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Age and origin of the Turnagain Alaskan-type intrusion and associated Ni-sulphide mineralization, north-central.. Scheel, J. Erik 2007

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A G E A N D ORIGIN O F T H ET U R N A G A I N A L A S K A N - T Y P E INTRUSION A N D ASSOCIATED NI-SULPfflDE MINERALIZATION, N O R T H - C E N T R A L COLUMBIA, CANADA  by J. E R I K S C H E E L B . S c . H . U n i v e r s i t y o f A l b e r t a , 2004  A THESIS SUBMITTED F O R P A R T I A L F U L F I L M E N T OF T H ER E Q U I R E M E N T S F O R T H ED E G R E E O F  MASTER OF SCIENCE in THE FACULTY OF GRADUATE (GEOLOGICAL  STUDIES  SCIENCES)  THE UNIVERSITY OF BRITISH C O L U M B I A M a y 2007  © J . E r i k S c h e e l , 2007  BRITISH  ABSTRACT T h e T u r n a g a i n A l a s k a n - t y p e i n t r u s i o n i n north-central B r i t i s h C o l u m b i a consists o f ultramafic to d i o r i t i c r o c k s a n d contains significant m a g m a t i c s u l p h i d e m i n e r a l i z a t i o n . T h e age o f the i n t r u s i o n is constrained b y U - P b and A r - A r g e o c h r o n o l o g y to be 1 9 0 ± 1 M a and the m i n i m u m d e p o s i t i o n a l age o f the youngest host r o c k s ( v o l c a n i c w a c k e ) is 301 M a . W h o l e r o c k N d i s o t o p i c c o m p o s i t i o n s are characteristic o f P a l e o z o i c a r c - d e r i v e d m a f i c r o c k s i n the northern C a n a d i a n C o r d i l l e r a (£Nd(i90) = +4 to +6), but i n d i c a t i v e o f variable crustal c o n t a m i n a t i o n i n s o m e samples ( E N d ( i 9 0 ) = +2 d o w n to -3.3). T h e age a n d tectonic characteristics o f the T u r n a g a i n i n t r u s i o n and its host r o c k s constrain the terrane it intrudes to be either Y u k o n T a n a n a o r Q u e s n e l l i a , but not A n c e s t r a l N o r t h A m e r i c a . T h e T u r n a g a i n parent m a g m a s were h y d r o u s , a r c - d e r i v e d , i n e q u i l i b r i u m w i t h mantle peridotite, a n d a n k a r a m i t i c . C r o s s - c u t t i n g a n d g e o c h e m i c a l relationships define the c r y s t a l l i z a t i o n and e m p l a c e m e n t sequence o f the T u r n a g a i n i n t r u s i o n to be: dunite (~For,i) —> w e h r l i t e (~Fog ) —> o l i v i n e c l i n o p y r o x e n i t e 7  (~Fo 5, M g # 8  c p x  = 0.92) —• hornblende c l i n o p y r o x e n i t e ( M g #  c p x  = 0 . 8 1 , M g # i = 0.65) —> h D  hornblendite (Mg#ht>i = 0.60) —> diorite. M i n e r a l a n d w h o l e - r o c k g e o c h e m i s t r y indicate that a l l ultramafic l i t h o l o g i e s are g e n e t i c a l l y related a n d relative d e p l e t i o n i n the H F S E , s p e c i f i c a l l y N b and T a , are consistent w i t h an arc mantle source for the parent m a g m a s . V a r i a t i o n s i n spinel c h e m i s t r y i n the T u r n a g a i n i n t r u s i o n are m a i n l y a f u n c t i o n o f p o s t - c r y s t a l l i z a t i o n reequilibration and oxidation. Primary (unmodified) chromite compositions, observed in c h r o m i t i t e samples, are C r - r i c h ( C r / ( C r + A l ) = 0.86-0.90) a n d F e - p o o r 3 +  ( F e / ( F e + C r + A l ) < 0 . 1 ) , i n d i c a t i n g their c r y s t a l l i z a t i o n f r o m a m a g m a w i t h r e l a t i v e l y l o w JO2 3 +  3 +  ( A F M Q < 0), w h i c h is substantially l o w e r than for other A l a s k a n - t y p e intrusions. A t these  2  2  r e l a t i v e l y r e d u c e d c o n d i t i o n s , S was d i s s o l v e d as sulphide (S ") rather than sulphate (SO4 ")• S u l p h u r ( 8 S = -9.7 to +1.4%o) a n d lead i s o t o p i c c o m p o s i t i o n s o f s u l p h i d e f r o m the ultramafic 3 4  r o c k s indicate that upper crustal s u l p h u r a n d l e a d were added to the parent m a g m a s b y a s s i m i l a t i o n o f graphitic, p y r i t i c metasedimentary i n c l u s i o n s ( 8 S = -17.9%o), w h i c h are f o u n d 3 4  o n l y i n the s u l p h i d e - m i n e r a l i z e d zones. T h u s , a d d i t i o n o f crustal carbon a n d s u l p h u r r e d u c e d the T u r n a g a i n m a g m a s a n d increased total S, w h i c h l e a d to early s u l p h i d e saturation.  TABLE OF CONTENTS ABSTRACT  ii  TABLE OF CONTENTS  iii  LIST OF TABLES  vi  LIST OF FIGURES  vii  LIST OF APPENDICES  ix  ACKNOWLEDGEMENTS  x  CHAPTER 1: GEOLOGICAL CONTEXT AND EXPLORATION HISTORY OF THE TURNAGAIN ALASKAN-TYPE INTRUSION, NORTH-CENTRAL BRITISH COLUMBIA 1 1.1 INTRODUCTION  2  1.2 EXPLORATION HISTORY OF THE TURNAGAIN INTRUSION  5  1.3 OVERVIEW OF THE THESIS  6  1.4 REFERENCES  9  CHAPTER 2: GEOCHRONOLOGY OF THE TURNAGAIN ALASKAN-TYPE INTRUSION, NORTH-CENTRAL BRITISH COLUMBIA, WITH IMPLICATIONS FOR THE TECTONIC EVOLUTION OF THE NORTHERN CANADIAN CORDILLERA 12 2.1 INTRODUCTION  13  2.2 GEOLOGICAL SETTING OF THE TURNAGAIN INTRUSION  14  2.3 GEOLOGY OF THE TURNAGAIN INTRUSION  19  2.4 SAMPLE DESCRIPTIONS AND ANALYTICAL TECHNIQUES  21  2.4.1 U-Pb zircon/titanite 2.4.2 Ar-Ar phlogopite/amphibole 2.4.3 Neodymium isotopes  21 24 25  2.5 RESULTS  26  2.5.1 U-Pb geochronology 2.5.1.1 Mela-diorite 2.5.1.2 Leuco-diorite 2.5.1.3 Volcanic wacke 2.5.1.4 Hornblendite 2.5.2 Ar-Ar geochronology 2.5.2.1 Hornblendite 2.5.2.2 Wehrlite 2.5.3 Rare earth elements and Nd isotopes 2.6 DISCUSSION 2.6.1 Age and source of the Turnagain intrusion  26 26 27 30 30 32 32 32 36 36 36  2.6.2 Age comparison with other Alaskan-type intrusions 2.6.3 Tectonic implications for northern British Columbia  43 47  2.7 CONCLUSION  49  2.8 ACKNOWLEDGEMENTS  50  2.9 REFERENCES  51  CHAPTER 3: CHROMITE CHEMISTRY OF THE TURNAGAIN INTRUSION, NORTHERN BRITISH COLUMBIA, AND THE REDOX STATES OF ALASKANTYPE PARENTAL MAGMAS 58 3.1 INTRODUCTION  59  3.2 REGIONAL GEOLOGY  60  3.3 GEOLOGY AND SPINEL CONTENT OF THE TURNAGAIN INTRUSION  60  3.3.1 Dunite 3.3.2 Wehrlite 3.3.3 Olivine clinopyroxenite 3.3.4 Hornblende clinopyroxenite and hornblendite 3.4 ANALYTICAL TECHNIQUES  62 65 65 67 67  3.5 RESULTS  69  3.5.1 Chromitite 3.5.2 Dunite 3.5.3 Wehrlite 3.5.4 Olivine clinopyroxenite 3.4.1 Hornblende clinopyroxenite 3.6 DISCUSSION  72 72 72 75 75 77  3.6.1 3.6.2 3.6.3 3.6.4  ..  Primary spinel compositions Reequilibration trends Compositional effects of serpentinization on spinel chemistry Implications for the redox state of the Turnagain intrusion  77 79 80 80  3.7 CONCLUSIONS  83  3.8 ACKNOWLEDGEMENTS  84  3.9 REFERENCES  85  CHAPTER 4: PETROLOGY AND METALLOGENY OF TURNAGAIN ALASKANTYPE INTRUSION AND ITS ASSOCIATED NI-SULPHIDE MINERALIZATION 89 4.1 INTRODUCTION  90  4.2 GEOLOGY OF THE TURNAGAIN INTRUSION  91  4.2.1 Regional geology 4.2.2 Ultramafic rocks 4.2.2.1 Dunite and chromitite 4.2.2.2 Wehrlite  91 94 ; 94 99  4.2.2.3 Olivine clinopyroxenite and clinopyroxenite 4.2.2.4 Hornblende clinopyroxenite 4.2.2.5 Hornblendite 4.2.3 Other rocks 4.2.3.1 Diorite 4.2.3.2 Hornfels 4.2.4 Sulphide 4.2.5 Inclusions 4.3 ANALYTICAL TECHNIQUES 4.3.1 Mineral chemistry 4.3.2 Major and trace elements 4.3.3 Platinum group elements 4.3.4 Sulphur isotopes - sulphide 4.3.5 Lead isotopes - sulphide 4.4 RESULTS 4.4.1 Olivine chemistry 4.4.2 Clinopyroxene chemistry 4.4.3 Amphibole and biotite chemistry 4.4.4 Major and trace element chemistry 4.4.4.1 High-Mg olivine-rich rocks 4.4.4.2 Intermediate-Mg clinopyroxene-rich rocks 4.4.4.3 Hornblendites 4.4.4.4 Dioritic rocks 4.4.5 Platinum group elements 4.4.6 Sulphur isotopic compositions 4.4.7 Lead isotopic compositions 4.5 DISCUSSION 4.5.1 Parent magma characteristics 4.5.2 Sequence of crystallization 4.5.3 Implications for associated volcanic rocks 4.5.4 Origin of sulphide mineralization in the Turnagain intrusion 4.5.5 Petrogenesis the Turnagain intrusion and associated Ni-sulphide mineralization  100 101 102 102 102 103 103 106 107 107 110 118 121 121 125 125 127 127 129 129 133 133 134 134 137 137 137 137 140 141 142 144  4.6 CONCLUSIONS  145  4.7 ACKNOWLEDGEMENTS  147  4.8 REFERENCES  148  CHAPTER 5: SUMMARY AND CONCLUSIONS  153  5.1 SUMMARY AND CONCLUSIONS  154  5.2 REFERENCES  157  LIST O F T A B L E S  Table 2.1: U-Pb TIMS analytical data from zircon and titanite grains separated from samples from the Turnagain intrusion Table 2.2:  40  28  Ar/ Ar step-heating results of mineral separates from ultramafic rocks of the Turnagain intrusion 34 39  Table 2.3: Major (wt. % oxide) and trace element abundances (ppm) in whole rock samples from the Turnagain intrusion  37  Table 2.4: Nd isotopic compositions of whole rock samples from the Turnagain intrusion  39  Table 2.5: Ages of Alaskan-type intrusions in B.C. and Alaska  44  Table 3.1: Representative spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion 70 Table 4.1: Representative olivine compositions from olivine-bearing ultramafic lithologies in the Turnagain intrusion Ill Table 4.2: Representative clinopyroxene compositions from clinopyroxene-bearing ultramafic lithologies in the Turnagain intrusion 113 Table 4.3: Amphibole compositions from ultramafic rocks of the Turnagain intrusion  115  Table 4.4: Biotite compositions from biotite-bearing ultramafic lithologies in the Turnagain intrusion... 117 Table 4.5: Major (wt. % oxide) trace element abundances (ppm) in mafic-ultramafic rocks of the Turnagain intrusion 119 Table 4.6: PGE concentrations of representative ultramafic rocks from the Turnagain intrusion  122  Table 4.7: Sulphur isotopic compositions of sulphide from the Turnagain intrusion and surrounding lithologies  123  Table 4.8: Pb isotopic compositions of selected sulphide fractions from the Turnagain intrusion and surrounding lithologies  124  vi  LIST OF FIGURES  Figure 1.1: Simplified geological map of the Turnagain Alaskan-type intrusion, modified from Clark (1975) 3 Figure 2.1: Terrane map of British Columbia, modified from Colpron & Nelson (2004)  15  Figure 2.2: Regional geological map of the area immediately surrounding the Turnagain intrusion, extracted and modified from Massey et al. (2005)  16  Figure 2.3: Geologic map of the Turnagain intrusion  18  Figure 2.4: Photomicrographs of zircon and titanite separates from the Turnagain intrusion  22  Figure 2.5: Concordia plots for U-Pb data from analyzed zircon fractions for diorite samples from the Turnagain intrusion 29 Figure 2.6: Concordia plots for U-Pb data from analyzed zircon fractions from a volcanic wacke sample from the Turnagain intrusion (04ES-00-07-02) 31 Figure 2.7: Concordia plots for U-Pb data from analyzed titanite fractions separated from a hornblendite dike (04ES-00-07-04) in the northwestern region of the Turnagain intrusion 33 Figure 2.8: Ar/ Ar incremental-heating age spectra and Ar/ Ar inverse isochron diagrams for mineral separates from the Turnagain intrusion 40  39  40  39  35  Figure 2.9: Chondrite-normalized rare earth element diagram for whole rock samples from the Turnagain intrusion, and whole rock samples from Erdmer et al. (2005) 38 Figure 2.10: Nd isotopic geochemistry of whole rock samples from the Turnagain intrusion  40  Figure 2.11: Ages of Alaskan-type intrusions in B.C. and Alaska  45  Figure 3.1: Simplified geological map of the Turnagain Alaskan-type intrusion  61  Figure 3.2: Photographs of chromitite in outcrop from the Turnagain intrusion  63  Figure 3.3. Photomicrographs of chromite textures from chromitite and dunite  64  Figure 3.4: Photomicrographs of chromite textures from wehrlite and olivine clinopyroxenite in the Turnagain intrusion  66  Figure 3.5: Photomicrographs of magnetite textures from sample DDH04-47-7-49, a hornblende clinopyroxenite from the western zone of the Turnagain intrusion  68  Figure 3.6: Chromite compositional ternary diagrams, represented by sample number  73  Figure 3.7: Binary plots of spinel compositions from the Turnagain intrusion. A) divalent vs. trivalent cation plot. B) Fe# vs. Cr/Cr+Al 74 Figure 3.8: Binary plots of spinel compositions from the Turnagain intrusion. A) Fe /(Fe +Cr+AI) vs. Ti0 . B) Ti vs. V 76 3+  3+  2  Figure 3.9: Expanded trivalent cation (Fe -Cr-Al) plot of Turnagain spinel compositions, focusing on those compositions nearest end-member chromite 78 3+  Figure 3.10: Expanded trivalent cation (Fe -Cr-Al) plot of Turnagain spinel compositions with the data density maxima for other Alaskan-type intrusions from Barnes & Roeder (2001) 82 3+  Figure 4.1: Geological map of the Turnagain intrusion showing sample locations chosen for whole rock geochemistry and sulphide sulphur and lead isotopic compositions  92  Figure 4.2: Photographs of dunite exposures in the Turnagain intrusion  93  Figure 4.3a: Photographs of outcrop-scale features from olivine cumulate lithologies in the Turnagain intrusion  95  Figure 4.3b: Photographs of outcrop-scale features in olivine-clinopyroxene cumulate lithologies in the Turnagain intrusion  96  Figure 4.4a: Photomicrographs (transmitted light, crossed-polars) of silicate mineral textures in the Turnagain intrusion from dunite and wehrlite 97 Figure 4.4b: Photomicrographs (transmitted light, crossed-polars) of silicate mineral textures in the Turnagain intrusion from olivine clinopyroxenite, hornblendite, and diorite 98 Figure 4.5: Photomicrographs of sulphide textures in the Turnagain intrusion  105  Figure 4.6: Photographs of sedimentary xenoliths in NQ size drillcore from the Turnagain intrusion  108  Figure 4.7: Olivine mineral chemistry  126  Figure 4.8: Clinopyroxene mineral chemistry  128  Figure 4.9: Select major element oxides and Mg# vs. MgO for whole rock samples and mineral analyses from the Turnagain intrusion 130 Figure 4.10: Compatible trace element geochemistry vs. MgO  131  Figure 4.11: Chondrite-normalized rare earth element diagrams for whole rocks from the Turnagain intrusion and whole rock samples from Erdmer et al. (2006) 132 Figure 4.12: PGE compositional variations for whole rocks from the Turnagain intrusion  135  Figure 4.13: Primitive-mantle normalized platinum group element diagrams for whole rocks from the Turnagain intrusion  136  Figure 4.14: Sulphur isotopic composition of sulphide vs. lithology in the Turnagain intrusion  138  Figure 4.15: Lead isotopic compositions ( Pb/ Pb vs. Pb/ Pb) of sulphide from the Turnagain intrusion 139 206  204  207  204  Figure 4.16: The effects of oxygen fugacity on sulphur speciation and saturation, after Jugo et al. (2004; 2005) 143  viii  LIST O F APPENDICES  Appendix I: Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion  160  Appendix II: Olivine compositions from olivine-bearing ultramafic rocks of the Turnagain intrusion  179  Appendix III: Clinopyroxene compositions from clinopyroxene-bearing ultramafic lithologies of the Turnagain intrusion  189  Appendix IV: Garnet compositions from a serpentine vein in dunite from the Turnagain intrusion  195  Appendix V: List of X-ray lines and mineral standards for E P M A  196  Appendix VI: Blind duplicate analyses from whole-rock geochemical samples  198  Appendix VII: Clinopyroxene compositions from clinopyroxene-bearing ultramafic lithologies of the Turnagain intrusion 200  ix  ACKNOWLEDGEMENTS T h e r e are m a n y people w h o have c o n t r i b u t e d i n s o m e part to the d e v e l o p m e n t and c o m p l e t i o n o f this thesis. I w o u l d never have written this thesis w i t h o u t the a d v i c e and support o f m y supervisors James Scoates and G r a h a m N i x o n , w h o have taught m e so m u c h since I first a r r i v e d at U B C . James was a l w a y s w i l l i n g to answer questions that I had about e v e r y t h i n g thesis-related or otherwise, regardless o f his o w n w o r k l o a d . James also spent significant amounts o f t i m e e d i t i n g various draft sections o f this thesis, and for that I a m e x t r e m e l y grateful. G r a h a m i n t r o d u c e d m e to the T u r n a g a i n property and i m p a r t e d his experiences o f w o r k i n g o n A l a s k a n - t y p e intrusions o n m e w i t h s k i l l and p r e c i s i o n . H e must also be thanked for h e l p i n g m e set-up necessary f i e l d gear, maps, air photographs, and l o d g i n g w h e n I v i s i t e d h i m i n V i c t o r i a . R i c h F r i e d m a n , Janet G a b i t e s , B r u n o K i e f f e r , T h o m a s U l l r i c h , and M a t i R a u d s e p p are t h a n k e d f o r their a n a l y t i c a l w o r k and a d v i c e d u r i n g the research phase o f this thesis. A l s o R i c h F r i e d m a n , D o m i n i q u e W e i s , and J i m M o r t e n s e n o f the P C I G R are thanked for consultations d u r i n g data interpretation and the i m p l i c a t i o n s thereof. I also thank A n d r e w G r e e n e , C a r o l i n e E m m a n u e l l e - M o r i s s e t , and R o b i n M a c k i e for s h a r i n g their thoughts on ultramafic r o c k s w i t h m e . H a r d C r e e k N i c k e l C o r p o r a t i o n , its president M a r k J a r v i s , and its past and present e m p l o y e e s T o n y H i t c h i n s , C h r i s B a l d y s , B r u c e N o r t h c o t e , and L e s l i e Y o u n g are a l l thanked for the ideas, support, a n d seasonal e m p l o y m e n t d u r i n g the duration o f this thesis as w e l l as for f u n d i n g the research project. O t h e r past and present H a r d C r e e k N i c k e l e m p l o y e e s , i n c l u d i n g Jeff K y b a , T y l e r K u h n , M a r k G r e e n h a l g h , and G r e g R o s s , must also be thanked for m a k i n g s u m m e r w o r k a great experience. J i m and S h a r o n R e e d at P a c i f i c W e s t e r n H e l i c o p t e r s must be thanked for transport d u r i n g the n u m e r o u s s u m m e r s spent i n the T u r n a g a i n c a m p . T h a n k s to J o h n Schussler, the first d r i l l e r o n the T u r n a g a i n property and f o r m e r o w n e r o f D J D r i l l i n g , for l o d g i n g i n B o u l d e r C i t y i n 2 0 0 4 and 2 0 0 5 . F i n a l l y , I l i k e to thank m y f a m i l y for their help and support d u r i n g the last 7 years o f m y a c a d e m i c career. I w o u l d l i k e to thank T o m C h a c k o , B o b L u t h , L a r r y H e a m a n , Sarah G l e e s o n , a n d J e r e m y R i c h a r d s at the U n i v e r s i t y o f A l b e r t a for h e l p i n g m e f i n d m y c a l l i n g i n g e o l o g y , and for m a k i n g the undergraduate p r o g r a m there one o f the best i n the continent. M a n y thanks to a l l m y friends at U B C and i n V a n c o u v e r , because w i t h o u t t h e m I w o u l d not have made it this far.  x  CHAPTER 1  GEOLOGICAL CONTEXT AND EXPLORATION HISTORY OF THE TURNAGAIN ALASKAN-TYPE INTRUSION, NORTH-CENTRAL BRITISH COLUMBIA  1.1 INTRODUCTION T h i s study focuses on the Turnagain Alaskan-type mafic-ultramafic intrusion, w h i c h is located 70 k m east o f Dease L a k e , B r i t i s h C o l u m b i a , Canada. The Turnagain intrusion is a 24 k m  2  pluton that is dominantly composed o f ultramafic cumulate rocks and m i n o r dioritic phases and that contains appreciable nickeliferrous sulphide mineralization (Figure 1.1). G l o b a l l y , Alaskan-type intrusions are characteristically sulphide-poor and no other intrusion found to date contains significant concentrations o f magmatic N i - b e a r i n g sulphide. The m a i n goal o f this thesis is to assess the o r i g i n and petrogenesis o f the Turnagain intrusion and to constrain the m e c h a m i s m o f sulphide mineralization b y c o m b i n e d field mapping and drillcore l o g g i n g , geochemistry (mineral chemistry, major and trace elements, N d - S - P b isotopes) and geochronology ( U - P b , A r - A r ) . T h e Turnagain intrusion is situated w i t h i n greenschist facies metasedimentary rocks currently assigned to the A n c e s t r a l N o r t h A m e r i c a n miogeocline (Gabrielse, 1998). The intrusion is entirely fault-bounded on a l l margins, and is situated 1.5 k m northeast o f the K u t c h o Fault, w h i c h is a major tectonic structure separating the miogeocline to the east from felsic plutons and mafic volcanics o f the Quesnel accreted terrane to the west. The term " A l a s k a n - t y p e , " synonymous w i t h " U r a l i a n - t y p e " , " U r a l i a n - A l a s k a n - t y p e " , and " z o n e d ultramafic", was first used by T a y l o r & N o b l e (1960) and N o b l e & T a y l o r (1960) and originally referred to mafic-ultramafic intrusions found i n the A l a s k a n Panhandle and i n the U r a l M o u n t a i n s , R u s s i a (e.g. D u k e Island, Irvine, 1962; N i z h n i i - T a g i l , Krause et al, 2006). These two belts, along w i t h other occurrences o f Alaskan-type intrusions, are t y p i c a l l y found in paleo-arc environments. The subduction zone or arc setting o f these intrusions has been qualified i n a large number o f studies (e.g. Irvine, 1974; T i s t l et al, 1994; Green et al., 2004; Batanova et al., 2005) by association w i t h other arc rocks, mineralogy, and geochemistry. Despite the fact that many more o f these bodies have been found throughout the w o r l d , the term " A l a s k a n - t y p e " is still retained. " Z o n e d ultramafic" refers to the observation that many o f these intrusions are zoned from the core outwards, from more mafic (or ultramafic) to less mafic rocks. T h i s zonation can be perfectly concentric, or completely absent, and is a c o m m o n , although not a diagnostic, trait o f Alaskan-type intrusions. It has long been k n o w n that A l a s k a n - t y p e intrusions can be spatially associated w i t h basaltic v o l c a n i c rocks ( F i n d l a y , 1969; Irvine, 1974), and a genetic l i n k between Alaskan-type intrusions and arc-derived ankaramitic/picritic magmas and lavas has recently been established ( M o s s m a n et al., 2000).  Intrusion Centre: X 58°29'N, 128°52'W  Horsetrail Zone  1 km Diorite, quartz diorite, and granodiorite, undivided  | Dunite, with minor wehrlite Wehrlite, with minor dunite and olivine clinopyroxenite  Homfels, sedimentary or volcanic protolith  Olivine clinopyroxenite and clinopyroxenite, undivided  Reverse fault, observed  Hornblende clinopyroxenite, with minor clinopyroxenite Hornblendite and clinopyroxene hornblendite, undivided  Normal fault, inferred —^  Fault (relative sense of motion indicated)  Figure 1.1: Simplified geological map of the Turnagain Alaskan-type intrusion, with its location in British Columbia shown as an inset in the upper right comer (also indicated are the locations of other major Alaskantype intrusions in B.C. and Alaska), modifiedfromClark (1975). The lithologies of the intrusion are shown in the legend; some units are composites (e.g. olivine clinopyroxenite and clinopyroxenite). The intrusion is entirely fault-bounded, and the large area of hornblende-rich lithologies with associated felsic rocks in the west is mostly interpretedfromboth airborne and ground geophysics, as well as informationfromdrill holes. Major mineralized zones are indicated with white ovals, as is the Discovery Showing. The DJ/DB zone is a hydrothermal Pt-Pd zone, whereas all other zones contain Ni-sulphide mineralization.  A r c - d e r i v e d ankaramites are composed o f o l i v i n e - and clinopyroxene-porphyritic basalt containing groundmass amphibole and plagioclase. A n k a r a m i t e dikes, t y p i c a l l y found crosscutting certain Alaskan-type intrusions (e.g. Greenhills, Spandler et al., 2003), are c o m m o n l y zoned from the interior to the margin, suggesting that the observed zonation i n A l a s k a n - t y p e intrusions may be the result o f c o m m o n petrogenetic processes. The mineralogy and crystallization sequence o f ankaramite and Alaskan-type intrusions is also nearly identical and the c h e m i c a l signatures o f both rock types indicates their c o m m o n o r i g i n from the mantle (e.g. Green et al,  2004).  The defining characteristic o f Alaskan-type intrusions is their mineralogy. T h e i r t y p i c a l order o f crystallization is olivine+chromite —> diopside —*• magnetite —> hornblende+calcic plagioclase. C h r o m i t e is an early (high temperature) c r y s t a l l i z i n g phase i n A l a s k a n - t y p e intrusions and t y p i c a l l y ceases to crystallize shortly after clinopyroxene saturation (Irvine, 1965). In general, mafic-ultramafic intrusions rarely contain primary magmatic hornblende, but primary hornblende is a c o m m o n mineral i n e v o l v e d rocks w i t h i n many A l a s k a n - t y p e intrusions. Orthopyroxene is t y p i c a l l y absent, save a few isolated examples (e.g. Salt C h u c k , A l a s k a , L o n e y & H i m m e l b e r g , 1992; Gabbro A k a r e m , E g y p t , H e l m y & E l M a h a l a w i , 2003), indicating that the parental magmas to these bodies were silica-undersaturated (Irvine, 1965). Plagioclase is generally absent as an early cumulus phase, and crystallizes after clinopyroxene or hornblende. The suppression o f early plagioclase crystallization is due to the relatively h i g h water contents o f the magmas as elevated water contents i n silicate magmas are k n o w n to suppress the crystallization o f plagioclase to l o w temperatures (e.g. Irvine, 1965; Gaetani et al., 1993). The presence o f small amounts o f primary phlogopite i n the most ultramafic parts o f intrusions is also a diagnostic feature, and may reflect the alkaline to subalkaline c h e m i c a l characteristics o f p r i m i t i v e Alaskan-type magmas (Findlay, 1969; Irvine, 1974; N i x o n et al., 1997). M a n y intrusions have lode and associated placer Pt ( ± Pd) mineral deposits (e.g. Tulameen, B . C . , F i n d l a y , 1969; A l t o Condoto, C o l u m b i a , T i s t l , 1994; N i z h n i i T a g i l , R u s s i a , Johan, 2002) and they are c o m m o n l y explored for platinum-group metals ( P G M ) . The majority o f these P G M are found i n chromitite as PtsFe (isoferroplatinum) (e.g. N i x o n et al., 1990; Johan et ah, 2000), however there are also occurrences o f Os-Ir alloys (e.g. Garuti et al., 2003) and possible alloys, such as Pt2CuFe (tulameenite, N i x o n et al., 1990), o f hydrothermal origin. T w o Alaskan-type intrusions contain significant sulphide (Salt C h u c k and Turnagain),  each w i t h a distinctive sulphide mineralogy and lithologic association. The Salt C h u c k intrusion contains P d - r i c h , bornite-bearing clinopyroxenite and gabbro ( L o n e y & H i m m e l b e r g , 1992). In contrast, the Turnagain intrusion contains disseminated to semi-massive pyrrhotite and pentlandite w i t h m i n o r secondary phases, but also contains a late-stage, hydrothermal PtP d zone associated w i t h a C u soil geochemical anomaly (Figure 1.1). Thirty-five o f the 39 k n o w n Alaskan-type intrusions (e.g. D u k e Island; Irvine, 1962) i n southeastern A l a s k a occur i n a 560 k m l o n g by 50 k m w i d e belt (Taylor, 1967). T h e other four occurrences (e.g. Salt C h u c k ; L o n e y et ah, 1987) are to the west o f this belt, are older, and have different petrological characteristics (e.g. more plagioclase, trace orthopyroxene). S i m i l a r large belts occur i n the U r a l M o u n t a i n s (15 large bodies; T a y l o r , 1967; K r a u s e , 2006), w h i c h is approximately 1000 k m l o n g and 60 k m w i d e ; the K a m c h a t k a Peninsula, F a r East R u s s i a (Batanova et al., 2005; and references therein), w h i c h contains over 20 Alaskan-type intrusions; and B r i t i s h C o l u m b i a , w h i c h has 9 k n o w n occurrences (e.g. Tulameen; F i n d l a y , 1969; Turnagain; C l a r k , 1980; N i x o n et al., 1997). Alaskan-type intrusions i n C o l u m b i a and E c u a d o r (Tistl, 1994; T i s t l et al., 1994) may belong to a larger belt that currently remains unconstrained and relatively unexplored. A tectonically dismembered belt that existed prior to the M i o c e n e opening o f the Sea o f Japan has been proposed to link A l a s k a n - t y p e intrusions i n Japan, northeastern C h i n a , and Far East R u s s i a (Ishiwatari & Ichiyama, 2004). There are also a number o f other Alaskan-type intrusions that occur as either single intrusions (e.g. Papua N e w G u i n e a ; Johan et al, 2000; Greenhills; M o s s m a n et al., 2000) or as small groups o f intrusions (e.g. F i f i e l d , A u s t r a l i a ; Johan, 2002).  1.2 EXPLORATION HISTORY OF THE TURNAGAIN INTRUSION Sulphide mineralization i n the Turnagain intrusion was discovered along the banks o f the Turnagain R i v e r ca. 1956, and this semi-massive sulphide s h o w i n g has henceforth been called the D i s c o v e r y s h o w i n g (Figure 1.1). Falconbridge N i c k e l M i n e s L t d . , interested i n the n i c k e l potential o f the semi-massive sulphide, o w n e d and explored the Turnagain property between 1966 and 1973 and drilled the major sulphide showings (Northwest, Horsetrail, F i s h i n g R o c k , D i s c o v e r y , H a t z l ; Figure 1) w i t h s m a l l , portable "packsack" drills. A i r b o r n e magnetic surveys were also f l o w n across the entire intrusion. A P h . D . thesis o n the geology and petrography o f the intrusion was completed b y T o m C l a r k i n 1975 at Queens U n i v e r s i t y (Clark, 1975), f o l l o w e d by several publications derived from the thesis ( C l a r k , 1978; C l a r k ,  1980). Interest i n the platinum-group element ( P G E ) potential o f A l a s k a n - t y p e intrusions in B r i t i s h C o l u m b i a during the 1980s resulted i n significant government survey m a p p i n g and associated geochemical studies (especially P G E ) o f these intrusions across the province  ( N i x o n etal, 1989; 1990; 1997). Interest i n the n i c k e l potential o f the intrusion was renewed w h e n B r e n - M a r L t d . acquired the property i n 1996 ( B r e n - M a r L t d . became Canadian M e t a l s E x p l o r a t i o n L t d . i n 2002, and then became H a r d Creek N i c k e l C o r p . i n 2004). Contour-defined and grid soil sampling was conducted over the entire intrusion to constrain existing n i c k e l targets and to find covered targets (the intrusion is only - 3 0 % exposed). A zone o f hydrothermal P t - P d - C u mineralization was discovered as a result o f extensive soil sampling i n the summer o f 2004. Sulphide mineralogical and chemical studies have been carried out by D r . H a r r y K u c h a at the U n i v e r s i t y o f K r a k o w , P o l a n d ( H a r d Creek N i c k e l internal reports), and are ongoing. Recent air photographs, and airborne and ground geophysics (magnetic, electromagnetic), were acquired i n late 2005. T o date, H a r d Creek N i c k e l C o r p . has drilled ~50 k m o f B Q and N Q drillcore i n - 1 7 0 holes, and has outlined a N i resource o f 429 M t (measured and indicated) containing 0.17% sulphide N i (see http://www.hardcreeknickel.com). The author spent 8 weeks i n the summer o f 2004 at the Turnagain property as part o f his field w o r k , during w h i c h time detailed mapping and sampling o f outcrops w i t h i n and around the Turnagain intrusion were conducted. In the summer o f 2005, the author conducted two weeks o f drillcore sampling from the Turnagain intrusion for sulphides o f various textures and tenors, and sulphide from the w a l l r o c k s where the contact had been penetrated by d r i l l i n g . The author also sampled for chromitite and w h o l e - r o c k geochemical samples. F o r the remainder o f the summer, the author was i n v o l v e d i n the summer exploration program o f H a r d Creek N i c k e l C o r p . , w h i c h i n v o l v e d l o g g i n g core and i n - f i l l mapping. The current map o f the Turnagain intrusion, based on the map o f C l a r k (1975), was created as a j o i n t effort b y the author and B r u c e Northcote (formerly o f H a r d Creek N i c k e l C o r p . ) .  1.3 O V E R V I E W O F T H E S I S  There are three complimentary studies on the Turnagain intrusion presented i n this thesis. P r i o r to this study, there was no geochronological data for the Turnagain intrusion, nor were there any w h o l e rock trace element or isotopic compositions. The m a i n objectives o f this thesis were 1) to determine the age and tectonic significance o f the intrusion and its host rocks, 2) to  characterize the lithologies and magmatic evolution o f the Turnagain intrusion using m i n e r a l and w h o l e rock chemistry, and 3) to ultimately constrain the o r i g i n o f the anomalous sulphide mineralization i n the intrusion. Chapters 2, 3, and 4 were prepared in manuscript format for submission to appropriate scientific journals, and as such they contain some similar introductory figures and geologic backgrounds, although o n l y information relevant to each specific study is reported i n each chapter. Chapter 2 describes the geochronology and tectonic setting o f the Turnagain intrusion. The age o f the intrusion is determined by the dating o f four ultramafic and mafic samples using both U - P b and A r - A r geochronological techniques. A fifth sample, representing the stratigraphically-highest w a l l r o c k s to the Turnagain intrusion, was also dated using detrital z i r c o n U - P b geochronology. The N d isotopic compositions o f eight w h o l e rock samples were determined to help constrain the source o f the Turnagain intrusion and to ascertain the relative degree o f crustal contamination. A d d i t i o n a l l y , available age data from other Alaskan-type intrusions i n B . C . and southeastern A l a s k a were c o m p i l e d i n an effort to constrain the temporal evolution o f their respective arc systems. T h e results from this study place important constraints on the source o f the Turnagain intrusion, terrane assessment, and the temporal evolution o f the host rocks to the intrusion. M i n e r a l separation (zircon, titanite, phlogopite, hornblende) was performed by the author, R i c h Friedman, H a i L i n , and T o m U l l r i c h at U B C . G w e n W i l l i a m s , B r u n o Keiffer, and Jane B a r l i n g were responsible for aquiring the N d isotopic compositions (sample dissolution, c o l u m n chemistry, and mass spectrometry), and U - P b and A r - A r goechonologic analyses were carried out b y R i c h F r i e d m a n and T o m U l l r i c h , respectively. Chapter 3 documents the chemistry o f chromite i n the Turnagain intrusion w i t h emphasis on the o r i g i n and significance o f compositional variations. Spinel grains from sixteen samples were analyzed by electron microprobe (a total o f 320 point analyses). F r o m these analyses, a primary spinel composition for the Turnagain intrusion has been defined. The intrasample chemical trends present i n the analyzed chromite grains are used to discriminate reequilibration w i t h o l i v i n e , clinopyroxene, interstitial l i q u i d , and the effects o f o x i d i z i n g and serpentinizing fluids. Establishment o f primary chromite compositions also provides constraints on the relative o x y g e n fugacity o f the parental magmas, w h i c h is critical for understanding the o r i g i n o f the nickeliferrous sulphide mineralization i n the Turnagain  intrusion. A l l analytical w o r k was carried out by the author w i t h supervision by M a t i Raudsepp. Chapter 4 involves a detailed petrological study o f the ultramafic and mafic rocks i n the Turnagain intrusion based on silicate mineral chemistry, w h o l e rock major/trace element geochemistry, platinum-group element chemistry, and sulphur and lead isotopes o f sulphides. T h e forsterite contents o f olivine c o n f i r m the p r i m i t i v e nature o f the Turnagain parent magmas (up to F092.5 i n o l i v i n e that has not reequilibrated w i t h chromitite) and the N i contents o f o l i v i n e provide a clear signal o f sulphide l i q u i d saturation during formation o f some o f the dunites, wehrlites, and o l i v i n e clinopyroxenites. The major element geochemistry o f 23 w h o l e rock samples was used i n tandem w i t h o l i v i n e , clinopyroxene, and amphibole mineral chemistry to constrain the c h e m i c a l relationships o f w h o l e rock samples relative to their mineralogy. These results have important implications for the crystallization sequence and emplacement history o f the magmas that formed the Turnagain intrusion. Trace element chemistry from the w h o l e rock suite further constrains the genetic relationship between a l l lithologies present i n the Turnagain intrusion and allows for recognition o f an arc affinity. Twenty-seven sulphur isotopic compositions and 14 lead isotopic compositions o f sulphide separates from hand samples and drillcore samples are used evaluate the extent o f crustal contamination i n v o l v e d i n sulphide saturation i n the Turnagain intrusion, w h i c h is important for understanding the formation o f nickeliferrous magmatic sulphide deposits i n A l a s k a n - t y p e intrusions. A l l microprobe analyses were carried out by the auther under the supervision o f M a t i Raudsepp at U B C . The author also produced the sulphide separates for P b and S isotopic anaysis, and Janet Gabites at U B C processed the sulphides for chemistry and perfomed the P b isotopic analyses. F i n a l l y , the appendices contain the full datasets for spinel, o l i v i n e , clinopyroxene, and garnet microprobe analyses, the X - r a y lines and standards for a l l microprobe analyses, and the comparison between w h o l e rock geochemical samples and respective b l i n d duplicates. A d d i t i o n a l l y , the U T M coordinates for all samples relevant to this thesis are listed i n the final appendix.  1.4 REFERENCES Batanova, V . G . , Pertsev, A . N . , K a m e n e t s k y , V . S . , A r i s k i n , A . A . , M o c h a l o v , A . G . , & Sobolev, A . V . (2005). Crustal evolution o f island-arc ultramafic magma: G a l m o e n a n pyroxenitedunite plutonic complex, K o r y a k H i g h l a n d (Far East Russia).  Journal of Petrology 46,  1345-1366 C l a r k , T . (1975). G e o l o g y o f an ultramafic c o m p l e x on the Turnagain R i v e r , northwestern B r i t i s h C o l u m b i a . U n p u b l i s h e d P h . D . dissertation,  Queens University, 453p  C l a r k , T . (1978). O x i d e minerals i n the Turnagain ultramafic complex, northwestern B r i t i s h Columbia.  Canadian Journal of Earth Sciences 15 (12), 1893-1903  C l a r k , T . (1980). Petrology o f the Turnagain ultramafic c o m p l e x , northwestern B r i t i s h Columbia.  Canadian Journal of Earth Sciences 17, 744-757  F i n d l a y , D . C . (1969). O r i g i n o f the Tulameen ultramafic-gabbro complex, southern B r i t i s h Columbia.  Canadian Journal of Earth Sciences 6, 399-425  Gabrielse, H . (1998). G e o l o g y o f C r y L a k e and Dease L a k e map areas, north-central B r i t i s h Columbia;  Geological Survey of Canada, B u l l e t i n 504, 147p  Gaetani, G . A . , G r o v e , T . L . , B r y a n , W . B . (1993). The influence o f water on the petrogenesis o f subduction-related igneous rocks. Nature 365,  332-334  Garuti, G . , Pushkarew, E . V . , Z a c c a r i n i , F . , C a b e l l a , R . , and A n i k i n a , E . (2003). C h r o m i t e composition and platinum-group mineral assemblage i n the U k t u s U r a l i a n - A l a s k a n - t y p e c o m p l e x (Central U r a l s , Russia).  Mineralium Deposita 38, 312-326  Green, D . H . , Schmidt, M . W . , & H i b b e r s o n , W . O . (2004). Island-arc ankaramites: P r i m i t i v e melts from fluxed refractory lherzolitic mantle.  Journal of Petrology 45, 391-403  H e l m y , H . M . , E l M a h a l l a w i , M . M . (2003). Gabbro A k a r e m mafic-ultramafic c o m p l e x , Eastern Desert, E g y p t : A late Precambrian analogue o f Alaskan-type complexes.  Mineralogy and  Petrology 11, 85-108 Irvine, T . N . (1962). M i n e r a l o g y and petrology o f the ultramafic c o m p l e x at D u k e Island, S . E .  A l a s k a . American Mineralogist 47, 193 Irvine, T . N . (1965). C h r o m i a n spinel as a petrogenetic indicator. Part 1. Theory. Canadian  Journal of Earth Sciences 2, 648-672 Irvine, T . N . (1974). Petrology o f the D u k e Island ultramafic c o m p l e x , southeastern A l a s k a .  Geological Society of America - Memoir 138, 240p  Ishiwatari, A . , & Ichiyama, Y . (2004). Alaskan-type plutons and ultramafic lavas i n F a r East Russia, northeast C h i n a , and Japan.  International Geology Review 46, 316-331  Johan, Z . , Slansky, E . , & K e l l y , D . A . (2000). P l a t i n u m nuggets from the K o m p i a m area, E n g a Province, Papua N e w G u i n e a : E v i d e n c e for an Alaskan-type complex.  Mineralogy and  Petrology 68, 159-176 Johan, Z . (2002). Alaskan-types complexes and their platinum-group element mineralization.  In: C a b r i , L . J . (ed.) The Geology, Geochemistry, Mineralogy and Mineral Benefwiation of Platinum-Group Elements. Canadian Institute o f M i n i n g , M e t a l l u r g y and Petroleum, Special V o l u m e 54, 669-719 K r a u s e , J . , B r u g m a n n , G . E . , Pushkarev, E . V . (2007). A c c e s s o r y and rock f o r m i n g minerals monitoring the evolution o f zoned mafic-ultramafic complexes i n the Central U r a l  Mountains. Lithos 95, 19-42 L o n e y , R . A . , H i m m e l b e r g , G . R . , Shaw, N . B . (1987). Salt C h u c k palladium-bearing ultramafic body, Prince o f W a l e s Island.  U.S. Geological Survey Circular Report C 0998, 126-127  L o n e y , R . A . , H i m m e l b e r g , G . R . (1992). Petrogenesis o f the P d - r i c h intrusion at Salt C h u c k , Prince o f W a l e s Island: A n E a r l y P a l e o z o i c A l a s k a n - t y p e ultramafic body. Canadian  Mineralogist 30, 1005-1022 M o s s m a n , D . J . , C o o m b s , D . S . , K a w a c h i , Y . , & R e a y , A . (2000). H i g h - M g arc ankaramitic dikes, Greenhills C o m p l e x , Southland, N e w Zealand.  Canadian Mineralogist 38, 191-216  N i x o n , G . T . , A s h , C . H . , C o n n e l l y , J . N . , Case, G . (1989). G e o l o g y and noble metal geochemistry o f the Turnagain ultramafic complex, northern B r i t i s h C o l u m b i a . B.C.  Ministry of Energy, Mines, and Petroleum Resources, O p e n F i l e 1989-18 N i x o n , G . T . , C a b r i , L . J . , & L a f l a m m e , J . H . G . (1990). Platinum-group-element mineralization in lode and placer deposits associated w i t h the Tulameen Alaskan-type c o m p l e x , B r i t i s h Columbia.  Canadian Mineralogist 28, 503-535  N i x o n , G . T . , H a m m a c k , J . L . , A s h , C . H . , C a b r i , L . J . , Case, G . , C o n n e l l y , J . N . , H e a m a n , L . M . , L a f l a m m e , J . H . G . , N u t t a l l , C , Paterson, W . P . E . , & W o n g , R . H . (1997). G e o l o g y and platinum-group-element British Columbia.  mineralization o f Alaskan-type ultramafic-mafic complexes i n  B.C. Ministry of Employment and Investment, B u l l e t i n 93, 141p  N o b l e , J . A . , & T a y l o r , H . P . , Jr. (1960). Correlation o f the ultramafic complexes o f southeastern A l a s k a w i t h those o f other parts o f N o r t h A m e r i c a and the W o r l d .  International Geological Progress Report Part XIII, 188-197  2f'  Spandler, C.J., Arculus, R.J., Eggins, S.M., Maurogenes, J.A., Price, R.C., & Reay, A.J. (2003). Petrogenesis of the Greenhills Complex, Southland, New Zealand: Magmatic differentiation and cumulate formation at the roots of a Permian island-arc volcano. Contributions to Mineralogy and Petrology 144, 703-721  Taylor, H.P., Jr., & Noble, J.A. (1960). Origin of the ultramafic complexes in southeastern Alaska. 21 International Geological Progress Report Part XIII, 175-187 st  Taylor, H.P., Jr. (1967). The zoned ultramafic complexes of southeastern Alaska. In: Wyllie, P.J. (ed.) Ultramafic and Related Rocks. New York: John Wiley and Sons, 97-121 Tistl, M . (1994). Geochemistry of platinum-group elements of the zoned ultramafic Alto Condoto complex, northwest Columbia. Economic Geology 89, 158-167 Tistl, M . , Burgath, K.P., Hoehndorf, A., Kreuzer, H., Munox, R., & Salinas, R. (1994). Origin and emplacement of Tertiary ultramafic complexes in northwest Columbia: Evidence from geochemistry and K-Ar, Sm-Nd, and Rb-Sr isotopes. Earth and Planetary Science Letters 126,41-59  CHAPTER 2  GEOCHRONOLOGY OF THE TURNAGAIN ALASKAN-TYPE INTRUSION, NORTH-CENTRAL BRITISH COLUMBIA, WITH IMPLICATIONS FOR THE TECTONIC EVOLUTION OF THE NORTHERN CANADIAN CORDILLERA  2.1 I N T R O D U C T I O N Alaskan-type intrusions, synonymous w i t h Uralian-type and zoned ultramafic intrusions (e.g. T a y l o r & N o b l e , 1960), are predominantly composed o f ultramafic cumulate rocks (e.g. dunite, wehrlite, hornblendite) w i t h m i n o r dioritic phases. The majority o f A l a s k a n - t y p e intrusions occur w i t h i n paleo-arcs (e.g. Quesnel terrane, B . C . , N i x o n et al, 1997; A l e x a n d e r terrane, A l a s k a , H i m m e l b e r g & L o n e y , 1995) that are island or continental i n nature, and a few occur i n cratonic environments (e.g. K o n d y o r C o m p l e x , R u s s i a , Johan, 2002). A number o f Alaskan-type intrusions have been studied w i t h respect to their platinum-group-element potential i n lode and associated placer deposits (e.g. U r a l M o u n t a i n s , Russia, G a r u t i et  al,  2003). In general, few precise ages o f crystallization are available for Alaskan-type intrusions, w h i c h is critical for understanding their tectonic setting and proposed relationships to contemporaneous intrusive rocks or v o l c a n i c sequences. The Turnagain intrusion, situated i n north-central B r i t i s h C o l u m b i a , is distinct from other Alaskan-type intrusions i n that it contains unusually h i g h , and perhaps economic, concentrations o f N i - s u l p h i d e mineralization. The current resource estimate (measured and indicated) is 428 M t grading 0.17% N i (http://www.hardcreeknickel.com). T h e age and tectonic history o f the Turnagain intrusion, as w e l l as the o r i g i n o f the magmas, are important for understanding the evolution o f the northern Canadian C o r d i l l e r a . N i x o n (1998) proposed two contrasting interpretations for the tectonic setting o f the Turnagain intrusion. The first interpretation is that the Turnagain intrusion was emplaced into m i o g e o c l i n a l metasedimentary rocks o f A n c e s t r a l N o r t h A m e r i c a i n a subduction zone environment. The second interpretation is that the Turnagain intrusion lies w i t h i n a series o f northeast-verging imbricated thrusts. T h i s study presents new U - P b and A r - A r geochronologic data, coupled w i t h w h o l e - r o c k N d isotopic compositions, to constrain the age and o r i g i n o f the Turnagain intrusion and its host rocks. D e t e r m i n i n g the precise age o f crystallization o f ultramafic rocks i n Alaskan-type intrusions is t y p i c a l l y difficult as abundances o f U - b e a r i n g (e.g. z i r c o n , baddeleyite) accessory minerals are relatively l o w to absent, and primary K - b e a r i n g (e.g. biotite, feldspar) phases tend to be altered. The results from this study have implications for the significance o f Alaskan-type intrusions and tectonic evolution o f a portion o f the northern Canadian C o r d i l l e r a .  2.2 GEOLOGICAL SETTING OF THE TURNAGAIN INTRUSION The Turnagain Alaskan-type intrusion is located approximately 70 k m east o f the t o w n o f Dease L a k e , i n north-central B r i t i s h C o l u m b i a (Figure 2.1). The intrusion is fault-bounded and p r o x i m a l to the K u t c h o Fault, w h i c h is a major tectonic structure that is interpreted to separate intrusive and v o l c a n i c sequences o f the accreted Quesnel terrane from passive m a r g i n sedimentary rocks and post-accretionary Cretaceous granitoids o f A n c e s t r a l N o r t h A m e r i c a (Gabrielse, 1998). The Quesnel terrane is part o f the Intermontane B e l t , a composite o f terraries that extend south into Washington State and north into Y u k o n Territory (Figure 2.1). Seven Alaskan-type intrusions have been identified i n the Quesnel terrane, i n c l u d i n g the Polaris intrusion and the Tulameen intrusion, w h i c h is the largest A l a s k a n - t y p e intrusion i n the w o r l d and is associated w i t h concentrations o f placer platinum-group metals i n both lode and placer occurrences (Findlay, 1963; N i x o n et al., 1990) (Figure 2.1). The T u l a m e e n is one o f the three precisely dated ( U - P b zircon) Alaskan-type intrusions i n B . C . (Rublee, 1994; N i x o n et al., 1997). The Alaskan-type intrusions o f Quesnellia are t y p i c a l l y associated w i t h dioritic plutons o f Triassic-Jurassic age and mafic volcanics, specifically the Late Triassic T a k l a , N i c o l a , and Stuhini groups. These mafic volcanics have been considered to be genetically associated w i t h Alaskan-type intrusions (e.g. F i n d l a y , 1969; Irvine, 1974; N i x o n et al., 1997), and the Turnagain intrusion is 20 k m northwest o f an exposure o f T a k l a v o l c a n i c s (Figure 2.2), although their genetic association w i t h the intrusion remains to be evaluated. N u m e r o u s Alaskan-type intrusions o f Cretaceous age occur w i t h i n the A l e x a n d e r terrane i n southeastern A l a s k a , i n c l u d i n g the D u k e Island intrusion (Irvine, 1967; Irvine, 1974; L o n e y & H i m m e l b e r g , 1992). F o u r other intrusions located to the west o f the Cretaceous intrusions are P a l e o z o i c i n age and include the Salt C h u c k intrusion, w h i c h exhibits extensive Pd-enriched Cu-sulphide mineralization at a major l i t h o l o g i c a l boundary ( L o n e y et al., 1987; L o n e y & H i m m e l b e r g , 1992; W a t k i n s o n & M e l l i n g , 1992). Pelagic sedimentary rocks o f the R o a d R i v e r and E a r n Groups ( - O r d i v i c i a n M i s s i s s i p p i a n ) were mapped b y Gabrielse (1998) to occur along the northern and eastern edges o f the Turnagain intrusion (Figure 2.2). The R o a d R i v e r and E a r n Groups have been interpreted to represent ocean basin sediments deposited on the margin o f Ancestral N o r t h A m e r i c a (Gabrielse, 1998; E r d m e r et al., 2005). The l i t h o l o g i c a l l y diverse R o a d R i v e r F o r m a t i o n i n the M c D a m e locality has a type thickness o f 95 m (Gabrielse, 1998) and varies from a lower member o f black, graptolitic, locally calcareous shale, a m i d d l e member o f  mid-Triassic to Jurassic Alaskan-type intrusions Turnagain intrusion Lunar Creek intrusion Polaris intrusion Tulameen intrusion mid-Cretaceous Alaskan-type intrusions O Duke Island Salt Chuck intrusion (Paleozoic)  Ancestral North America  Coast Plutonic Complex  Stikinia  Methow  Kootenay/Miogeocline (ANA) Cache Creek  •  Bridge River Cadwallader  Klinkit/Harper Ranch  Harrison  Yukon-Tanana  Shuksan  Quesnellia  Slide Mountain  Figure 2.1: Terrane map of British Columbia, modified from Colpron & Nelson (2004), showing the locations of the major Alaskan-type intrusions in British Columbia and southeastern Alaska. The region outlined by the white box is the area displayed in Figure 2.2. Note that the Turnagain intrusion is situated on the western edge of Ancestral North America.  Ancestral North America DPHq Nizi Formation DMEa Earn Group ODRo Road River Group €OKe Kechika Group €At u  p|g  Atan Group  Cache Creek CPgb  Carboniferous to Permian gabbro  CPrum Carboniferous to Permian ultramafic complexes MJCc Cache Creek Complex Stikinia uTS  Takla Group  "Kgd  Triassic granodiorite  EJum  Turnagain Alaskan-type ultramafic intrusion  EJgd  Eaglehead Pluton and equivalents  Stuhini Group, Mosley and Mount Moore Formations | Kutcho Formation, Sillika Assemblage  Ingenika Group  Quesnellia "RJTk  Late Intrusive/Extrusive rocks EKgr  Cassiar Batholith: granitoid  [_TQT  Tuya Formation  ImJLffl Laberge Group Quaternary Cover  MJdg  monzodiorite  F i g u r e 2.2: Regional geological setting of the area immediately surrounding the Turnagain intrusion, extracted and modified after Massey et al. (2005). Note that the western, northern, and eastern margins of the Turnagain intrusion are flanked by the Road River/Earn groups. The Kutcho Fault separates Ancestral North America from Quesnellia and Cache Creek. The white box represents the study area (shown in more detail in Figure 2.3) and the white oval represents the general study area of Erdmer et al. (2005).  