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Convergent margin Ni-Cu-PGE deposits : geology, geochronology, and geochemistry of the Giant Mascot magmatic… Manor, Matthew John 2014

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CONVERGENT MARGIN NI-CU-PGE DEPOSITS: GEOLOGY, GEOCHRONOLOGY, AND GEOCHEMISTRY OF THE GIANT MASCOT MAGMATIC SULPHIDE DEPOSIT, HOPE, BRITISH COLUMBIAbyMATTHEW JOHN MANORB.Sc., The University of Minnesota Duluth, 2012A THESIS SUBMITTED IN PARTIAL FULFILLMENT OFTHE REQUIREMENTS FOR THE DEGREE OFMASTER OF SCIENCEinTHE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES(Geological Sciences)THE UNIVERSITY OF BRITISH COLUMBIA(Vancouver)December 2014© Matthew John Manor, 2014iiAbstractThe Giant Mascot Ni-Cu-PGE deposit remains British Columbia’s only past-producing nickel mine (1958-1974) with ~4.2 Mt of ore grading 0.77% Ni, 0.34% Cu, minor Co, Ag, and Au, and unreported platinum group elements (PGE).  The deposit is  part of a new class of ‘convergent margin’ Ni-Cu-PGE sulphide deposits containing orthopyroxene and magmatic hornblende. The ultramafic-mafic intrusions that host these deposits have relatively small footprints, generally less than ~10 km 2 (e.g., Portneuf-Mauricie Domain, Québec; Huangshandong, China; Aguablanca, Spain), and they are becoming increasingly important economic resources globally. Zircon was successfully separated from feldspathic ultramafic rocks and yield a weighted 206 Pb/ 238 U age of crystallization for the Giant Mascot ultramafic intrusion of ca. 93 Ma (CA-TIMS, n=8), thus constraining the age of mineralization and distinguishing it as one of the world’s youngest Ni deposits. The Giant Mascot intrusion is a crudely elliptical, 4×3 km plug composed of ultramafic arc cumulates (olivine-orthopyroxene, hornblende-clinopyroxene ) that intruded the Late Cretaceous Spuzzum pluton. Sub-vertical pipe-like, lensoid and tabular bodies (n=28) host orthomagmatic Ni-Cu-PGE mineralization as disseminated, net-textured, semi-massive, and massive ores consisting of pyrrhotite, pentlandite, chalcopyrite, minor pyrite, troilite, and Pt-Pd-Ni bismuthotellurides. The sulphides have high tenors (3-14 wt% Ni, 0.1-17.1 wt% Cu, 84 ppb-5 ppm total PGE) and distinct iridium-group PGE concentrations that represent varying stages of monosulphide solid solution fractionation and subsequent metal enrichment of two magma types forming the Western and Eastern mineralized zones. Sulphur isotopes (n=34) for sulphides in ultramafic rocks reveal δ 34 S values (-3.4 to -1.3‰) lighter than typical mantle values and overlap with analyses from locally pyritiferous Settler schist (-5.4 to -1.2‰). Sulphide saturation in the Giant Mascot parental magma(s) was triggered in response to 1) reduction of an oxidized, mantle-derived arc magma, 2) addition of external sulphur and silica by assimilation of Settler schist and Spuzzum diorites, and 4) fractional crystallization. The presence of high-tenor sulphides indicates that orogenic Ni-Cu-PGE deposits may be of greater significance to future exploration globally than previously assumed.iiiPrefaceThis thesis was designed and funded as a project under Natural Resources Canada through the Geological Survey of Canada’s Targeted Geosciences Initiative 4 (TGI-4: 2011-2015) Magmatic-Hydrothermal Nickel-Copper-PGE-Chrome Ore System Project. All of the work presented in this thesis was collected, prepared, and presented by the author, M.J. Manor, under the supervision of Drs. J.S. Scoates (UBC), G.T. Nixon (British Columbia Geological Survey, Victoria), and D.E. Ames (Geological Survey of Canada, Ottawa). These supervisory authors were involved throughout the project in data collection, concept formation, and extensive manuscript edits. Dr. D. Weis (UBC) was the external supervisor and also contributed to manuscript edits.Chapter 1 contains a global compilation of orogenic Ni deposits that was compiled and prepared by myself with the appropriate sources cited in both the Table 1.1 and the references section. I produced Table 1.3, which is modified from Christopher and Robinson (1975) and Pinsent (2002). Chapter 2 comprises work from this thesis with the exception of Figures 2.7.1A and 2.7.2B, which are based on samples collected by coauthor G.T. Nixon in 2003 and 2011. All field mapping and rock descriptions are a combination of work from Aho (1954), Vining (1977), and an Open File map published as part of this project with both the GSC and BCGS [Manor, M.J., Wall, C.J., Nixon, G.T., Scoates, J.S., Pinsent, R.H., and Ames, D.E., 2014b, Preliminary geology and geochemistry of the Giant Mascot ultramafic-mafic intrusion, Hope, southwestern British Columbia; Geological Survey of Canada, Open File 7570; British Columbia Ministry of Energy and Mines, Open File 2014-03; scale 1:10 000]. I was responsible for organization of the project and producing all GIS maps and associated data, and C.J. Wall was my primary field assistant for both geological mapping and sample collection. G.T. Nixon was the supervisor of the project and completed final cartographic work. J.S. Scoates and D.E. Ames were supervisory authors, and geochemical data was used directly from work of R.H. Pinsent.Chapter 3 utilizes new data collected and compiled by M.J. Manor, with aid of J.S. ivScoates, G.T. Nixon, and D.E. Ames. Relevant data from Muir (1971), R. Eckstrand (1971, unpublished), McLeod (1975), Hulbert (2001), and Pinsent (2002) were used and cited as necessary. Preliminary work from Chapter 3 was published in BCGS Fieldwork 2013 [Manor, M.J., Scoates, J.S., Nixon, G.T., and Ames, D.E., 2014a, Platinum-group mineralogy of the Giant Mascot Ni-Cu-PGE deposit, Hope, B.C., in Geological Fieldwork 2013: British Columbia Ministry of Energy and Mines, British Columbia Geological Survey Paper 2014-1, p. 141–156]. I was the primary author responsible for data collection, manuscript composition, and concept formation. J.S. Scoates, G.T. Nixon, and D.E. Ames were supervisory authors who were involved in concept formation and initial manuscript edits. L. Aspler, R.F.J. Scoates, and M. Houlé contributed to final manuscript edits prior to publication. Figures 3.4 and 3.5 were re-drafted by Tracy Barry (GSC, Ottawa) and myself from originals in Aho (1954), Clarke (1969), Muir (1971), and McLeod (1975).vTable of ContentsAbstract                                                                                                     iiPreface                                                                                                      iiiTable of Contents                                                                                            vList of Tables                                                                                               ixList of Figures                                                                                               xAcknowledgements                                                                                        xvDedication                                                                                                  xviChapter 1    Introduction to ‘Convergent Margin’ Ni-Cu-PGE Deposits and the Giant Mascot Ni-Cu Mine, Southwestern British Columbia                                                             11 1  Introduction                                                                                        11.2.	 Classification	of	‘Convergent	Margin’	Ni-Cu-PGE	Deposits                                                    51 3  Giant Mascot Mine and Exploration History                                                    71 4  Previous Studies of the Giant Mascot Ni-Cu-PGE Deposit                                    131 5  Overview of the Thesis                                                                           17Chapter 2   Dating a Young Magmatic Ni-Cu-PGE Sulphide Ore Deposit in a Convergent Margin	Setting:	Geochronology	of	the	Giant	Mascot	Ultramafic	Intrusion,	Southwestern	British	Columbia                                                                                                   192 1  Introduction                                                                                       192 2  Geologic Background                                                                             212 3  Previous Work                                                                                     272 4  Sample Descriptions and Analytical Methods                                                  282 4 1  U-Pb zircon geochronology samples                                                         282 4 2  U-Pb zircon geochronology analytical methods                                            292 4 3  Scanning electron microscope imaging                                                      302 4 4  Laser ablation ICP-MS analysis of zircon                                                  342 4 5  40Ar/39Ar hornblende/biotite geochronology                                                34vi2 5  Results                                                                                              462 5 1  Growth zoning and internal structure of zircon                                           462 5 2  Ti-in-zircon thermometry                                                                   502 5 3  Chemical abrasion ID-TIMS zircon geochronology                                        522.5.3.1.  Pyroxenite   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 522.5.3.2.  Hornblende pyroxenite  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 552.5.3.3.  Hornblendite  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 552.5.3.4.  Spuzzum diorite   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 562.5.3.5.  Spuzzum quartz diorite  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 562 5 4  Laser ablation-ICP-MS zircon geochronology                                              582.5.4.1.  Plešovice and Temora 2 zircon standards   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 582.5.4.2. Giant Mascot ultramafic suite  . . . . . . . . . . . . . . . . . . . . . . . . . . . . 582.5.4.3.  Spuzzum pluton diorites  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 592 5 5  40Ar/39Ar biotite-hornblende geochronology                                                622.5.5.1.  Mylonite  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 622.5.5.2. Mafic enclaves in Spuzzum quartz diorite  . . . . . . . . . . . . . . . . . . . . . . 662 6  Discussion                                                                                          662 6 1  Age of the Giant Mascot intrusion and associated Ni-Cu-PGE ores                      662.6.2.	 Tectonic	significance	for	the	age	of	the	Giant	Mascot	intrusion                           692 7  Conclusions                                                                                       72Chapter 3    Origin of the ‘Convergent Margin’ Giant Mascot Ni-Cu-PGE Deposit, Southwestern British Columbia                                                                                          753 1  Introduction                                                                                       753 2  Geological Setting                                                                                 763 3  Geology of the Giant Mascot Ni-Cu-PGE Deposit                                             803 4  Giant Mascot Orebodies                                                                         843 5  Analytical Methods                                                                                90vii3 5 1  Scanning electron microscopy                                                               903 5 2  Electron microbeam analyses                                                               913 5 3  Sulphur isotopes                                                                              923 5 4  Chalcophile, platinum group element, and sulphur analyses                              933 5 5  Calculation procedure for whole-rock Ni, Cu, and PGE analyses to 100% sulphide   943 6  Results                                                                                              953 6 1  Ni-Cu-PGE sulphide mineralization                                                        953 6 2  Sulphide and platinum group element geochemistry                                    1043 6 3  Sulphur isotope geochemistry                                                              1143 6 4  Olivine compositions                                                                        1143 7  Discussion                                                                                        1233 7 1  Crystallization of sulphide liquid and late magmatic desulphurization                 1233 7 2  Formation of platinum group minerals (PGM)                                          1273 7 3  Metal enrichment in sulphide liquid at Giant Mascot                                    1283.7.4.	 Significance	of	nickel	contents	in	olivine                                                   1323 7 5  Mechanisms for sulphide saturation of the Giant Mascot Ni-Cu-PGE deposit         1343 8  Conclusions                                                                                      137Chapter 4    Summary and Conclusions                                                                1394 1  Summary of the Thesis and Key Findings                                                      1394 2  Directions for Future Work                                                                       1434.2.1.	 Petrogenesis	of	the	Giant	Mascot	ultramafic	suite	and	geometry	of	the	orebodies      1454 2 2  Mantle source conditions and crustal contamination                                     1464.2.3.	 Tectonic	significance	for	orogenic	Ni-Cu-PGE	deposits	in	British	Columbia           146References                                                                                                 150Appendices                                                                                               176Appendix A   List of Samples, Locations, and Analytical Techniques Used for Rocks from the Giant Mascot Ni-Cu-PGE Deposit, Spuzzum pluton, and Settler schist                                     176viiiAppendix B   Scans of Petrographic Thin Sections of Rocks from the Giant Mascot Ni-Cu-PGE Deposit, Spuzzum pluton, and Settler schist                                                           191Appendix	C.		Laser	Ablation	ICP-MS	Analyses	of	Zircon	from	the	Giant	Mascot	Ultramafic	Intrusive Suite and Spuzzum pluton: Spot Locations, Zircon Standards, and Trace Element Concentrations                                                                                           229Appendix D   Ti-in-zircon Thermometry Calculations                                                259Appendix E   Olivine Petrography and Locations of EMPA Spots                                   264Appendix F   Whole Rock Chalcophile and Platinum Group Element Analyses for Sulphide-Rich Rocks from the Giant Mascot Ni-Cu-PGE Deposit                                                    288Appendix G   Calculations for Base Metals and Platinum Group Elements in 100% Sulphide                                                                                                   293Appendix H   Modal Abundances, Petrography, and Sulphide and Platinum Group Mineral Chemistry of Select Sulphide-Rich Rocks from the Giant Mascot Ni-Cu-PGE Deposit            300Appendix I   Major and Trace Element Geochemistry for Whole Rock Samples and Duplicates from	the	Giant	Mascot	Ultramafic	Intrusion,	Spuzzum	pluton,	and	Settler	schist	                 346Appendix J   Field Trip Guide to the Giant Mascot Ni-Cu-PGE Deposit, Hope, B C               363ixList of TablesTable 1 1  Global compilation of orthopyroxene-bearing convergent margin Ni-Cu-PGE deposits  . . . 3Table 1 2  Giant Mascot mine and exploration history  . . . . . . . . . . . . . . . . . . . . . . . . . . 8Table 1 3  Summary of orebodies in the Giant Mascot Ni-Cu-PGE deposit  . . . . . . . . . . . . . . 14Table 2 1  U-Th-Pb analytical results for zircon from the Giant Mascot ultramafic intrusion and Spuzzum pluton   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 31Table 2 2  LA-ICP-MS instrumentation, operating conditions and quantification  . . . . . . . . . . . 36Table 2 3  U-Th-Pb laser ablation ICP-MS analytical results for zircon from the Giant Mascot   ultramafic intrusion and Spuzzum pluton  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 37Table 2 4  40Ar/ 39 Ar analytical results for hornblende and biotite from the Giant Mascot ultramafic intrusion and Spuzzum pluton  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42Table 2 5  Summary of 40Ar/ 39 Ar plateau and inverse isochron ages for the Giant Mascot ultramafic intrusion and Spuzzum pluton  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45Table 3 1  Mineralogy of Ni-Cu-PGE sulphides, Giant Mascot deposit, Hope, B.C.  . . . . . . . . . . 98Table 3 2  Representative base metal sulphide compositions from electron microprobe analysis,   Giant Mascot Ni-Cu-PGE deposit  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101Table 3 3  Whole rock chalcophile and platinum group element analyses for sulphide-rich rocks   from the Giant Mascot Ni-Cu-PGE deposit  . . . . . . . . . . . . . . . . . . . . . . . . 108Table 3 4  Sulphur isotope analyses from the Giant Mascot Ni-Cu-PGE deposit and associated   rocks  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115Table 3 5  Representative olivine compositions by EMPA for mineralized and unmineralized   lithologies in the Giant Mascot Ni-Cu-PGE deposit  . . . . . . . . . . . . . . . . . . . . 117Table 3 6  Chalcophile and platinum group element tenors in the Giant Mascot Ni-Cu-PGE   deposit  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129xList of FiguresFigure 1 1  World map (Mercator projection) showing the global distribution of ‘convergent margin’ and other major Ni-Cu-PGE deposits/mining districts   .  .  .  .  .  .  .  .  .  .  .  .  .  . 2Figure 1 2  Nickel grade (wt%) vs. ore resource in million tonnes (Mt) for ‘convergent margin’ relative to major Ni-Cu-PGE deposits globally.   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6Figure 1 3  Archive photographs from Western Miner (Stephens, 1959) showing the main mill site at the Giant Mascot Ni-Cu mine in the early years of production  . . . . . . . . . . . . . 6Figure 1 4  Aerial photograph (Google Earth, 2010) of the Giant Mascot mine site showing major orebodies and tunnels (projected to surface), adit entrances, dump locations, and access roads to the main mine site from Highway 1.   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10Figure 1 5  Photographs showing the current state of mining infrastructure at Giant Mascot. .  . . . 11Figure 1 6  Photographs showing fieldwork undertaken for this thesis in the summers of 2012 and 2013  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Figure 2 1  Geological terranes and major faults of the North American Cordillera in British Columbia and southeastern Alaska.  . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Figure 2 2  Geology of the Harrison Lake region showing the location of the Giant Mascot ultramafic intrusion and associated Ni-Cu-PGE deposit  . . . . . . . . . . . . . . . . . 23Figure 2 3  Simplified geologic map of the Giant Mascot ultramafic intrusion showing sample locations for U-Pb zircon (Zr) and 40Ar/ 39 Ar biotite (Bt) and hornblende (Hbl) geochronology.  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Figure 2 4  Photographs illustrating the relative age relationships between rocks from the Giant Mascot ultramafic intrusive suite and Spuzzum pluton.  . . . . . . . . . . . . . . . . . 26Figure 2 5  Photomicrographs in transmitted light of zircon populations selected for U-Pb geochronology samples   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 47Figure 2 6  Cathodoluminescence images of individual zircon grains from samples of the Giant Mascot ultramafic intrusion and Spuzzum pluton analyzed by U-Pb TIMS and laser ablation ICP-MS  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 48xiFigure 2 7  Backscatter (BSE) and secondary electron (SE) images of representative zircon grains from a hornblendite (13MMA-2-7-1).   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 49Figure 2 8  Ti and Hf concentrations (ppm) in zircon from the Giant Mascot ultramafic intrusion and Spuzzum pluton                                                                                51Figure 2 9  Plot of Th vs. U concentrations (ppm) in individual zircon grains from the Giant Mascot ultramafic suite and Spuzzum pluton measured by CA-ID-TIMS.  . . . . . . . 53Figure 2 10  Concordia diagrams showing CA-ID-TIMS U-Pb geochronological results for zircon from ultramafic rocks in the Giant Mascot ultramafic intrusion. . . . . . . . . . . . . . 54Figure 2 11  Concordia diagrams showing CA-ID-TIMS geochronological results for zircon from Spuzzum pluton diorites   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 57Figure 2 12  Concordia diagrams showing LA-ICP-MS geochronological results for zircon from ultramafic rocks in the Giant Mascot ultramafic intrusion  . . . . . . . . . . . . . . . . 60Figure 2 13  Concordia diagrams showing LA-ICP-MS geochronological results for zircon from Spuzzum pluton diorites.  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61Figure 2 14  40Ar/ 39 Ar hornblende inverse isochron diagrams for two mylonitized pegmatitic hornblendites (samples 11GNX-1-2-1 and 11GNX-1-2-2)  . . . . . . . . . . . . . . . . 63Figure 2 15  40Ar/ 39 Ar hornblende and biotite inverse isochron diagrams for ultramafic enclaves (sample 12MMA-2-1-2) in the Spuzzum pluton  . . . . . . . . . . . . . . . . . . . . . 64Figure 2 16  Summary of 40Ar/ 39 Ar results from the Giant Mascot ultramafic intrusion and Spuzzum pluton, compared to the age range (including 2σ error) of U-Pb zircon analyses.  . . . . 65Figure 2 17  U-Pb zircon CA-ID-TIMS geochronology summary for ages of the Giant Mascot ultramafic intrusion and Spuzzum pluton.  . . . . . . . . . . . . . . . . . . . . . . . . 68Figure 2 18  U-Pb zircon LA-ICP-MS geochronology summary for ages of the Giant Mascot ultramafic intrusion and Spuzzum pluton.  . . . . . . . . . . . . . . . . . . . . . . . . 70Figure 2 19  Simplified geologic map of the Yalakom-Fraser-Straight Creek fault system in southwestern British Columbia and northern Washington showing the age relationship between intrusive and metamorphic rock suites across the 49 th parallel.  . . . . . . . . . 73xiiFigure 3 1  Geology of the Harrison Lake region showing the location of the Giant Mascot ultramafic intrusion and associated Ni-Cu-PGE deposit  . . . . . . . . . . . . . . . . . 77Figure 3 2  Geologic map of the Giant Mascot ultramafic intrusion with orebodies and mine tunnels projected to surface.   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79Figure 3 3  Representative photomicrographs of the lithological units in the Giant Mascot intrusive suite and host rocks  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81Figure 3 4  Photomicrographs of representative silicate textures present in the Giant Mascot ultramafic intrusive suite  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82Figure 3 5  North-looking longitudinal (west-east) section of the entire Giant Mascot deposit, distinguishing orebodies of the western mineralized zone (WMZ) from those in the eastern mineralized zone (EMZ).   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 85Figure 3 6  Detailed cross sections and plans of orebodies in the western mineralized zone (WMZ), Giant Mascot deposit.   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 86Figure 3 7  Detailed cross sections and plans of orebodies in the central and eastern mineralized zones (EMZ)   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 88Figure 3 8  Principal ore types of mineralization in the Giant Mascot intrusive suite.   .  .  .  .  .  .  . 96Figure 3 9  Photomicrographs and backscatter electron (BSE) images of sulphide textures in the Giant Mascot intrusion  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100Figure 3 10  Ternary compositions of Fe-, Ni-, and S-bearing base metal sulphides in the Giant Mascot Ni-Cu-PGE deposit. .  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103Figure 3 11  Photomicrographs and backscatter electron (BSE) images of platinum-group and precious-metal minerals in Giant Mascot ores  . . . . . . . . . . . . . . . . . . . . . 105Figure 3 12  Compositions of platinum, palladium, and nickel-bearing tellurides and their host minerals at Giant Mascot.   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  106Figure 3 13  Base metal contents and platinum group element concentrations in sulphide-rich whole rock samples from the Giant Mascot Ni-Cu-PGE deposit.   .  .  .  .  .  .  .  .  .  .  .  .  .  .  109Figure 3 14  Platinum group element concentrations in sulphide-rich whole rock samples from the xiiiGiant Mascot Ni-Cu-PGE deposit.  . . . . . . . . . . . . . . . . . . . . . . . . . . . 110Figure 3 15  Cu/Pd vs. Pd for whole rocks in the Giant Mascot Ni-Cu-PGE deposit.   .  .  .  .  .  .  .  111Figure 3 16  Primitive mantle-normalized diagrams displaying abundances of Ni, Cu, and PGE for orebodies in the Giant Mascot Ni-Cu-PGE deposit   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  112Figure 3 17  Primitive mantle-normalized diagrams displaying abundances of Ni, Cu, and PGE in 100% sulphide for mineralization zones and sulphide textures in the Giant Mascot Ni-Cu-PGE deposit.   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  113Figure 3 18  Sulphur isotope compositions from sulphide-rich rocks in the Giant Mascot Ni-Cu-PGE deposit.  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116Figure 3 19  Plot of forsterite content (mol%) vs. nickel concentrations (ppm) in olivine for mineralized and barren dunite, peridotite, and pyroxenite rocks in the Giant Mascot intrusion.  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122Figure 3 20  Schematic paragenetic sequence for sulphide and silicate crystallization and post-ore remobilization, Giant Mascot Ni-Cu-PGE deposit.  . . . . . . . . . . . . . . . . . . . 124Figure 3 21  Backscatter election images (BSE) and photomicrographs of desulphurization textures in Giant Mascot ores. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126Figure 3 22  Plot of palladium vs. iridium concentrations (ppb) for sulphide ores in the Giant Mascot intrusion recalculated to 100% sulphide.  . . . . . . . . . . . . . . . . . . . . . . . . 131Figure 3 23  Plot of olivine-sulphide liquid Fe-Ni exchange coefficients (KDFe-Ni) vs. Ni concentrations (wt%) in 100% sulphide showing the oxidation state of Giant Mascot ores. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136Figure 4 1  Schematic model for the tectonic development of the southern Coast Plutonic Complex during the Early to Late Cretaceous.  . . . . . . . . . . . . . . . . . . . . . . . . . . 141Figure 4 2  Geologic map of the Giant Mascot ultramafic intrusion with orebodies and mine tunnels projected to surface, and CA-TIMS U-Pb zircon geochronology results for Giant Mascot ultramafic rocks and Spuzzum diorites  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  144Figure 4 3  Geology of the Harrison Lake region showing the location of the Giant Mascot xivultramafic intrusion and associated Ni-Cu-PGE deposit. . . . . . . . . . . . . . . . . 147Figure 4 4  Schematic model of the vertical crustal section through the Harrison Lake region of the southern Coast Plutonic Complex. .   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  148Figure C 1  U-Pb concordia diagrams for LA-ICP-MS analysis of the Plešovice and Temora 2 zircon standards . .   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  236Figure H 1  Atomic metal/S ratios for pyrrhotite EMPA analyses of pyrrhotite from the Giant Mascot Ni-Cu-PGE deposit. .  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340Figure I 1  MgO vs. select major and trace element variation diagrams for Giant Mascot ultramafic rocks and Spuzzum diorites  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355Figure I 2  A) N-MORB-normalized trace element concentrations for Giant Mascot ultramafic, Spuzzum pluton, and Settler schist rocks. B) Chondrite-normalized rare earth element concentrations for samples in the Giant Mascot ultramafic suite . . . . . . . . . . . . 356Figure J 1  Aerial photograph (Google Earth) of the Giant Mascot mine site showing major orebodies and tunnels (projected to surface), adit entrances, dump locations, and access roads to the main mine site from Highway 1  . . . . . . . . . . . . . . . . . . . . . . 365Figure J 2  Simplified geology of the Giant Mascot ultramafic intrusion   . . . . . . . . . . . . . 366Figure J 3  Photographs showing field relations of host rocks to the Giant Mascot ultramafic intrusion from Stops 1 and 2 and the Giant Mascot mine site from Stop 3   .  .  .  .  .  .  368Figure J 4  Photographs showing field relations of ultramafic rocks in the Giant Mascot ultramafic intrusion from Stops 4, 5, 6, and 7.  . . . . . . . . . . . . . . . . . . . . . . . . . . . 370xvAcknowledgementsTo think about the wealth of knowledge, organization, and support it has taken to finish this degree in two years is overwhelming. I must first and foremost acknowledge my academic advisors, Drs. James Scoates (UBC) and Graham Nixon (BCGS-Victoria), for their guidance, patience, and constant feedback for the duration of this project, and incredible training both in the field and with many difficult research problems. Specific expertise in nickel ore systems from Dr. Doreen Ames (GSC-Ottawa) is also much appreciated along with planning for fieldwork and other logistical endeavors, handled with the financial assistance of Angèle Miron. Thanks also to Dr. Dominique Weis for help interpreting geochemical data. Field seasons in both 2012 and 2013 would not have been possible without the assistance of Corey Wall, Wes Harmon, Lauren Harrison, and Alex Colyer. Logistics for travel to and from Giant Mascot were made possible only with the help and safe flying from Valley Helicopters in Hope, B.C., and access privileges to the mine from Barrick Gold Co. and the Fraser Valley Dirt Rider’s Association. Many thanks go to Rich Friedman, Janet Gabites, Hailin, Yeena Feng, Marg Amini, Vivian Lai, and Bruno Kieffer for preparatory lab work and U-Pb and 40Ar/ 39 Ar sample analyses, and Dr. Mati Raudsepp, Edith Czech, Elisabetta Pani, Jenny Lai, and Lan Kato (UBC) and Patricia Hunt (GSC-Ottawa) for training and guidance with SEM and EMPA analyses, and Ingrid Kjarsgaard (Ottawa) for petrographic and EMPA work on sulphides and PGM. Corey Wall and Dr. Emily Mullen are acknowledged for worthwhile discussions and guidance at every point during this thesis. Also to Dr. Jon Scoates for providing his invaluable expertise on details of magmatic ore deposits. To Sarah Jackson-Brown, Lauren Harrison, Anaïs Fourny, Tom Ver Hoeve, and Marina Martindale, thanks for providing a fun work environment over the past few years; and Luke Busta and Erica Whalen, thanks for many backcountry adventures to clear my mind. This project was funded by Natural Resources Canada as part of the Geological Survey of Canada’s Targeted Geosciences Initiative 4 (TGI-4) Magmatic-Hydrothermal Nickel-Copper-Platinum Group Element-Chromium program. Additional funds were supplied by a SEG-Canada Foundation Graduate Student Research Grant awarded to Matthew Manor in 2013.xviDedicationTo my parents You may not understand why I enjoy studying rocks (or even what a sulphide is!), but your support through this arduous chapter of my life means the world to me.1Chapter 1Introduction to ‘Convergent Margin’ Ni-Cu-PGE Deposits and the Giant Mascot Ni-Cu Mine, Southwestern British Columbia1 1  IntroductionMagmatic sulphide deposits associated with ultramafic-mafic rocks are host to the world’s most significant resources of nickel, copper, and platinum group elements. Exploration over the past century has focused predominantly on mineralization associated with komatiites (e.g., Mt. Keith, Kambalda, Perseverance, Raglan), rift-related magmatism (e.g., Noril’sk, Duluth, Eagle, Muskox, Voisey’s Bay, Pechenga, Jinchuan), and impact melts (Sudbury) (Fig. 1.1), with relatively little emphasis on convergent margin settings. Conventionally, subduction-zone environments are considered poor targets for nickel-copper-platinum group element (Ni-Cu-PGE) sulphide mineralization due to the relative paucity of ultramafic bodies with economic Ni-sulphides (Ripley, 2010). Although PGE mineralization in convergent margin settings is associated with Ural-Alaskan-type intrusions, which are ultramafic bodies devoid of orthopyroxene, their prospectivity with respect to Ni-sulphides remains unclear (Nixon et al., 1997; Ripley, 2010). Nonetheless, Ni-Cu-PGE deposits in orogenic settings hosted by ultramafic-mafic rocks containing orthopyroxene as an essential mineral are becoming an increasingly important resource or exploration target (e.g., Aguablanca, Spain; Portneuf-Mauricie Domain, Québec; Americano do Brasil and Limoeiro, Brazil) (Figs. 1.1, 1.2; Table 1.1 and references therein).This study focuses on the Giant Mascot ultramafic intrusion and associated Ni-Cu-PGE mineralization near Hope, southwestern British Columbia. The Late Cretaceous Giant Mascot intrusion (ca. 93 Ma) is composed of olivine-orthopyroxene cumulates that intruded the Spuzzum pluton (ca. 95 Ma) and Upper Triassic Settler schist during a period of arc magmatism. Concentrations of nickel-sulphide mineralization permitted mining from 1958-1974 that 2XWXWXWXWXWXWXWXW XWXWXW XWXXWXWXWXXXW XXW0 50 10025Kilometers0°0°60°E60°N30°N30°S120°E120°N0°60°N30°N30°S120°W 60°W0° 60°E 120°E60°WGiant MascotPortneuf-Mauricie Domain Quebec City3 214PMDThompsonRaglanVoisey’s BaySudburyPechenga Noril’skJinchuanMt. KeithPerseveranceKambaldaDuluth13 12268469710 5111524251823212019,221716zonedConvergent margin Ni depositslayeredno internal structureFigure 1.1100 kmNFigure 1.1. World map (Mercator projection) showing the global distribution of ‘convergent margin’ (diamonds) and other major (red circles) Ni-Cu-PGE deposits/mining districts. Numbers and diamond colours correspond to deposits and deposit types listed in Table 1.1, respectively. Refer to Sappin et al. (2011) for detailed geology of the Portneuf-Mauricie Domain (PMD) in the inset figure.3Table 1.1. Global compilation of orthopyroxene-bearing convergent margin Ni-Cu-PGE depositsGrade (wt.