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Geology and ore-deposition of Silback Premier mine White, William Harrison 1939

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GEOLOGY AND ORE-DEPOSITION Of SILEAK PREMIER MINE by William H. White, B.A.Sc. A t h e s i s submitted to the Department of Geology & Geography, U n i v e r s i t y of B r i t i s h Columbia, as p a r t i a l f u l f i l l m e n t of requirements f o r the Degree of Master of Appl i e d Science. A p r i l , 1939. CONTENTS CHAPTER I . INTRODUCTION ________ ________ i.„ PART ONE -,/• GENERAL GEOLOGY CHAPTER I I SUMMARY OF GEOLOGY — • 4 . CHAPTER I I I ROCK DISTRIBUTION & LITHOLOGY 1 . Bear R i v e r Formation :-- 6 . 2 . Salmon River Formation --- 8. 3 . Nass River' Formation • 8. 4 . Green Porphyry •-- — 9» 5. Red Porphyry — • i o . 6. Premier Porphyry - I I . 7 . Coast Range B a t h o l i t h 1 2 . 8. Q u a r t z - d i o r i t e Dykes -- •— 13 • 9 . Lamproph'yre Dykes - — •- --14. CHABTES IV GEOLOGIC SEQUENCE & STRUCTURE Table of Formations , 1 . Age and C o r r e l a t i o n --------— 1 5 . 2 . S i l l - l i k e Character of.the Porphgy 1 6 . 3 . Regional U p l i f t & F o l d i n g — —---- 1 7 . 4. Development of the Shear-pattern - 18. 5 . Method of B a t h o l i t h i c Emplacement 19. 6 . E r o s i o n a l Record • 2 0 . PART TWO / ORE-DEPOSITION & MINERALOGY CHAPTER V" GENERAL SUMMARY & CONCLUSIONS — - - - - - - — 2 1 . CHAPTER VI THE PRINCIPAL LOCUS OF DEPOSITION -1. The Footwall Contact —• 25 . 2 . Structures of the Northeast Zone ~ 2 6 . CHAPTER VII. GENERAL CHARACTER OF ORE-BODIES T. A t t i t u d e ~- • - 29. 2 . M i n e r a l i z a t i o n 29. 3 . Types of Ore-bodies • -- 32.. CHAPTER VIC I INFLUENCE OF DYKES, FAULTS, & CROSS/ FRACTURES ON ORE-DEPOSITION 3 3 . CHAPTER IX MINERALOGY 1. Base Metal Sulphides 3 7 . 2 . Gangue Minerals ; • • 3 9 . 3 . The Occurrence of Free Gold •-— 4l.» 4 . The Occurrence of Electrum - — • 4 l . 5 . The Occurrence of S i l v e r M inerals and Native S i l v e r 4 3 . continued CHAPTER X GENESIS OF THE ORES I . Source of Ore-solutions 45 . * » 2. Chemical s i g n i f i c a n c e of Replacement Phenomena & of 'Un-supported Nuclei'4 6 * 3 . Paragenesis • — — 48 , 4 . Method of Emplacement — — : — • - — - 4 9 * 5 . The Physico-chemical Aspects of Ore-solutions & Ore-deposition 5 1 . 6 . Depth Factors i n Ore-deposition .54. CHAPTER XI.THE PRIMARY CHARACTER OF SILVER MINERALS & •. NATIVE SILVER : — 55 • CHAPTER M FAVORABLE PROSPECTING AREAS — — - 5 7 . APPENDIX A - MICROPHOTOGRAPHS — — „ 6 i , APPENDIX B - MINERALOGI'C EXAMINATION OF SILBAK PREMIER ORE BY MEANS OF THE HAULTAIN 'SUPER-PANNER' & 'INFRA-SIZER' ------ •-- 72. APPENDIX C - OTHER OCCURRENCES OF ELECTRUM IN B.C. — — 7 7 . THE OCCURRENCE OF PRIMARY SILVER MINERALS AT THE DOLLY VARDEN MINE, ALICE ARM, B . C . — — 78 . MAPS -GEOLOGIC PLAN OF 1350 LEVEL & SECTIONS PROPERTY MAP SHOWING GENERAL GEOLOGY PLAN & PROJECTION OF MINE WORKINGS BIBLIOGRAPHY 1 . .Schofield, S..J., and Hanson, G.; Geology and Ore Qeposits of the Salmon River D i s t r i c t , B r i t i s h Columbia; Geol. Sur. Mem. 1 3 2 . 2 . Hanson, G.; P o r t l a n d Canal Area, B r i t i s h Columbia; Geol.Su M e m 1 7 5 . 3 . Burton, W.D.; "Ore-deposition at Premier Mine"; E c G e o l . V o l . XXI; No. 6; p. 578. (1926) 4. Means, A.H.;, "Geology of the Premier Mine" (1923) Not published. 5. Handbook of Chemistry and Physics, 22nd. Ed. 6. Schneiderhohn, H., and Ramdohr, P.; Lehrbuch der Erzmikroskopie, B e r l i n , 1933;. p255 • 7 . Bowen, N.L., "Ore-Deposits of the Western States"; Trans. A.l.M.M.E. ; 1933. ACKN01LEDG-EMENTS The research f o r t h i s Report was conducted i n the l a b o r a t o r i e s of the Department of Geology & Geography, U n i y e r s i t y of B r i t i s h Golumbias under the s u p e r v i s i o n of " Dr. Harry V. Warren, A s s i s t a n t Professor of Mineralogy & Petrography, whose e n t h u s i a s t i c a s s i s t a n c e was appreciated. The w r i t e r also extends h i s thanks to Mr. E.P.Davis, e s p e c i a l l y f o r h i s help i n the i d e n t i f i c a t i o n of s i l v e r minerals by the Iodine" F i l m i n g Method. Messrs. Jim McCammon, E l l i o t Schmidt, and C.E.Gordon Brown k i n d l y consented to the i n c l u s i o n of some of t h e i r f i n d i n g s , i n Appendix C. The w r i t e r wishes to acknowledge the help of Mr. Jim Donan, U n i v e r s i t y Fireman, i n the matter of mounting and p o l i s h i n g specimens f o r microscopic examination. Taking up t h i s work as a hobby, Mr. Donan i s now one of the best mineralographic t e c h n i c i a n s at the U n i v e r s i t y . Mr. Walter Bishop, of the Dept. of Mining $ Meta l l u r g y , gave h i s usual cheery as s i s t a n c e i n the Assay Lab. I n making mineralogic analyses with H a u l t a i n apparatus, the larg e number of assays required i s a major problem. This Report was w r i t t e n with the permission of Si l b a k Premier Mines, L t d . , and acknowledgement i s due the Mine O f f i c i a l s f o r a l l o w i n g the w r i t e r to c o l l e c t specimens and- consult Mine maps. (I) CHAPTER I . INTRODUCTION The impressive range of mountains which extend alogg the Coast of B r i t i s h Columbia from the Eraser R i v e r t& the Yukon comprises the c e n t r a l mass of the Coast Range B a t h o l i t h . The Jurasside orogeny and the i n t r u s i o n of t h i s B a t h o l i t h produced profound changes i n the e x i s t i n g sedimentary and v o l c a n i c rocks. Along the Western Contact these pre-Bathol-- i t h i c rocks were h i g h l y f o l d e d and metamorphosed, i n most cases "being completely a l t e r e d to mica s c h i s t s . M e t a l l i f e r o u s emanations from the B a t h o l i t h l o c a l i ' i z e d i n these s c h i s t as ?'" commercial deposits - c h i e f l y copper. Although the sediments and v o l c a n i c s on the Eastern Contact were ex t e n s i v e l y folded and f a u l t e d , metamorphism was not as i n t e n s e . The b e l t of m i n e r a l i z a t i o n , p r i n c i p a l l y of l e a d , z i n c , s i l v e r , and gold, i s r e l a t e d to minor, i n t r u s i v e s r a t h e r than to the c e n t r a l mass of the B a t h o l i t h . These o u t l i e r s are u s u a l l y stocks or s i l l s . -Although g e n e t i c a l l y r e l a t e d to the B a t h o l i t h , t h e i r emplace--ment generally preceded that of the main g r a n o d i o r i t e mass. Lo c a t i o n of The S i l b a k Premier Mine belongs to t h i s S i l b a k Premier ' I n t e r i o r B e l t of M i n e r a l i z a t i o n 1 , . I t i s l o c a t e d some ten miles north of the head of P o r t l a n d Canal, one of the l a r g e r f j i o r d s which p i e r c e the Coast Range. The property c o n s i s t s of 77 claims and f r a c t i o n s l y i n g between el e v a t i o n s of 600 and 4500 f e e t on the western slope of Bear River Ridge«, (2) Topography The main topographic features of the area adjacent to the Mine are: the Salmon River drainage b a s i n extending northward from the head of P o r t l a n d Canal; the Bear R i v e r Ridge p a r a l l e l i n g i t on the east; and the massive Coast Range Mountains on the west. The mountains have the smooth lower slopes c h a r a c t e r i s t i c of g l a c i a t i o n surmounted by f r e t t e d , u n - g l a c i a t --ed peaks. The peaks do not i n general extend f a r above the sur-r o u n d i n g country so that the s k y - l i n e , though remarkably l e v e l Vv— presents a jagged, saw-tooth p r o f i l e . The Coast Range Mountains have a mean e l e j v a t i o n of about 5500 f e e t , while the Bear R i v e r Ridge stands somewhat lower. The inter-peak areas are occupied l a r g e l y by g l a c i e r s , tongues of which may extend down the v a l l e y s to much lower l e v e l s . Thus the toe of the Salmon G l a c i e r , source of the Salmon R i v e r , i s only about 800 f e e t above s e a - l e v e l . The Salmon R i v e r drainage system i s composed of three main t r i b u t a r y v a l l e y s , more or l e s s p a r a l l e l and separated by smooth ridges of low r e l i e f . From west to east, . these are: the Salmon River v a l l e y , the upper p a r t of which i s occupied by Salmon G l a c i e r ; the p r e d i p i t o u s gorge through which Cascade Creek flows; and the broad v a l l e y occupied to the north by Long Lake and f a r t h e r south by the East Fork of Cascade Creek. Th&s t r i b u t a r y j o i n s the main creek through a deep gorge around the nose of S l a t e Mountain, producing a sharp topographic break. (3) The e r o s i o n a l h i s t o r y of t h i s drainage system w i l l be discussed i n more d e t a i l i n a l a t e r chapter. However i t may be noted here that the ancient drainage system was accentuated by the Ice and modified by p o s t - g l a c i a l stream-erosion. FART ONE GENERAL GEOLOGY (4) CHAPTER I I . SUMMARY OF GEOLOGY The S i l b a k Premier property i s u n d e r l a i n by sediments and v o l c a n i c s i n t r u d e d by p o r p h y r i t i c hypabyssal rocks. These rocks are probably Upper J u r a s s i c ; c e r t a i n l y they fc> . , • . are p r e - B a t h o l i t h i c . c The o l d e s t , the Bear R i v e r Formation, c o n s i s t s of v o l c a n i c flows, b r e c c i a s and w a t e r - l a i n t u f f . I t i s o v e r l a i n c conformably by the Salmon R i v e r Conglomerate and the Nass Ri v e r S l a t e s , both of which are marine. Neither of these rocks outcrop near the Mine. The p r e - B a t h o l i t h i c i n t r u s i v e rocks, which are g e n e t i c a l l y r e l a t e d , are known as Green Porphyry (gabbro), Red Porphyry ( q u a r t z - d l o r i t e ) , and Premier Porphyry ( q u a r t z - d l o r i t e ) . The Green Porphyry i s a stock. The Red and Premier porphyries are s i l l s which were i n t r u d e d along the bedding-planes of the t u f f while i t was s t i l l i n a h o r i z o n t a l , or only s l i g h t l y i n c l i n e d p o s i t i o n . Only the Premier Porphyry i s of economic importance i n the Mine,: The u p l i f t of the J u r a s s i c r e s u l t e d i n en echelon f o l d i n g og the e n t i r e C o r d i l l e r a n region along northwesterly-trending axes. I n the v i c i n i t y of S i l b a k Premier t h i s movement i s expressed by a steep, wes t e r l y - d i p p i n g monocline, which to the north give3 place to a broad syncline plunging north. (5) Stresses set up as a r e s u l t of t h i s f o l d i n g were r e l i e v e d by development of an i n t e r s e c t i n g northwest-northeast shear-pattern. The incompetent rocks developed shear-cleavage; while the more competent porphyry i n the v i c i n i t y of the Mine was i n t e n s e l y sheared along two main zones - one s t r i k i n g NE and the other NW. These zones are a major c o n t r o l l i n g f a c t o r i n ore-deposit! on and are f u r t h e r discussed i n P a r t 2. The next event of geologic i n t e r e s t was i n t r u s i o n of the Coast Range B a t h o l l t h . The Granodiorite i t s e l f outcrops only i n the southwestern corner of the property, but several l a r g e q u a r t z - d i o r i t e dykes, considered to be d i f f e r e n t -i a t e s of the B a t h o l i t h , t r a v e r s e the area i n a northwest d i r e c t i o n * The youngest rocks i n the area, the lamprophyre dykes, cut a l l other rocks. They have a general northwest s t r i k e and a,steep d i p southwest. The i n f l u e n c e of these dykes on ore-d e p o s i t i o n w i l l be discussed i n P a r t 2, The S i l b a k Premier deposits are considered to have been formed at moderate depth. At l e a s t 4000 f e e t of cover has been removed since T e r t i a r y Time. The g l a c i a t l o n of the P l e i s t o c e n e accentuated, but d i d not a l t e r the T e r t i a r y drainage system. P o s t - G l a c i a l stream-erosion has had a marked e f f e c t i n modifying the lower slopes i n the v i c i n i t y of the Mine." • . • (6) CHAPTER I I I . ROCK BISTRIBUTION & LITHOLOGY ' - I .