypidiomorphic. The plagioclase in 15PS-003 is extremely sericitized whereas in 15PS-002 it is completely unaltered. The dominant mafic minerals in both samples are hornblende (25%) and biotite (10%). Despite the extreme sericitization of plagioclase in 15PS-003, the mafic minerals are completely unaltered. Additionally, despite the melanocratic nature of these samples (35% mafic abundance), they contain the significantly lower abundances of oxides than any other samples in this thesis. The low proportions of oxides observed in thin section agree strongly with their anomalously low magnetic susceptibility measurements of 0.302 (15PS-002) and 0.267 (15PS-003) (Appendix 2). The next lowest magnetic susceptibility measurement of any sample is 3.49 (15PS-032 – Bennett batholith). Hornblende grains found within 15PS-002 are pleochroic light green to beige-clear, subhedral to euhedral, display good amphibole cleavage in euhedral grains and are commonly inter-grown with biotite (in equilibrium). Since hornblende grains vary from subhedral to Figure 16. Two versions of the same image (15PS-002). Plane polarized light (left) and cross polarized light (right). Scale bar is present in the bottom left corner of each image. 26  euhedral, contacts with plagioclase vary from sharp to curvilinear/non-angular. The curvilinear contacts indicate that these hornblende crystals are not xenocryts, and therefore crystallized at the same pressures and temperatures (equilibrium) as plagioclase. Plagioclase within 15PS-002 is andesine, determined by extinction angles (Michael-Levy method).   4.2.4 Mt. Bryde Pluton 15PS-124 (Figure 17) is the only sample collected from this pluton. It is medium-grained, equigranular, non-foliated, hypidiomorphic and holocrystalline. In thin section the plagioclase and potassium feldspar are difficult to differentiate due to both being extremely sericitized (>90% of grains). Both the plagioclase and potassium feldspar make up 60% of the sample in thin section. The few unaltered grains of plagioclase that are present (as chadacrysts within quartz) are completely unaltered, euhedral, moderately concentrically zoned, elongate, and andesine in composition, determined by extinction angles (Michael-Levy method). Although it is unlikely that the composition of the plagioclase chadacrysts are the same as the larger and altered plagioclase crystals, they are the best estimate. Mafic minerals in this sample are hornblende (15%) and biotite (5%), both are subhedral to euhedral and strongly pleochroic, ranging in sizes 3-5mm (hornblende) and 1-4mm (biotite). The hornblende displays good diagnostic cleavage. Both minerals are strongly associated with anhedral opaque minerals which are either found in contact or as inclusions. Figure 17. Two versions of the same image (15PS-124). Plane polarized light (left) and cross polarized light (right). Scale bar is present in the bottom left corner of each image. 27  4.3 Whole Rock Geochemistry  4.3.1 Major Oxides  Harker plots (major element oxides vs. silica content) are reported in Figure 18. Samples from the Bennett and Aishihik batholiths display moderate positive correlations of SiO2 with K2O and Na2O, while displaying strong negative correlations with CaO, MgO, Fe2O3(T), TiO2 and P2O5. Additionally, Al2O3 (alumina) content does not indicate any observable correlation with silica among these batholiths. The Aishihik batholith samples (68.58-72.17 SiO2 wt. %) are more silica rich when compared to the Bennett batholith samples (57.45-70.46 SiO2 wt. %), which agree with the results found in sections 4.1 and 4.2 that the Aishihik batholith is less abundant in mafic minerals. Since there is only one sample from the Mt. Bryde pluton, it is difficult to assess the major oxide vs. silica trends of this individual pluton, although it does agree with the general major oxide trends of the Bennett and Aishihik batholiths.  The two samples from the Fourth of July Batholith agree with some linear trends when compared with the Bennett and Aishihik batholiths (CaO, Fe2O3(T), K2O, Na2O, TiO2), although the alumina content of 15PS-003 (Fourth of July batholith) is significantly lower than the other nineteen samples (14.07%), with the next lowest being an Aishihik batholith sample (15.12%) - 15PS-071. Despite 15PS-003 being an outlier in alumina content, all twenty samples are peralimunous, which agrees with the occurrence of sub-millimeter garnet viewed in thin section among certain samples. Additionally, the Fourth of July batholith samples also have a significantly higher MgO component when compared to the other eighteen samples, which is to be expected based on the high abundance of mafic minerals outlined in sections 4.1 and 4.2. 15PS-132 (Bennett batholith) appears as an outlier when compared with other samples found within the batholith, resembling samples of the Fourth of July batholith in both silica (57.45%) and major oxide abundances. 28   Figure 18. Harker plots (major oxides vs. silica). Plots for P2O5, Al2O3, CaO, Fe2O3(T), K2O, Na2O, MgO and TiO2 are all to the same horizontal scale (SiO2 wt. %). 29  A total alkali-silica (TAS) plot of all samples is reported in Figure 19. All samples within the Bennett, Aishihik, Fourth of July and Mt. Bryde plutons plot below the alkaline-subalkaline division. The Bennett batholith samples are slightly more alkali rich than the Aishihik batholith with the exception of 15PS-089 which is the only sample to plot within the syenite field. 15PS-132 again plots very similar to the Fourth of July batholith samples, agreeing with the strong correlations between these samples found in the Harker plots (Figure 18). An AFM ternary diagram, which is used to determine whether subalkaline rocks follow a tholeiitic or calc-alkaline magma series, is provided in Figure 20. All samples with the exception of those from the Fourth of July batholith strongly follow a calc-alkaline magma series trend. Due to only having two samples from the Fourth of July batholith there is not enough data to determine if there is a strong calc-alkaline trend similar to that of the Bennett and Aishihik batholiths.  Figure 19. Total Alkali (Na2O + K2O wt. %) vs. Silica (SiO2) (TAS) plot. After Le Maitre et al. (2002). 30               4.3.2 Trace Elements Chondrite normalized rare earth element (REE) patterns are plotted using C1 chondrite values from Sun and McDonough (1989). Due to the limited number of samples from the Fourth of July batholith and the Mt. Bryde pluton, REE patterns were only produced for the Bennett and Aishihik batholith samples. The Bennett REE plot (Figure 21) shows an overall enrichment of REEs, with an overall higher enrichment of light REEs (La-Gd) than heavy REEs (Tb-Lu). La values range from 50.6 to 183 (12.0 to 43.5 ppm) within the Bennett batholith and Lu values range from 5.9 to 21.6 (0.149 to 0.540 ppm). Following a pattern similar to the Bennett batholith REEs, the Aishihik REE plot (Figure 22) also displays an enrichment of REEs, trending from being more enriched in LREEs than HREEs. For the Aishihik batholith, La values range from Figure 20. AFM diagram showing the relative proportions of oxides. Samples follow a calc-alkaline trend. 31  25.1 to 94.9 (5.95 to 22.5 ppm) and Lu values range from 6.02 to 7.09 (0.153 to 0.180 ppm). It should be noted that 15PS-089 (Aishihik) was relatively depleted in LREEs when compared to other samples within the batholith, it contained only 5.95 ppm La compared to the remainder of samples ranging from 14 to 22.5 ppm La. Six of the twelve Bennett batholith samples have equal or greater La ppm than the largest Aishihik batholith La ppm value (25.5). As evidenced when comparing Figures 20 and 21, the Bennett batholith samples are slightly more enriched in REEs than the Aishihik batholith samples. Primitive mantle normalized trace element patterns are plotted using values from Sun and McDonough (1989). The Bennett batholith trace element pattern (Figure 23) shows significant anomalies in Nb (negative), Pb (positive) and Sr (positive). The Aishihik batholith trace element pattern (Figure 24) also displays significant anomalies in Pb (positive) and Sr (positive). It should be noted 15PS-090 contains 38.5 ppm Nb, whereas the next largest value within the Aishihik batholith is 9.1 ppm Nb (15PS-071). With the exception of 15PS-090, all samples within the Aishihik batholith exhibit a negative Nb anomaly. Eu - an element which fractionates readily into plagioclase – exhibits no anomaly (positive or negative) in either the Bennett or Aishihik batholith patterns.         