Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

A Genetic model for the Sustut copper deposit, North-Central British Columbia Wilton, Derek Harold Clement 1978

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Notice for Google Chrome users:
If you are having trouble viewing or searching the PDF with Google Chrome, please download it here instead.

Item Metadata

Download

Media
831-UBC_1978_A6_7 W54.pdf [ 21.15MB ]
Metadata
JSON: 831-1.0052841.json
JSON-LD: 831-1.0052841-ld.json
RDF/XML (Pretty): 831-1.0052841-rdf.xml
RDF/JSON: 831-1.0052841-rdf.json
Turtle: 831-1.0052841-turtle.txt
N-Triples: 831-1.0052841-rdf-ntriples.txt
Original Record: 831-1.0052841-source.json
Full Text
831-1.0052841-fulltext.txt
Citation
831-1.0052841.ris

Full Text

A GENETIC MODEL FOR THE SUSTUT COPPER DEPOSIT, NORTH-CENTRAL BRITISH COLUMBIA by DEREK HAROLD CLEMENT WILTON .Sc . , Memorial U n i v e r s i t y of Newfoundland, 1 9 7 6 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES (Department of Geo log i ca l Sc iences) We accept t h i s t h e s i s as conforming to the requ i red standard THE UNIVERSITY OF BRITISH COLUMBIA August, 1978 © Derek Haro ld Clement W i l t o n , 1 9 7 8 In p resent ing t h i s t he s i s in p a r t i a l f u l f i l m e n t o f the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t he r agree that permiss ion fo r ex tens i ve copying o f t h i s t he s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r ep re sen ta t i ve s . It i s understood that copying or p u b l i c a t i o n o f t h i s t he s i s f o r f i n a n c i a l ga in s h a l l not be al lowed without my w r i t t e n permis s ion. Department of (&UjU><\ C c<>Q S 1 vt-*vt-e S The Un i ve r s i t y of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 i i Go my Sons, buy stout shoes, climb the mountains, search the valleys, the deserts, the sea shores, and the deep recesses of the earth. . .for in this way and in no other will you arrive at a knowledge of the nature and properties of things. P. Severinus (circa 1778) Thi s view from the East shows the Sustut Copper mass i f . The c l i f f s at the r i g h t are part of the North Zone, and those in the middle are part of the South Zone. The c i r que which cuts the property i n t o these por t ions can be seen between the two zones. i i i A GENETIC MODEL FOR THE SUSTUT COPPER DEPOSIT, NORTH-CENTRAL BRITISH COLUMBIA ABSTRACT Host of the Sustut Copper d e p o s i t , 230 mi le s (370 km) northwest of P r i n c e George, i s a 600 m t h i c k sequence of v o l c a n i c l a s t i c rocks o f the upper member o f the Upper T r i a s s i c Moosevale Format ion. Th i s u n i t s t r i k e s n o r t h -w e s t e r l y and d ips about 20 degrees to the south . Regional s t r a t i g r a p h i c nomenclature has been r a the r confused but the l a t e s t s u b d i v i s i o n by Monger and Church (1977) was used f o r t h i s r epo r t . The Moosevale Formation is mostly conglomerate and v o l c a n i c b r e c c i a w i t h l o c a l d i s cont inuous and t h i n l a ye r s of tu f faceous rocks . Fragments in the u n i t are ma in ly b a s i c to i n te rmed ia te v o l c a n i c rock. S i x r e l a t i v e l y common types o f fragments are recogn i zab le as being der i ved from coeval v o l can i sm. Logging of 10,000 f t of diamond d r i l l core r ep re sen t i ng four c r o s s -s e c t i o n s through the main ore zones was done in a r i gorous manner on a coding form designed f o r input i n to a computer. Computer output led to a r ab id v i s u a l and q u a n t i t a t i v e e v a l u a t i o n o f the da t a , p a r t i c u l a r l y as regards to p h y s i c a l c h a r a c t e r i s t i c s and i n t e r n a l s t r a t i g r a p h y of the host u n i t . No s t r a t i g r a p h i c s u b d i v i s i o n w i t h i n the upper member of the Moosevale Formation was accompl i shed. Th in s e c t i o n study of metamorphic mineral assemblages i n d i c a t e d the metamorphic grade of the host rocks i s p r e h n i t e - p u m p e l l y i t e f a c i e s . Th i s grade i s h i gher than that in o ther rocks of the same l i t h o l o g i c u n i t s at equ i v a l en t s t r a t i g r a p h i c l e v e l s e l sewhere. Copper - r i ch zones w i t h economic p o t e n t i a l appear to be r e s t r i c t e d to the upper 60 m of the 600 m t h i c k , coar se -g ra ined v o l c a n i c l a s t i c ho s t , though the re are minor occurrences throughout. The copper m i n e r a l s , mainly c h a l c o c i t e , b o r n i t e , c h a l c o p y r i t e and na t i v e copper, are e p i g e n e t i c and occur w i t h q u a r t z , e p i d o t e , p r e h n i t e , and carbonate in v e i n l e t s and in t abu l a r zones p a r a l l e l to b e d d i n g . P y r i t i z e d r o c k s u r r o u n d s some c o p p e r - b e a r i n g t a b u l a r z o n e s . V e i n s a r e n e g l i g i b l e i n t o t a l volume o f m i n e r a l i z e d rock and formed m a i n l y by open s p a c e f i l l i n g ; both open space f i l l i n g and metasomatism were o p e r a t i v e t o v a r i a b l e degrees i n t a b u l a r m i n e r a l i z e d z o n es. A c r u d e . v e r t i c a l z o n i n g i s a p p a r e n t i n some t a b u l a r z o n e s , where the i d e a l i z e d sequence f r o m m a r g i n t o c o r e i s : p y r i t e - c h a l c o p y r i t e - b o r n i t e - c h a l c o c i t e - n a t i v e c o p p e r . Most t a b u l a r zones show n e i t h e r t h e c o m p l e t e sequence nor a p e r f e c t l y s y m m e t r i c d i s t r i b u t i o n o f zones about a n a t i v e c o p p e r c o r e , and i n some c a s e s t h e r e i s no semblance o f a z o n a l d i s t r i b u t i o n o f o r e m i n e r a l s . S p e c i f i c ranges o f t e x t u r a l parameters (such as s o r t i n g , g r a i n s i z e , e t c . ) o f the h o s t rock, have been found t o have been p a r t i c u l a r l y amenable t o the o c c u r r e n c e o f copper m i n e r a l s . These q u a n t i f i e d t e x t u r a l p a r a m e t e r s have been.compared s t a t i s t i c a l 1 y w i t h copper m i n e r a l i z a t i o n and i l l u s t r a t e t h e c o r r e l a t i o n o f copper m i n e r a l s w i t h v o l c a n i c l a s t i c r o c k s t h a t have s e d i m e n t a r y f e a t u r e s i n d i c a t i n g a h i g h p o r o s i t y and p r o b a b l y a h i g h p e r m e a b i l i t y p r i o r t o m i n e r a l i z a t i o n . These, porous u n i t s w i t h i n t h e v o l c a n i c l a s t i c p i l e a r e r e p r e s e n t e d by the t a b u l a r c o p p e r z o n e s . Copper m i n e r a l s and n o n - m e t a l l i c metamorphic m i n e r a l s were p r e c i p i t a t e d f r o m t h e same s o l u t i o n s , b oth i n v e i n s and r e l a t i v e l y porous t a b u l a r z o n e s . A l i m i t e d geothermometry, based on s u l p h i d e phase r e l a t i o n s and an i n t e r p r e t e d o r i g i n t o i n t e r g r o w t h t e x t u r e s , i s c o n s i s t e n t w i t h t e m p e r a t u r e s o f d e p o s i t i o n o f 250 - 300*C i n d i c a t e d by gangue m i n e r a l a s s e m b l a g e s . The t a b u l a r c o p p e r zones and l o c a l s e t s o f v e i n l e t s appear t o have formed i n t e r c o n n e c t e d channelways permeable t o o r e f l u i d s t h a t p r e sumably were d e r i v e d f r o m below. Age o f m i n e r a l i z a t i o n i s u n c e r t a i n but v e r t i c a l m a f i c dykes t h a t c u t t h e Moosevale F o r m a t i o n s t r a t i g r a p h i c a l l y above t h e main m i n e r a l i z e d zones a r e c u t by v e i n s and thus a r e p r e m i n e r a l i z a t i o n . The upward f l o w o f the hot s o l u t i o n s w i t h i n a s t r u c t u r a l zone d e f i n e d V now by swarms of Cu-bear ing v e i n l e t s produced a con f i ned geothermal high that r e s u l t e d in a l o c a l node of p rehn i te -pumpe l1y i te f a c i e s . metamorphism and con-comi t tent development o f copper minera l s and p y r i t e . Tabular zones w i t h i n t e r -s t i t i a l ore f l u i d represent l o c i of f1u id-wal1 rock r e a c t i o n and o re -minera l zoning may be a t t r i b u t e d i n - p a r t to d i f f u s i o n outward from these l o c i . Sequent ia l development of ore minera l s as i n d i c a t e d by paragenet i c s t ud i e s and the observed zonal d i s t r i b u t i o n requ i re s an ore f l u i d i n i t i a l l y more o x i d i z i n g than the b a s a l t i c country rock. Continued r e a c t i o n to produce f i r s t n a t i v e copper f o l l owed " s u c c e s s i v e l y by c h a l c o c i t e , b o r n i t e , c h a l c o p y r i t e and f i n a l l y p y r i t e , r e s u l t e d in the ore s o l u t i o n near ing e q u i l i b r i u m w i t h the host . v i TABLE OF CONTENTS Page FRONT I SP I ECE . . . J . : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i i ABSTRACT . . i i i TABLE OF CONTENTS .. . . v i LIST OF FIGURES >.x LIST OF TABLES „ . . x i v LIST OF APPENDICES x v ACKNOWLEDGEMENTS .. . x v i CHAPTER 1: INTRODUCTION 1 1.1 Loca t i on and Access 1 1.2 Cl imate . k 1.3 G l a c i a t i o n k 1.4 H i s t o r y o f Development k 1.5 P rev ious Geo log i ca l Work 6 1.6 Purpose and Method 6 CHAPTER 2: REGIONAL STRATIGRAPHY AND STRUCTURE 9 2.1 Regional Geology 9 2.1.1 A s i t k a Group 9 2.1.2 Tak la and Hazelton Groups 12 2.1.3 Sustut Group 16 2.2 Regional S t ruc tu re s 16 2.3 Regional Metamorphic Grade 17 2.k Tec ton i c E vo l u t i o n 18 CHAPTER 3: PROPERTY GEOLOGY 19 3.1 I n t r oduc t i on 19 3.2 C l a s t Types 21 3.2.1 Ba sa l t C l a s t s 21 3.2.2 Aug i te Porphyry Basa l t C l a s t s „ . . . . .22 3.2.3 Fe ldspar Porphyry Andes i te C l a s t s 2k v i i Page 3.2.4 T r a c h y t i c - F e l d s p a r Ba sa l t (or Bladed Fe ldspar Porphyry Ba sa l t ) C l a s t s . . . . . 25 3.2.5 Gabbroic Basa l t C l a s t s •. 28 3.2.6 Hornblende Feldspar Porphyr ie s 28 3.2.7 Composit ion of Moosevale Formation C l a s t s With Rocks of Under ly ing Formations . . . . . . . . 2 8 3.2.8 Geochemistry of the V o l c a n i c C l a s t Types . . . . . . 30 3.2.9 Other C l a s t Types 36 3-3 Rock Types 37 3.3.1 V o l c a n i c l a s t i c Conglomerate Un i t s 39 3.3.2 Sandstone Un i t s . . . . .47 3.3.3 C r y s t a l Tu f f Un i t s 49 3.3.4 Lahar Units 49 3.3.5 A r g i l l i t e s and A r g i l l a c e o u s Mudstone Units . 51 3.3.6 Shale Un i t 52 3.3.7 Limestone Unit • 52 3.3.8 B a s a l t i c Dyke Unit 54 3.3.9 My l on i t e Unit . . 56 3.3.10 Background Chemistry of Some Rock Types 56 3.4 D i s cu s s i on o f the Depos i t ion o f the V o l c a n i c l a s t i c Sequence ..58 3.4.1 Sedimentary S t ruc tu re s 58 3.4.2 S t r a t i g r a p h y 60 3.4.3 Depos i t i ona l Environment 62 CHAPTER 4: METAMORPHIC PETROLOGY AND WHOLE ROCK TRACE ELEMENT CHEMISTRY...65 4.1 I n t r oduc t i on 65 4.1.1 C h l o r i t e ..65 4.1.2 Carbonate 66" 4.1.3 Ep idote o 68 4.1.4 Quartz 70 4.1.5 P rehn i t e 70 4.1.6 S e r i c i t e ... 71 4.1.7 Pumpe l l y i t e 71 4.1.8 A l b i t e 73 4.1.9 Hematite 73 4.1.10 Sphene 73 4.1.11 P y r o l u s i t e 74 4.2 Metamorphic React ions 74 4.3 Metamorphic Mineral. Assemblages 75 4.4 Temperatures o f Metarnorphism 77 4.5 Age of Metamorphism 78 4.6 Elemental Chemistry of Metamorphic Zones ..81 VI I I Page CHAPTER 5: ORE Ml NERALOGRAPHY AND FORM . 85 5.1 I n t r oduc t i on „ 85 5.2 Ore Lenses 86 5.2.1 Outcrop Appearance of Ore 87 5.2.2 Appearance of Ore Lenses i n D r i l l Core 93 5.2.3 L i t h i c Va r i ab le s and T h e i r R e l a t i o n to M i n e r a l i z a t i o n ..96 5.2.4 Optimum Ore Horizon . . . . . 101 5.2.5 Chemistry of the Ore Lenses 109 5.2.5 (a) Probabi 1 i ty P l o t of Assay Data 109 5.2.5 (b) Trace Element Chemistry of Ore Lenses ,109 5.2.5 (c) Major Oxide Chemistry o f Ore Lenses 114 5.2.6 Gangue Mineralogy of Ore Lenses 114 5.3 Su lph ide -Bea r i ng Veins 122 5.3.1 General Outcrop Appearance and Gangue Mineralogy 122 5.3.2 Ore Veins in D r i l l Core . .126 5.3.3 Post-Ore Movement i n Veins 127 5.3.4 Trace Element Chemistry of Vein Ma te r i a l 127 5.3.5 Age of the Vein M i n e r a 1 i z a t i o n 127 5.4 Opaque Mineralography 129 5.4.1 Magnet i te (and l lmen i t e ) 129 5.4.2 C h a l c o c i t e 133 5.4.2(a) Cha l c o c i t e in Ore Lenses 133 5.4.2(b) Cha l coc i t e in Veins 141 5.4.3 Bo rn i t e 142 5.4.3(a) Bo rn i t e in Ore Lenses 142 5.4.3(b) Bo rn i t e in Veins 144 , . 5.4.4 Nat ive Copper ...146 5.4.5 Chalcopy r i t e 146 5.4.6 P y r i t e 148 5.4.7 D igen i te 150 5.4.8 C o v e l l i t e 151 5.4.9 Ma l ach i t e and A z u r i t e 151 5.4.10 Cup r i t e and L imoni te 151 5.4.11 Greenock i te .....151 5.4.12 Hematite 153 5.4.13 Conclus ions on Opaque Minera l Assemblages 155 5.5 Analyses of Intergrowth and Replacement Textures 155 5.5.1 Cha lcoc i te -D igen i te „.. 158 5.5.2 Chal coc i te -Born i te and Di geni t e -Bo rn i te 160. 5.5.3 C h a l c o p y r i t e - B o r n i t e (and D igen i te ) 160 5.5.4 C o v e l l i t e a f t e r D i gen i te 167 5.5.5 D i gen i te and C o v e l l i t e a f t e r Bo rn i t e 167 5.6 R e l a t i o n s h i p o f Ore Veins and Lenses. 169 5.7 Zonat ion of M e t a l l i c M inera l s in Ore Lenses 171 i x Page CHAPTER 6: DISCUSSION OF DATA AND POSSIBLE GENETIC MODEL . . . . . 1 7 ^ 6.1 I n t r o d u c t i o n and Summary o f P h y s i c a l Fea tu re s ' . . . 17^ 6.2 P r e v i o u s l y Sugge s ted O r i g i n s . 175 6.2.1 S y n g e n e t i c Hypo the se s 175 6 . 2 . 2 M e t a m o r p h i c a l l y D e r i v e d Ore F l u i d Model „ 176 6 . 2 . 3 C h u r c h ' s Model „ 179 6 .3 A U n i f y i n g G e n e t i c Model f o r S u s t u t Copper D e p o s i t . 180 6.3-1 I n t r o d u c t i o n t o t he Model 180 6 . 3 . 2 P a r a g e n e t i c Sequence „ 182 6 . 3 . 3 Causes o f Ore Z o n a t i o n and S im i 1 a r Z o n a t i o n s f r om Othe r -Depo s i t s 183 6 . 3 . ^ C h e m i s t r y o f P r e c i p i t a t i o n 186 6 . 3 . 5 S i g n i f i c a n c e o f M i n e r a l Z o n i n g i n R e l a t i o n t o Chang i ng C h e m i s t r y o f S o l u t i o n 193 b.k U l t i m a t e O r i g i n o f H y d r o t h e r m a l F l u i d s 192* 6 .5 P o s s i b l e P r o s p e c t i n g T o o l s 195 BIBLIOGRAPHY 197 APPENDICES . . . . ' „ 202 X LIST OF FIGURES ' Page F i gu re 1: Locat ion of Sustut Copper. . . . . . 2 F i gu re 2: The North C l i f f s 3 F i gu re 3: S t r a t i g r a p h i c column o f the Sustut Copper Area 10 F i gu re 4: Regional geology of area around Sustut Copper 11 F i gu re 5: Ba sa l t c l a s t photomicrograph 23 F igure 6: Aug i te porphyry b a s a l t photomicrograph 23 F i gu re 1: Fe ldspar porphyry andes i te photomicrograph 26 F igure 8: T r a c h y t i c f e l d s p a r b a s a l t c l a s t i n outcrop ...26 F i gu re 3: T r a c h y t i c f e l d s pa r b a s a l t photomicrograph . . .27 F igure 10: Gabbroic b a s a l t photomicrograph „ 27 F i gu re 11: Hornblende porphyry photomicrograph. 23 F igure 12: Tota l a l k a l i v s . s i l i c a diagram 33 F igure 13(a): Major ox ide vs. s i 1 i ca va r i at ion diagrams 34 F i gu re 13(b) : Trace metal v s . s i 1 i ca v a r i at ion diagrams 35 F i gu re 14: Limestone c l a s t in v o l c a n i c l a s t i c rocks 38 F igure 15: Typ i ca l v o l c a n i c l a s t i c conglomerate 40 F i gu re 16: Bar graph showing r e l a t i v e abundances of rock types . ..41 F i gu re 17: Bar graph showing r e l a t i v e amounts o f mat r i x to coarse f r a c t i o n „ 43 F i gu re 18: Bar graph showing r e l a t i v e number o f obse rva t ions of s o r t i n g c h a r a c t e r i s t i c s . 44 F i gu re 19: Bar graph showing r e l a t i v e number of ob se rva t i on s of t e x t u r a l c l a s s i f i c a t i o n s . 45 F i gu re 20: Typ i ca l tu f faceous sandstone in te rbed 48 F i gu re 21: C r y s t a l t u f f photomicrograph 50 F igure 22: , Typ i ca l l a h a r i c un i t 50 F igure 23: Mud cracks in a r g i l l a c e o u s mudstone 53 x i Page F igure 24: Limestone r ee f in d r i l l ho le 47 . ....53 F i gu re 25: B a s a l t i c dyke o f North Zone 55 F igure 26: Typ i ca l r e p e t a t i v e l y graded bedding sequence. . .......61 F igure 27: Cross bedding in tu f faceous sandstones 6l F i gu re 28: S t r a t i g r a p h i c c r o s s - s e c t i o n . 63 F i gu re 29: Carbonate cement, to l i t h i c v o l c a n i c g ra in s 67 F igure 30: Typ i ca l metadomain form o f ep idote 67 F igure 31: Carbonate ve ins w i t h ep ido te envelopes 69 F igure 32: P rehn i t e ve in swarm 69 F i gu re 33: Pumpe l l y i t e (green) pseudomorphic a f t e r hornblende g ra i ns 72 F igure 34: S t a b i l i t y r e l a t i o n s o f the p rehn i te -pumpe l1y i te f a c i e s . 79 F i gu re 35: S t a b i l i t y f i e l d s o f a 1 b i t e - e p i d o t e - p l a g i o c l a s e - q u a r t z . . 8 0 F i gu re 36: Ma lach i te s t a i n on shear zone. 90 F igure 37'. Ore lens l o c a t i o n s on northern edge of c i r q u e 90 F igure 38: Outcrop v i ew of i n t r a c l a s t p y r i t e 92 F igure 39: Su lph ide m i n e r a l i z a t i o n b r e c c i a t i n g host rock 92 F igure 40: P ropor t ions o f each l i t h o l o g i c type m i n e r a l i z e d w i t h chal coc i te 97 F igure 41: P ropor t ions of each l i t h o l o g i c type m i n e r a l i z e d w i t h p y r i t e . 98 F igure 42: P ropor t i ons o f each percent mat r i x va lue m i n e r a l i z e d w i t h c h a l c o c i t e 99 F igure 43: P ropor t ions o f d i f f e r e n t t ex tu re groupings mineralized w i t h c h a l c o c i t e . 100 F igure 44: P ropor t ions o f s o r t i n g values m ine r a l i z ed w i t h chal coc i te 102 F igure 45: Grain s i z e c l a s s i f i c a t i o n chart w i t h p r opo r t i on o f each s i z e type m i n e r a l i z e d w i t h c h a l c o c i t e 103 F igure 46: Comparison of d i f f e r e n t types of s i g n i f i c a n t 1y c h a l c o c i t e -m ine ra l i z ed v a r i a b l e s w i t h each other in rock types AGGR. .105 x i i Page F igure 47: Optimum ore hor i zon diagram 108 F igure 48: P r o b a b i l i t y graph o f copper assay va l ue s . 110 F igure 49: C lose up o f ore lenses at sample l o c a t i o n W104. 117 F igure 50: Photomi crograph of W104 ore lens 117 F igure 51: Photomicrograph of opaque minera l s and gangue. 118 F igure 52: Photomicrograph of W32 ore l en s . 118 F igure 53: P y r i t e as rounded b lebs in c h l o r i t e 120 F igure 54: Su lph ides ' s p e c k l i n g ' ep idote masses in sample 6B3. ...120 F igure 55: Photomicrograph o f network p y r i t e masses 121 F igure 56: Ep idote v e i n l e t s c u t t i n g country rock o v e r l y i n g W104 ore l e n s . 124 F igure 57: A b o r n i t e and c h a l c o p y r i t e pod in a ca rbona te -qua r t z ve in near W76 .124 F igure 58: P r e h n i t e - q u a r t z - e p i d o t e - c a r b o n a t e v e i n , w i t h c h a l c o c i t e and b o r n i t e , c u t t i n g the North Zone dyke 130 F igure 59: D e t r i t a l magnet i te bed. 130 F igure 60: Scanning e l e c t r o n photomicrograph of a magnet i te in sample 88E2 w i t h elemental scans o f t h i s magnet i te and another from sample W33 132 F igure 61: S t r a i gh t -edged c h a l c o c i t e g ra ins as v o i d - f i l l i n g s in f i n e f r a c t i o n of conglomerate. 135 F i gu re 62: Blebs of c h a l c o c i t e concentrated in a q u a r t z - f i l l e d pore.135 F igure 63: Scanning e l e c t r o n photomicrograph, w i t h e lemental scan, of a c h a l c o c i t e g r a i n in sample 13C3 137 F igure 64: Scanning e l e c t r o n photomicrograph o f c h a l c o c i t e b lebs and a . l a r g e r c h a l c o c i t e g r a i n 138 F i gu re 65: Th i n , exso lved d i g e n i t e l a th s in c h a l c o c i t e 140 F igure 66: Typ i ca l c h a l c o c i t e hab i t in a qua r t z - ca rbona te v e i n . ..140 F igure 67: Myrmek i t i c in tergrowth of c h a l c o c i t e i n b o r n i t e 143 F igure 68: Bo rn i t e w i t h exso lved c h a l c o p y r i t e l a th s and supergene development o f d i g e n i t e . 143 x i i i Page F igure 69: Noncoherent e x s o l u t i o n of c h a l c o c p y r i t e in b o r n i t e I lb. .145 F igure 70: Nat i ve copper g r a i n w i t h c u p r i t e r im. . . . 147 F igure 71: C h a l c o p y r i t e o c c u r r i n g as i n t r a - phenoc r y s t m a t e r i a l . ..149 F igure 72: C h a l c o p y r i t e in quartz amygdule . . . .149 F igure 73: Scanning e l e c t r o n photomicrograph and elemental scan o f a g r eenock i t e g ra in 152 F igure 74: Photomicrograph of wispy chains and t r a i l s of hematiteI 1154 F igure 75: Ion d i s p e r s i o n p l a te s of copper and i r on w i t h i n a chal coc i te-hemati te in te rg rowth area 156 F igure 76: Phase diagram f o r the Cu-S system. 159 F igure 77: S tab le phases on the j o i n Cu^FeS^-Cu2S 161 F igure 78: S tab le phases on the j o i n Cu^FeS^-Cu^ ^S^ 161 F igure 79: S t ab le phases on the j o i n Cu^FeS^-CuFeS2_ x 162 F igure 80: Isothermal sec t ions in the Cu-Fe-S system at 200, 300 and 400*C. i 164 F igure 81 : Phase r e l a t i o n s in the Cu-Fe-S-0 system at 300 'C. ... . ..168 F igure 82: Conceptual model f o r genesis of Sustut Copper depo s i t . .181 F igure 83: S i m p l i f i e d paragenet ic mineral sequence fence diagram f o r Sustut Copper ores 184 F igure 84: Log f ^ vs_. pH diagram of the dominant aqueous su lphur s p e c i e i at 300'C and 1 bar pressure 187 •Figure 85: Log f r j o " ^S2 ^ ' a 9 r a f n ^ o r t n e Ou-Fe-Cd system at 300*C and 1 Bar pressure 192 F igure 86: Sustut Cu 'Geo log ' D r i l l c o r e Coding Format 204 F igure 87: I nequi granul ar t e x tu re c h a r t . t 207 F igure 88: S o r t i n g char t 207 x i v LIST OF TABLES Page TABLE I: Major Oxide Analyses for Dominant C las t Types. 3 T TABLE II: Trace Element Analyses fo r Vo l can i c C las t s 32 TABLE III: Trace Element Analyses for Deep Samples 57 TABLE IV: Major Oxide Analyses on Sample 88N4 59 TABLE V: Trace Element Analyses for Metamorphic Samples 82 TABLE VI: Major Oxide Analyses for Metamorphic Samples. 83 TABLE VII: Trace Element Analyses for Ore Lens Sets 112 TABLE VIII: Major Oxide Analyses for Ore Lens Set 115 TABLE IX: Trace Element Analyses for Vein Samples 128 X V LIST OF APPENDICES Page APPENDIX I: " G e o l o g " D r i l l Core Coding Format f o r Sustut Copper 202 "APPENDIX I I: F o s s i l I d e n t i f i c a t i o n ' . . 213 APPENDIX I ' l l : C ro s s - Sec t ions 217 APPENDIX IV: Map 1 and C ro s s - s e c t i on s 219 £~ 'r>\<xf>5 ivJ pe-c teUL £#//£CJ/Y&^ -i C e c K ^ v ^ " ^ ; &" $f xv i ACKNOWLEDGEMENTS These are many. Fa lconbr idge N i c ke l Mines L t d . has been very h e l p f u l in t h i s p r o j e c t from i t s i n c e p t i o n . ' The company granted easy access to the p roper ty and p r i v a t e company f i l e s . A l s o generous f i n a n c i a l support was granted to t h i s author by Fa l conb r idge . Employees of t h i s company who should r e c e i v e s p e c i a l thanks i n c l u d e : Mr. S.N. C h a r t e r i s f o r f i r s t suggest ing the p r o j e c t , Mr. J . J . McDougal l , f o r s e t t i n g up the p r o j e c t , p r ov i d i n g f i n a n c i a l support , and very h e l p f u l d i s c u s s i o n , Mr. D.H. Brown f o r l ook ing a f t e r f i n a n c e s , Mr. J . Hug i , and h i s son John J r . , f o r s e t t i n g up the camps i te, and f i n a l l y Mr. B. Downing, Mr. J . W i l son , and Dr. I. E l l i o t f o r f r u i t f u l d i s c u s s i o n . Spec i a l thanks go to Dr. A . J . S i n c l a i r f o r generous use of h i s t ime as my s u p e r v i s o r , the f r u i t i o n of ideas conta ined here in was dependent upon him. Dr. C l . Godwin i s g r a t e f u l l y acknowledged f o r help in des ign ing the computer-based ( ' Geo l og ' ) d r i l l core coding format and general d i s c u s s i o n . Dr. T.H. Brown was h e l p f u l in d i s c u s s i n g the chemistry of ore s o l u t i o n p r e c i p i t a t i o n . Dr. H. Wynne-Edwards was very h e l p f u l as my s upe r v i s o r dur ing the embryonic stages of t h i s p r o j e c t . Dr. H.J . Greenwood i s thanked f o r h e l p f u l d i s c u s s i o n . Mr. N. Stacey and Mr. G. Hodge are acknowledged f o r doing e x c e l l e n t draught ing work. Mr. Stacey a l s o ab ly a s s i s t e d the author in lab p repa ra t i on of samples and d i d atomic ab so rp t i on analyses f o r copper. Mr. B. Cranston prepared most o f the po l i s hed and t h i n s e c t i o n s . Mr. E. Montgomery a s s i s t e d in l o g i s t i c s and photography. D r . ' s R.V. Best and H.W. T ipper are thanked f o r f o s s i l i d e n t i f i c a -t i o n s . Ms. K. Scot t i s thanked f o r i n s t r u c t i o n in XRF techn iques . Ms. I. Mc ln ty re i s very g r a t e f u l l y acknowledged f o r t yp i n g the l i o n ' s share o f the f i n a l d r a f t . Thanks must a l so go to my graduate student co l leagues f o r h e l p f u l d i s c u s s i o n , these i n c l ude : R. Berman, R. Cook, R. L e t t , E .Perk in s , and G. N ixon. Last but by no means l e a s t , very s p e c i a l thanks go to Ms. S.E. N icker son f o r ab ly a s s i s t i n g in f i e l d work and f o r pa t i ence and a s s i s t ance dur ing the length o f t h i s p r o j e c t . 1 CHAPTER 1: INTRODUCTION  1.1 Locat i on and Access Sustut Copper depos i t i s in the Swannel1 Range of the Cass iar-Omineca Mountains, in northern B r i t i s h Columbia. The depos i t i s approx imate ly 370 km northwest of P r i n ce George and 193 km nor theas t of Smithers ( f i g . 1) and i s cente red at l a t i t u d e 56°37 ' and l ong i t ude 126*^5*. The c l a im group cove r i ng the depos i t i s approx imately 2k sq . km and l i e s 5-6 km east of Sustut Mounr t a i n , on the southeastern s lope o f Mount Savage. The topography i s rugged. E l e v a t i o n s in the area range from 2^30 m f o r Sustut Mountain to 1050 m f o r the Sustut R iver V a l l e y , g i v i n g a maximum r e l i e f o f 1380 m. On the p rope r t y , however, the maximum r e l i e f is 3^5 m from the summit of the North C l i f f s ( f i g . . 2) to t h e i r base. In a d d i t i o n to the North C l i f f s , the depos i t i s surrounded complete ly by c l i f f s which have a minimum r e l i e f of 225 m and which are s c a l e a b l e in on ly two or three chimneys. The t r e e l i n e extends on ly to 1575 m e l e v a t i o n , w e l l below exposures of the depo s i t . Area above the t r e e l i n e i s unde r l a i n by rock w i t h l o c a l moss cover , s c r e e , t a l u s , and fe lsenmeer. Access to the depos i t i s d i f f i c u l t . The extreme r e l i e f r equ i re s the use of a h e l i c o p t e r , normal ly based at Johansen Lake, which may be reached by f l o a t - p l a n e from P r i n ce George, o r by a poor grave l road from Fort St. John v i a Germanson's Landing. A c o n t i n u a t i o n of t h i s road, the Omineca Road, extends from Johansen Lake towards Fal conbr i dge N icke l Mines Ltd.'s Moose V a l l e y base camp and a br idge has been cons t ruc ted over the Moose Va le Creek, however, t h i s road i s 9-6 km at the c l o s e s t to the northern edge o f the p rope r t y . 2 V \ \ LOCATION MAP LEGEND \ T E C T O N I C B E L T S O F \ T H E C A N A D I A N \ C O R D I L L E R A S T U D Y A R E A B O R D E R S \ 300 Km 200 mi \ V V \ ' V ' \ C A S C A D E S  X B E L T F i gu re I: Loca t i on of Sustut Copper, n o r t h - c e n t r a l B r i t i s h Columbia. Figure 2: The North C l i f f s . These c l i f f s (viewed from the north) form the northern edge of Sustut Copper Depos i t . 1.2 C l imate The c l i m a t e i s c o l d and damp w i t h ex ten s i ve snow gene r a l l y u n t i l the end of J u l y . Weather dur ing the f i e l d season of 1977 was e x c e p t i o n a l l y good in comparison w i t h prev ious summers spent on the proper ty by personnel of Fa lconbr idge N i c ke l Mines L td . The author and h i s a s s i s t a n t a r r i v e d at the f i e l d camp on June 22 when there was an average snow cover of 1.5-1.8 m w i th d r i f t s up to 6 m deep. I n te rm i t t en t snow f l u r r i e s and general overcas t s k i e s w i t h fog were exper ienced u n t i l J u l y 23- A f t e r t h i s date me l t i ng of snow began in earnest and there were temperatures of up to 20-25 'C. Two tarns by the camp were not t o t a l l y i c e - f r e e u n t i l the beg inn ing of August. Bad weather c lo sed in again August 21 and snow f l u r r i e s recommenced n ine days p r i o r to departure from the camp on Sept. 6. The snow cover was never t o t a l l y mel ted, e s p e c i a l l y in the c e n t r a l po r t i on s of the nor thern h a l f of the proper ty . 1.3 G l a c i a t ion G l a c i a l f ea tu re s in the general area are t y p i c a l of a l p i n e - t y p e g l a c i a -t i o n and i nc l ude c i r q u e s , hanging v a l l e y s , and t runcated spurs a long w i t h t a l u s and moraines in the v a l l e y s . The Sustut R i ve r v a l l e y , w i t h i t s U-shape, was carved by P l e i s t o c e n e g l a c i a t i o n and has hanging v a l l e y s from both Mount Savage, at the d e p o s i t , and Sustut Mountain l ead ing i n t o i t . Phy s i o g r aph i -c a l l y there are two main po r t i on s to the d e p o s i t , a northern bowl, the 'No r th Zone 1 , which extends from the North C l i f f s to an e a s t e r l y t rend ing c i r q u e , and a southern bowl, the 'South Zone 1 , which extends to the south from the c i r q u e . Fresh water f o r the camp s i t e , in the South Zone, was p ro -v ided by three smal l tarns which are fed by me l t i n g snow. There are a l s o some smal l i c e sheets on the northern part s of Mount Savage. 1.4 H i s t o r y o f Development P l a c e r go ld had been found in the McConnell Creek region(NTS Mapsheet 94D) in 1907-1908 (Lord, 1948). I n te res t waned s h o r t l y t h e r e a f t e r , but f o l l o w i n g the repor t by C S . Lord (1946) of p l a c e r g o l d , i n t e r e s t was again b r i e f l y spu r red . B o r n i t e and c h a 1 c o c i t e - r i c h f l o a t in the Sustut R iver v a l l e y d i r e c t l y below the Sustut Deposit were not reported by any of the p ro spec to r s . In.. J 969 the Union O i l Co., in search of petro leum, mapped s t r a t i g r a p h i c s e c t i o n s across the nor thern pa r t of Mount Savage and other nearby peaks i n c l u d i n g Sustut Mountain and Dewar Peak. The Sustut Copper depos i t was not d i s covered u n t i l l a t e in August 1971, when, the ma lach i t e s t a i ned c l i f f on the eastern edge of the proper ty was observed by 0. Thomason dur ing h e l i c o p t e r reconnaissance by Fa lconbr idge N i cke l Mines L t d . This d i s cove ry was f o l l owed by d e t a i l e d mapping and sampling f o r the remain-der of the 1971 f i e l d season, r e s u l t s of which i n d i c a t e d economic concen t r a -t i on s of copper s u l p h i d e s . In 1972 a f i e l d camp of three permanent b u i l d i n g s was con s t r uc ted and diamond d r i l l i n g commenced. The d r i l l i n g and p roper ty mapping cont inued dur ing the f i e l d seasons of 1973 and 1974 a f t e r which e x p l o r a t i o n ceased u n t i l the w r i t e r ' s work dur ing the f i e l d season of 1977. One hundred and t h i r t y - n i n e d r i l l holes ( s i z e AQ) were completed to the end of 1974 w i t h a cumulat i ve depth of 16,925-1 m. At present the proper ty i s covered by Sustut Claims nos. 1-132 which a re held by Wesfrob Mines L t d . of Vancouver, a w h o l l y owned s u b s i d i a r y of Fa l conbr idge N i cke l Mines L t d . Fo l l ow ing the d i scovery of the Sustut d e p o s i t , in 1971, i n t e r e s t was high in the area and numerous c la ims were s taked in the immediate v i c i n i t y . Wesfrob Mines holds W i l l ow, W i l l , A s i t k a , S i t , Saddle and Vale c l a ims , BP M ine ra l s L t d . holds the BAP, DS, B i r c h c l a i m s ; Nomad Mines L td . holds the A s i t k a and Bob c l a i m s ; Rio T i n t o holds the A c l a i m s , . ( s e e GEM 1974). During the 1977 f i e l d season the on l y work in the area was being done by BP M ine ra l s L td . on the NIK c la ims near Johansen Lake, and by Cominco L t d . which d i d some f i e l d work around Johansen Lake and some d r i l l i n g at Duncan Lake. 6 1.5 P rev ious Geo log ica l Work The f i r s t g eo l o g i c a l map of the reg ion was a reconnaissance survey o f the McConnell Creek map area by C S . Lord 1946-1948 (G.S.C. Mem. #251). Lord de sc r i bed the ba s i c host rock u n i t , the vol c a n i c - t u f f a c e o u s - v o l c a n i e l a s t i c Tak la Group, and i t s s t r u c t u r e . The Union O i l Co., ( p r i v a t e repor t ) compi led a number of s t r a t i g r a p h i c s e c t i o n across the area in 1969, which has y i e l d e d the most d e t a i l e d l i t h o l o g i c data on subun i t s o f the Tak la Group to. date. :.. Church (1973, 1974) redef ined the fundamental un i t s of the Tak la and de sc r i bed the host rocks and t h e i r copper m i n e r a l i z a t i o n . Monger (1974), working to the northwest, developed a new s u b d i v i s i o n of the Tak la somewhat d i f f e r e n t from that of Church. These two s u b d i v i s i o n s have been combined to y i e l d the present s t r a t i g r a p h i c nomenclature (Monger S Church, 1977). Burns (1973) s tud ied the metamorphic minera l assemblages of what he termed the 1 Takla-Haze1 t o n 1 Group in the McConnell Creek area and o u t l i n e d low grade reg iona l metamorphic isograds. Ramage (1974) desc r ibed both the s t r a t i g r a p h y of the area, i n c l ud i n g the Sustut depo s i t , and the petrography of dominant c l a s t types w i t h i n the vol c a n i c l a s t i c host rocks. P e l l y (1974) de f ined a metamorphic i sograd f o r the depos i t and proposed reasons f o r c o l ou r d i f f e r e n c e s in the host rocks. Harper (1976, 1977) presented a syn -t he s i s of d e t a i l e d property geology, minera logy and an ore genesis model based on four seasons or work by g e o l o g i s t s o f Fa lconbr idge N i cke l Mines L t d . 1.6 Purpose and Method The purpose o f t h i s t h e s i s i s to de s c r i be the su lph ide mineralography and chemi s t r y , and host rock 1 i t ho l ogy , pe t r o l o g y , and chemistry of the Sustut Copper depos i t in o rder to develop a hypothes i s f o r ore genesis and emplacement. The e v o l u t i o n of a gene t i c model f o r the r e l a t i v e l y l a rge Sustut Copper depos i t might have important i m p l i c a t i o n s in e x p l o r a t i o n f o r and e v a l u a t i o n of o ther copper occurences in the a rea . 7 F i e l d work by the author had two main a reas , the most important being r i gorous re logg ing of core using a s p e c i a l l y designed coding system mod i f i ed from Blanchet and Godwin (1972). Time l i m i t a t i o n s would permit logg ing o f on ly about 3000 m of core which had to be s e l e c t e d w i t h great ca re , from the 16,925 m ava i 1ab le , to prov ide a 3~dimensiona1 image of the depos i t . D e t a i l s of the d r i l l log form (coding form) designed by the author are g iven in Appendix I. The system is based on an e i gh t y column format in which pa r a -meters such as copper assay va l ue s , rock type, amount and type o f both m e t a l l i c m i n e r a l i z a t i o n and a l t e r a t i o n m ine r a l s , and number of ve ins of a g iven a l t e r a t i o n minera l cou ld be recorded in a standard way. A l l these parameters were recorded at i n t e r v a l s of 1.52 m (equal to 5 f t . to match assay-l o g s ) . ( Smal le r i n t e r v a l s were used f o r reco rd ing abrupt r ecogn i zab le changes of l i t h o l o g y ) . Th is s y s temat i c r eco rd i ng i n t e r v a l s tandard i zed a l l d r i l l ho le data and f a c i l i t a t e d c o r r e l a t i o n between ho le s . Nineteen d r i l l holes w i t h a cumulat i ve length of about 3000 m were logged by t h i s method. P a r a l l e l l o g -g ing of the d r i l l core was a l s o recorded in f i e l d note books. The r e s u l t i n g data ( d r i l l logs) were key punched f o r computer p roces s i ng . The d r i l l holes logged were; 2, 6, 10, 13, 17, 25, 39, 44, 52, 53, 54, 77, 88, 96, 105, 110, 112, 116, and 132. In a d d i t i o n to core logg ing , f i e l d work a l s o e n t a i l e d s u r f a ce g e o l o g i c a l mapping of the p rope r t y . (Sample numbers of specimens c o l l e c t e d from outcrop were p r e f i x e d w i t h a W, wh i l e those from the d r i l l core were p r e f i x e d by the d r i l l ho le number). The base map used was a 1 i n . = 200 f t . s c a l e g e o l o g i c a l map o f the depos i t produced by g e o l o g i s t s of Fa lconbr idge N i c ke l Mines L t d . Petrography and metamorphic m inera l assemblages were s t ud i ed in 58 t h i n s e c t i o n s of a l l rock and c l a s t types and some ore ho r i zon s . Ore m i n e r a l -ography was desc r ibed from 98 po l i s hed s e c t i o n s , and f o l l o w up scanning e l e c t r o n microscope work was done on 6 s ec t i on s to determine e lementa l composi-t i o n of some opaque and/or gangue m ine r a l s . 8 Analyses f o r Zn,Cu,Ni ,Rb,Sr , and Na were c a r r i e d out on 47 samples us ing X-ray f l uo re scence techn iques . The samples were ground to a f i n e pow-der and then p e l l e t i z e d . Fur ther Cu analyses were c a r r i e d out on 27 samples which showed >100ppm Cu concen t ra t i on s in the XRF runs, us ing atomic absorp-t i o n . methods . Major .ox ide contents were determined on 24 samples by atomic absorpt i o n . 9 CHAPTER 2: REGIONAL STRATIGRAPHY AND STRUCTURE  2.1 Regional.- Geology The general s t r a t i g r a p h y o f the Sustut area is o u t l i n e d in f i g u r e 3, and the reg iona l geology i s shown in f i g u r e 4. The host u n i t to the Sustut Copper depos i t has been c a l l e d the Sustut-Wi11ow Unit by Meyer (1974) and the Moosevale Formation by Monger and Church (1977). For the purposes o f t h i s t h e s i s the nomenclature o f Monger and Church w i l l be accepted . General de s c r i p t i o n s o f un i t s o the r than the Moosevale Formation are taken from the l i t e r a t u r e a f i r s t - h a n d study of the reg iona l geology of the area was beyond the scope o f t h i s i n v e s t i g a t i o n . There has been some d i s cu s s i on as to the p o s i t i o n o f the Tak l a -Haze l t on Groups boundary, a problem that w i l l be e l abo r a t ed on below. Oldest known rocks in the area comprise the Lower Permian A s i t k a Group, which i s o v e r l a i n discomformably by Late T r i a s s i c v o l c a n i c and v o l c a n i c l a s t i c sedimentary rocks o f the Tak la Group. This group is in turn o v e r l a i n by a sedimentary u n i t , the e a r l y J u r a s s i c Hazelton Group which grades s t r a t i g r a p h i -c a l l y upwards i n to the Bowser Lake Assemblage in the extreme southwest. 2.1.1 A s i t k a Group Rocks of the A s i t k a Group occur on the nor theas tern f l a n k s o f Dewar Peak, Savage Mountain, and Sustut Peak. Maximum th icknes s of t h i s u n i t i s about 2450 m. As o r i g i n a l l y de f ined by Lord (1948), the un i t c o n s i s t s o f a sequence o f r h y o l i t i c lavas which are l o c a l l y s p h e r u l i t i c , and andes i te s commonly d i s -t i n c t l y amygda lo ida l , w i th a s s o c i a t e d t u f f s , and b r e c c i a s , c h e r t s , a r g i l l i t e s and l imes tones . The l imestones g e n e r a l l y c on s i s t o f c r i n o i d a l d e b r i s . Fo ram in i f e r a and c r i n o i d s from the 1 imestones near the top o f the A s i t k a un i t at Sustut Peak were i d e n t i f i e d as being Lower Permian in age,: Lord (1948). F o s s i l s from other l o c a t i o n s in the McConnell Creek Map a r ea , c o l l e c t e d by ERA PERIOD OR EPOCH Fm. NAME LORD 1946 Fm. NAME TIPPER 1959 BURiMS *73 MEYER '74 RAMAGE74 CHURCH I973J974 MONGER 1974,1976 MONGER 8 CHURCH'77 HARPER 1977 MESOZOIC JURASSIC UPPER . TAKLA GROUP UPPER DIVISION HAZELTON GROUP UNIT 3 BOWSER LK.GEJ UNIT 4 4c 4a MESOZOIC JURASSIC MIDDLE . TAKLA GROUP UPPER DIVISION BOWSER LK.GEJ MESOZOIC JURASSIC . TAKLA GROUP UPPER DIVISION TAKLA-HAZELTON GROUP HAZELTON GP UNIT 3 OL z § L U N 5 TELKWA Fm. MESOZOIC JURASSIC LOWER . TAKLA GROUP UPPER DIVISION TAKLA-HAZELTON GROUP HAZELTON GP MESOZOIC JURASSIC . TAKLA GROUP UPPER DIVISION TAKLA-HAZELTON GROUP HAZELTON GP UNIT 2c MESOZOIC JURASSIC . TAKLA GROUP UPPER DIVISION TAKLA-HAZELTON GROUP HAZELTON GP UNIT 2b MESOZOIC UPPER TRIASSIC . TAKLA GROUP cf MONGEU (I9TS) TAKLA GROUP TAKLA-HAZELTON GROUP SUSTUT -WILLOW UNIT TAKLA GROUP UNIT 2 TAKLA GROUP UNIT 2a TAKLA GROUP MOOSE" VALE Fm. MIDDLE (3a-d) MESOZOIC . TAKLA GROUP LOWER DIVISION TAKLA-HAZELTON GROUP TAKLA GROUP UNIT I TAKLA GROUP UNIT 1 TAKLA GROUP LOWER FORMATION Figure 3'- S t r a t i g r a p h i c column o f the Sustut Copper Area . Th is diagram shows the ch rono l o g i c a l development o f a s t r a t i g r a p h i c nomenclature. The upper member of the Moosevale Formation (shaded) i s the host to Sustut Copper Depos i t . iWW! 1 ' 1 ] ' ! 1 ! ' ' LEGEND J U R A S S I C i 1,1,1,1 i 1,1,1,1, i i 1,1 i, iilililiii! m U P P E R TR IASS IC ( T A K L A GP), P E R M I A N H A Z E L T O N . G R O U P M O O S E V A L E F m . S A V A G E M T N F m . D E W A R F m . A S I T K A G R O U P I N T R U S I O N S G E O L O G I C A L B O U N D A R Y F A U L T O U T C R O P WATERCOURSE META. ISOGRAD F igure k: Reg iona l geology of area around Sustut Copper ( a f t e r Monger and Church ( 1977) and Harper ( 1 9 7 7 J ) . ; ' Sus tut Copper p r ope r t y i s the area o u t l i n e d on Savage Mountain,.. The r e g i o n a l metamorphic i sog rad i s a f t e r Burns ( 1 9 7 3 ) . ' 12 Lord show t h i s un i t to range from p o s s i b l e Pennsy1 vanian to Lower Permian. The group as a whole; has an average d ip o f 50* southwester l y and is o v e r l a i n discomformably by the Tak la Group rocks . However, Monger (1974) working near Dewar Peak found that the contact was a f a u l t or at l e a s t " a sheared s t r a t i -g raph ic c o n t a c t " . 2.1.2 Tak la and Haze l ton Groups Armstrong (1946 £ 1949) f i r s t in t roduced the format ion name Takla Group f o r Upper T r i a s s i c to Upper J u r a s s i c b a s a l t i c and a n d e s i t i c v o l c a n i c and a s soc i a ted sedimentary rocks in the Fort S t . James Map Area (NTS 93K & N). He a l s o thought the Haze l ton Group of ande s i t e s , b a s a l t s and r e l a t e d b recc i a s were J u r r a s i c to p o s s i b l y Cretaceous in age. There was no v i s i b l e contact between the two groups in h i s area of mapping. Lord (1946, 1948), working in an area to the north of that of Armstrong ( 1 9 4 9 ) , de f ined Upper T r i a s s i c to middle Upper J u r a s s i c (Oxfordian) vo l can i c and v o l c a n i c l a s t i c rocks in the McConnell Creek Map Area as being Tak la Group e q u i v a l e n t s , and found no c o r r e l a t i v e rocks o f the Haze l ton Group in the a r e a . Tak la rocks were subdiv ided, i n t o two u n i t s , an Upper D i v i s i o n and a Lower D i v i s i o n , by Lo rd . Accord ing to Lord, the Tak la Group is a "conformable assemblage", having a t o t a l th ickness o f g r ea te r than 9900 m, w i th the Lower D i v i s i o n being 3000 m t h i c k . In the map a r e a , the Lower D i v i s i o n rocks com-p r i s e the bulk o f Dewar and Niven peaks, Savage Mountain and Sustut Peak, whereas Upper D i v i s i o n rocks are found on l y a long the extreme south, southwest margins of these peaks. Host to the Sustut Copper depos i t are Lower D i v i s i o n rocks. The base o f the Lower D i v i s i o n , accord ing to Lord (1946, 1948), is com-posed of i n t e r l a y e r e d b lack tuf faceous a r g i l l i t e s and green i sh t u f f s . These rocks are t h i n l y bedded and commonly show graded bedding from coarser t u f f s at the base to f i n e r a r g i l l i t e s on top. The sequence is conformable w i th ove r -!3 l y i n g agglomerates and p i l l o w l avas . These agglomerates are made up o f poo r l y so r ted c l a s t s of b a s a l t i c to a n d e s i t i c compos i t i on , in a mat i r x which i s • tu f faceous in nature and which c h a r a c t e r i s t i c a l l y c on t a i n s , " s tubby b lack aug i te phenocrysts up to one-quarter inch l o n g " , (Lord, p. 16). The lavas are both massive and p i l l o w e d andes i te s and b a s a l t s . Most commonly stubby aug i t e phenocrysts are seen in these l avas . Ove r l y i n g agglomerates con ta in c l a s t s o f under l y ing l a va s . T u f f s are abundant in the succes s ion w i th a u g i t e , p l a g i o -c l a se and hornblende g ra ins as common d e t r i t u s . The a r g i l l i t e s are present elsewhere in the sequence a l s o . Rare ly t h i n l imestone beds occur . The lavas decrease in amount upwards in the s e c t i o n and d i sappear complete ly in the uppermost p o r t i o n s o f the Lower D i v i s i o n . For example, the rocks which con-t a i n Sustut Copper depos i t are devoid o f l a va s . Though no d i a g n o s t i c f o s s i l s were found w i t h i n the Lower D i v i s i o n assemblage, Lord (1948) ass igned the un i t to the Upper T r i a s s i c because i t was younger than Lower Permian and i t passed conformably i n to the J u r a s s i c Upper D iv i s ion. . The Upper D i v i s i o n rocks are dominantly v o l c a n i c fragmentals at the base and sedimentary, w i t h some interbedded vol can ic , rocks towards the top of the sequence. The dominant rock types are t u f f s and agglomerates w i t h minor amounts o f f l ow rocks . The t u f f s con ta i n fragments o f p l a g i o c l a s e , rock c l a s t s of . t r a c h y t i c f e l d s p a r l a t h s , and les s commonly o r t h o c l a s e and qua r t z g ra i n s , , and are g e n e r a l l y of a n d e s i t i c compos i t i on . Fragments of f e l d s p a r porphyry and t u f f s are the dominant c l a s t types in the agglomerates. Fe ldspar g ra in s f r e -quent ly form the m a t r i x . The lavas t y p i c a l l y con ta in "numerous wh i te o r b u f f , l a th - shaped p l a g i o c l a s e phenocrysts , 1/16 to £ inch l ong , in a r edd i s h , m i c r o -c r y s t a l l i n e groundmass" (Lord, 1948 p. 21) . Greywackes, composed of cher t and v o l c a n i c rock fragments, conglomerates made up of dominantly cher ty c l a s t s o f p o s s i b l e A s i t k a Group a f f i n i t y , and b lack sha les and a r g i l l i t e s make up the sedimentary rock s . Thin rare l imestone beds are a l s o p resent . The age o f Lo rd ' s Upper D i v i s i o n , based on f o s s i l ev idence , is e a r l y Lower J u r a s s i c 14 (Lower L i a s ) through to Upper J u r a s s i c (Ox fo rd i an ) . Lord found no Haze l ton Group e q u i v a l e n t s in the McConnell Creek a rea . T i ppe r (1959) in a r e v i s i o n o f Tak la and Haze l ton Groups, suggested that L o rd ' s Upper D i v i s i o n of the Tak la Group, should be p laced w i t h i n the Haze l ton Group, thus r e s t r i c t i n g the Tak la in the McConnell Creek area to the Upper T r i a s s i c . T i p p e r ' s p r i n c i p a l reason f o r t h i s new boundary between the two groups was the d i f f e r e n c e in t e c t o n i c s t y l e s of the r e s u l t i n g two d i v i s i o n s . The Lower J u r a s s i c marked the beginning o f a pe r iod of t e c t o n i c a c t i v i t y wherein sediments were eroded and depos i ted in a t r an s g re s s i on upon the v o l c a n i c areas which had become emergent in Upper T r i a s s i c t imes . Th is s t a r t o f t r a n s g r e s -s i on i s shown by the presence of sediments w i t h i n Lo rd ' s Upper D i v i s i o n . Subsequent to suggest ions of T ippe r (1959), f i e l d usage o f Tak la and Haze l ton t e rm ino l og i e s in the area become somewhat confused. Geo log i s t s of Fa lconbr idge N i c ke l Mines L t d . (eg. Burns (1973), Ramage (1974)) he ld w i t h the common usage at t h i s po in t and r e f e r r e d to the T r i a s s i c and J u r a s s i c v o l -c an i c and vol c a n i c l a s t i c s as the Ta1ka-Hazelton Group. The host to the Sustut Copper depos i t was i n f o rma l l y r e f e r r e d to as the Sustut-Wi11ow Uni t (eg. Meyer, 1974).. Church (1973, 1974), working near Savage Mountain, proposed a d i v i s i o n o f the•success ion i n t o three main u n i t s . The lowest u n i t , c o n s i s t i n g o f a n d e s i t e s , b a s a l t s , b r e c c i a s c o n s i s t i n g of fragments of the fo rego ing l ava s , and t u f f s , corresponds to Lo rd ' s Lower D i v i s i o n . The middle un i t c o n s i s t s o f v o l c a n i c -l a s t i c rocks ; whereas, the upper un i t conta in s t u f f , a r g i . l l i t e , c h e r t , and l imes tone . Church proposed that the Tak l a -Haze l t on boundary be p laced e i t h e r near the top o f the-middle un i t where a p o l y m i c t i c conglomerate i n d i c a t e s a subaerial environment, or at the base of the upper u n i t . A boundary at the base of the upper un i t r e f l e c t s the d i f f e r e n t chemical composit ions of the lower and middle un i t s r e l a t i v e to the upper u n i t . Church, on the bas i s of a r c f u s i o n ana l y se s , found that the lower and middle un i t s were b a s a l t i c , w i t h some 15 a n d e s i t e , w h e r e a s t h e u p p e r u n i t w a s d a c i t i c a n d a n d e s i t i c , w i t h s o m e r h y o l i t e s . M o n g e r (1974, 1976) f o u n d t h a t t h e L o w e r a n d U p p e r D i v i s i o n b o u n d a r y ( L o r d , 19^8) s h o u l d h a v e b e e n p l a c e d i n t h e U p p e r T r i a s s i c r a t h e r t h a n b e t w e e n t h e T r i a s s i c a n d J u r a s s i c . T h i s w a s b a s e d u p o n i d e n t i f i c a t i o n o f U p p e r T r i a s -s i c ( l o w e r N o r i o n ) f o s s i l s , f o u n d i n t h e D e w a r P e a k r e g i o n , w i t h i n t h e b a s a l m e m b e r s o f L o r d ' s U p p e r D i v i s i o n . M o n g e r a l s o s u b d i v i d e d T a k l a r o c k s i n t o f o u r u n i t s . T h e b a s a l b a s a l t i c f l o w , a n d a s s o c i a t e d b r e c c i a s , a r e i n L o r d ' s L o w e r D i v i s i o n . T h e ; s e c o n d u n i t w a s d i v i d e d i n t o t h r e e s u b u n i t s o f w h i c h t h e l o w e s t i s c o r r e l a t i v e w i t h C h u r c h ' s u n i t 2, a n d t h e r e m a i n d e r a r e t h e b a s a l p a r t o f t h e J u r a s s i c H a z e l t o n G r o u p , w i t h i n t h e T e l k w a F o r m a t i o n o f t h a t g r o u p . T h i s s e c o n d u n i t i s made up o f b a s a l t i c a n d a n d e s i t i c b r e c c i a s , t u f f s , a n d p o l y m i c t i c c o n g l o m e r a t e . M o n g e r ' s t h i r d u n i t o f i n t e r b e d d e d s e d i m e n t a r y a n d v o l c a n i c r o c k s i s e a r l y t o m i d d l e J u r a s s i c i n a g e a n d w o u l d b e c o r r e l a t i v e w i t h t h e N i l k i t k w a a n d S m i t h e r s F o r m a t i o n s o f t h e H a z e l t o n G r o u p . T h e f i n a l u n i t i s c o r r e l a t i v e w i t h t h e M i d d l e t o L a t e J u r a s s i c B o w s e r L a k e A s s e m b l a g e a n d c o n s i s t s o f s e d i m e n t a r y a n d m i n o r v o l c a n i c r o c k s . H a r p e r (1976, 1977) c a l l e d t h e w h o l e g r o u p o f r o c k s , m a k i n g up t h e h o s t t o S u s t u t C o p p e r , t h e T a k l a G r o u p a n d s u b d i v i d e d t h e m i n t o t h r e e f o r m a t i o n s . T h e - L o w e r F o r m a t i o n o f l a v a s a n d b r e c c i a s f o r m s t h e n o r t h e r n p o r t i o n o f S a v a g e M o u n t a i n . T h e M i d d l e F o r m a t i o n c o n t a i n s t w o s u b u n i t s o f a g g l o m e r a t e s a n d t u f f s , t h e l o w e s t i s a t t h e b a s e o f t h e N o r t h C l i f f s , a n d t h e u p p e r o n e i s t h e h o s t t o t h e S u s t u t C o p p e r d e p o s i t . T h e U p p e r F o r m a t i o n c o n s i s t s o f v o l c a n i c s a n d -s t o n e s a n d c o n g l o m e r a t e s . T h e s e f o r m a t i o n s r a n g e i n a g e f r o m U p p e r T r i a s s i c i n t h r o u g h t h e J u r a s s i c . M o n g e r a n d C h u r c h ' s (1977) s t r a t i g r a p h i c s u b d i v i s i o n s w i l l b e u s e d h e r e a s t h e b a s i s f o r a d i s c u s s i o n o f t h e r e g i o n a l s t r a t i g r a p h y . I n t h e i r w o r k ( i b i d . ) t h e T a k l a G r o u p i s d e f i n e d a s U p p e r T r i a s s i c i n a g e a n d c o n s i s t s o f t h r e e f o r m a t i o n s : D e w a r F o r m a t i o n , S a v a g e M o u n t a i n F o r m a t i o n , a n d M o o s e v a l e 16 F o r m a t i o n . The Dewar and Savage M o u n t a i n F o r m a t i o n s , named f o r t he d e f i n i t i v e s e c t i o n s a t the r e s p e c t i v e m o u n t a i n s , a r e though t t o be p a r t l y c o e v a l . The Dewar F o r m a t i o n i s made up o f a r g i l l i t e , v o l c a n i c l a s t i c s a n d s t o n e s , and b r e c c i a s . The Savage Moun ta i n F o r m a t i o n has a b a s a l u n i t o f v o l c a n i c b r e c c i a , a m i d d l e p i l l o w l a v a u n i t , and an upper v o l c a n i c b r e c c i a u n i t . Monger (1977) s u b d i v i d e d t he M o o s e v a l e i n t o two members, t he l o w e r , 900 m t h i c k , member i s made up o f m a s s i v e v o l c a n i c l a s t i c c o n g l o m e r a t e s w i t h m ino r i n t e r b e d d e d s a n d s t o n e s and f o s s i 1 i f e r o u s sha les - , t he u p p e r , 600 m t h i c k , member a c t u a l h o s t t o S u s t u t C o p p e r , w i l l be d i s c u s s e d b e l o w . D i s c o m f o r m a b l y o v e r l y i n g t h e T a k l a Group i s t he T e l k w a F o r m a t i o n o f t he H a z e l t o n G roup . 