-BEAR RIVER FORMATION Rocks l o c a l l y known as the Bear River Formation u n d e r l i e the greater p o r t i o n of S i l b a k Premier property. These are the o l d e s t rocks exposed i n the area, "being c o r r e l a t e d w i t h the l a r g e r Hazelton Group of J u r a s s i c age . Of the 'Bear Ri v e r Epoch', S c h o f i e l d s a y s 1 , " The e a r l i e s t record i s one of vulcanlsm the f i r s t a c t i v i t y produced great l a v a flows whose surface cooled or f r o z e only to be broken up by f u r t h e r movement", - and t h i s seems a reasonable explanation of the a s t o n i s h i n g v a r i e t y of rocks observed i n the f i e l d . There appears to have been a rhythmic c y c l e of l a v a e j e c t i o n and b r e c c i a t i o n followed by more quiescent periods of ash~accumulation and r e s o r t i n g i n water. About 2000 f e e t of t h i s Formation ks exposed 4 but i t i s b e l i e v e d to be much t h i c k e r . Means has d i v i d e d the Bear R i v e r i n t o three members: lower, middle, and upper, and although they are more or l e s s interbedded, i t i s a convenient way i n which to t r e a t them. Lower Member - The lowest exposed Bear River rocks are B r e c c i a s , Flows encountered only above the 3000 foot e l e v a t i o n on Bear R i v e r Ridge. The dark-greenish to grey v o l c a n i c b r e c c i a s are composed of a n d e s i t i c fragments of a h i g h l y a l t e r e d nature cemented e i t h e r by l a v a or finely-bedded v o l c a n i c ash. The fragments vary from a f r a c t i o n of an i n c h to two f e e t or more i n diameter. F l o w - o r i e n t a t i o n i s commonly observed i n the m a t r i x 8 1. S u f f i x e s i n the t e x t correspond to numbers i n the Bibloigraphy (7) Thick beds of fine-fragmental t u f f s are d i s t i n g u i s h e d by t h e i r reddish or p u r p l i s h c o l o r . Mount Shorty Stevenson, some f i v e miles northeast of the Mine, i s e n t i r e l y composed of these purple t u f f s , while they are a l s o known w i t h i n the Mine workings. The bedding i n d i c a t e s d e p o s i t i o n i n water -d i f f e r e n t i a l p a r t i c l e s i z e s i n d i c a t e r e s o r t i n g while thin-bedded a r g i l l i t e bands suggest d e p o s i t i o n I n shallow, q u i e t l a k e s . The flow-rocks show s i m i l a r d i v e r s e characters. Dark-greenish massive rocks showing small l a t h s of hornblende i n an a p h a n i t i c groundmass are common. O r i g i n a l l y they appear to have been a n d e s i t i c lavas but are now l a r g e l y a l t e r e d to c h l o r i t e with the o c c a s s i o n a l development of b e a u t i f u l epidote needles. Opposed tb these are minor flows of creamy, v i t r e o u s , r h y o l i t e which show complicated f l o w - l i n e s and which appear to have been rh y t h m i c a l l y e x p e l l e d , producing a,'pseudo-bedding'. Middle Member - Occupying a r e l a t i v e l y small area, the t u f f Tuff i s the only sedimentary rock of importance i n the Mine. I t i s l i g h t to dark green i n c o l o r and the texture v a r i e s from f i n e - g r a i n e d to dense. Rarely I s i t so finely-bedded as to approach a s i l t s t o n e i n t e x t u r e . The w a t e r - l a i n o r i g i n of the t u f f i s not at once evident because bedding i s u s u a l l y o b l i t e r a t e d by l a t e r shearing. However, on the 2080 Level of the Mine a f o o t w a l l diamond d r i l l hole cut over 300 f e e t of bedded t u f f , p a r t i a l l y s i l i c l f i e d , i n which the bedding was preserved as r e g u l a r l y - s p a c e d , p a r a l l e l planes. These probably represent o r i g i n a l carbonaceous l a y e r s . (8) Upper Member - This rock i s exposed i n . t h e extreme southwestern Igneous G-reenstoiae corner of the property. I t i s a dark-greenish rock of massive t e x t u r e . The rough sub-conchoidal f r a c t u r e and somwhat c r y s t a l l i n e appearance are the only clues to i t s igneous o r i g i n . When sheared i t appears i d e n t i c a l to the t u f f , but I t s occurrence i n the Mine i s rare and unimportant. 2. SALMON RIVER FORMATION D i s t r i b u t i o n The Salmon River Conglomerate does not outcrop on S i l b a k Premier ground, but i t was seen along the eastern slope of Sl a t e Mountain, east of B,X.#I Claim,and again f a r t h e r north on the Lakeview property. L i t h o l o g y The Salmon River i s described by S c h o f i e l d as a, 'f i n e conglomerate bearing pebbles of the underlying v o l c a n i c r o c k s ' 1 . I n hand specimen i t i s a compact dark-colored rock w i t h l i g h t e r g rains g i v i n g i t a 1salt-and-pepper 1 appearance. A hand l e n s w i l l r e v e a l small sub-angular grains of dark m a t e r i a l and small angular quartz and f e l d s p a r p a r t i c l e s . 3 . NASS RIVER FORMATION P i s t r i b u t i o n Small, i s o l a t e d patches of Nass R i v e r S l a t e outcrop on top of S l a t e Mountain where they are separated from the Bear Ri v e r purple t u f f by a t h i n band of Salmon River Conglomerate. (9) Going north along Bear R i v e r Ridge, (the) Slate i s f i r s t encountered a t a p o i n t near the northeast corner post of B.X.#7 Claim where i t d i r e c t l y o v e r l i e s purple t u f f . L i t ho logy The Nass Ri v e r Formation i s i n r e a l i t y a dark a r g i l l i t e which i n places e x h i b i t s a s l a t y cleavage. Near the contact, mentioned above, the a r g i l l i t e s are i r o n - s t a i n e d and i n d i v i d u a l beds are h i g h l y contorted. The average dip i s a few degrees west. 4. GREEN PORPHYRY D i s t r i b u t i o n • Only two small e l l i p t i c a l stocks of t h i s rock outcrop on the property, one on the D o l l y Claim and the other on the" eastern boundary of M i s t §3 Claim, On the Mahood and Texas Claims there i s a prominent ridge of i n t r u s i v e rock which was o r i g i n a l l y mapped as Premier Porphyry, but on account of the augite which i t contains i t i s classed here w i t h the Green Porphyry. I t i s apparently a dyke, dippi n g steeply SW and s t r i k i n g a few degrees :/,w,est of north. I t was again observed forming one of the w a l l s of the East Fork gorge on the L e s l i e #5 Claim. LltBiology . I n hand specimen, the Green Porphyry i s h o l o c r y s t a l l i n e and shows small l a t h s of f e l d s p a r and crystal's of greenish pyroxene. I n t h i n s e c t i o n , 'abundant c o l o r l e s s augite i s v i s i b l e i n a groundmass of p l a g i o c l a s e and augite I2*". The other igneous rock mentioned do) i s l i g h t green i n c o l o r w i t h small phenocrysts of f e l d s p a r and a u g i t e . The G-reen Porphyry i s classed as a gabbro and resembles the 'Augite P o r p h y r i t e ' 1 stock on the Spider property north of Long Lake. ' 5. RED PORPHYRY D i s t r i b u t i o n Red porphyry outcrops over a roughly c i r c u l a r area of about 110 acres, i n c l u d i n g a l l of the Humbolt F r a c t i o n and p a r t s of the Hooligan,- O a k v i l l e §2, Humbolt #2, L e s l i e , L e s l i e #6, Mahood, and Texas Claims. Although' t h i s i s the surface rock over a l l mine workings north of B.C.#2 Shaft, none i s encountered underground. Thus i t s thickness must be l e s s than 300 f e e t . The only other outcrops of Red Porphyry are: a small c i r c u l a r patch about the middle of L e s l i e #5 Claim; a s i m i l a r area on the northern part of the L e s l i e Claim; and a l a r g e r mass on the B e l l #2 Claim, i n the northwest earner-of the property. L l t h o l o g y I n hand specimen, the Red Porphyry shows numerous, sm a l l , ragged phenocrysts of a white-weathering f e l d s p a r I n an a p h a n i t i c groundmass. Occassioh-, - a l phenocrysts of pink orthoclase up to i n l e n g t h , which are generally twinned a f t e r the Carlsbad Law, are t y p i c a l l y present. I n t h i n s e c t i o n , ' The groundmass i s seen to be composed of f i n e l a t h s of p l a g i o c l a s e together w i t h hematite and k a o l i n ' 4 . The Red Porphyry has about the composition of g r a n o d i o r i t e and I s considered a s i l l i n t r u s i o n r e l a t e d to the Premier Porphyry. ( I I ) 6« PREMIER PORPHYRY . * i This i s the p r i n c i p l e p r e - B a t h o l i t h l c i n t r u s i v e i n the Bear R i v e r Formation and i s the one w i t h which the S i l b a k Premier ore deposits are a s s o c i a t e d . I n the f o l l o w i n g pages i t w i l l be r e f e r r e d to merely as 'porphyry'. D i s t r i b u t i o n The porphyry i n t e r m i t t e n t l y outcrops over a l a r g e area i n the southwestern h a l f of the property. I t s southern l i m i t i s near the I n t e r n a t i o n a l Boundary where i t i s i n contact with g r a n o d i o r i t e of the Coast Range B a t h o l i t h ; the eastern l i m i t i s i t s contact w i t h t u f f i n the mine workings; while to the north, d r i l l i n g on the L e s l i e Claim discovered only several narrow bands of porphyry separated by t u f f . ThiS appears to i n d i c a t e a 'fingering-out' and probable northern termination of the i n t r u s i o n . S i l i c i f i e d rock contain-i n g i n d i s t i n c t fragments,v;ghi"ohv-oHterop.sr*alongL.»i:h-, switch-back on the M i s s o u r i Road, was formerly mapped as porphyry; but since ' d r i l l i n g immediately east f a i l e d to encounter porphyry w i t h i n 400 feet of the surface, t h i s rock i s considered a s i l i c i f i e d , fragmental t u f f . West of Premier property, a porphyry s e c t i o n , i n t e r r u p t e d only by a few greenstone pendants and q u a r t z - d i o r i t e dykes, i s exposed along the gorge of Cascade Creek from the I n t e r n a t i o n a l Bounar^ northward a distance of at l e a s t 8000 f e e t , L i t h o l o g y The porphyry i s grey to greyish-green i n c o l o r , while i t s texture v a r i e s from coarse and p c r p h y r i t i c to f i n e - g r a i n e d and dense. Where p o r p h y r i t i c i t i s e a s i l y i d e n t i f i e d by phenocrysts of orthoclase which may be (12) as much as i n c h long; but where i t i s non-porphyritic and dense i t resembles the t u f f , p a r t i c u l a r l y when bothaare s i l i c -- i f i e d . However, the l i g h t e r c o l o r and small-conchoidal f r a c t u r e of the porphyry serve w e l l enough as f i e l d guides. M i c r o s c o p i c a l l y , ' I t i s seen to be h i g h l y a l t e r e d to s e r i c i t e , which occurs i n abundant f o i l s , and c a l c i t e . The c r y s t a l o u t l i n e s of the f e l d s p a r s are I n t a c t , but the c r y s t a l s themselves are a mass of s e r i c i t e and c a l c i t e . Remnants of what appears to have been p l a g o i c l a s e are f a i r l y abundant and o c c a s s i o n a l grains of quartz occur. The rock i s 4 c l a s s i f i e d as a g r a n d d i o r i t e which borders on a monzonite' . 