%)No. on map 1 Deposit Geologic location Orogen AgeIntrusion size 2Intrusion type 3 Host rocks to mineralization 4 Resource5 Ni Cu ReferenceSW British Columbia, Canada1 Giant Mascot Spuzzum plutonCanadian CordilleraLate Cretaceous (ca. 93 Ma)< 4 km 2 zoned dunite/lherzolite/harzburgite 4.2 Mt 0.77 0.34 This studySW Spain2 Aguablanca Santa Olalla Igneous Complex VariscanCarboniferous (ca. 341 Ma)< 10 km 2 zonedpyroxenite (minor peridotite and mafics)31 Mt 0.66 0.46Tornos et al. (2001, 2004); Piña et al. (2006, 2008, 2011, 2013)3 Tejadillas Cortegana Igneous Complex VariscanCarboniferous (ca. 336 Ma)< 1.5 km 2 zoned harzburgite/gabbronorite prospect 0.16 0.08 Piña et al. (2012)Québec, Canada4Lac à la Vase (Rousseau)Portneuf-Mauricie Domain GrenvilleMesoproterozoic (ca. 1.4 Ga)< 6 km 2 zoned ol-websterite/opxite/mafics prospectSappin et al. (2009, 2011, 2012)5 Lac Nadeau Portneuf-Mauricie Domain Grenville < 6 km 2 zoned ol-websterite/opxite/mafics prospect6 Réservoir Blanc Portneuf-Mauricie Domain Grenville unknown NIS websterite/opxite/mafics prospect7 Lac Matte Portneuf-Mauricie Domain Grenville 1 km 2 NIS ol-websterite/opxite/mafics prospect8 Lac Kennedy Portneuf-Mauricie Domain Grenville 1 x 0.5 km layered ol-websterite/opxite/mafics prospect9 Boivin Portneuf-Mauricie Domain Grenville 160 x 70 m NIS websterite/opxite/mafics prospect10 Rochette West Portneuf-Mauricie Domain Grenville 150 m 2 NIS websterite/opxite/mafics prospect11 Lac Édouard Portneuf-Mauricie Domain Grenville < 300 m 2 layered ol-websterite/opxite/mafics 69,000 t Poirier (1988)Norway12 Espedalen Espedalen complex CaledonianMesoproterozoic (ca. 1.5 Ga)layered peridotite/pyroxenite/norite 50,000 t 0.37 0.16 Corfu and Heim (2013)Scotland13 Huntly-Knock Grampian region Caledonian Ordovician < 40 km 2 layered peridotite/ol-gabbro/norite 3 Mt 0.52 0.27Fletcher et al. (1989); Gunn and Shaw (1992); McKervey et al. (2007)New Brunswick14 Mechanic Avalon Terrane CaledonianNeoproterozoic (ca. 550 Ma)< 8 km 2 layered lherzolite/gabbronorite unknownPaktunc (1990); Gramma -tikopoulos et al. (1995)1 Numbers correspond to those in Figure 1.2; 2 Intrusion size approximate; 3  NIS=no internal structure; 4 ol=olivine, opxite=orthopyroxenite, qtz=quartz, hbl=hornblende; 5  Mt=million metric tonnes; t=metric tonnes4Table 1.1. (cont.) Global compilation of orthopyroxene-bearing convergent margin Ni-Cu-PGE depositsGrade (wt.%)No. on map 1 Deposit Geologic location Orogen AgeIntrusion size 2Intrusion type 3 Host rocks to mineralization 4 Resource5 Ni Cu ReferenceFinland15 Stormi (Vammala) Vammala Nickel Belt Svecofennian Paleoproterozoic (ca. 1.9 Ga)< 1.5 km 2 layered dunite/peridotite/pyroxenite 6.4 Mt 0.71 0.44Häkli et al. (1979); Papunen and Gorbunov (1985); Peltonen (1995a); Makkonen (2005)16 Kotalahti Kotalahti Intrusion Svecofennian Paleoproterozoic (ca. 1.9 Ga)< 1.5 km 2 zoned lherzolite/harzburgite/dunite 12.5 Mt 0.66 0.26Papunen and Koskinen (1985)China17 Kalatongke North Xinjiang Central Asian Permian 5 x 1 km zoned ol-norite/norite/diorite 33 Mt 0.8 1.3 Gao et al. (2012)18 Hongqiling No. 7North Xinjiang; Hulan FormationCentral Asian Permian < 100 m 2 layered opxite/harzburgite 245,000 t 2.31 0.63 Wei et al. (2013)19 Huangshandong North Xinjiang Central AsianPermian (ca. 274 Ma)< 3.5 km 2 layeredol-websterite/lherzolite/ol-gabbro50 Mt 0.52 0.27Gao et al. (2013); Mao et al. (2014)20 Poshi Pobei complex Central AsianPermian (ca. 274 Ma)< 2 km 2 zoned websterite/peridotite 14.7 Mt 0.3-0.6Xia et al. (2013); Mao et al. (2014)21 Poyi Pobei complex Central AsianPermian (ca. 278 Ma)3 x 1 km zoneddunite/lherzolite/ol-websterite1.6 Mt 0.5 Xia et al. (2013)22 XiangshanzhongNorth Xinjiang; Xiangshan intrusionCentral Asian Permian 2.5 x 0.5 km layeredlherzolite/ol-websterite/gabbro80,000 t 0.5 0.3 Tang et al. (2013)23 Erbutu Baoyingtu Group Central AsianPermian (ca. 294 Ma)< 200 m 2 layered ol-opxite/opxite 1 Mt <0.2 Peng et al. (2013)24 Lengshuiqing Yanbian Group Panxi arcNeoproterozoic (ca. 810 Ma)< 1 km 2 NISdunite/peridotite/ol-pyroxenite210,000 t 0.92 0.31 Munteanu et al. (2012)Japan25 HoromanOpirarukaomappu Gabbroic ComplexKuril arcTertiary (ca. 35 Ma)< 10 km 2 unknown gabbronorite/hbl gabbro unknownHonma (1997); Tomkins et al. (2012)Brazil26Americano do BrasilAmericano do Brasil Complex (Tocantins Province)Brasiliano/Pan-African Neoproterozoic (ca. 626 Ma)12 x 3 km layeredS1: websterite/gabbronorite; S2: dunite/wehrlite; G2: lherzolite/websterite3.1 Mt 1.12 1.02 Mota-e-Silva et al. (2011)1 Numbers correspond to those in Figure 1.2; 2 Intrusion size approximate; 3  NIS=no internal structure; 4 ol=olivine, opxite=orthopyroxenite, qtz=quartz, hbl=hornblende; 5  Mt=million metric tonnes; t=metric tonnes5produced approximately 4.2 Mt of ore with average grades of 0.77% Ni, 0.34% Cu, and minor Co, Au, and Ag (Christopher and Robinson, 1975). The Giant Mascot Ni-Cu-PGE deposit has been the site of numerous scientific studies and exploration programs, however important questions remain pertaining to the age of the ultramafic suite, extent of PGE mineralization, mechanism(s) responsible for the generation of magmatic sulphides, and geologic and geochemical characteristics of convergent margin Ni-Cu-PGE deposits. The focus of this thesis is to address fundamental ore-forming characteristics of convergent margin Ni-Cu-PGE deposits from the perspective of the Giant Mascot deposit to aid in future exploration for similar deposits in the Canadian Cordillera and other orogenic belts in Canada. 1 2  Classification	of	‘Convergent	Margin’	Ni-Cu-PGE	DepositsNickel deposits in convergent margin settings were recently classified as NC-7 (where NC = nickel-copper), encompassing Ural-Alaskan-type intrusions (e.g., Duke Island, Turnagain, Salt Chuck), and NC-5, which contains miscellaneous deposits associated with picritic to tholeiitic magmas not necessarily restricted to convergent margins (e.g., Giant Mascot, Råna, Moxie; Naldrett, 2010, 2011). Ural-Alaskan-type intrusions are ultramafic intrusions typically characterized by discontinuous, concentrically zoned intrusions of olivine-clinopyroxene cumulates in the core grading to peripheral feldspathic or hornblende-rich differentiates (Taylor, 1967). Alaskan-type intrusions are also characteristically devoid of orthopyroxene and base metal sulphide mineralization (Irvine, 1974). Platinum group element mineralization in Alaskan-type intrusions is predominantly hosted by PGE-rich chromitite seams and their respective placer deposits (Nixon et al., 1990; Johan, 2002). Ni-Cu-PGE mineralization has been observed in a limited number of occurrences that exhibit common petrologic features of Alaskan-type intrusions  (e.g., Turnagain, northwestern B.C., Nixon, 1998; Scheel et al., 2009; Duke Island, southeastern Alaska, Irvine, 1974; Thakurta et al., 2014). Ultramafic cumulates (dunite, peridotite, pyroxenite, hornblende pyroxenite, hornblendite) that contain abundant orthopyroxene and magmatic hornblende host Ni-Cu-PGE 6100 Mt Ni10 Mt Ni1 Mt Ni0.1 Mt Ni0.01 Mt Ni0.001 Mt NiGiant Mascot4.2 (0.77)Noril’sk1300 (1.77)Mt. Keith478 (0.60)Sudbury1648 (1.20)Jinchuan515 (1.06)Pechenga339 (1.18)Duluth4400 (0.20)Aguablanca 31 (0.66)121315 161718192021222324 26Ni grade (wt%)0.1110Ore resource (Mt)Figure 1.210.10.01 10 100 1000 10000Thompson150 (2.32)Kambalda67 (2.90)Perseverance52 (1.90)Raglan33 (2.72)Voisey’s Bay137 (1.59)Convergent margin Ni depositszonedlayeredno internal structureFigure 1.2. Nickel grade (wt%) vs. ore resource in million tonnes (Mt) for ‘convergent margin’ (diamonds) relative to major (red circles) Ni-Cu-PGE deposits globally (modified from Naldrett, 2011). Diagonal grey lines represent the Ni metal resource. Deposit tonnage (Mt) and wt% Ni grade (in brackets) are shown. Numbers and diamond colours on convergent margin deposit symbols correspond to deposits and deposit types in Table 1.1, respectively. Note axes are logarithmic.Figure 1.3A BFigure 1.3.  Archive photographs from Western Miner (Stephens, 1959) showing the main mill site at the Giant Mascot Ni-Cu mine in the early years of production. A) Primary crusher (centre) and secondary crusher (left), viewing to the south. B) Main mill site, viewing to the northwest.7mineralization in the Giant Mascot intrusion. A global compilation of ‘convergent margin’ Ni deposits (n=26) with similar characteristics (e.g., mineralogy, structure) shows deposits in the Central Asian Orogenic Belt (China), Portneuf-Mauricie Domain (Québec), and Iberian Massif (SW Spain) to be most similar to the Giant Mascot Ni-Cu-PGE deposit (Table 1.1, and references therein; Fig. 1.1). To characterize the deposits as ‘convergent margin’, petrographic studies must have identified the key mineralogical components of each intrusion, as well as the tectonic setting. Each deposit is classified as a product of arc magmatism in a specific subduction zone ranging from Paleoproterozoic to Tertiary in age. These ultramafic intrusions hosting Ni-Cu±PGE mineralization contain olivine-orthopyroxene cumulates with primary hornblende and footprints (i.e., areal exposures) generally less than 10 km 2 (ranging from 0.1 to 40 km 2). Similar to Ural-Alaskan-type intrusions, these convergent margin deposits can be layered, zoned, or contain no internal structure, and may also contain marginal hornblende or feldspathic differentiates (e.g., hornblende-bearing gabbronorite). Metal resources for mineralized intrusions range from 50,000 tonnes to 50 million tonnes and contain grades of 0.16 to 2.3 wt.% Ni and 0.08 to 1.3 wt.% Cu (n=16; Table 1.1; Fig. 1.2).Given the global abundance of convergent margin Ni deposits (n~26) with similar characteristics to the Giant Mascot intrusion (i.e., orthopyroxene + magmatic hornblende) and the increasing economic importance of these deposits, an updated classification is warranted. It is herein proposed that the current NC-7 class (Naldrett, 2010, 2011) be restructured to include all ‘convergent margin’ intrusions as two distinct sub-classes: A) Ural-Alaskan-type intrusions (e.g., Turnagain) containing PGE±Ni-Cu mineralization, and B) orthopyroxene-bearing ultramafic-mafic intrusions (e.g., Giant Mascot) that contain significant primary Ni-Cu±PGE mineralization.1 3  Giant Mascot Mine and Exploration HistoryNickel showings in the area were first discovered in 1923, and by 1937 diamond drilling had defined the major orebodies (Table 1.2). After a hiatus during and after World War II, exploration resumed in 1951, and the mine went into production in 1958 (Fig. 1.3). The deposit 8Table 1.2. Giant Mascot mine and exploration historyDate Activity Owner1923 Nickel showings first discovered at Pride of Emory by Carl Zofka1927-1933 Surface exploration B.C. Nickel Company1933 Underground development began B.C. Nickel Mines Limited3550 (No. 1 tunnel) and 3275 (No. 2 or Chinaman tunnel) developed1937 1.2 Mt of ore mined at 1.38% Ni and 0.50% CuProperty closed down - all drill core lost1938-1952 Property idle due to poor market conditions and World War II Pacific Nickel Mines Limited1951 Exploration programs resumedPulse survey conducted by Newmont Exploration, Co.Electromagnetic and magnetometer surveys conducted by McPhar Geophysics1952 Pacific Nickel Mines Limited and Newmont Mining Corporation of Canada mergeWestern Nickel Mines Limited2600 (main haulage), 2950, and 3250 levels developed; levels connected with internal inclined shaft1958 Mining beganJuly 1958: Closed due to market conditions1959Newmont Mining Corporation sold property interest to Giant Mascot Mines LimitedGiant Mascot Mines Limited opened mine as salvage operation1961Giant Mascot Mines Limited purchased Pacific Nickel Mines Limited and gained full controlGiant Mascot Mines Limited1968 November: mine closed due to collapse of a Brunswick stope1970 August: mine closed due to mill burning down1958-1974 Mine production4.2 Mt of ore mined at 0.77% Ni, 0.34% Cu, minor Co, Ag, Au1980 Ownership of mine transferred to Mascot Gold Mines Limited Mascot Gold Mines Limited1986 Exploration programs resumed with a focus on Au and PGE mineralization1988 Mascot Gold Mines Limited was acquired by International Corona CorporationInternational Corona CorporationExploration continued (results not released to the public)1992 Homestake Canada Limited acquired International Corona Corporation Homestake Canada LimitedBegan reclamation of the Giant Mascot Mine, sealed portals, groomed dumps, and seeded tailings2001 Filled a glory hole exposing the Pride of Emory and Brunswick deposits2001December: Final acquistion of Homestake Canada Limited by Barrick Gold CorporationBarrick Gold Corporation2001-present Reclamation of the Giant Mascot Mine by Barrick Gold Corporation9was mined for nickel and copper from 1958 to 1974 by open-stope methods, and produced approximately 4.2 Mt of ore with average grades of 0.77% Ni and 0.34% Cu along with minor Co, Ag and Au (Christopher, 1974; Christopher and Robinson, 1975). Platinum group element abundances in the ores of the Giant Mascot deposit were uncertain or unreported (Pinsent, 2002; Nixon, 2003). Metcalfe et al. (2002) reported “platinum values in excess of 1 gram”, although a specific source was not cited. Hulbert (2001) reported PGE analyses for six samples, but without geologic constraints or mineralogical information.The Giant Mascot deposit consists of 28 steeply dipping orebodies manifested as lensoid, pipe-like, and atypical tabular profiles, located along a west-east mineralized corridor (Table 1.3). Twenty-two of these were mined, including five major contributors to production: Pride of Emory, Brunswick #2 and #5, 4600, and 1500 – they average 22 metres wide by 47 metres long, extending vertically ~205 metres (Christopher and Robinson, 1975; Table 1.3). Mine workings and portals to the underground stopes are located north of Texas Creek on the southern slope of Zofka Ridge (Fig. 1.4).Since production ceased in 1974, exploration programs were conducted by Mascot Gold Mines Limited and International Corona Corporation to assess the economic viability of platinum group elements in ores at the mine site and tailings pile. In 1992, Homestake Canada Limited initiated reclamation on the former mine workings and adits. Presently, there is little mine infrastructure remaining (Figs. 1.6A-C). Portal adits were collapsed (Fig. 1.5D) and mine dumps have been contained and reworked since reclamation began (Figs. 1.5E, F). The roads to the mine are kept clear of brush by Fraser Valley Dirt Rider’s Association (FVDRA), who have been granted access by the current owners, Barrick Gold Corporation. However, only hiking and dirt biking is allowed due to unstable ground on the northern slopes of Texas Creek (Fig. 1.6F). Roads north of the mine are overgrown with alder trees, making certain roads impassable and other areas are only accessible efficiently by helicopter (Figs. 1.6A-C). In this study, mapping and sampling excursions were conducted by members of the Department of Earth, Ocean and Atmospheric Sciences (UBC) and the British Columbia Geological Survey, where work involved 10N1 kmMILL SITEFVDRA campsiteBC Nickel Mine RdEntry gatePride of EmoryBrunswick3550 East PortalDolly AditEmory Creek Road1Figure 1.4Z O F K A  R I D GEFigure 1.4. Aerial photograph (Google Earth, 2010) of the Giant Mascot mine site showing major orebodies and tunnels (projected to surface), adit entrances, dump locations, and access roads to the main mine site from Highway 1. The solid line is a driveable road and dashed line is a walking trail beginning at the entry gate. FVDRA=Fraser Valley Dirt Rider’s Association.11Figure 1.5A BDFECFigure 1.5.  Photographs showing the current state of mining infrastructure at Giant Mascot. A) Aerial photograph of the main mine site. B) Old mine buildings. C) Primary crusher and mine dump. D) Mill site underground portal entrance, collapsed during reclamation. E) Mine dump at the 3550 East Portal. F) Pride of Emory deposit, i.e., ‘Glory Hole’ (back), and Brunswick deposits (foreground).12A BDF GECFigure 1.6Figure 1.6.  Photographs showing fieldwork undertaken for this thesis in the summers of 2012 and 2013. A) A road north of the mine, overgrown with alder trees. B) Helicopter taking off from a drop at the 3550 East Portal dump, August 2012. C) A wet morning atop a ridge south of the mine site made for excellent views of Zofka Ridge, June 2013. D) Field crew from UBC and BCGS, August 2012. E) Mapping along the flanks of Texas Creek with relatively high water levels, June 2013. F) Landslide scar along the main access road from the FVDRA campsite destroyed the former roadbed. G) One of many waterfalls at Giant Mascot and the locality for one of nine geochronology samples (12MMA-2-4-1).13bushwhacking and technical footing on riverbeds, steep slopes, and wet flora (Figs. 1.6D-G). 1 4  Previous Studies of the Giant Mascot Ni-Cu-PGE DepositThe geological history of the Giant Mascot intrusion and associated sulphide mineralization has been debated since exploration began in 1923. Early studies by Cairnes (1924), Cockfield and Walker (1933), and Horwood (1936, 1937) first defined mineralization on the surface and later began to outline underground orebodies both spatially and petrographically. Field observations from these authors led to divergent proposals for ore formation as either magmatic or hydrothermal. Aho (1954, 1956) conducted a comprehensive geological and chemical study of the Giant Mascot ultramafic intrusion and associated nickel-copper mineralization. He interpreted the petrogenesis of the deposits to involve 1) magmatic segregation and ensuing injection of molten sulphides (i.e., magmatic injection); 2) deposition of sulphides from ascending water vapour (>650°C) and the reaction of orthopyroxene to olivine or the inverse (i.e., hydrothermal replacement); or 3) a form of both.Later studies near the end of the mine life included an assessment by Clarke (1969) indicating that the orebodies were structurally controlled along four observed fault trends. Another report released at mine closing contained a detailed overview of orebodies with size, grades, and mineralization and alteration styles (Table 1.3; Christopher, 1974; Christopher and Robinson, 1975). Detailed petrological and geochemical investigations were also undertaken as M.Sc. theses on the 4600 orebody by Muir (1971) and on the Climax and Chinaman orebodies by McLeod (1975). Earlier proposals advocating a hydrothermal origin were dismissed based on results from these latter two studies.The new millennium saw additional interest in the Giant Mascot area by the British Columbia Geological Survey with an investigation of platinum group element mineralization in the Harrison Lake-Cogburn Creek region by Pinsent (2002) who reported platinum group element concentrations in the ores of Giant Mascot and other sulphide showings. He concluded that the sulphides are magmatic in origin and that sulphide saturation and olivine fractionation 14Table 1.3.  Summary of orebodies in the Giant Mascot Ni-Cu-PGE depositDimensions (m) GradeOrebodyLocation within mineralized trendLength WidthVertical heightTons (x10 3 )Orebody shapeMineralization type 1Orientation of orebody 2Ni (wt%)Cu (wt%)Ni/Cu Host rocks Alteration and weatheringPride of Emory West 45.7 18.3 266.8 704pipe-like lensesM 320/53 1.46 0.38 3.84 dunite to orthopyroxenite talc in hornblende pyroxeniteBrunswick 1 West 33.5 18.3 160.1 123 pipe-like lens M 340/75 1.1 0.35 3.14dunite core to harzburgite to barren orthopyroxeniteBrunswick 2 West 54.9 21.3 251.5 570 lenticular M-NT 330/56 1.4 0.6 2.33 harzburgite actinolite in hanging wallBrunswick 2A West 33.5 21.3 106.7 290 lenticular M-NT 320/72 0.98 0.35 2.8 harzburgite actinolite in hanging wallBrunswick 2G West 21.3 19.8 91.5 131 lenticular M-NT 315/77 0.56 0.27 2.07 harzburgite actinolite in hanging wallBrunswick 5 West 36.6 21.3 182.9 409 elliptical pipe M 030/77 1.49 0.5 2.98dunite core to harzburgite to barren orthopyroxenitecrumbly duniteBrunswick 6 West 4.6 18.3 76.2 unknown lenticularBrunswick 7 West 27.4 15.2 61.0 23 M 330/68 2.37 0.75 3.16 orthopyroxenite crumbly duniteBrunswick 8 West 6.1 15.2 53.4 12 pipe-like lens M 020/79 1.75 0.61 2.86 orthopyroxeniteactinolite in hornblende pyrox -eniteBrunswick 9 West 6.1 12.2 unknown pipe-like lens MBrunswick 10 West 21.3 16.8 61.0 38 M 330/75 0.74 0.35 2.11 orthopyroxenite2663 West 15.2 18.3 99.1 102 pipe 320/68 0.86 0.32 2.69 peridotite core to barren pyroxenite crumbly peridotite; actinolite6800 West 15.2 15.2 91.5 47 tabular D 290/56 0.66 0.24 2.75 pyroxenite crumbly zone on 2950 level600 West 30.5 13.7 91.5 83 tabular 210/66 1.42 0.42 3.04 peridotite localized crumbling4600 Central 76.2 30.5 196.0 805 elliptical pipe M at contact 315/82 1.35 0.73 1.8olivine-barren core to olivine-rich rimactinolite in footwall; crumbling4400 Central 12.2 15.2 45.7 27 D 310/76 0.51 0.22 2.31 peridotite to pyroxenite crumbly and actinolite4300 Central 27.4 12.2 68.6 62 D 310/61 0.91 0.51 1.78 hornblende pyroxenite actinolite in fractures2200 Central 15.2 15.2 228.7 135 D 300/75 0.68 0.38 1.79 peridotite to barren pyroxenite1900 Central 15.2 24.4 91.5 45 pipe 300/63 0.86 0.45 1.91hornblende peridotite core to pyrox -enite to discontinuous hornblende pyroxenitetalc near footwall1800 Central 15.2 24.4 45.7 40 pipe 120/60 0.53 0.23 2.3 peridotite to pyroxenite talc1700 Central 3.7 3.7 15.2 1 2 dunite crumbly1600 Central 51.8 27.4 129.6 216 lenticular M 230/69 0.97 0.34 2.85dunite core to barren hornblende peridotitetalc and crumblyModified after Christopher and Robinson (1974)1 Orientations of pipe orebodies are reported as trend/plunge (tabular orebodies strike/dip) in right-hand rule notation2 M=massive and semi-massive, NT=net-textured, D-disseminated15Table 1.3. (cont.) Summary of orebodies in the Giant Mascot Ni-Cu-PGE depositDimensions (m) GradeOrebodyLocation within mineralized trendLength WidthVertical heightTons (x10 3 )Orebody shapeMineralization type 1Orientation of orebody 2Ni (wt%)Cu (wt%)Ni/Cu Host rocks Alteration and weathering1400 Central 15.2 18.3 142.7 53 310/65 0.71 0.32 2.21 peridotite to pyroxenite actinolite512 Central 9.1 15.2 68.6 28pipe and lenticular dikes225/75 1.08 0.41 2.63olivine pyroxenite shell to barren core (hornblende pyroxenite and hornblendite surround periphery)Portal zone East 189.0 2375 0.25 0.11 2.27peridotite ore, enclosed in hornblende pyroxenite2000 East 9.1 9.1 15.2 3 D-NT 315/80 1.33 0.33 4.031500 East 61.0 21.3 344.5 668 M-NT 030/55 1.37 0.45 3.04hornblende peridotite and hornblende pyroxenitecrumblyChinaman East 27.4 30.5 194.5 376 elliptical pipe D 300/68 0.73 0.3 2.43hornblende pyroxenite to barren peridotite coreactinolite-talc-magnetiteClimax East 15.2 27.4 182.3 211 cylindrical pipe D 330/63 0.78 0.36 2.16 peridotite to pyroxenite crumblyModified after Christopher and Robinson (1974)1 Orientations of pipe orebodies are reported as trend/plunge (tabular orebodies strike/dip) in right-hand rule notation2 M=massive and semi-massive, NT=net-textured, D-disseminated16were coeval. In contrast, Ash (2002) concluded that the Giant Mascot ultramafic suite represents the southernmost extension of an ophiolitic assemblage (Cogburn assemblage) mapped to the northwest and is now engulfed by the younger Spuzzum pluton. He further speculated that the Giant Mascot ores and coarse-grained hornblendite at the periphery of the ultramafic rocks were produced by metasomatic reaction between the ultramafic rocks and Spuzzum pluton. Subsequently, spinel compositions reported by Muir (1971) were re-examined by Nixon (2003), who proposed that the Giant Mascot ultramafic intrusion may be a remnant of the accreted Late Triassic flood basalt province of Wrangellia, similar to other known magmatic Ni-Cu-PGE sulphide deposits in the northern Cordillera (Hulbert, 1997). Taking a mineral deposit approach, Metcalfe et al. (2002) adopted an analogy with the Aguablanca Ni-Cu-PGE deposit in Spain, proposing that the Giant Mascot ultramafic suite originated via decompression melting of the mantle in a transpressional tectonic regime with subsequent emplacement of magmas at intermediate levels in the crust. Sulphide saturation was achieved by assimilation of sulphur-rich country rocks (i.e., Settler schist) resulting in the injection of pipe-like sulphide ore shoots and penecontemporaneous emplacement of felsic hybrid magmas (Spuzzum pluton). More recently as part of this study, the first platinum group minerals were identified and documented in the sulphide ores of Giant Mascot, and they are attributed to an orthomagmatic origin (Manor et al., 2014a; also see Chapter 3).The ages of rock units in the Giant Mascot intrusion and Spuzzum pluton have been a major topic of contention alongside the mode of ore formation. Earlier studies were inconclusive as to whether rocks of the Giant Mascot intrusion were younger (e.g., Cairnes, 1924; Aho, 1954; Aho, 1956; Muir, 1971; Vining, 1977) or older than the Spuzzum diorites (Cockfield and Walker, 1933; Horwood, 1936; McLeod, 1975; McLeod et al., 1976; Ash, 2002; Metcalfe et al., 2002). The first attempt at isotopic dating of the Giant Mascot intrusion used conventional K-Ar geochronology for hornblende-bearing rocks (95-119 Ma, n=4) and suggested an older age relative to the Spuzzum diorites (79-89 Ma, n=4; Mcleod, 1975; McLeod et al., 1976). Metcalfe et al. (2002) recalculated ages reported by McLeod (ibid.) using a modified decay constant of 17Steiger and Jäger (1977) and reported comparable age ranges for both the Giant Mascot (96-122 Ma, n=4) and Spuzzum intrusions (81-105 Ma, n=7), subsequently constraining the timing of metamorphism to 96-93 Ma.1 5  Overview of the ThesisThe main objectives of this study are 1) to determine the crystallization age of the ultramafic rocks that host magmatic sulphide mineralization, 2) to identify the mineralogical and chemical characteristics of sulphide and platinum group minerals, 3) to evaluate a suitable mechanism for sulphide saturation and formation of nickel sulphides, 4) to produce a comprehensive ore deposit model for Giant Mascot explaining the intrusion and mineralization history with respect to surrounding country rocks, and 5) to provide exploration criteria for convergent margin Ni-Cu-PGE deposits similar to Giant Mascot in the Canadian Cordillera and other convergent margin settings in Canada and elsewhere. Samples for this study were collected during the 2011, 2012, and 2013 field seasons, in addition to archival samples and data from Aho (1954, 1956), Muir (1971), Eckstrand (1971, unpublished), and Pinsent (2002), housed in collections of the British Columbia Geological Survey and Geological Survey of Canada. Chapter 2 focuses on U-Pb and 40Ar/ 39 Ar geochronology to constrain crystallization and cooling ages for both the Giant Mascot ultramafic intrusion and the Spuzzum pluton. During the 2012 and 2013 field seasons, the entire intrusion was re-mapped at a 1:10,000 scale (Manor et al., 2014b) to constrain the contact relationships. Zircon grains from ultramafic rocks and Spuzzum diorites were analyzed with modern chemical abrasion-ID-TIMS and laser ablation-ICP-MS geochronological techniques to accompany former K-Ar dating and address the geological relationships observed between rock suites. The cooling history of the deposit is also constrained by 40Ar/ 39 Ar geochronology for samples exhibiting significant inclusion and structural relationships with the Spuzzum pluton. Chapter 3 utilizes new results and archival data, along with findings from Chapter 2, to characterize the mineralogical, petrological, and chemical relationships between the Giant 18Mascot Ni-Cu-PGE deposit and its associated ultramafic rocks. This chapter documents the first detailed characterization of sulphide and platinum group minerals and the spatial variation and abundances of platinum group elements in Giant Mascot ores. Variations in sulphur isotopes, sulphide geochemistry, and olivine compositions provide insights into the nature and timing of sulphide saturation and metal upgrading processes and aid in constraining the initial compositions of the parental magma(s). Distinct characteristics of the ‘convergent margin’ Giant Mascot Ni-Cu-PGE deposit defined in this study can be utilized to explore for similar Ni deposits in the Canadian Cordillera and other orogenic belts in Canada. Chapter 4 summarizes the major conclusions of this thesis, avenues for future work, and the tectonic significance for Ni-Cu-PGE deposits in convergent margin environments.Lastly, the appendix contains supplementary data and figures, including: 1) list of samples, locations, and analytical techniques employed in this study; 2) petrographic thin section scans of the sample archive; 3) spot locations on zircon, standards, and trace element data for laser ablation ICP-MS work; 4) Ti-in-zircon thermometry calculations; 5) a comprehensive suite of olivine compositions, including unpublished archive analyses; 6) whole rock chalcophile and PGE analyses; 7) procedure and results for recalculation of geochemical data to 100% sulphide; 8) detailed petrography and sulphide chemistry; 9) whole rock and trace element geochemistry (Activation Laboratories); and 10) a field trip guide to the Giant Mascot Ni-Cu-PGE deposit and mine.19Chapter 2Dating a Young Magmatic Ni-Cu-PGE Sulphide Ore Deposit in a Convergent Margin	Setting:	Geochronology	of	the	Giant	Mascot	Ultramafic	Intrusion,	Southwestern British Columbia2 1  IntroductionDating ultramafic-mafic rocks that host nickel-copper-platinum group element (Ni-Cu-PGE) mineralization has been relatively limited due to the paucity of zircon compared to the dating of porphyry systems associated with intermediate to felsic rocks (e.g., Deckart et al., 2005; Allan et al., 2013; Hollings et al., 2013; Chelle-Michou et al., 2014). Precise geochronology, however, remains crucial in addressing knowledge gaps pertaining to the timing of mineralization in magmatic ore systems (e.g., Paces and Miller, 1993; Amelin et al., 1999; Kamo et al., 2003; Romeo et al., 2006; Scoates and Friedman, 2008; Mackie et al., 2009; Zhang et al., 2009; Scoates and Scoates, 2013). Advances in geochronology, including chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) U-Pb geochronology (Mattinson, 2005) coupled with implementation of the “EARTHTIME Initiative” to increase global collaboration and comparison between laboratories (Schmitz and Kuiper, 2013), now allows for high-precision dating of zircon with relative uncertainties as low as 0.02%. In situ techniques such as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), although less precise (~1%), provide high-spatial resolution that allows for age discrimination within and between zircon crystals and populations in single samples (e.g., Jackson et al., 2004; Gehrels et al., 2008; Schmitz and Kuiper, 2013; Schoene et al., 2013; Schoene, 2014).The host rocks to magmatic nickel deposits ranging in age from Archean to late Phanerozoic have been dated from a variety of tectonic settings (Naldrett, 2011). Deposits that currently dominate the global supply of nickel are typically high-tonnage and were emplaced 20in rift settings (e.g., Noril’sk, Duluth, Voisey’s Bay) or they are lower tonnage and higher-grade related to komatiitic magmas (e.g., Thompson, Perseverance, Kambalda; an exception being Mt. Keith; Ripley, 2010 and references therein). Conventionally, convergent margin environments are considered poor targets for Ni-Cu-PGE mineralization due to the apparent lack of ultramafic bodies containing economic Ni-sulphides (Ripley, 2010). Deposits in convergent margin settings (see Chapter 1, Table 1.1) are, however, becoming an increasingly important resource and attractive exploration target (e.g., Aguablanca, Spain, Piña et al., 2008; Portneuf-Mauricie Domain, Québec, Sappin et al., 2012; Huangshandong, China, Gao et al., 2013). Sulphide generation in supra-subduction zone environments is tied directly to magmatic conditions and processes (e.g., crystal fractionation, differentiation, assimilation) in crustal magma plumbing systems. Dating both ultramafic rocks with associated sulphide mineralization and their host rocks is key to understanding the mechanisms and tectonic setting responsible for sulphide generation in convergent margins.  