2.1.3 S u s t u t Group To t he s o u t h w e s t , o u t s i d e t he map a r e a , L o r d d e s c r i b e d t he y o u n g e s t r o c k s i n t he M c C o n n e l l C reek Map A r e a . These a r e the Upper C r e t a c e o u s S u s t u t Group c o n g l o m e r a t e s , s a n d s t o n e s , w i t h m i no r l e n s e s o f c o a l and f o s s i l wood f r a g m e n t s , and t u f f s . P e b b l e s i n t h e c o n g l o m e r a t e s a r e o f g r a n i t i c r o c k s , c h e r t s , f e l d -s p a r , p o r p h y r i e s , and a u g i t e r i c h l a v a s . L o r d t hough t t he c o n t a c t between t h i s g roup and h i s u n d e r l y i n g Upper J u r a s s i c , Upper D i v i s i o n was an a n g u l a r u n c o n -f o r m i t y . 2.2 R e g i o n a l S t r u c t u r e s The most p r om inen t s t r u c t u r a l f e a t u r e s i n the map a r e a a r e f a u l t s o f r e g i o n a l e x t e n t , the most s i g n i f i c a n t b e i n g t he Omineca F a u l t ( L o r d , 1 9^8 ) . T h i s f a u l t , a l s o known as t he Two Lake C reek l i n e a m e n t ( C h u r c h , 1973), t r e n d s n o r t h w e s t e r l y a l o n g Two Lake C reek t o t he s ou thwes t o f Savage M o u n t a i n . D e s p i t e t h e ab sence o f v i s i b l e s t r a t i g r a p h i c m a r k e r s , H a r p e r (1977) b e l i e v e s t he Omineca F a u l t t o have a v e r t i c a l d i s p l a c e m e n t o f s e v e r a l t h o u s a n d f e e t . Chu r ch (1974) s u g g e s t s t h a t t h i s f a u l t was a c t i v e o v e r a l ong p e r i o d o f t i m e w i t h t he o l d e s t movement o c c u r i n g b e f o r e p o r t i o n s o f the T r i a s s i c p i l l o w b a s a l t s were e r u p t e d , and l a t e r u p l i f t a l o n g i t may have p r o v i d e d t he s o u r c e a r e a s f o r p o l y -17 m i c t i c Tak la conglomerates. There are other minor f a u l t s present w i th the same t rend and a l s o another group which t rend gene r a l l y n o r t h e a s t e r l y . These two f a u l t d i r e c t i o n s are r e f l e c t e d in sma l l e r s c a l e f a u l t i n g and j o i n t i n g w i t h i n the p roper ty . Fa lconbr idge Nickel. Mines L t d . geo l o g i s t s suggest (eg. Harper, 1977) that the Sustut R iver V a l l e y i t s e l f may be f a u l t c o n t r o l l e d . Harper (1977) recogn ized three phases of f o l d i n g in the a rea . The f i r s t phase produced " g e n t l e f o l d s w i th a x i a l planes s t r i k i n g 110-130*" (Harper, 1977, p. 102). These are p o s s i b l y synchronous w i th the no r thwes te r l y f a u l t s . The second phase i s "minor warping or t i l t i n g ; maybe f a u l t a s s o c i a t e d " ( i b i d . , p.102) w i th a x i a l planes t rend ing 130-170". On the proper ty i t s e l f , f o l d i n g i s not ev ident but a general broad warping is i n d i c a t e d by the change in dips from the North C l i f f s o f 10' to 25' near d r i l l ho le no. 132. Church •( 1.973) e s t -imates the a x i s . t o t h i s warping as having a t rend of 167* w i t h a plunge of l4 ' SE. 2.3 Regional Metamorphic Grade Burns (1973) s t ud i ed reg iona l a l t e r a t i o n in the general area of the d e p o s i t . This study inc luded examinat ion of samples from- Dewar and Sustut Peaks, Savage Mountain, and severa l o ther mountains to the south. Burns found that rocks o f , and s t r a t i g r a p h i c a l l y above, the Moosevale Formation gene r a l l y had. metamorphic mineral assemblages c on s i s t en t w i th the z e o l i t e ( laumont i te) f a c i e s of low grade metamorphism, whereas the rocks below the Moosevale had assemblages of the h igher grade prehn i te -pumpel1y i te f a c i e s . From t h i s Burns de f i ned a metamorphic i sograd f o r the a rea , i n c l u d i n g Sustut Copper. Th i s i sog rad i s shown in f i g u r e k. On the southern edge of Dewar Peak, a l l the Moosevale Formation i s in the laumont i te f a c i e s (no data were c o l l e c t e d on the northern i n l i e r of Moosevale Format ion) . No data are a v a i l a b l e on the Moose-va le in the western edge of Savage Mountain but on the Sustut Copper property t h i s i sograd occurs near the top of the Moosevale, we l l above the depos i t 18 proper. Throughout Sustut Peak, the Moosevale Formation is c l a s s i f i e d by Burns as having laumont i te f a c i e s metamorphic grade. Thus the proper ty has an anomalous metamorphic grade when compared to o ther rocks at the same reg iona l s t r a t i g r a p h i c l e v e l .: A prehn i te -pumpel1y i te grade f o r the depos i t was conf i rmed by Ramage (1974), and a l s o by t h i s s tudy. 2.4 Tec ton i c E v o l u t i o n The Sustut Copper area i s near the eas te rn edge o f the Intermontane B e l t of the Canadian C o r d i l l e r a (Suther land Brown et al . ,1971) which extends from the c e n t r a l Yukon to s ou th - cen t r a l B r i t i s h Columbia. Th i s b e l t represents i s l a n d a rc vo lcan i sm and a s s oc i a t ed sediments of Mesozoic age w i th some f r i n g i n g reefs ( G a b r i e l s e , 1976 ). The i s l a n d a rc a f f i n i t y o f these v o l c an i c s i s seen in s t ud i e s of c l a s t l i t h o l o g i e s w i t h i n the depos i t (see be low). This sequence i s marine and i s o v e r l a i n by d a c i t i c v o l c a n i c s which are s u b a e r i a l . These i s l a n d a r c v o l c a n i c s are one p o r t i o n of the t o t a l e v o l u t i o n of the c o r d i l l e r a . From P r o t e r o z o i c to mid-Devonian time a m iogeosync l i na l sequence o f sediments was l a i d down as "a c on t i nen ta l t e r r a c e that developed along the western margin of the North American c r a t o n " ( i b i d . . p . 493). The A s i t k a Group, the basal sequence in the a rea , is thought to have been depos i ted on ocean ic c ru s t ( i b i d . ) wh i l e the l imestones developed on v o l c a n i c p l a t f o r m s . The T a k l a -Haze l ton i s l a nd a rc vo lcan i sm began we l l a f t e r the f i n i s h o f A s i t k a Group d e p o s i t i o n . Fo l l ow ing the depo s i t i on of the Haze l ton Group,successor bas ins (Gab r i e l s e , 1976) developed which e x h i b i t changes from near shore marine depo-s i t i o n (eg. w i th de l t a s ) to nonmarine (eg. l a c u s t r i n e sed iments ) . These successor bas in rocks comprise the Bowser Lake Assemblage. Thus the general sequence s t a r t e d w i t h miogeosync1ina1 and/or ocean ic c r u s t sed imenta t i on , led to i s l a n d arc vo lcan i sm of T r i a s s i c to m i d - J u r a s s i c age which g r adua l l y became subae r i a l in nature and which was in turn f o l l owed by near shore to nonmarine successor sediments. 19 - CHAPTER 3: PROPERTY GEOLOGY 3-1 Introduct ion Property geology s tud ie s are r e s t r i c t e d to examinat ion of the g rea te r than 600 m t h i c k upper member of the Moosevale Format ion. I n t e r p r e t a t i o n of the lower 420 m o f t h i s sequence i s based on study of the two deepest d r i l l ho les (88 and 110) -and a po r t i on of outcrop at the base of the North C l i f f s , as most su r face exposures a re p r e c i p i t o u s c l i f f s . The upper 180 m was examined in g rea te r d e t a i l , by outcrop mapping and logg ing o f o the r diamond d r i l l holes (DDH's), because major copper mineral occurrences are r e s t r i c t e d to t h i s l e v e l . At the base of t h i s member (the area from which samples SILT and AGGL were taken - see a t tached map in pocket) is a b l a c k , f o s s i 1 i f e r o u s s ha l e , which grades up in to a red, f o s s i 1 i f e r o u s a r g i l l i t e . Above the red u n i t are the t y p i c a l vol c a n i c l a s t i c sediments o f the Moosevale, but the contact between the two i s obscured in d e b r i s . The contact appears to be a s l i g h t angular uncon-fo rm i ty because the under l y i ng shales t rend n o r t h e a s t e r l y and d ip southeast -e r l y whereas the o v e r l y i n g rocks have no r thwes te r l y s t r i k e s and southwester ly d ips which are c on s i s t an t throughout the e n t i r e 600 m o f vol c a n i c l a s t i c rocks . F o s s i l s have not been found in f i n e - g r a v e l members w i t h i n the vol c a n i c l a s t i c u n i t , thus the lowermost a r g i l l i t e s and sha les appear to be d i s t i n c t i v e in t h e i r f o s s i 1 i f e r o u s na tu re . These f o s s i 1 i f e r o u s sha les comprise the top of the lower member o f the Moosevale Formation (Monger, 1977)- The lower member i s "p redominant l y massive b r e c c i a w i th interbedded graded sandstone and f o s s i l -i f e rou s mudstone" ( i b i d . , p . 15). Naming of l i t h o l o g i c types in the vol c a n i c l a s t i c u n i t s i s hampered by the p ro fu s ion of p o s s i b l e names in the geo log i c l i t e r a t u r e . These rocks have been c a l l e d b r e c c i a s , agglomerates, vol c a n i c l a s t i c conglomerates, fang lomerates, e t c . There is no nomenclature problem w i th some un i t s such as the lahars 20 c r y s t a l t u f f s . The dominant rock t y p e s , however, a r e made up o f a c o a r s e f r a c t i o n o f b a s a l t i c c l a s t s , . r a n g i n g from 1 m i n d i a m e t e r t o c o a r s e sand-s i z e , i n a f i n e r f r a c t i o n o f f e l d s p a r , a u g i t e , and s m a l l v o l c a n i c g r a i n s , w h i c h range i n s i z e from a f i n e mud t o a v e r y c o a r s e sand. The c o a r s e f r a c -t i o n c l a s t s a r e made up m a i n l y o f s i x d i f f e r e n t d i s t i n c t b a s a l t i c t o a n d e s i t i c c o m p o s i t i o n s w i t h s c a t t e r e d o c c u r r e n c e s o f o t h e r t y p e s o f c l a s t s . These r o c k s a r e m a i n l y c o n g l o m e r a t e s w i t h a much l e s s e r q u a n t i t y o f s a n d s t o n e s . The f r e s h -n e s s , r o u n d n e s s , and b a s a l t i c c o m p o s i t i o n o f c o a r s e c l a s t s , and the p r e s e n c e o f f r e s h f e l d s p a r and a u g i t e as s a n d s i z e - c l a s t s i n d i c a t e s t h a t the u n i t i s o f v o l c a n i c d e r i v a t i o n from r e l a t i v e l y c l o s e t o the s o u r c e a r e a o f the v o l c a n i s m . I t s h o u l d a l s o be n o t e d t h a t no c l a s t s a r e bomb-shaped, and t h a t t h e r e a r e no fiamme o r o t h e r examples o f w e l d i n g seen i n o u t c r o p o r t h i n s e c t i o n . Thus i t appears the c l a s t i c m a t e r i a l has been moved somewhat from i t s provenance t o a nearby b a s i n o f c l a s t i c d e p o s i t i o n , w i t h c l a s t s h a v i n g s u f f e r e d some m o d i f i -c a t i o n i n t r a n s i t . T u f f s and t u f f a c e o u s s a n d s t o n e s a r e f a i r l y abundant as t h i n l a y e r s , up t o 1 m t h i c k . These s a n d - s i z e d , e v e n - g r a i n e d u n i t s a r e v o l c a n i c i n o r i g i n but have.been reworked somewhat i n t r a n s i t . In summary, the Moosevale F o r m a t i o n c o n t a i n s a v a r i e t y o f t e x t u r a l t y p e s o f c l a s t i c r o c k s o f v o l c a n i c o r i g i n such as;, f i n e mudstone, s i l t s t o n e s , t u f f a c e o u s s a n d s t o n e s , v o l c a n i c l a s t i c c o n g l o -m e r a t e s , and l a h a r s . In a l l o f t h e s e r o c k t y p e s t h r o u g h o u t the sequence green and red c o l o u r s p r e d o m i n a t e and t o some e x t e n t a l t e r n a t e . In the c a s e o f t h e f i n e r - g r a i n e d r o c k s a p a r t i c u l a r u n i t can be e i t h e r red o r green whereas t h e c o a r s e r u n i t s can have d i f f e r e n t c o m b i n a t i o n s o f red and green i n m a t r i c e s and c l a s t s . The c o l o u r and g r a i n s i z e d i f f e r e n c e s a r e c h a r a c t e r i s t i c t h r o u g h -o u t the sequence. Thus, t h e r e a r e no g r o s s d i f f e r e n c e s i n c h a r a c t e r t h r o u g h -out the 600 m t h i c k p i l e . These two d i a d o c h i e s o f c o l o u r ( r e d vs_. green) and g r a i n s i z e ( c o a r s e vs. f i n e ) have l e d t o the c l a s s i f i c a t i o n used i n l o g g i n g d r i l l c o r e (see b e l o w ) . 21 . Ra re l y , o the r rock types are seen. Foremost in importance, are small l imestone reef s which probably f r i n g e d the v o l c a n i c c en t r e s . A s i n g l e ba s a l t dyke cuts the North Zone and i s exposed on su r face f o r a d i s tance o f about 540 m, w h i l e in the South Zone the dyke outcrops i r r e g u l a r l y . Where f a u l t i n g has been i n ten se , rnylonites are developed l o c a l l y . A d e s c r i p t i o n of these less abundant rock types f o l l ows an account of the l i t h o l o g y , pe t r o l o g y , and chemist ry of the v o l c a n i c and other fragments that c o n s t i t u t e the great bu lk of the Moosevale Formation. 3.2 C l a s t Types More than 95 percent o f coarse c l a s t s present, throughout the Moosevale Formation (and thus the Sustut depos i t ) are o f v o l c a n i c o r i g i n . These c l a s t s are subd iv ided i n t o s i x main types, some of which are very d i s t i n c t i v e in hand specimens, whereas others are d i s t i n g u i s h a b l e on ly in t h i n s e c t i o n . There are pe t rog raph i c v a r i a t i o n s w i t h i n each type, however a l l types seem to be r e l a t e d g e n e t i c a l l y , as shown by t h e i r s u r p r i s i n g l y s i m i l a r chemist ry and the f a c t that they are g radat iona l in pe t rog raph i c fea tu res ( t ex tu re and m inera logy ) . Thus, though there are d i f f e r e n c e s between the v o l c a n i c c l a s t types they are o f ten subt le compos i t iona l o r t e x t u r a l v a r i a t i o n s . The s i x c l a s t types in decreas ing order of abundance a r e ; b a s a l t , aug i te porphyry b a s a l t , f e l d s p a r porphyry ande s i t e , t r a c h y t i c - f e 1 d s p a r b a s a l t , gabbro ic b a s a l t , and hornblende f e l d s p a r porphyry. 3.2.1 Ba sa l t C l a s t s F i ne - g r a i ned ba sa l t i s by f a r the most common coarse c l a s t found w i t h i n the Moosevale Formation. These are present throughout the 600 m t h i c k sequence and on ly r a r e l y are they absent in a s i n g l e 5 - foot i n t e r v a l of vol c a n i c l a s t i c conglomerates. In hand specimen these c l a s t s are seen to be f i n e - g r a i n e d massive, g rey i s h v o l c a n i c rock. Small whi te f e l dspar. c r y s t a l s about 0.5 mm long, aug i t e phenocrysts about 1 mm long are v i s i b l e in some specimens. 22 Fresh c l a s t s g ene r a l l y are g rey i sh but r a r e l y are r edd i sh . Amygdules are r a r e l y seen and where present c on s i s t o f e i t h e r carbonate, c h l o r i t e , a l b i t e , or q u a r t z . In t h i n s e c t i o n ' ( f i g . 5) these c l a s t s conta in about 30 percent p l a g i o -c l a s e and up to 15 percent aug i te phenocrysts set in a p i l o t a x i t i c ma t r i x of p l a g i o c l a s e l a t h s . Small pseudomorphs o f c h l o r i t e a f t e r hornblende pheno-c r y s t s a re present here and can form up to 2 volume percent . Aug i te pheno-c r y s t s are absent in p laces but l o c a l l y are present as g l o m e r o p o r p h y r i t i c masses. A n o r t h i t e content of the p l a g i o c l a s e phenocrysts ranges from A n 0 Q to An c . Both p l a g i o c l a s e and aug i te phenocrysts are present as euhedral l o n g i t u d i n a l s e c t i o n s and c r o s s - s e c t i o n s . The dimensions o f the phenocrysts average about 0.3 by 0.3 mm f o r aug i te c r o s s - s e c t i ons , whereas p l a g i o c l a s e c r o s s - s e c t i o n s are up to 1.2 by 1.2 mm in s i z e and l o n g i t u d i n a l s e c t i on s average 0.45 by 0.3 mm. Some of the p l a g i o c l a s e phenocrysts show o s c i l l a t o r y zon i ng . Aug i te pheno-c r y s t s are not zoned p e r c e p t i b l y . Small a p a t i t e needles are present in the ma t r i x . 3.2.2 Aug i te Porphyry Ba sa l t C l a s t s These d i s t i n c t i v e c l a s t s are the second most common v o l c a n i c c l a s t t ype . They have been desc r ibed by a l l workers in the area (from Lord (1948) to Monger (1977)). In hand specimen there i s v a r i a b i l i t y , but a l l have l a r g e , up to 3 by 2.4 mm, euhedral aug i te c r y s t a l s v i s i b l e ( gene ra l l y the aug i t e pheno-c r y s t s appear to average 1 by 1 mm). V a r i a t i o n s are shown in c o l o u r , p ropor -t i o n o f amygdules, and v i s i b i l i t y of f e l d s p a r phenocryst s . Gene ra l l y the f r e s h e s t c l a s t s are very dark redd i sh (almost b lack) but pronounced red o r more r a r e l y dark green c l a s t s are seen. Amygdules are g e n e r a l l y p re sent , but in some cases a r e n ' t obvious in hand specimen. Some aug i t e porphyry c l a s t s have up to 20 percent amygdules v i s i b l e . Fe ldspar phenocrysts up to 0.5 mm in length are seen r a r e l y but mostly are not v i s i b l e in hand specimen. 23 F i g u r e 5 : B a s a l t c l a s t p h o t o m i c r o g r a p h ( x - n i c o l s ) . Note g 1 o m e r o p o r p h y r i t i c a u g i t e p h e n o c r y s t s w i t h opaque m a g n e t i t e s . T h i s view i s 1.1 cm a c r o s s . F i g u r e 6: A u g i t e p o r p h y r y b a s a l t p h o t o m i c r o g r a p h ( x - n i c o l s ) . Large a u g i t e p h e n o c r y s t s , w i t h opaque m i n e r a l s a r e i n a c r y p t o -c r y s t a l l i n e m a t r i x a l s o c o n t a i n i n g s m a l l e r p l a g i o c l a s e p h e n o c r y s t s . A u g i t e p h e n o c r y s t a t bottom o f p l a t e i s 6.4 mm a c r o s s . 2k . In t h i n s e c t i on ( f i g . 6) .these c l a s t s c on s i s t of c l i nopy roxene (aug i te) and p l a g i o c l a s e phenocrysts set in a p i l o t a x i t i c to f e l t e d groundmass of s m a l l e r p l a g i o c l a s e l a t h s . The groundmass may be g l a s s y . Opaque minera l s are found i n t e r g r a n u l a r l y grown w i t h p l a g i o c l a s e c r y s t a l s of the m a t r i x . P l a g i o c l a s e phenocrysts range from n i l to 30 percent in t h i n s e c t i on s and the An contents range from A n ^ to A n ^ . These phenocrysts a l s o u s u a l l y show o s c i l l a t o r y zoning w i t h some having a l b i t i c r ims. Larger p l a g i o c l a s e phenocrysts con ta in i n c l u s i o n s of c l i nopy roxene . The average s i z e o f these c r y s t a l s in d i f f e r e n t s e c t i on s ranges from 0.5 by .3 mm to 0.9 by 0.3 mm w i th some r a r e l y as l a rge as 2.1 by .75 mm. Pyroxene phenocrysts range from 10 to 30 percent in :the c l a s t s and are almost e x c l u s i v e l y a u g i t e , but in a couple o f s e c t i on s one or two small phenocrysts of e n s t a t i t e were i d e n t i f i e d . The e n s t a t i t e g ra in s are i n v a r i a b l y intergrown or inc luded in much l a r g e r aug i t e phenocry s t s . The aug i t e phenocrysts have two main forms: as l a r g e , euhed ra l , zoned t i t a n i f e r o u s c r y s t a l s o r as l a rge g1omeroporphyr i t i c masses of subhedral to anhedral aug i t e g r a i n s . These g l omeropo rphy r i t i c masses c o n t a i n i n t e r -grown opaque g r a i n s . In the l a r ge , zoned, s i n g l e aug i t e phenocry s t s , p l a g i o -c l a s e i n c l u s i o n s are found along c r y s t a l growth planes of the a u g i t e s . The aug i t e phenocrysts average 1.2 by 0.9 mm in s i z e , but are as l a r ge as 3 by 2.k mm.- Amygdules are present in a l l cases but in va ry ing amounts from 5 to 20 percent of a g iven s e c t i o n . About 1 to 2 percent hornblende c r y s t a l s , now rep laced by c h l o r i t e ( l o c a l l y w i t h hematite r ims ) , are p re sen t . 3.2.3 Fe ldspar Porphyry Andes i te C l a s t s T h i r d most common v o l c a n i c c l a s t type is the f e l d s p a r porphyry a n d e s i t e s . In hand specimen these are d i s t i n g u i s h e d r e a d i l y by the presence of equant to r e c t angu l a r phenocrysts of f e l d s p a r in a massive groundmass. The phenocrysts no rma l l y have dimensions o f 2 to 3 rom. Aug i te phenocrysts and/or amygdules are seen l o c a l l y . If f r e s h , these c l a s t s are very dark redd i sh (almost b lack) in c o l o u r . 25 When viewed in t h i n s e c t i o n ( f i g . 7) these c l a s t s c on t a i n 50 percent p l a g i o c l a s e phenocrysts of A n ^ to An^q compos i t i on , and 2 to 10 percent aug i t e phenocrys t s . The o v e r a l l t e x tu re i s stumpy euhedral to equant p l a g i o -c l a s e phenocrysts in a c r y p t o c r y s t a l 1 i n e ma t r i x . In f r e s h specimens t h i s ma t r i x i s seen to be a g las s w i th some p l a g i o c l a s e m i c r o l i t e s . The p l a g i o -c l a s e phenocrysts average 1.5 by 0.6 mm in s i z e , and show o s c i l l a t o r y zon ing . Some phenocrysts are a c t u a l l y glomeroporphyri t i c masses. The augiite pheno-c r y s t s average 0.6 by 0.45mm i n s l z e but glomeroporphy r i t i c masses range up to 1.65 by 0.9 mm. These aug i t e masses have intergrown magnetite c r y s t a l s . Amygdules, where p re sent , account f o r up to 5 percent of the c l a s t s . A p a t i t e needles are commonly v i s i b l e . 3.2.4 T r a c h y t i c - F e l d s p a r Ba sa l t (or Bladed Fe ldspar Porphyry Basalt) C1asts T r a c h y t i c - f e l d s p a r b a s a l t c l a s t s are the most d i s t i n c t i v e l ook ing in hand specimen of a l l c l a s t s seen ( f i g . 8). They c o n s i s t o f prominent bladed p l a g i o -c l a s e c r y s t a l s in a f i n e r groundmass. These p l a g i o c l a s e b lades are as long as 4 to 5 cm and up to 2 cm in w i d t h . There are a l s o r o se t t e s o f intergrown blades in some c l a s t s . The c l a s t s where f re sh are b l ack w i t h wh i te f e l d s p a r b l ades , but a s t rong red c o l o u r a t i o n o f the groundmass i s very common. This c l a s t type e x h i b i t s the g reates t t e x t u r a l v a r i a t i o n in t h i n s e c t i o n . At one end of the t e x t u r a l spectrum, the c l a s t s w i t h the l a r g e s t blades conta in 55 percent p l a g i o c l a s e and 10 percent aug i te phenocrysts set in a p i l o t a x i t i c groundmass of subhedral p l a g i o c l a s e l a th s and blades ( f i g . 9 ) ,anhedral aug i te phenocrysts and equant magnetite g r a i n s . The groundmass f e l d s p a r s in pa r t s are :i nc l uded suboph i t i c a l 1 y in some o f the a u g i t e . In some cases 50 percent o f the c l a s t i s p l a g i o c l a s e phenocrysts set in an o p h i t i c mat r i x o f subhedral p l a g i o c l a s e in a l l o t r i o m o r p h i c aug i t e s . At the o the r end o f the s ca l e 25 pe r -cent p l a g i o c l a s e arid 10 percent aug i te g l ome ropo rphy r i t i c masses of pheno-c r y s t s are in a mat r i x o f p i l o t a x i t i c p l a g i o c l a s e m i c r o l i t e s set in g l a s s . A l s o present in t h i s groundmass type are small aug i t e g ra i n s in termixed w i th Figure 7: Fe ldspar porphyry andes i te photomicrograph ( x - n i c o l s ) . Euhedral p l a g i o c l a s e phenocrysts in c rypto c r y s t a l l i n e groundmass. This s e c t i o n i s 1.1 cm ac ro s s . F igure 8: The l a rge T r a c h y t i c f e l d s pa r ba sa l t c l a s t in ou tc rop , wh i te c r y s t a l s are p l a g i o c l a s e . 27 F i g u r e 9: T r a c h y t i c f e l d s p a r b a s a l t p h o t o m i c r o g r a p h ( x - n i c o l s ) . T h i s f i g u r e shows l a r g e l a t h - l i k e p l a g i o c l a s e p h e n o c r y s t s w i t h i n t e r g r a n u1 a r a n h e d r a l a u g i t e . T h i s s e c t i o n i s 1.1 cm a c r o s s . F i g u r e 10: G a b b r o i c b a s a l t p h o t o m i c r o g r a p h ( x - n i c o l s ) . Note h y p i d i o m o r p h i c - g r a n u l a r t e x t u r e and q u a r t z - f i l l e d p o r e . T h i s s e c t i o n i s 1.1 cm a c r o s s . 28 p l a g i o c l a s e m i c r o l i t e s . Amygdules are found in a l l v a r i a t i o n s of t h i s c l a s t type. The l a r g e s t p l a g i o c l a s e c r y s t a l s are 2 by 1.5 cm. Ano r th i t e contents ranging from to A n ^ and the o p h i t i c to s u b o p h i t i c tex tu re s i n d i c a t e that t h i s type i s an a n d e s i t i c ba sa l t in na tu re . 3.2.5 Gabbroic Ba sa l t C l a s t s Th is type i s the lea s t common of the v o l c a n i c c l a s t s . In hand specimen these c l a s t s a re f i n e - g r a i n e d g ranu la r in t e x t u r e . In t h i n s e c t i o n the c l a s t s have an a l l o t r i o m o r p h i c - g r a n u l a r to hyp id i omorph i c - g ranu l a r t ex tu re ( f i g . 10). P l a g i o c l a s e c r y s t a l s are stubby t a b l e t s and c o n s t i t u t e as much as 60 percent of the rock as phenocrysts w i th 15 percent aug i t e phenocryst s . The aug i t e occurs as euhedral c r y s t a l s some of which are zoned. There are very rare amounts o f qua r t z in the groundmass g e n e r a l l y m i c r o g r a p h i c a l l y intergrown w i th f e l d s p a r . P l a g i o c l a s e and aug i te phenocrys t s , when p resent , average 1.2 by 0.45 mm and 0.9 by 0.6 mm in s i z e r e s p e c t i v e l y . A p a t i t e needles are seen in the groundmass. There i s a gross p i l o t a x i t i c t ex tu re to the p l a g i o c l a s e in these c l a s t s . 3.2.6 Hornblende Fe ldspar Porphyr ies These are a minor v a r i e t y of the f e l d s p a r po rphy r i e s . These c l a s t s con-t a i n up to 10 percent hornblende phenocrysts ( f i g . 11) up to 4 mm long and 2.5 mm -in cross s e c t i o n . P l a g i o c l a s e phenocrysts of compos i t ion An^g to A n ^ make up as much as 50 percent of the rock. These p l a g i o c l a s e phenocrysts are l a r g e -stubby euhedral c r y s t a l s averaging 1.5 by 0.45 mm in s i z e . F ive percent aug i t e phenocrysts are present as are rare e n s t a t i t e . c r y s t a l s . c The o v e r a l l t e x tu re in h ya l op i 1 i t i c . 3.2 .7 .Composit ion of Moosevale Formation C l a s t s Compared With Rocks of  Under l y ing Formations Both Monger (1977) and Church (1978, pe r s . comm.), who have s t ud i ed the Takla and Haze l ton s e c t i o n in the a rea , de sc r i be f low rocks under l y i ng the Moosevale Formation which have equ i va l en t compos i t ions to a l l the c l a s t types 29 F igure 1 1 : Hornblende porphyry photomicrograph (p lane-po l a r i z ed ) showing w e l l developed c r o s s - s e c t i o n s o f two hornblende c r y s t a l s . Sec t i on i s 2 . 9 cm ac ro s s . 30 in the Moosevale Formation, except f o r the f e l d s p a r po rphy r y•ande s i t i c c l a s t s . Church (1978 , per s . comm.) b e l i e v e s that format ion of these ande-s i t e s was contemporaneous w i t h Moosevale Formation depo s i t i on and represents an e a r l y stage in the p rog re s s i ve change in the modal compos i t ion o f vo lcan i sm from b a s a l t i c to d a c i t i c . A study of the r e f r a c t i v e i nd i ce s o f fused g la s s beads (Church, 1973) showed that v o l c a n i c s in the Dewar-Savage Mountain Formations are b a s a l t i c in compos i t i on , the Moosevale v o l c a n i c s are dominantly b a s a l t i c w i t h some andes i te compos i t ions (eg_. the f e l d s pa r porphyr ie s ) , whereas the o v e r l y i n g Hazelton rocks are main ly a n d e s i t i c w i th a s i g n i f i c a n t d a c i t i c component. 3 . 2 . 8 Geochemistry of the V o l c a n i c C l a s t Types P a r t i a l major ox ide analyses on the var ious v o l c a n i c c l a s t types are in Table 1. The analyses are p a r t i a l because i ron contents were not a s c e r t a i n e d e x a c t l y due to incomplete d i g e s t i o n of magnet i te. S i m i l a r l y , t i t a n i u m is l i k e -l y a l s o low because the magnetite i s t i t a n i f e r o u s . Analyses f o r Zn, Cu, N i , Sr, Rb, were made on some of the c l a s t types (Table 2 ) . F i gu re 12 i s a t o t a l a l k a l i vs. s i l i c a diagram w i th Macdonald and Ka t s u r a ' s (1964) and I r v i ne and Ba ragar ' s (1971) s u b d i v i s i o n s of a l k a l i c f i e l d s . A l l of the c l a s t and dyke samples p l o t in the a l k a l i b a s a l t f i e l d as de f i ned by Macdonald and Katsura ( i b i d . ) , and in the a l k a l i n e f i e l d as de f ined by I r v i ne and Baragar ( i b i d . ) . Th is a l k a l i n e nature of the Moosevale v o l c a n i c s a l s o has been demonstrated by Monger ( 1 9 7 7 ) -S i l i c a contents of the c l a s t s vary un i fo rmly from 45 to 53 pe rcen t . Thus the v o l c a n i c c l a s t s range from dominant ly b a s a l t i c to a n d e s i t i c . The dyke samples (W23 and W99) are more s i l i c a - p o o r than the v o l c a n i c s . F i gu re 13 is a s e r i e s o f major ox ide vs_. s i l i c a , and t r a ce metal vs . s i l i c a v a r i a t i o n diagrams; the v a r i a b i l i t y in the chemistry o f . t h e c l a s t types and between c l a s t s of one type i s apparent. Th is i s probably due to d i f f e r e n c e s in a l t e r a t i o n of the c l a s t s , as a l l c l a s t samples were at l e a s t s l i g h t l y a l t e r e d TABLE I MAJOR OXIDE ANALYSES FOP. DOMINANT CLAST TYpES ( j DYKE BASALT AUGITE PORPHYRY FELDSPAR PORPHYRY TRACHYT1C FELDSPAR HORNBLENDE PORPHYRY SAMPLES SAMPLES • BASALT SAMPLES ANDES 1TE SAMPLES BASALT SAMPLES SAMPLES OXIDE W23 W99 88F2 88A6 110H5 6A1 13C3 W97AP 1311 1 10C8 1 16A1 88A8 88D1 Si0 2 13.00 kZ .25 16 .75 hi.IS 53 .00 18.75 18 .00 16.13 50.50 51 .50 51.25 18.50 hS .50 Ti 0 2 1.03 0.82 0 .61 1.07 1 .30 1 .00 0 .59 1.22 0 .57 0 .80 1 .03 0 .92 0 .76 Al 203 16.33 16.90 19 .60 17.3*1 17 . 16 15.22 18 .96 .1*1.59 20.56 18.12 17.74 16.78 18 .90 T o t a l Fe 3.65 3 .68 3 .58 3.16 3 .21 3.09 3 . 19 3-87 2.11 2.91 3.37 3.11 2 .60 MnO 0.16 0 . 1 V 0, .21 0.11 0 .11 0.09 0 .13 0.18 0.11 0.16 0.17 0.19 0 .12 MgO 7.80 7. .10 1, .75 3.95 3 .65 2.65 3 .75 8 .55 . 1.80 1.00 1.65 1.10 2. .35 CaO 9.98 10, .10 5. .65 5.80 6 .85 7.35 6 .85 6.68 1 .70 3.85 1.10 5.75 6. .15 Na20 2.69 2. • 7't 1. .15 3.98 5. .60 5.91 1 .17 3-55 3.88 1 .75 3.86 1.06 1. .78 k 2o o.ai 0. .77 0. .61 2.96 0. .30 1 .01 2. .17 . 1.15 1.09 2.2.8 3.77 2.88 1, .87 p 2 o 5 0.56 0. ,'18 1 . .05 0.72 0. .72 0.81 0. .18 0.61 O.89 0.81 1.30 0.97 0. .61 L.0.1 . 2.58 3. ,1*t 2. ,81 2.36 2. .18 2.37 2. .25 3.03 1.6 2.75 3.01 2.55 2. .06 Cu — 0.015 0.007 0.008 0. .01 0.001 0. .02 0 . 18 0.001 — — 0.006 0,09 T o t a l 88.59 88. 7't 9 0 . 89.5*1 91. .09 88.25 90. .56 89.77 91.11 91.96 91-58 90.15 90 . 12 " " " " " " " T h e s e ana lyses were made by Min-En L a b r a t o r i e s , North Vancouver, B.C.. TABLE I I TRACE ELEMENT ANALYSES FOR VOLCANIC CLASTS (PP™ ± p r e c i s i o n ) Rock Type J sample No. Zn Cu Sr_ Rb Dyke W 9 9 7 3 . 0 0 ( + 0 „ 9 6 ) 1 4 7 . 7 5 (t37o77) 7 3 . 3 9 ( i U l 4 ) 3 2 1 . 1 2 ( ± 1 . 0 4 ) 1 1 . 6 2 ( ^ 0 . 0 2 ) Basa l t 8 8 F 2 1 3 6 . 9 9 ( * 0 . 8 1 ) 71 - 5 3 ( ± 1 - 6 3 J 0 . 0 0 7 6 6 . 8 0 ( * 0 . 5 0 ) 7 . 7 9 ( ± 0 . 1 3 ) 1 8 8 A 6 1 2 8 . 0 5 ( ^ - 8 1 ) 8 3 . i 6 ( + 2 . 5 4 ) 2 . 3 5 ( * 0 . 8 7 ) 3 2 3 . 6 6 ( ^ 0 . 0 8 ) 33.15(t0.33) 1 1 1 0 H 5 6 9 . 5 6 ( ± U 3 5 ) 1 0 2 . 0 9 ( ± 3 . 1 5 ) 8 . 9 4 ( + 0 . 6 8 ) 1 1 7 . 5 0 ( ± 0 . 1 4 ) 1 . 0 5 ( ± 0 . 0 8 ) Aug i te Porphyry 6 A 1 2 8 o 1 5 ( ± 0 o 8 3 ) 1 8 . 6 1 ( ± 2 . 1 5 ) 8 . 6 7 ( ± 1 . 1 1 ) 4 2 1 . 4 3 ( ± 0 . 9 2 ) 1 4 . 2 1 ( ± 0 . 0 5 ) 1 1 3 C 3 8 2 . 2 3 ( ± 2 0 0 1 ) 17^.91 (±57.93 ) 0 . 9 8 ( + 0 . 5 8 ) 4 6 7 . 2 9 ( ± 1 . 8 5 ) 4 0 . 8 3 ( ± 0 . 1 8 ) 1 W 9 7 A P 1 8 8 . 4 2 5 ( ± 0 . 9 4 ) 1 8 3 2 . 5 2 ( + 1 6 9 . 5 3 ) « 3 . 7 0 ( ± 0 . 0 6 ) 3 5 2 . 7 K ± 0 . 2 9 ) 1 8 . 2 0 ( ± 0 . 0 5 ) Fe ld spa r - 1 3 1 1 1 2 8 . 5 8 ( ± 4 . 0 3 ) 4 6 . 9 5 ( ± 2 . 0 2 ) 0 . 0 0 6 7 6 . 7 5 ( ± 1 . 9 4 ) 8 0 . 9 6 ( ± 0 . 3 4 ) Porphyry Trachy Fe ldspar 88A8 8 6 . 5 « ( ± 0 . 7 7 ) 6 8 . 5 9 ( ± 1 . 8 3 ) 1 8 . 5 8 ( ± 0 . 2 2 ) 4 0 3 . 5 3 ( ± 1 . 6 2 ) 4 8 . 1 1 ( ± 0 . 3 1 ) B a s a l t • Hornblende 8 8 D 1 5 1 . 7 5 U 0 . 6 6 ) 8 8 2 . 8 1 (±92.83) Porphyry . . . 0 . 0 0 3 1 1 . 7 2 ( ± 0 . 1 2 ) 2 5 . 0 6 ( ± 0 . 0 1 ) L E G E N D A lka l i ne-- I rv ine & B a r a g a r Alkal i BasaltS - M a c D o n a l d & K a t s u r a • D y k e A B a s a l t • A u g i t e por . a Fe I d spa r p o r . A T r a c h y - F e l d s p a r por. o H o r n b l e n d e por . I rv ine & B a r a g a r M a c D o n a l d & K a t s u r a T h o l e i i t i C Basa l tS - M a c D o n a l d & K a t s u r a Suba lka l ine - I rvine & B a r a g a r 46 48 50 S i 0 0 (%) Fi gure 12:. To ta l a l k a l i vs_. s i l i c a d iagram f o r l i t h i c c l a s t s and dyke rock. <J0 H ° / . N a 2 0 4 a-'Io K 2 0 3 V .TIOj 1.0 0.8 0.6-0.2 */• MnO 0.1 40 S3 JFA o o D A o o ° A A A • o D a CD A E O O 45 SO —1 54 ' / . M 5 O 7-5-> 3 H I.2H • / . P 2 O s °H 0.6H °/o CaO 4H ZO I N I6H ' 40 a A A A A, O 03 A • B • * A o-H O A A A : ° A • O n o A A n 6 45 %SI02 SO 54 F i g u r e 13a: Major o x i d e vs_. s i l i c a v a r i a t i o n diagrams f o r l i t h i c c l a s t s and dyke rock . (Legend i s the same as f o r F i g u r e 12). 35 90-1 Ni ( ppm) jo-] • © iso-\ A • Zn (ppm) I0H 50H I50H Cu(ppm) l 0H 5 H 40 I8&2 8 4 2 a A A A a 45 50 54 <7oSi0 2 Figure 13b: Trace metal v s . s i l i c a v a r i a t i o n diagrams f o r l i t h i c c l a s t s and dyke rock. (Legend is the same as f o r Fi gure 12). 36 and .some were moderately to h i gh l y a l t e r e d . Th is i s supported by the two dyke samples which have a cons i sent chemistry because they are not as a l t e r e d as the l i t h i c c l a s t s . These v a r i a t i o n diagrams are s i m i l a r in r e s u l t to those prepared by Monger (1977) f o r Moosevale Formation c l a s t s , except Monger 's sample c o l l e c t i o n was b ia sed in favour of the f e l d s p a r porphyry ande s i t e s . Monger a l s o found background copper contents in the Moosevale v o l c an i -c l a s t i c s ranged from approx imate ly 16 ppm to 90 ppm. Most o f t h i s w r i t e r ' s copper analyses agree, except that apparent background copper may vary from 18 to 175 ppm. Samples W97AP and 88D1 are c l o s e to su lph ide m i n e r a l i z e d zones, thus t h e i r high copper contents ( r e l a t i v e to t h i s a u t h o r ' s and Monger 's a n a l -yses) are probably a r e s u l t o f contaminat ion of the c l a s t s by ore m i n e r a l -i z a t i o n processes . The medium copper values of W99 and 13C3 might i n d i c a t e some contaminat ion , however copper contents of up to and s l i g h t l y above 100 ppm would be expected in normal ly d i s t r i b u t e d copper. (This high background con-ten t i s f u r t h e r e x h i b i t e d by a p r o b a b i l i t y p l o t of copper assay values - see be low). 3.2.9 Other C l a s t Types" There are seve ra l o the r types of c l a s t s seen in the v o l c a n i c conglomerates in very minor amounts. Most of these appear to be c l a s t s of reworked f i n e r -g ra ined sedimentary rocks o f the same sequence, and inc lude t u f f , mudstone, and s i l t s t o n e fragments, which have the same general roundness as the v o l c a n i c c l a s t s . These " o t h e r " fragments are r a r e l y l a r ge , g e n e r a l l y about 2 to 3 cm in d iameter . However they are s i g n i f i c a n t in that they i n d i c a t e there was reworking o f p r e - e x i s t i n g sediments. C h l o r i t e c l a s t s are seen r a r e l y . These c l a s t s are t y p i c a l l y rounded and mass ive. They a l s o are not la rge in s i z e and most commonly are seen 1 to k mm g ra in s in sandy lenses . In t h i n s e c t i o n euhedral c r y s t a l s of aug i t e are developed l o c a l l y in these c l a s t s . These g ra in s probably represent v o l c a n i c g la s s fragments, however they show no f l a t t e n i n g thus p r e c l ud i n g ash f low type 37 o r i g i n s . Limestone c l a s t s are very rare but are found s c a t t e r e d very w ide l y throughout the e n t i r e v o l c a n i c l a s t i c sequence ( f i g . 14) . These c l a s t s are 5 to 10 cm in diameter and in outcrop are most e a s i l y seen as depress ions formed by p r e f e r e n t i a l weather ing on exposed s u r f ace s . One such c l a s t (sample W1009) con ta in i ng f o s s i l deb r i s was submitted to the Geo log i ca l Survey of Canada f o r i d e n t i f i c a t i o n (Appendix If G.S.C. Report No. 4-BEBC-78). The f o s s i l s present were cora l fragments, gastropods, f o r a m i n i f e r a (Ammod ? s cu s ) , f i s h debr i s and. t ee t h , and conodonts (E p Tgondolel 1 a (p r i m i t i a) Mosher and Neogondolel 1a) The i n d i -cated age f o r t h i s c l a s t i s Late T r i a s s i c , Late Karn ian to e a r l y Nor ian . These c l a s t s i n d i c a t e probable reworking of small reef s b u i l t upon v o l c a n i c i s l ands and do not appear to i n d i c a t e a provenance from unde r l y i ng f o rmat ion s . (One small reef accumula t i on , apparent ly in p l a ce , i n t e r s e c t e d by DDH k~I, seems to support the l o c a l d e r i v a t i o n o f such c l a s t s ) . A l s o present are very minor c l a s t s of massive qua r t z , maybe i n d i c a t i n g debr i s from a d i s t a n t source. One of two c l a s t s of a d i a b a s i c nature are a l s o seen i n d i c a t i n g another minor phase in the v o l c a n i c a c t i v i t y . 3.3 Rock Types In t h i s s e c t i o n the phy s i c a l c h a r a c t e r i s t i c s o f each d i f f e r e n t rock type present in the upper member of the Moosevale Formation at Sustut Copper w i l l be de sc r i bed . The predominate rock type present i s the vol c a n i c l a s t i c cong lo -merates. These conglomerates are a l s o the rock type o f which the most intense d e s c r i p t i o n of phy s i c a l v a r i a b l e s was accompl ished w i t h the computer-based logg ing system. Sub s i d i a r y in importance are tu f faceous sandstones, c r y s t a l t u f f s , lahars and a r g i l l a c e o u s mudstones. Shale occurs on l y at the base of the North C l i f f s , and a l imestone reef is in a small p o r t i o n of DDH k~J. A l so descr ibed are the a l k a l i c ba sa l t dyke which cuts the North Zone, and my lon i tes caused by f a u l t i n g . 38 F igure 14: Limestone c l a s t in v o l c a n i c l a s t i c rocks . This p l a t e i s of sample W1009, which was f o s s i 1 i f e r o u s . Note the e a s i e r weather ing nature of the c l a s t r e l a t i v e to the host rock. 39 3-3-1 V o l c a n i c l a s t i c Conglomerate Un i t s V o l c a n i c l a s t i c conglomerates are the dominant rock type of the Moosevale Format ion. T h e i r c ha rac te r va r i e s in that p r opo r t i on of c l a s t types d i f f e r from p l a ce to p l a c e , r e l a t i v e amounts red and green c l a s t s vary, mat r i x co l ou r is e i t h e r red o r green, and t e x t u r a l c h a r a c t e r i s t i c s such as percent m a t r i x , s o r t i n g of f ragments, e t c . vary. F igure 15 shows a t y p i c a l conglomerate. In logg ing the d r i l l co re , c e r t a i n d i a g n o s t i c f ea tu re s of these conglomerates were recorded c o n s i s t e n t l y f o r core lengths of 1.52 m (5 f t . ) . The major c h a r a c t e r i s t i c de sc r i bed f i r s t f o r each 5 - foot i n t e r v a l was the co l ou r o f the mat r i x (or f i n e f r a c t i o n ) vs_. that o f dominant and minor c l a s t s ; in terms o f red and green. The author adopted the f o u r - l e t t e r code p r e v i o u s l y developed by g e o l o g i s t s o f Fa lconbr idge N icke l Mines L t d . s p e c i f i c a l l y f o r core l o gg i ng . Accord ing to t h i s code, a conglomerate w i t h a green ma t r i x , dominantly green c l a s t s , and minor red c l a s t s would be recorded as AGGR, wherein the A i n d i c a t e s a v o l c a n i c l a s t i c conglomerate, the f i r s t G s i g n i f i e s the green co l ou r o f the f i n e f r a c t i o n ( m a t r i x ) , the second G, the dominant co l ou r of coarse c l a s t s , and R the presence o f minor coarse fragments w i t h a red c o l o u r . Accord ing to t h i s code, ARRR is at one end of the s c a l e and i n d i c a t e s red mat r i x w i t h on l y red c l a s t s ; AGGG, at the o ther extreme, i n d i c a t e s a green ma t r i x w i th on l y green c l a s t s . E i gh t po s s i b l e v a r i a t i o n s in the s i n g l e rock type " A " can be de f i ned us ing t h i s s c a l e . F i g . 16 i s a h i s togram of the t o t a l number of obse rva t ions of each type of v o l c a n i c l a s t i c conglomerate, and o ther rock types found on the p rope r t y , that were recorded in the 19 d r i l l holes s t u d i e d . Of the 2101 rock type ob se rva t i on s made dur ing core l ogg ing , 1986 o r 95 percent are c l a s s i f i e d as being v o l c a n i c l a s t i c conglomerate. The dominant v a r i e t y i s AGGR, which accounts f o r kl percent o f a l l samples examined. The b i m o d a l i t y in g ra i n s i z e of these conglomerates was coded f o r each ob se r va t i on o f l i t h o l o g i c type us ing a two-way c l a s s i f i c a t i o n t a b l e developed 40 F igure 15: Typ i ca l v o l c a n i c l a s t i c conglomerate. This conglomerate conta ins a poor ly so r ted l a rge f r a c t i o n of l i t h i c c l a s t s in a f i n e r f r a c t i o n of coarse sand s i z e fragments. Interbedded w i t h t h i s conglomerate i s a small muddy l aye r which drapes over some l a r ge r c l a s t s . This view i s about 2 m ac ro s s . 1000 rv>! J22±23__ "?-> ^ -d- aX " ^ x o, /-TA $ $ ^ % \ % \«&\$ LITHOLOGY ' F i gu re 16: Bar graph showing r e l a t i v e abundances o f rock types . This graph represents the t o t a l number o f o b s e r v a t i o n s o f each rock type recorded in 10,000 f t of c o re . Note the l o g a r i t h m i c s c a l e f o r number o f samples, kl by B lanchet and Godwin (1972). F i g . 