16  laminated dolomite, and an upper member o f calcareous siltstone and shale. The entire package ranges i n biostratigraphic age from E a r l y O r d i v i c i a n to M i d d l e S i l u r i a n (Gabrielse, 1998). The E a r n G r o u p also exhibits extreme l i t h o l o g i c a l diversity depending on where it is observed. In general, the E a r n G r o u p is a darkly coloured slate to siltstone that is locally pyritic and ranges i n thickness from 50 to 1000 m i n northern B . C . (Gabrielse, 1998). It is has been biostratigraphically dated to be D e v o n i a n to M i s s i s s i p p i a n i n age. H o w e v e r , the age o f the phyllite to the north and east o f the Turnagain intrusion has not been determined and is currently assigned to the u n d i v i d e d R o a d R i v e r and E a r n Groups based on l i t h o l o g i c a l similarities w i t h these two sedimentary packages (Gabrielse, 1998). Constrastingly, the Sandpile, R a m h o r n , and M c D a m e formations, w h i c h are observed between the R o a d R i v e r F o r m a t i o n and the E a r n G r o u p elsewhere in B . C . , are not observed i n the v i c i n i t y o f the Turnagain intrusion. D u e to these discrepancies, the greenschist-facies pelagic sediments p r o x i m a l to the Turnagain intrusion are referred to as "graphitic p h y l l i t e " i n this manuscript. Graphitic pre-Devonian sediments are also associated w i t h the Y u k o n - T a n a n a terrane (Mortensen, 1992; S i m a r d et al., 2003; N e l s o n & Friedman, 2004) and have been observed stratigraphically b e l o w the L a y Range Assemblage (Ferri & M e l v i l l e , 1990), w h i c h is a volcano-sedimentary, arc-derived, package o f rocks observed i n Quesnellia. The graphitic phyllite to the north and east o f the Turnagain intrusion, possibly part o f the R o a d R i v e r F o r m a t i o n and E a r n Groups, is composed o f unfossiliferous, graphitic, and p y r i t i c slates and phyllites containing interbeds o f tuff, calcareous phyllite, and rare quartzite (Gabrielse, 1998; E r d m e r et al., 2005; Scheel et ah, 2005). The graphitic p h y l l i t e is t y p i c a l l y recessiveweathering and crops out along the Turnagain R i v e r to the north and southeast o f the intrusion, as w e l l as i n alpine areas to the east o f the Turnagain R i v e r (Figure 2.2). These rocks generally have a steeply-dipping cleavage and may be c o m p l e x l y folded (Erdmer et al., 2005; Scheel et al., 2005). The graphitic phyllites, and a metasedimentary i n c l u s i o n i n the northwestern part o f the Turnagain intrusion (Figure 2.3), c o m m o n l y contain 1 c m to 1 m-thick quartz veins that do not cross-cut the Turnagain intrusion. The few exposures o f the metasedimentary unit to the south o f the Turnagain intrusion have been interpreted by M a s s e y et al. (2005) as the N i z i F o r m a t i o n , and referred to b y Gabrielse (1998) as "uncorrelative". These metasediments are a grey-green, banded w a c k e , and appear similar to the hornfelsed unit that crops out i n the northwestern portion o f the intrusion (Figure 2.3). This unit (herein referred to as v o l c a n i c wacke) is described by E r d m e r  04ES-00-07-04 £Nd: +1.9 Ar-Ar age (hornblende):| 189.9 +/-1.4Ma U-Pb age (titanite): 190.3 +/-4.6 04ES-09-02-02 ENd: -3.9  04ES-00-07-02 ENd: +1.1 Depositional Age (U-Pb): -300 Ma Max Inheritance: -2100 Ma  A  DDH04-57-12-89.2 ENd: +4.4 U-Pb age (zircon): 185.2 +/- 0.34 Ma  04ES-00-07-01 U-Pb age (zircon): 189.2+/-0.6 Ma  Intrusion Centre: X 58°29'N, 128°52'W  04ES-00-07-03 Ar-Ar age (phlogopite) 189.9+/- 1.3 Ma 05ES-03-01-01 | ENd: +2.3  | Dunite, with minor wehrlite  1  km  | Diorite, quartz diorite, and granodiorite, undivided  Wehrlite, with minor dunite and olivine clinopyroxenite  Hornfels, sedimentary or volcanic protolith  Olivine clinopyroxenite and clinopyroxenite, undivided  Reverse fault, observed  Hornblende clinopyroxenite, with minor clinopyroxenite Hornblendite and clinopyroxene hornblendite, undivided  Normal fault, inferred Fault (relative sense of motion indicated) Neodymium isotope sample locality Geochronological sample locality*  Figure 2.3: Generalized geologic map of the Turnagain intrusion, modified after Clark (1975). Note that some lithological units are composites at this scale. The inset in the upper right corner shows the location of the Turnagain intrusion in British Columbia, as well as other major Alaskan-type intrusions. The main nickeliferous sulphide zones are marked with white ovals (from west to east: Northwest Zone, Horsetrail Zone, Hatzl Zone). The geochronological sample localities are marked as yellow stars and U-Pb and Ar-Ar ages, and initial e d values (for geochronological samples) are indicated as yellow stars. Other whole rock sample localities for Nd isotopic compositions are marked as blue stars. N  et al. (2005) as a "tuffeaceous phyllite w i t h m i n o r w a c k e " and is observed to conformably overlie " R o a d R i v e r " strata. H o w e v e r , Gabrielse (1998) proposed that this metasedimentary unit was separated from " R o a d R i v e r " strata by a fault. A westward extension o f this fault was postulated to merge into the north-bounding and east-bounding faults bounding the Turnagain intrusion, creating a s m a l l nappe. Because o f the inferred ages o f the v o l c a n i c w a c k e and the Turnagain intrusion (both considered to be Late Triassic), Gabrielse (1998) associated this apparently "fault-bounded" package o f rocks w i t h the Quesnel terrane. H o w e v e r , recent geochronological studies o f E r d m e r et al. (2005) indicate that the metasedimentary package, coupled w i t h its conformable nature to the underlying graphitic phyllites, is M i s s i s s i p p i a n i n age. The graphitic phyllite is also observed to be intruded by an E a r l y Jurassic "granodiorite" pluton (Erdmer et al., 2005), a relationship that is not observed i n "bona fide" A n c e s t r a l N o r t h A m e r i c a n lithologies ( J . K . M o r t e n s e n , pers. c o m m . , 2006). A d d i t i o n a l l y , relatively s m a l l (0.520 m) inclusions o f metamorphosed graphitic phyllite (containing graphite, quartz, and pyrrhotite bands) and v o l c a n i c w a c k e are observed in drillcore from the sulphide-mineralized zones w i t h i n the Turnagain intrusion.  2.3 G E O L O G Y O F T H E T U R N A G A I N INTRUSION The 3.5 k m x 8 k m Turnagain Alaskan-type intrusion was the subject o f a P h . D . dissertation by T o m C l a r k (1975) and subsequent publications (Clark, 1978; 1980). It is a crudely zoned mafic-ultramafic pluton that ranges from dunite to a hornblende-rich diorite i n the west-central portion (Figure 2.3). The central dunite is considered to represent the base o f the intrusion, whereas the hornblende-rich central portion o f the intrusion is considered to represent part o f the r o o f zone. Dunite i n the Turnagain intrusion contains M g - r i c h cumulus o l i v i n e (F089-F093) (Chapter 4), disseminated cumulus chromite, m i n o r intercumulus clinopyroxene and rare interstitial phlogopite. L o c a l accumulations o f chromite are observed as thin layers, rare beds, pods, schleiren, and w i s p y concentrations (see Chapter 3). In many A l a s k a n - t y p e intrusions, these chromitites are prospective for platinum-group element mineralization. W e h r l i t e i n the Turnagain intrusion occurs as either o l i v i n e cumulates or olivine-clinopyroxene cumulates (olivine: Fogs to F090). Disseminated sulphide reaches ~0.5 v o l . % i n most lithologies o f the Turnagain intrusion. In the sulphide-mineralized Horsetrail Z o n e (Figure 2.3), both dunite and wehrlite can contain significant abundances o f sulphide (typically 5 v o l . % , but up to 50 locally). O l i v i n e clinopyroxenite is a relatively u n c o m m o n lithology and is t y p i c a l l y an  vol.%  olivine-clinopyroxene cumulate w i t h o l i v i n e compositions ranging from F083 to F089. Hornblende clinopyroxenite w i t h local cumulus magnetite is rarely exposed and is t y p i c a l l y observed i n drillcore from the east-central part o f the intrusion. Hornblende clinopyroxenite is typically composed o f cumulus clinopyroxene and intercumulus amphibole; as such it c o m m o n l y grades into clinopyroxene hornblendite and  vice versa. Hornblendite is a recessive  lithology and is also rarely exposed. A fine-grained (<1 m m ) hornblendite dike, 30 to 50 c m i n w i d t h , i n the northwestern part o f the intrusion (Figure 2.3) contains abundant igneous amphibole (magnesiohastingsite) and accessory titanite. T h e crystallization sequence o f the Turnagain intrusion, from dunite —» wehrlite —• o l i v i n e clinopyroxenite —* hornblende clinopyroxenite —* hornblendite —• diorite, is constrained by cross-cutting and gradational contact relationships, as w e l l as by systematic mineral and w h o l e rock geochemical trends (see Chapter 4). The intrusion is fault-bounded on its northern and eastern margins margins (observed on surface, i n drillcore, and inferred from aeromagnetic data) against graphitic phyllite and on its western and southern margins by v o l c a n i c w a c k e . The entire intrusion is interpreted to represent a s m a l l klippe, however based on the results o f this study and others (Chapters 3 and 4), this k l i p p e was not significantly displaced. The metasedimentary rocks i n the northwest (Figure 2.3) are relatively coarse-grained (-1-2 m m ) compared to similar rocks south o f the Turnagain intrusion (<1 m m ) . T h e metasedimentary inclusion i n the northwest is composed o f hornfelsed v o l c a n i c w a c k e that contains abundant detrital z i r c o n . The v o l c a n i c w a c k e appears to represent an inclusion o f w a l l r o c k w i t h i n the Turnagain intrusion i n contrast to the lower-grade,  finer-grained,  metasediments observed to the south o f the intrusion. T h i s inclusion does not appear to be fault-bounded, but is i n igneous contact w i t h the ultramafic lithologies. S m a l l pods (1-5 c m w i d e ) o f amphibole-bearing t w o - m i c a granite, interpreted as partial melt, were observed by the author i n this inclusion, but not i n the metasedimentary rocks to the south. M e l a n o c r a t i c to leucocratic dioritic rocks i n the Turnagain intrusion have gradational contacts w i t h , or cross-cut, ultramafic rocks and represent the youngest intrusive phases. D i o r i t i c rocks are the o n l y zircon-bearing lithology present i n the Turnagain intrusion. T h e largest diorite occurrence is located i n the central part o f the intrusion (Figure 2.3). The margins o f this pluton are melanocratic (85 v o l . % amphibole, 14 v o l . % plagioclase) and fineto medium-grained (1-5 m m grain sizes), whereas the central part o f the pluton (as observed  from surface exposures) is dominantly composed of plagioclase and quartz. Texturally and mineralogically similar mafic diorite is also observed in drillcore as 4 cm to 1 m-wide dikes that intrude the hornblende-rich central portion of the intrusion and the adjacent dunite to the east. Leucocratic diorite dikes, predominantly composed of plagioclase and quartz, are commonly found cross-cutting the hornblende-bearing lithologies, however these felsic dikes are rarely found cutting ultramafic rocks elsewhere in the intrusion.  2.4 S A M P L E D E S C R I P T I O N S A N D A N A L Y T I C A L T E C H N I Q U E S 2.4.1 U-Pb Zircon/Titanite  Four samples were selected for U-Pb geochronology (see sample locations on Figure 2.3). Zircon (ZrSi0 ) was separated from three samples (04ES-00-07-01, DDH04-57-12, 04ES-004  07-02) and titanite (CaTiSi0 ) from a fourth sample (04ES-00-07-04). Sample 04ES-00-07-01 5  is a green-black, medium-grained diorite with relatively abundant (10-15 vol.%) large plagioclase crystals (subsequently referred to as mela-diorite) and occurs at the north-central margin of the large felsic body. At this location no ultramafic inclusions in the diorite were observed, however a similar lithology intersected in NQ drillcore in the north-central part of the intrusion locally contains abundant (10-70 vol.%) ultramafic xenoliths. Sample DDH0457-12 is a green-and-white, coarse-grained hornblende diorite with 20 vol.% euhedral amphibole (3 cm long), and 1 cm-wide euhedral plagioclase (subsequently referred to as leucodiorite). The sample was obtained from NQ drillcore from the west-central part of the Turnagain intrusion (see Figure 4.6: G,H, Chapter 4). The interval from which this sample was taken is gradational into hornblendite over a distance of 10 cm. Sample 04ES-00-07-02 is a hornfelsed volcanic wacke (epidote + plagioclase ± amphibole ± biotite ± quartz) from the northwestern part of the intrusion, and based on contact relationships (intruded by hornblendite) and degree of metamorphism (the mineral assemblage is indicative of epidoteamphibole hornfels facies) it is interpreted to represent an inclusion of wallrock. Sample 04ES-00-07-04 is a black, fine-grained equigranular hornblendite dike (-30 cm wide) that contains accessory titanite (1-2 vol.%), abundant wall-rock inclusions, and intruded rocks equivalent to the previous sample (volcanic wacke) (Figure 2.3). The morphologies of some of the zircon and titanite separates are exhibited in Figure 2.4. All sample preparation, geochemical separation and mass spectrometry were done at the Pacific Centre for Isotopic and Geochemical Research in the Department of Earth and 21  Figure 2.4: Photomicrographs of zircon and titanite separates from the Turnagain intrusion. The scale bar in each photo is 200 um. A) Mela-diorite (04ES-00-07-01); large, clear, broken grains, one of which is fraction F. B) Mela-diorite (04ES-00-07-01), fraction A; large equant, slightly elongate zircon grains. Note their similar size. C) Mela-diorite (04ES-00-07-01), fraction D; large zircon laths, some with minute inclusions. D) Leuco-diorite (DDH04-57-12),fractionH; slightly rounded, broken, prismatic grains of medium size. E) Volcanic wacke (04ES-00-07-02),fractionsD, F, G (pre-separation); intermediate zircon laths, clear and relatively inclusion-free. F) Hornblendite (04ES-00-07-04); colourless to slightly yellow titanite grains.  22  O c e a n Sciences, U n i v e r s i t y o f B r i t i s h C o l u m b i a . Z i r c o n and titanite were separated from the rocks using conventional crushing, grinding, and W i l f l e y table techniques. F i n a l concentration incorporated the use o f heavy liquids and a magnetic separator. Z i r c o n and titanite fractions were selected for analysis based on magnetic susceptibility, grain quality, size, and m o r p h o l o g y . U s i n g the technique o f K r o g h (1982), a l l z i r c o n fractions were air-abraded p r i o r to dissolution to m i n i m i z e the effects o f post-crystallization Pb-loss. Titanite grains were dissolved on a hotplate i n 7 m L screwtop P F A beakers for at least 48 hours at ~ 1 3 0 ° C . Z i r c o n grains were dissolved i n sub-boiled 4 8 % H F and 14 M H N O 3 (ratio o f - 1 0 : 1 , respectively) i n the presence o f a m i x e d  2 3 3  -  2 3 5  tj-  2 0 5  P b tracer for 40 hours at 2 4 0 ° C i n 300 u L P T F E or P F A  microcapsules contained i n high-pressure vessels ( P a r r ™ a c i d digestion vessels w i t h 125 m L P T F E liners). Sample solutions were then dried to salts at ~ 1 3 0 ° C . Z i r c o n residues were redissolved i n - 1 0 0 u L o f sub-boiled 3.1 M H C I for 12 hours at 2 1 0 ° C i n high-pressure vessels and titanite residues were redissolved on a hotplate i n - 1 m L o f sub-boiled 6.2 M H C I i n the same 7 m L screwtop P F A beakers for at least 24 hours at ~ 1 3 0 ° C . Titanite solutions were again dried to salts and were again redissolved on a hotplate, i n the same beakers, in 1 m L o f sub-boiled 3.1 M H C I at ~ 1 3 0 ° C for at least 24 hours. F o r z i r c o n fractions o f about 10 ug or less, 3.1 M H C I was transferred to 7 m L P F A beakers, dried to a small droplet after addition o f 2 u L o f 1 M phosphoric acid (H3PO4), and loaded directly onto R e filaments for analysis, as described b e l o w (referred to as the "no chemistry" method). F o r larger fractions o f both minerals, separation and purification o f P b and U e m p l o y e d i o n exchange c o l u m n techniques modified slightly from those described by Parrish et al. (1987). P b and U were sequentially, eluted into a single beaker; U from titanite solutions was purified by passing through columns a second time. Elutants were dried i n 7 m L screwtop P F A beakers on a hotplate at ~ 1 2 0 ° C i n the presence o f 2 u L o f ultrapure 1 M H3PO4. Samples were then loaded on single, degassed zone-refined R e filaments in 5 u L o f a s i l i c a gel ( S i C l ) phosphoric acid 4  emitter. Isotopic ratios were measured using a modified single collector V G - 5 4 R thermal ionization mass spectrometer equipped w i t h an analogue D a l y photomultiplier. Measurements were done i n peak-switching mode on the D a l y detector. A n a l y t i c a l blanks were <1 p g for U and for 1-3 p g P b for the "no chemistry" fractions. F o r dissolved z i r c o n and titanite that passed through ion exchange columns, a blank o f 2-10 p g P b was used. P b isotopic ratios were corrected for fractionation o f 0.32-0.37 % / a m u , based on replicate analyses o f the N B S - 9 8 2 P b standard reference material and the values recommended b y T h i r l w a l l (2000), and U  23  fractionation was determined directly on individual runs using the  " U tracer. Reported  precisions for Pb/U and Pb/Pb dates were determined by numerically propagating all analytical uncertainties through the entire age calculation using the technique of Roddick (1987). Standard concordia diagrams were constructed and regression intercepts calculated with Isoplot 3.09 (Ludwig, 2003). Unless otherwise noted, all errors are quoted at the 2a level. 2.4.2 Ar-Ar Phlogopite/Amphibole Two samples (04ES-00-07-03, 04ES-00-07-04) were selected for Ar-Ar geochronology. Sample 04ES-00-07-03, a black, medium-grained wehrlite located in the far southeastern corner of the Turnagain intrusion (Figure 2.3), was chosen because it contained 1-2 vol.% interstitial phlogopite. Amphibole was separated from sample 04ES-00-07-04, the hornblendite dike described above. The samples were crushed using a steel jaw crusher and sieved to obtain fragments ranging in size from 0.25 to 1.0 mm. The sieved fractions were washed in deionized water and then air-dried at room temperature after magnetite and metallic crusher fragments were removed with a hand magnet. The amphibole and phlogopite separates were hand-picked using a binocular microscope, wrapped in aluminum foil and stacked in an irradiation capsule with similar-aged samples, neutron flux monitors (Fish Canyon Tuff sanidine, 28.02 Ma; Renne et ah, 1998), optical grade CaF2 and potassium glass. The samples were irradiated with cadmium shielding on April 25-27, 2005 at the McMaster Nuclear Reactor in Hamilton, Ontario, for 84 M W H , with a neutron flux of approximately 3 x l 0  16  neutrons/cm . Total fusion analyses (n=72) of 21 neutron flux monitor positions produced errors of <0.5% in the J value. The samples were analyzed on June 3 and 6, 2005, at the Pacific Centre for Isotopic and Geochemical Research, University of British Columbia. Using a defocused beam of a 10W CO2 laser (New Wave Research MIR10), the mineral separates were step-heated at incrementally higher powers until fused. A VG5400 mass spectrometer, equipped with an ion-counting electron multiplier, analyzed the gas evolved from each step. A l l measurements were corrected for mass discrimination, mass spectrometer sensitivity, total system blank, radioactive decay during and subsequent to irradiation, and interfering Ar from atmospheric contamination and the irradiation of Ca, CI and K. Isotope production ratios were: ( Ar/ Ar) =0.0005±0.00006, ( Ar/ Ar) =l048±0.9, ( Ar/ Ar) =0.3542±0.0008, 40  39  37  K  39  36  Ca  Ca/K= 1.83±0.01 ( A r / A r ) . 37  39  Ca  K  39  Ca  The plateau and correlation ages were calculated using Isoplot 3.09 ( L u d w i g , 2003). Errors are quoted at the 2 a ( 9 5 % confidence) level and are propagated from a l l sources except mass spectrometer sensitivity and age o f the flux monitor. The best statistically-justified plateau and plateau ages for both samples were p i c k e d based on the f o l l o w i n g criteria: (1) three or more contiguous steps c o m p r i s i n g more than 5 0 % o f the  3 9  A r ; (2) a probability o f fit  o f the weighted mean age greater than 5%; (3) a slope o f the error-weighted line through the plateau ages equals zero at 5 % confidence; (4) the ages o f the t w o outermost steps o n a plateau are not significantly different from the weighted-mean plateau age (at 1.8a six or more steps o n l y ) ; and (5) the outermost t w o steps on either side o f a plateau must not have non-zero slopes w i t h the same sign (at 1.8a nine or more steps only).  2.4.3 Neodymium Isotopes A total o f eight samples were selected for n e o d y m i u m isotopic c o m p o s i t i o n measurements and were chosen to reflect the lithological range o f the Turnagain intrusion. Dunites were excluded from analysis due to their extremely l o w N d concentrations (<0.1-0.4 p p m ) . S a m a r i u m and n e o d y m i u m concentrations, as w e l l as major elements and other incompatible trace elements, were determined by I C P - M S at A c t i v a t i o n Laboratories L t d . (Actlabs) i n Ancaster, Ontario (see complete analytical techniques description i n Chapter 4). T h e accuracy o f the suite o f elements analyzed was determined by the use o f U S G S reference materials ranging i n composition from basalt to granite and by various in-house standard materials. R e l a t i v e standard deviations from three duplicated analyses are typically less than 5 % for most elements. L o w concentrations o f S m and N d i n one duplicate (sample 0 5 E S - 0 5 - 0 6 - 0 1 , a hornblende clinopyroxenite) resulted i n higher standard deviations; however w h e n concentrations o f S m and N d are an order o f magnitude higher than their respective detection limits (04ES-00-07-04) the standard deviation drops to b e l o w 5 % relative. The N d isotopic compositions o f samples from the Turnagain intrusion were measured at the Pacific Centre for Isotopic and G e o c h e m i c a l Research, U n i v e r s i t y o f B r i t i s h C o l u m b i a . The v o l c a n i c w a c k e and leuco-diorite samples ( 0 4 E S - 0 0 - 0 7 - 0 2 and D D H 0 4 - 5 7 - 1 2 , respectively) were digested i n T e f l o n bombs enclosed i n metallic bombs (modified K r o g h design) and placed for 120 hrs i n H F - H N O 3 - H C I O 4 (7:1:1) and 24 hrs i n H C I i n an o v e n at 190°C. A l l other samples were dissolved i n Savillex™ and subject to the above digestion procedure. T h e N d isotopic ratios were measured using a T h e r m o F i n n i g a n T r i t o n - T I thermal  ionization mass spectrometer ( T I M S ) i n static mode w i t h relay matrix rotation. The measured composition o f each sample is the average o f 125-130 separate analyses. The L a J o l l a N d standard was measured once g i v i n g a value o f  1 4 3  Nd  / 1 4 4  N d = 0.511858 ± 0.000008 (2a) and the  Rennes N d standard was measured 48 times w i t h i n one week g i v i n g a mean value o f 1 4 3  Nd  / 1 4 4  N d = 0.511960 ± 0.000008 (2a). T h e N d isotopic compositions o f procedural  duplicates o f three samples (04ES-09-02-02, 0 5 E S - 0 5 - 0 6 - 0 2 , 04ES-00-07-02) are w i t h i n the 2 a error (less than 0 . 0 0 1 % relative). A l l measurements were corrected using  1 4 6  Nd  / 1 4 4  Nd =  0.7219 for internal mass fractionation. The U S G S G S P - 2 reference material was also analyzed for its N d isotopic composition, and the results are w i t h i n the 2 a analytical error o f previously reported results ( W e i s et al., 2006).  2.5 RESULTS Three dates from two ultramafic samples (wehrlite and hornblendite) were obtained from the Turnagain intrusion using A r - A r and U - P b geochronological techniques. The two A r - A r samples are from opposite corners o f the intrusion (~8 k m apart) (Figure 2.3). A d d i t i o n a l U - P b (zircon) dates were determined from a mela-diorite, a leuco-diorite, and the hosted v o l c a n i c wacke i n c l u s i o n . N e o d y m i u m isotopic compositions were analyzed from the three geochronological samples, and five additional ultramafic samples.  2.5.1 U-Pb Geochronology 2.5.1.1 04ES-00-07-01 - M e l a - d i o r i t e T h e mela-diorite was sampled from the north-central m a r g i n o f the large dioritic body that intruded, and/or is gradational w i t h , the central part o f the Turnagain intrusion (Figure 2.3). The m a r g i n o f the diorite is hornblende-rich, l o c a l l y resembling hornblendite elsewhere i n the Turnagain intrusion. H o w e v e r , this hornblende-rich outer phase grades i n w a r d l y to a more felsic diorite over a distance o f - 1 0 0 m on surface. The presence o f euhedral (cumulus) plagioclase (~1 c m i n diameter) helps discriminate this lithology from feldspathic hornblendite elsewhere i n the Turnagain intrusion. The least magnetic fraction o f sample 04ES-00-07-01 yielded abundant (>500) z i r c o n grains t y p i c a l l y 150-250 u m i n length. T h e z i r c o n grains exhibit either equant (3:1 to 2:1) (Figure 2 . 4 B ) or lath (length/width 6:1 to 4:1) (Figure 2 . 4 C ) morphology and range i n colour from clear to pale y e l l o w . A distinct population o f grains exhibit inherited cores (not analyzed), some o f w h i c h are metamict. E a c h analyzed fraction  contained 2-18 grains w i t h the exception o f Fraction F (Figure 2 . 4 A ) , w h i c h is represented b y a single grain o f z i r c o n . U r a n i u m concentrations range from 123-283 p p m and T h / U ratios from 0.32 to 0.79 (Table 2.1). T h e U - P b data from the analyzed fractions y i e l d similar 206  p b /  238  T J  a g e s >  r  a  n  g  i  n  g  f  r o m  1 8 6 . 3 ± 0 . 4 M a to 1 8 9 . 2 ± 0 . 6 M a , the latter o f w h i c h (Fraction B ,  seven 75-100 p m equant grains) has the highest  2 0 6  Pb/  2 3 8  U and  2 0 7  Pb/  2 3 5  U and is interpreted to  be the m i n i m u m age o f crystallization o f the mela-diorite. E a c h o f the error ellipses (2a) for each o f the five fractions overlap concordia (Figure 2.5 A ) , however their distribution suggests that z i r c o n from a l l fractions may have undergone Pb-loss. A free-fit discordia line through a l l fractions ( M S W D =0.17) yields an upper intercept w i t h concordia o f 1 9 0 . 5 ± 6 . 6 M a (and a p o o r l y constrained lower intercept o f 7 0 5 ± 2 5 0 0 M a ) (Figure 2 . 5 A ) . A l t e r n a t i v e l y , a fixed regression (lower intercept at 0 M a ) yields an older upper intercept o f 1 9 9 . 2 ± 6 . 6 M a . N e i t h e r the upper intercept age o f 190.5 +6.6/-1.9 M a from the free-fit regression (lower error c o m b i n e d w i t h the error o f the oldest fraction), nor the fixed regression age o f 1 9 9 . 2 ± 6 . 6 M a are considered to represent the true crystallization age o f the mela-diorite, because the calculated upper intercept ages have relatively large 2 a errors due to the relatively small dispersion o f points along the fitted discordia lines. The better constrained m i n i m u m age o f 1 8 9 . 2 ± 0 . 6 M a o f fraction B is interpreted to be the m i n i m u m age o f the Turnagain intrusion. These results are consistent w i t h the A r - A r geochronological results (see below).  2.5.1.2 D D H 0 4 - 5 7 - 1 2 - Leuco-diorite T h i s sample, taken from a drillhole i n the south-central portion o f the intrusion (Figure 2.3), is a coarse-grained leucocratic hornblende diorite composed o f euhedral, cumulus plagioclase and amphibole. M u l t i p l e 10-50 c m - w i d e lithological variations were observed i n drillcore along the 9 m-thick interval (e.g. amphibole-rich phases, quartz-rich phases). F e w e r than 200 z i r c o n grains, 20-200 p m in length, were present i n the least magnetic fraction. B r o k e n lath (length/width 2:1 to 1.5:1) and some intact lath (length/width 4:1 to 3:1) morphologies are exhibited by most z i r c o n grains, and a l l grains are generally colourless (Figure 2.4). O f the four fractions analyzed, two were single grains (Fractions B and F ) , whereas fractions E and H (Figure 2 . 4 D ) contained 2 and 7 grains, respectively. U r a n i u m concentrations range from 183582 p p m and T h / U ratios range from 0.17 to 0.39 (Table 2.1). T h e U - P b data from the four analyzed fractions are concordant and y i e l d similar  Pb/  U dates from 1 8 3 . 6 ± 0 . 6 to  Table 2.1: U-Pb TIMS analytical data from zircon and titanite grains separated from samples from the Turnagain intrusion  Fraction  1  Wt U Pb* Pb (mg) (ppm) (ppm) Pb 2  3  206  4  204  Pb Th/U (pg) 5  6  Isotopic ratios (1CT,%) Pb/ U Pb/ Pb 7  206  Pb/ U 238  207  235  207  Apparent ages (2o,Ma) «Pb/ U Pb/ U Pb/ Pb 7  206  2  238  207  235  207  206  discordance to origin (%)  04ES-00-07-01 - mela-diorite  A, 2 B, 7 C, 18 D, 5 F, 1  35 32 38 19 41  229 145 123 254 283  4179 1557 3324 2207 1580  3.5 5.5 3.1 4.0 13.6  0.41 0.28 0.40 0.79 0.32  0.02946 (0.08) 0.02979(0.17) 0.02965 (0.11) 0.02932 (0.11) 0.02961 (0.14)  0.2036 (0.24) 0.2058 (0.63) 0.2045 (0.34) 0.2029 (0.42) 0.2038 (0.57)  0.05011 (0.21) 0.05012 (0.58) 0.05002 (0.31) 0.05020 (0.38) 0.04992 (0.53)  187.2 (0.3) 189.2 (0.6) 188.4 (0.4) 186.3 (0.4) 188.1 (0.5)  188.1 (0.8) 190.1 (2.2) 188.9 (1.2) 187.6(1.4) 188.3(2.0)  200.2 (9.5) 201 (27) 196 (14) 204(18) 191 (24/25)  6.6 5.7 4.0 8.9 1.7  1248 379 422 1520  2.4 4.1 13.9 11.9  0.17 0.30 0.26 0.39  0.02890 (0.16) 0.02921 (0.32) 0.02911 (0.17) 0.02915(0.09)  0.1984 (0.72) 0.2022 (2.20) 0.1998 (1.94) 0.2004 (0.23)  0.04979 (0.67) 0.05020 (2.1) 0.04979(1.86) 0.04986 (0.18)  183.6 (0.6) 185.6(1.2) 185.0(0.6) 185.2 (0.3)  183.7(2.4) 187.0 (7.5) 185.0(6.6) 185.5(0.8)  185 (31/32) 204 (93/98) 185(84/89) 188.4 (8.3)  0.8 9.3 0.0 1.7  45.4 112 46.4 97.2  3.90 3.20  0.02983 (1.75) 0.03009 (1.68)  0.2108 (7.2) 0.2163 (7.61)  0.05124(6.32) 0.05216 (6.77)  189.5(6.6) 191.1 (6.3)  194(25) 199 (28)  252 (267/320) 292 (283/343)  25.0 35.1  62.4 23000 4.0 11.2 5004 4.0 14.6 580 7.5 15.6 891 3.5 1316 6.1 16.9 364 11.6 5.5 776 4.2 13.1 11.2 539 13.9  0.35 0.31 0.51 0.34 0.46 0.40 0.41 0.37  0.29220 (0.11) 0.07265 (0.16) 0.07845 (0.30) 0.03863 (0.20) 0.06179 (0.22) 0.04786 (0.21) 0.04750 (0.26) 0.08063 (0.19)  5.2136 (0.15) 0.7948 (0.18) 0.9486 (0.50) 0.2805 (0.80) 0.6855 (0.32) 0.3450 (2.29) 0.3533 (0.26) 1.3242 (0.62)  0.12941 (0.07) 0.07935 (0.16) 0.07845 (0.30) 0.03863 (0.20) 0.08046 (0.24) 0.05228(2.18) 0.05395 (1.17) 0.11911 (0.54)  1652.5 (3.3) 452.1 (1.4) 486.9 (2.8) 244.4 (1.0) 386.5 (1.6) 301.4 (1.2) 299.1 (1.5) 499.9(1.9)  1854.5(2.5) 593.9(1.6) 677.4 (5.0) 251.0(3.5) 530.1 (2.7) 301 (12) 307.2 (6.7) 856.4 (7.2)  2089.9 (2.5) 1180.9(6.2) 1375.7 (16.3) 314 (33/34) 1208.2 (9.4) 298(97/103) 369 (52/54) 1943 (19)  23.7 63.9 67.0 22.6 70.0 -1.3 19.3 77.1  6.8 4.2 3.7 8.3 8.3  DDH04-57-12-89 - leuco-diorite  B*, 1 E*, 2 F, 1 H, 7  9 3 14 17  183 276 213 582  5.0 7.9 6.0 17.2  04ESOO-07-04 - hornblendite dike  T1.20 T2, 20  188 156  8.7 9.4  0.5 0.5  04ES-00-07-02 - volcanic wacke  A, 2 B, 5 C, 5 D, 3 E, 12 F, 2 G*, 5 H,4  1  2  3  4  5  6  7  25 30 5 13 8 12 4 11  202 152 175 97.1 260 113 271 132  All zircon grains selected for analysis were air-abraded prior to dissolution. Fraction ID (capital letter) followed by the number of grains: T1,12 for titanite fractions. Asterisk after fraction name signifies no chemistry samples. U blank correction of 1 pf ± 20%; U fractionation corrections were measured for each run with a double u - U spike. Radiogenic Pb. Measured ratio corrected for spike and Pb fractionation of 0.0028-0.0033/Amu ± 20% (Daly collector), which was determined by repeated analysis of NBS 982 Pb standard reference material throughout the course of this study. Total common Pb in analysis based on blank isotopic composition. Model Th/U derived from radiogenic Pb and the Pb/ Pb age of fraction. Blank and common Pb corrected; Pb procedural blanks were -2 pg (zircon), 14 pg (titanite) and U, 1 pg for zircon and titanite. Common Pb compositions are based on Stacey-Kramer model Pb at the interpreted age or the Pb/'^Pb age of the rock (Stacy and Kramers, 1975). 233  208  207  206  235  0.199  0.201  0.203  0.205  207  0.19  p  b  /  23  0.20  0.207 5  0.209  u  0.21  0.22  °W U  2  35  Figure 2.5: Concordia plots for U-Pb datafromanalyzed zirconfractionsfor diorite samplesfromthe Turnagain intrusion. Each ellipse (2CT error) represents the analysis of a single fraction; all fractions are labelled. A) Sample 04ES-00-07-01, a mela-diorite proximal to the ultramafic lithologies in the centre of the intrusion. B) Sample DDH04-57-12, leuco-diorite, sampled from a plagioclase-rich horizon in the hornblende-rich central region of the Turnagain intrusion. The shaded gray band is the decay constant error envelope of the concordia curve.  1 8 5 . 6 ± 1 . 2 M a . The age o f the oldest fraction (fraction H , 1 8 5 . 6 ± 1 . 2 M a ) , is interpreted as the m i n i m u m age o f crystallization o f the leuco-diorite (Figure 2 . 5 B ) .  2.5.1.3 0 4 E S - 0 0 - 0 7 - 0 2 - V o l c a n i c W a c k e T o constrain the age o f the host rocks, the v o l c a n i c wacke was sampled from the hornfelsed sedimentary unit i n the northwestern portion o f the intrusion (Figure 2.3), w i t h i n 50 m o f the hornblendite dike (04ES-00-07-04). Z i r c o n i n the least magnetic fraction is relatively abundant (>300 grains) and ranges i n colour from colourless to pale y e l l o w to dark red-brown. Three distinct z i r c o n morphologies are present i n this sample: (1) large lath-shaped fragments (aspect ratio 1.5:1), some >200 urn w i d e , (2) smaller laths ( - 2 0 0 um l o n g , aspect ratio o f 4:1) (Figure 2.4E) c o m m o n l y containing fluid inclusions and inherited cores, and (3) sub-equant grains (aspect ratio 2:1) ranging from <50 u m to - 2 0 0 u m i n diameter, the largest o f w h i c h are c o m m o n l y dark i n colour. A total o f eight fractions were analyzed c o m p r i s i n g 2-12 z i r c o n grains per fraction. U r a n i u m concentrations range from 97-260 p p m , w i t h a range o f T h / U ratios between 0.31 and 0.51 (Table 2.1). The U - P b data from these analyzed fractions y i e l d an extremely large range o f  Pb/  U dates (244 M a to 1652 M a , Figure 2 . 6 A ) . T h e results from  two fractions (F and G ) plot o n or near concordia at - 3 0 0 M a . F r a c t i o n F is concordant w i t h a 206  p b /  238  u  a  g  e  o f  3oi.4±i.2 M a (Figure 2 . 6 B ) , w h i c h is interpreted to be the m a x i m u m  depositional age o f the v o l c a n i c w a c k e . Fraction D has a significantly younger  Pb/  U age  (244 M a ) and is discordant, w h i c h is attributed to Pb-loss from - 3 0 0 M a . F r a c t i o n A (not shown on Figure 2.6) is h i g h l y discordant w i t h a age o f - 2 0 9 0 M a . T h e o l d  2 0 7  Pb/  2 0 6  2 0 6  Pb/  2 3 8  U age o f 1652 M a and a  2 0 7  Pb/  2 0 6  Pb  P b ages o f fractions A , B , C , and E indicate the presence o f  E a r l y Proterozoic z i r c o n grains i n the source o f the v o l c a n i c w a c k e . A regression line through the discordant and concordant grains (not i n c l u d i n g fraction D ) has an upper intercept w i t h concordia o f - 2 1 0 0 M a , w h i c h is considered to be the average age o f inheritance in the analyzed fractions.  2.5.1.4 0 4 E S - 0 0 - 0 7 - 0 4 - Hornblendite The fine-grained hornblendite was sampled from a 30 c m - w i d e dike that intrudes the v o l c a n i c wacke i n the northwestern part o f the Turnagain intrusion discussed above (Figure 2.3). T h e heavy mineral separate y i e l d e d abundant (>100 grains) colourless to pale y e l l o w to pale b r o w n titanite grains (Figure 2.4F). M o s t grains are anhedral and equant, w i t h an aspect ratio o f - 1 : 1 .  i  1  1  • T  T  •A  r  i  „  500  '  £  [-  C  y'  o  0.075  to  1  1  1  yi  0.085 r  00 CO CM  1  B 400  0.065  /  1  1  1  to 2100 Ma . <=>  H  /  /  -  E 0.055  300  CM  1/  -  ;  1 Fig. 2.6B  0.045  /D  0.035  200  04ES-00-07-02 volcanic wacke  /  0.025 0.0  0.2  0.4  0.6 207  0.0482  B  0.8 P  B  /  1.0  23  5  1.2  1.4  1.6  U  04ES-00-07-02 Volcanic Wacke  0.0480  0.0478 00 CO CM  ^  0.0476  Q_  to o N  0.0474  0.0472  0.0470 0.32  0.33  0.34  0.35  0.36  0.37  »W U  2  35  Figure 2.6: Concordia plots for U-Pb datafromanalyzed zirconfractionsfroma volcanic wacke samplefromthe northwestern part of the Turnagain intrusion (04ES-00-07-02). Allfractionsare labelled. A) All analyzed zircon grains exceptfractionA (7fractions,n=36 grains). The discordia line has a lower intercept of -300 Ma and an upper intercept of -2.1 Ga. B) Expanded view showing the concordant to nearly concordant results at -300 Ma (fractions F and G). The shaded gray band is the decay constant error envelope of the concordia curve.  B o t h o f the analyzed fractions contained 20 titanite grains each. U contents range from 7 to 9.4 ppm, w i t h T h / U ratios o f ~3.9 (Table 2.1). T h e U - P b data o f the t w o titanite fractions are concordant and the  z u o  P b / " ° U ages are 189.5 M a and 191.1 M a , respectively. The weighted  mean o f these two concordant and statistically identical results is 190.3 ± 4.6 M a (Figure 2.7), w h i c h is interpreted to represent the m i n i m u m crystallization age o f the hornblendite w h e n the rock c o o l e d through the closure temperature to P b diffusion i n titanite (see D i s c u s s i o n ) .  2.5.2 A r - A r Geochronology 2.5.2.1 0 4 E S - 0 0 - 0 7 - 0 4 - Hornblendite T h i s sample, also dated by the U - P b (titanite) method as documented above, y i e l d e d abundant, dark b r o w n to black, l o w - K ( C a / K =10-32), amphibole crystals. The amount o f  4 0  A r is  extremely h i g h i n the grain edge (up to 9 4 % ) , however the range i n A r i n the core o f the 4 0  grain is small (1.6-4.2%) (Table 2.2). The first eight heating steps (155 M a to 1279 M a , 6% o f total A r released) y i e l d a distorted initial age spectrum, however a well-defined plateau ( 1 8 9 . 3 ± 1 . 4 M a ) is observed for the remainder o f the heating steps ( 9 4 % o f all A r released) (Figure 2 . 8 A ) . A similar total gas age o f 1 9 0 . 1 ± 1 . 4 M a was also obtained. T h e inverse isochron age is 1 9 0 . 7 ± 2 . 3 M a ( M S W D =0.14) (Figure 2 . 8 B ) . T h e A r - A r results for this amphibole separate are consistent w i t h the U - P b (titanite) age o f 1 9 0 . 3 ± 4 . 6 M a . The plateau age obtained above is considered to represent the m i n i m u m age o f the hornblendite dike w h e n the rock c o o l e d through the closure temperature to A r diffusion i n hornblende (see Discussion).  2.5.2.2 0 4 E S - 0 0 - 0 7 - 0 3 - Wehrlite T h i s sample comes from an outcrop i n the far southeastern part o f the Turnagain intrusion, i n the southern portion o f the H a t z l Z o n e (Figure 2.3). A l t h o u g h phlogopite is not abundant i n this sample (<2 v o l . % ) , there were sufficient grains for A r - A r analysis. Phlogopite from this sample, w h i c h has h i g h - K interiors ( C a / K between 0.2-2), displays a large range i n A r (3.44 0  94.9%) relative to 0 4 E S - 0 0 - 0 7 - 0 4 (Table 2.2), but the flat plateau step analyses have a smaller range i n A r (3.7-48.9%). T h e age range i n this sample is somewhat smaller than the previous 4 0  sample (36-220 M a ) , w i t h a younger total gas age o f 181±1 M a . T h e plateau age o f 1 8 9 . 9 ± 1 . 3 M a (Figure 2 . 8 C ) , w h i c h represents 5 6 % o f all argon released during step heating analysis, is i n agreement w i t h the inverse isochron age o f 1 9 0 . 2 ± 1 . 8 M a ( M S W D =1.17, F i g u r e 2 . 8 D ) .  0.16  0.18  0.20 207  0.22  Pb/  235  0.24  0.26  U  Figure 2.7: Concordia plot for U-Pb datafromanalyzed titanitefractionsseparatedfroma hornblendite dike (04ES-00-07-04) in the northwestern region of the Turnagain intrusion. Each ellipse (2a error) represents the analysis of a singlefraction.The resultsfromthe two analyzedfractionsare concordant and nearly identical and the age is calculatedfromthe weighted mean of their Pb/ U ages. The shaded gray band is the decay constant error envelope of the concordia curve. 206  238  Table 2.2: 40Ar/39Ar step-heating results of mineral separates from ultramafic rocks of the Turnagain intrusion Laser Power (%)  <u  Ar/"Ar  2<T  "Ar/^Ar  2a  "Ar/"Ar  2o  "ArfAr  0.081 0.099 0.049 0.073 0.066 0.046 0.046 0.040 0.039 0.056 0.062 0.207  0.736 0.277 0.122 0.070 0.034 0.028 0.022 0.019 0.019 0.025 0.074 0.120  0.034 0.022 0.022 0.030 0.040 0.024 0.029 0.023 0.031 0.028 0.020 0.054  0.546 0.064 0.037 0.019 0.007 0.003 0.005 0.002 0.002 0.002 0.007 0.013  0.036 0.036 0.038 0.055 0.085 0.064 0.067 0.097 0.088 0.219 0.152 0.245  0.080 0.137 0.112 0.223 0.199 0.477 0.106 0.102 0.098 0.030 0.043 0.036 0.034 0.043 0.033 0.058  2.692 2.625 2.984 2.069 1.794 1.414 1.220 1.762 3.645 3.316 3.832 3.520 3.346 3.146 3.262 3.459  0.069 0.059 0.060 0.056 0.035 0.039 0.030 0.021 0.018 0.019 0.015 0.016 0.015 0.015 0.016 0.015  5.916 2.140 0.812 0.304 0.190 0.133 0.091 0.051 0.019 0.007 0.005 0.004 0.004 0.004 0.004 0.005  0.059 0.051 0.069 0.086 0.069 0.055 0.038 0.052 0.083 0.067 0.105 0.053 0.106 0.079 0.095 0.120  2o  ""ArV'Ar  2o-  8.559 2.121 3.852 5.897 11.413 11.664 11.603 11.586 12.294 13.025 12.445 13.599  5.177 0.652 0.427 0.322 0.251 0.199 0.123 0.070 0.073 0.142 0.336 0.934  107.792 41.445 73.620 22.806 25.934 10.879 10.938 7.627 7.632 3.653 12.213 2.122 10.733 0.967 9.376 0.788 10.787 0.488 11.490 0.252 11.522 0.194 11.589 0.157 11.560 0.175 11.650 0.151 11.652 0.170 11.610 0.188  '/cTAr*  Age (Ma)  2o  Ca/K  Cl/K  f Ar  94.91 89.74 73.78 48.87 14.52 7.40 10.83 3.73 3.41 3.85 14.23 21.21  142.2 36.3 65.4 99.1 187.2 191.1 190.1 189.9 200.8 212.1 203.2 220.9  82.7 11.0 7.1 5.3 3.9 3.1 1.9 1.1 1.1 2.2 5.2 14.3  7.40 2.78 1.22 0.700 0.343 0.284 0.218 0.194 0.195 0.258 0.754 1.22  0.001 0 0 0 0 0 0 0 0 0 0 0  0.46 2.89 4.49 3.95 9.38 10.96 11.84 24.26 19.59 7.89 3.27 1.02  94.15 89.50 90.16 89.00 87.87 75.96 71.05 60.77 30.28 10.22 4.20 3.04 2.67 1.85 1.63 3.55  1279 962.5 400.2 179.7 127.2 199.5 176.5 155.1 177.3 188.3 188.8 189.8 189.4 190.8 190.8 190.2  352.3 223.8 150.5 119.3 58.8 32.8 15.2 12.5 7.7 3.9 3.0 2.4 2.7 2.3 2.7 2.9  23.8 23.2 26.4 18.3 15.9 12.5 10.8 15.6 32.3 29.4 33.6 30.9 29.3 27.6 28.6 30.3  0.01 0.016 0.006 0.003 0.001 -0.003 0 0 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001  0.06 0.09 0.16 0.26 0.44 0.55 0.8 1.15 2.64 14.32 9.35 15.5 14.04 16.28 15.93 8.44  a 3  04ES-00-07-03 - wehrlite (phlogopite separate)  J = 0.009579±0.000012 Volume ' ArK = 681.36 Integrated Date = 181.08±0.99 3  167.703 20.646 14.667 11.511 13.320 12.567 12.982 12.007 12.698 13.514 14.475 17.217  2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.5 3.6 3.8 4.1  0.020 0.012 0.013 0.012 0.015 0.016 0.006 0.005 0.005 0.006 0.008 0.012  0.122 0.027 0.021 0.018 0.014 0.013 0.014 0.013 0.013 0.012 0.014 0.015  04ES-00-07-04 - hornblendite (amphibole separate) J = 0.009575±0.000012 Volume ArK = 510.3 Integrated Date = 190.92±1.36 Ja  1833.924 697.442 262.083 99.042 62.693 50.628 36.948 23.810 15.387 12.730 11.959 11.887 11.814 11.809 11.783 11.973  2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4 4.3 4.6 4.9 5.2 5.8  0.054 0.038 0.054 0.019 0.027 0.015 0.016 0.011 0.011 0.017 0.009 0.012 0.010 0.011 0.012 0.008  1.161 0.481 0.190 0.085 0.055 0.026 0.032 0.026 0.020 0.019 0.018 0.018 0.018 0.017 0.018 0.018  Measured values of A r / " A r , °Ar/ Ar, "Arl"Ar, and ™ArV°Ar are shown for each increment of step-heating. All errors are absolute 'Indicates atmospheric argon Volumes are 1E-13 c m NPT ,u  J  J  4^  33  400 i  0.0005  i  1  2  <  200  1  1  1  1  1  1  1  1  r  0.0004  300 (0  1  Amphibole 04ES-00-07-04: Hornblendite dike  Amphibole 04ES-00-07-04: Hornblendite dike  r  0.0003  36  Ar.  40  Ar 0.0002  Plateau age = 189.9 ± 1.4 Ma  100  (2o, including J-error of .5%)  0.0001  MSWD = 0.41, probability=0.88 39  20  40  60  Age = 190.7 ± 2.3 Ma Initial ' V / ^ A r =256±82  Includes 93.9% of the A r  MSWD = 0.14  80  0.0000 0.075  100  0.077  0.079  39  0.081  0.083  0.085  0.087  W A r  Cumulative Ar Percent -i  1  i  r  i  i  i  i  1  i  Biotite 04ES-00-07-03: Wehrlite  300  i  i  i  i  0.0005  |  0.0004  200  36  Ar °Ar  < 100  0.0002  Plateau age = 189.9 ± 1.3 Ma  Age = 190.2 ± 1.8 Ma  (2<T, including J-error of .5%) MSWD = 0.86, probability=0.46  Initial "Ar/^Ar =287±34  Includes 56.4% of the A r  MSWD = 1.17  39  20  0.0003  40  60  80  • 0.0000 0.071 0.073 0.075 0.077 0.079 0.081 0.083 0.085  100  WAT  Cumulative Ar Percent  Figure 2.8: Ar/ Ar incremental-heating age spectra and Ar/ Ar inverse isochron diagrams for mineral separatesfromthe Turnagain intrusion. A) Results for amphibole separatedfroma hornblendite dike (04ES-00-07-04) sampledfromthe northwestern part of the intrusion. B) Results for phlogopite separatedfroma wehrlite (04ES-00-07-03) sampled in the southeastern part of the Turnagain intrusion (southern Hatzl Zone). 40  39  40  39  The plateau age obtained above is considered to represent the m i n i m u m crystallization age o f the wehrlite w h e n the rock cooled through the closure temperature to A r diffusion i n phlogopite (see D i s c u s s i o n ) .  2.5.3 Rare Earth Elements and Nd Isotopes The S m - N d isotopic compositions o f eight w h o l e rock samples from the Turnagain intrusion were determined i n this study. W i t h respect to rare earth element ( R E E ) concentrations (Table 2.3), the samples have broadly subparallel chondrite-normalized patterns w i t h prominent L R E E - d e p l e t i o n for the ultramafic rocks (Figure 2 . 9 A ) . The leuco-diorite and the v o l c a n i c wacke exhibit distinctive L R E E - e n r i c h e d chondrite-normalized patterns (Figure 2 . 9 B ) . The v o l c a n i c wacke, as w e l l as the samples o f E r d m e r et al. (2005), fall w i t h i n or bracket the R E E range established for the L a y Range Assemblage (Ferri, 1997) and K l i n k i t G r o u p ( S i m a r d et al., 2003) (Figure 2 . 9 B ) . ( L a / Y b )  c n  values i n ultramafic rocks range from 0.27-2.0, w i t h the  v o l c a n i c wacke and hornblende diorite samples exhibiting ( L a / Y b )  c n  values o f 3.9 and 1.9,  respectively. The samples analyzed for N d isotopes (Table 2.4) show a w i d e range o f concentrations ( S m = 0.6-6 p p m , N d = 1.3-18.5 ppm), variable S m / N d values (0.33-0.45), a w i d e range i n  1 4 3  Nd/  1 4 4  N d (measured) from 0.512440 to 0.512997, and do not exhibit an  isochron relationship (Figure 2.1 O A ) . The majority o f Turnagain samples have  SNd(i90)  values  between +1.9 and +5.9 (05ES-05-04-01), whereas one sample (hornblende clinopyroxenite) exhibits a moderately negative  £Nd(i90)  at -3.4 (Figure 2 . 1 0 B ) .  2.6 DISCUSSION 2.6.1 Age and Source of the Turnagain Intrusion The Turnagain intrusion is a composite mafic-ultramafic pluton that contains a range o f lithologies from dunite to diorite (plagioclase + amphibole). F i e l d relationships, and mineral and w h o l e rock geochemistry (see Chapter 4) indicate the f o l l o w i n g general crystallization sequence: dunite —> wehrlite —> o l i v i n e clinopyroxenite —* hornblende clinopyroxenite —* hornblendite —• diorite. The A r - A r phlogopite date from the wehrlite (189.9+1.3 M a ) from the mineralized H a t z l Z o n e and the A r - A r hornblende date from the hornblendite (189.9+1.4 M a ) from the northwestern part o f the Turnagain intrusion are identical w i t h i n error and represent the ages o f closure to A r diffusion (i.e. c o o l i n g ages) at ~ 4 5 0 ° C (phlogopite) and ~ 5 7 5 ° C (hornblende) (closure temperatures from Hodges, 2003; and references therein). Titanite from  Table 2.3: Major (wt. % oxide) and trace (ppm) element abundances in whole rock samples from the Turnagain intrusion  Rock Type: Olivine Cpxite Sample Prefix: 05ES 05-01-01 Sample #:  Cpxite 05ES 05-04-01  Cpxite 05ES 03-01-02  Hbl Cpxite 04ES 09-02-02  Hblite 05ES 05-06-02  Hblite 04ES 00-07-04  41.93 2.16 12.21  Wacke  Diorite DDH04  04ES 00-07-02  57-12-89.2  53.56 0.29 20.82 4.14  Oxides (wt. %) Si0 Ti0 Al 0 Fe 0 *  51.23 0.20 1.05 7.45  48.99 0.38 2.21 7.65  49.04 0.29 2.07 8.55  47.14 0.75 4.20 11.64  38.53 2.32 12.06 15.51  14.30  49.67 0.80 16.19 10.01  MgO  22.45  18.65  20.30  16.46  12.99  MnO CaO Na 0  0.19 15.25 0.17  0.21 13.85 0.67  4.86 0.20 9.82 3.57  3.60 0.09 7.68 6.02  K 0  0.10  0.15 19.12 0.20 0.08  0.16 16.04  2  0.13 17.26 0.17  11.95 0.26 11.62 0.78  2  2  2  3  2  3  2  0.11  0.63 0.40  0.32  0.89  1.86  0.14 2.35 99.92 1.08  0.01 3.31 99.78 0.14  0.31 2.80 99.20 0.35  0.37 1.88 99.23 0.31  1.17 0.19 2.12 99.68 0.10  P 0 LOI Total S  99.34 0.42  2.20 99.65 0.04  0.03 3.37 99.36 0.33  Mg #:  0.857  0.829  0.825  0.737  0.624  0.624  0.491  0.633  Trace Elements (ppm) Co 98 Cr 3200 292 Cu Ni 511 55.4 Sc 81 V  59 1480 292 173 68.1 147  56 2690 47 56 41.8 265  151 1320 249 130 68.8 343  66  15 11  101 20  12 9  49 3 35 0.17  36.1 291 74  12.9 110  57  404 84 136 73.7 492 99  30 79  20  85 38 133 132 69.3 645 69 69 0.10  12.0 422 0.36  28 700 1.54 0.21 0.3 4.1  11 1980 0.07 0.09 0.1 2.3  2  Zn Rb Ba Th  5  18 1  36  12  0.29 0.16 0.3  0.5  0.08 0.1 1.8  1.6  0.12 0.2 3.9  La  0.19  0.52  1.56  4.47  2.11  6.61  10.50  1.50  Ce  0.8  3.8  14.5  0.18 35  2.0 5 0.41 71  0.64  13 2.57 62  7.0 34 1.40  20.5 36 3.35  21.6 12 2.65 949  3.4 5 0.52 2808  Nd Zr Hf  1.33 2  2.64 7  Sm  0.60  0.3 1.04  11.60 38 1.4 2.99  2.62 17 0.7 0.80  Eu Gd  0.204 0.80  1.020 3.21  0.386 0.86  Tb Dy  0.15  1.31 0.25  0.92  1.57  Ho Er Tm  0.18 0.49 0.07  Yb Lu  U Ta Nb  Pb Pr Sr  Y  60 3.60 12 0.4 1.16  12.60 14  0.277 1.36  0.928 3.62  0.25  0.63  1.56  3.49  0.31 0.86  0.31 0.90  0.65 1.84  0.44  0.12 0.74  0.13 0.81  0.26 1.49  0.053  0.100  0.108  5  10  8  0.318  0.7 3.69  336 8.64 30 1.3 3.26 1.310  284 18.25 49 2.1 5.95 1.845  4.10  7.18  0.76 4.74  1.33 7.91  0.56  0.15  3.42  0.95  0.97 2.79 0.39  1.62 4.54 0.65  0.70 2.13  0.19 0.57  0.31  2.25  3.82  0.09 0.53  0.193  0.310  0.530  1.82 0.287  0.073  19  28  42  19  4  Note: Blank entries represent values that were below detection limits. Abbreviated rock types: cpxite (clinopyroxenite), hblite (hornblendite) Mg# = Mg/(Mg+Fe) assuming all iron as F e 2 +  0.06  29  100  La  Ce Pr  Nd Sm Eu Gd Tb Dy Ho Er Tm Ol Clinopyroxenite  100  O  Y D LU  Hbl Clinopyroxenite  -&-05ES-05-01-01 -A-05ES-05-04-01  -«-04ES-09-02-02  -05ES-03-01-02  O-05ES-05-06-02 •-04ES-00-07-04  Hornblendite  -r  B  10  a.  E  CC  Erdmer et al. (2005) - • - MM100-13-4/PE00-74  1  Turnagain (this study)  - • - MM100-13-13/PE00-74  -04ES-00-07-02 (volcanic wacke)  - C — MM100-13-6/PE00-75  -DDH04-57-12-89.2 (hornblende diorite)  - • - MM100-13-11 /PE00-75  —i  La  i  i  Ce Pr  i  i—  Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu  Figure 2.9: Chondrite-normalized rare earth element diagrams for whole rock samples from the Turnagain intrusion, and whole rock samples of mafic to intermediate volcanicsfromErdmer et al. (2005) for comparison (normalizing valuesfromMcDonough & Sun, 1995). Note the wide range in concentrations of the rare earth elementsfromolivine clinopyroxenite to hornblendite, the broadly sub-parallel patterns with prominent LREEdepletion for the ultramafic rocks, and the distinctive LREE-enriched pattern for the hornblende diorite and the volcanic wacke. Note also that the volcanic wacke and the Erdmer et al. (2005) samples plot in or near the range of the Lay Range Assemblage (after Ferri, 1997).  Table 2.4: Nd isotopic compositions of whole-rock samples from the Turnagain intrusion  Rock Type  Sample No.  05ES-05-01-01 05ES-05-04-01 05ES-03-01-02 04ES-09-02-02A (a) 04ES-09-02-02A (b) 05ES-05-06-02 (a) 05ES-05-06-02 (b) 04ES-00-07-04 DDH04-57-12-89.2 04ES-00-07-02 (a) 04ES-00-07-02 (b)  clinopyroxenite clinopyroxenite clinopyroxenite hbl clinopyroxenite hbl clinopyroxenite hornblendite hornblendite hornblendite diorite volcanic wacke volcanic wacke  GSP-2 (n=14)  reference  Sm (ppm)  (ppm)  0.175 1.04 1.16 3.69 3.69 3.26 3.26 5.95 0.800 2.99 2.99  0.41 2.64 3.60 12.6 12.6 8.64 8.64 18.3 2.62 11.6 11.6  Nd  1 4 3  Nd  1 4 4  Nd  0.512997 0.512993 0.512754 0.512442 0.512438 0.512892 0.512900 0.512738 0.512865 0.512693 0.512695  20  147  1 4 4  0.000008 0.000010 0.000008 0.000005 0.000007 0.000004 0.000004 0.000005 0.000007 0.000008 0.000006  Sm Nd  0.2581 0.2382 0.1948 0.1770 0.1770 0.2281 0.2281 0.1971 0.1846 0.1558 0.1558  0.511374 0.000011  Hornblende has been abbrieviated to hbl Concentrations of Sm and Nd were measured by ICP-MS T u R and T ages with hyphens represent either negative ages or unreasonably large ages CH  D M  143  144  Nd  £ d N  (0)  Nd (190 Ma)  0.512676 0.512697 0.512511 0.512222 0.512218 0.512608 0.512617 0.512493 0.512641 0.512499 0.512501  7.0 6.9 2.3 -3.8 -3.9 4.9 5.1 1.9 4.4 1.1 1.1  ^Nd  TcHUR  TDM  (190 Ma)  (Ma)  (Ma)  5.5 5.9 2.3 -3.3 -3.4 4.2 4.4 1.9 4.8 2.1 2.1  891 1300 1522 1557 1225 1266 -  3175 2924 2942 3751 1490 1202 1197  I  I  •  0.5131  •  A  +  0.5129  5 0.5127  0.5125  _i  0.5123 0.13  i  0.15  i_ 0.17  0.19 147  Turnagain (this study)  •  • Hornblende clinopyroxenite  +  + Felsic Diorite X Volcanic wacke  0.25  0.27  Sm/ Nd -15  -20  -30  -25  B  A O  • Hornblendite  0.23  144  -10  10 A Clinopyroxenite  0.21  O Erdmer ef al. (2005)  x  • Dark green tuff X Plagioclase porphyry Granodiorite dyke • 'Road River" phyllite A Boya Formation (quartzite) A Boya Formation (muscovite schist) • Quartz-potassium feldspar porphyry  X X A 10  -5  -10  -15  -20  A  -30  -25  eNd (190 Ma) Figure 2.10: Nd isotopic geochemistry of whole-rock samples from the Turnagain intrusion. A) N d / N d vs. Sm/ Nd with a 190 M a reference isochron. Symbol size is greater than the 2a error for each analysis. B) Initial e d vs. rock type. The upper portion of the diagram illustrates the range in initial e in Turnagain lithologies and the lower portion shows results from Erdmer et al. (2005), recalculated at 190 Ma, for samples collected -10 km southeast of the Turnagain intrusion. The light blue field represents the range of e d for mafic volcanic rocks from Yukon-Tanana (from Piercey et al, 2006). 143  147  144  144  N  Nd  N  the same hornblendite sample yields a date o f 1 9 0 . 3 ± 4 . 6 M a (Figure 2.7), w h i c h represents the time o f closure to P b diffusion i n titanite ( ~ 6 5 0 ° C ) (Cherniak, 1993; Frost et al, 2000). A l l three dates from the ultramafic rocks o f the Turnagain intrusion are identical w i t h i n error and correspond to a range o f closure temperatures for the respective minerals and isotopic systems from 6 5 0 ° C d o w n to 4 5 0 ° C , w h i c h is consistent w i t h relatively rapid c o o l i n g o f the Turnagain intrusion f o l l o w i n g emplacement and crystallization. B a s e d on these three dates, the age o f crystallization and c o o l i n g o f ultramafic rocks from the Turnagain intrusion is 1 8 9 . 9 ± 0 . 9 M a (n=3, weighted mean age, 2a). T h e mela-diorite sample (04ES-00-07-01) exhibits gradational contacts w i t h hornblendite, but intrudes dunite (Figure 2.3). T h e closure temperature for P b diffusion i n z i r c o n is > 9 0 0 ° C (Cherniak & Watson, 2000), w h i c h is l i k e l y to be higher than the temperature o f the fractionated hydrous melt from w h i c h the z i r c o n i n this sample precipitated; thus the U Pb z i r c o n date for this sample can be interpreted as a crystallization age. A s noted previously, all analyzed z i r c o n i n this sample appears to have lost P b since the time o f crystallization. B a s e d o n the oldest least discordant fraction (Fraction B ) , the mela-diorite has a m i n i m u m crystallization age o f 1 8 9 . 2 ± 0 . 6 M a (Figure 2 . 5 A ) , w h i c h is identical w i t h i n error to the weighted mean A r - A r (phlogopite, hornblende) and U - P b (titanite) age noted above. T h e absolute crystallization age o f the Turnagain intrusion is inferred to be 1 8 9 . 4 ± 0 . 5 M a based on a weighted mean o f Fraction B from the mela-diorite and the A r - A r and U - P b titanite ages referred to above. T h e 1 8 5 . 2 ± 0 . 3 M a U - P b z i r c o n age o f the leuco-diorite ( D D H - 0 4 - 5 7 - 1 2 - 8 9 ) is approximately 4.5 m i l l i o n years younger than the crystallization age o f the Turnagain intrusion established above. T h i s younger age can be interpreted as (1) the true crystallization age o f the leuco-diorite, thus i m p l y i n g an extended period o f magmatism i n the formation o f the Turnagain intrusion; or (2) a function o f P b loss from z i r c o n i n this sample. F i e l d and petrographic relations suggest that the leuco-diorite is an integral part o f the 190 M a ultramafic and mafic rocks o f the Turnagain intrusion. The first interpretation is consistent w i t h the observation that late dioritic dikes are a c o m m o n feature o f many Alaskan-type intrusions (e.g. L u n a r Creek; N i x o n et al., 1997). In addition, a diorite to granodiorite composite pluton ~5 k m to the east-southeast o f the Turnagain intrusion (Figure 2.2), a body considered to be a s m a l l ultramafic ' R i n g C o m p l e x ' genetically related to the Turnagain intrusion ( C l a r k , 1975), was recently dated by E r d m e r et al. (2005) at 1 8 7 . 