Figure 21. C1 chondrite-normalized (Sun and McDonough 1989) rare-earth-element plot for samples from the Bennett batholith. Light-rare-earth-elements (LREE’s) are La to Eu and heavy rere-earth-elements (HREE’s) are Tb to Lu. 32   Figure 22. C1-chondrite normalized (Sun and McDonough 1989) rare-earth-element plot for samples from the Aishihik batholith. Light-rare-earth-elements (LREE’s) are La to Eu and heavy rere-earth-elements (HREE’s) are Tb to Lu. Figure 23. Primitive-mantle normalized (Sun and McDonough 1989) trace element plot for samples from the Bennett batholith. 33           4.4 Geochronology Analytical work and interpretations were done by Dr. James Crowley at Boise State University.  4.4.1 CA-TIMS Seven zircon grains from 15PS-032 (Bennett batholith) were analyzed, the five youngest of which yielded equivalent 206Pb/238U dates with a weighted mean date of 178.20 ± 0.05 / 0.10 / 0.22 Ma (MSWD = 2.0, probability of fit = 0.09) (Figure 25 and 26). This is the interpreted igneous crystallization age. Two other grains yielded slightly older dates of 178.44 ± 0.12 and 178.48 ± 0.12 Ma, interpreted as reflecting the presence of inherited components. Six zircon grains from 15PS-044 (Bennett batholith) were analyzed, the five oldest of which yielded equivalent 206Pb/238U dates with a weighted mean date of 114.14 ± 0.03 / 0.07 / 0.14 Ma (MSWD = 1.0, probability of fit = 0.44) (Figure 25 and 27). This is the interpreted igneous crystallization age. This age indicates that 15PS-044 is not a member of the Bryde (178 – 167 Ma) or Long Figure 24. Primitive-mantle normalized (Sun and McDonough 1989) trace element plot for samples from the Aishihik batholith. 34  Lake (192 – 180 Ma) plutonic suites. Six zircon grains from 15PS-123 (Mt. Bryde pluton) yielded equivalent 206Pb/238U dates with a weighted mean date of 172.52 ± 0.05 / 0.10 / 0.21 Ma (MSWD = 0.22, probability of fit = 0.95) (Figure 25 and 28). This is the interpreted igneous crystallization age.   4.4.2 LA-ICP-MS Twenty-eight grains from 15PS-032 yielded equivalent dates with a weighted mean of 177.5 ± 1.8 Ma (MWSD = 1.5, probability of fit = 0.05). Twenty-nine grains from 15PS-044 yielded equivalent dates with a weighted mean of 112.9 ± 1.3 Ma (MWSD = 0.7, probability of fit = 0.84). Twenty-nine grains from 15PS-123 yielded equivalent dates with a weighted mean of 171.8 ± 1.8 Ma (MWSD = 0.9, probability of fit = 0.65). For all three samples, it is concluded that that any inherited zircon cannot be resolved as being older than the dominant igneous zircon population because grains with different CL zoning patterns and brightness were analyzed and the weighted mean dates agree with the weighted mean dates determined by CA-TIMS. The chemical compositions of the zircon from all three samples are typical of zircon from plutons in magmatic arcs. Sample 15PS-032 has zircon with the most heterogeneous chemical compositions. For Figure 25 (right). Plots of ranked CA-TIMS U-Pb dates from zircon. Error bars are shown at 2σ. Grey boxes behind error bars represent with the weighted mean date of 2σ. Dates shown in white are not included in weighted mean calculations. 15PS-123, although not referenced in this thesis, is directly correlative with 15PS-124 from the Mt. Bryde pluton. MSWD = Mean square weighted deviation. (Crowley pers. comm., 2015). 35  example, the average Ti-in-zircon temperature calculated from 15PS-032 is 689 ± 48o C (1 standard deviation), compared with 789 ± 14o C for sample 15PS-044 and 771 ± 24oC for sample 15PS-123. Also, the average Eu anomaly (Eu/Eu*) is 0.45 ± 0.14 (1 standard deviation), compared with 0.34 ± 0.06 for sample 15PS44 and 0.23 ± 0.04 for sample 15PS-123.      Figure 26. Cathodoluminescence (CL) images from 15PS-032. Labels for grains dated by CA-TIMS are shown. (Crowley pers. comm., 2015). 36               Figure 27. Cathodoluminescence (CL) images from 15PS-044. Labels for grains dated by CA-TIMS are shown. (Crowley pers. comm., 2015). 37         Figure 28. Cathodoluminescence (CL) images from 15PS-123. Labels for grains dated by CA-TIMS are shown. (Crowley pers. comm., 2015). 38  Discussion  5.1 Nature and Timing of Bennett Batholith Magmatism Despite being a polyphase batholith, the dominant phase within the northwest-southeast trending Bennett batholith is a locally, weakly foliated (rarely biotite-bearing) hornblende monzogranite which ranged from equigranular to potassium feldspar megacrystic. The porphyritic to megacrystic phase is commonly referred to as the Bennett granite by previous workers (Hart 1990; Hart 1997; Tizzard and Johnston 2005). U-Pb zircon dating determined an Early Jurassic crystallization age of 178.20 ± 0.05 Ma for the Bennett granite (15PS-032 - Bryde suite portion of the Bennett batholith). Current age ranges for the Bryde Plutonic suite range from 178 to 171 Ma (Mihalynuk et al 1992; Gordey and Stevens 1994; Hart 1997). A new U-Pb zircon date of the Mt. Bryde pluton yielded a Middle Jurassic crystallization age of 172.52 ± 0.05 Ma, which agrees with previous data (173 ± 3 Ma, Ar40-Ar39 hornblende; 169 ± 2, Ar40-Ar39 biotite) (Gordey and Stevens 1994). Although current age ranges for the Bryde plutonic suite range from 178 to 171 Ma, the oldest age obtained from the Bennett batholith, Fourth of July batholith or Mt. Bryde pluton is currently Gordey and Stevens (1994) date of 173 ± 3 Ma. When taking errors into account, this indicates the Bennett granite is at the very least 2 Ma older than any other members of the Bryde suite studied herein, such as the Mt. Bryde pluton and Fourth of July batholith. Current age ranges for the Long Lake suite, representing the Aishihik batholith, are 192 to 181 Ma (Mihalynuk 1999). The Aishihik batholith is approximately 60 km northwest of the Bennett batholith, trending in a markedly similar northwest-southeast orientation in map view. It is interpreted as an east dipping syntectonic tabular intrusion (Johnston and Canil 2007) dominated by biotite hornblende granodiorite to granite. The Aishihik batholith was emplaced in between lithotectonic terranes that were in the process of accretion during the Cordilleran Orogeny in the Early to Middle Jurassic (Johnston and Canil 2007). Additionally, the Aishihik batholith may represent to oldest plutonic linkage between the Stikinia and Yukon-Tanana terranes (Hart 1997). 39  The Bennett granite similarly represents a plutonic linkage between the Stikinia and Yukon-Tanana terranes, as it intrudes the Tally Ho shear zone (THSZ) which has been interpreted to separate these two terranes (Tizzard and Johnston 2004). Tizzard and Johnston (2004) proposed that the folding of the THSZ occurred prior to the intrusion of the Bennett granite, as the granite appeared to cross-cut the folded shear zone. Rim myrmekite observed along potassium-feldspar phenocryst boundaries within easterly Bennett batholith samples (most pronounced in 15PS-043) provide evidence that this region of the batholith was experiencing minor progressive deformation associated with a ductile shear zone (Simpson and Wintsch 1989). Additionally, the most easterly and southerly sample (15PS-128) was a potassium-feldspar phyric hornblende monzogranite proto-mylonite (or Bennett granite proto-mylonite), suggesting active deformation was occurring during emplacement of this intrusion. Based on these observations it may be possible that the Bennett granite intruded the THSZ before it became fully inactive, indicating a) emplacement depths were satisfactory for minor progressive ductile deformation and b) the THSZ was still active during the Early Jurassic. Although, preliminary geothermobarometry results from continuing research suggest emplacement depths may have been relatively shallow for the Bennett batholith, with pressures in the range of 1.5 ± 1 kbar or emplacement depths of approximately 4.5 ± 3 km (Allan, pers. comm., 2016). Ongoing research will be needed to resolve this paradox and determine more precise estimates of emplacement depths.  5.2 A Case for the Long Lake Suite Using Hart’s (1997) definition of a plutonic suite: “Individual plutonic suites are defined by similarities in tectonic setting, composition, mineralogical, textural, geochemical and isotopic characteristics of constituent plutons”, a comparison of the Bennett and Aishihik batholiths can be made to determine what characteristics they share, and if they should be grouped within one plutonic suite. For the purpose of this discussion, the U-Pb age of 178.20 ± 0.05 Ma for the Bennett granite is inferred to be correlative with the Bennett batholith as a whole.  