45 shows a l l s i z e v a r i a t i o n s seen on Sustut Copper and a l so conta ins t h e . r e l a t i v e p ropor t i ons o f these c l a s s i f i c a t i o n s . As can be seen the f i n e f r a c t i o n (matr ix ) m a t e r i a l ranges from a c l a y (of<1/256 mm in d i amete r ) , to a coarse sand o f 1 mm d iameter, whereas the coa r se -g ra ined f r a c t i o n ranges from coarse sand (about 2 mm) to a bou lder s i z e (> 256 mm). The dominant f i n e f r a c t i o n s i z e , though, i s s i l t y to f i n e sandy, 1/256 to £ mm, and the major coarse f r a c t i o n s are small pebbles to bou lde r s , k to 256 mm. The percent mat r i x (as opposed to percent coarse f r a c t i o n ) was a l s o recorded at each i n t e r v a l and the p ropor t i on s are shown in f i g . 17- The pe r -centage of mat r i x (or f i n e f r a c t i o n ) present ranges from 20 to 90 pe rcent , w i t h the dominant amounts being 50 to 60 pe rcent . Average s o r t i n g o f every 5 - f o o t ( 1.52 m) i n t e r v a l was coded us ing a s o r t i n g guide (Appendix I) from Blanchet and Godwin (1972). Accord ing to t h i s code, s o r t i n g va lues from 1 to 9 are a s s i gned : a va lue o f 1 i s extremely poor s o r t i n g whereas 9 i s ext remely we l l s o r t e d . F i g . 18 shows that the s o r t i n g c h a r a c t e r i s t i c s o f these conglomerates range from 2 to 7 and the s o r t i n g , on the whole, i s poor. Textures o f these rocks were determined w i t h the i nequ i g r anu l a r t ex tu re char t o f B lanchet and Godwin (1972) reproduced in f i g u r e k$- This char t i s used as a two-way c l a s s -i f i c a t i o n scheme to f i r s t group specimens on the nature of the m a t r i x . Where the mat r i x i s f i l l e d w i t h v i s i b l e cement as we l l as some d e t r i t u s , the t ex tu re i s de f i ned as " open " , and where the mat r i x i s on ly d e t r i t u s ( i e . a t rue f i n e f r a c t i o n ) the t ex tu re i s " c l o s e d " . A f u r t h e r d i v i s i o n i s then based on the percentage o f the rock that forms the l a rge f r a c t i o n . The h i s togram of f ig.19 shows the number of ob se rva t i on s of each " t e x t u r a l " v a l ue . The very predom-inant t e x t u r e , 71 percent of a l l 5~foot samples, i s f o r a c l o s ed mat r i x w i t h 25 to 50 percent l a rge f r a c t i o n . The second-most important t e x t u r a l v a r i e t y i nc ludes 14 percent of a l l 5 - foo t samples and i s f o r an open mat r i x w i t h 25 to 50 percent coarse f r a c t i o n . F i gu re 17: Bar graph to coar se f r a c t i o n in showing r e l a t i v e amounts of mat r i x v o l c an i c 1 a s t i c cong lomerates. ( f i n e f r a c t i o n ) F i gu re 18: Bar graph showing r e l a t i v e number of ob se r va t i on s o f s o r t i n g c h a r a c t e r i s t i c s in vol c a n i c l a s t i c cong lomerates . iooo H Q. E co CO 0) E z 100 H 10H C l o s e d Framework Open F ramework n=1356 n=103 SSI n = 144 "2? C 5 -T n = 2 n=259 n = 13 n=1 i i T 1i& Sip n=24 10-25 25-50 50-75 > 75 <10 10-25 25-50 50-75 45 Volume Percentage Large F r a c t i o n F igure 19: Bar graph showing r e l a t i v e number of obse rva t i on s of t e x t u r a l c l a s s i f i c a t i o n s o f vol c a n i c l a s t i c conglomerates. 46 In surface mapping, the vol c a n i c l a s t i c conglomerates and t h e i r physical c h a r a c t e r i s t i c s are e s s e n t i a l l y i d e n t i c a l to what is seen in the core logging (though core data are probably more representative). The geology map (MAP 1 -in pocket) is based upon subdivision of the rocks into a dominantly green or red colouration. No attempt was made at d e t a i l e d textural subdivisions. However, considerable e f f o r t was expended trying to e s t a b l i s h an informal, stratigraphy to the Moosevale Formation based on l i t h o l o g y of coarse c l a s t s , but to no ava i 1 . The fin e f r a c t i o n s (matrices) consist of d e t r i t u s made up of grains of feldspars, augite, small l i t h i c c l a s t s (sand si z e and smaller), hornblende, magnetite, c h l o r i t e , rare quartz and very rare e n s t a t i t e . Small l i t h i c c l a s t s are generally subrounded to rounded. P l a g i o c l a s e , augite and hornblende are most commonly subangular to angular, but l o c a l l y are rounded. Generally, these grains are euhedral c r y s t a l s . The feldspars, being more r e s i s t a n t to weathering, are generally whole c r y s t a l s whereas the augite and hornblende are most often broken fragments. The amount of cement is v a r i a b l e , but in most cases some cement is present (i n the thin sections studied, amount of cement ranged from n i l to 70 percent). The cement types in decreasing order of abundance are; carbonate, c h l o r i t e , quartz, epidote, prehnite, hematite, and rare a l b i t e . In a given t h i n section two or three cement types are o r d i n a r i l y present. The epidote appears to be a product of r e c r y s t a l 1 i z a t i o n of a very f i n e s i l t y or clayey matrix, that prob-ably consisted mainly of p l a g i o c l a s e fragments. The hematite is an oxidation e f f e c t upon f i n e muds. Pore spaces or openings within the matrix i t s e l f are common with the above cement minerals and pumpellyite as normal f i l l i n g mater-i a l s . In general i t can be said that the permeability and porosity of the mat-rices (fine f r a c t i o n s ) have great var i a t i o n s from o r i g i n a l , impermeable close packed s i l t y arrangements to very open pores, now f i l l e d with cement. hi Fisher (1961, p. 1413) would c l a s s i f y these rocks as e p i c l a s t i c volcanic breccias and/or e p i c l a s t i c volcanic conglomerates which Imply rocks "derived by weathering and erosion of l i t h i f i e d or s o l i d i f i e d v o l c anic rock". Parsons (1969) also c a l l e d these types of sediments e p i c l a s t i c v o l c anic breccias and described t h e i r general s t r u c t u r a l features and groundmasses. The fragments are subrounded to rounded in a matrix of various sand and s i l t s i z e s , but. which has no pumice or shard fragments. " E p i c l a s t i c v o l canic breccias are usually rather well s t r a t i f i e d and show f a i r or moderate s o r t i n g . They are interbedded with better sorted sandstones and conglomerates." (Parsons, 19&9, p. 288). 3.3.2 Sandstone Units Sandstones are the second most common rocks present oh the Sustut Copper deposit, accounting for approximately 3 percent of a l l types ( f i g . 20). In hand specimen these rocks have, colour v a r i a t i o n s from pale green (due to epidote) to dark red (hematite-bearing). They are a l l generally massive but in some cases individual grains are readily v i s i b l e . Thickness of sandstone layers and lenses vary from 2 to 3 cm for small i n t e r v a l s , to large beds that are up to 6 m thi c k . In outcrop these sandstones are seen to be int e r c a l a t e d with the dominant v o l c a n i c l a s t i c conglomerates and for the most part have very r e s t r i c t e d areal extents. No one sandstone layer can be traced throughout the en t i r e property. In the d r i l l core the sandstones are most commonly present as upper portions of graded bedding sequences with the conglomerates as the base. In general, these sandstones are poorly sorted, immature, fel d s p a t h i c sediments. Grain sizes vary from what Pettijohn (1975) c a l l s granule gravels (2 to 4 mm) to g r i t t y sandstones ( >0.5 mm). Internally the grains are not consistent in size and show extreme ranges of up to 0.06 to 1.4 mm. The dominant grains are plagioclase feldspars which can account for 50 to 90 per-cent of grains present. Augite and l i t h i c c l a s t grains are next most 48 F igure 20: T y p i c a l tuf faceous sandstone i n te rbed in conglomerate. This sandstone l a ye r is p r e f e r e n t i a l l y weathered r e l a t i v e to the conglomerate. 49 abundant, w i t h hornblende being the f o u r t h . Other r a r e r g ra in s are magnet i te , ch . l o r t te , and le s s commonly l i m o n i t e . These g ra in s are cemented by combina-t i on s o f carbonate, qua r t z , c h l o r i t e , e p i d o t e , p r e h n i t e , hemat i te , and a l b i t e . Rarely red mud cement forms as much as 40 to 75 percent of the rock. Pore holes are q u i t e commonly present and are f i l l e d w i t h any o f the above cements. The l i t h i c g r a i n s a re subrounded to rounded whereas the f e l d s p a r , augite,. and hornblende g ra i n s are angu la r , and rare 1y t h e i r form is as euhedral c r y s t a l s . The "AREN" on the l i t h o l o g y h i s togram ( f i g . 16) r e fe r s to a d i s t i n c t i v e sandstone found on l y from 770 to 778.5 f t . l e v e l of DDH 132. This rock i s a g rey i sh wh i te coa r se -g ra ined sandstone, which conta in s l a rge f e l d s pa r g ra in s and rare l i t h i c f e l d s p a r porphyry c l a s t s . 3.3-3 C r y s t a l Tu f f Un i t s The c r y s t a l t u f f un i t s have dominant and d i s t i n c t i v e mineral c r y s t a l s . In hand specimen, numerous, euhedral p l a g i o c l a s e c r y s t a l s are v i s i b l e , and commonly o u t l i n e a crude bedding. These c r y s t a l s are in a f i n e r ma t r i x remin i scent o f a r h y o d a c i t i c porphyry. The c r y s t a l s are up to 1.5 mm long . The mat r i x i s most commonly medium reddish in c o l ou r but green matr i ces are seen. P e t r o g r a p h i c a l l y these t u f f s c on s i s t o f euhedral stubby p l a g i o c l a s e c r y s t a l s w i t h euhedral aug i te c r y s t a l s , and/or l i t h i c fragments ( f i g . 21). The m a t r i x , present from 40 to 60 pe rcen t , i s e i t h e r a f i n e (<0.00l6 mm), g ranu la r mass o f f e l d s p a r g ra ins o f c h l o r i t i z e d g l a s s ; or a combinat ion o f the two. These rocks are not very common and thus f i e l d r e l a t i o n s are obscure . However, at the top o f the North C l i f f s (sample W44 s i t e ) a 1 m t h i c k bed can be t raced f o r about 120 m, before d i sappear ing in rubb le . 3.3.4 Lahar Un i ts Lahars are one of the more s t r i k i n g rock types in the Moosevale Format ion. In outcrop they are seen to conta in a wide s i z e range o f rounded coarse f r a g -ments suspended in a muddy or s i l t y ma t r i x ( f i g . 22). Some of these c l a s t s are 1 m to 3 m in d iameter . The mud matr i ces are e i t h e r dark red or dark green in F i g u r e 21 : C r y s t a l t u f f p h o t o m i c r o g r a p h ( x - n i c o l s ) . T h i s p l a t e shows the t y p i c a l w e l l c r y s t a l l i z e d fo rm o f p l a g i o c l a s e and a u g i t e p h e n o c r y s t s i n a g r a n u l a r m a t r i x . T h i s s e c t i o n i s 1.1 cm a c r o s s . F i g u r e 22: T y p i c a l l a h a r i c u n i t w i t h l a r g e b l o c k s and muddy m a t r i c e s . The l a h a r i c m a t e r i a l i n t h i s p l a t e i s e x t e n s i v e l y i n t e r b e d d e d w i t h c o n g l o m e r a t e s . 51 c o l o u r . Gene ra l l y these very large c l a s t s are few and f a r between w i t h i n the mat r i x and in t h i s res.pect d i f f e r from the convent iona l conglomerates which have a more c o n s i s t e n t s i z e range of f ragments. The l a t e r a l extent of these lahars i s not great and they are probably best thought of as being l o c a l i s e d slump-ing f e a t u r e s . A g iven lahar may l o c a l l y form the base f o r a graded bedding sequence in which the top po r t i on i s a mudstone. In the d r i l l core these rocks would be grouped in w i th the regu la r conglomerates but t h e i r presence i s expressed by the very large s i z e o f some coarse f r a c t i o n s observed. The "F-SPAR POR. ' s " in f i g . 16 are observat ions of l ahar un i t s in which a complete 5 f t i n t e r v a l was occup ied by a s i n g l e c l a s t (j_e. the f e l d s p a r porphyry c l a s t s ) . Lahars are p a r t i c u l a r l y n o t i c eab l e i n t e r m i t t e n t l y in DDH 88, from the 1340 to 1460 and from the 1660 to 1680 f t l e v e l s . Here c l a s t s of up to 1.5 mm are suspended in a f i n e dark red a r g i l l a c e o u s mudstone ma t r i x . 3-3-5 A r g i l l i t e s and A r g i l l a c e o u s Mudstone Un i t s The d i f f e r e n c e between these two is tha t the mudstones are t h i n and show mudcrack s t r u c t u r e s , wh i l e the a r g i l l i t e s , sensu s t r i c t o , are t h i c k e r bedded. A r g i l l i t e s are found on ly in the lower sec t i on s of the Moosevale Formation where they form the base o f the upper member. These rocks are deep red in co l ou r and show microbedding f ea tu re s o f t h i n , 1 to 2 mm t h i c k , sandy and b l ack muddy l a y e r s . This rock type i s made up of 25 percent f e l d s p a r , 5 percent aug i t e and hornblende, 5 percent s h e l l and 10. percent opaque f r a g -ments in a c r y t o c r y s t a l 1 i n e m a t r i x . The g r a i n s i z e s are 0.16 to 0.04 mm f o r f e l d s p a r and 0.08 to 0.04 mm f o r aug i t e and hornblende g r a i n s . The s h e l l fragments look l i k e pelecypods and are probably Hal obi a. l i k e those i n the unde r l y i ng sha le ( s ec t i on 3-3-6), but are not adequately preserved f o r p o s i -t i v e i d e n t i f i c a t i o n . The 1025 to 1205 f t i n t e r v a l in DDH 110. is composed of i n t e r - and r e p e t a -t i ve -bedded red , ' green, and r a r e l y b lack a r g i l l i t e s w i th red and green t u f f -aceous sandstones. Each a r g i l l i t e l a ye r i s le s s than 1.5 m in t h i c k n e s s . 52 In hand specimen small (< 1 mm in diameter) white feldspar grains are commonly v i s i b l e . In thin section these a r g i l l i t e s e x h i b i t well defined bedding and often contain small scale (a few centimeters wide) graded beds. These rocks c o n s i s t of feldspar grains, 0.06 mm to 0.9 by 0.6 mm in diameter, and opaque grains 0.75 mm in diameter, set in an i r r e s o l v a b l e matrix which makes up 60 per-cent of the rock. No"argi11ites are seen.in the lower portions of DDH 88, but the a r g i l l a c e o u s matrix to the lahars at the 13^0-1460 and 1660-1680 foot l e v e l s is strongly reminiscent of the a r g i l l i t e s in DDH 110. Argil l a c e o u s mudstones are present in the upper 30 m of the host rock to the Sustut Copper deposit. Their thicknesses are seldom greater than 5 mm to 2 cm. These rocks are very dominantly red in colour and show extensive mud-cracking ( f i g . 23). The rare green ones are not mud-cracked. These mudstones are seen almost equally as tops to a graded bedding sequence, or s i t t i n g , non-graded, within the conglomerates, Their presence and associated mudcracks near the top of the MoosevaJe, indicate a. gradual and per i o d i c re-emergence of these rocks to subaerial weathering as the T r i a s s i c period closed. 3.3.6 Shale Unit The d i s t i n c t i o n between shales and a r g i l l i t e s is based on the c r i t e r i a that the shales have d e f i n i t e cleavage or parting p a r a l l e l to bedding ( P e t t i -john, 1975). The only shales, thus defined, on the property are those at the top of the lower unit of the Moosevale Formation. These shales are dark black in colour and are f o s s i 1 i f e r o u s . The f o s s i l s present have been i d e n t i f i e d (H.W. Tipper, 1978, pers. comm.) as the pelecypod, Hal obi a and indicate an Upper T r i a s s i c age for this unit. The shales themselves, consist of 0.08 to 0.04 mm grains of feldspar, with rare augite grains, in an u n i d e n t i f i -able matrix. 3-3-7 Limestone Unit Aside from rare limestone c l a s t s , the only in s i t u limestone bed found on the property was in DDH 47 in the South Zone. This limestone bed is the only one so f ar reported in the uppermost part of the Takla Group in t h i s area. Previous-ly f o s s i l s have been seen only in the lower unit of the Moosevale before reap-53 Figure 23: Mud cracks in a r g i l l a c e o u s mudstone. • Figure 24: Limestone reef in d r i l l hole 47. Note the f i n e f o s s i l fragments v i s i b l e in the l imestone and a l s o the upper contact (to r i g h t ) where l i t h i c c l a s t s are in termixed w i th the l imes tone. Th is p iece of core is about 1 f t l ong . pea r i ng i n the Lower J u r a s s i c Haze l ton Group. The base o f t h i s l imes tone bed i s at the 120 f oo t l e v e l of DDH k~j where i t r e s t s on top of a f i n i n g -upward s v o l c a n i c l a s t i c rock. From 120.5 to 120.ft. i t i s pure l imes tone w i t h abundant s h e l l d e b r i s , from 120 to 117-8 f t . t y p i c a l v o l c a n i c c l a s t s are mixed in u n t i l the l imestone f i n a l l y d i s appear s . F i gu re 2k shows t h i s bed. Thus the general h i s t o r y appears to be that the l imes tone was l a i d down du r i n g a p e r i o d o f qu iescence which ended w i t h the gradual r e i n t r o d u c t i o n o f c l a s t s i n t o the d e p o s i t i o n a l area w i t h r e s u l t a n t reworking and b r e c c i a t i o n . The f o s s i l s p resent i nc lude (Appendix I I : GSC r e p t . 4-BEBC-78), s h e l l f r a g -ments, sponge s p i c u l e s , a f i s h t oo th and a c r i n o i d columnal f ragment. These types o f l imes tones are found on ly in the h i gher Upper T r i a s s i c rock s , never in the Lower J u r a s s i c , in the complete T a k l a - H a z e l t o n Group areas (H.W. T i p p e r , 1978, pe r s . comm.). 3.3.8 B a s a l t i c Dyke Unit A 2 m wide dyke cuts th rough- the North Zone w i t h i n vary r e gu l a r and s t r a i g h t f a s h i o n ( f i g . 2 5). This dyke can be t r aced a l l ac ros s the North Zone in a n o r t h e a s t e r l y d i r e c t i o n from the c i r q u e - f a u l t ( that d i v i d e d the depo s i t i n t o the North and South Zones) before be ing l o s t in b locks near the North C l i f f s . The t h i c kne s s o f t h i s dyke i s remarkably c o n s i s t e n t throughout i t s e n t i r e l e n g t h . On the southern s i de o f the c i r q u e - f a u l t , the dyke i s seen i n t e r m i t t e n t l y over a d i s t ance of 150 m and appa ren t l y i s not n e a r l y as c o n t i n -uous as i;n the North Zone. The reason f o r the d i s c o n t i n u i t y o f the dyke to the south i s d i s r u p t i o n caused by l o c a l c o n c e n t r a t i o n s of c r o s s - c u t t i n g zones o f j o i n t s and f a u l t s . Dyke marg ins, i n p l a c e s , are marked by s l i c k e n s i d e s i n d i c a t i n g postdyke s hea r i ng . In ou tc rop the dyke i s dark g r e e n i s h - b l a c k in c o l o u r . Dark a u g i t e phenoc r y s t s , up to 2 mm in d iameter , and wh i te f e l d s p a r c r y s t a l s (< 1 mm in length) a re v i s i b l e . A 3 cm wide c h i l l e d margin i s present l o c a l l y . These c h i l l e d margins are very f i n e - g r a i n e d and pa le grey in c o l ou r w i t h a u g i t e c r y s t a l s up to 1 mm in s i z e . A l s o r a r e , 3 to 5 cm t h i c k o f f s h o o t s o f the dyke 55 F i g u r e 25: B a s a l t i c dyke o f N o r t h Zone i n c o n t a c t w i t h c o n g l o m e r a t e w a l l r o c k . The dyke i s the da r k g r e y m a t e r i a l on the l e f t o f the p l a t e . Carbonate and e p i d o t e v e i n l e t s o c c u r a l o n g the c o n t a c t o f the dyke and c o u n t r y r o c k . 56 are seen to int rude the enc l o s i n g v o l c a n i c l a s t i c rocks. Petrographica11y the dyke is a ba sa l t which c o n s i s t s of 10 to 30 percent subhedral p l a g i o c l a s e phenocrysts and g l omeropo rphy r i t i c masses, and 5 to 10 percent anhedral aug i t e g l ome ropo rphy r i t i c masses in a groundmass of subhedral to anhedral p l a g i o c l a s e l a t h s w i t h i n t e r g r a n u l a r aug i te and opaque g r a i n s . S uboph i t i c tex tu res are present to some degree in the groundmass. The An content o f the f e l d s pa r phenocrysts v a r i e s from An^Q to A n ^ . In the c h i l l e d margins sma l l e r phenocrysts of aug i te and f e l d s p a r are set in a g l a s sy ground-mass. Comparable dyke mate r i a l i s present at the 119-121.5 f t depth i n t e r v a l in DDH 132. Chemica l l y the dyke i s a l k a l i b a s a l t ( f i g . 12) The dyke seen on the Sustut depos i t i s apparent l y s i m i l a r to a group of ba sa l t and gabbro ic dykes which in t rude the o v e r l y i n g Haze l ton Group rocks immediately to the south (B.N. Church, 1978, pe r s . comm.). Thus, on geo l o g i c a l grounds, the dyke appears to be o f post Lower J u r a s s i c age. 3.3-9 My l on i t e Unit Although f a u l t i n g is l o c a l l y intense on the p roper ty , my lon i te i s found on l y in the 305 -313.4 f t i n t e r v a l of DDH 13- Here the core i s b leached and h i g h l y a l t e r e d to c h l o r i t e , carbonate, quar tz and l i m o n i t e . The c h l o r i t e is present as s l i c k e n s i d e s c u t t i n g through the rock. Fau l t gouge i s present at the head of the c i r que between the North and South Zones. Local in tense s 1 i c ken s i d i n g is seen throughout the p roper ty . 3.3-10 Background Chemistry of Some Rock Types Four samples from the base of the Upper Member o f the Moosevale Form-a t i o n were analysed f o r Zn, Cu, N i , S r , Rb (Table 3)- Samples 88N4 and 110J3 are from the bottoms of DDH1s 88 and 110 r e s p e c t i v e l y . Sample SILT i s from the sha le at the top o f the lower member of the Moosevale and sample AGGL i s from the bottom o f the upper member. Cu contents are h igh in 88N4 and SILT, moderate in 110J3 and low in AGGL. However, ranging from 18 to TABLE I I I TRACE ELEMENT ANALYSES FOR DEEP SAMPLES (ppm +preci.s ion) SAMPLE NO. Zn C_u Sr_ AGGL 123.33(^1.68) 18.24(10.15) 30.11(±0 .43) 509.05(±0.99) 69.56(+0.68) SILT 65.80 (+1 .10) 132.83(-26.63) 0.00 563.69(+0.76) 4 0 . 5 ( ± 0 . M ) 88N4 109.02(10.10) 139.08(±29.87) 6.66(to.309) 190.16(+0.13) 8.97(Io.48) " 0 J 3 98.73 (+1 .46) 56.44(+2.43) 10.89(±0.39) 21 3.55( +0.31) 26.27( + 0.01) 58 140 ppm, the copper contents appear to f a l l w i t h i n the range of expected background values as determined from the v o l c a n i c c l a s t s . Zn i s h ighest in AGGL, equ i v a l en t in_88N4 and 110J3, and lower in SILT. Ni is r e l a t i v e l y cons tant , but very Low in SILT. Sr i s h ighest in SILT and AGGL, and lower in the other two. Rb has a large v a r i a t i o n , but g e n e r a l l y shows the same d i f f e r e n c e s as in the c l a s t s . Table 4 has the p a r t i a l major ox ide analyses f o r sample 88N4. The values present are much the same as in the v o l c a n i c c l a s t s and they show that t h i s sample is not g r e a t l y metamorphosed (see 4.7 E lemental Chemistry of Meta-morphic Zones). The high but v a r i a b l e 18 to 175 ppm, background copper contents found in t h i s study, f o r v o l c a n i c c l a s t s and other rock types , has a l s o been shown by Hoffman (1977). Hoffman s tud ied the copper values in streams and f i n e f r a c -t i o n s of t a l u s from the general area of the Sustut Copper d e p o s i t . He found copper values of up to 235 ppm in streams and 450 ppm in the t a l u s f i n e s . -• These f i n e f r a c t i o n values had a mean of 120 ppm. 3.4 D i scus s ion o f the Depos i t ion of the V o l c a n i c l a s t i c Sequence  3.4.1 Sedimentary S t r u c t u r e s Bedding in su r f ace exposures and d r i l l cores has a no r thwes te r l y s t r i k e and a gent le sou thwes te r l y d i p , w i th some small v a r i a t i o n s in d ip angle on the p rope r t y . At the northern end of the.map area (_|_e_. the North C l i f f s ) d ips average 10" a t the southern edge (J_e. near DDH 132) the d ips are 20 to 25', and f u r t h e r to the south, .steepen to 55 to 60* (Harper, 1977). Changes in d ip from north to south are g rada t i ona l and un i fo rm. Local v a r i a t i o n s do occur due to the cross -bedded nature of some of the vol c a n i c l a s t i c s . Church (1973) a s c r i be s the d ip v a r i a t i o n s , between the north and south a reas , to a gen t l e monocline which has an ax i s of 167* and a plunge o f 14*SE. TABLE IV MAJOR OXIDE ANALYSES ON SAMPLE 88N4 OX 1 DE {%) S i 0 2 4 5 . 0 0 T i 0 2 * 1 . 28 A l 2 0 3 1 6 . 7 2 Fe * 4 . 4 9 MnO 0 . 1 7 MgO 5 .00 CaO 7 . 95 N a 2 0 3.91 K 2 0 1 . 00 p 2 o 5 0 . 64 L . O . I . 2 . 80 Cu 0.01 To t a 1 88.97 Tota l Fe and T i 0^ are low because t i t a n i f e r o u s magnetite was not d i s s o l v e d completely in the a n a l y t i c a l procedure. "''-•'""""These analyses were made by Min-En L a b o r a t o r i e s , North Vancouver, B.C.. 60 Proper ty s c a l e f o l d i n g i s absent. Folds are ev ident on ly on a-r eg i ona l s c a l e w i t h d i r e c t i o n s as determined by Harper (1977) and de sc r i bed above in the reg iona l geology chapter ( s e c t i o n 2.2): The most predominant sedimentary s t r u c t u r e present in the upper member o f the Moosevale Formation i s grad ing of beds. I nd i v i dua l graded beds range from 1 cm to 5 rn in t h i c kne s s . Complete t r a n s i t i o n s from lahars to mudstones occu r . In the deeper po r t i on s of the upper member o f the Moosevale Format ion, repeated graded beds are t y p i c a l . One such sequence i s about 18 m t h i c k . Tuffaceous sandy un i t s most g ene r a l l y are pa r t s o f graded sequences rather, than d i s t i n c t l y separate i n te rbeds . F igure 26 shows t y p i c a l grading of beds. Cross -bedding i s a l s o abundant through ' the Moosevale 'Format ion ( f i g . 27) . These c ros s -beds occur in the sandy un i t s o f the vol canic1 a s t i c p i l e , and average 0.3 to 1 m in t h i c kne s s . A predominant pa 1eo-current d i r e c t i o n i s not r e a d i l y v i s i b l e . a n d in f a c t may not e x i s t . Another common s t r u c t u r e i s mud c racks found most commonly in red mudstones. Other, le s s t y p i c a l , s t r u c t u r e s present i nc lude cut and f i l l bedding and trough c ro s s -bedd ing . D i f f e r e n t i a l weather ing of the vo l canic1 a s t i c sediments has occu r red r a r e l y . Tuffaceous sandy i n te rbeds , between conglomerate u n i t s , l o c a l l y are weathered more r e a d i l y than are the conglomerates, y i e l d i n g i nden ta t i on s in the outcrop ( f ig .20 ). 3.4.2 S t r a t i g r a p h y Attempts were made at d e f i n i n g an i n t e r n a l s t r a t i g r a p h y and s u b d i v i d i n g the upper member o f the Moosevale Format ion. Th is s u b d i v i s i o n o f the s t r a t i -graphy cou ld not be achieved by r ou t i ne outcrop mapping or d r i l l hole l ogg ing as no marker hor i zons of any s i g n i f i c a n t a rea l ex tent cou ld be i d e n t i f i e d . C o r r e l a t i o n s between d r i l l holes us.ing the computer-based core logs were the on ly means by which t h i s author cou ld a r r i v e a t an adequate s t r a t i g r a p h y , but c o r r e l a t i o n s even w i th these logs proved to be too ambiguous. The method of c o n s t r u c t i n g a s e c t i o n through the vol c a n i c l a s t i c s i nvo l ved Figure 26: T yp i c a l r e p e t a t i v e graded bedding sequence. This view is 3 rn a c ro s s . F igure 27: Cross bedding in tuf faceous sandstone. 62 p r i n t i n g s t r i p logs o f chosen v a r i a b l e s (note the d r i l l ho le s ec t i on s are pe rpend i cu l a r to s t r i k e , thus represent t rue c r o s s - s e c t i o n s . ) f o r each d r i l l ho le in a p a r t i c u l a r s e c t i o n and c r o s s - c o r r e l a t i n g between the d r i l l ho l e s . F igure 28 has one such s e c t i o n . The v o l c a n i c l a s t i c conglomerates cannot be d i v i d e d i n to subun i t s on the bas i s of t h e i r c o l o u r . The d i f f e r e n c e s in c o l o u r a t i o n between d i f f e r e n t l e v e l s in the c r o s s - s e c t i o n s do not f o l l o w bedding planes and are i n t e r d i g i t a t e d to a l a rge degree. Some of the t u f f -aceous sandstones do stand out as d i s t i n c t u n i t s , but even these p inch out and can not be c o r r e l a t e d across a s e c t i o n comp le te l y . It was noted dur ing the logging that the amount of d i f f e r e n t c l a s t types va r i ed con s i de r ab l y from one d r i l l hole to another . Ba sa l t s are most common fragment t ype , but any of the o ther types can become predominant in a g iven i n t e r v a l . On the ba s i s o f t h i s , c r o s s - ho l e c o r r e l a t i o n was attempted us ing the dominant l i t h i c c l a s t type v a r i a b l e ( i e . were there pe r i od s , now represented by cont inuous i n te rbeds , when d e t r i t a l i n f l u x o f one type of c l a s t predominated). Th i s approach a l s o produced ambiguous r e s u l t s and was aban-doned. Thus, no c o r r e l a t i o n between holes was found based on dominant c l a s t types and an adequate s u b d i v i s i o n of the upper member o f the Moosevale Form-a t i o n remains e l u s i v e . 3.4.3 Depos i t i ona l Environment The upper member o f the Moosevale Formation was depos i ted in a near shore, marine b a s i n . The concen t r a t i on of red mud-cracked s i l t s near the top of the sequence i n d i c a t e d that towards the end of d e p o s i t i o n o f t h i s u n i t , the bas in underwent r e p e t a t i v e subae r i a l exposure and submergence. The i n f i l l -ing o f the bas in was c y c l i c ( i n d i c a t e d by d i f f e r i n g predominances of c l a s t t ype s ) . At some po in t s in t ime, i n f i l l i n g p r a c t i c a l l y stopped and l imestone ree f s developed dur ing these per iods of qu iescence. D e t r i t u s a l s o i n d i c a t e s a p rog re s s i ve change in the chemical nature of vo lcan i sm w i t h i n the a rea , as shown by increase of a n d e s i t i c components over the contents of lower regions mi C O N G L O M E R A T E G R E E N C O N G L O M E R A T E SANDSTONE SECTION C-C F i gu re 28: S t r a t i g r a p h i c c r o s s - s e c t i o n . Numbered v e r t i c a l i s a long s e c t i o n l i n e O C 1 (see a t t a ched geology ma~p). l i n e s a re diamond d r i l l ho l e s . Th i s s e c t i o n in the s t r a t i g r a p h y (Church, 1973)- Cross -bedding and cut and f i l l s t r u c t u r e s , i n d i c a t e some l o c a l reworking of the depos i ted sediments dur ing qu iescenct pe r i od s . The member, in f a c t , c o n s i s t s o f a s e r i e s of i n t e r d i g i t a t e d and interbedded f a c i e s types which have i r r e g u l a r a r ea l extent s (shown by the lack of d e f i n e a b l e s u b u n i t s ) . F o s s i l s , c o l l e c t e d by t h i s w r i t e r (_i_e. W1009, desc r ibed in Appendix II), i n d i c a t e that the age of depo s i t i on i s o l d e r t han .p rev i ou s l y thought. Monger (1977) t e n t a t i v e l y p laced the Savage Mountain-Moosevale contact on the Ka rn i an -No r i an time boundary of the Upper T r i a s s i c . However, the f o s s i l s from over 600 m above the base of the upper member o f the Moosevale Formation are Late K a r n i a n - e a r l y Nor ian in age. The re f o re , the ac tua l time (and e r o -s i o na l ) gap between the ce s sa t i on o f Tak la Group depo s i t i o n (_j_e_. the top o f the Moosevale Formation) and the s t a r t o f Haze l ton Group depo s i t i on i s prob-ab ly g r ea te r than p r e v i ou s l y env i saged. 65 CHAPTER 4: METAMORPHIC PETROLOGY AND WHOLE  ROCK TRACE ELEMENT CHEMISTRY 4 . 1 1 n t r o d u c t ion Metamorphic (or a l t e r a t i o n ) m inera l s present in the Sustut rocks , i d e n t i f i e d by pe t rog raph i c study w i th some X-ray d i f f r a c t i o n c o n f i r m a t i o n , i n c l u d e ; c h l o r i t e (both penn i n i t e and c l i n o c h l o r e ) , carbonate (mainly c a l c i t e w i th very rare s i d e r i t e ) , e p i d o t e , qua r t z , p r e h n i t e , s e r i c i t e , pumpe l l y i t e , a l b i t e , hemat i te , z o i s i t e , phene, and p y r o l u s i t e . Ramage U974) inc luded p y r i t e as an a l t e r a t i o n m i n e r a l . The above mineralogy is c o n s i s t e n t w i t h the p r e h n i t e - p u m p e l l y i t e f a c i e s metamorph i srn de f i ned f o r the upper member of the Moosevale Formation on the Sustut Depos i t (Burns, 1973). The most s i g n i f i c a n t form o f secondary m i n e r a l i z a t i o n i s as cement i n the groundmass of the vol c a n i c l a s t i c rocks. Secondly, the minera l s occur as nebulous patches that rep lace a r e l a t i v e l y f i n e - g r a i n e d f r a c t i o n of the host rock, but do spread i n to coarse f r a c t i o n c l a s t s ( i e . metadomains). Next in importance are v e i n s , made up of the above assemblages, that cut through the host rocks . Metamorphic minera l s occur w i t h i n the l i t h i c v o l c a n i c c l a s t s a f t e r the groundmasses; where they p r e f e r e n t i a l l y r ep l ace primary minera logy, and/or they f i l l v e s i c l e s as amygdules. 4.1.1 C h l o r i t e P e n n i n i t e and c l l n o c h l o r e commonly rep lace v o l c a n i c c l a s t s . P e n n i n i t e i s most common i n amygdules, more so than c l i n o c h l o r e , but both c h l o r i t e s may be present in the same amygdule, one as rims to the o t h e r . As ide from amygdules, c h l o r i t e rep laces g l a s sy groundmasses, i s pseudomorphic a f t e r aug i t e and horn-b lende, and rep laces s p e c i f i c zones w i t h i n zoned p l a g i o c l a s e phenocrys t s . Aug i te and hornblende w i t h opaque h e m a t i t i c rims commonly have cores 66 of f i b r o u s c l i n o c h l o r e . In the dyke rocks , c h l o r i t e has rep laced groundmass aug i t e and both p l a g i o c l a s e and aug i t e phenocryst s . In the v o l c a n i c l a s t i c rocks as a whole, c h l o r i t e mainly occurs as e x t e n s i v e cement to the c o n s t i t u e n t g r a i n s . If another cement i s dominant, then c h l o r i t e can occur as patches w i t h i n the ma t r i x . A l t e r n a t i v e l y , c h l o r i t e rep laces aug i t e and small l i t h i c g r a i n s . C h l o r i t e a l s o occurs as s l i c k e n s i d e s on f r a c t u r e s . These s l i c k e n s i d e s become important in deeper po r t i on s of some d r i l l h o l e s , and in p laces i n d i c a t e that s t rong f a u l t i n g o r j o i n t i n g o c c u r r e d . C h a l c o p y r i t e i s smeared out on some s l i c k e n s i d e d s u r f a ce s . W i t h i n the h e a v i l y copper s u l p h i d e - m i n e r a l i z e d areas , c h l o r i t e loses i t s importance as an a l t e r -a t i o n minera l as i t is s ub s i d i a r y in q u a n t i t y to o ther m i n e r a l s . P y r i t e i s the major su lph ide mineral found w i t h c h l o r i t e ; c h a l c o p y r i t e can be i n t e r -grown w i t h c h l o r i t e . C h l o r i t e i s ext remely r a r e in v e i n l e t s , or m i c r o v e i n -l e t s . 4.1.2 Carbonate Carbonate i s n ' t very abundant in the l i t h i c c l a s t s ; i t i s l o c a l l y absent . The dominant occurrence o f carbonate i s as amygdules (some of which h a v e . c h l o r i t i c rims) and as smal l v e i n l e t s c u t t i n g c l a s t s . It a l s o forms pa t -ches that rep lace po r t i on s o f p l a g i o c l a s e and aug i t e c r y s t a l s , and l o c a l l y i s pseudomorphic a f t e r la rge aug i te c r y s t a l s . Carbonate can occur as patches w i t h i n the groundmasses of some v o l c a n i c c l a s t s . In dyke rocks t h i s m inera l has rep laced f e l dspars, mainly in i r r e g u l a r patches. The main occurrence of carbonate in the conglomerates i s as cement bonding the l i t h i c c l a s t s ( f i g . 2 9 ' ) , or as p o r e - f i l l i n g in the m a t r i c e s . This type o f cement i s more dominant than-any o ther (although va r i ou s d i f f e r -ent cement types may be in te rg rown) . Veins are another major form o f ca rbon-a t e . These ve ins range from m i c r o v e i n l e t s of 2 to 3 mm width to the l a rge ve ins o f up to 15 cm in w i d t h , v i s i b l e in ou tc rop . La rge - s ca le carbonate ve ins most o f t en con ta i n some qua r t z , ep ido te and/or p r e h n i t e , though there 6 7 F igure 29: Carbonate cement to l i t h i c v o l c a n i c g r a i n s . Th is photomicrograph ( p l ane -po l a r i z ed ) is about 1.1 cm ac ro s s . F igure 30: T yp i ca l metadomain form of ep ido te . The ep idote has p r e f e r e n t i a l l y replaced the f i n e f r a c t i o n in t h i s conglomerate. Th i s view is about 1 m ac ro s s . 68 are some ' p u r e ' carbonate v e i n s . Some of these ve ins c on t a i n s u l ph i de s . Carbonate i s p a r t i c u l a r l y abundant i n areas o f copper m i n e r a l i z a t i o n . 4.1.3 Ep idote In almost a l l of the v o l c a n i c c l a s t s , ep idote occurs mainly as a l t e r a t i o n of the groundmass. Most ly the ep ido te (with minor sphene) i s a c r y p t o c r y s t a l 1 i n e mass through the groundmass, but o c c a s s i o n a l l y l a r g e r , more c r y s t a l l i n e , g ra ins o c cu r . In groundmasses which con ta i n f e l t e d masses o f f e l d s p a r l a t h s , ep ido te g ra in s can be i n t e r s t i t i a l to the l a t h s . Epidote gra ins form d i s c r e t e patches in p l a g i o c l a s e phenocrys t s . Wel l developed, l a t h - l i k e ep ido te c r y s t a l s occur in some amygdules but are les s abundant than other a l t e r a t i o n minera l s that f i l l the amygdule. Epidote a s s o c i a t e d w i t h c h l o r i t e and/or carbonate r a r e l y a l t e r s aug i t e g r a i n s . In outcrop ep idote i s the most obvious of a l l metamorphic m inera l s because o f i t s d i s t i n c t i v e colour; and l o c a l c oncen t r a t i on in patches or metadomains. These metadomains are patches of ep ido te which f i l l open spaces and rep lace m a t r i x g ra in s of the host rocks , w i t h the end r e s u l t that l i t h i c c l a s t s are l e f t surrounded by an ep i do te mass ( f i g . 30). These metadomains a re gene ra l l y e l onga te , p a r a l l e l to bedding and r e s t r i c t e d to s p e c i f i c i n te rbeds w i t h i n the ho s t . S i ze s vary from s m a l l e r patches , 0.3 by 5 cm, to l a rge s c a l e replacements of beds, such as at W8, where the metadomain is t h i c k e r than 2 m and has a l a t e r a l dimension of over 60 m. These metadomains appear to be an in s i t u development, however a r e l a t i o n s h i p w i t h ve ins i s present in p laces where the metadomain can be veiwed in th ree dimensions. It seems that ve ins i n t e r s e c t the metadomain i n t e rbed , thus the f l u i d s which formed the ve i n f lowed i n to a de f ined i n te rbed and a l t e r e d the host rock. F igure 31 shows a carbonate v e i n which cuts through typica1" vol c a n i c l a s t i c conglomerate but which a l s o has ep ido te enve lopes . These envelopes are not ve in m a t e r i a l , they are a l t e r e d ( ep i do t i z ed ) host rock. This a l t e r a t i o n i s due to f l u i d s that formed the v e i n , spreading i n t o and a t t a c k i n g the host rock. Ep idote metadomains occur i r r e g u l a r l y 69 Figure 31: Carbonate ve ins w i th ep idote enve lopes. The carbonate v e i n l e t in the foreground i s on l y 2 to 3 cm t h i c k but the ep ido te envelope i s up to 10 cm wide. The carbonate i n the background i s k to 5 cm t h i c k . The ep idote envelopes are a l t e r a t i o n of the country rock. F igure 32: P rehn i t e v e i n l e t swarm at sample l o c a t i o n WI 14. through a l l d r i l l ho les to t h e i r bases. Ep idote a l s o occurs e x t e n s i v e l y as v e i n m a t e r i a l , g e n e r a l l y intergrown w i t h ca rbonate , qua r t z and/or p r e h n i t e . These ve in s may o r may not c o n t a i n s u l p h i d e s . The metadomain ep i do te occurs as replacement and overgrowth in the m a t r i x of the conglomerate. In cases where the e p i d o t i z a t i o n has been p a r t i c -u l a r l y i n t en se , l i t h i c c l a s t s , as w e l l as t h e i r m a t r i c e s , have a l l been e p i -d o t i z e d . In zones where ore m ine ra l s are c oncen t r a ted , i n d i v i d u a l fragments i n the host rocks are e x t e n s i v e l y overgrown by e p i d o t e . There appear to be s l i g h t d i f f e r e n c e s between ep ido te in r egu l a r metadomains and e p i d o t e in s u l p h i d e - r i c h zones. The ep i do te in the ore zones has a h i gher b i r e f r i g e n c e , and i s a darker green than i s the ep ido te in metadomains c o n t a i n i n g no copper mi nera1s . Z o i s i t e i s a minor minera l intergrown w i t h e p i d o t e , where the ep i do te i s concen t ra ted and best deve loped. 4.1.4 Quartz Quartz in c l a s t s dominant ly occurs as c r o s s - c u t t i n g v e i n s . Quartz commonly occur s i n i r r e g u l a r l y shaped pores in the groundmass (some of t h i s may be very rare pr imary qua r t z ) o r an amygdules w i t h o t he r gangue m i n e r a l s . W i t h i n the dyke rocks qua r t z i s present on ly as v e i n m a t e r i a l . W i t h i n the c o n g l o m e r i t i c rock s , qua r t z occur s as cement, as patches in the m a t r i x (po re s ) , or as v e i n s . The qua r t z in ve in s i s intergrown w i t h o the r a l t e r a t i o n m i n e r a l s , and in some, s u l ph i de m ine ra l s are p r e s e n t . Quartz i s most common as cement i n s u l p h i d e - r i c h rocks . 4.1.5 Prehni te P r e h n i t e content o f v o l c a n i c c l a s t s i s l e s s than tha t o f any o f the f o r ego i n g four m i n e r a l s . P r e h n i t e occurs mainly as ve ins or as patches in a groundmass. P r ehn i t e can a l s o rep lace the groundmass p a r t i a l l y , be pseudo-morphic a f t e r aug i t e (wi th c h l o r i t e . a n d / o r ca rbona te ) , or r a r e l y , occur in amygdules ( g e n e r a l l y w i t h some pumpe11yite). The on l y p r e h n i t e recogn i zed in dyke rocks occur s in v e i n s . 71 I n t e r g r anu l a r cement, and veins are the major forms of p rehn i te in the host v o l c a n i c l a s t i c rocks. Although p rehn i t e is nowhere the dominant cement i t i s commonly intergrown w i th o ther a l t e r a t i o n ' m i n e r a l s . The ve in p rehn i te occurs w i t h other gangue minera l s and su lph ides occur l o c a l l y , in these v e i n s . Pure p rehn i te veins occurs in l o c a l swarms of t h i n , 2 to 5 mm wide, v e i n l e t s ( f i g . 32 shows one such set a t W114). The best development o f p rehn i te i s w i t h i n s u l p h i d e - r i c h v o l c a n i c l a s t i c rocks . 4.1.6 S e r i c i te S e r i c i t e occurs as an a l t e r a t i o n of p l a g i o c l a s e phenocrys t s . The s e r i c i t -i z a t i o n o f p l a g i o c l a s e i s h i gh l y v a r i a b l e ; as some p l a g i o c l a s e has on ly i n c i p -ient s e r i c i t e , some i s very e x t e n s i v e l y a l t e r e d to s e r i c i t e . This a l t e r a t i o n mineral i s r e s t r i c t e d to p l a g i o c l a s e and does not occur in mat r i x m a t e r i a l or in v e i n s . Because t h i s mineral is i n c i p i e n t l y developed through p r a c t i -c a l l y a l l c l a s t t ypes , anywhere in the upper Moosevale s e c t i o n , s e r i c i t e i s most l i k e l y a d e u t e r i c m i n e r a l . 4.1.7 Pumpel1y i te Pumpe l l y i t e in Sustut rocks i s a minor metamorphic m i n e r a l . It i s seen most commonly as s m a l l , n e e d l e - l i k e l a th s intergrown w i t h o the r metamorphic m ine ra l s , sometimes these needles are arranged in r a d i a t i n g masses. These pumpe l l y i t e c r y s t a l s occur in groundmass a l t e r a t i o n s , amygdules and patches (with o the r m i n e r a l s ) , and r a r e l y in v e i n s . L o c a l l y pumpe l l y i t e i s a minor a l t e r a t i o n product of aug i te and/or hornblende c r y s t a l s , and r a r e l y i t i s t o t a l l y pseudomorphic a f t e r hornblende ( f i g . 33)- Dyke rocks have pumpel ly-i t e on ly r a r e l y as needles a f t e r p l a g i o c l a s e phenocrys t s . Pumpe l l y i t e i s not abundant enough to form a cement in the host conglomer-a te s , but i s sometimes intergrown as small l a th s w i t h o ther cementing m i n e r a l s . There i s more pumpe l l y i t e present in rocks which have s t rong su lph ide concen-t r a t i o n s . In s u l ph i de areas, and r a d i a t i n g masses of l a th s are more common and b e t t e r deve loped. 72 F igure 33: Pumpe l l y i te (green) pseudomorphic a f t e r hornblende g ra i n s . The l a r g e s t g r a i n i s .15 mm long. The c l a s t i s a f e l d spa r porphyry ande s i t e . 73 4.1.8 A l b i t e A l b i t e in c l a s t s occurs.most commonly as a replacement of p l a g i o c l a s e phenocry s t s . In i t s most i n c i p i e n t na tu re , t h i s a l t e r a t i o n takes the form of nebulous a l b i t i c rims on the phenocry s t s . Other p l a g i o c l a s e g ra in s are almost t o t a l l y rep laced by a l b i t e . A l b i t e can a l s o form v e i n s , u s u a l l y monominera l1 ic , or f i l l amygdules. A l b i t e in the dyke ma te r i a l rep laces p l a g i o c l a s e . A l b i t e can occur as a rare cement, but i t i s never abundant enough to form a major component in cementat ion. A l b i t i c ve ins are monominera11ic and of smal l e x t e n t . There i s no observed concen t r a t i on of a l b i t e in areas of s u l ph ide m i n e r a l i z a t i o n . Where present a l b i t e i s an a l t e r a t i o n a f t e r p l a g i o -c l a s e o n l y . 4.1.9 Hemat i te Hematite is ub iqu i tous thoughout c l a s t s in conglomerate, whether s u l p h i d e -r i c h o r not . Th i s mineral occurs as dust ings through p l a g i o c l a s e phenocry s t s , complete ou te r rims on some large aug i t e and hornblende phenocrysts (where the aug i t e or hornblende i s t o t a l l y a l t e r e d , the hematite is an ou te r r im to c h l o r i t e ) , a l t e r a t i o n products of a groundmass o r mat r i x , as ou te r rims on c l a s t s , and as cement to l i t h i c g r a i n s . In areas w i th high su lph ide content , hemat i te i s very abundant as a secondary mineral intergrown w i t h o the r gangue, or in i n t en se l y a l t e r e d p l a g i o c l a s e . 4.1.10 Sphene Sphene occurs in minor amounts wfth ep idote a l t e r a t i o n . It i s found mainly w i t h the ep ido te that a l t e r s c l a s t s and i s the reason f o r the t u r b i d appearance of these a l t e r a t i o n s . Sphene a l s o occurs w i th o ther gangue minera l s ( e s p e c i a l l y carbonate) where complete replacement of magnetite occurs (the sphene probably takes up the t i t a n i u m from the a l t e r e d magnet i t e s ) . Where ep ido te i s . c l e a r e r and be t t e r c r y s t a l l i z e d in s u l p h i d e - r i c h a reas , sphene is r a r e . 74 4.1.11 P y r o l u s i t e P y r o l u s i t e is found on carbonate f r a c t u r e s and ve i n s . It i s most s t r o n g l y developed where the f r a c t u r e s occur in the s u l p h i d e - r i c h a rea s . D e n d r i t i c hab i t i s o f t en p resent . 4.2 Metamorphic React ions The g rea te s t concent ra t i on s of metamorphic minera l s are s imple open space f i l l i n g s . These i nc lude cements, v e i n s , pore f i l l i n g s , and amygdules. M ine ra l s in these forms have obv i ou s l y been int roduced by, and p r e c i p i t a t e d from c i r c u l a t i n g s o l u t i o n s . These minera l s are more or les s in e q u i l i b r i u m w i t h each o t h e r , except that some minor c h l o r i t e of probable d e u t e r i c o r i g i n has been overgrown and rep laced by l a t e r p r e h n i t e , pumpe l l y i t e and/or ep ido te W i t h i n the c l a s t s though, metamorphic minera l s are developed as a l t e r -a t i o n s and replacements of p r e - e x i s t i n g m i n e r a l s . These r eac t i on s have a somewhat general form such that c e r t a i n elements are re leased p r e f e r e n t i a l l y from the degradat ion of a p r e - e x i s t i n g m i n e r a l . The c h l o r i t e s ( penn i n i t e and c l i n o c h l o r e ) are a low i r on type (Deer e_t_ aj_., 1974). Thus in the c h l o r -i t e (Mg^Al gFe 1 ( S i 3 2 0 g )9 1 0 ( 0H )g ) replacement of aug i te (Ca(Mg,Fe)(S i0 ) 2 ' ( ( A l . F e p ) x ) and hornblende (Ca 2 (Mg, Fe, A l ) (OH) 2 ((S i ,A1 ^ 1 ) 2 )), which have almost equal contents of Mg and Fe, Fe i s re leased and the Mg i s taken up in the c h l o r i t e . Ca, and Si are a l s o r e l ea sed , whereas H 20 i s consumed by the r e a c t i o n . The Fe probably appears as hemat i te , the Ca as carbonate, and the S i 0 2 as qua r t z and po r t i on s of these three elements are combined to form ep ido te as i s H 2 0. Development o f ep idote (Ca'FeAl 20.0H (S i 2 0^) (S iO^)) and p r e h n i t e (Ca 2 A l S i ^ 0.