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The giant mascot ultramafite and its related ores McLeod, James Albert 1975

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THE GIANT MASCOT ULTRAMAFITE AND ITS RELATED ORES by JAMES ALBERT McLEOD B.A.Sc., U n i v e r s i t y of B r i t i s h Columbia, 1969 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTERS OF APPLIED SCIENCE i n the Department of GEOLOGICAL SCIENCES We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA Jul y , 1975 In presenting th i s thes i s in pa r t i a l fu l f i lment o f the requirements for an advanced degree at the Univers i ty of B r i t i s h Columbia, I agree that the L ibrary sha l l make it f ree ly ava i lab le for reference and study. I fur ther agree that permission for extensive copying of th i s thesis for scho lar ly purposes may be granted by the Head of my Department or by his representat ives . It is understood that copying or pub l i ca t ion of this thes is for f i nanc i a l gain sha l l not be allowed without my written permission. Department of f-r £ o i t)C > f <xA *b C \ e f U € <. J The Univers i ty of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 i A B S T R A C T T h e G i a n t M a s c o t U l t r a m a f i t e i s o n t h e s o u t h e a s t e r n f l a n k o f t h e C o a s t C r y s t a l l i n e B e l t 1 0 0 m i l e s e a s t o f V a n c o u v e r , B . C . I t i s r o u g h l y e l l i p t i c a l ( 1 x 2 m i . ) , c r u d e l y z o n e d r a n g i n g f r o m p e r i d o t i t e t h r o u g h p y r o x e n i t e a n d h o r n -b l e n d e - p y r o x e n i t e t o m a r g i n a l h o r n b l e n d i t e . I t i s e n c l o s e d i n d i o r i t i c r o c k s o f t h e S p u z z u m I n t r u s i o n s . T w e n t y - e i g h t p i p e - l i k e o r e b o d i e s w i t h i n t h e u l t r a m a f i t e h a v e b e e n m i n e d f o r t h e i r m a s s i v e N i - C u o r e s . S t u d i e s o n t h e 3 0 5 0 l e v e l c r o s s - c u t s h o w t h a t s i l i c a t e s a n d s u l f i d e s i n p y r o x e n i t e s d i f f e r i n c o m p o s i t i o n f r o m t h o s e i n p e r l d o t i t e s . F u r t h e r m o r e , p e n t -l a n d i t e f r o m o r e b o d i e s d i f f e r s i n c o m p o s i t i o n f r o m a c c e s s o r y p e n t l a n d i t e ' i n u l t r a b a s i c r o c k s . K - A r d a t i n g y i e l d s m i n i m u m a g e s f o r o r e b o d i e s a n d u l t r a m a f i t e r a n g i n g f r o m 1 0 4 m . y . t o 1 1 9 m . y , H o r n b l e n d i t e d y k e s , t h e y o u n g e s t r o c k s i n t h e Eiine a r e d a t e d a t 9 5 m . y . K - A r a g e s o f S p u z z u m D i o r i t e n e a r t h e m i n e a n d s e v e r a l m i l e s t o t h e s o u t h a r e 8 9 m . y , T o n a l i t e , a b o r d e r p h a s e o f t h e S p u z z u m I n t r u s i o n s , y i e l d s a h o r n b l e n d e a g e o f 8 5 m . y . a n d a b i o t i t e a g e o f 7 9 m . y . , c o n s i s t e n t w i t h e a r l i e r i n v e s t i g a t i o n s . T e m p e r a t u r e s c a l c u l a t e d f r o m 1 5 c o e x i s t i n g c l i n o - a n d o r t h o p y r o x e n e p a i r s f r o m t h e 3 0 5 0 l e v e l c r o s s - c u t a v e r a g e 9 9 0 ° C f o r e q u i l i b r a t i o n o f t h e s e s i l i c a t e s . D i s t r i b u t i o n c o e f f i c i e n t s (mean K j ) = 0 . 7 3 8 ) f o r t h e s e s i l i c a t e s s u g g e s t a m a g m a t i c o r i g i n . T h e C l i m a x a n d C h i n a m a n o r e b o d i e s o n the 3 0 5 0 l e v e l c r o s s - c u t a r e s t e e p l y p l u n g i n g p i p e - l i k e , b o d i e s w i t h h i g h e r g r a d e s e c t i o n s c o n c e n t r a t e d i n t h e t r o u g h o r f o o t w a l l . T h e y a r e f o u n d a t p e r i d o t i t e - p y r o x e n i t e c o n t a c t s a n d a p p e a r s p a t i a l l y r e l a t e d t o n o r i t e . I t i s c o n c l u d e d t h a t t h e G i a n t M a s c o t U l t r a m a f i t e o r i g i n a t e d b y c l i a p i r i c r e - e m p l a c e m e n t o f c r u d e l y s t r a t i f o r m c r y s t a l m u s h e s a n d s u l f i d e m e l t s f r o m a d i f f e r e n t i a t i n g sub-volcanic magma chamber, p o s s i b l y an e a r l y phase of Spuzzum magmatic a c t i v i t y . This m a t e r i a l was subsequently engulfed by r i s i n g Spuzzum d i o r i t i c magmas which superimposed a hornblendite rim 01 the u l t r a m a f i t e . I l l TABLE OF CONTENTS page A b s t r a c t i Acknowledgements i i i I n t r o d u c t i o n 1 ( i ) L o c a t i o n 1 ( i i ) General Statement 1 ( i i i ) H i s t o r y 1 (iv) Previous I n v e s t i g a t i o n s 2 Regional Geology 4 (i ) Regional S e t t i n g 4 ( i i ) S t r a t i f i e d Rocks 4 ( i i i ) Metasedimentary Rocks 5 (iv) Gneiss 6 (v) G r a n i t o i d Rocks 6 (vi) U l t r a m a f i t e s 6 ( v i i ) S t r u c t u r e s 7 L o c a l Geology 9 (i ) I n t r o d u c t i o n 9 ( i i ) Metamorphic Rocks 9 ( i i i ) U l t r a b a s i c Rocks 10 (iv) F e l d s p a t h i c Rocks 11 (v) Orebodies 11 Pet r o l o g y of the 3050 L e v e l Cross-Cut 13 ( i ) General Statement 13 ( i i ) C l a s s i f i c a t i o n of Rock Types 13 iv page ( i i i ) D e s c r i p t i o n of Rock Types 14 (1) . N o r i t e 14 (2) U l t r a b a s i c Rocks 16 M i n e r a l i z a t i o n and Orebodies 25 ( i ) I n t r o d u c t i o n 25 ( i i ) Disseminated S u l f i d e s 25 ( i i i ) Net-Textured S u l f i d e s 27 (iv) Massive S u l f i d e s 28 (v) T e x t u r a l R e l a t i o n s Between the Various S u l f i d e s 31 (vi) Paragenesis 31 ( v i i ) Climax Orebody 38 ( v i i i ) Chinaman Orebody 4 0 Chemical Analyses of S i l i c a t e s and S u l f i d e s 48 ( i ) S i l i c a t e A n a l y t i c a l Techniques 48 ( i i ) S i l i c a t e Analyses 48 ( i i i ) S u l f i d e A n a l y t i c a l Techniques '. . . . 53 (iv) S u l f i d e Analyses 53 Thermal H i s t o r y of the U l t r a b a s i c Complex 58 (i ) I n t r o d u c t i o n 58 ( i i ) Methods 60 ( i i i ) D i s c u s s i o n and I n t e r p r e t a t i o n 70 O r i g i n of the U l t r a m a f i t e and i t s Ores 73 Conclusions 83 References C i t e d . 85 page Appendix 1. - Sample L o c a t i o n Map 89 Appendix 2. - Geology of Climax, 3050 L e v e l 90 Appendix 3. - Cu, N i , and Cu/(Cu+Ni) Assay Contour Maps of Chinaman and Climax Orebodies 9 2 Appendix 4. - Microprobe Analyses of S i l i c a t e s 108 Appendix 5. - Microprobe Analyses of S u l f i d e s 117 Appendix 6. - U n i v e r s a l Stage Composition Determinations 123 v i FIGURES page F i g . 1. L o c a t i o n and Tectonic Map of B.C 3 F i g . 2. Generalized Geology of the Northern Cascades Region 5 F i g . 3. Geology and M i n e r a l i z a t i o n (Giant Mascot Mine) 10 F i g . 4. C l a s s i f i c a t i o n and Nomenclature of U l t r a m a f i c Rocks 14 F i g . 5. Photograph of N o r i t e - P y r o x e n i t e Contact .... 17 F i g . 6. Photograph of Complex Age R e l a t i o n s h i p of N o r i t e to U l t r a b a s i c Rocks 17 F i g . 7. Photomicrograph of S t r a i n e d O l i v i n e Grains . 18 F i g . 8. Photomicrograph of Cumulus-Like O l i v i n e s • i n P o i k i l i t i c Grain of Hornblende 18 F i g . 9. Photomicrograph of Cumulus-Like Orthopyroxenes i n P o i k i l i t i c Hornblende .... 19 F i g . 10. Photograph of Sharp Contact at 7260 N. (Websterite and O l i v i n e - R i c h Pyroxenite) ... 23 F i g . 11. Photomicrograph of O l i v i n e Grains i n Hornblende 23 F i g . 12. Photograph of Fine Grained Hornblendite Dyke C u t t i n g Another Hornblendite Dyke 2 4 F i g . 13. Photograph of One Foot Wide Hornblendite Dyke w i t h Reaction Margin 24 v i i page F i g . 14. Photomicrograph of I n t e r s t i t i a l Po-Pn-Cpy Grains i n Fresh Pyroxenite 26 F i g . 15. Photomicrograph of Composite Po-Cpy Bleb and Magnetite Grain Enclosed i n O l i v i n e .... 26 F i g . 16. Photomicrograph of Net-Textured S u l f i d e s ... 29 F i g . 17. Photomicrograph of Massive S u l f i d e s 29 F i g . 18. Photograph of P r o t o c l a s t i c Texture of Chinaman Ore 30 F i g . 19. Photomicrograph of Cpy on Edge of Composite Gr a i n Separated from Po by Pn 30 F i g . 20. Photomicrograph of C h a l c o p y r i t e Replacing F r a c t u r e s i n S i l i c a t e s 32 F i g . 21. Schematic 1000°C Isothermal Diagram of the Cu-Fe-Ni-S System 33 F i g . 22. Schematic 850° Isothermal Diagram of the Cu-Fe-Ni-S System 35 F i g . 23. Low Temperature M i n e r a l Assemblages i n Ni-Cu Ores 36 F i g . 24. Apparant Paragenesis 37 F i g . 25. Ni Contour P l o t of Climax Ore at 3108' E l e v a t i o n , i n Percent 41 F i g . 26. Cu Contour P l o t of Climax Ore at 3108' E l e v a t i o n , i n Percent 41 F i g . 27. Cu / (Cu+Ni) P l o t of Climax Ore at 3108' E l e v a t i o n , R a t i o i n Percent 42 v i i i page F i g . 28. Ni Contour Plot of Chinaman Ore at 3160' Elevation, i n Percent 44 F i g . 29. Cu Contour Plot of Chinaman Ore at 3160' Elevation, i n Percent 45 F i g . 30. Cu / (Cu+Ni) Plot of Chinaman Ore at 3160' Elevation, Ratio i n Percent 46 F i g . 31. Quadrilateral Plot of Pyroxene Com-positions 3050 Cross-Cut 50 F i g . 32. Elemental V a r i a t i o n i n Orthopyroxene 3050 Cross-Cut 51 F i g . 33. Elemental Var i a t i o n i n Clinopyroxene 3050 Cross-Cut 52 F i g . 34. Fe-Ni-S Plots of Coexisting Pyrrhotite and Pentlandite • • • • 54 F i g . 35. Elemental Var i a t i o n i n Pentlandite 3050 Cross-Cut 56 F i g . 36. Mg and Fe D i s t r i b u t i o n C o e f f i c i e n t (Kp) - of Pyroxenes at Giant Mascot , 59 F i g . 37. Location of K-Ar Dating at Giant Mascot .... 66 F i g . 38. Location of K-Ar Dating of Spuzzum Plutonic Rocks 69 i x TABLES p a g e TABLE 1. - C l i m a x O r e C a l c u l a t i o n s 39 TABLE 2. - C h i n a m a n O r e C a l c u l a t i o n s 4 3 TABLE 3. - T e m p e r a t u r e D a t a o f C o e x i s t i n g P y r o x e n e P a i r s a n d K Q V a l u e s 62 TABLE 4. - K - A r S a m p l e s a n d A n a l y t i c a l R e s u l t s F o r U l t r a b a s i c a n d P l u t o n i c R o c k s a t t h e G i a n t M a s c o t P r o p e r t y , n e a r Hope, B.C. 72 ACKNOWLEDGEMENTS This thesis was done under the kind supervision of Dr. K.C. McTaggart to whom the author i s very indebted. Giant Mascot Mines Ltd., i s thanked f o r t h e i r f i n a n c i a l assistance and f o r providing f u l l access to the Giant Mascot Mine. In a d d i t i o n , Mr. F. Holland (mine general manager), Mr. L. DeRoux (chief mine geologist) and Mr. R. Gonzales (exploration geologist) are thanked f o r t h e i r help and h o s p i t a l i t y . Mr. D.P. Moore's invaluable assistance i n underground mapping and sampling and h i s asjtute observations are g r a t e f u l l y appreciated. His p h y s i c a l support made t h i s work p o s s i b l e . Dr. T.H. Brown i s thanked for h i s help and advice i n connection with the departments microprobe. Mr. A. L a c i s of the Department of Metallurgy i s thanked f o r h i s help i n the operation of that departments microprobe. Also., Mr. J . Harakal's help i n K-Ar age determinations i s appreciated. Dr. P. Christopher of the B.C. Department of Mines and Petroleum Resources was of, assistance i n supplying some data about the Giant Mascot Mine. Appreciation i s extended to the t e c h n i c a l s t a f f of the department f o r t h e i r generous "behind the scenes" help and to Ann Carr f o r typing t h i s manuscript. The author wishes to extend h i s g r a t i t u d e to a l l those f r i e n d s and colleagues whose moral support proved invaluable and, i n p a r t i c u l a r , to h i s wife Joanne. INTRODUCTION Location Giant Mascot Mine l i e s 7 miles northwest of the town of Hope, B.C. and 90 miles east of Vancouver, ( l a t i t u d e 49° 28' W., and longitude 121° 30' W). Access from Hope i s by paved highway f o r 7 miles and then 5 miles of gravel road which winds westward i n t o the rugged Coast Range mountains. General Statement The subject of t h i s study i s the geology and m i n e r a l i z a t i o n along the 3050 cross-cut, which give access to the two most re c e n t l y worked orebodies of Giant Mascot mine, - the Climax and the Chinaman. The w r i t e r and a colleague spent approximately three weeks ..during the spring of 1973 mapping and sampling the cross-cut and assembling mine records of the area of i n t e r e s t . A d d i t i o n a l sampling and specimen c o l l e c t i o n were made l a t e r during s e v e r a l b r i e f v i s i t s to the mine. Thin-sections and polished sections were studied under the microscope, and by e l e c t r o n microprobe, and K-Ar ages were determined fo r u l t r a b a s i c rocks which contain the ore deposits and f o r the surrounding p l u t o n i c rocks. H i s t o r y ' • :. The showings of the Giant Mascot property were discovered i n 1923. Exploration work was c a r r i e d on between 1923 and 1937 and again between 1951 and 1954. The property was brought into prod-uction i n 1958 and operated c o n t i n u a l l y u n t i l shut down i n September 1974. Previous Investigations E a r l y i n v e s t i g a t o r s include Cairnes (1924), C o c k f i e l d and Walker (1933), and Horwood (1937). Their conclusions are i n considerable c o n f l i c t with regard to the o r i g i n of the u l t r a b a s i c rocks and cont-ained m i n e r a l i z a t i o n and the r e l a t i o n s h i p of ultramafites to the surrounding d i o r i t e s . Aho (1956) provides the most d e t a i l e d and comprehensive account of the u l t r a m a f i t e , the orebodies, and t h e i r genesis. Recently, Muir (1971) studied the 4600 orebody at Giant . Mascot. The Department of Mines and Petroleum Resources has s t a r t e d a new i n v e s t i a g i o n of the mine. 3 4 REGIONAL GEOLOGY Regional Set t i n g The u l t r a b a s i c complex at Giant Mascot mine l i e s at the south-eastern flank of the Coast C r y s t a l l i n e B e l t , near the junction of the Coast and Cascade mountain systems ( F i g . 1). The Coast Cryst-a l l i n e B e l t i s one of uniform stra t i g r a p h y , structure and metallogeny as defined by Sutherland-Brown et. a l . , (1971). A map ( F i g . 2) i l l u s t r a t e s the various rock units present i n the region and these rock units are described below. S t r a t i f i e d Rocks Hozameen Group This w e l l s t r a t i f i e d group flanks the b a t h o l i t i c rocks on the east s i d e . The Group consists of p e l i t i c rocks, chert, b a s i c v o l c a n i c rocks and limestone that have been r e g i o n a l l y metamorphosed i n general to a low grade but l o c a l l y to high grade. Most e a r l y w r i t e r s b e l i e v e d the rocks to be l a t e Paleozoic, but Monger (1970) suggests that they may be as young as T r i a s s i c . C h i l l i w a c k Group The l i t h o l o g y of the Chilliwack Group i s more c l a s t i c than that of the Hozameen Group. S t r a t i g r a p h i c u n i t s are mostly p e l i t e s , sand-stones, and s i l t s t o n e s with l e s s e r v o l c a n i c rock. This group l i e s to the immediate west of b a t h o l i t i c rocks described and i s b e l i e v e d to be Pennsylvanian and Permian i n age. Metamorphism i s mostly low grade r e g i o n a l , but high grades are encountered i n the north. GRAN IT IC PLUTONS [ 7 3 L A T E T E R T I A R Y M ID -TERT IARY 1+ +| C R E T A C E O U S ? \Q<y\ J U R A S S I C ? PERIDOTITE LAYERED ROCKS C - C H U C K A N U T GP J -K - J U R A S S I C - C R E T \ t M - M E S O Z O I C . \ Gw'chon BathotiD* 0. P - P A L E O Z O I C ( 2 2 1 G N E I S S A From McTaggart (1970) F i g u e 2 : G e n e r a l i z e d geology o f the N o r t h e r n C a s c a d e s R e g i o n . | CHILLIWACK GR Evfl H O Z A M E E N GR Metasedimentary and Metavolcanic Rocks North of the Fraser River near Hope, p e l i t i c s c h i s t , p h y l l i t e and amphibolite o f high grade Barrovian s t y l e metamorphism a d j o i n the Scuzzy and Spuzzum plutons. The age of these rocks i s uncertain, but on the b a s i s of composition they are probably formed from the Upper Paleozoic Hozameen Group. The age of metamorphism i s thought to be roughly contemporaneous with Late Cretaceous plutonism (McTaggart and Thompson, 1967). Read (1960) suggested that meta-morphism preceded plutonism, as s t a u r o l i t e and s i l l i m a n i t e isograds do not p a r a l l e l the contact of the Spuzzum Pluton. 