The Giant Mascot Ni-Cu-PGE deposit remains British Columbia’s only past-producing nickel mine (1958-1974), having produced ~4.2 Mt of ore with an average grade of 0.77% Ni, 0.34% Cu, minor Co, Ag, and Au, and unreported PGE (Christopher and Robinson, 1975). In this chapter, the ages of ultramafic rocks that comprise the Giant Mascot intrusive suite and enveloping granitoid rocks of the Spuzzum pluton are determined using U-Pb geochronological techniques, specifically CA-ID-TIMS and LA-ICP-MS, and 40Ar/ 39 Ar geochronology. This integrated dating approach addresses the age and chemical relationship between intrusive units, regional metamorphism, effects of heating and crustal thickening from nearby younger intrusions, and examines regional correlations between the southern Coast Plutonic Complex and Northern Cascades of Washington State. The results of this study constrain the timing of magmatic events and ore formation and, to the best of our knowledge, establish Giant Mascot as the world’s youngest dated Ni-Cu-PGE deposit.212 2  Geologic BackgroundThe Giant Mascot ultramafic intrusion and associated Ni-Cu-PGE deposit lies at the southeastern margin of the Coast Plutonic Complex or Coast Mountains batholith, which extends for over 1800 km in the Northern Cordillera from southeastern Alaska to southwestern British Columbia and into the Northern Cascades in Washington State (Brown and McClelland, 2000; Reiners et al., 2002) (Fig. 2.1). The area is located east of Harrison Lake, approximately 12 km north of Hope, and is bounded by Harrison Lake to the west and the Fraser fault to the east (Fig. 2.1, 2.2). The Coast Plutonic Complex formed the locus of continental arc magmatism in the Northern Cordillera from the Jurassic to the Paleogene (170-45 Ma; Gehrels et al., 2009). Plutons and batholiths in the southern Coast Plutonic Complex are catazonal to epizonal, tonalitic to gabbroic intrusions that were emplaced in a magmatic arc setting during the Cretaceous (Fig. 2.2; 107-76 Ma; Richards, 1971; Brown and McClelland, 2000; Mitrovic, 2013). Metamorphic grade in the Harrison Lake area increases from greenschist in the southwest to amphibolite in the northeast where the Giant Mascot ultramafic suite and northern part of the Spuzzum pluton intruded the upper amphibolite Settler schist (Brown and Walker, 1993). Recent work demonstrates that peak metamorphic conditions (500-680°C and 6.5-10.3 kbar) occurred between 91 and 86 Ma in the northwestern Harrison Lake region in the vicinity of the Breckenridge pluton and enveloping Slollicum schist. (Fig. 2.2; Mitrovic, 2013).The rocks that host the Giant Mascot intrusion include the Late Cretaceous Spuzzum pluton and Upper Triassic Settler schist. The Spuzzum pluton is a compositionally zoned dioritic to tonalitic body that intrudes upper amphibolite metapelites of the Settler schist (Pigage, 1973; Richards and McTaggart, 1976; Vining, 1977; Gabites, 1985; Mitrovic, 2013) (Figs. 2.2, 2.3). The Giant Mascot ultramafic intrusion is a small crudely elliptical, 4×3 km body, consisting predominantly of dunite, peridotite (lehrzolite and harzburgite), pyroxenite (orthopyroxenite, websterite, and olivine websterite), hornblende pyroxenite, and hornblendite. The rocks are remarkably fresh, displaying primary igneous textures involving olivine, orthopyroxene, clinopyroxene, and hornblende, with minor biotite, plagioclase, and accessory rutile, apatite, and 22Vancouver58°N54°N50°N PacificOceanAlaskaYukonAlbertaUSASTCACCSMYTCCQNMTCDBRBRCKOKWRWRAXAXNAbNApHACache CreekWrangelliaAlexanderYukon-TananaStikiniaQuesnelliaCoast Plutonic ComplexNorth America (platform)MethowKootenayCadwalladerChilliwackBridge RiverHarrison LakeSlide MountainAXWRYTSTOkanaganOKQNHACDCKMTBRSMCCNAbNApCassiarCAInsularIntermontaneAncestral North AmericaTERRANESNMTeasternlimitofCordillerandeformationFigure 2.152°N54°N50°N124°W124°W132°W54°N0 100 200kilometresFigure 2.1. Geological terranes and major faults of the North American Cordillera in British Columbia and southeastern Alaska. Solid red outline in southwestern British Columbia indicates the Harrison Lake region and Giant Mascot study location. Map modified from Colpron and Nelson (2011).2349°45’N49°45’N49°30’N49°30’N121°30’W121°45’W121°30’W121°45’W122°W122°WGSLSLSLSESESESESECGCGUMHN5 kmFigure 2.2GSLSECGUMGambier GroupSlollicum schistSettler schistCogburn AssemblageUltramafic rocksH Harrison Lake GroupTerranesOphiolitic rocksSpuzzumGiant MascotHOPERiverFraserUrquhartFraserfaultHCHNSCCPLLACMMCCFCUSSMBCHBCunknownTertiary84-88 Ma89-96 Ma100-107 Ma154-156 MaIntrusive rocksCH - Chilliwack batholith MB - Mt. Barr batholith DP - Doctor’s Point pluton BC - Bear Creek pluton Scuzzy pluton Spuzzum pluton SC - Settler Creek pluton SS - Snowshoe pluton HN - Hornet Creek pluton CP - Cogburn pluton CC - Clear Creek pluton FC - Fir Creek pluton Breckenridge pluton AC - Ascent Creek plutonHC - Hut Creek plutonMM - Mt. Mason plutonGiant Mascot ultramafic- mafic intrusionUrquhart plutonLL - Lillooet plutonBS - Big Silver plutonCHDPCHBreckenridgeHarrison LakeScuzzyBSgeologic contactthrust faultfaultGiant Mascot Ni-Cu-PGE depositFigure 2.2. Geology of the Harrison Lake region showing the location of the Giant Mascot ultramafic intrusion and associated Ni-Cu-PGE deposit. The patterns for intrusive rocks indicate Late Cretaceous plutons that are coloured according to crystallization age (geology modified from Gabites, 1985; Monger, 1989; Brown et al., 2000; and Mitrovic, 2013).24zircon. Ni-Cu-PGE sulphide mineralization is present in 28 steeply plunging, pipe-like or lensoid bodies and also include several steeply dipping tabular bodies (Christopher and Robinson, 1975).Olivine-rich cumulates form the core of the zoned ultramafic intrusion with magmatic sulphide ores predominantly restricted to dunite, peridotite, and pyroxenite (Figs. 2.3, 2.4D; Manor et al. 2014b). Discrete dunite pods are present as relatively rare inclusions in peridotite, and pyroxenites commonly enclose sub-rounded peridotite clasts (Fig. 2.4C). Hornblende pyroxenite commonly forms centimeter-scale veins with sharp contacts in the pyroxenite and is the most extensive map unit in the Giant Mascot intrusion (Fig. 2.3). Hornblendite cuts all rock units in the intrusion as millimeter- to decimeter-scale veins and dikes (Figs. 2.4B, F, L) and is typically observed as a discontinuous pegmatitic rim at contacts with dioritic rocks (Fig. 2.3). Hornblende gabbro is present in two varieties: 1) coarse-grained to pegmatitic and closely associated with hornblendite (same map unit), commonly exhibiting comingling textures and a locally strong magmatic foliation; and 2) fine- to medium-grained and leucocratic (plagioclase-rich), typically displaying hornblendite schlieren and exhibiting gradational contacts with hornblendite that display flow banding of hornblende and plagioclase in both the hornblendite and hornblende gabbro (Fig. 2.4F). Gabbronorite (± hornblende) is interpreted as a minor, late differentiate of the Giant Mascot ultramafic intrusion occurring mostly as late veins that cut hornblendite and hornblende gabbro or more rarely comingled with hornblende pyroxenite (Fig. 2.4E). The youngest phases associated with the Giant Mascot intrusion are felsic pegmatite and aplite dikes and veins that cut hornblende pyroxenite, hornblendite, and hornblende gabbro (Fig. 2.4H). Spuzzum quartz diorites exhibit non-pervasive, moderate to strong metamorphic foliation defined by weak to moderate mafic mineral alignment. Field observations made during this study define the order of emplacement from oldest to youngest as: Spuzzum diorites >> dunite > peridotite > pyroxenite > hornblende pyroxenite > hornblendite = hornblende gabbro = gabbronorite > felsic pegmatite and aplite dikes/veins. 25Figure 2.3³0 500 1,00 0250Meters12MMA-5-4-1 (Zr)03GNX-3-1-1 (Zr)11GNX-1-3-1 (Zr)11GNX-1-2-1 & 11GNX-1-2-2 (Bt/Hbl)13MMA-2-7-1 (Zr)12MMA-2-3-1 (Zr)12MMA-2-4-1 (Zr)12MMA-2-1-2 (Bt/Hbl)12MMA-2-1-5 (Zr)12MMA-6-5-1 (Zr)hornblenditehornblende gabbroGiant Mascot ultramafic suite (ca. 93 Ma)Spuzzum pluton (ca. 95 Ma) Map symbolsSettler schist (Upper Triassic)hornblende pyroxeniteperidotitedunitegabbronorite-dioritegarnetiferous gabbronorite-dioritehornblende gabbronorite-dioritequartz dioritepyroxeniteSettler schistroad (dirt)stream or rivercontour (100m)geological contact, definedobserved outcropcontour (20m)geological contact, approximategeological contact, inferredfault, definedfault, approximatefault, inferred0 250 500metres1000Figure 2.3.  Simplified geologic map of the Giant Mascot ultramafic intrusion showing sample locations for U-Pb zircon (Zr) and 40Ar/ 39 Ar biotite (Bt) and hornblende (Hbl) geochronology. Sample symbols and colours correspond to those used in all subsequent figures (geology modified from Aho, 1954; Vining, 1977; and Manor et al., 2014b). Symbols indicate ultramafic rocks (circles), Spuzzum diorite (orange triangles), Spuzzum pluton quartz diorites (squares), and a mylonite and enclaves (diamonds).26Figure 2.4A B CFEDG H ILKJPxPxHb veinsPxDnDnDnPdSqdiSqdiHb dikesSgbnSgbngHbHbplagioclase clotsflow bandingSgbn/HGbSgbnHPxHGbplagioclase clotpegmatite veinPxsulphideweak modal layeringHpxuTrSsiliceous veinsSgbnenclavesHbmyloniteFigure 2.4. Photographs illustrating the relative age relationships between rocks from the Giant Mascot ultramafic intrusive suite and Spuzzum pluton. A) Dunite (Dn) cut by a pyroxenite vein, Dolly adit. B) Pyroxenite (Px) with at least three generations of hornblendite (Hb) veins. C) Pyroxenite containing inclusions of peridotite (Pd); locality for geochronology sample 12MMA-5-4-1. D) Large sulphide-bearing pyroxenite boulder displaying weak modal layering. E) Boulder with rare lobate inclusion of hornblende pyroxenite (HPx) exhibiting delicate protrusions in gabbronorite (Sgbn). F) Contact between hornblendite and gabbronorite/hornblende gabbro displaying flow banding and subsequently displaced by dextral faults 272 3  Previous WorkThe ages of the Giant Mascot ultramafic intrusion and Spuzzum diorites have been unresolvable in past studies due to complex field relationships and similar mineralogical and textural characteristics of the dioritic rocks. The diorite-gabbronorite has been recognized as a minor late differentiate of the Giant Mascot intrusion and thus was interpreted as younger than the Spuzzum diorites (e.g., Cairnes, 1924; Aho, 1954, 1956; Muir, 1971; Vining, 1977). Other workers interpret these rocks to be Spuzzum diorites and conclude that the Giant Mascot ultramafic rocks are older than the Spuzzum diorites (e.g., Cockfield and Walker, 1933a; Horwood, 1936; McLeod, 1975; McLeod et al., 1976; Ash, 2002; Metcalfe et al., 2002). The first attempt at isotopic dating of the Giant Mascot and Spuzzum intrusions used conventional K-Ar geochronology for hornblende-bearing rocks (95-119 Ma, n=4), reflecting an older age relative to the Spuzzum diorites (79-89 Ma, n=4; McLeod, 1975; McLeod et al., 1976). Additional K-Ar ages are reported by Metcalfe et al. (2002), which are recalculated ages from McLeod (ibid.) using a modified decay constant, and they yielded comparable dates for both the Giant Mascot (96-122 Ma, n=4) and Spuzzum intrusions (81-105 Ma, n=7). Brown and Walker (1993) also reported a concordant weighted mean 206 Pb/ 238 U age of 96.3 ± 0.5 Ma (n=2; air-abraded zircon) for a sample from the northwestern part of the Spuzzum pluton (~5 km NW of Giant Mascot), similar within uncertainty to the recalculated K-Ar ages of Metcalfe et al. (2002). The purpose of the present study is to determine the crystallization age and cooling history of the Giant Mascot ultramafic intrusion using modern U-Pb and 40Ar/ 39 Ar geochronological techniques to address the emplacement history and timing of orthomagmatic Ni-Cu-PGE mineralization, and to examine cut by a plagioclase-rich vein (black outline). G) Phlogopite-bearing hornblendite containing plagioclase clots (geochronology sample 13MMA-2-7-1). H) Hornblende gabbro cut by late plagioclase- and biotite-rich pegmatite veins. I) Garnetiferous gabbronorite-diorite (Sgbng) cut by siliceous veins interpreted to represent anatectic melts of the Settler schist (uTrS) injected into the gabbro (near the peak of Zofka Ridge). J) Shear zone mylonite at the contact of hornblendite and Spuzzum quartz diorite (Sqdi) (locality for 40Ar/ 39 Ar hornblende geochronology samples 11GNX-1-2-1 and 11GNX-1-2-2). K) Biotite-rich hornblendite enclaves hosted by Spuzzum quartz diorite exposed along the mine access road (locality for 40Ar/ 39 Ar hornblende and biotite geochronology sample 12MMA-2-1-2). J) Hornblendite dikes cut Spuzzum gabbronorite-diorite (Sgbn) near the 3550 East Portal dump. Scales for photographs include a Canadian twoonie (2.5 cm), knife blade (8 cm), scribe (13 cm), and hammer handles (50 cm). 28the tectonic significance of the Giant Mascot ultramafic intrusion in the southern Coast Plutonic Complex and Northern Cascades. 2 4  Sample Descriptions and Analytical Methods2 4 1  U-Pb zircon geochronology samplesA total of eight samples were collected from the Giant Mascot ultramafic suite and Spuzzum pluton (Fig. 2.3). The four samples collected from the Giant Mascot ultramafic suite include two pyroxenites (03GNX-3-1-1, 12MMA-5-4-1), a hornblende pyroxenite (12MMA-2-4-1), and a hornblendite (13MMA-2-7-1). Ultramafic rock samples collected for separation of accessory zircon contained 1) minor interstitial plagioclase, commonly present as clots, 2) coarse-grained to pegmatitic textures, or 3) both of the above. Four additional samples (11GNX-1-3-1, 12MMA-2-1-5, 12MMA-6-5-1, 12MMA-2-3-1) were collected from the Spuzzum pluton host. Giant Mascot sample 03GNX-3-1-1 is a greenish-black, coarse-grained feldspathic, phlogopite-hornblende pyroxenite (websterite) containing cumulus clinopyroxene (~60 vol.%) and orthopyroxene (30%), minor interstitial hornblende (5%), phlogopite (5%), and trace plagioclase, and minor accessory magnetite and ilmenite. Sample 12MMA-5-4-1 is a medium to coarse-grained pyroxenite (i.e., websterite) with cumulus orthopyroxene (60%), clinopyroxene (35%), minor interstitial hornblende (5%), and trace disseminated sulphide. Sample 12MMA-2-4-1 is an oikocrystic, locally feldspathic hornblende pyroxenite (websterite) containing 2-8 mm hornblende oikocrysts (15-20%) enclosing medium-grained, cumulus orthopyroxene (30%), clinopyroxene (45%), and minor sulphide blebs. Interstitial plagioclase (<10%) forms anhedral clots, predominantly around margins of hornblende oikocrysts. Sample 13MMA-2-7-1 is a black, pegmatitic, feldspathic hornblendite with minor phlogopite (<5%) (Fig. 2.4G). Spuzzum pluton sample 11GNX-1-3-1 is a biotite-hornblende quartz diorite, with a mylonitic fabric, that is located in a large podiform re-entrant along the eastern side of the Giant Mascot ultramafic intrusion (Fig. 2.3). Sample 12MMA-2-1-5 is a hornblende-biotite quartz 29diorite that contains hornblendite enclaves (Fig. 2.4K). Sample 12MMA-6-5-1 is a biotite-hornblende quartz diorite from a metre-scale fallen block (~5x4x2m) in a scree field along the northeast margin of the Giant Mascot ultramafic intrusion (Fig. 2.3). Sample 12MMA-2-3-1 is a medium-grained diorite containing plagioclase (60%), orthopyroxene (10%), clinopyroxene (10%), and hornblende (20%), with trace accessory biotite, magnetite, and ilmenite. The Spuzzum diorites vary in quartz content from 0-5 modal % (diorite), 5-15% (quartz diorite), and >15% (tonalite) towards the periphery of the intrusion (Vining, 1977).2 4 2  U-Pb zircon geochronology analytical methodsSample preparation, mineral separate extraction, chemical abrasion techniques, and measurement of isotope ratios of individual zircon grains were completed at the Pacific Centre for Geochemical and Isotopic Research (PCIGR) at the University of British Columbia, Vancouver, Canada. Chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) procedures at PCIGR are modified from Mattinson (2005) and Scoates and Friedman (2008). Zircon grains were separated from bulk rock samples using typical crushing, grinding, Wilfley table, and magnetic susceptibility techniques. The resultant separates were then handpicked in ethanol to allow for selection of the clearest, crack- and inclusion-free grains. Each batch was photographed and annealed in quartz glass crucibles at 900˚C for 60 hours. Annealed grains were then transferred into 3.5 mL PFA screwtop beakers along with 500 mL of <50% strength ultrapure HF and 50 mL of <14N HNO3. The beakers were placed in 125 mL PTFE liners and 2 mL HF and 0.2 mL HNO3 was added (same strength as beakers). The liners were then inserted into stainless steel Parr™ high-pressure dissolution devices, which were sealed and brought up to 175˚C for 12 hours. Beakers were then removed from liners and zircon was separated from the leachate. The zircon grains were rinsed with >18 MΩ.cm water and sub-boiled acetone after which 2 mL of sub-boiled 6N HCl was added and the beakers were set on a hotplate at 80˚-130˚C for 30 minutes and again rinsed with water and acetone. Masses were estimated from the dimensions (i.e., volumes) of grains at this stage (Table 2.1). Single grains 30were transferred into clean 300 mL PFA microcapsules, i.e., crucibles, and 50 mL of 50% HF and 5 mL of 14 N HNO3 were added. Each grain was spiked with the 233-235 U-205 Pb tracer solution, EARTHTIME ET535, capped and again placed in a Parr™ liner. Hyperfluoric and nitric acids in a 10:1 ratio, respectively, were added to the liner, which was then placed in Parr™ high-pressure device and dissolution was achieved at 240˚C for 40 hours. The resulting solutions were dried on a hotplate at 130˚C; 50 mL of 6N HCl was then added to microcapsules where fluorides were dissolved in high-pressure Parr™ devices for 12 hours at 210˚C. Hydrochloric acid solutions were transferred into clean 7 mL PFA beakers and dried with 2 mL of 0.5 N H3PO4. Lastly, samples were loaded onto degassed, zone-refined Re filaments in 2 mL of silicic acid emitter (Gerstenberger and Haase, 1997).  Isotopic ratios were measured on a modified single collector VG-54R or 354S (with Sector 54 electronics) thermal ionization mass spectrometer equipped with analogue Daly photomultipliers. Analytical blanks were 0.2 pg for U and up to 1 pg for Pb. Uranium fractionation was determined directly on individual runs using the EARTHTIME ET535 mixed 233-235 U-205 Pb isotopic tracer and Pb isotopic ratios were corrected for fractionation of 0.25%/amu based on replicate analyses of NBS-982 reference material (Scoates and Wall, in press). Data reduction was completed using the Excel-based program of Schmitz and Schoene (2007). Standard concordia diagrams, regression intercepts, and weighted averages were produced with Isoplot 3.09 (Ludwig, 2003). Unless otherwise noted all errors are quoted at the 2 sigma level. Analytical results are reported in Table 2.1.2 4 3  Scanning electron microscope imagingZircon grains were picked and transferred to a glass slide with double-stick tape and arranged in rows for respective samples. A ring measuring 25 mm in diameter and 8 mm tall was placed on the tape around the zircon grains and filled with an epoxy-hardener mix (5:1, respectively). This mix was allowed to dry overnight and then heated if not completely hardened. This grain mount was then sanded on coarse (400 grit) and fine sandpaper (600 grit) until the 31Table 2.1. U-Th-Pb analytical results for zircon from the Giant Mascot ultramafic intrusion and Spuzzum plutonCompositional Parameters 3,4,5 Radiogenic Isotope Ratios 6,7 Isotopic Ages 8,9SampleWeight2 (mg)U (ppm)Pb (ppm) Th/U206 Pb* (x10 -23  mol)mol % 206 Pb*Pb*/Pbc Pbc (pg)206 Pb/ 204Pb208 Pb/ 206 Pb207 Pb/ 206 Pb % error 207 Pb/ 235 U % error 206 Pb/ 238 U % error R**207 Pb/ 206 Pb ± 207 Pb/ 235 U ± 206 Pb/ 238 U ± 12MMA-5-4-1 (pyroxenite): UTME 607939  UTMN 5480490K 0.009 372 4.7 0.158 1.869 99.75% 110 0.39 7400 0.051 0.048215 1.005 0.088113 1.011 0.013254 0.268 0.155 109.85 23.71 85.74 0.83 84.88 0.23J 0.009 109 1.5 0.184 0.578 98.84% 24 0.56 1596 0.060 0.048328 0.618 0.092787 0.678 0.013925 0.103 0.631 115.38 14.58 90.10 0.58 89.14 0.09H 0.005 125 1.7 0.097 0.377 98.40% 17 0.50 1155 0.031 0.047125 2.754 0.090646 2.923 0.013951 0.365 0.513 55.55 65.66 88.11 2.47 89.31 0.32I 0.002 1597 23.6 0.328 2.218 99.21% 36 1.46 2332 0.105 0.047996 0.298 0.095904 0.345 0.014492 0.119 0.536 99.07 7.05 92.99 0.31 92.75 0.11F 0.008 1237 18.1 0.379 6.055 99.90% 297 0.49 18721 0.122 0.048017 0.124 0.096000 0.213 0.014500 0.151 0.818 100.09 2.94 93.08 0.19 92.80 0.14E 0.005 39 0.7 0.228 0.125 93.52% 4 0.71 285 0.071 0.046571 5.767 0.095096 6.054 0.014810 0.581 0.531 27.30 138.22 92.24 5.34 94.77 0.55L 0.002 261 3.9 0.183 0.291 98.72% 21 0.31 1441 0.060 0.049171 1.737 0.100657 1.844 0.014847 0.196 0.588 155.99 40.64 97.38 1.71 95.01 0.18A 0.003 142 2.3 0.202 0.238 96.64% 8 0.68 551 0.064 0.047424 1.559 0.097105 1.661 0.014850 0.139 0.754 70.65 37.07 94.10 1.49 95.03 0.13B 0.008 105 1.5 0.130 0.500 98.41% 17 0.67 1160 0.041 0.047670 1.155 0.097609 1.190 0.014851 0.229 0.249 82.93 27.39 94.57 1.07 95.03 0.22M 0.002 72 1.4 0.181 0.067 91.77% 3 0.50 225 0.058 0.048287 4.772 0.098919 5.046 0.014858 0.398 0.708 113.35 112.55 95.78 4.61 95.07 0.38D 0.002 124 2.0 0.238 0.162 96.45% 8 0.49 521 0.076 0.047545 1.980 0.097420 2.105 0.014861 0.249 0.545 76.70 47.02 94.39 1.90 95.09 0.23C 0.002 193 3.0 0.197 0.275 97.73% 12 0.52 816 0.063 0.048189 1.259 0.098769 1.345 0.014865 0.141 0.644 108.57 29.73 95.64 1.23 95.12 0.13N 0.001 97 1.8 0.187 0.061 91.67% 3 0.45 222 0.062 0.049508 5.594 0.101855 5.925 0.014921 0.461 0.737 171.96 130.51 98.49 5.56 95.48 0.4403GNX-3-1-1 (pyroxenite): UTME 608771  UTMN 5480630 C 0.004 636 10.5 0.499 1.463 97.16% 10 3.52 651 0.159 0.047686 0.719 0.095513 0.804 0.014527 0.189 0.541 83.72 17.05 92.63 0.71 92.97 0.17E 0.005 595 9.8 0.606 1.657 98.06% 16 2.70 954 0.195 0.048017 0.546 0.096178 0.617 0.014527 0.128 0.624 100.11 12.92 93.24 0.55 92.97 0.12A 0.004 466 8.1 0.683 1.073 97.02% 10 2.71 622 0.220 0.048177 0.881 0.096570 0.962 0.014538 0.136 0.642 107.95 20.80 93.61 0.86 93.04 0.13B 0.003 745 12.4 0.610 1.491 97.97% 15 2.54 913 0.196 0.047992 0.624 0.096262 0.694 0.014547 0.129 0.607 98.90 14.75 93.32 0.62 93.10 0.12D 0.003 273 4.5 0.336 0.547 96.41% 8 1.67 516 0.108 0.048291 1.364 0.096878 1.465 0.014550 0.156 0.681 113.55 32.16 93.89 1.31 93.12 0.1412MMA-2-4-1 (hornblende pyroxenite): UTME 608960  UTMN 5480264B 0.003 250 3.8 0.233 0.468 97.92% 13 0.82 888 0.075 0.048224 1.077 0.096393 1.146 0.014497 0.143 0.530 110.25 25.42 93.44 1.02 92.78 0.13C 0.002 678 9.8 0.218 0.942 98.98% 27 0.80 1818 0.070 0.048019 0.597 0.096008 0.643 0.014501 0.144 0.425 100.20 14.11 93.08 0.57 92.81 0.13D 0.002 1842 26.5 0.277 2.004 99.58% 68 0.69 4457 0.089 0.047876 0.265 0.095782 0.314 0.014510 0.111 0.581 93.15 6.28 92.88 0.28 92.86 0.10A 0.002 246 4.1 0.457 0.282 96.67% 9 0.80 555 0.146 0.047962 1.445 0.095983 1.535 0.014514 0.145 0.654 97.38 34.17 93.06 1.37 92.89 0.13E 0.002 143 2.5 0.347 0.209 94.80% 5 0.94 356 0.110 0.047537 2.129 0.095490 2.259 0.014569 0.183 0.732 76.27 50.56 92.60 2.00 93.24 0.1732Table 2.1. (cont.) U-Th-Pb analytical results for zircon from the Giant Mascot ultramafic intrusion and Spuzzum plutonCompositional Parameters 3,4,5 Radiogenic Isotope Ratios 6,7 Isotopic Ages 8,9SampleWeight2 (mg)U (ppm)Pb (ppm) Th/U206 Pb* (x10 -23  mol)mol % 206 Pb*Pb*/Pbc Pbc (pg)206 Pb/ 204Pb208 Pb/ 206 Pb 207 Pb/ 206 Pb % error 207 Pb/ 235 U % error 206 Pb/ 238 U % error R**207 Pb/ 206 Pb ± 207 Pb/ 235 U ± 206 Pb/ 238 U ± 13MMA-2-7-1 (hornblendite): UTME 609108  UTMN 5480627D 0.0080 81 1.2 0.267 0.3900 98.19% 15 0.59 1025 0.086 0.048195 1.006 0.096118 1.084 0.014464 0.102 0.786 108.86 23.74 93.19 0.96 92.58 0.09C 0.0070 933 13.4 0.299 3.9458 99.86% 202 0.46 13021 0.096 0.048054 0.214 0.096037 0.254 0.014494 0.108 0.553 101.95 5.06 93.11 0.23 92.77 0.10E 0.0070 779 10.8 0.160 3.2987 99.77% 119 0.63 8005 0.051 0.047866 0.352 0.095862 0.388 0.014525 0.160 0.421 92.64 8.34 92.95 0.35 92.96 0.15B 0.0131 2826 40.4 0.294 22.4378 99.95% 565 0.94 36561 0.094 0.047954 0.069 0.096176 0.242 0.014546 0.215 0.961 97.00 1.63 93.24 0.22 93.09 0.2012MMA-2-3-1 (Spuzzum diorite): UTME 608954  UTMN 5480432A 0.0037 52 0.8 0.175 0.1168 95.15% 5 0.49 381 0.055 0.046797 3.712 0.093355 3.918 0.014468 0.338 0.637 38.89 88.77 90.62 3.40 92.60 0.31C 0.0030 72 1.4 0.191 0.1306 90.84% 3 1.08 202 0.063 0.049455 4.609 0.098938 4.886 0.014509 0.396 0.720 169.48 107.59 95.80 4.47 92.86 0.36G 0.0030 49 0.8 0.181 0.0885 94.68% 5 0.41 348 0.059 0.048382 2.781 0.096828 2.958 0.014515 0.232 0.777 117.99 65.53 93.84 2.65 92.90 0.21L 0.0047 46 0.8 0.199 0.1333 94.89% 5 0.59 362 0.064 0.048351 3.110 0.097633 3.273 0.014645 0.347 0.509 116.46 73.32 94.59 2.96 93.72 0.32F 0.0030 91 1.8 0.193 0.1679 90.71% 3 1.41 199 0.063 0.049025 3.454 0.099419 3.670 0.014708 0.249 0.874 149.01 80.94 96.24 3.37 94.12 0.23K 0.0032 43 0.7 0.201 0.0855 95.28% 6 0.35 392 0.067 0.050246 2.864 0.102487 3.047 0.014793 0.249 0.755 206.37 66.40 99.07 2.88 94.67 0.23J 0.0032 116 1.8 0.177 0.2292 96.59% 8 0.67 542 0.057 0.047741 3.194 0.097760 3.340 0.014851 0.391 0.422 86.47 75.72 94.71 3.02 95.03 0.37E 0.0095 33 0.6 0.200 0.1947 95.35% 6 0.78 398 0.063 0.047205 2.165 0.096694 2.301 0.014856 0.200 0.703 59.60 51.58 93.72 2.06 95.07 0.19H 0.0030 189 2.8 0.149 0.3515 98.29% 16 0.50 1081 0.049 0.048847 1.361 0.100221 1.436 0.014880 0.199 0.436 140.52 31.93 96.98 1.33 95.22 0.19I 0.0048 102 1.6 0.201 0.3040 98.00% 14 0.51 926 0.066 0.048913 1.111 0.100388 1.176 0.014885 0.161 0.464 143.68 26.05 97.13 1.09 95.25 0.15B 0.0081 200 2.9 0.147 1.0027 98.76% 22 1.04 1490 0.047 0.048118 0.581 0.098772 0.632 0.014888 0.150 0.446 105.05 13.71 95.64 0.58 95.27 0.14M 0.0047 57 0.9 0.188 0.1664 96.25% 7 0.53 493 0.060 0.047831 2.371 0.099022 2.513 0.015015 0.225 0.659 90.92 56.15 95.87 2.30 96.07 0.2112MMA-2-1-5 (Spuzzum quartz diorite): UTME 610135  UTMN 5481062D 0.0030 62 1.2 0.213 0.1154 90.68% 3 0.97 199 0.068 0.047798 4.053 0.097721 4.294 0.014828 0.294 0.832 89.30 96.03 94.67 3.88 94.88 0.28E 0.0025 137 2.3 0.230 0.2125 95.45% 6 0.83 406 0.075 0.048610 2.709 0.099558 2.880 0.014854 0.232 0.754 129.06 63.72 96.37 2.65 95.05 0.22A 0.0027 57 1.0 0.229 0.0956 95.54% 6 0.37 415 0.072 0.047036 2.114 0.096341 2.243 0.014855 0.186 0.717 51.05 50.44 93.39 2.00 95.06 0.18B 0.0029 148 2.5 0.241 0.2661 95.34% 6 1.07 397 0.079 0.048874 2.396 0.100369 2.554 0.014894 0.224 0.727 141.77 56.22 97.12 2.37 95.31 0.2133Table 2.1. (cont.) U-Th-Pb analytical results for zircon from the Giant Mascot ultramafic intrusion and Spuzzum plutonCompositional Parameters 3,4,5 Radiogenic Isotope Ratios 6,7 Isotopic Ages 8,9SampleWeight2 (mg)U (ppm)Pb (ppm) Th/U206 Pb* (x10 -23  mol)mol % 206 Pb*Pb*/Pbc Pbc (pg)206 Pb/ 204Pb208 Pb/ 206 Pb 207 Pb/ 206 Pb % error 207 Pb/ 235 U % error 206 Pb/ 238 U % error R**207 Pb/ 206 Pb ± 207 Pb/ 235 U ± 206 Pb/ 238 U ± 12MMA-6-5-1 (Spuzzum quartz diorite): UTME 609078  UTMN 5481423E 0.0016 401 6.0 0.091 0.3941 97.29% 10 0.90 684 0.029 0.047983 2.140 0.097512 2.256 0.014739 0.276 0.470 98.44 50.62 94.48 2.04 94.32 0.26B 0.0009 163 3.7 0.211 0.0908 85.65% 2 1.25 129 0.070 0.049392 5.504 0.101298 5.844 0.014874 0.388 0.882 166.50 128.55 97.97 5.46 95.18 0.37A 0.0007 202 4.2 0.237 0.0877 88.43% 2 0.94 160 0.075 0.047507 5.405 0.097641 5.719 0.014906 0.368 0.863 74.81 128.39 94.60 5.17 95.38 0.35D 0.0014 268 7.2 0.060 0.2333 79.25% 1 5.02 89 0.019 0.047159 2.715 0.096947 2.853 0.014910 0.393 0.412 57.29 64.69 93.95 2.56 95.40 0.37C 0.0012 187 3.7 0.158 0.1440 90.87% 3 1.19 203 0.050 0.047609 3.742 0.101277 3.967 0.015428 0.288 0.794 79.89 88.81 97.95 3.70 98.70 0.2811GNX-1-3-1 (Spuzzum quartz diorite): UTME 608907  UTMN 5480667D 0.004 134 2.3 0.211 0.3219 94.61% 5 1.51 344 0.068 0.048292 1.439 0.098733 1.548 0.014828 0.156 0.723 113.61 33.95 95.61 1.41 94.89 0.15F 0.002 108 1.9 0.172 0.1604 94.04% 4 0.84 310 0.056 0.048472 2.328 0.099613 2.485 0.014905 0.199 0.803 122.38 54.82 96.42 2.29 95.37 0.19A 0.004 65 1.3 0.223 0.1414 90.54% 3 1.22 196 0.072 0.048439 3.087 0.099719 3.288 0.014931 0.253 0.806 120.76 72.71 96.52 3.03 95.54 0.24C 0.004 47 1.1 0.214 0.1101 84.84% 2 1.62 122 0.069 0.048461 4.081 0.099831 4.338 0.014941 0.320 0.814 121.83 96.11 96.62 4.00 95.60 0.30B 0.004 43 1.0 0.209 0.0997 85.76% 2 1.36 130 0.066 0.047588 5.104 0.105409 5.414 0.016065 0.357 0.877 78.82 121.16 101.76 5.24 102.74 0.361 A, B etc. are labels for fractions composed of single zircon grains or fragments; all fractions annealed and chemically abraded after Mattinson (2005) and Scoates and Friedman (2008); UTM coordinates based on NAD83 Zone 10 easting (UTME) and northing (UTMN).2 Nominal fraction weights estimated from photomicrographic grain dimensions, adjusted for partial dissolution during chemical abrasion.3  Nominal U and total Pb concentrations subject to uncertainty in photomicrographic estimation of weight and partial dissolution during chemical abrasion; mod el Th/U ratio calculated from radiogenic 208 Pb/ 206 Pb ratio and 207 Pb/ 235 U age4 Pb* and Pbc represent radiogenic and common Pb, respectively; mol % 206 Pb* with respect to radiogenic, blank and initial common Pb.5  Measured ratio corrected for spike and fractionation only. Mass discrimination of 0.25%/amu based on analysis of NBS-982; all Daly analyses.6  Corrected for fractionation, spike, and common Pb; up to 1 pg of common Pb was assumed to be procedural blank: 206 Pb/ 204Pb = 18.50 ± 1.0%; 207Pb/204Pb = 15.50 ± 1.0%;208 Pb/ 204Pb = 38.40 ± 1.0% (all uncertainties 1σ).  Excess over blank was assigned to initial common Pb, using the Stacey and Kramers (1975) two-stage Pb isotope evolution model at the nominal sample age.7  Errors are 2σ, propagated using the algorithms of Schmitz and Schoene (2007) and Crowley et al. (2007).8  Calculations are based on the decay constants of Jaffey et al. (1971). 206 Pb/ 238 U and 207 Pb/ 206 Pb ages corrected for initial disequilibrium in 230 Th/ 238 U using Th/U [magma] = 3.9  Corrected for fractionation, spike, and blank Pb only.