5 ± 2 . 9 M a ( U - P b zircon). T h i s age overlaps both  41  the ages o f the leuco-diorite and the ultramafic rocks o f the Turnagain intrusion. The composite R i n g C o m p l e x is described by E r d m e r et al. (2005) as a "medium-grained hornblende granodiorite to tonalite-diorite," w h i c h suggests that it may be a similar lithology to the mela-diorite o f the Turnagain intrusion. The date o f the granodiorite is a l o w e r intercept age w i t h concordia based on three o f the five analyzed fractions (see F i g . 5 o f E r d m e r et al., 2005). H o w e v e r , the oldest analyzed fraction (not used i n the above regression) is concordant and yields a  2 0 6  Pb/  2 3 8  U age o f 1 9 2 . 4 ± 0 . 8 M a , thus it is possible that this hornblende  granodiorite may be several m i l l i o n years older that its proposed crystallization age o f 1 8 7 . 5 ± 2 . 9 M a . T h e second interpretation o f the age o f the leuco-diorite from the Turnagain intrusion - Pb-loss from z i r c o n after crystallization at ca. 190 M a - is based on the observation o f Pb-loss i n a l l z i r c o n fractions from the mela-diorite (sample 04ES-00-07-01) and the  field  and petrographic characteristics o f the leuco-diorite sample. The hornblende diorite contains coarse (up to 1 c m i n width) euhedral crystals o f plagioclase and amphibole, interpreted to be cumulus phases that crystallized from an e v o l v e d plagioclase-amphibole-saturated m a g m a late i n the crystallization history o f the Turnagain intrusion. T h e drillcore from w h i c h the sample was collected contains 9 metres o f alternating plagioclase-rich and amphibole-rich bands, perhaps representing a layered sequence o f cumulate rocks. These observations require the leuco-diorite to have crystallized at the same time as the other dated samples, thus the obtained age o f 1 8 5 . 2 ± 0 . 3 M a is most l i k e l y a function o f Pb-loss from z i r c o n f o l l o w i n g crysallization. T h e M g - r i c h o l i v i n e (F092.5) o f some Turnagain dunites indicate that the Turnagain magmas equilibrated w i t h peridotitic mantle (with respect to major elements). H o w e v e r , the N d isotopic composition o f a l l lithologies i n the Turnagain intrusion (sNd(i90) +5.9 to -3.3) =  indicates that the intrusion was variably contaminated w i t h continental crust (depleted mantle SNd(i90Ma)  = +9 to +10; D e P a o l o & Wasserburg, 1976). The most positive £Nd(i90) results are  consistent w i t h the range observed i n P a l e o z o i c mafic v o l c a n i c rocks i n Y u k o n - T a n a n a (Piercey et al., 2006). The N d isotopic compositions o f the graphitic phyllite (Erdmer et al., 2005) and the v o l c a n i c w a c k e (this study) both indicate (respectively) their o r i g i n from, and contamination w i t h , continental crust (Figure 2.10). The variable 8Nd(i90) o f the analyzed ultramafic samples may reflect heterogeneous assimilation o f the v o l c a n i c wacke and the graphitic phyllite, both o f w h i c h are found as partially digested inclusions i n the Turnagain intrusion.  2.6.2 Age Comparison with other Alaskan-type Intrusions The mineralogy and mineral compositions o f Alaskan-type intrusions suggest that they form from relatively hydrous, a l k a l i c to subalkalic, p r i m i t i v e picritic/ankaramitic magmas (Irvine, 1974; Hernandez, 2000; M o s s m a n et al, 2000; Spandler et al, 2003; G r e e n et al,  2004;  Batanova et al, 2005) i n arc settings. The ages o f Alaskan-type intrusions, therefore, are important for understanding the temporal evolution o f arc systems. T h i s is particularly relevant to the C o r d i l l e r a n orogeny o f B . C . , Y u k o n , and southeastern A l a s k a , w h i c h consists o f numerous accreted allochthonous and parautochthonous terranes (e.g. M o n g e r et al, Schermer et al,  1982;  1984; Gabrielse & Y o r a t h , 1991; C o l p r o n et al, 2006) (Figure 2.1). The  published and reported ages o f Alaskan-type intrusions i n B . C . and southeastern A l a s k a are c o m p i l e d in Table 2.5 and shown w i t h respect to terranes i n Figure 2.11. O f the 9 k n o w n Alaskan-type intrusions i n B . C . and 39 i n southeastern A l a s k a , only 12 have been dated; mostly by the K - A r method during the 1960s. P r i o r to this study, the only precise U - P b z i r c o n ages o f Alaskan-type intrusions i n B . C . and A l a s k a were reported by Saleeby (1992), R u b i n & Saleeby (1992), Rublee (1994), and N i x o n et al. (1997) (Duke Island, U n i o n B a y , Tulameen, and L u n a r Creek+Polaris, respectively). There are two important observations that can be made regarding the age distribution o f Alaskan-type intrusions (see Figure 2.1 for terrane locations). Firstly, there are four age groups: - 4 3 5 - 4 0 0 M a , - 2 4 0 - 2 0 5 M a , - 1 9 5 - 1 8 5 M a , and - 1 2 5 - 1 0 0 M a . The oldest (Silurian-Devonian) and youngest (Cretaceous) age groups are found in the A l e x a n d e r terrane, whereas the intermediate age groups (Triassic-Jurassic) are found i n S t i k i n i a and Quesnellia (Figure 2.1). Secondly, the - 2 4 0 - 2 0 5 M a intrusions are observed i n both S t i k i n i a and Quesnellia, whereas the - 1 9 5 - 1 8 5 M a intrusions are found o n l y i n Quesnellia. Alaskan-type intrusions i n B . C . and southeastern A l a s k a also exhibit an age distribution relative to their host rocks. The oldest group o f intrusions (Salt C h u c k , D a l l Island, and S u k k w a n Island) intrude older gabbroic plutons as w e l l as the D e s c o n F o r m a t i o n (lower P a l e o z o i c metavolcanic and metasedimentary rocks; e.g. R u b i n & Saleeby, 1992), w h i c h is unconformably overlain by the G r a v i n a (Upper Jurassic-Lower Cretaceous metavolcanic and metasedimentary rocks) and A l v a (upper P a l e o z o i c - l o w e r M e s o z o i c metabasalt, marble, and argillite) sequences. The youngest age group is also dominantly hosted by the D e s c o n Formation, however the U n i o n B a y intrusion is hosted by the o v e r l y i n g G r a v i n a sequence ( R u b i n & Saleeby, 1992). T h i s implies that the youngest age group o f intrusions were  Table 2.S: Compilation of isotopic dates for Alaskan-type intrusions in British Columbia and southeastern Alask Terrane  Rock Type  Method (Mineral)  Wehrlite Hornblendite dike Hornblendite dike Mela-diorite Leuco-diorite  Ar-Ar Ar-Ar U-Pb U-Pb U-Pb  Ring Complex  diorite  U-Pb (zircon)  Lunar Creek  K-spar pegmatite Cross-cutting dike Cross-cutting dike  U-Pb (zircon) K-Ar (hornblende) K-Ar (hornblende)  Wrede Creek  Hornblende pegmatite Hornblende pegmatite  Johansson Lake  Intrusion  Age (Ma)  Uncertainty (2o)  Host Lithology  1.3 1.4 4.6 0.6 0.3  This study "Road River" phyllite, Lay Range Assemblage  187.5  2.9  "Road River" phyllite  Erdmeref al., 2005  237 190 182  2 8 13  Takla Group  Nixon etal., 1997 Gabrielse etal., 1980 Gabrielse et al., 1980  K-Ar (hornblende) K-Ar (hornblende)  219 225  20 16  Takla Group  Wong etal., 1985  Coase hornblendite  K-Ar (hornblende)  232  13  Takla Group  Stevens etal., 1982  Polaris  Qtz-hbl-plag pegmatite Peridotite Peridotite  U-Pb (zircon) K-Ar (biotite) K-Ar (hornblende)  186 167 156  2 9 15  Lay Range Assemblage  Nixon etal., 1997 Wanless etal., 1968 Wanless etal., 1968  Tulameen  Syenodiorite Hornblende clinopyroxenite Hornblende clinopyroxenite  U-Pb (zircon) K-Ar (hornblende) Ar-Ar (hornblende)  209.9 208 196  4.7 *20 *15  Nicola Group  Rublee, 1994 Nixon et al., 1997 -refs therein Nixon et al., 1997 -refs therein  Stikinia  Gnat Lakes  Hornblendite Hornblende clinopyroxenite  K-Ar (hornblende) K-Ar (hornblende)  230 227  10 14  Stuhini Group  Stevens etal., 1982  Alexander  Duke Island  Gabbro Hornblendite  U-Pb (zircon) Ar-Ar (hornblende)  109.5 118.5  1.5 10  Descon Formation  Saleeby, 1992 Meen etal., 1991  Union Bay  Gabbro pod in hornblendite  U-Pb (zircon)  101.9  Gravina Sequence  Rubin & Saleeby, 1992  Biotite clinopyroxenite  K-Ar (biotite)  429  11  Descon Formation  Loney etal., 1987  401.1  *20  Descon Formation  Himmelberg & Loney, 1995 -refs therein  440.5  *20  Descon Formation  Himmelberg & Loney, 1995 -refs therein  Quesnellia  Turnagain  1  Salt Chuck Dall Island  3  Sukkwan Island  3  0.6  2  The Ring Complex, originally described by Clark (1975), was interpreted to be ultramafic in nature (based on aeromagnetic results). However subsequent mapping by Erdmer etal., 2005, and the principal author, showed that the Ring Complex is a diorite pluton that intruded phyllites of th< Road River Group. See Discussion for details Conservative estimate of error o n Pb/ U age Age of intrusion derived from a personally communicated age to the refered authors, such that no specific data are available * These uncertainties are conservative estimates - no uncertainties are given by the original authors 1  2  3  4^  Reference  189.9 189.9 190.3 189.2 . 185.2  (phlogopite) (hornblende) (titanite) (zircon) (zircon)  2 0 6  2 3 8  80 Quesnellia Turnagain  phlogopite (wenrlite) hbl (hornblendite) hornblendite mela-diorite leuco-diorite  105  - 1 —  130  -I—  155  —I—  180  205  l—  230  T  T  E D  •  280  Method  =1  -  255  U-Pb (zircon) U-Pb (titanite) K-Ar Ar-Ar  1  •  Ring Complex Lunar Creek  • •  •  z  •  _  K-spar pegmatite hbl (x-cutting dike) hbl (x-cutting dike)  Wrede Creek hbl (pegmatite) hbl (pegmatite)  Johanson Lake hbl (hornblendite)  Polaris  qtz-hbl-plag pegmatite biotite (hornblendite) hbl (hornblendite)  Tulameen syenodiorite hornblende hornblende  Stikinia Gnat Lakes  hbl (hornblendite) hbl (hornblende cpxite)  Alexander Duke Island gabbro hornblendite  Union Bay gabbro  380  Salt Chuck biotite (clinopyroxenite)  405 I  430  Dall Island Sukkwan Island 80  105  -L  130  155  180  205  -L  230  255  280  Age (Ma) Figure 2.11: Compilation of ages of Alaskan-type intrusions in B.C. and southeastern Alaska arrangedfromnorth to south (top to bottom) with each bar representing the age with its associated analytical uncertainty (2a), its dating method and mineral dated. References for the above ages are found in Table 2.5.  45  emplaced through both the D e s c o n F o r m a t i o n and the G r a v i n a sequence, and that a second arc was built upon a preexisting, extinct, arc. The Triassic intrusions (-240-205 M a ) are t y p i c a l l y hosted i n the T a k l a ( M o n g e r , 1977) and N i c o l a (e.g. Shau, 1970) Groups, w h i c h are Triassic packages o f v o l c a n i c rocks that occur in Q u e s n e l l i a and S t i k i n i a (Dostal et al., 1999). The Gnat L a k e s Alaskan-type intrusion, however, is hosted i n the Stuhini G r o u p i n S t i k i n a , and Stuhini G r o u p , T a k l a G r o u p , and N i c o l a G r o u p are considered to be coeval (Dostal et al., 1999). The Jurassic (-195-185 M a ) group o f intrusions is represented by the Polaris and Turnagain intrusions, w h i c h have similar crystallization ages ( 1 8 6 ± 2 M a , 1 9 0 ± 1 M a , respectively) and host rocks. The Polaris intrusion is hosted i n the L a y Range Assemblage, w h i c h has been correlated w i t h the Harper R a n c h Subterrane and the K l i n k i t G r o u p (e.g. F e r r i , 1997) and is p r o x i m a l to the U p p e r Proterozoic Ingenika G r o u p , whereas the Turnagain is hosted by graphitic phyllites (possibly the R o a d R i v e r F o r m a t i o n and E a r n G r o u p ) and v o l c a n i c wacke that possibly correlates to the L a y Range Assemblage (see next section). The apparent 10 m i l l i o n year gap, based o n the few reliable U - P b dates, between the Late to M i d d l e Triassic and E a r l y Jurassic intrusions may be related to (1) a period o f quiescence i n arc magmatism, or (2) an artifact o f the lack o f geochronological data. M o n g e r & C h u r c h (1977) constrain the biostratigraphic age o f the T a k l a G r o u p from late C a r n i a n to early N o r i a n ( - 2 2 0 to 230 M a using the time scale o f O k u l i t c h , 1999). In addition, a Late Triassic angular unconformity w i t h the o v e r l y i n g E a r l y Jurassic Rossland G r o u p , a package o f v o l c a n i c rocks (with lateral facies changes gradational w i t h limestone and epiclastic rocks) that are texturally and mineralogically similar to the N i c o l a G r o u p , is observed i n southern Quesnellia (Beatty et al., 2006). T h i s succession is inferred to represent the uplift and erosion o f the N i c o l a G r o u p f o l l o w e d by eastward-shifted renewed arc magmatism ( o v e r l y i n g R o s s l a n d G r o u p ) at - 1 9 5 M a (Parrish and M o n g e r , 1992). The older biostratigraphic age o f the T a k l a G r o u p , i n comparison to the Late Triassic Alaskan-type intrusions, may indicate that its top has been removed by erosion. The youngest Alaskan-type intrusions, found at the easternmost extent o f Quesnellia (Figure 2.1), may corroborate the eastward shift o f arc magmatism i n Quesnellia during the E a r l y Jurassic. H o w e v e r , the number o f precisely-dated Alaskan-type intrusions i n B . C . is small (n=4). The apparent time gap may therefore s i m p l y be related to the lack o f dated Alaskan-type intrusions i n B . C . A 185-212 M a plutonic suite does occur i n the Y u k o n - T a n a n a terrane (Mortensen, 1992), w i t h w h o l e - r o c k compositions similar to the T a k l a G r o u p ( N e l s o n et al., 2006). Some plutons contain ultramafic rocks w i t h A l a s k a n -  46  type-like lithologies but have not yet been defined as Alaskan-type bodies per se ( J . K . Mortensen, pers. c o m m . , 2007). There is also an absence o f preserved Late Triassic or E a r l y Jurassic v o l c a n i c rocks, but there is no apparent age' gap o f early M e s o z o i c plutonic rocks i n Y u k o n - T a n a n a - presumably the basement to Quesnellia ( N e l s o n et al., 2006).  2.6.3 Tectonic Implications for Northern British Columbia The combined ages, host lithologies, and N d isotopic compositions o f the Turnagain intrusion have implications for its tectonic setting and relation to the accreted terranes o f the Canadian C o r d i l l e r a . The two major host lithologies, graphitic phyllite and latest Pennsylvanian/earliest P e r m i a n v o l c a n i c wacke, are both found as inclusions i n the Turnagain intrusion and appear to represent the host rocks to this fault-bounded intrusion. B a s e d on l i m i t e d fossil biochronology, the age o f the R o a d R i v e r F o r m a t i o n  sensu stricto is E a r l y O r d i v i c i a n to M i d d l e S i l u r i a n  elsewhere i n B . C . , and the o v e r l y i n g the E a r n G r o u p is U p p e r D e v o n i a n to M i s s i s s i p p i a n (Gabrielse, 1998). The u n d i v i d e d R o a d R i v e r and E a r n Groups (as mapped by Gabrielse (1998) i n the study area) are conformably overlain by v o l c a n i c and volcanosedimentary rocks that contain abundant Proterozoic inherited z i r c o n (Figure 2 . 6 A ) and are intruded at their base by a 337 M a porphyritic dike (Erdmer et al., 2005). A gradational contact (interbedded over 510 m) between the graphitic phyllite and the v o l c a n i c wacke was observed i n drillcore i n late 2006. The age o f the phyllite is uncertain, as only a few p o o r l y preserved graptolites have been found i n the Dease L a k e map area (Gabrielse, 1998; and references therein). A c c r e t e d terranes w i t h i n the Canadian C o r d i l l e r a , specifically the Quesnel, Stikine, and Y u k o n - T a n a n a terranes, have recently been argued to be genetically related ( N e l s o n et al., 2006), partially based on lithological similarities. F o r example, Alaskan-type intrusions are k n o w n i n S t i k i n i a and Quesnellia, and recent unpublished findings indicate their probable presence i n Y u k o n - T a n a n a (J. N e l s o n , pers. c o m m . , 2007). The association between carbonaceous phyllite and o v e r l y i n g volcanic/volcano-sedimentary rocks has been documented i n both Quesnellia and Y u k o n - T a n a n a (Ferri & M e l v i l l e , 1990; Mortensen, 1992; F e r r i , 1997; S i m a r d et al., 2003; N e l s o n & F r i e d m a n , 2004). In Quesnellia, such volcanic-volcaniclastic rocks have been included either i n the M i s s i s s i p p i a n - P e r m i a n L a y Range Assemblage or the D e v o n i a n - M i d d l e Permian Harper R a n c h Subterrane (Ferri & M e l v i l l e , 1990; F e r r i , 1997; Dostal  etal., 1999). The L a y Range Assemblage (Ferri, 1997) contains (1) a M i d d l e  Mississippian-late M i d d l e Pennsylvanian L o w e r Sedimentary d i v i s i o n , consisting  47  predominantly o f argillite and siltstone w i t h lesser limestone, tuff, and v o l c a n i c sandstones; and (2) an E a r l y Permian U p p e r M a f i c T u f f d i v i s i o n , consisting o f a variety o f tuffs, agglomerates, and lavas flows. The L a y Range Assemblage is considered correlative w i t h the M i d d l e M i s s i s s i p p i a n - E a r l y P e r m i a n K l i n k i t G r o u p i n Y u k o n - T a n a n a (Simard et al., 2003; N e l s o n & Friedman, 2004). The K l i n k i t G r o u p has been observed to tectonically overlie a succession o f phyllites, grits, and tuffs o f the D e v o n i a n - M i d d l e P e r m i a n Swift R i v e r succession (Simard et al., 2003; N e l s o n & Friedman, 2004), w h i l e the base o f the L a y Range Assemblage has been observed i n central B . C . by F e r r i & M e l v i l l e (1990) to conformably overlie carbonaceous p h y l l i t e . The base o f the Harper R a n c h Subterrane has not been observed (Dostal et al., 1999). Other similarities between Y u k o n - T a n a n a and Quesnellia p o s s i b l y include a shared A n c e s t r a l N o r t h A m e r i c a basement source. E r d m e r et al. (2002) documented 313-1058 M a detrital z i r c o n i n sedimentary rocks o f the Quesnellian N i c o l a Horst i n southcentral B . C . and Untershutz et al. (2002) documented a mixture o f p r i m i t i v e and e v o l v e d N d isotopic compositions in Triassic sandstones o v e r l y i n g the L a y Range Assemblage. F e r r i (1997) documented inherited Proterozoic z i r c o n i n P e r m i a n tuffs and lavas from the U p p e r M a f i c T u f f d i v i s i o n o f the L a y Range Assemblage. In summary, the " E a r n G r o u p ' V S n o w c a p Assemblage is overlain by the K l i n k i t G r o u p / L a y Range Assemblage/Harper R a n c h Subterrane, a l l o f w h i c h contain detrital z i r c o n o f Proterozoic age. The Turnagain intrusion is the first documented Alaskan-type intrusion to be hosted i n both L a y Range-equivalent rocks and older graphitic p h y l l i t e . The - 3 0 0 M a v o l c a n i c w a c k e , w i t h inherited Proterozoic zircons and trace element characteristics ( R E E ) similar to samples o f the L a y Range A s s e m b l a g e and the K l i n k i t G r o u p (Ferri, 1997; S i m a r d et al., 2003 - Figure 9 A ) (Figure 2 . 9 B ) , is l i k e l y a northern equivalent o f the L a y Range Assemblage. The " R o a d R i v e r " phyllite, as assigned by Gabrielse (1998), is conformably overlain by the L a y Range Assemblage and therefore constitutes part o f the same crustal block. The conformable nature o f these two rock packages is broadly consistent w i t h the first interpreted tectonic setting o f the Turnagain intrusion o f N i x o n (1998) as outlined i n the introduction, however this l i t h o l o g i c a l succession cannot be part o f A n c e s t r a l N o r t h A m e r i c a . These lithologies are intruded b y the Turnagain Alaskan-type intrusion, a composite mafic-ultramafic pluton o f arc affinity (see Chapter 4). N o conclusive terrane assignment can be made based on the presence o f L a y Range Assemblage-equivalent rocks, on the presence o f an E a r l y Jurassic arc-derived intrusion, or on the presence o f Precambrian inheritance. The  48  results of this study demonstrate that the succession of Cambrian(?) to Permian sedimentary rocks in this part of northern B.C., intruded by the Turnagain intrusion and the Ring Complex, was at the locus of arc magmatism during the Early Jurassic. If the assignment of the graphitic phyllite to the Road River/Earn Groups (Gabrielse, 1998) is correct, then the conclusions of Erdmer et al. (2005) - that an Early Jurassic subduction zone existed beneath Ancestral North America - are correct. However, if the graphitic phyllites are in fact part of the Snowcap assemblage or equivalents, then the lithologies around the study area are part of Yukon-Tanana or Quesnellia.  2.7 C O N C L U S I O N  The principal results from this geochronological study of the Turnagain Alaskan-type intrusion and host rocks in north-central British Columbia are 1) the crystallization age of mafic and ultramafic phases in the Turnagain intrusion, as determined by U-Pb (zircon, titanite) and ArAr (phlogopite, amphibole) geochronometry, is 190±1 Ma, 2) the range of whole rock Nd isotopic compositions from the Turnagain intrusion is £ N d ( i 9 0 ) +6 to +2 with a hornblende =  clinopyroxenite sample extending to £Nd(i90) = -3, indicating variable amounts of crustal contamination of mantle-derived parental magmas in an arc setting, 3) the minimum depositional age of the youngest host rocks to the Turnagain intrusion is 301 Ma (U-Pb zircon), or latest Pennsylvanian-earliest Permian, and 4) the hosting volcanic wacke in the study area, based on its age, REE geochemistry, and lithological similarities with other rocks in B.C. and Yukon, is equivalent to the Lay Range Assemblage, which is considered to be the basement to the Quesnellia terrane. The Turnagain intrusion, which intrudes the volcanic wacke and graphitic phyllite, is indicative of the presence of an Early Jurassic subduction zone in the study area and constrains the terrane assessment of the study area to be either Quesnellia or Yukon-Tanana. The association of other Alaskan-type intrusions in Quesnellia with the Lay Range Assemblage/Harper Ranch Subterrane is well-established, and may indicate the presence of unidentified Alaskan-type intrusions in the Klinkit Group of Yukon-Tanana, which would further support the proposed genetic relationships between Yukon-Tanana and Quesnellia.  49  2.8 A C K N O W L E D G E M E N T S W e w o u l d like to thank a number o f individuals at the Pacific Centre for Isotopic and G e o c h e m i c a l Research, U n i v e r s i t y o f B r i t i s h - C o l u m b i a , V a n c o u v e r : R i c h F r i e d m a n for U - P b T I M S chemistry and analyses, and his continuous input into data interpretation for this manuscript; T o m U l l r i c h for A r - A r analyses; G w e n W i l l i a m s and B r u n o K e i f f e r for sample preparation, digestion, and N d isotopic analyses; and D o m i n i q u e W e i s for assistance i n the interpretation o f the N d isotopic results. J i m Mortensen, L u k e Baranek, and R e z a Tafti are thanked for sharing their opinions and ideas concerning northern B . C . tectonics, and K a t r i n Breitsprecher for her helpful comments on this manuscript. The authors are grateful to H a r d Creek N i c k e l C o r p . for continued field support for this project and to J i m R e e d o f Pacific Western Helicopters for his exemplary logistical support i n the field. Special thanks to T o n y H i t c h i n s , B r u c e Northcote, C h r i s B a l d y s , and M a r k Jarvis (President) o f H a r d C r e e k N i c k e l C o r p . for their generous support and interactions throughout the period o f the p r i n c i p a l author's M . S c . thesis at U B C . F u n d i n g for this project was p r o v i d e d by a research grant from H a r d Creek N i c k e l C o r p . (formerly Canadian M e t a l s E x p l o r a t i o n L t d . ) .  2.9 REFERENCES Batanova, V . G . , Pertsev, A . N . , Kamenetsky, V . S . , A r i s k i n , A . 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Stratigraphy and structure o f the type area o f the upper Triassic N i c o l a group i n south-central B r i t i s h C o l u m b i a . Special  Paper - Geological Association of  Canada 6,123-135  55  Scheel, J . E . , N i x o n , G . T . , & Scoates, J.S. (2005). N e w observations on the Turnagain A l a s k a n type ultramafic intrusive suite and associated N i - C u - P G E mineralization.  Geological  Fieldwork 2004, B.C. Ministry of Energy, Mines, and Petroleum Resources. Paper 2005-1, 167-176 Schermer, E . R . , H o w e l l , D . G . , & Jones, D . L . (1984). The o r i g i n o f allochthonous terranes.  Annual Review of Earth and Planetary Sciences 12, 107-131 Simard, R - L . , D o s t a l , J., & Roots, C F . (2003). Development o f late P a l e o z o i c v o l c a n i c arcs i n the Canadian C o r d i l l e r a : an example from the K l i n k i t G r o u p , northern B r i t i s h C o l u m b i a and southern Y u k o n .  Canadian Journal of Earth Sciences 40, 907-924  Spandler, C . J . , A r c u l u s , R . J . , E g g i n s , S . M . , Mavrogenes, J . A . , Price, R . C . , & R e a y , A . J . (2003). Petrogenesis o f the Greenhills C o m p l e x , Southland, N e w Zealand: M a g m a t i c differentiation and cumulate formation at the roots o f a P e r m i a n island-arc v o l c a n o .  Contributions to Mineralogy and Petrology 144, 703-721 Stacey, J.S., & K r a m e r s , J . D . (1975). A p p r o x i m a t i o n o f terrestrial lead isotope evolution b y a two-stage m o d e l .  Earth and Planetary Science Letters 26, 207-221  Stevens, R . D . , D e l a b i a , R . N . , & Lachance, G . R . (1982). A g e determinations and geological studies; K - A r isotopic ages, Report 16.  Geological Survey of Canada, Paper 82-2, 56p  T a y l o r , H . P . , Jr., & N o b l e , J . A . (1960). 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H y d r o t h e r m a l o r i g i n o f platinum-group mineralization i n low-temperature copper sulphide-rich assemblages, Salt C h u c k intrusion, Alaska.  Economic Geology 87, 175-184  W e i s , D . , Kieffer, B . , M a e r s c h a l k , C , B a r l i n g , J . de Jong, J., W i l l i a m s , G . A . , Hanano, D . , Pretorious, W . , M a t t i e l l i , N . , Scoates, J.S., Goolaerts, A . , F r i e d m a n , R . M . , & M a h o n e y , J . B . (2006). H i g h - p r e c i s i o n isotopic characterization o f U S G S reference materials by T I M S and M C - I C P - M S .  Geochemistry Geophysics Geosystems 7 (8), Q 0 8 0 0 6 ,  d o i : 10.1029/2006GC001283 W o n g , R . H . , G o d w i n , C . I . , & M c T a g g a r t , K . C . (1985). 1977-Geology, K / A r dates, and associated sulphide mineralization o f Wrede Creek zoned ultramafic c o m p l e x ( 9 4 D / 9 E ) .  Geology in British Columbia, 1977-1981, 148-155  CHAPTER 3  CHROMITE CHEMISTRY OF THE TURNAGAIN INTRUSION, NORTHERN BRITISH COLUMBIA, AND THE REDOX STATES OF ALASKAN-TYPE PARENTAL MAGMAS  3.1 INTRODUCTION C h r o m i a n spinel, or chromite ( F e C ^ C U w i t h m i n o r amounts o f M g , A l , and F e  substitution),  3 +  is found as an accessory mineral i n a w i d e variety o f mafic and ultramafic rocks (e.g. Barnes & Roeder, 2001). It crystallizes from magmas that are broadly basaltic i n c o m p o s i t i o n and is typically one o f the earliest phases to saturate i n a mafic melt (e.g. Roeder, 1994). The abundance o f chromite i n many ultramafic and mafic rocks is generally l o w (1 v o l . % ) , although large accumulations called chromitite do occur i n a number o f layered maficultramafic intrusions (e.g. R o a c h et al., 1998), ophiolites, and Alaskan-type intrusions (e.g. Garuti et al., 2003; Krause et al., 2006) w o r l d w i d e . T h e composition o f chromite is extremely sensitive to its environment o f formation as w e l l as post-magmatic processes and thus can be a powerful petrogenetic indicator i n petrologic studies (e.g. Irvine, 1965; Irvine, 1967; D i c k & B u l l e n , 1984; Roeder & C a m p b e l l , 1985; Sack & G h i o r s o , 1991; S c o w e n etal,  1991;  Poustovetov & Roeder, 2000; P o w e r et al, 2000). V a r i a t i o n s i n chromite compositions may record changes i n m a g m a compositions and types o f co-precipitating phases (Roeder, 1994), o x y g e n fugacity (e.g. Poustovetov & Roeder, 2000), pressure (e.g. Roeder & R e y n o l d s , 1991), and may also record the effects o f sub-solidus re-equilibration and serpentinization (e.g. Roeder & C a m p b e l l , 1985). A recent c o m p i l a t i o n o f chromite compositions from mafic-ultramafic rocks w o r l d w i d e (Barnes & Roeder, 2001) includes o n l y seven referenced sources o f data for Alaskan-type intrusions. These intrusions are t y p i c a l l y composed o f ultramafic cumulate rocks, consisting o f M g - r i c h o l i v i n e , clinopyroxene, amphibole ± plagioclase, and they may be crudely to concentrically zoned. Alaskan-type intrusions occur mostly i n subduction zone settings and are proposed to have formed from relatively water-rich magmas ( H i m m e l b e r g & L o n e y , 1995; M o s s m a n et al, 2000; Johan, 2002; Spandler et al, 2003; Ishiwatari & Ichiyama, 2004; Green et al, 2004; Batanova et al, 2005). C h r o m i t e is a c o m m o n accessory mineral and is t y p i c a l l y disseminated i n the most magnesian lithologies (dunite and wehrlite). The earlier chromite compositional study o f C l a r k (1978) p r o v i d e d a good basis for this study, w h i c h provides an •i  o v e r v i e w o f spinel compositions from the Turnagain Alaskan-type intrusion i n northwestern B r i t i s h C o l u m b i a (Canada) w i t h the aims o f 1) significantly increasing the spinel compositional database for Alaskan-fype intrusions, 2) assessing the crystallization sequence and subsequent chemical modifications during c o o l i n g and serpentinization using chromite compositional variability and, importantly, 3) constraining the relative o x y g e n fugacity o f the  parental magmas for the Turnagain intrusion. The Turnagain Alaskan-type intrusion is unusual in that it contains zones w i t h significant N i - s u l p h i d e mineralization (428 M t - measured and indicated - @ 0.17% sulphide N i ; http://www.hardcreeknickel.com). G i v e n the proposed arc setting for Alaskan-type intrusions, they are considered to form from relatively o x i d i z e d parental magmas ( A F M Q = +1 to +3.5, e.g. C a r m i c h a e l , 1991; Parkinson & A r c u l u s , 1999) w i t h sulphur dissolved as sulphate (SO4 ") rather than sulphide (S ~) (Jugo et al., 2004) and 2  2  have thus traditionally been considered unfavourable environments for nickeliferrous ore deposits.  3.2 REGIONAL GEOLOGY N u m e r o u s Alaskan-type intrusions i n B r i t i s h C o l u m b i a occur w i t h i n the M e s o z o i c Quesnel accreted arc terrane, i n c l u d i n g the Tulameen (Findlay, 1969), Polaris (Foster, 1974), L u n a r Creek, W r e d e Creek, Johansson L a k e ( N i x o n et al, 1997), and Turnagain (Clark, 1975; 1978; 1980; N i x o n , 1998) intrusions. The Turnagain intrusion is located i n northwestern B . C . , approximately 70 k m east o f Dease L a k e , to the east o f the K u t c h o Fault, w h i c h is a regional strike-slip fault that represents the terrane boundary between A n c e s t r a l N o r t h A m e r i c a to the north and Quesnellia to the south (Gabrielse, 1998). The 24 k m Turnagain intrusion is 2  completely fault-bounded, and during the E a r l y Jurassic was thrust onto graphitic and pyritic phyllites currently assigned to the u n d i v i d e d O r d i v i c i a n - D e v o n i a n R o a d R i v e r F o r m a t i o n / E a r n G r o u p , a deep marine facies o f paleo-passive margin sedimentary units o f A n c e s t r a l N o r t h A m e r i c a (Gabrielse, 1998). C o n f o r m a b l y o v e r l y i n g the phyllite is a D e v o n i a n - M i s s i s s i p p i a n v o l c a n i c to sedimentary unit (Erdmer et al, 2005) that may be correlative to the L a y Range Assemblage (see Chapter 2). The crystallization age o f the Turnagain intrusion is constrained to be 190 M a using U - P b and A r - A r geochronological techniques (see Chapter 2).  I  3.3 GEOLOGY AND SPINEL CONTENT OF THE TURNAGAIN INTRUSION R o c k s o f the Turnagain intrusion are predominantly ultramafic cumulate rocks w i t h associated late dioritic phases and intrusions (Figure 3.1). The 3.5 k m x 8.5 k m Turnagain intrusion is elongate i n a N W - S E direction and the apparent thickness o f the intrusion is estimated at approximately 450 m based on inverse m o d e l i n g o f gravity data ( C . B a l d y s , pers. c o m m . , 2005). Exposures o f the intrusion are l i m i t e d to the northern and northeastern areas, w h i c h are above treeline, and near the N i - m i n e r a l i z e d zones (the Horsetrail Z o n e and satellite zones) i n  Intrusion Centre: X 58°29'N, 128°52'W  1 km  Dunite, with minor wehrlite  Diorite, quartz diorite, and granodiorite, undivided  Wehrlite, with minor dunite and olivine clinopyroxenite  Hornfels, sedimentary or volcanic protolith  Olivine clinopyroxenite and clinopyroxenite, undivided Hornblende clinopyroxenite, with minor clinopyroxenite Hornblendite and clinopyroxene hornblendite, undivided  -j j "^Zit  Reverse fault, observed Normal fault, inferred Fault (relative sense of motion indicated) Spinel sample locality  'White ovals indicate the mineralized zones (from W to E): Northwest Zone, Horsetrail Zone, Hatzl Zone.  Figure 3.1: Simplified geological map of the Turnagain Alaskan-type intrusion, modified from Clark (1975), with its location in British Columbia shown as an inset in the upper right corner (also indicated are the locations of other major Alaskan-type intrusions in B.C. and Alaska). The lithologies of the intrusion are shown in the legend; some units are composites (e.g. olivine clinopyroxenite and clinopyroxenite). The intrusion is entirely fault-bounded, and the large area of hornblende-rich lithologies with associated felsic rocks in the west is mostly interpreted from both airborne and ground geophysics, as well as information from drill holes. The N i sulphide-mineralized zones (Horsetrail and satellite zones) are outlined in white ovals. Sample locations with spinel chemistry discussed in this paper are indicated as white stars.  the southeastern part o f the intrusion, both northwest and southeast o f the Turnagain R i v e r (Figure 3.1). Chromite is c o m m o n i n the more magnesian o l i v i n e - r i c h cumulates and magnetite is t y p i c a l o f the more evolved, clinopyroxene/hornblende-bearing lithologies that comprise the west-central portion o f the intrusion. T h i s part is considered to represent the r o o f o f the intrusion and contains porphyritic, megacrystic, and pegmatoidal textured rocks and appears to intrude the underlying o l i v i n e cumulate rocks based on an interpretation o f aeromagnetic data and diamond d r i l l hole results (courtesy o f H a r d C r e e k N i c k e l C o r p . ) . In the section b e l o w , the t y p i c a l abundances and textures o f spinel i n rocks o f the Turnagain intrusion are described.  3.3.1 Dunite Dunite, the most abundant rock type i n the Turnagain intrusion, is p r i m a r i l y composed o f cumulus o l i v i n e and chromite w i t h m i n o r interstitial clinopyroxene (<10 v o l . % ) and rare phlogopite (0-1 v o l . % ) . Equigranular o l i v i n e is t y p i c a l o f most dunite; however, local postcrystallization deformation has produced dunite w i t h porphyroclastic textures. O l i v i n e grainsize ranges from 2 m m i n fine-grained equigranular dunite to 10 m m i n porphyroclastic dunite. K i n k bands, observed as discrete undulatory extinction bands i n individual o l i v i n e grains, and irregular grain boundaries are also observed. Serpentinization o f o l i v i n e i n dunite is c o m m o n , ranging from none to nearly complete, although the average amount o f serpentinization is - 1 0 % . Secondary magnetite is c o m m o n between o l i v i n e grains. C h r o m i t e i n dunite can be found as chromitite schleiren, pods, lamellae, and rarely as layers (max. 5 c m thick) (Figure 3.2). C h r o m i t e grain sizes are t y p i c a l l y the largest i n chromitite (up to 3 m m ) and slightly smaller i n dunite (up to 2 m m ) , and grain shapes are equigranular to euhedral (Figure 3.3; A and B ) . O l i v i n e may be encased w i t h i n chromitite, but more c o m m o n l y o l i v i n e grains are o n l y partially surrounded b y chromite and are present near the edge o f the chromitite. Dunite t y p i c a l l y contains up to 4 v o l . % disseminated euhedral to subhedral chromite (Figure 3.3 C ) both included w i t h i n o l i v i n e and along grain boundaries between o l i v i n e crystals, although 2 v o l . % is the t y p i c a l abundance. Secondary alteration has resulted i n the formation o f magnetite rims (~30 u m thick) as overgrowths on chromite, and i n some cases a 'ferritchromit' r i m ( C r - r i c h magnetite) has been produced (Figure 3.3D). Ferritchromit, w i t h no directly defined composition (e.g. K a n a r i s - S o t i r i o u et al., 1978; Z a k r z e w s k i , 1989; T a k a s h i & A d a c h i , 1995), is a term broadly used for C r - and A l - r i c h  Figure 3.2: Photographs of chromitite in outcrop from the north-central portion of the Turnagain intrusion. A) Chromitite schleiren, grading into dunite towards the lower part of the photograph. Cross-cutting veins are fdled with serpentine minerals. Pencil is approximately 12 cm long. B) Numerous chromitite schleiren, which may represent disrupted layers, within dunite. Hammer is approximately 50 cm long.  63  0 01  Srp  „  # ,  Figure 3.3: Photomicrographs of chromite textures from chromitite and dunite in the Turnagain intrusion. The white scale bar on each photo is 200 um in length. A) Reflected light, sample 05ES-01-01-01, cluster 5. The large central chromite grain lies within a thin chromitite seam enclosed in dunite consisting of olivine (01) and secondary serpentine (Srp). Note the polygonal shapes of the chromite grains. B) BSE (backscattered electron) image, sample 05ES-01-01-01, cluster 4. Massive chromitite showing equigranular grain shapes produced during slow cooling and recrystallization. A small chalcopyrite (Cpy) inclusion is found in a chromite grain in the bottom right of the photograph. C) BSE image, sample 04ES-10-05-01, cluster 2. This cluster, within a partially serpentinized dunite, shows the primary euhedral nature of the chromite grains as well as the initial development of a thin magnetite rim (bright material on edge of grains). D) Reflected light, sample 04ES-08-01-01. Note the sulphide inclusion in the centre of a chromite grain. The inclusion originally consisted of an immiscible sulphide liquid that crystallized into pyrrhotite (Po) and pentlandite (Pn); note that the habit of the sulphide inclusion is determined by its host chromite grain. The distinct rim around the chromite grain is 'ferritchromit' produced during serpentinization.  64  magnetite, or F e  -rich chromite, rims observed o n cumulus chromite (and rarely as entire  grains) i n serpentinized ultramafic rocks, w h i c h appear to be overgrowths rather than alteration products (Roeder et al., 2001). The thickness o f these rims appears to depend on factors such as position w i t h respect to o l i v i n e , clinopyroxene, and degree o f serpentinization. Since clinopyroxene is only rarely affected by serpentinization, chromite grains w i t h i n or partially encased by clinopyroxene t y p i c a l l y do not show secondary overgrowths/rims.  3.3.2 Wehrlite C u m u l u s o l i v i n e and interstitial clinopyroxene are the dominant phases i n wehrlite from the Turnagain intrusion; however, rare cumulus diopsidic clinopyroxene may occur. O l i v i n e grain size is comparable to that i n dunite (2 m m ) , although equigranular textures are less c o m m o n and only occur i n clinopyroxene-poor rocks. O l i v i n e contained, either partially or entirely, w i t h i n large clinopyroxene oikocrysts is t y p i c a l l y rounded. Porphyroclastic textures are rarely observed i n wehrlite, and clinopyroxene is t y p i c a l l y interstitial to o l i v i n e porphyroclasts and neoblasts. C u m u l u s clinopyroxene is c o m m o n l y finer grained than neighbouring o l i v i n e , w i t h grain sizes ranging from 75 um i n diameter up to 2 m m i n some samples. Serpentine minerals replace only o l i v i n e i n wehrlites, and secondary magnetite is c o m m o n along silicate grain boundaries. Chromite, t y p i c a l l y - 1 5 0 um i n diameter, i n wehrlite is ubiquitous, is always disseminated, and is less abundant than i n dunite (Figure 3.4; A and B ) . Wehrlite-hosted chromite grains are t y p i c a l l y concentrated i n specific areas, or clusters, and chromite grains i n wehrlite tend to exhibit subhedral and anhedral habits. The majority o f chromite grains are included i n o l i v i n e or along o l i v i n e - o l i v i n e or olivine-clinpyroxene grain boundaries, w i t h rare examples included i n interstitial clinopyroxene. Magnetite and ferritchromit rims are as c o m m o n i n wehrlite as those described i n dunite.  3.3.3 Olivine Clinopyroxenite T h i s lithology is t y p i c a l l y composed o f variable amounts o f cumulus o l i v i n e and clinopyroxene, although a few samples contain significant oikocrystic clinopyroxene (Figure 3.4C). T h i s latter type o f o l i v i n e clinopyroxenite c o m m o n l y contains more chromite than o l i v i n e clinopyroxenite where both the silicate minerals are cumulus (see D i s c u s s i o n ) . O l i v i n e grain size (-1 m m ) is significantly smaller compared to o l i v i n e i n wehrlite and dunite and  Figure 3.4: Photomicrographs of chromite textures from wehrlite and olivine clinopyroxenite in the Turnagain intrusion. The scale bar on each photo is 200 urn in length. A) BSE image, sample 04ES-10-06-01, cluster 5. This strongly serpentinized wehrlite contains few chromite grains and those present show well-developed magnetite/ ferritchromit rims, as well as a magnetite aureole (localized, veryfine-grainedmagnetite). B) BSE image, sample 04ES-15-01-05, cluster 1. Small, euhedral chromite grains between cumulus olivine grains with little to no magnetite rim. Note the presence offine-grainedmagnetite along grain boundaries between cumulus minerals and within fractures. C) Reflected light, sample 04ES-01-04-01, cluster 5. Cumulus olivine with abundant interstitial clinopyroxene (olivine clinopyroxenite). D) BSE image, sample 05ES-05-01-01, cluster 7. This grain is one of only two grains found in the entire thin section, which is a common feature of many Alaskan-type olivine clinopyroxenites. This small chromite grain is entirely encased within cumulus clinopyroxene.  66  clinopyroxene grains reach up to 15 m m across. The size o f the two cumulus silicate phases i n o l i v i n e clinopyroxenite appears to be directly proportional to their modal abundance (i.e. an o l i v i n e clinopyroxenite w i t h 60 v o l . % clinopyroxene w i l l generally have an equigranular texture, whereas an o l i v i n e clinopyroxenite w i t h 90 v o l . % clinopyroxene w i l l have significantly larger clinopyroxene and very small o l i v i n e ) . O l i v i n e i n o l i v i n e - p o o r clinopyroxenite is t y p i c a l l y strongly serpentinized. Chromite i n o l i v i n e clinopyroxenite is t y p i c a l l y found as inclusions w i t h i n cumulus clinopyroxene or o l i v i n e , is never interstitial to the silicate minerals, and rarely contains secondary magnetite rims (Figure 3.4; C , D ) . G r a i n sizes are t y p i c a l l y s m a l l , around 150 um, and chromite is c o m m o n l y euhedral (Figure 3.4D). C h r o m i t e abundance is significantly reduced (<0.5 v o l . % ) compared to wehrlite. C h r o m i t e i n o l i v i n e clinopyroxenite w i t h intercumulus clinopyroxene, or clinopyroxene oikocrysts, is c o m m o n l y very similar i n texture and size to chromite found i n both dunite and wehrlite.  3.3.4 Hornblende Clinopyroxenite and Hornblendite Hornblende clinopyroxenite and hornblendite occur i n two distinct settings w i t h i n the Turnagain intrusion. The first setting is as fine-grained dikes that are interpreted to represent e v o l v e d m a g m a compositions. Some o f these hornblendite dikes intrude a pendant o f w a l l r o c k in the northwestern part o f the intrusion (Figure 3.1). Hornblende-bearing rocks, some o f w h i c h are cumulate, also occur i n the west-central portion o f the intrusion. Hornblendite dikes c o m m o n l y contain subhedral ilmenite, whereas hornblende-rich lithologies o f the western portion o f the Turnagain intrusion t y p i c a l l y contain primary magnetite (Figure 3.5). A l t h o u g h its occurrence is limited, magnetite may be found as local accumulations i n hornblendeclinopyroxene-rich lithologies w i t h grains reaching up to 1 c m across. Magnetite is t y p i c a l l y m u c h larger than chromite (about 5 times larger), and is subhedral to anhedral. Some grains appear intergrown (Figure 3.5B) and ilmenite oxy-exsolution is c o m m o n .  3.4 ANALYTICAL TECHNIQUES The spinel content o f each sample, textural relationships to other phases, and relative degree o f alteration were carefully scrutinized using both transmitted and reflected light m i c r o s c o p y prior to analysis. Samples were selected to represent the various rock types found i n the Turnagain intrusion and the range o f spinel morphologies and spinel-silicate associations  67  Figure 3.5: Photomicrographs of magnetite texturesfromsample DDH04-47-7-49, a hornblende clinopyroxenite from the western zone of the Turnagain intrusion. The scale bar on each photo is 200 um in length. A) Cluster 3. This cluster contains large magnetite grains with oxy-exsolved lamellae of ilmenite (Ilm) and larger composite grains of ilmenite (internal and external) that are interpreted to represent granule exsolution. B) Cluster 7. Composite magnetite grain (at least 8 separate grains) with oxy-exsolved lamellae of ilmenite and larger composite granule exsolution blebs along grain boundaries.  68  described above. Some samples contained appreciable spinel, such that l o c a l accumulations o f larger spinel grains were referred to as "clusters". C h r o m i t e grains from three different clusters were analyzed i n each thin section. A total o f 16 samples were selected for microprobe analysis, carbon-coated, and documented using a P h i l i p s X L - 3 0 scanning electron microscope at the U n i v e r s i t y o f B r i t i s h C o l u m b i a , V a n c o u v e r , B C . Quantitative analyses were carried out i n wavelength-dispersion mode using a C a m e c a S X - 5 0 electron microprobe w i t h a beam diameter o f 10 u m , an accelerating voltage o f 15 k e V , and a beam current o f 20 n A w i t h 20 s peak count-time and 10 s background count-time. T h e N i contents o f chromite grains from chromitite samples were analyzed using a fixed matrix, a beam diameter o f 10 p m , an accelerating voltage o f 15 k e V , and a beam current o f 200 n A w i t h peak count-time extended to 100 s and a background time to 50 s. F o r the elements considered, the f o l l o w i n g standards, X - r a y lines and crystals were used: synthetic rhodonite, MnKa,  L I F ; diopside, CaKa,  AlKa,  T A P ; synthetic fayalite, VeKa,  CrKa,  L I F ; rutile, TiKa,  P E T , and SiKa,  T A P ; synthetic spinel,  L I F ; synthetic magnesiochromite, MgATa, T A P , and  P E T ; V metal, VKa, P E T ; synthetic N i S i 0 , ~NiKa, L I F . D a t a 2  4  reduction o f a l l analytical results was undertaken using the " P A P " <(>(pZ) procedure o f P o u c h o u & P i c h o i r (1985). U s i n g the higher beam current and counting times for N i as described above results i n an analytical precision o f <5% relative. A total o f 360 points were analyzed i n this study, 25 o f w h i c h were magnetite analyses. Individual grains, prior to analysis, had their selected point locations ordered from r i m to core. In the case o f grains on the edge o f chromitite schlieren, the part o f the grain closest to a neighbouring silicate was analyzed first, as opposed to the grain boundary i n contact w i t h other chromite. A l l spinels were assumed to be stoichiometric ( K a m p e r m a n et al., 1996) and cation abundances and ferrous/ferric iron were calculated using the method o f Barnes and Roeder (2001). T h i s method isolates T i and V into an u l v o s p i n e l component and is considered the most accurate calculation technique for cations i n spinel-group minerals.  3.5 RESULTS Table 3.1 contains representative chromite and magnetite analyses from the various ultramafic lithologies and the complete set o f spinel analyses from this study are presented i n A p p e n d i x I. B e l o w , the variations i n spinel chemistry are described for spinels from each o f the major rock types o f the Turnagain intrusion.  Table 3.1a: Representative spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion  Rock:  Chromitite  Dunite  Dunite  Dunite  Wehrlite  Sample: Cluster: Grain Number:  05ES-01 -04-01 6 1  04ES-19-01-02 2 1  04ES-03-02-01 5 1  04ES-08-01-01 2 1  04ES-11-03-03 4 2  Style: Zone:  I.  anh. Core  s. anh. Core  Mid  Rim  I. sub. Core  Mid  Rim  s. eu. Core  Mid  Rim  m. sub. Core  Mid  Rim  0.00 0.22 5.07 65.24 0.02 3.82 11.22 0.04 14.19 0.13 0.00 99.96  0.02 0.79 8.98 54.58 0.10 4.71 22.75 0.34 7.12  0.06 0.94 8.99 54.66 0.14 4.31 22.84 0.32 7.17  0.03 0.76 8.73 54.61 0.18 5.15 23.24 0.42 6.86  0.02 0.47 6.72 50.24 0.07 13.72 21.46 0.25 7.79  0.01 0.51 5.72 42.89 0.08 20.56 23.84 0.48 5.75  0.08 0.02 0.02 0.57 0.02 68.76 29.45 0.14 0.93  0.03 0.52 7.35 46.49 0.07 15.97 22.94 0.22 6.84  0.03 0.54 7.28 46.40 0.09 15.98 22.81 0.22 6.90  0.05 0.53 7.47 44.81 0.06 16.75 22.94 0.24 6.64  0.00 1.35 10.23 44.37 0.32 11.65 26.10 0.31 5.54  0.00 1.28 10.26 44.27 0.30 11.95 26.05 0.34 5.53  0.01 1.26 10.47 43.31 0.30 13.03 26.18 0.40 5.50  -  -  -  -  -  -  -  -  -  0.01 99.42  0.03 99.46  0.00 99.99  0.01 100.74  0.00 99.84  0.01 99.99  0.02 100.46  0.01 100.26  0.00 99.48  0.01 99.87  0.00 99.97  0.01 100.45  0.006 1.695 0.196 0.000 0.094 0.308 0.0010.695 0.004 0.000 3.001  0.020 1.472 0.361 0.002 0.121 0.649 0.010 0.362  0.024 1.472 0.361 0.003 0.110 0.651 0.009 0.364  0.019 1.469 0.350 0.004 0.132 0.661 0.012 0.348  0.012 1.351 0.270 0.002 0.351 0.610 0.007 0.395  0.013 1.184 0.234 0.002 0.550 0.701 0.015 0.298  0.000 0.017 0.001 0.000 1.977 0.941 0.005 0.053  0.013 1.260 0.297 0.002 0.412 0.657 0.006 0.349  0.014 1.259 0.295 0.002 0.413 0.655 0.006 0.353  0.014 1.227 0.305 0.001 0.436 0.664 0.007 0.343  0.035 1.202 0.413 0.007 0.300 0.748 0.009 0.283  0.033 1.198 0.414 0.007 0.308 0.746 0.010 0.282  0.032 1.167 0.420 0.007 0.334 0.746 0.012 0.279  -  -  -  -  -  -  -  -  -  -  -  0.000 2.998  0.001 2.995  0.000 2.997  0.000 2.998  0.000 2.999  0.000 2.995  0.001 2.998  0.000 2.998  0.000 2.997  0.000 2.997  0.000 2.997  0.000 2.997  0.817  0.854  0.753  0.685  0.601  0.009  0.640  0.628  0.624  0.607  0.186  0.137  0.151 0.209  0.155  0.219  0.210  0.222  0.216 0.157  0.216  0.057  0.119 0.280  0.000  0.062  0.179 0.068  0.640 0.150  0.623  0.099 0.048  0.753 0.185  0.757  0.112  0.160  0.174  Mid  Rim  0.00 0.22 5.94 62.86 0.05 5.82 11.78 0.00 14.14 0.17 0.01 100.99  0.00 0.28 5.81 63.01 0.01 5.70 11.64 0.05 14.18 0.17 0.01 100.85  0.005 1.615 0.228 0.001 0.142 0.320 0.000 0.685 0.004 0.000 3.001  0.007 1.621 0.223 0.000 0.140 0.317 0.001 0.688 0.004 0.000 3.001  Trivalent End Members 0.814 Cr/Z3+ AI/Z3+  0.115  Fe/I3+  0.072  0.070  Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 2  2  2  3  2  v o 2  3  3  FejOj FeO MnO MgO NiO CaO Total Cations (p.f.u.) Ti Cr AJ V Fe-"* Fe'** Mn Mg Ni Ca Total  0.178  0.991  -  -  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (sm< Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each secti  o  -  -  Table 3.1b: Representative spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion  Rock:  Wehrlite  Wehrlite  Olivine Clinopyroxenite  Olivine Clinopyroxenite  Hornblende Clinopyroxenite  Sample: Cluster: Grain Number:  04ES-16-08-01 6 3  04ES-10-06-01 1 2  04ES-06-06-01 4.5 2  05ES-05-01-01 8 1  DDH04^t7-7-49 5 1  Style: Zone: Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 2  2  2  3  2  vo 2  3  3  F e ^ FeO MnO MgO NiO CaO Total  s. eu. Rim  Mid  Mid  m. anh. Core  Mid  Rim  m. anh. Core  Mid  Mid  s. eu. Core  Mid  Rim  I. anh. Core  Mid  Rim  0.01 1.03 7.99 49.53 0.08 11.56 20.19 0.18 8.88  0.03 1.05 7.85 50.34 0.08 11.46 19.79 0.25 9.22  0.04 1.01 8.01 49.73 0.08 11.60 19.79 0.26 9.11  0.00 0.89 11.86 42.92 0.16 13.33 24.21 0.30 6.70  0.03 0.94 12.00 42.33 0.20 13.34 24.16 0.37 6.68  0.03 0.11 0.03 4.83 0.00 64.67 28.70 0.35 1.43  0.02 1.02 8.35 48.48 0.22 10.11 26.30 0.41 4.92  0.00 0.98 8.61 48.60 0.24 9.68 26.26 0.35 4.96  0.01 0.84 8.25 46.95 0.25 11.33 25.75 0.78 4.70  0.03 2.51 4.64 28.34 0.11 30.20 25.09 4.07 3.08  0.00 2.48 4.44 27.45 0.08 31.67 25.31 3.92 2.98  0.03 2.42 4.18 26.90 0.07 32.01 25.19 3.87 2.79  0.03 3.27 2.27 0.13 0.46 59.94 34.04 0.26 0.46  0.03 3.11 0.95 0.14 0.45 61.20 33.80 0.23 0.24  0.03 0.35 0.16 0.13 0.73 67.39 31.82 0.02 0.15  -  -  -  -  -  -  -  -  -  -  -  -  -  -  0.00 99.45  0.01 100.09  0.00 99.64  0.01 100.39  0.00 100.05  0.00 100.17  0.01 99.85  0.01 99.69  0.03 98.90  0.17 98.24  0.26 98.60  0.34 97.80  0.03 100.90  0.02 100.17  0.01 100.78  Cations (p.f.u.) Ti Cr Al V Fe"* Fe~* Mn Mg  0.026 1.329 0.320 0.002 0.295 0.573 0.005 0.449  0.027 1.340 0.311 0.002 0.290 0.557 0.007 0.463  0.026 1.329 0.319 0.002 0.295 0.560 0.007 0.459  0.023 1.140 0.470 0.004 0.337 0.680 0.009 0.336  0.024 1.127 0.476 0.005 0.338 0.681 0.011 0.335  0.003 0.145 0.002 0.000 1.846 0.910 0.011 0.081  0.027 1.330 0.342 0.005 0.264 0.763 0.012 0.255  0.026 1.333 0.352 0.005 0.253 0.762 0.010 0.257  0.022 1.303 0.341 0.006 0.299 0.756 0.023 0.246  0.069 0.821 0.200 0.003 0.833 0.769 0.126 0.168  0.068 0.795 0.192 0.002 0.873 0.775 0.122 0.163  0.067 0.787 0.182 0.002 0.891 0.779 0.121 0.154  0.092 0.004 0.100 0.011 1.687 1.064 0.008 0.026  0.089 0.004 0.043 0.011 1.751 1.074 0.008 0.014  0.010 0.004 0.007 0.018 1.929 1.012 0.001 0.008  Ni Ca Total  0.000 2.999  0.000 2.998  0.000 2.997  0.000 2.998  0.000 2.997  0.000 2.998  0.000 2.997  0.000 2.998  0.001 2.997  0.007 2.997  0.010 2.999  0.014 2.998  0.001 2.993  0.001 2.994  0.001 2.990  Trivalent End Members Crffi3+ 0.684 AI/X3+ 0.164  0.690  0.684  0.586  0.687  0.688  0.670  0.443  0.428  0.002  0.001  0.154  0.449  0.479  0.942  0.024 0.974  0.002 0.004  0.926  0.103 0.469  0.056  0.174  0.182 0.130  0.108  0.150  0.176 0.136  0.176  0.152  0.241 0.173  0.423 0.098  0.002  0.164 0.152  0.581 0.245  0.073  0.160  Fe/£3+  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (sm; Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each secti  -  0.994  3.5.1 Chromitite A l t h o u g h v o l u m e t r i c a l l y m i n o r i n the Turnagain intrusion, chromitite is petrologically important. Chromite grains from chromitites are characterized by the most C r - and M g - r i c h compositions o f all lithologies ( C r 0 = 59-67 wt.