6 Gneiss In the Hope area the Custer Gneiss l i e s between metasedimentary, metavolcanic, and b a t h o l i t i c rocks to the west and the Hozameen Group and diminishes to the north i n a wedge-like fashion. This rock c o n s i s t s of layered amphibolite, l e u c o c r a t i c gneiss, augen gneiss, minor marble and trondhjemite pegmatite.. The age of the gneiss i s uncertain. Zircons dated by Mattinson (1970) y i e l d Precambriah ages and he suggests an episode of metamorphism and migmatization i n the Upper Cretaceous. Granitoid Rocks The Spuzzum and Scuzzy Pluton i n the north.and the C h i l l i w a c k Pluton i n the south form a north-trending heterogeneous b e l t of g r a n i t i c rocks passing j u s t west of Hope and Yale. The Spuzzum Pluton, which consists of d i o r i t e and t o n a l i t e i s considered Late Cretaceous (Richards, 1971) and has been c l a s s i f i e d as catazonal to mesozonal. The contiguous Scuzzy Pluton to the north i s described (Roddick and Hutchison, 1969) as a granodiorite, but has d e f i n i t e trondhjemite trend. The age of t h i s pluton i s Late Cretaceous (Hutchison, 1970). Richards (1971) describes the l a t e Cenozoic C h i l l i w a c k Pluton as having up to nine phases, but c o n s i s t i n g mainly of quartz d i o r i t e to g r a n o d i o r i t e . S t r u c t u r a l and t e x t u r a l features and i t s age (26-29 my), suggest that i t was emplaced i n the epizone. Ultramafites Ultramafic rocks l i e to the east and west of the Spuzzum Bath-o l i t h . The eastern body, the Coquihalla Serpentine B e l t (Cairnes, 1930) .7 i s of the alpine type and forms the eastern contact of the Hozameen Group. This b e l t runs from 16 miles south-east of Hope to Boston Bar a distance of 40 miles and consists of serpentine, serepentinized p e r i d o t i t e , pyroxenite and gabbro. The ultramafite and the Hozameen rocks to the west form a t y p i c a l o p h i o l i t e succession and may have been emplaced as an obducted s l i c e . To the west, a le s s well defined b e l t composed of small bodies of pyroxenite, p e r i d o t i t e , hornblendite, dunite and gabbroic rocks appears f a u l t c o n t r o l l e d . North of the Fraser River t h i s f a u l t , the Shuksan Thrust, marks the eastern boundary of the C h i l l i w a c k Group. This b e l t extends from the border to The Old S e t t l e r mountain, then swings abruptly north-west. Much of the u l t r a m a f i c rock i s serpentinized and classed as a l p i n e type. A crudely zoned body ranging from hornblendite through pyroxenite to p e r i d o t i t e l i e s on the very eastern edge, but w i t h i n the Spuzzum d i o r i t e . This body, the Giant Mascot Ultramafite, i s described i n greater d e t a i l i n the following s e c t i o n . E x p l o r a t i o n by Giant Mascot Mines i n the v i c i n i t y of The Old S e t t l e r mountain has revealed u l t r a b a s i c rocks that are t e x t u r a l l y and l i t h o l o g i c a l l y s i m i l a r to the Giant Mascot Ult r a m a f i t e . These rocks are coarse-grained, fresh hornblende pyroxenites and p e r i d o t i t e s . The contact r e l a t i o n s h i p s of these u l t r a m a f i c rocks with the d i o r i t i c rocks tends to be ambiguous and c o n f l i c t i n g (K.C. McTaggart, pers. comm.). Structures The o v e r a l l s t r u c t u r a l trend of the area i s roughly n o r t h e r l y . Major f a u l t systems i n c l u d i n g the Shuksan thrust on the west, the 8 Hope and Yale f a u l t s on the immediate eastern flank of the b a t h o l i t h and the Hozameen f a u l t i n the east a l l trend n o r t h e r l y or northwest. These f a u l t systems i n turn separate and delineate major l i t h o l o g i c a l n ortherly trending b e l t s . Folding tends to be along northwest trending axes. According to Read (pers. comm.) metamorphism increases from both east and west towards the b a t h o l i t h i c rocks of the northern Cascades and south eastern Coast mountains. LOCAL GEOLOGY Introduction The present d e s c r i p t i o n of the geology around the Giant Mascot mine draws on the f i e l d work of several authors, but mainly on the de t a i l e d work of Aho (1956). The Giant Mascot Ultramafite i s approximately 2 miles long i n the east-west d i r e c t i o n and 1 mile wide i n a north-south d i r e c t i o n . In plan the body appears very i r r e g u l a r with many s a l i e n t s and re-entrants with surrounding d i o r i t e . In the southeast corner the complex i s i n contact with, or very close to, high grade metamorphic rocks. A s i m p l i f i e d g e o l o g i c a l plan i s shown i n (Fig. 3) a f t e r Aho (1956). Metamorphic Rocks Metamorphic rocks form i n c l u s i o n s within the u l t r a m a f i t e and the d i o r i t e and may abut the complex on the southeast corner. These rocks are mica s c h i s t s , l o c a l l y with garnet, kyanite or s t a u r o l i t e . They probably are high grade equivalents of the Upper Paleozoic Hozameen Group which they resemble i n composition (Monger, 1970). The rocks belong to the staurolite-almandine subfacies of the almandine-amphi-b o l i t e f a c i e s of Barrovian metamorphism. Contact metamorphism by the ultr a m a f i t e has produced'orthopyroxene subfacies rock of the orthoclase-c o r d i e r i t e - h o r n f e l s f a c i e s (Aho, 1956), believed to i n d i c a t e temper-atures of at l e a s t 600°C. This would i n d i c a t e a s o l i d u s temperature of •at l e a s t 1000°C f o r the ult r a m a f i t e (Winkler, 1967, pp.79-83). 10 , , T -i" i - . i-+ -f + + 4-, J - . + + + +T+ f 4=.< i, f -f- ;- + -!• + /,+ , + ,+ + •• T -V Y / + + ;- + + + + +• + - +• + -f--+- + + -JdfA"1" t- -t- -)-+ + + -+ + + * , + AT, + •+-+ ;+ -r +-+ - f + +-+ , + + -+ -+- + 1 •+ + -t- -h ,+ ,+ + -T , , T- -r- -r- - « + + + + + f- + + + + + , v - f + • + + • + + + + + + + -K^ e •+ + + + + +-+• + + +•+.+ • i i i i i i I _L I M d i r t , M i a o u I I I M M l T t AMD M I N E R A L I S A T I O N P A C I F I C N I C K E L M I N E S 6 C A u t OP r c t T _»000 BOOQ 4 o y g O M C MIL.ft from Aho (1956) Fig.3 U l t r a b a s i c Rocks Aho (1956) was the f i r s t to point out a crude zonation of the u l t r a -basic complex which consists e s s e n t i a l l y of pyroxenite with cores of per-i d o t i t e . The pyroxenite becomes in c r e a s i n g l y hornblendic outwards and a remarkable margin, up to 100 yards wide, of coarse-grained hornblendite i s present at the d i o r i t e - u l t r a b a s i c contact. The r e l a t i v e age of the d i o r i t e and the u l t r a m a f i t e i s unresolved, several authors holding c o n f l i c t i n g opinions. Aho (1956) found that i n a large part the u l t r a b a s i c rocks appear to cut the d i o r i t e s as had been observed by Cairnes (1924). Aho does concede that the reverse r e l a t i o n i s seen i n some places and distinguishes several d i f f e r e n t d i o r i t i c rocks. C o c k f i e l d and Walker (1933) concluded that the u l t r a -basics were intruded by surrounding d i o r i t e . Most authors s t r e s s that there i s a strong genetic r e l a t i o n s h i p between u l t r a b a s i c and the surrounding f e l d s p a t h i c rocks. Feldspathic Rocks The p r i n c i p a l country rock around the ultramafite c o n s i s t s of d i o r i t e , n o r i t e and t o n a l i t e . These rocks generally contain p l a g i o -clase of andesine to l a b r a d o r i t e composition, hypersthene, d i o p s i d i c augite, l e s s e r hornblende and b i o t i t e and a varying amount of quartz. These rocks have been grouped together as part of the complexly d i f f e r e n t i a t e d Spuzzum Pluton of Upper Cretaceous age. Large i n -trusions or xenoliths of d i o r i t e and n o r i t e are present w i t h i n the u l t r a m a f i t e , but t h e i r r e l a t i o n to the Spuzzum pluton i s not c e r t a i n . Orebodies ' . More than 28 orebodies have been located w i t h i n the u l t r a m a f i t e . They occur as steeply plunging, p i p e - l i k e ore zones and have been* c l a s s i f i e d as e i t h e r zoned or massive, (Aho, 1956). The zoned orebodies are c i r c u l a r or e l l i p t i c a l i n plan, pipe-line i n s e c t i o n , x^ith m i n e r a l i z a t i o n c o n c e n t r i c a l l y d i s t r i b u t e d around 12 an o l i v i n e - r i c h core of p e r i d o t i t e or within the core i t s e l f . The pe r i o d i t e gives way to an o l i v i n e pyroxenite and outward to ortho-pyroxenite. M i n e r a l i z a t i o n i s gradational to barren rock. This type of ore was believed to be of replacement o r i g i n . The massive ore-bodies occur as more i r r e g u l a r p i p e - l i k e structures and appear to be unzoned. The ore i s present as a uniform groundmass of s u l f i d e surrounding s i l i c a t e grains at l i t h o l o g i c contacts between various u l t r a m a f i c rock types. These ores generally have sharp contacts with w a l l rock but;may grade into disseminated ores. Commonly these orebodies show marginal "flow l i n e s " , banding, and "drag f o l d i n g " sugg-e s t i v e of magmatic i n j e c t i o n , (Aho, 1956). Aho states that these two categories may be end members of a continuum, as some ore zones have features of both categories. PETROLOGY OF THE 3050 LEVEL CROSS-CUT General Statement The 3050 l e v e l ( F i g . 37) cross-cut was washed and sampled from 6400N to 8600N and mapped at 1" = 20'. Sample l o c a t i o n s and a geologic map of the Climax area are appended. Representative rock samples were chosen f o r t h i n sectioning f o r d e t a i l e d p e t r o l o g i c a l study. M i n e r a l o g i c a l determinations of s i l i c a t e compositions were made by u n i v e r s a l stage and e l e c t r o n probe. C l a s s i f i c a t i o n of Rock Types The following rock c l a s s i f i c a t i o n ( F i g . 4) a f t e r Streckeisen (1967) was used by the author, with s l i g h t m o d i f i c a t i o n s . F e l s i c Rocks: D i o r i t e . . . . . . . . mainly adesine or o l i g o c l a s e , hornblende major mafic. Norite . . . . . . . . . . . . . . mainly bytownite or l a b r a d o r i t e , orthopyroxene major mafic. Hornblendite: . . . . . . . . . . . . . . hornblende, 80 - 100%, p l a g i o c l a s e , 0-20%. 14 horzfcurqite olivine orlhopyroienite / 1 0 OTlhopjTOx^mle Pendotiie's ol ivme cltnopyrOxenile. clinopyroienile Pyroseniles Ultramafic rocks composed cf oli-vine, orthopyroxene, and dinopyroxene. . .; Ultramafic rocks that contain horn-blende. olivine pyroxenites pyroxenites Pendoiiles Pyro*eni1es or.d Homblendiles pyroxene hornblendite hornblendite •'. Classification and nomenclature of (+ Bi + Car + Sp) St 95; opaque min-vitramafic rocks. 01 + Opx + Cpx + Hbl erals =£ 5. F i g . 4 D e s c r i p t i o n o f Rock Types N o r i t e Norite occurs along the 3050 l e v e l cross-cut as inclu s i o n s , host and fragments i n breccia and as apophyses into more basic material. The rock i s medium grained, l i g h t coloured, and shows a strong alignment of mafic minerals. 15 Norite i s composed of i n t e r l o c k i n g subhedral p l a g i o c l a s e l a t h s with mafic content u s u a l l y l e s s than 40%. P l a g i o c l a s e i s as c a l c i c as An90 i n some i n c l u s i o n s and as sodic as An65 i n apophyses. Normal zoning i s accentuated by dust i n c l u s i o n s which lend them a p i n k i s h t i n t . These are probably hematite produced by metamorphism. Very l i t t l e i n t e r -s t i t i a l quartz i s present i n these rocks. Hypersthene, mostly subhedral, the dominant pyroxene, contains " s c h i l l e r " i n c l u s i o n s and patches of clinopyroxene exsolution lamellae. Many of the grains are corroded or rimmed by a pale green, a c t i n o l i t e amphibole or rimmed or replaced by green-brown hornblende. Subordinate anhedral augite forms c l o t s around orthopyroxene and showsvarious stages of replacement from the core to rim by hornblende. Brown to green hornblende i s ubiquitous, rimming or r e p l a c i n g pyroxenes or forming p o i k i l i t i c grains enclosing pyroxenes and plag-i o c l a s e . Magnetite i s present as primary euhedral grains and as a product of a l t e r a t i o n of pyroxenes. Su l f i d e s a r e present i n various amounts, u s u a l l y as wormy, i n t e r s t i t i a l aggregates or blebs. A n o r i t e i n c l u s i o n encountered about 150' south of the Climax ore zone, a few fe e t across i s fresh n o r i t e i n the center becoming i n c r e a s i n g l y f i n e r grained toward the margin, and i s a hornfels at the margin, which intertongues with pyroxenite. The mineralogy i s p l a g i o c l a s e and orthopyroxene and suggests high temperature (700°C) contact metamorphism. From 8000N. to 8350N. many in c l u s i o n s of n o r i t e form sharp ( F i g . 5) to gradational contact with u l t r a b a s i c rock and i n places a c t u a l l y i n -corporate u l t r a b a s i c material. These i n c l u s i o n s and apophyses are usually accompanied by many hornblende-rich c l o t s and dykes. Figure 6 , demonstrates 16 the complex and uncertain age r e l a t i o n s of the n o r i t e with u l t r a b a s i c rock. U l t r a b a s i c Rocks (1) Mineralogy The u l t r a b a s i c rocks encountered i n the 3050 cross-cut contain fresh orthopyroxenes and clinopyroxenes, o l i v i n e s and hornblende. Feld-spars are scarce. A l l minerals except o l i v i n e occur as p o i k i l i t i c grains and a l l minerals except hornblende show some deformation ( F i g . 7). Cumulus-like textures are common e s p e c i a l l y with o l i v i n e and pyroxene-r i c h rocks ( F i g s . 8 and 9). Grain s i z e of these rocks range from f i n e to coarse but are generally medium, that i s 1-5 mm. Grains range from euhedral to anhedral. Pyroxenes grains are subhedral, o l i v i n e s tend to occur as corroded or wormy subhedral grains and hornblende i s present as anhedral p o i k i l i t i c , i n t e r s t i t i a l , or replacement grains. Cumulus-like textures are suggestive of magmatic o r i g i n . The formation of l a r g e p o i k i l i t i c grains of hornblende appear to be by l a t e stage replacement of ortho-and clinopyroxenes. O l i v i n e i n a l l rocks has a range of composition from Fo80 to Fo86 o * with the majority ranging from Fo84-86, (2V x=89±2 ). The more Mg-rich o l i v i n e i s found i n the more o l i v i n e - r i c h p e r i d o t i t e s . O l i v i n e i s cut by serpentine-magnetite v e i n l e t s and shows t y p i c a l "church-window" texture. Boundaries between o l i v i n e s and orthopyroxenes are regular, e s p e c i a l l y when o l i v i n e i s enclosed i n bronzite. Some d i o p s i d e - o l i v i n e boundaries are ragged and show extensive corrosion or a l t e r a t i o n as do hornblende-olivine boundaries. * 2V determined on the unive r s a l stage, compositions from probe and u n i v e r s a l stage. F i g . 5. Sharp contact of n o r i t e with pyroxenite, n o r i t e at top. F i g . 6. Complex age r e l a t i o n s h i p of n o r i t e to u l t r a -b a s i c rocks. Note hornblende pyroxenite i n c l u s i o n i n n o r i t e at hammer. Also top center and center shows pyroxenite fragments i n horn-blende pyroxenite. F i g . 8. Cumulus-like o l i v i n e s i n p o i k i l i t i c grain of hornblende . X10, p l a i n l i g h t . F i g . 