7 . COAST RANGE BATHOLITH .', D l s t r l b u t i o n I n the extreme SW corner of the property the contact of the Coast Range B a t h o l i t h w i t h rocks of the Bear River Formation d i a g o n a l l y b i s e c t s the I n t e r n a t i o n a l Claim. L i lino logy T y p i c a l of the marginal phases of the Coast Range B a t h o l i t h , the g r a n o d i o r i t e i s a coarse-grained, h o l o c r y s t a l l i n e rock w i t h a somewhat mottled, p o r p h y r i t i c appearance. C r y s t a l s of medium p l a g i o c l a s e , a small amount of quartz, and abundant hornblende are v i s l t e l e under a hand l e n s . B i o t l t e i s t y p i c a l l y absent. Although l o c a l l y termed 'granodiorite' i t s composition i s probably nearer that of a q u a r t z - d i & r i t e . (13) 8. QUARTZ-DIORITE DYKES D i s t r i b u t i o n ' A feature of the geology of the area i s the p e r s i s t e n c e of these l a r g e dykes. Of the three main dykes which cross S i l b a k Premier property, the w r i t e r has trac-ed two of them f o r over three m i l e s . The s t r i k e i s never more than a few degrees from N50W, while the d i p i s about 55°SW. The 'Main Dyke' which passes through the mine workings has an average width of 400 f e e t , while the other dykes i n the southwest quarter of the property are from 50 to 200 f e e t wide. Where a s p l i t occurs the change i n d i r e c t i o n i s abrupt, but w i t h i n a few f e e t the s t r i k e s of the two branches again swing p a r a l l e l to that of the o r i g i n a l dyke. Litnology The q u a r t z - d i o r i t e dykes resemble the Coast Range Granodiorite i n texture and composition. The border f a d e s , nowhere more than a few f e e t wide, are d i s t i n c t l y p o r p h y r i t i c w i t h small phenocrysts of f e l d s p a r i n a greenish, indurated, groundmass. I n the Mine the main quartz-d i o r i te dyke i s known as 'the granite dykett. This term w i l l berretainednihlarefe':rence to i t . 3* LAMPROPHYRE DYKES D i s t r i b u t i o n The lamprophyre dykes are commonly seen i n the mine workings and on the surface. They vary i n width from l e s s than an i n c h to 60 f e e t . Although the average s t r i k e i s NW with a dip of 60°SW, i n d i v i d u a l dykes may be quite i r r e g u l a r as to width, s t r i k e , and d i p . (14) LIthology I n hand specimen, the majority of the dykes are dark grey i n c o l o r w i t h a f i n e , even-grained texture. I n t h i n s e c t i o n , :iliey.rapeooharafcteri^edlbyry) 1 *-iICanor large content of (medium) f e l d s p a r i n long l a t h s and some 4 quartz....and hornblende 1 . Dyke margins are c h i l l e d , the aureole being l i g h t e r i n c o l o r and u s u a l l y about an i n c h wide, A minority of the dykes are more coarse-grained - the texture v a r y i n g from d l a b a s i c w i t h v i s i b l e l a t h s of p l a g i o c l a s e to f i n e l y p o r p h y r i t i c . Such dykes appear to represent a t e x t u r a l expression intermediate between the q u a r t z - d i o r i t e and lamprophyre dykes. The dykes are an important f a c t o r of ore-dep o s i t i o n , and f o r t h i s reason a d i s c u s s i o n of t h e i r r e l a t i o n to primary m i n e r a l i z a t i o n w i l l be l e f t f o r a l a t e r chapter. T.&BT.E OF .FORMATiQMS p l e i s t . & S Recent ppper I 4'-: ijurassicf R i v e r sand&graveljO-50 G l a c i a l D r i f t Jurasside Dykes 1 jLamprophyre Q , t z - d i o I n t r u s l v e Contact „. iGra n o d i b r i t e Coast Range B a t h o l i t h Intru«ive Contact, Premier Porphyry ( S i l l s ) JQtZ-dio.Por, -Pre-B a t h o l i t h i c I n t r u s i v e Conta^t__^_^^__„ NaTs R i v e r Formation j A r g i l l i t e s Salmon R i v e r Formation (Conglomerate ^een~J^V^7~' (Stock) |Gabbro Por. j R^ d" Porphyry ( S i l l s ) j f t t z - d i o . por. poo Imax < iffiax. jiooo/ j Upper iGreenstone r$r-, ,.V'.-Trrrr \ Bear R i v e r Middle fGreen Tuff §2000/ | 3 • : •. 1 L o w e r iuw o , ~ • > i lagglomerates & f Icoarse t u f f s i (15) CHAPTER IV. GEOLOGIC SEQUENCE & STRUCTURE I . AGE & CORRELATION A t t e n t i o n i s i n v i t e d to the Table of Format-i o n s on the opposite page w h i c h i s based on that published by the G e o l o g i c a l Survey-':,: but modified to show the three members of the Bear R i v e r Formation and the three p r e - B a t h o l i t h i c i n t r u s i v e s . On l i t h o l o g i c evidence the sedimentary, v o l -c anic, and associated i n t r u s i v e rocks of the Salmon Ri v e r Area wi t h the Hazelton Group, which i s considered Upper J u r a s s i c . There i s some dlsagreament among various w r i t e r s as to the ac t u a l age of these rocks. However, the f a c t of economic import-ance i s that they are d e f i n i t e l y p r e - B a t h o l i t h i c . Of t h i s there i s abundant evidence: 1. Both porphyry and t u f f are indurated near the Contact. 2. Pendants of t u f f occur w i t h i n the Gr a n o d i o r i t e . T h e q u a r t z - d i o r i t e dykes may be contempory w i t h , and an expression of, B a t h o l i t h i c i n t r u s i o n , Hanson c i t e s ah example of a dyke i n the Bear River V a l l e y , which, when 2 ' traced to the Contact, q u i c k l y l o s t i t s i d e n t i t y . The lamprophyre dykes are younger than the Granodi o r i t e . The w r i t e r noted a lamprophyre dyke on the Border Claim which crossed the Contact without apparent change. I t showed s i m i l a r c h i l l e d borders both i n greenstone and i n Granodiori te and i t was c l e a r l y a s t r u c t u r a l u n i t i n both rocks. (16) 2 . THE SILL-LIKE CHARACTER OF THE PORPHYRY S c h o f i e l d o r i g i n a l l y recognized the i n t r u s i v e rocks of the Salmon Ri v e r area as s i l l s - ' - , but several other i n v e s t i g a t o r s are i n c l i n e d to regard them as i r r e g u l a r stock-2 4 l i k e ' i n t r u s i o n s i J > . The f o l l o w i n g evidence of the s i l l - l i k e character of the Porphyries i s o f f e r e d : ( A t t e n t i o n i s d i r e c t e d to the Geologic P l a n and Sections which accompany t h i s Report.) 1 . The bedding-planes of the t u f f d ip 25 degrees i n the northern s e c t i o n of the mine and nearer 45 degrees i n the southern s e c t i o n * 2 . The Red Porphyry, which i s regarded as a hypabyssal i n t r u s i v e g e n e t i c a l l y r e l a t e d . t o the Premier Porphyry, i s e v i d e n t l y concordant with the t u f f s i n S e c t i o n A-A. 3* The general dip of the porphyry i n Sections A-A and B-B i s about 25 degrees, i . e. p a r a l l e l to the t u f f bedding. 4 . Where the bedding of the t u f f i s at a steeper angle, i n Sections C-C and D-D, the general dip of the porphyry i s greateE!. 1 5 . S c h o f i e l d c i t e s a case of g r a v i t y d i f f e r e n t i a t i o n . This was not observed by the w r i t e r . 6 . Pendants of t u f f are of a t y p i c a l l y e l l i p t i c a l shape with , a northwest s t r i k e p a r a l l e l to that of the t u f f bedding. 7 . The Geologic Sections i n d i c a t e a; maximum thickness of about 500 f e e t f o r an i n d i v i d u a l s i l l . E v i d e n t l y there are s everal s i l l s i n the area; those i n the Mine underlying those mapped on the surface. (17) (See Surface Map) . The l a r g e a r e a l exposure of porphyry i s r e a d i l y explained "by er o s i o n more or l e s s p a r a l l e l t o the s i i l s . 8. The Porphyry s i l l s are q u i t e i r r e g u l a r i n o u t l i n e . I n some cases tongues of porphyry have cross-cut the t u f f • bedding from one h o r i z o n to another. See Sections G-G & D-D. 3 . REGIONAL UPLIFT & FOLDING Regional u p l i f t and f o l d i n g followed deposit-i o n of the p r e - B a t h o l i t h i c rocks. The axes of f o l d i n g alang hove the e n t i r e Eastern Contact^a northwesterly, or ' C o r d i l l e r a n ' , trend. I n the Salmon River Area t h i s u p l i f t i s expressed by a s e r i e s of f o l d s trending west of north, and generally p i t c h i n g north. S i l b a k Premier Mine i s s i t u a t e d on a west e r l y - d i p p i n g monocline (or p o s s i b l y the eastern limb of a very l a r g e sync l i n e ) ; whi ch, to the north i n the v i d i n i t y of Sla t e Mountain, gives place to a broad s y n c l i n e p i t c h i n g about 10 degrees north. Farther north, i n the Long Lake area, the axes of f o l d i n g swing more nearly northwest. The anomalous s t r i k e of Porphyry i n the Northwest Zone, and the o f f s e t porphyry of 1308 W D r i f t , (See Geologic P l a n of 1350 L e v e l ) , suggest that u p l i f t began s l i g h t l y before,( Though It continued long a f t e r ) , emplacement of the porphyry s i l l s . (18) 4. DEVELOPMENT, OF THE SHEAR-PATTERN Stresses set up by the f o l d i n g were r e l i e v e d by shearing, and, to a l e s s o r extent by f a u l t i n g . The r e l a t i o n of shear d i r e c t i o n s to the a s i s of f o l d i n g may be i l l u s t r a t e d by a simple s t r e s s diagram: Minor component-—-1—\^~ I—^IB.jor component of shear - WNW / I of shear - NNE us \ V _ j - Normal component ' ' " of pressure - SW-NE \ A x i s of f o l d i n g - NW Shearing may be d i v i d e d i n t o : (a) production of a r e g i o n a l shear cleavage i n a l l o l d e r rocks, p a r i c u l a r l y i n the l e s s competent t u f f , and, (b) production of an i n t e r s e c t i n g NE-NW shear-pattern i n more competent rocks such as porphyry. This shear-pattern, i n the v i c i n i t y of S i l b a k Premier Mine, i s expressed by: 1. A zone of inten s e shearing, the s t r i k e of which v a r i e s from NE i n the o l d Premier workings to N20E i n Sebakwe se c t i o n . 2. A s i m i l a r zone s t r i k i n g NW which i n t e r s e c t s the f i r s t . 3 . Progressive o f f s e t t i n g of the NE Zone to the l e f t . 4. Northwest c r o s s - f r a c t u r i n g of some ore-bodies. 5 . The p r e v a i l i n g northwest s t r i k e of dykes. 