Compositionally, the samples of the Bennett and Aishihik batholiths are strikingly similar, primarily plotting within the monzogranite and granodiorite fields of the QAP diagram in section 4.1. Textural similarities between the batholiths include being: poikilitic, 40  holcrystalline, porphyritic to equigranular and non-foliated to weakly foliated (with the exception of Bennett samples proximal to the THSZ). The most distinct mineralogical difference between the Bennett and Aishihik batholiths is the abundance of mafic minerals, specifically biotite. All but one of the Aishihik samples contain biotite as a mafic phase, and in every sample in which it occurs it is dominant over hornblende. In contrast, only four of twelve Bennett batholith samples contain biotite, always as a secondary mafic phase to hornblende and never exceeding 5% in abundance. Additionally, Aishihik batholith samples are significantly more leucocratic when directly compared to samples from the Bennett batholith. Geochemically, both batholiths are subalkalic/calc-alkalic and exhibit similar major and trace element trends. Maximum and minimum temporal constraints on the accretion of peri-Laurentian terranes (which host the Aishihik and Bennett batholiths) to the western margin of ancestral North America put initial collisions at 188-181 Ma and final collisions at 175 to 172 Ma (Nelson et al. 2013). The Aishihik batholith intruded and pinned together the Stikinia and Yukon-Tanana terranes during the Early Jurassic (192 – 180 Ma) (Johnston et al, 1996; Hart 1997). It is also known that the Bennett granite phase of the Bennett batholith intruded the THSZ in the Early Jurassic (178 Ma), pinning the contact between the Stikinia and Yukon-Tanana terranes (Tizzard and Johnston 2004). The Aishihik and Bennett batholiths therefore shared similar tectonic settings because they: a) were both emplaced within the 188-172 Ma window of Stikinia’s accretion to the western margin of ancestral North America, b) are both interpreted as eastward-dipping stitching plutons between the Stikinia and Yukon-Tanana terranes (Johnston et al. 1996; Hart 1997; Johnston and Canil 2007; Tizzard and Johnston 2004), and c) share a markedly similar northwest-southeast trending orientation in map view along one axis.  5.3 Metallogenic Potential of the Bennett Batholith As stated in the introduction, Late Triassic to Early Jurassic magmatic belts which extend from southern British Columbia into the Yukon-Tanana Terrane of Yukon are known to collectively host the most important porphyry Cu-Au and Cu-Mo deposits in the Northern Cordillera. Preliminary geothermobarometry results indicate that the Bennett batholith may have been emplaced at relatively shallow depths (4.5 ± 3 km), indicating minimal erosion has occurred in this area since the Early Jurassic. As most known porphyry-style deposits are 41  emplaced at depths of 1 – 6 km and dominantly calc-alkalic, this would indicate the calc-alkalic Bennett batholith may have been suitable for porphyry generation. Due to being in intrusive/fault contact with the Tally-Ho shear zone (which may have still been active in the Early Jurassic), hosting aplite to (more rarely) pegmatite dykes, locally exhibitting significant chlorite/epidote alteration of hornblende and sericitic alteration of plagioclase feldspar, there is evidence that the Bennett batholith was likely experiencing hydrothermal activity during and/or post emplacement. The presence of magnetite as the dominant opaque mineral in thin section indicates that the magmatic system was relatively oxidized, which would favour porphyry generation.  Additionally, research done in this thesis resulted in a U-Pb date of 178.20 ± 0.05 Ma for the sample analyzed from the Bennett batholith, close to known porphyry hosting intrusions such as Lorraine (178 Ma) and Mt. Milligan (183 Ma) in central British Columbia.   Summary  The purpose of this study was to determine the potential of Early-Middle Jurassic intrusion-related mineralization in southwest Yukon by providing a comprehensive characterization of the Bennett batholith, and if possible, provide additional constraints on which plutonic suite it should be grouped. It was determined that sample 15PS-044, which was sampled from the Long Lake suite phase of the Bennett batholith, is Middle Cretaceous (114.14 ± 0.03) and most likely a member of the Whitehorse plutonic suite. Geochronological results revealed that the Bennett batholith is at the very least 2 Ma older than any other member of the Bryde plutonic suite within this thesis. Additionally, given the similarities in tectonic setting, preliminary results on depth of emplacement, compositional, textural, mineralogical and geochemical characteristics, it is very likely it is a southern extension of the northwest-southeast trending Aishihik batholith and should therefore be classified within the Long Lake plutonic suite. The Bennett batholith may have been a fertile system for copper-porphyry generation in terms of age, geochemical signature, emplacement depth and oxidation state, but further research is needed to confirm these findings. 42  References:  Belansky, P., and Stevens, C.H., 2006, Permian faunas of westernmost North America: Paleobiogeographic constraints on the Permian positions of Cordilleran terranes. Geological Association of Canada, Special Paper 46, p. 71-80.  Beranek, L.P., and Mortensen, J.K., 2011. The timing and provenance record of the Late Permian Klondike orogeny in northwestern Canada and arc-continent collision along western North America. Tectonics, v. 30, TC5017, doi:10.1029/2010/TC002849.  Bultman, T.R., 1979. Geology and Tectonic History of the Whitehorse Trough west of Atlin, British Columbia. Ph.D. thesis, Yale University, 284 p.   Colpron, M., Nelson, J.L., and Murphy, D.C., 2007a. Northern Cordilleran terranes and their interactions through time. GSA today, v. 17, no. 4/5, p. 4-10.  Colpron, M., Nelson, J.L., 2011. A Digital Atlas of Terranes for the Northern Cordillera. Accessed online from the Yukon Geological Survey (www.geology.gov.yk.ca), [December 2015].  Colpron, M., Nelson, J.L., and Israel, S., 2007b. A transect through the accreted terranes of the northern Canadian Cordillera from Cassiar, British Columbia to Kluane Lake, Yukon. Yukon Geological Survey, Open File 2007-3, 84 p.  Currie, L.D., and Parrish, R.R., 1993. Jurassic accretion of Nisling Terrane along the western margin of Stikinia, Coast Mountains, northwestern British Columbia. Geology v. 21, p. 235-238.  Crowley, J.L., Schoene, B., Bowring, S.A., 2007, U-Pb dating of zircon in the Bishop Tuff at the millennial scale: Geology 35:1123-1126.  43  Doherty, R.L., and Hart, C.J.R., 1988. Preliminary Geology of Fenwick Creek (105D/3) and Alligator Lake (105D/6) map areas: Indian and Northern Affairs Canada, Yukon Region, Open File 1988-2, 65 p.  Gerstenberger, H., Haase, G., 1997, A highly effective emitter substance for mass spectrometric Pb isotope ratio determinations: Chemical Geology 136:309-312.  Gordey, S.P. and Makepeace, A.J., 2001. Yukon bedrock geology in Yukon digital geology, Geological Survey of Canada Open File D3826 and Exploration and Geological Services Division, Yukon, Indian and Northern Affairs Canada, Compilation Map.  Hart, C.J.R., and Radloff, J.K., 1990. Geology of the Carcross, Fenwick Creek, Alligator Lake, Whitehorse and part of Robinson map areas (105D/2,3,6,11 & 7), Yukon. Indian and Northern Affairs Canada: Yukon Region, Open File 1990-4.  Hart, C.J.R., 1997. Magmatic and Tectonic Evolution of the Intermontane Superterrane and Coast Plutonic Complex in Southern Yukon Territory. Master’s thesis, University of British Columbia, 209 p.  Jaffey, A.H., Flynn, K.F., Glendenin, L.E., Bentley, W.C., and Essling, A.M., 1971, Precision measurements of half-lives and specific activities of 235U and 238U, Physical Review C, 4:1889-1906.  Johnston, S.T., Mortensen, J.K. and Erdmer, P., 1996. Igneous and metaigneous age constraints for the Aishihik metamorphic suite, southwest Yukon. Canadian Journal of Earth Science, vol. 33, p. 1543-1555.  Johnston, S.T. and Canil, D., 2007, Crustal architecture of SW Yukon, northern Cordillera: Implications for crustal growth in a convergent margin orogen: Tectonics, v. 26, p. 1-18.  Krogh, T.E., 1973, A low contamination method for hydrothermal decomposition of zircon and extraction of U and Pb for isotopic age determination: Geochimica et Cosmochimica Acta 37:485-494.  44  Le Maitre, R.W., Streckeisen, A., Zanettin, B., Le Bas, M.J, Bonin, B., Bateman, P., Bellieni, G., Dudek, A., Efremova, S., Keller, J., Lamere J., Sabine, P.A., Schmid, R., Sorensen, H., and Woolley, A.R., 2002. Igneous Rocks: A Classification and Glossary of Terms, Recommendations of the International Union of Geological Sciences, Subcommission of the Systematics of Igneous Rocks. Cambridge University Press.  Ludwig, K.R., 2003, User’s Manual for Isoplot 3.00. Berkeley Geochronology Center: Berkeley, CA, 70 p.  Mihalynuk, M.G., Nelson, J.L., and Diakow, L.J., 1994a. Cache Creek terrane: oroclinal paradox within the Canadian Cordillera. Tectonics, v. 13, p. 575-5-595.  