9. Cumulus-like orthopyroxenes i n p o i k i l i t i c hornblende. X10, p l a i n l i g h t . Orthopyroxene (En75 - 85) i s the main constituent of the pyro-xenites and the p r i n c i p a l pyroxene i n t h i s area of the u l t r a m a f i t e . Many grains show s c h i l l e r structure with exsolved lamellae and patches of clinopyroxene along cleavage traces. Many grains show a zoning i l l u s t r a t e d by a s l i g h t v a r i a t i o n i n 2V from rim to core. Occasionally, clinopyroxene or hornblende form jackets around orthopyroxenes. Ortho-pyroxene, although much of i t i s a i n t e r l o c k i n g mosaic of grains, may p o i k i l i t i c a l l y enclose o l i v i n e and may be enclosed by a l l other minerals. Clinopyroxene, mostly diopside (determined by microprobe) has a wide range of composition from Mg (44-53), Ca (40-48), and Fe (6-11), (Fig. 32), and i s present i n most pyroxenite and some p e r i d o t i t e . Most diopside i s mottled by hornblende and shows a great degree of replacement * Composition determined by probe and un i v e r s a l stage. 20 by i t . Clinopyroxene i s anhedral and intergranular but much of i t p o i k i l i t i c a l l y encloses bronzite and, i n a few rocks, o l i v i n e . Common hornblende i n the u l t r a b a s i c rocks i s brown to o l i v e green. T e x t u r a l l y i t ranges from mottled replacement patches, i n t e r s t i t i a l to large p o i k i l i t i c grains enclosing a l l types of primary s i l i c a t e s i n c l u d i n g rare p l a g i o c l a s e grains. Pl a g i o c l a s e i n the u l t r a b a s i c rocks and the hornblendites has a composition of An80-90, (bytownite). These grains, generally i n t e r -s t i t i a l , are found i n a few pyroxenites and most hornblendites but never i n o l i v i n e - b e a r i n g rocks. Accessory minerals are chromite and magnetite which both occur as euhedral primary grains within s i l i c a t e s . A l t e r a t i o n products common i n the ultr a m a f i c rocks are phlogopite a f t e r hornblende, c h l o r i t e , t a l c , a c t i n o l i t e - t r e m o l i t e , serpentine, magnetite, antho-p h y l l i t e , and carbonates. (11) Pyroxenite The most common pyroxenite i s a websterite, a medium grained, dark brown rock composed of two pyroxenes, bronzite and diopside. Although the orthorhombic pyroxene i s the more abundant, some rocks contain a greater proportion of clinopyroxene. Websterites predominate from about 6400N. i n the cross-cut to the south side (footwall) of the Climax ore zone ( F i g . 37 and App. 1). In t h i s area hornbleride i s present up to 5% i n a l l the pyroxenites. P l a g i o c l a s e i s very rare but may reach 2-3% i n some rocks. Websterites north of 7560N. and p a r t i c u l a r l y those north, of 8000N., which occur as bodies too small to be shown properly on a map tend to be .rich in hornblende. As the southeast edge of the Chinaman ore zone i s approached hornblende websterites become d e f i c i e n t i n clinopyroxene to the point where they are classed as orthopyroxenites. Pyroxenite grades to p e r i d o t i t e as the proportion of o l i v i n e increases. Minor o l i v i n e i s present i n pyroxenites f o r a distance of about 50' on the south (footwall) side of the Climax orebody. At the orebody the o l i v i n e content i n the rocks increases and the rock i s an o l i v i n e pyroxenite. Near the north edge of the Climax ore zone the rock becomes p e r i o d o t i t i c . In some places the o l i v i n e content changes abruptly, producing sharp contacts as at 7260N. , ( F i g . 10) where the rock changes from a websterite to an o l i v i n e pyroxenite. In most instances i n the more north e r l y sections of the 3050 cro s s -cut, o l i v i n e pyroxenites are modified by abundant hornblende, f r e q -uently p o i k i l i t i c . ( I l l ) P e r i d o t i t e P e r i d o t i t e shows a wide range of appearance depending upon the minerals present and the degree of a l t e r a t i o n . Fresh harzburgites such as those on the hanging w a l l of the Climax orebody are dense, hard, black rocks containing orthopyroxene and o l i v i n e . P o i k i l i t i c , f l a s h y , black, dense rocks found i n the northern part of the cross-cut are hornblende-peridotites containing orthopyroxene, minor c l i n o -pyroxene, hornblende and o l i v i n e . Just north of the Climax orebody for a distance of perhaps 300 feet the rock i s green, s o f t and a l t e r e d and crumbles i n the hand. 22 In such rocks, many of the pyroxenes have been a l t e r e d to hornblende and large plates of phlogopite have formed around o l i v i n e grains ( F i g . 11). In these rocks o l i v i n e shows some s e r p e n t i n i z a t i o n with abundant magnetite t r a i n s but i s s t i l l remarkably f r e s h . U r a l -i t i z a t i o n of pyroxene i s common and c h l o r i t e forms on the ragged edges and boundaries of phlogopite. (IV) Hornblendite Hornblendite occurs as dykes or veins and as large c l o t s or pegmatitic zones e s p e c i a l l y i n the northern Chinaman area of the cross-cut. Fine-grained, dense, black dykes or veins from a few mm. to 5-10 cm. cut a l l rock units and ore zones on the 3050 l e v e l . They have very sharp contacts. They are composed of aligned prismatic hornblende with i n t e r s t i t i a l p l a g i o c l a s e up to 10% (by-townite i n composition), ( F i g . 12). Larger, coarser grained, very i r r e g u l a r , discontinuous hornblende dykes occur mainly i n p r o t o c l a s t i c zones (which are d e s c r i b e d l a t e r ) south of the Chinaman orebody, some showing a r e a c t i o n margin ( F i g . 13). They appear to incorporate or form the host f o r bre c c i a fragments of u l t r a b a s i c and n o r i t e and d i o r i t e rocks; they also traverse such i n c l u s i o n s and appear as i n c l u s i o n s themselves. East of the Chinaman zone large c l o t s of coarse-grained horn-blende-plagioclase pegmatitic material i s present. Hornblende "• c r y s t a l s several inches long are cemented by i n t e r s t i t i a l p l a g i o c l a s e and minor quartz. This zone i s a pos s i b l e r e a c t i o n margin between the pyroxenites on the east edge of the Chinaman orebody and an adjacent n o r i t e revealed by d r i l l i n g to the immediate east. F i g . 11. O l i v i n e grains i n hornblende. Top r i g h t center, phlogopite a f t e r hornblende with i n c i p i e n t c h l o r i t e a l t e r a t i o n . Right s i d e Orthopyroxene unaltered. 10X, p l a i n l i g h t F i g . 12. A f i n e grained hornblendite dyke c u t t i n g another hornblendite dyke and host u l t r a -b a s i c rocks F i g . 13. One fo o t wide hornblendite dyke w i t h r e a c t i o n margin. P r o t o c l a s t i c area on south s i d e of Chinaman ore zone. MINERALIZATION AND OREBODIES Introduction S u l f i d e minerals on the 3050 l e v e l cross-cut occur as d i s -seminated grains, as v e i n l e t s and s c h l i e r e n , and as massive c l o t s a l l e x c l u s i v e l y i n u l t r a b a s i c rocks. The mineralogy i s simple, c o n s i s t i n g of p y r r h o t i t e , pentlandite, c h a l c o p y r i t e , magnetite and very minor p y r i t e . E a r l y i n v e s t i g a t o r s t e n t a n t i v e l y i d e n t i f i e d other Ni-bearing s u l f i d e s but none was seen i n t h i s area of the mine Some secondary or supergene minerals, c h a l c o c i t e , c o v e l l i t e and limonite, coat surfaces on exposed, weathered, s u l f i d e - b e a r i n g rock but a r e ; l o s t during preparation of polished sections. Disseminated S u l f i d e s A l l u l t r a b a s i c rock units within t h i s area of the mine contain the three p r i n c i p a l s u l f i d e s as singular or composite, xenomorphic blebs and i n t e r s t i t i a l f i l l i n g s between fresh euhedral to subhedral grains of o l i v i n e , orthopyroxene and i n some places clinopyroxene (Fig. 14). In many specimens these s u l f i d e s occupy p o s i t i o n s s i m i l a r to those occupied i n other specimens by i n t e r s t i t i a l horn-blende, and may be replaced by hornblende, p o s s i b l e as a l a t e stage magmatic reactio n . The occurrence of the s u l f i d e s i n ultramafi'c rocks resembles that of primary . c r y s t a l l i z a t i o n from an immiscible s u l f i d e phase. This resemblance i s enhanced by the presence of rounded or vermicular blebs of the s u l f i d e enclosed i n unaltered I mm. F i g . 14. I n t e r s t i t i a l po.-pn.-cpy. gr a i n s i n f r e s h p y r o x e n i t e . XI6, p l a i n l i g h t . Composite po.-cpy. bleb and magnetite grain enclosed i n o l i v i n e . X63, p l a i n l i g h t . 27 ' o l i v i n e and orthopyroxene grains ( F i g . 15). The chemical compositions of the accessory p y r r h o t i t e and pentlandite are v a r i a b l e and appear d i r e c t l y r e l a t e d to the l i t h o l o g i c a l u n i t that contains them, as expanded upon i n the following section. The s u l f i d e component appears to undergo a bulk compositional change from Cu- and N i - r i c h composite aggregates i n pyroxenites to more Cu- and Ni-poor aggregates i n the p e r i d o t i t e s . Net-Textured S u l f i d e s Net-texture can be considered an extension of the disseminated type where the s u l f i d e s expand to form a nearly continuous net between s i l i c a t e s , forming an interconnected, lacy texture. The s i l i c a t e s , p a r t i c u l a r l y o l i v i n e and bro n z i t e , are more euhedral than i n the disseminated type, forming unaltered i s o l a t e d c r y s t a l s i n a a l l o t r i o m o r p h i c s u l f i d e groundmass. The s u l f i d e s here appear to occur i n the same manner as the hornblende i n p o i k i l i t i c hornblende pyroxenites and p e r i d o t i t e s ( Fig. 16). The net-texture i s seen to occur i n weakly mineralized areas of the cross-cut, mainly i n pyroxenites, but are best developed and seen i n the low grade sections of the Climax and Chinaman ore zones. In p a r t i c u l a r , the net texture, i s w e l l developed i n the hanging w a l l part of the Climax orebody where o l i v i n e predominates as euhedral c r y s t a l s and also i n the core of the Chinaman ore zone. That these s u l f i d i c net-textured p e r i d o t i t e s can be mined economically i s due i n part to t h e i r proximity to more massive s u l f i d e s . Massive S u l f i d e s Massive s u l f i d e s form most of the ore. The s u l f i d e s form a continuous anhedral groundmass commonly up to 50% of the material present ( F i g . 17). Gangue minerals consist of euhedral c r y s t a l s of o l i v i n e and pyroxene which appear to " f l o a t " i n the s u l f i d e ground-mass. These c r y s t a l s are l a r g e r and b e t t e r developed than those found i n l e s s massive ores. In the Chinaman orebody, which is,, more hornblendic, large c r y s t a l s of hornblende, apparently primary c r y s t a l s , a r e enclosed by massive s u l f i d e s . Some s i l i c a t e c r y s t a l s show corrosion, and p a r t i a l to almost complete replacement. Such features as replacement along cleavages embayments and s k e t e t a l remains may be ascribed to s e l e c t i v e replacement, l a t e magmatic reactions or both. Massive ores, p a r t i c u l a r l y i n the Chinaman zone seem to have been modified by l a t e stage movements of the s u l f i d e minerals producing a p r o t o c l a s t i c texture ( F i g . 18). Fragments of d i s -seminated and net-textured material have been incorporated i n t o the massive s u l f i d e s . These fragments are rimmed by massive s u l f i d s t r i n g e r s and i n some instances appear fra c t u r e d and rehealed by s u l f i d e s t r i n g e r s . The p r o t o c l a s t i c texture led Aho (1956) to suggest a possible hydrothermal o r i g i n f o r the ore minerals. On the other hand, scattered anhedral grains t y p i c a l of primary accessories, euhedral s i l i c a t e s f l o a t i n g i n a groundmass of s u l f i d e and vermicular blebs of s u l f i d e s enclosed i n pyroxenes, 'olivines and e a r l y horn-blende support a magmatic o r i g i n f o r the ore minerals. F i g . 17. Massive s u l f i d e s with euhedral s i l i c a t e s f l o a t i n g " . X60, p l a i n l i g h t . F i g . 18. P r o t o c l a s t i c texture of Chinaman ore, fragments of disseminated and net-textured ore with s u l f i d e schlierenand f r a c t u r e f i l l i by s u l f i d e s . separated from p y r r h o t i t e by p e n t l a n d i t e . X 6 3 , p l a i n l i g h t 31 Te.xtural Relations Between the Various S u l f i d e s Disseminated to massive, p y r r h o t i t e , pentlandite, and c h a l -copyrite are a l l present i n ore samples and have roughly constant proportions, with p y r r h o t i t e the most abundant and chalc o p y r i t e the l e a s t . This proportion appears to be 70:20:10. P y r r h o t i t e forms an i r r e g u l a r , medium- to fine-grained mosaic of composite anhedral grains. Pentlandite usually occurs at p y r r h o t i t e grain boundaries, as does cha l c o p y r i t e , as medium- to fine-grained anhedra and composite masses. In some specimens, chalcopyrite i s seen to be separated from p y r r h o t i t e by pentlandite ( F i g . 19). In some instances pentlandite occurs as i r r e g u l a r blebs w i t h i n p y r r h o t i t e , and c h a l c o p y r i t e appears as cr o s s - c u t t i n g laths i n p y r r h o t i t e . Discontinuous aggregates of p y r r h o t i t e may be connected by pent-l a n d i t e and ch a l c o p y r i t e . Chalcopyrite p r i n c i p a l l y and to a l e s s e r extent pentlandite and p y r r h o t i t e form as c r o s s - c u t t i n g f i l l i n g s or replacements i n fractured s i l i c a t e s , ( F i g . 20), suggesting some remo b i l i z a t i o n of the s u l f i d e s ( F i g . 24). Chalcopyrite i s also seen to cut the other s u l f i d e s , mainly pentlandite. Pentlandite and infrequently chalcopyrite are seen to form l a t h s , flame-like and e x s o l u t i o n - l i k e textures i n p y r r h o t i t e . In the case of c h a l -copyrite, t h i s texture i s usually r e s t r i c t e d to very small, i s o l a t e d , composite s u l f i d e aggregates i n barren rock. , Paragenesis The Cu-Ni-Fe-S mineral assemblage seen at Giant Mascot are those seen at most n i c k e l i f e r o u s . p y r r h o t i t e deposits. Most orebodies Fig. 20. Chalcopyrite replacing fractures i n s i l i c a t e . X160, p l a i n l i g h t . of t h i s type are accepted as being magmatic i n o r i g i n (Craig and Kullerud, 1969) and are formed through unmixing, exsolution and re-eq u i l i b r a t i o n by slow cooling from a monosulfide s o l i d s o l u t i o n . Kullerud, Yund and Moh (1969), and Craig and Kullerud (1969), have made extensive reviews of the phase relations i n the various ternary systems and the quarternary system containing Cu-Ni-Fe-S and have offered several stable isothermal mineral assemblages i n the temper-ature ranges from above 1000°C to below 550°C. The paragenetic sequence seen at the Chinaman and Climax orebodies w i l l be interpreted in the l i g h t of these studies. The average bulk composition of the Giant Mascot ores are believed to l i e within the single phase region of the monosulfide s o l i d solution (Mss) at 1 0 0 0 U C as i l l u s t r a t e d i n f i g u r e 2 1 . This composition was. approximated by the use of s u l f i d e analyses of Horwood ( 1 9 3 7 ) , Aho ( 1 9 5 6 ) Muir ( 1 9 7 1 ) and estimates of p y r r h o t i t e - pentlandite - c h a l -c o p y r i t e proportions by the present author. As these p l o t s are a l l very s i m i l a r to that composition assigned to Sudbury, Hawley ( 1 9 6 2 ) , the Sudbury f i g u r e i s p l o t t e d . V a r i a t i o n s from the Sudbury bulk compositions w i l l account f o r i n d i v i d u a l paragenetic sequences and assemblages. s FIG. 21. Schematic 1,000° C isothermal d i a g r a m of the C u - . F e - X i - S system in the presence of vapor. T i e lines to S l i q u i d are omitted for c lar i ty . N o t e the wide extent of the homogeneous sulfide l iquid (st ippled) and the large region of l iquid i rnmiscibi l i ty (sulfur l i q u i d and sulfide l i q u i d ) . T h e M s s nearly spans the F e - X i - S face of the system. Points designated A and B are discussed in the text . 