** R = correlation coefficient of radiogenic isotope ratios34grains were exposed. Polish was applied in three intervals using different grits: 1) 6 μm, 2) 3 μm, and 3) 1 μm. The mount was carbon-coated and prepared in the Electron Microbeam/X-Ray Diffraction Facility at the University of British Columbia. High-resolution imaging for individual zircon grains was done on a Philips XL-30 scanning electron microscope (SEM) equipped with a Robinson cathodoluminesence detector at an operating voltage of 15kV.2 4 4  Laser ablation ICP-MS analysis of zirconFollowing cathodoluminescence imaging of both leached (i.e., chemically abraded) and unleached zircon (Appendix III), grain mounts containing the mineral samples and standards were cleaned with 3 N HNO3 acid prior to analysis to remove any surficial Pb contamination, a step that removes the necessity for pre-ablating the samples. Laser ablation, mass spectrometry, and data quantification and processing of samples were completed at PCIGR (Table 2.2). The laser was imaged onto the sample using different apertures allowing for a spot size between 5-120 μm. To ensure better stability, the whole laser path was fluxed by N2. This sample chamber facilitated the investigation of several samples within one analytical session and/or larger specimen also assuring high sensitivity, low fractionation and short washout times. Ablation was carried out in a cell with a volume of about 20 cm 3 , and a He gas stream that ensured better signal stability and lower U-Pb fractionation (e.g., Eggins et al., 1998). Standards were analyzed throughout the sequence, two for every five unknowns, to allow for drift correction and to characterize down-hole fractionation for U-Pb isotopic ratios. Laser ablation instrumentation, operating conditions, and quantification are summarized in Table 2.2. U-Pb analytical results can be found in Table 2.3 and trace element concentrations in Appendix III.2 4 5  40Ar/39Ar hornblende/biotite geochronologyTwo samples (11GNX-1-2-1, 11GNX-1-2-2) were collected from a mylonite at the contact with Spuzzum quartz diorite and pegmatitic hornblendite (Figs. 2.3, 2.4J) and another from a lobate hornblendite enclave in Spuzzum quartz diorite (same locality as U-Pb zircon 35sample 12MMA-2-1-5) (Figs. 2.3, 2.4K). Due to the low initial concentrations of K, at least two experiments were run for each sample to assess the reproducibility of ages. The results for all analyses (inverse isochron and plateau) are reported in Tables 2.4 and 2.5.The three samples were crushed in a ring mill, washed in distilled water and ethanol, and sieved to -40+60 mesh. Individual hornblende crystals were picked from bulk fractions of all three samples, and a second population of coarser-grained hornblende was picked from 11GNX-1-2-2; biotite was picked from 12MMA-2-1-2. Mineral separates were wrapped in aluminum foil and stacked in an irradiation capsule with similar-aged samples and neutron flux monitors (Fish Canyon Tuff sanidine [FCs], 28.201 ± 0.046 Ma) (Kuiper et al., 2008). The samples were irradiated on October 15-18, 2012 at the McMaster Nuclear Reactor in Hamilton, Ontario, for 180 MWH in the medium flux site 8C. Analyses (n=33) of 11 neutron flux monitor positions produced errors of <0.5% in the J value. Isotopic ratios were measured between December 2012 and June 2013 at PCIGR. The mineral separates were step-heated at incrementally higher powers in the defocused beam of a 10W CO2 laser (New Wave Research MIR10) until they fused. The gas evolved from each step was analyzed by a VG5400 mass spectrometer equipped with an ion-counting electron multiplier. All measurements were corrected for total system blank, mass spectrometer sensitivity, mass discrimination, radioactive decay during and subsequent to irradiation, and interfering Ar from atmospheric contamination and the irradiation of Ca, Cl and K [Isotope production ratios: (40Ar/ 39 Ar)K=0.0302±0.00006, ( 37 Ar/ 39 Ar)Ca=1416.4±0.5, ( 36 Ar/ 39 Ar)Ca=0.3952±0.0004, Ca/K=1.83±0.01(37 ArCa/ 39 ArK)]. Initial data entry and calculations were carried out using the software ArArCalc (Koppers, 2002), and plateau and correlation ages were calculated using Isoplot 3.09 (Ludwig, 2003). Uncertainties are reported at the 2-sigma (95% confidence) level and are propagated from all sources, except for mass spectrometer sensitivity and age of the flux monitor. The best statistically justified plateau and plateau age were picked based on the following criteria: 1) three or more contiguous steps comprise more than 60% of the 39 Ar; 2) probability of fit of the 36Table 2.2. LA-ICP-MS instrumentation, operating conditions and quantificationLaser Ablation (LA) samplerModel Resonetics RESOlution M-50-LR Class I Wavelength 193 nm (Coherent COMPex Pro 110 UV excimer laser source)Pulse duration (FWHM) 4 nsSample cell Laurin 2-volume cell, each with separate carrier gas-in port Gas flows:1) He carrier into cup 0.53 L/min2) He carrier into cell base 0.53 L/min3) Ar make up 0.53 L/minICP-MSModel Agilent 7700x quadrupole with additional interface rotary pumpShield torch UsedRF power 1350 WSampling depth 30-40 μmThO+/Th+ <0.2%U/Th sensitivity ratio (NIST612) 1.01-1.05Data acquisition parameters - spot analysisLaser spot Round, 17 μm nominal diameter (33 μm for 03GNX-3-1-1 and 11GNX-1-3-1)Laser energy density at sample 5 J/cm 2Laser repetition rate 5 HzIsotopes determined (dwell in ms) 29 Si, 43 Ca, 49 Ti, 85 Rb, 88 Sr, 89 Y, 90 Zr, 93 Nb, 139 La, 140Ce, 141Pr, Nd ( 143 Nd and  146 Nd), 147 Sm, 153 Eu, 163 Dy, 165 Ho, 166 Er, 169 Tm, 172 Yb, 175 Lu, 177 Hf, 181 Ta, 202Hg, Pb (204Pb, 206 Pb, 207 Pb, 208 Pb), 232 Th, and U ( 235 U and 238 U)Mass sweep time 705 msAnalysis time 100 s:  ~ 60 s gas blank, up to ~60 s of ablationQuantificationCalibration standards1) U-Pb geochronology Plešovice (Sláma et al., 2008) and Temora2 zircon (Black et al., 2004)2) Trace elements NIST612 glassData processing Igor ProTM Iolite extension (Paton et al., 2011)37Table 2.3.  U-Th-Pb laser ablation ICP-MS analytical results for zircon from the Giant Mascot ultramafic intrusion and Spuzzum plutonCompositional Parameters 3 Radiogenic Isotope Ratios Isotopic Ages (Ma)Sample/Spot 1 Integration2 U (ppm) Pb (ppm) Th (ppm) Th/U 207 Pb/ 206 Pb ±2σ error 207 Pb/ 235 U ±2σ error 206 Pb/ 238 U ±2σ error R** 207 Pb/ 235 U ± 206 Pb/ 238 U ± 12MMA-5-4-1 (pyroxenite): UTME 607939  UTMN 5480490 (CA-TIMS age = 92.78 ± 0.09 Ma)5 5 135 9 14 0.104 0.076 0.036 0.081 0.038 0.007 0.001 0.045 78 36 45.5 71L 1 342 12 87 0.254 0.047 0.013 0.051 0.015 0.008 0.001 0.462 50 15 48.4 4.23 3 338 8 25 0.074 0.049 0.036 0.069 0.050 0.010 0.001 0.031 67 47 66.3 5.45L 5 540 17 180 0.333 0.051 0.015 0.091 0.028 0.013 0.001 0.159 92 28 85 3.67 7 152 11 25 0.164 0.060 0.028 0.125 0.053 0.013 0.001 0.194 115 48 85.9 7.34 4 248 3 28 0.113 0.047 0.014 0.088 0.024 0.014 0.001 0.100 85 23 86.8 7.36L 6 485 17 120 0.247 0.055 0.018 0.105 0.038 0.014 0.001 0.193 99 35 86.8 6.42 2 247 11 53 0.215 0.054 0.023 0.107 0.045 0.014 0.001 0.306 112 45 90.2 8.56 6 177 7 28 0.158 0.051 0.019 0.103 0.040 0.014 0.001 0.507 97 37 90.7 4.54L 4 152 3 45 0.296 0.063 0.022 0.115 0.035 0.014 0.002 0.108 114 35 92.2 8.92L 2 349 16 136 0.390 0.050 0.015 0.101 0.030 0.014 0.001 0.199 96 27 92.5 6.21 1 513 12 98 0.191 0.045 0.016 0.101 0.035 0.015 0.001 0.200 96 32 92.6 7.23L 3 95 5 39 0.411 0.052 0.022 0.097 0.041 0.015 0.001 0.057 94 38 92.7 8.6Weighted mean 88.6 1.903GNX-3-1-1 (pyroxenite): UTME 608771  UTMN 5480630 (CA-TIMS age = 93.04 ± 0.06 Ma)8 12 1236 62 645 0.522 0.046 0.010 0.047 0.009 0.008 0.001 0.176 46.3 8.9 54 5.54L 4 378 14 115 0.304 0.056 0.012 0.063 0.014 0.009 0.001 0.095 61 13 57.9 4.12 2 1864 138 1350 0.724 0.049 0.007 0.059 0.006 0.009 0.001 0.022 57.9 5.6 60.5 3.58L 9 190 6 58 0.305 0.049 0.011 0.058 0.013 0.010 0.001 0.054 57 12 64.7 3.78 13 1350 110 939 0.696 0.049 0.006 0.064 0.008 0.010 0.000 0.135 62.7 7.3 66 2.44L 5 336 16 126 0.375 0.050 0.007 0.064 0.007 0.011 0.001 0.168 62.9 6.9 71.4 3.28L 10 212 8 60 0.283 0.044 0.007 0.059 0.008 0.012 0.001 0.038 58 8 74.8 4.28 14 2394 260 1742 0.728 0.049 0.005 0.073 0.006 0.012 0.000 0.090 71.1 5.5 78.1 2.32 3 566 35 225 0.398 0.044 0.008 0.072 0.012 0.013 0.000 0.082 70 12 83.4 2.710L 12 148 5 51 0.345 0.051 0.013 0.102 0.027 0.014 0.001 0.024 97 25 92 5.46L 7 222 12 83 0.374 0.051 0.008 0.101 0.016 0.014 0.001 0.370 97 15 92.5 57L 8 241 12 91 0.378 0.051 0.009 0.101 0.019 0.015 0.001 0.274 97 17 92.8 4.71 1 1713 125 1169 0.682 0.049 0.006 0.105 0.011 0.015 0.001 0.136 102 10 93.1 4.95L 6 196 8 68 0.347 0.052 0.009 0.099 0.018 0.015 0.001 0.271 95 16 93.1 4.16 8 1739 89 832 0.478 0.052 0.005 0.107 0.008 0.015 0.000 0.159 102.8 6.9 93.3 34 6 1562 128 804 0.515 0.044 0.004 0.086 0.008 0.015 0.001 0.351 83.8 7.2 94 4.49L 11 181 9 71 0.392 0.044 0.006 0.090 0.013 0.015 0.001 0.067 89 11 94.1 3.67 10 798 29 249 0.312 0.046 0.007 0.099 0.011 0.015 0.001 0.385 96 10 94.5 4.31 L=leached/annealed zircon; no L=unleached zircon; UTM coordinates based on NAD83 Zone 10 easting (UTME) and northing (UTMN).2 Integrations are created based on time-resolved laser profiles in Iolite; 3  U, Th, and Pb concentrations determined by Iolite using the Plešovice standard**  R=correlation coefficient of 206 Pb/ 238 U vs. 207 Pb/ 235 U38Table 2.3. (cont.) U-Th-Pb laser ablation ICP-MS analytical results for zircon from the Giant Mascot ultramafic intrusion and Spuzzum plutonCompositional Parameters 3 Radiogenic Isotope Ratios Isotopic Ages (Ma)Sample/Spot 1 Integration2 U (ppm) Pb (ppm) Th (ppm) Th/U 207 Pb/ 206 Pb ±2σ error 207 Pb/ 235 U ±2σ error 206 Pb/ 238 U ±2σ error R** 207 Pb/ 235 U ± 206 Pb/ 238 U ± 03GNX-3-1-1 (pyroxenite) cont.5 7 545 29 225 0.413 0.043 0.005 0.085 0.007 0.015 0.000 0.093 82.5 6.9 94.8 33L 3 101 5 37 0.366 0.036 0.008 0.073 0.016 0.015 0.001 0.445 70 15 96.1 41L 1 112 6 41 0.366 0.050 0.009 0.089 0.015 0.015 0.001 0.000 88 14 97.2 4.84 5 841 40 360 0.428 0.051 0.006 0.104 0.014 0.015 0.001 0.158 104 11 97.8 3.66 9 808 43 301 0.373 0.054 0.005 0.110 0.010 0.015 0.001 0.109 106.1 9.1 97.8 3.43 4 696 37 284 0.408 0.054 0.006 0.114 0.012 0.016 0.001 0.118 112 11 99.6 3.42L 2 118 6 45 0.381 0.050 0.011 0.100 0.021 0.016 0.001 0.140 95 19 99.6 410L 13 88 3 24 0.273 0.043 0.011 0.093 0.024 0.016 0.001 0.003 92 23 100.2 5.47 11 304 12 64 0.211 0.053 0.010 0.134 0.023 0.018 0.001 0.182 126 20 117.4 5.5Weighted mean 93.9 1.212MMA-2-4-1 (hornblende pyroxenite): UTME 608960  UTMN 5480264 (CA-TIMS age = 92.84 ± 0.06 Ma)13 14 1262 51 678 0.537 0.044 0.012 0.044 0.012 0.006 0.001 0.292 43 12 41.1 3.69 9 276 7 68 0.246 0.057 0.026 0.054 0.022 0.007 0.001 0.043 58 22 45.2 5.413 15 718 52 407 0.567 0.050 0.011 0.073 0.018 0.010 0.000 0.579 70 16 62.6 2.89 10 212 13 84 0.396 0.048 0.015 0.083 0.025 0.012 0.001 0.069 79 23 75.6 6.310 11 146 5 27 0.185 0.044 0.012 0.072 0.020 0.013 0.001 0.120 68 18 82.4 4.47 7 376 9 76 0.202 0.050 0.020 0.089 0.038 0.013 0.001 0.314 84 35 85.4 7.211 12 164 9 51 0.311 0.034 0.012 0.061 0.021 0.013 0.001 0.059 58 20 86.1 5.414 16 542 32 253 0.467 0.045 0.008 0.084 0.014 0.014 0.000 0.108 80 13 89.1 2.82 2 436 14 103 0.236 0.046 0.007 0.087 0.013 0.014 0.000 0.041 85 12 90.3 2.71 1 439 21 154 0.351 0.042 0.006 0.083 0.013 0.014 0.000 0.146 81 12 90.5 2.84 4 1198 50 420 0.351 0.042 0.006 0.076 0.011 0.014 0.000 0.079 74 10 90.6 2.26 6 1072 42 358 0.334 0.046 0.006 0.088 0.011 0.014 0.000 0.108 84 10 92.3 23 3 817 32 284 0.348 0.047 0.008 0.088 0.015 0.014 0.001 0.181 84 14 92.5 45 5 588 21 118 0.201 0.050 0.006 0.103 0.014 0.014 0.000 0.194 98 13 92.7 38 8 182 5 40 0.220 0.049 0.013 0.098 0.026 0.015 0.001 0.171 90 23 92.9 5.312 13 327 14 133 0.407 0.053 0.013 0.101 0.025 0.015 0.001 0.124 94 22 93.4 3.4Weighted mean 90.7 1.613MMA-2-7-1 (hornblendite): UTME 609108  UTMN 5480627 (CA-TIMS age = 93.01 ± 0.12 Ma)7 11 3095 96 1017 0.329 0.064 0.011 0.059 0.012 0.006 0.000 0.540 58 11 39.9 2.211 19 6482 335 3321 0.512 0.055 0.006 0.057 0.007 0.007 0.000 0.442 56.3 6.9 44.2 2.43 5 24947 1209 17205 0.690 0.053 0.004 0.054 0.006 0.007 0.000 0.626 53.6 5.9 44.5 2.914 24 47589 4085 37181 0.781 0.049 0.003 0.049 0.005 0.007 0.000 0.706 48.9 4.4 44.6 1.81 L=leached/annealed zircon; no L=unleached zircon; UTM coordinates based on NAD83 Zone 10 easting (UTME) and northing (UTMN).2 Integrations are created based on time-resolved laser profiles in Iolite; 3  U, Th, and Pb concentrations determined by Iolite using the Plešovice standard**  R=correlation coefficient of 206 Pb/ 238 U vs. 207 Pb/ 235 U39Table 2.3. (cont.) U-Th-Pb laser ablation ICP-MS analytical results for zircon from the Giant Mascot ultramafic intrusion and Spuzzum plutonCompositional Parameters 3 Radiogenic Isotope Ratios Isotopic Ages (Ma)Sample/Spot 1 Integration2 U (ppm) Pb (ppm) Th (ppm) Th/U 207 Pb/ 206 Pb ±2σ error 207 Pb/ 235 U ±2σ error 206 Pb/ 238 U ±2σ error R** 207 Pb/ 235 U ± 206 Pb/ 238 U ± 13MMA-2-7-1 (hornblendite)  cont.1 1 14383 706 21817 1.517 0.058 0.008 0.062 0.009 0.007 0.000 0.094 61 8.3 46.2 3.19 15 5431 319 2371 0.437 0.050 0.007 0.053 0.009 0.007 0.001 0.157 52.7 8.3 46.2 3.511 20 7125 482 3221 0.452 0.055 0.004 0.074 0.009 0.009 0.000 0.765 72.8 8.1 59.7 2.59 16 5621 360 2884 0.513 0.048 0.004 0.067 0.008 0.009 0.000 0.302 65.3 7.2 60.7 2.27 12 4293 269 2091 0.487 0.053 0.004 0.075 0.009 0.010 0.000 0.513 74.6 9.1 63.8 2.51 2 6656 374 3448 0.518 0.048 0.003 0.074 0.007 0.010 0.000 0.145 72.7 6.9 65 1.714 25 6522 571 3776 0.579 0.047 0.003 0.069 0.007 0.010 0.000 0.222 67.9 6.5 65.1 1.43 6 4815 230 2116 0.439 0.048 0.004 0.076 0.008 0.010 0.000 0.048 74 7.6 67.01 0.974 8 3370 93 931 0.276 0.063 0.006 0.103 0.012 0.012 0.000 0.216 100 11 76.8 2.411 21 5064 573 2974 0.587 0.053 0.005 0.089 0.011 0.012 0.000 0.516 87.8 9.2 76.9 2.21 3 3533 265 2576 0.729 0.050 0.005 0.097 0.011 0.013 0.000 0.215 93.9 9.8 83.2 2.73 7 3841 241 1782 0.464 0.055 0.006 0.108 0.015 0.013 0.001 0.159 104 14 84.3 3.214 26 6921 876 3795 0.548 0.051 0.004 0.099 0.011 0.013 0.000 0.004 96 9.8 86.3 1.96 10 1316 30 184 0.140 0.059 0.007 0.110 0.015 0.014 0.000 0.129 105 13 86.9 1.79 17 2466 180 721 0.292 0.051 0.007 0.099 0.013 0.014 0.000 0.005 95 12 87.6 2.215 27 982 24 162 0.165 0.054 0.005 0.100 0.012 0.014 0.000 0.164 97 11 89.9 2.68 14 2892 249 1482 0.512 0.054 0.004 0.103 0.011 0.014 0.001 0.279 98.8 9.9 90.2 3.82 4 9879 543 4865 0.492 0.054 0.005 0.108 0.012 0.014 0.000 0.143 103 11 92.2 1.47 13 1846 182 953 0.516 0.060 0.012 0.138 0.034 0.014 0.001 0.496 130 30 92.3 5.110 18 1153 20 113 0.098 0.052 0.006 0.105 0.013 0.015 0.001 0.144 100 12 93.7 3.713 23 23862 1924 15192 0.637 0.049 0.003 0.095 0.010 0.015 0.000 0.744 92 8.9 94.2 2.55 9 2422 124 413 0.171 0.092 0.010 0.184 0.024 0.015 0.001 0.058 174 19 94.5 3.412 22 31166 2545 20813 0.668 0.049 0.003 0.096 0.009 0.015 0.000 0.444 93.2 8.2 94.5 1.1Weighted mean 89.2 3.212MMA-2-3-1 (Spuzzum diorite): UTME 608954  UTMN 5480432 (CA-TIMS age = 95.20 ± 0.08 Ma)3 4 507 22 235 0.464 0.073 0.018 0.072 0.018 0.007 0.001 0.350 71 17 44.7 3.92 2 384 15 167 0.435 0.037 0.030 0.040 0.032 0.008 0.001 0.068 39 31 48.3 3.63 5 182 10 71 0.390 0.029 0.014 0.040 0.018 0.010 0.001 0.086 39 18 61.1 4.82 3 115 6 40 0.348 0.031 0.016 0.046 0.025 0.011 0.001 0.241 51 27 73.2 8.15L 5 141 7 40 0.284 0.057 0.025 0.101 0.046 0.013 0.001 0.045 94 42 81.3 6.75 7 155 4 28 0.181 0.040 0.014 0.066 0.023 0.013 0.001 0.309 63 22 84.9 5.73L 3 91 5 15 0.165 0.047 0.014 0.081 0.024 0.013 0.001 0.146 76 22 85.7 5.11L 1 86 10 25 0.291 0.048 0.013 0.106 0.030 0.014 0.001 0.151 97 27 87.2 5.71 L=leached/annealed zircon; no L=unleached zircon; UTM coordinates based on NAD83 Zone 10 easting (UTME) and northing (UTMN).2 Integrations are created based on time-resolved laser profiles in Iolite; 3  U, Th, and Pb concentrations determined by Iolite using the Plešovice standard**  R=correlation coefficient of 206 Pb/ 238 U vs. 207 Pb/ 235 U40Table 2.3. (cont.) U-Th-Pb laser ablation ICP-MS analytical results for zircon from the Giant Mascot ultramafic intrusion and Spuzzum plutonCompositional Parameters 3 Radiogenic Isotope Ratios Isotopic Ages (Ma)Sample/Spot 1 Integration2 U (ppm) Pb (ppm) Th (ppm) Th/U 207 Pb/ 206 Pb ±2σ error 207 Pb/ 235 U ±2σ error 206 Pb/ 238 U ±2σ error R** 207 Pb/ 235 U ± 206 Pb/ 238 U ± 12MMA-2-3-1 (Spuzzum diorite)  cont.6L 6 134 7 32 0.239 0.041 0.009 0.084 0.019 0.014 0.001 0.004 79 17 88.9 4.14 6 381 17 131 0.344 0.042 0.010 0.080 0.022 0.014 0.001 0.002 77 20 89 47L 7 253 6 35 0.138 0.043 0.014 0.085 0.028 0.014 0.001 0.217 80 25 89.5 74L 4 41 2 6 0.146 0.065 0.020 0.122 0.039 0.014 0.001 0.235 113 36 90 7.77 9 150 4 25 0.167 0.080 0.024 0.136 0.041 0.014 0.001 0.081 123 36 91.4 6.79 11 241 6 40 0.166 0.057 0.015 0.111 0.031 0.014 0.001 0.097 103 27 91.4 4.31 1 191 10 74 0.387 0.048 0.015 0.103 0.032 0.014 0.001 0.265 95 29 92.2 5.66 8 161 4 25 0.155 0.047 0.018 0.080 0.029 0.014 0.001 0.125 75 27 92.4 6.52L 2 29 4 5 0.172 0.046 0.020 0.096 0.042 0.015 0.001 0.045 94 39 92.6 6.58 10 99 4 16 0.162 0.058 0.023 0.107 0.040 0.015 0.001 0.053 96 35 94.1 7Weighted mean 89.2 1.812MMA-2-1-5 (Spuzzum quartz diorite): UTME 610135  UTMN 5481062 (CA-TIMS age = 95.02 ± 0.12 Ma)2 2 204 9 71 0.348 0.060 0.028 0.058 0.027 0.007 0.001 0.247 56 26 44.4 6.28 9 192 5 44 0.229 0.035 0.012 0.040 0.014 0.008 0.000 0.365 39 13 49.4 3.12 3 141 6 49 0.348 0.103 0.052 0.104 0.038 0.010 0.001 0.023 99 35 64.6 5.411 13 247 9 81 0.328 0.046 0.011 0.084 0.019 0.013 0.001 0.230 79 18 83.1 3.58 10 120 21 24 0.200 0.186 0.066 0.330 0.120 0.013 0.002 0.241 274 89 84.3 9.65 6 163 6 51 0.313 0.094 0.025 0.164 0.041 0.013 0.001 0.158 146 35 84.4 5.94 5 201 5 57 0.284 0.054 0.016 0.100 0.031 0.013 0.001 0.248 96 28 85.8 5.112 14 282 8 90 0.319 0.051 0.012 0.098 0.025 0.014 0.001 0.444 91 21 88.1 4.13 4 178 4 41 0.230 0.072 0.019 0.130 0.032 0.014 0.001 0.119 120 29 89.6 5.39 11 183 8 51 0.279 0.046 0.012 0.092 0.023 0.014 0.001 0.153 82 19 90.8 4.710 12 204 12 71 0.348 0.079 0.025 0.157 0.056 0.014 0.001 0.750 132 40 91.4 4.96 7 361 12 114 0.316 0.049 0.013 0.092 0.027 0.014 0.001 0.287 96 26 91.9 6.67 8 176 7 43 0.244 0.052 0.018 0.114 0.038 0.015 0.001 0.104 105 34 95.5 7.3Weighted mean 87.9 2.912MMA-6-5-1 (Spuzzum quartz diorite): UTME 609078  UTMN 5481423 (CA-TIMS age = 95.32 ± 0.21 Ma)3 3 97 4 28 0.289 0.047 0.019 0.061 0.023 0.008 0.001 0.019 57 21 54 4.94 4 125 8 35 0.280 0.054 0.025 0.064 0.026 0.009 0.001 0.028 59 23 57.8 5.92 2 104 4 27 0.260 0.050 0.022 0.065 0.027 0.010 0.001 0.106 60 25 62.2 5.67 7 176 5 36 0.205 0.038 0.012 0.076 0.022 0.013 0.001 0.105 71 20 82.6 4.36 6 118 6 41 0.347 0.055 0.025 0.078 0.033 0.013 0.001 0.022 70 29 83.2 6.78 8 247 12 83 0.336 0.063 0.015 0.111 0.027 0.014 0.001 0.111 103 24 90.4 3.81 L=leached/annealed zircon; no L=unleached zircon; UTM coordinates based on NAD83 Zone 10 easting (UTME) and northing (UTMN).2 Integrations are created based on time-resolved laser profiles in Iolite; 3  U, Th, and Pb concentrations determined by Iolite using the Plešovice standard**  R=correlation coefficient of 206 Pb/ 238 U vs. 207 Pb/ 235 U41Table 2.3. (cont.) U-Th-Pb laser ablation ICP-MS analytical results for zircon from the Giant Mascot ultramafic intrusion and Spuzzum plutonCompositional Parameters 3 Radiogenic Isotope Ratios Isotopic Ages (Ma)Sample/Spot 1 Integration2 U (ppm) Pb (ppm) Th (ppm) Th/U 207 Pb/ 206 Pb ±2σ error 207 Pb/ 235 U ±2σ error 206 Pb/ 238 U ±2σ error R** 207 Pb/ 235 U ± 206 Pb/ 238 U ± 12MMA-6-5-1 (Spuzzum diorite)  cont.9 9 102 2 22 0.216 0.049 0.021 0.087 0.036 0.015 0.001 0.106 76 31 93.6 5.110 10 201 8 47 0.234 0.043 0.011 0.082 0.021 0.015 0.001 0.417 77 19 94.1 5.65 5 131 10 49 0.374 0.065 0.027 0.108 0.042 0.015 0.001 0.276 93 35 94.5 7.611 11 169 7 51 0.302 0.042 0.012 0.078 0.022 0.015 0.001 0.080 73 21 94.5 5.212 12 115 4 25 0.217 0.042 0.013 0.076 0.024 0.015 0.001 0.143 70 22 94.6 61 1 96 3 23 0.240 0.048 0.017 0.096 0.032 0.015 0.001 0.126 86 29 94.8 7.8Weighted mean 93.1 211GNX-1-3-1 (Spuzzum quartz diorite): UTME 608907  UTMN 5480667 (CA-TIMS age = 95.47 ± 0.13 Ma)4L 4 1616 81 673 0.416 0.046 0.005 0.050 0.006 0.009 0.000 0.329 49.6 5.5 57.4 2.27L 8 1579 86 794 0.503 0.045 0.004 0.051 0.005 0.009 0.000 0.251 50.3 4.3 57.8 2.47L 9 438 28 206 0.470 0.051 0.007 0.066 0.009 0.012 0.001 0.470 64.6 8.5 74.6 3.61 1 145 4 31 0.214 0.050 0.008 0.068 0.011 0.012 0.001 0.301 66 10 74.8 3.54L 5 477 33 180 0.377 0.053 0.008 0.082 0.010 0.013 0.000 0.099 79.9 9.3 84.2 3.13L 3 471 33 166 0.352 0.048 0.007 0.077 0.009 0.014 0.001 0.183 75.5 8.9 86.9 3.811 11 217 10 67 0.309 0.048 0.007 0.097 0.013 0.014 0.001 0.153 94 12 92.6 3.210 10 152 4 34 0.224 0.046 0.007 0.089 0.014 0.015 0.001 0.325 88 13 94 3.96 6 115 4 27 0.235 0.049 0.010 0.100 0.019 0.015 0.001 0.052 96 18 94.1 4.75L 6 294 12 87 0.296 0.051 0.010 0.107 0.020 0.015 0.001 0.133 102 18 94.3 4.42L 2 555 29 220 0.396 0.052 0.005 0.103 0.009 0.015 0.001 0.165 99.1 8 94.5 3.24 4 153 6 37 0.242 0.051 0.010 0.103 0.018 0.015 0.001 0.216 98 16 94.9 3.73 3 78 3 17 0.218 0.052 0.013 0.101 0.022 0.015 0.001 0.230 95 20 95 5.48L 10 1374 79 715 0.520 0.045 0.004 0.099 0.009 0.015 0.001 0.416 95.7 8.4 95.1 3.67 7 148 9 59 0.399 0.052 0.009 0.107 0.018 0.015 0.001 0.137 102 16 95.2 41L 1 535 28 198 0.370 0.048 0.005 0.099 0.008 0.015 0.000 0.028 97.1 7.7 95.4 2.86L 7 770 40 307 0.399 0.049 0.005 0.101 0.010 0.015 0.000 0.464 98.9 9.4 95.4 39 9 75 3 17 0.227 0.047 0.008 0.103 0.018 0.015 0.001 0.010 98 17 96 4.32 2 114 4 26 0.228 0.048 0.009 0.107 0.020 0.015 0.001 0.155 104 18 97.3 4.75 5 133 5 25 0.188 0.049 0.008 0.104 0.017 0.015 0.001 0.108 99 15 97.7 4.412 12 75 3 18 0.240 0.045 0.010 0.098 0.021 0.015 0.001 0.067 96 20 98.7 5.18 8 127 5 29 0.228 0.049 0.010 0.104 0.020 0.016 0.001 0.037 103 19 99.4 5.1Weighted mean 95.27 0.951 L=leached/annealed zircon; no L=unleached zircon; UTM coordinates based on NAD83 Zone 10 easting (UTME) and northing (UTMN).2 Integrations are created based on time-resolved laser profiles in Iolite; 3  U, Th, and Pb concentrations determined by Iolite using the Plešovice standard**  R=correlation coefficient of 206 Pb/ 238 U vs. 207 Pb/ 235 U42Table 2.4. 40Ar/ 39 Ar analytical results for hornblende and biotite from the Giant Mascot ultramafic intrusion and Spuzzum plutonStepPower (%)40Ar/ 39 Ar 1σ 37 Ar/ 39 Ar 1σ 36 Ar/ 39 Ar 1σ Ca/K% 40Ar atmƒ 39 Ar 40Ar*/ 39 ArK1 Age (Ma) ±2σMafic enclave in Spuzzum quartz diorite: UTME 610135  UTMN 548106212MMA-2-1-2a (hornblende), J = 0.0043068 ± 0.0000215*1 2.3 961.18 16.30 3.21 0.45 2.842 0.114 5.89 87.34 1.99 121.94 763.32 314.372 2.6 69.08 1.03 0.95 0.32 0.228 0.009 1.75 97.36 2.72 1.82 14.15 37.193 3.0 39.96 0.39 10.61 0.46 0.092 0.005 19.58 66.18 11.01 13.61 103.03 21.554 3.5 18.39 0.15 17.13 0.43 0.023 0.002 31.76 28.60 74.20 13.29 100.66 7.375 3.9 14.65 0.14 14.18 0.43 0.006 0.002 26.24 4.35 8.72 14.15 106.98 8.576 5.0 21.45 0.36 17.66 0.73 0.034 0.011 32.75 40.60 1.35 12.90 97.8 47.67Integrated date 101.62 5.3212MMA-2-1-2b (hornblende), J = 0.0043068 ± 0.00002151 2.3 5274.56 290.03 4.61 9.41 17.792 1.989 8.47 99.66 0.18 17.86 133.99 7461.052 2.8 584.55 14.78 1.51 0.43 1.978 0.065 2.77 99.94 1.55 0.33 2.54 189.43 3.2 57.46 1.02 0.30 0.29 0.179 0.007 0.55 91.83 4.87 4.70 36.22 29.244 3.7 55.98 0.52 2.01 0.14 0.143 0.004 3.69 75.35 7.20 13.82 104.53 14.865 4.1 26.97 0.24 13.77 0.39 0.050 0.002 25.46 50.96 10.12 13.36 101.15 6.896 4.6 22.01 0.27 16.36 0.90 0.039 0.002 30.31 45.98 30.90 12.03 91.33 7.937 5.1 22.14 0.29 18.53 0.49 0.037 0.001 34.40 42.63 23.11 12.87 97.55 6.248 5.6 17.62 0.29 17.66 0.41 0.022 0.001 32.76 27.48 11.83 12.94 98.09 5.99 6.6 18.49 0.35 15.97 0.94 0.022 0.001 29.59 27.88 10.25 13.48 102.08 6.44Integrated date 98.04 2.8712MMA-2-1-2a (biotite), J = 0.0044462 ± 0.00002221 2.0 117.89 0.99 0.25 0.01 0.410 0.009 0.45 102.67 2.61 -3.14 -25.45 41.262 2.6 24.04 0.24 0.12 0.00 0.076 0.003 0.22 93.40 16.76 1.59 12.71 12.013 2.8 21.06 0.14 0.06 0.00 0.040 0.001 0.11 56.78 11.18 9.10 71.73 4.364 3.0 20.60 0.13 0.06 0.00 0.031 0.001 0.11 44.22 17.03 11.49 90.13 4.35 3.3 19.86 0.12 0.15 0.00 0.024 0.001 0.27 36.00 20.25 12.71 99.45 3.896 3.6 18.70 0.11 0.56 0.01 0.021 0.001 1.03 32.47 18.74 12.63 98.8 2.517 3.9 17.63 0.13 0.37 0.01 0.015 0.000 0.68 25.47 9.79 13.14 102.67 2.428 4.5 16.10 0.12 0.57 0.02 0.010 0.000 1.05 17.84 3.63 13.24 103.4 2.54Integrated date 97.07 1.2312MMA-2-1-2b (biotite), J = 0.0044462 ± 0.00002221 2.3 47.99 0.37 0.16 0.03 0.135 0.003 0.28 82.84 4.19 8.23 65.03 14.042 2.6 22.13 0.26 0.09 0.01 0.046 0.002 0.16 61.16 13.20 8.59 67.81 8.333 2.9 19.75 0.20 0.04 0.01 0.023 0.001 0.08 34.87 29.45 12.87 100.59 6.144 3.2 18.97 0.13 0.05 0.01 0.021 0.001 0.10 32.36 26.16 12.83 100.33 3.345 3.5 18.01 0.12 0.06 0.01 0.017 0.000 0.11 27.88 16.42 12.99 101.52 2.446 4.0 14.49 0.13 0.08 0.02 0.005 0.000 0.14 10.33 8.25 12.99 101.54 2.287 5.0 17.49 0.21 0.15 0.03 0.015 0.002 0.28 25.44 2.34 13.04 101.95 10.7Integrated date 99.94 1.411 40Ar*=radiogenic 40Ar; *J = irradiation parameter43Table 2.4. (cont.) 40Ar/ 39 Ar analytical results for hornblende and biotite from the Giant Mascot ultramafic intrusion and Spuzzum plutonStepPower (%)40Ar/ 39 Ar 1σ 37 Ar/ 39 Ar 1σ 36 Ar/ 39 Ar 1σ Ca/K% 40Ar atmƒ 39 Ar 40Ar*/ 39 ArK1 Age (Ma) ±2σMylonite (Spuzzum quartz diorite + hornblendite): UTME 608956  UTMN 548075011GNX-1-2-1 (hornblende), J = 0.0042652 ± 0.0000213 1 2.3 768.70 46.46 9.27 0.77 2.337 0.163 17.09 89.72 0.31 79.55 528.3 285.552 2.6 137.55 7.13 2.34 0.30 0.047 0.025 4.29 9.96 0.56 124.05 767.97 99.073 3 73.27 2.86 3.27 0.15 0.218 0.020 6.01 87.56 1.30 9.14 69.13 82.614 3.4 18.28 0.29 14.38 0.47 0.027 0.001 26.61 37.11 15.28 11.61 87.41 6.395 3.7 14.13 0.23 15.64 0.45 0.013 0.001 28.97 19.23 65.25 11.54 86.90 4.886 4 14.20 0.16 17.07 0.41 0.014 0.001 31.65 20.13 14.20 11.48 86.41 6.587 4.6 18.86 0.67 17.71 0.73 0.041 0.009 32.84 56.93 1.30 8.23 62.36 40.048 5.6 27.28 0.59 16.82 0.46 0.064 0.005 31.18 64.33 1.80 9.85 74.38 23.72Integrated date 87.29 3.2911GNX-1-2-1b (hornblende), J = 0.0056715 ± 0.00002841 2 907.86 160.72 8.57 2.57 2.770 0.625 15.79 90.08 0.01 90.60 749.83 1575.482 2.4 297.52 9.84 11.01 0.54 0.769 0.031 20.32 76.11 0.20 71.64 616.56 96.503 2.8 65.31 1.69 9.81 0.36 0.135 0.009 18.09 59.79 0.38 26.44 252.69 46.454 3.2 41.23 0.84 7.84 0.22 0.086 0.003 14.44 60.03 0.68 16.57 162.45 19.635 3.6 18.16 0.40 11.59 0.32 0.028 0.001 21.41 40.51 2.37 10.89 108.37 8.956 4 11.55 0.16 16.69 0.33 0.013 0.000 30.94 21.23 17.54 9.21 92.04 3.447 4.4 10.87 0.10 16.62 0.29 0.010 0.000 30.80 14.96 35.94 9.35 93.46 2.418 4.8 10.08 0.09 16.24 0.30 0.007 0.000 30.08 8.15 25.90 9.36 93.55 2.179 5.2 10.13 0.10 16.73 0.30 0.007 0.000 31.01 8.29 9.89 9.40 93.95 3.4210 6 10.41 0.11 16.81 0.32 0.010 0.001 31.16 14.27 3.64 9.03 90.34 3.9611 7 10.87 0.11 17.15 0.33 0.011 0.001 31.79 15.80 3.44 9.26 92.60 4.20Integrated date 93.73 1.2011GNX-1-2-1c (hornblende), J = 0.0056715 ± 0.00002841 2.3 260.03 15.13 260.84 386.39 0.712 0.069 585.55 98.77 0.30 3.92 39.80 1742.522 2.7 66.93 1.26 181.35 168.90 0.165 0.015 380.90 68.88 1.33 23.89 229.74 456.703 3.4 11.52 0.09 26.84 3.25 0.015 0.001 50.11 24.51 55.25 8.87 88.74 14.004 4 11.00 0.09 27.28 4.56 0.015 0.001 50.94 25.32 40.75 8.37 83.90 17.265 4.6 12.16 0.47 149.91 69.86 0.053 0.014 307.05 37.05 2.37 8.56 85.77 211.05Integrated date 86.9 10.8511GNX-1-2-2a (large hornblende), J = 0.0043001 ± 0.00002151 2.3 653.08 42.13 13.83 1.07 1.913 0.140 25.57 86.37 0.32 89.87 590.89 231.102 2.6 212.49 10.14 11.81 0.90 0.663 0.088 21.81 91.75 0.22 17.69 132.55 356.763 3 54.53 1.16 7.99 0.45 0.133 0.025 14.72 71.14 0.51 15.83 119.06 110.134 3.4 20.80 0.30 12.59 0.30 0.023 0.011 23.27 27.32 1.38 15.25 114.89 47.145 3.7 16.84 0.12 15.63 0.36 0.018 0.001 28.95 23.97 17.95 12.94 97.95 3.886 4 19.60 0.24 15.10 0.29 0.026 0.001 27.96 32.61 31.46 13.35 100.95 4.877 4.4 16.38 0.22 14.86 0.31 0.016 0.001 27.50 22.44 45.57 12.84 97.17 3.648 4.8 18.17 0.55 15.82 0.52 0.023 0.006 29.29 30.19 2.60 12.83 97.10 25.65Integrated date 98.41 2.321 40Ar*=radiogenic 40Ar; *J = irradiation parameter44Table 2.4. (cont.) 40Ar/ 39 Ar analytical results for hornblende and biotite from the Giant Mascot ultramafic intrusion and Spuzzum plutonStepPower (%)40Ar/ 39 Ar 1σ 37 Ar/ 39 Ar 1σ 36 Ar/ 39 Ar 1σ Ca/K% 40Ar atmƒ 39 Ar 40Ar*/ 39 ArK1 Age (Ma) ±2σ11GNX-1-2-2b (large hornblende), J = 0.0043001 ± 0.00002151 2.3 2850.76 427.55 2.49 16.05 9.101 1.426 4.57 94.33 0.13 161.98 955.85 1143.172 2.8 405.05 45.48 0.36 3.32 1.293 0.156 0.66 94.33 0.33 22.99 170.45 249.643 3.3 217.97 9.45 6.50 1.94 0.699 0.059 11.96 94.47 0.64 12.10 91.72 224.134 3.7 22.38 0.34 14.13 0.85 0.038 0.006 26.14 44.74 6.40 12.49 94.60 24.835 4.2 13.79 0.13 16.13 0.35 0.009 0.001 29.88 10.74 60.60 12.45 94.33 3.286 4.6 13.52 0.18 16.32 0.84 0.008 0.001 30.24 8.50 25.10 12.52 94.80 5.867 5.1 14.12 0.23 15.93 0.90 0.013 0.004 29.51 18.08 6.79 11.70 88.78 16.57Integrated date 94.3 2.8011GNX-1-2-2c (large hornblende), J = 0.0043001 ± 0.00002151 2.3 3966.75 2519.38 19.82 23.53 13.349 8.495 36.81 99.40 0.02 24.29 179.65 2292.912 2.8 125.27 7.21 4.24 2.85 0.324 0.029 7.78 76.17 0.30 29.94 219.03 95.333 3.3 46.78 1.73 1.56 1.03 0.115 0.018 2.86 72.24 0.31 13.00 98.38 77.284 3.8 16.83 0.22 11.93 0.54 0.019 0.003 22.04 27.84 4.68 12.24 92.79 12.665 4.3 13.23 0.16 13.71 0.43 0.007 0.000 25.35 6.58 18.50 12.48 94.50 2.726 4.8 13.17 0.25 13.82 0.37 0.007 0.000 25.56 7.18 41.21 12.35 93.56 3.897 5.2 13.38 0.17 15.21 0.52 0.008 0.001 28.16 7.41 23.02 12.52 94.86 4.168 5.6 13.72 0.19 15.21 0.77 0.009 0.002 28.15 10.28 3.16 12.44 94.27 9.889 6.5 13.22 0.13 17.39 0.50 0.009 0.001 32.25 8.33 8.81 12.27 92.98 3.10Integrated date 93.98 1.6211GNX-1-2-2a (hornblende), J = 0.0042926 ± 0.00002151 2.3 536.42 448.97 11.05 9.33 1.151 1.009 20.39 63.25 0.06 198.66 1115.1 1619.922 2.6 72.50 22.04 4.07 1.27 0.229 0.085 7.47 92.94 0.18 5.14 39.43 304.373 3.1 24.13 1.71 0.76 0.07 0.072 0.009 1.39 87.88 1.37 2.93 22.56 42.964 3.5 18.13 1.26 0.92 0.07 0.030 0.007 1.68 49.38 1.62 9.18 69.93 34.325 3.9 14.68 1.00 2.51 0.12 -0.020 0.008 4.60 -42.32 1.99 20.93 155.59 38.756 4.3 13.11 0.18 11.51 0.22 0.008 0.001 21.25 10.80 11.67 11.79 89.25 4.167 4.9 12.25 0.12 15.07 0.37 0.007 0.000 27.90 5.74 78.99 11.67 88.42 2.058 5.5 16.55 0.53 16.79 0.63 0.015 0.004 31.12 17.68 4.13 13.78 103.95 20.10Integrated date 88.69 1.8311GNX-1-2-2b (hornblende), J = 0.0042926 ± 0.00002151 2.3 44.09 2.88 8.00 0.70 0.148 0.029 14.73 97.66 1.26 1.04 8.03 127.852 2.6 9.50 0.18 2.03 0.45 0.010 0.003 3.73 29.66 3.14 6.69 51.20 15.443 3.2 9.25 0.16 7.62 0.47 0.003 0.002 14.04 4.54 6.00 8.88 67.62 8.584 3.6 11.85 0.17 12.65 0.38 0.007 0.002 23.37 8.60 11.42 10.93 82.88 7.595 4 12.41 0.11 13.23 0.43 0.008 0.000 24.45 10.30 44.66 11.23 85.15 2.546 4.4 12.53 0.20 10.83 0.57 0.009 0.002 19.98 13.62 10.48 10.91 82.75 7.397 5 11.36 0.16 9.04 0.29 0.006 0.001 16.66 8.35 15.91 10.48 79.55 6.978 6 17.34 0.31 12.77 0.95 0.028 0.004 23.61 41.89 7.14 10.17 77.25 16.67Integrated date 82.52 2.081 40Ar*=radiogenic 40Ar; *J = irradiation parameter45Table 2.4. (cont.) 40Ar/ 39 Ar analytical results for hornblende and biotite from the Giant Mascot ultramafic intrusion and Spuzzum plutonStepPower (%)40Ar/ 39 Ar 1σ 37 Ar/ 39 Ar 1σ 36 Ar/ 39 Ar 1σ Ca/K% 40Ar atmƒ 39 Ar 40Ar*/ 39 ArK1 Age (Ma) ±2σ11GNX-1-2-2c (hornblende), J = 0.0042926 ± 0.00002151 2.3 2770.62 161.79 4.11 1.96 10.314 0.642 7.55 94.54 0.26 151.58 906.29 593.992 2.9 47.53 1.05 0.22 0.80 0.154 0.011 0.40 82.57 0.75 8.29 63.21 39.423 3.3 25.74 0.35 1.44 0.22 0.064 0.003 2.64 63.06 3.62 9.52 72.42 12.264 3.7 34.56 0.32 1.00 0.15 0.098 0.004 1.83 72.14 5.32 9.64 73.29 14.365 4.1 36.24 0.37 2.80 0.31 0.099 0.003 5.14 69.16 5.41 11.20 84.90 11.326 4.6 26.28 0.20 6.36 0.24 0.061 0.002 11.70 57.23 13.02 11.29 85.58 7.687 5.2 19.79 0.23 9.12 0.25 0.039 0.001 16.80 47.23 27.15 10.51 79.80 4.438 5.6 17.70 0.22 10.90 0.45 0.030 0.001 20.11 39.38 23.35 10.82 82.06 4.699 6 19.83 0.20 10.42 0.33 0.037 0.001 19.22 43.41 12.71 11.30 85.68 3.8910 6.8 27.67 0.18 8.78 0.36 0.064 0.002 16.17 56.90 8.41 12.00 90.83 7.84Integrated date83.14 2.151 40Ar*=radiogenic 40Ar; *J = irradiation parameterTable 2.5.  Summary of 40Ar/ 39 Ar plateau and inverse isochron ages for the Giant Mascot ultramafic intrusion and Spuzzum plutonSample 1 Steps Plateau age (Ma, ±2σ) (40Ar/ 36 Ar)i* Inverse isochron (Ma, ±2σ) MSWD**Mafic enclave in Spuzzum quartz diorite: UTME 610135  UTMN 548106212MMA-2-1-2a, hbl 3-6 103.3 ± 5.5 289 ± 34 103.9 ± 6.6 0.5812MMA-2-1-2b, hbl 4-9 98.7 ± 3.1 288 ± 19 99.7 ± 7.7 3.312MMA-2-1-2a, biotite 5-7 100.6 ± 1.9 254 ± 10 106.2 ± 1.9 0.6612MMA-2-1-2b, biotite 3-7 101.3 ± 1.8 264 ± 12 104.2 ± 2.0 1.3Mylonite (Spuzzum quartz diorite + hornblendite): UTME 608956  UTMN 548075011GNX-1-2-1, hbl 3-8 86.5 ± 3.4 315 ± 19 84.2 ± 3.9 1.1911GNX-1-2-1b, hbl 6-11 93.0 ± 1.5 380 ± 22 89.1 ± 2.4 1.811GNX-1-2-1c, hbl 1-5 87 ± 11 425 ± 150 86 ± 13 0.3611GNX-1-2-2a, large hbl 2-8 98.4 ± 2.5 334 ± 21 93.8 ± 3.5 0.1811GNX-1-2-2b, large hbl 1-7 94.3 ± 3.0 306 ± 18 93.7 ± 2.9 0.1911GNX-1-2-2c, large hbl 1-9 94.0 ± 1.9 310 ± 21 93.4 ± 1.8 0.7811GNX-1-2-2a, hbl 6-8 88.7 ± 2.0 299 ± 160 88.3 ± 5.4 3.111GNX-1-2-2b, hbl 4-8 84.1 ± 2.3 259 ± 71 85.1 ± 3.1 0.9911GNX-1-2-2c, hbl 2-9 82.5 ± 2.4 263 ± 16 80.2 ± 6.1 2.21 hbl, hornblende*  (40Ar/ 36 Ar)i = initial ratio based on inverse isochron correlation diagram (errors reported at the 2σ level)**  MSWD is associated with inverse isochron ages46weighted mean age is greater than 5%; 3) slope of the error-weighted line through the plateau ages equals zero at 5% confidence; 4) ages of the two outermost steps on a plateau are not significantly different from the weighted-mean plateau age (at 1.8σ, six or more steps only); and 5) outermost two steps on either side of a plateau must not have non-zero slopes with the same sign (at 1.8σ, nine or more steps only). 2 5  Results2 5 1  Growth zoning and internal structure of zirconCathodoluminescence (CL) images from zircon grains reveal distinct internal differences. Zircon from ultramafic and mafic rocks is anhedral to subhedral and contains sector and oscillatory zones that are alternately brightly luminescent and dark (Figs. 2.5A, 2.6A). Zircon from the hornblendite (13MMA-2-7-1) is distinctively prismatic and characterized by altered and porous cores and oscillatory zoned rims (<5 μm brightly luminescent and dark zones) (Fig. 2.6A, 2.7). The Spuzzum pluton zircon is typically euhedral with oscillatory zoning and lacks the significant changes in luminescence observed in zircon from the Giant Mascot ultramafic rocks (Figs. 2.5B, 2.6B). Grains from 12MMA-6-5-1 are predominantly luminescent and contain anomalous dark rims. Oscillatory zoning in zircon grains from pyroxenite 12MMA-5-4-1 is very similar to grains from the Spuzzum pluton and they are interpreted below as xenocrysts (Fig. 2.6A). Zircon in ultramafic cumulates of the Giant Mascot intrusion is interstitial to olivine, pyroxene, and hornblende, reflecting crystallization at near-solidus temperatures (e.g., Scoates and Chamberlain, 1995; Corfu et al., 2003; Scoates and Wall, in press). The low aspect ratios and anhedral morphologies of zircon in pyroxenite and hornblende pyroxenite are indicative of relatively slow cooling in interstitial pockets, whereas the high aspect ratio and highly fractured, prismatic zircon in hornblendites may reflect more rapid crystallization (e.g., Corfu and Stott, 1998; Corfu et al., 2003). 4712MMA-5-4-1 (Px)13MMA-2-7-1 (Hb)12MMA-2-3-1 (Sgbn)B) Spuzzum plutonA) Giant Mascot ultramafic intrusion12MMA-6-5-1 (Sqdi)12MMA-2-1-5 (Sqdi) 11GNX-1-3-1 (Sqdi)03GNX-3-1-1 (Px)12MMA-2-4-1 (HPx)250 μm 250 μmFigure 2.5.1250 μm200 μm200 μm250 μm250 μm250 μmFigure 2.5.  Photomicrographs in transmitted light of zircon populations selected for U-Pb geochronology in A) samples of two pyroxenites (Px), a hornblende pyroxenite (HPx) and a hornblendite (Hb) from Giant Mascot ultramafic intrusion and B) samples of gabbronorite-diorite (Sgbn) and quartz diorite (Sqdi) from the Spuzzum pluton. 4830 µm 40 µm12MMA-5-4-1 (Px) A) Giant Mascot ultramafic intrusionB) Spuzzum pluton12MMA-2-4-1 (HPx)12MMA-2-3-1 (Sgbn) 12MMA-2-1-5 (Sqdi)12MMA-6-5-1 (Sqdi)11GNX-1-3-1 (Sqdi)13MMA-2-7-1 (Hb)03GNX-3-1-1 (Px)40 µm50 µm40 µm 40 µm50 µm 40 µm 70 µm 80 µm40 µm40 µm40 µm 40 µm40 µm50 µm40 µm50 µmFigure 2.5.2Figure 2.6.  