| g) (OH) 2 ) a f t e r the f e r ro-magnes i urn- r i ch groundmass (_i_e. composed o f abundant aug i te and hornblende) led to a re lease o f i ron and uptake of ca l cium and water . A l b i t i z a t i o n of p l a g i o c l a s e invo lved e xpu l s i on o f c a l c i u m . 75 Thus where a l t e r i n g f l u i d s have reacted w i th w a l l rock, i r o n , ca l c i um and s i l i c a are r emob i l i z ed from o r i g i n a l m ine ra l s , sometimes r e s u l t i n g in the format ion o f hemat i te , carbonate and s i l i c a o r the more hydrated minera e p i d o t e , p rehn i te and p u m p e l l y i t e . A.3 Metamorphic M inera l Assemblages The metamorphic minera l s present in the Sustut rocks can be grouped in a number o f s t a b l e assemblages ( s t ab l e assemblages imp l i e s that the mineral were found in contact and appear to be in e q u i l i b r i u m ) . These assemblages are somewhat d i f f e r e n t in va r i ous par t s of the Moosevale Format ion, but no d i s t i n c t i sog rada l d i v i s i o n s were i d e n t i f i e d . S t ab le assemblages present w i t h i n the l i t h i c v o l c a n i c c l a s t s a re : 1) c a r b o n a t e - c h l o r i t e - p r e h n i t e 2) c a r bona te - p r ehn i t e - qua r t z 3) c h l o r i te -carbonate-pumpel l y i te 4) c h l o r i te-carbonate- :quartz 5) c h l o r i t e - p u m p e l 1 y i t e 6) e p i do te - ca rbona te -qua r t z 7) e p i d o t e - c h l o r i t e - c a r b o n a t e 8) e p i d o t e - c h l o r i t e - p u m p e 1 l y i t e 9) epi d o t e - c h l o r i t e - q u a r t z - z o i s i te 10) e p i d o t e - p r e h n i t e - q u a r t z 11) p r e h n i t e - p u m p e l l y i t e 12) p r e h n i t e - q u a r t z - p u m p e l l y i t e Assemblages o c c u r i n g i n the dyke rocks i n c l ude : 13) c h l o r i t e - e p i d o t e - c a r b o n a t e 14) c h l o r i t e - e p i d o t e - q u a r t z 15) ep i dote-prehn i t e - c a r b o n a t e - q u a r t z - z o i s i te 16) ep idote-pumpe11yite 76 Metamorphic m ine ra l assemblages found main ly as i n t e r c l a s t m a t e r i a l i n s u l p h i d e - p o o r cong lomerates a r e : 17) c a r b o n a t e - c h l o r i t e 18) c a r b o n a t e - c h l o r i t e - p r e h n i t e - p u m p e l l y i t e IS) c a r b o n a t e - c h l o r i t e - q u a r t z 20) c a r b o n a t e - e p i d o t e - a l b i t e 21) c a r b o n a t e - e p i d o t e - z o i s i t e '22) c h l o r i t e - p r e h n i t e 23) e p i d q t e - c h l o r i t e - z o i s i t e 2k) e p i d o t e - p r e h n i t e 25) e p i d o t e - p r e h n i t e - c a r b o n a t e - p u m p e11 y i t e - z o i s i t e 26) ep i d o t e - p r ehn i t e - c a r b o n a t e - z o i s i te 27) e p i d o t e - p r e h n i t e - c h l o r i t e 28) e p i d o t e - p r e h n i t e - s h l o r i t e - c a r b o n a t e .23) e p i d o t e - p r e h n i t e - q u a r t z 30) e p i d o t e - q u a r t z 31) e p i d o t e - z o i s i t e 32) p r e h n i t e - p u m p e l l y i t e 33) q u a r t z - a - l b i t e Assemblages w i t h i n i n t e r c l a s t m a t e r i a l o f s u1 p h i d e - r i c h a rea s a r e : Ik) c a r b o n a t e - c h l o r i t e - q u a r t z 35) c a r b o n a t e - c h l o r i t e - q u a r t z - a ' l bi te 36) c a r b o n a t e - q u a r t z - z o i s i t e 37) c h l o r i t e - c a r b o n a t e - e p i d o t e 38) c h l o r i t e - e p i d o t e - 1 i m o n i t e 3S) e p i d o t e - c a r b o n a t e - z o i s i t e ko) e p i d o t e - c h l o r i t e - c a r b o n a t e - a l b i t e 77 41) e p i d o t e - p r e h n i t e 42) ep i do te - p r ehn i t e - c a rbona te 43) ep i do te -p rehn i t e - ca rbona te -qua r t z - pumpe 1 l y i t e kk) e p i d o t e - p r e h n i t e - c a r b o n a t e - q u a r t z - z o i s i t e k5) e p i d o t e - p r e h n i t e - c h l o r i t e - q u a r t z 46) e p i d o t e - p r e h n i t e - p u m p e l l y i t e kl) e p i d o t e - p r e h n i t e - q u a r t z - z o i s i t e 48) ep iddte -pumpe l1 i te kS) e p i d o t e - z o i s i t e . 5O) prehni t e - c h l o r i te -pumpe l l y i te As can be seen there are some assemblages which occur in more than one a rea . A l s o , a l l assemblages are o f the same general p r e h n i t e - p u m p e l l y i t e system. Some o f the above assemblages are e q u i v a l e n t to those that have been reported e lsewhere by other author s . For i n s t ance , R i c h t e r and Roy (1974), in a study of sub -g reensch i s t metamorphism in Maine, desc r ibed assemblages s i m i -l a r to 1, 5, 17, 18, and 50 in t h e i r p r e h n i t e - p u m p e l l y i t e zone, and the same assemblages as 8, 22, 27 and kl in t h e i r p u m p e l 1 y i t e - e p i d o t e - a c t i n o l i t e zone. J o l l y (1974) found assemblage 40 in h i s p r e h n i t e - p u m p e l l y i t e a r ea . The o the r assemblages above are somewhat s i m i l a r to o ther s reported by these au tho r s . A l so these assemblages are con s i s t en t w i t h Coomb1 s (1960) d e f i n i t i o n o f the p r e h n i t e - p u m p e l l y i t e f a c i e s . Therefore the Sustut Deposit rocks are de f i ned as being o f p r e h n i t e - p u m p e l l y i t e grade metamorphism, po s s i b l y g rad ing towards a c t i n o l i t i c f a c i e s (due to ep idote and z o i s i t e ) . 4.4 Temperatures of Metamorphism Burns (1973) has est imated that l i t h o s t a t i c pressure exer ted upon the upper Moosevale rocks , by o v e r l y i n g f o rmat i on s , was on the order of 3 kb. Thus i t w i l l be assumed that the metamorphic minera l s developed at t h i s p r e s -78 su re . L iou (1971) s tud ied and expe r imen ta l l y determined the s t a b i l i t y r e l a t i o n s h i p s of p r e h n i t e . The s t a b i l i t y f i e l d of the prehn i te -pumpe l1y i te f a c i e s i s shown by f i g . 34 ( i b i d . , p..528). L iou s t a ted that the r e a c t i o n ; 2 l aumont i te = p rehn i te + k a o l i n i t e + 3 qua r tz + 5 water is the lower l i m i t of the p r e h n i t e - p u m p e l l y i t e f a c i e s . Th is r e a c t i on i s p e r t i n e n t to the Tak la Group system as Burns (1973) showed that laumont i te i s the i n d i c a t i v e meta-morphic minera l in o v e r l y i n g rocks . From f i g . 34 at 3 kb p re s su re , t h i s r e a c t i o n i s in e q u i l i b r i u m at about 300*C, t he re fo re the Sustut Depos it meta-morphism should have occurred at temperatures exceeding 300*C. L iou de f i ned the upper l i m i t o f p rehn i te s t a b i l i t y by the r e a c t i o n ; 5 p r ehn i t e = 2 z o i s i t e + 2 g r o s s u l a r + 3 quar tz + 5 water . Again from f i g . 34, t h i s r e a c t i o n e q u i l i -b rates at 403 'C. Some z o i s i t e i s found in the rocks of the depos i t but no g r o s s u l a r i s p re sent . Therefore i t can be assumed that the metamorphism occur red below 403 'C, but the presence of z o i s i t e may i n d i c a t e that the upper s t a b i l i t y l i m i t o f p r ehn i t e may have been very s l i g h t l y exceeded. L i o u ' s data i n d i c a t e that the metamorphism of Moosevale rocks under l y ing the Sustut p roper ty occu r red between 300' and 403"C, and most l i k e l y at temperatures towards the h igher 1imi t . F i g . 35, from Thompson (1971, p.86) , shows the s t a b i l i t y f i e l d s as d e t e r -mined by Thompson f o r a n o r t h i t e , a l b i t e , l aumont i te , e t c . . A l b i t e , e p i d o t e , p l a g i o c l a s e and quar tz are s t ab l e together at 3 kb pressure w i t h temperatures above approx imate ly 325 'C. These same minera l s are in e q u i l i b i r i u m in the Sustut rocks , f u r t h e r i n d i c a t i n g the metamorphism occurred at temperatures above 300 'C. 4.5 Age o f Metamorphism The age of metamorphism w i t h i n the Tak la rocks can be es t imated on l y c rude -l y . Read and E i sbacher (1973) determined that metamorphism of the Sustut Group rocks , conformably above the Tak l a , occur red in Eocene times (49 to 53 m.a.) . 500 Temptro lure in *C F igure 34: S t a b i l i t y r e l a t i o n s of the p r e h n i t e - p u m p e l l y i t e f a c i e s (from L i o u , 1971, p. 528). The p r e h n i t e - p u m p e l l y i t e f i e l d i s shaded on t h i s diagram. 6 0 F igure 35-' S t a b i l i t y f i e l d s o f a l b i t e - e p i d o t e - p l a g i o c l a s e - q u a r t z (from Thompson, 1971, p. 86). The re levant s t a b i l i t y areas f o r Sus tut Copper are shaded. 81 Since these rocks are part of a sequence from the A s i t k a through Takla Groups, and s i n c e metamorphism i s gradational between a l l these groups, i t could be assumed that the Takla Group metamorphism was synchronous with that of the Sustut Group. However, Burns (1973) s t a t e s that the metamorphism could a l s o have been of Lower J u r a s s i c age ( r e l a t e d to the Omineca i n t r u s i o n s ) . If the dyke in the North Zone i s a c t u a l l y part of the i n t r u s i v e sequence of b a s i c rocks c u t t i n g the Lower J u r a s s i c sequence and i f metamorphism of the property occurred as a s i n g l e event then the age of metamorphism has to be post-Lower J u r a s s i c . This is because the dyke is found to be cut by prehni t e veins and a l s o has the same general metamorphic a l t e r a t i o n as i t s host rocks. 4.6 Elemental Chemistry of Metamorphic Zones Trace element analyses f o r Zn, Cu, N i , Sr, and Rb, and p a r t i a l major oxide analyses were done f o r three sets o f samples. A n a l y t i c a l data are in Tables 5 and 6 . The samples w i t h i n each set were s e l e c t e d to a s c e r t a i n i f any gross chemical v a r i a t i o n s occur between zones with metadomains of metamorphic minerals and surrounding less metamorphosed country rock. In the f i r s t s e t , W8A i s a sample o f very s t r o n g l y e p i d o t i z e d rock and W8C i s o f a conglomerate j u s t below W8A, which is r e l a t i v e l y unmetamorphosed and which contains v i s i b l e sulphide m i n e r a l i z a t i o n . Zn, Cu, and to a minor ext e n t , Ni are strongest in W8C (due to m e t a l l i c m i n e r a l i z a t i o n ) . Sr on the other hand i s enriched in the metamorphosed rock. The most s i g n i f i c a n t major oxide d i f f e r e n c e s between the two occurs in MgO, CaO, Na^O and v o l a t i l e s (L.O.I.) as CaO i s g r e a t l y enriched in W8A, and the other oxides are depleted r e l a t i v e to W8C . S i 0 2 and A1 2 0 are a l i t t l e lower in W8A a l s o . W i t h i n the second s e t , samples 110D1 and 110D4 are of f r e s h v o l c a n i c l a s t i c rock which bracket 110D3, which is an epidote metadomain zone (110D1 i s above 110D3, 110D4 i s below). Sr is enriched and Zn i s depleted in the metadomain. TABLE V TRACE ELEMENT ANALYSES FOR METAMORPHIC SAMPLES (ppm ± p r e c i s i o n ) SAMPLE NO. Zn Cu Nj_ Sr. J ^ . W8A 38.58( + 0.08) 449-541 + 5.87) .15.80(+0.79) 1220.42(11.64) 4.41 (+0.05) W8C 96.00(±0.01) 1 2 8 8 . 3 9 ( ± 1 6 5 J 5 ) 21.66(12.14) .260.15(10.78} 7.35(10.25) 110D1 146.56 '( +17.54) 9.50(18.25) 9.98( +0.64) 234.64(10.87) 7.30(±0.01) 11003 26.47(10.37) 26.16(11.40) 6 .86( +l . l4 ) 1633.97(^2.19) 1.69(^0.37) 110D4 133.03(10.89) 21.18(10.33) 8.69(10.43) 354.63(10.83) 1.79(^0.05) 6A3 102.11(12.29) 283.06(±66.03) 29.29.(±0.50) 235.35(10.18) 22.95(10.43) 6A4 76.98(12.18) 65.13(10.96) 32.96(10.77) 611.10(±1.46) 3.55( +0.29) 6A5 74.93(11.14) 66.55(^0.51) 17.58(10.74) 170.26(10.66) 1*».88(±'0.31) 00 TABLE VI MAJOR OX IDE ANALYSES FOR METAMORPHIC SAMPLES {%) OXIDE W8A W8C 1 1 OD 1 SAMPLE NO. • • • ; • 110D3 110D4 6A3 6A4 6A5 S! o 2 kk .75 47 .50 47 .75 55 .00 46 .00 44 .00 kk .25 47 .50 T i 0 2 * 0. 68 1 . 00 0. 93 0. 81 1 . 41 0. 97 1. 05 0. 96 AI2O3 14 .86 16 .60 18 .12 15 .40 18 .50 15 .94 16 .60 16 .30 Tota l Fe * k. 36 3. 27 3. 92 2. 80 4. 69 3. 59 3. 51 3. 27 MnO 0. 17 0. 14 0. 18 0. 12 0. 20 0. 19 0. 17 0. 15 MgO 1 . 10 . 4. 55 5. 85 0. 65 6. 15 6. 85 5. 45 5. 45 CaO 14 .70 6. 25 6. 25 15 .70 5. 80 9. 30 12 .15 8. 25 Na 20 1 . 33 4. 80 3. 99 0. 63 4. 35 3. 43 3. 63 4. 40 K 2 0 0. 49 0. 74 0. 62 0. 26 0. 37 1. 61 0. 35 1 . 10 p 2 o 5 0. 40 0. 64 0. 97 . 0. 64 1. 05 0. 72 0. 48 : 0. 81 L.O.I. 1. 10 3. 42 2. 87 0. 50 3. 06 2. 43 1 2. 22 1 . 94 Cu 0. 04 0. 13 - -- -°-03 0. 007 0. 007. Tota l 83.98 89.04 91.45 92.51 91.58 89.06 89.87 90.14 CO Tota l Fe and T iO - are low because t i t a n i f e r o u s magnetite was not d i s s o l v ed complete ly in the a n a l y t i c a l procedure. &**5V**These ana lyses were made by Min-En L abo r a t o r i e s , North Vancouver, B.C.. 8k Ni i s c o n s t a n t among the t h r e e . Cu i s l o w e s t i n 110D1 and e q u i v a l e n t i n the o t h e r two. Rb i s most common i n 110D1. In the major o x i d e c h e m i s t r y , the most n o t a b l e v a r i a t i o n s a r e i n c r e a s e d S i O ^ and CaO, and d e c r e a s e d A l ^ O ^ , MgO, Na^O, ^2^5 a n c ^ L.O.I, i n the metadomain r e l a t i v e t o the u n a l t e r e d samples. L i k e w i s e i n the t h i r d s e t , samples 6A3 and 6A5 a r e r e l a t i v e l y unmeta-morphosed sediment b r a c k e t i n g 6Ak, an. e p i d o t e metadomain. S r i s i n c r e a s e d and Rb d e c r e a s e d i n the metadomain. Ni i s s l i g h t l y h i g h e r i n 6A4, but the d i f f e r e n c e i s n e g l i g i b l e . Cu i s h i g h e s t i n 6 A 3 and Zn i s a l s o h i g h e r i n 6 A 3 . Cu v a l u e s i n 6/\k and :6A5, though, a r e not d e p l e t e d and a r e c o n s i s t e n t as background amounts. The major o x i d e s do not have s t r o n g v a r i a t i o n between the sampl e s , e x c e p t CaO i s h i g h e r i n the metadomain. The most s i g n i f i c a n t c h e m i c a l d i f f e r e n c e s between metadomains and c o u n t r y r o c k can be summarized a s ; i n c r e a s e i n CaO and S r (+ SiO^) and d e c r e a s e i n MgO, A l ^ O ^ and Rb c o n t e n t s o f the metadomains r e l a t i v e t o t h e c o u n t r y r o c k . These v a r i a t i o n s a r e ~ c o n s i s t e n t w i t h i n t r o d u c t i o n o f C a - r i c h s o l u t i o n s (as shown by c a r b o n a t e cement) and breakdown o f fe r r o - m a g n e s i u r n m i n e r a l s . Thus the e l e m e n t a l c h e m i s t r y i s c o n s i s t e n t w i t h the r e a c t i o n h y p o t h e s e s put f o r w a r d i n s e c t i o n k.3 above. 85 CHAPTER 5: ORE HINERALOGRAPHY AND FORM  5.1 I n t r oduc t i on A t o t a l of f ou r teen copper and i ron m ine ra l s , main ly s u l ph i de s , ox ides and minor amounts o f carbonates , have been i d e n t i f i e d in the Sustut depo s i t . Magnet ite i s found as a primary c o n s t i t u e n t in v o l c a n i c fragments and as d e t r i t a l g r a i n s . I lmen i te i s present mainly as in te rg rowths w i t h t i t a n i u m -r i c h magnet i tes . Hematite has two main forms: as a pr imary minera l w i th r e l a t i v e l y low abundance in v o l c an i c s rocks and fragments, and as d e t r i t a l g r a i n s , much les s common than the magnetites and more impo r t an t l y , as a sec -ondary mineral e x t e n s i v e l y intergrown w i th copper s u l p h i d e s . P y r i t e , one o f the more common su lph ides present , g ene ra l l y seems to be e p i g e n e t i c in o r i g i n a lthough some may predate the main m i n e r a l i z i n g event . C h a l c o p y r i t e i s a secondary minera l a l s o . Cha l c o c i t e is the most abundant copper su lph ide and forms the bulk of ore concent ra t i on s i n a s s o c i a t i o n w i t h les s abundant b o r n i t e . Nat ive copper occurs i r r e g u l a r l y and is not r e a l l y of ore grade. D igen i te i s present as replacements o f b o r n i t e , and as e x s o l u t i o n products of c h a l c o c i t e and b o r n i t e . C o v e l l i t e normal ly i s intergrown w i t h d i g e n i t e and b o r n i t e . Ma l a ch i t e , and r a r e r a z u r i t e , are present as a l t e r a t i o n products of copper s u l ph i de s . Cupr i te occurs r a r e l y as rims on g ra i n s o f n a t i v e copper. L imonite appears as ra re rims on c h a l c o p y r i t e . The r a r e s t su lph ide present i s g reenock i te which i s found in cha1 c o p y r i t e - r i c h zones. No s p h a l e r i t e was found in a s s o c i a t i o n w i t h g reenock i t e . Major su lph ide occurrences are r e s t r i c t e d to the upper 60 m of the Moose-va l e Formation on the Sustut p roper ty . However, spo rad i c su lph ides are present in d r i l l core to the bottoms of DDH's 88 and 110,. that is over a v e r t i c a l range o f 600 m. Most copper and su lph ide m i n e r a l i z a t i o n i s concent rated in ex ten s i ve t abu l a r zones which are roughly p a r a l l e l to bedding. W i th in these 86 zones a crude v e r t i c a l zonat ion of m e t a l l i c m inera l s i s p resent , from na t i ve copper cores , outward through c h a l c o c i t e , b o r n i t e , c h a l c o p y r i t e , and f i n a l l y to p y r i t e enve lopes. Th i s zonat ion i s not found to be p e r f e c t l y symmetrical in a l l p laces and l o c a l l y i s incomplete. In the 98 .po l i shed sec t i on s s t u d i e d , amounts of su lph ides p lus na t i ve copper ranged from n i l to 12 volume percent of the s e c t i on s and averaged about 5 pe rcent . Copper minera l s are found in l o ca l swarms o f t h i n , s t eep l y d ipp ing v e i n -l e t s which p inch and swe l l i r r e g u l a r l y . Quartz, carbonate, ep i do t e , and p rehn i te are intergrown w i th the ore minera l s in these v e i n s . In p laces tabu -l a r zones and v e i n l e t s merge; elsewhere v e i n l e t s cut t abu l a r zones. An aspect o f s u r f ace occurrences o f .copper m i n e r a l i z a t i o n is the presence o f an o range- red, s o - c a l l e d , 1 copper -mos s 1 ' wh i ch grows on rocks w i t h have a-h igher than background copper content . A c t u a l l y the 'moss ' i s of the green a lgae f a m i l y . It has been i d e n t i f i e d as T r e n t o p o h l i a i o l i t h u s ( L . ) . This a lgae i s common through the wor ld in areas o f h igh a l t i t u d e s and l a t i t u d e s , but has on l y been repor ted in two areas in B r i t i s h Columbia, o the r than Sustut Copper (Harper, 1973)- This 'moss ' does not grow on areas of high copper c oncen t r a t i o n , say g r ea te r than 1 percent , probably due to t o x i c i t y of large amounts of copper. Wherever t h i s 'moss ' i s seen one can be assured of f i n d i n g minor copper v a l ue s . F rac tu res and j o i n t s which cut through ore minera l zones and which may have caused small s c a l e m i g r a t i on o r l each ing o f minor amounts of copper g e n e r a l l y have the best growths of the 'moss 1 . 5.2 Ore Lenses The Sustut Copper depos i t was d i scovered as a r e s u l t of ob se r va t i on o f ma lach i te s t a i n i n g on c l i f f s surrounding the p r ope r t y . C lo se r examinat ion revealed that f i n e - g r a i n e d ore minera l s were d i s seminated through the f i n e f r a c t i o n s of the v o l c a n i c l a s t i c conglomerates. These ore d i s seminat ions were r e s t r i c t e d to l i t h o - f a c i e s interbeds w i t h i n the host v o l c a n i c l a s t i c rocks , 87 such that ore m i n e r a l i z a t i o n a c t u a l l y occurs as l en ses . The lenses are of i r r e g u l a r a rea l ex ten t s and p a r a l l e l bedding. The depos i t c on s i s t s o f a s e r i e s o f these l enses . Use of the computer based core logs led to the d e f i n -i t i o n of ph y s i c a l c h a r a c t e r i s t i c s o f the conglomerates which were conducive to ore m i n e r a l i z a t i o n . Chemical analyses o f ore lenses and t h e i r enve lop ing host rocks shows a very sharp c u t - o f f in copper va l ue s , grad ing outwards from the l enses . Gangue minera l s are e x t e n s i v e l y intergrown w i th the ore minera l s and the gangue i s of p r e h n i t e - p u m p e l l y i t e f a c i e s grade. In the f o l l o w i n g d e s c r i p t i o n o f ore minera l occur rence , areas in the depos i t are r e f e r r e d to by t h e i r sample number (eg. W104). The sample l o c a -t i on s are on the proper ty geology map ( i n the pocket at the end of t h i s t h e s i s ) . 5.2.1 Outcrop Appearance of Ore Copper occurrences were f i r s t d i scovered on the Sustut Property when ma lach i te s t a i n i n g was observed along the upper po r t i on s of the c l i f f s on the ea s te rn edge o f the depos i t ( i e . the c l i f f s p a r a l l e i i n g the Sustut R iver V a l l e y -see f r o n t p i e c e ) . The s t a i n i n g extended over a v e r t i c a l th i cknes s o f about 6 m, and was seen to c l o s e l y correspond to the bedding p lane . The zone of mala-c h i t e s t a i n can be t r aced along the c l i f f s s p o r a d i c a l l y from near the south -ern end o f the South Zone, i n to the c i r que to the north where i t ends. Other bands of ma lach i te appear along the northern edge of the c i r q u e , the ea s te rn c l i f f s of the North Zone and a l so on the North C l i f f s . Fo l low-up g e o l o g i c a l examinat ion showed the ma lach i te to be a su r face o x i d a t i o n e f f e c t developed on copper s u l p h i d e - r i c h t abu l a r l a y e r s . These l aye r s a l s o appeared to be up to 6 m t h i c k . A lthough best observed a long c l i f f f a ce s , some c o p p e r - r i c h l ayer s are seen to crop out . It was f i r s t thought that a l l these l ayer s def ined one s t r a t i f o r m , or even s t ra tabound, zone through the p rope r t y . However subsequent work has shown that there are severa l d i s t i n c t , t a b u l a r ore lenses which p a r a l l e l bedding. These lenses have d i f f e r i n g l a t e r a l and v e r t i c a l d imensions. Where seen in outcrop, su lph ides in the lenses are present as f i n e gra ined (on the order of 0.1 to 1 mm) d i s seminat i on s through v o l c a n i c l a s t i c sandstones and conglomerates. Amount o f s u l ph ide (based on v i s u a l e s t i m a -t i on s ) v a r i e s from 0.01 to 15 percent . M i n e r a l i z a t i o n i s mainly seen in m a t r i c e s , but where in tense , is d i s seminated in v o l c a n i c c l a s t s a l s o . Cha l co -c i t e w i t h b o r n i t e are the dominant su lph ides seen in the ore l en se s . Cha l co -p y r i t e is present in p laces w i th the b o r n i t e . Nat ive copper d i s semina t i on s are not r i c h and gene ra l l y are e i t h e r separate from su lph ides o r are a s soc -i a ted w i t h c h a l c o c i t e . P y r i t e a l s o commonly occurs wi thout other s u l p h i d e s . In the r i c h e s t lenses specu la r hematite o f t e n imparts a reddish t i nge to the mi nera1 i zed a r e a . On the north western edge of the North C l i f f s , an ore lens is seen to extend l a t e r a l l y f o r . o ve r 360 m. Th i s l en s , approx imate ly 1.5 to 3 m t h i c k , i s a long the 6575 to 6600 f t . e l e v a t i o n . Un fo r tuna te l y the author d i d not study t h i s lens in d e t a i l but i t s ex tent i n to the North Zone appears l i m i t e d , f o r i t i s not seen to crop out w i t h i n the North Zone even at l i k e l y e l e v a t i o n s as e x t r a p o l a t e d from known occur rences . A set o f lenses crop out at the head and on the North Zone s i de of the c i r q u e . One such lens occurs in contact w i t h the eas te rn s i de of the dyke r i g h t at the dyke ' s contact w i t h the f a u l t - d e f i n e d c i r que (sample W104 s i t e ) . Here, 1:0 to 15 percent , f i n e (< 0.5 mm) c h a l c o c i t e and b o r n i t e g ra in s f i l l i n t e r g r a n u l a r spaces in a medium g ra ined sandstone. A s soc i a ted w i th the s u l -phides are abundant ep idote and specu l a r hamat i te . This p a r t i c u l a r sandy un i t i s on the o rder o f 0.3 rn t h i c k and grades i n to sandy conglomerates ( i e . w i th a l a rge s i z e f r a c t i o n ) both above and below. These conglomerates are s u l p h i d e - r i c h a l s o , but v i s i b l e su lph ide- d ies out in 1.5 m upwards through the host rock. The l a t e r a l extent i s seen to be k by 3 m, but is probably l a r g e r as the bed i s obscured in d e b r i s . Th is lens is not seen on the o ther s ide o f the dyke-but t race amounts of na t i ve copper and c h a l c o c i t e are v i s i -89 ble in matrices of conglomerates here. As a result of i t s relative.impermea-b i l i t y to mineralizing solutions, the dyke is not v i s i b l y mineralized here. Near W112 ( i e . the sample location) an ore lens occurs which extends i r r e g u l a r l y along the head of the cirque. The i r r e g u l a r i t y is due to f a u l t -ing which has o f f s e t the lens. Minor amounts of copper minerals occur in these fr a c t u r e s and the whole b l u f f here is heavily overgrown by copper moss i n d i -cating the presence of minor disseminated copper sulphides. This indicates that some minor remobi1ization of copper from the lens occurred a f t e r f a u l t -ing. The lens i t s e l f consists of c h a l c o c i t e and bornite scattered through the matrix of a coarse sandstone-fine conglomerate in small (0.1 to 1 mm in diameter) quartz pores. Sulphide content is less than 0.5 percent. This lens appears to extend s p o r a d i c a l l y along the northern face of the cirque where i t is truncated by a f a u l t . Thickness is va r i a b l e , but is never greater than 1.5 m. Above t h i s lens at W19, malachite with minor amounts of a z u r i t e , and some 'copper moss 1, occur in a zone which is extensively sheared ( f i g . 3&) . This can be traced along the rock face for about 10 m, but in t h i s i n t e r v a l is not confined to a single bed and can be seen to occur in two p a r t l y over-lapping layers. These layers appear to be shear zones wherein the s i l t - s i z e d matrices took up deformational s t r a i n rather than the coarse f r a c t i o n . c l a s t s . The malachite is present because small amounts of copper may have been remo-b i l i z e d from the ore lens below (j_e_. sample WIOA ore lens) during the shearing. Twelve to f i f t e e n m above t h i s lens (near the W112 sample location) on the north face of the cirque, another richer lens crops out ( f i g . 37) at the s i t e of sample W32. This lens is about 1 m thick and consists of 5 to 10 percent fine-grained chalcocite and bornite in a coarse sandstone to f i n e conglomeratic rock. There is a sheared malachite zone above the lens l i k e that at sample area wl9- This lens is connected to the W112 lens below by mineralized gangue-fi1 led veins. 90 F i g u r e 36: M a l a c h i t e s t a i n on s hea r z o n e . T h i s zone i s j u s t above a s i g n i f i c a n t o r e l e n s . 1 1 • _ F i g u r e 37: Ore l e n s l o c a t i o n s on n o r t h e r n edge o f c i r q u e . T h i s v i e w i s t owards the N o r t h Zone w h i c h i s i n t h e b a c k g r o u n d . The m a j o r o r e l e n s a t W32 i s j u s t v i s i b l e , as i s a s m a l l e r one be low ( i e . t h i s l e n s i s p r o b a b l y a c o n t i n u a t i o n o f t h e W 1 l 2 l e n s ) . Between t h e s e two l e n s e s a r e a s e r i e s o f s u l p h i d e - r i c h v e i n s . V e i n s a l s o o c c u r b e l o w the W112 l e n s . The v e r t i c a l r e l i e f i s abou t 55 rn.. 91 At severa l p laces in the North Zone ore lenses are found at ground l e ve l (or at l e a s t sporad ic occurrences of su lph ides are found c ropp ing out in t h i s zone) . Near sample area W92, a rusty weather ing conglomerate i s v i s i b l e in which small r e l i c t g ra ins o f p y r i t e and/or c h a l c o p y r i t e were found in gaps in the mat r i x ( f i g .38 ). At V/98, ( i e . sample l o ca t i on ) d i s seminated na t i ve copper and rare c h a l c o c i t e are in sandy-cong lomerat ic ho r i zons near the dyke. Minor copper values and copper moss are found in va r ious areas of the North Zone that are cut by s t rong j o i n t i n g and/or f r a c t u r i n g . For example, at W95 the wa l l rock to a ca rbonate -quar t z coated f r a c t u r e zone conta ins c h a l c o c i t e and b o r n i t e in q u a r t z - f i l l e d patches. These qua r t z patches form cement to the somewhat open framework of the host conglomerate. At W100 and W33 j o i n t i n g is f a i r l y s t r ong , here t r a ce amounts of c h a l c o c i t e w i t h mala-c h i t e a n d copper moss occur in the host rock where j o i n t i n g i s s t r onge s t . Near (sample areas) W10, W11, and W12, on the south w a l l o f the c i r q u e , two d i s t i n c t ore lenses o c cu r . The lower lens i s approx imate ly 21 m below the edge of the c l i f f by DDH 104. This lens i s about 10 m in length and has sharp boundaries at l a t e r a l e x t r e m i t i e s . Its th i cknes s i s about 1.5 to 2 m. The ho r i zon c on s i s t s of c h a l c o c i t e and b o r n i t e w i t h minor amounts o f c h a l c o p y r i t e and rare p y r i t e d i s seminated through gangue-f i11ed po r t i on s o f mat r i ce s (or f i n e f r a c t i o n s ) and in c l a s t s in conglomerates. The l a ye r has an open frame-work. The upper c o p p e r - r i c h lens i s about 6 m above the f i r s t . Th i s copper lens has a l a t e r a l ex tent o f 120 m along the c l i f f face before d i s sappear ing near a f a u l t . Ma l ach i te i s very s t r ong l y developed on t h i s upper lens and makes the lens v i s i b l e . Between both lenses here, a barren pebbly conglomer-ate occu r s , which appears to have a much less open framework. Another h o r i z on , w i th a 6 m th ickness and a 30 m l eng th , occurs on the c l i f f at the southeastern edge o f the c i r q u e . This ho r i zon has a w e l l d e v e l -oped ma lach i te s t a i n . 32 F i g u r e 38: O u t c r o p view o f i n t r a c l a s t p y r i t e . The p y r i t e , as shown by b r o w n i s h s u l p h i d e w e a t h e r i n g , o c c u r s i n gaps between t h e c o a r s e f r a c t i o n c l a s t s . F i g u r e 39: S u l p h i d e m i n e r a l i z a t i o n b r e c c i a t i n g h o s t r o c k . The w h i t e tape i s 2 cm l o n g . An o f f s h o o t o f the s u l p h i d e zone o c c u r s j u s t below the tape where i t v i s i b l y d i s r u p t s b e d d i n g . The main s u l p h i d e zone o c c u r s below t h i s where i t wraps around a c o a r s e sandy fragment o f h o s t r o c k . T h i s p r o v e s s u l p h i d e i n t r o d u c t i o n was not s y n g e n e t i c . 93 The lens w i t h the l a r ge s t e x t e n t , observed by the w r i t e r , i s seen to crop out in the c l i f f s a long the ea s te rn s i de o f the South Zone ( f r o n t i s p i e c e ) . Th is l en s , which p a r a l l e l s bedding, extends from below DDH 109 more than 600 m • j u s t to the eas t o f DDH 39. Th i s t a b u l a r zone has a v a r i a b l e th i cknes s from 1 to 5 m. A pronounced ep ido te a l t e r a t i o n i s ev ident w i t h i n t h i s l en s . Samples W 5 7 to W60 and W64 are a l l from a small lens which occurs w i t h i n the South Zone. Th i s lens i s t runcated by a d ip s l i p f a u l t at one end and d i sappears in a j o i n t e d area at the o t h e r . The j o i n t i n g i s p a r a l l e l to bedding. The lens occurs in a p o r t i o n o f the host v o l c a n i c l a s t i c rocks which have e x t en -s i v e and r e p e t a t i v e small s c a l e graded bedding. The host rocks c o n s i s t of f i n e conglomerates w i t h f i n e to medium-grained sand i n te rbed s . The s u l ph i de s , b o r n i t e and c h a l c o c i t e , f i l l i n t e r s t i c e s in those rocks which have more open frameworks. The su lph ides are intergrown e x t e n s i v e l y w i t h s p e c u l a r i t i c hema-t i t e . The ore minera l s are u s u a l l y concent rated in coar se r sandy po r t i on s o f the graded beds. Evidence f o r p o s t - c o n s o l i d a t i o n i n t r o d u c t i o n of the su lph ides i s w e l l e x i b i t e d by one sample (W57) from t h i s area ( f i g . 39). In t h i s sample gangue-f i l l i n g s u l ph ide patches appear to i n t rude i n t o the bedding p lace o f the host rock and in doing so d i s r u p t and c r o s s - c u t the bedding, and b r e c c i a t e the host rock i n t o fragments. 5.2.2 Appearance of Ore Lenses in D r i l l Core Study o f the d r i l l core i n d i c a t e s that the ore lenses are p resent , i r r e -g u l a r l y , to near the base o f the Moosevale ' s upper member. The l a r g e s t and most c o p p e r - r i c h hor i zons are in the upper po r t i on s o f the depo s i t , w h i l e the lower ho r i zons are sma l l e r in volume and are dominantly cha1 c o p y r i t i c and/or p y r i t i c in compos i t i on . However, some minor c h a l c o c i t e zones are found in lower a reas . Nat i ve copper and g reenock i te are found on l y in the l a r g e r " " hor i zons near the top . 3k The ho r i zon w i t h the l a r ge s t v e r t i c a l exp re s s i on i s found in DDH 2 where a hor i zon extends f o r over 12 m, from 5 to 2kc f t from the top of the d r i l l ho l e . Large lenses are a l s o seen in DDH1s 39, 8 8 , 1 10, 6, 5 3 , 9 6 , 5 k , 10, where the hor i zons are k5, 39, 37, 36, 30 , 30, 28 , 27 m t h i c k r e s p e c t i v e l y . Commonly d i f f e r e n t lenses i n t e r s e c t e d in a s i n g l e d r i l l ho le are separated by barren i n t e r v a l s of 1.5 to 6m. A l s o , w i t h i n some of the l en se s , r i c h zones of up to 2 percent v i s i b l e s u lph ide are separated by large areas wherein the amount o f v i s i b l e su lph ide concen t r a t i on can be as l i t t l e as a t r ace in a f i v e foot i n t e r -v a l . Thus some of the l a r ge r lenses can a c t u a l l y be subd iv ided i n to sma l l e r ones on the ba s i s of amount of ore m i n e r a l i z a t i o n . A l l of the d r i l l holes s tud ied conta ined s i g n i f i c a n t amount of copper m i n e r a l i z a t i o n except DDH's 25 and 132. These l a t t e r two holes are f a i r l y r i c h in p y r i t e though. P o s i t i o n of lenses in r e l a t i o n to top of d r i l l holes v a r i e d c o n s i d e r a b l y , i n d i c a t i n g of course d i f f e r i n g topographic p o s i t i o n s from which the d r i l l ho les were s t a r t e d . C r o s s - s e c t i o n s through the ore lenses are much more e a s i l y s tud ied in d r i l l core than in o u t c r o p . A good example of how one of the lenses occurs i s found in DDH 6. No s u l ph i de i s present u n t i l 18 m below the c o l l a r of the d r i l l ho le where t r ace c h a l c o c i t e occurs in some q u a r t z - f i l l e d pores in the host conglom-e r a t e . C h a l c o c i t e , in these pores, occurs i r r e g u l a r l y downwards through the host rock s e c t i o n u n t i l k2 m below the s u r f a c e , the su lph ide lens is encountered. At the s t a r t o f t h i s zone ( lens) 0.1 to 0.5 percent c h a l c o c i t e and na t i ve cop-per are present in gangue-f i11ed pores, g r a d u a l l y the mat r i x framework becomes more open and f i l l e d w i t h gangue w i th a r e s u l t a n t increase in amount of c h a l c o -c i t e and n a t i v e copper d i sseminated through the m a t r i x . The h ighest grade sam-ple analysed (6B3: from 50 rn below the su r face) came from part of t h i s lens sequence ( a n a l y s i s proved copper grades of about 10 percent in t h i s sample). At t h i s po in t the conglomerate e x h i b i t s the most open framework seen in the i n t e r v a l , and intense ep idote w i th carbonate and q u a r t z , f i l l the 95 mat r i c e s . Ju s t 1 m below the l o c a t i o n of sample 6B3, the framework o f the mat r i x becomes c l o sed and c h a l c o c i t e is present to on l y 0.05 to 0.1 pe r cen t . Through to the end o f the zone, 30 m below, the c h a l c o -c i t e and n a t i v e copper contents vary from t r a ce to 2 percent , where the h ighes t grades c o r r e l a t e w i t h rocks having an open r a the r than c l o sed framework. Thus, ore m i n e r a l s . a r e r i c h e s t where the host conglomerate has the g rea te s t p r e - m i n e r a l z a t i o n p e r m e a b i l i t y as e x h i b i t e d now mainly by the presence of i n t e r s e r t a l cement.-Four c r o s s - s e c t i o n s were cons t ruc ted to inc lude the d r i l l holes s t ud i ed in d e t a i l (see c r o s s - s e c t i o n s a t t a ched ) . The two sec t i on s from the North Zone (Ls.DDH's 54-110-17_52 and 44-53 -52: see at tached property geology map where these s e c t i o n s are p l o t t e d as B-B' and A-A 1 r e s p e c t i v e l y ) show that the m i n e r a l i z a t i o n here appears to be a s i n g l e , s t r a t i f o r m lens . However most o f the holes a re shor t and do not g ive a d e t a i l e d view of lower s t r a t a . A smal l p y r i t i c lens occur s below the main lens in DDH 44. A l s o DDH 110 shows seve ra l seperated ore lenses to i t s bottom. DDH 17 appears to cut two lenses ; the major c h a 1 c o c i t e - n a t i v e - c o p p e r - b o r n i t e lens and a l s o a 12 m t h i c k p y r i t i c lens., 4.5 m below the major one. Sec t i on DDH 88-2-105-5-112 ( i n the South Zone - s e c t i o n C -C on the geology map) shows that there is a broad su lph ide swath c u t t i n g the upper po r t i on s of the depo s i t . However t h i s s u l ph i de zone i s ra ther i r r e g u l a r in form and doe sn ' t f o l l o w bedding at DDH1s 105, 6, 112. DDH 88 a l s o shows some ra the r l a rge su lph ide lenses through i t s l eng th . The l a s t s e c t i o n DDH 132-13" 116-10-39-96 ( a l s o in the South Zone - s e c t i o n D-D' on the geology map) revea l s severa l d i s t i n c t hor izons in the top u n i t s . For instance DDH 13 shows three d i s t i n c t ho r i zons w i t h i n i t s l eng th , as does DDH 10. Thus the ore m i n e r a l i z a t i o n occurs in separate l en so i d forms which p a r a l l e l bedding, but which are i r r e g u l a r in l a t e r a l and v e r t i c a l e x t en t , appear ing and d i sappear ing w i th suddeness. The lenses are a l s o separated by 96 barren rock. 5.2.3 L i t h i c Va r i ab l e s and t h e i r R e l a t i o n to M i n e r a l i z a t i o n Computer programs were designed f o r use w i t h the core log f i l e s , to a s c e r t a i n i f any, or a l l , or the v a r i a b l e s c o n s i s t e n t l y recorded on f i v e foot i n t e r v a l s f o r the host conglomerates, c o r r e l a t e d w i th ore minera l o ccu r rence . These programs mainly invo lved the p r i n t i n g out of matr i ces where the o r d i n a t e va lues were the d i f f e r e n t codes f o r the v a r i a b l e in ques t ion and the ab s i c ca was d i v i d e d i n t o d i f f e r e n t v i s u a l percentage values o f a p a r t i c u l a r ore minera l ( recorded in the l ogg ing ) . In each ( amount of mineral \^ s_. a de f ined v a r i a b l e were e x h i b i t e d . These values of number o f v a r i a b l e s w i t h ore m i n e r a l i z a t i o n were then compared as a p ropo r t i on o f that v a r i a b l e m i n e r a l i z e d vs . the t o t a l number o f ob se r va t i on s of the v a r i a b l e both m i n e r a l i z e d and unminera1 ized. Th is method o f s tudy ing the logs led to some i n t e r e s t i n g i n t e r p r e t a t i o n s . F i g . 40 i s a graph of the l i t h o l o g i c u n i t s , seen on the p rope r t y , vs . the p r o p o r t i o n of observat ions of each l i t h o l o g i c type which conta ined v i s i b l e c h a l c o c i t e . (Po l i shed s e c t i on s t ud i e s have shown that bo r n i t e is i n t i m a t e l y intergrown w i t h c h a l c o c i t e - thus where c h a l c o c i t e was v i s i b l y observed, bo rn -i t e can be assumed to be present a l s o ) . It is r e a d i l y seen from f i g . 40 that the rock type dominantly m i n e r a l i z e d w i t h c h a l c o c i t e i s AGGR, however i t i s a l s o obvious that conglomerates w i th mainly green c o l o u r a t i o n s are more h i g h l y m i n e r a l i z e d than o the r s . This c oncen t r a t i o n o f m e t a l l i c minera l s in green conglomerates i s shown even b e t t e r by p y r i t e ( f i g . kV. where over 50 percent of the ob se r va t i on s of rock type AGGG conta ined p y r i t e . F i g . 42 shows percentage mat r i x va lues (of the conglomerates) vs_. p ropor -t i o n o f each which conta ins v i s i b l e c h a l c o c i t e . C h a l c o c i t e thus occurs main ly in conglomerates w i th 50 to 70 percent m a t r i x . F i g . 4.3' has t ex tu re va lues v s . p r o p o r t i o n w i t h c h a l c o c i t e , c h a l c o c i t e i s found very dominantly in conglomer-ates w i t h a t e x t u r e of 25 to 50 percent l a rge f r a c t i o n in a c l o sed m a t r i x , and s e c o n d a r i l y in conglomerates w i t h 25 to 50 percent la rge f r a c t i o n in an open Yajmojrtt-i w r - <-£ O o T o o o •20 10 OL 0 I — V 9 * '^0 Cv 12, 6"^  L I T H 0 L 0 6 3 1 r J XP F i gu re 'lO:. P r o p o r t i o n s o f each l i t h o l o g i c type m i n e r a l i z e d w i t h c h a l c o c i t e . Th i s i s a draughted v e r s i o n o f a c ompu te r - r e t r i e ved t a b u l a t i o n . V e r t i c a l w id th of bar is the e r r o r s o f the e s t i m a t e (x The p r opo r t i on s are based on comparison o f a l l ob se r va t i on s o f each l i t h o l o g i c type. ± s if} a,. I U - 3 0 O ^ I 0 h JL "ft 61 I — — ^ > Figure 4 1 : Proportions of each l i t h o l o g i c type mineralized with p y r i t e . V e r t i c a l width of bar is the e r r o r of the estimate (x ± s j . (Draughted version of a computer-retrieved t a b u l a t i o n ) . •3 Oh 20 0 10 20 30 40 50 60 PERCENT. MATRIX 7 0 8 0 9 0 a^ mnpm j^uiii 'nj.nujiaj.wJ no F i gu re 42: P r o p o r t i o n s o f each percent mat r i x va lue ( i n conglomerates) m i n e r a l i z e d w i t h c h a l c o c i t e . V e r t i c a l w i d t h of. bar i s the e r r o r s o f the e s t imate (x ± s j . (Draughted v e r s i o n o f a c o m p u t e r - r e t r i e v e d t a b u l a t i o n j . -vx> <D CL E (0 CO CD C i_ (0 (1) DQ I U CJ CL O Cu C lo sed Framework 1.0 (X3 0.2 0.1.1 Open Framework . 100% n-1 I 1 1 1 1 — r - [ — I i 10-25 25-50 50-75 >75 <10 10-25 25-50 50-75 % Large Fract ion F i g u r e h3: P r o p o r t i o n s o f d i f f e r e n t t e x t u r e g r o u p i n g s m i n e r a l i z e d w i t h c h a l c o c i t e . V e r t i c a l w i d t h o f b a r i s the e r r o r s o f the e s t i m a t e (x ± s ) . The t e x t u r e o f <. 10 p e r c e n t l a r g e f r a c t i o n i n an open framework can be n e g l e c t e d as i n s i g n i f i c a n t as o n l y one o b s e r v a t i o n o f t h i s t e x t u r e was made l i e . n = l ) . ( D r a u g h t e d v e r s i o n o f computer t a b u l a t i o n ) . I U I mat r i x . Comparison of s o r t i n g values vs . p r o p o r t i o n c o n t a i n i n g c h a l c o c i t e ( f i g . 4 4 ) shows an i n t e r e s t i n g c o r r e l a t i o n wherein moderately s o r t ed conglomerates ( i e . s o r t i n g va lues o f 4 and 5) a re dominantly m i n e r a l i z e d . Th is ob s e r v a t i o n i s important as i t i n d i c a t e s that p o r o s i t y o f the conglomerates r e f l e c t s the amount o f m i n e r a l i z a t i o n . Conglomerates w i t h moderate s o r t i n g c h a r a c t e r i s t i c s shou ld be more porous towards incoming f l u i d s than those w i t h other s o r t i n g v a l u e s , as the f i n e f r a c t i o n <Je_. mat r i x ] g ra in s are very angu lar in nature thus the g r e a t e r the u n i f o r m i t y of g r a i n s i z e in medium to coa r se - g ra i ned c l a s t i c r ock s , the g r e a t e r should be the p o r o s i t y . When the g r a i n s i z e i s p l o t t e d v s . p r o p o r t i o n of samples that c o n t a i n c h a l c o c i t e ( f i g . 4 5 ) , i t i s found that the conglomerates most f a vou rab le f o r m i n e r a l i z a t i o n have a l a rge f r a c t i o n of l a r ge pebble s i z e in a f i n e sand m a t r i x ( i e . g r a i n s i z e R i n f i g . 4 5 ) . Four o the r s i z e types a l s o had g r ea te r than 20 percent of ob se r va t i on s m i n e r a l i z e d ( i e . g r a i n s i z e s L,' M, N, in f i g . 4 5 ) . It is obv ious that f i n e f r a c t i o n s i z e s g r ea te r than or equal to f i n e sand s i z e , and coarse f r a c t i o n s i z e s of small pebbles or l a r g e r , c on ta i n the most c h a l c o -c i t e . G rea te r than 10 percent m i n e r a l i z e d samples were found i n g r a i n s i z e s ; B, K, Q, W, X and Y (from f i g . 4 5 ) which had s i l t o r f i n e sand f i n e f r a c t i o n s to v e r y ' c o a r s e sand, o r small pebble to cobble s i z e 1arge fragments. G ra i n s i z e s ; <, V, Z, T, E, H, C ( f i g . 4 5 ) were shown to be t o t a l l y unminera1 i zed wi th c h a l c o c i t e . 5 . 2 . 4 Optimum Ore Hor i zon It has been shown that rocks w i t h c e r t a i n d i s t i n c t i v e phys-ical c h a r a c t e r -i s t i c s are more l i k e l y to be m i n e r a l i z e d than are rocks w i t h o the r c h a r a c t e r -i s t i c s . But do these s p e c i f i e d v a r i a b l e s occur together in the host r ock s , and thus d e f i n e ho r i zon s o r in terbeds in the v o l c a n i c l a s t i c p i l e that are more h i g h l y m i n e r a l i z e d than any o ther s ( i e . are there optimumly m i n e r a l i z e d l i t h o l o g i c u n i t s p re sent ) ? ~ — re io c • re -« - i re -\ 0 - c -ui . . O • -\ rr O r r -a re o - i Q I T 01 — rr O — rj 5 i/i cu rr O re -I-I .— in XI o . -1 H- rr v i 3 •~*{r, < -—. 0) O — ' -1 c a> re c w ~ 3 rr —• re - J C CD -\ < OJ re — - i — Ul N — re o CL z o — o o c o r r OJ o o o a re cr • c OJ <: rr (D — -I O rr D — O • QJ z CL rr o FRO?'-'- CC. BEARING S A M P L E S - ro o o o o ro OJ -4b tr OJ -i ZOl 103 OC LU d _ J -LU o DQ N — L U co 1 CO 2 CQ o < o CC o rge z LU re _ j ~ ~ O CQ l - CQ AC LU C L _ re cc E LL <n DC LU _ J LU Z> CO z cc < cc < o O LU CC u V. COARS &SMALLE F INER F R A C T I O N GRA IN S I Z E C L A Y S I L T S A N D f i n e med. c o a r s e 1 /256 8 1/15 4 1/4 2 1 mm 0 phi £ a to co CM 1 < 0.0 n = 2 --V=Yoo~ T t CD C D I V 0.0 n = 2 W .13 n = 55 X .11 n =143 Y .07 n=15 Z 0.0 n = 1 P .03 n = 39 Q .14 n =278 Ills "n""=699 S .09 n = 6 7 T 0.0 n= 6 CM I CM J .10 n = 21 K .12 n=121 ill = n=~52~ SHI E 0.0 n = 17 F .05 n=37 G .06 n = 31 : H 0.0 n = 9 B : .14 n = 7 C o.o n = 8 F igure 45: G r a i n s i z e c l a s s i f i c a t i o n cha r t w i t h p r o p o r t i o n of each g r a i n s i z e type m i n e r a l i z e d w i t h c h a l c o c i t e . This char t is mod i f i ed from Blanchet and Godwin (1972) Codes f o r each g r a i n s i z e c l a s s i f i c a t i o n occur at the top of each b lock in t h i s d i a -gram. The n o . ' o f ob se r va t i on s (_i_e_. n=) of each c l a s s are represented at the bottom of the b l o c k . The n o . ' s in the cent re of the b l o ck s represent the p r o p o r t i o n o f each c l a s s m i n e r a l i z e d w i t h c h a l c o c i t e . Strong c h a l c o c i t e b l ock s are shaded. 104 In o rde r to a s c e r t a i n t h i s , the d i f f e r e n t v a r i a b l e s o f s o r t i n g , g r a i n s i z e and percentage mat r i x ( f i n e f r a c t i o n ) w i t h the h i ghe s t p r o p o r t i o n m iner -a l i z e d in the rock type AGGR were p l o t t e d aga in s t each o t h e r . In each o f the three ma t r i ce s thus de f i ned ( i e . g r a i n s i z e vs_. s o r t i n g , g r a i n s i z e v s . pe r -centage m a t r i x , and percentage ma t r i x vs_. s o r t i n g ) the p r o p o r t i o n o f rocks wi.th both v a r i a b l e s m i n e r a l i z e d was determined. The three mat r i ce s thus gen-e r a ted are shown in f i g . 