6 . Normal l e f t - h a n d f a u l t i n g 7. Minor p a r a l l e l shear-zones on e i t h e r side and at va r y i n g distances from the Main Zones. These shear zones and t h e i r a s s ociated f a u l t s are i n t i m a t e l y r e l a t e d to ore - d e p o s i t i o n . A d i s c u s s i o n of t h i s r e l a t i o n s h i p w i l l be l e f t f o r a l a t e r chapter. (19) 5 . THE METHOD OF BATHOLITHIC INTRUSION . , Because of the prevalence of q u a r t z - d l o r i t e dykes i n the southwestern h a l f of the property, Means i s of the o p i n i o n that Granodiorite underlies the S i l b a k Premier Mine at r e l a t i v e l y shallow depth. The f o l l o w i n g f i e l d evidence does not seem to substantiate t h i s theory: 1. The dykes have a northwesterly sfeoike and a southwesterly d i p . • 2. The a t t i t u d e of the Contact i s p a r a l l e l to t h a t of the dyke 3. Bands of greenstone, engulfed i n G r a n o d i o r i t e , are elongated p a r a l l e l to the Contact and show a s l a t y cleav^age i n that d i r e c t i o n . The w r i t e r submits that f o r the S i l b a k Premier area a l l e a s t , the method offl emplacement was: i n t r u s i o n of l a r g e dykes along p r e - e x i s t i n g s t r u c t u r a l l i n e s - i n t h i s case the NW shear. -' followed by progressive stoping and sinking, of the i n t e r v e n i n g b l o c k s . The'dykes now seen are>fche advance-guards of an i n v a s i o n which has stopped short. The c o n t r a s t i n g Ideas may be i l l u s t r a t e d by,, simple diagrams thus: I f t h i s theory i s accepted i t f o l l o w s that S i l b a k Premier property i s not u n d e r l a i n at' any r e l a t i v e l y -shallow depth by the Coast Range B a t h o l i t h (20) 6. EROSIONAL RECORD During the Cretaceous e r o s i o n to a peneplain exposed the Coast Range Batholith- 1-. I n the Saibmon Ri v e r Area t h i s o l d peneplain i s marked approximately by the present s k y - l i n e of the Coast Ranges, A f t e r r e - e l e v a t i o n , e r o s i o n proceeded through the T e r t i a r y , and by the end of that Period modern topography had been approximately e s t a b l i s h e d . I n the v i c i n i t y of S i l b a k Premier Mine the T e r t i a r y surface i s represented by the top of S l a t e Mountain at an e l e v a t i o n of 4000 f e e t . The Salmon G-laciar V a l l e y i s an e x c e l l e n t example of... the a n t i q u i t y of the drainage system. I t i s a 'through v a l l e y ' from the low summit of which i c e flows north i n t o the Nas's River System and south i n t o the Salmon R i v e r . This low d i v i d e i s t y p i c a l of that between adjacent drainage ba s i n s , and since the v a l l e y has been f i l l e d w i t h Ice since the P l e i s t o c e n e Time, the drainage basins must be T e r t i a r y . T e r t i a r y topography wafs accentuated, but probably not g r e a t l y d i s l o c a t e d , by the Ice, I n general, sur-faces above 2500 f e e t e l e v a t i o n ar/3 of g l a c i a l o r i g i n . Examples of such surfaces are, Long Lake and the Chickamen V a l l e y s . P o s t - g l a c i a l s t r e a n e r o s i o n has been extensive. V-shaped va l l e y s . a n d p r e c i p i t o u s gorges are c h a r a c t e r i s t i c of the lower slopes. P o s t - g l a c i a l stream e r o s i o n has been respon-s i b l e f o r the steep-sided lower v a l l e y of East Fork Creek, adjacent to the Mine; and i e c i d e n t l y , f o r the removal of most of the- Northwest Ore-Zone. PART TWO ORE-DEPOSITION & MINERALOGY The ore-bodies of the o l d Premier Mine which occurred adjacent to the I n t e r s e c t i o n of the Northeast and Northwest Zones are now l a r g e l y exhausted and i n a c c e s s i b l e . Their l o c a l l i z a t i o n and mineralogy have been discussed by former i n v e s t i g a t o r s ^ ' ^ * The p r i n c i p a l ore-bodies now being mined occur i n t e r m i t t e n t l y along the Northeast Zone. I t i s these ore-bodies with which the w r i t e r i s f a m i l i a r and on the examination of which t h i s Report i s based. The riamesr'Gf t h e e t h r e e p r o p e r t i e s now combined to form the S i l b a k Premier property are s t i l l used to describe sections of the Mine. Thus the most southerly s e c t i o n i s known as Premier; the next, B.C.Silver; w h i l e the most no r t h e r l y s e c t i o n , north of the g r a n i t e dyke, i s the Sebakwe S e c t i o n . These names are used i n t h i s Report i n d e s c r i b i n g l o c a t i o n s i n the Mine. (21) CHAPTER Y . GENERAL SUMMARY & CONCLUSIONS I . CHARACTER OF THE NORTHEAST ZONE The Northeast Zone i s gen e r a l l y i n porphyry not f a r from the f o o t w a l l contact. I t i s su c c e s s i v e l y o f f s e t to the l e f t , each succeding s e c t i o n showing a progressive change of a t t i t u d e - i n the Premier and B . C . S i l v e r r Sections the s t r i k e i s N4-5-60°E and the d i p i s about 60°SW; while i n the' Sebakwe S e c t i o n the s t r i k e averages N20°E and the d i p , 55°SW'. The Northeast Zone i s c h a r a c t e r i z e d by inte n s e s i l i c i f i c a t i o n which gradually diminishes toward the w a l l s . M i n e r a l i z e d sections og the Zone u s u a l l y c o n s t i t u t e ore-bodies, 2• CHARACTER OF THE DEPOSITS The ore-bodies occur as i n t e r m i t t e n t m i n e r a l i z e d sections of the Northeast Zoiaae, These have a char-: a c t e r i s t i c rake of about 60°E and have the' same general a t t i t u d e as the Zone. Two general types are recognized, one i n porphyry c h a r a c t e r i z e d by i r r e g u l a r s t r i n g e r s and bunches of sulphides, p a r t i a l l y - d i g e s t e d fragments of wa l l - r o c k , and by gra d a t i o n a l w a l l s ; while the other, i n greenstone, has abrupt w a l l s and unaltered fragment-5 of w a l l - r o c k around which the sulphides a r e - o f t e n banded* ; Barren sulphide bodies are c h a r a c t e r i z e d by abnormal amounts of p y r i t e and by the occurrence of s p h a l e r i t e and galena i n l o c a l bunches, un- r e l a t e d to the p y r i t e . (22) 3 . MINERALOGY OF THE ORE-BODIES * i S i l b a k Premier ore c o n s i s t s of about 20$ base metal sulphides i n a gangue of quartz and c a l c i t e . The minerals i n order of abundance are: p y r i t e , s p h a l e r i t e , galena, ch a l c o p p r i t e and p y r r h o t i t e , with small and va r y i n g amounts of gold, electrum, a r g e n t i t e , p y r a r g y r i t e , p o l y b a s i t e , and l o c a l l y , n a t i v e s i l v e r . Deposition occurred i n four general stages:-A pre-mineral stage represented by f r a c t u r i n g and s i l i c e o u s replacement of wa l l - r o c k ; a primary stage of f r a c t u r i n g and d e p o s i t i o n of p y r i t e and some c h a l c o p y r i t e and gold; a second-ary stage of s p h a l e r i t e , galena, c h a l c o p y r i t e , a r g e n t i t e , p o l y b a s i t e , and electrum, accompanied by some f r a c t u r i n g and r e - s o l u t i o n , and a f i n a l stage ch a r a c t e r i z e d by the d e p o s i t i o n of a r g e n t i t e , p o l y b a s i t e , n a t i v e s i l v e r , and f i n a l l y , c a l c i t e . The eleetrum has a composition of 65% gold and 35% s i l v e r corresponding to a volume r a t i o of 1 : 1 . Thisfe composition i s constant over the range i n v e s t i g a t e d of 750 f e e t . A r g e n t i t e , p y r a r g y r i t e , p o l y b a s i t e , and native s i l v e r are of primary o r i g i n , having been deposited from q u i t e a l k a l i n e hypogene s o l u t i o n rather l a t e r than the other sulphides. 4 . LOCALLIZAT1ON OF SULPHIDE BODIES The f o l l o w i n g f a c t o r s are e s s e n t i a l to the de p o s i t i o n and l o c a l l i z a t i o n of base metal sulphide bodies: (23) I«, I n i t i a l f r a c t u r i n g and s i l i c e o u s replacement of wal l - r o c k along f r a c t u r e zones. 2. R e - f r a c t u r i n g of t h i s s i l i c e o u s zone to provide avenues of ascent f o r the mineral-bearing s o l u t i o n s . C r o s s - f r a c t -u r i n g may serve t h i s purpose but t h i s does not make f o r ' very s a t i s f a c t o r y ore-bodies. -3. S t r u c t u r a l 'dams', such as pre-mineral dykes or t h i c k , g o u g e - f i l l e d f a u l t - p l a n e s . These are not always present, arid i n such cases the o r e - l i m i t s are determined by the l i m i t s of primary f r a c t u r i n g , 4. P h y s i c a l character of wal l - r o c k - porphyry i s a competent rock which maintains f r a c t u r e s u f f i c i e n t l y long to allo w of i n j e c t i o n of the o r e - s o l u t i o n s . 5.Chemical character of wal l - r o c k - porphyry i s suc c e p t i b l e to s i l i c a replacement, while t u f f , p a r t i c u l a r l y the dense v a r i e t y of greenstone, i s not e a s i l y replaced. 5. LP CALL! ZA TI ON OF ELECgRUM 1N. A SULPHIDE BODY A d d i t i o n a l to the e s s e n t i a l p o i n t s l i s t e d above, the d e p o s i t i o n of electrum i n a sulphide body depends on: I . Secondary f r a c t u r i n g a f t e r d e p o s i t i o n of p y r i t e . 2» The presence of two u n l i k e mineral surfaces i n a facture-i n p y r i t e , o r , mi c r o - f r a c t u r e s l e s s than 5 microns wide. JL A ' f a i r l y high concentration of calcium i n the o r e - s o l u t i o n may be neeessary - c e r t a i n l y c a l c i t e i s t y p i c a l l y present. (24) 6 . DEPTH FACTORS 1. The t h e o r e t i c a l l i m i t of ore- d e p o s i t i o n i s that p o i n t at which pneumatolltic vapors condense to form a hydrothermal l i q u i d . 2. No change i n mineralogy, q u a l i t a t i v e l y or q u a n t i t a t i v e l y , i n d i c a t e s t i m t t h i s l i m i t has y et been approached i n •y S i l b a k Premier workings. 3 .Geologic evidence I n d i c a t e s that the deposits were formed at. :a minimum depth of 4000 f e e t . Isometric a r g e n t i t e i n d i c a t e s a minimum temperature of formation of 180°C. -.4... Consequently the deposits are thought to have .formed under a temperature between 200 and 500°G, and under a minimum pressure of 125 Atmospheres. 4. The decrease w i t h depth of the s i l v e r content of the ores i n d i c a t e s a r a p i d v e r t i c a l zoning, a r g e n t i t e extending to deeper horizons than the other s i l v e r minerals. The s i l v e r content may decrease i n d e f i n i t e l y or approach some minimum, 7 7. CLASSIFICATION OF THE 0REv DEPOSITS The S i l b a k Premier ore deposits are f i s s u r e f i l l i n g s of a s i l i c e o u s replacement zone and are of the low-grade mesothermal type. I n r e a l i t y there are three types of ore represented i n these deposits which are un-related except that they are a l l r e l a t e d to the general s t r u c t u r e : a s i l v e r deposit of short v e r t i c a l range; a poly sulphide deposit containing electrum, and a low-grade s i l i c e o u s and p y r i t i c gold d e p o s i t . (25) CHAPTER VI . THE PRINCIPAL LOCUS OF DEPOSITION - j l . THE FOOTWALL CONTACT The porphyry s i l l s and t h e i r r e l a t i o n to the t u f f have "been discussed i n P a r t One, and are i l l u s t r a t e d by the Geologic P l a n and Sections which accompany t h i s Report. Regarding o r e - d e p o s i t i o n , the f o o t w a l l contact i s the more important. I n the southwest p a r t of the Mine t h i s contact has a steep dip above 4—Level and tends to f l a t t e n below the L e v e l . This c o n d i t i o n a l s o holds f o r the s e c t i o n from 1304 Dr. to 1335 X-cut, but i n the 1308 W.Drift and Sebakwe sections the contact assumes a more gentle and re g u l a r d i p . On the Geologic P l a n the porphyry of 1308 W. D r i f t and Sebakwe sections has been shown as a separate body o f f s e t about 300 f e e t west. This c o n s t r u c t i o n i s based on d r i l l i n t e r s e c t i o n s and on the f a c t that no tracfe of a f a u l t could be detected which might, o f f set the porphyry. -The contact i s gently undulating w i t h occass-i o n a l bulges i n t o the f o o t w a l l . Elongate pendants of t u f f are commonly found i n the porphyry, l y i n g p a r a l l e l to the f o o t w a l l , not f a r from the contact. (26) 2. STRUCTURES OF THE NORTHEAST ZONE - •; The Northeast Zone may be (ftlvided roughly i n t o three sections s u c c e s s i v e l y o f f s e t to the l e f t . These w i l l be r e f e r r e d to as: 1304 D r i f t - 1335 Cross-cut Section; 1308 W. D r i f t S e c t i o n , and Sebakwe Section. The l a t t e r c o n s i s t s of a t l e a s t f o u r short efifsets i n en echelon arrangement. Section 1304 Dr. The Zone f o l l o w s the main porphyry-tuff contact to 1335 X-C. . •v along 1304 D r i f t . A branch along 1324 D r i f t corresponds with a f o o t w a l l bulge of the contact, while an i n -termediate spur i s followed by 1332 D r i f t . About 100 f e e t north of the j u n c t i o n of 1332 D r i f t with 1304 D r i f t a f a u l t which s t r i k e s NW and d i p s 50°SW d i s p l a c e s the Zone about 100 f e e t northwest. St i s again encountered i n 1302 D r i f t , along which i t continues, somwwhat weaker, u n t i l l i t disappears i n the t u f f j u s t north of 1335 X-C. A p a r a l l e l f o o t w a l l zone along 1326 and 1328 D r i f t s i s in. porphyry a few f e e t from the contact. This may be the f a u l t e d c o n t i n u a t i o n of the 1324 D r i f t branch. ; This s e c t i o n of the Zone i s i n t e n s e l y s i l i c i f -i e d and moderately to stfcongly m i n e r a l i z e d . M i n e r a l i z a t i o n i s generally confined to the c e n t r a l part of the Zone. I t jrarles from f i v e to f i f t e e n f e e t wide, but strong s i l i c i f i c a t i o n may extend f o r a hundred f e e t i n t o the hanging w a l l and a short distance i n t o the f o o t w a l l . The average s t r i k e i s N50E and the d i p about 60°NW. Above 1350 L e v e l the Zone i s i n porphyry, but due to the more gentle contact d i p below the L e v e l , i t continues downward (27) through dense, compact, greenstone. Here the Zone i s narrow wit h s i l i c l f i c a t i o n andfrnineralizationaeonfined between barren, u n s i l i c i f i e d w a l l s . Stopes l o c a t e d on t h i s S e c t i o n of the Zone are: IOA&B, I2A&B, I3F, I3A&B, 13C&D, l4A, 15C&D. 1308 W. Dr. No apparent s t r u c t u r a l connection e x i s t s S e c t i o n between the preceding S e c t i o n and t h i s one. L i k e tilie former, t h i s zone i s i n porphyry w i t h i n a few f e e t of the f o o t w a l l contact. The Zone i s very h i g h l y s i l i c i f l e d * The c e n t r a l s i s f e e t or so i s almost pure quartz but sulphide min-e r a l i z a t i o n i s comparatively weak. S i l i c i f i c a t i o n decreases r a p i d l y toward the w a l l s , p a r t i c u l a r l y toward the f o o t w a l l . .This s e c t i o n of the Zone s t r i k e s N45E and d i p s 57GNW. . ' The only stope developed here i s 1 3 H , note-worthy because of the occurrence of v i s i b l e electrum, ruby,and na t i v e s i l v e r . Sebakwe S e c t i o n The Sebakwe S e c t i o n , which i s separated from preceding Sections by the 400-foot Granite dyke, i s o f f s e t about 250 f e e t west from the s t r i k e of the 1308 S e c t i o n . The four zones i n ensechMem arrangement are: 1313-1315 D r i f t s , 1333 D r i f t , 1338 D r i f t , and 1341 D r i f t . The 1313-1315 D r i f t s e c t i o n , which i s i n porphyry near the f o o t w a l l contact with a l a r g e t u f f pendant, s t r i k e s N30E and dips about 55°NW. S i l i c i f i c a t i o n i s quite wide di m i n i s h i n g gradually toward' the hanglngwall. M i n e r a l i z a t i o n v a r i e s from moderate to i n t e n s e . (28) 1333 D r i f t Zone i s o f f s e t about 250 f e e t west of 1315 D r i f t , Although m i n e r a l i z a t i o n i s p a r t i c u l a r l y intense the'- values are comparatively low. The s t r i k e i s N20E and the d i p 55°NW. I n the east end of 1333 d r i f t the zone encounters t u f f j u s t north of 1337 X-Cut and q u i c k l y loses i t s i d e n t i t y . 1338 D r i f t Zone i s low-grade and poorly-defined, while the 1341 Zone, at the time of w r i t i n g , was known only f r o n d r i l l - h o l e i n t e r s e c t i o n s . The l a t t e r i s i n t u f f near a porphyry contact, s t r i k e s N20E, and i s unique i n i t s high s i l v e r : gold r a t i o . (29) CHAPTER VII GENERAL CHARACTER- OF ORE-BODIES I . ATTITUDE The ore-bodes have the same strikes and d i p s as the s i l i c e o u s zones which contain them. They also have a c h a r a c t e r i s t i c rake of about 60°east. 2.: MINERALIZATION A b r i e f d e s c r i p t i o n of the ore-bodies i s given to i n d i c a t e the general m i n e r a l i z a t i o n and str u c t u r e s observed i n them. Passages i n quotation marks are taken d i r e c t l y from f i e l d notes made i n the stopes. 13A stope This i s the downward c o n t i n u a t i o n of o l d . "• - ' ' Premier 4h stope. Mining width v a r i e s from 10 to 20 f e e t w i t h average values. The s i l v e r j g o l d r a t i o i s high, about 4 d : l . "The ore c o n s i s t s of hi g h l y s i l i c e o u s zone from 1 0 . t o 20 f e e t wide. The s i l i c a i s of a greenish-white c o l o r i n which may be seen a few remnants of porphyry fragments. Dark green patches of c h l o r i t e (?) occur s p a r i n g l y throughout the s i l i c e o u s m a t e r i a l . M i n e r a l i z a t i o n i s i r r e g u l a r l y d i s t r i b -uted, as bunches rather than s t r i n g e r s . 'Black sulphides' ( s p h a l e r i t e , galena, s i l v e r m i n e r a l s ) , tend to form d e n d r i t i c patterns through the gangue, i n places f i l l i n g minute f r a c t u r e s . Both walls,, which are-porphyry,, are only s l -i g h t l y s i l i c i f i e d and ore-boundaries are qu i t e abrupt" 13B stope As seen i n l 3 3 2 D r i f t , the zone i s q u i t e narrow and the o r e - l i m i t s abrupt. About 2 f e e t of the c e n t r a l part c o n s i s t s of s o l i d , banded sulphides of i r o n , zind (30) and lead c a r r y i n g better-than-average values. '-L-nis stope was i n t e r e s t i n g i n that electrum was observed as a t h i n p l a t i n g on the po l i s h e d surface of a Northwest postsmineral f a u l t . Stopes s i m i l a r to 13B are 17A and 18A&B. 13E contains s i m i l a r s o l i d bands of sulphides but the values are cu r i o u s l y low, 15D stope "The width v a r i e s from 15 to 30 f e d t . Ore .consists of high l y s i l i c e o u s porphyry ^ fragments separated by areas of greenish, 'replacement s i l i c a ' , c o n t a i n i n g i r r e g u l a r s t r i n g e r s and bunches of f i n e - g r a i n e d mixed sulphides. S t r i n g e r s are u s u a l l y p a r a l l e l to the stope . Porphyry remnants have no d e f i n i t e o u t l i n e s . The ore i s c r i s s - c r o s s e d by s t r i n g e r s of milk-white ' l a t e r ' quartz, f r e e of sulphides except where porphyry remnants occur . The ore has economic l i m i t s - i t grades i n t o s i l i c i f l e d porphyry f r e e of m i n e r a l i z a t i o n . " I5A stope i s s i m i l a r . 15B i s also s i m i l a r except that f o r comparable values, the percentage of sulphides i n the l a t t e r i s much l e s s . 13H stope This curious l i t t l e stope i s i n t e r e s t i n g i n that i t i s bounded o n - a l l four sides by almost barren zone-material. I t i s s i t u a t e d i n a narrow tongue of porphyry with t u f f s on both foot and hangingwall. Values are ex c e p t i o n a l l y high. The s i l v e r t g o l d r a t i o i s only about 10:1. Electrum, ruby s i l v e r , and nati v e s i l v e r are v i s i b l e i n hand specimen. No l i m o n i t i z a t i o n or other s i g n of supergene e n r i c h -ment was observed. The w r i t e r understands that low to medium values are being obtained i n a r a i s e some distance above and northeast of 13H stope. (3D IOA stope "The stope i s from 9 to 20 f e e t wide. Both w a l l s are dark massive greenstone, u n s i l i c i f i e d andlbarremvaTheaore:^ both f o o t w a l l and hangingwall. The ore c o n s i s t s of a s i l i c e o u s breccia-zone i n which greenstone fragments,varying i n s i z e from ^ i n c h to 3 f e e t , are quite angular; unaltered except f o r a minor development of p y r i t e c r y s t a l s ; and appear quite s i m i l a r to the w a l l s . The s i l i c e o u s gangue i s of a greenish-white c o l o r and may c o n t a i n bands of darker green which are frequently seen c o n c e n t r i c a l l y p a r a l l e l i n g the boundaries, of greenstone f r a g -ments. The g angue aleo contains i r r e g u l a r masses of dark green c h l o r i t e ( ? ) . M i n e r a l i z a t i o n c o n s i s t s of somewhat sinuous s t r i n g e r s of medium-grained, mixed sulphides, which o f t e n show banding p a r a l l e l to t h e i r r a t h e r abrupt borders. Bunches of barren brown s p h a l e r i t e are common. Chalcopyrite occurs sparing-l y i r i ^ i r r e g u l a r bunches or occupies small f i s s u r e s which are not always .completely f i l l e d by the Sulphide, The. ore i s c r i s s -crossed by narrow white quartz s t r i n g e r s , unminerallzed and barren" "This ore-body i s c h a r a c t e r i z e d by b e t t e r -than-.ayera.ge values and by a very low s i l v e r ; g o l d r a t i o of l e s s than 2:1'.' 6A stope, nearly 4-00 f e e t below and some distance southwest, i s s i m i l a r to IOA except that the s i l v e r : gold r a t i o i s over 3:1, 4AE i s the eastward c o n t i n u a t i o n of Premier 4A stope. The zone occurs i n dense compact greenstone, and i s s i m i l a r to IOA except that the s i l v e r : g o l d r a t i o i s much higher, i n 4AE stope the w r i t e r observed,"alternating bands of sulphides and quartz, i n d i v i d u a l l y not over i i n c h wide, each band having sharp contactsswith the adjacent ones". (32) 3. TYPES OF ORE-BODIES On the evidence of f i e l d observations a c l a s s i f i c a t i o n of S i l b a k Premier ore-bodies can be made thus: 1. Replacement Type", c h a r a c t e r i z e d by rounded, p a r i a l l y digested fragments of porphyry. The ore may c o n s i s t of bunches or i r r e g u l a r s t r i n g e r s of sulphides, with m i n e r a l i z a t i o n grading o f f toward the w a l l s , or, the sulphides may occur i n s o l i d bands p a r a l l e l to the gen-e r a l a t t i t u d e of the stope. I n the l a t t e r case the stopes are u s u a l l y narrow w i t h quite abrupt ore-boundaries on both w a l l s . 2. "Breccia-Zone F i l l i n g Type", c h a r a c t e r i z e d by: compact greenstone w a l l s , u n s i l l c l f l e d and barren, against which the ore has abrupt boundaries; angular fragments of barren greenstone, c o n c e n t r i c a l l y surrounded by bands of s i l i c a and mixed sulphides; and by f i s s u r e s only p a r t i a l l y f i l l e d by sulphides. , (33) CHAPTER VIII INFLUENCE OF DYKES, FAULTS, & CROSS/FRACTURES ON ORE-DEPOSITION The Northwest Shear-Zone I s expressed i n the Mine by dykes, f a u l t s and c r o s s - f r a c t u r e s which have a northwesterly s t r i k e and a southwesterly d i p . Whether these s t r u c t u r e s i n f l u e n c e o r e - d e p o s i t i o n or not depends on whether they are pre-mineral or post-mineral. Pre-mineral dykes would tend to provide impervious w a l l s to s o l u t i o n movements, while g o u g e - f i l l e d f a u l t -planes would also serve as 'dams'. Pre-mineral c r o s s - f r a c t u r e s could concievably serve as avenues of access f o r mineral-bearing s o l u t i o n s . Dykes The general d i s t r i b u t i o n , I I t h o l o g y , and geologic age of dykes was discussed i n Part One. I n order to determine t h e i r age i n r e l a t i o n to m i n e r a l i z -a t i o n , one must consider them I n r e l a t i o n to the ore-bodies. The f o l l o w i n g quatations are taken d i r e c t l y from f i e l d notes: (I5C stope) "A lamp dyke i n the east end s t r i k e s NW and di p s 48°SW» On or w i t h i n a few inches of. the hangingwall of t h i s dyke, small s t r i n g e r s of s o l i d sulphides, mostly p y r i t e , occupy f r a c t u r e s i n quartz p a r a l l e l to the dyke. Nearby are s i m i l a r s t r i n g e r s of galena. The dyke I s i t s e l f sparsely m i n e r a l i z e d with p y r i t e and a few sdattered grains of galena. There i s a p a r a l l e l shatter-zone on the f o o t w a l l side of the dyke. The ore here i s low-grade and d i s s i m i l a r i n appearance to that on the hangingwall s i d