Cathodoluminescence images of individual zircon grains from samples of the Giant Mascot ultramafic intrusion and Spuzzum pluton analyzed by U-Pb TIMS and laser ablation ICP-MS. A) Zircon from ultramafic and mafic rocks containing laminar zones that are alternately bright and dark representing oscillatory and sector zoning; note that zircon from a hornblendite (13MMA-2-7-1) displays altered and porous cores enclosed by oscillatory growth zones. B) Zircon from Spuzzum pluton diorites also showing oscillatory and sector zoning with more subtle luminescence contrast. Rock abbreviations: Px=pyroxenite, HPx=hornblende pyroxenite, Hb=hornblendite, Sgbn=Spuzzum gabbronorite-diorite, Sqdi=Spuzzum quartz diorite.49μP μPμPμPA BC BSE BSESESEDuranothorite[U,Th]SiO 4Figure 2.5.3plagioclasealtered/pitted corepitslaser spotPDJPDWLFULPFigure 2.7.  Backscatter (BSE) and secondary electron (SE) images of representative zircon grains from a hornblendite (13MMA-2-7-1). Circular holes in grains are 17 μm spots from laser ablation ICP-MS analysis. A) An untreated grain containing abundant pits from alteration throughout the zircon grain (SE). B) A plagioclase inclusion in zircon (SE). C) Abundant fine-grained inclusions of uranothorite [U,Th]SiO4 in zircon as in A), (BSE). D) Altered zircon grain with a patchy altered core surrounded by a relatively intact magmatic rim (BSE).502 5 2  Ti-in-zircon thermometryMinimum crystallization temperatures of zircon (hereafter Tzrn) in the ultramafic rocks were calculated using the Ti-in-zircon thermometry method of Ferry and Watson (2007):log(ppm Ti-in-zircon) = (5.711 ± 0.072) – (4800 ± 86) / T(K) – logaSiO2 + loga TiO2If rutile is present, the activity of Ti equals one ( aTiO2=1). As all zircon-bearing Giant Mascot ultramafic rocks utilized in this study are rutile-bearing, then aTiO2=1 (Watson and Harrison, 2005). Estimation of the silica activity, a SiO2, for ultramafic rocks where quartz is absent requires utilizing coexisiting mineral phases with respect to pure SiO2 (e.g., Frost and Beard, 2007). The silica activity of ultramafic rocks containing the assemblage olivine-orthopyroxene-clinopyroxene-hornblende is constrained by the olivine-orthopyroxene buffer (2En = Fo + SiO2), which yields aSiO2= 0.8 for a pressure of 1 kbar and T=800°C (Frost and Beard, 2007). Thermobarometry calculations using the garnet-biotite-plagioclase-aluminosilicate-quartz assemblage indicate that the northeastern part of the Spuzzum pluton, ~5 km north of Giant Mascot, reached a maximum pressure of 5-6 kbars (Brown and Burmester, 1991). The silica buffer is slightly pressure dependent and decreases in silica activity by 0.2 log units between 1-10 kbars (Frost and Beard, 2007). Assuming that the emplacement of Giant Mascot ultramafic rocks occurred at a pressure of 5-6 kbars, silica activity values will decrease by ~0.1 log units and yield aSiO2= 0.7. All rocks from the Spuzzum pluton examined in this study contain coexisting zircon, rutile, and quartz, thus aSiO2=1  and a TiO2=1 .Calculated Tzrn for two pyroxenites range from 646-799°C, with averages of 696 ± 68°C (12MMA-5-4-1, n=9) and 720 ± 44°C (03GNX-3-1-1, n=27; Fig. 2.8). Zircon from a hornblende pyroxenite (12MMA-2-4-1) has a lower Tzrn=601-682°C with an average of 640 ± 72°C (n=9), and zircon in a hornblendite (13MMA-2-7-1) gives a wide range of Tzrn=662-837°C, averaging 762 ± 58°C (n=24; Fig. 2.8). The relatively higher Tzrn and larger errors recorded from zircon in the hornblendite are likely the result of the microporous and altered grains (Fig. 2.7). The calculated Tzrn for a Spuzzum diorite (12MMA-2-3-1) range from 681-816°C with an 51~ 600°C~ 700°C~ 800°C~ 850°C05101520253035402000 4000 6000 8000 10000 12000 14000Hf zircon  (ppm)Ti zircon (ppm)03GNX-3-1-1 Px (720 ± 44°C)Giant Mascot ultramafic intrusion Spuzzum pluton12MMA-5-4-1 Px (696 ± 68°C) 12MMA-2-4-1 HPx (640 ± 72°C)13MMA-2-7-1 Hb (762 ± 58°C)12MMA-2-3-1 Sgbn (741 ± 62°C)11GNX-1-3-112MMA-2-1-512MMA-6-5-1 Sqdi (741 ± 49°C)Figure 2.13Figure 2.8.  Ti and Hf concentrations (ppm) in zircon from the Giant Mascot ultramafic intrusion and Spuzzum pluton with colours that correspond to individual samples (see legend) and correlate to map locations in Fig. 2.3. Error bars for Ti and Hf represent uncertainties at the 2σ level. Dashed lines indicate minimum zircon crystallization temperatures calculated from the Ti-in-zircon method of Ferry and Watson (2007). See text for details.  52average of 741 ± 62°C (n=16; Fig. 2.8). Zircon from three Spuzzum quartz diorites (11GNX-1-3-1, 12MMA-2-1-5, and 12MMA-6-5-1) indicate a wide range of Tzrn from 658-844°C and a similar average of 741 ± 49°C (n=43; Fig. 2.8). The overall average crystallization temperature for zircon in the Giant Mascot intrusion is slightly lower (~710°C) than the Spuzzum pluton (~740°C), although they are identical within error. Relatively low Tzrn in both rock packages indicates that the parental magmas must have been zircon-undersaturated when they were emplaced in the mid-crust, similar to the ca. 90-96 Ma Mt. Stuart batholith in the Northern Cascades (e.g., Miller et al., 2007).2 5 3  Chemical abrasion ID-TIMS zircon geochronology2.5.3.1.  PyroxeniteZircon in pyroxenites is anhedral to subhedral and variable in size (50-250 μm). Grains from 03GNX-3-1-1 are characterized by relatively large aspect ratios (~2:1 to 5:1, up to 250 μm in length), whereas grains from 12MMA-5-4-1 are smaller (predominantly <50 μm) with a large proportion of euhedral morphologies (Fig 2.5). For 03GNX-3-1-1, the analytical results for five single zircon fractions are concordant with U concentrations ranging from 273 to 745 ppm and relatively high Th/U (0.336-0.683; Fig. 2.9). A weighted 206 Pb/ 238 U age of 93.04 ± 0.06 Ma (2σ, MSWD=1.02) is interpreted as the crystallization age of this Giant Mascot pyroxenite (Fig. 2.10A). Populations of both magmatic and xenocrystic zircon are recognized in sample 12MMA-5-4-1 (Fig. 2.10B). The U-Pb results for two zircon grains (I and F; Table 2.1) are concordant with high U concentrations of 1597 and 1237 ppm and Th/U of 0.328 and 0.379, respectively. The weighted mean 206 Pb/ 238 U age of these two grains is 92.78 ± 0.09 Ma (2σ, MSWD=0.34), which is slightly younger than the other pyroxenite. The remaining 11 analyzed grains are inferred to be xenocrysts from the Spuzzum pluton and have generally lower U concentrations (39-372 ppm), lower Th/U (0.097-0.238), and yield concordant results with a weighted 206 Pb/ 238 U age of 95.07 ± 0.07 Ma (2σ, n=8; MSWD=0.91), indistinguishable from the age of the Spuzzum pluton given below (sections 2.5.3.4 and 2.5.3.5). The U-Pb results for three zircon fractions (K, 53Figure 2.603GNX-3-1-1xenocrystic zirconprimary zirconGiant Mascot Spuzzum 12MMA-2-3-112MMA-6-5-111GNX-1-3-112MMA-2-1-512MMA-5-4-112MMA-2-4-113MMA-2-7-1Th/U = 0.25Th/U = 0.5Th/U = 1.0INSETINSETU (ppm)50010001500200025003000Th (ppm)100 200 300 400 500 600 700 800 9005010015020020 30 40 50Th/U = 0.1Th/U = 0.25Th/U = 0.5Th/U = 1.010Figure 2.9.  Plot of Th vs. U concentrations (ppm) in individual zircon grains from the Giant Mascot ultramafic suite and Spuzzum pluton measured by CA-ID-TIMS. Dashed lines are reference Th/U ratios. Data points are colour coded according to rock type (see Fig. 2.3). The location of the inset is marked by the red box. Analytical uncertainty is smaller than the symbol size.540.0132 0.0140 0.0148 0.090 0.098 0.10684 88 92 96 12MMA-5-4-1: Pyroxenite (Px)   206Pb/238U207 Pb/ 235 USpuzzum pluton xenocrystsWeighted 206 Pb/ 238 U age = 95.07 ± 0.07 Ma (n=8, MSWD=0.91)     Pb-lossPb-loss 0.01445 0.01465 0.0952 0.0960 0.0968 93 92.5 93.5 Primary magmatic grainsWeighted 206 Pb/ 238 U age = 92.78 ± 0.09 Ma (n=2, MSWD=0.34)     0.01450 0.01454 0.01458 0.095 0.097 0.099 03GNX-3-1-1: Pyroxenite (Px)   206Pb/238U207 Pb/ 235 UWeighted 206 Pb/ 238 U age = 93.04 ± 0.06 Ma (n=5, MSWD=1.02)     93.393.192.792.50.01448 0.01452 0.01456 0.01460 0.094 0.096 0.098 92.6 93.0 93.4 12MMA-2-4-1: Hornblende pyroxenite (HPx)   Weighted 206 Pb/ 238 U age = 92.84 ± 0.06 Ma (n=4, MSWD=0.61)     pyroxenite (?) antecrystμP0.01446 0.01450 0.01454 0.01458 92.4 92.8 93.2  13MMA-2-7-1: Hornblendite (Hb)   Weighted 206 Pb/ 238 U age = 93.01 ± 0.12 Ma  (n=2, MSWD=1.15)     minor Pb-loss0.0950 0.0958 0.0966 0.0974 Figure 2.7.1BADCFigure 2.10. Concordia diagrams showing CA-ID-TIMS U-Pb geochronological results for zircon from ultramafic rocks in the Giant Mascot ultramafic intrusion. A) pyroxenite (03GNX-3-1-1), B) pyroxenite (12MMA-5-4-1), C) hornblende pyroxenite (12MMA-2-4-1), D) hornblendite (13MMA-2-7-1). Each ellipse (2σ error) represents the analytical result for a single grain of zircon; ellipses with dashed borders indicate analyses that were not included in the calculated 206 Pb/ 238 U weighted mean for the respective sample. Light grey field indicates the extent of decay constant uncertainty on concordia. The colours of the ellipses correspond to map units and symbols shown in Fig. 2.3.55J, and H) span a range of 206 Pb/ 238 U ages from ~84 to 89 Ma and are inferred to reflect Pb loss (Fig. 2.10B).2.5.3.2.  Hornblende pyroxeniteZircon in a feldspathic hornblende pyroxenite sample is anhedral and typically <100 μm in length. U-Pb data for five single zircon grains span a wide range of U concentrations (143-1842 ppm) with Th/U=0.218-0.457, including several analyses that are higher than those for the pyroxenites above (Fig. 2.9). The analytical results for four zircon grains are concordant with a weighted 206 Pb/ 238 U age of 92.84 ± 0.06 Ma (2σ, n=4; MSWD=0.61), similar to the above pyroxenites. The remaining grain (E) has a concordant 206 Pb/ 238 U age of 93.24 ± 0.17 Ma, identical within error to pyroxenite 12MMA-5-4-1, and is interpreted to be an antecryst (Fig. 2.10C).2.5.3.3.  HornblenditeZircon in this feldspathic hornblendite (Fig. 2.4G) is relatively large (up to 350 μm in length with aspect ratios of ~5:1) and contains porous and altered cores with abundant inclusions (<5 μm) of uranothorite [(U,Th)SiO4] (Figs. 2.5.1, 2.5.2, 2.5.3). The analytical results for four zircon fractions attain the highest U concentrations (81-2826 ppm) with similar Th/U (0.160-0.299) compared to zircon from other samples of the Giant Mascot ultramafic suite (Fig. 2.9). Concordant U-Pb data from two grains (B and E) yield a weighted 206 Pb/ 238 U age of 93.01 ± 0.12 Ma (2σ; MSWD=1.15), similar to both pyroxenites and the hornblende pyroxenite. Discordant results for the other two grains (C and D) have slightly younger ages (92.77 ± 0.10 and 92.58 ± 0.09 Ma, respectively), which are interpreted to reflect Pb loss since the time of crystallization (Fig. 2.10D).562.5.3.4.  Spuzzum dioriteZircon in a diorite from the Spuzzum pluton (12MMA-2-3-1) is subhedral to euhedral, <100 μm in length with aspect ratios up to 2:1 (Fig. 2.5). The U-Pb data for 12 grains indicate U concentrations (33-200 ppm) and Th/U (0.147-0.201), both of which are distinctly lower than in zircon from the ultramafic rocks (Fig. 2.9). The analytical results of five grains give a weighted mean 206 Pb/ 238 U age of 95.20 ± 0.08 Ma (2σ, n=5; MSWD=1.03), which is interpreted as the crystallization age of this Spuzzum diorite. Concordant U-Pb results for three grains (A, C, and G) give a weighted mean 206 Pb/ 238 U age of 92.81 ± 0.16 Ma (2σ; MSWD=1.3). Data for zircon grains F and L have ages of ~94 Ma, both of which are interpreted to have lost Pb (Fig. 2.11A). The results for one zircon grain (K) are discordant (54%), consistent with Pb loss. The data from fraction M are concordant and this grain is inferred to be a xenocryst (~96 Ma).2.5.3.5.  Spuzzum quartz dioriteZircon in Spuzzum quartz diorites is euhedral and variable in size with grains from 11GNX-1-3-1 characterized by the largest sizes (~250 μm in length, 2:1 to 4:1 aspect ratios) (Fig. 2.5). Grains from both 12MMA-2-1-5 and 12MMA-6-5-1 are euhedral and smaller (<150 μm in length) with lower aspect ratios ~2:1 (Fig. 2.5). From sample 11GNX-1-3-1, U-Pb data for five zircon fractions are concordant (U=43-134 ppm, Th/U=0.172-0.223; Fig. 2.9). A weighted mean 206 Pb/ 238 U age of 95.47 ± 0.13 Ma (2σ, n=3; MSWD=1.08) is interpreted as the crystallization age of this Spuzzum quartz diorite. Concordant results for fraction D give an age younger than the weighted mean (94.89 ± 0.15 Ma), which is inferred to reflect Pb-loss. Fraction B is likely a xenocryst as it yields concordant results with an anomalously old age (~102 Ma; Fig. 2.11B). Results for five zircon grains from 12MMA-6-5-1 have higher U concentrations (163-401 ppm) and relatively low Th/U (0.060-0.237; Fig. 2.7). The weighted mean 206 Pb/ 238 U age of 95.32 ± 0.21 Ma (2σ, n=3; MSWD=0.46) is indistinguishable from the other two quartz diorites and diorite. Concordant U-Pb data for zircon fraction E yield an age of 94.32 ± 0.26 Ma. Grain (C) is interpreted to be a xenocryst that crystallized at ~98 Ma (Fig. 2.11C). For 12MMA-2-1-5, 570.01478 0.01486 0.01494 94.4 94.8 95.2 95.6 12MMA-2-1-5: Spuzzum quartz diorite (Sqdi)   206Pb/238U206Pb/238U207 Pb/ 235 UWeighted 206 Pb/ 238 U age = 95.02 ± 0.12 Ma (n=3, MSWD=0.63)     0.093 0.101 0.097 0.0146 0.0144 0.0148 0.0150 0.090 0.098 0.106 92 94 96   12MMA-2-3-1: Spuzzum diorite (Sgbn)   Primary magmatic grainsWeighted 206 Pb/ 238 U age = 95.20 ± 0.08 Ma (n=5, MSWD=1.03)      Pb-lossPb-lossxenocryst ADCB0.0147 0.0151 0.0155 0.100 0.108 94 96 98 100 Weighted 206 Pb/ 238 U age =95.32 ± 0.21 Ma (n=3, MSWD=0.46)    xenocrystPb-loss12MMA-6-5-1: Spuzzum quartz diorite (Sqdi)0.092 207 Pb/ 235 U0.0148 0.0152 0.0156 0.0160 0.096 0.104 0.112 94 96 98 100 102 104 11GNX-1-3-1: Spuzzum quartz diorite (Sqdi)   Weighted 206 Pb/ 238 U age = 95.47 ± 0.13 Ma (n=3, MSWD=1.08)     Pb-lossxenocrystFigure 2.7.2Figure 2.11. Concordia diagrams showing CA-ID-TIMS geochronological results for zircon from Spuzzum pluton diorites. A) 12MMA-2-3-1, B) 11GNX-1-3-1, C) 12MMA-6-5-1, D) 12MMA-2-1-5. Symbology as in Fig. 2.10.58analytical results from four grains show similar U concentrations (57-148 ppm), higher Th/U (0.213-0.241), and a weighted mean 206 Pb/ 238 U age of 95.02 ± 0.12 Ma (2σ, n=3; MSWD=0.63), just outside the 2σ level of uncertainty for 11GNX-1-3-1. The results for zircon fraction B (95.31 ± 0.12 Ma) were excluded from the weighted mean age due to a high MSWD (>2; Fig. 2.11D).2 5 4  Laser ablation-ICP-MS zircon geochronology2.5.4.1.  Plešovice and Temora 2 zircon standardsThe U-Pb results for the zircon standards Plešovice and Temora 2 are concordant with weighted mean 206 Pb/ 238 U ages of 337.12 ± 0.94 Ma (2σ, n=25; MSWD=0.28) and 416.5 ± 2.0 Ma (2σ, n=24; MSWD=0.69; Appendix C), respectively. The ages of both standards are within error of the accepted ages of 337.13 ± 0.37 Ma (Plešovice; Sláma et al., 2008) and 416.50 ± 0.22 Ma (Temora 2; Black et al., 2004).2.5.4.2.  Giant Mascot ultramafic suite U-Pb data for unleached (n=4) and leached (n=3) zircon in a pyroxenite (12MMA-5-4-1) are concordant and reveal similar U concentrations (135-513 ppm and 95-540 ppm) and Th/U (0.074-0.215 and 0.247-0.411), respectively (Table 2.3). A cluster of in situ analyses give a weighted mean 206 Pb/ 238 U age of 88.6 ± 1.9 Ma (2σ, n=10; MSWD=1.17; Fig. 2.12A). Results from three spots (3, 5, 1L) have younger ages interpreted to reflect Pb loss. U-Pb data for unleached (n=6) and leached (n=6) zircon from another pyroxenite (03GNX-3-1-1) are concordant and show higher U concentrations (304-2394 ppm and 88-378 ppm) and Th/U (0.211-0.728 and 0.273-0.392), respectively. Data from one of two clusters yields a weighted mean 206 Pb/ 238 U age of 93.9 ± 1.2 Ma (2σ, n=11; MSWD=0.31; Fig. 2.12B), which is within error of the TIMS age for the same sample (see section 2.4.2.1). U-Pb data from the other cluster give a weighted mean 206 Pb/ 238 U age of 98.3 ± 1.5 Ma (2σ, n=7; MSWD=0.51; Fig. 2.12B). Results yielding younger ages for both leached and unleached zircon are inferred to represent the effects of Pb loss.59U-Pb data from unleached zircon (n=9) in a feldspathic hornblende pyroxenite (12MMA-2-4-1) are concordant with relatively high U concentrations (146-1262 ppm) and Th/U (0.185-0.567) and yield a weighted mean 206 Pb/ 238 U age of 90.7 ± 1.6 Ma (2σ, n=10; MSWD=2.6; Fig. 2.12C), which lies within error of the above pyroxenites and just outside of the uncertainty on the TIMS age (see section 2.4.3.2). Four integrations (9, 10, 14, 15) from two spots are significantly younger than the weighted mean age and are interpreted to reflect Pb loss.Results from unleached zircon (n=3) in a feldspathic hornblendite (13MMA-2-7-1) are concordant and have the highest U concentrations (982-48,000 ppm) and Th/U (0.140-1.52) compared to all other samples. Anomalously high U contents are attributed to ablation of uranothorite inclusions in altered and pitted cores (Fig. 2.7C). U-Pb data reveal three distinct groups by weighted mean 206 Pb/ 238 U ages, all with large scatter (high MSWD): 1) 89.2 ± 3.2 Ma (2σ, n=15; MSWD=30; Fig. 2.12D), interpreted as the crystallization age of this hornblendite; 2) 65.1 ± 2.6 Ma (2σ, n=6; MSWD=10.3); and 3) 43.8 ± 2.4 Ma (2σ, n=6; MSWD=3.6). The latter two (i.e., youngest) groups are interpreted to reflect Pb loss and post-crystallization processes related to regional intrusion or metamorphic thermal effects.2.5.4.3.  Spuzzum pluton dioritesThe U-Pb analytical results for unleached (n=4) and leached (n=4) zircon from a Spuzzum diorite (12MMA-2-3-1) are concordant and have the lowest U concentrations (99-507 ppm and 29-253 ppm) and Th/U (0.155-0.464 and 0.138-0.291), respectively (Table 2.3). The data yields a weighted mean 206 Pb/ 238 U age of 89.2 ± 1.8 Ma (2σ, n=14; MSWD=1.3; Fig. 2.13A), and four younger dates from an unleached grain are interpreted to reflect Pb loss.From a Spuzzum quartz diorite (12MMA-2-1-5), results for unleached zircon are concordant (U=120-361 ppm, Th/U=0.200-0.348; Fig. 2.13B). The U-Pb data give a weighted mean 206 Pb/ 238 U age of 87.9 ± 2.9 Ma (2σ, n=9; MSWD=2.4; Fig. 2.13B), and results of three analyses (integrations 2, 3, 9) are consistent with Pb loss. Results for 13 zircon analyses (seven unleached and six leached) from a Spuzzum quartz diorite (11GNX-1-3-1) have similar U 600.006 0.010 0.014 0.04 0.12 0.20 60 unleachedCA-TIMS = 92.78 ±  0.09 Ma CA-TIMS = 93.04 ±  0.06 MaCA-TIMS = 92.84 ±  0.06 Ma CA-TIMS = 93.01 ±  0.12 MaleachedWeighted 206 Pb/ 238 U age = 90.7 ± 1.6 Ma (n=10, MSWD=2.6)     Weighted 206 Pb/ 238 U age = 89.2 ± 3.2 Ma (n=15, MSWD=30)     Weighted 206 Pb/ 238 U age = 65.1 ± 2.6 Ma (n=6, MSWD=10.3)     Weighted 206 Pb/ 238 U age = 43.8 ± 2.4 Ma (n=6, MSWD=3.6)     Weighted 206 Pb/ 238 U age = 88.6 ± 1.9 Ma (n=10, MSWD=1.17)     Weighted 206 Pb/ 238 U age = 93.9 ± 1.2 Ma (n=11, MSWD=0.31)     100 0.005 0.009 0.013 0.017 0.04 0.12 0.20 30 50 70 90 110 0.005 0.009 0.013 0.017 0.03 0.07 0.11 0.15 30 50 70 110 90 unleachedleached12MMA-5-4-1: Pyroxenite (Px) 03GNX-3-1-1: Pyroxenite (Px)12MMA-2-4-1: Hornblende pyroxenite (HPx) 13MMA-2-7-1: Hornblendite (Hb)Figure 2.10.1207 Pb/ 235 U207 Pb/ 235 U206Pb/238U206Pb/238UA BDC0.008 0.016 0.04 0.12 0.20 100 60 Figure 2.12. Concordia diagrams showing LA-ICP-MS geochronological results for zircon from ultramafic rocks in the Giant Mascot ultramafic intrusion. A) pyroxenite (12MMA-5-4-1), B) pyroxenite (03GNX-3-1-1), C) hornblende pyroxenite (12MMA-2-4-1), D) hornblendite (13MMA-2-7-1). Each ellipse represents one integration from the spot analysis of zircon with propagated 2σ error. Black ellipses represent unleached zircon grains and red ellipses correspond to chemically abraded zircon (i.e., leached; 900°C for 60 hours).610.005 0.009 0.013 0.017 0.04 0.12 0.20 50 90 0.007 0.011 0.015 0.04 0.12 50 70 90 110 12MMA-2-1-5: Spuzzum quartz diorite (Sqdi)12MMA-6-5-1: Spuzzum quartz diorite (Sqdi)11GNX-1-3-1: Spuzzum quartz diorite (Sqdi)207 Pb/ 235 U207 Pb/ 235 U206Pb/238U206Pb/238UFigure 2.10.2Weighted 206 Pb/ 238 U age = 87.9 ± 2.9 Ma (n=9, MSWD=2.4)     Weighted 206 Pb/ 238 U age = 93.1 ± 2.0 Ma (n=7, MSWD=0.51)     Weighted 206 Pb/ 238 U age = 95.27 ± 0.95 Ma (n=16, MSWD=0.70)     BDC0.009 0.011 0.013 0.015 0.04 0.08 0.12 60 80 unleachedleached100 unleachedleached12MMA-2-3-1: Spuzzum diorite (Sgbn)0.006 0.010 0.014 0.04 0.12 0.20 60 Weighted 206 Pb/ 238 U age = 89.2 ± 1.8 Ma (n=14, MSWD=1.3)     100 ACA-TIMS = 95.20 ±  0.08 Ma CA-TIMS = 95.02 ±  0.12 MaCA-TIMS = 95.47 ±  0.13 Ma CA-TIMS = 95.32 ±  0.21 MaFigure 2.13.  Concordia diagrams showing LA-ICP-MS geochronological results for zircon from Spuzzum pluton diorites. A) 12MMA-2-3-1, B) 12MMA-2-1-5, C) 11GNX-1-3-1, D) 12MMA-6-5-1. Symbology as in Fig. 2.12.62concentrations (75-217 ppm and 294-1616 ppm) and Th/U (0.188-0.399 and 0.296-0.520), respectively, to the other diorite and two quartz diorites. The concordant U-Pb data yield a weighted mean 206 Pb/ 238 U age of 95.27 ± 0.95 Ma (2σ, n=16; MSWD=0.70; Fig. 2.13C), within error of the TIMS age (see section 2.5.2.5). Slightly discordant results for spots (3L, 4L, 7L, and 1) have the youngest dates, which are inferred to reflect Pb loss. Results for zircon from another Spuzzum quartz diorite (12MMA-6-5-1) are concordant with U concentrations (96-247 ppm) and Th/U (0.205-0.374), similar to the two quartz diorites and diorite. A weighted mean 206 Pb/ 238 U age of 93.1 ± 2.0 Ma (2σ, n=7; MSWD=0.51; Fig. 2.13D) is within error of the TIMS age (see section 2.5.2.5) and the remaining results (spots 2, 3, 4, 6, 7) reflect Pb loss.2 5 5  40Ar/39Ar biotite-hornblende geochronologySamples and results for both a mylonitized hornblendite and a hornblendite enclave are reported in Tables 2.4 and 2.5, Figures 2.14 and 2.15, and a summary Figure 2.16. For age interpretations, inverse isochron ages were favoured over step-heating spectra as omitting assumed atmospheric 40Ar/ 36 Ar allows for trapped 40Ar/ 36 Ar (i.e., excess 40Ar) to be more easily detected and thus provide more reliable age determinations (Kuiper, 2002). 2.5.5.1.  MyloniteThe results for nine individual K-poor hornblende grains (Ca/K=5-310) from the mylonitized hornblendite (11GNX-1-2-1 and 11GNX-1-2-2; Fig. 2.4J) span a wide range of inverse isochron (39 Ar/ 40Ar vs. 36 Ar/ 40Ar) ages from 80.2 ± 6.1 to 93.8 ± 3.5 Ma (plateau ages, 82.5 ± 2.4 to 98.4 ± 2.5 Ma; Tables 2.4 and 2.5; Fig. 2.14). Initial 40Ar/ 36 Ar ratios are variable (259-425), with three samples overlapping within uncertainty the composition of atmospheric Ar of 298.56 ± 0.31 (Lee et al., 2006; Table 2.5). Large hornblende grains (11GNX-1-2-2a–c) are unaffected by mylonitization, whereas smaller crystals are interpreted as neoblasts formed during recrystallization. Collectively, the 40Ar/ 39 Ar geochronological results from this mylonite sample range from a magmatic age of 93 Ma, equivalent to the CA-TIMS and LA-ICP-MS 630.001 0.003 0.02 0.06 Age = 84.2 ± 3.9 MaInitial 40 Ar/ 36 Ar = 315±19MSWD=1.19  36Ar/40Ar39 Ar/ 40 Ar11GNX-1-2-1 hornblende 11GNX-1-2-1b hornblende 11GNX-1-2-1c hornblende11GNX-1-2-2a hornblende 11GNX-1-2-2b hornblende 11GNX-1-2-2c hornblende11GNX-1-2-2a large hbl 11GNX-1-2-2b large hbl 11GNX-1-2-2c large hblFigure 2.8.10.001 0.003 0.02 0.06 0.10 Age = 89.1 ± 2.4 MaInitial 40 Ar/ 36 Ar = 380±22MSWD=1.8  0.001 0.003 0.02 0.06 0.10 Age = 86 ± 13 MaInitial 40 Ar/ 36 Ar = 425±150MSWD=0.36  0.001 0.003 0.005 0.02 0.06 Age = 88.3 ± 5.4 MaInitial 40 Ar/ 36 Ar = 299±160MSWD=3.1  0.001 0.003 0.005 0.02 0.06 0.10 Age = 85.1 ± 3.1 MaInitial 40 Ar/ 36 Ar = 259±71MSWD=0.99  Age = 80.2 ± 6.1 MaInitial 40 Ar/ 36 Ar = 263±16MSWD=2.2  0.0015 0.0035 0.02 0.04 0.06 0.001 0.003 0.02 0.04 0.06 Age = 93.8 ± 3.5 MaInitial 40 Ar/ 36 Ar = 334±21MSWD=0.18  0.001 0.003 0.02 0.06 0.10 Age = 93.7 ± 2.9 MaInitial 40 Ar/ 36 Ar = 306±18MSWD=0.19  0.001 0.003 0.02 0.06 0.10 Age = 93.4 ± 1.8 MaInitial 40 Ar/ 36 Ar = 310±21MSWD=0.78  Figure 2.14. 40Ar/ 39 Ar hornblende inverse isochron diagrams for two mylonitized pegmatitic hornblendites (samples 11GNX-1-2-1 and 11GNX-1-2-2) in a shear zone at the contact of the Spuzzum quartz diorite and hornblendite zone at the margin of the Giant Mascot intrusion. Each ellipse represents a temperature step during step-heating showing 2σ error.640.0004 0.0012 0.0020 0.0028 0.03 0.05 0.07 36Ar/40Ar39 Ar/ 40 ArFigure 2.8.2Age = 103.9 ± 6.6 MaInitial 40 Ar/ 36 Ar = 289±34MSWD=0.58  12MMA-2-1-2a hornblende 12MMA-2-1-2b hornblende12MMA-2-1-2b biotite12MMA-2-1-2a biotite0.001 0.002 0.003 0.004 0.02 0.04 0.06 Age = 99.7 ± 7.7 MaInitial 40 Ar/ 36 Ar = 288±19MSWD=3.3  0.001 0.003 0.02 0.06 Age = 106.2 ± 1.9 MaInitial 40 Ar/ 36 Ar = 254±10MSWD=0.66  Age = 104.2 ± 2.0 MaInitial 40 Ar/ 36 Ar = 264±12MSWD=1.3  0.001 0.003 0.03 0.07 Figure 2.15.  40Ar/ 39 Ar hornblende and biotite inverse isochron diagrams for ultramafic enclaves (sample 12MMA-2-1-2) in the Spuzzum pluton. Each ellipse represents a temperature step during step-heating showing 2σ error.651101051009590858075110105100959085807540 Ar/39Ar or 206 Pb/238 U Date  (Ma)Giant MascotSpuzzumZZB BH H HHHHHHLH LH LH11GNX-1-2-111GNX-1-2-2 12MMA-2-1-2CA-ID-TIMS U-Pb zircon40 Ar/ 39 Ar 40 Ar/ 39 ArH = hornblendeLH = large hornblendeB = biotiteZ = zirconMineral analyzedopen system (mylonitized hornblendite)pegmatitic hornblenditehornblendite enclavesFigure 2.9Figure 2.16.  Summary of 40Ar/ 39 Ar results from the Giant Mascot ultramafic intrusion and Spuzzum pluton, compared to the age range (including 2σ error) of U-Pb zircon analyses. Each bar represents one individual 40Ar/ 39 Ar inverse isochron date with maximum extent of 2σ error. Symbols and colours correspond to sample locations in Fig. 2.3. Letters above each bar indicate the mineral analyzed: H=hornblende, LH=large hornblende, B=biotite, Z=zircon.66zircon results, down to ~80 Ma, consistent with open-system recrystallization and Ar-loss related to shearing (Fig. 2.16). 2.5.5.2.  Mafic enclaves in Spuzzum quartz dioriteBiotite and hornblende were separated from a biotite-hornblendite enclave displaying elongate and lobate contacts with Spuzzum quartz diorite (12MMA-2-1-2; Fig. 2.4K). Two experiments on both biotite and hornblende yielded inverse isochron ages of 104.2 ± 2.0 and 106.2 ± 1.9 Ma (plateau ages, 98.7 ± 3.1 and 103.3 ± 5.5 Ma) and 99.7 ± 7.7 and 103.9 ± 6.6 Ma (plateau ages, 100.6 ± 1.9 and 101.3 ± 1.8 Ma), respectively (Tables 2.4 and 2.5; Fig. 2.15). Initial 40Ar/ 36 Ar ratios for hornblende (288-289) are within uncertainty of atmospheric Ar, whereas the results for biotite are low (254-264). Hornblende has Ca/K from ~3-35, indicating K-poor and Ca-rich grains, and biotite has low Ca/K (0.11-1.03). These 40Ar/ 39 Ar results correlate with geological field observations in the Spuzzum pluton (Fig. 2.16).2 6  Discussion2 6 1  Age of the Giant Mascot intrusion and associated Ni-Cu-PGE oresThere is a relatively small database of published U-Pb geochronologic results for ultramafic rocks associated with Ni-Cu-PGE or PGE mineralization (e.g., Hamilton et al., 1998; Oberthür et al, 2002; Scoates and Friedman, 2008; Mackie et al., 2009; Scoates and Wall, in press). Globally, nickel deposits range from Archean to Phanerozoic in age (Naldrett, 2011; Maier and Groves, 2011; and references therein), with the oldest deposits hosted in komatiites of the ca. 2.9 Ga Lake Johnston (e.g., Maggie Hays; Heggie et al., 2012) and Forrestania (e.g., Porter and Mckay, 1981; Begg et al., 2010) greenstone belts in the Yilgarn Craton, Western Australia. The Muskox mafic-ultramafic intrusion, Nunavut, hosts basal Ni-sulphide mineralization at ca. 1269 Ma (Mackie et al., 2009), and mineralization in the Noril’sk Ni-Cu-PGE deposit, Siberia, is constrained to ca. 251 Ma (Kamo et al., 2003). Convergent margin Ni-Cu-PGE mineralization in the Aguablanca breccia stock, Spain, has a U-Pb zircon age of 338.6 ± 670.8 Ma (Romeo et al., 2006) and a cluster of deposits in the Xinjiang region, northwestern China are slightly younger (ca. 270-298 Ma; Mao et al., 2008). Canadian analogues with zircon ages from the Portneuf-Mauricie Domain include the Lac Édouard (1164.7 ± 3.6 Ma), Rochette West (1386.1 ± 1.2 Ma), and Lac Nadeau (1396 +6/-4 Ma) Ni-Cu±PGE deposits (Sappin et al., 2009). The new U-Pb geochronologic results reported in this study for the Giant Mascot ultramafic intrusive suite constrain the crystallization age to a narrow interval (~260 ka) at 93 Ma and thus the timing of orthomagmatic Ni-sulphide mineralization (Figs. 2.17, 2.18). Consequently, the Giant Mascot Ni deposit is the youngest dated Ni deposit worldwide (e.g., see compilations in Naldrett, 2010 and 2011).The ca. 93 Ma Giant Mascot ultramafic suite intrudes the ca. 95 Ma Spuzzum pluton, thus defining a 2 million year magmatic hiatus in plutonism prior to two resolvable magmatic episodes at ~93.0 Ma and ~92.8 Ma (Figs. 2.17A, B). Field mapping by Aho (1954) and Manor et al. (2014b) identify sharp intrusive contacts in individual orebodies and the entire intrusion, as well as the presence of abundant diorite inclusions, indicating that the Giant Mascot ultramafic suite was assembled from a series of magmatic injections ascending through sub-vertical crustal conduits. The Spuzzum pluton and Settler schist both exhibit local evidence of anatectic melting, where xenocrystic zircon is entrained in the Giant Mascot pyroxenite (12MMA-5-4-1; Table 2.1; Figs. 2.10B, 2.17) and garnetiferous gabbro is cut by siliceous veins (Fig. 2.4I). These field relations suggest that silica was added to the Giant Mascot parental magma(s), which has implications for the formation of Ni-sulphides as silica addition lowers the S solubility threshold to a point where sulphide saturation may be more easily achieved (e.g., Irvine, 1975; Ripley and Li, 2012; further discussion in Chapter 3).Zircon from the Giant Mascot intrusion and Spuzzum pluton is characterized by different U concentrations (>250 ppm and <200 ppm) and Th/U (>0.25 and <0.25), respectively (Table 2.1; Fig. 2.9). This distinction is especially useful in interpreting the magmatic age of a Spuzzum diorite sample (12MMA-2-3-1) for which analyses present a range of dates from ~93-95 Ma (Figs. 2.11B, 2.17). Analyses of zircon by LA-ICP-MS show that three of nine ages 6892.492.692.893.093.293.492.492.692.893.093.293.4**+AB 13MMA-2-7-1 Hb12MMA-5-4-1Px 12MMA-2-4-1  HPx03GNX-3-1-1 Pxpyroxenite xenocryst206 Pb/238 U Date (Ma)206 Pb/238 U Date (Ma)13MMA- 2-7-1 12MMA-2-3-112MMA-5-4-1 12MMA- 2-4-103GNX- 3-1-1Px Px HPx Hb Sgbn Sqdi Sqdi Sqdi12MMA-6-5-112MMA-2-1-5 11GNX-1-3-193.01 ± 0.1295.07 ± 0.07(Spuzzum xenocrysts)92.78 ± 0.0984.88 ± 0.23 (n=1)102.74 ± 0.36 (n=1)92.84 ± 0.0693.04 ± 0.0695.21 ± 0.0895.32 ± 0.2195.02 ± 0.1295.47 ± 0.13U=2826 ppm89.0 89.8 90.6 91.4 92.2 93.0 93.8 94.6 95.4 96.2 97.0 97.8 98.6 89.0 89.8 90.6 91.4 92.2 93.0 93.8 94.6 95.4 96.2 97.0 97.8 98.6 ***** ********+++ +   = Pb-loss+ = xenocryst*GIANT MASCOT SPUZZUMFigure 2.11Figure 2.17.  U-Pb zircon CA-ID-TIMS geochronology summary for ages of the Giant Mascot ultramafic intrusion and Spuzzum pluton. A) all samples, and B) enlarged summary of dates from ultramafic rocks only. Each bar represents an individual 206 Pb/ 238 U date with maximum extent of 2σ error. Black horizontal lines indicate weighted mean 206 Pb/ 238 U crystallization ages for each sample. Sample symbology as in Fig. 2.3. Samples (individual zircon grains) that are inferred to have undergone Pb-loss (*) or represent xenocrysts (+) are also indicated.69(i.e., 03GNX-3-1-1, 12MMA-2-1-5, 11GNX-1-3-1) are identical within error of their respective CA-TIMS ages, however the remaining sample ages are systematically younger (Figs. 2.18). Individual spot analyses of zircon from both the Giant Mascot ultramafic suite and Spuzzum pluton reveal complex internal age variation interpreted to represent either periods of increased thermal activity either by regional metamorphism or magmatic activity, or diffusive Pb-loss (Fig. 2.18). Probability curves show four distinct ages: ca. 95 Ma, 85 Ma, 65 Ma, and 45 Ma. The first, at ca. 95-90 Ma, corresponds to magmatism that generated the ca. 95 Ma Spuzzum pluton and ca. 93 Ma Giant Mascot ultramafic suite, although the precision of the LA-ICP-MS analyses are unable to distinguish between these as in the CA-TIMS results. Peaks near 85 Ma may be related to the intrusion of the large, ~25x50 km Scuzzy pluton at 86.42 ± 0.04 Ma (CA-TIMS U-Pb zircon; Mitrovic, 2013), which is located ~20 km north of Giant Mascot (Fig. 2.2). The younger peaks observed at ca. 65 Ma and 45 Ma possibly correlate to thermal effects from the Tertiary Mt. Barr and Chilliwack batholiths that intruded ~15-20 km south of the Giant Mascot ultramafic suite (Figs. 2.2, 2.18).2 6 2  Tectonic	significance	for	the	age	of	the	Giant	Mascot	intrusionThe new U-Pb and 40Ar/ 39 Ar geochronologic results from the Giant Mascot ultramafic suite and Spuzzum pluton provide insight into the genesis of ultramafic rocks and regional tectonic and metamorphic history of the Harrison Lake region and southeastern Coast Plutonic Complex (Figs. 2.16, 2.17, 2.18). Rocks comprising the ca. 93 Ma Giant Mascot ultramafic suite are interpreted to have formed from conduit-style arc magmatism, thus ruling out that the ultramafic rocks are: 1) related to the southernmost extension of the Cogburn ophiolitic assemblage, which is now engulfed by the younger Spuzzum pluton (Ash, 2002); or 2) a remnant the accreted Late Triassic flood basalt province of Wrangellia (Nixon, 2003), similar to other known magmatic Ni-Cu-PGE sulphide deposits in the northern Cordillera (Hulbert, 1997). This intrusive age relationship is critical in understanding the generation of immiscible sulphides in convergent margins.70F ig u re 2. 