%, M g O = 10-14 wt.%) w i t h 2  correspondingly l o w T i 0  2  3  (0.24-0.66 w t . % ) , V 0 2  3  (0.01-0.34 w t . % ) , A 1 0 (4.60-7.14 w t . % ) , 2  3  and F e 0 (3.82-6.88 wt.%) contents (Figures 3.6-3.7). T w o samples (05ES-01-03-01 and 2  3  05ES-01-04-01) contain relatively N i - r i c h chromite grains ( N i O = 0.13-0.20 w t . % ) . A l l chromite analyses from chromitite are distinguished by F e / ( F e + C r + A l ) <0.1 (Figure 3 . 7 A ) . 3 +  3 +  There is no iron-enrichment trend present i n the chromite analyses from chromitites indicating that their compositions l i k e l y record primary spinel compositions and that they have not been modified by subsolidus or post-magmatic processes (see D i s c u s s i o n ) .  3.5.2 Dunite C h r o m i t e analyses from dunite span a relatively large range i n composition ( C r 0 = 34-56 2  3  wt.%, T i 0 = 0.01-1.01 wt.%, F e O = 20-29 wt.%, F e 0 = 3.5-18.6 wt.%) compared to 2  2  3  chromite from chromitites (Figure 3.6-3.7). W i t h the exception o f sample 0 4 E S - 1 9 - 0 1 - 0 2 , spinel analyses from each dunite sample show an overall iron-enrichment trend (Figure 3 . 7 A ) , w h i c h is a c o m m o n feature o f Alaskan-type intrusions (Barnes & Roeder, 2001). A l l F e - r i c h 3 +  spinel compositions from dunite represent analyses o f magnetite/ferritchromit rims around chromite grains and are associated w i t h serpentine-group mineral replacement o f o l i v i n e . A n a l y s e s o f spinel grains from sample 0 4 E S - 1 9 - 0 1 - 0 2 have F e / ( F e + C r + A l ) < 0 . 1 , similar to 3+  3+  those from the chromitites described above.  3.5.3 Wehrlite S i m i l a r to the dunite samples, chromite analyses from wehrlite i n the Turnagain intrusion show a w i d e compositional range (Figures 3.6-3.7) and are relatively enriched i n A 1 0 2  15.4 wt.%), T i 0  2  3  (7.5-  (0.7-1.8 wt.%) and F e 0 (10-18 w t . % ) . Magnetite and ferritchromit 2  3  compositions, w h i l e rare, are nonetheless present and indicate that similar post-secondary process occurred i n both wehrlite and dunite. Chromite analyses from one wehrlite sample (04ES-15-01-05) have markedly l o w F e / ( F e + C r + A l ) compared to the above wehrlites 3 +  3 +  (Figure 3.6). T h e compositions o f chromite from this sample have the lowest F e 0 2  3  (0.94-3.97  wt.%) o f a l l spinel analyses from the Turnagain intrusion, and relatively l o w C r / C r + A l (0.68-  Figure 3.6: Chromite compositional ternary diagrams. A) Trivalent cation (Fe -Cr-Al) plot of all Turnagain spinel compositions. All samples are represented by sample number. Chromites plot in the lower 40% of the diagram with the exception of magnetite rim analyses, which plot at or near the Fe apex, and ferritchromit analyses, which plot in the intermediate part of the diagram. B) Ternary diagram (Mg-Fe -Fe ) of all Turnagain spinel compositions. 3+  3+  2+  3+  Chromitite •  05ES-01-01-01  0.9  • 05ES-01-04-01  0.8  • 04ES-19-01-02  magnetite  0.9 h  • 05ES-01-03-01 Dunite  0.8  • 04ES-08-01-01  r  O04ES-10-05-01  0.7  • 04ES-03-02-01  0.7  Wehrlite • 04ES-10-06-01  <0.6  O +  "ferritchromit"  • 04ES-11-03-03 • 04ES-15-01-05 • 04ES-16-05-01  A 0.5 0  o  Ol cpxite A04ES-06-06-01 A04ES-01-04-01  ,0.4  0.6  O  A04ES-05-01-01 Hbl cpxite  <  t 0.5 P 0.4  DDH04-47-7-49 XDDH05-84-19-104  0.3  0.3  0.2  0.2  0.1  chromitites  0.2  0.1  0.4  0.6  0.2  0.8  Fe /(Fe + Mg) 2+  0.4  0.6  0.8  Fe /(Fe + Mg)  2+  2+  2+  Figure 3.7: Binary plots of spinel compositions from the Turnagain intrusion represented by sample number. These plots are projections of the spinel prism (Irvine, 1965). A) Fe /(Fe +Mg) (Fe#) vs. Fe /(Fe +Cr+Al), or divalent vs. trivalent cation plot. A distinct Fe-enrichment trend exists for most Turnagain chromite compositions, a typical feature of Alaskan-type intrusions, with the exception of chromite grains from the chromitites and other chromite grains with Fe /(Fe +Cr+Al) <0.1. B) Fe# vs. Cr/Cr+Al. Chromite grains from the chromitites have significantly lower Fe /(Fe +Mg) compared to other spinel analyses. Magnetite analyses are not plotted due to their very low Cr and Mg contents. 2+  3+  2+  3+  2+  2+  3+  3+  0.73), h i g h T i 0  (1.1-2.5 wt.%), and h i g h V 0  2  2  3  (0.06-0.38 w t . % ) . In terms o f their trivalent  cation abundances (Figure 3 . 6 A ) , chromite compositions from i n d i v i d u a l wehrlite samples, w i t h the exception o f the above sample, are characterized b y intermediate s l o p i n g trends i n terms o f trivalent cations (decreasing C r , increasing F e  3 +  and A l ) . C h r o m i t e compositions from  sample 04ES-15-01-05 plot i n the field o f the " C r - A l trend" o f Barnes and R o e d e r (2001) and l i k e l y reflect the effect o f exchange w i t h A l - b e a r i n g clinopyroxene (see D i s c u s s i o n ) .  3.5.4 Olivine Clinopyroxenite M o s t o l i v i n e clinopyroxenite sampled i n the Turnagain intrusion, and indeed i n other A l a s k a n type intrusions (Irvine, 1965), is d e v o i d o f chromite. A few samples o f o l i v i n e clinopyroxenite from the Turnagain intrusion contain chromite, however the nature o f the grains (small sizes, l o w abundances) appears to have a l l o w e d for more extensive subsolidus to post-magmatic compositional modifications compared to spinel grains from the previously described rock types. Chromite grains from o l i v i n e clinopyroxenite are relatively enriched i n F e O (23-27 wt.%>), F e 0 (9.7-17.2 wt.%), T i 0 2  3  2  (0.9-2.1 wt.%) and V 0 2  3  (0.22-0.54 w t . % ) , and depleted  i n A 1 0 (5.68-9.40 wt.%) compared to analyses from the other rock types. One notable 2  3  exception is sample 0 4 E S - 0 1 - 0 4 - 0 1 , where the spinel grains are characterized by F e / ( F e + C r + A l ) < 0 . 1 (Figure 3.7), and overlap w i t h the analyses from the dunite sample 3+  3+  0 4 E S - 1 9 - 0 1 - 0 2 . S p i n e l analyses from sample 05ES-05-01-01 are also distinct w i t h high amounts o f T i 0  (2.5-3.2 wt.%) and F e / ( F e + C r + A l ) > 0 . 4 (Figure 3 . 7 A , 3 . 8 A ) , w h i c h 3+  2  3+  indicates that a l l analyzed grains are ferritchromit i n composition. T h i s sample contains s m a l l (150 um) chromite grains entirely encased w i t h i n cumulus diopside (Figure 3.4H), thus the ferritchromit composition o f the spinels i n this sample is l i k e l y the result o f subsolidus reequilibration w i t h the hosting clinopyroxene. W i t h respect to trivalent cations, chromite grains from o l i v i n e clinopyroxenite do not show the strong intrasample variations as seen in the dunites and wehrlites.  3.5.5 Hornblende Clinopyroxenite In Alaskan-type intrusions, liquidus magnetite generally begins to crystallize after an extended period o f clinopyroxene saturation and after the cessation o f chromite crystallization. C h r o m i t e ceases to crystallize shortly after clinopyroxene saturation because C r is compatible i n clinopyroxene (e.g. Irvine, 1965; F i n d l a y , 1969; H i l l & Roeder, 1974; C l a r k , 1978). A n a l y s e s  75  4.0  3.5  •  05ES-01-01-01  •  05ES-01-04-01  •  05ES-01-03-01  0.025  A  Chromitite  B  x  X  Dunite • 04ES-19-01-02 •  04ES-08-01-01  X  O04ES-10-05-01 •  3.0  0.020  04ES-03-02-01  Wehrlite •  X  04ES-10-06-01  X  • 04ES-11-03-03 • 04ES-15-01-05 • 04ES-16-0&O1  2.5  X  Ol cpxite  0.015  A04ES-06-06-01  X  A04ES-01-04-01  X  A04ES-05-01-01 Hbl cpxite DDH04-47-7-49  e.2.0  X  a.  XDDH06-84-19-104|  CM  6  o  X  X  p 1.5  1.0  r  0.5  0.2  0.4  0.6  0.8  Fe /(Fe + Cr + Al) 3+  Ti (c.p.f.u.)  3+  Figure 3.8: Binary plots of spinel compositionsfromthe Turnagain intrusion. A) Fe /(Fe +Cr+Al) vs. Ti0 . Spinel analysesfromthe Turnagain intrusion show a wide range of Ti contents. Note that both magnetite-bearing samples plot parallel to the Y-axis at almost constant Fe #. Coupled increases (positive trends) are indicative of re-equilibration with interstitial melt, while increasing Fe without increasing Ti is indicative of serpentinization. B) Ti vs. V. Most samples are characterized by nearly vertical trends with the exception of magnetite from DDH04-47-7-49. Note the V-enrichment of magnetitefromsample DDH05-84-19-104. 3+  3+  2  3+  3+  o f spinel from two cumulus magnetite-bearing hornblende clinopyroxenites, both from drillcore, show contrasting compositions. Spinel from sample D D H 0 5 - 8 4 - 1 9 is nearly pure end-member magnetite ( F e 0 = 67.1-67.8 wt.%, C r 0 2  3  2  3  = 0.37-0.60 wt.%, A 1 0 = 0.06-0.18 2  3  w t . % ) , whereas magnetite from sample D D H 0 4 - 4 7 - 4 9 shows slight A l enrichment ( A 1 0 2  0.12-3.77 wt.%) and relative V enrichment ( V 0 2  high T i 0  2  3  3  =  = 0.22-0.73 w t . % ) , and exhibits relatively  (0.15-4.0 wt.%) (Figure 3.8).  3.6 DISCUSSION 3.6.1 Primary Spinel Compositions A l t h o u g h spinel is an extremely sensitive petrogenetic indicator i n igneous rocks, the composition o f primary spinel grains may be changed or reset by syn- and post-magmatic processes (e.g. Roeder & C a m p b e l l , 1985, P o w e r et al., 2000). In particular, reequilibration w i t h interstitial melt and/or hosting silicate minerals and serpentinization can significantly change the composition o f spinel (e.g. Roeder & C a m p b e l l , 1985; Sack & G h i o r s o , 1991; S c o w e n et al., 1991; Roeder, 1994; M e l i n n i et al., 2005). A n important observation from this study is that spinel grains from chromitite schleiren, w i s p s , pods, and layers have the most C r r i c h , A l - and F e - p o o r , and lowest Fe# compositions i n the Turnagain intrusion (Figures 3.63+  3.7), suggesting that they represent primary or near primary compositions. C h r o m i t e grains i n the chromitites d i d not significantly interact w i t h the hosting o l i v i n e or interstitial melt and thus preserved the highest temperature spinel compositions that crystallized from the most primitive (highest M g O ) magmas. Chromitite sample 05ES-01-04-01 contains chromite w i t h the lowest Fe# (0.30-0.35) consistent w i t h the primary nature o f these grains. In Figure 3.9, chromite analyses from most o f the dunite, wehrlite, and o l i v i n e clinopyroxenite samples plot along vectors that converge towards the field o f each o f the chromitite compositions, w h i c h indicates that the compositions closest to the chromitite field have undergone the least amount o f re-equilibration. The p r o x i m i t y o f dunite, wehrlite, and o l i v i n e clinopyroxenite chromite compositions to those from chromitite samples, coupled w i t h the region o f C r - A l - F e  space  where sample-specific compositional vectors intersect, is consistent w i t h derivation from a primary m a g m a composition similar to that w h i c h precipitated the chromitites.  Chromitite  Dunite  Wehrlite  O l cpxite  ^05ES-01-01-01 •04ES-19-01-02  • 04ES-10-06-01 A 0 4 E S - 0 6 - 0 6 - 0 1  •  • 04ES-11-03-03 A 0 4 E S - 0 1 - 0 4 - 0 1  05ES-01-04-01 • 0 4 E S - 0 8 - 0 1 - 0 1  • 05ES-01 -03-01 O 0 4 E S - 1 0 - 0 5 - 0 1  • 04ES-15-01 -05  • 04ES-03-02-01  •04ES-16-05-01  Figure 3.9: Trivalent cation (Fe -Cr-Al) plot of Turnagain spinel compositions, focusing on those compositions nearest end-member chromite (inset in upper left shows entire ternary diagram). No rim compositions are plotted. Chromite grainsfromchromitites plot near the Cr-apex, whereas all compositionsfromwehrlites plot systematically to more Al-rich compositions than spinel grainsfromdunite. Note the wehrlite (04ES-15-01-05) and olivine clinopyroxenite (04ES-01-04-01) samples with anomalously low Fe and high Al contents. Arrows indicate trends of spinel compositionsfromindividual samples. Note the direction of trends (some arrows trend almost directly towards the Fe apex, whereas others trend towards increased Al and Fe ), which explained by different reequilibration processes, and that all trends converge towards the area of the chromitite analyses. 3+  3+  3+  3+  3.6.2 Re-equilibration Trends A l l chromite grains, except those from the chromitites, have undergone substantial compositional modification at h i g h temperatures during c o o l i n g and interaction w i t h e v o l v e d interstitial melt, enclosing silicates, or o x i d i z i n g fluids. The intersample change o f chromite Fe# from chromitite to other lithologies at near-constant F e , as exhibited by specific samples 3 +  in Figures 3.6, 3.7, and 3.9, is l i k e l y the result o f olivine+chromite fractionation - o l i v i n e depletes the melt i n M g during crystallization and chromite depletes the melt i n C r such that co-precipitating chromite w i l l have progressively higher Fe# and lower C r / A l . T h e spinel trends w i t h intermediate slopes on Figure 3.9, w h i c h contains o n l y core and intermediate position analyses (no rims)mostly from wehrlite and o l i v i n e clinopyroxenite, converge towards the chromitite field and exhibit intrasample variations toward higher A l and F e  3 +  with  increasing Fe#. These trends can be explained by equilibration w i t h e v o l v e d interstitial melt: the melt w i t h w h i c h these chromite grains were i n contact (either directly or by diffusion through o l i v i n e ) was l i k e l y relatively r i c h i n C a , A l , T i , and F e  . A l t h o u g h the compositions  o f some samples i n this trend may be related to their crystallization from a fractionated l i q u i d , the dunite sample that parallels them d i d not and thus exhibits compositions related to reequilibration w i t h trapped melt. Chromite compositions w i t h F e / ( F e + C r + A l ) > 0 . 1 , w h i c h 3+  3+  also exhibit an increase i n Fe# (Figure 3.7), appear to have been modified by subsolidus reequilibration w i t h enclosing or enveloping o l i v i n e and by o x i d i z i n g fluids. The chromite compositions from dunites 04ES-03-02-01 and 04ES-08-0T-01 overlap i n the C r - A l - F e ternary (Figure 3.9), extending parallel to the C r - F e  3 +  j o i n but are distinct w i t h respect to Fe#  (Figure 3 . 7 A ) . M o s t o f the spinel grains i n these two samples occur along o l i v i n e grain boundaries, not inside o l i v i n e , and the increase i n F e / ( C r + A l + F e ) can be attributed to 3 +  3 +  oxidation b y fluids that l o c a l l y precipitated magnetite (but d i d not i n v o l v e serpentinization). The increase o f chromite Fe# is the result o f the exchange o f F e  2 +  from o l i v i n e to chromite  during c o o l i n g ; the spinel grains from these two dunite samples do not show enrichments i n A l or T i , thus the trend towards lower Fe# is best explained by exchange w i t h o l i v i n e , i n the absence o f interstitial melt. T h e unusual spinel compositions from wehrlite sample 0 4 E S - 1 5 01-05 and o l i v i n e clinopyroxenite sample 04ES-01-04-01 - relatively h i g h A l / C r and l o w F e  3 +  - m a y be attributed to their silicate mineralogy. These samples contain cumulus o l i v i n e and chromite surrounded b y 2 cm-diameter C r - r i c h (see Chapter 4) clinopyroxene oikocrysts. T h e v o l u m e ratio o f clinopyroxene to chromite is approximately 50:1, such that the significant  compositional changes exhibited by the chromite i n these two samples is o n l y w e a k l y reflected i n the hosting clinopyroxene.  3.6.3 Compositional Effects of Serpentinization on Spinel Chemistry Magnetite and ferritchromit rims around chromite grains i n many rocks from the Turnagain intrusion were formed during serpentinization. These rims, where w i d e enough to analyze w i t h a 10 u m electron beam, exhibit compositions distinct from the primary spinel compositions i n the chromitites and the high-temperature re-equilibrated compositions p r e v i o u s l y documented (Figure 3.9). The chromite analyses from dunite, wehrlite, and o l i v i n e clinopyroxenite samples that plot near the F e  3 +  apex i n Figure 3 . 6 A are nearly pure magnetite i n c o m p o s i t i o n and l i k e l y  reflect nucleation o f magnetite around pre-existing chromite during serpentinization. Ferritchromit rims are recognized by i n d i v i d u a l spot analyses that plot further towards the C r F e j o i n than their respective intrasample c h e m i c a l trends (e.g. 0 4 E S - 1 0 - 0 5 - 0 1 ; F i g u r e 3.9). 3 +  3+  These ferritchromit rims are characterized by l o w e r C r , slightly l o w e r A l , and higher F e compared to other analyses and reflect the F e - r i c h and C r - p o o r nature o f the serpentinizing fluids from w h i c h these rims formed. It is unclear whether ferritchromit rims are products o f nucleation or reaction w i t h serpentinizing fluids. H o w e v e r , some samples exhibit both ferritchromit and magnetite rims (e.g. 0 4 E S - 0 3 - 0 2 - 0 1 ) , suggesting that ferritchromit represents a reaction product between magnetite-saturated serpentinizing fluids and chromite w i t h a coreto-rim order o f formation o f chromite —> ferritchromit —> magnetite.  3.6.4 Implications for the Redox State of the Turnagain Intrusion The low F e  3 +  content o f chromite grains from the chromitites i n the Turnagain intrusion  (Clark, 1978) is consistent w i t h a l o w F e / F e 3 +  2 +  ratio (i.e. relatively l o w o x y g e n fugacity) i n  the parental m a g m a (e.g. P a r k i n s o n & A r c u l u s , 1999). H o w e v e r , most A l a s k a n - t y p e intrusions appear to have formed from relatively o x i d i z e d arc magmas, w i t h calculated A F M Q ( l o g units o f o x y g e n relative to the fayalite-magnetite-quartz synthetic buffer) values between +1 to +3.5 (e.g. B a l l h a u s et al,  1991; C a r m i c h a e l , 1991; R o h r b a c h et al, 2005). U n d e r such o x i d i z e d  conditions, sulphur w i l l be dominantly dissolved as S O 2 , SO3, or SO4 " rather than sulphide ( S ) and the magmas w i l l not saturate i n an i m m i s c i b l e sulphide l i q u i d unless they are reduced 2  t o 7 O 2 values b e l o w F M Q (Jugo et al, 2004; 2005). T h e presence o f significant amounts o f sulphide i n the Turnagain intrusion indicates that the magmas achieved sulphide saturation and  therefore the o x y g e n fugacity was substantially lower than that t y p i c a l for other Alaskan-type intrusions (e.g. Garuti et al., 2003). In Figure 3.10, an expanded v i e w o f the C r - A l - F e  3 +  ternary, a l l chromite compositions from this study are plotted by lithology, w i t h the data density m a x i m a ( 5 0 % and 90%) o f chromite compositions from other A l a s k a n - t y p e intrusions from Barnes & Roeder (2001). The majority o f chromite compositions from the Turnagain intrusion lie to lower F e  3 +  values than the established compositional fields. T h e compositions  from chromitites contain significantly less F e  3 +  than other chromite compositions and higher  C r / A l , w h i c h suggests that the chromitites crystallized from magmas w i t h a lower o x y g e n fugacity than the parental magmas o f other Alaskan-type intrusions. T h e l o w F e  3 +  field for  other Alaskan-type intrusions on Figure 3.10 may represent compositions that result from reequilibration w i t h clinopyroxene as observed i n this study. A l t h o u g h not shown o n Figure 3.10, chromite compositions from chromitite i n the Turnagain intrusion plot w e l l w i t h i n the boninite field (see Barnes & Roeder, 2001), w h i c h may indicate that the magmas parental to the Turnagain intrusion also originated from a mantle previously depleted by partial melting. Decompression melting at back-arc ridges segregates Pt alloys i n the residue (lithospheric mantle) w h i c h , i f remelted by slab-derived fluids, w o u l d generate a P t - r i c h basaltic melt (Kepezhinskas & Defant, 2 0 0 1 ; Batanova et al., 2005). The remelting o f a Pt-enriched, previously depleted mantle, i n a subduction zone setting may explain w h y many Alaskan-type intrusions are relatively enriched i n Pt (Green et al., 2004; Batanova et al., 2005). Inclusions o f phyllite are observed i n drillcore from the sulphide-mineralized zones o f the Turnagain intrusion (Chapter 4) and reduction o f the Turnagain parental magmas was l i k e l y achieved by the local assimilation o f this graphitic, pyritic phyllite (Chapter 2 and 4). A s s i m i l a t i o n o f the pyrite-bearing phyllite also contributed additional S to the magma, thus i n c r e a s i n g a n d a l l o w i n g for early sulphide saturation. The relatively reducedJO2 o f the Turnagain parental magmas not only lead to early sulphide saturation, but resulted i n the crystallization o f F e  -poor chromite as represented b y the chromitites. Chromite compositions  from chromitites, therefore, may represent a possible reconnaissance exploration tool for assessing the relative redox state o f parental magmas to ultramafic rocks where o n l y o l i v i n e is co-crystallizing, and thus may be used as an indicator o f the potential for magmatic sulphide mineralization i n Alaskan-type intrusions.  Figure 3.10: Trivalent cation (Fe -Cr-Al) plot of Turnagain chromite compositions (inset in upper left shows entire ternary diagram). All samples are distinguished by lithology. Chromite compositions from the Turnagain intrusion are overlain by the data density maxima for other Alaskan-type intrusionsfromthe compilation of Barnes & Roeder (2001). The 50% field is coloured dark grey (50% of all Alaskan-type spinel data plot within thisfield)and the 90% percent field is shaded light grey. In general the Turnagain spinel compositions have significantly lower Fe and high Cr/(Cr+Al)relative to other Alaskan-type spinels, which is consistent with relatively low oxygen fugacity of the parental magmas of the Turnagain intrusion. 3+  3+  82  3.7 CONCLUSION The p r i n c i p a l results o f this study o n spinel compositions i n ultramafic rocks from the Turnagain Alaskan-type intrusion are 1) primary spinel compositions are relatively F e - p o o r 3+  and C r - r i c h compared to published results from other A l a s k a n - t y p e intrusions, especially chromite from chromitite, 2) chromites from dunite, wehrlite and o l i v i n e clinopyroxenite exhibit intrasample trends that can be related to a variety o f processes, i n c l u d i n g o l i v i n e fractionation, re-equilibration w i t h interstitial melt, re-equilibration w i t h coexisting silicate phases, oxidation, and serpentinization, 3) most intrasample re-equilibration trends can be interpolated to originate from the field o f spinel compositions from chromitites, suggesting that a l l lithologies i n the Turnagain intrusion crystallized from a similar parental magma, and 4) chromite compositions from chromitite are extremely F e - p o o r , indicating their 3+  crystallization from a m a g m a characterized by a relatively l o w o x y g e n fugacity compared to other A l a s k a n - t y p e intrusions. The reduced nature o f the parental magmas, attributed to the assimilation o f graphitic and pyritic country rocks, appears to have promoted local sulphide saturation. Therefore the F e  3 +  content o f chromite from chromitites may be used as a  reconnaissance exploration tool for assessing the relative redox state and sulphide mineralization potential o f Alaskan-type intrusions.  3.8 A C K N O W L E D G E M E N T S W e w o u l d like to thank M a t i Raudsepp at the U n i v e r s i t y o f B r i t i s h C o l u m b i a for use o f the electron microprobe and support during the research phase o f this manuscript, as w e l l as C a r o l i n e - E m m a n u e l l e Morisset at the Pacific Centre for Isotopic and G e o c h e m i c a l Research, U n i v e r s i t y o f B r i t i s h C o l u m b i a , for her input into this manuscript. The authors are grateful to H a r d C r e e k N i c k e l C o r p . for continued field support for this project and to J i m R e e d o f Pacific Western Helicopters for his exemplary logistical support i n the field. Special thanks to T o n y H i t c h i n s , B r u c e Northcote, C h r i s B a l d y s , and M a r k Jarvis (President) o f H a r d C r e e k N i c k e l C o r p . for their generous support and interactions throughout the p e r i o d o f the p r i n c i p a l author's M . S c . thesis at U B C . F u n d i n g for this project was p r o v i d e d by a research grant from H a r d C r e e k N i c k e l C o r p . (formerly C a n a d i a n M e t a l s E x p l o r a t i o n L t d . ) .  3.9 R E F E R E N C E S Ballhaus, C , B e r r y , R . F . , & Green, D . H . (1991). H i g h pressure experimental calibration o f the olivine-orthopyroxene-spinel o x y g e n geobarometer: implications for the o x i d a t i o n state o f the upper mantle. Contributions to Mineralogy and Petrology 107 (1), 27-40 Barnes, S.J., & Roeder, P . L . (2001). T h e range o f spinel compositions i n terrestrial mafic and ultramafic rocks. Journal of Petrology 42 (12), 2279-2302 Batanova, V . G . , Pertsev, A . N . , K a m e n e t s k y , V . S . , A r i s k i n , A . A . , M o c h a l o v , A . G . , & Sobolev, A . V . (2005). Crustal evolution o f island-arc ultramafic magma: G a l m o e n a n p y r o x e n i t e dunite plutonic c o m p l e x , K o r y a k H i g h l a n d (Far East Russia). Journal of Petrology 46, 1345-1366 C a r m i c h a e l , I . S . E . (1991). T h e redox states o f basic and silicic magmas: a reflection o f their source regions? Contributions to Mineralogy and Petrology 106,  129-141  C l a r k , T . (1975). G e o l o g y o f an ultramafic c o m p l e x o n the Turnagain R i v e r , northwestern B . C . ; unpublished P h D thesis, Queen's University, 454p. C l a r k , T . (1978). O x i d e minerals i n the Turnagain ultramafic complex, northwestern B r i t i s h C o l u m b i a . Canadian Journal of Earth Sciences 15, 1893-1903 C l a r k , T . (1980). Petrology o f the Turnagain ultramafic c o m p l e x , northwestern B r i t i s h C o l u m b i a . Canadian Journal of Earth Sciences 17, 744-757 D i c k , J . B . , & B u l l e n , T . (1984). C h r o m i a n spinel as a petrogenetic indicator i n abyssal and alpine-type peridotites and spatially associated lavas. Contributions to Mineralogy and Petrology 86, 54-76 Erdmer, P . , M i h a l y n u k , M . G . , Gabrielse, H . , H e a m a n , L . M . , & Creaser, R . A . (2005). M i s s i s s i p p i a n v o l c a n i c assemblage conformably o v e r l y i n g C o r d i l l e r a n m i o g e o c l i n a l strata, Turnagain R i v e r area, northern B r i t i s h C o l u m b i a , is not part o f an accreted terrane. Canadian Journal of Earth Sciences 42, 1449-1465 F i n d l a y , D . C . (1969). O r i g i n o f the Tulameen ultramafic-gabbro c o m p l e x , southern B r i t i s h C o l u m b i a . Canadian Journal of Earth Sciences 6, 399-425 Foster, F . (1974). H i s t o r y and o r i g i n o f the Polaris ultramafic c o m p l e x i n the A i k e n L a k e area o f north-central B r i t i s h C o l u m b i a ; unpublished B . S c . thesis, University of British Columbia, 66p. Gabrielse, H . (1998). G e o l o g y o f C r y L a k e and Dease L a k e m a p areas, north-central B r i t i s h C o l u m b i a ; Geological Survey of Canada, B u l l e t i n 504, 147p  Garuti, G., Pushkarev, E.V., Zaccarini, F., Cabella, R., & Anikina, E. (2003). Chromite composition and platinum-group mineral assemblage in the Uktus Uralian-Alaskan-type complex (Central Urals, Russia). Mineralium Deposita 38, 312-326 Green, D.H., Schmidt, M.W., & Hibberson, W.O. (2004). Island-arc ankaramites: primitive melts from fluxed refactory lherzolitic mantle. Journal of Petrology 45, 391-403 Hill, R., & Roeder, P. (1974). The crystallization of spinel from basaltic liquid as a function of oxygen fugacity. Journal of Geology 82, 709-729 Irvine, T.N. (1965). Chromian spinel as a petrogenetic indicator. Part I. Theory. Canadian Journal of Earth Sciences 2, 648-672 Irvine, T.N. (1967). Chromian spinel as a petrogenetic indicator. Part II. Petrological applications. Canadian Journal of Earth Sciences 4, 71-103 Jugo, P.J., Luth, R.W., & Richards, J.P. (2004). Experimental data on the speciation of sulfur as a function of oxygen fugacity in basaltic melts. Geochimica et Cosmochimia Acta 69 (2), 497-503 Jugo, P.J., Luth, R.W., & Richards, J.P. (2005). An experimental study of the sulfur content in basaltic melts saturated with immiscible sulfide or sulfate liquids at 1300°C and 1.0 GPa. Journal of Petrology 46 (4), 783-798 Kamenetsky, V.S., Crawford, A.J., & Meffre, S. (2001). Factors controlling chemistry of magmatic spinel: An empirical study of associated olivine, chrome-spinel and melt inclusion from primitive rocks. Journal of Petrology 42 (4), 655-671 Kamperman, M . , Danyushevsky, L.V., Taylor, W.R., & Jablonski, W. (1996). Direct oxygen measurements of Cr-rich spinel: Implications for spinel stoichiometry. American Mineralogist SI, 1186-1194 Kanaris-Sotiriou, R., Gibb, G.F., Carswell, D.A., & Curtis, C D . (1978). Trace-element distribution and ore formation in vein-metasomatised peridotite at Kalskaret, near Tafjord, South Norway. Contributions to Mineralogy and Petrology 67, 289-295 Kepezhinskas, P., & Defant, M.J. (2001). Nonchondritic Pt/Pd ratios in arc mantle xenoliths: Evidence for platinum enrichment in depleted island-arc mantle sources. Geology 29, 851854 Krause, J., Brugmann, G.E., Pushkarev, E.V. (2007). Accessory and rock forming minerals monitoring the evolution of zoned mafic-ultramafic complexes in the Central Ural Mountains. Lithos 95, 19-42  Mellini, M . , Rumori, C , & Viti, C. (2005). Hydrothermally reset magmatic spinels in retrograde serpentinites: formation of "ferritchromit" rims and chlorite aureoles. Contributions to Mineralogy and Petrology 149, 266-275 Nixon, G.T., Hammack, J.L., Ash, C.H., Cabri, L.J., Case, G., Connelly, J.N., Heaman, L . M . , Laflamme, J.H.G., Nuttall, C , Paterson, W.P.E., & Wong, R.H. (1997). Geology and platinum-group-element mineralization of Alaskan-type ultramafic-mafic complexes in British Columbia. Geological Survey of British Columbia Bulletin 93, 141p. Nixon, G.T. (1998). Ni-sulphide mineralization in the Turnagain Alaskan-type complex: A unique magmatic environment. B. C. Ministry of Energy, Mines and Petroleum Resources Paper 1998-1, 18-1 - 18-12 Parkinson, I.J., & Arculus, R.J. (1999). The redox state of subduction zones: insights from arcperidotites. Chemical Geology 160, 409-423 Pouchou, J.L., & Pichoir, F. (1985): PAP <f>(pZ) procedure for improved quantitative microanalysis. Microbeam Analysis, 1985, 104-106. Poustovetov, A.A., & Roeder, P.L. (2000). The distribution of chromium between basaltic melt and chromian spinel as an oxygen geobarometer. Canadian Mineralogist 39, 309-317 Power, M.R., Pirrie, D., Anderson, J.C.0., & Wheeler, P.D. (2000). Testing the validity of chrome spinel as a provenance and petrogenetic indicator. Geology 28 (11), 1027-1030 Roach, T A . , Roeder, P.L., & Hulbert, L.J. (1998). Composition of chromite in the upper chromitite, Muskox layered intrusion, North West Territories. Canadian Mineralogist 36, 117-135 Roeder, P.L., & Campbell, I.H. (1985). The effect of postcumulus reactions on composition of chrome-spinels from the Jimberlana intrusion. Journal of Petrology 26 (3), 763-786 Roeder, P.L., & Reynolds, I. (1991). Crystallization of chromite and chromium stability in basaltic melts. Journal of Petrology 32 (5), 909-934 Roeder, P.L. (1994). Chromite: from the fiery rain of chondrules to the Kilauea Iki lava lake. Canadian Mineralogist 32, 729-746 Roeder, P.L., Poustovetov, A.A., & Oskarsson, N . (2001). Growth forms and composition of chromian spinel in MORB magma: diffusion-controlled crystallization of chromian spinel. Canadian Mineralogist 39, 397-416  Rohrbach, A . , Schuth, S., Ballhaus, C , M u n k e r , C , M a t v e e v , S., & Qopoto, C . (2005). Petrological constraints on the o r i g i n o f arc picrites, N e w G e o r g i a G r o u p , S o l o m o n Islands.  Contributions to Mineralogy and Petrology 149, 685-698  Sack, R . O , & G h i o r s o , M . S . (1991). C h r o m i t e as a petrogenetic indicator. M i n e r a l o g i c a l Society o f A m e r i c a -  Reviews in Mineralogy 25, 323-354  S c o w e n , P . A . H . , Roeder, P . L . , & H e l z , R . T . (1991). Reequilibration o f chromite w i t h i n K i l a u e a I k i lava lake, H a w a i i .  Contributions to Mineralogy and Petrology 107, 8-20  Takashi, A . , & A d a c h i , M . (1995). Ilvaite from a serpentinized peridotite i n the A s a m a igneous complex, M i k a b u greenstone belt, Sambagawa metamorphic terrain, central Japan.  Mineralogical Magazine 59, 489-496 Z a k r z e w s k i , M . A . (1989). C h r o m i a n spinels from K u s a , Bergslagen, Sweden. American  Mineralogist 74, 448-455  88  CHAPTER 4  PETROLOGY AND METALLOGENY OF THE TURNAGAIN ALASKAN-TYPE INTRUSION AND ASSOCIATED NI-SULPHIDE MINERALIZATION  4.1 INTRODUCTION Alaskan-type intrusions are synonymous w i t h U r a l i a n - A l a s k a n - t y p e and zoned ultramafic intrusions. The term " U r a l i a n - A l a s k a n - t y p e " originates from the two largest concentrations o f these intrusions, i n the U r a l M o u n t a i n s (n>15) o f R u s s i a (Taylor, 1967) and i n southeastern A l a s k a (n=39) ( H i m m e l b e r g & L o n e y , 1995). These intrusions are p r i m a r i l y composed o f o l i v i n e - and clinopyroxene-rich cumulate rocks and may contain appreciable hornblendeand/or feldspar-bearing lithologies. M a n y o f these intrusions are associated w i t h island arcs and they are o n l y rarely observed i n other tectonic environments (e.g. K o n d e r , Inagli, C h a d , and S i b a k h complexes; Johan, 2002). Alaskan-type intrusions i n the U r a l M o u n t a i n s (Garuti et al, 2003), i n C o l u m b i a and E c u a d o r (Tistl, 1994), B r i t i s h C o l u m b i a (Findlay, 1969), A l a s k a ( H i m m e l b e r g and L o n e y , 1995), and A u s t r a l i a (Barron et al, 1991) have been associated w i t h past and present placer platinum-group metal ( P G M ) m i n i n g operations. O n l y a few A l a s k a n type intrusions contain appreciable sulphide mineralization, i n c l u d i n g Salt C h u c k , A l a s k a ( L o n e y et al, 1987; L o n e y & H i m m e l b e r g , 1992), D u k e Island, A l a s k a (Thakurta et al, 2004), and Turnagain, B r i t i s h C o l u m b i a ( C l a r k , 1975; N i x o n , 1998). The Turnagain Alaskan-type intrusion is a fault-bounded ultramafic intrusion (3.5 x 8 k m ) composed predominantly o f dunite and wehrlite w i t h m i n o r amphibole-bearing phases, w h i c h are cross-cut by intermediate to felsic intrusions and dikes. There are two distinct styles o f mineralization i n the Turnagain intrusion: (1) N i - ( C u ) - s u l p h i d e mineralization that occurs i n the most magnesian rock types (dunite and wehrlite) w i t h m i n o r local platinum-group element ( P G E ) enrichment, and (2) m i c r o s c o p i c crystals o f sperrylite (PtAs2) and stibiopalladinite (PdsSb2) o f probable hydrothermal origin, w h i c h was discovered i n 2004 w i t h i n hornblendeclinopyroxene lithologies. N i - s u l p h i d e was first discovered i n 1956 along the Turnagain R i v e r and the property was staked by Falconbridge ( C l a r k , 1975). In the 1990s, the property was acquired by B r e n - M a r Resources (now H a r d Creek N i c k e l Corporation) and is actively being explored today. The historic N i - r i c h sulphide s h o w i n g , the Horsetrail Z o n e , has been extensively drilled w i t h over 100 diamond d r i l l holes. Other showings and prospects i n the intrusion have been explored as w e l l and the current N i resource (measured and indicated) is 428 M t grading 0.17% N i (http://www.hardcreeknickel.com), w h i c h represents an increase o f 2 0 0 % from the 2005 estimate. T h i s study focuses o n the petrology and geochemistry o f the Turnagain intrusion to better constrain the emplacement and crystallization o f magmas that formed the intrusion, and  to assess the origin of Ni-sulphide mineralization in this Alaskan-type intrusion. As part of recent mineral exploration by Hard Creek Nickel Corp., the entire intrusion has been systematically remapped and resampled. Newfieldand petrographic observations, mineral and whole-rock chemistry (including platinum-group elements), and S and Pb isotopes in sulphide separates are presented in an effort to determine the processes responsible the genesis of the Turnagain intrusion and its localized Ni-sulphide mineralization. 4.2 G E O L O G Y OF T H E T U R N A G A I N INTRUSION 4.2.1 Regional Geology  The 28 km Turnagain intrusion is located approximately 70 km east of Dease Lake, British 2  Columbia, in the Omineca Belt (Figure 4.1). This belt is composed of accreted terranes, including Quesnellia, Cache Creek, Slide Mountain, and Yukon-Tanana. The Turnagain intrusion is situated on the eastern edge of Quesnellia and structurally overlies lithologies currently assigned to Ancestral North America, which are Cambrian to Mississippian in age and consist of steeply-dipping graphitic, variably pyritic slates and phyllites of the Road River Group (Gabrielse, 1998) that contain interbeds of marble and tuff. Phyllites flank the eastern, northern, and western edges of the Turnagain intrusion, which is entirely fault-bounded. There is no observed hornfelsing of the surrounding phyllite. The contact between ultramafic rocks and phyllite was observed in numerous drillholes (e.g. DDH03-07, DDH06-158) and, although it is intensely talc-carbonate altered, original fabrics may be locally preserved. Post-intrusive deformation, exhibited by faulting and shearing, in both the Turnagain intrusion and the surrounding phyllites, grades from minor to intense generally in a WNW direction. The steeply-dipping phyllites were likely faulted along pre-existing cleavage, although local quartz-cemented phyllite breccia has been observed at the ultramafic-country rock contact in recent drill holes. A weakly metamorphosed volcanic wacke has been observed in both outcrop and drillcore to the south of the Turnagain intrusion. This unit, considered to correlate with the hornfels unit in the northwestern part of the intrusion (Figure 4.1), has also been correlated to a similar unit to the southeast of the Turnagain intrusion (Erdmer et al., 2005). Surface exposure of the Turnagain intrusion is generally poor (~20% of the total surface area is exposed) and much of the outcrop occurs in the northern third of the intrusion above treeline in the alpine region (Figure 4.2). The Horsetrail Zone contains scattered outcrops exposing most of the major lithologies, and other rare outcrops are found along the 91  Intrusion Centre: X 58°29'N, 128°52'W  B  Volcanic wacke  Dunite, with minor wehrlite  - j — Reverse fault, observed  Wehrlite, with minor dunite and olivine clinopyroxenite Olivine clinopyroxenite and clinopyroxenite, undivided Hornblende clinopyroxenite, with minor clinopyroxenite Hornblendite and clinopyroxene hornblendite, undivided Diorite, quartz diorite, and granodiorite, undivided  -j  Normal fault, inferred  _^  Fault (relative sense of motion indicated)  Hornfels, sedimentary or volcanic protolith  "Cr S isotopic sample locality *  Whole rock geochemical sample locality Geological contact, observed Geological contact, inferred  — — • Fault, inferred —  — Reverse fault, inferred  ^—^— (Listric?) Fault, observed  Figure 4.1: A) Simplified geological map of the Turnagain Alaskan-type intrusion showing major lithologies, structures, and sample locations for whole rock geochemistry and sulphide sulphur and lead isotopic compositions. Note that some lithologies are composites (e.g. olivine clinopyroxenite). Also shown are the main mineralized zones (from W to E): Northwest Zone, greater Horsetrail Zone (including Silesia to the south, and Fishing Rock to the east), Hatzl Zone, Cliff Zone, Duffy Zone, and Highland Zone. The inset in the upper right comer shows a map of British Columbia with the location of the Turnagain intrusion, and other major Alaskantype intrusions in B.C. and Alaska. B) Interpreted cross-section (Z-Z') through the Turnagain intrusion, with all major lithologies, structures and contacts indicated.  92  Figure 4.2: Photographs of dunite exposures in the Turnagain intrusion. A ) Photograph of the resistant dunite core in the alpine region (view to the northwest). B) Photograph showing the extensive exposures of dunite in the highest elevations of the alpine region (view to the northwest). C) Photograph of a ridge of dunite, looking to the southwest from the top of the hornfels (volcanic wacke) knob in the northwest corner of the intrusion. The lack of outcrop beyond this ridge coincides with a magnetic-low anomaly. D) Photograph of the dunite core from within a long valley in the northern part of the intrusion, looking southeast. The small ridge (just visible in the lower left-hand corner) is primarily composed of wehrlite. The valley is filled with talus and runs parallel to the northern-bounding fault of the intrusion.  Turnagain R i v e r . The southern and western areas o f the Turnagain intrusion are completely covered b y 5-15 m o f t i l l , wheras east o f the Turnagain R i v e r m u c h o f the intrusion is covered w i t h up to 50 m o f glaciofluvial gravels. Contacts between lithologies i n the northern region o f the Turnagain intrusion are generally observed, whereas most contacts i n and around the Horsetrail Z o n e are inferred from d r i l l core. Contacts i n the western and southern areas are inferred from airborne and ground geophysics as w e l l as recent d r i l l core. The current geological map for the Turnagain intrusion, w h i c h is continuously updated based on results from n e w d r i l l i n g i n relatively u n k n o w n areas, is largely based on the efforts o f C l a r k (1975) and N i x o n (1998). The original mapping and petrographic investigations o f C l a r k (1975; 1978; 1980) lead to a wealth o f fundamental information about the Turnagain intrusion. Subsequent investigations by N i x o n et al. (1989) and N i x o n (1998) focused on the origin o f the Turnagain intrusion w i t h respect to regional geological interpretations, as w e l l as the o r i g i n o f associated N i - ( C u ) - s u l p h i d e and platinum-group element ( P G E ) mineralization.  4.2.2 Ultramafic Rocks 4.2.2.1 Dunite and Chromitite W i t h the exception o f hornblendite and diorite, the majority o f the rocks exposed i n the Turnagain intrusion are dominated b y cumulus o l i v i n e and/or clinopyroxene. D u n i t e is volumetrically the most important lithology i n the Turnagain intrusion and occurs i n outcrop throughout the alpine regions o f the intrusion, but is also observed i n a l l major outcroppings i n the Horsetrail Zone and the C l i f f Z o n e (northeastern corner o f the intrusion, Figure 4.1). Dunite weathers to a b u f f colour that is especially apparent i n the alpine exposures (Figure 4 . 2 B , Figure 4.3.1 A ) . M o s t dunite is composed o f large amounts o f o l i v i n e (>90 v o l . % ) w i t h small amounts o f interstitial clinopyroxene, disseminated chromite, and l o c a l l y interstitial phlogopite. O l i v i n e grain size i n dunite is c o m m o n l y ~1 m m (Figure 4.4.1 A ) , however o l i v i n e as large as 2 c m across or larger has been observed. U n c o m m o n l y large o l i v i n e occurs i n association w i t h m u c h smaller o l i v i n e (<1 m m ) i n a porphyroclastic texture, w h i c h is interpreted to represent the product o f h i g h strain at high temperature. O l i v i n e (~1 cm) w i t h irregular grain boundaries, as w e l l as parting, has also been observed i n samples from the alpine area or i n associated dunite b e l o w treeline (Figure 4 . 4 . I B ) . Disseminated chromite is c o m m o n l y 200-300 p m i n diameter, exhibits euhedral to subhedral habits, and m a y have magnetite or ferritchromit overgrowths (Chapter 3). C h r o m i t e can also contain polyphase  Figure 4.3.1: Photographs of outcrop-scale features in the Turnagain intrusion. A) Disrupted chromitite schleiren in alpine dunite. Hammer is 50 cm long. B) Olivine clinopyroxenite in alpine area with two crosscutting dunite "dikes". Hammer is 30 cm long. C) Wehrlite showing atypical differential weathering of olivine (buff) and interstitial clinopyroxene (grey). Pencil is 12 cm long. D) Modal banding in wehrlite in the northwestern alpine region. Hammer is 30 cm long.  95  Figure 4.3.2: Photographs of outcrop-scale features in the Turnagain intrusion (continued). E) Modal banding in wehrlite, represented by alternating modal abundances of clinopyroxene (grey) and olivine (buff). Pencil is 12 cm long. F) Thick band (~1 m) of olivine clinopyroxenite (grey) within wehrlite (brown). Hammer is 30 cm long. G) Two olivine clinopyroxenite dikes (grey) cutting dunite (brown) parallel to the eastern dunite-olivine clinopyroxenite contact in the northwest. The photograph was taken 2 m east of the contact. H) Olivine clinopyroxenite dike swarm, cutting dunite, at the termination of exposure. This dike swarm originatesfromthe easternmost dunite-olivine clinopyroxenite contact and is continuous for over 100 m. Hammer is 30 cm long.  Figure 4.4.1: Photomicrographs (transmitted light, crossed-polarizers) of silicate mineral textures in the Turnagain intrusion. Scale bars (solid white bars) on all photos are 1 mm in length. A) Dunite (04ES-19-01-03) showing typical annealed texture (120° grain boundary intersections). Small black dots are disseminated chromian spinel. Note the large difference in size between individual olivine grains. B) Dunite (04ES-06-01-01) showing strong parting in olivine and irregular grain boundaries. C) Oikocrystic clinopyroxene in wehrlite (04ES-15-05-04). Note the well-preserved euhedral crystal faces of some olivine grains. D) Wehrlite (05ES-05-05-01) exhibiting large (1 mm) and small (<200 urn) olivine grains, as well as small to medium (300 um) cumulus clinopyroxene grains.  Figure 4.4.2: Photomicrographs (transmitted light, crossed- polarizers) of silicate mineral textures in the Turnagain intrusion (continued). Scale bars (solid white bars) on all photos are 1 mm in length. E) Olivine clinopyroxenite (04ES-10-02-03) with abundant cumulus clinopyroxene and rarely-preserved olivine (mostly serpentinized). Note the core of an olivine in the upper-middle-left of the photograph with a serpentine margin. F) Fine-grained hornblendite dike (04ES-20-11-01) with randomly-oriented amphibole grains. Not visible at this scale are small crystals of titanite along amphibole grain boundaries. G) Diorite (DDH04-57-12.89.2) with large (cumulus) plagioclase grain. H) Diorite (DDH04-57-12-89.2) with large twinned, euhedral (cumulus), amphibole grain.  silicate inclusions or sulphide inclusions. Chromitite, observed i n dunite from the alpine region o f the intrusion (Figure 4.3.1 A ) , is sparsely distributed and occurs as wisps, bands, rare layers, pods, and schleiren. It c o m m o n l y contains coarser chromite than dunite, up to 1 m m i n some cases, and is almost completely u n i m o d a l ( 9 9 % chromite). The irregular distribution and habit o f chromite i n the chromitites suggests that these rocks were disrupted or deformed at h i g h temperatures f o l l o w i n g crystallization. Dunite has been observed to cross-cut other ultramafic lithologies or the Turnagain intrusion, especially rocks that are spatially close to the alpine dunite. Dunite and o l i v i n e clinopyroxenite are locally juxtaposed together i n the northwestern part o f the intrusion (Figure 4.1), w i t h no fault or obvious intrusive relationship, w h i c h may indicate the presence o f primary igneous layering. H o w e v e r , i n the above example, ~3 c m - w i d e dunite dikes were observed cutting the o l i v i n e clinopyroxenite (Figure 4 . 3 . I B ) . Continuous dikes (over 100 m) o f o l i v i n e clinopyroxenite (up to 10 c m w i d e ) have also been observed cutting dunite (Figure 4 . 3 . 2 G , H ) . C l a r k (1975) noted deformation o f igneous layering at the contact w i t h dunite i n the northwestern part o f the Turnagain intrusion. Serpentinized dunite is c o m m o n near major faults, although dunite t y p i c a l l y contains only m i n o r amounts (~10 v o l . % ) o f serpentine minerals. A l p i n e dunite c o m m o n l y contains small fractures filled w i t h green, slickensided serpentine, and dunite from other parts o f the intrusion is black due to an abundance o f secondary magnetite. B l a c k serpentine also contains traces o f elemental carbon, graphite, and l o c a l l y sulphide. L i z a r d i t e (green, well-foliated) is the most c o m m o n serpentine mineral. C r y s o t i l e (fibrous and white) is o n l y rarely found associated w i t h serpentine veins/slips, and antigorite (massive meshes o f interlocking needles) is generally o n l y found i n the Horsetrail Z o n e .  4.2.2.2 W e h r l i t e M o s t exposures o f wehrlite occur i n the northwestern alpine region o f the Turnagain intrusion (Figure 4.1), around/within the Horsetrail Z o n e , and i n the C l i f f Z o n e . Phlogopite from a wehrlite i n the H a t z l zone (far southeastern edge o f the intrusion) was dated at 1 8 9 ± 1 . 3 M a b y A r - A r geochronology (see Chapter 2 for details). T w o types o f wehrlite occur i n the Turnagain intrusion. T h e most c o m m o n type is composed o f cumulus o l i v i n e (1-5 m m ) and interstitial clinopyroxene (Figure 4 . 3 . I C ) . It t y p i c a l l y weathers to a light b r o w n c o l o u r and is easily distinguished from dunite i n alpine exposures. L o c a l l y , clinopyroxene forms oikocrysts  99  up to 2 c m w i d e (Figure 4 . 4 . I C ) . Wehrlite also contains disseminated chromite (50-150 pm) and rare interstitial phlogopite. The other type o f wehrlite contains what is interpreted to represent cumulus clinopyroxene (Figure 4 . 3 . I D , 4.3.2E) and occurs i n exposures i n the northwestern part o f the intrusion as w e l l as i n exposures east o f the Turnagain R i v e r ( C l i f f Zone) (Figure 4.1). T h i s cumulus clinopyroxene has an elongate, prismatic habit and is t y p i c a l l y finer-grained than coexisting o l i v i n e , about 200 p m i n diameter (Figure 4 . 4 . I D ) , although l o c a l l y clinopyroxene up to 3 m m i n length can occur. Wehrlite dikes have been observed to cross-cut dunite. B o t h types o f wehrlite c o m m o n l y contain abundant serpentine (up to 85 v o l . % ) replacing o l i v i n e .  4.2.2.3 O l i v i n e C l i n o p y r o x e n i t e and C l i n o p y r o x e n i t e O l i v i n e clinopyroxenite and c o m m o n l y pegmatitic clinopyroxenite are exposed i n the northwestern part o f the Turnagain intrusion (Figure 4.1) (clinopyroxenite is rarely exposed elsewhere and is generally only observed in drillcore). Interlayered o l i v i n e clinopyroxenite and wehrlite/dunite have been observed i n recent drillcore from east o f the Turnagain R i v e r , however layering is t y p i c a l l y absent from outcrop exposures. Pegmatitic clinopyroxenite is observed as dikes that cross-cut dunite and wehrlite, and has also been observed i n the northwest as segregations, presumably representing trapped volatile-rich residual melt, w i t h i n o l i v i n e clinopyroxenite. M o s t o l i v i n e clinopyroxenite i n the Turnagain intrusion is composed o f cumulus o l i v i n e and clinopyroxene (both ~2 m m in diameter) w i t h m i n o r amounts o f finegrained interstitial clinopyroxene. O l i v i n e clinopyroxenite weathers grey i n colour w i t h small o l i v i n e grains weathering to a b u f f colour. L o c a l l y , modal banding has been observed (Figure 4.3.2F). A few examples o f o l i v i n e clinopyroxenite occur without cumulus clinopyroxene (e.g. sample 05ES-02-01-01) and instead contain cumulus o l i v i n e w i t h i n o i k o c r y t i c clinopyroxene (Figure 4 . 4 . I C ) . Chromite is rare i n o l i v i n e clinopyroxenite (see Chapter 2). Where present, chromite is fine-grained (<150 pm) and is c o m m o n l y encased i n cumulus clinopyroxene. C h r o m i t e i n o l i v i n e clinopyroxenite also does not exhibit significant secondary magnetite growth on the rims o f grains, as observed i n dunites and wehrlites. D i k e s o f o l i v i n e clinopyroxenite and clinopyroxenite have been observed cross-cutting both wehrlite and dunite, and locally biotite occurs along the contacts. These dikes are c o m m o n l y pegmatitic, and one such example contains clinopyroxene crystals up to 20 c m i n length. O l i v i n e is  100  typically completely serpentinized i n olivine clinopyroxenite (Figure 4.4.2E), although unaltered cores may be preserved. Magnetite clinopyroxenite, an intermediate rock type between o l i v i n e clinopyroxenite and hornblende clinopyroxenite, has only been observed i n drillcore from the east-central portion o f the intrusion (Figure 1). Magnetite clinopyroxenite exhibits two types o f magnetite: (1) cumulus (primary) magnetite crystals up to 5 m m i n diameter coexisting w i t h coarse (1-3 c m i n length) clinopyroxene, and (2) round blebs o f intergrown serpentine and secondary magnetite (up to 3 cm) i n a matrix o f small diopside crystals (~1 m m ) . C u m u l u s magnetite may exhibit modal banding and is interpreted to be comagmatic w i t h its hosting clinopyroxene. The magnetite-serpentine blebs from the second type o f magnetite clinopyroxenite are interpreted to represent clasts o f dunite that were brecciated during the intrusion o f their host clinopyroxenite.  4.2.2.4 Hornblende Clinopyroxenite A l t h o u g h outcrops o f hornblende clinopyroxenite are scarce, it comprises a major portion ( - 1 0 % o f the surface area) o f the Turnagain intrusion. M u c h o f the hornblende clinopyroxenite in the intrusion occurs i n the west-central portion o f the intrusion i n an area called the D J - D B Z o n e , w h i c h is a zone that is prospective for P G E mineralization (Figure 4.1). H o w e v e r a prominent d i k e - l i k e body (1.2 k m long x 15 m wide), exposed at the southern margin o f the interbanded wehrlite and o l i v i n e clinopyroxenite i n the northwest, provides the best exposure (Figure 4.1). Unweathered hornblende clinopyroxenite is generally porphyritic i n texture and contains bright grey-green, equant clinopyroxene (1-4 c m long) and interstitial black amphibole (up to 2 c m long). Some samples contain abundant interstitial biotite, up to 35 v o l . % . Magnetite crystals, t y p i c a l l y 7 m m up to 1 c m i n diameter, occurs i n about 2 0 % o f a l l hornblende clinopyroxenite. L o c a l l y , magnetite i n hornblende clinopyroxenite represents 5 vol.