34 The l i q u i d u s temperature may be as low as 1000 UC at which point a p y r r h o t i t i c n ickel-bearing l i q u i d (Mss, F i g . 21) phase A coexists with a copper-rich l i q u i d , phase B. Upon cooling at some temperature above 850°C i t i s possible f o r a copper-enriched l i q u i d to segregate from the Mss and form two s u l f i d e phases, a N i - p y r r h o t i t e s o l i d s o l u t i o n and a chalcopyrite s o l i d s o l u t i o n (Cpss). This mechanism may account f o r the chalcopyrite r i c h segregations and v e i n i n g seen at Giant Mascot and many other Cu-Ni deposits r e l a t e d to u l t r a b a s i c rocks ( F i g . 22). In general the bulk compositions of Ni-Cu s u l f i d e ores commonly l i e within the quaternary Mss. down to 500°C. P y r i t e may form i n some quat-ernary systems at temperatures of 743°C where t i e l i n e s are established between Cpss and p y r i t e . This i s very s u l f u r dependant and a small decrease i n s u l f u r w i l l prevent p y r i t e formation. At some temperature below 600°C a chalcopyrite and/or pentlandite (ss) can exsolve from the Mss and w i l l continue to do t h i s as the temperature i s lowered and the p y r r h o t i t i c Mss becomes depleted i n Ni and Cu. At temperatures of 500°C the Mss can only accomodate 1% Cu but may contain greater than 5% N i . In most cases as at Giant Mascot the exsolution temperature f o r pentlandite i s considerably lower than 600°C and pentlandite formation follows that of chalcopyrite from the Mss. At temperatures of 590°C Cpss w i l l break-down into two cubic phases (chalocpyrite and cubanite). The absence of cubanite and s c a r c i t y of p y r i t e can be explained by the f a c t that* below 334°C t h i s mineral p a i r forming i n Ni-poor assemblages, reacts to form chalcopyrite and p y r r h o t i t e . A more l i k e l y explanation of t h e i r absence i s that at Giant Mascot, where 5% or more N i i s present, Cpss and n i c k e l -i f e r o u s p y r r h o t i t e Mss can coexist and no cubanite - p y r i t e assemblage 35 36 i s formed. Ac very low temperatures, considerably below 300 UC, the.Mss breaks down to an assemblage.of p y r r h o t i t e and pentlandite - p y r i t e . Relations involving the formation of pen t l a n d i t e ' - p y r i t e are not c l e a r . The minor p y r i t e seen at Giant Mascot appears as l a t e stage v e i n i n g or intergrowths with pentlandite. In f i g u r e 23 the common assemblages at low temperatures observed i n most massive Ni-Cu ores which in c l u d e those of Giant Mascot are shown. s Kk.,7.3. L o w i!»iu[)«.T;tiur>; m i n e r a l a iMen ib . lage * i n X i ' - C i ! o r e s . T h e must v.tmiuvm a . - ' - o c i a u o i i s a r e i n d i c a t e d b y *o\'ul l i n e s w h e r e a s r!jv»e '•wMiswrn a r e i;»ti;t—ttttl b y <tt.--h?d l i n e s . • 37 In summary the paragenesis and mineral assemblages noted at Giant Mascot are w e l l documented by laboratory experimental workers. An i l l u s t r a t i o n of the sequence of formation of s i l i c a t e s and s u l f i d e phases at Giant Mascot i s shown i n fig u r e 24. • Apparent Paragenesis F i g . 24 Time Chromite Magnetite . . O l i v i n e O/pxn C/pxn P y r r h o t i t e P l a g i o c l a s e Chalcopyrite (1) Hornblende Chalcopyrite (2) Pentlandite P y r i t e Approximate Temperatures 1000°C 850°C 600°C 400°C < 300°C Climax Orebody The Climax orebody, crudely c y l i n d r i c a l , i n t e r s e c t e d by the 3050 l e v e l cross-cut at 6900N., see map, Appendix 1, has maximum dimensions of 90 x 50 feet i n plan. The mineralized zone plunges at 63° i n a N. 30° W. d i r e c t i o n with a v e r t i c a l length of almost 600 f e e t , terminating at the 2700 foot l e v e l . The ore zone occurs at the contact between p e r i d o t i t e (hanging wall) and pyroxenite. The pyroxenite on the south s i d e of the ore zone i s websterite with minor o l i v i n e and becomes more b r o n z i t i c and o l i v i n e r i c h i n the high grade area. The contact between the pyroxenite and p e r i d o t i t e i s sharp and corresponds to t e x t u r a l and tenor changes i n the ore minerals. In general, the w a l l rocks of the Climax ore zone range from p e r i d o t i t e through pyroxenite to n o r i t e which i s present on the western edge. This orebody corresponds to Aho's massive type, an ore zone at or near the contact between two rock u n i t s with no zonal d i s t r i b u t i o n of l i t h o l o g i c a l or ore u n i t s . See Map 1, Appendix 2, f o r the general geology of the Climax area. O l i v i n e and pyroxene i n the ore zone show deformational s t r a i n as evidenced by twinning and undulatory e x t i n c t i o n . Other features such as drag f o l d s , banding and marginal flow l i n e s as c i t e d by Aho (1956) as c r i t e r i a f o r what he c a l l e d , "massive, i n j e c t i o n o r i g i n ore", are not reported at the Climax body. The tenor of the orebody appears to change v e r t i c a l l y with an apparent maximum Ni and Cu content at the 3108 foot e l e v a t i o n acc-ompanied by a low r a t i o of Ni/Cu. This i s deduced from c a l c u l a t i o n s of r i n g d r i l l i n g assay tests on three l e v e l s and the o v e r a l l grade and 39 tonnage of the orebody as i l l u s t r a t e d i n Table 1. Table 1 Climax Ore C a l c u l a t i o n s Elev. Tons/vert.ft. N i % Cu.% Ni/Cu 3198 446 1.01 .38 2.66 3108 435 1.33 .66 2.00 2959 414 1.08 .43 2.51 Average of block between 3298 and and 2700 / , 353 0.78 0.36 2. 16 T o t a l Tonnage = 211,000 On the basis of these somewhat incomplete data i t can be concluded that the orebody decreases i n s i z e and Ni grade down the plunge. Zonation of the ore minerals i s i l l u s t r a t e d remarkably w e l l i n f i g u r e s 25, 26, and 27, which are computer contour p l o t s of N i , Cu and Cu/(Cu+Ni) r e s p e c t i v e l y at the 3108 foot l e v e l . A d d i t i o n a l l e v e l contour p l o t s which do not show zonation as well are appended. N i c k e l values are seen to increase c o n c e n t r i c a l l y inward with the highest grade zone corresponding to the footwall or "trough" of the ore pipe. Copper values behave i n a s i m i l a r fashion but a high grade zone i s noted on . the western side of the orebody. This feature i s f u r t h e r r e f l e c t e d i n the Cu/(Cu+Ni) p l o t which shows the highest r a t i o on the western side of the e l l i p t i c a l shaped ore plan. This western bi a s of m i n e r a l i z a t i o n i s noted on l e v e l s above and below the 3108. The western boundary i s near a large adjacent n o r i t e implying some genetic l i n k between mineral-40 i z a t i o n or l o c a l i z a t i o n of ore minerals and n o r i t i c phases within the u l t r a m a f i t e . Chinaman Orebody The Chinaman orebody i s i n t e r s e c t e d i n the 3050 l e v e l cross-cut at 8540N. I t i s crudely e l l i p t i c a l and elongate i n the d i r e c t i o n of plunge when viewed i n plan. The maximum dimensions of the ore zone are 90 x 100 feet with a v e r t i c a l extent of 638' terminating at the 2700 foot l e v e l . The mineralized zone plunges a t 68 i n a N. 60 W. d i r e c t i o n . Above 3200 fee t and below 2800 fee t the ore zone consists of two or three d i s c r e t e units which become small, low grade, and much fa u l t e d . The r e l a t i o n s h i p of ore to the g e o l o g i c a l rock u n i t s i s not w e l l known but i t appears that the core of the mineralized zone i s a low grade to barren p e r i d o t i t e . The ore zone forms a p a r t i a l envelope around p e r i d o t i t e and v e r t i c a l l y i s discontinuous forming more than one mineral zone i n hornblendic pyroxenite. This u n i t i s surrounded by very hornblende-rich phases. The f o o t w a l l , south and east side, appears to be a hornblendite, pyroxenite, and n o r i t e b r e c c i a . Further east, n o r i t e , p o s s i b l y a large i n c l u s i o n , has been in d i c a t e d by d r i l l i n g . Although mapping i s inconclusive, study of d r i l l l ogs and d i s -cussion with mine personnel suggest that t h i s orebody corresponds to Aho's zoned type which he describes as being zoned i n a c y l i n d r i c a l fashion around or i n a p e r i d o t i t e core with other rock u n i t s concentr-i c a l l y r i n g i n g the core. S p e c i f i c a l l y t h i s orebody c l o s e l y resembles the 1900 orebody which he described as "more complex, lower' i n grade, X a I c CL 3108 NI X' i i 1 1 1 1 1 . — . 6340.Q Eflofl.O CQOO.O 7000^0 ^7020.0 7040.0 70CQ.0 7080.0 7100.0 F i g . 25. Ni contour p l o t of Climax ore at 3108' e l e v a t i o n , i n percent. CL 3108 cu ; g-j 1 1 1 1 — — i 1 1 1 BQ40.0 E9C0.0 0080.0 7000.0 7020.0 7U'J3.0 7000.0 7CG0.0 7100.0 E-flXIS F i g . 26. Cu contour p l o t of Climax ore at 3018' e l e v a t i o n , i n percent. js 42 6343.0 6S6O.0 F i g . 27. Bssa.a laco.a 7020 a E-BXIS 73J0.Q 7Q60.0 7na].0 71S0.0 Cu/(Cu+-Ni) plot of Climax ore at 3108' elevation. Ratio i n percent. lower i n r a t i o of n i c k e l to copper and more hornblendic than the others, and i s more suggestive of replacement o r i g i n . " The tenor of the Chinaman ore and the size appear to change e r r a t -i c a l l y i n v e r t i c a l d i r e c t i o n . This v a r i a t i o n can be a t t r i b u t e d to the st r u c t u r a l nature of the ore zones at d i f f e r e n t elevations. The larga low grade sections, e s p e c i a l l y on the 3207 l e v e l , are r e a l l y three adjacent zones mined as one orebody, whereas three zones are distinguished on the 3292 l e v e l and the grade i s higher but tonnage lower. This kind of structure does not hold true i n the lower reaches of the ore zone. C a l c u l a t i o n s from r i n g d r i l l i n g assay r e s u l t s from the are i l l u s t r a t e d i n the following Table 2. Chinaman orebody Table 2 . Chinaman Ore C a l c u l a t i o n s Elev. Tons/vert.ft. N i % Cu% Ni/Cu 3292 613 .67 .29 2.31 3207 945 .42 .16 2.63 3160 727 .61 .37 1.65 2802 432 .50 .21 2.38 Average between 2700 of block 3338 and 589 .73 .30 2.43 T o t a l Tonnage =376,000 Zonal features of the ore minerals by element are presented i n f i g u r e s 28, 29, and 30, which are computer drawn contour p l o t s of assay information on the 3160 l e v e l of N i . , Cu., and Cu/(Cu+Ni). A d d i t i o n a l l e v e l contour pl o t s which do not i l l u s t r a t e zonation as w e l l are appended. Both the N i and Cu p l o t s show the elongation i n the d i r e c t i o n of plunge with the c o n c e n t r i c a l l y zoned higher grade parts corresponding to the "trough" or footwall region of the ore zone. The Cu/(Cu+Ni) r a t i o also appears higher here but i n general t h i s p l o t i s e r r a t i c and does not support Aho, (1956), who p r e d i c t s that the copper values should be higher on the periphery and lower towards the core of the orebody. I t i s also worth noting that the bias of the higher grade m i n e r a l i z a t i o n i s towards the n o r i t i c rocks to the east i n much the same manner as i n the Climax body. hi These two orebodies which account for greater than 10% of the t o t a l production to the present time mined at Giant Mascot seem to correspond to Aho's, (1956), two-type c l a s s i f i c a t i o n of massive (Climax) and zoned (Chinaman). Although he ascribes a magmatic i n j e c t i o n o r i g i n to the former and a replacement o r i g i n to the l a t t e r i t i s believed by the w r i t e r , and t h i s subject w i l l be expanded upon i n more d e t a i l l a t e r , that both types of ore have magmatic i n j e c t i o n o r i g i n with the "zoned" type being modified by l a t e r geologic events. 48 CHEMICAL ANALYSES OF SILICATES AND SULFIDES S i l i c a t e A n a l y t i c a l Techniques Chemical analyses of s i l i c a t e minerals were made withj^ARL SEMQ scanning electron microprobe. The probe was run at 15 Kev. with a specimen current of 25 to 30 n.A. Sample information was gathered i n the "peak-seek" mode and output c o l l e c t e d and r e f i n e d by the on-board computer using Bence-Albee c o r r e c t i o n f a c t o r s . The re f i n e d data, i n weight percent, are printed out at a teletype terminal. Grains i n each rock specimen were analyzed using an inc i d e n t beam approximately 10/-*•• i n diameter. This beam s i z e was selected i n an attempt to avoid exsolution lamallae. In most instances elemental a n a l y s i s was believed good to ±1% of the amount percent, but i n the case of S i and Ca the error x<ras l a r g e r , p o s s i b l y greater than ±2%. A t o t a l of 30 rock specimens y i e l d e d 29 orthopyroxene, 17 c l i n o -pyroxene and 13 o l i v i n e compositions. In most cases the analyses were made i n the centre of a grain and 8 elements were determined. D e t a i l e d work on specimens of a l l three minerals was c a r r i e d out to determine homogeneity and to test f o r the presence of a d d i t i o n a l elements. A complete tabulation of a l l analyses i n weight percent and as mole f r a c t i o n s i s given i n Appendix 4. S i l i c a t e Analyses F i g . 31, a part of the pyroxene q u a d r i l a t e r a l , i l l u s t r a t e s the chemical compositions of the pyroxenes and of c o e x i s t i n g p a i r s . Ortho-pyroxenes range i n composition from En„ , to En 7 C. l n and, clinopyroxenes 49 range from I f c ^ , . to Wo^^, E n ^ g 5 to E n 5 2 ; 7 5 and F s ^ to F s ^ g . Olivines, not plotted, range from Fo o r i n to Fo . o U . U bO.O_> Tie-lines in the pyroxene quadrilateral show close parallelism suggesting sound analytical technique. The shift of the tie-lines indicates bulk compositional changes. Iron-enrichment trends within a particular rock unit may define a zoning or cryptic layering. Elemental variation plots of orthopyroxenes along the 3050 cross-cut, Fig. 32, show high Fe in pyroxenites and corresponding low Fe in perid-otites. This i s particularly well il l u s t r a t e d at 7260N. where a small pyroxenite unit shows a marked change in orthopyroxene composition when compared to the large peridotite units that surround i t . Although not readily apparent in the i l l u s t r a t i o n , i n the Chinaman orebody and the brecciated footwall on the south, those orthopyroxenes high i n Fe are from pyroxenitic rocks and those with low Fe/ ratios are found i n • • • . • Fe+Mg peridotites. From the Climax orebody south, the elemental variation suggest a discrete change in bulk composition and though not detectable megascopically the change might be considered evidence of heterogeneity within the pyroxenite. The Ca-variation appears sympathetic to Fe-variation i n the pyro-xenite up to the l i t h o l o g i c a l boundary in the Climax zone and again in and near the Chinaman orebody. In most other places Ca content varies sympathetically with Mg. An i l l u s t r a t i o n of elemental variation i n clinopyroxenes, Fig. 33, i s included although paucity of data makes interpretation d i f f i c u l t . As i n the case of orthopyroxenes Fe tends to be high when Mg i s low and (Mg,Ca)Si0 3 QUADRILATERAL PLOT OF PYROXENE COMPOSITIONS 3050 CROSS-CUT FIGURE3I s ' 6 / / ' / / // '// // ft >'i if! /// 'iii' /// // ' * /// , 11 ,!! M, j j '<,;'i !fiSi /'/ 1;; ;< 1111 'H 11 in 1 // / II 1 I 1 i i i 1 " MgS I0 3 ~7~ JO ,, 11 I'I I 'I • .1 25 26 3C 80 Mg •21 (Mg.FeJSIO, O :a_, Mg F e J 8 5 2 0 7 5 104 A t . % F IGURE 32 7 5 10 / i. 9 ¥ V yi 0 — 0 O (y n I V*/ O 7 § CH INAMAN S oo i i SS j ~1 ELEMENTAL VARIATION IN ORTHOPYROXENE 3050 CROSS-CUT | PDT. P X N I T E . H B L I T E . J00 . I I NORITE Mg Fe Ca Mg FeJ 50 15 Mg Fe. 40 5 A t % Mg Fe 50 15 Mg Fe 40 5 CH INAMAN t i o o oo oo ELEMENTAL VARIATION IN C L I N O P Y R O X E N E 3050 CROSS-CUT Mg Fe Ca — .100' I I PDT. I | PXN ITE . I | H B L I T E , I NORITE *• 1 Ln ro 53 vice-versa, and t h i s r e l a t i o n s h i p i s dependant upon l i t h o l o g y . Ca generally shows c l e a r inverse r e l a t i o n s h i p s with Mg and i s sympathetic to Fe change except i n the Climax ore zone. O l i v i n e , which i s not pl o t t e d , may be compositionally re l a t e d to a rock type. In the Climax orebody o l i v i n e i n the footwall pyroxenite i s lower i n magnesium, Fo ., than that i n the hanging wall p e r i d o t i t e , OH Fo . This may be more apparent than r e a l due to the uncertainty i n oo a n a l y t i c a l e r r o r . S u l f i d e A n a l y t i c a l Techniques Chemical analyses of s u l f i d e minerals was made with a J o e l e l e c t r o n microprobe a t the Department of Metallurgy, U.B.C. This probe uses a 20° take-off angle and was,run at 25 Kev. and 0.8 milliamps. Standard-i z a t i o n using pure metal standards i s done manually and output i s i n d i g i t a l form as r e l a t i v e i n t e n s i t i e s of sample to standard. The unrefined data i s then prepared f o r computer c o r r e c t i o n s using the "MAJIC I I " program and run on the U.B.C, IBM 370 computer. This program corrects f or background, dead time l o s s , absorption e f f e c t s , fluorescence e f f e c t s and i o n i z a t i o n penetration l o s s e s . I t i s believed that the r e s u l t s are q u a n t i t a t i v e l y accurate to ±4% of the element present. Twenty-nine samples were prepared and analyzed, y i e l d i n g 29 p e n t l -andite and 28 p y r r h o t i t e compositions. These minerals were analyzed f o r Fe, Ni, Cu, Co, and S by d i f f e r e n c e . A complete tabulation of these analyses i n weight percent and atomic percent i s shown i n Appendix 5. Su l f i d e Analyses F i g . 