133040506070809010011012013030405060708090100110120130206P b /23 8U  D a te ( M a )13MMA-2-7-1 12MMA-2-3-1Spuzzum  CA-TIMS12MMA-5-4-1 12MMA-2-4-103GNX-3-1-1 Px Px HPx Hb Sgbn Sqdi Sqdi Sqdi12MMA-6-5-112MMA-2-1-5 11GNX-1-3-1GIANT MASCOT SPUZZUMGiant MascotCA-TIMSFigure 2.18.  U-Pb zircon LA-ICP-MS geochronology summary for ages of the Giant Mascot ultramafic intrusion and Spuzzum pluton. Each bar represents an individual 206 Pb/ 238 U date with maximum extent of 2σ error. Horizontal shaded regions indicate the range of CA-TIMS ages in Fig. 2.17. Curves represent kernel density plots of individual samples. Sample symbology as in Figs. 2.3 and 2.17.71Vertical displacement and magma loading of plutons in the region is constrained to an interval of about 30 million years from ca. 110-80 Ma (Mitrovic, 2013). This coincides with four distinct metamorphic events (M1 to M4) that reached amphibolite facies conditions (M3) due to progressive magmatic loading between 96 and 91 Ma (Brown and Walker, 1993; Brown et al., 2000; Mitrovic, 2013, and references therein). U-Pb geochronologic and thermobarometric results determined peak metamorphic conditions for the Settler schist (91-84 Ma, monazite; Brown and Walker, 1993; Brown et al., 2000), the northeastern Spuzzum pluton (~5-6 kbars at ~550-600°C, andalusite; Brown and Burmester, 1991), and the Breckenridge pluton and Slollicum schist (91-86 Ma at 6.5-10.3 kbars and 500-680°C, zircon and garnet; Mitrovic, 2013). The northeastern corner of the Spuzzum pluton was overprinted by solid-state foliation from strain aureole effects from the ca. 91 Ma Urquhart pluton (Fig. 2.2; Brown and Burmester, 1991; Brown and McClelland, 2000). Tectonic activity in the Harrison Lake region is also present as four deformational events (D1 to D4; Brown and McClelland, 2000). Mylonitized hornblendite displays late stage deformation fabrics (D4) introduced by a post-emplacement (ca. 92-91 Ma; Brown and McClelland, 2000) dextral strike-slip shear zone (Figs. 2.4J, 2.16).Magmatic foliation is present throughout the Spuzzum pluton and is overprinted by a relatively non-pervasive metamorphic fabric, evidenced by recrystallized quartz and plagioclase with aligned mafic minerals (e.g., Vining, 1977; Brown and McClelland, 2000). 40Ar/ 39 Ar systematics of biotite and hornblende from hornblendite enclaves in the Spuzzum pluton (Fig. 2.4K) indicate that thermal effects from metamorphism did not reach the closure temperatures for Ar diffusion of biotite (350°C; Harrison et al., 1985) or hornblende (570°C; Harrison, 1981) (Figs. 2.15, 2.16). Both the Spuzzum and Giant Mascot intrusions may have been relatively resistant to circulating metamorphic fluids due to the strong rheology of the diorites, however fluids were present following crystallization of the ultramafic rocks as confirmed by the local presence of metamorphic minerals (e.g., talc, tremolite, chlorite, anthophyllite, and serpentine). The absence of penetrative deformation or heating by regional upper-amphibolite facies conditions (>500°C) in the Giant Mascot intrusion is supported by the presence of primary 72cumulus textures with unannealed grain boundaries (see Chapter 3, Figs. 3.3, 3.4). In addition, textures of the associated Ni-Cu-PGE sulphide mineralization are orthomagmatic and display evidence for sub-solidus transtensional cracks into which Cu-rich liquid migrated (see Chapter 3, Figs. 3.8, 3.9). Minor remobilization and desulphurization is observed in the sulphide assemblage, however there is no evidence of recrystallization of silicate or sulphide liquids (see Chapter 3; Figs. 3.20, 3.21). The Northern Cascades of Washington State, USA, are a continuation of the southern Coast Plutonic Complex where the Settler schist and Chiwaukum schist terranes have been correlated based on isotopic, structural, and metamorphic evidence (e.g., Misch, 1977; Monger, 1985; Brown and Walker, 1993). This evidence has supported the “Baja British Columbia” hypothesis and the reconstruction of displacement along the orogen-parallel Straight Creek-Fraser fault system (Fig. 2.19; Cowan et al., 1997). The ca. 96 Ma Big Jim Complex (Kelemen and Ghiorso, 1986) is a hornblende-bearing ultramafic-mafic intrusion analogous to the Giant Mascot intrusion and hosted by the Chiwaukum schist and Mt. Stuart batholith (ca. 96-90 Ma), which is similar to the Spuzzum pluton in both composition and age (Matzel et al., 2006). The age correlation of plutonic bodies in the Northern Cascades and southern Coast Plutonic Complex may indicate approximately 170 km of dextral displacement along the Straight Creek-Fraser fault system (Fig. 2.19; Brown and Walker, 1993; Umhoefer and Schiarizza, 1996). The Late Cretaceous age of plutons and similarities of ultramafic-mafic intrusions in both the southern Coast Plutonic Complex and Northern Cascades indicate that similar intrusions hosting Ni-sulphides may be more abundant than previously considered.2 7  ConclusionsThis study reports the first integrated geochronologic approach (U-Pb CA-ID-TIMS zircon, U-Pb LA-ICP-MS zircon, 40Ar/ 39 Ar hornblende and biotite) to constrain the timing of orthomagmatic Ni-Cu-PGE sulphide mineralization in the Giant Mascot ultramafic intrusion in southwestern British Columbia. Zircon from the Giant Mascot ultramafic intrusion and 73HopeCanadaMt. Stuart batholith (ca. 90-96 Ma)Big Jim Complex(ca. 96 Ma)Giant Mascot intrusion (ca. 93 Ma)Straight Creek faultFraser faultEntiat faultHozameen faultRoss Lake faultYalakom fault50ºN49ºN48ºN120ºE122ºE51ºNUSA100 kmChilliwack batholith (ca. 30 Ma)Spuzzum pluton(ca. 95 Ma)Settler schist (Upper Triassic)Chiwaukum schist (Triassic?)Figure 2.14Figure 2.19.  Simplified geologic map of the Yalakom-Fraser-Straight Creek fault system in southwestern British Columbia and northern Washington showing the age relationship between intrusive and metamorphic rock suites across the 49th parallel. The contemporaneous dioritic to tonalitic Spuzzum pluton (ca. 95 Ma) and Mt. Stuart batholith (ca. 90-96 Ma) are each associated with mafic-ultramafic bodies, the Giant Mascot intrusion (ca. 93 Ma) and Big Jim Complex (ca. 96 Ma), respectively. These intrusive suites are located on opposite sides of the dextral Fraser-Straight Creek fault (geology modified after Umhoefer and Schiarizza, 1996; and Matzel et al., 2006).74Spuzzum diorites define two distinct populations that are distinguished by U concentrations (250-2826 ppm vs. <200 ppm) and Th/U (>0.25 vs. <0.25, respectively). The ca. 93 Ma Giant Mascot ultramafic suite intruded the ca. 95 Ma Spuzzum pluton, ruling out previous hypotheses of ophiolite origin or association with Wrangellia flood basalts. The Late Cretaceous age, determined by CA-TIMS U-Pb geochronology, distinguishes the Giant Mascot Ni-Cu-PGE deposit as one of the world’s youngest Ni deposits. Individual zircon grains contain complex internal age variations that reflect regional thermal effects from magmatic and metamorphic activity in the Harrison Lake region. The petrologic and geochronologic similarities between the Giant Mascot ultramafic suite and Spuzzum pluton, and the Big Jim complex and Mt. Stuart Batholith, Washington, USA, provides evidence for significant displacement (~170 km) on the dextral Fraser-Straight Creek fault.75Chapter 3Origin of the ‘Convergent Margin’ Giant Mascot Ni-Cu-PGE Deposit, Southwestern British Columbia3 1  IntroductionMagmatic nickel-copper-platinum group element (Ni-Cu-PGE) deposits are typically associated with ultramafic-mafic rocks in a variety of tectonic settings (summary in Naldrett, 2011). Supra-subduction zone or ‘convergent margin’ environments host a variety of increasingly important resources and exploration targets that only recently are becoming documented (e.g., Aguablanca, Spain, Piña et al., 2008, 2012, 2013; Portneuf-Mauricie Domain, Québec, Sappin et al., 2009, 2011, 2012; Huangshandong, China, Gao et al., 2013; Sun et al., 2013; Mao et al., 2014; c.f. Chapter 1, Table 1.1). Conventionally, subduction zone environments are considered poor targets for Ni-Cu-PGE sulphide mineralization due to the paucity of ultramafic bodies containing economic Ni-sulphides (Ripley, 2010). Platinum group element mineralization in these arc settings may be associated with Ural-Alaskan-type intrusions (ultramafic rock suites typically devoid of orthopyroxene; e.g., Duke Island, Irvine, 1974), yet their prospectivity with respect to Ni-sulphides remains poorly understood (Nixon et al., 1997). Partial melting in the mantle wedge beneath arcs may produce magmas that are enriched in sulphide and PGE depending on the degree of melting (Hamlyn et al., 1985; Keays, 1995; Barnes and Lightfoot, 2005; Mungall et al., 2006). Ascent of these basaltic to high-MgO magmas into the crust may lead to conditions where sulphide saturation occurs with consequent segregation of immiscible sulphide droplets that begin to scavenge metals from the host silicate melt (Naldrett, 2011). Metal enrichment is quantified by the silicate/sulphide mass ratio, or R-factor, and is characteristic of dynamic ore-forming systems (Campbell and Naldrett, 1979). Critical controls on ore-forming processes are also exerted by the redox state of the magma required for forming sulphide (S 2-) rather than sulphate (S 6+ ) species in the melt (e.g., Carroll and 76Rutherford, 1985; Luhr, 1990; Jugo et al., 2005; Jugo, 2009). Magmas generated in the mantle wedge above subducting slabs are generally attributed to the dehydration of relatively oxidized fluids associated with the descending slab, which leads to the formation of oxidized parental magmas that ascend to emplacement depths in the crust (Ballhaus et al., 1991; Brandon and Draper, 1996; Parkinson and Arculus, 1999; Kerrick and Connolly, 2001; Rohrbach et al., 2005).The Giant Mascot Ni-Cu-PGE deposit in the Canadian Cordillera remains British Columbia’s only past-producing nickel mine (1958-1974), having produced ~4.2 Mt of ore with an average grade of 0.77% Ni, 0.34% Cu, minor Co, Ag, and Au, and unreported PGE (Christopher and Robinson, 1975). The ‘convergent margin’ intrusion that hosts the sulphide ores is a crudely elliptical plug, 4×3 km in size, composed of ultramafic cumulates. In this chapter, we provide the first systematic documentation of the geochemistry, mineralogy and textural features of the Ni-Cu-PGE sulphide mineralization and associated platinum-group minerals (PGM) in the Giant Mascot intrusion. New geologic mapping also provides insight to mineralogical and textural characteristics of the ultramafic host rocks (Manor et al., 2014b). Ore formation is examined by utilizing epi- and diascopic microscopy, scanning electron microscopy, electron microbeam analyses, sulphur isotopes, whole rock chalcophile and PGE geochemistry, and modeling calculations. The results of this study reveal a complex intrusive history for ultramafic magma(s) that eventually achieved sulphide saturation and metal enrichment upon emplacement in the crust. Knowledge generated here may be used to guide future Ni-Cu-PGE exploration in the Canadian Cordillera and other convergent margins globally. 3 2  Geological SettingThe Giant Mascot Ni-Cu-PGE deposit is located east of Harrison Lake, approximately 12 km north of Hope in southwestern British Columbia. The Harrison Lake region lies at the southeastern margin of the Coast Plutonic Complex or Coast Mountains batholith, an agglomeration of intrusive suites related to continental arc magmatism that were emplaced in the Middle Jurassic (~170 Ma) to Eocene (~45 Ma; Gehrels et al., 2009) (Fig. 3.1). The 7749°45’N49°30’N49°30’N121°30’W121°45’W121°30’W121°45’W121°45’W122°W122°WGSLSLSLSESESESESECGCGUMHN5 kmFigure 3.1GSLSECGUMGambier GroupSlollicum schistSettler schistCogburn AssemblageUltramafic rocksH Harrison Lake GroupTerranesOphiolitic rocksSpuzzumGiant MascotHOPERiverFraserUrquhartFraserfaultHCHNSCCPLLACMMCCFCUSSMBCHBC100-107 Ma154-156 MaCP - Cogburn pluton CC - Clear Creek pluton FC - Fir Creek pluton Breckenridge pluton unknownTertiary84-88 Ma89-96 MaIntrusive rocksCH - Chilliwack batholith MB - Mt. Barr batholith DP - Doctor’s Point pluton BC - Bear Creek pluton Scuzzy pluton Spuzzum pluton SC - Settler Creek pluton SS - Snowshoe pluton HN - Hornet Creek pluton AC - Ascent Creek plutonHC - Hut Creek plutonMM - Mt. Mason plutonGiant Mascot ultramafic- mafic intrusionUrquhart plutonLL - Lillooet plutonBS - Big Silver plutonCHDPCHBreckenridgeHarrison LakeScuzzyBSgeologic contactthrust faultfaultGiant Mascot Ni-Cu-PGE depositAlaskan-type intrusionsPacificOceanUSAVancouverCPCkm0 100 200NWT AlbertaYukonAlaska BCGiant MascotTurnagainDuke IslandSalt ChuckFigure 3.1.  Geology of the Harrison Lake region showing the location of the Giant Mascot ultramafic intrusion and associated Ni-Cu-PGE deposit. The patterns for intrusive rocks indicate Late Cretaceous plutons that are coloured according to crystallization age (geology modified from Gabites, 1985; Monger, 1989; Brown et al., 2000; and Mitrovic, 2013).The inset (modified after Colpron and Nelson, 2011) shows the location of the Giant Mascot intrusion in southwestern British Columbia relative to Alaskan-type ultramafic intrusions that host Ni-Cu-PGE mineralization. 78Coast Plutonic Complex extends over 1800 km from southeastern Alaska to southwestern British Columbia and the Northern Cascades in Washington State (Brown and McClelland, 2000; Reiners et al., 2002). Plutons and batholiths in the southern Coast Plutonic Complex are catazonal to epizonal, tonalitic to gabbroic intrusions that were emplaced in a magmatic arc setting during the Cretaceous (Fig. 3.1; Richards, 1971; Brown and McClelland, 2000; Mitrovic, 2013). Tertiary intrusions are also present in this region (e.g., Mt. Barr and Chilliwack batholiths) (Fig. 3.1).Rocks hosting the mineralization and associated ultramafic rocks at Giant Mascot include the Upper Triassic Settler schist and Late Cretaceous Spuzzum pluton (Fig. 3.2). The Settler schist is an upper amphibolite grade metamorphic complex consisting of pelitic and quartzofeldspathic schist and micaceous quartzite, locally containing garnet, staurolite, kyanite, minor graphite, and trace pyrite (Pigage, 1973; Mitrovic, 2013). This schist occurs on the east and southeast margins of the intrusion (Manor et al., 2014b). In the western part of Zofka Ridge, a large raft (120 m×200 m×350 m depth) of Settler schist is in contact with hornblende pyroxenite to the west and gabbronorite on all other sides (Aho, 1954; Manor et al., 2014b) (Fig. 3.2). Adjacent to the northern contact of this raft, a 70×100 m zone of garnetiferous gabbronorite/diorite is cut by siliceous veins that may represent anatectic melts of the Settler schist protolith (Manor et al., 2014a).The ca. 95 Ma Spuzzum pluton is a 60×20 km granitoid intrusion that is compositionally zoned from pyroxene diorite in the core to hornblende diorite towards the margins with an outermost rim of tonalite (Richards and McTaggart, 1976; Vining, 1977; Gabites, 1985). Variably melanocratic, medium-grained, hornblende-biotite quartz diorite and diorite-gabbronorite contains orthopyroxene, clinopyroxene, hornblende, and biotite that form 15-55% of the mode. Locally, lobate and elongate hornblendite enclaves (± biotite) are present. The diorites are moderately to strongly foliated, interpreted to represent primary magmatic foliation (c.f., Vining, 1977) with a variable metamorphic overprint. The strongest metamorphic foliation is observed in a large raft of quartz diorite in the ultramafic suite along the upper mine road 79Figure 3.2³0 500 1,00 0250Metershornblenditehornblende gabbroGiant Mascot ultramafic suite (ca. 93 Ma)Spuzzum pluton (ca. 95 Ma) Map symbolsSettler schist (Upper Triassic)hornblende pyroxeniteperidotitedunitegabbronorite-dioritegarnetiferous gabbronorite-dioritehornblende gabbronorite-dioritequartz dioritepyroxeniteSettler schistroad (dirt)stream or rivercontour (100m)geological contact, definedobserved outcropcontour (20m)geological contact, approximategeological contact, inferredfault, definedfault, approximatefault, inferredOrebodies (projected to surface) Mine tunnels0 250 500metres1000Pride of EmoryBrunswick 1-10460019005121600ChinamanClimax606500 mE 607500 mE 608500 mE 609500 mE5481000 mN5480000 mN5481000 mN5480000 mNFigure 3.2.  Geologic map of the Giant Mascot ultramafic intrusion (modified from Aho, 1954; Vining, 1977; Manor et al., 2014b) with orebodies and mine tunnels projected to surface. Orebodies are selectively labeled for reference to Figures 3.5, 3.6, and 3.7. UTM coordinates are reported as NAD83 Zone 10. 80(Fig. 3.2). Deformation features of the Spuzzum pluton include textures with relatively minor recrystallization of quartz and plagioclase, bent plagioclase crystals, and weak to moderate mafic mineral alignment along bands of recrystallized quartz.3 3  Geology of the Giant Mascot Ni-Cu-PGE DepositThe ca. 93 Ma Giant Mascot ultramafic intrusive suite (Chapter 2) consists predominantly of dunite, peridotite, pyroxenite, hornblende pyroxenite, and hornblendite (Fig. 3.2). The rocks are remarkably fresh and display primary igneous textures involving olivine, orthopyroxene, clinopyroxene, and hornblende, with minor biotite, and plagioclase, and accessory zircon, titanite, rutile, and apatite (Fig. 3.3, 3.4). Cumulates are weakly deformed, observed as bent or broken olivine, orthopyroxene, clinopyroxene, and hornblende, and strain-banded olivine. Minor secondary, metamorphic mineralogy varies in intensity and occur mostly at grain boundaries as tremolite-actinolite, chromian Mg-chlorite, talc, anthophyllite, serpentine, carbonate, and rare zeolite. Cumulates comprise the majority of the intrusive suite and include heterogeneously distributed mineral assemblages typically devoid of clinopyroxene with interstitial, and rare cumulus, hornblende: olivine-hornblende, olivine-orthopyroxene-hornblende, orthopyroxene-hornblende, olivine-orthopyroxene.Dunite occurs in the core of the intrusion and, although minor in volume, is a major host of nickel mineralization. The rock is fine-grained and contains 90-95 vol.% equigranular, cumulus olivine with sparse euhedral chromite inclusions and secondary Cr-magnetite and serpentine (Fig. 3.3A, 3.4A). Interstitial minerals include orthopyroxene, sulphide (pyrrhotite, pentlandite, chalcopyrite, and pyrite), and minor hornblende and clinopyroxene (Fig. 3.4A). Peridotite, the other major host of mineralization, is represented by fine to medium-grained lherzolite and harzburgite orthocumulates with variable amounts of hornblende. Olivine (40-80%; ~Fo84; Muir, 1971) occurs as cumulus crystals enclosed in subpoikilitic pyroxene (Fig. 3.4B). Intergranular orthopyroxene (30-60%) is the dominant pyroxene (En84; Muir, 1971) accompanied by variable proportions of clinopyroxene and interstitial hornblende (0-10%; 81BEHcpxopxolhblchlplbtplqtzcpxhblADGolhblcpxopxplcpxopxhblCFIolopxcpxhblhblplqtz +plbtgtplDuniteHornblende pyroxenitePeridotiteHornblenditePyroxeniteHornblende gabbroGabbronorite-diorite Quartz diorite Settler SchistFigure 3.1XPL TLTLTLTLTLTLTLTLTLXPLXPLXPLXPLXPLXPLXPLXPLFigure 3.3.  Representative photomicrographs of the lithological units in the Giant Mascot intrusive suite and host rocks. Scanned images of thin sections, 2 x 4 cm, in cross-polarized light (XPL) and transmitted light (TL). Ultramafic units: A) dunite (sample 12MMA-7-8-1); B) peridotite (12MMA-7-10-1); C) pyroxenite (12MMA-5-4-1); D) hornblende pyroxenite (12MMA-2-4-1); E) hornblendite (11GNX-1-2-1). Mafic units: F) hornblende gabbro (13MMA-9-9-3). Country rocks: G) Spuzzum gabbronorite/diorite (12MMA-9-1-2); H) Spuzzum quartz diorite (12MMA-2-1-5); I) Settler schist (13MMA-5-1-1). Mineral abbreviations: ol = olivine; opx = orthopyroxene; cpx = clinopyroxene; hbl = hornblende; bt = biotite; pl = plagioclase; chl = chlorite; qtz = quartz; gt = garnet.82Figure 3.21 mm 1 mm1 mm1 mm 1 mm1 mm1 mm0.5 mm0.5 mmA B CFEDG H IFigure 3.4.  Photomicrographs of representative silicate textures present in the Giant Mascot ultramafic intrusive suite. A) Cumulus olivine with minor interstitial orthopyroxene. Spinel is present as either inclusions in olivine and orthopyroxene or at grain boundaries (13MMA-3-10-1). B) Cumulus olivine with interstitial orthopyroxene and minor clinopyroxene with one olivine inclusion. Spinel and sulphide (pyrrhotite-chalcopyrite-magnetite composite blebs) are present (13MMA-3-8-1). C) Interstitial hornblende containing abundant subhedral to euhedral olivine inclusions. Anthophyllite and talc are relatively minor alteration products on the margins of hornblende and olivine, respectively (13MMA-3-8-1). D) Intergrowths of olivine, orthopyroxene, and hornblende with interstitial sulphide. Phlogopite is replaced by chlorite at sulphide grain boundaries (179-E-410). E) Cumulus orthopyroxene and clinopyroxene with interstitial light brown hornblende that contains inclusions of euhedral orthopyroxene with clinopyroxene exsolution lamellae. Clinopyroxene cores are altered to hornblende (12MMA-5-4-1). F) Composite grain of orthopyroxene and clinopyroxene with sulphide (pyrrhotite-pentlandite-chalcopyrite) inclusions, replaced by hornblende; replacement of clinopyroxene is more pronounced than orthopyroxene (12MMA-2-4-1). G) Euhedral oikocrystic hornblende with subhedral orthopyroxene inclusions surrounded by marginal plagioclase that is host to zircon (see Fig. 2.7.1C). Oikocrysts are present amongst a medium-grained groundmass of cumulus orthopyroxene and clinopyroxene (12MMA-2-4-1). H) Cumulus hornblende with clusters of interstitial disseminated pyrrhotite and chalcopyrite. Coarse-grained hornblende contains inclusions of biotite (13MMA-1-4-1). I) Moderately foliated plagioclase (var. labradorite) and clinopyroxene, with minor orthopyroxene. The margins of clinopyroxene are replaced by green hornblende (12MMA-5-2-1). Mineral abbreviations: ol = olivine; opx = orthopyroxene; sp = spinel; cpx = clinopyroxene; sul = sulphide; hbl = hornblende; tlc = talc; ath = anthophyllite; chl = chlorite; phl = phlogopite; pl = plagioclase; bt = biotite.83Figs. 3.4B-D) and rare cumulus hornblende. Local alteration of olivine is restricted to fractures as serpentine with rare magnetite and hematite (Fig. 3.4D); orthopyroxene and clinopyroxene locally alter to talc along grain boundaries, and rarely, clinopyroxene is observed as fine exsolution lamellae in orthopyroxene. Pyroxenite is typically barren of mineralization and forms medium-grained orthocumulates of websterite, olivine websterite, and orthopyroxenite (Fig. 3.3). Brown orthopyroxene (En82; Muir, 1971) is typically subhedral and prismatic, forming rare oikocrysts, and is more abundant than black-green clinopyroxene (55-90% total pyroxene). Clinopyroxene is commonly replaced by hornblende along cleavage planes in the cores of grains and is interpreted as late-magmatic replacement; similar replacement in orthopyroxene is less prominent (Figs. 3.4E, F). Olivine (5-35%) is present as intergranular grains or inclusions, whereas hornblende (0-10%) is interstitial. Locally, plagioclase (5-10%) occurs in clots. Hornblende-bearing units in the Giant Mascot ultramafic intrusive suite include hornblende pyroxenite and hornblendite. Hornblende pyroxenites are medium-grained hornblende websterite and orthopyroxenite, commonly oikocrystic and locally feldspathic (Figs. 3.3D, 3.4G). Orthopyroxene (En77-81; Muir, 1971) and clinopyroxene abundances are highly variable (20-60% total pyroxene) and textures are predominantly cumulus. Pyroxene grains are commonly enclosed by oikocrystic hornblende (20-80%), which ranges in diameter from 4 to 50 mm. These rocks rarely contain sulphide; exceptions are reported in the Chinaman, Climax and 4300 orebodies, which hosted disseminated and minor massive sulphide mineralization (Table 1.3; Fig. 3.5; Christopher and Robinson, 1975). Hornblendite commonly occurs at marginal contacts with Spuzzum gabbronorite/diorite and quartz diorite, where it forms locally feldspathic pegmatite zones up to 40 m wide at the contact (Figs. 3.3E, 3.4H; Manor et al., 2014b). These pegmatitic zones contain prismatic hornblende (90-98%) ranging in length from 4 to 25 cm and are locally altered in part to cummingtonite-tremolite intergrowths and anthophyllite. Hornblendite in the remainder of the intrusion, including dikes, are typically medium-grained (2-10 mm) and exhibit relatively little alteration. Clinopyroxene (0-5%) is interstitial or forms euhedral inclusions in pegmatitic hornblende. Locally, plagioclase clots (An80-90; McLeod, 1975) 84may attain 30% of the mode. Minor, generally unmineralized, hornblende gabbro and felsic pegmatite and aplite dikes comprise the youngest units in the Giant Mascot intrusion.3 4  Giant Mascot OrebodiesThe major Ni-Cu-PGE sulphide mineralization in the Giant Mascot intrusion is mostly hosted in olivine-rich rocks, including dunite, peridotite, and olivine-bearing pyroxenite, however a few occurrences in hornblende pyroxenite (e.g., Chinaman orebody) and rare sulphide dikes exist (e.g., Aho, 1954). Sulphide orebodies occur in 28 steeply dipping, north-northwest-plunging, pipe-like (e.g., Pride of Emory, Brunswick #1, 1900, 4600) and lensoid (e.g., Brunswick #2, 1600) structures and similarly dipping atypical tabular profiles (e.g., 512, 600, and 6800) that have widths of 6 to 75 m and lengths of 15 to 350 m (Table 1.3; Fig. 3.5; Christopher, 1974; Christopher and Robinson, 1975). During production, orebodies were classified as either “zoned” or “unzoned” based primarily on textural characteristics of the ores (Aho, 1954, 1956; Christopher and Robinson, 1975). Zoned orebodies are concentrically zoned and typically consist of disseminated to net-textured mineralization surrounding massive ore confined to olivine-rich peridotite and dunite (e.g., Brunswick #1, #5, #6, and 512, 1600, 1900, 4600, Climax, and Chinaman; Figs. 3.6B, D, 3.7A-D). Unzoned orebodies are predominantly lensoid or tabular structures containing semi-massive to massive mineralization (e.g., Pride of Emory, Brunswick #2, #8, and #9; Fig. 3.6A, C). Zoned and unzoned orebodies are both intimately associated with olivine-bearing ultramafic rocks (Aho, 1954, 1956).Clarke (1969) documented four primary fault orientations in the Giant Mascot ultramafic suite and associated orebodies (reported as right hand rule notation): 1) 310-315/50-75; 2) 015-030/70-90 or 195-210/70-90; 3) 350-010/55-90 or 170-190/55-90; 4) 330-030/20-30. The steeper fault trends (i.e., 1, 2, and 3) are closely associated with mineralization and may have aided the movement and concentration of sulphides (Clarke, 1969), although structures in each group can be unmineralized. Group 1 faults are interpreted to have preceeded ore formation and are proposed as the main control on mineralization in the ore zones of the Brunswick, 1400, 1900, 85Modied from Clarke (1969) and Christopher & Robinson (1974) Giant Mascot Mines Ltd., Longitudinal ProjectionWEST EASTFigure 3.34000 EL3500 EL3000 EL4500 EL3 00 0E5 00 0E7 00 0E9 00 0EOriginal outcropsPride of Emory46001900160015001400512Nickel StarMolly6004300 4400ClimaxChinaman22001500Dolly2663Subsidence PlugBR-5ABR-2BR-16800BR-102950 LEVEL3250 LEVEL 3275 LEVEL2600 LEVEL3550 LEVELPORTAL         ZONEMILLSHAFTMAIN HAULAGEBrunswick (BR) orebodiesOrebodies Prior to Mining2000BR-2ABR-8BR-7WMZ EMZFigure 3.5.  North-looking longitudinal (west-east) section of the entire Giant Mascot deposit, distinguishing orebodies of the western mineralized zone (WMZ) from those in the eastern mineralized zone (EMZ). Section extends from the Brunswick orebodies in the northwest to the Portal Zone and mill in the southeast (modified after Clarke, 1969; Christopher and Robinson, 1975). BR = Brunswick.86NBrunswick No. 1 OrebodyZ o n e d  d u n i t e  c o r e  t o  o r t h o p y r o x e n i t e  m a r g i n3800Raise 60604570803800CrosscutWest3 8 0 0 C r o s s c u t3400CrosscutS u lp h id es 3 0 m b elow  lev el10 mL i m i t o f  o reFigure 3.4AB1219m1176m1130m1082m1036m975mSurface1280mComposite plan showing ore at all levelsandGeology at 3550 Level3550 LevelPride of Emory Orebody3200 Raise3200 Crosscut100 mCross sectionQuartz dioriteQuartz dioriteQuartz diorite Quartz dioriteO re a t 103 6 mO re a t  117 6 m3550 LEVELN3200 Raise3 2 0 0 C r o s s c u tM a g n etometerou tlin eO re a t 113 0mOre  a t su rf a c e( 126 5m)O r e a t 108 2mAAA’A’100 mPride of Emory OrebodyUnzoned ZonedHPxHPxHbPdPdolivine orthopyroxenitePxPxPxPxPxSettler schistSettler schistDnFigure 3.6.  Detailed cross sections and plans of orebodies in the western mineralized zone (WMZ), Giant Mascot deposit (modified from Aho, 1954). A) Pride of Emory massive ore lens. B) Brunswick #1 orebody. Note the concentric nature of ultramafic lithologies and concentration of sulphide mineralization in zoned dunite-peridotite. C) Brunswick #2 massive ore lenses. D) Brunswick #5, #6, and #7 orebodies. Dn = dunite; Pd = peridotite; Px = pyroxenite; HPx = hornblende pyroxenite; Hb = hornblendite.87NBrunswick No. 5, 6 and 7 Orebodies3 4 0 0 C r o s s c u t20 mL i m i t  o f  o r e65803 4 0 0 R a i s eNo. 6No. 7No. 5L i m i t  o f  o r e(45 m below level)Hornblende orthopyroxeniteHornblende orthopyroxenite616040 5575 18643800  stope3800crosscutwest10 mNBrunswick No. 2 OrebodiesFigure 3.4 (cont.)CDUnzonedZonedPdPdPxPxDnDndioritedikesPdPxPxolivine orthopyroxeniteolivine orthopyroxenitePddiorite-norite Figure 3.6. (continued).  88O r e  be l o w  le v el 1600EOre intersection1 6 0 0  R a i se1 6 0 0  C r o s s c u t20 m1600 OrebodiesN8070601 9 0 0  C r os s c u tL i mi t  o f  o r e15 mN1900 Orebody1 9 0 0 R a i s e60Figure 3.5ABZonedZoneddiorite-noritediorite-noritePdPdPdHPxHb dikesPxPxPxdiorite-noriteFigure 3.7.  Detailed cross sections and plans of orebodies in the central and eastern mineralized zones (EMZ) (modified from Aho, 1954; Clarke, 1969; McLeod, 1975). A) 1600 orebodies (central zone), which contain the highest-grade PGE mineralization in the intrusion. B) 1900 orebody in the central zone. Note the concentric zoning of ultramafic units associated with sulphide mineralization. C) Climax orebody (eastern zone). D) 4600 orebody (central zone); thick black lines indicate faults. Pd = peridotite; Px = pyroxenite; HPx = hornblende pyroxenite; Hb = hornblendite.89Figure 3.5 (cont.)NClimax Orebody10 m6900 N7000 N7000 EApproximate outline of Climax ore258520olivine pyroxenite3 0 5 0  C r os s c u t(McLeod, 1975)Cross section4600 Orebody30 m3550 Level4 000 E4 500 E3250 Level2950 Level(Clarke, 1969)CDZonedZonedPdPdPxPxdiorite-norite Figure 3.7. (continued).904600, and possibly Pride of Emory orebodies. Group 2 faults are commonly associated with tabular ore zones (e.g., 512, 600 and 1600) and orientations associated with group 3 faults are observed in all ore zones, typically associated with disseminated ore textures. The fourth group of faults is interpreted to be post-ore, with the exception of ore shoot terminations in the 600 and 1500 orebodies (Clark, 1969). These fault orientations appear to reflect brittle faults that formed following emplacement of the sulphide orebodies, thus, it is not clear how such structures would have exerted control on the deposition of magmatic sulphides. Some mineralization has been attributed as being controlled and consequently terminated by faults (Aho, 1954; Clarke, 1969; Muir, 1971; McLeod, 1975), however the geometrical complexity of zoned deposits and their associated mineralization cannot be entirely attributed to these structural features (e.g., Pinsent, 2002). The Giant Mascot orebodies, similar to original descriptions by Aho (1956), are thus interpreted as sub-vertical crustal conduits through which subsequent magma pulses ascended (Figs. 3.6, 3.7).3 5  Analytical MethodsPetrographic and geochemical analyses in this study utilized over 100 polished thin sections from a new collection based on geologic mapping in 2012 and 2013 (Manor et al., 2014b), and >100 from both BCGS and GSC-Ottawa archives (see Appendix I for the full record of thin sections and analyses completed on each).3 5 1  Scanning electron microscopyPolished petrographic thin sections (n=10) were carbon coated and prepared in the Electron Microbeam/X-Ray Diffraction Facility at the University of British Columbia, Vancouver (UBC) and the SEM Facility at the Geological Survey of Canada, Ottawa (GSC). At UBC, back-scattered electron (BSE) imaging and qualitative energy-dispersive spectrometry (EDS) were carried out on a Philips XL-30 scanning electron microscope (SEM) equipped with a Bruker Quanta 200 energy-dispersion X-ray microanalysis system. An operating voltage of 9115 kV was used, with a spot diameter of 6 μm, and peak count time of 30 s. At the GSC, BSE imaging and EDS analyses were acquired on a Zeiss EVO 50 series SEM with extended pressure capability (up to 3000 Pascals), and equipped with a backscattered electron detector (BSD), Everhart-Thornley secondary electron detector (SE), and variable pressure secondary electron detector (VPSE). The Oxford EDS system includes the X-MAX 150 Silicon Drift Detector, INCA Energy 450 software and Aztec microanalysis software. An operating voltage (EHT) of 20 kV was used, with a probe current of 400 pA to 1 nA, and peak count time of 30 s.3 5 2  Electron microbeam analysesNickel concentrations in olivine were determined on polished petrographic thin sections (n=15), carbon coated and prepared in the Electron Microbeam/X-Ray Diffraction Facility at UBC, Vancouver. For each sample, five olivine grains were selected for analysis and core-mid-rim transects were probed with a fully-automated Cameca SX-50 scanning electron microprobe with four vertical wavelength-dispersion X-ray (WDX) spectrometers and a fully integrated SAMx energy-dispersion X-ray (EDX) spectrometer. Major elements in olivine were analyzed using a 15 keV accelerating voltage, 20 nA beam current, 10 µm diameter beam, 30 s peak count time, and 10 s background count time. A second analysis on identical spots was used to determine more precise Ni and Ca concentrations at a 15 keV accelerating voltage, 100 nA beam current, 10 µm diameter beam, 100 s peak count time, and 10 s background count time. Natural and synthetic standards were used for calibration and procedural set-up of the instrument prior to each day of analysis. Data were reduced by the “PAP” Φ(ρZ) procedure of (Pouchou and Pichoir, 1991). All analyses are reported in Appendix V.Quantitative mineral analyses of sulphides and platinum group minerals were determined on carbon-coated, polished petrographic thin sections (n=9) using an automated four-spectrometer Cameca Camebax MBX electron microprobe by wavelength-dispersive X-ray analysis at the Department of Earth Sciences, Carleton University, Ottawa. Raw X-ray data were converted to elemental weight percent by the Cameca PAP matrix correction program. Tellurides 92and precious metal minerals were analyzed using a 20 keV accelerating voltage, 35 nA beam current, 2 µm diameter beam, and counting time of 10 s or 40,000 accumulated counts. 