e , " The majority of Lamprophyry dykes cut through the ore. They have sharp boundaries and had no apparent e f f e c t . o n a t t i t u d e or m i n e r a l i z a t i o n of the ore-bodies.In some cases, (1332 Dr.)"fragments of ore have been d i s p l a c e d and c a r r i e d short distances by the l i q u i d magma" (34) As regards the main G-ranite dyke, the f o l l o w i n g passage r e f e r s to i t s hangingwall contact as seen on I 6 7 0 Level immediately 'east of 16A stope: "A narrow s t r i n g e r p a r a l l e l to the contact c o n s i s t s of c o a r s e l y - c r y s t a l l i n e p y r i t e , galena, and s p h a l e r i t e i n a quartz gangue. The border f a c i e s of the g r a n i t e contain somewhat crushed c r y s t a l s of p y r i t e . ( e v i d e n t l y there was movement subsequent to m i n e r a l i z a t i o n ) . A g o u g e - f i l l e d f a u l t -plane on the g r a n i t e contact contains the three sulphides mentioned." Gases have been cite<§ from the Premier Mine where m i n e r a l i z a t i o n has widened along dykes . The evidence i n d i c a t e s that the g r a n i t e dyke i s pre-mineral i n age. The p e r i o d of lamprophyre dyke i n t r u s i o n began p r i o r to m i n e r a l i z a t i o n , although the greatest a c t i v i t y was post-mineral. The g r a n i t e dyke and pre-mineral lamprophyre dykes must be considered a p o t e n t i a l f a c t o r s i n the l o c a l l i z a t i o n of ore-bodies. F a u l t s The w r i t e r f i n d s tlaat a r a p i d and e f f i c i e n t method oft determining the. r e l a t i v e age of a f a u l t i n t e r s e c t i n g a poly sulphide ore-body k&&tmgm3®&&22B, i s to examine the gouge under a microscope (preferably d a r k - f i e l d ) . Assuming no recurrence of movement, i f the f a u l t i s pre-mineral no sulphides w i l l be present; i f contempory only c e r t a i n e a r l i e r minerals w i l l be observed; while i f the f a u l t i s post-mineral> the gouge w i l l c o n t a i n a l l the sulphides of the ore. C e r t a i n fault-gouges appear to b e ' s t r a t i f i e d ' , with s l l c k e h - s i d e d planes d i v i d i n g the. various mambers. This seems to i n d i c a t e a recurrence of movement and i n t h i s case the (35) method c i t e d above cannot be a p p l i e d . However, although the w r i t e r has not t e s t e d ' i t , the p r o b a b i l i t y i s that the various members of* the gouge woulf c o n t a i n mineral assemblages i n d i c a t i v e of the r e s p e c t i v e periods of movement. Movement represented by p o l i s h e d and s t r i a t e d planes such as are found i n some ore-bodies cannot be dated by the method c i t e d . On t e s t i n g s e v e r a l fault-gouges from the S i l b a k Premier Mine, i t was found that periods of movement were ^ prve-mineral, eomtempory w i t h the e a r l y stages of mineral-i z a t i o n , and post-mineral. For i n s t a n c e , the f a u l t s o f f s e t t i n g the porphyry i n the east end of 4AE stope are pre-mineral -the gouge contains no mashed sulphides; a f a u l t i n the east end of 15D West stope i s contempory w i t h the early stage of m i n e r a l i z a t i o n - the gouge contains p y r i t e but no galena or s p h a l e r i t e although the l a t t e r two sulphides are abundant i n adjacent ore; while the f a u l t mentioned above, on the g r a n i t e dyke contact, i s e n t i r e l y post-mineral - the gouge contains p y r i t e , galena,and s p h a l e r i t e . Many, i n f a c t the m a j o r i t y , of the post-mineral f a u l t s show considerable recurrence of movem ent. A t h i c k fault-gouge would be a most e f f e c t i v e 'dam' to the movement of m i n e r a l i z i n g s o l u t i o n s . Hence any pre-mineral f a u l t i s a p o t e n t i a l l o c a l l i . z i n g f a c t o r . (36) C r o s s - f r a p t u r i n g G r o s s - f r a c t u r i n g of ore-bodies i s commonly observed, often i n conjunction with small lamprophyre idgtkes. Apparently a pre-dyke Shatter-zone e x i s t e d of which the dykes took advantage. Examples of t h i s ^ i n l S C stope, mentioned above, and on 1220 Level East, at the east end of 12B stope^ I n both cases such a c o n d i t i o n appears to have a f f e c t e d the ore-bodies. C r o s s - f r a c t u r i n g appears to have been a c o n t r o l l i n g f a c t o r i n I s o l a t e d cases. I n 16B stope,"... s c a t t e r -ed, mixed sulphides and numerous quartz s t r i n g e r s have a general NW s t r i k e which i s at an angle to the s i l i c i f i & d zone". C r o s s - f r a c t u r i n g was apparently a minor f a c t o r i n the l o c a l l i z -a t i o n of some of the Premier ore-bodies. The Geologic Map i n d i c a t e s that two-way f r a c t u r i n g was responsible f o r . t h e ore of 21 stope, and a s i m i l a r c o n d i t i o n i s suggested by the map of 4G ore-body. C r o s s - f r a c t u r i n g may^-be considered a minor f a c t o r i n f l u e n c i n g o r e - d e p o s i t i o n . However, i t has iaot proved of great importance I n S i l b a k Premier Mine. (37) CHAPTER mil. MINERALOGY The f o l l o w i n g account of the mineralogy of S i l b a k Premier ore i s based on microscopic examination of over t h i r t y p o l i s h e d s e c t i o n s of specimens from various ore-bodies. With modern microscopic equipment sudfc as that a v a i l a b l e i n the U n i v e r s i t y l a b o r a t o r i e s , i t i s generally p o s s i b l e to examine precious metal r e l a t i o n s h i p s i n ore c a r r y i n g as l i l l l e as 0.25 ounces per ton. With t h i s i n mind, the w r i t e r s e l e c t e d specimens t y p i c a l of the ore-bodies from which they were taken* Spectac-u l a r specimens of 'High-Grade' were avoided since such m a t e r i a l i s i n d i c a t i v e of very l o c a l c o n d i t i o n s not t y p i c a l of the ore-body i n general. The average S i l b a k Premier ore contains about 20% base metal sulphides. I n order of abundance these are: . p y r i t e , s p h a l e r i t e , galena, c h a l c o p y r i t e , and p y r r h o t i t e . The other m e t a l l i c minerals present i n small and v a r y i n g amounts are: a r g e n t i t e , p y r a r g y r i t e , p o l y b a s i t e , electrum, native gold, and l o c a l l y , native s i l v e r . The p r i n c i p a l gangue minerals are quartz and c a l c i t e . I . BASE METAL SULPHIDES Under the microscppe there i s a s t r i k i n g contrast between the mineral a s s o c i a t i o n s and textures charac-t e r i s t i c of average to high grade ores, and those t y p i c a l of low grade or barren sulphide bodies. (38) Mineral A s s o c i a t i o n s and Textures T y p i c a l of Ore-Bodies: * :. P y r i t e occurs i n i r r e g u l a r grains up to 2mm. I n diameter. These are e x t e n s i v e l y f r a c t u r e d , the f r a c t u r e s generally being long, narrow and i r r e g u l a r , f i l l e d by galena and s p h a l e r i t e i n t i m a t e l y a s s o c i a t e d . Small amounts of c a l c i t e are t y p i c a l l y present. L o c a l l y , c h a l c o p y r i t e may a l s o take p a r t i n t h i s f r a c t u r e - f i l l i n g . Where p y r i t e i s absent, galena and s p h a l e r i t e form d e n d r i t i c p a t t e r n s i n a groundmass of quartz and c a l c i t e . M i neral A s s o c i a t i o n s and Textures T y p i c a l of Barren Sulphide Bodies: P y r i t e i s g e n e r a l l y present i n great abundance. Massive p y r i t e i s seen to be 'micro-brecciated 1, the f r a c t u r e surfaces being e i t h e r i n contact or i n juxta-pos-i t i o n 7 w i t h the i n t e r v e n i n g spaces f i l l e d by quartz, and o c e a s s i o n a l l y , c h a l c o p y r i t e . A l t e r n a t i v e l y , the p y r i t e grains may be s m a l l , equi-dimensional, rounded, and widely-separated, with the i n t e r v e n i n g spaces f i l l e d by e i t h e r galena or s p h a l e r i t e , never.both. Where p y r i t e i s absent, galena and s p h a l e r i t e form l a r g e , c o a r s e l y - c r y s t a l l i n e masses not i n t i m a t e l y a s s o c i a t e d . These c o n t r a s t i n g s t r u c t u r e s are i l l u s t r a t e d by F i g s . 5,6,7,8. The microphotographs showing electrum also i n d i c a t e the s t r u c t u r e s and a s s o c i a t i o n s t y p i c a l of ore-bodies. S p h a l e r i t e & Galena Next to p y r i t e i n abundance are s p h a l e r i t e and galena. As described above, t h e i r t y p i c a l occurrence i s one of i n t i m a t e a s s o c i a t i o n i n f r a c t u r e s (39) i n p y r i t e or i n d e n d r i t i c patterns i n quartz and c a l c i t e . Replacement of p y r i t e by s p h a l e r i t e i s i n d i c -ated by very ragged contacts (Fig.4) and ' s o l u t i o n i n l e t s ' along the p y r i t e borders. T y p i c a l p p h a l e f i t e always contains minute i n c l u s i o n s of c h a l c o p y r i t e and p y r r h o t i t e . These tend to be euhedral and appear to have a l i n e a r o r i e n t a t i o n . Occassional i n c l u s i o n s of s p h a l e r i t e i n p y r i t e c r y s t a l s are seen. I n t h i s ex 1 case, the s p h a l e r i t e does not contain and c h a l c o p y r i t e or p y r r h o t i t e i n c l u s i o n s . Chalcopyrite Small amounts of c h a l c o p y r i t e were present i n a l l P o l i s h e d s e c t i o n s . I t has two p r i n c i p -a l modes of occurrence, as s m a l l , i r r e g u l a r masses i n o r i g i n a l un-fractured quartz, and as occassional f r a c t u r e - f i l l i n g s i n p y r i t e or quartz. Besides i t s minor occurrence i n s p h a l e r i t e , i t was also observed as small, rounded i n c l u s i o n s i n s o l i d p y r i t e c r y s t a l s . Tetrahedrite No grey copper was found i n the sections examined. I t has been described from the deposits of Premier as o c c u r r i n g i n r e l a t i v e l y l a r g e masses i n some of the upper ore-bodies but was absent from the primary 3 4 ore below 2-Level tsame e l e v a t i o n as 1826 L e v e l ) . L o c a l masses of grey copper have been found i n some Sil b a k ore-bodies, but i t i s not a t y p i c a l c o n s t i t u e n t of the ores 2. GANGUE MINERALS Quartz and c a l c i t e are by f a r the most abund-ant gangue minerals. Andalusite and c h l o r i t e have been (4-0) described from the deposits of Premier- 5, and are probably present i n S i l b a k Premier ore-zones i n amounts s u f f i c i e n t to account f o r most of the alumina, i r o n , and magnesia of the replaced porphyry. B a r i t e occurs i n l o c a l masses on nearly a l l l e v e l s . A pink mineral which i s o c c a s s i o n a l l y seen as l o c a l masses i n the ore-zones has proved to be or t h o c l a s e , not rhodonite as was suspected. Quartz I n t h i s Report quartz i s te r m e d , ' o r i g i n a l ' , 'secondary', o r , ' t e r t i a r y ' , s o l e l y on i t s obser-ved character. This i s merely- f o r convenience and I s not meant to convey the impression of three d i s t i n c t periods of s i l i c a i n j e c t i o n . O r i g i n a l quartz i s e a s i l y i d e n t i f i e d by i t s dark, p i t t e d surface. I t s contact with sulphides or secondary -quartz i s quite abrupt (Figsvl&2), although minor p y r i t e m i n e r a l i z a t i o n , but not galena or s p h a l e r i t e , may extend i n t o i t a short distance along minute f r a c t u r e s * Chalcopyrite com-monly occurs as small i r r e g u l a r masses i n un-fractured m a t e r i a l . Secondary quartz shows smooth grey surfaces of high r e l i e f . I t f i l l s f r a c t u r e s I n p y r i t e and i s i t s e l f f r a c t u r e d , these being f i l l e d by l a t e r sulphides. T e r t i a r y quartz appears to have c r y s t a l l i z e d l a t e r than galena. I t i s o c c a s s i o n a l l y seen to have developed I t s c r y s t a l o u t l i n e a t the expense of galena, s p h a l e r i t e and secondary quartz. (Fig.3) (41) C a l c l t e The t y p i c a l occurrence of c a l c i t e i s w i t h the l a t e r sulphides andpplectrTSmaihupyrite f r a c t u r e s . I t also occurs with secondary or t e r t i a r y quartz as i r r e g u l a r , anastomosing masses. S t r i n g e r s of c a l c i t e are frequenly seen c r i s s - c r o s s i n g the ore. I t i s never present i n barren p y r i t e bodi'es. Secondary c a l c i t e i s commonly developed on the surfaces of open water-courses. 