34, i s a part of the Fe - N i - S e q u i l a t e r a l t r i a n g l e which shows the chemical nature of the pentlandites and coexi s t i n g p y r r h o t i t e s . 55 Pentlandite e x h i b i t s a wide v a r i e t y of compositions with N i ^ ^ ^ to N i ^ g F e 2 9 0 t 0 F e 4 0 7 a n d S32 1 t D S41 9 w e i S h t P e r c e n t . A t y p i c a l pental-d i t e , #7, y i e l d s a composition of Fe^o n> N i 3 3 91' C o l 86' S34 04' P y r r h o t i t e ranges from Fe c_ c , S., c to Fe,- .., S., and may contain J J . J 4 O . J u J . / J o . J Ni up to 1.26 weight percent. A t y p i c a l p y r r h o t i t e , #7, y i e l d s a composition of F e 5 8 > g o N i < 3 ? S ^ ^ . T i e - l i n e s between the two minerals are generally p a r a l l e l from the most s u l f u r - r i c h to sulfur-poor p a i r . This probably lends credence to the accuracy of analysis and e q u i l i b r a t i o n between the mineral p a i r . The s h i f t s i n the t i e - l i n e s i n d i c a t e a changing bulk composition of the s u l f i d e s and seem to be r e l a t e d to the petrology of the rock units from which the minerals are derived. I l l u s t r a t e d i n F i g . 35, i s an elemental v a r i a t i o n p l o t of p e n t l -andite along the 3050 cross-cut. A pattern of p a r a l l e l Fe - Ni v a r i a t i o n s i s present i n the pyroxenite south of the Climax orebody and a general increase i n the Fe - N i value i s present as the ore zone i s approached. Co content i s high and i r r e g u l a r and then drops dramatically near and i n the orebody. Within the Climax zone Ni values are extremely high and Co i s c o n s i s t e n t l y below 0.50 atomic percent. The hanging w a l l p e r i d o t i t e y i e l d s a pentlandite with Fe very high and Ni very low. The o v e r a l l r e s u l t appears to be one of F e - r i c h , Ni-poor pentlandite i n per-i d o t i t e except i n ore zones, and high Ni-Fe pentlandites i n pyroxenites. Co values also appear higher i n the pentlandites from pyroxenites than those from p e r i d o t i t e s . The Chinaman zone pentlandites behave s i m i l a r l y to those i n the Climax orebody. These pentlandites of high N i content, sympathetic Fe values and low Co content seem to be d i s t i n c t l y character-i s t i c of ore zones. At % FIGURE 35 Fe Ni. 30 20 CL IMAX CH INAMAN J L o CO o o ... . 1 ELEMENTAL VARIATION IN PENTLAND ITE 3050 CROSS-CUT Ni Fe Co 100 PDT. P X N I T E . HBL I TE . NORITE P y r r h o t i t e analyses have not been p l o t t e d as they appear to have a random and narrow Fe spread along the cross-cut. Further, t h e i r Ni content i s generally low and large c o r r e c t i o n factors suggest questionable r e s u l t s . Three p y r r h o t i t e s with the greatest amount of Fe correspond to pentlandites that are F e - r i c h . Within the two orebodies the p y r r h o t i t e e x h i b i t s s i m i l a r Fe contents with l i t t l e f l u c t u a t i o n . - Elemental v a r i a t i o n s i n two s i l i c a t e minerals and one s u l f i d e mineral along the 3050 cross-cut c l e a r l y vary with the d i f f e r e n t l i t h o l o g i c a l units encountered and the orebodies. The marked v a r i a t i o n i n mineralogy between rock units l i m i t s the possible mechanisms of formation f o r the u l t r a b a s i c complex. These w i l l be discussed i n a l a t e r s e c t i o n . 58 THERMAL HISTORY OF THE ULTRABASIC COMPLEX Introduction Kretz, (1961), demonstrated that the d i s t r i b u t i o n c o e f f i c i e n t 2+ (Kp) r e l a t i n g Mg and Fe d i s t r i b u t i o n between coexisting Ca-rich and Ca-poor pyroxenes d i f f e r s between magmatic (K Q = 0.73) and metamorphic (Kp = 0.57) assemblages. The d i s t r i b u t i o n c o e f f i c i e n t i s dependant upon temperature, pressure and s o l i d s o l u t i o n constituents other than 2+ Mg and Fe . Atkins, (1969), however shows low values from co-e x i s t i n g pyroxene p a i r s c o l l e c t e d near the base of the Bushveld Complex (0.64 to 0.70). See F i g . 36. These low values are a t t r i b u t e d mainly to the greater hydrostatic pressure under which these pyroxenes were formed. In t h i s study the chemical nature of the pyroxenes resembles c l o s e l y those from s i m i l a r studies on the Skaergaard (Brown, 1957), the S t i l l w a t e r (Hess, 1960), and the Bushveld (Atkins, 1969). Wood and Banno, (1973), using an empirical approach, derived an expression f o r c a l c u l a t i n g e q u i l i b r a t i o n temperatures of 2-pyroxene assemblages. Their method gives temperatures f o r almost a l l exper-imental data f o r multicomponent systems to within ±60° C of the observed temperatures. They st r e s s that t h i s empirical approach may lead to considerable e r r o r outside of the temperature-composition range covered by the experiments used i n i t s derivations. As the temperature of formation and composition of the pyroxenes from Giant Mascot are believed compatible with those used i n Wood and Banno's study, the use of t h e i r expression may be j u s t i f i e d . Mg AND Fe D ISTR IBUTION COEFF IC IENT ( K p ) OF PYROXENES AT GIANT MASCOT 60 Methods The values were determined using the following equation, (Kretz 1961, 1963): 1-X° x c mg mg where X = ° , mg r — i n orthopyroxene. Mg + Fe c Mg and X = i n clinopyroxene. mg 2+ Mg + Fe The expression f or T(in°K), Wood and Banno 1973: -10202  cpx _ T = ln( aMg oSi o0,) - 7.65X° p x + 3 . 8 8 ( X ° p X ) Z - 4.6 2 2 6 mg mg opx a M g 2 S i 2 0 6 where a ^ p x „ . _ i s the a c t i v i t y of e n s t a t i t e component i n clinopyroxene. M g 2 S i 2 0 6 and a ° p X „ . n i s the a c t i v i t y of e n s t a t i t e component i n orthopyroxene. M g 2 S i 2 0 6 „ , „opx _ 2+ . ana X = Fe i n orthopyroxene. mg — Fe + Mg 61 Ml M2 The a c t i v i t y a„, „. = X„ x X., , assumes the large ions J M g 2 S i 2 0 6 Tig Tig present i n the orthopyroxene and clinopyroxene structures occupy M2 s i t e s while the smaller octahedrally coordinated ions occupy Ml. The ions have been assigned to the two s i t e s as follows; M2 Ml C a 2 + A l 3 * « + ~ 3+ Na Cr Mn 2 + T i 4 + F e ^ I f the occupancies of the two s i t e s by these ions are subtracted, 2+ 2+ the M2 and Ml s i t e s that remain are f i l l e d by Mg and Fe ions i n a random d i s t r i b u t i o n . Thus a^, _. _ becomes; Mg ' . ( l - ( C a 2 + + Na + + M n 2 + ) ) M 2 x _Mg___ . ( 1 - ( A 1 3 + + 2+ 2+ Mg+Fe Mg+Fe ' C r 3 * + T i 4 + + Fe 3 4")),,, Ml 2+ For the purposes of t h i s study a l l Fe was considered Fe 2+ following Wood and Banno, (1973). Also Mn was not analyzed f o r i n most pyroxenes but i s considered to have an i n s i g n i f i c a n t e f f e c t on the c a l c u l a t e d temperature. Giant Mascot D i s t r i b u t i o n C o e f f i c i e n t s Seventeen p a i r s of Ca-rich and Ca-poor coexisting pyroxenes were analyzed by e l e c t r o n microprobe. The r e s u l t i n g d i s t r i b u t i o n co-e f f i c i e n t s (Kp) are l i s t e d i n the r i g h t hand column of table 3. The 62 TEMPERATURE DATA OF COEXISTING PYROXENE PAIRS AND K n VALUES. TABLE 3. Sample No. X F e cpx 3 En opx a En °c T c KD 1 = 26A .186 .091 .598 1035 .788 2 = 28A-2 .190 .064 .600 975 .695 3 = 32A-1 .202 .025 .608 835* .714 4 = 34A-1 .205 .096 .561 1035 .620* 5 = 36A-3 6 = 41A-1 7 = 43A-1 .187 .063 .615 970 .743 8 = 44A-1 .190 .058 .600 960 .670 9 = 46A-1 .170 .156 .630 1140* .749 11 = 47A-1 .144 .053 .676 970 .720 12 = 90A-1 13 = 92A-1 14 = 85A 15 = 82A-1 .214 .062 .587 950 .739 16 = 78A-1 .130 .106 .711 1090 .870* 17 =104A .133 .088 .624 1005 .769 18 =106A .159 .074 .668 1010 .755 19 =108A .230 .074 .544 975 .781 20 -114A 21 =121A 22 =130A .236 .076 .560 970 .780 23 =132A 24 =134A-2 25 =136A .166 .082 .656 1020 .685 26 =140A 27 =152A-1 .224 .053 .559 925 .703 28 =156A-1 .211 .048 .587 915 .781 29 =160A-2 30 =162A-1 *anomo!ous 63 values range from 0.62 to 0.87 with a mean of 0.739. I f the high and low values are discarded the range i s more reasonable, (0.67 to 0.79), with a mean of 0.738. The high and low values are from Fe-poor and Fe-r i c h pyroxene pa i r s r e s p e c t i v e l y and they are anomalous with regard to the remaining 15 p a i r s . The value of obtained from t h i s work suggests that the pyroxenes are magmatic. Although t h i s value i s greater than those of the Bushveld i t i s reasonable to assume that the high pressure of formation of Bushveld pyroxenes (^Okm.) would r e s u l t i n a reduced K^, (Atkins, 1969) . The value obtained i s more l i k e that of the Skaergaard, (-*2km.) although that body appears to have formed at a higher temperature. Pyroxene Geothermometry Of the 17 p a i r s of pyroxenes analyzed, 15 y i e l d remarkably s i m i l a r temperatures. Disregarding the high and low values, representing pyroxenes extremely Ca-poor and Ca-rich r e s p e c t i v e l y , the range of temperatures calculated f o r the Giant Mascot Ultramafite i s 915° C to 1090° C. The mean of the 15 temperatures i s 990° C. The er r o r according to Wood and Banno should be no greater than ±60° C. A l l temperatures and pertinent data used i n the c a l c u l a t i o n s are l i s t e d i n table 3. McTaggart, (pers. comm.), using the same methods ca l c u l a t e d a temperature f o r a n o r i t i c rock at the mine and obtained a temperature of e q u i l i b r a t i o n of 850° C. The a p p l i c a t i o n of the Wood and Banno, (1973), expression f o r the temperatures of e q u i l i b r a t i o n of c l i n o - and orthopyroxenes y i e l d s 64 r e s u l t s that are remarkably consistent with other igneous assemblages (Bushveld, Skaergaard). There seems to be no c o r r e l a t i o n between the temperatures of e q u i l i b r a t i o n (formation)and values. The bulk composition of the rock undoubtably has an e f f e c t on the and T values but no c o r r e l a t i o n between a p a r t i c u l a r l i t h o l o g i c u n i t and a set of temperatures of i s r e a d i l y seen. Those temperatures calculated from o l i v i n e - b e a r i n g rocks are s l i g h t l y higher o v e r a l l than those from pyroxenites but a high temperature from a pyroxenite provides the exception to the r u l e . 65 RADIOMETRIC AGES Hornblende, and where possible a b i o t i t e concentrate was obtained from the rock to be analyzed. In one case the hornblende occurred as p o i k i l i t i c grains enclosing orthopyroxenes and no attempt was made to separate them. The concentrates were subsequently sent to the Depart-ment of Geophysics at U.B.C. to be dated by the K-Ar method. Ultr a b a s i c Rocks Four samples f o r radiometric dating were c o l l e c t e d along the 3050 cross-cut .(Fig« 37). They represent four d i f f e r e n t rock types, a l l r i c h i n hornblende. Sample 157A-1 was taken to represent the mineralized hornblendite of the Chinaman orebody. I t consists of coarse 1 to 2 cm. prismatic hornblende with i n t e r s t i t i a l and massive mixtures of pyrrhotite,. pent-l a n d i t e and chalcopyrite. The hornblende i s f r e s h megascopically but i n t h i n - s e c t i o n some c h l o r i t e a l t e r a t i o n i s seen. The i r o n - n i c k e l s u l -f i d e s are penecontemporaneous with hornblende, but chalcopyrite appears to be l o c a l l y l a t e r as i t f i l l s or reheals f r a c t u r e s i n hornblende c r y s t a l s . The apparent age of c r y s t a l l i z a t i o n of the hornblende y i e l d s an age of 108 ± 4 m.y. This age i s also the minimum age of the main ore minerals although some chalcopyrite i s younger than hornblende. Sample 141A was c o l l e c t e d approximately 100 fe e t east of the Chinaman orebody and i s a coarse-grained f e l d s p a t h i c hornblendite. In hand-specimen i t appears as a fr e s h , almost pegmatitic reaction rock ORE BODIES 67 between the u l t r a b a s i c s and a n o r i t e . Coarse 1 to 2 cm. hornblende c r y s t a l s contain i n t e r s t i t i a l p l a g i o c l a s e . Minor c h l o r i t e and c a l c i t e are also seen i n t h i n - s e c t i o n as a l t e r a t i o n minerals and some quartz i s present i n the p l a g i o c l a s e - r i c h groundmass. The apparent age of the hornblende c r y s t a l l i z a t i o n i s 104 ± 4 m.y. This date suggests a minimum age f o r the u l t r a b a s i c rocks and the en-closed n o r i t e body as the date obtained i s that of the reaction margin of the two rock u n i t s . Sample 120A i s t y p i c a l of a large volume of host rock within the complex. I t i s a hornblendic pyroxenite with large p o i k i l i t i c hornblende c r y s t a l s to 1 cm. containing orthopyroxenes from 0.2 to 2.0 mm. The groundmass i s a mixture of t i g h t l y i n t e r l o c k i n g ortho- and clinopyroxenes. Radiometric dating was done on the whole rock. The apparent age of the hornblendic pyroxenite was determined as 119 ± 4 m.y. This whole rock age may be somewhat high because of a d i -l u t i o n e f f e c t caused by the very low radiogenic nature of pyroxene. In any event, the a v a i l a b l e K-Ar dating places the minimum age of the u l t r a -basics between 104 ± 4 to 119 ± 4 m.y. Sample 79A-2, was selected from a hornblendite dyke, as i t repre-sents the youngest rock u n i t seen i n underground mapping. I t i s a f i n e -grained, 0.1 to 1.0 mm., monomineralic rock of oriented prisms of fresh hornblende. These fine-grained hornblende or f e l d s p a t h i c hornblende d^kes cut a l l other rocks and contacts are knife-edge sharp. Most of these dykes or veins are 2 to 4 inches wide and follow a random, sinuous course. The apparent K-Ar age i s 95 ± 4 m.y. 68 Granitoid Rocks Several samples from the surrounding p l u t o n i c rocks were c o l l e c t e d and three were selected f o r age dating. Their locations are shown i n F i g . 