46 w i t h p r o p o r t i o n m i n e r a l i z e d w i t h c h a l c o c i t e w r i t -t e n ' in each b l o c k . In g r a i n s i z e vs_. s o r t i n g , rocks w i t h a s o r t i n g o f 4 and a g r a i n s i z e o f R, and.wi th a s o r t i n g o f 5 and g r a i n s i z e s o f R and L, con-t a i ned the most c h a l c o c i t e . In g r a i n s i z e vs . percentage ma t r i x the b l ock s w i t h g r a i n s i z e s L and R and 60 percent mat r i x ( f i n e f r a c t i o n ) , g r a i n s i z e o f _(_ and 50 pe rcent m a t r i x , and g r a i n s i z e R w i th 70 percent ma t r i x had more . c h a l c o c i t e than o the r v a r i a b l e combinat ions of these two. F i n a l l y in pe r cen -tage m a t r i x vs.. s o r t i n g the g r ea te s t c oncen t r a t i on s of c h a l c o c i t e o ccu r red where s o r t i n g was 4 and 50 percent m a t r i x , s o r t i n g was 5 and 60 percent m a t r i x , and where the s o r t i n g was 4 o r 5 and the mat r i x was 70 percent of the rock. When a l l th ree p l o t s are combined i n t o a three d imens ional m a t r i x ( f i g . 47), i t becomes apparent that there i s an area where some of the h i ghe s t p r o -p o r t i o n s o f c h a l c o c i t e m i n e r a l i z e d f o r a l l p l o t s c o i n c i d e . Th is area t h e r e -fore de f i ne s the d i f f e r e n t combinat ions o f h i g h l y m i n e r a l i z e d v a r i a b l e s p r e -sent i n the host v o l c a n i c s ( i e . optimum combined v a r i a b l e s present in a c t u a l r o c k ) . Th i s area i s .where s o r t i n g i s 5, g r a i n s i z e i s e i t h e r L or R, and percentage ma t r i x i s 60 p e r cen t . In c o n c l u s i o n , i t was found that in comparing l i t h i c v a r i a b l e s o f the conglomerates and c h a l c o c i t e o ccu r rence , c e r t a i n p h y s i c a l c h a r a c t e r i s t i c s o f these rock s , made the rocks conducive to being m i n e r a l i z e d . Thus, the reason f o r ' i r regu- lar i ty in tha a rea l extents of the o re lenses i s tha t the m i n e r a l i z a t i o n was r e s t r i c t e d to c e r t a i n f a c i e s , or i n t e r b e d s , w i t h i n the vo1 c a n i c l a s t i c p i l e ; % M A T R I X L U N if) < DC O O T H E R 5 0 % 6 . 0 % • 7 0 % O T H E R . 0 6 1 2 n =49 . 1 2 5 i >3 Tl =112 p 5 2 T n = 119 ] . 2 ^ i 3 ! , ' , '•n;!=|!421; L . 1 7 6 5 n = 17 . 2 2 2 2 n = 18 4 4 0 0 0 n = 5 r . 0 0 0 0 n = 1 R . 3 4 7 8 n = 23 . 2 9 2 5 n = 147 . 6 1 3 2 n = 1 0 6 . 5 0 8 5 n = 59 ( . 3 3 3 3 n = 6 . 4 2 8 6 n = 21 . 3 5 7 1 n = 28 . 3 3 3 3 n = 21 F i g u r e 46: Comparison o f d i f f e r e n t types o f s i g n i f i c a n t l y c h a l c o c i t e r m i n e r a l i z e d v a r i a b l e s w i t h each o the r i n rock type AGGR. a) Comparison o f s i g n i f i c a n t l y m i n e r a l i z e d pe rcent m a t r i x v a l ue s w i t h s i g n i f i c a n t l y m i n e r a l i z e d va lues o f g r a i n s i z e in rock type AGGR. n va l ue s in each b l o c k i n d i c a t e no. o f o b s e r v a t i o n s of the g i ven va lues t o g e t h e r . i n AGGR. P r o p o r t i o n o f each o f these i n t e r s e c t i o n s m i n e r a l i z e d w i t h c h a l c o c i t e i s p resented i n bo ld numerals i n each b l o c k . o S O R T I N G N O T H E R 4 5 O T H E R . 1 4 6 7 n = 225 . 1 6 6 7 n =24 . 2 6 0 3 n =73 L . 1 4 2 9 n =35 . 0 0 0 0 n =0 . 6 6 6 7 n =6 R . 4 2 3 7 n =177 . 5 3 1 3 n =32 . 5 0 9 4 n =106 ( . 4 3 3 3 n = 30 . 1 4 2 9 n = 7 . 3 5 9 0 n =39 F i gu re ' l6b: Comparison of s i g n i f i c a n t l y m i n e r a l i z e d s o r t i n g and g r a i n s i z e va l ue s i n AGGR. E x p l a n a t i o n o f each b l o c k i s the same as i n f i g . ' i 6 a . % M A T R I X O T H E R 5 0 % 6 0 % 7 0 % . 1 2 8 2 . 1 9 4 9 . 3 9 1 3 ;! . 4 2 8 6 O T H E R n = 78 n = 195 n =138 : n = 56 . 0 0 0 0 . 5 0 0 0 . 3 6 3 6 . 0 0 0 0 4 n = 4 n = 20 n =33 n =6 . . 4 6 1 5 . 3 4 9 2 . 4 7 1 3 . 3 6 0 7 5 n = 13 n = 63 n = 87 n = 61 o z H DC o F i gu re 46c: Comparison of s i g n i f i c a n t l y m i n e r a l i z e d s o r t i n g and percent m a t r i x va lues in AGGR. B lock d e s c r i p t i o n s ' as i n f i g . 46a. ( A l l three o f these f i g u r e s (_i_e. 46a,b,c) a re draughted ve r s i on s of compu te r - r e t r i e ved t a b u l a t i o n s ) . SORTING Figure 47: Optimum ore ho r i z on diagram. This diagram i s a combinat ion o f the th ree f i g u r e s in f i g . 4 6 . Mo. 's in each b lock represent the p ropo r t i on s of the v a r i a b l e i n t e r s e c t i o n s m i n e r a l i z e d . Th i s diagram shows that there i s an area (shaded) where a l l three v a r i a b l e s have a common h igh p r o p o r t i o n of m i n e r a l -i z a t i o n . Thus any AGGR ho r i zon w i t h the phy s i c a l c h a r a c t e r i s t i c s as de f i ned by t h i s area would be p r e -f e r e n t i a l l y m i n e r a l i z e d r e l a t i v e to o ther sub-types of AGGR and r e l a t i v e to o t h e r rock t ypes . 109 5-2.5 Chemistry of the Ore Lenses  5.2.5(a) P r o b a b i l i t y P l o t o f Assay Data A p r o b a b i l i t y p l o t o f assay data f o r the n ine teen holes s t ud i ed was con -s t r u c t e d us ing methods de sc r i bed by S i n c l a i r (1976)- Assay va lues were taken from data ob t a i ned by Fa l conbr idge N i c ke l Mines L t d . The assays used, were f o r twenty foo t sampl ing i n t e r v a l s . Not a l l the assays were in twenty f oo t i n t e r v a l s but the author combined i n t e r v a l s o f f i v e and/or ten f e e t in o r de r to get twenty foot i n t e r v a l va lues where p o s s i b l e , i f a g iven s ho r te r s e c t i o n cou ld not be combined to y i e l d a s tandard twenty foo t va lue then the assay va lues were d i s c a rded f o r the purposes of the p l o t . In t h i s manner, one hun-dred and seventy - seven assay values were used to c o n s t r u c t the graph ( f i g . 48). The assay data i n d i c a t e a bimodal d i s t r i b u t i o n o f v a l ue s , w i t h an i n f l e c -t i o n po i n t a t 60 p e r cen t . Thus popu l a t i on A, w i t h the h igher assay v a l u e s , accounts f o r 60 percent o f the value sp read, w h i l e p o p u l a t i o n B accounts f o r 40 p e r cen t . The upper popu l a t i on A i s i n f e r r e d to represent copper va lues p resent in the m i n e r a l i z e d zones, whereas B represent s background copper con -t e n t s . Thresho ld f o r popu l a t i on A (from the lower two p e r c e n t i l e ) is i n d i c a t e d as 180 ppm copper, and the t h r e sho l d f o r B (from i t s upper two p e r c e n t i l e ) i s found to be 300 ppm copper. Values in the range 185~300 ppm can belong to e i t h e r p o p u l a t i o n . The i n tense i n f l e c t i o n po in t o f t h i s bimodal d i s t r i b u t i o n i n d i c a t e s t ha t there i s a very s t rong d i f f e r e n t i a t i o n and d i s t i n c t i o n between m i n e r a l i z e d zones and background contents (|_e. there i s no rea l g r ada t i on from one. popu-l a t i o n to another , and thus the m i n e r a l i z e d zones are a very d i s t i n c t f e a t u r e r e l a t i v e l y u n r e l a t ed to background v a l u e s ) . 5.2.5(b) Trace Element Chemistry of Ore Lenses Ana lyses f o r Zn, Cu, N i , Rb, and Sr were done f o r s i x sets of samples. These set s were taken from country rock sur round ing the zones, in o rde r to a s c e r t a i n what chemical v a r i a t i o n s occur between a m i n e r a l i z e d lens and i t s no F igure 48: P r obab i 1 i t y graph of copper assay va lue s . "The percent copper i s based on twenty foot assay i n t e r v a l s . One hundred and s e v e n t y - f i v e assay values are represented on t h i s graph. ' ' 111 host- rocks . Table 7 shows the analyses f o r the va r i ou s s e t s . The values r epo r ted are based on two analyses o f the samples by means o f X-ray f l u o r e s c e n c e . Some samples, w i t h high copper con tent s , were checked by atomic ab so rp t i on methods, and the r e s u l t s were combined w i t h those from the XRF ana lyses to y i e l d the r e s u l t a n t average v a l u e . D i s cu s s i on of the chemis t ry w i l l i n vo l ve d e s c r i p t i o n of each sample set ( see a t tached map f o r sample l o c a t i o n s ) . In the f i r s t set o f samples; 44A1 is from 2.85 m below the c o l l a r of DDH 44, i t i s a conglomerate w i t h d i s seminated n a t i v e copper, 44B2, 21.33 m below, has s t rong n a t i v e copper m i n e r a l i z a t i o n through the m a t r i x w i t h minor c h a l c o c i t e , 44B8, from a depth o f 44.7 m, conta in s p y r i t e , and f i n a l l y 44C1 (54.12 m) is t o t a l l y devoid of any s u l p h i d e . Both 44A1 and 44B2 c o n t a i n nea r l y 2 percent copper, whereas the p y r i t e zone has 0.01 percent copper and the unminera1ized a r e a , <0.01 pe r cen t . S t ron t ium is s t ronges t in the p y r i t e zone, as i s rub id i um. The two c o p p e r - r i c h samples are dep le ted i n rub id ium, r e l a t i v e to the o the r two samples. Z i nc i s f a i r l y constant and n i c k e l i s lowest in the unm ine r a l i z ed sample. Sample 6A7 i s unminera1 ized core from 35.88 m in DDH 6, 6A8 (39.01 m)has t r a c e c h a l c o c i t e in carbonate patches in the m a t r i x , 6B3 (84.9 m) i s from a h i g h -grade copper zone where the framework i s open, 6C9 (84.9 m) is from an unminer-a l i z e d a r ea . Copper i s very abundant in 6B3, approach ing 10 pe rcen t , and decreases s i g n i f i c a n t l y from the ore zone to a low at 6C9. Z i n c shows a s l i g h t enr ichment i n 6B3, and u n i f o r m i t y in the o the r samples. N i c ke l i s s l i g h t l y r i c h e r in 6B3, and less i n 6C9. S t ront ium i s much h i g h e r - i n 6B3 than i n the o the r s where i t i s con s t an t . Rubidium i s lowest in 6B3 and h ighes t in 6A7. Sample W32A i s from the middle o f a s t rong c h a l c o c i t e - b o r n i t e lens on the nor th s i d e of the c i r q u e , W97GM is of groundmass to conglomerate immediately below W32A ( i t has some v i s i b l e c h a l c o c i t e and b o r n i t e i n gangue). W97AP i s an a u g i t e porphyry c l a s t set in the groundmass of W97GM, and W i l l i s wa l l rock of a m i n e r a l i z e d v e i n zone 18 m below W32A. Copper i s very abundant in W32A, over 6 percent and i s r i c h e r in the groundmass (W97GM) than in a c l a s t (W97AP). TABLE VI I TRACE ELEMENT ANALYSES FOR ORE LENS SETS Cppm I p r e c i s i o n ) Sample No. Zn_ Cu Ni Sjr Rb 44A1 131.40(±1.37) 15558(11.40) 2 1 . 29 (H .87) 70.24(10.37) 1.38(10.23) 44B2. 113.60(12.82) 18071.10(10.55) 17.75(10.59) 245.07(10.26) 5.43(10.13) 44B8 97.64(11.99) 1 15.94.(113.26) 12.44(12.01) 571.65(10.90) 49.69(10.06) 44C1 76.51(11.34) 56.75(±2.19) 4 . 8 8 ( H ) 367.23(10.23) • 17.19(10.23) 6A7 88.44(12.29) 240.72(14.17) 18.91(10.74) 237.74(10.08) 21.71(10.05) 6A8 86.09(10.30) 2228.72(1217.48) 15.27(10.96) 192.33(10.05) 20.61(10.05) 6B3 183.50(15.77) 94894.80(14205.65) 30.94(10.86) 546.41(+0.53) 1.30(10.38) 6C9 90.11(11.44) 63.33(11.91) 5.39(10.02) 232.64(10.10) 9.22(10.24) W11 1 78.71(10.16) 123.91(118.12) 8.21(10.29) 268.46(10.55) 12.42(10.19) W32A 165.08(12.37) 61794.55(1750) 61.08(10.81) 261.13(10.37) 0.85(10.16) W97AP 188.425(10.94) 1832.52(1169.53) 83.70(10.06) 352.71(10.29) 18.2(10.05) W97GM 170.81(12.84) 5569.56(1504.71) 22.24(10.18) 270.79(10.20) 22.52(10.24) W2 111.33(16.06) 32913.80(+1586.2) 35.25(18.15) 176.64(10.07) 2.03(10.26) W3 83.25(10.81) 183.89(164.20) 27.68(10.90) 101.23(10.03) 2.33(10.14) W4 61.32(10.39) 86.75(10.75) 31.25(11.72) 99.64(10.50) 0.68(10.25) 132C 3 96.50(12.66) 42.71(11.71) 10.95(11.14) 150.22(10.55) 90.91(10.72) 132C7 84.54(12.06) 101.21(12.78) 19.50(10.43) 687.64(12.52) 12.06(10.28) W12 156.38(12.29) 56504.45(11895.90) 37.76(10.10) 857.69(116.17) 20.58(10.21) W13 92.85(10.05) 1163.26(130.77) 27.57(11.68) 467.02(10.8')) 18.64(10.39) W98 125.52(11.00) 10674(1994.75) '. 39.18(10.35) 206.45(10.10) 1 .91(10.30) W 9 9 73.00(10.96) 147.75(137.77) 73.39(±1.14) 321.12(11.04) 11 .62(10.02) W103 94.37(11.00) 7128.48(10.19) 20.44(10.15) 189.48(10.06) 6.88(10.18) 113 Copper is present in t r a ce amounts at the bottom o f the m i n e r a l i z e d a r ea . Z inc i s most abundant i n the c oppe r - r i c h p o r t i o n s . N i c ke l i s h ighes t in W97AP, and s e c o n d a r i l y so in W32A. St ront ium i s f a i r l y cons tant and rubidium shows a great d e p l e t i o n in the most h i gh l y m i n e r a l i z e d sample. Sample W2 i s from the centre of a s m a l l , 0.3 m t h i c k , ore lens at the western edge o f the South Zone. W3 was taken from 1.5 m below t h i s ho r i z on and W4 f o r 1.5 m above the lens . Z i n c i s h i ghe s t i n the ore zone and some-what lower above the zone than under i t . Copper i s very h igh in W2 and much lower in W3 and W4. N i c ke l i s cons tant , s t r o n t i u m i s h i ghes t in W2 and r u b i -dium is low in W4 r e l a t i v e to samples W2 and W 3 . 132C3, from 183 m below the c o l l a r of DDH 132, i s a b leached area which conta in s 1 pe rcent p y r i t e , 132C7 i s from 29.1 m below 132C3 and i s barren conglomerate.- Copper i s present as background l e v e l s in both samples, but i s somewhat s t r onge r i n the barren co re . Z inc and n i c k e l are cons tan t . S t r o n -t ium i s much s t r o n g e r in 132C7 w h i l e the reverse i s t r ue f o r rub id ium. W12 i s the c e n t r a l pa r t of a c h a l c o c i t e - b o r n i t e - c h a l c o p y r i t e ore lens on the southern edge of the c i r q u e . WI3 comes from 9 m above the two lenses at W12 and has some m a l a c h i t e - s t a i n i n g . Copper i s r i c h e s t in W12 (over 5 per - , cent) and i s h i ghe r than background in W13- N i c k e l i s about even between the two, w h i l e s t r o n t i u m i s more abundant i n W12. Z i n c i s more p reva l en t i n W12 than in W13. Rubidium is present in s i m i l a r amounts in bo th . W98 i s a specimen o f w a l l rock to the dyke that con ta in s d i s seminated n a t i v e copper w i t h a t r a c e o f c h a l c o c i t e . Th i s host rock has a c l o s ed frame-work and the copper m ine ra l s are present in q u a r t z - f i l l e d pores in the m a t r i x . A sample 1.5 m from W98 (W103) is of a rock w i t h a medium to coarse sandy-mat r i x and open framework. Th is specimen has minor amounts of n a t i v e copper and c h a l c o c i t e in qua r t z pores, but s t rong n a t i v e copper m i n e r a l i z a t i o n i s present as d i s s em ina t i on s through l i t h i c c l a s t s . F i n a l l y , W99 i s copper m i n e r a l i z a t i o n - f r e e dyke rock by W98. The t r a c e element chemis t ry shows that 114 z i n c ' i s most abundant in the c o p p e r - r i c h samples. WS9 has t y p i c a l back-ground copper v a l u e s . N i c k e l , s t r on t i um and rub id ium are h ighes t in W39• In summary, some general r e l a t i o n s h i p s of t r a ce elements and copper m i n e r a l i z a t i o n can be gleaned from the a n a l y t i c a l da t a . Z inc and s t r o n t i u m u s u a l l y have t h e i r g r ea te s t concen t ra t i on s in c o p p e r - r i c h a reas . N i c ke l .is f a i r l y c on s t an t through the rocks however there may be a s l i g h t enr ichment in the copper zones ( n i c k e l i s s t ronges t in s ing1e vo l c an i c c l a s t s , r a t he r than whole r o c k s ) . Rubidium is appa ren t l y dep l e ted in copper a rea s . A l s o i t i s i n t e r e s t i n g to see the sharp c u t o f f in grade between ore lenses and t h e i r host rocks (eg. W2-W3-W4). It seems that there is no g rada t i on of copper va lues between the two areas , which agrees w i t h what was seen in the p r o b a b i l i t y p l o t o f assay va lues . No areas have a g reat d e p l e t i o n in copper con tent , there ' a re p laces w i th low background con ten t s , but c o n s i s t e n t zones from which copper has been removed to be p r e c i p i t a t e d elsewhere are not seen. Background copper con ten t s , as determined from these ana l y se s , agree w i t h the h igh background copper values found in c l a s t s and o the r rock types ( s e c -t i o n 3-3-10 above ) . 5.2.5(c) Major Oxide Chemistry of Ore Lenses P a r t i a l major ox ide ana ly ses , in Tab le 8, were c a r r i e d out on samples W12 and'W13. The most s i g n i f i c a n t f ea tu re s are d e p l e t i o n s in SiO^, MgO ( s t rong d e p l e t i o n ) , Na^O and K^O in h i gh l y m i n e r a l i z e d areas vs_. le s s m i n e r a l i z e d , and the s t r ong i nc rease in CaO in the o re l e n s . 5-2.6 Gangue M inera logy of the Ore Lenses Ore m i n e r a l s in the lenses are i n t i m a t e l y intergrown w i t h gangue m ine r a l s i d e n t i c a l to those formed by metamorphism o f the host rocks . Zones of abun-dant s u l p h i d e s c o n t a i n la rge amounts of e p i d o t e and p r e h n i t e . Quartz , c a rbon -ate and c h l o r i t e are a l s o common in these zones. In thus appears that meta-morphic and o re m inera l s have formed by the same s o r t of processes . 115 TABLE V I I I MAJOR OXIDE ANALYSES FOR ORE LENS SET (%) OXIDE WI 2 WI 2 S i 0 2 43.13 46 .50 T i 0 2 * * 0.91 0.96 A 1 2 0 3 1 5.20 1 5.86 1 Fe * * 2.91 3.64 MnO 0.11 0.1 7 MgO 1 .75 6.35 CaO 9.65 5. 30 Na 2 0 3.25 : 4.13 K 2 0 0.66 1 .70 p 2 o 5 0.64 0.81 L . O . I . - 0 . 4 9 * 3. 76 Cu 5. 65 0.12 T o t a l 83.37 8 9 . 3 P o s s i b l e O x i d a t i o n Total Fe and T i 0^  are low because t i t a n i f e r o u s magnet ite was not d i s s o l v ed complete ly in the a n a l y t i c a l procedure "»»»»»These analyses were done by Min-En L a b o r a t o r i e s , North Vancouver, B.C.. 116 The ore lens sample l o c a t i o n near W104 ( f i g . 49) has very intense ep i do te development w i th s t rong p r e h n i t e , carbonate and qua r t z overgrowths. C h a l c o c i t e and bo r n i t e are present as i r r e g u l a r l y shaped g ra i n s in ep idote and p r e h n i t e a l t e r a t i o n patches. F i g . 50 shows these ore and metamorphic minera l i n te rg rowths . In the lens at the head of the c i r que (W112), g ra in s of s u l ph i de occur in the open mat r i x of the host conglomerates. Best development o f the su lph ides i s seen where they e i t h e r have ep ido te rims o r are i n t e r g r a n u l a r to q u a r t z . In r a re p laces where c h l o r i t e and carbonate overgrow and rep lace p l a g i o c l a s e g r a i n s , ore minera l s are intergrown w i th them. Approx imate ly 5 to 6 m above t h i s lens (W22), opaques ' s p e c k l e ' (or dust) p rehn i te and ep i do te that a l t e r the m a t r i x . Sample W17, from near t h i s a rea , shows the same s t rong s peck l i n g of p r ehn i t e and ep idote w i t h ore ( f i g . 5 ? ) . In the W32A lens no o r i g i n a l l i t h i c g ra ins are v i s i b l e as they are a l l overgrown by kS percent p r e h n i t e , 30 percent ep i do t e , 10 percent qua r t z w i t h l e s s e r amounts of z o i s i t e , pumpe l l y i t e and c h l o r i t e . The rock now c o n s i s t s o f very l a r ge , i r r e g u l a r patches o f p rehn i te w i th i n t e r g r a n u l a r qua r t z and . l a r ge masses of i n te r connec ted , s m a l l e r , ep idote and z o i s i t e g r a i n s . The l a r g e s t , i r r e g u l a r l y - s h a p e d su lph ides occur in the quar tz patches , in which there are gene ra l l y s t r a i g h t edges on the opaques where they are in contact w i t h the q u a r t z . Sma l le r g ra i n s o f su lph ide are s c a t t e r e d through the p reh -n i t e o r ep ido te ( f i g . 52). Sample W10, from the lens on the south s ide of the c i r q u e (see sample l o c a t i o n on at tached map) con ta in s la rge patches of carbonate w i t h c h l o r i t e , q u a r t z , ep i do t e , and z o i s i t e in the ma t r i x . The su lph ides (bo rn i te , c h a l c o c i t e and c o v e l 1 i t e ) occur in three a reas ; w i th c h l o r i t e , qua r t z , ep ido te and z o i s i t e a f t e r f e l d s p a r s , or in ca rbonate -ep idote patches in the m a t r i x . Sample W11, from the same a rea , has ore m i n e r a l s , up to 0.15 mm. in diameter in large ' c h l o r -i t e patches in the ma t r i x , and even l a r ge r g ra ins are p r e s e n t - i n quar tz patches . Opaques are a l s o present in the ep idote g ra ins and, to a minor 117 F igure 49: Close up of ore lenses at sample l o c a t i o n W104. Note intense ep idote a l t e r a t i o n w i th the very s t rong s u l ph i de c oncen t r a t i o n . Fresh sur faces show a s u b t l e reddish t inge to m i n e r a l i z e d rock due to secondary hemat i te . The width of t h i s p l a t e i s about 1.8 m.. F igure 50: Photomicrograph of W104 ore lens ( x - n i c o l s ) . Opaque g ra in s of c h a l c o c i t e and b o r n i t e are i n t i m a t e l y intergrown w i th h i gh l y b i r e f r i g e n t ep ido te (with minor p rehn i te ) g r a i n s . This s e c t i on i s 1.1 cm ac ro s s . 118 F igure 51: Photomicrograph of opaque minera l s and gangue-sample W17 - ( p i a n e - p o l a r i z e d ) . The main gangue i s p r e h n i t e w i t h l e s se r ep i do te . Su lph ides ( bo rn i te and c h a l c o c i t e ) speck le gangue masses, l a r ge r su lph ide gra ins are intergrown w i t h gangue. This s e c t i o n i s 1.1 cm acros s . F igure 52: Photomicrograph o f W32 ore lens ( x - n i c o l s ) . Large su lph ide ( bo rn i t e and c h a l c o c i t e ) gra ins are i n t e r -grown w i th b i r e f r i g e n t p rehn i te and ep ido te , and w i th wh i t e quar tz areas. Note s t r a i g h t edges on su lph ides where they are in contact w i t h qua r t z . As can be seen, host rock i s extremely a l t e r e d . Th i s s e c t i o n is 1.1 cm ac ro s s . 119 e x t e n t , in the carbonate cement. DDH 25 at the northwestern edge of the South Zone, i s ba r ren , but i t does con ta i n numerous p y r i t e zones. In one such zone (25A5. from 7-62 m below the c o l l a r ) , p y r i t e occurs in c h l o r i t e patches in the m a t r i x . C h l o r i t e i s a l s o seen to rep lace aug i te s in t h i s specimen, however p y r i t e i s not in t h i s form of c h l o r i t e . Sample 2A2 (from DDH 2) is from a p y r i t e area too. In t h i s specimen the rock i s cemented by carbonate and c h l o r i t e . P y r i t e i s p re -sent as round i n c l u s i o n ' b a l l s ' in the c h l o r i t e cement ( f i g . 53)-Sample 6B3 had the h i ghes t copper content ('v 10 percent )ana 1 ysed. In t h i n s e c t i o n t h i s rock was i n t e n s e l y a l t e r e d by ep idote (80 p e r c e n t ) , p r e h n i t e , c a r -bonate, and q u a r t z . R e l i c t c l a s t s have opaques in pores in t h e i r groundmasses, and r e l i c t f e l d s pa r g ra in s a l s o con ta i n opaque su lph ides in a l t e r a t i o n patches Best development o f s u l ph ide (up to 2.7 by 0-3 mm) i s found in ep ido te and p r e h n i t e masses ( f i g . 54). A l l ep idote g ra in s are h e a v i l y dusted w i t h s u l -ph ide s . Ore i s a l s o intergrown w i th quar tz and p rehn i t e patches . However, not a l l s u l ph i de areas are intergrown w i t h gangue. Where p y r i t e i s s t r onges t (and les s commonly c h a l c o p y r i t e ) i t i s not g e n e r a l l y found w i th a l t e r a t i o n m ine ra l s . I ts most common forms, in areas o f h igh c o n c e n t r a t i o n , are as network masses which f i l l the mat r i x to l i t h i c c l a s t s ( f i g . 55), or as rims surrounding smal l l i t h i c g r a i n s . In these forms the p y r i t e act s as i t s own a l t e r a t i o n medium, r e p l a c i n g matr i ces by i t s e l f . In summary, copper su lph ides are seen to be i n t i m a t e l y intergrown w i t h e p i d o t e , p r e h n i t e , carbonate, quar tz and c h l o r i t e . P y r i t e where r i c h , i s in p laces an e x c e p t i o n . Th is common s p a t i a l r e l a t i o n s h i p o f a l t e r a t i o n and ore m inera l s e xp l a i n s some of the chemical v a r i a t i o n s seen between ore lenses and barren country rock. The increase in ca l c i um and s t ron t i um in ore zones i s caused by the presence w i t h i n these zones of carbonate, formed by. the same m i n e r a l i z i n g episode that p r e c i p i t a t e d copper m i ne r a l s . Th is a l s o accounts f o r a decrease in s i l i c a , sodium, potassium and magnesium contents as m inera l s 120 F igure 53: P y r i t e as rounded blebs ( ' b a l l s ' ) in c h l o r i t e ( p l a n e - p o l a r i z e d ) . This shows p y r i t e is e p i g e n e t i c as i t is intergrown w i th a secondary gangue m i n e r a l . This s e c t i o n is 1.1 cm ac ro s s . F igure 54: Sulphides ' s p e c k l i n g ' ep ido te masses in sample 6B3 ( x - n i c o l s ) . This sample analysed over 10 percent copper and t h i s f i g u r e shows the r e l a t i o n o f very b i r e f r i g e n t ep idote gangue and c h a l c o c i t e - b o r n i t e m i n e r a l i z a t i o n . This s e c t i o n is 1.1 cm acros s . 121 F igure 5 5 : Photomicrograph of network p y r i t e masses (white) that have replaced m a t r i x . Sec t i on is 1 .1 cm ac ross . 122 c o n t a i n i n g these elements were p r e f e r e n t i a l l y broken down (_i_e. aug i te s and f e l d s p a r s ) due to the metamorphic a l t e r a t i o n . 5-3 Su lph ide -Bear ing Veins  5.3-1 General Outcrop Appearance and Gangue Mineralogy S i g n i f i c a n t amounts of su lph ides are present in gangue-r ich v e i n s , a l -though t h e i r abundance of conta ined copper i s minimal compared to o re l en se s . As p r e v i o u s l y s t a t e d , most metamorphic minera l s on the property are observed in the form of both ve in and t a b u l a r metadomains. However not a l l ve ins con-t a i n o re minera l s and those that do occur in l o c a l s t eep l y d ipp ing swarms. Dominant su lph ides in these ve ins are c h a l c o c i t e , b o r n i t e , and c h a l c o p y r i t e , l e s s common are veins w i t h p y r i t e or n a t i v e copper. The most common ve in m a t e r i a l s are carbonate and q u a r t z . Ep idote i s f a i r l y t y p i c a l a l s o , and p rehn i te i s seen megascop ica l l y to a l e s s e r e x t e n t . Combinations o f carbonate, quar tz and ep ido te are found together commonly, whereas p r ehn i t e - c a rbona te -qua r t z ve ins a re les s abundant. F i e l d i d e n t i f i c a -t i o n o f p r e h n i t e was not very c o n s i s t e n t , and subsequent t h i n s e c t i o n study has shown that p rehn i te i s indeed common. In the North Zone veins are best developed near DDH 16. Here (J_e_. sample l o c a t i o n W36)quartz-epidote-carbonate ve ins con ta i n r i c h concen t r a t i on s o f b o r n i t e - c h a l c o c i t e - d i g e n i t e . These ve ins s t r i k e 010* to 020* and d ip v e r t i c a 1 l y "to- 80"SW, and pinch and swe l l a long t h e i r lengths (widths from 5 or 6 cm to 3 mm) . Copper sulphide ' s are not present f o r the f u l l lengths of- the veins but are concentrated in pods where the veins reach a maximum th i c kne s s . I nd i v i dua l veins are as much as 3.6"m in s t r i k e length and swarms have a den s i t y o f two veins per 5 f t in a d i r e c t i o n p e r p e n d i c u l a r to s t r i k e . The gangue morphology i s i n t e r e s t i n g where we l l deve loped, as i t shows su lph ide concen t r a t i on in centres of ve ins w i t h q u a r t z , whereas the ve in edges are composed of carbonate and e longate ep ido te c r y s -t a l s . In patches of massive s u l ph i de , small euhedral quar tz c r y s t a l s are 123 common, growing in vugs in the su lph ide mass. A l s o in the North Zone are two areas o f s t rong f r a c t u r i n g w i th ore min-e r a l c oa t i n g s . The major zone is in the area of sample l o c a t i o n s W40-W41-W42, W.95 and W100. Near W40-W41-W42 the dominant f r a c t u r e d i r e c t i o n i s 165/84E. However there are quar tz and quar tz -ca rbonate ve ins that cut through at 020/ 70SE. The quar tz ve ins are s inuous. Intergrown w i t h these ve ins are bo r n i t e w i t h c h a l c o c i t e . The host rock to the f r a c t u r e systems con ta in s c h a l c o c i t e and b o r n i t e in q u a r t z - f i l l e d pores in t h e i r ma t r i c e s . Exposed f r a c t u r e su r -faces commonly have copper moss c oa t i n g s . Around W95 and W100. the f r a c t u r e s and ca rbonate -quar tz ve ins have common trend of 025/75SE. Wall rocks to these v e i n - f r a c t u r e s c on ta i n l a r g e , open, q u a r t z - f i l l e d areas in the matr ices f i l l e d w i th c h a l c o c i t e and b o r n i t e . A second f r a c t u r e zone i s near DDH kh. There are on l y j o i n t s here, no v e i n s . These j o i n t s ( 0 3 7 / v e r t i c a l ) have malach i te and/or copper moss c o a t i n g s . The host rocks (W33) con ta i n 5 percent d i s seminated na t i v e copper . Below the ore lens at W32, qua r t z -ca rbonate ve i n s , w i t h 5 to 10 mm in d iameter c h a 1 c o c i t e - b o r n i t e g r a i n s , occu r . The v e i n s , which are mainly 2 to 3 cm wide, cut through a green host rock. Minor ma lach i te and copper moss are present on t h e i r s u r f a ce s . The su lph ide gra ins are intergrown w i t h the gangue m ine ra l s and on ly rare t r ace s of su lph ide are present in the host rocks . These ve in s do not cut across the ore l en s . S i m i l a r l y , below the second ore lens here, another group of q u a r t z - c a r b o n a t e - e p i d o t e - s u l p h i d e m i n e r a l i z e d ve ins (028/88NW) crop out (WHO). These 1.25 to 15 cm wide ve ins con ta i n 10 to 15 percent b o r n i t e , c h a l c o c i t e , d i g e n i t e and c o v e l l i t e , w i t h at tendant ma lach i te and a z u r i t e . Two to three cm wide ep idote ve in s , w i th minor s u l p h i d e , cut through the rocks j u s t above the W104. ore lens ( f i g . 5&). These v e r t i c a l l y d i pp i ng veins have the same general s t r i k e as those at W36. Numerous s m a l l , < 1 mm wide, carbonate v e i n l e t s cut through the ore ho r i zon at sample l o c a -t i o n s W10-W11-W12. These v e i n l e t s are s t r ong l y m i n e r a l i z e d w i t h c h a l c o p y r i t e , 124 F igure 56: Epidote v e i n l e t s c u t t i n g country rock over -l y i n g W104 ore l en s . The intense red c o l o u r a t i o n on the su r face is the 'copper moss ' . The ep ido te v e i n l e t s are not very wide here. F igure 57: A b o r n i t e and c h a l c o p y r i t e pod in a carbonate-quar tz ve in near W76. Note the s t rong ma lach i te and a z u r i t e a l t e r a t i on. 125 which l o c a l l y makes up to 50 volume percent of the v e i n l e t . Near sample l o ca t i on s W115 and W116 (see geology map) two sets o f c h a l c o -c i t e - b o r n i t e m i n e r a l i z e d ve ins are seen in the host rock. The o l d e r set (117/ 79NE) con ta in s the on ly outcrop occurrence o f g reenock i te l oca ted by t h i s w r i t e r , the younger set (036/vert ica1) c on ta i n no g r eenock i t e . Ma l ach i te and c h a l c o c i t e are present in a c a rbona te -qua r t z - ep i do te ve in (024/74SE) at sample l o c a t i o n W15. Two set s o f veins c on t a i n i n g su lph ides are a l s o present by sample area W49- The o l d e r set (090/66S) c o n s i s t s of c h a l c o c i t e and ma lach i te in 3 to 40 mm wide ep i do t e - c a rbona te - qua r t z v e i n s . One of these ve ins i s connected w i t h the ore lens at W2, where i t appears to t r unca te one s ide of the l en s . The ve in does not occur above the l en s . The younger set of ve ins (60/76SE) c on t a i n t r a ce c h a l c o c i t e in ep i do te - ca rbona te -qua r t z gangue. In the c e n t r a l p o r t i o n of the South Zone, a group of i s o l a t e d , t h i c k , s u l p h i d e - r i c h ve ins crop ou t . At sample l o c a t i o n W55, a 7-5 cm t h i c k , c a r -b o n a t e - e p i d o t e - b o r n i t e - m a l a c h i t e ve in (110/62NE) occu r s . Sample W56 has a c a r b o n a t e - e p i d o t e - c h a l c o c i t e - c h a l c o p y r i t e - m a 1 a c h i t e - a z u r i t e ve in (145/50NE), To the south of DDH 88, near the top o f a small w a t e r f a l l , a 6.35 cm wide e p i d o t e - q u a r t z - c a r b o n a t e - m a l a c h i t e - v e i n (110/68NE) cuts the country rock. Th is p a r t i c u l a r ve in has f r a c t u r e o f f s h o o t s which e x h i b i t copper moss a long t h e i r s e l v age s . Th is ve i n i s c r o s s - c u t by o t he r veins ( 065/ve r t i c a1 ) , which c on t a i n no s u l p h i d e s . A s e r i e s of ve ins w i t h intense su lph ide m i n e r a l i z a t i o n occurs in the general reg ions o f DDH1s 41 and 120. At DDH 120, a s t rong f a u l t d i s r u p t s the country rock a t 112/64NE. Th i s f a u l t occurs along what appears to be a t h i c k su lph ide ve in zone. Through the s t r i k e of the f a u l t from DDH 120 to 60 m d i s -t a n t , carbonate zones con ta in numerous patches of h igh-grade su lph ide m i n e r a l s . At W80 carbonate mate r i a l conta ins massive blebs of c h a l c o p y r i t e (up to 3 cm in d iameter) and b o r n i t e (up to 10 cm in d i amete r ) . Some of the c h a l c o p y r i t e 126 e x h i b i t s e x c e l l e n t b o t r y o i d a l t ex tu re s in the carbonate. W8l samples show a carbonate ve in zone w i t h b o r n i t e - c h a l c o c i t e and c o v e l l i t e . F i ve to ten mm wide, pure ve ins of su lph ide are seen to invade the host rock in p laces here. These ve ins are c r o s s - cu t by ep ido te -ca rbonate ones (041/80SE). At sample l o c a t i o n W79, a 5 cm wide ep ido te - ca rbona te ve in zone i s p re sen t . Th is group (040/&6NW) conta in s up to 5 percent bo rn i t e and c h a l c o c i t e , and these m i n e r a l -i zed ve ins c r o s s - c u t two sets of unminera l i zed ve ins (060/80NW and 120/58NE). Through the area near the l o c a t i o n o f samples W73-W74-W76, a s e r i e s of veins (118/65NE), which have va r y i n g amounts o f . s u l p h i d e , o ccu r . The gangue miner-a l s are quar tz -ca rbonate ,and su lph ides are complex in tergrowths o f c h a l c o -p y r i t e - b o r n i t e - c h a l c o c i t e - m a l a c h i t e . The ve ins p inch and s w e l l , from > 15 to < 1 cm, e x t e n s i v e l y in t h e i r l eng th s , the su lph ides range from pure c h a l c o -p y r i t e to massive b o r n i t e w i t h c h a l c o p y r i t e ( f i g . 5 7 ) . F i n a l l y , around DDH 128 zones of s u l ph i de -bea r i n g ve ins are p re sent . At sample l o c a t i o n W67, ca rbona te -ep i do te -qua r t z ve ins (142/84NE) con ta i n c h a l c o -p y r i t e - b o r n i t e - c h a 1 c o c i t e - m a 1 a c h i t e . These ve ins p inch and swe l l e x t e n s i v e l y , and d i sappear r a p i d l y . W71 samples are of la rge carbonate ve in s (138/59NE) which have p y r i t e - c h a 1 c o p y r i t e - b o r n i t e . Three to four percent d i s seminated p y r i t e i s present in some po r t i on s of the wa l l rock. It t he re f o re appears that the s u l p h i d e - m i n e r a l i z e d ve ins in the North Zone g e n e r a l l y s t r i k e n o r t h e a s t e r l y and are more or le s s v e r t i c a l , whereas those in the South Zone s t r i k e no r thwes te r l y and d ip to the no r thea s t . 5.3.2 Ore Veins in D r i l l Core A l l ore minera l s of t a b u l a r zones are present in ve i n s , s i m i l a r l y , meta-morphic minera l s c h a r a c t e r i s t i c of t abu l a r zones are a l s o found in ve in s . Some broad g e n e r a l i z a t i o n s concern ing occurrences of ve ins in d r i l l core are p o s s i b l e . Veins are ub i t i quou s through every l e ve l of a l l ho l e s . However m e t a l l i c minera l s are most abundant in ve ins below the main ore ho r i z on s . In DDH's 88 and 110, f o r example, ore minera l s are present in the hor izons mainly 127 as d i s s em ina t i on s , but through to t h e i r bottoms most of these minera l s are present as t r ace s in w i de l y d i sper sed v e i n l e t s . The s c a t t e r e d ore lenses deep in the holes g e n e r a l l y have some s t rong ve i n component. In DDH's 96 and 116, where the upper ore lenses are more separated and d i s t i n c t , there i s a s t rong ve in c o n t r i b u t i o n to the ore m i n e r a l i z a t i o n in these ho r i zon s . Another f ea tu re i s tha t the p y r i t i c par t s of DDH's 25 and 132, have very few ve i n s . Thus in s t r o n g , cont inuous ore ho r i z on s , copper su lph ides are mainly p re -sent as d i s s e m i n a t i o n s , w i t h l i t t l e c o n t r i b u t i o n to t o t a l s u l ph ide content from ve ins u n t i l below the main ho r i zon s . P y r i t i c areas have minor s u lph ide c o n t r i b u t i o n from ve in m a t e r i a l . 5-3-3 Post-Ore Movement in Veins F a u l t i n g and j o i n t i n g commonly have a f f e c t e d p r e - e x i s t i n g v e i n s . Th i s e f f e c t i s e x h i b i t e d as movement along the plane of the v e i n , and sometimes by s m a l l - s c a l e remob i1 i z a t i on of s u l ph i de s . Movement i s i nd i c a t ed by s l i c k e n -s i d i n g and s t r e t c h i n g out of gangue mate r i a l and s u l ph i de g r a i n s . Two good examples a re : sample l o c a t i o n W43, where the p lane of a former e p i d o t e - s u l p h i d e ve in became the p lane o f a l a t e r f a u l t , and the ep ido te became s1 i c kens ided , . and sample l o c a t i o n W56, where a f r a c t u r e s u r f a c e , w i t h ma 1 a c h i t e - a z u r i t e -c h a 1 c o c i t e - c h a l c o p y r i t e and ep i do t e , i s e x t e n s i v e l y s i i c k e n s i d e d . 5.3.4 Trace Element Chemistry of Vein Ma te r i a l Table 9 con ta in s t r a ce elements a n a l y t i c a l data of a ve in se t . W87 is a sample of w a l l rock r i g h t at the contact of a 3 to 5 cm wide ep i do te - ca rbona te -c h a 1 c o c i t e - b o r n i t e - m a l a c h i t e v e i n . Sample W88 i s w a l l nock 0.6 m from the con-t a c t , and sample W89 i s 1.5 m from the c on t a c t . Z i n c , copper and ni eke1! 'decrease w i t h d i s tance from the v e i n . Rubidiurn' i s ' 1 owest near t h e ' v e i n ; S t r o n t i urn,-^sur-p r i s i n g l y , is 1owest n e a r ' t h e ve in and appears ' d ep l e ted ' i n amount r e l a t i v e to o the r samples. 5.3.5 Age of the Vein M i n e r a l i z a t i o n Though there are some 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 p resent , a l l o f the s u l p h i d e - r i c h ve ins appear to have, formed penecontempouraneous1y. The ac tua l TABLE IX TRACE ELEMENT ANALYSES FOR VEIN SAMPLES (ppm t p r e c i s i o n ) SAMPLE NO. Zn Cu_ NJ_ £ L ' ' J i t W87 !48.49(±».15) j7364.17(^1227.2) 46.18(10.20) 99 . 8 ( + 0.57 ) 3.06( + 0.26) W88 93.l4(+3.54) 100.27(+2.44) 30.70(+0.19) 199.87( + 0.49) 31.09(^0.06) W89 85.75( +0.82) 98.69(+0.96) 22.72(+0.02) 199.88(10.53) 21 .7 ( + 0.07) OO 129 age of these ve in s can on ly be roughly approx imated. They predate the major f a u l t i n g episodes as evidenced by the s 1 i c k en s i d i n g on some su lph ide sur faces ; but they postdate the North Zone dyke. Th is r e l a t i o n s h i p i s seen near the northern end of the dyke (sample l o c a t i o n W101) where p r e h n i t e - q u a r t z - e p i d o t e -carbonate ve ins w i t h intergrown b o r n i t e and c h a l c o c i t e c r o s s - cu t the dyke ( f i g . 58). These p a r t i c u l a r ve ins resemble those near DDH 16 and they a l s o have equ i v a l en t t r end s . At t h e i r most northern occur rence in the dyke, the ve ins are in the p lane o f the contact between dyke and w a l l rock, but towards the south they d e f i n i t e l y cut through the dyke. If the assumption that the dyke is c o r r e l a t i v e w i t h the ba s i c i n t r u s i v e s in the Haze l ton Group to the south, then the ore ve ins formed in post-Lower J u r a s s i c t imes . Regard less , the m i n e r a l -ized dyke i s s i g n i f i c a n t l y younger than the m i n e r a l i z e d conglomerates, i n d i c a -t i n g a s u b s t a n t i a l time i n t e r v a l between fo rmat ion o f the vol c a n i e l a s t i c p i l e and the m i n e r a l i z i n g ep i sode. 5.4 Opaque Mineralography In t h i s s e c t i o n the d e t a i l e d t e x t u r a l and minera1ographic fea tu re s of the opaque m ine ra l s s t ud i ed in po l i s hed s e c t i o n are de s c r i bed . These s tud ie s are important because they de f i ne a paragenet i c sequence f o r ore m i n e r a l i z a t i o n . 5.4.1 Magnet i te (and l lmen i te ) Magnet i te i s ub iqu i tous through the e n t i r e upper member of the Moosevale Formation and everywhere appears pyrogen ic . It i s present as an i n t e r s e r t a l o r i n t e r g r a n u l a r phase in v o l c a n i c c l a s t s , or as d e t r i t a l g ra in s in a f i n e f r a c t i o n to l a rge c l a s t s . Genera l l y the c l a s t magnetites are le s s a l t e r e d , l a r g e r , and more euhedral than are the d e t r i t a l ones. The magnetites formed e a r l y in the c r y s t a l l i z a t i o n sequence of the v o l c a n i c s as shown by g ra in s which appear to f o rm-nuc le i f o r the c r y s t a l l i z a t i o n of g l omeropo rphy r i t i c masses of aug i te s in some c l a s t s . 130 F igure 5 8 : P r e h n i t e - q u a r t z - ep i do t e - c a r bona te v e i n , w i th c h a l c o c i t e and b o r n i t e , c u t t i n g the North Zone dyke. In t h i s f i g u r e , the dyke i s the lower p l a t e to v e i n i n g , w h i l e country rock i s the upper p l a t e . The t h i c k e s t ve in is about 4 cm wide. F igure 5 9 : D e t r i t a l magnetite bed. These magnetite g ra in s are r e l a t i v e l y una l te red and show only s ub t l e rounding. These gra ins average about . 1 5 mm in d iameter. 131 Ra re d e t r i t a l m a g n e t i t e s can be seen i n hand s p e c i m e n . But g e n e r a l l y t h e g r a i n s a r e t o o s m a l l , though a s l i g h t a t t r a c t i o n o f a magnet i s some-t i m e s s e e n . One i n t e r e s t i n g r a r e f e a t u r e ( p r e s e n t i n o n l y 3 p l a c e s i n a l l 3000 f t o f c o r e - ' ) i s bands o f d e t r i t a l m a g n e t i t e s . These bands a r e a c t u a l l y s m a l l , 2 t o 3 cm t h i c k , beds o f m a g n e t i t e g r a i n s , w i t h m i no r p r i m a r y h e m a t i t e g r a i n s , i n sandy p o r t i o n s o f t h e v o l c a n i c 1 a s t i c s . F i g . 59 i s a p h o t o m i c r o g r a p h o f one s u c h bed w i t h m a g n e t i t e g r a i n s t h a t a v e r a g e 0.15 mm i n d i a m e t e r and h e m a t i t e s t h a t a v e r a g e 0.12 mm i n d i a m e t e r . G r a i n s o f bo t h o x i d e s a r e e u h e d r a l t o s u b h e d r a l . The se m a g n e t i t e bands p r o b a b l y " r e p r e s e n t f o s s i l p l a c e r d e p o s i t s . M a g n e t i t e i n c l a s t s has two ma in f o r m s ; as l a r g e w e l l d e v e l o p e d c r y s t a l s , and more commonly as s m a l l e r , more i r r e g u l a r ( i n shape) i n t e r g r a n u l a r g r a i n s ' . The l a r g e e u h e d r a l g r a i n s a r e up t o 1.2 mm i n d i a m e t e r , but g e n e r a l l y a v e r a g e 0.1 t o 0.2 mm. C l e a v a g e , shown by t r i a n g u l a r p i t t i n g , o r t w i n n i n g , i s some-t i m e s o b s e r v e d . A s 1 i g h t ' m a r t i t i z a t i o n i s p r e s e n t i n r a r e m a g n e t i t e g r a i n s , w h e r e i n s m a l l b l a d e s o f h e m a t i t e o v e r g r o w t h e m a g n e t i t e . The i n t e r g r a n u l a r g r a i n s a r e s u b h e d r a l t o a n h e d r a l and u s u a l l y a p p e a r as d i s s e m i n a t i o n s b e t -ween f e l t e d , g roundmass p i a g i o c l a s e s . The se g r a i n s a r e most o f t e n < 0.02 mm in d i a m e t e r . D e t r i t a l m e g n e t i t e g r a i n s a r e abou t t h e same s i z e and shape as t h o s e i n t h e g r oundmas s , howeve r , f r a c t u r e d e d g e s , o r i n r a r e c a s e s r o u n d i n g , a r e more common, i n d e t r i t a l g r a i n s . A l l m a g n e t i t e s have a t l e a s t a m i n o r t i t a n i u m c o n t e n t . F i g . 60 i s a . s c a n -n i n g e l e c t r o n mi c r o ' s c ope p h o t o m i c r o g r a p h o f a - m a g n e t i t e and e l e m e n t a l s c a n s o f two d i f f e r e n t m a g n e t i t e s a m p l e s . As can be s e e n , t i t a n i u m i s a' component i n b o t h . In a r e a s o f s t r o n g m e g n e t i t e c o n c e n t r a t i o n , r a r e i l m e n i t e g r a i n s a r e s e e n , but f most i m p o r t a n t l y some l a r g e m a g n e t i t e s have ' e x s o l u t i o n l a m a l l a e 1 o f i l m e n i t e A c c o r d i n g t o B u d d i n g t o n and L i n d s l e y ( 1 9 6 4 ) , l a m a l l a e o f t h i s t y p e a r e due t o o x i d a t i o n o f an o r i g i n a l i1 m e n i t e - m a g n e t i t e s o l i d s o l u t i o n , r a t h e r t h a n t h e u n m i x i n g o f a s o l i d s o l u t i o n . F igure 60: Scanning e l e c t r o n photomicrograph of a magnet ite in sample 8 8 E 2 w i th elemental scans of t h i s magnetite and another from sample W33. Both scans i n d i c a t e a t i t a n i u m component to the magnet i te . The magnetite i n W33 a l s o has a t r a ce amount of copper. The p l a t e i s about .09 mm ac ro s s . 133 The f r e she s t magnet i te i s in areas of low su l ph i de con ten t , but even the most una l te red magnet ites have f r a c t u r e s in them which are f i l l e d w i th carbonate or some o the r gangue. There is a p rog radat ion of magnetite a l t e r a -t i o n seen w i t h i n c r ea s i n g s u l ph i de content . With t r a c e amounts o f s u l p h i d e , the magnetites show on ly minor a l t e r a t i o n , however, as the su lph ide content increases the magnet i tes become s k e l e t a l in form and u l t i m a t e l y they are t o t a l l y rep laced by gangue, l eav i ng on ly a pseudomorphic s k e l e t a l o u t l i n e where su lph ides are most abundant. The s k e l e t a l magnetites are a l t e r e d mainly by sphene, w i t h ep ido te and carbonate (+quartz). The pseudomorphed ske letons are t o t a l l y rep laced by carbonate and sphene, and commonly are surrounded by wispy haloes o f secondary hemat i te . Magnet i te i s intergrown w i t h p y r i t e , c h a l c o p y r i t e , c h a l c o c i t e , b o r n i t e , d i g e n i t e , c o v e l l i t e , o r secondary hemat i te. Gene ra l l y the su lph ides occur as a f i l l i n g of c racks in the magnet ite g r a i n s , w i t h on ly p y r i t e , c h a l c o c i t e and hemat i te a c t u a l l y developed on magnet i te. Su lph ide s , e s p e c i a l l y p y r i t e , form overgrowths on s k e l e t a l r e l i c t magnetite g r a i n s . 5.4.2 C h a l c o c i t e The d e s c r i p t i o n of c h a l c o c i t e occurrence i s d i v i d e d i n t o two p o r t i o n s ; c h a l c o c i t e in ore l en se s , and c h a l c o c i t e in m i n e r a l i z e d ve i n s . Th is d i v i s i o n was made so that comparison of c h a l c o c i t e forms between these two ore depos i t types cou ld be ach ieved . 