3 . THE OCCURRENCE OF FREE GOLD Native gold was o r i g i n a l l y i d e n t i f i e d i n 'Super-panner Tips' (See Appendix Bt) . Examination of p o l i s h e d s e c t i o n s , under high power, f i n a l l y revealed i t s occurrence as minute i n c l u s i o n s i n un-fractured o r i g i n a l quartz and i n s o l i d p y r i t e c r y s t a l s . The s i z e range i s from l e s s than one micron up to twenty microns. Due to the d i f f i c u l t y of determining i t , no q u a n t i t a t i v e estimate was made of the f r e e gold i n the various ore s e c t i o n s . I t was i d e n t i f i e d i n nearly a l l . t h o s e examined but appeared, to be most p l e n t i f u l i n sections from IOA stope and 1556 D r i f t . 4 . THE OCCURRENCE OF ELECTRUM This g o l d - s i l v e r a l l o y i s the p r i n c i p a l source of gold i n S i l b a k Premier ore. Represent!tive, ore samples from various e l e v a t i o n s i n the Mine, when analyzed w i t h H a u l t a i h apparatus, proved to contain electrum having an average constant composition of ka,65%, Ag, 35% - which corresponds fb<b a volume (42) r a t i o of 1:1. See Appendix A f o r r e s u l t s of H a u l t a i n Analyses. * i I n p o l i s h e d s e c t i o n electrum may be i d e n t i f i e d by i t s smooth pale yellow surface, and i t s s e c t i l i t y . With KCN i t etches more slowly than pure gold. I t has more or l e s s p o s i t i v e etch eeaetlons w i t h F e C l j and HgGl^. Figs.11 to 18 i l l u s t r a t e the mineral a s s o c i a t -ions of electrum. The most usual mode of occurrence i s i n wiu.3 f r a c t u r e - z o n e s " i n p y r i t e up to 100 microns wide, associated with galena, sphalerite,and c a l c i t e . I t may a l s o f i l l r a t h e r narrower f r a c t u r e s i n p y r i t e , IF galena i s a l s o present i n the same f r a c t u r e . Occassipnally electrum was seen alone i n f r a c t u r e s i n o r i g i n a l quartz. Here the c o n t r o l l i n g f a c t o r seems to have been the width of the f r a c t u r e , since the electrum occurred . only where the width was l e s s than 5 microns. Only one example was seen i n which electrum was associated w i t h a r g e n t i t e (Fig.13) and t h i s appeared to be a c a s u a l , r a t h e r than a genetic r e l a t i o n s h i p . Nearly a l l the microphotpgraphs i l l u s t r a t e the extremely in t i m a t e a s s o c i a t i o n of electrum and galena - without • "fehe c o l o r d i f f e r e n c e the boundary could not be e a s i l y detected. S i m i l a r occurrences of electrum are given i n Appendix C. Electrum i s o c c a s s i o n a l l y found i n the Mine, as a t h i n p l a t i n g on p o l i s h e d and s l i c k e n - s i d e d f a u l t - p l a n e s i n high-sulphide ore. A p r o v i s i o n a l explanation i s that electrum was an o r i g i n a l c o n s t i t u e n t of the ore. Grinding of the f a u l t has p u l v e r i z e d the b r i t t l e sulphides, while the s e c t i l e metal has been spread out as a t h i n f i l m . A rough c a l c u l a t i o n w i l l (4-3) show that the electrum contained i n one cubic f o o t of 2 ounce ore, i f reduced to a f i l m 20 microns t h i c k , w i l l spread over an area of- 50 square inches. Very l i t t l e g r i n d i n g of the f a u l t would therefore account f o r these unusual p l a t i n g s of electrum. An obvious o b j e c t i o n to t h i s explanation, f o r which no answer IS i s forthcomming, Ahow to account f o r the p u l v e r i z e d sulphides and the consequent increase i n volume. However, the electrum ^ could not have been o r i g i n a l l y deposited i n a post-mineral / f a u l t , % n d the w r i t e r p r e f e r s t h i s explanation to any nebulous ' theory i n v o l v i n g secondary enrichment of gold. .5. THE OCCURRENCE OF SILVER MINERALS & NATIVE SILVER A r g e n t i t e This mineral accounts f o r the bulk of the s i l v e r i n the normal ore. When i n small quant-i t i e s i t i s r a t h e r d i f f i c u l t to i d e n t i f y i n p o l i s h e d s e c t i o n s . However i f the s e c t i o n be f i l m e d w i t h a standard i o d i n e f i l m i n g s o l u t i o n , the a r g e n t i t e assumes a b r i l l i a n t ^ blue c o l o r e a s i l y detected. By t h i s method a r g e n t i t e was found i n specimens from 1820 L e v e l , 1670 L e v e l , 1525 L e v e l , 1350 L e v e l , and IOA stope. I t was,more abundant i n those specimens from, the upper l e v e l s . A r g e n t i t e occurs w i t h galena and s p h a l e r i t e f i l l i n g f r a c t u r e s i n quartz and p y r i t e . I t i s a l s o a common cons t i t u e n t of 'black sulphide' d e n d r i t e s . Small grains were commonly seen i n un-fractured o r i g i n a l quartz. I t i s not t y p i c a l l y associated with electrum. I n a s e c t i o n from 13H stope, argentitewas seen to occupy a v e i n l e t i n quartz i n t i m a t -ely a s s o ciated w i t h native s i l v e r . (44) Galena No i n c l u s i o n s of any d e s c r i p t i o n were observed I n the galena and.lt i s i n f e r r e d that t h i s min-e r a l c a r r i e d l i t t l e or no s i l v e r . A c a l c u l a t i o n from 'Super-panner' r e s u l t s i n d i c a t e s an upper l i m i t of 2 .5 ounces per, ton of pure galena. P y r a r g y r i t e No ruby s i l v e r s were found i n the s e c t i o n s . I t occurs i n small l o c a l masses i n various ore-bodies, at l e a s t down to the d l e v a t i o n of 1350 L e v a l . P o l y b a s i t e This mineral was i d e n t i f i e d i n a s e c t i o n from 13H stope where I t occurred i n i n t i m a t e a s s o c i a t i o n w i t h n a t i v e s i l v e r , galena, and s p h a l e r i t e . (Fig.I9) Native s i l v e r F i g s . 19&20 i l l u s t r a t e the occurrence of native s i l v e r i n the I3H ore-body i n v e i n l e t s i n quartz or p y r i t e associated-with argent!te. I t was a l s o observed as d i s c r e t e grains with p o l y b a s i t e , galena, and s p h a l e r i t e . G a l c i t e i s t y p i c a l l y present. r\ (45) CHAPTER IX. GENESIS OF THE ORES ,*;-!• This c h a p t e r - w i l l i n c l u d e s e v e r a l p o i n t s r e l a t i v e ,to' the genesis of Si l b a k Premier ores. I t w i l l a l s o i n c l u d e a b r i e f d i s c u s s i o n - o f the general physico-chemical aspects of ore - d e p o s i t i o n , using S i l b a k Premier as an example. While i t i s tru e that we know l i t t l e or nothing about the composition of the s o - c a l l e d , ' o r e - s o l u t i o n s ' , or the conditions under which they e x i s t e d , a t l e a s t we may study the r e s u l t s of t h e i r s o l i d i f i c a t i o n - the ores. From such a study c e r t a i n observed ? s l a t i o n s h i p s might w e l l be explained i n the l i g h t of known physico-chemical laws. Therefore, the w r i t e r hopes to be pardoned f o r d i g r e s s i n g a short distance from the subject of h i s Thesis i n t o t h i s l i t t l e - k n o w n and h i g h l y s p e c u l a t i v e f i e l d . I . SOURCE OF ORE-SOLUTIONS There can be l i t t l e doubt that the mineral-bearing emanations responsible f o r the S i l b a k Premier deposits were a f i n a l expression of B a t h o l i t h i c Intrusion? , :/!.. Ore-deposition was eontempory with the general period of - lamprophyre dyke i n t r u s i o n , which I s generally considered a l a t e stage of B a t h o l i t h i c I n t r u s i o n . 2. Sulphide d e p o s i t s , s i m i l a r i n mineralogy to those of Si l b a k Premfcfer, occur i n the area i n close a s s o c i a t i o n with the Granodiorite, i . e . i n roof pendants. (46) 2. CHEMICAL SIGNIFICANCE OF REPLACEMENT PHENOMENA AND OF 'UN-SUPPORTED NUCLEI' When examining p o l i s h e d s e c t i o n s under a microscope a person i s w e l l advised not to b e l i e v e a l l he sees. Thus an apparent replacement r e l a t i o n may be only a t e x t u r a l . one, while an ,'un-supported nucleus' may be merely a cross-cut ' i n l e t ' . Replacement-should be admitted only when i t i s i n accord with, known chemical laws, f o r there i s no reason why an o r e - s o l u t i o n should not obey such laws. An 'un-supported nucleus' should be admitted only when: (a) the borders of the enclo s i n g mineral are smooth and i n t a c t , (b) the borders of the i n c l u s i o n are smooth and r e g u l a r , and (c) when other s i m i l a r i n c l u s i o n s are present. I n S i l b a k Premier ore there i s evidence of replacement of p y r i t e and c h a l c o p y r i t e by s p h a l e r i t e . This i s p l a u s i b l e since both i r o n and copper are below zinc i n the Electro-motive S e r i e s . Presumably s p h a l e r i t e could also' replace galena, but no d e f i n i t e evidence of t h i s could be found. Another i n t e r e s t i n g case i s the replacement of galena and a r g e n t i t e by an unknown l i q u i d , w ith the ,contempory d e p o s i t i o n of c a l c i t e (Fig.18)* "1though no chemical explanation can be made f o r t h i s phenomenum,(apparently i t represents a t r a n s i e n t r e t u r n of more a c i d c o n d i t i o n s ) , i t does e x p l a i n the spread of ± the pe r i o d of galena d e p o s i t i o n and answers the question of how a r g e n t i t e can ass o c i a t e both w i t h galena and the l a t e r native s i l v e r . (47) ' Un-supported n u c l e i e i t h e r permeability of the enclosing mineral or p r i o r (or eontempory) c r y s t a l l i z a t i o n of the included mineral. I n the absence of in f o r m a t i o n to the contrary, the l a t t e r axp&anation appears more probable. The presence of 'un-supported n u c l e i ' i s not at variance with the chemistry of the problem. I n such a complex s o l u t i o n i t i s not reasonable to expect complete e q u i l i b r i u m to ob t a i n at a l l times I n S i l b a k Premier ore the f o l l o w i n g have been i d e n t i f i e d as ''un-supported n u c l e i : gold and c h a l c o p y r i t e i n o r i g i n a l quartz and i n p y r i t e ; a r g e n t i t e i n o r i g i n a l quartz; galena and s p h a l e r i t e i n p y r i t e ; and c h a l c o p y r i t e and p y r r h o t i t e i n s p h a l e r i t e . The c h a l c o p y r i t e and p y r r h o t i t e i n c l u s i o n s i n s p h a l e r i t e are i n t e r e s t i n g i n that they are a r e s u l t of replace-ment, not af p r i o r primary c r y s t a l l i z a t i o n . The r e l a t i v e Heats of Formation of c h a l c o p y r i t e , p y r r h o t i t e , and p y r i t e are, 1 8 , 2 3 , and 35 ^. When the z i n c - r i c h l i q u i d c o n t a i n i n g some i r o n and copper began to c r y s t