38, along with some e a r l i e r age determinations. Sample #7 was c o l l e c t e d 0.1 miles west from the contact between high grade s c h i s t s and p l u t o n i c rocks on the road to the mine. This sample (T. Richards, pers. comm.) probably represents the t o n a l i t e phase of the Spuzzum Pluton and i s a f o l i a t e d medium-grained fresh f e l s i c rock. I t consists of andesine, quartz, hornblende, b i o t i t e and minor c h l o r i t e . Both a b i o t i t e and hornblende K-Ar date was obtained at 79.4 ± 2.5 and 85.1 ± 2.8 m.y. r e s p e c t i v e l y . Sample #4 i s a d i o r i t e that corresponds to Richards (1971) phase II d i o r i t e having hypersthene, clinopyroxene, hornblende and p l a g i o c l a s e as major constituents. This sample was c o l l e c t e d within a few hundred feet of the u l t r a b a s i c complex. The l o c a t i o n i s about 400 f e e t along the lower haulage road, at the i n t e r s e c t i o n of the road and a small t r i b u t a r y to Texas Creek. A hornblende-pyroxene concentrate of t h i s sample gives a K-Ar date of 89.6 ± 3.1 m.y. Sample #8 i s a phase I I d i o r i t e (Richards, 1971) c o l l e c t e d several miles to the south of the mine. The sample l o c a t i o n i s 1.8 miles west of Haig junction on the north side of the Fraser River i n a road cut on the main highway. This hornblende concentrate y i e l d e d a K-Ar date of 89.5 ± 2.8 m.y. 69 LOCATION OF K-Ar DAT ING OF FIGURE 38 S P U Z Z U M PLUTON IC ROCKS 79b BIOTITE 89h H O R N B L E N D E 70 Discussion and Int e r p r e t a t i o n Only one sample provided both a b i o t i t e and hornblende K-Ar date. In t h i s case the hornblende gives an older date by nearly 6 m.y. I t should be expected that hornblende would y i e l d an older age as the mineral tends to "freeze i n " radiogenic argon at a higher temperature than does b i o t i t e . This retention i s due to a more compact c r y s t a l structure. How-ever, the age spread appears too great f o r t h i s to be the only reason and i t i s possible that unusually slow cooling of the i n i t i a l magma would account f o r the di f f e r e n c e . Because of low potassium content i n ultramafic samples, see table 4, they were reanalyzed and sample 157A-1 was dated twice. No s i g n i f i c a n t d ifferences were found. Contamination of samples by the presence of pyroxene and c h l o r i t e though undesirable, i s believed to have l i t t l e or no e f f e c t on the re-sultant age, (R.L. Armstrong, pers. comm.). The age of c r y s t a l l i z a t i o n of the ult r a m a f i t e s , or at l e a s t the time when rocks ceased to lose radiogenic argon, ranges between 104 and 119 m.y. Late hornblendite dykes that cut the ultramafite are dated at 95 m.y. The enclosed n o r i t e s or n o r i t i c phase must be at l e a s t 104 m.y. o l d . The Chinaman orebody i n p a r t i c u l a r would seem to have a minimum age of 108 m.y., t h i s would probably represent the age of a l l orebodies i n the complex. The surrounding p l u t o n i c rocks y i e l d K-Ar ages that are concordant ages with Spuzzum i n t r u s i o n s (Richards, 1971). T o n a l i t i c rocks, as suggested by Richards, are the younger at 79.4 to 85.1 m.y. D i o r i t i c . rocks near the ul t r a m a f i t e , s i m i l a r p e t r o l o g i c a l l y to those several miles to the south and c l a s s i f i e d as phase I I d i o r i t e s by Richards (1971) 71 y i e l d ages at both locat i o n s of 89.6 m.y. These dates agree f a i r l y w e l l with those of the type l o c a l i t y of Spuzzum plutonism (McTaggart and ; Thompson, 1967) northwest of Stout, B r i t i s h Columbia, a t o n a l i t i c rock dated at 76 m.y. The dating of the p l u t o n i c rocks alone suggest that the Giant Mascot Ultramafite i s older than the Spuzzum Intrusions. Comparison of K-Ar dates from ultramafites and surrounding Spuzzum d i o r i t e s does not completely s e t t l e the problem of the r e l a t i v e ages of these two rock types because there are several v a r i e t i e s of d i o r i t e and not a l l of these have been sampled or dated. I t i s apparent, however that the u l t r a m a f i t e i s at l e a s t as o l d and possibly older than c e r t a i n d i o r i t e s that do appear to belong to the Spuzzum Intrusions. 7 2 TABLE 4 . K/Ar samples and ana l y t i c a l re su l t s fo r u l t r aba s i c and p lu ton ic rocks at the Giant Mascot Property, near Hope, B.C. Spec. No. Min. Rock %K a 40* 40 Ar /Ar 40* -5 A r ^ u :10 3 Cm J (stp)/g Age myr 79A-2 Hbl. Hb l i te 0.183 0.64 0.07043 95+4 120A Whole Rock Hbl. pyrox. 0.130 0.43 0.06357 119+4 141A Hbl. Fe ld . Hb l i te 0.258 0.64 0.1093 104-4 157A-1 Hbl. Min. Hb l i t e 0.258 0.61 0.1154 108+4 4 Hbl. - pxn. Dio. 0.334 0.43 0.1214 89.6+3.1 7a B io . Q.D. 5.860 0.836 1.881 79.4+2.5 7b Hbl . Q.D. 0.464 0.580 0.160 85.112.8 8 Hbl. Dio. .536 0.580 0.1945 89.512.8 Constants used in age c a l c u l a t i o n s : V K 4 0 /K 73 ORIGIN OF THE ULTRAMAFITE AND ITS ORES Ruckmick and Noble (1959), Taylor (1967), and McTaggart (1971), c l a s s i f i e d the Giant Mascot Ultramafite as belonging to the Alaskan zoned type. I r v i n e , (1967) d i s q u a l i f i e d i t on the grounds that i t con-tains orthopyroxenes. Findlay (1969) d i s q u a l i f i e d i t on t h i s basis and suggested that i t was "a v a r i a n t of the 'normal' CordilTeran alpine-type i n t r u s i o n " . Naldrett (1973) i s unable to c l a s s i f y i t at a l l i n h i s otherwise d e t a i l e d c l a s s i f i c a t i o n system. Early i n v e s t i g a t o r s of the Giant Mascot Ultramafite proposed diverse o r i g i n s f o r the complex. Cairnes (1924) concluded that the u l t r a b a s i c rocks with t h e i r r e l a t e d ore minerals were magmatic i n o r i g i n and cut the surrounding d i o r i t e s . C o c k f i e l d and Walker (1933) believed that the u l t r a b a s i c rocks were intruded by surrounding d i o r i t e and that the ore was hydrothermal i n o r i g i n . Horwood (1936, 1937) believed hornblendite to be the p r i n c i p a l rock type, that the s u l f i d e ore and pyroxenite had segregated from the hornblendite and that these were i n j e c t e d i n t o t h e i r present p o s i t i o n followed by r e l a t e d d i o r i t e i n t r u s i o n s . McTaggart (1971) favors a metasomatic o r i g i n f o r zoned ultramafites and proposed that d i o r i t e and gabbros might be younger than the u l t r a -mafite. Muir, (1971) concluded that the Giant Mascot Ultramafite formed from a i n i t i a l mass of hornblende pyroxenite which intruded along a diorite-metamorphic rock contact. Subsequently he suggested a number of p l u g - l i k e o l i v i n e and s u l f i d e bodies were intruded along the d i o r i t e -hornblende pyroxenite contact. Aho (1956) whose work at Giant Mascot i s the most d e t a i l e d to date, offered two hypothesis of o r i g i n , magmatic and metasomatic. The magmatic 7 4 h y p o t h e s i s i n v o k e d f r a c t i o n a l c r y s t a l l i z a t i o n o f a b a s i c p a r e n t m a g m a f o l l o w e d b y g r a v i t a t i v e d i f f e r e n t i a t i o n a n d f i n a l i n j e c t i o n a s a c r y s t a l m u s h i n t o t h e s u r r o u n d i n g d i o r i t e s t h u s a c c o u n t i n g f o r h i s m a s s i v e o r e -b o d i e s . T h e m e t a s o m a t i c h y p o t h e s i s w a s p r o p o s e d t o a c c o u n t f o r t h e o r i g i n o f t h e z o n e d m i n e r a l i z e d p i p e s b y t h e a d d i t i o n o r r e m o v a l o f S i G ^ a n d d e p o s i t i o n o f s u l f i d e s . H e e x t e n d e d t h i s h y p o t h e s i s t o t h e w h o l e u l t r a -m a f i c m a s s a n d s u g g e s t e d t h a t t h e l a r g e s c a l e z o n i n g f r o m p e r i d o t i t e t o p y r o x e n i t e a n d t o h o r n b l e n d i t e i s c a u s e d b y h i g h t e m p e r a t u r e r e d i s t r i b u -t i o n o f s i l i c a , l i m e e t c . i n a p r e - e x i s t i n g u l t r a b a s i c i n t r u s i o n . T h e o r i g i n o f t h e u l t r a m a f i c r o c k s a n d r e l a t e d s u l f i d e m i n e r a l i z a -t i o n i s b e l i e v e d t o b e t h e r e s u l t o f a c o m p l e x p r o c e s s . T h e o r e b o d i e s a n d r e l a t e d r o c k s a s d e s c r i b e d b y A h o ( 1 9 5 6 ) , M u i r ( 1 9 7 1 ) a n d b y t h e p r e s e n t a u t h o r a r e s i m i l a r i n s h a p e , m i n e r a l t e x t u r e s , m i n e r a l a s s e m b l a g e s a n d r e l a t i o n o f l i t h o l o g i c a l u n i t s . O n t h e o t h e r h a n d , t h e d i v e r s e o r i g i n s a n d m e c h a n i s m s o f f o r m a t i o n , a s p r e v i o u s l y o u t l i n e d , f o r t h e v a r i o u s o r e b o d i e s a n d t h e r e l a t e d r o c k s s e e m i n c o m p l e t e o r i m p r o b a b l e t o t h i s a u t h o r . A g e o l o g i c a l m a p i n F i g . 3 , A h o ( 1 9 5 6 ) , s h o w s t h e p r i n c i p a l r o c k u n i t s i n t h e a r e a . T h e c o u n t r y r o c k i s a d i o r i t e w i t h i n c l u s i o n s o f m e t a m o r p h i c r o c k . T h e u l t r a m a f i t e i s a c r u d e l y z o n e d b o d y w i t h a h o r n -b l e n d e r e a c t i o n m a r g i n w i t h h o r n b l e n d e p y r o x e n i t e g r a d i n g i n w a r d s t o p y r o x e n i t e a n d c e n t e r s o f p e r i d o t i t e . I n c l u s i o n s w i t h i n t h e u l t r a m a f i t e a r e h i g h g r a d e m e t a m o r p h i c s c h i s t s a n d h o r n f e l s e d n o r i t e . F e l s i c i n c l u -s i o n s a n d c r o s s - c u t t i n g r e l a t i o n s h i p s a t u l t r a m a f i c - d i o r i t e c o n t a c t s l e d A h o ( 1 9 5 6 ) a n d M u i r ( 1 9 7 1 ) t o p o s t u l a t e a y o u n g e r a g e f o r t h e u l t r a m a f i t e . T h e p o s s i b i l i t y t h a t t h e s e i n c l u s i o n s d o n o t b e l o n g t o t h e S p u z z u m I n -t r u s i o n s i s s u p p o r t e d b y t h e f a c t t h a t t h e y a r e u s u a l l y n o r i t e s a s 75 opposed to Spuzzum d i o r i t e s , they have a much better developed f o l i a t i o n and the p l a g i o c l a s e composition i s usually much more c l a c i c , b a s i c bytownite as opposed to andesine-labradorite, c h a r a c t e r i s t i c of the Spuzzum, Also Aho (1956) states that u l t r a m a f i c - d i o r i t e contacts show c o n f l i c t i n g age r e l a t i o n s h i p s . K-Ar age determinations support the idea that the ultramafite i s older than the Spuzzum D i o r i t e . This work and others y i e l d ages of d i o -r i t e c r y s t a l l i z a t i o n from 80 to 89 m.y. with the oldest date obtained a few hundred feet from the south east corner of the u l t r a m a f i t e . The t o n a l i t e border phase of the Spuzzum appears younger and a hornblende-bio t i t e p a i r dated at 85 and 79 m.y. r e s p e c t i v e l y suggest a protracted cooling f o r the Spuzzum plutonism. K-Ar dating of hornblendic rocks from within the ultramafite y i e l d older ages of c r y s t a l l i z a t i o n . From the center of the complex a horn-blendic-pyroxenite y i e l d s a minimum age of c r y s t a l l i z a t i o n of 119 m.y. and a coarse-grained hornblendite between an i n t e r n a l n o r i t e and u l t r a -mafic y i e l d s a date of 104 m.y. suggesting a minimum f o r both n o r i t e and u l t r a m a f i t e . Hornblende from the Chinaman orebody y i e l d s a minimum age of c r y s t a l l i z a t i o n of 108 m.y. Young hornblendite dykes, observed to cut a l l u l tramafic rock u n i t s , y i e l d an age of 95 m.y., s t i l l older than Spuzzum rocks. I t may be argued that the age d i f f e r e n c e i s f a l s e and due to the capacity of ultramafic rocks f o r " f r e e z i n g i n " radiogenic components e a r l i e r than does d i o r i t e but t h i s s t i l l places the u l t r a -mafite i n a p o s i t i o n of being at l e a s t as old as Spuzzum plutonism. More r e a l i s t i c a l l y , i t can be argued that the ultramafic i s the older rock mass and Spuzzum plutonism caused an uneven younging e f f e c t , r e s e t t i n g the radiogenic clock. 76 From the evidence obtained i t i s suggested that the ultramafite c r y s t a l l i z a t i o n i s a minimum of 15 m.y. older than the Spuzzum Intrusions and the actual age of the ult r a m a f i t e may be considerably older. This sequence of events may we l l explain some of the secondary features seen by Aho i n the study of the orebodies, the b r e c c i a t i o n and p r o t o c l a s t i c textures along the footwall of the 1900 and Chinaman ore zones and a crude metasomatic imprint (hornblendite margin) on the ultramafite i t s e l f . D i s t r i b u t i o n c o e f f i c i e n t s f o r pyroxenes ind i c a t e o r i g i n by magmatic c r y s t a l l i z a t i o n of Giant Mascot ultramafic rocks. Pyroxene geothermometry suggests e q u i l i b r a t i o n with a minimum mean temperature of c r y s t a l l i z a t i o n of 990°C. These considerations suggest that the Giant Mascot Ultramafite originated from a magmatic source and that Spuzzum Plutonism, intermediate i n composition, did not e f f e c t K^'s or temperatures of pyroxene e q u i l i b r a -t i o n . Further, at temperatures of formation i n the range of 1000°C a s u l f i d e l i q u i d could coexist with the ultramafic magma. Chemical analyses of s i l i c a t e s and a s u l f i d e mineral within the ultramafite show marked compositional v a r i a t i o n s from p e r i d o t i t e s to pyroxenites. Pentlandites are d i f f e r e n t compositionally i n each of the two rock units and are d i f f e r e n t again i n ore zones. I t seems c e r t a i n that no theory of sing l e magmatic i n j e c t i o n or accumulation can explain these observations but that multiple i n j e c t i o n s of d i f f e r e n t compositions, possibly followed by separate ore i n j e c t i o n s , may. Textures must be taken into account i n working out a hypothesis of o r i g i n . T e x t u r a l l y the p e r i d o t i t e s show olivine-pyroxene or o l i v i n e -hornblende t e x t u r a l types i n d i s t i n g u i s h a b l e from heteradcumulates found i n layered rocks from Rhum, Skaergaard etc. Pyroxenites appear adcumu-l a t e - l i k e i n texture although heteradcumulate-like textures are seen. 77 In p a r t i c u l a r , hornblende i n pyroxenites forms clear heteradcumulate textures. M i c r o s c o p i c a l l y o l i v i n e s and pyroxenes appear somewhat deformed near contacts suggesting movement a f t e r some c r y s t a l l i z a t i o n . This i s also true of some s u l f i d e s , p a r t i c u l a r l y chalcopyrite i n the Chinaman orebody. Between the contact of p e r i d o t i t e and websterite at the Climax ore zone t h i s deformation i s noted along with v a r i a b l e amounts of o l i v i n e which appear to make a hybrid-type rock between the two end member rock u n i t s . I t has been suggested by Muir (1971) that a s i m i l a r occurrence i n the 4600 orebody i s the r e s u l t of mixing of two c r y s t a l mushes to produce what he c a l l e d a "hybrid zone". S t r u c t u r a l l y , the ore zones appear r e l a t e d to l i t h o l o g i c a l contacts mainly between p e r i d o t i t e and pyroxenite, forming steeply plunging pipe-l i n e orebodies with the s u l f i d e s concentrated mainly on the footwall of the pipe. The ore zones are e i t h e r massive s u l f i d e concentrations be-tween the two p r i n c i p a l u ltramafic phases or i n a p i p e - l i k e body, zoned from hornblende r i c h rocks to p e r i d o t i t e i n the cores with ore minerals concentrated along the footwall. The proximity of n o r i t i c phases within the ultramafite appear to have some influence, possibly s t r u c t u r a l , on the l o c a l i z a t i o n of ore. The majority of the orebodies l i e along a l i n e near the south-west part of the complex with some exceptions, the Chinaman being more c e n t r a l to the u l t r a m a f i t e . The ore zones appear to terminate downwards at approximately the 2600 foot e l e v a t i o n . This termination may be influenced by the bottoming of the ultramafic rocks at 250 to 400 feet below t h i s l e v e l as in d i c a t e d by downhole d r i l l i n g which encounters metamorphic and d i o r i t i c rocks. Some orebodies reach the surface; others weaken or 78 diminish, or are f a u l t e d o f f . The author considers the following hypotheses f o r the o r i g i n of the Giant Mascot Ultramafite and i t s ores: (1) M u l t i p l e i n j e c t i o n s of u l t r a b a s i c magmas, of d i f -f e r i n g compositions, to form a zoned complex of the