5.4.2(a) C h a l c o c i t e in Ore Lenses C h a l c o c i t e , where p r e s e n t . i n po l i shed s e c t i o n s , ranged from 0.15 to 10 volume percent . The most common mode.of occurrence o f c h a l c o c i t e , is i n t e r -serta.l in the mat r i x of host vol can i c l ast i c rocks , but commonly small amounts of c h a l c o c i t e are d i s seminated in la rge l i t h i c c l a s t s . C h a l c o c i t e g ra in s occur in s i x main forms of the above two modes. These forms are c h a r a c t e r i s -t i c of a l l su lph ides and n a t i v e copper, and a s i n g l e ore minera l can occur in severa l forms in a s i n g l e hand specimen. The forms are d i scus sed in order 134 of dec reas ing importance. The l a r ge s t c h a l c o c i t e g ra i n s are present w i th quartz and carbonate, i n t e r s e r t a l to sand s i z e g ra in s of the mat r i x component. Th i s t e x t u r e seems to have developed as a r e s u l t of cementation of a porous and permeable sand s i z e host by p r e c i p i t a t i o n o f ore and metamorphic minera l s in vo ids ( f i g . 61). The c h a l c o c i t e g ra in s having t h i s form are up to 2 mm in d iameter , and aver -age around 0.3 to 0.4 mm in d iameter . The l a r ge r g ra ins are i r r e g u l a r in form, but g e n e r a l l y have some s t r a i g h t edges. Commonly groups o f l a r ge c h a l -c o c i t e g ra i n s have i n d i v i d u a l g ra in s in terconnected by small v e i n l e t s of c h a l -c o c i t e which cut through the e n c l o s i n g gangue. Edges of such g r a i n s are norma l l y s e r r a t e . If the pore i s not l a r g e , t r a i n s of these smal l m ic rove i r i -l e t s may spread from a c e n t r a l l a r g e r g r a i n . In other pores the l a rge c h a l -c o c i t e g r a i n may be c e n t r a l to numerous, sma l l e r (< 0.01 mm in d iameter) blebs of c h a l c o c i t e . One la rge c h a l c o c i t e g r a i n had mic rove in1et s extend ing from i t s main mass and c r o s s - c u t t i n g ne ighbour ing l i t h i c c l a s t s . Th i s form of c h a l c o c i t e i s c h a r a c t e r i s t i c s o f the r i c h e s t s ec t i on s of ore l en se s . The second most important form, found in low ore grade areas and a l s o w i t h the vo id f i l l i n g s , are as s m a l l , d i s seminated b lebs . These b lebs are rounded in nature and are spread throughout the mat r i x . T h e i r s i z e ranges from 0.004 to 0.1 mm in d iameter , averag ing 0.01 to 0.02 mm. A s u b s i d i a r y type of t h i s form is found wherein the small blebs are concent rated in a cen-t r a l area ( f i g . 62). These areas a re mainly in gangue-f i11ed pores , o r in p l a g i o c l a s e c r y s t a l s in the mat r i x ( f i n e f r a c t i o n ) . The b lebs are o f equ i v a -l en t s i z e as the w ide l y d i s seminated ones, and the c oncen t r a t i o n areas are 0.1 - 0.5 mm in d iameter . In the r i c h e s t copper zones, another t ex tu re that i s e x h i b i t e d l o c a l l y , i s a network or r e t i c u l a t e t e x tu re in which small d e t r i t u s is enmeshed in a network of c h a l c o c i t e . Gene ra l l y the c h a l c o c i t e forms a long g r a i n boundaries when the d i s t ance between g ra in s is smal l ( i e . on the order of 0.01 mm). 135 F igure 6 l : S t ra ight -edged c h a l c o c i t e g ra in s as v o i d - f i l l i n g s in f i n e f r a c t i o n of conglomerate. The c h a l c o c i t e here is i n t e r grown w i t h qua r t z . The g reen i sh ma te r i a l w i th the h ighest r e f r a c t i o n is l i t h i c c l a s t s . This s e c t i o n is about 2 mm across F igure 62: Blebs of c h a l c o c i t e concentrated in a qua r t z -f i l l e d pore. In the upper l e f t - h a n d corner a small magnetite g ra i n is v i s i b l e . This s e c t i o n is 2 mm ac ro s s . 136 The . l a r ge s t networks have widths of 0.5 mm, but average 0.1 to 0.3 mm. Although c h a l c o c i t e i s most abundant in the mat r i x o f the v o l c a n i c -l a s t i c s , some does occur in the la rge c l a s t s . C l a s t s which conta in c h a l c o -c i t e most commonly have a d e f i n i t e p o r p h y r i t i c t e x t u r e w i t h p l a g i o c l a s e in a c r y p t o c r y s t a 1 1 i n e groundmass. C h a l c o c i t e in c l a s t s i s p r e f e r e n t i a l l y in the groundmass pa r t o f a c l a s t adjacent to a zone o f m i n e r a l i z e d f i n e f r a c t i o n . Another form of c h a l c o c i t e in large c l a s t s i s as smal l replacement patches in p l a g i o c l a s e phenocrys t s . Th is form is present in c h a 1 c o c i t e - r i c h zones where the l i t h i c c l a s t s c on ta i n la rge phenocrysts . In ra re cases the c h a l c o c i t e occurs as se lvages and/or complete rims to the phenocrys t s . A form found both in mat r i x ( f i n e f r a c t i o n ) and les s commonly in c l a s t s , is m i c r o v e i n l e t s of c h a l c o c i t e . These v e i n l e t s mainly c r o s s - cu t small gangue patches or g ra in s in a m a t r i x , but are a l s o seen to cut through c l a s t s , or even phenocrysts in the c l a s t s . Width of these f ea tu re s i s 0.01 to 0.1 mm, averag ing 0.05 mm, w h i l e the length i s u s u a l l y 0.1 mm but can be up to 1 mm. F i g . 6 3 i s a scanning e l e c t r o n microscope (SEM) photomicrograph and elemental scan o f a l a rge c h a l c o c i t e g r a i n intergrown w i t h gangue. F i g . 64 shows the sma l l e r rounded b l e b - l i k e form and la rge i n t e r s e r t a l form of c h a l -c o c i t e . C h a l c o c i t e i s commonly in contact w i t h magnet i te . The main t e x t u r e form of the two i s as overgrowths of c h a l c o c i t e on magnet i te or as i r r e g u l a r replacements of magnet i te by c h a l c o c i t e . C h a l c o c i t e l o c a l l y f i l l s f r a c t u r e s in magnet i te but has not a c t i v e l y rep laced magnet i te . In zones of g r ea te s t c h a l c o c i t e c o n c e n t r a t i o n , some b o r n i t e i s g e n e r a l l y p resent , most commonly intergrown w i th c h a l c o c i t e . The v a r i e t y of tex tu re s e x h i b i t e d by these two minera l s range from s imple g r a i n boundary contact s to i n t r i c a t e myrmek i t i c i n te rg rowths . The myrmek i t i c intergrowths are most com-monly present in the l a r ge s t g ra ins in the mixed s u l ph i de a rea. This type of t e x t u r e is found where one su lph ide is in a much g rea te r abundance than 137 13C3 Figure 6 3 : Scanning e l e c t r o n photomicrograph, w i t h elemental scan, of a c h a l c o c i t e g r a i n in sample 13C3• The c h a l c o c i t e ( l i g h t grey) i s e x t e n s i v e l y intergrown w i th gangue (dark g rey ) . The elemental scan is fo r a p o r t i o n o f the c h a l c o c i t e (j_e. not w i t h gangue). This p l a t e i s about .4 mm ac ro s s . 138 F i g u r e 64: S c a n n i n g e l e c t r o n p h o t o m i c r o g r a p h o f c h a l c o c i t e b l e b s and a l a r g e r c h a l c o c i t e g r a i n . The c h a l c o c i t e i s l i g h t g r e y . Note the rounded n a t u r e o f the b l e b s . T h i s s e c t i o n i s about 0.04 mm a c r o s s . 139 the o t he r . Intergrowths of c h a l c o c i t e and na t i ve copper are not common, but do occur . Most t y p i c a l l y these t ex tu re s are in areas of high n a t i v e copper content , w i t h sma l l e r amounts of c h a l c o c i t e . Gene ra l l y c h a l c o c i t e occurs as smal l g ra in s i n . c o n t a c t w i t h a much l a r g e r n a t i v e copper g r a i n . Sometimes c h a l c o c i t e rims n a t i v e copper g r a i n s . In one area small i n c l u s i o n s of c h a l c o c i t e occur red in a l a rge na t i v e copper g r a i n and v i c e ve r sa . Minute c h a l c o c i t e and na t i v e cop-per b lebs are sometimes concent rated in a s i n g l e gangue pa t ch , but not in contact w i t h each o the r . Age r e l a t i o n s between the two minera l s are very d i f f i c u l t to determine but i t appears that n a t i v e copper format ion very s l i g h t l y p re -dates that of c h a l c o c i t e . C h a l c o c i t e and c h a l c o p y r i t e are never found in d i r e c t c on t a c t . The two m ine ra l s r a r e l y occur together in a:si:ngl.e specimen and i f so are not i n t e r -grown. In on ly one p l ace was c h a l c o c i t e observed in contact w i t h p y r i t e . In t h i s case a m i n i s c u l e g r a i n of p y r i t e (< 0.01 mm) was growing w i t h smal l c h a l c o c i t e g ra in s in a s t rong secondary hematite a rea . C h a l c o c i t e i s intergrown e x t e n s i v e l y w i t h d i g e n i t e , even more so than w i t h b o r n i t e . C h a l c o c i t e and d i g e n i t e very commonly occur t oge the r , and most c h a 1 c o c i t e - r i c h areas have at l e a s t a minor d i g e n i t e component. T y p i c a l -l y - a c h a l c o c i t e g r a i n w i l l c on ta i n a patch of d i g e n i t e w i t h s m a l l , t h i n (< 0.05 mm in width) needles of d i g e n i t e l amel lae extending from the patch i n t o the c h a l c o c i t e host ( f i g . 65) . Ne i ther the needle-1amel1ae nor the d i g -e n i t e patch need occur in the same c h a l c o c i t e g r a i n . These l ame l l ae can account f o r up to 50 percent of the c h a 1 c o c i t e - d i g e n i t e g r a i n , but a re gen-e r a l l y le s s than 10 percent . In on l y one case was a myrmek i t i c in terg rowth o f the two seen: here wavy pa t te rn s o f a l t e r n a t i n g d i g e n i t e and c h a l c o c i t e were present in a s i n g l e g r a i n (sample W104). The c h a 1 c o c i t e - d i g e n i t e g ra in s in v iew o f the l ame l l ae and myrmek i t i c t e x t u r e s , appear to be due to unmix-ing o f a former s o l i d s o l u t i o n ( i e . they are penecontemporaneous). S i m i l a r 140 F igure 65: Th i n , exso lved d i g e n i t e l a th s in c h a l c o c i t e . The c h a l c o c i t e is whi te and d i g e n i t e appears as the very t h i n b lue l a ths c u t t i n g through the c h a l c o c i t e mass. P i n k i s h b o r n i t e is in contact w i th the c h a 1 c o c i t e - d i g e n i t e g r a i n . Gangue appears as the brown mate r i a l in the p l a t e . This s e c t i o n i s 0.46 mm ac ro s s . F igure 66: Typ i ca l c h a l c o c i t e hab i t i n a qua r t z - ca rbonate v e i n . Quartz and carbonate are the green background. The c h a l c o c i t e here has very we l l developed s t r a i g h t edges. The minute b lue g ra in s are composed of intergrown d i g e n i t e and c o v e l l i t e . This s e c t i on is 2 mm ac ro s s . 141 types of e x s o l u t i o n tex tu res have been de sc r i bed by B r e t t (1964) f o r c h a l c o -c i t e - b o r n i t e s o l i d s o l u t i o n s . Very r a r e l y , in on ly one sample, a re c h a l c o c i t e and c o v e l l i t e found in c o n t a c t , in t h i s case i t was a s imple g r a i n boundary con tac t . Both minera l s occur together commonly but in terg rowth tex tu re s are not present . Cup r i t e i s intergrown w i t h c h a l c o c i t e r a r e l y . The c u p r i t e is an o x i d a t i o n of the c h a l -c o c i t e , and they are on ly found together where na t i v e copper i s p resent . C h a l c o c i t e and g reenock i te never occur together . Secondary hematite i s q u i t e f r e q u e n t l y , complexly intergrown w i t h c h a l -c o c i t e . In f a c t a s u b t l e redd i sh t i n ge i s imparted to the r i c h e s t c h a l c o c i t e zones by the presence of t h i s hemat i te . These intergrowth tex tu re s w i l l be de sc r i bed f u r t h e r in the hematite s e c t i o n below. 5.4.2(b) C h a l c o c i t e in Veins W i th i n ve in s c o n t a i n i n g s u l p h i d e s , the most s i g n i f i c a n t ore form is as network masses. These are q u i t e o f t en l a rge in s i z e , up to a maximum of 5 cm ac ro s s . Large g r a i n s , up to 0.5 mm ac r o s s , w i t h s t r a i g h t edges are a l s o f r e -quent l y seen ( f i g . 66). These s t r a i g h t - edged g ra in s l o c a l l y occur at the con tac t between quar tz and carbonate gangue and g e n e r a l l y are i n te rconnected by m i c rove in1e t s of s u l ph ide s . Smal le r (< 0.1 mm in d i amete r ) , b l e b - l i k e g ra in s a re d i s seminated through the v e i n gangue. When the host rock to one of these ve ins i s observed, the su lph ides are g e n e r a l l y found to extend i n t o the hos t , main ly as d i s semina t i on s o f smal l i r r e g u l a r g r a i n s , or as small m i c r o v e i n l e t s . B o r n i t e appears to equa l , or s l i g h t l y surpass , the amount of c h a l c o c i t e in these v e i n s . T yp i c a l t ex tu re s present in the ve ins a re ; myrmek i t ic i n t e r -growths o f b o r n i t e and c h a l c o c i t e , and patches and n e e d l e - l i k e l ame l l ae o f d i g e n i t e and c h a l c o c i t e . C o v e l l i t e i s le s s commonly seen w i th c h a l c o c i t e , and ma l ach i t e is present as a l t e r a t i o n haloes around some c h a l c o c i t e g r a i n s . 142 5 - 4 . 3 B o r n i t e 5 . 4 . 3 ( a ) B o r n i t e i n Ore Lenses . The r a t i o o f c h a l c o c i t e t o b o r n i t e i s a round 6 0 : 4 0 . B o r n i t e fo rms a r e much t h e same as t h o s e o f c h a l c o c i t e , e x c e p t t h e r e a r e n ' t as many s t r a i g h t -edged g r a i n s , nor as many s m a l l d i s s e m i n a t e d g r a i n s . T h e r e a r e two main t y p e s o f b o r n i t e p r e s e n t w i t h one t y p e h a v i n g two s u b g r o u p s . Each t y p e has d i s t i n c -t i v e t e x t u r e s , c o l o u r s and i n t e r g r o w t h s w i t h o t h e r s p e c i f i c s u l p h i d e s . The most common t y p e o f b o r n i t e ( b o r n i t e I) i n c h a l c o c i t e - r i c h a r e a s has a p i n k c o l o u r and l a c k s c h a l c o p y r i t e e x s o l u t i o n l a m a l l a e . T h i s p i n k b o r n i t e l o c a l l y i s i n t e r g r o w n c h a l c o c i t e , o f t e n t i m e s w i t h m y r m e k i t i c t e x t u r e s ( f i g . 67) . Some o f t h i s i n t e r g r o w n c h a l c o c i t e c o n t a i n s e x s o l v e d l a m a l l a e d i g e n i t e . A l s o v e r y r a r e l y d i g e n i t e has a m y r m e k i t i c t e x t u r e w i t h t h i s b o r n i t e . C h a l c o c i t e and p r i m a r y d i g e n i t e a r e not p r e s e n t i n t h e same b o r n i t e g r a i n e x c e p t where d i g e n i t e has e x s o l v e d f r om c h a l c o c i t e . D i g e n i t e i s a l s o a v e r y common r e p l a c e -ment m i n e r a l o f t h e s e b o r n i t e s . Most o f t e n the d i g e n i t e a l t e r a t i o n may be i n t e r g r o w n w i t h t h e s e g r a i n s . In o t h e r a r e a s , d i g e n i t e may f o r m a t h i n wedge a t t h e c o n t a c t between c h a l c o c i t e and b o r n i t e i n a g r a i n . V e r y l a r g e b o r -n i t e g r a i n s commonly have d i g e n i t e r ims and s e l v a g e s a l o n g f r a c t u r e s w h i c h c u t t h r o u g h t h e g r a i n . I f t h e d i g e n i t e r e p l a c e m e n t a r e a becomes l a r g e , r o s e t t e s o f c o v e l l i t e o c c u r r e p l a c i n g t h e d i g e n i t e . R a r e l y , m i c r o v e i n 1 e t s o f d i g e n i t e i n vade t he b o r n i t e h o s t f r o m the main d i g e n i t e mass. The second b o r n i t e t y p e ( b o r n i t e I I ) i s d i s t i n g u i s h e d by r e g u l a r e x s o l -u t i o n l a m a l l a e o f c h a l c o y r i t e ( f i g . . 6 ' 8 ) . These l a m a l l a e a r e a p p r o x i m a t e l y 0 .002 mm w i d e and 0.04 mm l o n g . T h i s e x s o l u t i o n t e x t u r e a p p e a r s c o h e r e n t i n n a t u r e , w h i c h as d e f i n e d by B r e t t (1964, p.1244) o c c u r s when " t h e r e i s l a t t i c e c o n t i n u i t y a c r o s s t h e i n t e r f a c e between e x s o l v i n g phase o f h o s t p h a s e " . In t h e c a s e o f t h e s e b o r n i t e s , t h e c h a l c o p y r i t e l a m a l l a e e x i s t s . a s r e g u l a r , s t r a i g h t , l a t h s w h i c h o c c u r a l o n g w e l l - d e f i n e d p l a n e s w i t h i n t h e h o s t b o r n i t e . B o r n i t e II can be d i v i d e d i n t o two s u b g r o u p s ; t he ma jo r one h a v i n g a y e l l o w -143 Figure 67: Myrmek i t i c intergrowth of c h a l c o c i t e in b o r n i t e . The bo r n i t e is l i g h t pink in c o l ou r and forms the background in t h i s p l a t e . The c h a l c o c i t e i s wh i t e . This s e c t i o n i s 2 mm acros s . F igure 68: B o r n i t e w i t h exso lved c h a l c o p y r i t e l a th s and supergene development of d i g e n i t e . The b o r n i t e i s y e l l o w i s h -pink and the d i g e n i t e is l i g h t b l ue . C h a l c o p y r i t e l a ths are best seen in d i g e n i t e . The d i g e n i t e was produced by o x i d a t i o n of b o r n i t e . Dark blue patches are c o v e l l i t e which has replaced d i g e n i t e . This s e c t i on is 0.46 mm ac ro s s . 144 i s h -p i nk co l ou r and u sua l l y up to 8 volume percent c h a l c o p y r i t e l ama l lae ( bo rn i t e l l a ) , the secondary group are y e l l o w e r in co lou r and can have g rea te r than 8 percent c h a l c o p y r i t e l ama l lae ( b o r n i t e l i b ) . C h a l c o p y r i t e is a l s o p re -sent l o c a l l y as s imple g ra ins in contact w i t h b o r n i t e g r a i n s . Ne i the r of these groups is found in contact w i t h c h a l c o c i t e . . Gra ins of b o r n i t e l l a that l o c a l l y c o n t a i n no c h a l c o p y r i t e l ama l l ae , are in many cases p a r t l y replaced by d i g e n i t e . The d i g e n i t e g e n e r a l l y takes the form of rims around g r a i n s , or se lvages on f r a c t u r e s in g r a i n s . Where the d i g e n i t e i s p a r t i c u l a r l y abundant as patches r e p l a c i n g b o r n i t e , c o v e l l i t e i s intergrown w i t h the d i g e n i t e . Replacement may be so ex ten s i ve in p laces that c h a l c o p y r i t e l ama l l ae are seen in d i g e n i t e (+ c o v e l l i t e ) patches in b o r n i t e g ra in s where the b o r n i t e has been t o t a l l y rep laced ( f i g . 6 8 ) . In b o r n i t e l l b c h a l c o p y r i t e e x s o l u t i o n has gone to the stage where c h a l -c o p y r i t e forms rounded blebs or l a r ge r i r r e g u l a r blades in b o r n i t e ( i e . reached the stage of noncoherence as in f i g . 69). In i t s most intense form t h i s non-coherent e x s o l u t i o n y i e l d s almost myrmek i t i c intergrowths of b o r n i t e and c h a l -c o p y r i t e . U s u a l l y i t i s e x h i b i t e d by f a t t e r b l a d e - l i k e l ama l l ae . Very r a r e l y d i g e n i t e exso l ves w i t h some of these blades and forms complete rims around the c h a l c o p y r i t e blades in the host b o r n i t e . (Cha1 c o p y r i t e - d i g e n i t e e x s o l u -t i o n in b o r n i t e has been desc r ibed by Morimoto e_t a_l_. (1959)) • These bo rn i t e s are strong1y rep 1aced by d i g e n i t e and c o v e l l i t e , which mainly occur as i r r e g u -l a r patches. C o v e l l i t e is b e t t e r developed in b o r n i t e l l b than in any o the r type and f r e q u e n t l y occurs a f t e r these b o r n i t e s ( l i b ) w i thout d i g e n i t e . No b o r n i t e i s found in c on tac t , or even in the same general l o c a l e , as p y r i t e , n a t i v e copper or g reenock i t e . B o r n i t e l o c a l l y has overgrown magnet ite and i s commonly i n t i m a t e l y intergrown w i t h secondary hemat i te . 5.4.3(b) B o r n i t e in Veins R e l a t i o n s h i p s of b o r n i t e and o ther su lph ides in ve ins are comparable to those seen in the ore lenses- The three types of b o r n i t e are present in v e i n s . 145 F igure 69: Noncoherent e x s o l u t i o n of c h a l c o p y r i t e in bo r n i t e l l b . The bo rn i t e i s p i n k i s h . The c h a l c o p y r i t e occurs as rounded b lebs w i t h i n the b o r n i t e mass. D i gen i te and minor c o v e l l i t e (blue co lour ) occur as selvages on f r a c tu re s c u t t i n g the b o r n i t e mass, due to supergene o x i d a t i o n . This s e c t i o n i s 1 mm ac ro s s . 146 Bo rn i t e I has no c h a l c o p y r i t e l ama l lae and is the on ly b o r n i t e type i n t e r -grown w i th c h a l c o c i t e . The b o r n i t e l l a and l l b are a l s o p resent . In some massive b o r n i t e Mb g r a i n s , the d i g e n i t e envelopes to c h a l c o p y r i t e l ama l lae are w e l l developed. D i g e n i t e a l s o occurs commonly as rims and selvages on f r a c t u r e s in these l a r ge bo rn i t e s l i b . C o v e l l i t e i s present as rims and se lvages on f r a c t u r e s where d i g e n i t e is not p resent . 5.4.4 Nat i ve Copper Nat i ve copper i s best developed as network masses in the mat r i x of the host vol c a n i c l a s t i c s . These networks are up to 0.5 to 1 cm wide. Copper a l s o occurs as vo id f i l l ins and/or small d i s seminated (< 0.01 mm) g r a i n s . Another common t ex tu re i s as minute g ra i n s ( "dust " ) d i s seminated in a l t e r e d f e l d s p a r phenocrysts of l a r ge c l a s t s . If there is a l a rge amount of copper, i t some-times rims and enc loses phenocrys t s , replaces phenocrysts and even surrounds e n t i r e c l a s t s . S e r r a te edges are found on the i n te rmed ia te s i z e d g ra in s . ( i e . 0.01 to 0.02 mm). Copper g ra in s g e n e r a l l y have c u p r i t e rims complete ly surrounding the g r a i n . F i g . 70 i s a scanning e l e c t r o n microscope photomicrograph of one such g r a i n and r im. A s i de from the c u p r i t e , n a t i v e copper i s on l y found in contact w i t h c h a l c o c i t e . D i g e n i t e and/or c o v e l l i t e may be present in the same sec-t i o n as n a t i v e copper but n a t i v e copper i s nowhere in contact w i th these s u l -ph ides . Na t i ve copper i s ra re i n . ve i n s and i s on ly seen in those w i t h no b o r n i t e , p y r i t e , c h a l c o p y r i t e o r g r eenock i t e . C u p r i t i c rims to n a t i v e copper are com-mon in v e i n s . 5.4.5 C h a l c o p y r i t e C h a l c o p y r i t e m i n e r a l i z a t i o n is present in th ree main s e t t i n g s . The most notab le occurrence i s where other copper su lph ides are p resent . In t h i s case c h a l c o p y r i t e i s a minor phase o c c u r r i n g as t h i n l a th s in b o r n i t e . However c h a l c o p y r i t e may a l s o be present in these areas as l a r ge r masses having mutual F igure 70: Nat ive copper g r a i n w i t h c u p r i t e r im. The na t i ve copper i s the l i g h t grey mate r i a l in the cen t re o f the mass and c u p r i t e i s the s l i g h t l y darker grey r im. This scanning e l e c t r o n photomicrograph i s about O.kS mm ac ro s s . 148 g r a i n boundaries w i th b o r n i t e . Small (< 0.01 to 0.1 mm) i r r e g u l a r shaped b lebs of c h a l c o p y r i t e are u s u a l l y s c a t t e r ed through the groundmasses too. C h a l c o p y r i t e is a l s o intergrown w i t h d i g e n i t e and/or c o v e l l i t e , where these two l a t t e r minera l s have rep laced b o r n i t e . The second type of c h a l c o p y r i t e occurrence is the case where c h a l c o -p y r i t e i s the dominant s u l ph i de . The l a r ge s t g r a i n s , up to 0.5 mm in d i a -meter a re in these zones. The major t e x tu re f o r c h a l c o p y r i t e here i s as la rge network masses in sand s i z e mat r i x of v o l c a n i c l a s t i c conglomerates. Cha lco -p y r i t e a l s o occurs as l o c a l vo id f i l l i n g s , masses in and around phenocrysts in l a r ge c l a s t s ( f i g . 7 1 ) , m i c r o v e i n l e t s c r o s s - c u t t i n g c l a s t s or t h e i r pheno-c r y s t s , and as sma l le r d i s seminated g r a i n s . In one case c h a l c o p y r i t e was observed in a quar tz amygdule ( f i g . 72). C h a l c o c i t e is nowhere present in c h a l c o p y r i t e - r i c h zones, and d i g e n i t e and c o v e l l i t e are on ly r a r e l y present in such zones. Greenock i te occurs s p o r a d i c a l l y in cha1 c o p y r i t e - r i c h zones and has a mutual g r a i n boundary t e x t u r e w i t h c h a l c o p y r i t e . L imon i te commonly rims c h a l c o p y r i t e g r a i n s . P y r i t e was seen in contact w i t h c h a l c o p y r i t e in on ly one example. The f i n a l type of c h a l c o p y r i t e m i n e r a l i z a t i o n i s as ra re minute g ra in s w i t h i n p y r i t i c zones. The c h a l c o p y r i t e i s present as s m a l l , < 0.01 mm, w ide l y separated g r a i n s . D i r e c t contact w i t h p y r i t e is r a r e . 5.4.6 P y r i t e Amount of p y r i t e in the po l i s hed s ec t i on s s t ud i ed , v a r i e d from a very smal l t r a c e to over 25 volume percent . The p y r i t e occurs in seve ra l forms. Most commonly p y r i t e occurs as i r r e g u l a r l y shaped g r a i n s , up to 0.6 mm in d iameter but averaging 0.1 to 0.2 mm, i n t e r s e r t a l to sand s i z e ma t r i x g r a i n s . These p y r i t e g ra in s t y p i c a l l y form net or mesh textu res where p y r i t e i s abundant. Smal ler < 0.01 mm in d iameter , rounded blebs of p y r i t e are a l s o t y p i c a l l y d i s seminated through the mat r i x of v o l c a n i c l a s t i c conglomerates. These b lebs are the t y p i c a l form of p y r i t e in i t s areas of low c o n c e n t r a t i o n . 149 Figure Jl: Cha l c opy r i t e o c c u r r i n g as i n t r a -phenoc r y s t mate r i a l in the groundmass of a l i t h i c c l a s t . The s i l i c a t e phenocrysts are the r e f r a c t i v e brownish g r a i n s . This s e c t i o n i s about 2 mm ac ro s s . F igure 72: C h a l c o p y r i t e in a quartz amygdule. Sec t i on is 4 mm ac ro s s . • 150 P y r i t e occurs in c l a s t s , too, where i t rep laces the groundmass or c r o s s - c u t s phenocrys t s . Textures i n d i c a t e that the p y r i t e i s in l a r ge par t superimposed upon the host v o l c a n i c l a s t i c rocks as are copper s u l p h i d e s . However very r a r e l y cubes of p y r i t e are present in l i t h i c c l a s t s , and may represent an e a r l i e r stage of p y r i t e m i n e r a l i z a t i o n . But, no p y r i t e i s found as cubes in la rge c l a s t s except where the re i s o ther evidence of a superimposed m i n e r a l i z i n g event. Thus, i t seems u n l i k e l y that much, i f any, p y r i t e predates the main m i n e r a l -i z i n g episode that inc ludes copper s u l p h i d e s . When p y r i t e e x h i b i t s s t rong net t e x t u r e s wrapping around and between mat r i x g r a i n s , broad d i f f u s e l i m o n i t i c haloes a re o f t en developed through the remainder of the host rock. DDH 25, which almost is t o t a l l y p y r i t i c , con ta in s areas of intense l i m o n i t i c a l t e r a t i o n . P y r i t e is g e n e r a l l y a s o l i t a r y s u l -phide in ra re contac t w i t h on ly c h a l c o p y r i t e . Rare t races of p y r i t e occur in the same areas as c h a l c o p y r i t e , b o r n i t e or g r e e n o c k i t e , but s t rong concen-t r a t i o n s o f p y r i t e g e n e r a l l y are devoid of copper m ine ra l s . P y r i t e may have rep laced margins of magnetite g r a i n s , or have overgrown gangue pseudomorphic a f t e r magnet i te . Genera 11y where in contact w i t h magnet i te, p y r i t e f i l l s f r a c t u r e s or has g r a i n boundary contact s w i t h the outer margins of the magne-t i t e gra i ns . P y r i t e i s r a re in ve i n s . Where p re sen t , the p y r i t e is very s u b s i d i a r y to other su lph ide s and i s not in contact w i t h them. L o c a l l y ve ins are pure p y r i t e . 5.4.7 D i gen i t e D i g e n i t e ' s most common occurrences a r e , a ga i n , as e x s o l u t i o n w i t h c h a l -c o c i t e , replacements of b o r n i t e , and minor e x s o l u t i o n w i t h b o r n i t e . D i gen i t e is a l s o present to a minor extent as small (< 0.01 to 0.1 mm), s o l i t a r y d i s -seminat ions in c h a 1 c o c i t e - b o r n i t e areas. C o v e l l i t e is sometimes intergrown w i th the d i g e n i t e in these g r a i n s . . C o v e l l i t e i s present as ro se t te s r e p l a c i n g 151 some d i g e n i t e masses. D i gen i te occurs in ve ins in the same manner as in the ore l en se s . 5-4.8 C o v e l 1 i te The dominant a s s o c i a t i o n s of c o v e l l i t e are desc r ibed above. C o v e l l i t e is a l s o present as minor d i s seminated , s o l i t a r y g r a i n s . Sometimes these g ra ins are corroded and rimmed by c u p r i t i c a l t e r a t i o n . C o v e l l i t e in ve ins and ore lenses is the same. 5.4.9 M a l a c h i t e and A z u r i t e M a l a c h i t e , and much sma l l e r amounts of a z u r i t e , are formed as a l a t e r a l t e r a t i o n of the main copper m i n e r a l s . T y p i c a l l y these carbonates form d i f -fuse haloes around g ra in s of copper s u l p h i d e . Both are found on ve ins and ore l enses . 5-4.10 Cup r i t e and L imon i te C u p r i t e i s present as o x i d a t i o n rims on na t i ve copper g r a i n s , and r a r e l y w i t h c h a l c o c i t e and c o v e l l i t e . L imon i te rims c h a l c o p y r i t e and forms d i f f u s e a l t e r a t i o n haloes around p y r i t i c a reas . 5-4.11 Greenock i te Greenock i te is by f a r the r a r e s t su lph ide of those so f a r i d e n t i f i e d in the Sustut depo s i t . Its amount nowhere exceeds 2 volume percent of a g iven sample. I ts presence is i n d i c a t e d by b r i g h t o range-ye l low spot s , of 1 to 2 mm in d i amete r , which occur in some co re . Thi.s c o l o u r a t i o n i s a d i f f u s e ha lo of CdS around the main g reenock i te g r a i n . The g reenock i te g ra in s are i r r e g u l a r patches up to 0.2 mm in d iameter. These g ra ins have intense y e l l o w i s h i n t e r -' n a l r e f l e c t i o n and are y e l l o w i s h under crossed n i c h o l s . F i g . 73 is a scanning e l e c t r o n microscope photomicrograph and elemental scan of a g r eenock i t e g r a i n . No s p h a l e r i t e nor galena have been i d e n t i f i e d w i th the g reenock i t e , or in any o ther areas of the depos i t . But the elemental scan shows there i s a l i t t l e z i n c present in the g reenock i te g r a i n . Greenock i te is found on ly in c h a l c o -p y r i t e zones of ore lenses , and on ly in contact w i th c h a l c o p y r i t e . Minor py r -96D4 Figure 73: Scanning e l e c t r o n photomicrograph and elemental scan o f a g reenock i t e . Note the minor z i n c component. This s e c t i o n i s about O.kh mm ac ro s s . 153 r i t e may be present in a given area w i t h g reenock i te but the two are not in con tac t . No o the r su lph ide i s found a s s o c i a t ed w i t h g reenock i t e . Only one example of g reenock i te in a ve i n has been seen by the author . At sample l o c a t i o n WI 15 t races of g reenock i te occur in a < 5 mm t h i c k , carbon-a t e - r i c h v e i n . 5.4.12 Hemati te There are two generat ions of hematite in the Sustut rocks. The f i r s t generat ion i s pyrogenic hematite (hematite I) formed w i th the v o l c a n i c c l a s t s . Hematite I i s much le s s abundant than the pyrogen ic magnet i te. Th is hematite has the same general t ex tu re s as o u t l i n e d above f o r magnet i te. Hematite I i s a l s o present as d e t r i t a l g ra in s w i th magnet ite ( f i g . 5 9 ' ) . The primary hema-t i t e has not s u f f e r e d as much a l t e r a t i o n and replacement as the magnetites and thus i s g e n e r a l l y present as more or le s s euhedral g r a i n s . The second genera t i on of hematite (hematite II) i s the more important and dominant in amount. Th i s hematite formed at the same time that p y r i t e and copper su lph ide s were developed. Hematite II is ub iqu i tous through n a t i v e copper and copper su lph ide core and i s i n t i m a t e l y intergrown w i t h the copper-r i c h s u l ph i de s . Hematite II has developed s p e c t a c u l a r forms on a m ic ro scop i c s c a l e . In g e n e r a l , hematite II occurs as minute s p i k e s , needles , l a th s and i r r e g u l a r masses (< 0.004 mm in s i z e ) which form in te rconnected cha in s , r i n g s , t r a i l s , c i r c l e s , r ims , e t c . ( f i g . .74). These cha i n s , e t c . , have broad, d i f -fu se , red i n t e r n a l l y r e f l e c t i n g haloes about them. Hematite II is a l s o p re -sent as minute (< 0.01 mm in diameter) blebs which g e n e r a l l y are d i sseminated through the mat r i x of copper su lph ide zones. The l a r ge r g ra i n s of c h a l c o c i t e and b o r n i t e , o c c u r r i n g i n te r se r t a11y and as network masses, do not have any a s soc i a ted hematite II. Smal ler d i s semin -ated su lph ide g r a i n s , however, are g ene r a l l y rimmed and surrounded by the hematite cha in s . Commonly these hematite II chains and the su lph ides are intergrown w i t h w e l l d e f i n e d , d i s c r e t e hematite II l a th s which are as l a rge 154 F igure 74: Photomicrograph of wispy chains and t r a i l s of hematite I I. There is a s l i g h t reddish halo around the hemat i te. The l a r ge r wh i te gra ins are mainly c h a l c o c i t e wi th minor hemat i te . Th is s e c t i o n i s 0.46 mm ac ro s s . 155 as 0.01 by 0.04 mm. These intergrowths seem to be i n d i c a t i v e of contempor-aneous c r y s t a l l i z a t i o n . The common in te rg rowth of hematite II and c h a l c o -c i t e i s shown in f i g . 15 as a s e r i e s of scanning e l e c t r o n microscope photo-micrographs showing a c h a l c o c i t e - h e m a t i t e area and two ion d i s p e r s i o n p l a t e s of copper _vs_. i ron w i t h i n the a rea . Magnet i te may be p a r t i a l l y overgrown and rep laced by t h i s hematite on margins. Hematite II is the reason f o r the general redd i sh t i nge found in the r i c h e s t copper a reas . Hematite II a l s o occurs in p l a g i o c l a s e phenocrysts of l a r ge c l a s t s w i t h i n the ore zones. It appears that hematite II i s p o s s i -b l y de r i ved by a l t e r a t i o n of pyrogenic magnet ite and primary s i l i c a t e s . The hemat i te II is not intergrown w i t h p y r i t e or c h a l c o p y r i t e . 5.4.13 Conc lus ions on Opaque Minera l Assemblages Na t i ve copper i s found w i t h c h a l c o c i t e on l y . C h a l c o c i t e and b o r n i t e are e x t e n s i v e l y intergrown and in t h e i r general areas d i g e n i t e and c o v e l l i t e are p resent . C h a l c o c i t e does not occur w i t h a l l b o r n i t e areas , e s p e c i a l l y the b o r n i t e w i t h exso lved c h a l c o p y r i t e , which i s never found w i th c h a l c o c i t e . Minor c h a l c o p y r i t e i s found i n mos t b o r n i t e a rea s , but not w i t h b o r n i t e I. Where c h a l c o p y r i t e i s abundant i t i s intergrown e x t e n s i v e l y on ly w i t h g reen-o c k i t e . P y r i t e is very r a r e l y in contact w i t h c h a l c o p y r i t e , and g e n e r a l l y these two su lph ide s occur s epe r a t e l y . Greenock i te i s found on ly in c h a l c o -p y r i t e - r i c h zones. C h a l c o c i t e , b o r n i t e , d i g e n i t e , c o v e l l i t e , c h a l c o p y r i t e , p y r i t e , and hemat i te II have overgrown pyrogenic magnet i tes . F i n a l l y hema-t i t e II is c l o s e l y a s s oc i a ted and intergrown w i th c h a l c o c i t e , b o r n i t e I, d i g e n i t e , and/or c o v e l l i t e . 5-5 Ana 1yses of Intergrowth and Replacement Textures As de s c r i bed in the fo rego ing m ine ra log raph i c sec t i on s there are seve ra l d i f f e r e n t types of in tergrowth and replacement t e x t u r e s . These tex tu re s w i l l be d i s cu s sed i n d i v i d u a l l y and eva luated in terms o f t h e i r po s s i b l e r e l a t i o n to 156 F igure 75: Ion d i s pe r s i o n p l a te s of copper and i r on w i t h i n a c h a l c o c i t e - h e m a t i t e II i n te rg rowth a rea . 75a: Th i s p l a t e shows the area where the f o l l o w i n g two p la te s were taken. The l i g h t grey mate r i a l is c h a l c o c i t e and hemat i te . A l l p l a t e s are 0.46 mm ac ro s s . Fe igure 7 5 b : These two p l a te s are d i s p e r s i o n analyses or copper and i r on r e s p e c t i v e l y . They show the intense ntergrowths of copper, as c h a l c o c i t e , and i r o n , as hemat i t e . 158 ore genes i s . 5-5-1 C h a l c o c i t e - D i g e n i t e Buerger (1941) found that c h a l c o c i t e (Cu 2S) was transformed to d i g e n i t e (Cu^S^) upon heat ing in d i r e c t contact w i t h a i r , due to 0^ atoms being taken in to the c h a l c o c i t e l a t t i c e s t r u c t u r e , thus, e f f e c t i v e l y decreas ing Cu content r e l a t i v e to the an ions . Some of the samples here were prepared by heat ing the sample and a p l a s t i c b r i que t f o r 5 minutes at 150*C u n t i l the b r i que t melted to form a cas ing f o r the sample. Thus some d i g e n i t e - c h a 1 c o c i t e i n t e r -growths in thse samples could conce ivab ly be due to t h i s hea t i ng . However t e x t u r a l s tud ie s de sc r i bed f o r . t h i s minera l p a i r were con f ined to those sam-ples which were not heated dur ing p repa ra t i on of po l i s hed s e c t i o n s . There-fo re t h e i r tex tu res can be accepted as being r e p r e s e n t a t i v e of ore in p l a ce . C ra i g (1974) s t a t e s that d i g e n i t e has a complete s o l i d s o l u t i o n w i t h c h a l c o c i t e at temperatures above ^93 ' C Roseboom (1966) subd iv ided the s tab -i l i t y f i e l d s of the phase diagram ( f i g . 76) i n to d j u r l e i t e - c h a l c o c i t e and d j u r 1 e i t e - d i g e n i t e assemblages. D i gen i t e - cha1coc i t e assemblages are thus de f ined as not e x i s t i n g at room temperature. D j u r l e i t e was not i d e n t i f i e d by the author in any of the Sustut samples, however d e f i n i t e r e cogn i t i o n of d j u r l e i t e vs. c h a l c o c i t e can be achieved on ly by X-ray d i f f r a c t i o n and even then the d i f f r a c t i o n pat te rns of the two.minera ls are very s i m i l a r . I d e n t i -f i c a t i o n of d j u r l e i t e or c h a l c o c i t e w i th the r e f l e c t e d l i g h t microscope i s imposs ib le as both m inera l s have s i m i l a r c h a r a c t e r i s t i c s (Roseboom, 1962). Cook (1972) specu la tes that most na tu ra l c h a l c o c i t e s are a c t u a l l y d j u r -l e i t e . For the purpose of t h i s t he s i s a l l copper minera l s oompos i t i ona l l y be-tween Cu^ and Cu^ are r e f e r r e d to as c h a l c o c i t e . D j u r l e i t e i s undoubtly present in the Sustut depos i t but in unknown amounts. It i s l i k e l y to be the " c h a l c o -c i t e " . . present in the s t a b l e p a i r of d i g e n i t e - c h a 1 c o c i t e . It is assumed that d i g e n i t e - c h a 1 c o c i t e in tergrowths represent unmixing from a s o l i d s o l u t i o n formed above 93'C. 159 1 ', 'i '' 'i 'i '• '• V i I I I I I ;' .' i ' i '| I i1 i' i ' i I I I'I \ l .'| 'i l i 1 . 'i • CuxS X= 1.70 1.60 1.90 2.0C '2.10 F igure 76: Phase diagram f o r the Cu-S system (from Roseboom, 1966, p. 648). As can be seen, below 93* C d j u r l e i t e enters any s o l i d s o l u t i o n of c h a l c o c i t e and d i g e n i t e as a phase, and t h e r e f o r e c h a 1 c o c i t e - d i g e n i t e intergrowths are metastab le at room temperature. 160 5-5-2 Cha1cocite-Bornite and Digenite-Bornite The myrmekitic intergrowths of c h a l c o c i t e - b o r n i t e , and the rarer d i genite-bornite intergrowths probably are formed by unmixing of a p r e - e x i s t i n g s i n g l e , high-temperature bornite phase. Fig. 77 from Brett (1963, p. 194) shows phases on the Cu^S-Cu^FeS^ j o i n . At Sustut, intergrowths are about 50:50, cha1cocite:bornite. Thus, a minimum temperature of formation of this s o l i d s o l u t i o n is 200"C (as shown by the "steepness of the solvus on the bornite s i d e " ( i b i d . , p. 195). S i m i l a r l y , f i g . 78, also from Brett (1963, p.193), i l l u s t r a t e s the m i s c i b i l i t y gap along the digenite-bornite j o i n . In Sustut examples, intergrowths range from 20 to 50 mole percent digenite, indic a t i n g a minimum temperature of formation of 250'C. These vermicular intergrowths also indicate (Brett, 1962) that i n i t i a l concentrations of both phases i n v o l -ved were high, as lamaller exsolution is more common where bulk composition is close to an end member. 5-5-3 Chalcopyrite-Born?te (+Digenite) According to Morimoto and Kullerud (1961), bornite at high temperatures can accommodate substantial v a r i a t i o n s in the amounts of iron to copper and/ or amounts of metal to sulphur. With decreasing temperature, such high-tem-perature bornite undergoes ,a l a t t i c e rearrangement closer to the s t o i c h i o -metric composition Cu^FeS^ and in the process the non-stoichiometric compon-ents are exsolved as separate phases. Two d i f f e r e n t parental bornite s o l i d s o l u t i o n s are present on the Sustut property: bornite I contains excess Cu and S in the form of c h a l c o c i t e and/or digenite; bornite II (a and b) contain excess Fe as c r y s t a l .jographi cal 1 y. o r i ented-1 aths .-of chalcopyrite. Fig. 79. (from Brett', 1963, p. 195) shows the chal copy r i te-born i te s o l i d s o l u t i o n m i s c i b i l i t y gap. Sustut bornites have about 10 volume percent exsolved chalcopyrite (approximately 3 mole percent chalcopyrite) which i n d i -cates, from the diagram, a temperature of over 400'C. However such temper-ature determinations are t e n t a t i v e at best and, one can say with confidence, 1 6 1 350 300 250 200 co 150 o. e >- 100 50 us B & e O O O O Tt K * • + • + + cc-bn ss. \ High bn High bn + cc N. s ^228* _* L * I_-l\fa'J Low>-bn U Low bn + cc ~ 0 10 20 30 40 50 60 70 80 90 100 , C u 2 s Mol per cent " 5 4 j Figure 77: Stable phases on the j o i n Cu^FeS^-Cu.S (from B r e t t , 1963, p. 194). 350 300 p 250 o = 200 a k_ a> £ 150 100 50 D D U a 0 0 0 o • D O O 1 i 1 — D O O bn-dg ss. o o , 0 T r O D D oal High dg / High bn +high dg \ _ /„S_ S SLJZ-l-M Low bn + high dg 228° ^ . B ^ * * " " " / Low dg + low bn r " i i/ § § § 6 6 SS Lowdg(+dj) / t 1 / 1 1 1 1 1 - J -~ 0 10 20 30 40 50 60 70 80 90 100 Cu9.2S5 Mol per cent Cu5FeS4 Figure 78: Stable phases on the j o i n Cu^FeS^-Cu 9 2 S 5 (from B r e t t , 1963, p. 193). 162 400 350 300 250 200 150 100 50 1 1 1 1 1 1 1 1 1 * -8 * ><• -l \ 4-cp -1 8 High bn + cp ( High bn-i-^T i i u Low bn +cp 1 Low bn-T i i i i *-i i T 1 ! 9 1 i i i i 1 1 2 ? 1 I I I ! 228° 0 10 20 CuFeS2_x 30 40 50 60 Mol per cent 70 80 90 100 C u 5 F e S 4 Figure 79 : Stable phases on the j o i n Cu^FeS^-CuFeS (from Brett, 1963, p. 1 9 5 ) . 163 on l y roughly approximates the minera l depo s i t i on temperatures. There were two d i s t i n c t b o r n i t e s o l i d s o l u t i o n s present in the Sustut o r e s . In one (bo rn i te I) the phases b o r n i t e , c h a l c o c i t e and d i g e n i t e are p re sen t , and in the o ther ( bo r n i t e II) the phases b o r n i t e , c h a l c o p y r i t e and d i g e n i t e occur . But the phases c h a l c o c i t e and c h a l c o p y r i t e were not in e q u i -l i b r i u m and thus there was not a chemical t i e l i n e between the two phases. F i g . 80 has three diagrams, from Yund and Ku l l e rud (1966), f o r the Cu-Fe-S system at 2 0 0 ' , 300 ' , and 400 'C. The 200'C diagram shows c h a l c o c i t e and d i g e n i t e e x i s t i n g as seperate phases, and both bo rn i t e and c h a l c o p y r i t e have smal l s o l i d s o l u t i o n f i e l d s . T ie l i n e s connect c h a 1 c o c i t e - d i g e n i t e , c h a l c o -c i t e - b o r n i t e , d i g e n i t e - b o r n i t e and born i te-cha1 c o p y r i t e . The d i g e n i t e - c h a 1 -c o c i t e - b o r n i t e s could have formed at t h i s temperature, as cou ld the c h a l c o -p y r i t e - b o r n i t e s , but a c h a l c o p y r i t e - d i g e n i t e - b o r n i t e cou ld not have formed as a s o l i d s o l u t i o n at t h i s temperature (because d i g e n i t e - c h a l c o p y r i t e are not in e q u i l i b r i u m ) . At 300'C d i g e n i t e - b o r n i t e form a s o l i d s o l u t i o n , c h a l -c o c i t e i s a s o l i t a r y phase and c h a l c o p y r i t e has a l a r ge r s o l i d s o l u t i o n f i e l d . Both types of b o r n i t e cou ld have formed at t h i s temperature because the d i g e n i t e - b o r n i t e and the c h a l c o p y r i t e s o l i d s o l u t i o n s are connected and the c h a l c o c i t e f i e l d i s separate from the c h a l c o p y r i t e thus the d i s e q u i l i b r i u m between these two phases i s ma in ta ined. At 400'C an equ i v a l en t s i t u a t i o n e x i s t s . Very g e n e r a l l y , the b o r n i t e s o l i d s o l u t i o n s i n d i c a t e temperatures of fo rmat ion of g rea te r than 200 'C. A l l of the temperatures suggested by e x s o l u t i o n tex tu re s are c on s i s t en t w i t h those der i ved from study of metamor-ph i c minera l assemblages above. The d i g e n i t e - c h a 1 c o p y r i t e - b o r n i t e intergrowths are a l s o i n t e r e s t i n g be-cause they q u a l i t a t i v e l y show the unmixing path of components, from an o r i -g i n a l bu lk compos i t ion to exso lved p roduct s , due to decreas ing temperatures. When o r i g i n a l l y formed at e l e va ted temperatures, t h i s b o r n i t e (_i_e. l l b ) con-t a i ned excess i ron and copper. With a decrease in temperature, the i r o n , 60 Weight per cent S , Weight per cent — 200*C F igure 80: Isothermal s e c t i o n s in the Cu-Fe-S system at 200, 300, 400 'C (from Yund and K u l l e r u d , 1966, pp. 472-474). ( c h a l c o c i t e , c c ; d i g e n i t e , dg; b o r n i t e , bn; c h a l c o p y r i t e , cp ; c u b a n i t e , cb ; p y r r h o t i t e , po; p y r i t e , py; c o v e l l i t e , cv ; i d a i t e , i d ) . . 60 Weight per cent S •A A TV Cu bru cb, Weight per cent 300'c Figure 80 (cont 'd. ) Fe 167 was e x p e l l e d from the b o r n i t e l a t t i c e , such that c h a l c o p y r i t e began forming as l a t h s in the c r y s t a l l o g r a p h i c d i s c o n t i n u i t i e s of the b o r n i t e . Th i s e x p u l -s i on of c h a l c o p y r i t e , moved the bulk b o r n i t e compos i t ion from c h a l c o p y r i t e i n t o c o p p e r - r i c h areas . With the e x s o l u t i o n of most o f the c h a l c o p y r i t e and a f u r t h e r decrease in temperature, the bo rn i t e s o l i d s o l u t i o n was too copper-r i c h f o r i t s s t o i c h i o m e t r i c compos i t i on . When a temperature of above 200'C was reached, d i g e n i t e was exso lved in order to remove the c o p p e r - r i c h com-ponent (at the temperature o f 200'C and below, d i g e n i t e and b o r n i t e have sep-e ra te s t a b i l i t y f i e l d s , thus the two minera l s cou ld be in s o l i d s o l u t i o n un-t i l t h i s temperature- f i g , 80) . The removal of d i g e n i t e from the s o l i d s o l u t i o n , moved the bulk b o r n i t e compos i t ion towards s t o i c h i o m e t r y . 5-5.4 C o v e l l i t e a f t e r D i g e n i t e Un l i ke the p r e v i o u s l y de sc r i bed intergrowths of su lph ides which almost c e r t a i n l y r e su l t ed from unmixing of s o l i d s o l u t i o n s , c o v e l l i t e occurs as a l a t e r replacement of d i g e n i t e . Comparable replacement has been reported by v a r -ious authors (eg. S i l l i t o e and C l a r k e , 1969) who record c o v e l l i t e flame l ama l l ae in d i g e n i t e masses, as w e l l as c o v e l l i t e se lvages on f r a c t u r e s c u t t i n g d i g e n i t e g r a i n s . Th i s replacement, they s t a t e , is due to o x i d a t i o n of the d i g e n i t e . C o v e l l i t e has rep laced degeni te in the Sustut samples in a s i m i -l a r way. Flame l ama l l ae patches of S i l l i t o e et_ a_]_. (1969) are the same as the r o s e t t e replacements de sc r i bed by t h i s w r i t e r . 