3 5 3  Sulphur isotopesIndividual sulphide minerals (e.g., pyrrhotite, pentlandite, chalcopyrite, pyrite) were extracted from sulphide-rich samples (n=39) using a Dremel 400 Series XPR hand-held drill with a 1/32” drill bit. Careful attention was paid to the sulphide minerals being extracted to estimate the percentage of S in the sample for approximately 3 mg of sulphide powder. Whole rocks of the Settler schist rocks (n=5) were analyzed due to unsuccessful separation of sulphide mineral separates (i.e., pyrite) and low S contents determined by whole rock geochemistry (Actlabs; see Appendix IX). The amount of sample powder was dependent on the initial S concentration in the whole rock and adjusted as needed (0.05 mg for 1 wt% S). All powders (n=49), including five blind duplicates, were analyzed at the G.G. Hatch Stable Isotope Laboratory at the University of Ottawa, Canada. Organic solids from vials were weighed into tin capsules with at least double the amount of tungstic oxide (WO3). Calibrated internal standards were prepared with every batch of samples for normalization of the data. Each analysis required 100 µg of S. Samples were loaded into an Elementar Vario Micro Cube elemental analyzer and flash combusted at 1800°C. Released gases (N2, CO2, H2O, and SO2) were carried by ultra-pure helium through the elemental analyzer to be cleaned, then gas chromatograph separation removed SO2 by moving gases through a series of adsorption traps (i.e., “trap and purge”). Isotopic compositions of organic sulphur (SO2) were measured by a ThermoFinnigan Delta XP isotope ratio mass spectrometer coupled with a ConFlo IV. The measured isotope for sulphur was 34 S assuming mass-dependent fractionation. Values are reported relative to the Vienna Canyon Diablo Troilite (VCDT) and analytical precision for δ34 S is 0.2‰.933 5 4  Chalcophile, platinum group element, and sulphur analysesPlatinum group element (Ir, Ru, Rh, Pt, Pd, Au) and chalcophile element (Ni, Cu, Co) concentrations of 39 whole rock samples and three duplicates were measured by the nickel-sulphide fire-assay (NiS-FA) ICP-MS and atomic absorption spectroscopy techniques, respectively, at Geoscience Laboratories in Sudbury, Ontario, Canada. Samples were crushed to 74 µm (200 mesh) using a high chrome steel mill to avoid contamination of precious metals. Nickel sulphide fire-assay techniques at Geolabs are detailed by Richardson and Burnham (2002), following procedures from Shazali et al. (1987) and Jackson et al. (1990). Nickel, sulphur, sodium carbonate, and sodium tetraborate were added to a 15 g aliquot of sample powder, and fused for 1.5 hours in a fire-clay crucible at 1050°C. Following cooling, the crucible was broken to recover a nickel sulphide button. This button was dissolved with HCl in a closed Teflon™ vessel to remove any NiS matrix. The co-precipitation of the NiS button with tellurium produced a concentrate containing all Au and PGE lost during button dissolution. Concentrates were then vacuum-filtered, re-dissolved in aqua regia, and brought to volume with deionized water prior to analysis by a Perkin-Elmer ELAN 5000 inductively coupled plasma mass spectrometer (ICP-MS). Osmium was not reported due to the potential loss as a volatile oxide during the aqua regia re-dissolution stage. Reference materials used were CANMET-certified TDB-1, WPR-1, WGB-1, and WMG-1, and an in-house komatiite sample OKUM. The remaining <74 µm pulps from the same crush as the NiS-FA method were mixed with a three-acid (hydrofluoric, nitric, and perchloric) mix in an open Teflon™ digestion vessel and heated until dry. A solution was produced by adding a second acid mixture, transferred to a 50 mL volumetric container and diluted with 10% HNO3 respective to the volume of sample. Chalcophile element (Ni, Cu, Co, Cd, Zn, Li, Pb) concentrations were measured by atomic absorption methods with a Varian Atomic Absorption Spectrometer AA280FS Series. Sulphur and carbon measurement techniques are outlined in Amirault and Burnham (2013). Sample material was taken from a 0.2 g pre-measured aliquot and combusted from radio-frequency inductive heating with a constant stream of purified oxygen. Gases (CO2 and SO2) 94were produced and detected by non-dispersive infrared (NDIR) cells. Concentrations were then measured by a LECO CS844 carbon and sulphur analyzer. Results for all analyses are reported in Appendix VI.3 5 5  Calculation procedure for whole-rock Ni, Cu, and PGE analyses to 100% sulphideCorrections for metal contents in 100% sulphide (i.e., tenor) were calculated for 39 samples from this study and 12 samples from Hulbert (2001), including eight samples from McLeod (1975) and four samples from Eckstrand (1971, unpublished data). The correction parameters from Naldrett et al. (2000) were used for Ni, Cu, Co, S, Ir, Ru, Rh, Pt, Pd, and Au, a method that utilizes the presence of significant Ni contents in olivine to correct for the Ni tenor in sulphide. Kerr (2003) used a more simplified approach by accounting for generalized ‘nonsulphide Ni’ to explain any Ni not included in the true tenor. The measured elemental concentrations were first converted to atomic proportions to determine the amount of S in pyrrhotite, pentlandite, and chalcopyrite; pyrrhotite was assigned the remaining S from the calculation. Based on normalized sulphide proportions, the amount of S and Fe applied to pyrrhotite, pentlandite, and chalcopyrite in massive sulphide were determined by multiplying by the ideal stoichiometric S wt% (36.5, 33.3, and 34.9 wt %, respectively) and Fe wt% (63.5, 36.2, and 30.4 wt%, respectively) in each of the three minerals. Proportions of sulphide were then determined based on the computed S in massive sulphide, and Fe associated with sulphide was iterated based on this sulphide proportion. The total S in massive sulphide relative to the original S assay was used as a conversion factor to determine the raw sulphide metal contents (i.e., tenor). Platinum group elements were calculated with the same conversion factor, assuming that the PGE originated from the sulphide melt by orthomagmatic processes with no hydrothermal input. The final step, to determine the proportions of non-sulphide, was to account for significant Ni contents in olivine in the Giant Mascot ores. Naldrett et al. (2000) account for this by calculating the Ni/Fe in sulphide and assuming a constant 25% modal proportion of olivine in each sample. Tests introducing actual modal percentages and Ni concentrations of olivine in each sample 95indicate there is no significant shift in the data and that the calculation procedure used previously is robust. The amount of Ni attributed to olivine was then used to re-calculate the raw Ni content in sulphide and achieve a final Ni tenor.3 6  Results3 6 1  Ni-Cu-PGE sulphide mineralizationAt both outcrop and hand-sample scale, mineralization is defined by disseminated, net-textured, semi-massive and massive textures, and is locally present Cu-rich veins that fill fractures in silicate minerals (Figs. 3.8A-H). Polished ore samples reveal rare discontinuous intrastratal folds that are interpreted to record syndepositional ductile deformation during emplacement of the orebodies (Fig. 3.8G), or rare brecciated textures in which olivine and pyroxene cumulates form inclusions in sulphide (Fig. 3.8H).The predominant base metal sulphide minerals, present in all ores of the Giant Mascot intrusion, are pyrrhotite, pentlandite, chalcopyrite, and minor pyrite (Table 3.1). Of the Fe-Ni-sulphides in Giant Mascot ores, pyrrhotite is the most abundant (Figs. 3.8, 3.9), present as both magnetic, monoclinic (Fe7S8), and non-magnetic, hexagonal (e.g., Fe11S12) varieties (e.g., Becker et al., 2010). Pyrrhotite compositions (n=61) range from Fe52.7S38.0 to Fe62.3S38.6 (average=Fe60.2Ni0.71S39.0) and contain up to 1.10 wt% Ni (Table 3.2; Figs. 3.10A, B; Appendix VIII). Coexisting troilite (n=11) compositions are nearly stoichiometric (Fe1.02S) with a restricted range of Fe contents characteristically higher than pyrrhotite (62.9-64.5 wt.%; Figs. 3.10A, B). Pentlandite has an average composition of (Ni4.7Fe4.4Co0.1)Σ9.2S8 (n=64) with up to 3.52 wt% Co and 0.08 wt% Ag, whereas argentopentlandite is invariably found in chalcopyrite and contains 11.8 to 12.3 wt% Ag with an average composition of Ag12.1(Ni18.9Fe37.4Co0.01)S31.6 (n=3; Fig. 3.10A). Violarite (Fig. 3.9K) and polydymite are interpreted as low temperature or late post-ore metamorphic products of pentlandite.Compositions of coexisting pyrrhotite and pentlandite are representative of their respective orebodies (Fig. 3.10B). The Pride of Emory orebody contains the most Ni-rich 96pnpocp1 cmcppo+pn+cppo+pnpo+pn ol+pyxolhblhblol+pyxhbl pyxpyxFDBAHCGE1 cm1 cm 1 cm1 cm1 cm1 cm1 cmpo+pnpo+pnpo+pn+cp1 cmFigure 3.6Figure 3.8.  Principal ore types of mineralization in the Giant Mascot intrusive suite. A) moderately net-textured pyrrhotite, pentlandite and chalcopyrite in pyroxenite (11AV-201). B) weakly net-textured pyrrhotite, pentlandite and chalcopyrite in pyroxenite (11AV-200). C) massive pyrrhotite, pentlandite and minor chalcopyrite in hornblende pyroxenite (71-EI-659). D) disseminated pyrrhotite and pentlandite within hornblendite (71-EI-622). E) massive pyrrhotite containing chalcopyrite veins and a rounded silicate inclusion (photo by R.H. Pinsent) (RHP01-076). F) hornblendite with chalcopyrite veins (71-EI-624). G) folded layers of disseminated pyrrhotite, pentlandite and olivine-rich peridotite at the contact with dunite (179-E-709; Aho, 1954). H) strongly net-textured pyrrhotite and pentlandite in peridotite (11AV-204). Mineral abbreviations: po = pyrrhotite; pn = pentlandite; cp/cpy = chalcopyrite; hbl = hornblende; pyx = pyroxene; ol = olivine.97pyrrhotite and pentlandite; massive pyrrhotite contains between 0.55-1.2 wt% Ni and 52.7-60.3 wt% Fe, with rare examples of Ni-rich pyrrhotite as an inclusion in chromite (2.4 wt% Ni) and blocky texture (8.1 wt% Ni; Table 3.2; Appendix VIII; Fig. 3.10B). Coexisting pentlandite has the highest Ni and lowest Fe contents (35-37 wt% Ni and 28.7-31.6 wt% Fe. The 1600 and 4600 orebodies host pyrrhotite that contains lower Ni (0.4-0.8 wt%) and higher Fe (60.2-61.5 wt%) contents with relatively lower Ni and higher Fe abundances in pentlandite (34.9-36.1 wt% Ni and 31.3-32.6 wt% Fe; Fig. 3.10B). Pyrrhotite from the Climax and Chinaman orebodies and associated 3050 Crosscut records the largest range in Fe contents (58.5-61.1 wt%) and lowest Ni (0.1-0.9 wt%), whereas coexisting pentlandite exhibits the most variable Ni contents (33.8-38.6 wt%). The Climax orebody also hosts the most Ni-rich pentlandite in a pentlandite-pyrite symplectite that yields 40.1 wt% Ni and in an inclusion in chromite with 36.5 wt% Ni and 17.5 wt% Fe (Fig. 3.10A). Troilite is dominant (troilite:pyrrhotite = >1:1) in samples 12MMA-5-8-5A and RHP01-109 and coexists with the most Ni-poor, Fe-rich pentlandite in Giant Mascot ores (30.1-31.6 wt% Ni and 34.8-37.7 wt% Fe; Fig. 3.10B).Chalcopyrite compositions do not vary with texture (i.e., massive vs. veins), are stoichiometric, and average Cu1.02Fe1.03S2 (n=31; Fig. 3.9). Pyrite shows minimal variation in Fe content (average=[Fe0.97Co0.03]S2; n=36) (Fig. 3.10A); however, massive pyrite (Figs. 3.9A, L, 3.9B) has distinctly lower Ni contents (0-0.1 wt%) compared to those of secondary pyrite veins (0.12-0.54 wt%; Figs. 3.9D, F, L), with an anomalous pyrite-pentlandite symplectite yielding the highest Ni contents (3.92 wt%). Secondary pyrite veins also contain 0.7-3.08 wt% Co, which chemically distinguish them from secondary marcasite flames and veins (0.02-0.65 wt%) (Appendix VIII).Sulpharsenide minerals, such as gersdorffite (NiAsS), cobaltite (CoAsS) and nickeline (NiAs) are typically associated with platinum group minerals (PGM) or precious metal minerals (PMM) (Figs. 3.11F, J). Most of the PGM identified are tellurides or bismuthotellurides, predominantly merenskyite (PdTe2), moncheite (PtTe2) and melonite (NiTe2) (Table 3.1; Figs. 3.12A, B). The PGM are dominantly associated with pentlandite (Figs. 3.11B, C; 3.12C) and 98Table 3.1.  Mineralogy of Ni-Cu-PGE sulphides, Giant Mascot deposit, Hope, B.C. †Mineral1 Formula Description 2 Photographic evidenceMajor ore mineralspyrrhotite Fe1-xS most abundant sulphide, po:pn = 2:1; massive or veins in fractures in silicatesFigs. 3.8, 3.9A-F, J-L, 3.11A, B, D, E, H, K, and 3.21A, D, E, G, Hpentlandite (Fe,Ni)9S8dominant Ni-ore mineral; massive and blocky or exsolution lamellae in po, tro, Ag-pnFigs. 3.8, 3.9A-D, G, H, 3.11A-C, E-H, K, L, and 3.21A, B, D, F, Gchalcopyrite CuFeS2massive; may fill late fractures in silicates and pyrrhotite Figs. 3.8, 3.9A, B, D-G, I-L, 3.11A, B, E, G-J, L, and 3.21C-HMinor and trace ore mineralsFe-, Ni-bearingpyrite FeS2intergrown with po, pn, and cp; symplectitic intergrowths with pn and cpFigs. 3.9A, L, 3.11B, H, and 3.21FNi-pyrite (Fe,Ni)S2veins in po and pn Fig. 3.9D, F, Lbravoite (Fe,Co,Ni)S2rare; in fracture in pomarcasite FeS2flames in po or late veins in cp and po Fig. 3.9Etroilite FeS exsolution lamellae in po and locally massive Figs. 3.11C, F and 3.21Cmagnetite Fe3O4euhedral inclusions in po or veins cutting po and cp; commonly associated with symplectitic textures at grain boundariesFig. 3.9F and 3.21C, E, F, Hargentopentlandite Ag(Fe,Ni)8S8exsolution lamellae and euhedral inclusions in cp Figs. 3.9G and 3.11Imackinawite (Fe,Ni)1+xS exsolution lamellae in pn and rare cp Figs. 3.9H and 3.11Iviolarite FeNi2S4alteration of pn at rim or crystallographic interfaces Fig. 3.9Kpolydymite Ni2+ Ni3+2S4rare; alteration of pn associated with cpCu-sulphidescubanite Cu3FeS4exsolution lamellae in cp and generally associated with troilite-rich assemblagesFigs. 3.9I, 3.11I, and 3.21Cgeffroyite (Ag,Cu,Fe)9(Se,S)8rare; inclusion in cpNi-arsenidesgersdorffite-cobaltite (Ni,Co)AsS rare; euhedral intergrown with Pd-melonite, in pn Fig. 3.11Fnickeline NiAs rare; inclusion in intergrown po-tro or at tip of cp grain Fig. 3.11JPb-, Zn-sulphidesgalena PbS in fractures of gangue or rare inclusions in po, tro, and cpsphalerite (Zn,Cd)S rare; in cp Figs. 3.9J and 3.21CBi-, Te-bearinghedleyite Bi2+xTe1-xrare; in silicatetellurobismuthite Bi2Te3rare; inclusion in po-pn, or at contactnative tellurium Te rare; inclusions in po or pn and at sulphide-silicate interfacesnative bismuth Bi rare; inclusions in po or pn and at sulphide-silicate interfaces Fig. 3.11K† Mineral chemistry can be found in Appendix VIII1Bold minerals indicate most abundant mineral in respective group2Mineral abbreviations: po=pyrrhotite, pn=pentlandite, cp=chalcopyrite, py=pyrite, tro=troilite, Ag-pn=argentopentlandite, cub=cubanite99Table 3.1.  (cont.) Mineralogy of Ni-Cu-PGE sulphides, Giant Mascot deposit, Hope, B.C. †Mineral1 Formula Description 2 Photographic evidencePlatinum group mineralsmerenskyite (Pd,Ni,Pt)(Te,Bi)2most common PGM (3-23 μm); associated with po, pn, cp, py, and tro; inclusions in sulphides or occur at sulphide-sulphide or sulphide-silicate interfaces Fig. 3.11A, B, Lmoncheite (Pt,Pd)(Te,Bi)2very common (2-56 μm); inclusions in po, pn, cp, or silicate, or occur at sulphide-sulphide, sulphide-silicate interfaces, or in stringers (<160 μm) with cp and Ag-pnFig. 3.11D, E, Gpalladian melonite (Pd,Ni)(Te,Bi)2common; inclusions in po, pn, and tro (<30 μm) Fig. 3.11C, Ffroodite PdBi2rare; satellite grain in silicate contacting cpsperrylite PtAs2rare; inclusions (<50 μm) in cp or at cp-po-silicate interface Fig. 3.11Hhollingworthite RhAsS rare; composite grain with Ni-merenskyite in cp-pn vein Fig. 3.11LPrecious metal mineralshessite Ag2Te most common PMM (3-8 μm); satellite grains in fractures in sili-cates, inclusions in cub, cp, pn, and silicate, at sulphide-sulphide or sulphide-silicate interfaces, or intergrown with moncheiteFig. 3.11C, E, Galtaite PbTe rare; associated with cp Fig. 3.11J† Mineral chemistry can be found in Appendix VIII1Bold minerals indicate most abundant mineral in respective group2Mineral abbreviations: po=pyrrhotite, pn=pentlandite, cp=chalcopyrite, py=pyrite, tro=troilite, Ag-pn=argentopentlandite, cub=cubanite100ADBEHCFIJ K LFigure 3.70.1 mm 0.1 mm 0.1 mm0.1 mm25 μm0.1 mm25 μm0.1 mm0.1 mm0.25 mm 0.5 mm10 μmGpo po popo popocpcpcpcpcpcpcppnpnpnpnpn pnpnpnopxopxopxcpxspvl popnpopopnpycppncp opxamph cpxcppoAg-pnmkcubtromrcpy pypypy-cppnmagsil silsilFigure 3.9.  Photomicrographs and backscatter electron (BSE) images of sulphide textures in the Giant Mascot intrusion. A) blocky pentlandite, massive chalcopyrite and pyrite, and symplectitic chalcopyrite-pyrite hosted by massive pyrrhotite (71-EI-636). B) troilite exsolution lamellae, pentlandite flames and minor chalcopyrite in massive pyrrhotite (12MMA-5-8-5A). C) two forms of pentlandite, blocky grains and exsolution lamellae, hosted by massive pyrrhotite (71-EI-615C). D) blocky pentlandite, pyrite-pentlandite intergrowths and chalcopyrite in pyrrhotite, with a pyrite vein cutting the intergrowths and pyrrhotite (71-EI-634). E) net-textured pyrrhotite containing chalcopyrite veins and marcasite flames (71-EI-636). F) pyrrhotite and chalcopyrite containing veins of pyrite and magnetite (M29-21). G) argentopentlandite with pentlandite exsolution lamellae hosted by chalcopyrite (BSE) (71-EI-624A). H) massive pentlandite containing mackinawite [(Fe,Ni)1+xS] exsolution lamellae (12MMA-5-8-5A). I) massive chalcopyrite containing cubanite exsolution lamellae (RHP01-078). J) net-textured pyrrhotite, pentlandite, and chalcopyrite, with intergrown spinel and chalcopyrite-bearing fractures interstitial to orthopyroxene and clinopyroxene (12MMA-5-8-1). K) pyrrhotite and pentlandite (altered to violarite) interstitial to orthopyroxene, clinopyroxene, and amphibole; fractures in orthopyroxene and clinopyroxene are filled with chalcopyrite with evidence of localized microfaults (RHP01-109). L) blocky pentlandite, veins of pyrite intergrown with chalcopyrite, and pentlandite exsolution lamellae at chalcopyrite grain boundaries, hosted in massive and strongly anisotropic pyrrhotite (RHP01-152). Mineral abbreviations: po = pyrrhotite; pn = pentlandite; Ag-pn = argentopentlandite; cp = chalcopyrite; py = pyrite; tro = troilite; mrc = marcasite; mag = magnetite; mk = mackinawite; cub = cubanite; vl = violarite; amph = amphibole; opx = orthopyroxene; cpx = clinopyroxene; sil = silicate.101Table 3.2.  Representative base metal sulphide compositions from electron microprobe analysis, Giant Mascot Ni-Cu-PGE depositClimax Pride of Emory 1600 4600 3050 CrosscutSample 71-E1-615A SVA-75.8-14.5 11AV-200 11AV-201 179-E-410 179-E-847 M29-21 71-E1-624A 71-EI-659ARock Texture 1 NT D NT D D SM SM vein MRock type 2 pyroxenite opx hornblenditeol-hbl pyroxenite peridotite peridotitehbl peridotite peridotitehornblendite dikehbl pyroxenitePyrrhotite, Fe1-xSTexture † massive massiveblebs in amph  incl in chr massive massive massiveinter-growthrimmed by mt massiveS 39.84 39.23 38.01 39.66 38.65 38.94 38.80 38.92 39.65 38.78Fe 59.96 60.10 60.24 57.53 59.97 60.28 60.99 60.27 60.18 59.90Ni 0.60 1.07 0.55 2.35 0.82 0.64 0.69 0.64 0.08 0.49Cu 0.02 0.04 0.01 0.03 0.03 0.00 0.00 0.00 0.10 0.00Co 0.00 0.06 0.03 0.03 0.04 0.02 0.02 0.01 0.00 0.04Ag 0.00 0.00 0.00 0.03 0.00 0.00 0.00 0.01 0.02 0.05Total 100.43 100.51 98.83 99.63 99.51 99.87 100.49 99.85 100.04 99.26Pentlandite, (Fe,Ni)9S8Texture flame flameremnant in posymp with py blocky flameinter-growth blocky blocky flameS 32.92 32.43 32.91 32.03 32.99 32.76 33.45 32.91 32.53 33.32Fe 31.93 28.90 28.70 29.60 30.56 32.14 31.94 31.65 29.97 30.43Ni 35.26 35.19 35.00 35.05 36.51 34.94 36.08 35.30 36.75 35.96Cu 0.00 0.03 0.00 0.00 0.01 0.08 0.08 0.00 0.00 0.01Co 0.32 3.45 3.52 0.80 0.97 0.12 0.10 0.62 0.22 1.49Ag 0.02 0.00 0.03 0.00 0.04 0.04 0.00 0.00 0.00 0.00Total 100.45 100.00 100.16 97.47 101.09 100.08 101.66 100.48 99.48 101.19Chalcopyrite, CuFeS2Texture massive massive around po incl in po massive cp-py symp incl in po incl in po massive rims pyS 34.40 33.93 33.35 34.46 34.46 34.47 34.48 34.36 34.73 34.20Fe 30.65 30.57 29.94 30.01 30.91 30.96 30.66 30.86 31.04 31.22Ni 0.01 0.05 0.05 0.04 0.01 0.07 0.00 0.00 0.01 0.00Cu 35.16 34.23 33.27 34.60 34.58 33.98 34.87 34.46 34.90 34.33Co 0.01 0.00 0.00 0.00 0.00 0.04 0.00 0.00 0.01 0.00Ag 0.05 0.01 0.00 0.06 0.02 0.00 0.01 0.06 0.00 0.00Total 100.28 98.80 96.61 99.15 99.98 99.54 100.02 99.73 100.68 99.75Pyrite, FeS2Texture vein in pn massivereplaced by mt vein vein cp-py symp vein in po massive vein massiveS 54.00 53.49 53.66 53.50 53.67 53.45 54.17 54.14 54.27 53.98Fe 44.80 45.23 45.70 44.13 46.01 45.62 44.53 44.51 45.94 47.36Ni 0.17 0.00 0.07 0.53 0.54 0.07 0.25 0.00 0.27 0.03Cu 0.00 0.00 0.02 0.35 0.10 0.27 0.03 0.06 0.05 0.00Co 2.93 1.35 0.30 2.27 1.88 2.23 2.00 1.30 1.44 0.84Ag 0.00 0.02 0.02 0.04 0.00 0.03 0.04 0.00 0.00 0.05Total 101.90 100.10 99.77 100.83 102.20 101.68 101.01 100.00 101.97 102.26*  down-plunge of the Chinaman orebody†  symp, symplectic intergrowth; amph, amphibole; incl, inclusion; cp, chalcopyrite; mt, magnetite; pn, pentlandite; po, pyrrhotite; py, pyrite; Cr-sp, chromian spinel; opx, orthopyroxene; chr, chromite; spy, sperrylite1 D, disseminated sulphides; NT, net-textured sulphides; SM, semi-massive sulphides; M, massive sulphides2 opx, orthopyroxene; ol, olivine; hbl, hornblende3  Note in samples 12MMA-5-8-5A and RHP01-109, troilite analyses are provided rather than pyrite102Table 3.2. (cont). Representative base metal sulphide compositions from electron microprobe analysis, Giant Mascot Ni-Cu-PGE depositDDH-U-3841* DDH-U-3869 3550 East Portal dump Mill site dumpSample 71-EI-632 71-EI-635 71-EI-639B 71-E1-657 RHP01-078 RHP01-15212MMA-5-8-5A RHP01-109Rock Texture 1 D NT NT NT NT NT D DRock type 2 hbl pyroxenite peridotitehbl pyroxenite hbl pyroxeniteol-opx hornblendite harzburgitehbl peridotite hbl pyroxenitePyrrhotite, Fe1-xSTexture † incl in cp massive massive massive rims pn fracture fill incl in Cr-spflame in troiliteflame in troiliteS 38.21 39.50 40.31 39.20 39.83 38.67 38.84 38.58 38.20Fe 61.05 59.45 59.47 60.04 60.11 61.45 60.11 62.29 61.47Ni 0.13 0.66 0.41 0.46 0.55 0.25 0.30 0.12 0.51Cu 0.20 0.02 0.00 0.00 0.00 0.09 0.05 0.00 0.00Co 0.03 0.01 0.00 0.03 0.04 0.01 0.01 0.00 0.01Ag 0.00 0.00 0.00 0.00 0.02 0.05 0.03 0.08 0.02Total 99.63 99.64 100.18 99.73 100.55 100.53 99.34 101.06 100.22Pentlandite, (Fe,Ni)9S8Texture flame blockypy-pn symp blocky flame blockyincl in Cr-sp incl in troilite incl in opxS 32.43 33.21 33.23 33.30 33.12 33.11 34.47 32.95 33.26Fe 31.16 30.60 30.81 31.15 30.99 33.26 33.00 36.95 35.69Ni 35.52 36.80 36.34 35.53 35.90 34.55 32.08 30.38 31.14Cu 0.01 0.00 0.00 0.00 0.01 0.03 0.07 0.00 0.06Co 0.89 0.54 0.54 0.91 0.19 0.21 0.17 0.62 0.79Ag 0.06 0.00 0.03 0.01 0.06 0.07 0.03 0.05 0.02Total 100.06 101.14 100.96 100.90 100.27 101.23 99.83 100.96 100.95Chalcopyrite, CuFeS2Texture incl in chr intergrowth massive massive spy intergrowth massive incl in po massive intergrowthS 34.57 33.78 34.86 34.06 34.30 34.13 34.72 33.96 34.50Fe 31.17 31.39 30.49 30.67 30.14 30.59 31.14 31.00 30.60Ni 0.27 0.01 0.00 0.01 0.01 0.00 0.17 0.00 0.01Cu 34.40 34.04 33.97 34.65 34.02 34.91 34.49 35.38 34.55Co 0.03 0.00 0.03 0.01 0.00 0.01 0.00 0.01 0.00Ag 0.03 0.05 0.01 0.05 0.02 0.00 0.01 0.05 0.00Total 100.47 99.27 99.36 99.44 98.49 99.64 100.53 100.40 99.66Pyrite, FeS2troilite, FeS3Texture vein in pn incl in pnpy-pn symp incl in cp flame in pn incl in po intergrowth massive massiveS 52.92 54.61 53.81 54.28 53.49 54.14 53.72 36.18 36.49Fe 44.44 45.43 44.14 45.36 43.70 45.71 46.07 64.06 63.10Ni 0.20 0.08 3.92 0.02 0.09 0.07 0.06 0.00 0.00Cu 1.03 0.02 0.00 0.25 0.02 0.09 0.03 0.02 0.00Co 2.41 1.85 1.56 2.14 2.63 2.03 0.98 0.03 0.01Ag 0.01 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.00Total 101.02 102.00 103.43 102.05 99.94 102.03 100.85 100.29 99.60*  down-plunge of the Chinaman orebody†  symp, symplectic intergrowth; amph, amphibole; incl, inclusion; cp, chalcopyrite; mt, magnetite; pn, pentlandite; po, pyrrhotite; py, pyrite; Cr-sp, chromian spinel; opx, orthopyroxene; chr, chromite; spy, sperrylite1 D, disseminated sulphides; NT, net-textured sulphides; SM, semi-massive sulphides; M, massive sulphides2 opx, orthopyroxene; ol, olivine; hbl, hornblende3  Note in samples 12MMA-5-8-5A and RHP01-109, troilite analyses are provided rather than pyrite103SNiFe n=183Figure 3.8pentlandite(Fe,Ni) 9 S 8argentopentlanditeAg(Fe,Ni) 8 S 8pyrrhotiteFe 1-x StroiliteFeSpyrite/marcasiteFeS 2Fe=30Ni=0Ni=10Ni=30Ni=40Fe=60Fe=~68 Fe=40S=40S=30AB Pride of Emory (West)1600 + 4600 (Central)Climax, Chinaman, and 3050 Crosscut (East)12MMA-5-8-5ApyrrhotitepentlanditeTroilite-richRHP01-109inclusion in chromiteinclusion in chromitepn-py symplectite Figure 3.10.  Ternary compositions of Fe-, Ni-, and S-bearing base metal sulphides in the Giant Mascot Ni-Cu-PGE deposit. A) Ternary diagram shows characteristic compositions of pyrrhotite, pentlandite, argentopentlandite, pyrite, and troilite. B) Enlarged portions of the above ternary diagram are highlighted by a red line for pyrrhotite and troilite (left) and pentlandite (right). Coloured lines enclose mineral compositions observed in each mineralization zone. Note the most Fe-rich and Ni-poor pentlandites are associated with troilite, shown by tie lines where the two minerals coexist. Analyses are EPMA results in weight percent normalized to 100%.104other base metal sulphides. Generally, PGM may be fully enclosed in sulphide, at sulphide-sulphide or sulphide-silicate interfaces, in sulphide veins in other sulphides or less commonly in silicates and as satellite grains in fractured silicates. Merenskyite and moncheite are the most common PGM in the Giant Mascot deposit. Merenskyite occurs as three compositional varieties: Pt-rich, Ni-rich, and near-stoichiometric merenskyite (Figs. 3.11A, B; 3.12C) and moncheite is present as either stoichiometric or Pd-rich compositions (Figs. 3.11D, E); the Pd-rich variety has an average composition of [(Pt0.35Pd0.31)(Te1.87Bi0.14)] (n=3). Palladian melonite is less abundant, but common, and has an average composition of [(Ni0.84Pd0.23)(Te1.87Bi0.13)] (n=11; Figs. 3.11C, F). As-bearing PGM (i.e., sperrylite and hollingworthite) are rare and associated with chalcopyrite (Fig. 3.11H). Precious metal minerals are typically tellurides, but form ligands with Ag (e.g., hessite), and less common, Pb (e.g., altaite) (Table 3.1). 3 6 2  Sulphide and platinum group element geochemistryA comprehensive ore geochemical study of 44 mineralized samples from 11 Giant Mascot orebodies includes results of base metal sulphide (Ni and Cu), platinum group element (PGE: Os, Ir, Ru, Rh, Pd, Pt) concentrations, and Au whole rock geochemistry (Table 3.3). Sulphur contents range from 0.97-33 wt% and are directly proportional to the modal abundance of sulphide (i.e., mineralization texture) with relatively little association with rock type (Fig. 3.13). Analyses of olivine-rich rocks (e.g., dunite, peridotite) show elevated Ni, Cu, Pd, and Pt concentrations (averages: 1.8 wt% Ni, 0.7 wt% Cu, 239 ppm Pd, 124 ppm Pt), consistent with host rocks containing the majority of sulphide mineralization. These rocks are also characterized by Ni contents above that of stoichiometric pentlandite reflecting another mineralogical host for nickel (e.g., olivine) (Fig. 3.13A).Variations in chalcophile element contents are a function of mineralization type as the net-textured ores are lowest in Ni, Cu, and PGE, and the semi-massive, massive, and disseminated ores are richest (Fig. 3.14). Disseminated sulphides have low S (0.97-12.8 wt%), high Ni and PGE, and low Cu (average Ni/Cu=3.6, Cu/Pd=2.3 ×104; Figs. 3.14, 3.15). In net-10525 μm10 μm5 μm01 mm10 μm1 μm25 μm25 μm50 μmA B CD E FH IJBSEBSEBSEL10 μmK10 μmG5 μmBSEBSE BSE BSEcpholsil pnpnBipnpncpopxopxcppnPd-monhshspo Pd-Bi-Temerpo tropocpcpcpcpcppnpn pnpnpnpnpypyponcsilsilsilsilsilsilolsilAg-pnAg-pn tropoaltcubmkgfmermermelmelhshspkspysilmagmonmonpo hsopx silcpFigure 3.9Figure 3.11.  Photomicrographs and backscatter electron (BSE) images of platinum-group and precious-metal minerals in Giant Mascot ores. A) bright white anhedral merenskyite hosted by pentlandite at the grain boundary of chalcopyrite, both within pyrrhotite (71-EI-615A). B) merenskyite hosted in pyrite and chalcopyrite, and associated with pyrrhotite and pentlandite (BSE) (179-E-847). C) bright white, anhedral palladian melonite tipped by hessite and fully enclosed in troilite proximal to pentlandite flames (12MMA-5-8-5A). D) moncheite hosted by a chalcopyrite and argentopentlandite compound vein within fractured olivine (BSE) (RHP01-078). E) moncheite fully enclosed by silicates, a smaller elongate moncheite at the boundary of pentlandite and silicate, and small satellite grains of hessite fully enclosed in silicates and along silicate-sulphide boundaries (BSE) (RHP01-152). F) bright white, anhedral palladian melonite intergrown with euhedral gersdorffite, hosted by pentlandite containing magnetite veins, and surrounded by troilite (12MMA-5-8-5A). G) Palladian moncheite in a pentlandite vein, and hessite in chalcopyrite veins in orthopyroxene (RHP01-078). H) bright white sperrylite at the boundary of chalcopyrite and pyrrhotite, blocky pentlandite and pentlandite flames proximal to pyrite (71-EI-657). I) cream-coloured parkerite enclosed in chalcopyrite containing argentopentlandite, mackinawite and cubanite flames (RHP01-109). J) altaite in contact with chalcopyrite, nickeline, and silicates (BSE) (RHP01-109). K) Euhedral bismuth grain in contact with pyrrhotite, which contains pentlandite flames, and silicate 106PGM Host MineralsAg-pentlandite pentlanditechalcopyrite pyrrhotite pyrite silicates troilite35302520151050n=79numbermoncheite [Pt(Te,Bi) 2]Ptmelonite [NiTe 2]merenskyite [Pd(Te,Bi) 2]PdNiNi-merenskyite, EDSNi-merenskyite, EMPAPd-moncheite, EMPAPd-melonite, EMPAmerenskyite, EDSmerenskyite, EMPA moncheite, EDSPt-merenskyite, EDSPt-merenskyite, EMPAA BCFigure 3.10chalcopyrite, EDSchalcopyrite, EMPA pentlandite, EDSpentlandite, EMPApyrrhotite, EDSpyrrhotite, EMPApyrite, EMPA silicates, EDSAg-pentlandite, EDStroilite, EMPATeNi+Pd+PtBimerenskyite [Pd( Te,Bi) 2]moncheite [Pt( Te,Bi) 2] michenerite [PdBiTe]sobolevskite [PdBi]froodite [PdBi 2]kotulskite [Pd( Te,Bi)]melonite [NiTe 2]Figure 3.12.  Compositions of platinum, palladium, and nickel-bearing tellurides and their host minerals at Giant Mascot. A) Ternary plot showing the distribution of telluride and bismuthotelluride varieties for the Pt moncheite, Pd merenskyite, and Ni melonite end-members, where base lines indicate solid-solution series between minerals. B) Ternary plot showing Ni+Pd+Pt, Te and Bi for platinum-group minerals in Giant Mascot ores. The most common PGM are tellurides containing Pd and Pt along with minor Bi and Ni. C) Histogram showing the most common host minerals for PGM, predominantly pentlandite, pyrrhotite and chalcopyrite. PGM are fully enclosed, at sulphide-sulphide or sulphide-silicate interfaces, or in fracture fillings.  Analyses plotted in Figs A) and B) are based on EDS and EMPA results normalized to 100%.