%) o f the rock. E x a m p l e s o f this rock type i n the D J - D B Z o n e are c o m m o n l y pegmatitic, consisting o f large (up to 10 c m wide) equant clinopyroxene and abundant interstitial amphibole. A l t h o u g h t y p i c a l l y unaltered, large amounts (up to 85 v o l . % ) o f secondary b r o w n amphibole were noted i n hornblende clinopyroxenite adjacent to the large b l o c k o f hornfels i n the southern D J zone ( D D H 0 5 - 8 4 ) .  4.2.2.5 Hornblendite Hornblendite i n the Turnagain i n trusion is poorly exposed but makes up about 20 v o l . % o f the ultramafic lithologies. Hornblendite may contain coarse, equant clinopyroxene or interstitial plagioclase, and rarely biotite. There are three types o f hornblendite present i n the Turnagain intrusion. The first type is megacrystic to pegmatitic (with crystals up to 5 c m i n length) and found i n the D J - D B Zone i n the west-central portion o f the intrusion. The other two types contain abundant (50-60 v o l . % ) cumulus amphibole, up to 1 c m i n w i d t h , and 10-20 v o l . % cumulus amphibole, respectively, w i t h fine-grained interstitial hornblende matrices (<50 pm). Hornblendite c o m m o n l y grades into hornblende clinopyroxenite or feldspathic hornblendite, w h i c h contains sub-rounded plagioclase grains 3-10 m m i n length, rarely w i t h irregular grain boundaries, w i t h i n a matrix o f hornblende crystals up to 2 c m long. E x a m p l e s o f hornblendite containing m i n o r amounts o f clinopyroxene are observed to have either porphyritic clinopyroxene surrounded by coarse-grained hornblende (1-2 c m i n length) or oikocrystic hornblende encasing fine (2 m m ) clinopyroxene. Exposures o f hornblendite are rare, and the most accessible outcrop o f hornblendite is found as a splay o f u n k n o w n length o f f the above mentioned hornblende-rich ' d i k e ' (Figure 4.1). T h i s 30 c m - w i d e splay is characterized by finegrained anhedral amphibole (Figure 4.4.2F) and intrudes the metasedimentary b l o c k i n the northwest. Sample 04ES-00-07-04 from this dike was dated using both A r - A r (amphibole) and U - P b (titanite) methods, and the obtained ages from this sample are 1 8 9 ± 1 . 4 M a and 1 9 0 . 3 ± 4 . 6 M a , respectively (see Chapter 2). A l t e r a t i o n i n amphibole-bearing lithologies is distinct from that observed i n olivine-bearing rocks i n the Turnagain intrusion. A l t h o u g h minor, alteration minerals i n hornblendite include chlorite and epidote after amphibole, chlorite after clinopyroxene and plagioclase, and sericite after plagioclase.  4.2.3 Other Rocks 4.2.3.1 D i o r i t e D i o r i t e covers 10% o f the exposed surface area i n the Turnagain intrusion and occurs m a i n l y i n the central part o f the intrusion (Figure 4.1). A l t h o u g h this unit is referred to as diorite, the central occurrence is actually a mixture o f diorite, quartz diorite, and m i n o r granodiorite, and contains an outer margin ( - 1 0 m thick) w i t h significant amphibole (up to 95 v o l . % ) . T h i s margin may be easily confused for hornblendite ( C l a r k , 1975). H o w e v e r , the presence o f cumulus/porphyritic plagioclase helps to distinguish diorite from feldspathic hornblendite. It is  102  c o m m o n for diorite to contain brecciated clasts o f dunite, wehrlite, and o l i v i n e clinopyroxenite. In general, diorite contains 75 v o l . % amphibole, 20 v o l . % plagioclase, and m i n o r amounts o f quartz, biotite, apatite, and z i r c o n . A n outcrop o f diorite from the northern margin o f the central body (sample 04ES-00-07-01), near the contact w i t h dunite, y i e l d e d a U P b (zircon) m i n i m u m age o f 1 8 9 . 2 ± 0 . 6 M a (see Chapter 2). D i o r i t e also occurs as thin (5-20 c m i n width) dikes that are observed to intrude the more magnesian lithologies o f the Turnagain intrusion. These dikes are t y p i c a l l y felsic, w i t h 5 v o l . % amphibole, and also contain abundant quartz. One very coarse-grained leucocratic diorite (sample D D H 0 4 - 5 7 - 1 2 - 8 9 . 2 ) , w i t h large cumulus crystals o f amphibole and plagioclase (Figure 4 . 4 . 2 G , H ) , y i e l d e d a U - P b (zircon) age o f 1 8 5 . 2 ± 0 . 3 5 M a (Chapter 2).  4.2.3.2 Hornfels The hornfels unit (Figure 4.1) refers specifically to a greenish-gray, banded, volcanosedimentary rock (volcanic wacke) found either as large b l o c k s i n the northwest (Figure 4 . 2 C ) and southwest parts o f the intrusion, or as xenoliths observed i n drillcore. T h e hornfels unit is equigranular, w i t h grain sizes t y p i c a l l y between 0.5-1 m m , and is composed o f approximately 45 v o l . % epidote, 35 v o l . % plagioclase, 10 v o l . % amphibole, 5 v o l . % quartz, and 5 v o l . % biotite. The large b l o c k o f hornfels i n the northwest part o f the intrusion contains pods and seams o f t w o - m i c a granite not observed elsewhere that are interpreted to represent partial melts o f country rock. Detrital zircons (subrounded to angular) are c o m m o n i n this lithology and one sample from the northwestern portion o f the intrusion (sample 0 4 E S - 0 0 - 0 7 02) y i e l d e d a m i n i m u m U - P b (zircon) depositional age o f 301 M a (latest Pennsylvanianearliest Permian) w i t h Precambrian inheritance (see Chapter 2). T h i s unit c o m m o n l y contains alternating 1-10 m m - w i d e bands o f quartz- and chlorite-rich horizons, w h i c h may represent original bedding planes. B a s e d on the above evidence, this unit is interpreted to be a v o l c a n i c wacke that was intruded by, and incorporated into, the Turnagain intrusion.  4.2.4 Sulphide Sulphide occurs i n nearly a l l rocks i n the Turnagain intrusion. H o w e v e r it is observed predominantly i n dunite and wehrlite. " B a r r e n " olivine-dominated cumulate rocks (dunite and wehrlite) i n the Turnagain intrusion t y p i c a l l y contain 0.5-1 v o l . % disseminated sulphide. Sulphide abundances i n the mineralized zones (Horsetrail Z o n e and associated satellite zones;  103  Figure 4.1) range from 2 v o l . % up to 20 v o l . % or more. These zones contain disseminated, blebby, m i n o r net-textured and rarely semi-massive sulphide. The Northwest, Silesia, and F i s h i n g R o c k Zones (to the west, south, and east o f the Horsetrail, respectively, Figure 4.1) are relatively small compared to the Horsetrail Z o n e , w h i c h is unconstrained at depth ( T . H i t c h i n s , pers. c o m m . , 2004). The mineralization to the east o f the Turnagain R i v e r , i n an area called the H a t z l Z o n e , is currently unconstrained w i t h respect to grade, tonnage, or spatial distribution. A l l o f the zones were o r i g i n a l l y interpreted to be separate areas o f sulphide mineralization, but n e w and proposed d r i l l i n g results indicate that m a n y o f them are connected at depth. The typical sulphide assemblage w i t h i n the mineralized zones consists o f pyrrhotite (~90 v o l . % o f total sulphide) and pentlandite w i t h trace amounts o f chalcopyrite. Pentlandite is distinguished from pyrrhotite i n hand sample and drillcore b y its lighter colour and reflection o f light from cleavage planes. V i s u a l estimates o f the n i c k e l grade are inaccurate because the N i content in pentlandite ranges from 10 to 45 w t . % ( H a r d C r e e k N i c k e l C o r p . internal reports). Sulphide i n clinopyroxene- and amphibole-rich lithologies, rocks that are not prospective for N i , t y p i c a l l y consists o f v a r y i n g proportions o f pyrrhotite, pyrite, and chalcopyrite. C l a r k (1975) and H . K u c h a ( H a r d C r e e k N i c k e l C o r p . internal reports) studied the sulphide mineralogy i n detail and also observed m i n o r amounts o f violarite, bornite, millerite, molybdenite, vallerite, mackinawite, and oxysulphides. Disseminated sulphides are t y p i c a l l y fine-grained (0.1-0.5 m m ) and occur throughout most o f the o l i v i n e - r i c h lithologies o f the Turnagain intrusion. Disseminated ore i n the Horsetrail Z o n e is c o m m o n near the margins o f the zone, however it is l o w grade (<0.17% sulphide nickel) and represents the l i m i t o f currently economic sulphide mineralization. Serpentinized dunite and wehrlite p r o x i m a l to the northern bounding fault, i n the H i g h l a n d Z o n e (Figure 4.1), contain ~0.5 v o l . % disseminated pentlandite, similar i n texture to sulphide shown i n Figure 4 . 5 C . These fine-grained pentlandite occurrences are interpreted to have formed by N i - e n r i c h m e n t o f primary sulphide during serpentinization. B l e b b y sulphide is c o m m o n i n the mineralized zones (e.g. Northwest Zone) and is observed as small (2-3 m m ) to large (-1.5 cm), sub-rounded (Figure 4 . 5 A ) to elongate (Figure 4 . 5 D - F ) , sulphide aggregations. The aggregations are t y p i c a l l y surrounded by o l i v i n e grains and some sulphide is c o m m o n l y present between o l i v i n e grains adjacent to the sulphide bleb. These blebs are interpreted to represent isolated droplets o f sulphide l i q u i d that crystallized in situ. N o t e that the bleb shown i n Figure 4 . 5 A is completely surrounded by magnetite, w h i c h is  Figure 4.5: Photomicrographs (reflected light, crossed polars) of sulphide textures in the Turnagain intrusion. Scale bars on all photos are 200 nm in length. Colours in silicate minerals represent minor surficial and internal reflections. A) Dunite (DDH03-12-4) showing a fringe of secondary magnetite surrounding a single sulphide bleb containing pyrrhotite (brown) and pentlandite (light yellow). B) Dunite (05ES-02-02-02) containing intergrown semi-massive pyrrhotite and chalcopyrite. Note the small needles of serpentine (black) around the edges of the massive sulphide, as well as the sulphide outside the main sulphide mass. C) Dunite (DDH04-36-16) with small blebs of pentlandite and two thin serpentine veins. D) Wehrlite (DDH04-36-5) showing an elongate bleb of pyrrhotite with smaller crystals of pentlandite. E) Wehrlite (DDH04-28-6) showing an elongate bleb of pyrrhotite with magnetite and pentandite crystals. Note the tweed-like texture in the bottom portion of the bleb. F) Wehrlite (DDH03-08-13) showing a pyrrhotite bleb with minor chalcopyrite and two large pentlandite grains. The grey grains are chromian spinel.  a c o m m o n feature o f sulphide i n partially serpentinized rocks i n the Turnagain intrusion. Occurrences o f angular sulphide blebs (some up to 3 c m i n width) have been noted i n drillcore from a l l o f the major m i n e r a l i z e d zones. These blebs typically contain the same proportion o f pyrrhotite and pentlandite as the more rounded blebs, however angular blebs are also observed i n o l i v i n e clinopyroxenite, not just dunite and wehrlite. O l i v i n e clinopyroxenite i n the Turnagain intrusion does not contain contemporaneous N i - r i c h sulphide mineralization, most l i k e l y because it formed from a less magnesian, sulphur- and nickel-depleted m a g m a compared to the magma(s) that formed dunite and wehrlite, and as such the rare angular blebs c o u l d not have precipitated in situ. The angular are interpreted to represent clasts o f sulphide, originally i n a massive h o r i z o n , that were brecciated during a m a g m a influx or turbidity current and subsequently redistributed ( W . Peredery, pers. c o m m . , 2006). Net-textured sulphide is not c o m m o n i n the Horsetrail, Northwest, Silesia, and F i s h i n g R o c k Zones or the D i s c o v e r y s h o w i n g (Figure 4.1), but is noted i n local accumulations and horizons. T h i s sulphide texture typically contains o l i v i n e grains o f v a r y i n g sizes w i t h i n a sulphide matrix. D u e to the amount o f pentlandite present i n such horizons (up to 10 v o l . % ) , net-textured sulphides represent a high-grade target for exploration. H o w e v e r their apparent thickness is c o m m o n l y o n l y a few centimetres and rarely exceeds 20 c m . Semi-massive and massive sulphide (Figure 4 . 5 B ) occurs i n a l l economic zones w i t h i n the Turnagain intrusion. The difference between the t w o types o f sulphide lies i n their ganguemineral content: semi-massive sulphide contains abundant silicate and other minerals (e.g. graphite), whereas massive sulphide does not. B o t h o f these sulphide textural types typically have sharp contacts w i t h surrounding rocks indicating that they may represent sulphide that was r e m o b i l i z e d . Such horizons o f massive and semi-massive sulphide are t y p i c a l l y o n l y 5 c m or less i n w i d t h and are dominantly composed o f pyrrhotite and m i n o r chalcopyrite w i t h trace amounts o f pentlandite. Semi-massive and massive sulphides i n the Turnagain intrusion therefore are rarely prospective for n i c k e l .  4.2.5 Inclusions X e n o l i t h s o f country rock w i t h i n the Turnagain intrusion are restricted to the m i n e r a l i z e d zones, and these have only been observed i n drillcore. N o inclusions have been observed i n areas o f abundant outcrop (e.g. alpine dunite, Figure 4.2) or nearly continuous exposure. The inclusions w i t h i n the Turnagain intrusion are, without exception, hornfelsed equivalents o f  1 0 6  w a l l r o c k s . Figure 4.6 displays inclusions from six different d r i l l holes w i t h i n mineralized zones. The two most c o m m o n l y encountered inclusions are metavolcanic w a c k e ( M V w k ) and metaphyllite ( M P h y ) . The third type o f inclusion, calc-silicate ( C S ) , occurs as isolated inclusions (Figure 4 . 6 E , F ) or as interbeds w i t h i n the other types o f inclusions (Figure 4 . 6 A ) . The metavolcanic wacke, described as the hornfels unit above (section 4.2.3.2), also occurs as smaller b l o c k s w i t h i n drillcore (Figure 4 . 6 A - C ) . T h e inclusions o f metavolcanic w a c k e are typically identical i n mineralogy and texture to the larger blocks o f hornfels. R a r e l y , the metavolcanic wacke inclusions are slightly coarser grained and contain small seams o f t w o m i c a granite (partial melt) that may cross-cut banding. It is u n c o m m o n , but noted, to observe interbeds o f metavolcanic wacke and metaphyllite i n the same i n c l u s i o n (Figure 4 . 6 B , C ) . M e t a p h y l l i t e inclusions ( M P h y ) are texturally and m i n e r a l o g i c a l l y different from their " R o a d R i v e r " phyllite predecessors. M e t a p h y l l i t e c o m m o n l y contains brown-coloured areas that are m i n e r a l o g i c a l l y dominated by graphite and pyrrhotite w i t h interlayered quartz (Figure 4 . 6 B - D ) . Graphite and pyrrhotite w i s p s and seams (typically semi-massive sulphide), interpreted to represent partially digested inclusions o f phyllite, were also previously observed by C l a r k (1975) w i t h i n ultramafic lithologies. T h e lack o f pyrite (FeS2) and the abundance o f pyrrhotite (Fei.xS) indicate that sulphur was released into the host magma during contact metamorphism o f the phyllite inclusions. Calc-silicate inclusions ( C S ) are t y p i c a l l y white i n c o l o u r and relatively s m a l l (as small as 2-3 c m i n width). H o w e v e r , as noted above, they may occur as interbeds w i t h i n either metavolcanic w a c k e or metaphyllite. Calc-silicate inclusions are fine-grained (<1 m m ) and typically consist o f a mixture o f carbonate (calcite, magnesite), wollastonite, diopside, quartz, and l o c a l l y grossular. N o t e that i n Figure 4 . 6 E and F the calc-silicate inclusions have a slight reddish colour indicating their h i g h garnet content. Calc-silicate xenoliths t y p i c a l l y do not display extensive digestion, incorporation into their host rocks, or redox halos.  4.3 A N A L Y T I C A L TECHNIQUES 4.3.1 Mineral Chemistry T h e o l i v i n e , clinopyroxene, amphibole, and biotite contents o f each sample, textural relationships w i t h other phases, and relative degree o f alteration were carefully documented using both transmitted and reflected light m i c r o s c o p y prior to analysis. Samples were selected to represent the various rock types found i n the Turnagain intrusion. F o r each sample, t y p i c a l l y  107  Figure 4.6: Photographs of sedimentary xenoliths in NQ size drillcore (2006)fromthe Turnagain intrusion. Core boxes are 1.5 m long, white lines indicate interlithological contacts, and labels indicate lithology. A) DDH06-123, 201-218 m. Inclusion of interbedded metavolcanic wacke (MVwk) and calc-silicate (CS) within altered dunite (AltDn) changing down-hole to a larger MVwk inclusion. B) DDH06-130, 202-219 m. Large inclusion of coarsely interbedded MVwk and metaphyllite (MPhy). C) DDH06-143, 71-88 m. Large inclusion of gradationally bedded MVwk and MPhy. Note the very small (5-20 cm) beds of MVwk in the transition zone between the two lithologies. D) DDH06-163, 294.5 m. Strongly hornfelsed metaphyllite. The only minerals present are quartz (white-blue) and a fine-grained mixture of graphite and pyrrhotite (brown). Scale-bar is 10 cm long. E) DDH06-152,247-263 m. Inclusion of CS within AltDn. Note the slight reddish colour associated with grossular. The grey zones within the inclusion are interpreted to be highly-altered dunite. F) DDH06-153, 174-190 m. Small inclusion of CS in AltDn. This inclusion also contains grossular, but unlike the inclusion documented above, contains no intermixed dunite.  three different grains were analyzed w i t h three spot analyses per grain (core, intermediate position, and r i m ) . Representative analyses for o l i v i n e and clinopyroxene, and complete analyses for amphibole and biotite are found i n Tables 4.1 to 4.4, respectively. C o m p l e t e analytical results for o l i v i n e and clinopyroxene are listed i n A p p e n d i c e s II and III. Garnet analyses are listed i n A p p e n d i x I V . A total o f 25 samples were selected for microprobe analysis, carbon-coated, and documented using the P h i l i p s X L - 3 0 scanning electron microscope at the U n i v e r s i t y o f B r i t i s h C o l u m b i a , V a n c o u v e r , B . C . Quantitative analyses were carried out i n wavelength-dispersion mode u s i n g the C a m e c a S X - 5 0 electron microprobe w i t h a beam diameter o f 10 urn, an accelerating voltage o f 15 k e V , and a beam current o f 20 n A w i t h 20 s peak count-time and 10 s background count-time. A list o f X - r a y lines and elements considered, as w e l l as their standards, can be found i n A p p e n d i x V . D a t a reduction o f a l l analytical results was undertaken using the " P A P " <)>(pZ) procedure o f P o u c h o u & P i c h o i r (1985). A total o f 354 points were analyzed (207 o l i v i n e , 91 clinopyroxene, 48 amphibole, 8 biotite, 9 garnet). O l i v i n e and clinopyroxene were assumed to be stoichiometric. Ferric iron in o l i v i n e was assumed to be zero, and ferric iron i n clinopyroxene was calculated using the stoichiometric technique o f L i n d s l e y (1983). In amphibole, ferric iron and other cation ratios were calculated using the method o f H o l l a n d & B l u n d y (1994) and mineral names were assigned using the nomenclature o f L e a k e et al. (1997). C h e m i c a l compositions o f amphibole were calculated o n the basis o f 23 oxygens (16 cations ideal, w i t h vacancy i n A site). Biotite stoichiometry was calculated using standard techniques (22 oxygens, 16 cations, 2 O H ± C I ± F ideal). The term 'biotite' refers to the biotite solid solution containing phlogopite (Mg# = 0.85-1.00) and annite ( M g # = 0.000.15) end-members. Garnet cation distributions were also calculated using standard stoichiometric techniques.  4.3.2 Major and Trace Elements F o r w h o l e rock analyses, o n l y the freshest portions o f individual samples were taken i n the field and any remaining weathered surfaces were systematically removed during sample processing. A l l samples were crushed using a hydraulic piston crusher between W C plates. A 100 gram aliquot o f each crushed sample was powdered using the F r i t s c h Pulverisette planetary m o n o - and-multi m i l l s i n agate jars.  no  Table 4.1a: Representative olivine compositions from olivine-bearing ultramafic lithologies of the Turnagain intrusion  Rock type:  Chromitite  Chromitite  Dunite  Dunite  Dunite  Wehrlite  Sample: Cluster:  05ES-01-01-01 1  05ES-01 -04-01 2  04ES-10-05-01 1  04ES-08-01-01 2  04ES-19-01-02 2  04ES-10-06-01 5  Style: Zone:  porph. rim  porph. mid  porph. core  mgb. rim  mgb. mid  mgb. core  cumu. rim  cumu. mid  cumu. core  cumu. rim  cumu. mid  cumu. core  cumu. rim  cumu. mid  cumu. core  porph. porph. rim mid  porph. core  41.58 0.02 7.31 0.15 50.49 0.25 0.05 99.85  41.11 0.02 8.73 0.15 49.82 0.33 0.07 100.23  41.10 0.03 8.81 0.19 49.81 0.23 0.06 100.23  41.71 0.21 3.93 0.10 54.01 0.36 0.07 100.39  41.71 0.01 4.74 0.09 52.79 0.47 0.10 99.92  41.90 0.02 4.79 0.09 53.01 0.51 0.13 100.45  42.17 0.00 3.44 0.43 54.63 0.00 0.02 100.69  41.26 0.01 8.91 0.15 49.59 0.35 0.07 100.33  40.86 0.00 9.17 0.17 49.61 0.30 0.13 100.24  40.86 0.00 9.08 0.18 49.53 0.10 0.10 99.85  40.66 0.02 9.70 0.16 48.77 0.07 0.18 99.57  40.85 0.06 10.31 0.17 48.67 0.12 0.15 100.35  41.48 0.04 7.85 0.12 50.39 0.22 0.34 100.43  41.45 0.03 7.44 0.19 51.18 0.13 0.08 100.48  41.22 0.03 7.36 0.16 51.00 0.25 0.04 100.06  40.91 0.00 8.87 0.33 49.57 0.25 0.03 99.95  40.70 0.00 9.66 0.21 48.68 0.31 0.04 99.61  40.47 0.06 10.46 0.21 47.94 0.39 0.02 99.56  1.008 0.000 0.148 0.003 1.825 0.005 0.001 2.991  1.001 0.000 0.178 0.003 1.808 0.006 0.002 2.999  1.000 0.001 0.179 0.004 1.808 0.005 0.002 2.998  0.992 0.004 0.078 0.002 1.915 0.007 0.002 3.000  1.001 0.000 0.095 0.002 1.889 0.009 0.002 2.999  1.001 0.000 0.096 0.002 1.887 0.010 0.003 2.999  0.998 0.000 0.068 0.009 1.927 0.000 0.000 3.002  1.004 0.000 0.181 0.003 1.799 0.007 0.002 2.996  0.997 0.000 0.187 0.004 1.805 0.006 0.003 3.003  1.000 0.000 0.186 0.004 1.807 0.002 0.003 3.000  1.000 0.000 0.200 0.003 1.789 0.001 0.005 2.999  1.000 0.001 0.211 0.004 1.776 0.002 0.004 2.998  1.003 0.001 0.159 0.002 1.817 0.004 0.009 2.995  1.000 0.000 0.150 0.004 1.840 0.002 0.002 2.999  0.999 0.001 0.149 0.003 1.842 0.005 0.001 3.000  1.000 0.000 0.181 0.007 1.806 0.005 0.001 3.000  1.002 0.000 0.199 0.004 1.786 0.006 0.001 2.998  1.000 0.001 0.216 0.004 1.767 0.008 0.001 2.997  92.5 7.5  91.1 8.9  91.0 9.0  96.1 3.9  95.2 4.8  95.2 4.8  96.6 3.4  90.8 9.2  90.6 9.4  90.7 9.3  90.0 10.0  89.4 10.6  92.0 8.0  92.5 7.5  92.5 7.5  90.9 9.1  90.0 10.0  89.1 10.9  Oxides (wt. %)  Si0 Cr 0 FeO MnO MgO NiO CaO Total 2  2  3  Cations (p.f.u.)  Si Cr Fe Mn Mg Ni Ca Total End Members (%)  Fo Fa  Crystal textural style is abbreviated: porph. (porphyroclast), cumu. (cumulus), def. (deformed), mgb. (modified grain boundaries) Note: Other phases (cpx, chr) were also analyzed on certain sections, such that "Cluster refers to a specific location on each section  Table 4.1 b: Representative olivine compositions from olivine-bearing ultramafic lithologies of the Turnagain intrusion  Rock type:  Wehrlite  Wehrlite  Wehrlite  Olivine Cpxite  Olivine Clinopyroxenite  Olivine Clinopyroxenite  Sample: Cluster:  04ES-09-01-01 1  04ES-09-01-01 4  04ES-15-01-05 1  04ES-06-06-01 1  05ES-05-01-01 4  04ES-01-04-01 1  Style: Zone:  porph. porph. rim mid  porph. core  porph. mid  porph. mid  porph. core  def. rim  def. mid  def. core  cumu. rim  cumu. mid  cumu. core  cumu. rim  cumu. mid  cumu. core  cumu. rim  cumu. mid  cumu. core  40.06 0.00 12.69 0.28 45.82 0.20 0.05 99.09  39.91 0.00 13.18 0.18 45.41 0.25 0.05 98.98  40.23 0.00 12.98 0.19 45.67 0.22 0.01 99.31  39.83 0.00 12.78 0.21 45.66 0.18 0.00 98.67  39.78 0.00 12.40 0.24 45.72 0.25 0.02 98.41  39.92 0.00 13.07 0.19 45.64 0.19 0.02 99.04  40.53 0.02 10.79 0.22 47.80 0.27 0.02 99.65  40.69 0.02 11.50 0.18 47.44 0.29 0.08 100.22  40.49 0.00 11.17 0.24 47.53 0.38 0.06 99.88  39.92 0.04 12.96 0.25 46.30 0.10 0.03 99.61  40.09 0.02 12.87 0.23 46.01 0.04 0.04 99.31  40.32 0.02 13.14 0.21 46.53 0.05 0.05 100.33  39.22 0.00 '14.95 0.23 44.46 0.08 0.03 98.98  39.43 0.01 15.63 0.26 44.21 0.08 0.01 99.62  39.17 0.02 15.61 0.22 44.25 0.14 0.02 99.44  40.44 0.01 12.27 0.16 46.38 0.09 0.00 99.35  40.18 0.01 12.73 0.22 46.67 0.11 0.03 99.95  40.31 0.02 12.75 0.21 46.55 0.05 0.05 99.95  1.005 0.000 0.266 0.006 1.713 0.004 0.001 2.995  1.004 0.000 0.277 0.004 1.704 0.005 0.001 2.996  1.007 0.000 0.272 0.004 1.705 0.004 0.000 2.993  1.004 0.000 0.269 0.005 1.715 0.004 0.000 2.996  1.004 0.000 0.262 0.005 1.720 0.005 0.001 2.996  1.003 0.000 0.275 0.004 1.710 0.004 0.001 2.997  1.002 0.000 0.223 0.005 1.762 0.005 0.001 2.997  1.003 0.000 0.237 0.004 1.744 0.006 0.002 2.996  1.001 0.000 0.231 0.005 1.752 0.007 0.002 2.999  0.997 0.001 0.271 0.005 1.724 0.002 0.001 3.001  1.003 0.000 0.269 0.005 1.716 0.001 0.001 2.996  1.000 0.000 0.272 0.005 1.720 0.001 0.001 2.999  0.996 0.000 0.318 0.005 1.683 0.002 0.001 3.004  0.997 0.000 0.331 0.006 1.667 0.002 0.000 3.003  0.993 0.000 0.331 0.005 1.673 0.003 0.001 3.006  1.008 0.000 0.256 0.003 1.723 0.002 0.000 2.992  0.999 0.000 0.265 0.005 1.729 0.002 0.001 3.001  1.001 0.000 0.265 0.004 1.724 0.001 0.001 2.998  86.6 13.4  86.0 14.0  86.2 13.8  86.4 13.6  86.8 13.2  86.2 13.8  88.8 11.2  88.0 12.0  88.4 11.6  86.4 13.6  86.4 13.6  86.3 13.7  84.1 15.9  83.4 16.6  83.5 16.5  87.1 12.9  86.7 13.3  86.7 13.3  Oxides (wt. %)  Si0 Cr 0 FeO MnO MgO NiO CaO Total 2  2  3  Cations (p.f.u.)  Si Cr Fe Mn Mg Ni Ca Total End Members (%)  Fo Fa  Crystal textural style is abbreviated: porph. (porphyroclast), cumu. (cumulus), def. (deformed), mgb. (modified grain boundaries) Note: Other phases (cpx, chr) were also analyzed on certain sections, such that "Cluster" refers to a specific location on each section  Table 4.2a: Representative clinopyroxene compositions from clinopyroxene-bearing ultramafic lithologies of the Turnagain intrusion  Rock Type:  Wehrlite  Wehrlite  Wehrlite  Olivine Clinopyroxenite  Olivine Clinopyroxenite  Olivine Clinopyroxenite  Sample: Cluster:  04ES-10-06-01 1  04ES-11-03-03 6  04ES-09-01-01 5  04ES-06-06-01 5  05ES-05-01-01 6  04ES-01-04-01 2  Style: Zone:  cumu. rim  cumu. mid  cumu. core  inter. rim  inter. mid  inter. core  inter. rim  inter. mid  inter. core  cumu. rim  cumu. mid  cumu. core  cumu. rim  cumu. mid  cumu. core  inter. rim  inter. mid  inter. core  Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 FeO* MnO MgO CaO Na 0 Total  54.02 0.17 1.17 0.58 3.03 0.07 17.66 23.24 0.25 100.20  53.50 0.16 1.11 0.73 2.70 0.10 17.53 23.69 0.29 99.81  54.01 0.19 1.10 0.68 2.73 0.13 17.60 23.25 0.28 99.98  54.20 0.14 0.78 0.42 3.02 0.12 17.61 23.61 0.27 100.17  54.41 0.17 0.95 0.57 3.52 0.12 17.55 22.61 0.29 100.19  54.03 0.19 0.93 0.53 3.54 0.17 17.64 22.67 0.29 100.00  54.78 0.08 0.25 0.13 2.06 0.10 17.46 25.03 0.05 99.94  54.27 0.12 0.36 0.16 2.83 0.09 17.66 24.11 0.12 99.71  54.42 0.06 0.41 0.20 3.02 0.08 17.40 24.18 0.13 99.89  54.19 0.16 0.74 0.48 2.86 0.13 17.54 23.43 0.20 99.74  53.96 0.11 0.88 0.50 3.19 0.12 17.24 23.47 0.18 99.66  54.14 0.14 1.08 0.61 3.39 0.14 17.47 22.83 0.19 99.99  53.91 0.22 1.12 0.42 3.98 0.12 17.09 23.38 0.29 100.52  53.61 0.25 1.20 0.54 4.43 0.09 17.48 22.35 0.29 100.24  53.29 0.18 1.23 0.42 4.31 0.15 17.45 22.32 0.24 99.59  53.84 0.12 0.81 0.61 3.09 0.11 17.70 22.66 0.22 99.15  54.76 0.11 0.80 0.71 3.51 0.13 17.95 22.77 0.22 100.95  54.56 0.12 0.71 0.59 3.29 0.06 18.15 22.67 0.21 100.37  Cations (p.f.u.) Si Ti A1 ' Al' " Cr Fe * Fe * Mn Mg Ca Na Total  1.962 0.004 0.038 0.008 0.021 0.009 0.073 0.002 0.940 0.938 0.009 4.004  1.967 0.005 0.033 0.014 0.019 0.000 0.083 0.004 0.956 0.907 0.010 3.999  1.968 0.004 0.032 0.018 0.019 0.000 0.088 0.003 0.953 0.905 0.009 3.998  1.960 0.007 0.040 0.009 0.015 0.012 0.120 0.004 0.946 0.885 0.009 4.006  1.961 0.006 0.039 0.004 0.010 0.021 0.095 0.003 0.934 0.927 0.009 4.011  1.953 0.007 0.047 0.006 0.017 0.019 0.107 0.004 0.936 0.903 0.010 4.009  1.958 0.007 0.042 0.010 0.016 0.013 0.122 0.003 0.951 0.875 0.010 4.007  1.958 0.005 0.042 0.011 0.012 0.017 0.115 0.005 0.956 0.879 0.008 4.009  1.974 0.004 0.026 0.004 0.014 0.009 0.080 0.003 0.966 0.917 0.008 4.004  1.958 0.007 0.042 0.009 0.022 0.007 0.105 0.003 0.939 0.904 0.009 4.004  1.982 0.002 0.018 0.021 0.013 0.000 0.072 0.002 0.918 0.955 0.013 3.997  1.976 0.003 0.024 0.010 0.020 0.000 0.106 0.004 0.966 0.881 0.008 3.998  1.981 0.003 0.019 0.014 0.014 0.000 0.099 0.003 0.957 0.896 0.010 3.997  1.973 0.004 0.027 0.007 0.012 0.009 0.083 0.004 0.956 0.921 0.009 4.005  1.978 0.005 0.022 0.019 0.016 0.000 0.107 0.004 0.952 0.881 0.010 3.994  1.971 0.005 0.029 0.011 0.015 0.002 0.106 0.005 0.959 0.886 0.010 4.001  1.961 0.007 0.039 0.011 0.018 0.006 0.092 0.004 0.939 0.917 0.009 4.003  1.972 0.007 0.028 0.009 0.013 0.000 0.101 0.004 0.930 0.928 0.008 4.000  46.4 49.1 4.5  47.7 49.1 3.2  46.6 49.1 4.3  47.0 48.8 4.2  45.4 49.1 5.5  45.4 49.2 5.4  49.1 47.7 3.2  47.6 48.5 3.9  47.8 47.8 4.4  46.8 48.7 4.5  47.0 48.0 5.0  45.9 48.8 5.3  46.8 47.6 5.7  44.9 48.8 6.3  45.1 49.0 5.9  45.6 49.6 4.8  45.1 49.5 5.4  44.9 50.0 5.1  0.920  0.898  0.919  0.903  0.888  0.910  0.886  0.893  0.922  0.899  0.929  0.900  0.918  0.899  0.900  0.969  0.913  0.907  2  2  2  3  2  3  2  ,1V  v  3  2  End Members (%) Wo En Fs Mg#  Crystal textural style is abbreviated: cumu. (cumulus), inter, (intercumulus) Note: Other phases (ol, chr, mt) were also analyzed on certain sections, such that "Cluster" refers to a specific location on each thin section  Table 4.2b: Representative clinopyroxene compositions from clinopyroxene-bearing ultramafic lithologies of the Turnagain intrusion  Rock Type:  Hornblende Clinopyroxenite  Hornblende Clinopyroxenite  Hornblende Clinopyroxenite  Sample: Cluster:  DDH04-47-7-49 5  04ES-09-02-02 3  DDH05-84-19-104 5  Style: Zone:  cumu. rim  cumu. mid  cumu. core  cumu. rim  cumu. mid  cumu. core  cumu. rim  cumu. mid  cumu. core  Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 FeO* MnO MgO CaO Na 0 Total  49.54 0.65 4.79 0.00 7.73 0.16 13.43 23.37 0.24 99.91  49.73 0.53 4.52 0.01 7.41 0.20 13.41 23.19 0.28 99.28  49.90 0.62 4.48 0.03 7.06 0.15 13.92 23.09 0.28 99.54  53.33 0.17 0.68 0.04 6.42 0.22 15.67 23.05 0.13 99.70  52.74 0.17 0.90 0.07 6.90 0.22 15.55 22.30 0.13 98.97  53.79 0.04 0.30 0.02 6.54 0.24 15.32 24.16 0.06 100.47  50.74 0.44 3.83 0.03 7.56 0.13 13.78 23.15 0.26 99.92  51.37 0.35 2.94 0.01 7.45 0.18 13.93 23.31 0.19 99.73  50.77 0.40 3.60 0.00 7.48 0.16 13.87 23.26 0.27 99.79  1.918 0.010 0.082 0.047 0.000 0.021 0.211 0.006 0.775 0.932 0.007 4.011  1.897 0.011 0.103 0.055 0.000 0.036 0.198 0.005 0.772 0.931 0.010 4.018  1.913 0.010 0.087 0.043 0.000 0.031 0.175 0.004 0.813 0.933 0.007 4.015  1.854 0.018 0.146 0.066 0.000 0.052 0.190 0.005 0.750 0.937 0.009 4.026  1.870 0.015 0.130 0.070 0.000 0.041 0.192 0.006 0.752 0.934 0.010 4.020  1.867 0.018 0.133 0.065 0.001 0.042 0.179 0.005 0.776 0.926 0.010 4.021  1.977 0.005 0.023 0.007 0.001 0.010 0.189 0.007 0.866 0.916 0.005 4.005  1.972 0.005 0.028 0.011 0.002 0.010 0.206 0.007 0.867 0.893 0.005 4.005  1.985 0.001 0.015 0.000 0.001 0.015 0.187 0.008 0.843 0.955 0.002 4.011  49.9 39.9 10.1  49.7 40.0 10.2  49.2 41.3 9.5  46.5 43.9 9.6  45.4 44.1 10.5  48.1 42.4 9.4  48.8 40.4 10.8  48.6 40.4 11.0  49.0 40.6 10.4  0.780  0.791  0.816  0.818  0.829  0.828  0.802  0.790  0.805  2  2  2  3  2  3  2  Cations (p.f.u.) Si Ti  Ar' At"" Cr Fe * Fe * Mn Mg Ca Na Total 3  2  End Members (%) Wo En Fs Mg#  Crystal textural style is abbreviated: cumu. (cumulus), inter, (intercumulus) Note: Other phases (ol, chr, mt) were also analyzed on certain sections, such that "Cluster" refers to a specific location on each thin section  Table 4.3a: Amphibole compositions from ultramaficrocksof the Turnagain intrusion  Rock Type:  Hornblende Clinopyroxenite  Sample Cluster  DDH04-47-7-49 1  6  DDH05-84-19-104 3  9  inter. Mid  inter. rim  inter. mid  inter. core  cumu. cumu. rim mid  cumu. mid  cumu. core  cumu. cumu. rim mid  cumu. mid  cumu. core  40.14 1.36 13.39 0.03 7.00 5.50 0.09 13.68 12.13 1.61 1.81 0.05 0.00 1.97 98.76  40.23 1.40 13.34 0.03 6.54 5.76 0.15 13.62 12.15 1.58 1.87 0.03 0.00 1.98 98.70  39.88 1.48 13.25 0.04 6.95 5.55 0.12 13.58 12.20 1.51 1.90 0.04 0.00 1.96 98.46  39.85 1.31 13.05 0.03 5.78 7.37 0.09 13.03 12.15 1.84 1.93 0.14 0.00 1.93 98.50  40 08 1.42 13.28 0.00 6.26 5.94 0.12 13.55 12.14 1.54 1.96 0.08 0.00 1.95 98.32  40.81 1.17 12.77 0.05 6.74 5.62 0.13 13.85 12.22 1.69 1.56 0.16 0.00 1.94 98.71  40.31 1.41 12.80 0.05 6.05 6.46 0.09 13.56 12.16 1.75 1.78 0.06 0.00 1.96 98.46  40.66 1.36 12.71 0.00 6.61 5.39 0.12 14.07 12.15 1.72 1.63 0.06 0.00 1.97 98.44  48.15 0.81 7.49 0.23 3.98 6.11 0.16 16.18 12.32 1.16 0.54 0.09 0.10 1.99 99.31  48.71 1.26 7.78 0.17 3.82 5.41 0.17 17.10 11.72 0.84 0.68 0.06 0.16 1.99 99.86  48.75 1.23 7.36 0.13 3.64 5.58 0.15 17.08 11.65 0.75 0.59 0.10 0.09 2.01 99.11  49.25 0.89 7.18 0.15 3.70 5.75 0.13 16.56 11.84 1.19 0.48 0.07 0.10 2.01 99.32  49.09 1.22 7.21 0.22 3.61 5.16 0.15 17.21 11.95 0.86 0.56 0.09 0.09 2.02 99.43  47.23 1.46 8.27 0.21 4.25 6.60 0.15 15.53 11.40 1.17 0.73 0.18 0.07 1.97 99.23  46.00 1.87 9.71 0.15 4.17 5.33 0.12 15.96 11.55 0.98 0.91 0.18 0.16 1.93 99.01  48.10 1.25 7.59 0.16 3.59 6.69 0.14 15.86 12.09 1.07 0.55 0.11 0.17 1.95 99.31  5.897 2.103 0.351 0.173 0.000 0.803 2.933 0.015 0.698 0.027 0.000 1.917 0.083 0.401 0.286 15.687  5.967 2.033 0.313 0.152 0.003 0.784 3.032 0.011 0.684 0.022 0.000 1.910 0.090 0.375 0.344 15.719  5.986 2.014 0.326 0.157 0.004 0.733 3.020 0.019 0.717 0.024 0.000 1.913 0.087 0.370 0.355 15.725  5.955 2.045 0.287 0.166 0.004 0.781 3.022 0.015 0.693 0.031 0.000 1.921 0.079 0.357 0.362 15.720  5.991 2.009 0.303 0.148 0.003 0.653 2.921 0.012 0.927 0.033 0.000 1.923 0.077 0.460 0.371 15.831  5.992 2.008 0.332 0.160 0.000 0.704 3.019 0.015 0.743 0.027 0.000 1.916 0.084 0.362 0.374 15.736  6.064 1.936 0.300 0.130 0.006 0.753 3.067 0.017 0.698 0.028 0.000 1.917 0.083 0.404 0.295 15.699  6.027 1.973 0.283 0.159 0.006 0.681 3.022 0.012 0.808 0.029 0.000 1.919 0.081 0.427 0.340 15.767  6.049 1.951 0.278 0.152 0.000 0.741 3.119 0.015 0.671 0.024 0.000 1.913 0.087 0.408 0.309 15.717  6.941 1.059 0.213 0087 0.026 0.432 3.477 0.020 0.737 0.008 0.000 1.895 0.105 0.220 0.099 15.319  6.936 1.064 0.241 0.135 0.019 0.409 3.630 0.020 0.546 0.000 0.098 1.788 0.115 0.117 0.124 15.241  6.988 1.012 0.231 0.133 0.014 0.393 3.650 0.018 0.561 0.000 0.107 1.790 0.103 0.105 0.107 15.212  7.051 0.949 0.262 0.096 0.017 0.399 3.535 0.016 0.675 0.000 0.014 1.816 0.170 0.161 0.088 15.249  7.005 0.995 0.218 0.130 0.025 0.388 3.661 0.018 0.559 0.000 0.056 1.827 0.117 0.119 0.102 15.221  6.834 1.166 0.244 0.159 0.024 0.463 3.351 0.018 0.740 0.000 0.059 1.767 0.174 0.154 0.135 15.289  6.650 1.350 0.304 0.203 0.017 0.453 3.440 0.015 0.568 0.000 0.075 1.788 0.136 0.139 0.167 15.306  6.939 1.061 0230 0.135 0.018 0.389 3.411 0.017 0.799 0.000 0.008 1.869 0123 0.175 0.100 15.276  1.983 0.017 0.000  1.983 0.017 0.000  1.988 0.012 0.000  1.992 0.008 0.000  1.989 0.011 0.000  1.963 0.037 0.000  1.978 0.022 0.000  1.959 0.041 0.000  1.985 0.015 0.000  1.985 0.015 0.000  1.931 0.023 0.046  1.911 0.016 0.073  1.934 0.025 0.041  1.937 0.017 0.046  1.937 0.023 0.041  1.924 0.045 0.031  1.883 0.045 0.072  1.895 0.028 0.077  0.657  0.662  0.674  0.676  0.672  0.649  0.676  0.679  0.670  0.749  0.775  0.775  0.765  0.785  0.726  0.758  0.740  inter. core  inter. rim  inter. mid  inter. core  inter. rim  39.39 1.54 14.07 0.06 7.32 5.54 0.17 13.14 12.24 1.64 1.60 0.05 0.00 1.96 98.73  39.17 1.53 14.04 0.00 7.68 5.19 0.13 13.19 12.18 1.58 1.62 0.08 0.00 1.95 98.34  39.35 1.62 13.71 0.02 7.05 5.78 0.15 13.05 12.32 1.67 1.39 0.07 0.00 1.95 98.13  39.38 1.56 13.99 0.07 7.80 5.48 0.12 13.18 12.31 1.72 1.50 0.06 0.00 1.97 99.14  39.82 1.49 14.20 0.00 6.93 4.73 0.10 13.79 12.35 1.66 1.50 0.06 0.00 1.97 98.62  39.47 1.56 13.89 0.00 7.08 5.80 0.13 13.06 12.15 1.67 1.50 0.07 0.00 1.95 98.35  39.59 1.55 13.98 0.00 7.16 5.60 0.12 13.21 12.18 1.68 1.50 0.07 0.00 1.96 98.59  5.864 2.136 0.315 0.185 0.000 0.818 2.918 0.018 0.713 0.034 0.000 1.924 0.076 0.402 0.307 15.710  5.868 2.132 0.339 0.172 0.007 0.821 2.918 0.021 0.691 0.032 0.000 1.921 0.079 0.395 0.305 15.700  5.855 2.145 0.329 0.172 0.000 0.864 2.939 0.017 0.649 0.030 0.000 1.920 0.080 0.378 0.309 15.687  5.897 2.103 0.318 0.183 0.002 0.795 2.915 0.019 0.725 0.043 0.000 1.935 0.065 0.421 0.267 15.687  5.849 2.151 0.297 0.174 0.009 0.872 2.919 0.016 0.680 0.034 0.000 1.924 0.076 0.418 0.284 15.702  5.901 2.099 0.381 0.166 0.000 0.772 3.046 0.013 0.587 0.036 0.000 1.926 0.074 0.404 0.284 15.688  5.899 2.101 0.347 0.175 0.000 0.796 2.911 0.017 0.725 0.028 0.000 1.918 0.082 0.403 0.286 15.689  OH CI F  1.980 0.020 0.000  1.987 0.013 0.000  1.980 0.020 0.000  1.983 0.017 0.000  1.984 0.016 0.000  1.985 0.015 0.000  Mg#  0.656  0.659  0.660  0.657  0.653  0.691  Oxides (wt. %) 2  2  2  3  Fe£) * 3  FeO* MnO MgO CaO Na^  KjO CI F HjO* Total  39.25 1.65 13.92 0.00 7.28 5.70 0.14 13.10 12.23 1.65 1.61 0.08 0.00 1.95 98.57  Cations (p.f.u.)  Si  Al(iv) Al(vi)  Ti Cr Fe '* Mg Mn 3  Fe *<M, 2  Ca(M>  Fe ^, Ca Na, 2  {B)  B)  N a  m  K Total  4  inter. Rim  inter. rim  Si0 TiCb Al 03 Cr 0  04ES-O9-02-02 2  7  inter. core  inter. core  inter. rim  4  inter. mid  inter. mid  Description Location  Hornblende Clinopyroxenite  Hornblende Clinopyroxenite  Crystal textural style is abbreviated: cumu. (cumulus), inter, (interstitial), porph. (porphyritic) Note: Other phases (cpx, mt, phlog) were also analyzed on certain sections, such that "Cluster" refers to a specific location on each thin section * Calculated  Table 4.3b: Amphibole compositions from ultramafic rocks of the Turnagain intrusion  Rock Type:  Hornblendite  Sample Cluster  05ES-05-06-02 2  Hornblendite 04ES-00-07-04 1  6  5  4  3  2  porph. mid  porph. core  porph. porph. rim mid  porph. mid  porph. core  porph. porph. rim mid  porph. mid  porph. core  cumu. rim  cumu. mid  cumu. mid  cumu. core  porph. porph. mid rim  porph. core  porph. porph. rim mid  porph. core  porph. porph. mid rim  porph. core  40.98 2.11 12.73 002 5.30 8.27 0.16 12.57 11.61 1.95 0.98 0.11 0.00 1.96 98.74  41.28 1.97 12.80 0.00 5.33 8.10 0.15 12.67 11.44 .1.87 1.07 0.07 0.00 1.97 98.71  41.44 1.98 12.51 0.02 5.16 8.91 0.20 12.36 11.68 1.86 1.07 0.09 0.00 1.97 99.26  40.71 2.12 12.92 0.04 5.40 8.58 0.19 12.20 11.53 1.90 1.02 0.14 0.00 1.94 98.68  41.01 2.07 13.16 0.03 4.58 8.00 0.18 12.75 11.73 1.85 1.12 0.06 0.00 1.98 98.53  40.78 1.97 13.30 0.02 5.92 6.94 0.10 13.26 10.81 1.80 1.76 0.10 0.00 1.97 98.72  40.90 1.99 12.50 0.00 5.85 8.34 0.23 12.26 11.35 1.82 1.04 0.11 0.00 1.95 98.32  40.69 2.13 13.05 0.01 5.22 8.35 0.19 12.32 11.50 1.87 1.07 0.12 0.00 1.95 98.46  40.70 2.08 13.29 0.00 4.71 8.71 0.14 12.29 11.71 1.93 1.11 0.08 0.00 1.97 98.73  40.73 2.03 12.93 0.05 5.01 8.09 0.14 12.59 11.68 1.88 1.10 0.08 0.00 1.96 98.27  46.98 1.58 9.44 0.17 4.05 4.26 0.11 16.96 11.97 0.95 0.83 0.08 0.17 1.98 99.54  45.39 1.93 11.12 0.11 4.11 4.71 0.16 16.18 11.72 1.11 1.00 0.13 0.17 1.96 99.81  44.75 1.77 11.10 0.07 4.66 4.23 0.17 16.16 11.78 1.08 0.94 0.15 0.15 1.94 98.95  45.00 1.39 10.97 0.05 4.58 4.21 0.11 16.41 11.67 1.16 0.85 0.09 0.15 1.95 98.60  43.13 1.56 11.80 0.06 4.60 9.38 0.34 12.40 11.65 1.78 0.75 0.17 0.00 1.97 99.60  45.79 1.34 10.57 0.01 1.30 12.37 0.45 10.97 10.89 1.01 1.25 0.32 0.00 1.92 98.19  42.72 2.23 11.30 0.06 4.59 9.24 0.37 12.47 11.44 1.73 0.72 0.21 0.01 1.94 99.01  41.28 2.39 12.49 0.04 4.52 11.28 0.31 10.86 11.48 1.73 0.97 0.11 0.00 1.96 99.42  42.00 2.24 11.87 0.09 4.26 11.14 0.34 10.98 11.21 1.61 0.82 0.10 0.00 1.95 98.60  41.64 2.26 12.18 0.11 4.55 10.86 0.33 11.08 11.48 1.69 0.81 0.14 0.02 1.94 99.09  42.41 2.09 11.54 0.01 5.02 9.48 0.22 12.29 11.57 1.71 0.86 0.11 0.00 1.97 99.26  42.16 1.96 11.62 0.02 5.40 9.52 0.26 12.16 11.68 1.75 0.90 0.21 0.00 1.94 99.57  4226 2.10 11.42 0.03 5.38 9.26 0.27 12.28 11.56 1.72 0.81 0.15 0.00 1.95 99.21  6.082 1.918 0.344 0.228 0.001 0.629 2.779 0.021 0.997 0.000 0.013 1.857 0.129 0.413 0.203 15.616  6.105 1.895 0.341 0.236 0.002 0.594 2.792 0.020 1.015 0.000 0.015 1.853 0.132 0.431 0.187 15.617  6.137 1.863 0.381 0.220 O.OOO 0.596 2.807 0.018 0.978 0.000 0.030 1.822 0.148 0.391 0.204 15.594  6.154 1.846 0.343 0.222 0.003 0.577 2.736 0.026 1.094 0.000 0.012 1.859 0.129 0.406 0.203 15.609  6.082 1.918 0.357 0.238 0.004 0.607 2.717 0.024 1.053 0.000 0.019 1.845 0.136 0.415 0.195 15.610  6.104 1.896 0.412 0.232 0.003 0.512 2.828 0.023 0.989 0.000 0.007 1.871 0.122 0.413 0.214 15.626  6.057 1.943 0.385 0.221 0.003 0.661 2.936 0.013 0.782 0.000 0.080 1.720 0.200 0.319 0.334 15.652  6.128 1.872 0.335 0.225 0.000 0.659 2.738 0.029 1.015 0.000 0.030 1.822 0.148 0.379 0.198 15.577  6.082 1.918 0.381 0.239 0.001 0.587 2.745 0.023 1.023 0.000 0.021 1.841 0.138 0.404 0.205 15.608  6.071 1.929 0.407 0.233 0.000 0.529 2.733 0.018 1.080 0.000 0.007 1.872 0.122 0.437 0.212 15.649  6.092 1.908 0.371 0.229 0.005 0.563 2.808 0.018 1.006 0.000 0.007 1.871 0.122 0.423 0.210 15.633  6.711 1.289 0.299 0.170 0.019 0.436 3.611 0.014 0.451 0.000 0.058 1.832 0.109 0.154 0.151 15.305  6.501 1.499 0.379 0.207 0.012 0.443 3.456 0.019 0.483 0.000 0.081 1.799 0.120 0.187 0.182 15.369  6.466 1.534 0.357 0.192 0.008 0.506 3.481 0.021 0.434 0.000 0.077 1.825 0.098 0.203 0.173 15.377  6.511 1.489 0.381 0.151 0.006 0.499 3.539 0.014 0.410 0.000 0.100 1.810 0.091 0.235 0.157 15.391  6.358 1.642 0.407 0.173 0.007 0.510 2.724 0.043 1.135 0.000 0.021 1.841 0.138 0.369 0.141 15.510  6.827 1.173 0.683 0.151 0.001 0.146 2.438 0.056 1.525 0.000 0.017 1.740 0.243 0.048 0.237 15.285  6.338 1.662 0.315 0.248 0.007 0.512 2.758 0.046 1.115 0.000 0.032 1.818 0.150 0.346 0.135 15.482  6.171 1.829 0.372 0.268 0.005 0.508 2.419 0.040 1.388 0.000 0.022 1.839 0.139 0.362 0.185 15.547  6.300 1.700 0.398 0.252 0.011 0.481 2.455 0.044 1.359 0.000 0.038 1.802 0.160 0.308 0.158 15.465  6.226 1.774 0.374 0.255 0.013 0.512 2.470 0.041 1.336 0.000 0.022 1.839 0.139 0.351 0.154 15.505  6.291 1.709 0.307 0.233 0.001 0.560 2.717 0.027 1.154 0.000 0.022 1.839 0.139 0.352 0.162 15.514  6.256 1.744 0.287 0.218 0.002 0.603 2.690 0.032 1.167 0.000 0.014 1.857 0.130 0.373 0.171 15.545  6.278 1.722 0.277 0.235 0.004 0.601 2.720 0.034 1.130 0.000 0.021 1.840 0.138 0.356 0.154 15.510  OH Cl F  1.964 0.036 0.000  1.971 0.029 0.000  1.983 0.017 0.000  1.977 0.023 0.000  1.964 0.036 O.OOO  1.986 0.014 0.000  1.976 0.024 0.000  1.973 0.027 0.000  1.970 0.030 0.000  1.979 0.021 0.000  1.981 0.019 0.000  1.900 0.020 0.079  1.888 0.033 0.079  1.894 0.037 0.069  1.907 0.023 0.071  1.956 0.044 0.000  1.919 0.081 0.000  1.942 0.054 0.005  1.973 0.027 0.000  1.975 0.025 0.000  1.955 0.036 0.009  1.971 0.028 0.001  1.944 0.055 0.002  1.962 0.038 0.000  Mg#  0.629  0.632  0.636  0.619  0.618  0.652  0.658  0.616  0.627  0.629  0.641  0.793  0.774  0.774  0.778  0.620  0.591  0.624  0.558  0.566  0.569  0.610  0.601  0.608  Description Location  porph. mid  Oxides (wt. %)  Si0 TiOj 2  AI2O3  Cr Q, FeA* FeO* MnO MgO CaO 2  NaJD  K0 Cl F HzO* Total 2  40.82 2.03 12.88 0.01 5.61 8.11 0.16 12.51 11.63 1.88 1.07 0.14 0.00 1.95 98.81  Cations (p.f.u.)  Si  Al(iv) Al(vi)  Ti Cr Fe ** Mg Mn 3  Fe * 2  w)  Ca M) (  Fe * 2  Ca (B) Na , Na K Total (B)  (B  (A)  Crystal textural style is abbreviated: cumu. (cumulus), inter, (interstitial), porph. (porphyritic) Note: Other phases (cpx, mt, phlog) were also analyzed on certain sections, such that "Cluster" refers to a specific location on each thin section * Calculated  Table 4.4: Biotite compositions from biotite-bearing ultramafic rocks of the Turnagain intrusion  Rock Type:  Hornblende Clinopyroxenite  Sample: Cluster:  DDH05-84-19-104 6  Description: Location:  Wehrlite 05ES-03-01-01 2  11  inter. mid  inter. core  inter. mid  inter. core  inter. rim  inter. core  36.47 1.31 14.89 0.03 17.70 0.02 14.64 0.61 0.15 0.24 9.44 0.04 0.00 1.96 97.51  36.55 1.54 15.27 0.00 15.98 0.02 16.16 0.49 0.09 0.24 9.31 0.09 0.00 1.97 97.72  36.84 1.56 15.12 0.01 17.75 0.00 15.01 0.65 0.09 0.21 9.87 0.03 0.00 1.99 99.13  36.33 1.53 15.14 0.00 17.39 0.00 14.68 0.53 0.14 0.18 9.73 0.04 0.00 1.96 97.66  39.16 1.10 13.85 1.16 4.61 0.06 24.95 0.44 0.08 0.06 8.73 0.00 0.10 2.08 96.36  39.06 1.15 14.30 1.22 5.19 0.07 23.75 0.51 0.06 0.06 9.30 0.04 0.08 2.06 96.85  5.550 2.450 0.220 0.150 0.003 2.253 0.003 3.321 0.037 0.024 0.072 1.833 15.916  5.494 2.506 0.200 0.174 0.000 2.008 0.003 3.622 0.029 0.015 0.070 1.786 15.906  5.520 2.480 0.190 0.176 0.001 2.224 0.000 3.351 0.038 0.014 0.062 1.887 15.944  5.516 2.484 0.226 0.174 0.000 2.208 0.000 3.323 0.032 0.022 0.054 1.884 15.923  5.639 2.350 0.000 0.119 0.132 0.555 0.007 5.354 0.025 0.012 0.016 1.604 15.812  5.630 2.370 0.059 0.124 0.139 0.626 0.009 5.103 0.029 0.009 0.017 1.710 15.824  Cl F OH  0.011 0.000 1.989  0.023 0.000 1.977  0.007 0.000 1.993  0.011 0.000 1.989  0.000 0.006 1.994  0.011 0.004 1.985  Mg#  0.60  0.64  0.60  0.60  0.91  0.89  Oxides (wt. %)  Si0 Ti0 Al 0 Cr 0 FeO MnO MgO BaO CaO Na 0 K0 Cl F H 0* Total 2  2  2  3  2  3  2  2  2  Cations (p.f.u.)  Si AI ' (IV  A  |(VD  Ti Cr Fe Mn Mg Ba Ca Na K Total  Crystal textural style is abbreviated: inter, (interstitial) Note: Other phases (ol, cpx, chr, mt) were also analyzed on certain sections, such that "Cluster" refers to a specific location on each thin section * Calculated  M a j o r and trace element concentrations (Table 4.5) o f 23 w h o l e r o c k powders, 3 b l i n d duplicates, and one procedural duplicate ( A p p e n d i x V I ) were analyzed at A c t i v a t i o n Laboratories L t d . (Actlabs) i n Ancaster, Ontario. F o r the major elements, a 0.2 g sample was fused i n a graphite crucible after it was m i x e d w i t h a combination o f l i t h i u m metaborate/lithium tetraborate. T h e mixture, once molten, was poured into 5 % HNO3 and shaken for 30 minutes until dissolved. The samples then were analyzed for selected trace elements and major oxides using a simultaneous/sequential Thermo J a r r e l l - A s h E n v i r o II inductively coupled plasma optical emission spectrometer ( I C P - E O S ) . A d d i t i o n a l trace elements were analyzed by both the I N A A (instrumental neutron activation analysis) and I C P M S (inductively couple plasma mass spectrometry) methods. Internal calibration was achieved using a variety o f international reference materials and independent control samples. F o r the I N A A analyses, 1.5-2.5 g o f sample was w e i g h e d into s m a l l polyethylene vials and irradiated w i t h control international reference material C A N M E T W M S - 1 and N i C r flux wires at a thermal neutron flux o f 7 x 1 0  12  ncm'V i n the M c M a s t e r N u c l e a r Reactor. T h e samples were 2  measured on an Ortec high-purity G e detector l i n k e d to a Canberra Series 95 multichannel f o l l o w i n g a 7-day decay. A c t i v i t i e s for each element were compared to a detector calibration developed from multiple international certified reference materials and decay- and weightcorrected. F o r the I C P - M S analyses, 0.25 g o f sample was digested i n H F , f o l l o w e d b y a mixture o f FINO3 and H C I O 4 , heated and taken to dryness. The samples were brought back into solution w i t h H C I . Samples were analyzed using a P e r k i n E l m e r O p t i m a 3000 I C P . In-lab standards or certified reference materials were used for quality control. The n o r m a l i z i n g values for the R E E (chondrite) and extended trace elements (primitive mantle) are from M c D o n o u g h & Sun (1995).  4.3.3 Platinum Group Elements The P G E concentrations o f 21 w h o l e rock samples, 3 b l i n d duplicates, and 1 procedural duplicate were determined b y the N i S fire-assay technique at Geoscience Laboratories (Sudbury, Ontario) f o l l o w i n g the procedures outlined i n Jackson et al. (1990) and R i c h a r d s o n & B u r n h a m (2003). N i c k e l , sulphur, s o d i u m carbonate and s o d i u m tetraborate are added to a 15 g aliquot o f sample powder. T h i s mixture is then fused for 1.5 hrs in a fire-clay crucible at 1 0 5 0 ° C , after w h i c h the crucible is broken to recover the n i c k e l sulphide button after c o o l i n g . T h e button, i n order to remove the N i S matrix, is then dissolved using h y d r o c h l o r i c acid i n a  Table 4.5a: Major (wt. % oxide)and trace element abundances (ppm) in mafic/ultramafic rocks of the Turnagain intrusion Rock Type: Sample Prefix: Sample #: Oxides (wt. %) Si0 Ti0 Al 0 Fe 0 * MgO MnO CaO Na 0 K 0  Dunite Dunite Dunite Dunite Dunite Dunite Wehrlite Wehrlite Wehrlite Wehrlite Wehrlite 04ES 04ES 04ES 04ES 05ES 05ES 04ES 04ES 05ES 05ES 05ES 03-01-02 06-01-01 03-02-01 07-02-01 04-06-01 04-05-01 03-04-01 07-02-04 05-06-01 05-02-01 05-03-01  38.17 0.04 0.32 7.15 48.54 0.10 0.29 0.02 0.20  38.08 0.01 0.05 9.26 48.00 0.14 0.01 0.03 0.03  37.04 0.01 0.03 12.02 46.86 0.13 0.13 0.01 0.04  35.64 0.01 0.07 7.72 45.13 0.10  LOI Total S  5.06 99.93 0.09  3.72 99.36 0.07  Mg #:  0.931  Trace Elements (ppm) Co 141 Cr 2580 Cu 9 Ni 3310 Sc 3.2  2  2  2  3  2  3  2  2  P O 2  35.80 0.04 0.61 9.78 41.26 0.13 0.05 0.04 0.09  37.86 0.03 0.17 14.93 41.18 0.19 1.43 0.02 0.03  38.14 0.02 0.15 13.69 42.40 0.21 1.06 0.03 0.12  39.04 0.09 0.37 12.12 43.10 0.20 2.94 0.05 0.08  39.19 0.03 0.18 13.53 42.73 0.21 2.08 0.03  0.08  36.47 0.03 0.22 14.22 41.56 0.23 0.06 0.04 0.11  38.49 0.05 0.33 11.32 43.02 0.18 2.07 0.06 0.10  3.37 99.65 0.39  11.29 100.10 0.11  7.00 99.95 0.08  11.44 99.23 0.18  4.06 99.91 1.39  3.96 99.77 0.18  0.92 99.41 0.03  1.79 99.77 0.18  4.18 99.79 0.06  0.911  0.885  0.921  0.853  0.893  0.845  0.860  0.876  0.862  0.883  160 2850 18 2185 3.2  209 2000 492 1760 3.6  126 3360 5 1790 2.8  163 1600 34 1190 5.7  125 4350  46  34  35  55  206 3640 261 1740 10.9 114 102  167 2660 126 988 8.7 12 58  163 3740 72 1080 15.0 31.5 56.5  175 4240 471 1590 9.7 7 62  136 5390 17 1940 11.7 27 69  0.03 7 0.22  7 0.14  7 0.15  0.07 0.016 0.07  0.07 0.022 0.09 0.01 0.09 0.02 0.06 0.01 0.06 0.008 1  5  V  Zn Rb Ba Th U Ta Nb La Ce Pb Pr Sr Nd Zr Hf Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Y  42 2 16  2 0.31  2360 3.8 14 61 8 0.13 0.10  0.2  0.44 0.2  0.41 0.6  2 0.15 0.07  0.02  0.08 0.01 0.07 0.01 0.05 0.01 0.06 0.008  0.01  0.02 2 0.14  0.08 3 0.40 2  4 0.15  3 0.09  0.05  0.12 0.021 0.13 0.02 0.16 0.04 0.12 0.02 0.12 0.017 4  0.07 0.013 0.07 0.01 0.08 0.02 0.05 0.01 0.05 0.006 2  0.04  0.02 0.03 0.01 0.02  0.02 4  Note: Blank entries represent values that were below detection limits. Abbreviated rock types: cpxite (clinopyroxenite), hblite (hornblendite) Abbreviated minerals: ol (olivine), hbl (hornblende) Mg# = Mg/(Mg+Fe) assuming all iron as Fe * * Total 2  0.06 0.04 0.02 0.04 0.004  0.10 0.039 0.13 0.02 0.16 0.03 0.10 0.01 0.09 0.015 0  0.06 0.01 0.04 0.01 0.04 0.006  Table 4.5b: Major (wt. % oxide)and trace element abundances (ppm) In mafic/ultramafic rocks of the Turnagain intrusion Rock Type: Sample Prefix: Sample #: Oxides (wt. %) Si0 Ti0 Al 0 Fe 0 * MgO MnO CaO Na 0 K 0  Cpxite Hbl Cpxite Hblite Hblite Diorite Wacke Wehrlite Wehrlite Wehrlite Ol Cpxite Ol Cpxite Cpxite DDH04 04ES 05ES 05ES 05ES 04ES 05ES 05ES 05ES 04ES 05 ES 04ES 05-01-02 03-01-01 05-05-01 10-02-04 05-01-01 05-04-01 03-01-02 09-02-02 05-06-02 00-07-04 57-12-89.2 00-07-02  38.20 0.04 0.21 18.60 37.72 0.25 2.28 0.06 0.01  37.07 0.07 0.50 15.13 34.25 0.16 1.56 0.02 0.08  42.85 0.11 0.42 10.71 35.67 0.17 7.40 0.03 0.05  50.62 0.19 1.00 8.07 21.74 0.15 17.76 0.17 0.12  51.23 0.20 1.05 7.45 22.45 0.13 17.26 0.17 0.10  48.99 0.38 2.21 7.65 18.65 0.15 19.12 0.20 0.08  s  2.45 99.83 0.66  11.07 99.92 1.65  2.38 99.78 0.23  99.08 0.78  99.34 0.42  Mg #:  0.801  0.818  0.868  0.842  181 1910 233 956 14.5 54 34  163 1380 248 777 28.8 49 41  110 2610 381 335 58.8 101 22  2  2  2  3  2  3  2  2  P2O5  LOI Total  Trace Elements (ppm) Co 192 Cr 683 Cu 475 Ni 858 11.1 Sc V 23 Zn 88 Rb Ba Th U Ta Nb 0.5 La 0.07 Ce 0.2 Pb Pr 0.03 Sr 7 Nd 0.23 Zr Hf Sm 0.11 Eu 0.032 Gd 0.13 Tb 0.02 Dy 0.13 Ho 0.03 0.08 Er Tm 0.01 Yb 0.08 Lu 0.011 2 Y  2.20 99.65 0.04  49.04 0.29 2.07 8.55 20.30 0.19 15.25 0.17 0.11 0.03 3.37 99.36 0.33  47.14 0.75 4.20 11.64 16.46 0.16 16.04 0.63 0.40 0.14 2.35 99.92 1.08  38.53 2.32 12.06 15.51 12.99 0.21 13.85 0.67 0.32 0.01 3.31 99.78 0.14  41.93 2.16 12.21 14.30 11.95 0.26 11.62 0.78 0.89 0.31 2.80 99.20 0.35  53.56 0.29 20.82 4.14 3.60 0.09 7.68 6.02 1.17 0.19 2.12 99.68 0.10  49.67 0.80 16.19 10.01 4.86 0.20 9.82 3.57 1.86 0.37 1.88 99.23 0.31  0.857  0.829  0.825  0.737  0.624  0.624  0.633  0.491  98 3200 292 511 55.4 81 18  59 1480 292 173 68.1 147 20  56 2690 47 56 41.8 265 57  85 38 133 132 69.3 645 69  1  12  36 0.29 0.16  0.3 0.52 2.0 5 0.41 71 2.64 7 0.3 1.04 0.318 1.31 0.25 1.57 0.31 0.86 0.12 0.74 0.100 10  0.5 1.56 3.8  151 1320 249 130 68.8 343 49 3 35 0.17 0.08 0.1 1.8 4.47 14.5 13 2.57 62 12.60 14 0.7 3.69 0.928 3.62 0.63 3.49 0.65 1.84 0.26 1.49 0.193 19  66 404 84 136 73.7 492 99 12.0 422 0.36 0.12 0.2 3.9 6.61 20.5 36 3.35 284 18.25 49 2.1 5.95 1.845 7.18 1.33 7.91 1.62 4.54 0.65 3.82 0.530 42  15 11 12 9 12.9 110 29 11 1980 0.07 0.09 0.1 2.3 1.50 3.4 5 0.52 2808 2.62 17 0.7 0.80 0.386 0.86 0.15 0.95 0.19 0.57 0.09 0.53 0.073 4  30 79 101 20 36.1 291 74 28 700 1.54 0.21 0.3 4.1 10.50 21.6 12 2.65 949 11.60 38 1.4 2.99 1.020 3.21 0.56 3.42 0.70 2.13 0.31 1.82 0.287 19  6 0.06  0.19 0.5  0.5 0.09 0.3  0.17 0.8  0.19 0.8  ,0.09 \ 4 0.59  0.07 14 0.53  0.18 32 1.33  0.18 35 1.33 2  0.24 0.051 0.28 0.05 0.32 0.06 0.17 0.02 0.14 0.022  0.24 0.077 0.30 0.06 0.35 0.07 0.19 0.03 0.16 0.022  0.61 0.200 0.84 0.16 0.95 0.18 0.52 0.07 0.42 0.055 2  0.60 0.204 0.80 0.15 0.92 0.18 0.49 0.07 0.44 0.053 5  Note: Blank entries represent values that were below detection limits. Abbreviated rock types: cpxite (clinopyroxenite), hblite (hornblendite) Abbreviated minerals: ol (olivine), hbl (hornblende) Mg# = Mg/(Mg+Fe) assuming all iron as Fe * * Total 2  0.64 60 3.60 12 0.4 1.16 0.277 1.36 0.25 1.56 0.31 0.90 0.13 0.81 0.108 8  69 0.10 0.06 1.6 2.11 7.0 34 1.40 336 8.64 30 1.3 3.26 1.310 4.10 0.76 4.74 0.97 2.79 0.39 2.25 0.310 28  closed Teflon vessel. A n y A u or P G E that may have been dissolved during button dissolution are recovered by co-precipitation w i t h t e l l u r i u m . T h i s produces a concentrate that contains A u and a l l P G E . The concentrate is vacuum-filtered and re-dissolved i n aqua regia p r i o r to analysis by I C P - M S . O s m i u m is not reported because, at the aqua regia re-dissolution stage, it may be lost as a volatile o x i d e . P G E concentrations i n the samples, detection limits, duplicate results, and reference material values are reported i n Table 4.6. The n o r m a l i z i n g values for P G E (primitive mantle) are from M a i e r & Barnes (1999).  