5.5 - 5 D i gen i te and C o v e l l i t e a f t e r Bo rn i t e To account f o r d i g e n i t e - c o v e l 1 i t e replacement of b o r n i t e at Sus tut , r e f -erence is made to Tay l o r and K u l l e r u d ' s (1970) study of the Cu-Fe-S-0 system as i l l u s t r a t e d in f i g . 8 l . Phases present in t h i s system, but no t ' in the samples s tud ied a re : p y r r h o t i t e , i d a i t e and cuban i te . S t ab le phase assem-blages in the Sustut depos i t are c o p p e r - c h a l c o c i t e - m a g n e t i t e - h e m a t i t e , c h a l -coc i t e -d i gen i te-hemat i t e - m a g n e t i t e , c ha l c o c i te -born i te-magnet i te-hemat i t e , cha1 copyr i t e -py r i te-hemat ite-magnet i te and borni t e - c h a l c o p y r i te-hemat i t e -Cu Fe F igure 81: Phase r e l a t i o n s in the Cu-Fe-S-0 system at 300 'C (from Tay lo r and K u l l e r u d , 1970, p. 316). Phase abb re v i a t i o n s are the same as those in f i g u r e 80. Hemat i te, hm; magnet i te, mg. 169 magnetite. C o v e l l i t e is not a primary stable phase with any other phases on Sustut and is never stable with magnetite as a phase in the Cu-Fe-S-0 system. As the authors (ibid.) state, a bulk composition, on the sulphur side of a compositional l i n e through c h a l c o c i t e - b o r n i t e - c h a l c o p y r i t e - p y r i t e , would not be s t a b l e with magnetite alone and hematite must necessarily be present. The presence of hematite, coeval with the sulphides in the Sustut ores i n d i -cates that the bulk compositions were thus on the sulphur side. This oxid-ation also brought c o v e l l i t e within s t a b i l i t y f i e l d s . " I f magnetite, in co-existance with bornite, is oxidized to hematite, the bornite composition must change toward s u l f u r across the bornite s o l i d s o l u t i o n f i e l d . Oxidation s l i g h t l y beyond that required to convert a l l magnetite w i l l lead to forma-tion of i d a i t e and/or c o v e l l i t e rims on bornite " ( i b i d , pp. 317~318). It appears that further oxidation causes t o t a l breakdown of bornite to c o v e l l i t e . The view held by t h i s writer is that sulphides were introduced into host rocks containing magnetite. As the sulphides were p r e c i p i t a t i n g , oxidation began which started to break down magnetite and release iron from s i l i c a t e s to form hematite. Bornite was a l t e r e d f i r s t to digenite and f i n a l l y to cov-e l l i t e by a l a t e r supergene oxidation. Supergene oxidation of ore minerals is a lso shown by limonite weathering of p y r i t e and limonite rims on chalco-p y r i t e . 5.6 Relationship of Ore Veins and Lenses Comparison of ore veins and lenses shows s t r i k i n g s i m i l a r i t i e s in ore mineralogy, intergrowth textures, gangue mineralogy, etc. A l l m e t a l l i c min-erals occur in both deposit-types, and have the same r e l a t i v e proportions with respect to each other (except p y r i t e , which is much more abundantly d i s -seminated through the host vol canic1 a s t i c rocks). A l l three bornite types ( i e . I, Ma, Mb) occur in veins as well as lenses, and they have the same intergrowth textures in both modes. Digenite is exsolved from c h a l c o c i t e 170 in ve ins and lenses , a l s o . The d i s e q u i l i b r i u m between some su lph ide phases i s mainta ined in the two modes of occurrence ( i e . c h a l c o c i t e does not occur w i t h c h a l c o p y r i t e , n a t i v e copper occurs w i th c h a l c o c i t e o n l y , e t c . ) . In ore lenses , the ore minera l s occur mainly as open space f i l l i n g s w i t h -in the host conglomerates, which i s what the ore ve ins are ( i e . the ve ins are f r a c t u r e - f i l l i n g s ) . In both cases, the ore minera l s are e x t e n s i v e l y i n t e r -grown w i t h the same gangue m ine ra l s . Those intergrown gangue m i n e r a l s , p reh-ni t e - e p i d o t e - c a r b o n a t e - q u a r t z , are a l s o of the h ighest metamorphic f a c i e s w i t h i n the general area o f the depo s i t . It appears that the ore minera l s formed at the same time as the metamorphic minera l s in both cases . The common nature of the ore minera lography, in both ve in s and lenses , very s t r ong l y suggests that ore m ine ra l s , in both modes of occur rence , formed from the same- s o l u t i o n s . For example, i t is very hard to env i sage two sep-e r a t e o re - fo rming episodes deve lop ing equ i va l en t general b o r n i t e assemblages which evolved i n to e x a c t l y the same three bulk b o r n i t e compos i t ions ( i e . the b o r n i t e s in both ve ins and lenses must have formed from the same system). Another f a c t o r suggest ing a common o r i g i n f o r the two o re - f o rms , i s the i n te rg rowth of ore m ine ra l s of both forms w i t h the same metamorphic m ine ra l s . The metamorphic event which caused development of the metamorphic minera l s (gangue) was obv i ou s l y synchronous w i th ore mineral i n t r o d u c t i o n . Thus, the o re minera l s of both modes formed at the same time ( i e . there were not two d i f f e r e n t metamorphic events which caused development of the metamorphic mi ne r a l s ) . F i n a l l y the i n t e r - r e l a t i o n s h i p between the two ore- forms i s most s t r ong l y shown by t h e i r common s p a t i a l occur rences . Numerous examples a re seen through-out the depos i t in which ore ve ins appear below ore lenses ( a c t u a l l y grading i n t o them) and above ore lenses (again grading outwards) . The ore ve ins do not a c t u a l l y cut through the ore lenses . 171 A good example of this vein-lens sequence occurs in the North Zone. At sample location W36, well developed gangue-sulphide veins crop out. Just below these veins, the ore lens by (sample location) W32 occurs. No veins cut through outcrop expressions of this lens. However, below this lens, another group of sulphide-rich veins occur (W96). S t i l l further below this area, small ore lenses with interconnected ore veins occur to the base of • the c l i f f (_i_e. sample locale Will). At W104 abundant ore veins occur above a tabular ore lens. A small ore lens occur at sample area W2 which is cut by a cha1cocite-rich vein at one of its lateral extremities. It appears that the lens here, so isolated from other copper occurrences, may owe its existence to the same fluids which pre-cipitated the vein material. Near sample lo c a l i t i e s W10-W11-W12, an ore lens appears to-be superimposed on country rock which has been cut by numerous, small sulphide-rich veins. And so on through the deposit, it appears that the veins and lenses are spatially related in that veins are abundant above and below, but not in, ore lenses. Thus, the writer suggests that the veins appear to have been feeders to, and releases from, the ore lenses for ore-forming fluids. The lenses, then, like the veins, are post-dyke and pre-faulting. 5-7 Zonation of Metallic Minerals in Ore Lenses If the vertical distribution of the ore minerals is viewed vertically (ie. with d r i l l core), a general zonation pattern of the minerals becomes apparent. The four cross-sections A-A1,B-B1,C-C1 and D-D' (attached - in back) show the distribution of sulphides and native copper as a histogram based on visually estimated amounts (these cross-sections were constructed from a computer gen-erated strip log of depth, and amount and type of metallic mineralization at each level, variables that had been recorded consistently in relogging of the cores). The most complete zonal pattern is shown in DDH 88 where a very minor amount of native copper is central to a large chalcocite zone. This 172 zone i s f r i n g e d s u c c e s s i v e l y by o ve r l app i ng zones con ta i n i n g sma l l e r amounts of b o r n i t e and c h a l c o p y r i t e , f o l l owed by an outer zone of abundant p y r i t e . Elsewhere throughout DDH 88 there are sma l l e r su lph ide lenses , some w i t h wel1-deve loped zona t i on . In o the r d r i l l ho l e s , t h i s zonat ion i s developed i r r e g u l a r l y and seldom i s p e r f e c t l y formed. One zone, or more, can be e n t i r e l y or p a r t l y mi s s ing w i t h i n a g iven d r i l l ho le . R e l a t i v e amounts of minera l s w i t h i n t h e i r r e s -p e c t i v e zones v a r i e s c on s i de r ab l y , from d r i l l ho le to d r i l l h o l e , a l s o . ( I t should be noted that most of the c h a l c o c i t e , a s ide from that a s s o c i a t ed w i t h n a t i v e copper, conta ins a b o r n i t e component. Thus, the rea l b o r n i t e d i s t r i -bu t i on i s more ex ten s i ve than shown in the at tached c r o s s - s e c t i o n s ) . D e t a i l e d d e s c r i p t i o n s of minera l zon ing , e x h i b i t e d by the d r i l l holes in c r o s s - s e c t i o n s A - A 1 , B-B 1 , C-C 1 and D-D1 (attached - in back) , are in Appen-d i x I I I . Th i s zon ing sequence is a l s o found in po l i s hed s e c t i o n s t u d i e s . Na t i ve copper occurs on ly w i t h c h a l c o c i t e . C h a l c o c i t e occurs w i t h more c o p p e r - r i c h b o r n i t e s ( i e . b o r n i t e I) but i s not found w i t h c h a l c o p y r i t e , or b o r n i t e con-t a i n i n g c h a l c o p y r i t e . Furthermore, cha1 c o p y r i t e - b o r n i t e s are in contact w i t h c h a l c o p y r i t e but not p y r i t e . C h a l c o p y r i t e i s best developed where i t is a s o l i t a r y s u l ph ide but does have a g rada t i on w i t h p y r i t e . And l i k e w i s e p y r i t e i s s t r onge s t when s o l i t a r y . There may a l s o be a l a t e r a l zonat ion through the property as w e l l , w i t h an ou te r p y r i t e zone complete ly sur round ing some coppe r - r i c h areas . For example DDH 54 conta ins mainly p y r i t e but is c l o se to and on the same s t r a t i -g raph ic l e v e l as the c h a l c o c i t e zone of DDH 110. A l so DDH 132 at a d i s t a n c e from the c o p p e r - r i c h ore lenses in s e c t i o n D-D 1, conta ins on ly p y r i t e . With p y r i t e as i t s on ly s u l ph ide , the core from DDH 25 is of an area to the west of a major copper zone exposed in c r o s s - s e c t i o n C -C 1 . P y r i t e occurs near W92 which appears to be an outer f r i n g e to the west of the main copper s u l -173 phide occurrences of the North Zone. Robertson (1975) de sc r i bed a somewhat s i m i l a r zonat ion pa t te rn in a copper depos i t near Mount Bohemia, M ich igan, where c h a 1 c o c i t e - b o r n i t e - h e m a t i t e zones grade i n t o p y r i t e - c h a l c o p y r i t e areas w i th i nc rea s i ng d i s t ance from a f a u l t , a long which the m i n e r a l i z i n g f l u i d s apparent ly f lowed. Th i s zonat ion is e s s e n t i a l l y the same as that of the Sustut depo s i t , i n c l u d i n g rare n a t i v e copper cores . There are a l s o two bo r n i t e types present . Through chemical s t u d i e s , Robertson found that copper was d i s t r i b u t e d s ymmet r i ca l l y r e l a t i v e to the f a u l t and decreased in abundance outwards from t h i s f a u l t , to l e s s , than 0.1 percent . Sulphur has the same symmetrical d i s t r i b u t i o n and decreased outwards from the f a u l t , bu t . i t s l a t e r a l extent was much g r ea te r than that of copper. This increased d i s t ance of su lphur occurrence corresponded w i t h the appearance of p y r i t e . To t a l i ron on the o ther hand showed no v a r i a t i o n away from the f a u l t . t t appears that t o t a l i ron i s more or l e s s uni form in and near the Sustut Copper depos i t too. 174 CHAPTER 6: DISCUSSION OF DATA AND POSSIBLE GENETIC MODEL  b. l I n t r oduc t i on and Summary of Phy s i c a l Features In t h i s chapter the var ious genet i c models f o r the Sustut Copper depos i t suggested by o the r authors w i l l be cons ide red . F i n a l l y t h i s w r i t e r w i l l present a d e t a i l e d g e n e t i c model based on the r e s u l t s o f h i s own s t u d i e s . Any such model would have to take in to account and e x p l a i n the f o l l o w i n g phy s i ca l and chemical f ea tu re s of the Sustut depo s i t . 1) The depo s i t has a l o ca l high in metamorphic grade compared w i t h o the r Moosevale Formation rocks at the same s t r a t i g r a p h i c l e ve l e l sewhere, that i s , the depos i t i s p rehn i te -pumpe l1y i te f a c i e s and the o the r Moosevale rocks are laumont i te f a c i e s . 2) Copper and s u l ph i de minera l s occur mainly as open space f i l l i n g s , o r as overgrowths and replacements of p r e - e x i s t i n g pyrogen ic m ine ra l s , and are intergrown i n t i m a t e l y w i t h t y p i c a l metamophic m inera l s o f the p r e h n i t e -pumpe l l y i t e f a c i e s . 3) Major concen t r a t i on s of copper minera l s are found in t abu la r zones w i t h i n the vo l c a n i c l a s t i c host rocks , that are p a r a l l e l to bedding and are most abundant in the upper 60 m of the v o l c a n i c p i l e . 4) Ore m ine ra l s a l s o occur in l o ca l swarms of t h i n ve ins w i t h the same gangue ma te r i a l as is found in the t abu l a r c o p p e r - r i c h l en se s . 5) Equ i va len t t ypes , p r opo r t i on s , in tergrowths and replacement t ex tu re s of ore m inera l s are found in the lenses and v e i n s . In f a c t , the two geometr ic forms of copper c oncen t r a t i on are r e l a t e d s p a t i a l l y and are i n te rconnected . 6) Tabular zones and ve ins are r i c h in Cu, N i , Zn, Ca, and Sr, and g e n e r a l l y a re poorer i n Rb, MgO, S i 0£, and A12*^ 3 r e l a t i v e to country rocks . A l so the Cu contents show no g radat ion from c o p p e r - r i c h lenses to enc l o s i n g copper-poor rock s , j u s t a sharp break in va lue s . 175 7) Temperatures of format ion o f the depo s i t , as determined from meta-morphic minera l assemblages and su lph ide minera l i n te rg rowths , are i n d i c a t e d as being over 200'C and under 403*C, most l i k e l y 300 to 400 'C. 8) The su lph ide minera l s have d i s t i n c t s t a b l e assemblages and a zonat ion is present in the ore lenses w i t h na t i ve copper cores to outwardly changing zones o f c h a l c o c i t e , c h a l c o c i t e and b o r n i t e , b o r n i t e and c h a l c o p y r i t e , c h a l c o p y r i t e and g reenock i te , f i n a l l y w i t h an outermost f r i n g e of p y r i t e . 9) Age of m i n e r a l i z a t i o n i s probably post-Lower J u r a s s i c (as the ore ve ins cut the dyke and the dyke is most l i k e l y c o r r e l a t i v e w i th i n t r u s i o n s i n the Lower J u r a s s i c Hazel ton Group). 6.2 P r e v i o u s l y Suggested O r i g i n s  6.2,1 Syngenet ic Hypotheses Syngenet ic models have been suggested v e r b a l l y to the author and are desc r i bed b r i e f l y i n p r o p r i e t a r y repor t s d e a l i n g w i t h o r i g i n of the Sus tut . d e p o s i t . At l e a s t three vo l canogen i c - s yngene t i c d e p o s i t i o n a l models have been proposed, a l l of which could have been compl i cated by l a t e r superimposed f e a t u r e s . The f i r s t s yngenet i c model invo lves v o l c a n i c s ( p y r o c l a s t i c s and lavas) which were depos i t ed in sha l low ba s i n s , w i t h near shore environments, where the v o l -canism was induced by r i f t i n g and f a u l t i n g . The su lph ides in t h i s case are cons idered to .be interbedded w i t h tu f faceous mudstones, l imes tones , and a v a r i e t y o f a r e n i t e s de r i ved from the adjacent h igher ground. The second model i nvo l ves a ba s i na l v o l c a n i c sequence w i th the su lph ides being introduced i n to the pyro -c l a s t i c s by f uma ro l i c a c t i v i t y . F i n a l l y the t h i r d model would have the su lph ide s e x i s t i n g as e j e c t a in the f l ank s of a cen t re of v o l c a n i c i t y (eg. the m ine ra l r i z a t i o n p r e v i o u s l y formed a stockwork in a v o l c a n i c t h r o a t ) . The most compel l ing argument aga in s t any of these syngenet ic hypotheses i s that the ore minera l s are not concent ra ted in the l i t h i c v o l c a n i c c l a s t s , but occur as open space f i l l i n g s and as s p a t i a l and apparent ly gene t i c i n t e r -176 growths w i t h metamorphic m i n e r a l s . Furthermore, those ore m inera l s which are present in l i t h i c c l a s t s , occur as overgrowths and replacements o f p r e - e x i s t i n g s i l i c a t e m i n e r a l s , o r as amygdules. A l s o , ne i t he r s yngenet i c model can account f o r the zonal d i s t r i b u t i o n - o f su lph ides around na t i ve copper co re s . in regard to the f i r s t sugges t ion , though ore lenses are r e s t r i c t e d to c e r t a i n i n te rbed s , w i t h i n a ba s i na l sequence, the in terbeds are not d i s t i n c t l y d i f f e r e n t s ed imento l og i ca l f a c i e s ( i e . host rocks to the lenses are not r e s t r i c t e d to one type o f sedimentary depos i t i n the v o l c a n i c l a s t i c p i l e , f o r in s tance mudstones, but are w i t h i n in te rbeds which had the same gross chemical and d e t r i t a l environment, va ry ing on l y by minor phy s i ca l c h a r a c t e r i s t i c s ) . In the second case, no phy s i ca l ev idence f o r f umaro l i c a c t i v i t y i s p re sen t , and no chemical sediments i n d i c a t i v e of such a c t i v i t y (eg. z e o l i t e s ) occur in t h e . Sustut depos i t (the carbonates present on Sustut are r e e f s , not chemical d e p o s i t -i o n s ) . F i n a l l y , i f the s u l ph ide s occurred as a stockwork in a vent which was subsequent ly d i s r up ted e x p l o s i v e l y , some su lph ides should be conta ined w i t h i n v o l c a n i c c l a s t s , and t e x t u r a l fea tu res should i n d i c a t e a p r e - b r e c c i a t ion age of m i n e r a l i z a t i o n . Such f ea tu re s have not been seen in the d e p o s i t . 6.2.2 Metamorphica11y Derived Ore F l u i d Model J o l l y ' s (1974) model f o r the o r i g i n of na t i ve copper depo s i t s w i t h i n the Keweenawan ba sa l t s of Michigan has been quoted as an analogue o f the Sustut depo s i t (eg. Harper, 1977). The two depos i t s con t ra s t markedly in s i z e , but have many s i m i l a r g e o l o g i c a l f e a t u r e s . Nat ive copper in the Keweenawan b a s a l t s occur s as open space f i l l i n g s , and les s commonly as replacements o f the host rock, w i t h c h l o r i t e - a l b i t e - p u m p e l l y i t e - q u a r t z - p r e h n i t e - e p i d o t e , or w i t h p r e h n i t e . Background copper contents of una l te red po r t i on s of these ba sa l t s range from kO to 90 ppm. There i s a l s o a zonat ion o f metamorphic m inera l s in these b a s a l t s that roughly p a r a l l e l s s t r a t i g r a p h y , wherein a 1 b i t e - p r e h n i t e - 1 a u m o n t i t e - c h l o r i t e -analc ime-sphene and rare n a t i v e copper assemblages occur at the top o f the b a s a l t i c p i l e ; a 1 b i t e -pumpe l 1 y i t e - p rehn i t e - na t i v e c o p p e r - q u a r t z - c h l o r i t e - s p h e n e -177 ep idote are in the midd le ; and a l b i t e - e p i d o t e - q u a r t z - c h l o r i t e - s p h e n e -purnpel l y i te assemblages are at the base. J o l l y suggests that the development of the deepest metamorphic minera l assemblage was caused by dehydrat i ve metamorphism which e xpe l l ed water from the ba sa l t s at t h i s l e v e l . Copper and z i n c were leached out by t h i s water removal and were conta ined as c h l o r i d e complexes in the wate r s . These s o l u t i o n s rose through the v o l c a n i c p i l e u n t i l they reached a l e v e l where temperature and pressure were such that h yd ra t i v e metamorphism cou ld take p l a c e . This h yd r a t i v e metamorphism brought about the development of pumpe l l y i t e (and prehn i te ) which captured some of the r i s i n g waters . The copper ions were p r e c i p i t a t e d w i th t h i s pumpe l l y i t e development due to reduc t i on of Cu ions by o x i d a t i o n of magnetite to hemat i te , and breakdown of pumpe l l y i t e to e p i d o t e . Z inc on the other hand d i d not p r e c i p i t a t e and was complete ly removed from the system. Copper su lph ides were not developed because the S content o f the waters was too 1 ow. There are a number of reasons why t h i s model i s not a p p l i c a b l e to the Sustut d e p o s i t . Throughout the upper member of the Moosevale Formation, meta-morphic minera l assemblages are f a i r l y constant w i t h no f a c i e s v a r i a t i o n s v i s i b l e w i t h i n the p i l e . E x t r a p o l a t i o n of the types o f a l t e r a t i o n present below the 616 m of the Moosevale Formation v i s i b l e in d r i l l core i s tenuous, but Burns (1973) de sc r ibed a l l the rocks as having p rehn i te -pumpe l1y i te grade metamorphism. Accord ing to Burns, the f i r s t appearance o f an a l t e r n a t i v e f a c i e s does not occur u n t i l the a c t i n o l i t e - b e a r i n g A s i t k a Group is encountered, that i s 2400 m s t r a t i g r a p h i c a l l y below the Sustut depo s i t . The background copper contents of the A s i t k a Group are comparable to those of the Moosevale Formation, accord ing to Monger (1977) (jj_e. no great d e p l e t i o n in copper contents i s apparent ) . On the W i l l ow p rope r t y , to the south, across the Sustut R i ve r from the Sustut d e p o s i t , sha le at the top of the lower member of the Moosevale Form-a t i o n conta ins d i s semina t i on s of c h a l c o p y r i t e and c h a l c o c i t e , grading up to 178 30 volume percent (Church 1973)° Th i s s u l ph ide m i n e r a l i z a t i o n , w e l l below the s t r a t i g r a p h i c l e v e l of the Sustut d e p o s i t , imp l ie s that the d e h y d r a t i v e -h y d r a t i v e system envisaged by J o l l y f o r the Keweenawan b a s a l t s , e i t h e r was not present in the format ion o f the Sustut depo s i t , or encompassed a much t h i c k e r s t r a t i g r a p h i c s e c t i o n below the upper member of the Moosevale Format ion. Another problem of a p p l i c a t ion invo lves the ba s i c d i f f e r e n c e in m e t a l l i c components between the two d e p o s i t s . Nat ive copper i s the on ly ore minera l present i n the Keweenawan depo s i t s and sulphur i s d e f i c i e n t in these d e p o s i t s . At Su s tu t , on the o the r hand, na t i ve copper i s on ly a minor c o n s t i t u e n t w i t h su lph ides predominat ing. Thus, any f l u i d s i n t r oduc i ng copper i n to Sustut rocks a l s o had a l a rge su lphur component, which may have been even g rea te r than that o f copper (j_e. p y r i t e has a g reater s p a t i a l extent than do any o f the copper s u l p h i d e s ) . J o l l y ' s model does not take in to account d e r i v a t i o n of su lphur from host rocks nor does i t suggest any means f o r i n t r o d u c t i o n o f su lphur i n to the o re - f o rm ing chemical system by metamorphism. Z inc in the Sustut depos i t i s s l i g h t l y enr iched w i t h i n copper su lph ide zones and shows no measurable d e p l e t i o n in other areas of host rock, whereas z i n c in the Keweenawan ba sa l t s i s dep le ted in dehydrated areas and i s f l u shed out of the ore system. Another major f e a t u r e , not e xp l a i ned by J o l l y ' s model, i s the minera l z ona t i on found in v e r t i c a l s ec t i on s through ore lenses of Sus tut . If f l u i d s advanced upwards through the Sustut s e c t i o n from zones of dehyd ra t i on , then any zona t i on formed should be on ly one- s ided as the chemical changes in w a l l r ock -o re f l u i d reac t ions would be at the f r o n t o f the advancing f l u i d s or behind the f r o n t , but not on e i t h e r s i de of a c e n t r a l core as a c t u a l l y seen. Harper (1977), us ing J o l l y ' s model as a bas i s f o r the Sustut o re - f o rm ing p roces s , thought that p y r i t e may have pre-dated copper m i n e r a l i z a t i o n and thus acted as a c a t a l y s t to copper p r e c i p i t a t i o n ( i e . o r i g i n a l p y r i t e may have 179 f u rn i s hed some of the su lphur needed to form the copper s u l p h i d e s ) . Harper a l s o argued aga ins t a " c onven t i ona l hydrothermal plumbing system e p i g e n e s i s " because of a lack of feeders f o r hydrothermal s o l u t i o n s . The arguments aga in s t Ha rpe r ' s ideas above are that p y r i t e has indeed proved, upon c l o se examinat ion , to be an e p i g e n e t i c minera l penecontempouraneous w i t h copper su lph ide f o rma t i on . F i n a l l y , the ore ve ins do appear to be i n te rconnected w i t h ore lenses and could conce ivab ly be a plumbing system. The w r i t e r does not wish to prec lude the p o s s i b l e minor c o n t r i b u t i o n o f metamorph ica l ly de r i ved water and ions , but format ion of Sustut ore lenses s o l e l y , o r even dominant ly , by these waters does not seem p l a u s i b l e accord ing to the phy s i ca l and chemical paramenters as determined in t h i s s tudy. 6.2.3 Church ' s Model Church (1973 and 1978 pers . comm.) f e l t that Sustut copper m i n e r a l i z a t i o n took p l ace s h o r t l y a f t e r d e p o s i t i o n of the Moosevale fo rmat ion and predated reg i ona l metamorphism which " s e a l e d the i n t e r s t i t i a l rock p o r e s " . The hydro-thermal s o l u t i o n s , which c a r r i e d the copper and o ther i on s , were a l a t e r stage (or d e u t e r i c ) development o f the vo lcan i sm (w i t h i n the area) which f lowed through the r e cen t l y depos i ted vol c a n i c l a s t i c s a long f r a c t u r e channelways u n t i l impermeable interbeds were reached through which the f l u i d s c o u l d n ' t f l ow . Due to the stoppage of f l o w , the copper was then p r e c i p i t a t e d . Th is p a r t i c u l a r model faces two main problems. In the f i r s t i n s t ance , the copper m i n e r a l i z a t i o n v i s i b l y c u t s , and thus po s tda te s , the b a s a l t i c dyke of the North Zone. Th i s dyke was d e f i n i t e l y int ruded i n t o a l r eady con so l i da ted Moosevale Formation rocks and i s most l i k e l y c o r r e l a t i v e w i t h o ther ba s i c i n t r u s i o n s which po s t -da te the Hazel ton Group. Th i s i n d i c a t e s that the dyke was in t ruded a f t e r the Lower J u r a s s i c Hazelton Group and t h e r e f o r e the copper m i n e r a l i z a t i o n i s at l e a s t of Lower J u r a s s i c age. The second problem is that the copper and metamorphic m i n e r a l i z a t i o n are i n t i m a t e l y intergrown and appear 180 to have a common genes i s . The copper minera l s do not predate format ion of metamorphic m i n e r a l s . 6,3 A U n i f y i n g Genet ic Model f o r Sustut Copper Deposit  6.3.1 I n t r oduc t i on to the Model The w r i t e r b e l i e v e s that copper and s u l p h u r - r i c h hydrothermal s o l u t i o n s f lowed upwards through permeable passageways, mainly f r a c t u r e swarms, in the upper Moosevale Formation at the Sustut d e p o s i t . Th is upward f low cont inued u n t i l c e r t a i n permeable interbeds w i t h i n the vo l c a n i c l a s t i c sequence were encountered, whereupon the s o l u t i o n s spread l a t e r a l l y through the i n te rbeds . With the f l u i d i n f l u x f i l l i n g pore space in the i n t e rbed s , the s o l u t i on s then f lowed upwards from the interbeds i n t o o v e r l y i n g host rock, u n t i l o ther i n t e r -beds were encountered in which l a t e r a l f l ow aga in o c cu r r ed . These f l u i d - f i l l e d in terbeds are now represented by the c h a l c o c i t e - b o r n i t e ore l en se s . This model i s shown s c h e m a t i c a l l y in f i g u r e 82. The f r a c t u r e channelways, that fed and in te rconnected the ore l enses , are represented now by swarms of t h i n su1phide-gangue ve ins which cut through the p roper ty . The feeder mechanics of these ve ins i s supported by severa l l i n e s of ev idence . Most obvious is the c l o s e s p a t i a l i n t e r r e l a t i o n of ve ins and ' o re l en se s . As p r e v i o u s l y s t a t e d , i n outcrop ore ve in s appear above and below ore l en se s , and are not apparent w i t h i n ore l en se s . A l s o q u a l i t a t i v e examinat ion o f d r i l l core revea l s that ve i n m i n e r a l i z a t i o n is most s i g n i f i c a n t below the main ore ho r i zons where l en so id ore forms become le s s common and important . The s t e e p l y d i pp i ng or v e r t i c a l nature of the ve ins i s a l s o c on s i s t en t w i t h t h e i r a c t i n g as channelways f o r deeply der i ved hydrothermal f l u i d s . The same hydrothermal s o l u t i o n s from which the copper ions p r e c i p i t a t e d , were a l s o r e spon s i b l e f o r the development of the open s p a c e - f i l l i n g metamorphic m i n e r a l s . Th i s c onc l u s i on f o l l ows n a t u r a l l y from the obse rva t ions that the j^w^REeTiON-tfF OR£^ FLUIDS TABULAR COPPER „ F igure 82: Conceptual model f o r genesis of Sustut Copper d e p o s i t . The upper diagram shows the depo s i t l o c a l i z e d in a s t r u c t u r a l l y c o n t r o l l e d thermal high that caused a n o d e - l i k e i r r e g u l a r i t y in the reg iona l metamorphic i sograd. The lower diagram i s a h i gh l y i d e a l i z e d i l l u s t r a t i o n o f copper minera l and p y r i t e zoning w i t h i n a m i n e r a l i z e d t abu la r zone. In r e a l i t y , zones o ve r l ap e x t e n s i v e l y . V e r t i c a l l i n e s are schematic r ep re sen ta t i on o f ve in swarms. Dominant minera l s in zones are as f o l l o w s : Cu -na t i ve copper, c c - c h a l c o c i t e , b o - b o r n i t e , cp-cha1 c o p y r i t e , p y - p y r i t e . 182 s u l ph i de and metamorphic minera l s are i n t i m a t e l y intergrown and thus appear to have a common o r i g i n . The interbeds which are m i n e r a l i z e d p r e f e r e n t i a l l y have been desc r ibed p r e v i o u s l y as o p t i m a l l y su1 phi de -m ine r a l i z ed hor izons ( s e c t i o n 5-2.4, above). The reason that hydrothermal s o l u t i o n s f lowed l a t e r a l l y through these l e v e l s and no o ther s is because these interbeds had h igher p e r m e a b i l i t i e s than the o the r subun i t s ' W i t h i n the general v o l c a n i c l a s t i c p i l e . It should be noted tha t where s u l p h i d e - r i c h ve in s cut impermeable host rock, smal l gangue-f i11ed pores , w i t h i n the host rock c l o s e to the v e i n , l o c a l l y c on t a i n s u l ph i de s . The i r random nature and a rea l ex tent s occur because (as. s t a ted in the Property Geology chapter) in terbeds in the Moosevale e x i s t as seperate f a c i e s w i t h i n a v o l -c a n i c l a s t i c p i l e made up of w ide l y d i f f e r i n g , i n t e r d i g i t a t e d sed imento log i ca l t ypes . The metamorphic grade o f the depos i t i s h igher than that o f o the r rocks at equ i v a l en t s t r a t i g r a p h i c l e v e l s because of the e f f e c t o f the r i s i n g , hot hydrothermal s o l u t i o n s which r a i s ed the temperature of the rocks i n to which the s o l u t i o n s i n t r uded . The Sustut depos i t can be l i k ened to a node o f r e l a t i v e l y h igher grade metamorphism w i t h i n the reg iona l l aumont i te f a c i e s . A l l of the open s p a c e - f i 1 1 i n g metamorphic minera l s at Sustut are of the p r e h n i t e -pumpe l l y i t e f a c i e s and no z e o l i t e s are present . Thus, i f the m i n e r a l i z i n g s o l u t i o n s caused development of minera l s of the p r e h n i t e - p u m p e l l y i t e f a c i e s , then they e f f e c t i v e l y increased the metamorphic grade. The r e s t r i c t i o n o f s i g n i f i c a n t copper occurrencesand p r e h n i t e - p u m p e l l y i t e . f a c i e s w i t h i n the upper member of the Moosevale Formation to the Sustut d e p o s i t , may i n d i c a t e that the f r a c t u r e channelways d i d not e x i s t in o ther areas of t h i s member and t h e r e f o r e f l u i d s cou ld not r i s e . b.3.2 Paragenet ic Sequence The s i m p l i f i e d pa ragenet i c sequence fo r the m e t a l l i c m inera l s found on 183 Sustut i s shown in f i g u r e 83. Magnetite and minor hematite are pyrogen ic . The su lph ides and n a t i v e copper are hydrothermal in o r i g i n and are represented on the diagram in o rde r o f t h e i r appearance (hematite II appears he re ) . Some minor d i g e n i t e and a l l of the c o v e l l i t e are c l a s s i f i e d as supergene - they r e su l t ed from l a t e r o x i d a t i o n of p r e - e x i s t i n g s u l ph i de s . Th i s o x i d a t i o n i s assumed to be un re la ted to the main m i n e r a l i z i n g ep i sode. 6.3.3 Causes o f Ore Zonat ion and S i m i l a r Zonat ions from Other Deposits The zona t i on o f m e t a l l i c su lph ides around na t i ve copper cores was caused by outward m i g r a t i o n of sulphur (with some copper) s o l u t i o n s from an in terbed in to which hydrothermal s o l u t i o n s had o r i g i n a l l y f l owed. The porous in terbed can be thought of as a locus from which m i n e r a l i z i n g s o l u t i o n f r on t s advanced in to adjacent country rock. A one - s ided zonat ion w i t h equ i va l en t m i n e r a l o g i c a l changes as those in the Sustut d e p o s i t , has been descr ibed by Brown (1971) f o r the White P ine Copper Deposit of M i ch i gan . In t h i s depo s i t , c h a l c o c i t e (with rare na t i ve copper) occurs at a de f ined s t r a t i g r a p h i c l e v e l w i t h i n the Nonesuch Sha le, 6 to 15 m above the base o f t h i s u n i t . Th is c h a l c o c i t e de f i ne s Brown's " c u p e r i f e r o u s zone" which grades upwards to zones of b o r n i t e , s t a b l e w i t h c h a l c o c i t e , a second b o r n i t e , not w i t h c h a l c o c i t e , c h a l c o p y r i t e , and f i n a l l y p y r i t e . Greenock i te occurs in the c h a l c o p y r i t e - p y r i t e zones. Th i s zonat ion is seen in t abu l a r zones at Sus tut , bu t . the zonat ion occurs both above and below the cen t r a l copper co re . Brown v i s u a l i z e s the White P ine depos i t (and zonat ion) as the product of an "upward advancing m i n e r a l i z a t i o n f r o n t ( f r i n g e ) " caused by the m ig ra t i on of c o p p e r - r i c h s o l u t i o n s p r o g r e s s i v e l y up through the Nonesuch Formation from under-l y i n g a reas . The p y r i t e of the Nonesuch predates copper m i n e r a l i z a t i o n , thus Brown says the copper p r e c i p i t a t e d around and rep laced the o r i g i n a l p y r i t e . Brown s ta te s that the upward m ig ra t i on of the f l u i d s cou ld conce ivab ly be exp la i ned by e i t h e r ' d i f f u s ion or i n f i l t r a t i o n mechanisms. The u l t i m a t e source of the copper "may l i e in primary magmatic c o n t r i b u t i o n s or e x t r a c t i o n of metals P y r o g e n i c H y d r o t h e r m a l S u p e r g e n e M a g n e t i t e H e m a t i t e N a t i v e C o p p e r C h a l c o c i t e D i g e n i t e B o r n i t e C h a r c o p y r i t e G r e e n o c k i t e P y r i t e C c v e i I i t e J j j F igure 83: S i m p l i f i e d paragenet ic mineral sequence fence diagram f o r Sustut Copper o r e s . 185 from the t h i c k v o l c an i c - s ed imen ta r y p i l e of the Keweenawan bas i n" ( i b i d. , p. 543). Robertson (1975) has desc r ibed a s i m i l a r zoning p a t t e r n ' o f m e t a l l i c m inera l s in the Mount Bohemia depos i t of M ich igan. Rober t son ' s model f o r the o r i g i n of t h i s depos i t i n vo l ve s upward movement of c o p p e r - r i c h hydrothermal s o l u t i o n s a long f r a c t u r e s and then movement "outward along r e l a t i v e l y permeable f l ow tops and broken dyke marg ins " ( i b i d . , p. 1202). The zona t i on e x i s t s as c h a l c o c i t e , nearest the i n f i l t r a t i o n po in t of s o l u t i o n s i n to permeable l e v e l s , which grades i n to b o r n i t e that occurs in two forms. A c o p p e r - r i c h b o r n i t e forms nearest c h a l c o c i t e , whereas f u r t h e r outward, a b o r n i t e forms w i t h some exso lved c h a l c o p y r i t e . C h a l c o p y r i t e occurs next , and f i n a l l y p y r i t e makes an appearance as the outermost s u l p h i d e . Robertson a s c r i be s the zonat ion to e i t h e r ; a s o l u t i o n of constant compos i t ion g r adua l l y m ig ra t i ng through the host rocks and p r e c i p i t a t i n g s u l ph i de minera l s as concen t ra t i on and redox r e l a t i o n s pe rm i t t ed ; o r to a s o l u t i o n of changing compos i t ion through t ime, which f i r s t depos i ted p y r i t e , changed chem ica l l y and reacted w i t h some of the p y r i t e and produced c h a l c o p y r i t e , e t c . , u n t i l cha1coc i te was produced as the f i n a l p roduct . Brown (1974) conducted p r e c i p i t a t i o n chromatography exper iments on Cu-Cd-Zn-Pb s o l u t i o n s in o rder to determine the s i g n i f i c a n c e of g reenock i te m i n e r a l i z -a t i o n in c h a l c o p y r i t e - p y r i t e zones of the White P ine depos i t (as above). He found that when such a s o l u t i o n was pumped in to a s i l i c a g e l , CdS (g reenock i te) always p r e c i p i t a t e d b e f o r e , and advanced ahead o f , copper s u l p h i d e s . This i n d i c a t e s that the g reenock i t e has a g rea te r m o b i l i t y than the copper su lph ides and " can be apparent l y d i s p l a c e d over s i g n i f i c a n t d i s t ance s by rap id i n f i l t r a t i o n of s o l u t i o n s c on ta i n i n g metal ions of l e s s mobi le metal s u lph ide s ( i e . Cu s u l p h i d e s ) " ( i b i d . , p c 274). Greenock i te is found in the c h a l c o p y r i t i c zones both above and below the cores of ore hor izons at Su s tu t , and would seem to have formed from an advancing f l u i d f r o n t that preceded copper s u l ph ide s which are s ymmet r i ca l l y arranged behind g reenock i te in the ore h o r i z o n s . Th is w r i t e r t h e r e f o r e suggests f o r Sus tut , that zona t i on around the c e n t r a l 186 l o c i of c h a 1 c o c i t e - n a t i v e copper cores is due to outward m i g r a t i o n , of the s e l f -same hydrothermal s o l u t i o n s that depos i ted the co re s , as advancing f l u i d f r o n t s . The w r i t e r b e l i e v e s the zonat ion was caused by p rog re s s i ve chemical changes ( to be desc r ibed be low) . Greenock i te is found in f a c t to be at the head of the f r o n t , ahead of the copper s u l ph i de s , as experiments by Brown (1974) would have suggested. 6.3-4 Chemistry of P r e c i p i t a t i o n To p rec lude d i s c u s s i o n of p r e c i p i t a t i o n mechanics, as many phy s i ca l and chemical c o n s t r a i n t s as po s s i b l e should be p laced on the o re - fo rming system. The pH of the system i s taken as being near neu t ra l because c a l c i t e is i n t e r -grown e x t e n s i v e l y w i t h the m e t a l l i c m ine ra l s . The Cu ions were C u + and they were in c h l o r i d e complexes as C u C ^ (these forms are the most w ide l y accepted modes o f t r an spo r t of Cu in hydrothermal s o l u t i o n s , t h i s is not to suggest that a l l copper ions are in the +1 s t a t e , o r that a l l copper ions are complexed s o l e l y by c h l o r i d e i on s , but f o r the sake o f a q u a l i t a t i v e ana l y s i s of o r e -forming chemi s t r y , some s i m p l i f y i n g assumptions are neces sa ry ) . F igure 84 i s a pH v s . log fg diagram w i t h the major aqueous su lphur spec ie s present at 300'C and 1 bar p re s su re . (300'C is an acceptab le temperature as a l l i n d i c a t i o n s show the temperature of fo rmat ion of the depos i t was in t h i s neighbourhood ( i e . 300 to 400°C) , thermodynamic data f o r t h i s S system i s of poor q u a l i t y above 300*C and 1 bar p r e s s u r e ) . Neutra l pH at 306 'C, from Barnes et a l . (1966), i s about 5.73. The breakdown o f magnetite to hematite occurs at a log f^ of about -30.00 (Helgeson et a l . , 1969), t h i s puts a c o n s t r a i n t on the oxygen f u ga c i t y of the s o l u t i o n as magnet i te d i s s o l v e d and hematite p r e c i p i t a t e d w i t h the onset of ore m i n e r a l i z a t i o n . Thus, from f i g u r e 84, the dominant su lphur spec ies present in the o re - f o rm ing s o l u t i o n s , at the o u t s e t , would have been HSO^ (us ing a s t a r t i n g pH of 5.73 and log f of g rea te r than -30.00) . 2 The i n i t i a l hydrothermal s o l u t i o n s were more o x i d i z i n g (and the re fo re les s reducing) and more c o p p e r - r i c h than the host rocks they invaded. This i s 187 o o to _ I o OD. I 0.0 2.0 A.D 5.7 PH 8.0 lff.O 12.0 14.0 F igure 8k: Log f - vs_. pH diagram o f the dominant aqueous su lphur spec ie s 2 at 300"C and 1 bar pres sure. This i s a computer-generated f i g u r e . I n i t i a l c o n t r a i n t s on f l u i d compos i t ion are pH of 5.7 and log f . of -30.00. 2 188 shown by the breakdown o f p y r o g e n i c m a g n e t i t e w i t h r e s u l t a n t f o r m a t i o n o f h e m a t i t e , and o f c o u r s e , t h e p r e c i p i t a t i o n o f c oppe r m i n e r a l s . As the r e a c t i o n o f w a l l r o c k and f l u i d p r o g r e s s e d , t h o u g h , the f l u i d became more reduced i n n a t u r e (j_e. t h e f . d e c r e a s e d and t he f_ i n c r e a s e d i n t h e s o l u t i o n ) such t h a t 2 b2 p y r i t e fo rmed as a f i n a l p r o d u c t o f t h e r e a c t i o n s . The z o n a t i o n d e s c r i b e d above i n d i c a t e s n a t i v e c o p p e r fo rmed f i r s t . C u p r i t e and c h a l c o c i t e f o r m a t i o n was a l m o s t penecontempouraneous w i t h the n a t i v e c oppe r p r e c i p i t a t i o n . C o i n c i d e n t w i t h t he f o r m a t i o n o f t h e s e c o p p e r m i n e r a l s , m a g n e t i t e , and f e r r o - m a g n e s i u r n s i l i c a t e s o f t h e ho s t r o c k s were b r e a k i n g down and r e l e a s i n g i r o n i on s to t h e s o l u t i o n . The i r o n was i n t h e o x i d i z e d f e r r i c s t a t e and p r e c i p i t a t e d as h e m a t i t e . The o r e m i n e r a l o g r a p h y shows n a t i v e c o p p e r , c u p r i t e and c h a l c o c i t e i n t e r g r o w n , and c h a l c o c i t e i n t e r g r o w n w i t h h e m a t i t e II i n t h e same g e n e r a l a r e a s . The g e n e r a l f o rm o f t h e p r o g r e s s i v e p r e c i p i t a t i o n r e a c t i o n s w i l l be p r e -s e n t e d b e l o w . These r e a c t i o n s a r e s t e p w i s e and w r i t t e n such t h a t c o n s i s t e n c y between t h e c h a n g i n g n a t u r e o f t h e f l u i d s and w a l l r o c k i s m a i n t a i n e d . Components d e s t r o y e d o r c r e a t e d a r e q u a l i t a t i v e l y c o r r e c t but use o n l y t h e supposed ma jo r s p e c i e s p r e s e n t i n t he s o l u t i o n . Thu s , they a r e o n l y a g u i d e as t o what happens and s h o u l d not be c o n s t r u e d as t h e o n l y , o r even n e c e s s a r i l y c o r r e c t , r e a c t i o n s o c c u r i n g i n t h e s y s t e m . A s suming n a t i v e c o p p e r p r e c i p i t a t e d f i r s t , : the r e a c t i o n can be v i ewed a s : 1 ) 2 C u C 1 2 ( a q ) + H 2 ° * 2 C U + 2 H C 1 ( a q ) + 2 C 1 ( a q ) + * ° 2 0^ i s not a c t u a l l y p r e s e n t w i t h i n t he s o l u t i o n and t h e r e f o r e most l i k e l y combines w i t h t he c o p p e r t o f o r m c u p r i t e a s : 2) Cu + J f0 2 * CuO O x i d a t i o n o f m a g n e t i t e t o h e m a t i t e w o u l d a l s o use some o f t h e 0^ f rom r e a c t i o n 1. Aqueous HCI was w r i t t e n as a p r o d u c t i n r e a c t i o n 1 i n o r d e r t o b u f f e r t h e pH o f t he s o l u t i o n and not l o w e r i t . T h i s i s p a r t i a l l y c o r r e c t as H e l g e s o n (19&9) d e s c r i b e d the l o g ' o f t h e d i s s o c i a t i o n c o n s t a n t , a t 3 0 0 " C , f o r HCI as 189 being -1.24 which i n d i c a t e s a K of .0575, meaning reactants are more s t a b l e (H +) (CI") than products (_i_e. K = — ( n C l ) — ^' P r o < ^ u c t ' o n °^ excess CI in the s o l u t i o n thus cou ld cause the product H + to react and c rea te HC1. It should be noted that the ac tua l H + and CI c o n t r i b u t i o n to the s o l u t i o n would be very minor add i t i o n s to the f l u i d s content of these ions and any HC1 product ion i s a c t u a l l y neg l i g i b l e . P roduc t i on o f n a t i v e copper and c u p r i t e e f f e c t i v e l y decreased the f and 2 increased the f_ to the extent that c h a l c o c i t e format ion became s t a b l e . Th is b 2 p roduc t i on of c h a l c o c i t e occured at near l y the same time as that of na t i ve copper and c u p r i t e and occured w i t h the o x i d a t i o n and p r e c i p i t a t i o n o f i r on ions (as hematite 11) in t roduced i n to the s o l u t i o n by breakdown of primary minera l s in the host rock. Th is r e a c t i on could have gone as : 3) 2 C u C l - ( a q ) + H S 0 - ( a q ) * Cu 2S + H C 1 ( a q ) + 3 C l ^ q ) + 2 0 2 however 0 2 c ou l d not a c t u a l l y be a phase w i t h i n the system ( i e . the log f^ is less than - 2 0 ) . In i t s p lace magnetite would be o x i d i z e d to hemat i te . React ion 3 would then a c t u a l l y be: 4) 2CuC l~ , » + H S 0 7 , » + 8Fe,0. + C u o s + HC1, x + 3C1T \ + 12Fe„0. 