Mihalynuk, M.G., 1999. Geology and Mineral Resources of the Tagish Lake Area, (NTS 104M/8, 9, 10E, 15 and 104N/12W) Northwestern British Columbia. British Columbia Geological Survey Bulletin 105.   Monger, J.W.H., Price, R.A., and Tempelman-Kluit, D.J., 1982. Tectonic accretion and the origin of the two major metamorphic and tectonic welts in the Canadian Cordillera. Geology, v. 10, p. 70-75.  Morrison, G.W., Godwin, C.I., and Armstrong, R.L. 1979. Interpretation of isotopic ages and 87Sr/86Sr initial ratios for plutonic rocks in the Whitehorse map area, Yukon. Canadian Journal of Earth Sciences, v. 16, p. 1988-1997.  Murphy, D.C., van der Heyden, P., Parrish, R.R., Klepacki, D.W., Mcmillan, W., Struik, L.C., and Gabites, J., 1995, New geochronological constraints on Jurassic deformation of the western edge of North America, southeastern Cnadian Cordillera. Geological Society of America, Special Paper 299, p. 159-171.  Nelson, J.L., Colpron, M., Piercey S.J., Dusel-Bacon, C., Murphy, D.C., and Roots, C.F., 2006. Paleozoic tectonic and metallogenic evolution of peri-cratonic terranes in Yukon, northern British Columbia and eastern Alaska. Geological Association of Canada, Special Paper 45, p. 323-360.  45  Nelson, J.L., Colpron, M., Israel, S., 2013. The Cordillera of British Columbia, Yukon and Alaska: Tectonics and Metallogeny. Society of Economic Geology, Special Paper 17, p. 53-109.  Piercey, S.J., Nelson, J.L., Colpron, M., Dusel-Bacon, C., Murphy, D.C., Simard, R.-L, and Roots, C.F., 2006, Paleozoic magmatism and crustal recycling along the ancient Pacific margin of North America, northern Cordillera. Geological Association of Canada, Special Paper 45, p. 281-322.  Sláma, J., Košler, J, Condon, D.J., Crowley, J.L., Gerdes, A., Hanchar, J.M., Horstwood, M.S.A., Morris, G.A., Nasdala, L., Norberg, N., Schaltegger, U., Schoene, B. Tubrett, M.N, Whitehouse, M.J. 2008. Plešovice zircon — A new natural reference material for U–Pb and Hf isotopic microanalysis. Chemical Geology, 249: 1-35.  Simpson, C. and Wintsch, R. P., 1989, Evidence for deformation-induced K-feldspar replacement by myrmekite: J. Metam. Geol., v. 7, p. 261-275.  Tempelman-Kluit, D.J. 1974. Reconnaissance geology of Aishihik Lake, Snag and part of Stewart River map-areas, west-central Yukon. Geological Survey of Canada, Paper 73-41.  Tempelman-Kluit, D.J. 1976. The Yukon Crystalline Terrane, enigma in the Canadian Cordillera. Geological Society of American Bulletin, v. 87, p. 1343-1357.  Tizzard, A. and Johnston, S., 2005. Structural evolution of the Tally Ho shear zone (NTS 105D), southern Yukon. In: Yukon Exploration and Geology 2004, D.S. Emond, L.L. Lewis and G.D. Bradshaw (eds.), Yukon Geological Survey, p. 237-246.  Watson, E.B., Wark, D.A., Thomas, J.B. 2006. Crystallization themometers for zircon and rutile. Contributions to Mineralogy and Petrology, 151: 413-433.  Yukon Bedrock Geology Dataset. Accessed from the Yukon Geological Survey (www.geology.gov.yk.ca), [December 2015].  46  APPENDICIES  APPENDIX 1: Sample Photos and Descriptions   15PS-002  Field photos:    Potassium Feldspar Staining: Unstained  Stained         47  Thin Section Description: PPL  XPL   Texture:  Medium grained, equigranular, non-folated, non-vesicular, panidiomorphic, holocrystalline  Mineralogy:  Plagioclase (62%) - Size: 4-6 mm - Clear, euhedral, elongate, very good polysynthetic twinning, sharp contact with hornblende, rarely concentric zonation obscures twinning - Michael-Levy Method: Average extinction angle of 21 degrees in 5 euhedral grains (18-22) - Alteration: None.  Quartz (3%) - Size: 3-5 mm - Clear, anhedral to subhedral, moderately undulose, crystals are composed of single grains rather than aggregates of finer crystals coalescing together (as found in most other samples), grains are only 1-2 mm when infilling void space between other euhedral minerals, inclusions of hornblende or biotite common - Alteration: None.  Hornblende (25%) - Size: 3-6 mm - Pleochroic light green to beige-clear, subhedral to euhedral, good amphibole cleavage in euhedral grains, intergrowth with biotite is extremely common (cogenetic), little to no oxides present/associated - Alteration: None.  Biotite (10%) - Size: 2-4 mm - Pleochroic from dark brown to beige-clear, subhedral to euhedral, intergrowth with hornblende is extremely common (cogenetic), little to no oxides present/associated - Alteration: None.  Accessory Minerals:  Oxides (<<1%) – Extremely sparse, opaque, anhedral, sub-mm to 1 mm, found as inclusions or along contacts of mafic minerals  Rock Name: Biotite-bearing hornblende diorite   48  15PS-003  Field photos:    Potassium Feldspar Staining: Unstained  Stained          49   Thin Section Description: PPL  XPL    Texture:  Medium grained, equigranular, non-folated, non-vesicular, hypidiomorphic, holocrystalline  Mineralogy:  Plagioclase (55%) - Size: 4-6 mm - Off grey, subhedral, elongate, polysynthetic twinning is obscured by pervasive alteration in >95% grains - Plagioclase composition could not be determined due to alteration - Alteration: Extremely sericitized.  Quartz (10%) - Size: 3-5 mm - Clear, anhedral to subhedral, moderately undulose, crystals are composed of single grains rather than aggregates of finer crystals coalescing together (as found in most other samples), grains are only 1-2 mm when infilling void space between other euhedral minerals, inclusions of hornblende or biotite common - Alteration: None. -  Hornblende (25%) - Size: 3-6 mm - Pleochroic light green to beige-clear, very varied from anhedral to euhedral, good amphibole cleavage in euhedral grains, intergrowth with biotite is extremely common (cogenetic), little to no oxides present/associated - Alteration: None. Biotite (10%) - Size: 2-4 mm - Pleochroic from dark brown to beige-clear, subhedral to euhedral, intergrowth with hornblende is extremely common (cogenetic), little to no oxides present/associated - Alteration: None.  Accessory Minerals:  Oxides (<<1%) – Extremely sparse, opaque, anhedral, sub-mm to 1 mm, found as inclusions or along contacts of mafic minerals,   Rock Name: Heavily sericitized biotite-bearing hornblende quartz-diorite 50  15PS-015  Field photos:    Potassium Feldspar Staining: Unstained  Stained    Thin Section Description: PPL XPL 51     Texture:  Medium to coarse grained, porphyritic, non-folated, non-vesicular, hypidiomorphic, holocrystalline  Mineralogy:  Plagioclase (30%) - Size: 4-6 mm - Off grey, euhedral, elongate, polysynthetic twinning is obscured by pervasive alteration in most grains, concentric zonation common in unaltered grains - Plagioclase composition could not be determined due to alteration - Alteration: Extremely sericitized.  K-feldspar phenocrysts (25%) - Size: 4-6 mm - Clear, euhedral, tabular, good carlsbad twins, rare inclusions of 1-2 mm euhedral hornblende, rarely sub-mm perthitic exsolution lamellae, sericite veinlets penetrate cleavage planes - Alteration: Minorly to moderately sericitized.  Quartz (25%) - Size: 3-5 mm - Clear, anhedral to subhedral, rarely undulose, crystals are composed of single grains rather than aggregates of finer crystals coalescing together (as found in most other samples), grains are only 1-2 mm when infilling void space between other euhedral minerals - Alteration: None. Chlorite (15%) - Size: 3-6 mm - Pleochroic light green to clear, euhedral, heavily intergrown with hornblende with wavy contacts between the two minerals, epidote is commonly present as inclusions - elongate laths along cleavage planes - Alteration: Chlorite is likely not primary, an alteration product from relict biotite and hornblende crystals.   Hornblende (3%) - Size: 1-2 mm - Pleochroic light green to beige-clear, euhedral, good amphibole cleavage, almost all grains found as inclusions within K-feldspar or quartz which have shielded it from alteration - Alteration: None.  Accessory Minerals:  Sphene (<<1%) – Clear, sub-millimeter, euhedral, diamond habit, found as inclusions in feldspar phenocryts  Oxides (<<1%) – Opaque, anhedral, sub-mm to 1 mm, found as inclusions or along contacts of chlorite  52   Apatite (1%) – Clear, 1-2 mm, euhedral, elongate prismatic habit, found as inclusions within quartz or feldspar  Epidote (1%) - Pleochroic clear to pale-yellow, anhedral, found abundantly as inclusions along cleavage planes of chlorite crystals  Rock Name: Chloritized, potassium-feldspar phyric, hornblende-monzogranite                                 53  15PS-021  Field photos:    Potassium Feldspar Staining: Unstained  Stained              54  Thin Section Description: PPL  XPL   Texture:  Medium grained, megacrystic, non-folated, non-vesicular, panidiomorphic, holocrystalline  Mineralogy:  Plagioclase (30%) - Size: 3-5 mm - Clear to off grey, subhedral, elongate, contact with euhedral hornblende is not as distinct as k-feldspar, moderate polysynthetic twinning - Plagioclase composition could not be determined due to lack of polysynthetic twinning - Alteration: Moderate sericitization.  