Alaskan type (Ruckmick and Noble, 1959). (2) The emplacement of an ultramafic body i n a s o l i d or magmatic state with subsequent metasomatic modifica-t i o n by Spuzzum Plutonism. (3) M u l t i p l e i n j e c t i o n of c r y s t a l mush and s u l f i d e melts derived from a d i f f e r e n t i a t i n g i n t r u s i o n located at some greater depth. (4) D i a p i r i c re-emplacement of rudely s t r a t i f o r m se-quences of cumulates and s u l f i d e s s t i l l i n a "mushy" form and derived from a d i f f e r e n t i n g sub-v o l c a n i c i n t r u s i o n ( I r v i n e , 1974). The f i r s t hypothesis would account f o r the o r i g i n of the ultramafite provided that more than one center of i n j e c t i o n was operative at one time within the stock and that subsequently the Spuzzum in t r u s i o n s d i s -rupted and rearranged the zoning, and metasomatized the u l t r a m a f i t e . Also the s i z e and age r e l a t i o n s h i p s of the ultramafite to the surrounding g r a n i t i c terrane i s remarkably s i m i l a r to those of the Alaskan type. I t must be pointed out however, that the Giant Mascot Ultramafite d i f f e r s i n several important respects from the Alaskan type. These diff e r e n c e s are: (1) the lack of graded l a y e r i n g i n rhythmical beds as noted i i i some Alaskan Complexes; (2) the presence of several crudely zoned p e r i d o t i t e centers; (3) l a t e hornblendite dykes c u t t i n g a l l rock i 79 units at Giant Mascot; (4) the abundance of orthopyroxene; (5) the presence of pl a g i o c l a s e ; (6) the r e s t r i c t e d compositional range of o l i v i n e (FOg^-Fo^g); (7) the r e s t r i c t e d compositional range of c l i n o -pyroxene ( D i g g H e d ^ - D i ^ Hed^^) compared to Alaskan clinopyroxene (Dig^Hed^-Di^QHed^Q); and (8) the presence of abundant N i and Cu s u l -f i d e s at Giant Mascot. Some of these chemical d i f f e r e n c e s may be the r e s u l t of d i f f e r i n g compositions of i n i t i a l magmas or the much smaller s i z e (and therefore l e s s d i f f e r e n t i a t e d ? ) of the Giant Mascot body. Naldrett (1973) suggests the chemical d i f f e r e n c e s may not be a t t r i b u t e d to d i f f e r e n t mechanisms of formation but to the depths at which u l t r a -mafic magmas have o r i g i n a t e d . Furthermore, there are serious objections to the Ruckmick-Noble hypothesis. The younger, more u l t r a b a s i c magmas i n Alaska are not seen to cut the older l e s s u l t r a b a s i c rocks. Further, there remains the more general problem of producing a dunite or p e r i d o t i t e magma. The second mechanism, i n v o l v i n g metasomatism of a p r e - e x i s t i n g ultramafite has some support i n that alpine ultramafites to the north-west of Giant Mascot i n the v i c i n i t y of The Old S e t t l e r mountain show increasing metamorphic grade where i n contact with Spuzzum d i o r i t e . Pyroxenites are there developed with minor Ni-Cu showings and these resemble those at Giant Mascot. Trommsdorff and Evans, (1972), have described, i n the Swiss Alps, s e r p e n t i n i t e s metamorphosed to pyroxene, amphibole and o l i v i n e . Thus, i f an alpine ultramafite were engulfed by the Spuzzum magmas, conversion and metasomatism might occur and give r i s e to a zoned body with t h i s mineral assemblage. N i c k e l m i n e r a l i z a t i o n could possibly r e s u l t by r e d i s t r i b u t i o n and concentration during meta-morphism of n i c k e l o r i g i n a l l y held i n s i l i c a t e s such as o l i v i n e and per-80 haps released during s e r p e n t i n i z a t i o n . This mechanism i s not acceptable f o r Giant Mascot because s u l f i d e textures suggest a magmatic o r i g i n with p r e c i p i t a t i o n from a l i q u i d which would be at l e a s t at 1000°C. Temperatures of formation or equi-l i b r a t i o n of the ul t r a m a f i t e (2-pyroxene geothermometer) was apparently near 1000°C., much higher than would be reasonably expected i n a sizeable i n c l u s i o n heated by Spuzzum d i o r i t e magma. Furthermore, textures of the p r i n c i p a l u l t r a b a s i c minerals are more magmatic-looking than metamorphic. Although the general hypothesis seems untenable, i t seems c e r t a i n that the coarse-grained hornblendite margin i s metasomatic, but the metamorphic e f f e c t extends not much further than 100 yards..... In addition, during the emplacement of the Spuzzum, there were developed l a t e hornblendite dykes which cut a l l rock units within the complex, and there was also some r e d i s t r i b u t i o n of ore minerals (which, i n c i d e n t a l -l y , l e d Aho to postulate a hydrothermal o r i g i n f o r some orebodies). The t h i r d hypothesis, i n j e c t i o n of c r y s t a l mushes from a d i f f e r e n t i a t -ing body (Bowen and T u t t l e , 1949), appears to o f f e r a p l a u s i b l e explana-t i o n f o r the genesis of the Giant Mascot Complex. Several i n j e c t i o n s of mushes ranging i n composition from hornblendic pyroxenite, to pyroxenite, to p e r i d o t i t e i n that order with the l a t e r , more magnesian, magmas em-placed along several centers would account f o r the crude zonation of the ultramafite on the whole and the zonation around some ore zones. The ore-forming s u l f i d e melts would be, apparently, i n j e c t e d l a s t or along with the p e r i d o t i t e mush which, on cooling, formed the host rock f o r the net-textured and massive s u l f i d e s . This hypothesis although p l a u s i b l e i s complex and incomplete. A simpler and more complete one, that of Irvine (1974), r e t a i n s the idea 81 of c r y s t a l mushes derived from a d i f f e r e n t i a t i n g body but o f f e r s an al t e r n a t i v e method of emplacement. A fourth hypothesis, making use of Irvine's mechanism (1974), i n -volves d i a p i r i c re-emplacement of rudely s t r a t i f o r m sequences of "mushy" cumulates and s u l f i d e s , that have p r e c i p i t a t e d i n a d i f f e r e n t i a t i n g sub-volc a n i c magma chamber i n the order: s u l f i d i c p e r i d o t i t e , pyroxenite to hornblende pyroxenite. These magmas may represent the e a r l i e s t Spuzzum magmatism. Diapirism could r e s u l t from additions of magmas (Spuzzum?) from depth through feeders into the magma chamber, from upward force applied by the r i s i n g Spuzzum magmas or from tectonic compression. Although erosion has removed the postulated o v e r l y i n g volcanoes, to the east, the Spences Bridge (Lower Cretaceous) and the Kingsvale ( l a t e Lower Cretaceous) Groups ranging i n composition from andesites to basalts (Rice, 1947) show that volcanism was widespread at this time. This process of re-emplacement by d i a p i r i s m might r e a d i l y explain the crude zonation within the ultramafite (excluding the marginal horn-blendite) and accounts very well f o r several features seen on the 3050 cross-cut such as: (1) The sharp change i n mineral composition both s i l i c a t e s and s u l f i d e from one rock type to an-other. (2) The hybrid pyroxenite on the footwall of the Climax orebody, possibly the consequence of mixing of two c r y s t a l mushes. (3) The strained s i l i c a t e s i n the Climax zone between pyroxenite and p e r i d o t i t e . 8 2 ( 4 ) T h e p r o t o c l a s t i c z o n e o n t h e f o o t w a l l o f t h e C h i n a m a n o r e b o d y . ( 5 ) T h e c l o s e s p a t i a l r e l a t i o n s h i p o f s u l f i d e s t o p e r i d o t i t e a n d p a r t i c u l a r l y n e t - t e x t u r e d p e r i -d o t i t e s i n t h e o r e z o n e s . ( 6 ) T h e h e t e r a d c u m u l a t e - l i k e n a t u r e o f t h e s i l i -c a t e s . W i t h t h e m e t a s o m a t i c e f f e c t s o f s u b s e q u e n t S p u z z u m m a g m a s o n t h e u l t r a m a f i t e , t h i s m e c h a n i s m a p p e a r s t o a c c o u n t r e a s o n a b l y w e l l f o r t h e c o m p l e x g e o l o g i c a l f e a t u r e s o b s e r v e d a t G i a n t M a s c o t . R i c h a r d s ( 1 9 7 1 ) n o t e d s e v e r a l s m a l l u l t r a b a s i c b o d i e s i n t h e S p u z z u m , f r o m h o r n b l e n d i t e u p t o 5 f e e t l o n g , t o p e r i d o t i t e a n d p y r o x e n i t e l e n s e s , a b o u t 6 i n c h e s i n l e n g t h . T h e s e a r e a l i g n e d w i t h t h e f o l i a t i o n i n t h e d i o r i t e o r c u t a c r o s s f o l i a t i o n b u t a r e , n e v e r -t h e l e s s , i r r e g u l a r l y e l o n g a t e d a l o n g f o l i a t i o n d i r e c t i o n s . P y r o x e n i t e c o n t a i n s a u g i t e a b o u t 1 0 % m o r e F e - r i c h a n d h y p e r s t h e n e 1 0 - 2 0 % m o r e F e - r i c h t h a n t h o s e a t G i a n t M a s c o t . I n a d d i t i o n t h e s e s m a l l b o d i e s a l l c o n t a i n q u a r t z a n d a n d e s i n e , a n d t h u s d i f f e r f r o m u l t r a m a f i t e s a t G i a n t M a s c o t . R i c h a r d s ( 1 9 7 1 ) s u g g e s t s t h a t t h e s e b o d i e s a r e f o r m e d b y m e t a s o m a t i c r e p l a c e m e n t o f t h e d i o r i t e s a l o n g p r e - e x i s t i n g f r a c t u r e s . A n a l t e r n a t i v e i s t h a t t h e s e a r e s t r o n g l y m e t a m o r p h o s e d u l t r a m a f i c x e n o l i t h s . C h e m i c a l c o m p a r i s o n s b e t w e e n t h e s e s m a l l p y r o x e n i t e l e n s e s a n d S p u z z u m d i o r i t e s s t r o n g l y s u p p o r t t h e f i r s t h y p o t h e s i s . CONCLUSIONS A b r i e f summary of some of the more important findings made during the course of t h i s study are given below: (1) K-Ar dating indicates that the ultramafite (119 m.y.) i s as o l d as or probably older than Spuzzum Plutonism (89 m.y.). (2) Formation or e q u i l i b r a t i o n of pyroxene p a i r s occurred at a mean minimum temperature of 990°C. (3) Pyroxene pai r s have a mean d i s t r i b u t i o n c o e f f i c i e n t of 0.738, i n d i c a t i v e of magmatic formation. (4) Pyroxene, and p a r t i c u l a r l y orthopyroxene, i s markedly d i f f e r e n t i n adjacent pyroxenites and p e r i d o t i t e s , with Mg-rich pyroxenes i n p e r i d o t i t e . (5) The composition of o l i v i n e appears to vary l i t t l e but the most Mg-rich i s found i n the Climax hanging w a l l . (6) Pentlandite i s Fe- and N i - r i c h with l i t t l e Co i n ore-bodies, i s Co-rich and s l i g h t l y Fe- and Ni-poor i n pyroxenites and i s F e - r i c h and Ni-poor i n p e r i d o t i t e . (7) Mineral textures i n the more magnesian rock units are s i m i l a r to cumulate textures observed i n layered complexes. (8) Contacts between ultramafic rock units are usually sharp on a megascopic scale and gradational microscopically. (9) The Climax and Chinaman orebodies are steeply plunging p i p e - l i k e bodies with the higher grade sections concentrated i n the trough or footwall zone. (10) The Climax orebody l i e s at a contact between pyroxenite and p e r i d o t i t e whereas the Chinaman appears to be crudely zoned around a p e r i d o t i t e core. Both are s p a t i a l l y r e l a t e d to a n o r i t e body. In conclusion, the wr i t e r maintains that the genesis of the Giant Mascot Ultramafite involves a d i a p i r i c re-emplacement of rudely s t r a t i f o r m c r y s t a l mushes and s u l f i d e s from a d i f f e r e n t i a t i n g sub-volcanic body, possibly an early phase of Spuzzum magma a c t i v i t y . Subsequently t h i s material was engulfed by the r i s i n g Spuzzum d i o r i t i c magmas and a metasomatic hornblendite marginal zone was imposed on the ultr a m a f i t e . REFERENCES CITED Aho, A.E. (1956) Geology and genesis of u l t r a b a s i c n i c k e l - copper -py r r h o t i t e deposits at the P a c i f i c N i c k e l Property, southwestern B r i t i s h Columbia. Econ. Geol. v o l . 51, pp. 444-481. Armstrong, R.L. (pers. comm.) Associate Professor, Dept. of Geological Sciences, Univ. of B.C. Atkin s , F.B. (1969) Pyroxenes of the Bushveld I n t r u s i o n , South A f r i c a . Journ. of Pet., v o l . 10, pp. 222-249. Bowen, N.L., and T u t t l e , O.F. (1949) The System Mg0-Si0 2-H 20. Geol. Soc. Amer., B u l l . 60, pp. 439-460. Brown, G.M. (1957) Pyroxenes from the e a r l y and middle stages of f r a c t i o n a t i o n of the Skaergaard i n t r u s i o n , East Greenland. Miner. Mag. 31, pp. 511-543. Cairnes, C.E. (1924) N i c k e l i f e r o u s mineral deposit, Emory Creek, Yale Mining D i v i s i o n , B r i t i s h Columbia. Geol. Surv. Can., Summ. Rept., pp. 100-106. (1930) The serpentine b e l t of Coquihalla Region, Yale D i s t r i c t , B r i t i s h Columbia. Geol. Surv. Can., Summ. Rept, f o r 1929, pp. 144-197. Co c k f i e l d , W.E., and Walker, J.F. (1933) The n i c k e l bearing rocks near Choate, B r i t i s h Columbia. Geol. Surv., Can. Summ. Rept., pp. 62-68. Craig, J.R., and Kulle r u d , G. (1969) Phase r e l a t i o n s i n the Cu-Fe-Ni-S system and t h e i r a p p l i c a t i o n to magmatic ore deposits, i n Magmatic Ore Deposits, Monograph 4, Econ. Geol., pp. 344-358. 8 6 Findlay, D.C. (1969) O r i g i n of the Tulameen ultr a m a f i c gabbro complex, southern B r i t i s h Columbia. Can. J. Earth. S c i . , v o l . 6, pp. 399-426. Hess, H.H. (1960) S t i l l w a t e r igneous complex, Montana: a q u a n t i t a t i v e mineralogical study. Mem. geol. Soc. Am. 80. Horwood, H.C. (1936) Geology and mineral deposits at the mine of B.C. N i c k e l Mines, L t d . , Yale D i s t r i c t , B r i t i s h Columbia. Geol. Surv. Can., Memoir 190. (1937) Magmatic segregation and m i n e r a l i z a t i o n of the B.C. N i c k e l Mine, Choate, B.C. Trans. Royal Soc. Canada, sec 4, pp. 5-14. Hutchison, W.W. (1970) Geological Survey paper Ser i e s , Age Determinations and Geological Studies. Geol. Surv. Can., Paper 71-2. I r v i n e , T.N. (1967) The Duke Island Ultramatic Complex, southeastern Alaska. Ultramafic and r e l a t e d rocks (ed. P.J. W y l l i e ) , pp. 84-96, New York John Wiley and Sons. (1974) Petrology of the Duke Island Ultramafic Complex Southeastern Alaska. Geol. Soc. Amer., Mem. 138. Kretz, R. (1961) Some app l i c a t i o n s of thermodynamics to coex i s t i n g minerals of v a r i a b l e composition. J . Geol. 69, pp. 361-387. (1963) D i s t r i b u t i o n of magnesium and i r o n between ortho-pyroxene and c a l c i c pyroxene i n n a t u r a l mineral assemblages. Ibi d . 71, pp. 772-785. Kullerud, G., Yund, R.A., and Moh, G.H. (1969) Phase r e l a t i o n s i n the Cu-Fe-S, Cu-Ni-S, and Fe-Ni-S systems, _in Magmatic Ore Deposits, Monograph 4, Econ. Geol., pp. 323-343. Mattinson, J.M. (1970) Uranium-Lead Geochronology of the Northern Cascades, Washington (abs.) Geol. Soc. Amer., C o r d i l l e r a n Section, 66th Annual Meeting, pp. 116. McTaggart, K.C., and Thompson, R.M. (1967) Geology of part of the northern Cascades i n southern B r i t i s h Columbia. Can. J. Earth S c i . , v o l . 4, pp. 1191-1228. McTaggart, K.C. (1970) Tectonic History of the Northern Cascade Mountains. Geol. Assoc. of Canada, s p e c i a l paper No. 6, pp. 137-148. ' (1971) On the o r i g i n of ultramafic rocks. B u l l . Geol. Soc. Amer., v o l . 82, pp. 23-42. Monger, J.W.H. (1970) Hope map-area, west h a l f , B r i t i s h Columbia. Geol. Surv. Can., Paper 69-47. Muir , J.E. (1971) A study of the petrology and ore genesis of the Giant N i c k e l 4600 Orebody, Hope, B.C. Unpublished M. Sc. t h e s i s , U n i v e r s i t y of Toronto, Toronto, Canada. Nal d r e t t , A.J. (1973) N i c k e l s u l f i d e deposits - Their c l a s s i f i c a t i o n and genesis, with s p e c i a l emphasis on deposits of v o l c a n i c assoc-i a t i o n . Can. Inst. Mining Met., v o l . 