4.3.4 Sulphur Isotopes - Sulphide A total o f 27 samples from sulphide-rich lithologies i n c l u d i n g 3 b l i n d duplicates, sampled from drillcore and outcrop, were analyzed for their sulphur isotopic composition. Samples o f massive sulphide were sampled using a scriber w i t h a tungsten-carbide tip and a l l other samples were crushed using a steel hammer and base. Sulphide was then hand-picked u s i n g a binocular microscope to assure the lack o f any attached silicate, oxide, or other phases. 5 S 3 4  was determined on separates that y i e l d e d appreciable sulphide. M o s t ultramafic samples contained p y r r h o t i t e ± p e n t l a n d i t e w i t h trace amounts o f pyrite, although some also contained chalcopyrite. Hornblende-rich samples typically contained pyrite and/or chalcopyrite (see Table 4.7). Sulphur was extracted online w i t h continuous-flow technology, using a F i n n i g a n M A T 252 isotope-ratio mass spectrometer, at the Queen's F a c i l i t y for Isotope Research, Queen's U n i v e r s i t y , K i n g s t o n , Ontario. A l l values are reported i n units o f per m i l (%o), and were corrected using the N I S T standard 8556. Sulphur is reported relative to C a n o n D i a b l o Troilite ( C D T ) . A n a l y t i c a l precision for 8 S is 0.3 % o . 3 4  4.3.5 Lead Isotopes - Sulphide A total o f 16 sulphide samples from sulphide-rich lithologies, 2 duplicates, sampled from drillcore and outcrop, and the standard reference material N B S - 9 8 1 were analyzed for their lead isotopic composition and the results are presented i n Table 4.8. A l l samples were subject to the separation procedure described above for sulphur isotopes. Sulphide separates chosen for analysis were then leached i n dilute h y d r o c h l o r i c acid to remove surface contamination before dissolution i n nitric acid. Ion exchange columns were e m p l o y e d for the separation and purification o f P b . T h e samples were converted to bromide form, and the solution was passed through i o n exchange columns i n h y d r o b r o m i c acid, and the lead eluted i n 6 N h y d r o c h l o r i c acid. A p p r o x i m a t e l y 25-50 n g o f the  121  Table 4.6: PGE concentrations of representative ultramafic rocks from the Turnagain intrusion  Rock Type: Sample: prefix  number  dunite dunite dunite dunite dunite dunite wehrlite wehrlite wehrlite wehrlite wehrlite wehrlite wehrlite wehriite ol cpxite ol cpxite cpxite cpxite hbl cpxite hblite hblite  03-01-02 06-01-01* 03-02-01 07-02-01 04-06-01 04-05-01 03-04-01 07-02-04 05-06-01* 05-02-01 05-03-01 05-01-02 03-01-01 05-05-01 10-02-04 05-01-01 05-04-01 03-01-02 09-02-02 05-06-02 00-07-04*  04ES 04ES 04ES 04ES 05ES 05ES 04ES 04ES 05ES 05ES 05ES 05ES 05ES 05ES 04ES 05ES 05ES 05ES 04ES 05ES 04ES  Detection Limit:  MgO (wt. %)  S (wt. %)  Ni (ppm)  Ir (ppb)  Ru (ppb)  Rh (PPb)  Pd (PPb)  Pt (PPb)  Au (PPb)  Cu (ppm)  Pd/Pt  Cu/Pd  51.2 50.2 48.7 50.8 44.7 47.0 43.0 44.3 43.8 43.6 45.0 38.7 38.5 36.6 21.9 22.6 19.1 21.1 16.9 13.5 12.4  0.09 0.07 0.39 0.11 0.08 0.18 1.4 0.18 0.03 0.18 0.06 0.66 1.7 0.23 0.78 0.42 0.04 0.33 1.1 0.14 0.35  3310 2185 1760 1790 1190 2360 1740 988 1080 1590 1940 858 956 777 335 511 173 56 130 132 136  13.6 1.63 1.76 2.77 1.17 1.3 1.46 3.36 1.2 2.94 4.21 1.17 0.07 1.05 0.48 1.86 0.23 0.06  9.44 4.67 2.73 3.34 0.87 3.09 3.04 2.62 0.24 2.25 4.25 2.36 0.16 2.25 0.15 0.5  6.27 0.515 1.81 0.98 1.62 0.55 1.41 8.1 1.88 3.29 4.68 0.75 0.1 0.88 0.28 1.53 0.29 0.17  44.47 0.975 24.13 3.51 10.26 8.57 9.53 82.62 35.33 52.33 85.42 6.72 1.77 8.49 6.4 33.32 4 4.22 0.86  1.97  9 18 492 5 34  0.82 0.98 0.97 1.19 1.06 0.65 1.21 1.24 1.28 1.01 0.64 1.04 2.56 0.85 0.90 0.69 0.44 0.97 2.50  247 18750 21071 1196 3134  0.06  0  0.17  36.44 0.96 23.35 4.18 10.85 5.58 11.54 102.58 45.08 52.61 54.6 7.02 4.54 7.23 5.75 23.15 1.77 4.11 2.15 0.41 4.11  4.35  0.76  0.04  0.13  0.08  0.11  0.14  0.71  1.85  2.37 2.90 5.89 17.65 1.72 0.89 1.12 1.12 0.77 8.02  TDB Intl STD TDB Intl STD Accepted Value:  1-0506 1-0507  0.08 0.07 n/a  0.27 0.26 n/a  0.48 0.46 n/a  4.91 4.70 5.8  22.87 22.71 22.4  6.45 6.05 6.3  original duplicate original duplicate original duplicate  06-01-01 05-07-01 05-06-01 00-07-01 00-07-04 03-02-01  1.77 1.49 1.2 1.2 0.06 0.06  5.18 4.16 0.22 0.26  0.53 0.5 1.67 2.09 0.17 0.17  1.18 0.74 45.29 44.87 4.10 4.11  1.2 0.75 35.08 35.58 4.48 4.22  5.24 6.53 0.75 0.77  04ES 05ES 05ES 04ES 04ES 05ES  Some rock types have been abbreviated: cpxite (clinopyroxenite), hblite (hornblendite) The last part of the table contains 2 internal standard analyses and 3 sample sets (sample followed by its respective blind duplicate) Samples with an asterisk represent the average between the specific analysis and its blind duplicate Blank entries represent analyses that were below detection  261 126 72 471 17 475 233 248 381 292 292 47 249 133 84  0.94  22617 1228 1597 8953 311 67664 51322 34302 66261 12613 164972 11436 115814 324390 20463  Table 4.7: Sulphur isotopic data from the Turnagain intrusion and surrounding lithologies  Depth (m) Mineralogy  Texture  S content (%) 6 S (CDT) 34  Sample  Rock Type  DDH03-12-4  dunite  31.9  po+pn  diss, to crs. bleb., mt rim  37.6  -9.7  DDH04-29-9  dunite  63.8  po+pn  fine bleb.  14.6  -9.0  DDH03-16-24  dunite  166  po+pn  msv. remob.  42.7  -6.9  05ES-02-02-02  dunite  N/A  po+pn+cpy+py crs. bleb., mt rim  32.0  -6.7  05ES-02-02-02A dunite  N/A  po+pn  net tex., mt frac.  40.2  -6.4  DDH03-18-13  dunite  84.8  po+pn  diss, to crs. bleb.+ inter.  41.0  -5.4  05ES-02-04-01  dunite  N/A  po+pn  diss, to inter.  37.7  -5.3  DDH04-37-6  dunite  39.7  po+/-pn+/-cpy fine bleb. + minor remob.  33.3  -5.1  DDH04-24-31  dunite  220.4  po+cpy+/-pn  fine to med. bleb.  38.4  -4.1  DDH04-36-16  dunite  108.1  po+pn  diss, to fine bleb.  29.6  -3.4  DDH04-36-5  wehrlite  39.7  po+pn  diss, to med. bleb.  40.9  -8.4  DDH04-33-5  wehrlite  37.9  po+pn  crs. bleb.  33.8  -8.2  DDH04-23-11  wehrlite  76.2  po+pn  net tex., mt rim + frac.  36.8  -8.0  DDH03-06-25  wehrlite  181.5  po+pn  msv. remob.  32.3  -5.4  05ES-03-01-01  wehrlite  N/A  po+pn  crs. bleb.  37.4  -5.2  DDH04-28-6  wehrlite  44.8  po+pn+/-cpy  fine bleb, to net tex.  37.0  -4.8  DDH03-05-45  wehrlite  325  po  med. bleb, to inter.  42.9  -4.7  DDH03-07-25  wehrlite  183  po+pn+cpy  fine bleb., mt rim + frac.  35.4  -3.9  DDH04-35-5  wehrlite  40.1  po+pn  diss, to med. bleb.  32.2  -3.5  05ES-02-01-01  wehrlite  N/A  po+pn+cpy  net tex., heavy alt.  30.2  -1.7  DDH03-08-13  wehrlite  100.7  po+/-pn  diss, to fine bleb.  35.2  -1.1  DDH03-05-8  clinopyroxenite  89.7  po  remob.  38.6  -1.3  DDH03-09-18  clinopyroxenite  134.3  po  med. bleb.  41.3  -0.6  DDH04-47-17  hbl clinopyroxenite 126.5  py  crs. bleb.  58.4  1.4  DDH03-03-59  hornblendite  426  py  med. bleb.  43.2  -0.1  04ES-13-01-02  felsic tuff(?)  N/A  py  porph.  45.5  -1.7  DDH03-07-54  graphitic phyllite  389  py  porph.  55.8  -17.9  Textures are abbreviated as follows: med. (medium), crs. (coarse), diss, (disseminated), bleb, (blebby), msv. (massive), net tex. (net textured), porph. (porphyroblastic), remob. (remobilized), inter, (interstitial), mt rim (magnetite rim), frac. (fracture) Minerals are abbreviated as follows: po (pyrrhotite), pn (pentlandite), cpy (chalcopyrite), py (pyrite) N/A in "Depth" column indicates that the sample is from a surface exposure  Table 4.8: Pb isotopic compositions of selected sulphide fractions from the Turnagain intrusion and surrounding lithologies  Sample  Rock T y p e  Depth  Mineral  Number  207PW  206Pb/ 204Pb  2a  207Pb/  208PW  204Pb  2a  204Pb  2a  208PW  206Pb  2a  206Pb  2a  DDH03-16-24  dunite  166  po±pn  18.794  0.015  15.679  0.012  38.36  0.03  0.8343  0.0006  2.027  0.001  05ES-02-02-02  dunite  N/A  po+pn+cpy±py  18.845  0.027  15.644  0.025  38.62  0.07  0.8302  0.0005  2.042  0.002  05ES-02-02-02A  dunite  N/A  po+pn  18.826  0.022  15.632  0.026  38.50  0.08  0.8303  0.0004  2.045  0.002  DDH04-37-6  dunite  39.7  po±pn±cpy  18.944  0.030  15.681  0.031  38.46  0.09  0.8278  0.0004  2.030  0.002  DDH03-06-25  wehrlite  181.5  po+pn  19.003  0.023  15.675  0.017  38.72  0.05  0.8249  0.0007  2.023  0.002  DDH04-28-6  wehrlite  44.8  po+pn±cpy  19.078  0.025  15.724  0.022  38.62  0.06'  0.8242  0.0002  2.024  0.001  DDH03-05-45  wehrlite  325  po  18.561  0.021  15.527  0.017  38.40  0.04  0.8366  0.0006  2.054  0.001  DDH03-07-25  wehrlite  183  po+pn+cpy  18.882  0.035  15.648  0.034  37.91  0.10  0.8287  0.0004  2.008  0.002  DDH03-08-13  wehrlite  100.7  po±pn  18.726  0.020  15.584  0.016  38.50  0.04  0.8322  0.0007  2.041  0.001  DDH03-05-08  clinopyroxenite  89.7  po+pn  18.106  0.015  15.636  0.012  38.12  0.03  0.8636  0.0007  2.091  0.002  DDH04-47-17  hbl clinopyroxenite  126.5  py±po  18.732  0.015  15.605  0.013  38.45  0.03  0.8331  0.0006  2.038  0.001  DDH03-03-59  hornblendite  426  po+pn  18.855  0.024  15.634  0.016  38.71  0.05  0.8292  0.0009  2.039  0.002  04ES-13-01-02  felsic tuff  N/A  py  19.155  0.033  15.649  0.033  38.57  0.10  0.8170  0.0004  2.013  0.002  DDH03-07-54  graphitic phyllite  389  py  18.920  0.020  15.629  0.024  38.47  0.08  0.8260  0.0004  2.033  0.002  Minerals are abbreviated as follows: po (pyrrhotite), pn (pentlandite), cpy (chalcopyrite), py (pyrite) Note: All errors are kj absolute N/A in "Depth" column indicates that the sample is from a surface exposure  lead i n chloride form was loaded o n a rhenium filament using a phosphoric a c i d - s i l i c a gel emitter, and isotopic compositions were determined i n peak-switching mode using a m o d i f i e d V G 5 4 R thermal i o n i z a t i o n mass spectrometer at the Pacific Centre for Isotopic and G e o c h e m i c a l Research, U n i v e r s i t y o f B r i t i s h C o l u m b i a . The measured ratios were corrected for instrumental mass fractionation o f 0.10%/amu (Faraday collector) per mass unit based o n repeated measurements o f the N . B . S . S R M 981 Standard Isotopic Reference M a t e r i a l and the values recommended by T h i r l w a l l (2000). Errors were n u m e r i c a l l y propagated i n c l u d i n g a l l mass fractionation and analytical errors, using the technique o f R o d d i c k (1987). A l l errors are quoted at the 2CT level.  4.4 RESULTS 4.4.1 Olivine Mineral Chemistry O l i v i n e core compositions from olivine-bearing ultramafic rocks o f the T u r n a g a i n intrusion become progressively less magnesian from chromitites (F091.96) through dunites (F089-92.5) and wehrlites (F085-90) to o l i v i n e clinopyroxenites (~Fo83-87) (Figure 4 . 7 A , Table 4.1). T h e most M g - r i c h o l i v i n e i n dunite not associated w i t h chromitite is F092.5, w h i c h is consistent w i t h crystallization from a p r i m i t i v e parent m a g m a i n e q u i l i b r i u m w i t h o l i v i n e i n mantle peridotite, as originally proposed by N i x o n (1998). O l i v i n e grains from chromitites extend to more M g r i c h compositions (up to F096), however these are l i k e l y due to F e - M g exchange between o l i v i n e and neighbouring chromite during sub-solidus re-equilibration ( C l a r k , 1978). The progressive decrease i n the forsterite content o f o l i v i n e w i t h decreasing o l i v i n e abundance i n the Turnagain cumulate rocks is consistent w i t h progressive decrease i n the M g / F e o f the parent magma(s) due to continued o l i v i n e precipitation. There is a general positive correlation between the forsterite and N i contents i n o l i v i n e for a l l olivine-bearing lithologies in the Turnagain intrusion (Figure 4 . 7 B ) . Three distinct groups can be identified w i t h i n this trend. T h e first group contains the majority o f the o l i v i n e core analyses, ranging from F091 and N i = 3150 p p m d o w n to F083.5 and N i = 1000 p p m , and reflects progressive M g and N i depletion due to o l i v i n e crystallization. T h e second group consists o f o l i v i n e grains enclosed w i t h i n or adjacent to chromitite. These compositions extend to higher M g (F096) and N i (2750-4715 ppm) contents, and appear to reflect sub-solidus exchange between o l i v i n e and chromite as noted above. The third group consists o f o l i v i n e core compositions that are distinctly depleted i n N i at a g i v e n F o content, relative to the o l i v i n e  125  -r—i—i—•—i—i—i—i• chromitite cores • chromitite rims ol cpxitek  O dunite cores • dunite rims • wehrlite cores • wehrlite rims  wehrliteh  A ol cpxite cores A ol cxpite rims dunite  chromitite  88  84  82  90  i  -i—I—r—i—i—i—r  92  Fo content i  i  i  i  i  r  5000 P B  94  96  98  n—i—i—i—i—i—i—r  4000 H  82  84  86  88  90  Fo content  92  94  96  98  Figure 4.7: Olivine chemistryfromthe Turnagain intrusion. A) Forsterite content vs. rock type showing the intraand interlithological olivine compositional variation (cores andrims).Note the systematic progressive decrease in Fo content of olivine from dunite through wehrlite to olivine clinopyroxenite. Olivine in chromitite has Mg-rich olivine extending up to Fo due to subsolidus re-equilibration with chromite B) Forsterite content vs. Ni (ppm) showing three distinct populations: olivinefromdunite, wehrlite, and olivine clinopyroxenite with "normal" Ni concentrations (1); olivinefromchromitite (2) with high Mg/Fe and Ni; and dunite, wehrlite, and olivine clinopyroxenite showing relative Ni depletion (3) compared to the first population. 96  compositions i n the first group (Figure 4 . 7 B ) . T h i s N i depletion is consistent w i t h the effect o f sulphide l i q u i d saturation and segregation i n the parent magma(s) to these specific dunite, wehrlite, and olivine clinopyroxenite samples, w i t h N i being strongly partitioned into the sulphide liquid relative to coexisting o l i v i n e (e.g. sulphide/silicate l i q u i d partition coefficient for N i i n basaltic melts is - 8 0 0 (Peach et al,  1990)).  4.4.2 Clinopyroxene Mineral Chemistry C l i n o p y r o x e n e (diopside) compositions i n the Turnagain intrusion range from M g # = 0.77 to 0.97 (Figure 4 . 8 A , Table 4.2), where M g # = M g / ( M g + F e ) . There are no systematic 2 +  compositional differences between interstitial and cumulus clinopyroxene. There is also relatively little variation i n clinopyroxene M g # i n wehrlite and o l i v i n e clinopyroxenite, and significant variation between o l i v i n e clinopyroxenite and hornblende clinopyroxenite (Figure 4 . 8 A ) . The lower M g # (0.84) o f clinopyroxene from hornblende clinopyroxenite is consistent w i t h its crystallization from more e v o l v e d magmas depleted i n M g due to abundant early o l i v i n e (and clinopyroxene) crystallization. The A l and T i contents o f clinopyroxene are also distinctive between the different lithologies o f the Turnagain intrusion. The magnesian diopside grains i n wehrlite and o l i v i n e clinopyroxenite are A l - p o o r (AI2O3 = 0.25-1.54 wt.%) (Figure 4 . 8 B ) , whereas the lower M g # o f clinopyroxene grains from hornblende clinopyroxenites extend to higher A 1 0 (0.30-5.27 wt.%) and T i 0 (0.04-0.72 wt.%) contents. 2  3  2  4.4.3 Amphibole and Biotite Chemistry P r i m a r y cumulus amphibole i n the Turnagain intrusion occurs i n hornblende clinopyroxenite, hornblendite, and hornblende diorite. D u e to the significant size difference between cumulus amphibole (-200-1000 pm) and interstitial amphibole (<75 pm) i n hornblendites (Figure 4.4.2F), o n l y cumulus amphibole was analyzed (Table 4.3). A m p h i b o l e is generally halogenpoor ( C l + F = 1-5% o f O H site), contains a moderate amount o f alkalis ( N a + K = 0.315-0.908 c.p.f.u.), T i (0.096-0.239 c.p.f.u.), and A l (1.213-2.480 c.p.f.u.), and has a compositional range between magnesiohastingsite and hornblende (based o n the classification scheme o f L e a k e et al,  1997) (Table 4.3). S m a l l amounts o f biotite (1-3 v o l . % ) are c o m m o n l y observed i n dunite  and wehrlite, whereas hornblende clinopyroxenite may contain 10 v o l . % biotite. Rare, but l o c a l l y significant pegmatoidal biotite clinopyroxenite, observed both at surface and i n d r i l l core from the D J Z o n e (Figure 4.1), may contain 50-60 v o l . % biotite. The biotite occurrence i n  127  1  1  1 — i — i — i — i — i — i — i — i — i — • wehrlite cores • wehrlite rims  A  • ol cpxite cores ^  m  w  * ol cpxite rims • hbl cpxite cores  w  • hbl cpxite rims i iHiitt  ol cpxite h  MM  k•  A  wehrlite k-  i  i  i  0.75  0.025  0.85  0.95  Mg#  ~l—' " — i — i — I — i — i — i — i  1—r  B  • wehrlite cores • wehrlite rims 0.02  • ol cpxite cores O,  Aol cpxite rims  t  • hbl cpxite cores  3 0.015  #  O hbl cpxite rims  4-1 d  ~  9*  •  0.01  0.005  j  0.05  i i_  J  L  0.1  0.15  0.2  0.25  Al (c.p.f.u.) Figure 4.8: Clinopyroxene chemistryfromthe Turnagain intrusion. A) Mg# vs. rock type. Note that clinopyoxene from olivine clinopyroxenite and wehrlite have similar Mg#. B) Al vs. Ti. Note the small range both Al and Ti in the Mg-rich lithologies, but the wide range (and linear correlation) of Al and Ti contents in hornblende clinopyroxenite.  these rocks suggests that it crystallized i n place o f hornblende. B i o t i t e analyses i n wehrlite are typically more magnesian (phlogopite, M g # = 0.90) than analyses i n hornblende clinopyroxenite (biotite, M g # = 0.60) (Table 4.4).  4.4.4 Major and Trace Element Geochemistry W h o l e rock samples from the Turnagain intrusion display a large distribution i n major element oxide contents (Figure 4.9) and trace element concentrations, w h i c h are largely controlled by the abundance and type o f cumulus minerals, and the relative proportions o f cumulus to intercumulus phases. There are four m a i n lithological groupings: (1) h i g h - M g rocks (dunite and wehrlite), (2) intermediate-Mg rocks (olivine clinopyroxenite and hornblende clinopyroxenite), (3) hornblendites, and (4) dioritic rocks, represented by one sample ( D D H 0 4 57-12-89) i n this study.  4.4.4.1 G r o u p 1: H i g h - M g O l i v i n e - r i c h R o c k s These rocks are dominated by cumulus o l i v i n e and chromite w i t h interstitial, and rarely cumulus, clinopyroxene. T h e i r w h o l e rock M g O contents range from 35 to 51 w t . % and they have a restricted range i n M g # (0.80-0.95), consistent w i t h the presence o f abundant cumulus o l i v i n e (>Fooo) and m i n o r amounts o f clinopyroxene. W i t h respect to elements compatible i n o l i v i n e or chromite, the h i g h - M g rocks contain significant C r (500-5500 ppm) and N i (8003400 ppm) (Figure 4.10). The h i g h - M g rocks are also extremely poor i n a l l elements not incorporated into o l i v i n e or chromite (e.g. C a , A l , T i , R E E ) to the extent that incompatible trace element abundances are generally at or below detection limits for nearly a l l o f the dunites analyzed. Wehrlites exhibit slightly concave-down chrondrite-normalized rare earth element patterns (Figure 4.11 A ) ranging from 0.3-0.8 x chondrite (La) w i t h a ( L a / Y b )  c n  o f 0.4-0.9.  Wehrlites generally exhibit similar extended trace element patterns (Figure 4.1 I B ) . T h e single dunite sample (05ES-04-05-01) w i t h trace element concentrations significantly above detection limits has distinctive L R E E - e n r i c h m e n t relative to a l l other ultramafic samples from the Turnagain intrusion (Figure 4.11 A ) . T h i s sample contains abundant 1-2 m m serpentine veinlets w i t h m i n o r rutile and chlorite, thus the distinctive chemistry is likely due to postcrystallization modification during fluid-rock interaction and serpentinization, w h i c h may have implications for m i n o r L R E E m o b i l i t y i n rocks o f the Turnagain intrusion during serpentinization.  129  Whole Rocks | ^ Dunite _ Wehrlite |A Olivine cpxite  I  45  09  Minerals Olivine (dunite) • Olivine (wehrlite) A Olivine (ol cpxite)|  • A • O O  Hbl cpxite |0 Hblite U- Diorite X Wacke  I  9  -i—i—i—i—|—i—i—i—i—i—i—i—  B  _i  10  20  30  40  .  •  i  10  50  .  •  20  i  30  40  MgO (wt. %)  MgO (wt. %) -I—rj—i—i—|—i—i—i  Cpx (wehrlite) Cpx (ol cpxite) Cpx (hbl cpxite) hbl (hbl cpxite) hbl (hblite)  |—i—i—i—i—|—I—I—i—i—| i i  8 o  ce X  + 10  20  30  40  10  20  E i  i  i—I—|  i  i  fl  r i  |  i  i  i  i  |  i  i  -I—I—i—I I I i^Q—I F  4|  i—i—|—  f:  =•* 0.75  2  30  MgO (wt. %)  MgO (wt. %)  O «  10  + x  • * • • i i_ 20  _l  30  MgO (wt. %)  I  40  1  I  I  I  I  50  I  -^QOt^- -  L  1  20  30  MgO (wt. %)  Figure 4.9: Select major element oxides and Mg# vs. MgO for whole rock samples from the Turnagain intrusion. Individual whole rock analyses are plotted as large symbols shaded in grey, with the exception of hornblendite (open circles). Mineral analysesfromspecific lithologies have the same symbol as the whole rock sample, however they are smaller and variably shaded i.e. olivine from dunite is diamond-shaped, but smaller and open. Whole rock Mg# = Mg/(Mg+Fe). Note the large compositional gap between dunite/wehrlite and olivine clinopyroxenite/hornblende clinopyroxenite. All ultramafic rock types have high Mg# (-0.80) reflecting accumulation of olivine and/or clinopyroxene, whereas the hornblendites have relatively low Mg# (0.63). Abbreviations are: cpx (clinopyroxene), cpxite (clinopyroxenite), hbl (hornblende), hblite (hornblendite).  130  II I  I Whole I Rocks  ^  I I  I  I  II  I  I  —i—i—i—|—l—i—i—r—  I I  Minerals  Dunite Wehrlite  A Olivine cpxite  E a  a 3000  0  Hbl cpxite  0  Hblite  • E  -|- Diorite X Wacke  |  a a  4L  2000  Olivine (dunite) • Olivine (wehrlite) A Olivine (ol cpxite)| • Cpx (wehrlite) A Cpx (ol cpxite) • Cpx (hbl cpxite) O hbl (hbl cpxite)  B  hbl (hblite)  • -I*-  4*20  30  20  40  30  40  MgO (wt. %)  MgO (wt. %) 70  ;D  • • A  60  50  E o. a  u  co  40  10  0 30  MgO (wt. %)  40  -  •  30 20  20  • X  ;+  B  i i 20  i  i i i  30  MgO (wt. V4  Figure 4.10: Select trace element concentrations vs. MgO for whole rock samplesfromthe Turnagain intrusion. The same symbol style as Figure 9 is applied here. The large compositional gap present in Figure 9, between olivine cumulate rocks and clinopyroxene4iornblende cumulate rocks, is also apparent with respect to trace elements.  100  I I  I  I  I  I  I  I  I  I  I  l  I  I  I  i  i  I  I  i  i  i  r  Ba Ta Nb La Ce Pr Sr Nd Zr Hf Sm Eu Gd Tb Ti Dy Ho Er Tm Yb Lu Y  Figure 4.11: Chondrite-normalized rare earth element and primitive mantle-normalized trace element diagrams for whole rocks from the Turnagain intrusion (normalizing values from McDonough and Sun, 1998). A) Ultramafic rocksfromthe Turnagain intrusion, showing a progressive overall enrichment in REE and in LREE from wehrlite to olivine clinopyroxenite to hornblendite. Note that, with the exception of one sample, REE concentrations in the dunite samples were near or below detection limits and have not been plotted. B) Note the very low abundances of trace elements in the most magnesian rock types, consistent with their status as cumulate rocks, and the prominent negative Zr-Hf and Ta-Nb anomalies in all rock types where concentrations are above detection limits.  4.4.4.2 G r o u p 2: Intermediate-Mg C l i n o p y r o x e n e - R i c h R o c k s O l i v i n e clinopyroxenite and hornblende clinopyroxenite, like the h i g h - M g o l i v i n e - r i c h rocks, exhibit major element oxide contents that correlate w i t h their clinopyroxene-dominant mineralogy. T h e y have a relatively restricted M g O range (16-22 wt.%) and M g # (0.75-0.85), both o f w h i c h are lower than i n the o l i v i n e - r i c h rocks, w h i c h is consistent w i t h the presence o f abundant cumulus clinopyroxene. C l i n o p y r o x e n e - r i c h lithologies have relatively h i g h w h o l e rock A 1 0 (1-2 wt.%) and C a O (16-20 wt.%) contents (Figure 4.9) and exhibit moderate C r 2  3  enrichment (1200-3200 ppm) (Figure 4 . 1 0 A ) . N o t e that, w i t h respect to major elements, the w h o l e rock hornblende clinopyroxenite sample (05ES-05-06-02) plots between its respective amphibole and clinopyroxene mineral compositions i n Figure 4.9. Chondrite-normalized R E E patterns show a concave-down shape similar to the h i g h - M g group ( ( L a / Y b )  c n  = 0.3-2.0), but  w i t h higher R E E contents (0.8-9 x chondrite L a ) (Figure 4.11 A ) . The clinopyroxene-rich rocks also have similar p r i m i t i v e mantle-normalized trace element patterns to h i g h - M g rocks, but again w i t h higher overall abundances. Negative T a - N b and Z r - H f anomalies are present where the abundances o f these elements are above detection limits (Figure 4.1 I B ) .  4.4.4.3 G r o u p 3: Hornblendites The w h o l e r o c k hornblendite samples are characterized by moderate M g O contents (12-13 wt.%) w i t h a relatively l o w M g # (0.64) (Figure 4.9) and have significantly higher C a O (-13 w t . % ) , A I 2 O 3 (-13 w t . % ) , and T i 0 2 (-2.4 wt.%) contents compared w i t h h i g h - M g rocks. Incompatible trace elements are also enriched i n hornblendites (10-30 x chondrite L a ) (Figure 4.11 A ) compared w i t h clinopyroxene-rich lithologies. The hornblendites, similar to the intermediate-Mg and h i g h - M g rocks, display concave-down R E E patterns w i t h ( L a / Y b )  c n  from  0.6-1.2. N o t e that the two analyzed hornblendite samples have sub-parallel R E E patterns but distinctly different concentrations. The most R E E - r i c h hornblendite (04ES-00-07-04) is an extremely fine-grained rock (grain size <1 m m ) and thus has a composition closest to the original silicate magma (where the interstitial amphibole and other accessory phases represent the c h i l l e d melt). The other hornblendite (05ES-05-06-02) is coarse-grained and contains substantial large cumulus amphibole crystals resulting i n d i l u t i o n to lower incompatible element concentrations. The p r i m i t i v e mantle-normalized trace element patterns o f the hornblendites are sub-parallel to the clinopyroxene-rich lithologies and o l i v i n e - r i c h lithologies,  133  albeit at higher concentrations (Figure 4.1 IB), and exhibit prominent negative Ta-Nb and ZrHf anomalies.  4.4.4.4 Group 4: Dioritic Rocks The dioritic rocks are represented by a single whole rock sample in this study (DDH04-57-12). This sample is a cumulate-textured hornblende diorite composed of coarse amphibole (15 vol.%) and plagioclase (80 vol.%) and contains moderate silica (55 wt.%) and high alumina (21 wt.%) contents and has a comparable Mg# (0.64) to the hornblendites (Figure 4.9). These characteristics are consistent with the high modal plagioclase and moderate amphibole contents of this sample. The hornblende diorite contains low abundances of all incompatible trace elements, comparable to dunite (Table 4.5), reflecting its cumulate nature. This sample displays a significant positive Eu anomaly (Eu/Eu* = 1.418) and, with respect to primitive mantle-normalized trace elements, displays high positive Sr and Ba anomalies (2800 ppm and 1980 ppm, respectively), which is consistent with the high modal abundance of cumulus plagioclase.  4.4.5 Platinum-Group Elements Concentrations of Pt and Pd in whole rock samples from the Turnagain intrusion range from <0.14-85 ppb Pt and 0.4-102 ppb Pd, respectively (Figure 4.12A, Table 4.6 ). Pt/Pd ratios vary between 0.4-2.5 with an average value of 0.9 and a median value of ~1 (Figure 4.12A). The absolute abundances of the PGE vary systematically between rock types (Figures 4.12, 4.13). Most olivine clinopyroxenite and all hornblende-bearing lithologies have low to negligible PGE contents, dunite is characterized by low to moderate PGE concentrations, and wehrlite contains the highest PGE concentrations of all ultramafic lithologies in the Turnagain intrusion. There is no correlation between whole rock PGE content and sulphur (Figure 4.12B), which suggests that the PGE reside as discrete P G M alloy phases (e.g. Pt3Fe, or isoferroplatinum) in wehrlite. Primitive mantle-normalized PGE patterns show an overall increase from Ir to Pt with a Pt/Ir ratio varying from 0.6-72 (mean value of 19.1), with some samples exhibiting a negative Ru anomaly (Figure 4.13); a common trait of P G M alloys in chromitites from other Alaskan-type intrusions (G. Nixon, pers. comm., 2007).  20  40  60  80  100  120  P d (ppb) 200  i i I i i  i  •  •  r  B  180 • dunite  160  • wehrlite 140  A olivine clinopyroxenite • hornblende clinopyroxenite|  Q. 120  a. •a  i  a. Q-  • hornblendite  100  80 60 40 20 0  o ~. 0.2  ° 0.4  • 0.6  A 0.8  1  1.2  1.4  1.6  1.8  S (wt. %) Figure 4.12: Platinum-group element compositional variations for whole rocksfromthe Turnagain intrusion. A) Pd vs. Pt. B) S vs. Pt+Pd. Note that wehrlite samples contain the highest Pt and Pd abundances. The absence of a positive correlation between sulphur and metal contents indicates that the PGE are likely contained in discrete platinum group minerals or alloys and not in sulphides.  135  Figure 4.13: Primitive-mantle normalized platinum group element diagrams for whole rocksfromthe Turnagain intrusion (normalizing valuesfromMaier and Barnes (1999)). The thick black line in all graphs represents the detection limits. Wehrlites have the highest overall abundances of PGE and distinct positive slopesfromRu to Pt.  136  4.4.6 Sulphur Isotopic Compositions T h e range o f sulphur isotopic compositions o f sulphide separates from lithologies i n the Turnagain intrusion and p r o x i m a l host rocks is presented i n Figure 4.14. Pyrite from the R o a d R i v e r phyllite has the most negative 8 S value at -17.8 %o (Table 4.7). Sulphides from dunite 3 4  and wehrlite (mostly pyrrhotite and pentlandite) show large ranges i n their sulphur isotopic compositions ( 8 S = -10 %o to -1 %o), w i t h dunite sulphide shifted to more negative values 34  ( 8 S = -9.7 %o to -3.4 %o) relative to wehrlite sulphide ( 5 S = -8.4 %o to -1.1 %o). Sulphide 34  34  separates from o l i v i n e clinopyroxenite and hornblende-bearing lithologies i n the Turnagain intrusion have sulphur isotopic compositions close to mantle values (0 ± 3 %o, Schneider, 1970; Sakai et al., 1984; R i p l e y , 1999). There is no direct correlation between the presence o f alteration associated w i t h sulphide i n dunite and wehrlite (see F i g u r e 4.6) and its sulphur isotopic c o m p o s i t i o n .  4.4.7 Lead Isotopic Compositions The range o f lead isotopic compositions o f sulphide separates from various lithologies w i t h i n , and p r o x i m a l to, the Turnagain intrusion is: 15.72,  2 0 8  Pb/  2 0 4  2 0 6  Pb/  2 0 4  P b = 18.11-19.16 ,  2 0 7  Pb/  2 0 4  P b = 15.53-  P b = 37.91-38.72 (Table 4.8). There is no apparent correlation between the lead  isotopic c o m p o s i t i o n o f a sulphide separate and its host lithology. T h e sulphide analyses form a broadly linear array between the mantle P b growth curve and the upper continental crust (Zartman & Z o e , 1981) and/or average C o r d i l l e r a n shale curve ( G o d w i n & Sinclair, 1982), w h i c h is interpreted as a m i x i n g line (Figure 4.15 A ) . T h e P b isotopic c o m p o s i t i o n o f most o f the sulphide separates is shifted towards more radiogenic values relative to mantle values, indicating a greater contribution o f P b from crustal sources.  4.5 DISCUSSION 4.5.1 Parent Magma Characteristics The petrology and geochemistry o f rocks from the Turnagain A l a s k a n - t y p e intrusion indicate that it was formed by the emplacement and crystallization o f M g - r i c h , p r i m i t i v e , hydrous magmas i n an arc setting. T h e p r i m i t i v e nature o f the parent magmas is constrained by the M g r i c h o l i v i n e compositions (up to F092.5) i n dunite that has not re-equilibrated w i t h chromite. T h e hydrous nature o f the parent m a g m a is supported by 1) primary interstitial phlogopite i n the olivine-clinopyroxene cumulates, 2) late interstitial to cumulus hornblende i n rocks from  1  f  1  I  1  1  1  I  1  I  1  1  1  I  1  1  1  1  1  #  Hornblendite |Clinopyroxene Hornblendite Olivine Clinopyroxenite Wehrlite  1  1  •  Im 'i  Dunite  •  Felsic Tuff Road River Phyllite  A.  1  -20  1  1  1  1  -15  1  1  1  1  1  1  1  1  .1  1  1  -10  5 S (CDT) M  Figure 4.14: Sulphur isotopic composition of sulphide vs. lithology in the Turnagain intrusion. Note the wide variation in 5 S in both dunite and wehrlite, extending towards the highly negative value of pyritefromthe Road River phyllite (8 S = -17.9 %o). The blue region represents the mantle range of 8 S. 34  34  34  138  15.8  -i—i—i—i—i—i—r \2o  ~i—i—I—r  A 0 Ma  15.7  400 Ma 0 Ma  800 Ma  -Q  CL  •* o  15.6  !B CL  Dunite • DDH03-16-24-166  15.5  • 05ES-02-02-02 O05ES^)2-02-02A • DD0H4-37-6-39.7a  400 Ma  Wehrlite 15.4  • DDH03-06-25-181.5  16.9  17.4  17.9  18.4  2M  18.9  • DDH04-38^6-44.8 A  19.4  Pb/ Pb J04  • DDH03-05-45-325 • DDH03-07-25-183A  |2a  •  B  DDH03-08-13-100.7  Hornblendite  39.5  • DDH04-47-17-126.5 • DDH03-03-5&426  Road River  39.0  X04ES-13-01^32  •Q Q.  DDH03-07-34-38.9  ^ 38.5 -Q  CL  00  o  tM  38.0  37.5  37.0 16.9  17.4  17.9  18.4  206  18.9  19.4  Pb/ Pb 204  Figure 4.15: Lead isotopic compositions (A: Pb/ Pb vs. Pb/ Pb, B: Pb/ Pb vs. Pb/ Pb) of sulphide from the Turnagain intrusion with upper continental crust and mantle growth curvesfromZartman & Doe (1981) and the shale curve from Godwin and Sinclair (1982). 206  204  207  204  206  204  208  204  139  the central part o f the intrusion, 3) the late appearance o f plagioclase as a cumulus phase relative to clinopyroxene and hornblende (e.g. Gaetani et al,  1993), and 4) the presence o f a  fine- grained hornblendite dike (sample 04ES-00-07-04) that intruded w a l l r o c k s o f the Turnagain intrusion. Sub-parallel trace element patterns, especially the rare earth elements ( R E E ) , indicate a genetic association between the different ultramafic rock types o f the Turnagain intrusion. The range i n concentrations reflects the relative abundances o f cumulus o l i v i n e (and spinel), w h i c h both contain extremely l o w abundances o f incompatible trace elements, cumulus and interstitial clinopyroxene, hornblende, and accessory minerals that crystallized from an evolved interstitial melt. The arc geochemical signature for the Turnagain parent magmas is based on combined trace element and N d isotopic (see Chapter 2) characteristics o f the analyzed samples. The prominent negative high field strength element ( H F S E ) anomalies (Figure 4.1 I B ) , specifically N b and T a , is t y p i c a l o f arc-derived magmas, reflecting (for example) the retention o f the H F S E i n refactory minerals such as rutile during subduction and magma genesis (e.g. R y e r s o n & Watson, 1987). A d d i t i o n a l l y , the most radiogenic N d compositions o f samples from the Turnagain intrusion (Chapter 2) fall w i t h i n the general range o f Paleozoic arc-derived mafic volcanic rocks from the northern Canadian Cordillera ( e  N d  = +4 to +7; Piercey et al, 2006).  4.5.2 Sequence of Crystallization The relative order o f crystallization and emplacement i n the Turnagain intrusion is dunite —> wehrlite —* o l i v i n e clinopyroxenite —> hornblende clinopyroxenite —* hornblendite —• diorite. The entire sequence o f rocks crystallized and cooled d o w n to ~ 3 5 0 ° C at 1 9 0 ± 1 M a , based on the c o m b i n e d results from U - P b and A r - A r geochronometry (Chapter 2). Cross-cutting relations and ferromagnesian silicate M g / ( M g + F e ) (e.g. F o n i n e , M g # x , M g # b i ) 2 +  0  V  c p  h  are  consistent w i t h the sequential crystallization and emplacement o f ultramafic and mafic lithologies i n the Turnagain intrusion. Dunite (~Foai) cumulates are cross-cut b y wehrlite dikes, wehrlite (-Fogy) is cross-cut b y olivine clinopyroxenite dikes, o l i v i n e clinopyroxenite (-Fogs, M g #  c p x  = 0.92) is cross-cut by hornblende clinopyroxenite dikes, hornblende  clinopyroxenite ( M g #  c p x  = 0.81, M g # i = 0.65) is cross-cut by hornblendite dikes, and n b  hornblendite ( M g # b i = 0.60) is cross-cut by diorite. Later lithologies t y p i c a l l y cross-cut all h  earlier lithologies (e.g. diorite dikes are observed to intrude dunite at the southeastern contact between these two lithologies (Figure 4.1)), however some contacts between lithologies (e.g.  dunite-wehrlite) may be gradational. There are local examples o f dunite dikes cutting olivine clinopyroxenite (Figure 4 . 3 . I B ) , near the contact between these two lithologies i n the northwestern part o f the intrusion (Figure 4.1). These " d i k e s " are interpreted to represent fractures w i t h i n the o l i v i n e clinopyroxenite through w h i c h primitive melts were injected. The primitive melts dissolved clinopyroxene and precipitated olivine, similar to dunite dikes observed i n ophiolites ( K e l e m e n & D i c k , 1995; B r a u n & K e l e m e n , 2002). Alternatively, the dikes c o u l d represent injected dunite cumulates. The dunite dikes i n the Turnagain intrusion do not appear to present replacive dunites as observed i n other Alaskan-type intrusions (e.g. D u k e Island, A l a s k a ; Irvine, 1974). C o m b i n e d w i t h trace-element and P G E results, the chemical and lithological constraints on the evolution o f the Turnagain intrusion i m p l y that a l l lithologies are genetically related and that they crystallized from an e v o l v i n g magma i n an open system.  4.5.3 Implications for associated volcanic rocks B a s e d on petrologic and geochemical relations, the Turnagain intrusion can be interpreted as part o f a magmatic feeder system to an arc volcano. The relationship between Alaskan-type intrusions and basaltic v o l c a n i c rocks has been discussed since some o f the earliest studies o f these intrusions (e.g. F i n d l a y , 1969; Irvine, 1974; C l a r k , 1975). T h i s association has t y p i c a l l y been spatial, as belts o f basaltic v o l c a n i c rocks have been observed to be broadly sub-parallel to belts o f Alaskan-type intrusions. A temporal association between v o l c a n i c rocks and Alaskan-type intrusions has been established i n B . C . (Late Triassic T a k l a / N i c o l a / S t u h i n i Groups; N i x o n et al, 1997), C o l u m b i a (Tistl et al, 1994), and K a m c h a t k a (Batanova et  al,  2005), and a genetic relationship between ankaramitic dikes and Alaskan-type intrusions was proposed by M o s s m a n et al (2000). A r c ankaramite and picritic ankaramite have been observed as v o l c a n i c rocks near, or intruded by, Alaskan-type intrusions i n southern A l a s k a (Irvine, 1974) and the K a m c h a t k a Peninsula, R u s s i a (Batanova et al, 2005), and as dikes cross-cutting Alaskan-type intrusions in N e w Zealand ( M o s s m a n et al, 2000; Spandler et  al,  2003) and central M e x i c o (Hernandez, 2000). A r c ankaramite dikes, w i t h a whole rock C a O / A i 2 0 3 > l , share three key characteristics w i t h Alaskan-type intrusions: mineralogy, crystallization sequence, and zonation. Ankaramite dikes are t y p i c a l l y composed o f o l i v i n e and clinopyroxene phenocrysts set i n a groundmass containing hornblende and m i n o r plagioclase. The crystallization sequence i n the ankaramite dikes is o l i v i n e —> clinopyroxene —> hornblende —• plagioclase, similar to that i n many Alaskan-type intrusions. F i n a l l y , the  141  zonation i n these dikes is delimited b y olivine and clinopyroxene phenocrysts at the centre, w h i c h reduce i n size outwards and grade into fine-grained hornblende that may contain interstitial plagioclase adjacent to the margin. Extrusive equivalents o f the Turnagain and other Alaskan-type intrusions should occur as olivine+clinopyroxene-phyric basalts i n the field, characterized b y p r i m i t i v e mineral compositions, and as such may potentially be found i n any arc mafic v o l c a n i c formations o f E a r l y Jurassic age i n B . C . (e.g. Rossland G r o u p , southern B.C.).  4.5.4 Origin of sulphide mineralization in the Turnagain intrusion The presence o f abundant sulphide, predominantly pyrrhotite and pentlandite, i n the Turnagain intrusion is unusual for Alaskan-type intrusions. Basalts generated i n subduction zone settings (arc basalts) typically contain 900-2500 p p m sulphur, higher than mid-ocean ridge basalts at comparable F e O (Wallace, 2005). The speciation o f dissolved S i n arc magmas is important i n the genesis o f magmatic sulphide i n the Turnagain intrusion. Sulphur may exist i n multiple valence states (S ", S°, S , S ) depending on the relative oxygen fugacity (/O2) o f its hosting 2  4 +  6 +  magma. The relative o x y g e n fugacity and sulphur content o f basaltic melts, illustrated i n Figure 4.16, are critical factors i n assessing the development o f sulphide saturation (e.g. Jugo et al., 2004; 2005). At7D2 values at or below the reference oxygen buffer fayalite + O2 <->• magnetite + quartz ( F M Q ) , the dominant sulphur species i n basaltic liquids is sulphide (S ") 2  (Figure 4 . 1 6 A ) , where A F M Q is the J0  2  relative to F M Q . M a g m a s w i t h a relatively high  fd  2  (greater than A F M Q = 0 to +1) w i l l have S dominantly speciated as sulphate ( S 0 ~ ) , and as 2  4  such need significantly more S (approximately an order o f magnitude more) to become sulphate-saturated (Figure 4 . 1 6 B ) . This is consistent w i t h the observations that most arc magmas are relatively o x i d i z e d (e.g. Ballhaus et al., 1991; Carmichael, 1991; Parkinson & A r c u l u s , 1999; Rohrbach et al, 2005), and the general absence o f magmatic sulphide deposits associated w i t h most arc plutonic and volcanic rocks. A s documented i n this study, the Turnagain intrusion contains abundant localized sulphide mineralization (pyrrhotite+pentlandite), thus requiring that the7D2 o f the parent magmas was relatively l o w , especially compared w i t h other typical arc magmas (Figure 4.16). This reduced nature o f the parent magmas is consistent w i t h the extremely l o w ferric iron content and F e / S F e (e.g. 3 +  Parkinson & A r c u l u s , 1999) o f chromite from chromitite i n the intrusion (Figure 3.10; Chapter 3). In addition, relatively early sulphide saturation i n the crystallization sequence o f the  142  1.0  T  1  1  r  Typical Arc Volcanics  0.9  SO. ' 2  X  o  O 0.6  re  o o  0.5  E  0.4  5 0.3 3 0.2 (A  »2-  0.1 0.0  10.00  -  3  -  ceo  2  -  1  0  1  2  3  oxidation state (AFMQ)  4  c-  B  ? 1.00  c a> c o u 3  0.10  basalt  I J  Q. 3  (0  trachyandesite Typical Arc Vocanics  CCO (hydrous)'  Arc Peridotites  I  0.01 - 4 - 3 - 2 - 1  0  1  1  2  3  4  oxidation state (AFMQ) Figure 4.16: Diagrams showing the effects of oxygen fugacity on sulphur speciation and saturation in silicate magmas. The ranges in/0 for arc magmas (Carmichael, 1991; Rohrbach et al., 2005) and arc peridotites (Parkinson & Arculus, 1999) are plotted as closed lines. A) Oxidation state (log AFMQ) vs. sulphate mole fraction, modified from Jugo et al'. (2004). Note the transition between sulphide (S ) and sulphate (S0 ') between AFMQ = 0 to +2.5. B) Oxidation state (log AFMQ) vs. sulphur content required to induce saturation, modified from Jugo et al. (2005). An order of magnitude more sulphur is needed to saturate a silicate magma in sulphate than sulphide. 2  2  2  4  Turnagain intrusion is demonstrated by the. local presence o f crystallized mss inclusions in chromite grains (Figure 3 . 3 D , Chapter 3) and N i - d e p l e t i o n o f o l i v i n e in some dunite and wehrlite samples (Figure 4 . 7 B ) . Sulphide separates from the Turnagain intrusion display S S values from +1 %o 3 4  (mantle-like; e.g. R i p l e y , 1999) d o w n to -9.7 %o (Figure 4.14), shifted i n the direction o f pyrite from the enclosing graphitic phyllite (-17.9 %o). M a n y o f the analyzed sulphide separates exhibit h i g h l y radiogenic Pb isotopic compositions (Figure 4.15), consistent w i t h the incorporation o f crustal P b , and some w h o l e rock ultramafic samples exhibit l o w 8 N  q  values  (Figure 2 . 1 0 B ; Chapter 2) outside the range for typical mafic volcanics. C o m b i n e d , these results indicate that crustal material was added to the Turnagain parent magmas, especially S, w h i c h may have aided i n achieving sulphide saturation. Inclusions o f graphitic, pyritic phyllite are observed i n drillcore from areas p r o x i m a l to or w i t h i n the sulphide-mineralized zones o f the Turnagain intrusion (Figure 4.6). The pyrite i n these inclusions has been completely converted to pyrrhotite, w h i c h is indicative o f the prograde reaction 2 FeS2 <-> 2 F e S + S . The 2  phyllite inclusions released sulphur and carbon into the surrounding mafic l i q u i d during heating and partial assimilation, w i t h the graphite acting as a reducing agent, possibly f o l l o w i n g reactions such as C 0 " ( i t ) *-> C02( ) + 0 ~( i ) ( N i x o n , 1998) or C( ) +0( it) 2  3  2  me  g  me  t  S  me  CO( ). T h e fact that partially digested phyllite w i t h remnant graphite is still present i n many g  ultramafic rocks from the m i n e r a l i z e d zones indicates that the magmas p r o x i m a l to these inclusions may have had a jOi near the C C O buffer (carbon-carbon monoxide) ( A F M Q = -1 at upper crustal pressures and hydrous conditions; Parkinson & A r c u l u s , 1999). Therefore the phyllite inclusions acted as both a sulphur source and a reducing agent, thus a l l o w i n g the Turnagain intrusion to achieve early sulphide saturation.  4.5.5. Petrogenesis of the Turnagain intrusion and associated Ni-sulphide mineralization T h e Turnagain Alaskan-type intrusion was formed i n a subduction zone and the parent magma were l i k e l y generated from the fluid-fluxed partial melting o f a peridotitic mantle wedge (e.g. Spandler et al., 2003; G r e e n et ah, 2004; Batanova et al, 2005). The parental magma generated i n this setting was hydrous, l i k e l y volatile-rich (S, C l ) , and p r i m i t i v e , as defined by the high forsterite content o f o l i v i n e (F092.5). T h i s magma ascended through the mantle lithosphere and o v e r l y i n g crust w i t h relatively m i n o r interaction, based on the h i g h l y magnesian o l i v i n e compositions, the mineral assemblage o f the hornfelsed v o l c a n i c wacke  144  (epidote + plagioclase ± amphibole ± biotite), and the w h o l e rock N d isotopic compositions o f the various lithologies (Chapter 2), until it reached the upper crust. T h e intrusion was emplaced and crystallized w i t h i n a tectonically active environment, perhaps explaining the presence o f erratic chromitite schieren in dunite and rare m o d a l layering i n other lithologies (interpreted to have formed b y magmatic turbidity currents), as evidenced by the presence o f Alaskan-type intrusions along major structures ( N i x o n et al,  1997; Krause et al., 2006). The  magmas differentiated and cooled i n a relatively short interval o f time at 190 M a , producing the entire range o f lithologies present i n the Turnagain intrusion, w i t h periodic injections o f p r i m i t i v e melt, as evidenced from the near-constant P t / P d ratio and possibly the dunite dikes. Stoping o f roof- and w a l l - r o c k s , as observed by hornfelsed inclusions o f phyllite and volcanic wacke, introduced significant amounts o f local crustal material that were partially incorporated into the magma. Metasedimentary inclusions are only observed w i t h i n or near areas containing abundant sulphide. T h e pyrite-rich graphitic phyllite, the dominant host rock enclosing the intrusion, released S and C into the surrounding magma during heating. M a n y Alaskan-type intrusions are t y p i c a l l y hosted i n intrusive rocks, v o l c a n i c sequences, and j u v e n i l e clastic sedimentary rocks, and as such do not appear to be prospective for magmatic sulphide mineralization. The c o m p o s i t i o n o f the host rocks o f the Turnagain intrusion is distinct from those that host other Alaskan-type intrusions, and thus the k e y factor that promoted locally abundant sulphide mineralization i n Turnagain intrusion was this distinctive package o f pyritic and graphitic phyllites.  4.6 C O N C L U S I O N T h e o r i g i n , emplacement, and crystallization o f the Turnagain Alaskan-fype intrusion i n northcentral B r i t i s h C o l u m b i a are constrained b y 1) the high fersterite content (F092.5) o f o l i v i n e from the central dunite, 2) the progressively decreasing F o content o f olivine, M g # o f clinopyroxene and hornblende, and decreasing w h o l e rock M g # from ultramafic lithologies i n the intrusion, 3) cross-cutting relationships between lithologies, 4) sub-parallel rare earth element ( R E E ) patterns between ultramafic lithologies, 5) the presence o f phlogopite i n early o l i v i n e cumulates (dunite, wehrlite), the presence o f late, primary hornblende i n clinopyroxene-hornblende cumulates, and the absence o f early plagioclase, and 6) high field strength element ( H F S E ) depletions, especially T a and N d , i n a l l ultramafic rocks. These results indicate that the Turnagain parent magmas were primitive melts generated i n the mantle, w i t h i n a subduction zone setting, and that each lithology  145  i n the crystallization sequence formed from progressively fractionated magmas. Disseminated to semi-massive N i - s u l p h i d e mineralization, w h i c h occurs i n a number o f zones w i t h i n the Turnagain intrusion, is variable i n tenor and texture. A number o f features constrain the origin o f the sulphide-rich zones: 1) o l i v i n e from select dunite and wehrlite samples exhibits N i - d e p l e t i o n , 2) the 8 S values o f sulphide separates span a w i d e range, from mantle-like values ( 0 ± 1 . 1 %o) d o w n 3 4  to light values (-9.7 %o), w i t h the most magnesian rocks (dunites) systematically shifted to lighter 8 S values, 3) the P b isotopic compositions o f the sulphide separates indicate the presence o f a 3 4  significant component o f radiogenic P b derived from upper crustal rocks, and 4) partially digested inclusions o f graphitic phyllite found i n the mineralized zones contain pyrrhotite instead o f pyrite. These results indicate that the sulphide mineralization i n the Turnagain intrusion occurred as a result o f assimilation o f local upper crustal material, specifically the hosting R o a d R i v e r phyllite, w h i c h contains significant graphite and pyrite ( 8 S = -17.9%o). The graphite acted as a reducing 34  agent such that sulphur i n the parent magmas was dominantly speciated as sulphide (S ~) rather 2  than sulphate (SO4 "), w h i c h is typical o f most arc-derived magmas. The reduced nature and the 2  addition o f crustal sulphur a l l o w e d for sulphide saturation to occur i n the regions o f the Turnagain intrusion where the majority o f graphitic phyllite inclusions occur, and where the addition o f crustal S was needed to saturate i n earlier lithologies. The composition o f the country rocks was critical i n a l l o w i n g the Turnagain Alaskan-type intrusion to host magmatic N i - s u l p h i d e mineralization.  146  4.7 A C K N O W L E D G E M E N T S I am grateful to H a r d Creek N i c k e l Corp. for continued field support for this project and to J i m R e e d o f Pacific Western Helicopters for his exemplary logistical support i n the field. Special thanks to T o n y Hitchins, B r u c e Northcote, C h r i s B a l d y s , and M a r k Jarvis (President) o f H a r d Creek N i c k e l C o r o . for their generous support and interactions throughout the period o f m y M . S c . thesis at U B C . Thanks to M a t i Raudsepp at the U n i v e r s i t y o f B r i t i s h C o l u m b i a for guidance in the use o f the electron microprobe and support during the research phase o f this manuscript, Janet Gabites at the Pacific Centre for Isotopic and G e o c h e m i c a l Research ( U B C ) for processing the sulphide P b isotopic analyses, and A n d r e w Greene for input into this manuscript. Thanks also to R e z a Tafti o f the M i n e r a l Deposits Research U n i t ( U B C ) for support during the research phase o f this manuscript as w e l l as D r . A k i r a Isiwatari for m a i l i n g his published works on the Alaskan-type intrusions i n K a m c h a t k a , C h i n a , and Japan. 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M i n e r a l o g i c and sulfur isotopic studies o f C u - N i mineralization i n the D u k e Island C o m p l e x , A l a s k a . Abstracts with Programs - Geological Society of America 36, 515-516 T h i r l w a l l , M . F . (2000). Inter-laboratory and other errors i n Pb-isotope analyses investigated using a  2 0 7  Pb-  2 0 4  P b double spike. Chemical Geology 163, 299-322.  