K-feldspar phenocrysts (30%) - Size: 1.5-2 cm - Clear, euhedral, tabular, good carlsbad twins, abundant inclusions of euhedral hornblende, sphene and apatite. Rare inclusions of plagioclase, sericite veinlets penetrate cleavage planes, very sharp contact with hornblende - Alteration: Locally restricted minor sericitization.  Quartz (20%) - Size: 3-5 mm - Clear, subhedral, moderately undulose, crystals are composed of single grains rather than aggregates of finer crystals coalescing together (as found in most other samples) - Alteration: None.  Hornblende (15%) - Size: 2-4 mm - Pleochroic light green to beige-clear, euhedral, good amphibole cleavage, minimally associated with oxides, simple twins common, inclusions of sphene common - Alteration: Minimal fraction of grains have been completely altered to epidote but retain hornblende habit  Chlorite (4%) - Size: 1-3 mm - Pleochroic from olive green to clear, found in contact with sericitic plagioclase and hornblende indicating it is likely a alteration product  Accessory Minerals:  Sphene (2%) – Clear, sub-millimeter, euhedral, diamond habit, found abundantly as inclusions in feldspar phenocryts 55   Oxides (<<1%) – Opaque, anhedral, sub-mm to 1 mm, found as inclusions within QAP minerals or along contacts of hornblende  Apatite (<<1%) – Clear, sub-millimeter, euhedral, elongate prismatic habit, common as inclusions within feldspar phenocryst  Epidote (<<1%) - Pleochroic clear to pale-yellow, anhedral, found as sub-mm aggregate of crystals which coalesces to form habit of relict hornblende (assumed to be alteration product of hornblende)  Rock Name: Moderately altered, potassium-feldspar phyric, hornblende monzogranite                               56  15PS-028  Field photos:    Potassium Feldspar Staining: Unstained  Stained      57  Thin Section Description: PPL  XPL   Texture:  Medium grained, equigranular, non-folated, non-vesicular, panidiomorphic, holocrystalline  Mineralogy:  Plagioclase (30%) - Size: 3-5 mm - Clear, subhedral, elongate, contacts are commonly penetrated by anhedral hornblende, minimal polysynthetic twinning, rarely zoned - Plagioclase composition could not be determined due to lack of polysynthetic twinning - Alteration: Moderate sericitization.  K-feldspar (25%) - Size: 3-5 mm - Clear, subhedral, tabular, good carlsbad twins, rare inclusions sub-millimeter euhedral plagioclase, moderate amount of grains are concentrically zoned, rarely display perthitic exsolution lamellae  - Alteration: Locally restricted minor sericitization.  Quartz (27%) - Size: 3-5 mm - Clear, subhedral, moderately undulose, crystals are composed of single grains rather than aggregates of finer crystals coalescing together (as found in most other samples) - Alteration: None.  Hornblende (10%) - Size: 2-4 mm - Pleochroic light green to beige-clear, subhedral, good amphibole cleavage, always associated with oxides, simple twins common, no alignment - Alteration: Very minor chloritization. Biotite (4%) - Size: 3-5 mm - Pleochroic dark brown to clear, euhedral, simple twins common, closely associated/in contact with amorphous oxides and hornblende, commonly contain inclusions of quartz along basal cleavage planes, always sharp/distinct contacts with surrounding minerals - Alteration: Very minor chloritization. Chlorite (2%) - Size: 1-3 mm 58  - Pleochroic from olive green to clear, subhedral to euhedral, commonly equant, found in contact with sericitic plagioclase indicating possible alteration product from biotite  Note: There is one local area within the section which is heavily sericitically altered, containing the same modal abundances of minerals but with maximum grain sizes of 1 mm. Oxides are extremely pervasive in this region giving a mottled appeared, they are evenly distributed. All biotite in this region has been completed altered to chlorite.  Accessory Minerals:  Sphene (<<1%) – Clear, sub-millimeter, euhedral, diamond habit, found as inclusions in other minerals  Oxides (2%) – Opaque, anhedral, sub-millimeter, disseminated as inclusions within chloritized hornblende or as larger grains along boundaries.  Rock Name: Biotite-bearing hornblende monzogranite 59  15PS-032  Field Photos:    Potassium Feldspar Staining: Unstained  Stained         60  Thin Section Description: PPL  XPL   Texture:  Medium grained, porphyritic with phaneritic groundmass, non-folated, mineralogically aligned, hypidiomorphic  Mineralogy:  Phenocrysts:  K-feldspar (25%) - Size: 5-12 mm - Clear, subhedral to euhedral, tabular, contacts with groundmass are sharp and dominated by aggregates of quartz with sparse hornblende, very good carlsbad twins, rare inclusions sub-millimeter plagioclase and sphene - Alteration: None  Groundmass:  Plagioclase (35%) - Size: 2-4 mm - Clear, subhedral, elongate, contacts are commonly penetrated by anhedral hornblende, good polysynthetic and simple twinning - Plagioclase composition is Andesine based on average extinction angle of 4 euhedral grains – 22O Range: 20-24 - Alteration: Minor sericitization  K-feldspar (5%) - Size: 1-3 mm - Clear, anhedral, poor carlsbad twins, very rare inclusions of sub-millimeter sphene, otherwise see above. - Alteration: None Quartz (25%) - Size: 2-4 mm - Clear, anhedral, poorly undulose, aggregates of grains penetrate contacts of k-feldspar - None.  Hornblende (10%) - Size: 2-4 mm - Pleochroic forest green to tan, anhedral, always found with abundant sub-millimeter inclusions of amorphous opaque mineral, rarely found with inclusions of sphene, simple twins common - Alteration: Some grains include fine aggregates of chlorite and biotite   61  Accessory Minerals:  Sphene (1%) – Clear, sub-millimeter, euhedral, diamond habit  Oxides (1%) – Opaque, anhedral, sub-millimeter, disseminated as inclusions within hornblende, rarely found as inclusions within plagioclase  Rock Name: Potassium-feldspar phyric hornblende monzogranite                                     62  15PS-033  Field Photos:    Potassium Feldspar Staining: Unstained   Stained      63  Thin Section Description: PPL  XPL   Texture:  Medium grained, equigranular, non-folated, non-vesicular, hypidiomorphic, holocrystalline  Mineralogy:  Plagioclase (35%) - Size: 2-4 mm - Clear, subhedral, elongate, inclusions of sub-mm quartz and chlorite common, good polysynthetic and simple twinning - Plagioclase is too altered to accurately determine An% - Alteration: Majority of grains are sericitized  K-feldspar (25%) - Size: 1-3 mm - Clear, anhedral, poor carlsbad twins, very rare inclusions of sub-millimeter sphene. - Alteration: Moderately sericitized Quartz (20%) - Size: 2-4 mm - Clear, anhedral, poorly undulose, aggregates of grains penetrate contacts of k-feldspar - None. Chlorite (15%) - Size: 1-2 mm - Pleochroic forest green to tan, anhedral, mostly found as sub-mm clusters/aggregates which coalesce to form larger domains where hornblendes used to be, always associated with biotite - Alteration: Alteration product of hornblende crystals Biotite (5%) - Size: 1-2mm - Pleochroic tan-brown to beige, anhedral, mostly found as sub-mm clusters/aggregates which coalesce to form larger domains where hornblendes used to be, always associated with chlorite - Alteration: Alteration product of hornblende Hornblende (<1%) - Size: 1-2mm - Pleochroic forest green to tan, anhedral, rarely found as most crystals have been completely altered to chlorite/biotite - Alteration: Completely altered to biotite/chlorite  Accessory Minerals:  Sphene (<<1%) – Clear, sub-millimeter, euhedral, diamond habit  64  Oxides (<<1%) – Opaque, anhedral, sub-millimeter, disseminated as inclusions within chloritized hornblende, rarely found as inclusions within plagioclase   Rock Name: Heavily altered hornblende monzogranite                                        65  15PS-043  Field Photos:    Potassium Feldspar Staining: Unstained  Stained        66  Thin Section Description: PPL  XPL   Texture:  Coarse grained, porphyritic with phaneritic groundmass, non-folated, non-vesicular, mineralogically aligned, hypidiomorphic, holocrystalline, myrmekitic, poikilitic   Mineralogy:  Phenocrysts:  K-feldspar (30%) - Size: 1-2 cm - Clear, subhedral to euhedral, tabular, contacts with groundmass are sharp and dominated by aggregates of myrmekitic quartz with sparse hornblende, very good carlsbad twins, rare inclusions sub-millimeter euhedral plagioclase, sphene, and hornblende, rarely zoned, moderately aligned - Alteration: None  Groundmass:  Plagioclase (35%) - Size: 2-4 mm - Clear, subhedral, elongate, contacts are commonly penetrated by anhedral hornblende, good polysynthetic and simple twinning - Plagioclase composition is Andesine (An32) based on average extinction angle of 3 euhedral grains – 16O Range: 14-18 - Alteration: Minor sericitization  Quartz (25%) - Size: 2-4 mm - Clear, anhedral, aggregates of finer grains common at contacts of k-feldspar, rarely myrmektic along K-feldspar grain boundaries, moderately undulose - Alteration: None  Hornblende (10%) - Size: 2-6 mm - Pleochroic forest green to tan, subhedral to euhedral, always found with abundant sub-millimeter inclusions of amorphous opaque mineral and quartz, rarely found with inclusions of sphene, simple twins common, moderately aligned - Alteration: Minor chlorite alteration.   