(179-E-847). L) Intergrown merenskyite, hollingworthite, and other Pd-Bi tellurides in a composite vein of chalcopyrite and pentlandite in silicate (71-EI-615A). Mineral abbreviations as in Figure 3.9, except: mer = merenskyite; mel = palladian melonite; mon = moncheite; Pd-mon = palladian moncheite; hs = hessite; spy = sperrylite; pk = parkerite; hol = hollingworthite; alt = altaite; nc = nickeline; ger = gersdorffite; ol = olivine; opx = orthopyroxene. Refer to Table 3.1 for additional textural descriptions.107textured sulphides, there is a wider range of S contents (2.3-32 wt%), relatively higher Ni, elevated Cu (Ni/Cu=2.9), and lower PGE (Cu/Pd=1.5×10 5 ). The semi-massive sulphides have a smaller range of S concentrations (13-19 wt%), Ni/Cu=1.9, and moderate PGE values (Cu/Pd=3.5×10 4). For massive sulphides, the results yield the highest S and average Ni contents (22-30 wt% and <2.5 wt%, respectively), and Ni/Cu and Cu/Pd similar to those from semi-massive sulphides (2.3 and 4.8×10 4, respectively; Figs. 3.14, 3.15). Platinum group elements in the ores are characterized by variable concentrations of iridium-group PGE (IPGE: Os, Ir, Ru) and palladium-group PGE (PPGE: Rh, Pd, Pt) and Au (Fig. 3.14). Net-textured sulphides are significantly lower in IPGE relative to disseminated sulphides, with the exception of sample RHP01-152 (Figs. 3.14, 3.16D, 3.17). Two compositional groups are identified that are geographically distinct: 1) IPGE-poor orebodies in the western mineralized zone (WMZ; Fig. 3.5; e.g., Pride of Emory and Brunswick cluster), and 2) IPGE-rich orebodies in central and eastern orebodies of the eastern mineralized zone (EMZ; Fig. 3.5; e.g., 1600, 1900, 4600, Chinaman, Climax, and 3050 Adit) (Figs. 3.14, 3.16D, 3.17). The IPGE-poor WMZ is dominated by net-textured sulphides that have the highest average Ni and Cu (Ni/Cu=3.4; Cu/Pd=1.4 ×10 5 ) and the lowest abundances of IPGE (Pd/Ir=3.1-96) and PPGE (Pd/Pt=1.3-70). Conversely, relatively elevated IPGE (Pd/Ir=2.8-35) and PPGE (Pd/Pt=0.49-9.7) and lower Ni and Cu (Ni/Cu=1.8-2.9; Cu/Pd=2.6-3.6 ×10 4) characterize the IPGE-rich EMZ (Fig. 3.14). Primitive mantle-normalized patterns show a large variation in PGE abundances, including pronounced positive Rh and Pd anomalies and negative Pt anomalies (Figs. 3.16, 3.17). The IPGE-poor group shows the lowest Ir and Ru abundances. Samples from the Dolly Adit and 3050 East Portal dumps have widely varying PGE contents, similar to samples from the Pride of Emory (Fig. 3.16D).108Table 3.3.  Whole rock chalcophile and platinum group element analyses for sulphide-rich rocks from the Giant Mascot Ni-Cu-PGE depositwt% ppm ppbSample Rock type 1 Texture 2 S Ni Cu Co Ir Ru Rh Pt Pd Au1600 orebody179-E-847 dunite SM 15.7 30973 13609 346 272 378 182 170 768 8.63179-E-410 peridotite D 11.6 44145 1303 715 136 196 142 323 824 7.421900 orebody179-E-364 ol pyroxenite D 5.39 12541 4020 358 12.3 13.9 14.5 14 136 42.2179-E-367 hbl opxite NT 2.31 4061 4104 167 4.13 5.44 4.44 19.6 59.8 49.54600 orebodyM29-30 hbl opxite D 0.97 2560 2962 102 1.42 1.91 1.26 101 49 37.43050 CrosscutEI-71-621* pyroxenite D 4.56 11000 3600 280 7.5 b.d.l. 15 150 150 61EI-71-622* pyroxenite M 3.42 6000 4600 230 3.6 25 4 46 51 11EI-71-659A hbl pyroxenite M 28.87 39748 1891 2717 50.3 66.4 44.2 81.2 178 4.2EI-71-659* hbl pyroxenite M 21.9 23000 6700 1300 21 28 24 b.d.l. 150 5EI-71-659B hbl pyroxenite M 30.2 32000 16000 2000 19 50 16 31 93 6EI-71-624 hblite dike vein 10.1 32000 2200 570 51 59 100 89 630 33Pride of Emory13MMA-9-6-1A peridotite SM 12.82 393 1773 804 6.59 7.37 6.82 5.49 150 2.613MMA-9-6-1B peridotite SM 12.55 13036 4013 599 6.97 7.59 6.52 71.1 146 12.213MMA-9-6-4 peridotite NT 7.48 9007 3420 367 4.42 3.42 6.32 16.3 55.7 13.911AV-200 pyroxenite NT 12.03 23097 5191 711 2.56 1.35 8.69 8.34 137 7.611AV-201 pyroxenite D 8.94 19591 5965 530 2.06 0.97 5.54 115 198 26.411AV-202a pyroxenite NT 9.61 12942 3837 754 1.08 1.2 2.14 3.63 20 2.6611AV-204 pyroxenite NT 11.79 27587 3695 870 12 13.7 10.4 12.2 289 3.74179-E-763 pyroxenite NT 11 11989 6757 489 4.34 6.26 1.18 2.53 13.6 4.29179-E-345 opxite NT 10.1 13104 1009 590 0.32 0.42 0.81 0.87 18.2 3.04Brunswick orebodies179-E-2 dunite D 5.83 15926 12747 440 3.76 4.6 3.36 16.2 66.8 15.2179-E-839 ol pyroxenite NT 16.6 16583 13759 812 3.33 5.66 2.53 25.5 37.9 6.33179-E-765 pyroxenite 14.7 16835 2104 709 6.55 9.95 3.01 0.71 49.5 2.91179-E-838 opxite NT 17.7 19263 24937 793 7.35 11.4 4.39 58.5 77.4 7.56ChinamanEI-71-623 pyroxenite D 10.5 31000 4500 530 70 46 100 500 820 73ClimaxEI-71-615 pyroxenite D 3.55 9100 5600 190 5.3 23 8 470 730 813550 East Portal dumpRHP01-075 peridotite SM 19.1 20514 7288 978 7.81 13.6 5.32 6.99 49.3 9.98RHP01-152 peridotite NT 32.6 84034 47696 2027 508 644 369 1511 2018 25.612MMA-5-8-1 pyroxenite NT 14.31 13577 7239 614 5.47 8.17 4.26 0.66 40.8 20.112MMA-5-8-2 pyroxenite NT 10.5 8890 10053 587 0.66 1.01 0.56 16.3 25.5 6.9312MMA-5-8-4 pyroxenite NT 19.97 20249 5971 1027 7.61 12.8 5.45 65.7 59.7 13.212MMA-5-8-6 pyroxenite NT 14.9 26425 4680 729 0.65 0.48 2.34 53 170 28RHP01-077 pyroxenite D 7.05 14124 2439 422 7.53 9.29 6.59 3.84 94.2 6.46RHP01-151 pyroxenite D 6.29 8676 1056 311 2.33 3.59 1.7 4.02 25.4 5.2312MMA-5-8-3 hbl pyroxenite NT 7.43 6752 1362 497 0.51 0.81 0.5 0.33 16.9 13.912MMA-5-8-5 hbl pyroxenite D 2.37 7446 2515 201 14.1 20 11.8 253 186 49Dolly Adit dump12MMA-7-10-2 pyroxenite NT 12.76 19990 5895 741 23 25.6 27.6 245 226 25.912MMA-7-10-3 pyroxenite NT 14.09 27872 14944 979 8.31 7.3 14.9 123 420 1912MMA-7-10-4 pyroxenite D 6.87 11124 4409 420 17.3 20.4 16.4 14.1 107 3.7812MMA-7-10-5 pyroxenite D 12.78 21584 2411 930 8.47 8.66 11.9 2.19 323 1.3612MMA-7-10-6 pyroxenite D 3.71 9126 2393 301 3.35 3.75 4.33 61.5 88.5 20.212MMA-7-10-7 pyroxenite D 1.22 1548 5934 88 0.34 0.32 0.6 104 318 111Pride of Emory dumpRHP01-088 pyroxenite SM 8.45 14128 16133 518 8.51 4.21 26.2 12.7 193 4.5*Analyses from Hulbert (2001); b.d.l., below lower limit of detection1 hbl, hornblende; opxite, orthopyroxenite; ol, olivine; hblite, hornblendite2 Mineralization texture of sulphide minerals in whole rock; D, disseminated; NT, net-textured; SM, semi-massive; M, massive109Figure 3.11A BDFCEpyroxeniteperidotitedunitehornblenditehbl pyroxeniteNi (wt%)S (wt%) S (wt%)S (wt%) S (wt%)24685 10 15 20 25 30 5 10 15 20 25 305 10 15 20 25 30 5 10 15 20 25 30stoich. pentlanditeCu (wt%)12345Pd (ppb)500100015002000Pt (ppb)5001000150010310410310210210101Pd (ppb)Pt (ppb)1:12 4 6 81234Cu (wt%)Ni (wt%)5Figure 3.13.  Base metal contents and platinum group element concentrations in sulphide-rich whole rock samples from the Giant Mascot Ni-Cu-PGE deposit. Symbols and colours correspond to rock type. A) Ni vs S; dashed line is stoichiometric pentlandite. B) Cu vs S. C) Pd vs S. D) Pt vs S. E) Cu vs Ni. F) Pd vs Pt (note logarithmic axes). hbl = hornblende.110S (wt%)50 10 15 20 25 30Pd/Pt10010100010.1S (wt%)50 10 15 20 25 30 35 35Pd/Ir1001011000 dump sampleFigure 3.121031031021021010.10.1 101Ru (ppb) n=16103104103 104102102101011 0.10.01Pd (ppb)Ir (ppb)Ir (ppb)n=161031041041031021021010110.10.1Pt (ppb)Ir (ppb)Ir (ppb)n=16103103102102101101Rh (ppb)n=160.10.1EastCentralWestdisseminatednet-texturedsemi-massivemassiveveinA BDFCEFigure 3.14.  Platinum group element concentrations in sulphide-rich whole rock samples from the Giant Mascot Ni-Cu-PGE deposit. Shapes correspond to locations (west, central, east, or dump) along Zofka Ridge (see Fig. 3.3). Symbol colours represent mineralization textures. Light grey shaded region encompasses dump samples. Anomalous sample RHP01-152 is displayed with a grey “×”. A) Ru vs Ir. B) Rh vs Ir. C) Pd vs Ir. D) Pt vs Ir. E) Pd/Ir vs S. F) Pt/Pt vs S. Note logarithmic axes for PGE.111Pd (ppb)Cu/Pd102 103 1041010.1102103104105depletedMANTLEenriched106disseminatednet-texturedsemi-massivemassivecp-rich veinFigure 3.13R=250R=1000sulphide removalR=2500Figure 3.15.  Cu/Pd vs. Pd for whole rocks in the Giant Mascot Ni-Cu-PGE deposit. The red star represents a modeled initial silicate magma composition based on R-factor calculations, containing 107 ppm Cu and 1 ppb Pd, with chalcophile and PGE contents recalculated to 100% sulphide using the method of Naldrett et al. (2000). Black lines show the evolution of sulphide melt fractionation at R=250, 1000, and 2500. See text for details.1120.01 0.1 1 10 100 1000 10000 0.01 0.1 1 10 100 1000 10000 0.01 0.1 1 10 100 1000 10000 0.01 0.1 1 10 100 1000 10000 Ni Ir Ru Rh Pt Pd Au Cu Ni Ir Ru Rh Pt Pd Au Cu Ni Ir Ru Rh Pt Pd Au Cu Ni Ir Ru Rh Pt Pd Au Cu Rock/Primitive Mantle Rock/Primitive Mantle West EastCentral UnknownPride of Emory (n=9)3050 East Portal dump (n=10)Dolly Adit dump (n=6)RHP01-152Brunswick orebodies3050 Crosscut(n=9)Chinaman1600 (n=2)46001900 (n=2)ClimaxFigure 3.14A BDCFigure 3.16.  Primitive mantle-normalized diagrams displaying abundances of Ni, Cu, and PGE for orebodies in the Giant Mascot Ni-Cu-PGE deposit. Shaded regions encompass ranges of analyses as indicated. A) West. B) East. C) Central. D) Dump samples, location unknown. Whole rock analyses are normalized to primitive mantle values from Lyubetskaya and Korenaga (2007).1130.01 0.1 1 10 100 1000 10000 0.01 0.1 1 10 100 1000 10000 0.01 0.1 1 10 100 1000 10000 0.01 0.1 1 10 100 1000 10000 Ni Ir Ru Rh Pt Pd Au Cu Ni Ir Ru Rh Pt Pd Au Cu Ni Ir Ru Rh Pt Pd Au Cu Ni Ir Ru Rh Pt Pd Au Cu 100% sulphide/Primitive Mantle 100% sulphide/Primitive Mantle A BDCIPGE-poor (West)IPGE-rich (Central+East)Disseminated oresNet-textured ores Massive + Semi-massive oresCu-veinFigure 3.15Figure 3.17.  Primitive mantle-normalized diagrams displaying abundances of Ni, Cu, and PGE in 100% sulphide for mineralization zones and sulphide textures in the Giant Mascot Ni-Cu-PGE deposit. A) IPGE-poor western orebodies (green shaded region) and IPGE-rich central (blue lines) and eastern orebodies (orange lines). B) Disseminated ores. C) Net-textured ores. D) Massive (red lines) and semi-massive (pink lines) ores, and a Cu-rich vein. Abundances in 100% sulphide are calculated by the method of Naldrett et al. (2000) and are normalized to primitive mantle values from Lyubetskaya and Korenaga (2007).1143 6 3  Sulphur isotope geochemistryThe sulphur isotopic compositions (δ34 S) of mineral separates from the Giant Mascot ores (n=44) range from -1.3 to -3.4‰ VCDT, which is distinguishably lighter than values for volcanic and plutonic rocks related to subduction zones globally (in the range of +1 to +6 ‰; Ueda and Sakai, 1984; Ishihara and Sasaki, 1989; Alt et al., 1993; de Hoog et al., 2001; Luhr and Logan, 2002) (Table 3.4; Fig. 3.18). One pyrite separate from the Spuzzum quartz diorite has a relatively high δ 34 S=1.9‰ VCDT. For the locally pyritiferous Settler schist, whole rock analyses reveal a slightly larger range of δ34 S (-5.4 to -1.2‰ VCDT; n=4) compared to the ultramafic rocks (Fig. 3.18). 3 6 4  Olivine compositionsThe forsterite (Fo) contents in olivine from barren and mineralized rocks of the Giant Mascot ultramafic intrusion range from Fo80.6-89.11, and have Ni concentrations of 336-3859 ppm (Fig. 3.19). A dunite with disseminated sulphides (12MMA-7-8-1) has the most restricted range of forsterite contents (Fo83.7-84.8) (Table 3.5; Fig. 3.19; Appendix V). Mineralized and barren peridotite yield similar olivine compositions of Fo83.0-89.1 and Fo82.5-88.1, respectively. Pyroxenites with sulphide mineralization have the largest range of olivine compositions (Fo80.6-88.2), and barren pyroxenites are restricted to Fo82.1-83.8. Cores and rims of olivine can vary in Fo content as much as ~2.5 mol%, and rims are typically more Mg-rich than cores in mineralized samples. Barren rocks show more homogenous compositions with relatively smaller compositional variation (Fo87.4-88.1 and Fo82.1-85.0) and more Fe-rich rims (Table 3.5).The nickel concentrations in olivine are highly variable. Anomalously high nickel contents (>2000 ppm) occur in the range of Fo80.6-87.4 (Fig. 3.19). Olivine in dunite contains Ni concentrations of 731-1464 ppm. Mineralized peridotite and pyroxenite show the highest and most variable Ni concentrations (336-3859 ppm and 336-3439 ppm, respectively) compared to lower concentrations in barren peridotite (576-1797 ppm) and pyroxenite (666-1018 ppm) (Fig. 3.19).  115Table 3.4.  Sulphur isotope analyses from the Giant Mascot Ni-Cu-PGE deposit and associated rocksSample Locality1 Rock type 2 Texture 3Mineral separate 4 S (wt.%) δ34 S (‰) †179-E-847 1600 peridotite SM po 9.0 -1.6179-E-410 1600 peridotite D po 16.1 -2.3179-E-364 1900 ol pyroxenite D po-py 22.2 -3.3179-E-367 1900 hbl opxite NT cp 16.8 -3.3M29-21 4600 peridotite SM po 33.5 -2.8M29-30 4600 hbl opxite D cp 12.5 -2.971-EI-622 Chinaman pyroxenite D po-py 38.7 -3.371-EI-624 Chinaman hornblendite D cp 33.8 -2.771-EI-659 3050 Crosscut hbl pyroxenite M pn-cp 41.9 -3.5179-E-2 Brunswick #1 dunite NT cp 20.4 -3.4179-E-2 Brunswick #1 dunite NT po 16.8 -3.2179-E-625 Brunswick #1 ol pyroxenite NT py-po 9.3 -1.9179-E-839 Brunswick #2 ol pyroxenite SM po 14.4 -2.5179-E-765 Brunswick #8 pyroxenite n.k. po 22.7 -3.7179-E-838 Brunswick #8 opxite NT po 9.6 -2.413MMA-9-6-1A Pride of Emory peridotite SM-M po-pn 34.0 -2.2179-E-763 Pride of Emory pyroxenite NT po 24.8 -2.611AV-200 Pride of Emory pyroxenite NT po-cp 32.4 -1.611AV-201 Pride of Emory pyroxenite NT po-pn-cp-py 32.1 -1.511AV-202 Pride of Emory pyroxenite NT po-py 36.6 -1.611AV-204 Pride of Emory pyroxenite NT po-py 35.6 -2.4179-E-345 Pride of Emory opxite NT po 20.5 -3.413MMA-9-6-2 Pride of Emory hbl pyroxenite D po 38.9 -2.1RHP01-075 3550 East Portal dump peridotite M po 14.5 -2.0RHP01-152 3550 East Portal dump peridotite NT cp 30.3 -1.5RHP01-151 3550 East Portal dump pyroxenite D po 35.0 -2.512MMA-5-8-1 3550 East Portal dump pyroxenite NT po-cp 21.0 -2.212MMA-5-8-6 3550 East Portal dump pyroxenite NT po-cp 34.5 -1.3RHP01-077 3550 East Portal dump pyroxenite D po 34.3 -2.212MMA-5-8-3 3550 East Portal dump opxite NT po-cp-py 30.9 -2.012MMA-5-2-1 3550 East Portal dump gabbronorite n.m. py 49.5 -1.912MMA-7-10-6 Dolly’s Adit dump peridotite D po-cp 28.0 -2.012MMA-7-10-2 Dolly’s Adit dump peridotite NT po-cp-pn 32.4 -1.812MMA-7-10-3 Dolly’s Adit dump pyroxenite NT po-py-cp 32.6 -1.8RHP01-088 Dolly’s Adit dump pyroxenite SM po 13.3 -2.012MMA-2-1-5 610135 mE/5481062 mN quartz diorite n.m. py 54.3 1.912MMA-4-1-1 610342 mE/5481216 mN schist n.m. WR 0.1 -5.413MMA-5-1-1 608222 mE/5478687 mN schist n.m. WR 0.6 -1.213MMA-5-13-1 608687 mE/5479118 mN schist n.m. WR 0.1 -2.113MMA-7-1-1 610808 mE/5484413 mN schist n.m. WR 0.3 -2.9†  Analytical precision = ± 0.2‰1 610135mE/5481062 mN = UTME (easting) / UTMN (northing); UTM coordinates based on NAD83, Zone 10. 2 hbl, hornblende; ol, olivine; opxite, orthopyroxenite3  Mineralization texture of sulphide minerals; D, disseminated; NT, net-textured; SM, semi-massive, M, massive; n.m., no sulphide mineralization; n.k., not known4 po, pyrrhotite; pn, pentlandite; cp, chalcopyrite; py, pyrite; combination of minerals indicates intergrown sulphides; WR, whole rock analysis 116Figure 3.16quartz dioriteSettler schist(WR) -5 -4į 34 S (‰)-3 -2 -1 0 1 2 3-5 -4 -3 -2 -1 0 1 2 3 4 5 64 5 6pyroxeniteRock Typeperidotiteorthopyroxeniteol pyroxenitehornblenditehbl pyroxenitehbl orthopyroxenitegabbronoriteduniteMORB mantleSubduction zone mantlen=43(pyrite)2σFigure 3.18.  Sulphur isotope compositions from sulphide-rich rocks in the Giant Mascot Ni-Cu-PGE deposit. The orange field represents a range of δ34 S compositions from volcanic arcs, including the Marianas arc (+1.4 to +5.5‰; Alt et al., 1993); Indonesian arc (+4.7 ± 1.4‰, 1σ; de Hoog et al., 2001); Mexican arc (+2.7 to +6.4; Luhr and Logan, 2002); Japanese arc (+4.4 ± 2.1‰, 1σ; Ueda and Sakai, 1984); and Sierra Nevada batholith (+1.6 to +4.0‰; Ishihara and Sasaki, 1989), taken to represent δ 34 S values of the mantle wedge. The grey field represents a range of δ34 S compositions from MORB glasses as -0.91 ± 0.5‰, taken to represent MORB mantle values (Labidi et al., 2012). A single sample from Spuzzum quartz diorite contained pyrite separated by standard mineral separation techniques (refer to Chapter 2.4.2). Settler schist samples are whole rock analyses. ol = olivine; hbl = hornblende. Note the limited range of isotopic compositions for ultramafic rocks and the overlapping values for country rocks.117Table 3.5.  Representative olivine compositions by EMPA for mineralized and unmineralized lithologies in the Giant Mascot Ni-Cu-PGE depositLocation Central1 3550 East Portal dump 1Rock type dunite dunite harzburgite harzburgite hornblende harzburgite hornblende harzburgiteSample 12MMA-7-8-1 12MMA-7-8-1 RHP01-152 RHP01-152 RHP01-078 RHP01-078Grain* 2 5 2 5 4 5Texture † cumulus cumulus cumulus inclusion cumulus cumulusGrain location core mid rim core mid rim core mid rim core mid rim core mid rim core mid rimOxides (wt%)SiO240.37 39.55 39.96 40.06 40.48 40.34 40.04 40.83 40.60 40.93 40.77 40.44 40.16 40.33 40.33 39.30 39.42 40.37Cr2O30.04 0.00 0.00 0.00 0.02 0.05 0.48 0.01 0.00 0.02 0.00 0.06 0.00 0.01 0.01 0.00 0.02 0.00FeO 15.01 14.95 14.98 14.77 14.75 14.49 12.55 12.31 12.03 12.77 12.87 12.41 13.00 13.05 12.89 13.27 13.39 13.11MnO 0.20 0.20 0.24 0.13 0.17 0.18 0.19 0.16 0.16 0.16 0.20 0.29 0.17 0.21 0.25 0.16 0.25 0.19MgO 44.92 44.94 44.71 44.75 44.98 45.28 46.29 46.79 46.93 47.01 46.48 46.94 46.39 46.33 45.91 46.37 46.53 46.49Al2O30.01 0.00 0.01 0.01 0.00 0.00 0.26 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00CaO 0.01 0.01 0.01 0.01 0.01 0.01 0.03 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00NiO 0.19 0.18 0.19 0.17 0.16 0.13 0.36 0.46 0.45 0.37 0.32 0.32 0.49 0.49 0.49 0.35 0.34 0.32Total 100.74 99.84 100.10 99.90 100.58 100.48 100.20 100.57 100.17 101.27 100.65 100.47 100.20 100.40 99.89 99.46 99.96 100.48Cations (p.f.u.)Mg 1.667 1.686 1.672 1.673 1.669 1.681 1.713 1.720 1.731 1.719 1.711 1.730 1.719 1.714 1.706 1.736 1.735 1.717Al 0.000 0.000 0.000 0.000 0.000 0.000 0.008 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000Si 1.005 0.995 1.002 1.005 1.008 1.005 0.994 1.007 1.004 1.004 1.006 1.000 0.998 1.001 1.005 0.987 0.986 1.000Ca 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000Cr 0.001 0.000 0.000 0.000 0.000 0.001 0.009 0.000 0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.000 0.000 0.000Mn 0.004 0.004 0.005 0.003 0.004 0.004 0.004 0.003 0.003 0.003 0.004 0.006 0.004 0.004 0.005 0.003 0.005 0.004Fe 0.312 0.315 0.314 0.310 0.307 0.302 0.261 0.254 0.249 0.262 0.266 0.256 0.270 0.271 0.269 0.279 0.280 0.272Ni 0.004 0.004 0.004 0.003 0.003 0.003 0.007 0.009 0.009 0.007 0.006 0.006 0.010 0.010 0.010 0.007 0.007 0.006Total 2.994 3.005 2.997 2.995 2.992 2.995 2.997 2.993 2.996 2.996 2.993 3.000 3.002 2.999 2.995 3.013 3.014 3.000End Members (%)Fo2 84.2 84.3 84.2 84.4 84.5 84.8 86.8 87.1 87.4 86.8 86.6 87.1 86.4 86.4 86.4 86.2 86.1 86.4Fa2 15.8 15.7 15.8 15.6 15.5 15.2 13.2 12.9 12.6 13.2 13.4 12.9 13.6 13.6 13.6 13.8 13.9 13.7Mg-number3 0.842 0.843 0.842 0.844 0.845 0.848 0.868 0.871 0.874 0.868 0.866 0.871 0.864 0.864 0.864 0.862 0.861 0.863Ni (ppm) 1459 1396 1461 1357 1257 993 2865 3614 3530 2872 2486 2517 3859 3825 3853 2780 2665 2522*  Grain 1,2,3, etc. correspond to the selected olivine grain (1-5) in that particular sample†  sul-sil, sulphide borders olivine but is not fully enclosed; sul, olivine is fully included in sulphide; inclusion, olivine as an inclusion within another silicate min eral1 sulphide present in sample; 2 Fo = Mg 2+ /(Mg 2+ +Fe 2+ ) x 100; Fa = 100-Fo; 3  Mg-number = Mg/(Mg+Fe)118Table 3.5. (cont.) Representative olivine compositions by EMPA for mineralized and unmineralized lithologies in the Giant Mascot Ni-Cu-PGE depositLocation 1600 orebody 1 4600 orebody 1 Dolly Adit dump 1Rock type hornblende harzburgite olivine websterite olivine websterite olivine websterite olivine websterite pyroxeniteSample 179-E-410 M29-21 M29-21 RHP01-118 RHP01-118 12MMA-7-10-2Grain* 1 1 5 4 5 1Texture † sul-sil sul sul-sil sul-sil sul sul-silGrain location core mid rim core mid rim core mid rim core mid rim core mid rim core mid rimOxides (wt%)SiO239.86 39.80 39.86 40.63 40.62 40.82 40.75 40.57 40.79 39.70 40.05 40.24 40.37 40.23 40.27 40.28 40.08 40.45Cr2O30.04 0.00 0.02 0.00 0.00 0.00 0.01 0.00 0.00 0.02 0.00 0.02 0.00 0.03 0.00 0.00 0.00 0.00FeO 13.79 14.02 13.54 13.01 13.25 11.47 12.41 12.69 11.41 15.86 15.62 14.44 15.77 15.34 14.79 15.00 15.07 15.45MnO 0.24 0.21 0.20 0.23 0.19 0.26 0.22 0.23 0.23 0.22 0.25 0.23 0.17 0.22 0.26 0.25 0.22 0.20MgO 45.76 45.81 45.90 46.19 46.82 47.87 46.75 46.89 48.02 44.41 44.16 45.51 44.79 44.68 45.27 44.54 44.36 44.21Al2O30.00 0.00 0.01 0.03 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.01 0.00 0.01CaO 0.00 0.00 0.01 0.02 0.02 0.01 0.00 0.01 0.00 0.01 0.02 0.01 0.02 0.02 0.02 0.02 0.02 0.02NiO 0.38 0.36 0.32 0.18 0.18 0.13 0.15 0.16 0.11 0.26 0.22 0.19 0.22 0.21 0.16 0.19 0.19 0.26Total 100.07 100.21 99.87 100.30 101.07 100.57 100.29 100.55 100.57 100.49 100.32 100.64 101.34 100.73 100.76 100.31 99.95 100.60Cations (p.f.u.)Mg 1.705 1.706 1.711 1.706 1.719 1.752 1.722 1.726 1.757 1.662 1.652 1.688 1.658 1.662 1.679 1.661 1.661 1.646Al 0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000Si 0.996 0.994 0.997 1.007 1.000 1.002 1.007 1.002 1.001 0.997 1.005 1.001 1.003 1.004 1.002 1.008 1.007 1.010Ca 0.000 0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.000 0.001 0.001 0.001Cr 0.001 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.000Mn 0.005 0.004 0.004 0.005 0.004 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.004 0.005 0.006 0.005 0.005 0.004Fe 0.288 0.293 0.283 0.270 0.273 0.235 0.256 0.262 0.234 0.333 0.328 0.300 0.328 0.320 0.308 0.314 0.317 0.323Ni 0.008 0.007 0.006 0.004 0.004 0.003 0.003 0.003 0.002 0.005 0.004 0.004 0.004 0.004 0.003 0.004 0.004 0.005Total 3.003 3.006 3.003 2.993 3.000 2.998 2.993 2.998 2.999 3.003 2.995 2.999 2.997 2.996 2.998 2.992 2.993 2.990End Members (%)Fo2 85.5 85.3 85.8 86.4 86.3 88.2 87.0 86.8 88.2 83.3 83.5 84.9 83.5 83.9 84.5 84.1 84.0 83.6Fa2 14.5 14.7 14.2 13.7 13.7 11.9 13.0 13.2 11.8 16.7 16.6 15.1 16.5 16.2 15.5 15.9 16.0 16.4Mg-number3 0.855 0.853 0.858 0.864 0.863 0.882 0.870 0.868 0.882 0.833 0.834 0.849 0.835 0.838 0.845 0.841 0.840 0.836Ni (ppm) 2983 2829 2499 1427 1401 1004 1147 1237 897 2071 1710 1488 1746 1664 1218 1520 1512 2061*  Grain 1,2,3, etc. correspond to the selected olivine grain (1-5) in that particular sample†  sul-sil, sulphide borders olivine but is not fully enclosed; sul, olivine is fully included in sulphide; inclusion, olivine as an inclusion within another silicate min eral1 sulphide present in sample; 2 Fo = Mg 2+ /(Mg 2+ +Fe 2+ ) x 100; Fa = 100-Fo; 3  Mg-number = Mg/(Mg+Fe)119Table 3.5. (cont.) Representative olivine compositions by EMPA for mineralized and unmineralized lithologies in the Giant Mascot Ni-Cu-PGE depositLocation Mill site dump 1 Pride of Emory 1Rock type pyroxenite pyroxenite harzburgite harzburgite olivine orthopyroxenite olivine orthopyroxeniteSample 13MMA-1-2-2 13MMA-1-2-2 11AV-201 11AV-201 11AV-200 11AV-200Grain* 2 4 1 3 3 4Texture † cum cumulus cumulus sul-sil inclusion sil-sulGrain location core mid rim core mid rim core mid rim core mid rim core mid rim core mid rimOxides (wt%)SiO240.47 40.28 40.22 40.12 39.86 40.00 39.61 39.80 39.82 39.96 39.31 40.09 40.55 40.48 40.86 40.49 40.34 40.16Cr2O30.02 0.00 0.01 0.01 0.00 0.00 0.00 0.01 0.01 0.04 0.04 0.00 0.00 0.02 0.02 0.02 0.00 0.03FeO 0.03 0.04 0.02 16.98 17.08 16.95 15.92 16.01 13.86 15.96 15.79 14.54 14.94 13.92 14.16 14.42 14.15 14.38MnO 15.28 15.24 15.24 0.13 0.15 0.16 0.16 0.22 0.21 0.22 0.18 0.21 0.21 0.13 0.19 0.16 0.17 0.16MgO 0.12 0.18 0.12 43.04 43.12 43.01 44.19 43.85 45.92 43.87 43.77 45.27 44.86 45.15 45.37 45.86 45.31 44.94Al2O344.60 44.07 44.27 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00CaO 0.00 0.02 0.01 0.02 0.01 0.02 0.00 0.01 0.00 0.00 0.01 0.01 0.09 0.00 0.00 0.00 0.00 0.00NiO 0.32 0.31 0.30 0.42 0.42 0.44 0.20 0.23 0.13 0.21 0.22 0.16 0.21 0.15 0.19 0.19 0.18 0.22Total 100.84 100.15 100.19 100.72 100.64 100.57 100.08 100.14 99.95 100.26 99.32 100.28 100.87 99.86 100.78 101.16 100.16 99.90Cations (p.f.u.)Mg 1.655 1.648 1.654 1.613 1.619 1.615 1.660 1.647 1.712 1.645 1.658 1.686 1.662 1.681 1.675 1.691 1.685 1.678Al 0.001 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000Si 1.008 1.010 1.008 1.009 1.004 1.008 0.998 1.003 0.996 1.005 0.999 1.001 1.008 1.011 1.012 1.001 1.006 1.006Ca 0.000 0.001 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.002 0.000 0.000 0.000 0.000 0.000Cr 0.001 0.001 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.001 0.000 0.000 0.000 0.000 0.000 0.000 0.001Mn 0.002 0.004 0.002 0.003 0.003 0.003 0.003 0.005 0.005 0.005 0.004 0.004 0.004 0.003 0.004 0.003 0.004 0.003Fe 0.318 0.320 0.319 0.357 0.360 0.357 0.336 0.337 0.290 0.336 0.335 0.304 0.311 0.291 0.293 0.298 0.295 0.301Ni 0.006 0.006 0.006 0.009 0.008 0.009 0.004 0.005 0.003 0.004 0.004 0.003 0.004 0.003 0.004 0.004 0.004 0.004Total 2.992 2.989 2.991 2.991 2.996 2.992 3.002 2.997 3.004 2.995 3.001 2.999 2.992 2.989 2.988 2.998 2.994 2.994End Members (%)Fo2 83.9 83.7 83.8 81.9 81.8 81.9 83.2 83.0 85.5 83.1 83.2 84.7 84.3 85.3 85.1 85.0 85.1 84.8Fa2 16.1 16.3 16.2 18.1 18.2 18.1 16.8 17.0 14.5 17.0 16.8 15.3 15.7 14.8 14.9 15.0 14.9 15.2Mg-number3 0.745 0.743 0.744 0.819 0.818 0.819 0.832 0.830 0.855 0.831 0.832 0.847 0.843 0.853 0.851 0.850 0.851 0.848Ni (ppm) 2532 2402 2373 3321 3292 3439 1562 1811 1011 1619 1695 1268 1668 1167 1510 1505 1448 1699*  Grain 1,2,3, etc. correspond to the selected olivine grain (1-5) in that particular sample†  sul-sil, sulphide borders olivine but is not fully enclosed; sul, olivine is fully included in sulphide; inclusion, olivine as an inclusion within another silicate min eral1 sulphide present in sample; 2 Fo = Mg 2+ /(Mg 2+ +Fe 2+ ) x 100; Fa = 100-Fo; 3  Mg-number = Mg/(Mg+Fe)120Table 3.5. (cont.) Representative olivine compositions by EMPA for mineralized and unmineralized lithologies in the Giant Mascot Ni-Cu-PGE depositLocation Central2Rock type peridotite peridotite peridotite peridotite pyroxeniteSample 13MMA-3-10-1 13MMA-3-10-1 12MMA-7-8-2 12MMA-7-8-2 13MMA-3-7-1Grain* 1 4 2 5 2Texture † cumulus cumulus cumulus sul-sil cumulusGrain location core mid rim core mid rim core mid rim core mid rim core mid rimOxides (wt%)SiO240.58 40.13 40.57 40.04 40.03 40.24 40.01 40.12 40.13 39.88 40.25 40.02 39.67 39.98 40.09Cr2O30.00 0.00 0.01 0.00 0.01 0.02 0.00 0.02 0.01 0.02 0.00 0.03 0.00 0.01 0.01FeO 12.12 12.06 12.07 11.43 12.12 11.83 16.01 16.34 16.15 15.50 15.57 15.13 16.71 16.46 16.71MnO 0.19 0.15 0.18 0.16 0.17 0.19 0.16 0.24 0.16 0.26 0.26 0.22 0.27 0.16 0.22MgO 47.22 47.17 47.23 47.67 47.92 47.42 43.91 43.84 43.84 43.74 44.18 44.73 43.07 42.62 43.16Al2O30.00 0.00 0.00 0.00 0.00 0.00 0.02 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.03CaO 0.00 0.01 0.00 0.01 0.01 0.00 0.02 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.02NiO 0.22 0.22 0.18 0.22 0.22 0.23 0.13 0.12 0.13 0.10 0.10 0.07 0.11 0.11 0.12Total 100.34 99.73 100.25 99.52 100.47 99.94 100.26 100.67 100.44 99.50 100.38 100.21 99.86 99.36 100.36Cations (p.f.u.)Mg 1.738 1.747 1.739 1.765 1.764 1.752 1.645 1.638 1.640 1.648 1.650 1.670 1.627 1.613 1.620Al 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001Si 1.002 0.997 1.002 0.995 0.989 0.997 1.005 1.006 1.007 1.008 1.008 1.003 1.005 1.015 1.010Ca 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.001 0.001Cr 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.000 0.000 0.000Mn 0.004 0.003 0.004 0.003 0.004 0.004 0.003 0.005 0.003 0.005 0.006 0.005 0.006 0.003 0.005Fe 0.250 0.251 0.249 0.237 0.250 0.245 0.337 0.342 0.339 0.328 0.326 0.317 0.354 0.350 0.352Ni 0.004 0.004 0.004 0.004 0.004 0.005 0.003 0.002 0.003 0.002 0.002 0.001 0.002 0.002 0.002Total 2.998 3.003 2.998 3.005 3.011 3.003 2.994 2.994 2.993 2.992 2.992 2.997 2.995 2.985 2.990End Members (%)Fo2 87.4 87.5 87.5 88.2 87.6 87.7 83.0 82.7 82.9 83.4 83.5 84.1 82.1 82.2 82.2Fa2 12.6 12.5 12.5 11.9 12.4 12.3 17.0 17.3 17.1 16.6 16.5 16.0 17.9 17.8 17.8Mg-number3 0.874 0.875 0.875 0.881 0.876 0.877 0.830 0.827 0.829 0.834 0.835 0.841 0.821 0.822 0.822Ni (ppm) 1734 1694 1418 1754 1705 1778 1050 912 988 782 768 576 865 885 924*  Grain 1,2,3, etc. correspond to the selected olivine grain (1-5) in that particular sample†  sul-sil, sulphide borders olivine but is not fully enclosed; sul, olivine is fully included in sulphide; inclusion, olivine as an inclusion within another silicate min eral1 sulphide present in sample; 2 Fo = Mg 2+ /(Mg 2+ +Fe 2+ ) x 100; Fa = 100-Fo; 3  Mg-number = Mg/(Mg+Fe)121Table 3.5. (cont.) Representative olivine compositions by EMPA for mineralized and unmineralized lithologies in the Giant Mascot Ni-Cu-PGE depositLocation Dolly Adit dump 2Rock type peridotite peridotite pyroxenite pyroxeniteSample 12MMA-7-10-1 12MMA-7-10-1 12MMA-7-9-2 12MMA-7-9-2Grain* 2 3 1 2Texture † cumulus cumulus cumulus cumulusGrain location core mid rim core mid rim core mid rim core mid rimOxides (wt%)SiO240.37 40.66 40.70 40.40 40.19 40.07 39.71 39.26 39.19 38.80 39.09 38.85Cr2O30.01 0.02 0.00 0.01 0.00 0.03 0.01 0.00 0.00 0.00 0.02 0.00FeO 14.51 14.62 15.37 15.18 15.08 14.58 15.80 15.84 16.11 15.55 15.34 16.50MnO 0.18 0.19 0.21 0.24 0.18 0.24 0.20 0.21 0.23 0.24 0.14 0.25MgO 44.71 45.21 44.25 44.75 44.77 44.94 43.30 43.86 43.82 43.93 44.55 43.39Al2O30.01 0.00 0.02 0.01 0.01 0.02 0.01 0.00 0.00 0.00 0.00 0.02CaO 0.02 0.01 0.01 0.02 0.15 0.01 0.01 0.02 0.00 0.00 0.01 0.00NiO 0.13 0.12 0.17 0.11 0.11 0.08 0.11 0.12 0.12 0.11 0.12 0.11Total 99.93 100.82 100.73 100.72 100.49 99.97 99.15 99.31 99.46 98.63 99.27 99.12Cations (p.f.u.)Mg 1.668 1.672 1.643 1.662 1.667 1.678 1.640 1.661 1.659 1.675 1.685 1.653Al 0.000 0.000 0.001 0.000 0.000 0.001 0.000 0.000 0.000 0.000 0.000 0.001Si 1.010 1.009 1.014 1.006 1.004 1.004 1.009 0.997 0.995 0.992 0.992 0.993Ca 0.001 0.000 0.000 0.001 0.004 0.000 0.000 0.000 0.000 0.000 0.000 0.000Cr 0.000 0.000 0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.000 0.000 0.000Mn 0.004 0.004 0.004 0.005 0.004 0.005 0.004 0.005 0.005 0.005 0.003 0.005Fe 0.304 0.303 0.320 0.316 0.315 0.305 0.336 0.337 0.342 0.333 0.325 0.353Ni 0.003 0.002 0.003 0.002 0.002 0.002 0.002 0.003 0.002 0.002 0.002 0.002Total 2.990 2.991 2.986 2.993 2.996 2.996 2.991 3.003 3.005 3.008 3.008 3.007End Members (%)Fo2 84.6 84.6 83.7 84.0 84.1 84.6 83.0 83.2 82.9 83.4 83.8 82.4Fa2 15.4 15.4 16.3 16.0 15.9 15.4 17.0 16.9 17.1 16.6 16.2 17.6Mg-number3 0.846 0.846 0.837 0.840 0.841 0.846 0.830 0.832 0.829 0.834 0.838 0.824Ni (ppm) 1008 933 1315 859 853 597 828 967 919 881 940 838*  Grain 1,2,3, etc. correspond to the selected olivine grain (1-5) in that particular sample†  sul-sil, sulphide borders olivine but is not fully enclosed; sul, olivine is fully included in sulphide; inclusion, olivine as an inclusion within another silicate mineral1 sulphide present in sample; 2 Fo = Mg 2+ /(Mg 2+ +Fe 2+ ) x 100; Fa = 100-Fo; 3  Mg-number = Mg/(Mg+Fe)122Pride of Emory46001600Figure 3.17ol:sul = 25:1olol:opx = 1:19 wt% Ni6.5 wt% NiTLSNi in olivine (ppm)5001500250035004500Fo content in olivine 808284868890pyroxenitepyroxeniteperidotiteol pyroxeniteol orthopyroxenitehbl peridotiteperidotiteduniteMineralizedBarrendunitefractional crystallization (1% increments)Figure 3.19.  Plot of forsterite content (mol%) vs. nickel concentrations (ppm) in olivine for mineralized and barren dunite, peridotite, and pyroxenite rocks in the Giant Mascot intrusion. Purple, orange, and yellow shaded regions encompass compositional fields for the specified orebodies. Calculated fractional crystallization trends are shown for olivine, olivine+orthopyroxene, and olivine+sulphide in the proportions indicated. Thick dashed lines show equipotential lines for Fe-Ni exchange between olivine and sulphide with variable Ni content. Grey arrows show equilibration paths for Ni contents in olivine for barren samples that have interacted with sulphide liquid. Trapped liquid shift arrow indicates olivine that has reacted with interstitial melt during crystallization. ol = olivine; opx = orthopyroxene; hbl = hornblende; sul = sulphide; TLS = trapped liquid shift. See text for modeling details and discussion.1233 7  Discussion3 7 1  Crystallization of sulphide liquid and late magmatic desulphurizationMagmatic systems that host many of the world’s largest Ni-Cu-PGE and PGE deposits are generated from parent magmas that are typically high temperature and relatively dry (i.e, contain little dissolved H2O) (e.g., Boudreau et al., 1997; Li et al., 2003; Barnes et al., 2010). The magmas form by high degree partial melting in the mantle (>20-25%) that melts olivine and sulphide to release Ni, Cu, and PGE into coexisting silicate melt (Barnes et al., 1985; Hamlyn et al., 1985; Keays, 1995; Barnes and Lightfoot, 2005). In contrast, Mungall et al. (2006) demonstrate that relatively low degrees of partial melting (<10%) can liberate all sulphide and associated PGE from the upper mantle residue at moderate to high oxygen fugacities ( fO2), characteristics of the mantle wedge in subduction zone environments, and melting along the mss-spinel cotectic at volatile saturation (e.g., water). Hydrous Mg-rich (10-18 wt% MgO) arc magmas containing up to 7 wt% H2O have been also been attributed to partial melting (5-20%) of the mantle wedge (Ulmer, 2001).Sulphide compositions and textures in the Giant Mascot intrusive suite provide a record of cooling and crystallization of the magmatic sulphide melt formed upon sulphide saturation (Figs. 3.9, 3.20). Sulphide blebs occur within and between olivine and orthopyroxene, with few observed inclusions of sulphide in chromite, confirming the presence of a sulphide melt early in the crystallization history (Figs. 3.9, 3.11, 3.20). The coarse pentlandite may have c