76, pp. 183-201. Read, P.B. (1960) Geology of the Fraser V a l l e y between Hope and Emory Creek, B r i t i s h Columbia. Unpublished M.A.Sc. t h e s i s , U n i v e r s i t y of B r i t i s h Columbia. Rice, H.M.A. (1947) Geology and Mineral Deposits of the Princeton Map-Area, B r i t i s h Columbia. Geol. Surv. Can., Mem. 243. Richards, T.A. (1971) Pl u t o n i c rocks between Hope, B.C. and the 49th p a r a l l e l . Unpublished Ph.D. t h e s i s , U n i v e r s i t y of B r i t i s h Columbia. Roddick, J.A. and Hutchison, W.W. (1969) Northwestern part of Hope Map-area, B r i t i s h Columbia. Geol. Surv. Can., Paper 69-1A, pp. 29-38 Ruckmick, J.C., and Noble, J.A. (1959) O r i g i n of the u l t r a m a f i c complex at Union Bay, southeastern Alaska. B u l l . Geol. Soc. Amer., 70, pp. 981-1018. Streckeisen, A. (1967) C l a s s i f i c a t i o n and Nomenclature of Igneous Rocks, ( F i n a l Report of an Inquiry). Neues Jahrbuch fur Mineralogi Abhandlungen 107, pp. 144-240., in Geotimes, October 1973. Sutherland-Brown, A., e t . a l . (1971) Metallogeny the Canadian C o r d i l l e r a . Can. Inst. Mining Met., v o l . 74, pp. 121-145. Taylor, H.P., J r . (1967) The zoned ultramafic complexes of southeastern Alaska, i n Ultramafic and r e l a t e d rocks (ed. P.J. W y l l i e ) , New York, John Wiley and Sons. Trommsdorff, V., and Evans, B.W. (1972) Progressive metamorphism of A n t i g o r i t e s c h i s t i n the B e r g e l l T o n a l i t e aureole ( I t a l y ) . Am. Jour. S c i . , v o l . 272, pp. 423-437. Wood, B.J., and Banno, S. (1973) Garnet-Orthopyroxene and Orthopyroxene Clinopyroxene r e l a t i o n s h i p s i n simple and complex systems. Contr. Mineral. P e t r o l . , v o l . 42, pp. 109-124. Appendix 1 Sample Location Map Appendix 2 Geology of Climax z o o o 7000E. S / / / /9a/ 2 O O 05 CD !l j Pelt. •Pxnite • f ] Norite • •v • Joint . ~xr~~ Fault App rox . Ou t l i ne C l i m a x O r e GEOLOGY OF CLIMAX 3 0 5 0 X-CUT 92 Appendix 3 Cu, N i , and Cu/(Cu+Ni) Assay Contour P l o t s , Chinaman and Climax Orebodies 76 «1 i o CM 3206. CU/NI+CU -r O « . 0 IDSO.O GUO.O 6830.0 6820.0' BP«.0 GS60.0 6DC3.0 t>?00.0 F-OXIS -1 -1 1 1 63JO.0 M«).D 69C3.D 6°f0.0 —I 1 IOOO.O IOIO.O •/OO.O oo 100 o L O CD C\J CO , — i 1 1 r i i ^ i •D9S8 D'D>53 D ' K 3 3 0 D C 9 8 C K S 3 D K S 3 D'D?S3 O ' K i S D D 0 S 3 SIXb'-N 101 8 7060.0 _1 & eoi 105 8 O'OOOt SIXO-N 108 Appendix 4 Microprobe Analyses of S i l i c a t e s N.B. For sample number c o r r e l a t i o n see p. 62. MICROPROBE ANALYSIS OF ORTHOPYROXENES 1 2 3 4 5 6 7 8 S i 55.37 54.84 54.18 54.90 53.40 54.695 54.567 54.96 Al 3.13 2.62 2.38 2.28 2.64 2.128 2.110 1 .52 T i .23 .18 .07 .24 .32 .239 .420 .20 Cr .42 .12 .23 .19 .26 .190 .252 .12 Fe 12.09 12.74 13.41 12.68 13.94 14.062 12.236 11 .93 Mn n.d. n.d. n.d. n.d. n.d. n .d. n.d. n.d. Mg. 29.72 30.03 29.78 27.60 26.47 28.631 29.896 28.49 Ca .68 .69 .35 1 .09 1.24 1.154 .796 1.20 Na '.03 " - - - .07 .012 .052 .02 K n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. 101.67 101.22 100.40 98.95 98.34 101 .111 100.329 98.44 Ox i d e s Formulae based on 6 oxyqens S i Al Al T i Cr Fe Mn Mg Ca Na K 1.928\ ? .072; L .056\ .006 .012 .352 \ 1.543 .025 .002 / ,00 1.99 1 .572 .026 .00 .01 1.924 .076 .024\ .002 .006 .398 V 2 1.577 .013 -J 2.00 ,020 1.9681 .032j .064> .006 .0051 .380 1.475 .042 2.00 1 .972 1.944\ .056^ .0571 .009 .007 .424 1.437 .048 .005 j 2.00 1.99 1 .937 .063 .026\ .006 .005 •416>2 1 .511 .044 .001 2.00 .01 1 5 .932 .068 .020"! .011 .007 .362 2.00 1 .577 .030 .003 2.01 1.977\ .023; . 0 4 n .005 .003 \ .359 V 1 .527 .046 .001 2.00 1 .98 Mg = 80 45% Mg = 79.65% Mg = 79.30% Mg = 77 .75% Mg = 75.25% Mg = 76 .65% Mg = 80 .05% Mg = 78.85% Fe = 18 25% Fe = 18.95% Fe = 20.05% Fe = 20 .00% Fe = 22.20% Fe = 21 .10% Fe = 18 .40% Fe = 18.65% Ca = 1 30% Ca = 1.40% Ca = 0.65% Ca = 2 .25% Ca = 2.55% Ca = 2 .25% Ca = 1 .55% Ca = 2.50% c o n t 1 . d . . . . / 2 9 10 11 12 13 14 15 16 S i 56.075 - 56.325 56.869 57.247 53.824 55.544 53.232 55.62 AT 2.074 1.673 1.595 2.316 2.557 2.279 2.166 1.78 T i .165 .134 .205 .384 .197 .248 .320 .04 Cr .344 .370 .214 .370 .323 .482 .173 .12 Fe 11.305 12.028 9.612 8.809. 8.500 8.190 13.920 8.67 M.n .160 .140 n.d. n.d. . n.d. n.d. n.d. n.d. Mg 30.863 31.131 32.088 32.526 31 .164 32.482 28.772 32.44 Ca 1 .110 1.043 1.079 .648 .759 1 .212 .526 .92 Na .011 - .042 .081 - - .057 -K - - n.d. n. d. n.d. n.d. n.d. n.d. 102.107 101.844 101.704 102.381 97.325 100.437 99.166 99.59 Ox i d e s Formulae based on 6 oxygens S i Al A l T i Cr Fe Mn Mg Ca Na K l l 9 4 2 \ 2 00 .Q58J ^ u u .027\ .004, .009 .327 \ .005 1.593 \ .041 j .0017 2.007 1.960] 2 0 .040; u u .028^ .003 .010 \ •350 V 9 9 .004 ' 1 562 039 .00 .002 1.949] . 0 5 l j .042^1 .010 .010 .251 n.d. 1.650 .024 .005 n.d./ 2.00 1.99 1 .931 .069 .039\ .005 .009 .255\ n.d. 1.666 .029 n.d./ 00 2.003 1.683 .045 .00 .00 .00 .02 .00 1 .695 .034 .06 Mg = 81.20% Mg = 80.00% Fe = 16.70% Fe = 18.00% Ca = 2.10% Ca = 2.00% Mg = 83.75% Fe •= 1 4 / Ca = 2. Mg = 85.65% Fe = 13.10% Ca = 1.25% Mg = 85.45% Fe = 13.05% Ca = 1 Mg = 85.60% Fe = 12.10% Ca = 2.30% Mg = 77.85% Fe = 21.15%: Ca = 1.00% Mg = 8 5 . 4 0 S Fe .= 12.70% Ca = 1.70% 17 18 19 . 20 21 22 23 24 S i 57.507 55.094 53.074.- 55.016% 52.171 51.954 52.303 56.229 Al 1.985 1.538 2.953 2.962 2.079 2.935 4.912 2.425 T i .093 .144 .170 .154 .198 .155 .053 .060 Cr .185 .052 .065 .808 - .038 - .217 Fe 8.895 10.538 15.021 9.557 24.146 15.634 11.495 9.710 Mn n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. Mg 32.504 31.253 28.176 31 .122 22.211 28.441 30.161 32.246 Ca 1 .122 .937 1.286 2.275 .816 .636 .661 .619 Na - .005 - .267 - .033 .037 .058 K n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. 102.291 99.671 100.749 102.161 101.621 99.826 99.622 101.564 O x i d e s Formulae based on 6 oxygens S i Al Al T i Cr Fe Mn Mg Ca Na K 1.961 .039 . 0 4 n .024 .005 .254 2.00 } 2.04 1 .652 .041 1.9471 2 .0537 c' .015^ .004 .002 .311 00 }2.01 1.646 .035 1.503 .049 2.00 2.03 1.902V 2 oo .098/ ^ , u u .023' .004 .022 .276 1 .604 .084 .018 2.03 1.926 .074, .016" .005 .746 1 .222 .032 •2.00 'Z.C-2. 1 .536 .025 .002 2.00 2.05 1 .860 .140 .066 .001 .342 1.599 .025 .002 2.00 1 .9391 . . 0 6 1 J C .037^ .001 .006 01 •2.03 .280 V V2.0 1 .657 .023 .004j Mg Fe Ca 84.80% 13.10% 2.10% Mg = 82.60% Fe = 15.65% Ca = 1.75% Ma = 75.10% Fe = 22.45% Ca•= 2.45% Mg = 81.65% Fe = 14.05% Ca-- • 4.30% Mg = 61.10% Mg = 75.45% Mg = 81.30% Mg = 84.50' Fe = 37.30% Fe = 23.35% Fe = 17.40% Fe = 14.30! Ca = 1.60% Ca = 1.20% Ca = 1.30% Ca = 1.20! 25 26 27 28 29 30 S i 54.253 54.121 54.209 55.614 55.035 54.919 A l 2.593 2.452 1.819 2.175 3.027 2.344 T i .101 .156 .057 .054 .035 .184 Cr .315 .232 .385 .032 .309 .545 Fe 11 .130 11.778 14.489 14.267 10.236 11.225 Mn n.d. n.d. n.d. n .d. n.d. n.d. Mg 31 .270 32.071 28.179 29.889 31.484 30.576 Ca .675 .529 1.066 .919 .498 .792 Na - .002 - - .022 .059 K n.d. n.d. n.d. n .d. n.d. n.d. 100.337 TOT.341 100.204 102.95 100.646 100.644 O x i d e s Formulae based on 6 oxygens S i A l A l T i Cr Fe Mn Mg Ca Na K 1 .912 .088 .020") .003/ .0091 . 3 2 8 \ 0 1.642 .025 2.00 ,03 1.896) 2 0 ( J .101/ ^ , u u .003^ .001 .0061 .345' 1.674 .020 2.046 1-942.X 2. 0 0 .058; .019^ .001 .011 ;434 Jz.oi 1.505 .041 1 .933 I o 00 . 0 6 7 / ^'uu .022) .001 .001 .415 1.548 .034 V J 2.02 .045V .001 .008 .299 ) 1.638 .019 .001 2 .01 } 1 .929 .071 .026^ .005 .015 .330 2 oo Z.oi 1.601 .030 .004 Mg = 82.30% Fe = 16.45% Ca = 1.25 % Mg = 82.20% Fe = 16.85% Ca = 0.95% Mq = 76.05% Fe = 21.90% Ca = 2.05% Mg = 77.50% Fe = 20.80% Ca = 1.70% Mg = 83.75% Fe = 15.30% Ca = 0.95% Mg = 81.65% Fe = 16.85% Ca = 1.50% MICROPROBE ANALYSIS OF CLINOPYROXENES 1 2 3 4 7 • 8 9 10 11 S i 54.00 52.11 52.47. 52.87 51.918 53.19 53.803 54.175 53.937 Al 3.52 2.97 3.66 2.60 2.472 1.37 3.109 2.890 1 .902 T i " .45 .50 .58 .40 .402 .28 .344 .453 .288 Cr .58 .39 .36 .31 .503 .32 .528 .580 .609 Fe 4.64 4.92 5.04 4.53 5.052 4.63 4.961 4.678 3.761 Mn n.d. n.d. n.d. n.d. n.d. n.d. .093 .060 n.d. Mg 16.80 17.06 15.72 16.01 16.625 16.46 18.106 17.778 17.242 Ca 21.69 22.47 23.87 21.29 22.381 22.74 19.456 18.483 23.537 Na .39 .46 .57 .20' .364 .31 .394 .447 .315 K n.d. n.d. n.d. n.d. n.d. n.d. - -101.07 100.88 102.27 98.21 100.717 99.30 100.794 99.544 102.491 O x i d e s Formulae based on 6 Oxygens S i Al AT T i Cr Fe Mn Mg Ca Na K ]; 9 $ 2. ooo .064" .012 .017 • 1 4 0 >2.003 .904 .839 .027 7 .00 2.03 2.00 .884 .845 .014 1.98 1.914-1 2 Q 0 .086/ ^'UU . 0 2 0 .011 .014 .156 .914 .884 .026 r2.02 1 ) .961 .039 .020^ .008 .009 .143 2.00 .905 .898 J ' >2.005 1.9641 .036/ .087' .012 .017 .142 .002 .961 .718 .031 2.00 1.97 1 .941 .059 .022 .008 .017 .113 .925\ .907 .022 •2.0V Mg = 48.00 Fe = 4.45 Ca = 44.55 Mg = 47.50 Fe = 7.65 Ca = 44.85 Mg = 43.95 Fe = 7.90 Ca = 48.15 Mg = 47.25% Fe = 7.50% Ca = 45.25% Mg = 46.80% Fe •= 8.00% Ca = 45.20% Mg = 46.40 Mg = 5195% Mg = 52.75% Mg = 47.60% Fe = 7.55 Fe = 7.95% Fe = 7.80% Fe = 5.80% Ca =46.05 Ca = 40.10% Ca = 39.45% Ca = 46.60% c o n t ' d . 7 2 15 16 17 18 19 22 25 27 28 S i 51.768 52.24 54.027 53.663 50.783 53.007 52.207 52.253 52.361 Al 2.109 2.06 1.803 2.167 3.913 3.503 3.786 2.792 3.039 T i .466 .16 .054 .100 .359 .483 .308 .348 .381 Cr .504 .95 .697 .738 .201 .086 .660 .382 .289 Fe 6.019 4.23 3.857 4.503 6.479 6.882 4.285 5.926 5.631 Mn n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. Mg 16.859 18.22 18.260 17.645 15.547 16.020 17.541 15.474 16.543 Ca 22.447 20.88 22.690 22.800 21.270 21.681 22.009 22.422 23.291 Na .344 .49 .194 .294 .393 .504 .486 .435 .337 K n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. Ixides 100.517 99.23 101.582 101.910 98.945 102.166 101.282 100.032 101.872 Formulae based on 6 Oxygen s S i 1 .904W Al .091 J T i .005^ Al • -T i .006/ Cr .015 Fe .1851 Mn n.d. \ Mg .924 Ca .885 Na. .024 K n.d. / 2.00 2.04 1 .03 1 .940 .060. .016^ .001 .019 .116 n.d. .977 .873 I .013 \ n.d. / 2.00 01 2.00 2.022 1 .892*1 .108 J .064^ .010 .006 .202 n.d .863 ( .849 \ .028 n . d . y 2.00 2.02 .911 .089 2.000 .060] .013 .002 .207 n.d .861 ' .8381 .035 ] n.d. / • 2.01 ,00 .03 1.9241 .076 J f 2.00 1.897C .103/ .045^ .009 .011 .182 .027^ .010 .008 .171 .849 .885 .031 J V 2.01 .893 .904 .024 2.00 .2.04 Mg = 46.35% Fe = 9.30% Ca = 44.35% Mg = 51.15 Fe = 6.70 Ca = 42.15 Mg = 49.70% Fe = 5. Ca = 44.< •Mg = 48.25% Fe = 6.90% Ca = 44.85% Mg = 45.10% Mg Fe = 10.55% Fe Ca = 44.35% Ca 45.00% Mg = 49.05% 10.80% Fe = 6.70% 44.20% Ca = 44.25% Mg = 44.35% Fe = 9.45% Ca = 46.20% Mg Fe Ca 45.40% 8.70% 45.90% MICROPROBE ANALYSIS OF OLIVINES 11 12 12A 13 13A 14 S i Al T i Cr Fe Mn Mg Ca Na K 39.90 18.04 44.13 102.07 39.88 15.94 45.81 101.63 40.892 14.774 .147 45.650 .004 101 .467 40.490 14.838 .134 45.984 .004 101.450 40.892 .033 12.942 n.d. 47.235 n.d. 101.102 40.185 .010 14.002 n.d. 47.404 .004 n.d. 101.605 40.226 13.251 n.d. 47.043 .004 n.d. 100.524 Ox i d e s Formulae based on 4 oxygens S i A l T i Cr Fe Mn Mg Ca Na K .993 .376 1.637 .989 .330 1.692 1.007 .304 .003 1.677 .0002 .999 .306 .003 1.692 .0002 1.003 .265 1.727 .988 .288 1.737 .995 .274 n.d. 1.735 n.d. Fo = 81 Fa = 18.80% Fo = 83.80% Fo = 84.60% Fo = 84.70% Fo = 86.65% Fo = 85.80% Fo = 86 Fa = 16.20% Fa = 15.40% : Fa = 15.30% Fa = 13.35% Fa = 14.20% Fa = 13 c o n t ' d . ./2 16 17 20 23 24 26 29 Si 39.460 40.143 38.045 39.794 40.363 38.886 39.347 A l - .549 .036 - - .020 -T i .020 - .002 .040 - - .035 Cr - .370 .089 - - . - -Fe 14.150 15.139 19.791 15.456 14..381 16.986 14.724 Mn n .d. n.d. n.d. n.d.. - n.d. n.d. Mg 47.130 45.662 44.363 45.654 46.826 45.512 45.886 Ca .016 .047 - - -- Na - - - - - .002 -K n.d. n.d. n.d. n.d. - n.d. n.d. 100.760 101.879 102.326 100.991 101.570 101.406 99.992 Oxides Formulae based on 4 oxygens S i .980 .988 .957 .991 .993 .973 .987 Al - .016 .001 - - -T i - - - .001 - -Cr - .007 .002 - - -Fe .294 .312 .416 .322 .296 .355 .309 Mn n.d. n.d. -n.d. n.d. • - -Mg 1.745 1.676 1.664 1.694 1.717 1 .698 1.716 Ca - - - .001 -Na - • - - - -K n.d. . n.d. -n .d. n.d. Fo = 85.55% Fo = 84.30% Mg = 80. 0% Fo = 84.0% Fo = 85.40% Fo = 82.70% Fo = 84 Fa = 14.45% Fa = -15.70% Fe = 20. 0% Fa = 16.0% Fa = 14.60% Fa = 17.30% Fa = 15 Appendix 5 Microprobe Analyses of S u l f i d e s SULFIDE SAMPLE Mo. CORRELATION 1 • =•• 26A 2 = 28A-2 3 = 32A-1 4 = 34A-1 5 = / 36A-3 6 = 41A-1 7 = 43A-1 8 =• 44A-1 9 = 46A-1 10 = 47A-1 11 = . 90A-1 12 . = 92A-1 13 = 87A 14 = 85A 15 = 82A-1 15 = 78A-1 17 = 104A 18 = 106A 19 - 108A 20 ' = 114A 21 = 121A 22 = 130A-1 23 = 132A-1 24 = 140A-1 25 = 152A-1 26 = 156A-1 27 = 157A-1 28 • ' = 160A-2 29 = 162A-1 ELECTRON MICROPROBE ANALYSES OF PENTLANDITE AND PYRRHOTITE P e n t l a n d i t e Wt% Fe Ni Cu Co S 28.77 27.31 2.01 41 .91 29.99 33.53 .02 2.85 33.61 27.30 28.70 .02 3.41 40.56 28.41 28.90 .03 5.30 37.36 30.55 32.16 .03 3.86 33.40 27.29 31.09 .01 7.22 34.38 30.17 33.91 .02 1.86 34.04 P e n t l a n d i t e At% Fe Ni Cu Co S 22.19 20.04 1.47 56.31 24.35 25.90 .01 2.19 47.54 21 .25 21 .25 .02 2.51 54.98 22.55 21.81 3.98 51.64 24.84 24.87 .02 2.97 47.29 22.08 23.93 5.54 48.45 24.43 26.12 .01 1.43 48.01 P y r r h o t i t e Wt% Fe Mi Cu Co S 53.53 .17 46.31 59.42 .55 40.02 55.26 .28 44.46 57.17 .28 42.55 60.39 .68 .03 38.90 58.11 .66 .08 41.15 58.90 .37 40.73 P y r r h o t i t e A t % Fe Ni Cu Co S 39.84 .12 60.04 45.83 .40 53.76 43.56 .20 56.34 43.46 .20 56.34 46.88 .51 .02 52.59 44.54 .48 .05 54.92 45.24 .27 54.49 cont'd.. Pentlandite Wt% Pentlandite At% Pyrrhotite Wt% .11 10 11 12 13 14 Fe 31.04 31.17 30.25 31.90 33.42 38.97 39.25 Ni 34.80 34.63 35.29 35.39 31.13 25.44 25.20 Cu .04 ..04 . - - .04 - 01 Co .62 .68 .56 .54 .59 .77 *71 S 33.50 33.49 33.90 32.17 34.81 34.82 34.82 Fe 25.21 25.32 24.52 26.13 26.90 31.29 31.51 Ni 26.89 26.76 27.20 27.57 23.83 19.43 19.24 Cu .03 .03 - . - .03 .59 Co .48 .53 .43 .42 .45 .59 .54 S 47.40 47.37 47.85 45.89 48.80 48.70 48.69 Fe 59.03 59.48 57.91 61.11 59.16 62.24 62.28 Ni .40 .52 1.26 .68 .22 .01 .01 Cu - .18 - - .01 -Co .01 - - - - - • -S 40.56 39.82 40.82 38.20 40.60 37.75 37.71 Pyrrhotite \t% Fe ' 45.38 45.93 44.47 47.63 45.48 48.67 48.67 Ni .29 .38 .92 .51 .16 -Cu - .12 • - .01 - — Co .01 - - - _ S 54.32 53.96 54.60 51.86 54.35 51.32 51 .32 cont'd. Pentlandite Wt% Pentlandite At% Pyrrhotite Wt% Pyrrhotite At% 15 16 17 Fe 29.76 34.78 35.06 Ni 33.15 30.37 26.71 Cu - - .03 Co 1.78 1.43 1.29 S 35.29 33.42 36.92 Fe 23.91 28.23 27.82 Ni 25.34 23.44 20.17 Cu - - .02 Co 1.36 1.10 .97 S 49.39 47.23 51.03 Fe 58.20 63.70 59.50 Ni .41 - .01 Cu - - .03 Co - - -S 41.39 36.29 40.46 Fe 44.54 50.19 45.76 Ni .30 - .01 Cu - - .02 Co S 55.16 49.81 54.24 • /3 18 19 29.85 33.25 28.13 32.90 2.06 34.83 4.32 34.66 20 21 40.22 25.00 .08 .82 33.88 I.A. 24.05 25.49 22.71 25.26 1 .57 48.89 3.30 48.73 59.05 .46 57.91 .55 .02 40.47 .02 41 .52 45.43 .34 44.28 .40 .01 54.22 .02 55.30 32.47 19.20 .06 .63 47.64 .A. 62.54 59.19 .40 37.46 .07 40.33 48.94 45.57 .30 51.05 .05 54.08 cont'd.. ./4 22 23 24 25 25 27 28 29 Pentlandite Wt% Ni Cu Co S 28.89 33.04 3.78 34.29 31.35 32.58 1 .87 34.21 30.06 33.29 .01 1.86 34.79 28.39 34.34 3.00 34.27 31.11 33.74 .53 34.62 27.60 30.90 .04 5.85 35.61 30.49 35.14 .06 .29 34.03 30.06 34.84 .08 .43 34.59 Pentlandite At% Fe Ni Cu Co S 23.27 25.43 2.90 48.31 25.34 25.05 1.43 48.17 24.22 25.52 .01 1.42 48.83 22.97 26.43 2.30 48.30 25.09 25.88 .40 48.63 22.15 23.59 4.45 49.78 24.68 27.06 .04 .22 47.99 24.25 26.74 .06 .33 48.62 Pyrrhotite Wt% Fe Mi Cu Co S 58.36 .66 40.97 59.94 .35. 39.70 58.89 .42 40.69 57.84 1 .05 41.11 59.25 .81 39.94 58.34 .56 .12 .06 40.92 59.05 .60 40.34 57.40 .57 .02 42.01 Pyrrhotite At% Fe 44.77 Ni .48 Cu . Co S 54.75 46.31 .26 53.43 45.25 .31 54.44 44.34. .76 54.89 45.72 .59 53.69 44.71 .41 .08 .05 54.69 45.46 .44 54.09 43.77 .41 .01 55.80 Appendix 6 U n i v e r s a l Stage Composition Determinations Sample No. O/pxn (En) C/pxn (Ca:Mg:Fe) O l i v i n e 26A 82 46:44:10 — 28A-2 80 45:45:10 -30A-1 82 44:48:8 -32A-1 83 45:45:10 34A-1 82 44:46:10 3 6 A-3 80 44:47:9 -41A-1 82 - -42A-1 82 43:52:5 -43A-1 84 44:48:8 -44A 82 44:48:8 -46A-1 84 - -47A-1 86 45:45:10 86 76A-1 - 42:53:5 87 78A-1 88 42:47:11 86 82A-1 81 44:50:6 80 85A 87 - 87 87A 84 - . 79 89A 87 - 87 90A-1 87 85 92A-1 92 - 87 104A 86 45:43:12 85 106A 86 - 80 108A 84 45:45:10 • • -114A 86 - 87 120A 82 - . -121A 82 - -126A-1 - - -130A-1 81 45:45:10 -131A-2 82 44:48:8 -132A 81 - 79 135A-1 82 - -138A-2 85 - 87 140A 87 - 80 1.56A-1 82 44:46:10 -159A 82 - -160A-2 84 - 87 162A 86 - -

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