67  Accessory Minerals:  Sphene (<<1%) – Clear, sub-millimeter, euhedral, diamond habit, found as inclusions in other minerals  Oxides (<<1%) – Opaque, anhedral, sub-millimeter, disseminated as inclusions within chloritized hornblende or as larger grains along boundaries.   Rock Name: Aligned, leucocratic, potassium-feldspar phyric hornblende monzogranite                                     68  15PS-044  Field Photos:    Potassium Feldspar Staining: Unstained  Stained   69   Thin Section Description: PPL  XPL   Texture:  Medium grained, equigranular, non-folated, non-vesicular, hypidiomorphic, holocrystalline, sericitic  Mineralogy:  Plagioclase (40%) - Size: 2-4 mm - Clear, subhedral, elongate, contacts are commonly penetrated by subhedral hornblende, good polysynthetic and simple twinning, rarely zoned - Plagioclase is too altered to accurately determine An% - Alteration: Strongly sericitized  K-feldspar (25%) - Size: 2-4 mm - Clear, anhedral to subhedral, tabular, poor carlsbad twins, rare inclusions sub-millimeter euhedral plagioclase, sphene, and hornblende, rarely zoned - Alteration: Moderately sericitized.  Quartz (25%) - Size: 1-3 mm - Clear, anhedral, moderately undulose, aggregates of finer grains common at contacts of k-feldspar - Alteration: Moderately sericitized  Hornblende (8%) - Size: 2-6 mm - Pleochroic forest green to tan, subhedral to euhedral, always found with abundant sub-millimeter inclusions of amorphous opaque mineral and quartz, rarely found with inclusions of sphene, simple twins common, moderately aligned - Alteration: Minor chloritization  Biotite (2%) - Size: 1-3 mm - Pleochroic from clear to tan-green, subhedral, strongly associated with oxides and hornblende - Alteration: Minor chloritization.    70  Accessory Minerals:  Sphene (<<1%) – Clear, sub-millimeter, euhedral, diamond habit, found as inclusions in other minerals  Oxides (<<1%) – Opaque, anhedral, sub-millimeter, disseminated as inclusions within chloritized hornblende or as larger grains along boundaries.  Epidote (<<1%) – Pleochroic clear to pale-yellow, anhedral, sub-mm, rarely found as inclusions within plagioclase, follows orientation of twinning plane, commonly found as veinlets from which sericitic alteration radiates outward    Rock Name: Heavily altered, biotite-bearing hornblende monzogranite                                   71  15PS-045  Field Photos:              72   Potassium Feldspar Staining: Unstained  Stained    Thin Section Description: PPL  XPL    73    Texture:  Medium grained, porphyritic, non-folated, non-vesicular, hypidiomorphic, holocrystalline  Mineralogy:  Plagioclase (36%) - Size: 1-4 mm - Clear, subhedral, elongate, contacts are commonly penetrated by anhedral hornblende, good polysynthetic and simple twinning, rarely zoned - Plagioclase composition is Andesine (An33) based on average extinction angle of 4 euhedral grains – 17O Range: 15-18 - Alteration: Moderate sericitization.  K-feldspar Phenocryts (30%) - Size: 7-15 mm - Clear, anhedral to subhedral, tabular, poor carlsbad twins, rare inclusions sub-millimeter euhedral plagioclase, sphene, and hornblende, rarely zoned - Alteration: Minor sericitization.  Quartz (30%) - Size: 1-3 mm - Clear, anhedral, moderately undulose, aggregates of finer grains common at contacts of k-feldspar phenocryts - Alteration: None.  Hornblende (3%) - Size: 1-2 mm - Pleochroic light green to beige-clear, anhedral to subhedral, heavily mottled with evenly distributed sub-millimeter oxides, rarely found with inclusions of sphene, simple twins common, no alignment - Alteration: Minor amounts of chlorite and actinolite within anhedral grains  Accessory Minerals:  Sphene (1%) – Clear, sub-millimeter, euhedral, diamond habit, found as inclusions in other minerals  Oxides (<1%) – Opaque, anhedral, sub-millimeter, disseminated as inclusions within chloritized hornblende or as larger grains along boundaries.  Epidote (<<1%) – Pleochroic clear to pale-yellow, anhedral, sub-mm, found as veinlet within groundmass  Rock Name: Leucocratic, hornblende-bearing potassium feldspar phyric monzogranite  74  15PS-046-1  Field Photos:    Potassium Feldspar Staining: Unstained  Stained       75   Thin Section Description: PPL  XPL   Texture:  Medium grained, porphyritic with phaneritic groundmass, non-foliated, non-vesicular, hypidiomorphic  Mineralogy:  Phenocrysts:  K-feldspar (15%) - Size: 5-12 mm - Clear, subhedral to euhedral, tabular, along grain boundaries plagioclase and hornblende often penetrate into phenocrysts, phenocrysts are very weakly aligned, carlsbad twins are common, rare inclusions sub-millimeter sphene - Alteration: Sericitization of plagioclase and biotite alteration from hornblende found within minerals along grain boundaries, not within the phenocryst itself  Groundmass:  Plagioclase (35%) - Size: 2-4 mm - Clear, subhedral, elongate, contacts are commonly penetrated by anhedral hornblende, good polysynthetic and simple twinning - Plagioclase composition is Andesine (An40) based on average extinction angle of 4 euhedral grains – 22O Range: 20-24 - Alteration: Minor sericitization  K-feldspar (5%) - Size: 1-3 mm - Clear, anhedral, poor carlsbad twins, very rare inclusions of sub-millimeter sphene, otherwise see above. - Alteration: None Quartz (20%) - Size: 2-4 mm - Clear, anhedral, poorly undulose, aggregates of grains penetrate contacts of k-feldspar - None.  Hornblende (20%) - Size: 2-4 mm - Pleochroic forest green to tan, anhedral, always found with abundant sub-millimeter inclusions of amorphous opaque mineral, rarely found with inclusions of sphene, simple twins common  76  - Alteration: Some grains include fine aggregates of chlorite and biotite  Accessory Minerals:  Sphene (1%) – Clear, sub-millimeter, euhedral, diamond habit  Oxides (1%) – Opaque, anhedral, sub-millimeter, disseminated as inclusions within hornblende, rarely found as inclusions within plagioclase  Rock Name: Potassium-feldspar phyric hornblende monzogranite                                  77  15PS-071-1  Field Photos:    Potassium Feldspar Staining: Unstained  Stained   78   Thin Section Description: PPL  XPL    Texture: Medium-grained, equigranular, phaneritic, non-foliated, non-vesicular, hypidiomorphic, holocrystalline  Mineralogy:  Plagioclase (55%) - Size: 1-4 mm - Clear, subhedral to euhedral, good polysynthetic twinning, commonly occur as sub-millimeter inclusions within larger K-feldspar grains, rarely grains display perpendicular polysynthetic twinning which resembles tartan but twins do not penetrate each other - Plagioclase Composition is Oligoclase via Michael-Levy Method: 15O from 5 best grains with a range of 11 – 18O - Alteration: Minor sericitization K-Feldspar (15%) - Size: 1-5 mm - Clear, subhedral, good carlsbad twinning, when tartan twinning is present the grain displays strong undulose extinction, rims mostly composed of fine quartz aggregate which has partially eaten away grain boundary - Alteration: Minor sericitization Quartz (20%) - Size: 1-6 mm - Clear, anhedral, strongly undulose, sericite veins favor the penetration of quartz over other minerals such as feldspars and mafics, grain size varies dramatically due to quartz infilling pore space around pre-existing minerals - Alteration: Sericite veins penetrate through crystals but do no pervasive alteration Hornblende (5%) - Size: 1-3 mm - Strongly pleochroic from forest green to tan, subhedral, displays good 120-60O amphibole cleavage, commonly associated with biotite as intergrowths or in contact, rarely in contact with sphene   - Alteration: Commonly altered to biotite along edges, rarely rims are poorly oxidized Biotite (5%) - Size: 1-4 mm - Pleochroic from dark brown to tan-yellow, subhedral, mostly grow in interstitial space of grain boundaries between quartz and feldspars, very commonly oxides are found as inclusions or in contact with biotite grains, some relict hornblendes which retain parallelogram habit have been altered to sub-millimeter aggregates of biotite - Alteration: Rarely chloritized     79  Accessory Minerals:  Sphene (1%) - Euhedral, diamond rhomb habit, sub millimeter up to 1 mm, occur