T i s t l , M . (1994). Geochemistry o f platinum-group elements o f the zoned ultramafic A l t o Condoto C o m p l e x , Northwest C o l o m b i a . Economic Geology 89, 158-167 T i s t l , M . , Burgath, K . P . , Hoehndorf, A . , Kreuzer, H . , M u n o x , R . , & Salinas, R . (1994). O r i g i n and emplacement o f Tertiary ultramafic complexes i n northwest C o l u m b i a : E v i d e n c e from geochemistry and K - A r , S m - N d , and R b - S r isotopes. Earth and Planetary Science Letters 126,41-59 W a l l a c e , P . J . (2005). V o l a t i l e s i n subduction zone magmas: concentrations and fluxes based on melt i n c l u s i o n and volcanic gas data. Journal of Volcanology and Geothermal Research 140,217-240 Zartman, R . E . , & D o e , B . R . (1981). Lead-isotope evolution. U. S. Geological Survey Professional Paper P 1275,  169-170  CHAPTER 5  SUMMARY AND CONCLUSIONS  5.1 S U M M A R Y A N D C O N C L U S I O N S T h i s comprehensive study o f the Turnagain Alaskan-type intrusion i n north-central British C o l u m b i a , Canada, is based on the combined results o f field relations, petrography, mineral (spinel, o l i v i n e , clinopyroxene, and amphibole) chemistry, w h o l e rock major and trace element geochemistry, n e o d y m i u m isotopic geochemistry, sulphide sulphur and lead isotopic geochemistry, and A r - A r and U - P b geochronology. The major goals o f this study included 1) constraining the age and source o f the parent magmas to the Turnagain intrusion, 2) evaluating the o r i g i n and petrogenesis o f the intrusion, and 3) identifying the mechanism(s) responsible for the genesis o f anomalous nickeliferrous sulphide mineralization i n an Alaskan-type intrusion. The magmas parental to the Turnagain intrusion were hydrous and primitive, and were derived i n a subduction zone. The intrusion consists o f cumulate dunite (~Fo ii ine = 91), 0  wehrlite (~Fo ii ine = 87), olivine clinopyroxenite (~Fo ii ine = 85, M g # 0  V  clinopyroxenite ( M g #  0  c p x  V  c p x  V  = 0.92), hornblende  = 0.81, M g # b i = 0.65), hornblendite (Mg# bi = 0.60), and diorite. T h i s h  n  intrusive sequence and their relative order o f emplacement is constrained by cross-cutting relationships. O l i v i n e , clinopyroxene, and amphibole chemistry suggest that a l l lithologies crystallized from a progressively fractionating parent magma. Trace element geochemistry, especially the rare earth elements, o f w h o l e rock ultramafic samples indicates a genetic relationship between a l l lithologies, and corroborates their relationship b y crystallization from a progressively e v o l v i n g l i q u i d . A l l lithologies i n the Turnagain intrusion, based on the similarity o f A r - A r (phlogopite, hornblende) and U - P b (zircon, titanite) geochronological results, were emplaced and crystallized i n a short time interval at 1 9 0 ± 1 M a . The presence o f irregularly distributed chromitite schleiren i n the central dunite, w h i c h may have formed b y gravity flows i n a upper crustal magma chamber, is consistent w i t h the emplacement o f the Turnagain intrusion i n an active tectonic setting. The hydrous nature o f the Turnagain intrusion, based o n the presence o f early interstitial and late cumulus hydrous phases and late plagioclase, indicate that the parent magmas were generated i n a subduction zone setting and the h i g h forsterite content o f olivine i n dunite ( m a x i m u m o f F092.5 i n olivine that d i d not reequilibrate w i t h chromite) requires that the parent magmas were i n e q u i l i b r i u m w i t h the peridotitic mantle from w h i c h they were generated. C h r o m i t e i n the Turnagain intrusion exhibits c h e m i c a l trends that can be related to specific magmatic and post-magmatic processes. A l l disseminated chromite, due to its  154  relatively small v o l u m e proportion i n dunite, wehrlite, and o l i v i n e clinopyroxenite has been compositionally modified by o l i v i n e and clinopyroxene fractionation, oxidation, reequilibration w i t h silicate phases, and equilibration w i t h interstitial l i q u i d . E a c h o f these processes is clearly delineated on chromite compositional plots that establish postcrystallization processes based on inter- and intra-sample trends. P r i m i t i v e chromite compositions ( C r / ( F e + C r + A l ) = 0.90, F e / ( F e + M g ) = 0.3, F e / ( F e + C r + A l ) = 0.75) i n 3+  2 +  2 +  3 +  3 +  the Turnagain intrusion occur in chromitite and are the most p r i m i t i v e spinel compositions observed i n Alaskan-type intrusions to date. The ferric iron content o f chromite from chromitite, and the F e / S F e , i n the Turnagain intrusion is extremely l o w and reflects the 3 +  relatively l o w o x y g e n fugacity (/02) o f the parent magmas. The relatively reduced nature o f the Turnagain intrusion may have been an intrinsic property o f its parent magmas, however the majority o f arc-derived plutonic rocks are relatively o x i d i z e d ( A F M Q = +1 to +3.5, e.g. C a r m i c h a e l , 1991). T h e r e f o r e ^ reducing agent added to the magmas was required to lower the /O2 enough to a l l o w the parent magmas to saturate i n sulphide (e.g. Jugo et al., 2004; 2005). Thus the ferric iron content and F e / S F e o f chromite from chromitite i n Alaskan-type 3 +  intrusions c o u l d be considered as a possible exploration tool for evaluating the sulphide mineralization potential o f Alaskan-type intrusions. Sulphide i n the Turnagain intrusion occurs i n l o c a l i z e d areas o f dunite and wehrlite as disseminated to semi-massive pyrrhotite and pentlandite w i t h other minor phases (e.g. violarite, molybdenite). Hornfelsed inclusions o f w a l l r o c k s have been intersected i n drillcore w i t h i n the sulphide-mineralized zones. The inclusions are dominantly volcanic wacke, graphitic phyllite, and lesser quartzite and marble. The inclusions o f graphitic phyllite are the most important i n the context o f sulphide mineralization i n the Turnagain intrusion because they contain sulphide and graphite. The graphitic phyllite p r o x i m a l to the Turnagain intrusion is pyrite-rich (FeS2), whereas the inclusions contain pyrrhotite (FeuxS). The prograde reaction between these two minerals released sulphur into the Turnagain magmas, and the graphite in the inclusions acted as a reducing agent. The l o c a l i z e d N i - s u l p h i d e mineralization i n the Turnagain intrusion is therefore the result o f the interaction between sulphur- and graphite-rich fluids released from the graphitic phyllite inclusions and the p r i m i t i v e , hydrous parent magmas. A s s i m i l a t i o n o f crustal material is also demonstrated by systematic variations i n sulphide sulphur and lead, and whole-rock n e o d y m i u m isotopic compositions. Sulphur isotopic analyses o f sulphide separates ( 5 S = +1.2 to -9.7 %o) indicate that crustal sulphur 34  155  was added to the Turnagain intrusion, especially the more magnesian lithologies. The lead isotopic results (  2 0 6  Pb/  2 0 4  P b = 18.11-19.15 ,  2 0 7  Pb/  2 0 4  P b = 15.53-15.72 ,  2 0 8  Pb/  2 0 4  P b = 37.91-  38.72) indicate that m u c h o f the lead i n sulphide originated from an upper crustal source. F i n a l l y , the n e o d y m i u m isotopic results from ultramafic rocks i n the Turnagain intrusion indicate that the mantle-derived parent magmas (eNd = +5 to +6) were heterogeneously contaminated b y crustal material such that some results are shifted towards more crustal values ( £ N d ( i 9 0 ) = +2  to  -3).  F i n a l l y , the Turnagain intrusion, w h i c h ascended through and stalled i n graphitic phyllite and volcanic wacke, was dated by A r - A r and U - P b geochronology at 1 9 0 ± l M a , w h i c h has implications for the tectonic history o f this part o f northern B r i t i s h C o l u m b i a . The w a l l r o c k s were previously assigned to the paleo-passive margin o f Ancestral N o r t h A m e r i c a b y Gabrielse (1998) as the undifferentiated R o a d R i v e r and E a r n Groups, w i t h an o v e r l y i n g volcanic/sedimentary package o f " u n k n o w n affinity". The graphitic phyllites are, however, conformably overlain by a volcanic wacke, as observed i n outcrop by Erdmer et al. (2005) and i n drillcore (this study). A m i n i m u m depositional age o f 301 M a for the volcanic wacke was determined by U - P b dating o f detrital z i r c o n . The volcanic wacke also contains z i r c o n grains w i t h numerous Precambrian inherited cores. The lithological characteristics, age, and R E E chemistry o f the volcanic wacke are similar to the L a y Range Assemblage/Harper R a n c h Subterrane o f Quesnellia and the K l i n k i t G r o u p o f Y u k o n - T a n a n a . Inclusions o f " R o a d R i v e r " phyllite and v o l c a n i c wacke i n two E a r l y Jurassic arc-derived intrusions (the Turnagain intrusion and R i n g C o m p l e x to the southeast) requires that the w a l l r o c k s were situated i n crust above a subduction zone, and the only k n o w n subduction zones o f E a r l y Jurassic age were located beneath the Stikine, Quesnel, and Y u k o n - T a n a n a terranes. Therefore the volcanic wacke and graphitic phyllites, along w i t h the Turnagain Alaskan-type intrusion, belong to either the Quesnel terrane or the Y u k o n - T a n a n a terrane. H o w e v e r , these two terranes (along w i t h the Stikine terrane) may have been part o f a super-terrane after - 3 6 0 M a (e.g. Simard et al., 2003; N e l s o n & Friedman, 2004; N e l s o n et al., 2006). Alaskan-type intrusions are w e l l documented i n Q u e s n e l l i a (e.g. N i x o n et al., 1997), but none have been described to date i n Y u k o n - T a n a n a . I f Alaskan-type intrusions were to be found hosted i n the K l i n k i t G r o u p , the proposed genetic association between Quesnellia and Y u k o n - T a n a n a w o u l d be further supported.  5.2 REFERENCES C a r m i c h a e l , I . S . E . (1991). The redox states o f basic and silicic magmas: a reflection o f their source regions? Contributions to Mineralogy and Petrology 106, 129-141 Erdmer, P . , M i h a l y n u k , M . G . , Gabrielse, H . , Heaman, L . M . , & Creaser, R . A . (2005). M i s s i s s i p p i a n volcanic assemblage conformably o v e r l y i n g C o r d i l l e r a n m i o g e o c l i n a l strata, Turnagain R i v e r area, northern B r i t i s h C o l u m b i a , is not part o f an accreted terrane.  Canadian Journal of Earth Sciences 42, 1449-1465 Gabrielse, H . (1998). G e o l o g y o f C r y L a k e and Dease L a k e map areas, north-central B r i t i s h C o l u m b i a ; Geological Survey of Canada, B u l l e t i n 504, 147p Jugo, P . J . , L u t h , R . W . , & Richards, J.P. (2004). Experimental data o n the speciation o f sulfur as a function o f o x y g e n fugacity i n basaltic melts. Geochimica et Cosmochimia Acta 69 (2), 497-503 Jugo, P . J . , L u t h , R . W . , & Richards, J.P. (2005). A n experimental study o f the sulfur content i n basaltic melts saturated w i t h i m m i s c i b l e sulfide or sulfate liquids at 1 3 0 0 ° C and 1.0 G P a . Journal of Petrology 46 (4), 783-798 N e l s o n , J . L . , & Friedman, R . (2004). Superimposed Quesnel (late Paleozoic-Jurassic) and Y u k o n - T a n a n a (Devonian - M i s s i s s i p p i a n ) arc assemblages, Cassiar M o u n t a i n s , northern B r i t i s h C o l u m b i a : field, U - P b , and igneous petrochemical evidence. Canadian Journal of Earth Sciences 41, 1201-1235 N e l s o n , J . L . , C o l p r o n , M . , Piercey, S.J., D u s e l - B a c o n , C , M u r p h y , D . C , & Roots, C F . (2006). P a l e o z o i c tectonic and metallogenetic evolution o f pericratonic terranes i n Y u k o n , northern B r i t i s h C o l u m b i a and eastern A l a s k a . In: C o l p r o n , M . , and N e l s o n , J . L . (ed.) Paleozoic E v o l u t i o n and M e t a l l o g e n y o f Pericratonic Terranes at the A n c i e n t Pacific M a r g i n o f N o r t h A m e r i c a . Geological Association of Canada, Special Paper 45, 323-260 N i x o n , G . T . , H a m m a c k , J . L . , A s h , C . H . , C a b r i , L . J . , Case, G . , C o n n e l l y , J . N . , Heaman, L . M . , L a f l a m m e , J . H . G . , N u t t a l l , C , Paterson, W . P . E . , & W o n g , R . H . (1997). G e o l o g y and platinum-group-element mineralization o f Alaskan-type ultramafic-mafic complexes i n B r i t i s h C o l u m b i a . Geological Survey of British Columbia B u l l e t i n 93, 141p  157  Piercey, S.J., N e l s o n , J . - A . L . , D u s e l - B a c o n , C , Simard, R . - L . , Roots, C F , (2006). Paleozoic magmatism and crustal r e c y c l i n g along the A n c i e n t Pacific M a r g i n o f N o r t h A m e r i c a , Northern C o r d i l l e r a . In: C o l p r o n , M . , and N e l s o n , J . L . (ed.) Paleozoic E v o l u t i o n and M e t a l l o g e n y o f Pericratonic Terranes at the A n c i e n t Pacific M a r g i n o f N o r t h A m e r i c a . Geological Association of Canada, Special Paper 45, 281-322 Simard, R - L . , D o s t a l , J . , & Roots, C F . (2003). Development o f late Paleozoic volcanic arcs in the Canadian C o r d i l l e r a : an example from the K l i n k i t G r o u p , northern B r i t i s h C o l u m b i a and southern Y u k o n . Canadian Journal of Earth Sciences 40, 907-924  APPENDICES  159  Appendix I: Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion Chromitite  Rock:  Chromitite  Sample: Cluster: Grain Number:  05ES-01-01-01 7 1  6 1  4 1  5 1  05ES-01-04-01 7 1  3 1  m. anh. Rim  Mid  Core  m. sub. Rim  Mid  Core  m. sub. Rim  Mid  Core  m. eu. Rim  Mid  Core  m. anh. Rim  Mid  Core  I. anh. Rim  Mid  Mid  Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 V 0 Fe 0 FeO MnO MgO NiO CaO Total  0 02 0 63 7 02 58 93 0 34 5 01 19 21 0 10 9 74 0 10 0 00 101 11  0 02 0 61 6 82 59 39 0 30 4 47 18 64 0 15 9 88 0 06 0 00 100 34  0.03 0.66 6.70 59.52 0.32 4.57 18.70 0.19 9.89 0.08 0.00 100.64  0 01 0 55 6 53 60 32 0 28 4 35 18 17 0 10 10 19 0 05 0 00 100 56  0 02 0 60 6 61 59 60 0 34 4 78 18 23 0 13 10 19 0 06 0 00 100 57  0 02 0 61 6 63 59 77 0 26 4 57 18 14 0 16 10 18 0 07 0 00 100 40  0.00 0.59 6.77 59.17 0.33 5.06 18.41 0.14 10.09 0.05 0.00 100.61  0 00 0 51 6 25 59 90 0 27 4 59 18 08 0 14 10 02 0 06 0 00 99 82  0 16 0 54 6 16 60 97 0 23 4 24 18 37 0 16 10 00 0 05 0 01 100 89  0.01 0.61 6.77 59.12 0.33 5.09 18.08 0.19 10.24 0.06 0.02 100.51  0 02 0 59 6 64 59 05 0 31 5 12 17 86 0 14 10 30 0 06 0 01 100 08  0 00 0 56 6 46 59 34 0 29 5 01 17 89 0 14 10 22 0 06 0 01 99 97  0 00 0 65 7 14 59 03 0 31 4 76 18 19 0 14 10 29 0 09 0 00 100 58  0 00 0 55 6 61 59 86 0 31 4 85 18 01 0 17 10 30 0 08 0 00 100 74  0 03 0 54 6 53 60 40 0 34 4 83 17 99 0 09 10 48 0 07 0 00 101 30  0.00 0.22 4.60 66.65 0.00 3.98 11.55 0.00 14.23 0.16 0.01 101.40  0.00 0.21 5.84 63.40 0.03 5.62 11.32 0.00 14.42 0.20 0.00 101.05  0.08 0.24 5.83 62.91 0.01 6.05 11.14 0.00 14.51 0.20 0.02 100.99  Cations (p.f.u.) Ti Cr Al V Fe ** Fe * Mn Mg Ni Ca Total  0.016 1.550 0.275 0.008 0.125 0.534 0.003 0.483 0.003 0.000 2.997  0.015 1.572 0.269 0.007 0.112 0.522 0.004 0.493 0.002 0.000 2.996  0.016 1.572 0.264 0.007 0.115 0.522 0.005 0.493 0.002 0.000 2.996  0.014 1.592 0.257 0.006 0.109 0.507 0.003 0.507 0.001 0.000 2.997  0.015 1.572 0.260 0.008 0.120 0.509 0.004 0.507 0.002 0.000 2.996  0.015 1.580 0.261 0.006 0.115 0.507 0.004 0.507 0.002 0.000 2.997  0.015 1.561 0.266 0.007 0.127 0.514 0.004 0.502 0.001 0.000 2.997  0.013 1.596 0.248 0.006 0.116 0.510 0.004 0.503 0.002 0.000 2.998  0.014 1.608 0.242 0.005 0.106 0.512 0.005 0.497 0.001 0.000 2.990  0.015 1.559 0.266 0.007 0.128 0.504 0.005 0.509 0.002 0.001 2.997  0.015 1.564 0.262 0.007 0.129 0.500 0.004 0.514 0.002 0.000 2.996  0.014 1.575 0.256 0.006 0.127 0.502 0.004 0.512 0.002 0.000 2.998  0.016 1.553 0.280 0.007 0.119 0.506 0.004 0.510 0.002 0.000 2.998  0.014 1.576 0.259 0.007 0.121 0.501 0.005 0.512 0.002 0.000 2.998  0.014 1.580 0.255 0.007 0.120 0.498 0.002 0.517 0.002 0.000 2.996  0.005 1.714 0.176 0.000 0.097 0.314 0.000 0.690 0.004 0.000 3.001  0.005 1.625 0.223 0.001 0.137 0.307 0.000 0.697 0.005 0.000 3.001  0.006 1.612 0.223 0.000 0.148 0.302 0.000 0.701 0.005 0.001 2.997  Trivalent End Members 0.795 Cr/I3+ 0.141 AI/I3+ 0.064 Fe/I3+  0.805 0.138 0.058  0.806 0.135 0.059  0.813 0.131 0.056  0.805 0.133 0.061  0.808 0.133 0.059  0.799 0.136 0.065  0.814 0.127 0.059  0.822 0.124 0.054  0.798 0.136 0.065  0.800 0.134 0.066  0.805 0.131 0.065  0.796 0.143 0.061  0.805 0.133 0.062  0.808 0.130 0.062  0.862 0.089 0.049  0.819 0.112 0.069  0.813 0.112 0.074  Style: Zone:  2  2  2  3  2  2  3  3  2  J  /T  3  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (small) Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each section  Appendix l(continued): Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion Rock:  Chromitite  Sample: Cluster: Grain Number:  05ES-01-04-01 7 1  Style: Zone:  Chromitite 6 1  5 1  05ES-01-03-01 1 ]  4 1  2 1  Core  I. anh. Rim  Mid  Mid  Core  I. anh. Rim  Mid  Mid  Core  I. anh. Rim  Mid  Mid  Core  I. eu. Rim  Mid  Mid  Core  I. eu. Rim  Oxides (wt. %) Si0 TiOj Al 0 Cr 0 V 0 Fe 0 FeO MnO MgO NiO CaO Total  0.09 0.24 5.80 63.75 0.03 5.44 11.68 0.00 14.26 0.18 0.05 101.53  0.00 0.22 5.07 65.24 0.02 3.82 11.22 0.04 14.19 0.13 0.00 99.96  0.00 0.27 5.80 62.85 0.02 5.43 11.59 0.02 14.09 0.16 0.01 100.26  0.00 0.30 5.82 63.17 0.00 5.97 11.68 0.07 14.26 0.18 0.00 101.44  0.00 0.22 5.94 62.86 0.05 5.82 11.78 0.00 14.14 0.17 0.01 100.99  0.00 0.30 5.26 64.23 0.04 4.35 12.69 0.03 13.40 0.12 0.00 100.43  0.00 0.27 5.88 62.47 0.01 5.52 12.03 0.00 13.80 0.14 0.01 100.14  0.00 0.29 5.92 62.92 0.02 5.36 12.15 0.00 13.86 0.17 0.02 100.70  0.05 0.28 5.99 63.28 0.00 5.20 12.28 0.00 13.85 0.15 0.01 101.09  0.00 0.23 4.77 64.51 0.00 4.30 12.48 0.04 13.29 0.13 0.00 99.75  0.03 0.25 5.77 62.62 0.03 5.37 11.62 0.05 13.96 0.15 0.01 99.87  0.10 0.23 5.82 62.89 0.05 5.51 11.86 0.03 13.92 0.16 0.06 100.61  0.00 0.27 5.96 63.00 0.07 5.54 12.04 0.01 14.01 0.15 0.02 101.07  0.00 0.21 4.88 62.90 0.01 6.45 14.58 0.05 12.23 0.10 0.03 101.42  0.00 0.22 5.18 61.92 0.00 6.51 14.26 0.08 12.29 0.09 0.00 100.56  0.04 0.22 5.46 61.88 0.03 6.63 13.93 0.09 12.63 0.12 0.00 101.02  0.00 0.23 5.54 61.03 0.00 6.85 13.67 0.07 12.62 0.12 0.01 100.13  0.00 0.23 5.48 62.10 0.02 6.12 13.39 0.09 12.87 0.14 0.00 100.44  Cations (p.f.u.) Ti Cr Al V Fe"* Fe"* Mn Mg Ni Ca Total  0.006 1.628 0.221 0.001 0.132 0.315 0.000 0.687 0.005 0.002 2.997  0.006 1.695 0.196 0.000 0.094 0.308 0.001 0.695 0.004 0.000 3.001  0.007 1.626 0.224 0.001 0.134 0.317 0.001 0.688 0.004 0.000 3.001  0.007 1.616 0.222 0.000 0.145 0.316 0.002 0.688 0.005 0.000 3.001  0.005 1.615 0.228 0.001 0.142 0.320 0.000 0.685 0.004 0.000 3.001  0.007 1.670 0.204 0.001 0.108 0.349 0.001 0.657 0.003 0.000 3.000  0.007 1.621 0.227 0.000 0.136 0.330 0.000 0.675 0.004 0.000 3.001  0.007 1.623 0.228 0.000 0.132 0.331 0.000 0.674 0.004 0.001 3.001  0.007 1.626 0.229 0.000 0.127 0.334 0.000 0.671 0.004 0.000 2.998  0.006 1.693 0.187 0.000 0.107 0.346 0.001 0.657 0.004 0.000 3.001  0.006 1.627 0.223 0.001 0.133 0.319 0.001 0.684 0.004 0.000 2.999  0.006 1.622 0.224 0.001 0.135 0.324 0.001 0.677 0.004 0.002 2.996  0.007 . 1.618 0.228 0.001 0.136 0.327 0.000 0.679 0.004 0.001 3.000  0.005 1.639 0.189 0.000 0.160 0.402 0.001 0.601 0.001 2.998  0.006 1.623 0.202 0.000 0.162 0.395 0.002 0.607  0.005 1.609 0.212 0.001 0.164 0.383 0.002 0.619  0.000 2.998  0.000 2.996  0.006 1.600 0.217 0.000 0.171 0.379 0.002 0.624 0.000 2.998  0.006 1.621 0.213 0.000 0.152 0.370 0.002 0.633 0.000 2.997  Trivalent End Members 0.822 Cr/I3+ 0.111 AI/S3+ 0.067 Fe/£3+  0.854 0.099 0.048  0.820 0.113 0.067  0.815 0.112 0.073  0.814 0.115 0.072  0.843 0.103 0.054  0.817 0.115 0.069  0.819 0.115 0.066  0.820 0.116 0.064  0.852 0.094 0.054  0.820 0.113 0.067  0.819 0.113 0.068  0.817 0.115 0.068  0.824 0.095 0.080  0.817 0.102 0.082  0.811 0.107 0.083  0.805 0.109 0.086  0.816 0.107 0.077  2  2  3  2  2  3  3  2  3  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (small) Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each section  -  -  Appendix l(continued): Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion Rock:  Chromitite  Dunite  Sample: Cluster: Grain Number:  05ES-01-03-01 2 1  04ES-19-01-02 1 1  4 1  3  Mid  Mid  Core  m. anh. Rim  Mid  Mid  Core  m. eu. Rim  Mid  Mid  Core  I. sub. Mid  Mid  Mid  Mid  Mid  Mid  Core  0.02 0.25 5.45 61.93 0.02 6.37 13.57 0.02 12.82 0.13 0.00 100.57  0.01 0.22 5.56 61.29 0.03 6.72 13.41 0.02 12.85 0.14 0.01 100.25  0.02 0.24 5.53 61.44 0.03 6.73 13.50 0.06 12.83 0.12 0.00 100.50  0.01 0.24 5.26 62.68 0.02 6.61 14.52 0.07 12.42 0.13 0.02 101.98  0.02 0.23 5.55 62.32 0.01 6.53 14.24 0.16 12.52 0.12 0.01 101.70  0.02 0.24 5.52 61.23 0.02 6.88 13.79 0.09 12.61 0.13 0.01 100.53  0.02 0.28 5.66 61.91 0.03 6.28 14.01 0.00 12.68 0.13 0.01 100.99  0.00 0.21 4.93 62.33 0.00 6.50 13.75 0.01 12.59 0.11 0.01 100.45  0.00 0.21 5.47 61.24 0.04 6.56 13.61 0.06 12.61 0.13 0.02 99.94  0.02 0.25 5.59 62.19 0.02 6.33 13.86 0.05 12.76 0.13 0.01 101.22  0.00 0.22 5.47 62.63 0.00 6.54 13.71 0.08 12.91 0.14 0.01 101.70  0.04 0.77 8.74 53.75 0.18 6.37 23.15 0.34 7.05 0.00 100.40  0.02 0.81 8.87 55.41 0.15 4.31 22.63 0.30 7.35 0.00 99.83  0.03 0.82 8.86 55.43 0.15 4.34 22.21 0.24 7.64 0.00 99.73  0.08 0.73 8.81 55.51 0.15 4.32 21.78 0.35 7.72  0.00 0.89 8.75 54.45 0.15 4.65 22.26 0.31 7.41 0.01 98.88  0.01 0.71 8.37 54.04 0.12 5.70 23.16 0.39 6.68  0.01 99.47  0.06 0.80 8.81 55.75 0.15 4.66 22.23 0.29 7.73 0.00 100.48  Cations (p.f.u.) Ti Cr Al V Fe"* Fe' * Mn Mg  0.006 1.615 0.212 0.000 0.158 0.374 0.001 0.630  0.006 1.602 0.216 0.001 0.167 0.371 0.001 0.633  0.006 1.603 0.215 0.001 0.167 0.373 0.002 0.631  0.006 1.620 0.203 0.001 0.163 0.397 0.002 0.605  0.006 1.612 0.214 0.000 0.161 0.390 0.004 0.610  0.006 1.599 0.215 0.000 0.171 0.381 0.002 0.621  0.007 1.608 0.219 0.001 0.155 0.385 0.000 0.621  0.005 1.633 0.193 0.000 0.162 0.381 0.000 0.622  0.005 1.608 0.214 0.001 0.164 0.378 0.002 0.624  0.006 1.612 0.216 0.000 0.156 0.380 0.001 0.624  0.005 1.616 0.210 0.000 0.161 0.374 0.002 0.628  0.020 1.439 0.349 0.004 0.162 0.656 0.010 0.356  0.021 1.487 0.355 0.003 0.110 0.642 0.009 0.372  0.021 1.485 0.354 0.003 0.111 0.630 0.007 0.386  0.019 1.490 0.352 0.003 0.110 0.618 0.010 0.391  0.020 1.483 0.349 0.003 0.118 0.626 0.008 0.388  0.023 1.474 0.353 0.003 0.120 0.637 0.009 0.378  0.018 1.470 0.339 0.003 0.147 0.667 0.011 0.342  Ni Ca Total  0.000 2.996  0.001 2.997  0.000 2.996  0.001 2.997  0.000 2.997  0.000 2.997  0.000 2.997  0.000 2.998  0.001 2.997  0.000 2.996  0.000 2.997  0.000 2.996  0.000 2.998  0.000 2.997  0.001 2.995  0.000 2.995  0.000 2.999  0.000 2.998  Trivalent End Members 0.814 Cr/I3+ 0.107 AI/I3+ 0.080 Fe/X3+  0.807 0.109 0.084  0.808 0.108 0.084  0.816 0.102 0.082  0.811 0.108 0.081  0.806 0.108 0.086  0.811 0.111 0.078  0.822 0.097 0.081  0.810 0.108 0.083  0.812 0.109 0.079  0.813 0.106 0.081  0.738 0.179 0.083  0.762 0.182 0.056  0.762 0.182 0.057  0.763 0.180 0.057  0.760 0.179 0.061  0.757 0.181 0.062  0.751 0.173 0.075  Style: Zone: Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 2  2  2  3  2  vo 2  3  3  Fe 0 FeO MnO MgO NiO CaO Total 2  T  3  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (small) Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each section  -  -  0.00 99.18  Appendix l(continued): Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion  Rock:  Dunite  Sample: Cluster: Grain Number:  04ES-19-01-02 2 1  Style: Zone: Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 2  2  2  3  2  vo 2  3  3  Fe 0 FeO MnO MgO NiO CaO Total 2  3  Cations (p.f.u.) Ti Cr Al V Fe-"* Fe'** Mn Mg Ni Ca Total  2  I. anh. Rim  Mid  Mid  Mid  Mid  Mid  Mid  Mid  Mid  Mid  Core  s. sub. Rim  Mid  Core  m. sub. Rim  0.02 0.79 8.98 54.58 0.10 4.71 22.75 0.34 7.12 0.01 99.42  0.25 0.05 0.04 3.34 0.03 67.65 28.29 0.09 2.12  0.01 0.55 2.71 48.55 0.19 18.21 22.00 1.07 6.29  0.00 0.72 8.87 54.85 0.13 4.84 22.73 0.33 7.16  0.07 0.73 8.95 54.41 0.14 4.61 22.38 0.37 7.20  0.17 0.74 8.85 55.04 0.15 4.84 22.29 0.35 7.47  0.02 0.88 8.92 54.73 0.15 4.76 21.67 0.35 7.86  0.00 0.77 8.88 55.44 0.11 4.58 21.76 0.31 7.84  0.01 0.89 9.04 55.68 0.14 4.05 21.90 0.33 7.89  0.05 0.81 9.05 54.92 0.15 4.79 21.75 0.27 7.91  0.05 0.76 8.94 54.68 0.18 4.79 22.76 0.32 7.20  0.06 0.39 2.15 32.04 0.12 35.06 22.88 0.73 5.43  0.05 0.78 8.78 55.15 0.16 4.49 23.26 0.31 6.91  0.01 0.81 9.01 54.72 0.16 4.09 22.83 0.40 7.01  0.03 0.83 9.00 55.01 0.13 4.16 22.92 0.28 7.11  0.03 0.42 7.37 52.94 0.20 8.83 21.74 0.69 7.17  0.01 01.86  0.01 99.58  0.01 99.63  0.02 98.88  0.01 99.91  0.04 99.39  0.02 99.72  0.00 99.92  0.03 99.73  0.00 99.68  0.00 98.86  0.02 99.90  0.00 99.03  0.00 99.46  0.00 99.39  0.001 0.098 0.002 0.001 1.887 0.877 0.003 0.117  0.015 1.362 0.113 0.004 0.486 0.652 0.032 0.333  0.018 1.4770.356 0.003 0.124 0.647 0.009 0.364  0.019 1.473 0.361 0.003 0.119 0.641 0.011 0.368  0.019 1.473 0.353 0.003 0.123 0.631 0.010 0.377  0.023 1.469 0.357 0.003 0.121 0.615 0.010 0.398  0.020 1.484 0.354 0.002 0.117 0.616 0.009 0.396  0.022 1.486 0.360 0.003 0.103 0.618 0.010 0.397  0.021 1.468 0.360 0.003 0.122 0.615 0.008 0.399  0.019 1.470 0.358 0.004 0.123 0.647 0.009 0.365  0.011 0.920 0.092 0.003 0.958 0.695 0.022 0.294  0.020 1.483 0.352 0.004 0.115 0.662 0.009 0.351  0.021 1.482 0.364 0.004 0.105 0.654 0.012 0.358  0.021 1.483 0.361 0.003 0.107 0.653 0.008 0.361  0.011 1.440 0.299 0.004 0.229 0.625 0.020 0.368  0.001 2.995  0.020 1.472 0.361 0.002 0.121 0.649 0.010 0.362 0.000 2.998  0.000 2.986  0.000 2.998  0.000 2.999  0.001 2.995  0.000 2.990  0.002 2.997  0.001 2.999  0.000 2.998  0.001 2.996  0.000 2.996  0.000 2.995  0.001 2.996  0.000 2.998  0.000 2.997  0.000 2.997  0.757 0.186 0.057  0.753 0.185 0.062  0.049 0.001 0.950  0.694 0.058 0.248  0.755 0.182 0.063  0.754 0.185 0.061  0.756 0.181 0.063  0.754 0.183 0.062  0.759 0.181 0.060  0.763 0.185 0.053  0.753 0.185 0.063  0.754 0.184 0.063  0.467 0.047 0.486  0.761 0.180 0.059  0.760 0.186 0.054  0.760 0.185 0.055  0.732 0.152 0.116  s. anh. Rim  Mid  Core  0.03 0.76 8.73 54.61 0.18 5.15 23.24 0.42 6.86 0.00 99.99  0.06 0.94 8.99 54.66 0.14 4.31 22.84 0.32 7.17  0.019 1.469 0.350 0.004 0.132 0.661 0.012 0.348 0.000 2.997  0.024 1.472 0.361 0.003 0.110 0.651 0.009 0.364  Trivalent End Members 0.753 Cr/Z3+ - 0.179 AI/I3+ 0.068 Fe/I3+  3 1  2  -  0.03 99.46  -  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (small) Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each section  Appendix l(continued): Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion Rock:  Dunite  Dunite  Sample: Cluster: Grain Number:  04ES-19-01-02 3 2  04ES-03-02-01 2 1  4 1  2  Mid  Mid  Mid  Core  m. sub. Rim  Mid  Mid  Mid  Mid  Core  I. sub. Mid  Mid  Mid  Mid  Mid  Core  m. sub. Mid  Mid  0.02 0.80 9.21 54.64 0.22 4.32 22.95 0.47 7.05  0.02 0.81 9.04 55.28 0.14 4.25 22.73 0.40 7.24  0.01 0.83 9.01 55.27 0.14 3.85 22.66 0.27 7.27  0.05 0.79 9.12 55.68 0.17 3.57 22.80 0.29 7.24  0.07 0.02 0.03 5.58 0.04 65.02 29.52 0.08 1.34  0.04 0.50 0.54 34.24 0.08 33.26 25.69 1.17 3.16  0.05 0.48 7.16 45.71 0.08 15.95 25.01 0.24 5.37  0.00 0.43 7.11 47.15 0.07 15.11 23.93 0.30 6.02  0.01 0.47 6.97 47.76 0.04 14.53 23.54 0.29 6.23  0.03 0.43 7.08 48.05 0.06 14.21 23.16 0.25 6.47  0.03 0.44 7.02 44.92 0.10 16.12 24.75 0.32 5.22  0.01 0.44 6.85 46.79 0.08 15.74 24.34 0.35 5.74  0.01 0.41 6.81 46.99 0.08 15.19 23.70 0.25 6.01  0.03 0.48 6.76 47.96 0.09 14.78 23.37 0.29 6.39  0.02 0.41 6.81 48.41 0.11 14.62 23.11 0.27 6.58  0.00 0.45 6.66 47.32 0.09 15.06 22.71 0.23 6.61  0.07 0.41 1.18 29.87 0.06 36.60 25.32 1.13 3.24  0.00 0.43 7.04 45.24 0.08 16.39 24.53 0.31 5.48  0.01 99.68  0.02 99.94  0.00 99.31  0.00 99.72  0.02 101.71  0.03 98.72  0.00 100.05  0.00 100.13  0.00 99.84  0.00 99.74  0.00 98.93  0.00 100.34  0.01 99.45  0.01 100.16  0.02 100.36  0.02 99.15  0.01 97.89  0.00 99.51  0.020 1.469 0.369 0.005 0.111 0.652 0.013 0.357  0.021 1.482 0.361 0.003 0.108 0.644 0.011 0.366  0.021 1.490 0.362 0.003 0.099 0.646 0.008 0.370  0.020 1.494 0.365 0.004 0.091 0.647 0.008 0.366  0.001 0.165 0.001 0.001 1.828 0.922 0.002 0.075  0.014 1.009 0.024 0.002 0.933 0.801 0.037 0.175  0.013 1.258 0.294 0.002 0.418 0.728 0.007 0.278  0.011 1.290 0.290 0.002 0.393 0.693 0.009 0.311  0.012 1.309 0.285 0.001 0.379 0.683 0.008 0.322  0.011 1.315 0.289 0.001 0.370 0.670 0.007 0.334  0.012 1.251 0.292 0.002 0.427 0.729 0.010 0.274  0.011 1.282 0.280 0.002 0.411 0.706 0.010 0.296  0.011 1.296 0.280 0.002 0.399 0.691 0.007 0.313  0.012 1.310 0.275 0.002 0.384 0.675 0.009 0.329  0.011 1.318 0.276 0.002 0.379 0.665 0.008 0.338  0.012 1.304 0.273 0.002 0.395 0.662 0.007 0.343  0.012 0.886 0.052 0.002 1.033 0.794 0.036 0.181  0.011 1.251 0.290 0.002 0.431 0.718 0.009 0.286  0.000 2.997  0.001 2.998  0.000 2.998  0.000 2.996  0.001 2.995  0.001 2.997  0.000 2.997  0.000 2.999  0.000 2.999  0.000 2.998  0.000 2.997  0.000 2.999  0.000 2.999  0.000 2.998  0.001 2.998  0.001 2.999  0.000 2.996  0.000 2.999  Trivalent End Members 0.754 Cr/I3+ 0.189 AI/I3+ 0.057 Fe/I3+  0.759 0.185 0.055  0.764 0.186 0.051  0.766 0.187 0.047  0.083 0.001 0.917  0.513 0.012 0.475  0.639 0.149 0.212  0.654 0.147 0.199  0.664 0.144 0.192  0.666 0.146 0.188  0.635 0.148 0.217  0.650 0.142 0.208  0.656 0.142 0.202  0.665 0.140 0.195  0.668 0.140 0.192  0.661 0.139 0.200  0.449 0.026 0.524  0.634 0.147 0.219  Style: Zone: Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 2  2  2  3  2  vo 2  3  3  Fe 0 FeO MnO MgO NiO CaO Total 2  3  Cations (p.f.u.) Ti Cr Al V Fe"* Fe' * Mn Mg Ni Ca Total T  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (small) Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each section  Appendix l(continued): Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion Rock:  Dunite  Sample: Cluster: Grain Number:  04ES-03-02-01 4 1  5 1  2  Mid  Mid  Core  I. sub. Mid  Mid  Mid  Mid  Mid  Mid  Mid  Core  I. sub. Rim  Mid  Mid  Mid  Mid  Mid  Mid  0.03 0.43 6.95 47.56 0.09 15.27 23.93 0.27 6.11  0.02 0.43 6.98 47.49 0.06 14.69 23.01 0.27 6.47  0.01 0.42 6.88 48.44 0.08 14.44 22.81 0.22 6.78  0.02 0.46 6.06 42.83 0.06 19.59 25.90 0.39 4.45  0.05 0.47 6.81 43.67 0.09 17.60 25.67 0.37 4.64  0.00 0.46 6.98 44.09 0.13 17.30 25.52 0.27 4.91  0.03 0.47 7.06 44.96 0.08 16.78 25.01 0.35 5.25  0.00 0.41 6.88 45.19 0.11 16.37 24.44 0.31 5.45  0.00 0.45 6.94 46.01 0.10 16.32 24.59 0.30 5.63  0.03 0.42 6.92 46.56 0.07 15.30 24.24 0.20 5.71  0.03 0.39 6.71 46.01 0.09 15.80 23.65 0.36 5.83  0.08 0.02 0.02 0.57 0.02 68.76 29.45 0.14 0.93  0.03 0.74 0.60 27.18 0.01 40.45 26.57 1.09 2.88  0.00 0.58 6.36 38.63 0.07 23.24 26.02 0.62 4.31  0.03 0.45 6.85 44.90 0.10 17.07 24.94 0.38 5.23  0.00 0.44 6.81 47.74 0.12 14.79 23.00 0.29 6.55  0.00 0.42 6.80 49.07 0.10 14.31 21.18 0.25 7.78  0.00 0.41 6.88 49.83 0.11 13.51 21.31 0.28 7.73  0.02 100.67  0.01 99.42  0.00 100.07  0.01 99.77  0.01 99.39  0.00 99.68  0.00 99.97  0.01 99.18  0.00 100.35  0.00 99.46  0.00 98.86  0.01 99.99  0.00 99.54  0.00 99.84  0.02 99.95  0.00 99.75  0.01 99.92  0.00 100.06  Cations (p.f.u.j Ti Cr Al V Fe ** Fe^* Mn Mg  0.011 1.295 0.282 0.002 0.396 0.689 0.008 0.314  0.011 1.304 0.286 0.001 0.384 0.669 0.008 0.335  0.011 1.320 0.280 0.002 0.375 0.657 0.006 ' 0.348  0.012 1.198 0.253 0.001 0.521 0.766 0.012 0.235  0.013 1.218 0.283 0.002 0.467 0.758 0.011 0.244  0.012 1.223 0.289 0.003 0.457 0.749 0.008 0.257  0.012 1.240 0.290 0.002 0.441 0.730 0.010 0.273  0.011 1.255 0.285 0.003 0.433 0.718 0.009 0.285  0.012 1.262 0.284 0.002 0.426 0.713 0.009 0.291  0.011 1.286 0.285 0.002 0.402 0.708 0.006 0.298  0.010 1.278 0.278 0.002 0.418 0.695 0.011 0.306  0.000 0.017 0.001 0.000 1.977 0.941 0.005 0.053  0.021 0.799 0.026 0.000 1.132 0.826 0.034 0.160  0.015 1.081 0.265 0.002 0.619 0.770 0.019 0.228  0.012 1.240 0.282 0.002 0.449 0.729 0.011 0.272  0.011 1.308 0.278 0.003 0.386 0.666 0.008 0.338  0.011 1.330 0.275 0.002 0.369 0.607 0.007 0.398  0.011 1.348 0.278 0.002 0.348 0.610 0.008 0.394  Ni Ca Total  0.001 2.997  0.000 2.999  0.000 2.999  0.000 2.998  0.000 2.996  0.000 2.999  0.000 2.998  0.000 2.999  0.000 2.999  0.000 2.998  0.000 2.998  0.000 2.995  0.000 2.998  0.000 2.999  0.001 2.997  0.000 2.999  0.000 2.999  0.000 2.999  Trivalent End Members 0.656 Cr/X3+ 0.143 AI/Z3+ 0.201 Fe/Z3+  0.661 0.145 0.194  0.669 0.142 0.190  0.607 0.128 0.264  0.619 0.144 0.237  0.621 0.147 0.232  0.629 0.147 0.224  0.636 0.144 0.219  0.640 0.144 0.216  0.652 0.144 0.204  0.648 0.141 0.212  0.009 0.000 0.991  0.408 0.013 0.578  0.550 0.135 0.315  0.629 0.143 0.228  0.663 0.141 0.196  0.674 0.139 0.187  0.683 0.141 0.176  Style: Zone: Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 v o Fe 0 FeO MnO MgO 2  2  2  3  2  2  3  3  2  3  NiO CaO Total  J  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (small) Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each section  Appendix l(continued): Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion Rock:  Dunite  Dunite  Sample: Cluster: Grain Number:  04ES-03-02-01 5  04ES-08-01-01 1 1  2 1  2  2  1  2  Core  s. eu. Rim  Mid  Core  s. eu. Rim  Mid  Core  m. sub. Mid  Mid  Mid  Mid  Mid  Core  s. eu. Rim  Mid  Core  I. sub. Rim  Mid  0.02 0.47 6.72 50.24 0.07 13.72 21.46 0.25 7.79  0.01 0.48 7.70 44.00 0.06 17.56 22.87 0.29 6.68  0.02 0.46 6.96 47.32 0.08 15.39 22.41 0.17 7.05  0.00 0.48 7.04 47.22 0.11 15.57 22.57 0.26 7.00  0.12 0.39 5.94 38.98 0.06 22.67 24.38 0.52 4.87  0.05 0.49 6.87 44.74 0.05 16.87 24.82 0.21 5.33  0.01 0.48 6.94 45.08 0.08 16.76 25.03 0.25 5.28  0.01 0.70 4.78 34.02 0.07 27.82 24.47 1.32 4.22  0.00 0.55 7.07 39.23 0.08 22.78 24.32 0.49 5.63  0.00 0.49 7.08 41.17 0.07 20.39 23.33 0.23 6.20  0.05 0.48 6.99 42.61 0.07 19.73 23.39 0.14 6.37  0.02 0.49 6.99 43.95 0.06 18.83 22.99 0.24 6.67  0.02 0.48 6.96 43.80 0.09 18.57 22.82 0.17 6.71  0.05 0.53 7.47 44.81 0.06 16.75 22.94 0.24 6.64  0.03 0.54 7.28 46.40 0.09 15.98 22.81 0.22 6.90  0.03 0.52 7.35 46.49 0.07 15.97 22.94 0.22 6.84  0.05 0.02 0.00 2.06 0.01 67.87 29.51 0.08 1.09  0.00 1.01 2.91 30.59 0.04 33.99 26.50 1.27 3.30  0.01 100.74  0.00 99.64  0.00 99.87  0.00 100.25  0.01 97.94  0.00 99.43  0.02 99.90  0.00 97.42  0.00 100.15  0.00 98.96  0.00 99.83  0.01 100.25  0.00 99.63  0.00 99.48  0.01 100.26  0.02 100.46  0.00 100.69  0.00 99.62  Mn Mg  0.012 1.351 0.270 0.002 0.351 0.610 0.007 0.395  0.012 1.202 0.314 0.001 0.456 0.661 0.009 0.344  0.012 1.289 0.283 0.002 0.399 0.646 0.005 0.362  0.012 1.282 0.285 0.003 0.402 0.648 0.008 0.358  0.011 1.107 0.252 0.001 0.613 0.732 0.016 0.261  0.013 1.241 0.284 0.001 0.445 0.728 0.006 0.278  0.013 . 1.245 0.286 0.002 0.440 0.731 0.007 0.275  0.019 0.985 0.206 0.002 0.766 0.749 0.041 0.231  0.014 1.080 0.290 0.002 0.597 0.708 0.015 0.292  0.013 1.140 0.292 0.002 0.538 0.683 0.007 0.324  0.012 1.169 0.286 0.002 0.515 0.679 0.004 0.330  0.013 1.198 0.284 0.001 0.489 0.663 0.007 0.343  0.013 1.201 0.285 0.002 0.485 0.662 0.005 0.347  0.014 1.227 0.305 0.001 0.436 0.664 0.007 0.343  0.014 1.259 0.295 0.002 0.413 0.655 0.006 0.353  0.013 1.260 0.297 0.002 0.412 0.657 0.006 0.349  0.000 0.062 0.000 0.000 1.935 0.935 0.003 0.062  0.028 0.883 0.125 0.001 0.934 0.809 0.039 0.180  Ni Ca Total  0.000 2.998  0.000 2.999  0.000 2.998  0.000 2.999  0.000 2.993  0.000 2.997  0.001 2.999  0.000 2.999  0.000 2.999  0.000 2.999  0.000 2.997  0.000 2.998  0.000 2.998  0.000 2.997  0.000 2.998  0.001 2.998  0.000 2.997  0.000 2.999  Trivalent End Members 0.685 Cr/I3+ 0.137 AI/I3+ 0.178 Fe/X3+  0.610 0.159 0.231  0.654 0.143 0.202  0.651 0.145 0.204  0.562 0.128 0.311  0.630 0.144 0.226  0.632 0.145 0.223  0.503 0.105 0.392  0.549 0.147 0.304  0.579 0.148 0.273  0.593 0.145 0.262  0.608 0.144 0.248  0.610 0.144 0.246  0.623 0.155 0.222  0.640 0.150 0.210  0.640 0.151 0.209  0.031 0.000 0.969  0.455 0.064 0.481  Style: Zone: Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 V 0 Fe 0 FeO MnO MgO 2  2  2  3  2  2  3  3  2  3  NiO CaO Total Cations (p.f.u.) Ti Cr Al V Fe * Jr  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (small) Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each section  Appendix l(continued): Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion  Rock:  Dunite  Sample: Cluster: Grain Number:  04ES-08-01-01 2 2  3 1  2  Mid  Mid  Mid  Mid  Mid  Mid  Mid  Core  s. sub. Rim  Mid  Core  I. sub. Rim  Mid  Mid  Mid  Mid  Mid  Mid  0.00 0.45 5.89 44.28 0.08 18.94 24.13 0.24 5.69  0.01 0.46 6.98 45.96 0.09 16.84 22.95 0.17 6.77  0.00 0.50 7.10 46.79 0.05 15.79 21.96 0.19 7.31  0.03 0.43 7.24 47.40 0.05 15.14 21.97 0.19 7.29  0.01 0.47 7.10 47.52 0.06 15.28 21.73 0.22 7.47  0.00 0.47 7.17 47.83 0.06 15.04 22.05 0.20 7.33  0.03 0.47 7.22 47.95 0.10 14.76 22.24 0.15 7.28  0.01 0.47 7.10 47.69 0.05 15.44 22.00 0.22 7.39  0.03 0.54 7.32 45.01 0.06 16.15 23.86 0.28 5.95  0.01 0.54 7.32 45.87 0.07 15.47 24.10 0.25 5.90  0.01 0.58 7.27 45.92 0.04 15.48 23.98 0.26 5.95  0.13 0.01 0.01 1.07 0.02 68.97 28.99 0.10 1.38  0.02 0.55 7.49 44.08 0.08 18.05 23.45 0.19 6.55  0.03 0.53 7.40 44.28 0.09 17.02 22.97 0.23 6.55  0.01 0.52 7.28 44.61 0.06 17.77 23.05 0.26 6.68  0.00 0.49 7.25 45.44 0.10 16.94 22.84 0.19 6.84  0.01 0.48 7.26 46.12 0.11 16.57 22.81 0.28 6.90  0.02 0.47 7.06 45.96 0.05 16.19 22.49 0.23 6.83  0.00 99.70  0.00 100.23  0.02 99.71  0.00 99.73  0.00 99.86  0.01 100.15  0.01 100.20  0.00 100.37  0.00 99.19  0.02 99.54  0.02 99.53  0.02 100.69  0.00 100.46  0.00 99.11  0.00 100.25  0.00 100.09  0.00 100.53  0.00 99.31  0.012 1.229 0.243 0.002 0.500 0.708 0.007 0.298  0.012 1.251 0.283 0.002 0.437 0.661 0.005 0.348  0.013 1.274 0.288 0.001 0.409 0.633 0.005 0.375  0.011 1.289 0.293 0.001 0.392 0.632 0.006 0.374  0.012 1.290 0.288 0.001 0.395 0.624 0.006 0.382  0.012 1.296 0.289 0.001 0.388 0.632 0.006 0.374  0.012 1.298 0.291 0.002 0.380 0.637 0.004 0.371  0.012 1.290 0.286 0.001 0.397 0.629 0.006 0.377  0.014 1.243 0.301 0.001 0.424 0.697 0.008 0.310  0.014 1.262 0.300 0.002 0.405 0.701 0.007 0.306  0.015 1.264 0.298 0.001 0.406 0.698 0.008 0.309  0.000 0.032 0.000 0.000 1.962 0.916 0.003 0.078  0.014 1.197 0.303 0.002 0.467 0.674 0.006 0.336  0.014 1.218 0.304 0.002 0.445 0.668 0.007 0.340  0.013 1.214 0.295 0.001 0.460 0.664 0.008 0.343  0.013 1.237 0.294 0.002 0.439 0.658 0.006 0.351  0.012 1.250 0.293 0.002 0.427 0.653 0.008 0.352  0.012 1.261 0.289 0.001 0.423 0.653 0.007 0.353  0.000 2.999  0.000 2.999  0.001 3.000  0.000 2.998  0.000 2.999  0.001 2.999  0.000 2.998  0.000 2.999  0.000 2.998  0.001 2.999  0.001 2.999  0.001 2.992  0.000 2.998  0.000 2.997  0.000 2.999  0.000 2.999  0.000 2.999  0.000 2.998  Trivalent End Members 0.623 Cr/I3+ 0.123 AI/I3+ 0.254 Fe/I3+  0.635 0.144 0.221  0.646 0.146 0.208  0.653 0.149 0.198  0.654 0.146 0.200  0.657 0.147 0.197  0.659 0.148 0.193  0.654 0.145 0.201  0.631 0.153 0.216  0.642 0.153 0.206  0.642 0.152 0.206  0.016 0.000 0.984  0.609 0.154 0.237  0.619 0.154 0.226  0.616 0.150 0.234  0.628 0.149 0.223  0.634 0.149 0.217  0.639 0.146 0.214  Style: Zone: Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 2  2  2  3  2  vo 2  3  3  Fe 0 FeO MnO MgO NiO CaO Total 2  3  Cations (p.f.u.) Ti Cr Al V Fe '* Fe'** Mn Mg Ni Ca Total J  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (small) Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each section  Appendix l(continued): Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion Rock: Sample: Cluster: Grain Number: Style: Zone:  Dunite 3 2  Wehrlite  04ES-10-05-01 6 1  5 1  2  4 1  2  04ES-11-03-03 4 1  2  Core  m. eu. Rim  Mid  Core  s. eu. Mid  Core  s. eu. Rim  Mid  Core  m. eu. Rim  Mid  Core  s. eu. Mid  Core  s. eu. Rim  Mid  m. sub. Rim  Mid  Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 V 0 Fe 0 FeO MnO MgO NiO CaO Total  0 00 0 54 7 08 46 35 0 04 16 45 22 73 0 23 6 93  0 00 0 58 4 89 46 77 0 19 17 12 20 27 2 90 6 36  0 05 0 79 7 54 50 65 0 26 9 43 25 39 0 34 5 35  0 10 0 70 7 48 51 00 0 22 9 50 24 33 0 39 5 88  0.05 0.80 7.64 49.33 0.26 10.62 25.08 0.54 5.42  0 00 0 78 7 59 50 39 0 26 9 73 25 15 0 38 5 47  0 04 0 52 0 65 33 65 0 09 34 34 20 38 3 07 5 26  0 03 0 75 7 57 51 05 0 21 9 37 25 36 0 38 5 37  0 00 0 73 7 66 50 85 0 24 9 47 25 10 0 38 5 53  0 02 0 70 7 68 48 88 0 25 10 56 24 83 0 96 5 07  0.00 0.75 7.78 51.15 0.24 9.15 25.16 0.29 5.61  0.02 0.76 7.75 50.78 0.24 9.56 24.90 0.40 5.70  0 00 0 64 6 90 53 29 0 21 8 66 23 09 0 30 6 72  0 02 0 64 6 87 53 68 0 24 8 52 23 05 0 33 6 81  0 01 0 61 5 86 49 81 0 27 12 95 20 56 2 39 6 72  0.01 0.66 7.00 52.52 0.23 8.45 23.46 0.31 6.34  0 06 0 67 2 73 15 26 0 10 49 60 27 85 1 03 2 18  0.03 1.51 9.00 41.57 0.32 14.16 26.50 0.38 4.83  0 01 100 36  0 02 99 11  0 00 99 82  0 01 99 59  0.00 99.73  0 02 99 76  0 01 98 01  0 00 100 09  0 00 99 96  0 02 98 97  0.00 100.14  0.00 100.11  0 02 99 83  0 00 100 16  0 00 99 19  0.00 98.98  0 01 99 50  0.01 98.31  Cations (p.f.u.) Ti Cr Al V Fe"* Fe"* Mn Mg  0.014 1.259 0.287 0.001 0.425 0.653 0.007 0.355  0.015 1.303 0.203 0.004 0.454 0.597 0.086 0.334  0.021 1.390 0.308 0.006 0.246 0.737 0.010 0.277  0.018 1.397 0.305 0.005 0.248 0.705 0.011 0.303  0.021 1.354 0.312 0.006 0.277 0.728 0.016 0.280  0.020 1.382 0.310 0.006 0.254 0.730 0.011 0.283  0.014 0.982 0.028 0.002 0.954 0.630 0.096 0.289  0.020 1.397 0.309 0.005 0.244 0.734 0.011 0.277  0.019 1.391 0.312 0.005 0.247 0.726 0.011 0.285  0.018 1.354 0.317 0.006 0.278 0.728 0.029 0.265  0.019 1.395 0.316 0.006 0.238 0.726 0.008 0.289  0.020 1.385 0.315 0.006 0.248 0.718 0.012 0.293  0.017 1.452 0.280 0.005 0.225 0.665 0.009 0.345  0.016 1.457 0.278 0.005 0.220 0.662 0.010 0.348  0.016 1.374 0.241 0.006 0.340 0.600 0.071 0.350  0.017 1.445 0.287 0.005 0.221 0.683 0.009 0.329  0.019 0.448 0.120 0.002 1.387 0.866 0.032 0.121  0.040 1.156 0.373 0.007 0.375 0.779 0.011 0.253  0.000 3.000  0.001 2.998  0.000 2.995  0.000 2.993  0.000 2.995  0.001 2.997  0.000 2.997  0.000 2.997  0.000 2.998  0.001 2.997  0.000 2.998  0.000 2.997  0.001 2.998  0.000 2.996  0.000 2.997  0.000 2.997  0.000 2.996  0.000 2.995  Trivalent End Members Cr/23+ 0.639 0.146 AI/I3+ 0.216 Fe/X3+  0.665 0.104 0.232  0.715 0.159 0.127  0.716 0.157 0.127  0.697 0.161 0.143  0.710 0.159 0.130  0.500 0.014 0.486  0.716 0.158 0.125  0.713 0.160 0.126  0.694 0.163 0.143  0.716 0.162 0.122  0.711 0.162 0.127  0.742 0.143 0.115  0.745 0.142 0.113  0.703 0.123 0.174  0.740 0.147 0.113  0.229 0.061 0.709  0.607 0.196 0.197  2  2  2  3  2  2  3  3  2  3  Mi  Nl  Ca Total  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (small) Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each section  Appendix l(continued): Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion Rock:  Wehrlite  Sample: Cluster: Grain Number:  04ES-11-03-03 4 1  2 1  2  2  Mid  Mid  Core  m. sub. Rim  Mid  Mid  Core  I. irreg. Rim  Mid  Mid  Mid  Mid  Mid  Mid  Core  m. anh. Mid  Core  0 01 1 45 9 54 42 62 0 28 13 46 26 44 0 39 5 08  0.00 1.44 9.62 42.70 0.27 13.67 26.53 0.38 5.14  0 00 1 48 9 61 42 64 0 35 13 71 26 57 0 36 5 21  0.01 1.26 10.47 43.31 0.30 13.03 26.18 0.40 5.50  0 00 1 28 10 27 43 96 0 29 12 24 26 04 0 34 5 52  0 00 1 29 10 24 44 58 0 30 11 66 26 05 0 34 5 54  0 00 1 35 10 23 44 37 0 32 11 65 26 10 0 31 5 54  0.02 1.36 9.23 45.81 0.26 11.17 24.88 0.40 5.96  0.01 1.66 9.25 45.10 0.21 11.77 25.27 0.27 6.08  0 03 1 55 8 82 46 26 0 20 11 24 25 14 0 27 6 04  0 06 1 49 8 69 46 57 0 20 11 28 25 05 0 31 6 05  0 01 1 37 8 37 47 81 0 18 10 32 24 78 0 26 6 04  0 05 1 26 8 03 48 57 0 21 10 72 24 92 0 31 6 03  0 03 1 19 7 80 49 40 0 19 10 09 24 75 0 38 5 97  0.03 1.19 7.57 49.08 0.21 10.01 24.43 0.37 5.97  0.04 1.59 9.36 44.73 0.29 11.36 26.32 0.35 5.27  0.04 1.56 9.48 44.05 0.28 12.09 26.27 0.81 5.07  0 01 99 28  0.01 99.76  0 00 99 92  0.01 100.45  0 00 99 95  0 00 100 00  0 01 99 87  0.07 99.17  0.02 99.65  0 02 99 57  0 02 99 70  0 02 99 16  0 02 100 12  0 01 99 81  0.01 98.88  0.02 99.33  0.00 99.65  Cations (p.f.u.) Ti Cr Al V Fe-"* Fe'** Mn Mg  0.038 1.169 0.390 0.006 0.351 0.767 0.012 0.263  0.037 1.166 0.391 0.006 0.355 0.766 0.011 0.264  0.038 1.161 0.390 0.008 0.355 0.765 0.011 0.268  0.032 1.167 0.420 0.007 0.334 0.746 0.012 0.279  0.033 1.190 0.414 0.007 0.315 0.746 0.010 0.282  0.033 1.206 0.413 0.007 0.300 0.745 0.010 0.282  0.035 1.202 0.413 0.007 0.300 0.748 0.009 0.283  0.035 1.250 0.376 0.006 0.290 0.718 0.012 0.307  0.043 1.225 0.375 0.005 0.304 0.726 0.008 0.311  0.040 1.260 • 0.358 0.004 0.291 0.724 0.008 0.310  0.039 1.267 0.352 0.005 0.292 0.721 0.009 0.310  0.036 1.309 0.342 0.004 0.269 0.718 0.008 0.312  0.033 1.320 0.325 0.005 0.277 0.717 0.009 0.309  0.031 1.348 0.318 0.004 0.262 0.715 0.011 0.307  0.031 1.353 0.311 0.005 0.263 0.712 0.011 0.310  0.041 1.224 0.382 0.007 0.296 0.762 0.010 0.272  0.040 1.204 0.386 0.006 0.315 0.759 0.024 0.261  Ni Ca Total  0.000 2.997  0.001 2.997  0.000 2.997  0.000 2.997  0.000 2.997  0.000 2.997  0.000 2.997  0.003 2.996  0.001 2.997  0.001 2.997  0.001 2.995  0.001 2.998  0.001 2.996  0.000 2.997  0.000 2.996  0.001 2.995  0.000 2.995  Trivalent End Members 0.612 Cr/I3+ 0.204 AI/I3+ 0.184 Fe/£3+  0.610 0.205 0.186  0.609 0.205 0.186  0.607 0.219 0.174  0.620 0.216 0.164  0.628 0.215 0.156  0.628 0.216 0.157  0.653 0.196 0.151  0.643 0.197 0.160  0.660 0.188 0.153  0.663 0.184 0.153  0.682 0.178 0.140  0.687 0.169 0.144  0.699 0.165 0.136  0.702 0.161 0.136  0.644 0.201 0.156  0.632 0.203 0.165  Style: Zone: Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 2  2  2  3  2  vo 2  3  3  Fe 0 FeO MnO MgO NiO CaO Total 2  3  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (small) Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each section  Appendix l(continued): Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion Rock:  Wehrlite  ;  Sample: Cluster: Grain Number:  04ES-11-03-03 1 1  Wehrlite 04ES-15-01-05 7 1  2  6 1  2  s. eu. Rim  Mid  Core  m. sub. Rim  Mid  Mid  Mid  Mid  Core  s. eu. Mid  Core  m. sub. Mid  Mid  Mid  Core  m. sub. Mid  Mid  Core  0.02 1.75 10.07 41.38 0.28 13.34 27.12 0.55 4.75  0.00 1.72 9.82 42.63 0.27 12.79 27.14 0.36 4.92  0.06 1.69 9.87 42.79 0.28 12.67 27.31 0.37 4.84  0.03 1.81 10.18 39.97 0.25 14.07 26.22 1.00 4.91  0.03 1.58 9.69 43.41 0.29 12.19 26.33 0.38 5.25  0.02 1.52 9.87 44.05 0.32 12.13 26.35 0.37 5.42  0.02 1.59 9.98 43.83 0.29 12.26 26.64 0.33 5.37  0.00 1.56 9.83 44.25 0.33 12.25 26.52 0.34 5.46  0.01 1.64 10.07 43.39 0.28 12.43 26.34 0.31 5.53  0.03 1.17 14.94 48.11 0.35 3.71 23.66 0.34 7.57  0.04 1.48 15.41 48.54 0.31 2.21 23.62 0.20 7.89  0.03 1.41 14.31 50.35 0.20 2.35 22.71 0.48 8.14  0.02 1.67 14.38 51.19 0.17 1.51 23.39 0.28 8.16  0.03 1.37 14.27 50.31 0.22 2.47 22.94 0.27 8.12  0.03 1.46 14.27 50.07 0.23 2.40 22.70 0.30 8.25  0.04 1.38 14.45 49.22 0.18 2.68 23.49 0.27 7.64  0.05 1.51 14.52 49.73 0.14 2.35 23.44 0.30 7.83  0.00 1.34 14.10 50.37 0.21 2.40 23.13 0.18 7.96  0.02 99.27  0.00 99.64  0.00 99.89  0.00 98.44  0.00 99.16  0.01 100.05  0.00 100.30  0.00 100.55  0.02 100.02  0.02 99.90  0.00 99.69  0.04 100.03  0.02 100.79  0.02 100.03  0.02 99.74  0.00 99.36  0.00 99.87  0.02 99.70  0.046 1.135 0.412 0.006 0.348 0.787 0.016 0.246  0.045 1.165 0.400 0.006 0.333 0.785 0.011 0.254  0.044 1.167 0.401 0.006 0.329 0.788 0.011 0.249  0.047 1.103 0.419 0.006 0.370 0.766 0.029 0.256  0.041 1.189 0.396 0.007 0.318 0.763 0.011 0.271  0.039 1.194 0.399 0.007 0.313 0.756 0.011 0.277  0.041 1.186 0.403 0.006 0.316 0.762 0.009 0.274  0.040 1.194 0.395 0.007 0.315 0.757 0.010 0.278  0.042 1.175 0.407 0.006 0.320 0.754 0.009 0.282  0.029 1.253 0.580 0.008 0.092 0.652 0.010 0.372  0.037 1.260 0.597 0.007 0.055 0.649 0.005 0.386  0.035 1.308 0.554 0.004 0.058 0.624 0.013 0.399  0.041 1.320 0.553 0.004 0.037 0.638 0.008 0.397  0.034 1.307 0.553 0.005 0.061 0.630 0.008 0.398  0.036 1.303 0.554 0.005 0.059 0.625 0.008 0.405  0.034 1.290 0.565 0.004 0.067 0.651 0.008 0.378  0.037 1.295 0.564 0.003 0.058 0.646 0.008 0.385  0.033 1.315 0.549 0.005 0.060 0.639 0.005 0.392  0.001 2.996  0.000 2.997  0.000 2.994  0.000 2.996  0.000 2.995  0.001 2.996  0.000 2.996  0.000 2.997  0.001 2.997  0.001 2.995  0.000 2.995  0.001 2.996  0.001 2.998  0.001 2.996  0.001 2.996  0.000 2.996  0.000 2.996  0.001 2.998  Trivalent End Members 0.599 Cr/23+ 0.217 AI/I3+ 0.184 Fe/S3+  0.614 0.211 0.175  0.615 0.212 0.173  0.583 0.221 0.195  0.625 0.208 0.167  0.627 0.209 0.164  0.623 0.211 0.166  0.627 0.208 0.165  0.618 0.214 0.168  0.651 0.301 0.048  0.659 0.312 0.029  0.681 0.289 0.030  0.691 0.289 0.019  0.680 0.288 0.032  0.680 0.289 0.031  0.671 0.294 0.035  0.676 0.294 0.030  0.684 0.285 0.031  Style: Zone: Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 2  2  2  3  2  vo 2  3  3  Fe 0 FeO MnO MgO NiO CaO Total 2  3  Cations (p.f.u.) Ti Cr Al V Fe"* Fe"* Mn Mg Ni Ca Total  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (small) Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each section  Appendix l(continued): Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion Rock:  Wehrlite  Wehrlite  Sample: Cluster: Grain Number:  04ES-15-01-05 6 2  5 1  2 Mid  Core  m. sub. Mid  Mid  Mid  Mid  Mid  Core  s. eu. Rim  Mid  Core  0.01 1.14 14.57 50.56 0.24\. 