2(aq) 4(aq) 3 ^ 2 (aq) (aq) 2 3 Reactant i r on content in 4 (w r i t t en as magnetite) i s mainly schematic as some i r o n would be c o n t r i b u t e d from s i l i c a t e s . As t h i s r e a c t i o n progressed the system would move away from na t i ve copper s t a b l e f u r t h e r i n to the c h a l c o c i t e f i e l d . This p rog re s s i on changes the s o l u t i o n chemist ry f u r t h e r as i l l u s t r a t e d by a decrease in f n and increase in f_ . As the s o l u t i o n changed the b o r n i t e s t a b i l i t y 2 2 f i e l d would be e v e n t u a l l y reached. Coupled w i t h a decrease in the f - , the °2 dominant su lphur spec ie s in s o l u t i o n changed s l o w l y . F igure 84 shows e q u i l i b r i a between su lphur phases HSO^ and h^S, at neut ra l pH, occurs in a log fg range of -29 to -30. With the onset of bo r n i t e s t a b i l i t y , some H2S was probably invo lved in the r e a c t i o n as a major su lphur spec i e s . Magnet i te was s t i l l being o x i d i z e d to hematite II du r i ng bo r n i t e p r e c i p i t a t i o n , as shown by minera log raph ic i n t e r -190 growths o f b o r n i t e and hematite I I. The bo rn i t e fo rmat ion can be v i s u a l i z e d as: 5 ) 5 C u C , 2 ( a q ) + F e ( a q ) + 2 H S 0iV<aq) + 2 H 2 S ( a q ) + l 6 F e 3°<. * Cu 5 FeS A + 1 0 C l " a q ) + 2 4 F e 2 0 3 + 6 H| a q ) This r e a c t i o n is a c t u a l l y the in termed iate one in the fo rmat ion of ' b o r n i t e . Bo rn i t e has an e x ten s i v e s o l i d s o l u t i o n f i e l d . B o r n i t e I (the copper-r i c h v a r i e t y ) would have more copper than s t o i c h i o m e t r i c Cu^-FeS^. This bo rn i t e type was the f i r s t formed o f the bo rn i t e s and as phys io -chemica l changes were t a k i n g p lace w i t h i n the s o l u t i o n , the bo rn i te s became p r o g r e s s i v e l y more i r o n -r i c h and copper-poor ( i e . b o r n i t e s l l a and l i b ) . When the b o r n i t e I f i r s t s t a r t e d f o rm ing , HSO^ was probably s t i l l the main su lphur spec ies i n s o l u t i o n . With p ro -g r e s s i v e decrease, in the o x i d i z i n g nature of the f l u i d s , the amount of H S^ i nc reased and the o x i d a t i o n of magnet ite to hematite slowed ( i e . as the bo rn i t e s became i r o n - r i c h ) . When the s o l u t i o n began p r e c i p i t a t i n g the l a s t of the b o r n i t e s (the i r o n - r i c h ones ) , the redox r e l a t i o n s of the r e a c t i o n changed such that o x i d a t i o n of H^S became more important than o x i d a t i o n o f magnet i te . This i s shown in the mineralography as hematite i s intergrown most commonly w i t h b o r n i t e I and le s s commonly w i t h bo rn i t e s l l a and l i b . With p r e c i p i t a t i o n of the most i r o n - r i c h b o r n i t e s , the s o l u t i o n entered a f - - f _ s t a t e wherein the c h a l c o p y r i t e s t a b i l i t y f i e l d was en t e r ed . The 2 2 p r e c i p i t a t ion of c h a l c o p y r i t e i n d i c a t e s that the copper ion content had decreased r e l a t i v e to that i n the o r i g i n a l s o l u t i o n . The c h a l c o p y r i t e p r e c i p i t a t i o n probably occured as: • 6 ) C u C 1 2 ( a q ) + F e U q ) + 2 H 2 S ( a q ) * C u F e S 2 + K a q ) + 2 C 1 ( a q ) H^S i s now the dominant su lphur spec ies due to o x i d a t i o n s t a t e of the system at that po i n t . Iron is present i n the f e r r i c s t a t e though as the f i s °2 such that fer rous i r on is not s t a b l e . F i n a l l y the s o l u t i o n reaches a stage in which p y r i t e becomes s t a b l e . At t h i s po in t the s o l u t i o n was in i t s most reduced s t a t e . This r eac t i on can be viewed as: 191 7) 2 F e t + + , + 2 H 0 S , v Z FeS. + kH+. , + F e t + v (aq) 2 (aq) 2 (aq) (aq) In e f f e c t , f e r r i c i ron is reduced in t h i s r e a c t i o n 7 to fe r rous i r o n . The increase in the fe r rous i r on content cou ld conce i vab l y have caused the p r e c i p i t a t i o n o f c h l o r i t e . This would e x p l a i n the ex ten s i ve in tergrowth of p y r i t e w i t h ch1 o r i t e . Thus the s o l u t i o n has changed p r o g r e s s i v e l y from an o x i d i z i n g nature to a reducing one. F igure 85 i s a log f_ vs_. log f^ diagram, at 300*C and 1 bar pres sure , U 2 b 2 wi th the s t a b i l i t y f i e l d s of a l l re levant phases in the Cu-Fe-S-0 system represented. The p rog re s s i ve r e a c t i on path, as suggested above in the equat ions 1 - 7, de sc r i be s a s t r a i g h t l i n e path from na t i ve c o p p e r - c u p r i t e s t a b l e , in the hematite realm, to p y r i t e s t a b l e in the hemat i te realm ( i e . from A to B on the f i g u r e ) . The s t a b i l i t y r e l a t i o n s of g reenock i te (CdS) and monteponite (CdO) are a l s o represented on t h i s diagram. (The r e l a t i o n s o f these two phases were determined us ing the data of Robie et a l . (1978) ). The CdS-CdO e q u i l i b r i u m l i n e i s on ly approximate as the thermodynamic data f o r these two minera l s are not of h igh q u a l i t y . However, i t i s apparent that CdS i s s t a b l e through a l l pa r t s of the r e a c t i o n path f o r the su lph ide m ine ra l s . S ince g reenock i t e is found on ly w i t h c h a l c o p y r i t e , at i t s time of p r e c i p i t a t i o n the dominant su lphur spec ies was H 2 S. The p r e c i p i t a t i o n probably occurred as: 8) C d C l - 3 ( a q ) + H 2 S ( a q ) * CdS + 2 H ; a q ) + 3 C l " a q ) The prescence o f g reenock i te w i t h c h a l c o p y r i t e may i n d i c a t e that the CdCI^ content was low enough that su lphur spec ies in the form of H 2S ( i e . s u l f i d e , not s u l f a t e ) was necessary in o rder to p r e c i p i t a t e (?e. H 2S becomes dominant w i t h i n the c h a l c o p y r i t e s t a b l e r e g i on ) . This may be i n f l uenced by the f a c t that CdS p r e c i p i t a t i o n from HSO^ would invo lve a re l ea se of C>2 which could not have occured as i n d i c a t e d by the low f^ cond i t i on s o f the s o l u t i o n and host rocks at t h i s s tage. This hypothes i s i s more reasonable than Brown's (1974) suggest ion that g reenock i te occurred outermost in an advancing f l u i d f r o n t due to the 192 T = 3 0 0 ° C P = Q r s I \ i i - 1 0 T e n o r t t © + H e m o t t cr o LU « - 3 0 X o cr o C u p r i t e + H em o 1 1 1 e C o p p e r + Hen io t i o p p e r T Ff C o p p e r + F - 5 0 H - 6 0 C o p p e r + Jo "C "D - 5 0 40 T r on T T i 9 i Q. CJ - 3 0 - 2 0 LOG fl (SULFUR GflS) Q . I a (J - 1 0 i i M a I c CD Figure 85: Log f . - log f . diagram f o r the Cu-Fe-Cd system at 300 ' C 2 2 and 1 bar p re s su re . This i s a computer-generated f i g u r e . The reac t i on path f o r p r e c i p i t a t i o n of m e t a l l i c minera l s in the Sustut depos i t runs from A to B on t h i s diagram. A i s the supposed i n i t i a l compos i t ion of hydrothermal s o l u t i o n s and B the f i n a l compos i t ion a f t e r r e a c t i on w i t h w a l l rock. Phase abb rev i a t i on s are the same as in f i g u r e 80. Monteponite, CdO; g r e e n o c k i t e , CdS; cadmium, Cd; magnet i te , Mt. 193 g rea te r m o b i l i t y o f Cd ions . 6.3.5 S i g n i f i c a n c e o f Mineral Zoning in R e l a t i o n to Changing Chemistry of S o l u t i o n The r e a c t i o n path desc r ibed in f i g u r e 85 e x a c t l y corresponds to the idea l zona t i on of the m e t a l l i c m inera l s w i t h i n the Sustut ore body. Thus the o r i g i n of the ore lenses and t h e i r zonat ions can be po s tu l a ted as f o l l o w s ; the hydrothermal s o l u t i o n s which f lowed i n t o optimum ore hor izons were much more o x i d i z i n g than the host rocks ( i n f a c t the hosts were r e l a t i v e l y reduc ing ) . Upon f l u i d i n f l u x , the s o l u t i o n s and w a l l rock began to react i n o rde r to a t t a i n an e q u i l i b r i u m between the d i f f e r i n g o x i d a t i o n s t a t e s . Ferro-magnesiurn s i l i c a t e s and magnet i te were broken down in the host rocks and na t i ve copper w i t h c u p r i t e p r e c i p i t a t e d from s o l u t i o n . C h a l c o c i t e then began p r e c i p i t a t i o n as the o x i d a t i o n s t a t e was lowered in the s o l u t i o n (and f . was e f f e c t i v e l y i n c rea sed ) . 2 The s o l u t i o n was thus p r o g r e s s i v e l y changing. Along w i t h p r e c i p i t a t i n g copper m i n e r a l s , the s o l u t i o n began to mig rate outwards from i t s locus of i n f l u x i n to surrounding country rock. When c h a l c o c i t e -n a t i v e coppe i—cupr i t e p r e c i p i t a t e d w i t h metamorphic minera l s w i t h i n the cores of the ore zones, the chemica l l y changed s o l u t i o n reacted w i t h f r e s h wa l l rock away from the co re s . Th i s s o l u t i o n was s t i l l o x i d i z i n g r e l a t i v e to the host r ock s , except the s o l u t i o n had changed such that c oppe r - r i c h b o r n i t e s t a r t e d to p r e c i p i t a t e . This outward m i g r a t i on of c o n t i n u a l l y changing s o l u t i o n compos i t ions which reac ted w i t h f r e s h w a l l rock, caused p rog re s s i ve , d i f f e r e n t i a l p r e c i p i t a -t i o n o f s u l ph i de m ine r a l s . When the s o l u t i o n reached i t s maximum i n f i l t r a t i o n po i n t i n the hos t , i t had ach ieved a reduc ing s t a t e almost l i k e tha t o f the country rock (j_e. country rock f - f compos i t ion was near B on f i g u r e 85) U2 b2 and the most reduced s u l ph i de , p y r i t e , was p r e c i p i t a t e d . At t h i s po in t copper had been e f f e c t i v e l y removed from s o l u t i o n , as had cadmium and most l i k e l y o the r metals ( i e. when CdCl^ was removed from s o l u t i o n in the c h a l c o p y r i t e f i e l d where s u l ph i de su lphur spec ies (_i_e.H ?S) was dominant, o ther t r a ce metals cou ld 194 conce i vab l y have been drawn out of s o l u t i o n w i th t h i s su lphur change). Thus in the end the s o l u t i o n had ach ieved a redox s t a t e equ i v a l en t to that of the host rocks such that e q u i l i b r i u m was reached and the s o l u t i o n was a l s o dep leted in aqueous metal complexes. The idea l z ona t i on p a t t e r n i s , at bes t , i r r e g u l a r l y developed i n the Sustut d e p o s i t . The i r r e g u l a r i t i e s could be caused by incomplete r e a c t i on of f l u i d and wa l l rock, impermeable l aye r s through which s o l u t i o n s cou ld not f low and thus had to react in a s i n g l e a rea , or sma l le r c oncen t r a t i on s (or amounts) of i n f l u x i n g s o l u t i o n s r e l a t i v e to the host rock. Areas such as those cut by DDH's 25 and 132, tend to i n d i c a t e that there is a broad p y r i t i c ha lo to the whole upper Moosevale Formation that conta ins the ore l en se s . Th is i s conce i vab l e as s o l u t i o n s f u r t h e s t from t h e i r source l o c i would p r e c i p i t a t e p y r i t e , thus the broad halo could be a r e s u l t o f the most o u t -ward m i g r a t i on of hydrothermal s o l u t i o n s from a complete area o f copper concen-t r a t i o n (J_e_. the upper Moosevale) . 6.4 U l t ima te O r i g i n of Hydrothermal F l u i d s The o r i g i n of the hydrothermal s o l u t i o n s is p r ob l emat i c a l as not enough data were gathered on the rocks d i r e c t l y under l y ing the depos i t to deal d i r e c t l y w i t h t h i s problem. Sulphur i sotope analyses cou ld shed some l i g h t on the o r i g i n of the su lphur , but u n f o r t u n a t e l y these analyses were not completed in time f o r t h i s t h e s i s . The high background copper contents of the whole reg iona l sequence of rocks ( i n c l u d i n g the A s i t k a Group), suggest that a mechanism which leached copper values from the host rocks cou ld have led to concen t r a t i on and p r e c i p i t a t i o n h igher up in the sequence. Th i s is a g e n e r a l i z a t i o n o f Ha rpe r ' s (1977) and J o l l y ' s (1974) models. Problems a r i s e when a s s i gn ing the hydrothermal f l u i d s to t h i s mode of o r i g i n . In the f i r s t p lace there does not seem to be any great d e p l e t i o n in copper contents on the property and no area w i t h i n the reg ion has had such a d e p l e t i o n reported by o t h e r s . 195 A second ques t i on is where d id the aqueous su lphur spec ies come from. Ne i the r J o l l y (1974) nor Harper (1977) have suggested how the vast quan t i t y of su lphur cou ld have been de r i ved from host rocks . Turek ian (1972) s t a te s that average su lphur content of ba sa l t s is about 300 ppm and o f sandstones is about 240 ppm. S ince most of the Takla Group is v o l c a n i c l a s t i c in nature, a background su lphur content can be ass igned of between 240 and 300 ppm. In the case of the Keweenawan b a s a l t s , the average sulphur content would be above that of the Tak l a Group, however as J o l l y (1974) s t a ted there was no ev idence o f su lphur m o b i l i z a -t i o n . Evidence f o r b i o g e n i c o r i g i n of s u l ph i de i s t o t a l l y l a c k i n g i n the reg iona l area of Su s tu t . Shales are a very minor p o r t i o n o f the sequence. Another s i g n i f i c a n t problem w i t h in s i t u d e r i v a t i o n , i s the d i f f e r e n t o x i d a t i o n s t a t e s of the s o l u t i o n and the copper-host Tak la Group. The Tak la Group rocks had a low o x i d a t i o n s t a t e as shown by a log fp of <~30.00. The hydrothermal s o l u t i o n s had a higher o x i d a t i o n s t a t e i n d i c a t e d by a log fg o f >-25.00. It is imposs ib le to de r i ve a f l u i d w i t h a h i gher o x i d a t i o n s t a t e than the parent . Th i s w r i t e r does not wish to t o t a l l y r u l e out the po s s i b l e c o n t r i b u t i o n o f metamorph ica l ly de r i ved f l u i d s (from the Tak la Group) to the hydrothermal s o l u t i o n s from which the Sustut Copper Deposit was p r e c i p i t a t e d . However, a n o n - b a s a l t i c source i s e s s e n t i a l to produce the necessary o x i d a t i o n s t a te o f the ore f l u i d . Presumably such a f l u i d cou ld be de r i ved from an unde r l y i ng i n t r u s i o n , f o r example. No such i n t r u s i o n (or i n t r u s i v e s u i t e ) has been found in l o c a l mapping and may on l y be extant at great depth. 6.5 P o s s i b l e P ro spec t i ng Tools The Sustut Copper Deposit o f f e r s a unique oppo r t un i t y to study a hydro-thermal copper occurance (of economic p o t e n t i a l ) that has not undergone s t rong deformat ion o r po s t - o re metamorphism. There fo re i t i s more o r le s s i n the same form as at the time o f f o rmat i on . For t h i s reason g e n e r a l i z a t i o n s , based on a 196 mode of f o rma t i on , cou ld be used in o rder to l o c a t e another depos i t of s i m i l a r t ype . If the Tak la rocks had a g ene r a l l y un i fo rm p e r m e a b i l i t y throughout, c oncen t r a t i o n of su lph ides may not have occured as the su lph ides would have been d i s seminated through the host. Thus the most obvious f ea tu re to look f o r would be a t h i c k sequence of v o l c a n i c l a s t i c (or v o l c a n i c ) rock which con ta in s seperate and d i s t i n c t in terbeds (or f a c i e s ) that have v i s i b l y d i f f e r e n t pe rmeab i l -i t i e s and p o r o s i t i e s due to amygdules, f l ow top s , f r a c t u r e zones, porous t u f -faceous u n i t s , e t c . If such a s t r a t i g r a p h i c sequence i s found, f o l l ow -up i n v e s t i g a t i o n should n a t u r a l l y i nvo l ve d e t a i l e d examinat ion f o r small lenses of s u l p h i d e - b e a r i n g host rock. These lenses may be of small enough extent that they cou ld be missed by reconnaissance mapping (as indeed Sustut was). Another h e l p f u l c l u e i s the appearance of w ide l y d i spe r sed g ra ins of p y r i t e s c a t t e r e d through such a p i l e . In.the case of Su s tu t , t h i s p y r i t e i s an envelope around c e n t r a l c o p p e r - r i c h a reas . Another method of p ro spect ing would i n vo l ve mapping of reg iona l meta-morphic f a c i e s and look ing f o r the source and a po s s i b l e d r i v i n g fo rce f o r the development of the metamorphic m ine ra l s . If the metamorphism appears to be due to some s o r t of i n t r u s i v e , and i f permeable zones are present w i t h i n the host rocks , then the host rock should be examined c a r e f u l l y f o r introduced s u l p h i d e s . Small s u l ph i de -bea r i n g v e i n l e t s c r o s s - c u t t i n g a host rock at steep ang les would a l s o be i n d i c a t i v e of po s s i b l e l e n s o i d concen t ra t i on s of s u l p h i d e . The host rock in t h i s case should be looked at f o r p o s s i b l e porous zones i n t e r s e c t e d by these v e i n l e t s . The host rocks to be examined in any of the cases above should be of a general b a s a l t i c nature as high copper contents of ba s a l t s may be the source of p o s s i b l e concen t r a t i on s of m i n e r a l i z a t i o n o r , more impo r tan t l y , the low o x i d a t i o n s t a t e of such ba s i c rocks could r e s u l t in a p r e c i p i t a t i n g mechanism f o r hydro-thermal f l u i d s o f a higher o x i d a t i o n s t a t e . 197 BIBLIOGRAPHY Armstrong, J . E . , 1946. T a k l a , B r i t i s h .Columbia. Geo l . Surv. Can., Map 844A. Armstrong, J e E e , "19^ *9 • Fort St. James Map Area, Cas s i a r and Coast D i s t r i c t s , B r i t i s h Columbia. Geol.. Surv. Can., Mem. 252, 210p.. Barnes, H.L., Helgeson, H.C., and E l l i s , A . J„ , 1966. I o n i z a t i o n Constants in Aqueous S o l u t i o n s , J_n Handbook of Phy s i ca l Constants , ed. C l a r k , S.P.. G.S.A., Mem. 97, pp. 401-413 B l anche t , P.H., and Godwin, C . I . , 1972. "Geolog System" f o r Computer and Manual Ana l y s i s of Geo log i c Data f o r Porphyry and Other Depos i t s . Econ. G e o l . , v. 67, No. 6, pp. 796-813. B l anche t , P.H. and Godwin, C. I . , 1978. Geolog: De t a i l ed d e s c r i p t i o n of rocks a s s oc i a ted w i t h vo lcanogen ic depo s i t s . Western Miner, F e b . v o l . , pp. 41-44. B r e t t , P.R., 1962. E x s o l u t i o n Textures and Rates in S o l i d S o l u t i on s Invo lv ing B o r n i t e . Carnegie Inst . Wash. Yearbook 61, pp. 155-157. B r e t t , P.R., 1963. The Cu-Fe-S System. Carnegie Inst. Wash. Yearbook 62, PP. 193-196. B r e t t , P.R., 1964. Exper imental Data from the System Cu-Fe-S and t h e i r Bear ing on E x s o l u t i on Textures in Ores. Econ. G e o l . , v. 59, pp. 1241-1269. Brown, A . C , 1971. Zoning in the White Pine Copper Depos i t , Ontonagon County, M ich i gan . Econ. G e o l . , v. 66, pp. 543"573. Brown, A . C , 1974. An Ep i gene t i c O r i g i n f o r S t r a t i f o r m Cd-Pb-Zn Su lph ides in the Lower Nonesuch Sha le , White P ine , M ich igan. Econ. G e o l . , v. 69., pp. 271-274. Buddington, A . f . , and L i n d s l e y , D.H., 1964. I ron-T i tan ium Oxide M ine ra l s and S yn the t i c Equ i v a l en t s . J ou r . P e t . , v. 5, p t . 2, pp. 310-357. Buerger, N.W., 1941. The C h a l c o c i t e Problem. Econ. G e o l . , V. 36, pp. 19~43. Burns, P . J . , 1973. S t r a t i g r aphy and Low Grade Metamorphism of the ' T a k l a -H a z e l t o n 1 Group, McConnell Creek Map-Area, No r th -Cent ra l B r i t i s h Columbia. Unpub. BSc t h e s i s at U n i v e r s i t y of B r i t i s h Columbia, 56p.. Ca rm i chae l , I.S.E., Turner, F . J . , and Verhoogen, J . , 1974. Igneous Pe t r o l o g y . McGraw-Hi l l Book Co., New York, 737p.• Church, B.N., 1973. Geology of the Sustut Area. B.C. Dept. of Mines and Petroleum Resources; Geology, E x p l o r a t i o n , and Min ing in B r i t i s h Columbia, pp. 411-443. Church, B.N., 1974. Geology of the Sustut Area. B.C. Dept. of Mines and Petroleum Resources; Geology, E x p l o r a t i o n , and Mining in B r i t i s h Columbia; pp. 305-309. 198 Cook, W o R . J r . , 1972. Phase Changes in Cu^S as a Funct ion of Temperature, in S o l i d S ta te Chemist ry . N a t l . Bur. of Stds. Spec. Pub. No. 364, pp. 703-712. Coombs, D.S., i960. Lower Grade Minera l Fac ies in New Zealand. Int. Geo l . Cong. XXI, Copenhagen, Report, P t . 13, pp. 339-351. C r a i g , J .R . , 1974. The Cu-S System, in S u l f i d e M inera logy . Min. Soc. Am. Short Course Notes, pp. CS58-CS76. Cress , P., D i r k sen , P., Graham, J.W. ,1970. Fo r t r an IV w i t h Watfor and W a t f i v , P r e n t i c e - H a l l Inc., New Je r sey , 447p.. Deer, W.A., Howie, R.A., and Zussman, J . , 1974. An I n t r oduc t i on to the Rock Forming M i n e r a l s . Longman, London, 528p.. F i s h e r , R.V., 1961. Proposed C l a s s i f i c a t i o n of V o l c a n i c l a s t i c Sediments and Rocks. G.S.A. B u l l . , v. 72, pp. 1409-1414. G a b r i e l s e , H., 1976. Environments of Canadian C o r d i l l e r a Depos i t i ona l Bas ing, J_n Circum P a c i f i c Energy and Minera l Resources. AAPG, Mem. 25, pp. 492-502. G a r r e l s , R.M., and C h r i s t , C L . , 1965. S o l u t i o n s , M i n e r a l s , and E q u i l i b r i a . Harper and Row, New York, 450p.. Geology, E x p l o r a t i o n and Min ing in B r i t i s h Columbia, 1974, B.C. Dept. of Mines and Petro leum Resources, pp. 293~305.. Godwin, C I . , Hindson, R.E., and B lanchet , P.H., 1977. Geolog: A Computer-Based Scheme f o r De t a i l ed A n a l y s i s o f S t r a t i g r a p h y , E s p e c i a l l y as a p p l i e d to Data from D r i l l Holes in Coal E x p l o r a t i o n or Development. CI MM B u l l . , v. 70, pp. 1-19.. Harper, G., 1973. Annual Report of Progress in 1972 on the Sustut C la ims. In terna l Dept. , Fa l conbr idge N icke l Mines L t d . , 87p.. Harper, G„, 1974. Annual Report o f Progress dur ing 1974 on the Sustut C la ims. Interna l Dept. , Fa lconbr idge N i cke l Mines L t d . , 49p.. Harper, G., 1976. Geology of the Sustut Copper Depos i t B r i t i s h Columbia. Paper presented at the 78th Annual General Meeting of the CIMM. Harper, G. , 1977. Geology o f the Sustut Copper Depos it in B r i t i s h Columbia. CIMM, B u l l . , v. 70, pp. 97-104. Helgeson, H . C , 1969. Thermodynamics of Hydrothermal Systems at E levated Temperatures and P res su res . Am. Jour . S c i . , v. 267, pp. 729-804. Helgeson, H . C , Brown, T .H . , and Leeper, R.H., 1969. Handbook of T h e o r e t i c a l A c t i v i t y Diagrams. Freeman, Cooper and Co., San Franc i sco, 253p-. 199 Hoffman, S . J . , 1977= Talus Fine Sampling as a Regional Geochemical E x p l o r a t i o n Technique in Mountainous Regions. Jour , of Geo. E x p l . , v. 7, PP. 349-360V I r v i ne , T .N . , and Baragor, W.R.A., 1971. A Guide to the Chemical C l a s s i f i c a t i o n of the Common V o l c a n i c Rocks. Can. Jou r . Earth S c i . , v. 8, pp. 523-548. J o l l y , W.T., 1974. Behaviour of Cu, Zn, and Ni dur ing P rehn i te -pumpe l1y i te Rank Metamorphism of the Keweenawan B a s a l t s , Northern M ich igan. Econ. G e o l . , v. 69, pp. 1118-1125. J o l l y , W.T., 1974. Regional Metamorphic Zonat ion as an a i d in study of Archean T e r r a i n s : A b i t i b i Region, O n t a r i o . Can. M in . , v. 12, pp. 499-508. Ker r , P.F., 1959. Op t i c a l M inera logy. McGraw-Hi l l Book Co., London, 442p.. L i o u , J . G o , 1971. Synthes i s and S t a b i l i t y Re l a t i o n s of P r ehn i t e , C a 2 A l 2 S i 3 0 1 0 ( 0 H ) 2 . Am. M in . , v. 56, pp. 507-531. Lord, C S . , 1946. McConnell Creek, B r i t i s h Columbia. Geo l . Surv. Can., Map 46-6. Lord, C.S., 1948. McConnell Creek Map A rea , Ca s s i a r D i s t r i c t , B r i t i s h Columbia. Geo l . Surv. Can., Mem. 251, 72p.. MacDonald, G.A., and Kat sura , T., 1964. Chemical Composit ion of Hawai ian Lavas. Jou r . P e t . , v. 5, pp. 477 _ 522. Monger, J.W.H., 1974. The Tak la Group near Dewar Peak, McConnell Creek Map Area (94D), B r i t i s h Columbia. Geo l . Surv. Can., Paper 74-1, P t . , B, pp. 29-30. Monger, J .W.H., 1977. The T r i a s s i c Tak la Group in McConnel1 Creek Map-Area, No r th -Cen t ra l B r i t i s h Columbia. Geo l . Surv. Can., Paper 76-29, 45p.. Monger, J .W.H., and Church, B.N., 1977» Revised S t r a t i g r aphy of the Tak la Group, Nor th -Cent ra l B r i t i s h Columbia. Can. Jou r . Earth S c i . , v. 14, pp. 318-326. Monger, J.W.H., and Pater son, I.A., 1974. Upper P a l eo zo i c and Lower Mesozoic Rocks o f the Omineca Mountains. Geo l . Surv. Can.,Paper 74-1, P t . , A, pp. 19-20. Morimoto, N., G r i e g , J.W., Tunnel 1, G., 1960. Re-examination of a Bo rn i t e from the Carn Brea Mine, Co rnwa l l . Carnegie Ins t . Wash. Year Book 59, pp. 122-126. Morimoto, N., and K u l l e r u d , G., 1961. Polymorphism in B o r n i t e . Am. M i n . , v. 46, pp. 1270-1282. Parsons, W.H., 1969- C r i t e r i a f o r Recogn i t i on of V o l c a n i c B r e c c i a s : Review. G.S.A. Mem. 115, pp. 263-304. 200 Pel 1y, D o , 1974. Pet ro logy and P o s s i b l e Genesis of the Red and Green Co lou ra t i on s in the Tak la V o l c a n i c s , McConnell Creek Map Sheet, Nor th -Cent ra l B r i t i s h Columbia. Unpub. BASc The s i s , U n i v e r s i t y of B r i t i s h Columbia, 23p.. P e t t i John, F.J. , '19 75 - Sedimentary Rocks. 3rd e d i t i o n , Harper and Row P u b l i s h e r s , New York, 628p„. P h i l l i p s , W.R . ,1971. M inera l O p t i c s , P r i n c i p l e s and Techniques. W.H. Freeman Co., San Francisco,, 249p.. Ramage, D.R., 1974. S t r a t i g r a p h y and Petro logy of a P y r o c l a s t i c Success ion of the Tak l a -Haze l t on Group, Nor th -Cent ra l B r i t i s h Columbia. Unpub. BSc The s i s , U n i v e r s i t y of B r i t i s h Columbia, 97p.» Read, P.B., and E i sbacher , G., 1973- Regional Z e o l i t e A l t e r a t i o n of the Sustut Group, B r i t i s h Columbia. Abst . of paper presented at Annual Meeting of the C o r d i l l e r a n Sec t i on of the G.A.C.. R i c h t e r , D.A., and Roy, D „ C , 1974. Sub-Greenschi st Metamorphic Assemblages in Northern Maine. Can. M i n . , v. 12, pp. 469-474. Robertson, J.M., '1975. Geology and Mineralogy of some Copper Su lph ide Depos its near Mount Bohemia, Keweenaw County, M ich igan. Econ. G e o l . , v. 70, p p o 1202-1224. Rob ie , R.A., Hemingway, B.S., and F i s h e r , J .R . , 1978. Thermodynamic P r o p e r t i e s of M ine ra l s and Re lated Substances. U.S.G.S. B u l l e t i n 1452, 456p.. Roseboom, E.H„, 1962. D j u r l e i t e , Cu qcS, a New M i n e r a l . Am. M i n . , v. 47, pp. 1181-1184. Roseboom, E.H., 1966. An I n v e s t i g a t i o n of the System Cu-S and some Natura l Copper S u l f i d e s Between 25* and 700*C. Econ. G e o l . , v. 61, pp. 641-672. Schouten, C , 1962„ Determinat ion Tables f o r Ore Microscopy. E l s e v i e r Pub. Co., Amsterdam, 242p.. S i l l i t o e , R.H., and C l a r k , A .H . , 1969. Copper and Copper- I ron Su l ; h i de s as the I n i t i a l Products of Supergene Ox i da t i o n , Capiapo Min ing D i s t r i c t , Northern C h i l e . Am. M i n . , v. 54, pp. 1684-1710. S i n c l a i r , A . J . , 1976. A p p l i c a t i o n s of P r o b a b i l i t y Graphs i n M inera l E x p l o r -a t i o n . Assn. of E x p l o r a t i o n Geochemists, Spec. V o l . No. 4, 95p.. Suther land-Brown, A., Cathro, R . J . , Pante leyev , A., and Ney, C.S., 1971. Metal logeny of the Canadian C o r d i l l e r a . CIMM B u l l e t i n , v. 64, No. 709, pp. 37-61. T a y l o r , L.A., and K u l l e r u d , G., 1970. Minera l Assemblages in the Cu-Fe-S-0 System.. Carnegie Ins t . Wash. Yearbook 69, pp. 315 -318. 201 Thompson, A .B . , ' 1 971 . Ana 1 c i t e - A l b i t e E q u i l i b r i a at Low Temperatures. Am. Jou r . S c i . , v. 271, pp. 79~92. T i p p e r , H.W., 1959. Rev i s i on of the Hazelton and Tak la Groups of Cent ra l B r i t i s h Columbia. Geo l . Surv. Can., B u l l e t i n 47, 60p.. T i p p e r , H.W., and R i cha rd s , T .A . , ' 1 976 . J u r a s s i c S t r a t i g r a p h y and H i s t o r y of No r th -Cent ra l B r i t i s h Columbia. Geo l . Surv. Can., B u l l e t i n 270, 73p.. Tu rek i an , K.K., 1972. Chemistry o f the Ea r th . H o l t , R inehar t and Winston Inc., New York, 131 p.. Uytenbogaardt, W., 1968. Tables f o r M i c ro scop i c I d e n t i f i c a t i o n o f Ore M i n e r a l s . Hafner Pub. Co., New York, 242p.. W i l l i a m s , H. , Turner, F . J . , and G i l b e r t , C M . , 1954. Petrography, An I n t roduc t i on to the Study of Rocks in Thin S e c t i o n s . W.H. Freeman and Co., San F r a n c i s c o , 406p.. W i l t o n , D.H., and S i n c l a i r , A . J . , 1978. O r i g i n of the Sustut Copper Depos i t , Cent ra l B r i t i s h Columbia. CIMM B u l l . , v. 7], pp. 129. W i l t o n , D.H., and S i n c l a i r , A . J . , 1 9 7 8 . Genet ic Model f o r the Sustut Copper Deposit in T r i a s s i c V o l c a n i c l a s t i c Rocks, Cent ra l B r i t i s h Columbia, paper submitted to the 1978 IAG0D o r g a n i z a t i o n a l committee f o r i n c l u s i o n i n symposium volume. Yund, R.A., and K u l l e r u d , G., 1966. Thermal S t a b i l i t y o f Assemblages in the Cu-Fe-S System. Jou r . P e t . , v. 7, pp. 454-488. 202 APPENDIX I "GEOLOG" DRILL CORE CODING FORMAT FOR SUSTUT COPPER I n t roduc t i on The vas t q u a n t i t y of d r i l l core requ i red that any re - l ogg ing be s t anda rd i zed c o n s i s t e n t l y f o r a l l holes recorded and that the data be p laced in a computer based f i l e such that qu ick access t o , and comparison of data could be ach i eved . Thus, w i t h a computer f i l e a l l the v a r i a b l e s recorded cou ld be manipulated w i t h respect to each o t h e r , such that the s i g n i f i c a n t v a r i a b l e s f o r copper occurence and thus o r i g i n cou ld be a s c e r t a i n e d . The v a r i a b l e s chosen were those the author thought would have been use fu l based on prev ious logs of the core obta ined from Fa lconbr idge N i cke l Mines L t d . p r i o r to the s t a r t of the f i e l d season. The format was fo rmulated p r i o r to the a u t h o r ' s a r r i v a l at the f i e l d camp but on the whole the v a r i a b l e s s e l e c t ed were more than adequate to record each d r i l l ho le . The format used was a v a r i a t i o n on the "Geo l o g " concept developed by Blanchet and Godwin (1972). Th i s p a r t i c u l a r system was chosen as i t was r e l a t i v e l y s imple to i n co rpo ra te i n to f i e l d work, was r e s t r i c t e d to a r i g i d e i g h t y column format (thus l i m i t i n g complex i ty of e n t r i e s ) and had shown i t s v e r s a t i l i t y in a p p l i c a t i o n to o the r d i f f e r e n t types of d e p o s i t s . The v a r i a b l e s chosen (and the reason they were chosen) a re : 1) . rock type and, in the case of the dominant vol c a n i c l a s t i c conglomerates (or b r e c c i a s ) , s u b d i v i s i o n on the bas i s of co lou r of the mat r i ce s v s . dominant c l a s t vs_. minor c l a s t , type of c l a s t s p resent , t e x t u r e , s o r t i n g , and g r a i n s i z e of c l a s t s . Th is data would be used to t r y to de f i ne a s t r a t i g r a p h y . 2) t ype , grade and mode of occurence of a l t e r a t i o n m ine ra l s . It was thought that the depos i t o r i g i n a t e d from metamorphic f l u i d s f l ow ing through the host rocks (Harper; 1977), thus the i n c l u s i o n of d e t a i l e d in fo rmat ion on the metamorphic minera l assemblages. 203 3) type, percent p resent , and mode of occurence of the ac tua l m e t a l l i c mi n e r a l s . k) type and number of a l t e r a t i o n minera l v e i n s . Th i s was inc luded in o rde r tha t r e l a t i o n s h i p s between s u l ph i de m i n e r a l i z a t i o n and v e i n i n g , i f p re sen t , cou ld be a s ce r t a i ned '(eg. were l e n s o i d ore bodies fed by hydrothermal v e i n s ? ) . 5) type of s t r u c t u r e p re sent , i f any, and i t s angle from a pe rpend i cu l a r plane to the core a x i s . F i gu re 86 shows the ac tua l coding form. It c on s i s t s of t w e n t y - f i v e rows which are subd iv ided in to f i v e groups of f i v e . The f i r s t row f o r each group, o u t l i n e d by t h i c k e r l i n e s , represents a f i v e foot i n t e r v a l from the prev ious lead row. The secondary rows in between are f o r comment cards or f o r en t ry of o the r d e s c r i p t i o n cards i f the f i v e foot i n t e r v a l must be subd iv ided (eg. i f the rock type changes two feet from the prev ious bottom i n t e r v a l , then a card f o r t h i s new l e ve l is i n se r ted between i n t e r v a l s ) . The form a l s o has a v i s u a l log column so that v a r i a b l e s can be represented as a manual s t r i p l o g . Th i s would be used, f o r i n s tance , i f the i n fo rmat ion was not keypunched f o r computer use ( i e . the logs are used as the f i n a l data s e t ) . The Codes T i t l e c a r d : Each d r i l l hole has a t i t l e card w i t h i d e n t i f y i n g c h a r a c t e r i s t i c s o f t ha t d r i l l h o l e . The f i r s t column conta in s a T to i n d i c a t e that t h i s l i n e in the computer f i l e i s at the s t a r t o f a new h o l e . Then, there are 3 columns f o r the ho le number ( r i g h t j u s t i f i e d ) , k columns f o r the d ip (the f i r s t two columns are the degrees of d i p , and the l a s t two are the minutes ) , k columns f o r the bear ing i f the ho le i s i n c l i n e d (degrees and minutes) and 18 columns f o r the UTM c o - o r d i n a t e s . With the complet ion of the t i t l e c a rd , d e s c r i p t i o n of the d r i l l ho le l i t h o l o g y beg ins . Each l i n e represents a s i n g l e computer c a r d . HOLE NUMBER P A G E OF V I S u A Assay Int. A S S A Y D A T A Cu Assay DEPTH TO BOTTOM OF INTEBVAL, 12. d. R O C K T Y P E H Rx typtt is nnt Ang-: « | n h * l i 6 SUSTUT CU 'GFOI .OG' DR I LLCORE COD ING FORMAT 1 3 22 1-7-JB tnr r n l n u r s £ FRAGMENT ID. £1 H A J . EP •Ha*. CL HE ALTERATION MINERALS CB 3 9 U P QZ Fig Ham How ZE XL PH PU OTH 5 3 cu PY MINERALIZATION CP BN HS CC OTHER FRACTURES STRUCTURES 205 Column 1: Th i s column i s used to i n d i c a t e that the remainder of the card i s e i t h e r to be noted f o r some reason, or e x t r a comments on a preceding i n t e r v a l are to be made. Codes: C_-indicates a more d e t a i l e d d e s c r i p t i o n of the i n t e r v a l above. It i s f o l l owed by w r i t t e n d e s c r i p t i o n , D_-indicates that a dyke i s present in the i n t e r v a l . E_-indicates the card is an end card (eg. f o r ho le 110, format would be END OF HOLE 110 w i t h the E in column 1). F - i n d i c a t e s a f a u l t i s present in the i n t e r v a l . J _- ind icates the rock type of the i n t e r v a l i s a d i s t i n c t i n t e r -bed (eg.a tu f faceous l aye r ) M - i nd i c a t e s the core f o r the i n t e r v a l was miss ing and thus logg ing was e x t r apo l a t ed from logs of Fa lconbr idge N icke l Mines L t d . . S - i n d i c a t e s that comments f o l l o w rock type d e c l a r a t i o n . T_- indicates the card i s a t i t l e card (see above). X - i n d i c a t e s some of the core is m i s s i n g , ^ - i n d i c a t e s the i n t e r v a l i s a v e i n . Columns 2 and 3: These columns s t a t e the copper assay i n t e r v a l in fee t (again r i g h t j u s t i f i e d ) . Columns h to 6: Copper assay va l ue . The decimal is absent, but would be between k and 5 (J_e_. 1.58 percent = 158 in the f o rmat ) . Columns 7 to 11: Depth to base of i n t e r v a l de sc r i bed in ( f t ) . Decimal po int i s mi s s ing aga i n , but i t would be between 10 and 11. These depths would g e n e r a l l y be in f i v e foot i n t e r v a l s throughout the hole except where there is a s i g n i f i c a n t change in rock c h a r a c t e r i s t i c s between i n t e r v a l s . Column k would be l e f t blank i f the depth was les s than 1000ft (J_e. the depth i s r i g h t j u s t i f i e d ) . 206 Column 12: Type m o d i f i e r : where comments d i r e c t l y f o l l o w rock name, or i f rock type was o the r than vol c a n i c l a s t i c s (see below), a l e t t e r C i s p laced in t h i s column. Otherwise t h i s column i s l e f t b lank. Columns 13 t o 16: Rock type: a f ou r l e t t e r code i s used. >90 percent o f the rock types i n t e r s e c t e d are v o l c a n i c l a s t i c sediments, thus the code nomenclature used by g e o l o g i s t s of Fa lconbr idge N i cke l Mines L t d . has been adapted to code t h i s dominant rock type. AG£R- indicates agglomerate (or v o l c a n i c l a s t i c con-glomerate) w i t h a green mat r i x ( f i r s t G_) , dominantly green c l a s t s and minor red c l a s t s . Other examples a re : ARGR-red m a t r i x , green > red c l a s t s , ARR6-red m a t r i x , red > green c l a s t s . AGGG-green m a t r i x , green c l a s t s . e t c . There are a t o t a l of e i gh t po s s i b l e rock types w i t h i n t h i s code framework. Other l i t h o l o g i e s present and t h e i r codes a re : AREN-arenaceous sandstone ARGL -a rg i 1 1 i te CASN-casi ng FELS - fe l s i t e MYLN-myloni te SAND-sandstone TUFF- tu f f WACK-wacke If rock type i s one of these o the r types then the regu la r formats o f columns 17 to 28 do not app ly , the type m o d i f i e r column i s f i l l e d and 17 to 28 are used to de s c r i be co lou r and/or t e x t u r e of t h i s o ther rock type. The co l ou r and t e x t u r e are not coded but are j u s t entered as d e s c r i p t i o n s . 207 Columns 17 to 28: ( f o r vol c a n i c l a s t i c conglomerates). Column 17: Percent of matrix in i n t e r v a l . Column 18: Percent of major coloured fragment. Column 19: Percent of minor coloured fragment. Code: Scale of 1 to 10 where each u n i t = 10 percent l_i_e_. 10%=1 50%=5) i f <10 percent then T(race) i s used. Column 20 : Grain s i z e of c l a s t s vs_. matrix. The i nequi granular g r a i n s i z e shown in f i g u r e 45 i s used. Column 21: Texture of the vo1 c a n i c l a s t i c s . The inequigranu1ar texture chart of Blanchet and Godwin (1972) i s used ( f i g . 8 7 ) . TEXTURE CODES FOR 1. IGNEOUS <*) lnequigramiJ»T (Forphyritic , C ongto.me r»tic> Struciur* or F r imf ' C t k p e t c c D i t ^ c oi fe T" fiction OO 1 10-25 2i" be 1 2 3 4 Open, dit rup'.ed 6 1 s 9 Column 22: Fig. 87 The s o r t i n g chart in f i g u r e 88 is used. • ASSIGNED VALUE v. w e l l s o r t e d 8 mod. poorly v. poorly sorted sorted sorted Fig. 88 Column 23: M a t r i x provenance- i f the f i n e f r a c t i o n to c l a s t s i s f e l d s p a r i c h , then F_ is placed in the column, otherwise i t i s l e f t blank. Column 24: L i t h o l o g i c a l name o f dominant c l a s t . 208 Co 1 umn 25: Percent of t o t a l , c l a s t s = dominant c l a s t . Column 26: L i t h o l o g i c a l name of minor c l a s t . Col urhh 27: Percent of t o t a l c l a s t s = minor c l a s t . Column 28: L i t h o l o g i c a l name of t r a ce c l a s t . Codes: Percents are a 1 to 10 s c a l e (eg. 101=1), <10%=T_(race) . L i t h o l o g i c a l names are one l e t t e r codes: A-andes i te B -basa l t C -chert rj-d_i abase E_- f e l d s p a r porphyry F_ - fe l s i te _G -g j an i t i c H - t rachyandes i te j_-dacj_te L_-g2_ass IP-augite porphyry £-q_uartz R^-di o t i t i c _S_-£ediment T - t u f f Y - rhyo1 i t i c Columns 29 to 52: A l t e r a t i o n m ine ra l s : nine po s s i b l y d e f i n i t i v e metamorphic minera l s are l i s t e d . These are ep idote (EP), c h l o r i t e (CH), hematite (HE), carbonate (CB) , qua r t z (QZ) , z e o l i t e (ZE) , p rehn i t e (PH) , and pumpe l l y i t e (PL)) . The f i r s t column f o r each mineral (Amt) r e fe r s to the amount of mineral p resent . Th is code i s based upon a 1 to 5 s c a l e where; 1 means the mineral i s j u s t 209 v i s i b l e i n the i n t e r v a l , wh i l e 5 means the mineral has e x t e n s i v e l y a l t e r e d the i n t e r v a l to the stage that the rock type has almost complete ly gone to that m i n e r a l . The next two columns (How) a l l ow f o r the d e s c r i p t i o n of two modes ( i f needed) o f occurence f o r each m i n e r a l . Codes f o r the modes a re : A-amygdules E_-envelopes ou t s i de f r a c t u r e s G - l o c a l i s e d to fragments K - s 1 i c kens ided sur faces L_-vug j o i n i n g M^-local ised to mat r i x P_-patches, b l eb s , metadomains, e t c . _R-r_ims on c l a s t s S-s_elvages on edges of ve ins U^pseudomorphs a f t e r m e t a l l i c minera l V-ve ins ( f r a c t u r e f i l l i n g ) X-any combinat ion - to be exp l a i ned in the comments (eg. i f a mineral was found in amygdules, rims on c l a s t s and in ve ins an X^would be p laced in the How column and a comment card would be i n i t i a l i z e d immediately f o l l o w i n g the i n t e r v a l d e s c r i p t i o n . On t h i s comment card would be X=A,R_,V_ i n d i c a t i n g the modes f o r X ) . Columns 53 to 55: (OTH) - r e f e r to any metamorphic mineral present which i s not de f i ned in the prev ious columns. These minera l s are thus less common in the d r i l l h o l e s . Column 55 is f o r the mode of occurence of the m i n e r a l . Type codes f o r these minera l s a re : CY-c lay LI -1imon i te 2 1 0 P L - p y r o l u s i t e S P - s e r p e n t i n e Columns 56 t o 67: Mi n e r a 1 i z a t i on w i t h e i ght poss i b l e m e t a l 1 i c mi n e r a 1 s a r e l i s t e d . These a r e n a t i v e c o p p e r (CU) , p y r i t e (PY) , c h a l c o p y r i t e ( C P ) , b o r n i t e ( BN ) , s p e c u l a r h e m a t i t e (HS) , and c h a l c o c i t e ( C C ) . The f i r s t co lumn o f each p a r t i s f o r t h e v i s u a l p e r c e n t o f m i n e r a l p r e s e n t . The codes f o r p e r c e n t a r e : j * - r_are t r a c e T - t_ race M-.05 - .1% 5.-.1 - .5% 2_-o5 - n 2 - 1 - 2 % E_->2% The l a s t co lumn (How) o f each p a r t , r e f e r s t o t h e mode o f o c c u r e n c e o f t he mi n e r a 1 . These codes a r e : A-amygdu1es C ^ - d i s c r e t e m e t a l c j a s t D_-d i s semi n a t e d G _ - l o c a l i s e d t o f r a g m e n t K - s 1 i c k e n s i d e d s u r f a c e s P_-pa i n t R-_rims on c l a s t s S_-s_elvages on v e i n s \/ -ve ins ( f r a c t u r e f i l l i n g ) > - v e i n s > d i s s . = - v e i n s = d i s s . 211 <-vei ns.<di ss . Columns 68 to 71: (OTHER)-refers to the o the r p o s s i b l e m i n e r a l i z a t i o n types which are not as abundant as the above ones. Columns 68 to 69 (ID) are f o r the i d e n t i t y o f the m i n e r a l . The codes f o r less xommon minera l s a re : AZ-azur i te C I - cup r i te C V - c o v e l 1 i t e GN-g_reenocki te GR-graphi te MA-ma1ach i te MT-magnet i te S P - s p h a l e r i t e Column 70 i s f o r the v i s u a l percent and column 71 i s f o r the mode o f occurence o f the m i n e r a l . Columns 72 to 75: These are f o r record ing the number of carbonate, e p i d o t e , q u a r t z , and combinat ion ve ins r e s p e c t i v e l y ( i e . column 72 i s the number o f carbonate ve in s ) w i t h i n the i n t e r v a l . The number symbols j _ to 0_ r e f e r to 1 to 10 v e i n s , A_ - 1_ are f o r 11 to 36 v e i n s , and i f the number o f veins i s >36, then a + i s entered i n the proper column. In a f o l l o w i n g comment card the number o f ve ins i s then de f i ned (eg. i f there are 54 ep ido te v e i n s , a + i s entered in column 73, and in a comment card +=54 i s w r i t t e n ) . The combinat ion ve ins (column 75), are any ve ins which are e i t h e r combinations o f the preceding three types , o r are made o f d i s t i n c t l y d i f f e r e n t ve i n m a t e r i a l s not mentioned above. If on ly one type o f ve in is present in the i n t e r v a l , then the number i s p laced in the column and the mineralogy i s e xp l a i ned in a f o l l o w i n g comment ca rd . However i f there i s more than one 2 1 2 . other type then a _^ i s placed in the column and the numbers and types of veins are exp la ined in a fo l lowing comment card leg. i f there are four prehnite and two c h l o r i t e veins in the interva l _^ is put in column 75 and in a comment card -=kPH + 2 C H is w r i t t e n ) . Codes for d i f f e r e n t vein types are: CH -ch lo r i te CQ-carbonate > quartz CE-carbonate > epidote EC-epidote > carbonate EQ-epi dote > quartz HE-hematite PH-prehn i te QE-quartz > epidote QC-quartz > carbonate Columns 76 to 80: (STRUCTURES): These columns are fo r descr ib ing what types o f s t ruc tures ( i f any) are present in the i n t e r v a l . 79 and 80 are fo r the angle of the s t ruc tu re to a perpendicu lar plane to the core axis ( in degrees) . Codes for the s t ructures a re : BED-beddi ng CNT-contact GBP-graded bedding SFR-s1i ckens i ded f rac tures VEhhdominant ve in ing d i r e c t i o n 213 APPENDIX I I FOSSIL IDENTIFICATION Th i s appendix conta in s a copy of G.S.C. Report 4-BEBC-78 which de s c r i be s f o s s i l i d e n t i f i c a t i o n s f o r two samples c o l l e c t e d by t h i s w r i t e r . Sample 47-120 ' i s from the 120ft l e v e l of DDH kj. Sample W1009 is from an outc rop w i t h UTM coord inates of 49,340N and 49, l80E. 2.14 Report Ho. 4-BEBC-78 Report on microfauna recovered from 2 insoluble residues collected by Derek Wilton from NTS 94D, McConnell Creek map area, Sustut Copper, northern B.C. "The relevant parts of any manuscript prepared for pub-l i c a t i o n that paraphrase or quote from this paper should be referred to the writer , Geological Survey of Canada, Vancouver, for possible revision." G.S.C. Locality: 95344- Field No. 47 - 12Q 1 NTS 94D, McConnell Creek map area; Sustut Copper, B.C. Determinations: Shell fragments Sponge spicules Fish tooth Crinoid columnal fragment AGE: Indeterminate G.S.C. Locality: 95345 Field No. V /1009 NTS 9 4 D , McConnell Creek map area, Sustut Copper, B.C. Determinations: Coral fragments Gastropods Foraminifera - Ammodiscus Fish debris Fish teeth 2 215 -2-(determinations for V71009 continued) Conodonts: Epigondolella fragments - most l i k e l y Bpigondolella primitia Mosher Neogondolella sp. - blade frag-ment only. AGE: Late Triassic, Late Karnian - early Norian. r 217 APPENDIX I I I CROSS-SECTIONS Th i s appendix prov ides a w r i t t e n d e s c r i p t i o n to accompany the a t tached c r o s s - s e c t i o n s : A - A ' , B-B 1 , C - C , and D-D 1. Ore minera l s are represented on these c r o s s - s e c t i o n s i n h i s togram form w i t h symbols as exp l a i ned in the legends . Each l e v e l on these d r i l l h o l e - h i s t o g r a m s is a f i v e foot i n t e r v a l . Percentages f o r the v a r i o u s m ine ra l s are based pu re l y on v i s u a l e s t ima t i on s of content w i t h i n the co r e . The c r o s s - s e c t i o n s from the North Zone (j_e. A-A ' and B-B ' ) have the best de f i ned n a t i v e copper co re s , but they a l s o have poor development of the ou te r b o r n i t e , c h a l c o p y r i t e , and p y r i t e zones. In s e c t i o n A-A ' (DDH's 53~52); DDH 44 has a n a t i v e copper -cha1coc i te zone, then 10 m below t h i s , a smal l p y r i t e - c h a l c o p y r i t e - b o r n i t e zone; DDH 53 has on l y n a t i v e coppe r - cha 1 coc i t e ; and i n DDH 52 a c h a l c o c i t e - n a t i v e copper core has an upper b o r n i t e - c h a l c o p y r i t e -p y r i t e f r i n g e but no f r i n g e on the bottom. In s e c t i o n B-B' (54-110-17 _52); DDH 54 has some c h a l c o c i t e and n a t i v e copper mixed w i t h i n a dominant ly p y r i t e zone; DDH 110 , . i n i t s upper o re lens has two c h a l c o c i t e - n a t i v e copper cores tha t grade to p y r i t e - c h a 1 c o c i t e f r i n g e s , a l though the uppermost expected f r i n g e has been-removed by e r o s i o n ; and DDH 17 c on ta i n s a c h a l c o c i t e - n a t i v e copper co re w i t h an u p p e r ' b o r n i t e - c h a l c o p y r i t e f r i n g e and a p y r i t e - c h a l c o p y r i t e zone 6 m bel Sma l l e r zones are present through to the base of DDH 110, but no zone i s p a r t i c u l a r l y w e l l developed. S e c t i o n C-C 1 (88-2-IO5-67J.12}^contaj ns;;DDH ,88'.wi th the above mentioned d i s t i n c t z o n a t i o n and a l s o sma l l e r s u l ph i de l en se s , some w i t h w e l l developed z o n a t i o n . t h r o u g h o u t ; DDH 2 which has an e x t e n s i v e p y r i t e zone w i t h two smal l cha 1 c o c i t e - b o r n i t e zones sandwiched w i t h i n the p y r i t e ; in DDH 105 a smal l cha 1 c o c i t e - b o r n i t e zone is in the cen t re of an asymmetric p y r i t e - c h a l c o p y r i t e 218 zone w i t h a smal l i s o l a t e d c h a 1 c o c i t e - b o r n i t e zone at the top ; DDH 6 con ta in s a l a r g e c h a 1 c o c i t e - n a t i v e copper 2one w i t h a smal l py r i te - cha1 c o p y r i t e lower f r i n g e ; and DDH 112 has a n a t i v e copper -cha1coc i te core zone w i t h a lower p y r i t e - c h a l c o -p y r i t e f r i n g e but no upper p y r i t e - c h a l c o p y r i t e f r i n g e . In s e c t i o n D-D' (132-13-116-10-39-96); DDH 96 has two chal coc i te.-b o r n i t e zones i r r e g u l a r l y sandwiched between p y r i t e - c h a l c o p y r i t e assemblages; DDH 35 has a broad chal coc i t e - na t i ve copper zone w i t h a smal'l born i t e - c h a l c o -p y r i t e lower f r i n g e ; DDH 10 c o n s i s t s o f three seperated c h a 1 c o c i t e - r i c h l en se s ; DDH 116 a l s o has three separate c h a l c o c i t e i n t e r s e c t i o n s , the uppermost one c o n t a i n i n g some n a t i v e copper; DDH 13 has three w ide l y separated c h a l c o c i t e zones w i t h a broad minor py r i t e - cha1 c o p y r i t e area between the lower two, and f i n a l l y DDH 132 c on ta i n s no a p p r e c i a b l e c o n c e n t r a t i o n Of copper m ine ra l s but has th ree p y r i t e zones, one of which con ta i n s c h a l c o p y r i t e in i t s . c e n t r e . 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            data-media="{[{embed.selectedMedia}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
https://iiif.library.ubc.ca/presentation/dsp.831.1-0052841/manifest

Comment

Related Items