mostly as inclusions within feldspars or in contact with hornblendes Oxides (x) –  - Anhedral, opaque, always in contact or proximal to hornblende or biotite grains, more rarely form inclusions within biotite or hornblende   Rock Name: Leucocratic, biotite and hornblende-bearing granodiorite                                  80  15PS-087  Field Photos:    Potassium Feldspar Staining: Unstained  Stained      81  Thin Section Description: PPL  XPL   Texture:  Medium grained, porphyritic with phaneritic groundmass, moderately-foliated, non-vesicular, hypidiomorphic, holocrystalline, myrmekitic  Mineralogy:  Phenocrysts:  K-Feldspar (0% - Only present in hand sample)  Groundmass:  Plagioclase (40%) - Size: 1-4 mm - Clear, subhedral, elongate, commonly occur in clusters of grains displaying good polsynthetic twinning in perpendicular orientations, poorly zoned, penetrated by vermicular intergrowths of quartz along boundaries, rarely contain inclusions of sub-millimeter sphenes - Alteration: Minor sericitization localized in cores  K-feldspar (25%) - Size: 1-3 mm - Clear, subhedral, tabular, carlsbad twinning common and more rarely tartan twinning present - Alteration: Minor sericitization  Quartz (35%) - Size: 1-5 mm - Clear, anhedral, moderately undulose, myrmekite texture displayed by vermicular intergrowth of quartz along the rims of some plagioclase crystals which are also commonly found in contact with K-feldspar - Alteration: None.  Biotite (5%) - Size: 1-2 mm - Pleochroic beige to dark brown, anhedral to subhedral, elongate, inclusions of sub-millimeter amorphous oxides, quartz and sphene, larger sphenes penetrate into biotite grains, birds eye extinction present in some grains - Alteration: Minorly chloritized and/or oxidized along cleavage plane     82  Accessory Minerals:  Sphene (2%) – Clear, euhedral 1-2 mm diamond crystals, commonly in contact with oxides or oxidized biotite, simple twins common, oxides commonly penetrate fracture planes  Oxides (1%) – Opaque, sub-millimeter to 1 mm, anhedral, only found as inclusions or in contact with biotite and/or sphene   Rock Name: Leucocratic, biotite-bearing potassium-feldspar phyric monzogranite                                   83  15PS-089  Field Photos:    Potassium Feldspar Staining: Unstained  Stained      84  Thin Section Description: PPL  XPL   Texture:  Medium to coarse-grained, porphyritic with phaneritic groundmass, minorly foliated, non-vesicular, hypidiomorphic, holocrystalline   Mineralogy:  Plagioclase (53%) - Size: 2-5 mm - Clear, subhedral, concentrically zoned, good polysynthetic twinning, rarely cored by K-feldspar which displays perthitic exsolution lamellae similar to phenocrysts - Alteration: Disseminated sericite found within most cores - Plagioclase composition is Oligoclase based on average extinction angle of 5 euhedral grains – 11O Range: 9-14 K-Feldspar Phenocrysts (15%) - Size: 5-12 mm - Clear, subhedral to euhedral, very pronounced perthitic exsolution lamellae is found in all phenocrysts, sub-mm plagioclase phenocrysts displaying good polysynthetic twinning are commonly found as inclusions near the edges of K-spar phenocrysts, along grain boundaries plagioclase often penetrates into phenocrysts, phenocrysts are well aligned, very rarely displays carlsbad twins - Alteration: Very minor sericitization Quartz (25%) - Size:2-4 mm - Clear, anhedral, aggregates of fine sub-mm crystals form larger “grains”, infill between pore space of other well-formed minerals, poor undulatory extinction - Alteration: None. Hornblende (5%) - Size: 1-4 mm - Moderately pleochroic beige to dark forest green, subhedral to anhedral, simple twinning common, displays good amphibole cleavage, commonly contain inclusions of round-anhedral sub-millimeter sphenes, amorphous oxides commonly found in contact - Alteration: Strong pervasive oxidation – dark brown along rims and cleavage planes, poorly chloritized Chlorite (2%) - Size: 1-2 mm - Strongly pleochroic light to dark forest green, subhedral, inclined extinction, grain boundaries are irregular, pronounced cleavage in one directon, abundant sub-mm inclusions of sphene crystals, possibly alteration products of relict biotite crystals - Alteration: Slightly oxidized along rims of larger grains.   85  Accessory Minerals:  Sphene (<<1%) – Clear, anhedral to euhedral, diamond habit, found as sub-mm inclusions within most minerals present  Epidote (<<1%) – Pleochroic clear to pale-yellow, anhedral, sub-mm, found as inclusion within a plagioclase crystal, close to the plagioclase grain-boundary, follows orientation of twinning plane  Oxides (<<1%) – Opaque, isotropic, anhedral, associated with chlorite and hornblende either as inclusions or in contact, sub-millimeter  Rock Name: Weakly chloritized, potassium-feldspar phyric hornblende granodiorite                                  86  15PS-090  Field Photos:    Potassium Feldspar Staining: Unstained  Stained        87   Thin Section Description: PPL  XPL   Texture:  Medium to coarse-grained, porphyritic with phaneritic groundmass, non-foliated, non-vesicular, glomerophyric, panidiomorphic  Mineralogy:  Phenocrysts:  K-Feldspar (15%) - Size: 1-2 cm - Alteration: Minor sericite - Clear, subhedral, glomerophyric, no preferred orientation, poikilitic with sub-millimeter biotite-altered hornblende, contact with groundmass is hummocky indicating instability & is often penetrated by flame-like structures of quartz, good carlsbad twinning visible in thin section & hand sample  Groundmass:  Plagioclase (60%) - Size: 2-5 mm - Alteration: Minor sericite alteration within cores of concentrically zoned crystals - Clear, subhedral to euhedral, no preferred orientation, found as inclusions and/or exsolved laths within large K-feldspar phenocrysts, sometimes concentrically zoned with perpendicular directions of polysynthetic twinning, zoning inhibits accurate analysis of anorthite percentage via Michael-Levy method Quartz (20%) - Size: 2-6 mm - Alteration: None. - Translucent, anhedral clusters which form macroscopic crystals, moderate to strong undulatory extinction, finer crystals are usually found along the rims of biotite grains Biotite (5%) - Size: 1-3 mm clusters of sub-mm grains - Alteration: Ultra-fine cryptocrystalline aggregate may be altered to sericite, Or may be biotite altered hornblende? - Subhedral, pleochroic clear-yellow to brown, larger grains contain very fine sub-mm gas-filled cavities which are clear in PPL and isotropic in XPL, occur in clusters of sub-mm biotite grains which are inter-grown together in no preferred orientation, clusters often contain cryptocrystalline aggregate of ultra-fine grained anhedral biotite. Larger aggregates may be alteration remnants of pre-existing hornblende crystals.   Accessory Minerals:  88  Garnet: - Colorless, euhedral, equant hexagonal habit, isotropic, found as poikiocrysts within or in contact with biotite Oxides - Anhedral, locally associated with biotite/relict hornblendes, occasionally as inclusions within K-feldspar phenocrysts  Rock Name: Biotite-bearing potassium-feldspar phyric granodiorite  89  15PS-092  Field Photos:    Potassium Feldspar Staining: Unstained  Stained   Thin Section Description: PPL  XPL    90   Texture:  Medium to coarse-grained, equigranular, phaneritic, non-foliated, non-vesicular, panidiomorphic, holocrystalline  Mineralogy:  Plagioclase (55%) - Size: 2-5 mm - Alteration: Minor sericitization - Clear, sub-millimeter subhedral perthitic exsolutes found only within larger K-feldspar grains, polysynthetic twinning is hindered by overprinting of tartan twins, primarily found along the edges of concentrically zoned K-feldspars  K-feldspar (13%) - Size: 3-6 mm - Alteration: None - Clear, subhedral to euhedral tabular grains commonly displaying perthitic exsolution laminae, concentric zoning occurs in majority of grains which is more rarely coupled with tartan twinning  Quartz (25%) - Size: 1-4 mm, although they occur in clusters which are usually 4-7 mm - Alteration: None - Translucent, anhedral to euhedral (smaller grains more often anhedral, larger are euhedral), commonly occurs as sub-millimeter scale aggregate clusters surrounding biotite or hornblende, larger grains also form clusters that compose regions of pure quartz up usually 4-7 mm  Biotite (8%) - Size: 2-6 mm - Alteration: Larger grains un-altered, smaller grains vary from minor to complete chloritization - Pleochroic clear-yellow to dark brown, generally subhedral with exception to finer sub-millimeter scale elongate euhedral grains grown in the cores of larger grains, <1 mm sphene is commonly found as inclusions or in contact along the edges, contacts with surrounding minerals most commonly fine aggregate of clustered quartz crystals  Hornblende (2%) - Size: 1-2 mm - Alteration: Edges altered to biotite?  - Strongly pleochroic yellow to dark green, anhedral to subhedral with occasional sub-millimeter scale euhedral grains, good 60-120O amphibole cleavage, inclusions of amorphous oxides common and sub-millimeter biotite grains scattered along edges, usually in contact with quartz with very fine sub-millimeter aggregate of quartz crystals around edges  Accesory Minerals:  Sphene (2%) - Up to 1mm, euhedral diamond-shaped crystals, very high relief, almost always in contact with oxides  Oxides (1%) - Up to 0.5mm, anhedral blebs which primarily form the cores to sphenes, always proximally close and/or in contact with chlorite or biotite   Rock Name: Leucocratic biotite-bearing granodiorite    91  15PS-124 Field Photos:    Potassium Feldspar Staining: Unstained  Stained          92   Thin Section Description: PPL  XPL   Texture:  Medium-grained, equigranular, weakly foliated, non-vesicular, panidiomorphic, holocrystalline Mineralogy: Plagioclase - Size: 2-5mm - Alteration: Highly sericitized (up to 90% of grains), un-altered grains commonly found as poikocrysts within large (6-7 mm) anhedral quartz crystals - ***(Observations on un-altered plagioclase were all conducted on poikocrysts within quartz) - Clear, euhedral, elongate, moderate concentric zoning, display good polysynthetic twinning, average extinction angle based on 5 crystals – 23O, Andesine based on Michael-Levy method  Quartz  - Size: 2-4mm (rarely up to 7mm) - Alteration: none - Translucent, anhedral, rarely undulose, rarely display simple twins, some regions are poikilitic with unaltered plagioclase  Hornblende (15%) - Size: 3-5mm - Alteration: None - Strongly pleochroic from dark green to light-green/beige, subhedral to euhedral commonly in diamond habit, inclusions of fine (<1mm) anhedral mineral with high birefringence (completely overprinted with sericite) also contains inclusions of amorphous oxides (<1-2mm) and euhedral biotite, good ~60-120O cleavage  Biotite (5%) - Size: 1-4mm - Strongly pleochroic from colorless to brown, subhedral to euhedral, larger grains commonly contain inclusions of euhedral plagioclase, or conversely found as <1mm euhedral inclusions within hornblende, subhedral sericitized plagioclase rarely is grown into euhedral biotite crystals. Found in contact with plagioclase, quartz, and hornblende, as well as isolated within a medium-grained quartz groundmass.  Rock Name: Heavily sericitized, biotite-bearing hornblende granodiorite   93  15PS-128 No field photos taken. Potassium Feldspar Staining: Unstained  Stained   Thin Section Description: PPL   XPL   Texture:  Medium to coarse-grained, porphyritic, moderately foliated, non-vesicular, hypidiomorphic, holocrystalline, mylonitic Mineralogy: Plagioclase (50%) - Size: 4-6mm - Alteration: Pervasive sericitic alteration in >90% of grains  94  - Least altered crystals are found as perthitic textures which contain 1-2mm clear plagioclase found within large (8-10 mm) K-feldspar phenocrysts. These are white to off-white, subhedral, elongate and display good polysynthetic twinning. - Commonly found in contact with hornblende although pervasive alteration of both minerals limits observations of grain-boundary relationships  K-Feldspar Phenocrysts (20%) - Size: 8-10 mm - Alteration: <<1mm sericite veining is common although alteration is mainly limited to perthitic plagioclase - Clear to off-white, augen/lens shaped, anhedral, aligned with other K-Feldspar phenocrysts and hornblende crystals, commonly displays perthitic exsolution of plagioclase and inclusions of sub-millimetre amorphous quartz and euhedral sphene  Quartz (10%) - Size: 2-4 mm - Alteration: None - Translucent, anhedral, found in clusters which are aligned with long axis of K-feldspar phenocrysts, also found as sub-millimetre scale inclusions within K-feldspar or along phenocrysts boundaries as myrmekite  Hornblende (19%) - Heavily altered to actinolite and epidote  Accessory Minerals: Sphene (1%) – High relief, euhedral, occurs as sub-millimeter scale inclusions often found in K-feldspar and more rarely hornblende Magnetite – Amorphous   Rock Name: Potassium-feldspar phyric hornblende quartz-monzonite proto-mylonite                    95  15PS-130  Field Photos:    Potassium Feldspar Staining: Unstained  Stained     96  Thin Section Description: PPL  XPL    Texture:  Medium to coarse-grained, equigranular, phaneritic, non-foliated, non-vesicular, panidiomorphic, holocrystalline  Mineralogy:  Plagioclase (35%) - Size: 2-4 mm - Alteration: None - Clear, subhedral to euhedral, grains mostly display good polysynthetic twinning, crystals which are not inclusions are concentrically zoned, found as sub-millimeter scale inclusions within K-feldspar and more rarely hornblende, average extinction angle based on 5 euhedral crystals – 7O, Albite based on Michael-Levy method K-Feldspar (35%) - Size: 4-6 mm - Alteration: Rarely sericitized along grain boundaries - Clear, anhedral to subhedral, tartan and carlsbad twinning common, larger grains (6-8 mm) contain inclusions of sub-millimeter biotite and plagioclase, contact with biotite is usually made up by fine aggregate of chloritized biotite grains, often displays undulose extinction Quartz (15%) - Size: 2-4 mm - Alteration: None - Translucent, anhedral to subhedral, rarely undulose, usually occur as clusters infilling void space of other euhedral crystals Hornblende (10%) - Size: 2-5 mm but up to 1 cm - Alteration: Very rarely rims are oxidized - Moderately pleochroic pale to dark green, dominantly euhedral rhombus and diamond shaped habit, sub-millimeter scale grains are occasionally found in undulating contact with biotite (comagmatic?), contain sub-millimeter inclusions of sphene, displays good 60-120O amphibole cleavage, almost all oxides present are found as inclusions or associated with hornblende crystals Biotite (5%) - Size: 2-5 mm - Alteration:  - Outer edges of chlorite sometimes altered to green mineral with blue birefringence - Strongly pleochroic beige to dark brown, subhedral to euhedral equant laths/squares often intergrown with hornblende, also often found in contact with oxides although crystals can be found in contact with all minerals present in section. Outer edges of the grains are slightly chloritized   97   Accessory Minerals: Sphene (1%) – Euhedral, diamond/rhombus habit, found primarily as inclusions within hornblende Oxides – Anhedral to euhedral, square/cubic habit, almost solely found in contact or within hornblende  Rock Name: Biotite-bearing hornblende monzogranite                                       98    15PS-132  Field Photos:    Potassium Feldspar Staining: Unstained  Stained   Thin Section Description: PPL XPL  99     Texture:  Medium grained, equigranular, non-folated, non-vesicular, panidiomorphic, holocrystalline  Mineralogy:  Plagioclase (55%) - Size: 2-4 mm - Clear, anhedral to subhedral, elongate, poor polysynthetic twinning, commonly intergrown with hornblende, no zoning present - Plagioclase composition could not be determined due to lack of good polysynthetic twinning - Alteration: None.  Quartz (10%) - Size: sub-mm to 2 mm - Clear, anhedral to subhedral, poorly undulose, often occur as aggregates of finer grains that are only 1-2 mm and infill void space between other minerals, inclusions of hornblende or biotite common - Alteration: None.  Hornblende (30%) - Size: 1-4 mm - Pleochroic light green to beige-clear, anhedral to subhedral, poor amphibole cleavage in euhedral grains, oxides are present as inclusions and appear as localized/mottled clusters - Alteration: Most grains are in contact with actinolite – a possible alteration product.  Actinolite (5%) - Size: 1-2 mm - Very poorly pleochroic from lighter to darker shades of green, anhedral, form fine aggregates of grains exhibiting acicular habit around and/or in contact with hornblende - Alteration: Possible alteration product.  Accessory Minerals:  Oxides (<<1%) Sparse, opaque, anhedral, sub-mm to 1 mm, found as inclusions or along contacts of hornblende – most commonly as mottled/localized clusters  Rock Name: Melanocratic, actinolite-bearing hornblende granodiorite   100  Appendix 2: Sample Location/Descriptions Table                  101  Appendix 3: ImageJ Modal Abundance Calculations                102   Appendix 4: Whole Rock Geochemical Data                 103    104              105            106  Appendix 5: U-Pb CA-TIMS Data Table  107  Appendix 6: U-Pb LA-ICP-MS Data Tables   15PS-032 108      109  15PS-044    110   111  15PS-123    112   113  Appendix 7: SEM-Plagioclase-HBL Compositions for Geothermobarometry     HBL compositions for 15PS-002, 15PS-130, 15PS-071    114        115   Plag compositions for 15PS-002, 15PS-130, 15PS-071    116       

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