2.39 23.03 0.23 8.06  0.02 1.83 14.50 50.62 0.16 0.94 23.50 0.22 8.04  0.07 1.23 15.92 47.60 0.41 3.27 23.37 0.32 8.00  0.04 1.96 15.54 48.93 0.32 1.40 23.79 0.29 8.18  0.03 1.35 15.49 49.09 0.29 2.80 22.90 0.30 8.42  0.02 1.20 15.44 48.44 0.38 2.87 22.64 0.26 8.33  0.07 2.54 14.86 48.75 0.20 0.99 23.84 0.26 8.24  0.02 1.86 15.01 49.11 0.30 1.70 23.50 0.26 8.15  0.04 1.24 8.00 37.46 0.09 18.91 25.66 1.55 3.89  0.02 0.99 8.92 43.84 0.09 14.09 25.82 0.33 5.09  0.03 0.90 8.90 43.86 0.12 14.28 25.40 0.35 5.28  0.00 100.24  0.01 99.85  0.00 100.20  0.00 100.43  0.00 100.66  0.00 99.58  0.01 99.75  0.02 99.91  0.03 96.85  0.02 99.21  0.03 99.15  0.031 1.306 0.562 0.005 0.059 0.632 0.006 0.394  0.028 1.310 0.563 0.005 0.059 0.631 0.006 0.394  0.045 1.316 0.562 0.004 0.023 0.646 0.006 0.394  0.030 1.227 0.612 0.009 0.080 0.637 0.009 0.389  0.048 1.259 0.596 0.007 0.034 0.647 0.008 0.397  0.033 1.259 0.592 0.006 0.068 0.621 0.008 0.407  0.030 1.255 0.596 0.008 0.071 0.621 0.007 0.407  0.063 1.265 0.575 0.004 0.024 0.654 0.007 0.403  0.046 1.273 0.580 0.006 0.042 0.644 0.007 0.398  0.034 1.071 0.341 0.002 0.515 0.776 0.047 0.210  0.026 1.207 0.366 0.002 0.369 0.752 0.010 0.264  0.024 1.207 0.365 0.003 0.374 0.739 0.010 0.274  0.001 2.996  0.001 2.997  0.000 2.997  0.000 2.998  0.000 2.993  0.000 2.995  0.000 2.996  0.000 2.995  0.000 2.995  0.001 2.996  0.001 2.997  0.001 2.998  0.001 2.997  0.673 0.294 0.033  0.678 0.292 0.031  0.678 0.291 0.031  0.692 0.296 0.012  0.639 0.319 0.042  0.666 0.315 0.018  0.656 0.309 0.036  0.653 0.310 0.037  0.679 0.308 0.013  0.672 0.306 0.022  0.556 0.177 0.267  0.621 0.188 0.190  0.620 0.188 0.192  Core  m. eu. Mid  Mid  Mid  Mid  0.03 1.23" 12.46 52.16 0.17 2.85 23.75 0.28 7.35  0.06 1.30 14.98 49.44 0.24 2.80 23.18 0.29 8.01  0.04 1.58 14.72 49.38 0.21 2.27 23.26 0.21 8.03  0.03 1.22 14.67 50.01 0.24 2.57 22.97 0.25 8.08  0.02 1.26 14.53 50.30 0.22 2.38 23.03 0.23 8.05  0.02 100.30  0.07 100.38  0.06 99.77  0.03 100.08  0.02 100.03  0.030 1.365 0.500 0.003 0.067 0.661 0.008 0.362  0.031 1.371 0.488 0.004 0.071 0.660 0.008 0.364  0.032 1.278 0.577 0.005 0.069 0.634 0.008 0.390  0.039 1.284 0.571 0.004 0.056 0.640 0.006 0.394  0.030 1.297 0.567 0.005 0.063 0.630 0.007 0.395  0.003 2.994  0.001 2.997  0.001 2.997  0.003 2.995  0.002 2.996  Trivalent End Members 0.693 Cr/I3+ 0.259 AI/I3+ 0.048 Fe/Z3+  0.706 0.259 0.035  0.710 0.253 0.037  0.664 0.300 0.036  0.672 0.299 0.029  Style: Zone: Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 2  2  2  3  2  vo 2  3  3  Fe 0 FeO MnO MgO NiO CaO Total 2  3  Cations (p.f.u.) Ti Cr Al V Fe"* Fe'"* Mn Mg Ni Ca Total  s. sub. Rim  Mid  0.07 1.09 12.65 50.37 0.20 3.64 23.72 0.34 6.97  0.03 1.21 12.69 51.63 0.14 2.67 23.65 0.28 7.26  0.08 99.15  0.03 99.59  0.028 1.339 0.501 0.005 0.092 0.667 0.010 0.350  04ES-16-08-01 6 1  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (small) Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each section  Appendix l(continued): Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion Rock:  Wehrlite  Sample: Cluster: Grain Number:  04ES-16-08-01 6 2  Style: Zone:  2  Mid  Core  s. eu. Rim  Mid  Mid  Core  s. sub. Rim  Mud  Mid  Core  m. sub. Rim  Mid  Mid  Mid  Mid  Mid  Mid  11 79 60 05 09 28 05 19 31  0 00 1 06 8 08 47 84 0 04 11 86 24 86 0 23 5 89  0 06 1 01 7 92 48 90 0 06 11 94 21 20 0 27 8 12  0.01 1.03 7.99 49.53 0.08 11.56 20.19 0.18 8.88  0 04 1 01 8 01 49 73 0 08 11 60 19 79 0 26 9 11  0.03 1.05 7.85 50.34 0.08 11.46 19.79 0.25 9.22  0.03 1.03 7.99 50.02 0.09 10.92 20.46 0.20 8.70  0 06 1 69 9 82 38 04 0 11 16 52 25 57 1 61 4 64  0.03 0.92 10.40 42.19 0.06 14.19 25.68 0.45 5.18  0.01 0.74 9.40 46.21 0.06 11.45 24.50 0.33 5.72  0 02 0 71 9 18 48 86 0 10 10 38 24 52 0 34 6 05  0 05 0 87 4 87 38 97 0 10 22 43 24 77 2 04 3 75  0 04 1 25 9 15 44 45 0 11 13 40 26 01 0 36 5 29  0.04 1.15 8.87 45.29 0.09 13.21 25.11 0.28 5.81  0.03 0.96 8.35 47.93 0.09 11.69 24.14 0.33 6.27  0.05 0.97 8.28 48.31 0.08 11.69 23.69 0.30 6.62  0.01 1.00 8.38 48.39 0.07 11.41 23.76 0.34 6.56  0.04 1.10 8.28 48.70 0.09 11.38 23.88 0.37 6.63  0 00 97 46  0 02 99 87  0 02 99 51  0.00 99.45  0 00 99 64  0.01 100.09  0.00 99.43  0 04 98 09  0.00 99.10  0.00 98.42  0 00 100 17  0 09 97 94  0 05 100 11  0.03 99.89  0.00 99.80  0.01 100.00  0.02 99.94  0.01 100.47  0.021 1.310 0.280 0.002 0.359 0.723 0.067 0.231  0.027 1.306 0.329 0.001 0.308 0.718 0.007 0.303  0.026 1.318 0.318 0.001 0.306 0.604 0.008 0.413  0.026 1.329 0.320 0.002 0.295 0.573 0.005 0.449  0.026 1.329 0.319 0.002 0.295 0.560 0.007 0.459  0.027 1.340 0.311 0.002 0.290 0.557 0.007 0.463  0.026 1.343 0.320 0.002 0.279 0.581 0.006 0.440  0.045 1.058 0.407 0.003 0.438 0.753 0.048 0.244  0.024 1.155 0.424 0.001 0.370 0.743 0.013 0.267  0.019 1.272 0.386 0.001 0.300 0.713 0.010 0.297  0.018 1.321 0.370 0.002 0.267 0.701 0.010 0.308  0.024 1.122 0.209 0.002 0.615 0.754 0.063 0.204  0.032 1.210 0.371 0.002 0.347 0.749 0.011 0.272  0.030 1.233 0.360 0.002 0.342 0.723 0.008 0.298  0.025 1.304 0.339 0.002 0.303 0.695 0.009 0.322  0.025 1.309 0.334 0.002 0.301 0.679 0.009 0.338  0.026 1.312 0.339 0.002 0.294 0.681 0.010 0.335  0.028 1.313 0.333 0.002 0.292 0.681 0.011 0.337  0.000 2.993  0.001 3.000  0.001 2.996  0.000 2.999  0.000 2.997  0.000 2.998  0.000 2.998  0.001 2.996  0.000 2.998  0.000 2.999  0.000 2.998  0.004 2.996  0.002 2.997  0.001 2.997  0.000 2.997  0.000 2.997  0.001 2.999  0.000 2.997  Trivalent End Members 0.672 Cr/I3+ 0.144 AI/I3+ 0.184 Fe/I3+  0.672 0.169 0.159  0.678 0.164 0.158  0.684 0.164 0.152  0.684 0.164 0.152  0.690 0.160 0.150  0.692 0.165 0.144  0.556 0.214 0.230  0.593 0.218 0.190  0.650 0.197 0.153  0.675 0.189 0.136  0.577 0.107 0.316  0.627 0.193 0.180  0.637 0.186 0.177  0.670 0.174 0.156  0.673 0.172 0.155  0.675 0.174 0.151  0.678 0.172 0.151  Oxides (wt. %) Si0 Ti0 2  2  AI O 2  3  Cr 0 2  vo 2  3  3  Fe 0 FeO MnO MgO NiO CaO Total 2  3  Cations (p.f.u.) Ti Cr Al V Fe"* Fe'** Mn Mg  s. eu. Rim  4 1  3  0 0 6 46 0 13 24 2 4  KM NI  Ca Total  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (small) Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each section  Appendix l(continued): Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion Rock:  Wehriite  Wehrlite  Sample: Cluster: Grain Number:  04ES-16-08-01 4 2  5 1  04ES-10-06-01 6 1  2  2  Mid  Core  m. sub. Mid  Mid  Mid  Mid  Mid  Core  s. eu. Rim  Mid  Core  m. sub. Rim  Mid  Core  m. sub. Rim  Mid  Core  0.01 1.01 8.39 47.81 0.07 12.07 23.59 0.30 6.72  0.02 1.09 8.31 47.74 0.08 11.54 23.55 0.31 6.61  0.04 0.99 11.74 42.95 0.09 12.65 24.23 0.32 6.51  0.03 0.90 10.90 45.30 0.11 11.62 24.18 0.31 6.50  0.05 0.80 10.46 46.69 0.08 11.14 24.23 0.39 6.38  0.08 0.81 9.94 46.20 0.07 11.15 23.12 0.35 6.71  0.04 0.79 10.15 47.18 0.12 10.97 24.50 0.33 6.25  0.01 0.80 10.24 46.85 0.07 10.84 24.29 0.32 6.27  0.04 1.04 8.06 45.50 0.10 13.27 25.62 0.51 4.93  0.05 0.92 7.69 48.74 0.03 11.87 24.97 0.28 5.68  0.02 0.88 7.48 49.40 0.13 11.68 25.01 0.31 5.75  0.04 1.24 10.25 34.72 0.19 20.34 24.12 2.71 4.72  0.01 1.00 10.62 40.68 0.23 15.91 25.51 0.35 5.66  0.03 1.11 10.37 40.35 0.19 16.44 25.77 0.39 5.54  0.69 0.28 1.29 10.29 0.02 58.44 26.10 0.90 3.06  0.04 1.07 10.31 40.46 0.16 16.56 25.66 0.45 5.52  0.04 1.07 10.50 41.22 0.19 15.88 25.90 0.31 5.59  0.00 99.97  0.02 99.28  0.00 99.53  0.01 99.86  0.01 100.23  0.00 98.44  0.00 100.35  0.00 99.70  0.19 99.25  0.10 100.32  0.05 100.71  0.00 98.34  0.02 99.99  0.00 100.16  0.10 101.16  0.02 100.27  0.03 100.73  0.026 1.294 0.339 0.002 0.311 0.675 0.009 0.343  0.028 1.302 0.338 0.002 0.299 0.679 0.009 0.340  0.025 1.152 0.469 0.002 0.323 0.687 0.009 0.329  0.023 1.215 0.436 0.002 0.297 0.686 0.009 0.329  0.020 1.252 0.418 0.002 0.284 0.687 0.011 0.323  0.021 1.259 0.404 0.002 0.289 0.666 0.010 0.344  0.020 1.266 0.406 0.003 0.280 0.695 0.009 0.316  0.021 1.264 0.412 0.002 0.279 0.693 0.009 0.319  0.027 1.258 0.332 0.002 0.349 0.749 0.015 0.257  0.024 1.329 0.312 0.001 0.308 0.720 0.008 0.292  0.023 1.343 0.303 0.003 0.302 0.719 0.009 0.294  0.033 0.963 0.424 0.004 0.537 0.708 0.081 0.247  0.026 1.100 0.428 0.005 0.409 0.730 0.010 0.289  0.028 1.092 0.418 0.004 0.423 0.737 0.011 0.282  0.008 0.297 0.056 0.000 1.606 0.797 0.028 0.167  0.028 1.094 0.416 0.004 0.426 0.734 0.013 0.282  0.027 1.108 0.421 0.004 0.406 0.736 0.009 0.283  0.000 2.999  0.001 2.998  0.000 2.997  0.000 2.997  0.000 2.997  0.000 2.995  0.000 2.997  0.000 2.999  0.007 2.997  0.004 2.997  0.002 2.998  0.000 2.996  0.001 2.997  0.000 2.997  0.004 2.962  0.001 2.996  0.001 2.996  Trivalent End Members 0.666 Cr/Z3+ 0.174 AI/I3+ 0.160 Fe/Z3+  0.671 0.174 0.154  0.593 0.241 0.166  0.624 0.224 0.152  0.641 0.214 0.145  0.645 0.207 0.148  0.649 0.208 0.144  0.647 0.211 0.142  0.649 0.171 0.180  0.682 0.160 0.158  0.689 0.156 0.155  0.501 0.220 0.279  0.568 0.221 0.211  0.565 0.216 0.219  0.152 0.028 0.820  0.565 0.215 0.220  0.573 0.217 0.210  Style: Zone: Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 2  2  2  3  2  vo 2  3  3  Fe 0 FeO MnO MgO NiO CaO Total 2  3  Cations (p.f.u.) Ti Cr Al V Fe * Fe'** Mn Mg Ni Ca Total JT  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (small) Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each section  Appendix l(continued): Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion Rock:  Wehrlite  Sample: Cluster: Grain Number:  04ES-10-06-01 2 1  Style: Zone: Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 2  2  2  3  2  vo 2  3  3  Fe 0 FeO MnO MgO NiO CaO Total 2  3  Cations (p.f.u.) Ti Cr Al V Fe"* Fe"* Mn Mg Ni Ca Total  Olivine Clinopyroxenite 1 1  04ES-06-06-01 8 1  2  7 1  2  m. sub. Rim  Mid  Core  m. anh. Rim  Mid  Core  m. anh. Rim  Mid  Core  m. sub. Mid  Mid  Mid  Core  s. anh. Mid  Core  m. anh. Rim  Mid  Mid  0.00 0.91 12.76 40.57 0.20 13.53 22.71 2.03 6.39 0.01 99.12  0.02 0.96 11.86 43.47 0.14 12.68 24.23 0.60 6.56 0.00 100.51  0.05 0.89 11.74 43.64 0.16 12.20 23.94 0.27 6.72  0.01 0.79 12.14 43.35 0.13 12.38 23.02 0.31 7.17  0.00 0.94 11.14 43.98 0.16 12.95 23.86 0.30 6.84  0.03 0.94 11.50 43.81 0.16 12.66 23.74 0.28 6.96  0.03 0.11 0.03 4.83 0.00 64.67 28.70 0.35 1.43  0.03 0.94 12.00 42.33 0.20 13.34 24.16 0.37 6.68  0.00 0.89 11.86 42.92 0.16 13.33 24.21 0.30 6.70  0.00 1.13 9.09 46.48 0.32 10.52 25.65 0.48 5.30  0.02 1.09 9.18 47.13 0.36 10.00 25.37 0.73 5.38  0.02 1.06 9.16 47.69 0.28 9.96 25.83 0.39 5.34  0.00 1.08 9.10 48.02 0.34 9.68 25.76 0.41 5.43  0.00 0.90 8.81 44.03 0.34 13.94 26.25 0.93 4.59  0.06 1.03 9.40 44.41 0.39 12.61 26.54 0.31 4.94  0.02 1.11 7.13 42.33 0.43 16.23 25.42 1.56 4.42  0.03 1.28 7.68 45.25 0.36 12.52 26.42 0.65 4.56  0.06 1.10 7.49 45.57 0.33 13.12 25.72 1.09 4.66  0.01 99.62  0.09 99.38  0.01 100.17  0.00 100.08  0.00 00.17  0.00 100.05  0.01 100.39  0.00 98.97  0.00 99.26  0.02 99.76  0.03 99.84  0.00 99.80  0.03 99.72  0.03 98.69  0.03 98.77  0.01 99.16  0.023 1.088 0.510 0.005 0.345 0.644 0.058 0.323 0.000 2.998  0.024 1.154 0.469 0.003 0.321 0.680 0.017 0.329  0.023 1.167 0.468 0.004 0.311 0.677 0.008 0.339  0.020 1.156 0.483 0.003 0.314 0.650 0.009 0.361  0.024 1.173 0.443 0.003 0.329 0.673 0.009 0.344'  0.024 1.167 0.456 0.003 0.321 0.669 0.008 0.349  0.003 0.145 0.002 0.000 1.846 0.910 0.011 0.081  0.024 1.127 0.476 0.005 0.338 0.681 0.011 0.335  0.023 1.140 0.470 0.004 0.337 0.680 0.009 0.336  0.030 1.278 0.372 0.007 0.275 0.746 0.014 0.275  0.028 1.290 0.375 0.008 0.260 0.735 0.022 0.277  0.027 1.300 0.372 0.006 0.258 0.745 0.012 0.274  0.028 1.307 0.369 0.008 0.251 0.742 0.012 0.279  0.024 1.210 0.361 0.008 0.365 0.763 0.027 0.238  0.027 1.214 0.383 0.009 0.328 0.767 0.009 0.255  0.030 1.187 0.298 0.010 0.433 0.754 0.047 0.234  0.034 1.262 0.319 0.008 0.332 0.779 0.019 0.240  0.029 1.266 0.310 0.008 0.347 0.756 0.032 0.244  0.000 2.998  0.000 2.996  0.003 2.998  0.000 2.998  0.000 2.997  0.000 2.998  0.000 2.997  0.000 2.998  0.000 2.997  0.000 2.995  0.001 2.996  0.001 2.997  0.000 2.996  0.001 2.993  0.001 2.994  0.001 2.995  0.001 2.994  0.594 0.241 0.165  0.600 0.241 0.160  0.592 0.247 0.161  0.603 0.228 0.169  0.600 0.235 0.165  0.073 0.001 0.926  0.581 0.245 0.174  0.586 0.241 0.173  0.664 0.193 0.143  0.670 0.195 0.135  0.673 0.193 0.134  0.678 0.192 0.130  0.625 0.186 0.188  0.631 0.199 0.170  0.619 0.155 0.226  0.659 0.167 0.174  0.658 0.161 0.180  Trivalent End Members 0.560 Cr/I3+ 0.263 AI/I3+ 0.178 Fe/X3+  -  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (small) Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each section  Appendix i(continued): Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion  Rock:  Olivine Clinopyroxenite  Sample: Cluster: Grain Number:  04ES-06-06-01 7 1  Olivine Clinopyroxenite  4.5 1  2  04ES-01-04-01 5 1  2  2  Core  m. anh. Rim  Mid  Core  I. anh. Mid  Mid  Mid  Core  m. anh. Mid  Mid  Core  m. irreg. Rim  Mid  Mid  Core  s. eu. Mid  Core  0.02 1.11 7.67 45.38 0.37 13.08 26.25 0.76 4.61  0.03 1.22 5.68 42.41 0.39 17.21 25.92 1.50 3.91  0.03 1.44 6.23 42.90 0.54 15.80 26.93 0.93 4.02  0.05 2.11 0.34 21.09 0.24 42.67 27.42 2.22 2.15  0.04 1.05 8.74 46.87 0.27 10.27 26.42 0.35 4.73  0.05 1.05 8.60 47.79 0.24 10.02 26.05 0.47 4.96  0.05 1.04 8.49 48.06 0.25 9.72 25.90 0.49 4.99  0.02 1.07 8.53 48.20 0.22 9.56 26.19 0.42 4.88  0.01 0.84 8.25 46.95 0.25 11.33 25.75 0.78 4.70  0.00 0.98 8.61 48.60 0.24 9.68 26.26 0.35 4.96  0.02 1.02 8.35 48.48 0.22 10.11 26.30 0.41 4.92  0.05 0.85 8.52 53.59 0.30 5.58 24.73 0.29 5.87  0.02 0.86 8.29 55.09 0.25 4.93 24.78 0.29 6.09  0.05 0.87 8.17 55.38 0.23 4.71 24.67 0.24 6.17  0.01 0.79 8.10 55.37 0.26 4.83 24.30 0.32 6.29  0.04 0.90 8.99 53.34 0.26 4.88 23.73 0.37 6.46  0.03 0.86 8.86 52.62 0.27 5.27 23.35 0.26 6.57  NiO CaO Total  0.00 99.25  0.09 98.36  0.06 98.88  0.02 98.31  0.00 98.74  0.02 99.24  0.00 99.00  0.00 99.10  0.03 98.90  0.01 99.69  0.01 99.85  0.25 100.03  0.05 100.67  0.02 100.50  0.00 100.27  0.08 99.05  0.07 98.17  Cations (p.f.u.) Ti Cr Al V Fe"* Fe'** Mn Mg  0.029 1.260 0.317 0.009 0.346 0.771 0.023 0.241  0.033 1.206 0.241 0.009 0.466 0.780 0.046 0.210  0.038 1.209 0.262 0.013 0.424 0.803 0.028 0.213  0.060 0.632 0.015 0.006 1.218 0.870 0.071 0.121  0.028 1.298 0.361 0.006 0.271 0.774 0.010 0.247  0.028 1.316 0.353 0.006 0.262 0.759 0.014 0.258  0.027 1.326 0.349 0.006 0.255 0.756 0.014 0.260  0.028 1.330 0.351 0.005 0.251 0.765 0.012 0.254  0.022 1.303 0.341 0.006 0.299 0.756 0.023 0.246  0.026 1.333 0.352 0.005 0.253 0.762 0.010 0.257  0.027 1.330 0.342 0.005 0.264 0.763 0.012 0.255  0.022 1.452 0.344 0.007 0.144 0.709 0.008 0.300  0.022 1.484 0.333 0.006 0.126 0.706 0.008 0.309  0.022 1.494 0.328 0.005 0.121 0.704 0.007 0.314  0.020 1.496 0.326 0.006 0.124 0.694 0.009 0.320  0.023 1.449 0.364 0.006 0.126 0.682 0.011 0.331  0.023 1.442 0.362 0.006 0.137 0.677 0.008 0.339  Ni Ca Total  0.000 2.995  0.004 2.994  0.002 2.993  0.001 2.995  0.000 2.995  0.001 2.995  0.000 2.995  0.000 2.997  0.001 2.997  0.000 2.998  0.000 2.997  0.009 2.994  0.002 2.996  0.001 2.995  0.000 2.997  0.003 2.996  0.003 2.996  Trivalent End Members 0.655 Cr/23+ 0.165 AI/I3+ 0.180 Fe/I3+  0.630 0.126 0.244  0.638 0.138 0.224  0.339 0.008 0.653  0.673 0.187 0.140  0.681 0.183 0.136  0.687 0.181 0.132  0.688 0.182 0.130  0.670 0.176 0.154  0.688 0.182 0.130  0.687 0.176 0.136  0.748 0.177 0.074  0.764 0.171 0.065  0.769 0.169 0.062  0.769 0.168 0.064  0.747 0.188 0.065  0.743 0.186 0.071  Style: Zone: Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 2  2  2  3  2  vo 2  3  3  Fe 0 FeO MnO MgO 2  3  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (small) Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each section  Appendix l(continued): Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion Rock:  Olivine Clinopyroxenite  Olivine Clinopyroxenite  Sample: Cluster: Grain Number:  04ES-01-04-01 6 1  05ES-05-01-01 8 1  2  Hornblende Clinopyroxenite DDH04-47-7-49 3 1  9 1  I. anh.  m. sub. Rim  Mid  Mid  Core  m. anh. Rim  Mid  Mid  Core  s. eu. Rim  Mid  Core  Rim  Mid  Core  Mid  Mid  Mid  Mid  0.02 0.84 8.77 54.05 0.23 4.91 23.53 0.23 6.62  0.03 0.81 7.99 55.06 0.19 4.96 23.61 0.28 6.55  0.33 0.76 7.80 55.11 0.19 5.48 23.28 0.34 6.72  0.32 0.72 7.70 55.11 0.22 5.59 23.11 0.27 6.79  0.24 0.84 7.00 39.85 0.24 19.25 25.89 1.13 3.95  0.03 0.83 8.95 52.54 0.32 5.46 25.73 0.36 5.25  0.04 0.85 8.83 53.14 0.28 5.54 25.95 0.30 5.32  0.01 0.86 8.73 53.67 0.27 4.95 25.62 0.35 5.43  0.03 2.42 4.18 26.90 0.07 32.01 25.19 3.87 2.79  0.00 2.48 4.44 27.45 0.08 31.67 25.31 3.92 2.98  0.03 2.51 4.64 28.34 0.11 30.20 25.09 4.07 3.08  0.01 3.08 6.63 29.49 0.19 26.23 26.10 3.54 3.59  0.02 3.13 6.48 30.10 0.15 26.42 27.29 2.02 4.01  0.02 3.13 6.50 30.21 0.20 26.69 27.49 1.96 4.07  0.03 0.15 0.12 0.12 0.69 67.96 31.70 0.08 0.09  0.02 2.83 0.69 0.15 0.48 61.90 33.48 0.20 0.23  0.05 3.62 2.71 0.18 0.43 58.63 34.32 0.26 0.51  0.05 3.73 1.22 0.18 0.38 60.00 34.40 0.21 0.31  NiO CaO Total  0.16 99.35  0.02 99.51  0.04 100.04  0.08 99.90  0.15 98.51  0.06 99.52  0.02 100.27  0.02 99.90  0.34 97.80  0.26 98.60  0.17 98.24  0.10 98.96  0.03 99.67  0.04 100.31  0.00 100.95  0.04 100.01  0.00 100.71  0.00 100.48  Cations (p.f.u.) Ti Cr Al V Fe"* Fe"* Mn Mg  0.022 1.464 0.354 0.005 0.127 0.674 0.007 0.338  0.021 1.496 0.324 0.004 0.128 0.679 0.008 0.336  0.020 1.487 0.314 0.004 0.141 0.664 0.010 0.342  0.018 1.488 0.310 0.005 0.144 0.660 0.008 0.346  0.022 1.124 0.294 0.006 0.517 0.772 0.034 0.210  0.021 1.434 0.364 0.007 0.142 0.743 0.010 0.270  0.022 1.441 0.357 0.006 0.143 0.744 0.009 0.272  0.022 1.460 0.354 0.006 0.128 0.737 0.010 0.278  0.067 0.787 0.182 0.002 0.891 0.779 0.121 0.154  0.068 0.795 0.192 0.002 0.873 0.775 0.122 0.163  0.069 0.821 0.200 0.003 0.833 0.769 0.126 0.168  0.083 0.836 0.280 0.004 0.708 0.783 0.108 0.192  0.084 0.846 0.272 0.004 0.707 0.811 0.061 0.212  0.083 0.843 0.271 0.005 0.709 0.812 0.059 0.214  0.004 0.004 0.005 0.017 1.944 1.008 0.003 0.005  0.081 0.005 0.031 0.012 1.776 1.068 0.006 0.013  0.102 0.005 0.119 0.011 1.648 1.072 0.008 0.028  0.106 0.005 0.054 ' 0.009 1.706 1.087 0.007 0.017  Ni Ca Total  0.006 2.997  .0.001 2.997  0.001 2.981  0.003 2.981  0.006 2.985  0.002 2.995  0.001 2.995  0.001 2.997  0.014 2.998  0.010 2.999  0.007 2.997  0.004 2.998  0.001 2.997  0.002 2.997  0.000 2.991  0.002 2.994  0.000 2.993  0.000 2.993  Trivalent End Members 0.753 Cr/23+ 0.182 AI/I3+ 0.065 Fe/I3+  0.768 0.166 0.066  0.766 0.162 0.072  0.766 0.160 0.074  0.581 0.152 0.267  0.739 0.188 0.073  0.742 0.184 0.074  0.752 0.182 0.066  0.423 0.098 0.479  0.428 0.103 0.469  0.443 0.108 0.449  0.458 0.154 0.388  0.464 0.149 0.387  0.463 0.148 0.389  0.002 0.003 0.995  0.002 0.017 0.980  0.003 0.067 0.930  0.003 0.031 0.966  Style: Zone: Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 2  2  2  3  2  v o 2  3  3  Fe 0 FeO MnO MgO 2  3  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (small) Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each section  Appendix l(continued): Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion Rock:  Hornblende Clinopyroxenite  Sample: Cluster: Grain Number:  DDH04-47-7-49 3 1  Style: Zone: Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 V 0 Fe 0 FeO MnO MgO 2  2  2  3  2  2  3  3  2  3  NiO CaO Total  Hornblende Clinopyroxenite DDH05-84-19-104 9 1  5 1  4 1  8 1 I. anh.  Core  Rim  Mid  Mid  Core  Rim  Mid  Mid  Core  I. interg. Rim  Mid  Mid  Core  Rim  Mid  Mid  Core  0.01 3.55 3.45 0.15 0.42 57.77 34.13 0.30 0.58  0.03 4.00 0.16 0.09 0.22 61.29 34.56 0.26 0.22  0.05 2.33 3.77 0.17 0.52 60.21 33.29 0.23 0.67  0.02 2.03 1.30 0.13 0.59 63.38 33.29 0.17 0.27  0.04 2.56 1.43 0.11 0.49 62.12 33.50 0.17 0.33  0.03 0.35 0.16 0.13 0.73 67.39 31.82 0.02 0.15  0.03 3.04 0.78 0.12 0.45 61.56 33.76 0.25 0:19  0.03 3.19 1.12 0.15 0.45 60.85 33.83 0.22 0.29  0.03 3.27 2.27 0.13 0.46 59.94 34.04 0.26 0.46  0.02 0.15 0.03 0.49 0.94 67.70 32.00 0.02 0.12  0.00 0.09 0.06 0.45 0.94 67.60 31.87 0.06 0.10  0.04 0.08 0.07 0.47 0.87 68.25 32.00 0.08 0.11  0.03 0.01 0.04 0.46 0.92 67.51 31.60 0.06 0.14  0.01 0.21 0.04 0.60 0.85 67.23 31.70 0.08 0.12  0.04 0.07 0.13 0.48 0.97 67.13 31.62 0.06 0.16  0.03 0.08 0.18 0.37 0.95 67.77 32.03 0.06 0.09  0.03 0.08 0.18 0.38 0.95 67.50 31.76 0.08 0.14  0.00 100.37  0.00 100.83  0.00 101.25  0.01 101.19  0.02 100.76  0.01 100.78  0.04 100.21  0.00 100.12  0.03 100.90  0.04 101.50  0.03 101.19  0.04 102.02  0.00 100.77  0.09 100.93  0.01 100.67  0.00 101.56  0.03 101.13  I. anh.  I. anh.  Cations (p.f.u.) Ti Cr Al V Fe"* Fe'** Mn Mg  0.100 ' 0.004 0.152 0.010 1.622 1.065 0.010 0.032  0.114 0.003 0.007 0.006 1.749 1.096 0.008 0.013  0.065 0.005 0.164 0.013 1.673 1.028 0.007 0.037  0.057 0.004 0.058 0.015 1.792 1.046 0.005 0.015  0.072 0.003 0.063 0.012 1.761 1.056 0.005 0.018  0.010 0.004 0.007 0.018 1.929 1.012 0.001 0.008  0.087 0.004 0.035 0.011 1.762 1.074 0.008 0.011  0.091 0.004 0.050 0.011 1.739 1.074 0.007 0.017  0.092 0.004 0.100 0.011 1.687 1.064 0.008 0.026  0.004 0.015 0.002 0.023 1.925 1.011 0.001 0.007  0.003 0.013 0.003 0.024 1.929 1.010 0.002 0.005  0.002 0.014 0.003 0.022 1.931 1.006 0.003 0.006  0.000 0.014 0.002 0.023 1.934 1.006 0.002 0.008  0.006 0.018 0.002 0.021 1.922 1.007 0.002 0.007  0.002 0.014 0.006 0.024 1.923 1.006 0.002 0.009  0.002 0.011 0.008 0.024 1.925 1.011 0.002 0.005  0.002 0.011 0.008 0.024 1.925 1.006 0.002 0.008  Ni Ca Total  0.000 2.995  0.000 2.996  0.000 2.991  0.000 2.993  0.001 2.993  0.001 2.990  0.001 2.994  0.000 2.994  0.001 2.993  .0.001 2.989  0.001 2.990  0.001 2.988  0.000 2.988  0.004 2.990  0.001 2.987  0.000 2.988  0.001 2.988  Trivalent End Members 0.002 Cr/23+ 0.085 AI/I3+ 0.912 Fe/I3+  0.002 0.004 0.994  0.003 0.089 0.908  0.002 0.031 0.967  0.002 0.035 0.964  0.002 0.004 0.994  0.002 0.019 0.978  0.002 0.028 0.970  0.002 0.056 0.942  0.008 0.001 0.992  0.007 0.001 0.992  0.007 0.002 0.991  0.007 0.001 0.992  0.009 0.001 0.990  0.007 0.003 0.990  0.006 0.004 0.990  0.006 0.004 0.990  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (small) Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each section  Appendix l(continued): Spinel compositions from spinel-bearing ultramafic rocks of the Turnagain intrusion  Rock:  Hornblende Clinopyroxenite  Sample: Cluster: Grain Number:  DDH05-84-19-104 1 1  Style: Zone:  I. anh. Rim  Mid  Mid  Core  0.05 0.08 0.18 0.37 0.91 67.80 31.85 0.02 0.17 0.02 101.46  0.01 0.14 0.15 0.38 0.93 67.77 32.10 0.00 0.11 0.00 101.59  Oxides (wt. %) Si0 TiOj Al 0 Cr 0 V 0 Fe 0 FeO MnO MgO NiO CaO Total  0.00 101.16  0.02 0.05 0.06 0.42 0.86 68.12 31.98 0.01 0.09 0.01 101.61  Cations (p.f.u.) Ti Cr Al V Fe"* Fe'"* Mn Mg Ni Ca Total  0.001 0.011 0.002 0.022 1.937 1.010 0.000 0.006 0.000 2.990  0.001 0.012 0.003 0.022 1.936 1.010 0.000 0.005 0.000 2.990  0.002 0.011 0.008 0.023 1.926 1.006 0.001 0.010 0.001 2.987  0.004 0.011 0.006 0.023 1.925 1.013 0.000 0.006  Trivalent End Members 0.006 Cr/£3+ 0.001 AI/I3+ 0.993 Fe/I3+  0.006 0.001 0.992  0.006 0.004 0.990  0.006 0.003 0.991  2  2  3  2  2  3  3  2  3  0.01 0.04 0.04 0.37 0.89 67.86 31.85 0.00 0.11  -  -  0.000 2.989  Crystal textural style is abbreviated: euh. (euhedral), sub. (subhedral), anh. (anhedral), interg. (intergrown), irreg. (irregular); I. (large), m. (medium), s. (small) Grain number refers to a particular grain within a cluster: most clusters have multiple grain Note: Other phases (ol, cpx, hbl) were also analyzed on certain sections, such that Cluster refers to a specific location on each section  Appendix II: Olivine compositions from olivitie-bearing ultramafic lithologies of the Turnagain intrusion  Rock type:  Chromitite  Chromitite  Sample:  05ES-01-01-01  Cluster:  1  05ES-01-04-01 1  8  3  2  Style:  porph.  porph.  porph.  porph.  porph.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  mgb.  Zone:  rim  mid  mid  mid  core  rim  mid  mid  core  rim  mid  mid  mid  core  rim  mid  core  rim  41.58  41.11  40.91  40.76  40.93  40.86  41.02  40.99  40.91  40.95  41.12  41.11  41.87  41.51  41.82  41.71  0.02  0.00  40.81 0.00  41.10  0.02  0.03  0.00  0.00  0.01  0.00  0.01  0.00  0.01  0.01  0.01  0.21  8.73  8.81  8.57  8.81  8.72  8.43  8.81  8.33  8.64  8.57  8.68  8.16  8.65  0.03 5.27  0.02  7.31  0.00 5.04  5.26  3.93  0.15  0.17  0.14  0.19  0.15  0.17  0.17  0.19  0.17  0.19  0.15  0.07  0.09  0.06  0.10  49.82  49.71  49.86  49.79  49.95  49.95  49.79  52.73  52.69  52.61  0.33  0.28  0.32  0.33  0.35  0.35  49.85 0.27  49.77  0.25  49.81 0.23  49.61  NiO  49.93 0.32  0.11 49.95  0.12  MgO  0.15 50.49  0.36  0.40  0.31  0.40  0.42  0.52  0.45  54.01 0.36  Oxides (wt. %) Si0  2  Cr 0 FeO 2  3  MnO  CaO  0.05  0.07  0.09  0.05  0.06  0.04  0.09  0.06  0.08  0.03  0.06  0.07  0.07  0.07  0.11  0.12  0.13  0.07  Total  99.85  100.23  99.96  99.81  100.23  99.58  99.80  100.05  99.92  99.96  99.97  99.99  99.82  100.18  100.24  100.23  100.35  100.39  Cations (p.f.u.) Si Cr  1.008  1.001  0.999  0.998  1.000  0.999  1.000  0.998  1.000  1.000  0.998  1.000  1.003  1.001  1.002  0.996  1.001  0.992  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  0.001  0.000  0.004  Fe  0.148  0.178  0.180  0.175  0.179  0.179  0.172  0.180  0.170  0.176  0.175  0.177  0.166  0.176  0.101  0.106  0.105  0.078  Mn  0.003  0.003  0.004  0.003  0.004  0.003  0.003  0.004  0.004  0.003  0.002  0.004  0.003  0.001  0.002  0.001  0.002  Mg  1.825  1.808  1.810  1.820  1.808  1.813  1.816  1.812  1.813  1.811  1.816  1.808  1.882  1.885  1.878  1.915  Ni  0.005  0.006  0.005  0.006  0.005  0.006  0.006  0.007  1.816 0.007  0.002 1.817  0.005  0.007  0.008  0.006  0.008  0.008  0.010  0.009  0.007  Ca  0.001  0.002  0.002  0.001  0.002  0.001  0.002  0.002  0.002  0.001  0.002  0.002  0.002  0.002  0.003  0.003  0.003  0.002  Total  2.991  2.999  3.001  3.002  2.998  3.001  3.000  3.002  3.000  2.999  3.002  3.000  2.997  2.998  2.998  3.002  2.998  3.000  Fo  92.5  91.1  91.0  91.2  91.0  91.0  91.3  91.0  91.4  91.1  94.9  94.7  94.7  96.1  8.9  9.0  8.8  9.0  9.0  8.7  9.0  8.6  91.1 8.9  91.6  7.5  91.1 8.9  91.2  Fa  8.4  8.9  5.1  5.3  5.3  3.9  End Members (%) 8.8  Crystal textural style is abbreviated: porph. (porphyroclast), cumu. (cumulus), def. (deformed), mgb. (modified grain boundaries) Note: Other phases (cpx, chr) were also analyzed on certain sections, such that "Cluster" refers to a specific location on each section  Appendix II (continued): Olivine compositions from olivine-bearing ultramafic lithologies of the Turnagain intrusion  Rock type:  Chromitite  Chromitite  Sample:  05ES-01-04-01  Cluster:  2  05ES-01-03-01 7  3  5  6  Style:  mgb.  mgb.  mgb.  cumu.  cumu.  cumu.  porph.  porph.  porph.  porph.  mgb.  mgb.  mgb.  mgb.  mgb.  mgb.  mgb.  Zone:  mid  mid  core  rim  mid  core  rim  mid  mid  core  rim  mid  core  rim  mid  mid  core  41.71  41.59  41.90  41.14  41.50  41.56  41.43  41.41  41.58  41.38  41.32  41.58  41.52  41.50  0.01  0.03  0.00  0.00  0.00  41.25 0.04  6.44  6.52  6.24  0.01 6.44  0.03  4.70  0.03 6.47  0.00  4.33  0.00 6.64  0.00  4.82  0.09 3.81  0.00  4.74  0.02 4.79  41.78 0.02  41.57  0.01  6.44  5.83  6.39  6.40  6.20  0.09  0.07  0.09  0.05  0.08  0.10  0.13  0.11  0.12  0.10  0.14  0.12  0.14  0.09  52.88  53.01  53.62  53.35  53.35  51.70  51.60  51.43  51.76  51.73  52.04  51.64  51.96  NiO  0.47  0.51  0.63  0.59  0.61  0.41  0.41  0.40  0.42  0.43  0.41  0.43  0.10  0.10  0.13  0.11  0.08  0.12  0.09  0.12  0.13  0.13  0.13  0.14  0.40 0.08  0.46  CaO  0.43 0.14  51.56 0.44  0.08 51.49  0.13  52.79 0.47  0.08 51.37  0.13  0.14  0.12  Total  99.92  99.93  100.45  99.45  99.92  100.47  100.18  100.46  100.31  100.02  100.23  100.25  100.02  100.10  100.08  100.22  100.09  Si  1.001  0.999  1.001  0.993  1.006  1.000  0.999  1.000  1.001  0.998  0.999  1.001  1.002  1.000  0.995  0.000  0.000  0.000  0.990 0.002  0.995  Cr  0.000  0.000  0.000  0.000  0.000  0.001  0.000  0.000  0.000  0.001  0.000  0.000  0.001  Fe  0.095  0.097  0.096  0.077  0.087  0.094  0.130  0.131  0.134  0.131  0.126  0.130  0.130  0.117  0.129  0.129  0.125  Mn  0.002  0.002  0.001  0.002  0.002  0.002  0.002  0.002  0.003  0.002  0.003  0.002  0.003  0.002  1.889  1.887  1.923  1.908  1.901  1.845  0.003 1.854  0.002  Mg Ni  0.001 1.892  1.855  1.852  1.858  1.859  1.858  1.867  1.853  1.856  1.869  0.009  0.009  0.010  0.012  0.011  0.012  0.008  0.008  0.008  0.008  0.008  0.008  0.009  0.008  0.009  0.008  0.008  Ca  0.002  0.003  0.003  0.003  0.002  0.003  0.002  0.003  0.003  0.004  0.003  0.003  0.004  0.002  0.003  0.004  0.003  Total  2.999  3.001  2.999  3.007  3.005  3.006  2.993  3.000  3.001  2.998  2.999  3.002  3.001  2.998  2.998  3.000  3.003  Fo  95.2  95.1  95.2  96.2  95.6  95.3  93.4  93.4  93.3  93.4  93.7  93.5  93.4  94.1  93.5  93.5  93.7  Fa  4.8  4.9  4.8  3.8  4.4  4.7  6.6  6.6  6.7  6.6  6.3  6.5  6.6  5.9  6.5  6.5  6.3  Oxides (wt. %) Si0  2  Cr 0 FeO 2  3  MnO MgO  Cations (p.f.u.)  End Members (%)  Crystal textural style is abbreviated: porph. (porphyroclast), cumu. (cumulus), def. (deformed), mgb. (modified grain boundaries) Note: Other phases (cpx, chr) were also analyzed on certain sections, such that "Cluster" refers to a specific location on each section  Appendix Ii (continued): Olivine compositions from olivine-bearing ultramafic lithologies of the Turnagain intrusion  Rock type:  Dunite  Dunite  Sample:  04ES-10-05-01  Cluster:  3  2  Dunite  04ES-10-05-01  04ES-06-01-01  1  1  2  Style:  mgb.  mgb.  mgb.  mgb.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  porph.  porph.  porph.  porph.  porph.  porph.  porph.  Zone:  rim  mid  mid  core  rim  mid  mid  core  rim  mid  core  rim  mid  core  rim  mid  mid  core  41.05  40.72  40.76  41.22  40.43  40.85  41.04  40.90  42.17  41.26  40.86  41.02  41.14  41.06  40.97  40.65  41.29  40.92  0.00  0.00  0.00  0.00  0.01  0.00  0.07  0.00  0.01  0.00  0.01  0.04  0.12  0.09  0.05  0.00  0.01  FeO  8.91  9.47  9.09  8.66  8.85  8.52  8.77  8.42  0.00 3.44  8.91  9.17  8.91  9.33  8.88  9.54  8.92  9.26  9.50  MnO  0.16  0.18  0.16  0.16  0.16  0.12  0.12  0.43  0.15  0.17  0.18  0.21  0.15  0.17  0.21  0.14  0.14  MgO  Oxides (wt. %) Si0  2  Cr 0 2  3  49.74  0.18 48.52  49.19  49.55  49.77  49.59  49.61  49.29  48.81  49.83  49.00  49.52  47.90  49.15  0.35  0.30  0.31  0.30  0.30  49.59 0.41  54.63  0.29  49.78 0.27  49.58  NiO  0.00  0.30  0.31  0.34  0.29  0.35  0.29  0.29  0.31  CaO  0.17  0.06  0.02  0.05  0.05  0.05  0.05  0.02  0.13  0.06  0.25  0.04  0.30  0.02  0.66  0.05  Total  100.33  0.25 99.49  0.35 0.07  99.59  99.92  99.55  99.45  100.13  99.48  100.69  100.33  100.24  99.79  100.12  100.37  100.41  99.67  99.55  100.08  Cations (p.f.u.) Si Cr  1.000  1.003  1.001  1.006  0.993  1.001  1.000  1.002  0.998  1.004  0.997  1.004  1.005  0.998  1.014  1.001  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.001  0.002  0.001  0.000  0.000  Fe  0.181  0.195  0.187  0.177  0.182  0.175  0.001 0.179  1.000 0.002  0.997  0.000  0.172  0.068  0.181  0.187  0.182  0.191  0.181  0.195  0.183  0.190  0.194  Mn  0.003  0.004  0.004  0.003  0.003  0.003  0.002  0.002  0.003  0.004  0.004  0.004  0.003  0.003  0.004  0.003  Mg Ni  1.806  1.782  1.800  1.802  1.822  1.812  1.808  1.811  0.009 1.927  1.799  1.805  1.798  1.806  1.783  1.810  1.755  0.006  0.007  0.006  0.006  0.005  0.006  0.006  0.008  0.000  0.007  0.006  0.006  1.778 0.007  0.003 1.792  0.006  0.007  0.006  0.006  0.006  0.004  0.007  0.002  0.000  0.001  0.001  0.001  0.000  0.002  0.003  0.002  0.007  0.001  0.008  0.001  0.017  0.001  3.000  2.997  2.999  2.994  0.001 3.007  2.999  2.997  2.998  3.002  2.996  3.003  2.996  2.993  2.997  2.997  3.001  2.985  2.998  Fo  90.9  90.1  90.6  91.1  90.9  91.2  91.0  90.8  90.6  90.8  90.3  90.9  90.2  90.2  9.9  9.4  8.9  9.1  8.8  9.0  3.4  9.2  9.4  9.2  9.7  9.1  9.8  90.8 9.2  90.2  9.1  91.3 8.7  96.6  Fa  9.8  9.8  Ca Total End Members (%)  Crystal textural style is abbreviated: porph. (porphyroclast), cumu. (cumulus), def. (deformed), mgb. (modified grain boundaries) Note: Other phases (cpx, chr) were also analyzed on certain sections, such that "Cluster" refers to a specific location on each section  Appendix II (continued): Olivine compositions from olivine-bearing ultramafic lithologies of the Turnagain intrusion  Rock type:  Dunite  Dunite  Sample:  04ES-06-01-01  Cluster:  3  Dunite 04ES-03-02-01  04ES-08-01-01 2  1  1  3  2  Style:  mgb.  mgb.  mgb.  mgb.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  Zone:  rim  mid  mid  core  rim  mid  core  rim  mid  core  rim  mid  core  rim  mid  core  rim  mid  40.99  41.04  41.02  41.44  40.78  40.87  40.78  40.86  40.66  40.85  40.78  41.02  40.79  41.25  40.85  40.91  40.72  40.84  0.00  0.00  0.00  0.03  0.03  0.08  0.00  0.02  0.06  0.01  0.00  0.02  0.00  0.02  0.01  0.00  0.00  8.98  9.10  9.29  0.02 7.67  10.23  10.09  10.12  9.08  9.70  10.31  9.46  9.99  9.88  8.20  9.14  9.35  9.28  9.08  0.20  0.20  0.19  0.17  0.16  0.15  0.17  0.18  0.17  0.14  0.20  0.12  0.16  0.16  0.14  0.14  0.14  49.31  49.16  50.77  48.45  48.53  49.53  0.16 48.77  48.67  49.32  48.88  48.97  50.10  49.39  49.37  49.58  49.40  cumu..  Oxides (wt. %) Si0  2  Cr 0 FeO 2  3  MnO MgO NiO  0.27  49.53 0.27  0.32  0.13  48.56 0.14  0.10  0.07  0.12  0.03  0.14  0.11  0.02  0.00  0.17  0.15  0.10  0.18  0.15  0.11  0.17  0.18  0.16 0.17  0.16  0.00  0.06 0.07  0.12  0.15  0.13 0.16  0.05  CaO  0.16  0.15  0.10 0.14  Total  99.91  100.14  100.00  100.20  100.07  99.88  99.89  99.85  99.57  100.35  99.85  100.41  100.06  99.83  99.89  100.06  100.03  99.70  Cations (p.f.u.) Si  1.002  1.002  1.003  1.003  1.001  1.004  1.001  1.000  1.000  1.000  0.999  1.002  0.999  1.004  1.000  1.000  0.996  1.001  Cr  0.000  0.000  0.000  0.000  0.001  0.002  0.000  0.000  0.001  0.000  0.000  0.000  0.000  0.000  0.000  0.186  0.190  0.155  0.210  0.207  0.186  0.200  0.211  0.194  0.204  0.202  0.187  0.191  0.190  0.186  Mn  0.004  0.004  0.004  0.003  0.003  0.003  0.208 0.004  0.000 0.167  0.000  Fe  0.000 0.184  0.004  0.003  0.004  0.003  0.004  0.002  0.003  0.003  0.003  0.003  0.003  Mg Ni  1.798  1.802  1.793  1.832  1.777  1.774  1.776  1.807  1.789  1.776  1.801  1.780  1.789  1.818  1.802  1.799  1.808  1.804  0.005  0.005  0.006  0.002  0.003  0.003  0.001  0.002  0.001  0.002  0.001  0.003  0.002  0.001  0.003  0.002  0.003  0.002  Ca  0.004  0.000  0.004  0.004  0.004  0.003  0.005  0.004  0.003  0.004  0.005  0.004  2.996  2.998  2.995  2.995  3.000  2.999  2.998  3.001  2.998  2.996  3.000  3.000  0.004 3.004  0.004  2.998  0.005 3.000  0.002  2.997  0.001 2.997  0.000  Total  Fo  90.7  90.7  90.4  92.2  89.4  89.5  89.5  90.7  90.0  89.4  89.8  91.6  90.6  90.4  90.5  90.7  9.3  9.3  9.6  7.8  10.6  10.5  10.5  9.3  10.0  10.6  90.3 9.7  89.7  Fa  10.3  10.2  8.4  9.4  9.6  9.5  9.3  2.999  End Members (%)  Crystal textural style is abbreviated: porph. (porphyroclast), cumu. (cumulus), def. (deformed), mgb. (modified grain boundaries) Note: Other phases (cpx, chr) were also analyzed on certain sections, such that "Cluster" refers to a specific location on each section  Appendix II (continued): Olivine compositions from olivine-bearing ultramafic lithologies of the Turnagain intrusion  Rock type:  Dunite  Dunite  Wehrlite  Sample:  04ES-03-02-01  Cluster:  2  3  Style:  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  porph.  porph.  porph.  porph.  porph.  porph.  porph.  Zone:  core  rim  mid  core  rim  core  rim  mid  core  rim  core  rim  mid  mid  mid  core  mid  mid  40.85  40.74  41.67  41.56  41.48  41.45  41.22  41.45  41.31  40.91  40.27  40.70  40.16  40.47  40.16  40.38  0.01  40.49 0.04  41.00  0.05  0.02  0.00  0.03  0.04  0.03  0.00  0.01  0.00  0.01  0.00  0.00  0.00  7.34  9.00  8.57  7.66  7.51  7.85  7.36  7.56  7.02  8.87  10.58  9.66  0.02 10.87  0.06  9.35  0.03 7.44  10.46  10.88  9.84  MnO  0.20  0.23  0.15  0.16  0.21  0.12  0.19  0.16  0.21  0.12  0.33  0.19  0.21  0.22  0.32  49.63  49.99 0.12  49.13  50.88  51.00  50.39  51.18  51.00  0.22  0.13  0.25  0.25  48.68 0.31  0.11 98.54  0.18  0.02  0.03  0.34  0.08  0.04  0.06  0.00  0.03  0.05  0.04  0.04  0.39 0.02  47.60 0.27  48.79  0.25  48.03 0.27  47.85  0.17  51.08 0.21  49.57  0.09 0.15  50.85 0.27  0.21 47.94  0.21  MgO  0.16 49.97  99.09  99.96  100.55  100.58  100.43  100.48  100.06  100.41  99.75  99.95  99.39  99.61  99.52  04ES-10-06-01  04ES-19-01-02 1  3  2  4  5  Oxides (wt. %) Si0  2  Cr 0 FeO 2  3  NiO  0.12  CaO  0.10  Total  100.31  0.10  0.36  0.31  0.03  0.03  99.56  99.15  99.67  Cations (p.f.u.) Si  0.996  1.002  0.998  1.000  1.005  1.002  1.003  1.000  0.999  1.002  1.002  1.000  0.998  1.002  0.996  1.000  0.999  0.995  Cr  0.001  0.000  0.001  0.000  0.000  0.001  0.001  0.000  0.001  0.000  0.000  0.000  0.000  0.000  0.000  0.001  0.000  0.000  0.175  0.155  0.151  0.159  0.150  0.149  0.153  0.142  0.181  0.219  0.199  0.226  0.216  0.226  0.203  0.004  0.002  0.004  0.003  0.004  0.002  0.007  0.004  0.004  0.005  0.004  0.004  0.007  1.833  1.817  1.840  1.842  1.832  1.847  1.806  1.774  1.786  1.769 0.007  1.767  1.765  1.793  0.008  0.005  0.006  Fe  0.191  0.151  0.186  Mn  0.004  0.005  0.003  0.003  Mg Ni  1.804  1.833  1.806  1.816  0.003 1.829  0.002  0.002  0.002  0.002  0.003  0.005  0.004  0.002  0.005  0.005  0.004  0.005  0.005  0.006  0.003  0.003 2.997  0.005  0.004  0.000  0.001  0.009  0.002  0.000  0.001  0.001  0.001  2.995  2.997  2.995  2.999  2.998  2.998  3.000  3.002  3.003  0.001 2.997  0.001  3.000  0.001 2.998  0.001  3.000  0.001 3.000  0.002  3.002  3.001  3.005  Fo  90.4  92.4  90.7  91.2  92.2  92.4  92.0  92.5  92.5  90.9  89.0  90.0  88.7  89.1  88.6  89.8  Fa  7.6  9.3  8.8  7.8  7.6  8.0  7.5  7.5  92.3 7.7  92.8  9.6  7.2  9.1  11.0  10.0  11.3  10.9  11.4  10.2  Ca Total End Members (%)  Crystal textural style is abbreviated: porph. (porphyroclast), cumu. (cumulus), def. (deformed), mgb. (modified grain boundaries) Note: Other phases (cpx, chr) were also analyzed on certain sections, such that "Cluster" refers to a specific location on each section  Appendix II (continued): Olivine compositions from olivine-bearing ultramafic lithologies of the Turnagain intrusion  Wehrlite  Wehrlite  Rock type:  Wehrlite  Sample:  04ES-10-06-01  Cluster:  4  3  Style:  porph.  porph.  porph.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  porph.  porph.  porph.  porph.  Zone:  core  rim  mid  rim  mid  mid  core  rim  mid  core  rim  mid  mid  core  rim  mid  mid  mid  40.43  40.42  40.55  40.38  40.23  40.07  40.51  40.68  40.71  41.00  40.39  40.45  40.37  40.07  40.23  40.38  0.00  0.00  40.61 0.04  40.47  0.02  0.07  0.02  0.00  0.03  0.01  0.02  0.03  0.01  0.04  0.00  0.02  0.04  0.00  0.02  11.16  11.13  11.04  11.67  11.52  11.66  11.67  11.11  11.69  10.95  10.13  11.28  10.65  12.93  13.15  13.51  13.08  0.20 47.79  0.21  0.18  0.18  0.21  0.21  0.26  0.25  0.25  0.23  0.24  0.27  0.21  0.32  47.23  47.36  47.06  0.22 47.32  11.14 0.21  46.86  47.62  47.74  47.91  48.98  47.68  48.12  46.06  46.31  45.86  46.15  04ES-11-03-03  04ES-16-08-01 4  2  2  5  Oxides (wt. %) Si0  2  Cr 0 FeO 2  3  MnO  0.21  0.18  MgO  47.54  NiO  47.50 0.26  0.18  0.16  0.22  0.22  0.09  0.31  0.23  0.17  0.19  0.10  0.16  0.15  0.02  0.05  0.13 0.14  0.23  0.02  0.35 0.04  0.16  CaO  0.05  0.08  0.05  0.09  0.06  0.03  0.03  0.06  0.08  0.01  0.01  0.03  0.03  Total  99.60  99.63  99.98  99.96  99.88  99.59  99.69  98.49  100.34  100.07  99.99  100.72  99.91  99.69  99.82  99.96  99.99  100.13  0.35  Cations (p.f.u.) Si  1.002  1.001  1.001  1.004  1.001  1.003  0.998  1.004  0.999  1.002  1.003  1.000  0.998  0.999  1.005  0.998  1.003  1.003  Cr  0.000  0.000  0.000  0.001  0.001  0.000  0.000  0.001  0.000  0.001  0.000  0.000  0.000  0.231  0.228  0.241  0.238  0.242  0.242  0.233  0.230  0.226  0.233  0.220  0.269  0.001 0.274  0.000  0.231 0.004  0.000 0.207  0.001  Fe  0.000 0.241  0.282  0.272  0.004  0.004  0.004  0.004  0.004  0.005  0.004  0.004  0.004  0.006  0.005  0.005  0.005  0.005  0.006  0.004  0.007  1.757  1.772  1.720  1.704  1.710  0.004  0.003  1.710 0.004  0.002  0.003  0.003  Mn Mg Ni  1.754  1.756  1.758  1.740  1.746  1.742  1.751  1.749  1.750  1.754  1.759  0.005  0.007  0.007  0.003  0.003  0.005  0.004  0.003  0.004  0.004  0.002  1.781 0.006  Ca  0.001  0.001  0.001  0.001  0.004  0.001  0.002  0.002  0.001  0.001  0.002  0.002  0.000  0.000  2.998  2.999  2.999  2.995  2.996  0.001 2.997  0.002  Total  3.002  2.995  3.001  2.997  2.996  3.000  3.000  3.001  2.994  3.000  0.001 2.997  2.996  Fo  88.4  88.4  88.5  87.8  88.0  87.8  87.8  88.3  87.9  88.4  11.6  11.5  12.2  12.0  12.2  12.2  11.7  12.1  11.6  89.6 10.4  88.3 11.7  86.4  11.6  88.6 11.4  89.0  Fa  11.0  13.6  86.3 13.7  85.8 14.2  86.3 13.7  0.001  End Members (%)  Crystal textural style is abbreviated: porph. (porphyroclast), cumu. (cumulus), def. (deformed), mgb. (modified grain boundaries) Note: Other phases (cpx, chr) were also analyzed on certain sections, such that "Cluster" refers to a specific location on each section  Appendix II (continued): Olivine compositions from olivine-bearing ultramafic lithologies of the Turnagain intrusion  Rock type:  Wehrlite  Wehriite  Sample:  04ES-11-03-03  Cluster:  2  4  Style:  porph.  porph.  porph.  porph.  porph.  porph.  porph.  porph.  porph.  porph.  porph.  porph.  porph.  cumu.  cumu.  cumu.  cumu.  porph.  Zone:  core  rim  mid  mid  core  rim  mid  mid  core  rim  mid  mid  core  rim  mid  mid  core  rim  39.82  40.18 0.04  40.68  40.93  40.58  40.17  40.03  40.10  40.17  40.06  39.91  40.02  40.23  40.29  39.86  39.81  39.88  39.98  0.01  0.00  0.02  0.02  0.00  0.00  0.01  0.00  0.00  0.02  0.00  0.00  0.06  0.03  12.93  12.45  11.91  10.13  12.28  13.54  13.48  13.55  13.90  0.00 12.69  13.18  12.98  12.98  9.51  12.40  12.77  0.00 12.97  13.12  0.27  0.24  0.30  0.32  45.76  46.11  45.71  45.50 0.20  04ES-09-01-01 1  5  4  3  Oxides (wt. %) Si0  2  Cr 0 FeO 2  3  0.00  MnO  0.55  0.32  0.36  0.34  0.29  0.29  0.26  46.48  46.95  46.62  45.82  0.18 45.41  45.79  45.67  0.22 44.44  0.10  0.18  45.53 0.12  45.58  0.15  47.90 0.16  0.26 45.47  0.19  45.48 0.32  0.28 45.24  0.24  MgO  0.16  0.21  0.16  0.20  0.25  0.20  0.22  0.19  0.26  0.04  0.01  0.02  0.04  0.02  0.04  0.04  0.01  0.03  0.05  0.05  0.03  0.01  0.01  0.20 0.04  0.22  CaO  0.01  0.02  0.11  Total  99.14  99.64  100.01  99.51  99.99  99.69  99.54  99.41  100.00  99.09  98.98  99.28  99.31  94.67  98.59  99.18  99.15  99.23  NiO  0.28  Cations (p.f.u.) Si  1.002  1.001  1.006  1.009  1.006  1.005  1.003  1.006  1.003  1.003  1.007  1.039  1.004  0.999  1.002  1.004  0.000  0.001  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.001  0.001  0.000  0.000  0.272  0.259  0.246  0.209  0.283  0.282  0.000 0.284  0.000  Fe  0.000 0.254  1.005 0.000  1.004  Cr  0.290  0.266  0.277  0.272  0.272  0.205  0.261  0.268  0.273  0.275  Mn  0.012  0.007  0.007  0.007  0.006  0.006  0.005  0.006  0.006  0.006  0.004  0.005  0.004  0.005  0.006  0.006  0.007  Mg Ni  1.705  1.726  1.731  1.760  1.723  1.698  1.702  1.692  1.693  1.713  1.704  1.705  1.708  1.717  1.712  1.703  0.006  0.003  0.002  0.003  0.004  0.003  0.003  0.004  0.003  0.004  0.005  1.711 0.004  0.005 1.724  0.004  0.004  0.004  0.004  0.005  0.004  Ca  0.001  0.000  0.000  0.001  0.001  0.000  0.001  0.000  2.995  2.997  2.994  2.995  2.996  2.993  2.961  0.000 3.000  0.003  2.993  0.001 2.994  0.001  2.990  0.001 2.996  0.000  2.997  0.001 2.997  0.001  2.998  0.000 2.994  0.001  Total  2.998  2:996  Fo  86.2  86.9  87.5  89.4  87.1  85.7  85.8  86.6  86.0  86.3  86.2  89.3  86.8  86.6  13.8  13.1  12.5  10.6  12.9  14.3  14.2  85.6 14.4  85.4  Fa  14.6  13.4  14.0  13.7  13.8  10.7  13.2  13.4  86.3 13.7  86.1 13.9  End Members (%)  Crystal textural style is abbreviated: porph. (porphyroclast), cumu. (cumulus), def. (deformed), mgb. (modified grain boundaries) Note: Other phases (cpx, chr) were also analyzed on certain sections, such that "Cluster" refers to a specific location on each section  Appendix II (continued): Olivine compositions from olivine-bearing ultramafic lithologies of the Turnagain intrusion  Rock type:  Wehrlite  Wehrlite  Olivine Cpxite  Sample:  04ES-09-01-01  04ES-15-01-05  Cluster:  4  1  4  04ES-06-06-01 1  5  Style:  porph.  porph.  porph.  def.  def.  def.  def.  cumu.  cumu.  cumu.  cumu.  cumu.  mgb.  mgb.  mgb.  mgb.  cumu.  cumu.  Zone:  mid  mid  core  rim  mid  mid  core  rim  mid  mid  mid  core  rim  mid  mid  core  rim  mid  39.83  39.78  39.92  40.53  40.69  40.72  40.49  40.77  40.45  40.33  40.67  40.76  40.97  40.79  39.92  40.09  0.00  0.00  0.02  0.02  0.01  0.00  0.04  0.00  0.00  0.00  0.04  0.00  0.00  0.04  0.02  12.40  13.07  10.79  11.50  10.48  0.00 11.17  40.51 0.00  40.50  0.00 12.78  11.21  10.92  11.67  11.37  11.50  8.10  10.95  10.68  10.28  12.96  12.87  0.15 48.30  0.24  0.22  0.23  0.21  0.22  0.21  0.28  0.24  0.25  0.23  48.32  48.08  47.69  47.73  47.79  49.85  47.90  0.19 47.97  0.24  47.53  48.27  46.30  46.01 0.04  Oxides (wt. %) Si0  2  Cr 0 2  3  FeO MnO  0.21  0.24  0.19  0.22  MgO  45.66  45.72  45.64  47.80  0.18 47.44  NiO  0.18  0.25  0.19  0.27  0.29  0.29  0.38  0.32  0.02  0.08  0.05  0.06  0.07  0.07  0.07  0.25 0.04  0.29  0.02  0.18 0.04  0.27  0.02  0.28 0.04  0.32  0.00  0.23 0.04  0.27  CaO  0.08  0.05  0.10 0.03  Total  98.67  98.41  99.04  99.65  100.22  100.00  99.88  100.79  100.04  100.24  100.39  100.65  99.46  99.89  99.69  99.92  99.61  0.04 99.31  Cations (p.f.u.) Si  1.004  1.004  1.003  1.002  1.003  1.001  1.001  0.998  0.997  0.996  1.001  1.001  1.002  1.000  1.001  1.003  0.997  1.003  Cr  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  0.001  0.000  0.269  0.262  0.275  0.223  0.216  0.231  0.000 0.229  0.001  Fe  0.000 0.237  0.225  0.241  0.234  0.236  0.166  0.226  0.221  0.211  0.271  0.269  Mn  0.005  0.005  0.004  0.004  0.003  0.005  0.004  0.005  0.004  0.006  0.005  0.004  0.005  1.720  1.744  1.771  1.764  1.767  1.756  1.751  1.749  1.818  1.763  1.767  1.770  Ni  0.004  0.005  1.710 0.004  0.005 1.724  0.005  1.715  0.005 1.752  0.005  Mg  0.005 1.762 0.005  0.006  0.006  0.007  0.005  0.006  0.005  0.006  0.006  0.004  0.005  0.005  0.006  0.002  0.001  Ca  0.000  0.001  0.002  0.001  0.002  0.001  0.001  0.002  0.002  0.002  0.001  0.001  0.002  0.001  2.997  2.997  2.996  2.998  2.999  3.002  3.001  3.004  2.999  2.999  2.997  3.000  2.999  0.001 2.997  0.001  2.996  0.001 2.996  0.001  Total  3.001  2.996  Fo  86.4  86.8  86.2  88.8  88.0  89.1  88.4  88.5  88.7  87.9  88.2  88.1  88.9  89.3  86.4  86.4  13.6  13.2  13.8  11.2  12.0  10.9  11.6  11.5  11.3  12.1  11.8  11.9  91.6 8.4  88.6  Fa  11.4  11.1  10.7  13.6  13.6  1.716  End Members (%)  Crystal textural style is abbreviated: porph. (porphyroclast), cumu. (cumulus), def. (deformed), mgb. (modified grain boundaries) Note: Other phases (cpx, chr) were also analyzed on certain sections, such that "Cluster" refers to a specific location on each section  Appendix II (continued): Olivine compositions from olivine-bearing ultramafic lithologies of the Turnagain intrusion  Rock type:  Olivine Clinopyroxenite  Sample:  04ES-06-06-01  Cluster:  1  Olivine Clinopyroxenite 05ES-05-01-01 4  3  4  3  Style:  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  Zone:  mid  mid  core  rim  mid  mid  core  rim  mid  mid  mid  core  rim  mid  core  rim  mid  core  40.38  40.13  40.32  40.36  40.44  40.13  40.28  40.35  40.35  40.24  40.44  40.23  39.14  39.25  39.23  39.22  39.43  39.17  0.02  0.00  0.02  0.02  0.00  0.02  0.05  0.04  0.00  0.00  0.00  0.00  0.00  0.01  0.00  0.01  0.02  12.65  12.36  13.14  12.80  0.05 12.15  12.72  12.98  12.66  12.60  12.76  12.68  12.89  15.51  15.55  15.59  14.95  15.63  15.61  Oxides (wt. %) Si0 Cr 0 2  2  3  FeO MnO  0.24  0.22  0.21  0.26  0.33  0.22  0.23  0.21  0.25  0.21  0.22  0.26  0.30  0.26  0.24  0.23  0.26  0.22  MgO NiO  46.43 0.07  46.41  46.53  46.25  46.78  46.66  46.34  46.13  45.79  45.66  46.39  44.13  44.10  44.02  44.46  44.21  44.25  0.10  0.05  0.08  0.09  0.06  0.06  0.03  46.58 0.03  0.09  0.10  0.10  0.13  0.03  0.05  0.03  0.02  0.01  0.01  0.03  0.03  0.02  0.35  0.04  0.06  0.11 0.00  0.08 0.03  0.14  0.03  0.12 0.02  0.08  CaO  0.01  0.02  Total  99.83  99.24  100.33  99.79  99.86  99.81  99.92  99.46  99.87  99.11  99.44  99.90  99.27  99.29  99.19  98.98  99.62  99.44  Cations (p.f.u.) Si  1.004  1.003  1.000  1.005  1.003  0.999  1.002  1.006  1.002  1.008  1.010  1.001  0.994  0.996  0.997  0.996  0.997  0.993  Cr  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  0.263  0.258  0.272  0.266  0.265  0.270  0.001 0.264  0.001  Fe  0.001 0.252  0.262  0.267  0.265  0.268  0.329  0.330  0.331  0.318  0.331  0.331  Mn  0.005  0.005  0.005  0.005  0.007  0.005  0.005  0.004  0.005  0.004  0.005  0.005  0.005  0.005  0.005  1.721  1.729  1.720  1.716  1.730  1.731  1.718  1.715  1.725  1.710  1.700  1.721  1.669  1.667  1.683  0.006 1.667  0.005  Mg Ni  0.006 1.671  0.001  0.002  0.001  0.002  0.002  0.001  0.001  0.001  0.001  0.002  0.002  0.002  0.003  0.002  0.002  0.002  0.002  0.003  Ca  0.001  0.001  0.001  0.000  0.001  0.001  0.002  0.001  0.000  0.001  2.995  3.001  2.992  2.996  2.990  2.999  3.006  3.004  3.003  0.001 3.004  0.000  2.995  0.000 2.992  0.009  2.999  0.000 2.997  0.001  2.995  0.001 2.997  0.001  Total  3.003  3.006  Fo  86.7  87.0  86.4  86.7  86.5  86.5  83.5  83.5  83.4  84.1  83.4  83.5  13.3  13.6  13.3  86.8 13.2  86.5  13.0  87.3 12.7  86.7  13.3  86.3 13.7  86.6  Fa  13.5  13.5  13.5  16.5  16.5  16.6  15.9  16.6  16.5  1.673  End Members (%) 13.4  Crystal textural style is abbreviated: porph. (porphyroclast), cumu. (cumulus), def. (deformed), mgb. (modified grain boundaries) Note: Other phases (cpx, chr) were also analyzed on certain sections, such that "Cluster" refers to a specific location on each section  Appendix II (continued): Olivine compositions from olivine-bearing ultramafic lithologies of the Turnagain intrusion  Rock type:  Olivine Clinopyroxenite  Sample:  Olivine Clinopyroxenite  04ES-01-04-01  04ES-01-04-01 4  3  5  1  Style:  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  cumu.  Zone:  mid  rim  mid  core  rim  mid  core  rim  mid  core  39.23 0.02  40.44  40.18  40.31  40.52  40.36  40.10  40.19  39.94  0.01  0.01  0.02  0.00  0.00  0.05 12.41  0.00  0.00  40.43 0.02  12.94  12.76  12.88  0.18 46.30  0.21  0.21  46.59  46.61 0.12  Cluster:  Oxides (wt. %) Si0  2  Cr 0 FeO 2  3  15.67  12.27  12.73  12.75  11.37  12.47  MnO  0.24  0.16  0.22  0.21  0.21  MgO  43.96  46.38  46.67  46.55  0.22 47.29  46.59  0.19 46.97  NiO  0.12  0.09  0.11  0.05  0.07  0.02  0.06  0.16  0.07  CaO  0.03  0.00  0.03  0.05  0.02  0.02  0.05  0.01  0.04  0.03  Total  99.27  99.35  99.95  99.95  99.50  99.68  99.82  99.78  99.61  100.30  Cations (p.f.u.) Si  0.996  1.008  0.999  1.001  1.005  1.004  0.996  1.001  0.997  1.001  Cr  0.000  0.000  0.000  0.000  0.000  0.000  0.001  0.000  0.000  Fe  0.333  0.256  0.265  0.265  0.236  0.259  0.258  0.270  0.266  0.000 0.267  Mn  0.005  0.003  0.005  0.004  0.005  0.004  0.004  0.004  0.004  0.004  Mg Ni  1.665  1.723  1.729  1.724  1.748  1.728  1.740  1.720  1.733  1.721  0.002  0.002  0.002  0.001  0.001  0.000  0.001  0.003  0.001  0.002  Ca  0.001  0.000  0.001  0.001  0.000  0.001  0.001  0.000  0.001  0.001  Total  3.003  2.992  3.001  2.998  2.995  2.996  3.002  2.998  3.003  2.998  83.3 16.7  87.1  86.7  86.7  88.1  86.9  87.1  86.4  86.7  86.6  12.9  13.3  13.3  11.9  13.1  12.9  13.6  13.3  13.4  End Members (%) Fo Fa  Crystal textural style is abbreviated: porph. (porphyroclast), cumu. (cumulus), def. (deformed), mgb. (modified grain boundaries) Note: Other phases (cpx, chr) were also analyzed on certain sections, such that "Cluster" refers to a specific location on each section  oc  Appendix III: Clinopyroxene compositions from clinopyroxene-bearing ultramafic lithologies of the Turnagain intrusion  Rock Type:  Dunite  Wehrlite  Sample: Cluster:  04ES-08-01-01 n/a  04ES-10-06-01 1.  Style: Zone: Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 FeO* MnO MgO CaO Na 0 Total 2  2  2  3  2  3  2  Cations (p.f.u.) Si Ti Al" Al " Cr Fe" Fe" Mn Mg Ca Na Total v)  | v  End Members (%) Wo En Fs Mg#  Wehrlite 04ES-15-01-05 2  3  2  5  3  inter, mid  inter, core  cumu. rim  cumu. mid  cumu. core  cumu. rim  cumu. mid  cumu. core  cumu. rim  cumu. mid  cumu. core  inter. rim  inter, mid  inter, core  inter, rim  inter, mid  inter, core  inter, rim  54.46 0.07 0.92 0.47 2.38 0.06 16.92 24.49 0.37 100.15  52.28 0.09 0.90 0.61 2.79 0.03 16.59 25.03 0.41 98.73  54.02 0.17 1.17 0.58 3.03 0.07 17.66 23.24 0.25 100.20  53.50 0.16 1.11 0.73 2.70 0.10 17.53 23.69 0.29 99.81  54.01 0.19 1.10 0.68 2.73 0.13 17.60 23.25 0.28 99.98  52.14 0.14 1.06 0.65 4.93 0.09 17.39 22.49 0.26 99.14  53.96 0.15 1.17 0.65 2.88 0.11 17.52 23.16 0.26 99.87  53.60 0.15 1.32 0.82 2.89 0.09 17.46 23.12 0.31 99.75  53.69 0.15 1.10 0.51 3.61 0.14 17.42 22.80 0.23 99.66  53.09 0.16 1.03 0.43 4.60 0.10 16.78 22.16 0.24 98.60  53.69 0.16 1.10 0.57 3.19 0.10 17.44 22.94 0.26 99.46  52.48 0.27 1.54 0.85 2.28 0.07 17.90 23.11 0.23 98.73  53.64 0.30 1.33 0.88 2.48 0.11 17.22 23.72 0.26 99.94  53.61 0.34 1.45 0.85 2.43 0.04 17.06 23.80 0.28 99.87  53.16 0.39 1.45 0.87 2.41 0.08 17.00 24.04 0.28 99.68  54.32 0.25 1.05 0.70 2.67 0.09 17.63 23.46 0.25 100.42  53.53 0.30 1.35 0.94 2.85 0.05 17.33 23.40 0.29 100.05  52.76 0.26 1.22 0.76 2.59 0.04 17.45 23.59 0.26 98.92  1.964 0.005 0.036 0.014 0.017 0.004 0.088 0.002 0.958 0.905 0.009 4.002  1.956 0.004 0.044 0.004 0.021 0.019 0.063 0.003 0.956 0.928 0.010 4.010  1.962 0.004 0.038 0.008 0.021 0.009 0.073 0.002 0.940 0.938 0.009 4.004  1.967 0.005 0.033 0.014 0.019 0.000 0.083 0.004 0.956 0.907 0.010 3.999  1.968 0.004 0.032 0.018 0.019 0.000 0.088 0.003 0.953 0.905 0.009 3.998  1.959 0.004 0.041 0.016 0.024 0.004 0.084 0.003 0.951 0.905 0.011 4.002  1.966 0.004 0.034 0.014 0.015 0.005 0.106 0.004 0.951 0.895 0.008 4.002  1.972 0.004 0.028 0.017 0.013 0.000 0.143 0.003 0.929 0.882 0.009 3.999  1.968 0.004 0.032 0.015 0.016 0.001 0.097 0.003 0.953 0.901 0.009 4.000  1.963 0.005 0.037 0.006 0.016 0.012 0.111 0.004 0.969 0.874 0.008 4.006  1.978 0.003 0.022 0.011 0.019 0.000 0.099 0.004 0.954 0.899 0.007 3.996  1.963 0.003 0.037 0.000 0.017 0.021 0.088 0.004 1.002 0.869 0.007 4.011  1.978 0.004 0.022 0.010 0.014 0.000 0.087 0.004 0.955 0.916 0.007 3.998  1.974 0.004 0.026 0.010 0.011 0.004 0.087 0.004 0.940 0.935 0.007 4.002  1.975 0.003 0.025 0.013 0.014 0.000 0.098 0.004 0.940 0.920 0.006 3.999  1.972 0.003 0.028 0.013 0.017 0.000 0.098 0.002 0.947 0.912 0.008 4.000  1.984 0.002 0.016 0.005 0.008 0.003 0.094 0.003 0.947 0.935 0.004 4.002  1.972 0.004 0.028 0.019 0.018 0.000 0.103 0.004 0.949 0.891 0.007 3.995  49.1 47.2 3.7  50.9 47.0 2.2  46.4 49.1 4.5  47.7 49.1 3.2  46.6 49.1 4.3  45.5 49.0 5.5  46.5 49.0 4.5  46.7 49.0 4.3  45.8 48.7 5.4  45.1 47.5 7.3  46.2 48.8 5.0  47.1 50.8 2.1  47.8 48.3 3.9  48.2 48.0 3.8  48.7 47.9 3.5  46.9 49.0 4.2  47.1 48.6 4.3  47.9 49.3 2.8  0.936  0.927  0.920  0.898  0.919  0.901  0.870  0.907  0.896  0.910  0.906  0.918  0.915  0.914  0.905  0.907  0.909  0.903  Crystal textural style is abbreviated: cumu. (cumulus), inter, (intercumulus) Note: Other phases (ol, chr, mt) were also analyzed on certain sections, such that "Cluster" refers to a specific location on each thin section * Total Fe  Appendix 111 (continued): Clinopyroxene compositions from clinopyroxene-bearing ultramafic lithologies of the Turnagain intrusion  Wehrlite  Rock Type:  Wehrlite  Wehrlite  Cluster:  04ES-15-01-05 5  04ES-16-08-01 1  Style: Zone: Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 FeO* MnO MgO CaO Na 0 Total 2  2  2  3  2  3  2  Cations (p.f.u.) Si Ti Al" ' Al " Cr Fe" Fe'* Mn Mg Ca Na Total v  , v  End Members (%) Wo En Fs Mg#  04ES-11-03-03 1  5  3  6  3  inter. mid  inter. core  inter. rim  inter. mid  inter. core  inter. rim  inter. mid  inter. core  inter. rim  inter. mid  inter. core  inter. rim  inter. mid  inter. core  inter. mid  inter. . core  inter. rim  inter. mid  inter. core  53.60 0.33 1.40 1.10 2.54 0.07 17.32 23.68 0.30 100.35  53.39 0.31 1.38 0.88 2.43 0.05 17.31 23.58 0.33 99.66  54.36 0.13 0.68 0.50 2.93 0.08 17.84 23.56 0.24 100.33  54.21 0.10 0.51 0.54 3.22 0.05 18.16 23.17 0.22 100.19  53.91 0.19 1.07 0.71 3.70 0.10 17.37 23.31 0.22 100.57  52.85 0.16 1.31 0.75 2.99 0.09 18.33 22.33 0.24 99.06  53.94 0.19 0.95 0.79 3.12 0.12 17.63 23.64 0.26 100.63  53.35 0.18 1.01 0.73 3.23 0.11 17.37 23.02 0.25 99.26  53.43 0.16 1.05 0.64 2.93 0.09 17.95 22.98 0.23 99.48  53.17 0.24 1.17 0.75 3.63 0.10 17.10 22.90 0.25 99.32  53.72 0.27 1.20 0.68 3.53 0.13 17.14 23.15 0.23 100.05  54.14 0.14 0.68 0.46 3.18 0.13 17.35 24.07 0.20 100.36  54.61 0.16 0.78 0.42 2.86 0.09 17.48 24.04 0.20 100.64  54.35 0.13 0.71 0.37 2.70 0.15 17.68 24.18 0.20 100.47  54.16 0.14 0.88 0.60 3.30 0.12 17.60 23.08 0.30 100.18  54.60 0.12 0.77 0.50 3.28 0.08 17.70 23.05 0.29 100.38  54.20 0.14 0.78 0.42 3.02 0.12 17.61 23.61 0.27 100.17  54.41 0.17 0.95 0.57 3.52 0.12 17.55 22.61 0.29 100.19  54.03 0.19 0.93 0.53 3.54 0.17 17.64 22.67 0.29 100.00  1.969 0.005 0.031 0.011 0.019 0.000 0.107 0.004 0.955 0.891 0.008 4.000  1.967 0.004 0.033 0.024 0.020 0.000 0.103 0.003 0.956 0.874 0.009 3.995  1.964 0.005 0.036 0.011 0.020 0.002 0.106 0.002 0.953 0.895 0.007 4.001  1.974 0.003 0.026 0.012 0.018 0.000 0.102 0.003 0.951 0.903 0.008 3.999  1.936 0.007 0.064 0.004 0.025 0.029 0.042 0.002 0.984 0.914 0.008 4.014  1.956 0.008 0.044 0.013 0.025 0.000 0.076 0.003 0.937 0.927 0.009 3.999  1.956 0.009 0.044 0.018 0.025 0.000 0.074 0.001 0.928 0.930 0.010 3.996  1.947 0.011 0.053 0.010 0.025 0.007 0.067 0.002 0.928 0.944 0.010 4.003  1.969 0.007 0.031 0.014 0.020 0.000 0.081 0.003 0.952 0.911 0.009 3.996  1.952 0.008 0.048 0.010 0.027 0.004 0.083 0.002 0.943 0.914 0.010 4.002  1.947 . 1.949 0.007 0.009 0.053 0.051 0.009 0.000 0.022 0.032 0.025 0.003 0.055 0.074 0.002 0.001 0.960 0.939 0.923 0.933 0.009 0.011 4.001 4.013  1.953 0.009 0.047 0.013 0.025 0.003 0.071 0.002 0.944 0.924 0.012 4.002  1.961 0.006 0.039 0.010 0.015 0.010 0.113 0.005 0.928 0.909 0.009 4.005  1.961 0.006 0.039 0.010 0.014 0.015 0.108 0.004 0.939 0.901 0.011 4.007  1.965 0.005 0.035 0.005 0.012 0.016 0.102 0.005 0.937 0.917 0.008 4.008  1.960 0.007 0.040 0.009 0.015 0.012 0.120 0.004 0.946 0.885 0.009 4.006  1.961 0.006 0.039 0.004 0.010 0.021 0.095 0.003 0.934 0.927 0.009 4.011  1.953 0.007 0.047 0.006 0.017 0.019 0.107 0.004 0.936 0.903 0.010 4.009  47.7 48.5 3.8  47.7 48.7 3.6  46.7 49.2 4.1  45.8 49.9 4.3  46.5 48.2 5.3  45.3 51.7 3.0  47.1 48.9 4.0  46.5 48.8 4.6  46.2 50.2 3.6  46.4 48.2 5.4  46.5 47.9 5.5  47.8 48.0 4.2  47.5 48.1 4.4  47.9 48.7 3.4  46.1 48.9 5.0  45.9 49.0 5.1  47.0 48.8 4.2  45.4 49.1 5.5  45.4 49.2 5.4  0.898  0.930  0.903  0.903  0.902  0.960  0.927  0.928  0.936  0.921  0.918  0.945  0.927  0.931  0.894  0.899  0.903  0.888  0.910  Crystal textural style is abbreviated: cumu. (cumulus), inter, (intercumulus) Note: Other phases (ol, chr, mt) were also analyzed on certain sections, such that "Cluster" refers to a specific location on each thin section * Total Fe  Appendix III (continued): Clinopyroxene compositions from clinopyroxene-bearing ultramafic lithologies of the Turnagain intrusion  Rock Type:  Wehrlite  ;  Sample: Cluster:  04ES-09-01-01 2  Olivine Clinopyroxenite 04ES-06-06-01 2  6  5  6  5  Style: Zone:  inter, mid  inter, core  inter, rim  inter, mid  inter, core  inter, rim  inter, mid  inter, core  numu. rim  cumu. mid  cumu. core  cumu. rim  cumu. mid  cumu. mid  cumu. mid  cumu. core  cumu. rim  cumu. mid  cumu. mid  Oxides (wt. %) Si0 Ti0 Al 0 Cr 0 FeO* MnO MgO CaO Na 0 Total  53.50 0.24 1.16 0.62 3.17 0.14 17.19 23.35 0.26 99.61  53.99 0.24 0.86 0.46 3.29 0.12 17.08 23.71 0.22 99.96  54.78 0.08 0.25 0.13 2.06 0.10 17.46 25.03 0.05 99.94  54.27 0.12 0.36 0.16 2.83 0.09 17.66 24.11 0.12 99.71  54.42 0.06 0.41 0.20 3.02 0.08 17.40 24.18 0.13 99.89  54.33 0.10 0.32 0.16 2.22 0.08 17.59 24.67 0.11 99.58  54.31 0.17 0.49 0.26 2.57 0.12 17.64 24.30 0.14 100.00  54.37 0.12 0.34 0.15 2.33 0.11 17.49 24.69 0.12 99.72  53.76 0.19 1.00 0.56 4.03 0.14 17.80 22.34 0.23 100.05  54.38 0.11 0.78 0.66 3.27 0.12 17.59 23.06 0.20 100.16  53.83 0.12 0.85 0.60 3.56 0.12 18.43 22.25 0.21 99.97  54.19 0.16 0.74 0.48 2.86 0.13 17.54 23.43 0.20 99.74  54.21 0.14 0.84 0.40 3.02 0.12 17.32 23.97 0.19 100.21  53.96 0.11 0.88 0.50 3.19 0.12 17.24 23.47 0.18 99.66  54.64 0.08 0.50 0.28 3.21 0.11 17.49 24.03 0.12 100.47  54.14 0.14 1.08 0.61 3.39 0.14 17.47 22.83 0.19 99.99  54.16 0.20 0.98 0.65 3.51 0.15 17.62 22.87 0.23 100.34  53.96 0.15 1.33 0.70 3.39 0.10 17.60 22.38 0.26 99.87  54.04 0.18 1.09 0.70 3.56 0.07 17.59 22.98 0.20 100.41  1.957 0.006 0.043 0.006 0.016 0.019 0.111 0.005 0.950 0.886 0.011 4.010  1.964 0.006 0.036 0.012 0.012 0.011 0.111 0.004 0.928 0.912 0.010 4.005  1.958 0.007 0.042 0.010 0.016 0.013 0.122 0.003 0.951 0.875 0.010 4.007  1.958 0.005 0.042 0.011 0.012 0.017 0.115 0.005 0.956 0.879 0.008 4.009  1.974 0.004 0.026 0.004 0.014 0.009 0.080 0.003 0.966 0.917 0.008 4.004  1.973 0.003 0.027 0.000 0.015 0.014 0.084 0.001 0.985 0.904 0.008 4.015  1.961 0.005 0.039 0.006 0.020 0.010 0.103 0.003 0.942 0.908 0.008 4.005  1.944 0.004 0.056 0.001 0.022 0.033 0.059 0.003 1.005 0.880 0.009 4.016  1.959 0.005 0.041 0.000 0.023 0.017 0.077 0.004 0.954 0.920 0.009 4.009  1.962 0.005 0.038 0.006 0.021 0.009 0.090 0.004 0.953 0.907 0.009 4.004  1.958 0.005 0.042 0.003 0.019 0.020 0.070 0.003 0.980 0.902 0.008 4.010  1.958 0.007 0.042 0.009 0.022 0.007 0.105 0.003 0.939 0.904 0.009 4.004  1.962 0.007 0.038 0.013 0.020 0.000 0.108 0.004 0.933 0.906 0.008 3.999  1.982 0.002 0.018 0.021 0.013 0.000 0.072 0.002 0.918 0.955 0.013 3.997  1.976 0.003 0.024 0.011 0.018 0.000 0.095 0.003 0.968 0.891 0.008 3.998  1.976 0.003 0.024 0.010 0.020 0.000 0.106 0.004 0.966 0.881 0.008 3.998  1.978 0.003 0.022 0.008 0.017 0.000 0.100 0.002 0.981 0.880 0.007 3.999  1.966 0.003 0.034 0.002 0.026 0.010 0.091 0.005 0.971 0.888 0.009 4.005  1.970 0.002 0.030 0.002 0.028 0.006 0.091 0.004 0.974 0.887 0.009 4.003  47.1 48.2 4.7  47.4 47.5 5.1  49.1 47.7 3.2  47.6 48.5 3.9  47.8 47.8 4.4  48.7 48.3 3.0  48.0 48.5 3.5  48.8 48.1 3.2  44.7 49.6 5.7  46.0 48.9 5.1  44.4 51.1 4.5  46.8 48.7 4.5  47.6 47.9 4.5  47.0 48.0 5.0  47.3 47.9 4.8  45.9 48.8 5.3  45.6 48.9 5.5  45.2 49.5 5.4  45.8 48.8 5.4  0.895  0.894  0.886  0.893  0.922  0.919  0.903  0.942  0.926  0.931  0.905  0.899  0.956  0.929  0.909  0.900  0.9