a l l i z e as s p h a l e r i t e , some i r o n remained i n s o l i d s o l u t i o n i n the blende, some went to make up the i r o n content of c h a l c o p y r i t e , while the remainder formed p y r r h o t i t e i n s t e a d of p y r i t e , due to the lower Heat of Formation of the p y r r h o t i t e . Evidence c o n t r i b u t i n g to t h i s explanation i s , that while a l l the t y p i c a l s p h a l e r i t e contains c h a l c o p y r i t e and p p y r r h o t i t e i n c l u s i o n s , that s p h a l e r i t e ^ which occurs as 'un-supported n u c l e i ' I n p y r i t e , contains no i n c l u s i o n s what-so-ever. (48) 3* PARAGENESIS OF THE ORE MINERALS \^ C a l c i t e The.paragenesis i s presented i n diagramatic form because i t i s thus p o s s i b l e to i l l u s t r a t e more c l a a r l y the i n t e r - r e l a t e d f a c t o r s . The paragenesis f a l l s n a t u r a l l y i n t o four stages - pre-mineral, primary, secondary, and f i n a l . The pre-mineral stage i s c h a r a c t e r i z e d by primary f r a c t u r i n g and s i l i c e o u s repalcement; the primary stage, by r e - s o l u t i o n of s i l i c a and d e p o s i t i o n of p y r i t e , some c h a l c o p y r i t e , and gold; the t h i r d stage,by d e p o s i t i o n of c h a l c o p y r i t e , galena, s p h a l e r i t e electrum, a r g e n t i t e , secondary quartz, and some c a l c i t e ; while the f i n a l stage i s ch a r a c t e r i z e d by r e - d e p o s i t i o n of some galena and a r g e n t i t e , and by the d e p o s i t i o n of nati v e s i l v e r and c a l c i t e ^ (49) A t t e n t i o n i s i n v i t e d to, the p o s i t i o n s of f r a c t u r i n g on the diagram. These periods of f r a c t u r i n g are of utmost importance. I f pre-mineral f r a c t u r i n g does not occur, there can be no d e p o s i t i o n of any d e s c r i p t i o n ; i f there i s no primary f r a c t u r i n g , only a barren s i l i c e o u s aone r e s u l t s ; while i f secondary f r a c t u r i n g f a i l s , a t y p i c a l low-grade or barren sulphide body i s formed-. The formation of an ore-body requires f r a c t u r i n g to occur at the p o s i t i o n s i n d i c a t e d on the diagram. It..may now beeseen how an ore-body can l o c a l -l i z e i n a s i l i c e o u s zone without the a i d of un-related s t r u c t -ures, such as pre-mineral dykes or f a u l t s . As s t r e s s i s a p p l i e d , p a rts of the zone merely deform w i t h i n the e l a s t i c l i m i t of the material,(which may vary considerably depending on the degree of replacement, and p o s s i b l y , on the q u a n t i t a t i v e development of p y r i t e ) , while i n other p a r t s , the s t r e s s b u i l d s up u n t i l l i t exceeds the e l a s t i c l i m i t - and the zone f r a c t u r e s , thus producing c o n d i t i o n s favorable to or e - d e p o s i t i o n . Thus the a l t e r n a t i o n of ore-body and barren zone i s due to the more or l e s s rhythmic a l t e r n a t i o n of overstressed and understressed sections of the zone. 4. METHOD OF EMPLACEMENT OF ORE-BODIES In Chapter V I I . i t was stated ttetat the majority of S i l b a k Premier ore-bodies are of the replacement type. As f a r as the emplacement of the o r i g i n a l s i l i e e o u s zone (50) i s concerned, the evidence i n d i c a t e s s i l i c a repalcement of rock-forming minerals by emanations permeating outward from the main zone of f r a c t u r e along microscopic f r a c t u r e s i n the w a l l -rock. The method of emplacement of the sulphide bodies was dominently one of i n j e c t i o n along (primary) f r a c t u r e planes i n the s i l i c e o u s zone, accompanied by progressive r e - s o l u t i o n and r e - d e p o s i t i o n of the o r i g i n a l s i l i c e o u s m a t e r i a l . F i g s . I & 2 i l l u s t r a t e t h i s method of emplacement. These ore d e p o s i t s , t h e r e f o r e , are not s t r i c t l y of the replacement type, Rather they are sulphide f i l l i n g s of a b r e c c l a t e d s i l i c e o u s zone. (51) 5 » THE PHYSICO-CHEMICAL ASPECTS OF ORE-SOLUTIONS & OREr'DEPOSITION Production of a Primary A c i d O r e - s o l u t i o n : Progressive c r y s t a l l i z a t i o n of a magma f i n a l l y r e s u l t s i n a r e s i d u a l 'pegmatitic' l i q u i d which contains a l l the hy p e r f u s i b l e components of the o r i g i n a l magma, i . e . water, f l u r i n e , boron, s i l i c o n , i r o n , lead,, z i n c , e t c . This pegmatitic l i q u i d i s a l k a l i n e i n i t s r e a c t i o n , and i f i t c r y s t a l l i z e s under s u f f i c i e n t pressure the r e s u l t i s a pegmatite. However, i f the pegmatitic l i q u i d migrates i n t o areas of reduced pressure, i t experiences a 'second b o i l i n g ' induced by r i s e of the vapor j?-?*., consequent to the s u b t r a c t i o n of c r y s t a l s w i t h f a l l i n g temperature. The vapor produced i s a c i d i n i t s r e a c t i o n , i . e . S 1 0 2 / 4 H F S 1 F 4 / 2 H 2 0 w i l l go to the l e f t under moderate pressure. F a c t u a l evidence of the a c i d character of the vapor i s found i n fumaroles and volcanoes. When t h i s vapor condenses, the l i q u i d , a c i d i n r e a c t i o n , contains a l l the components of the vapor - i r o n , l e a d , z i n c , copper, s i l v e r , gold, s i l i c a , and probably a small amount of GOg. This c o n s t i t u t e s the a c i d hydrothermal o r e - s o l u t i o n . ? iegua££pPgfe^tl.on Under Increas^gly_A3>ari-™ Condi t i ons: As t h i s a c i d o r e - s o l u t i o n permeates through a porous fracture-zone, i t w i l l d i s s o l v e a l k a l i - r i c h , rock-forming minerals, gradually becomming more a l k a l i n e i n the. process. Most of the common m e t a l l i c sulphides are soluble i n acids but more or l e s s i n s o l u b l e i n a l k a l i e s . The order of (52) i n c r e a s i n g s o l u b i l i t y i n a l k a l i n e s o l u t i o n i s : S i 0 2 , Bu//, Fe//, Zn, Pb, and CaO^. Consequently, under p r o g r e s s i v e l y a l k a l i n e c o n d i t i o n s , we would expect the normal sequence of f s d e p o s i t i o n to be: quartz, c h a l c o p y r i t e , P y r i t e , S p h a l e r i t e , »i Galena, and C a l c i t e . This order of d e p o s i t i o n i s i n general agr'e&ment w i t h the paragenesis of S i l b a k Premier ores, and i n f a c t , w i t h t h a t of most ores of t h i s type. However, there are c e r t a i n anomalies which t h i s order of d e p o s i t i o n does not e x p l a i n . Anomalies to the t h e o r e t i c a l sequence of chemical d e p o s i t i o n : 1. The r e - s o l u t i o n of various minerals, i n the case of S i l b a k Premier, s i l i c a , galena, a r g e n t i t e , c a l c i t e . I t i s probable that the newly-formed c r y s t a l s are i n e q u i l i b r i u m ..with the remaining l i q u i d . I t i s concievable that d i f f e r e n t i a l pressures consequent to f r a c t u r i n g would a l t e r condit-ions of e q u i l i b r i u m s u f f i c i e n t l y to allow s o l u t i o n of c r y s t a l s already formed. R e — s o l u t i o n may also represent a t r a n s i e n t r e t u r n to more a c i d c o n d i t i o n s . 2. The complete and abrupt d e p o s i t i o n of p y r i t e cannot be explained simply on a b a s i s of r e l a t i v e s o l u b i l i t y i n a l k a l i n e s o l u t i o n . E q u i l i b r i u m would o b t a i n at some con-c e n t r a t i o n of i r o n i n the s o l u t i o n ; consequently we would expect the d e p o s i t i o n of a minor amount of p y r i t e , o r some other ferrous mineral, 0t©occur d i s t i n c t l y l a t e r i n the sequence. This i s not generally true. I t i s thought that, while r e l a t i v e a l k a l i n e s o l u b i l i t i e s i s the dominent f a c t o r . (53) some other f a c t o r s have operated to render the d e p o s i t i o n of any one mineral more abrupt and complete. me Effect ..of R e l a t i v e ElectgaQtive Forces on Ore-d epnsi-M on: The lleetromotivetforceBvofftheevariousltoase metalrsulphides, '--expressed i n v o l t s compared to copper i n pure t e r , i s as f o l l o w s : ^ wa Chalcopyrite /18 to /30 P y r i t e /18 Galena /15 S p h a l e r i t e -20 to - 4 0 Assuming that t h i s r e l a t i v e order holds f o r an o r e - s o l u t i o n from which p y r i t e i s c r y s t a l l i z i n g , i f a p o t e n t i a l between that of p y r i t e and that o-f galena were maintained, the e f f e c t would be to i n h i b i t the c r y s t a l l i z a t i o n of galena and to extend t h a t of p y r i t e past the e q u i l i b r i u m concentration ;#f i r o n in., the s o l u t i o n - i t might even cause the complete r e -moval of i r o n from the s o l u t i o n . Th-eisamerrfeasonfengueanndtibe appliedetpochalcopyrite because of i t s v a r i a b l e p o t e n t i a l , but t h i s seems to strengthen the case, since c h a l c o p y r i t e has a considerable range of d e p o s i t i o n . I t appears p o s s i b l e that t h i s mineral c r y s t a l l i z e s i n accordance with i t s e q u i l i b r i u m concen-t r a t i o n i n a p r o g r e s s i v e l y more a l k a l i n e s o l u t i o n . The t y p i c a l mode of occurrence of electrum i s between u n l i k e mineral surfaces, or between l i k e mineral surfaces only when the surfaces are very close together (low r e s i s t a n c e ) . This s t r o n g l y suggests t h a t • p o t e n t i a l s induced by the ass o c i a t e d minerals i s a dominent f a c t o r , i n the de p o s i t i o n of electrum. (54) 6. THE DEPTH FACTOR IN ORE-DEPOSITION , , I f the ternary order of pegmatitic l i q u i d , pneumatol^tlc vapor, hydrothermal.solution, discussed i n the preceding s e c t i o n , he accepted; i t f o l l o w s that the lower l i m i t of d e p o s i t i o n w i l l be that depth, a t which the pneuma t o l l t i c vapor condenses to the hydrothermal s o l u t i o n . The vapor being above i t s c r i t i c a l temperature, i t a l s o f o l l o w s that the p o s l t i o i of t h i s lower l i m i t , w i l l be a f u n c t i o n of pressure, not of tem-perature. We have no knowledge of the pressures and temperat-ures e x i s t i n g at t h i s t h e o r e t i c a l p o i n t , nor do we know the r e l a t i v e s o l u b i l i t i e s of m e t a l l i c sulphides under such extreme con d i t i o n s * However, we do recognize a rough zonal arrangement of ore deposits adjacent to a b a t h o l i t h -the r e t r e a t i n g order of the deposits i s e ; p y r i t e , c h a l c o p y r i t e , l e a d - z i n c - s i l v e r s I n any p a r t i c u l a r d e p o s i t , t h e r e f o r e , we would expect to f i n d a change i n the r e l a t i v e s o l u b i l i t i e s expressed by a change i n mineralogy as the lower l i m i t was approached. The examination of S i l b a k Premier ores revealed no change i n the mineral assemblage, nor I n the general q u a n t i t a t i v e mineralogy over a v e r t i c a l range of 750 f e e t . Therefore, i f sulphide bodies e x i s t at depth, there i s no physico-chemical reason why these should not c o n s t i t u t e ore-bodies. There may even be an increase i n the p r o p o r t i o n of f r e e g There i s evidence of a r a p i d v e r t i c a l zoning of s i l v e r . This i s t y p i c a l of s i l v e r ore-bodies. At depth i n the S i l b a k Premier Mine the s i l v e r values may disappear or approach some low l i m i t i n g v i g ure. (55) CHAPTER 3CI THE PRIMARY CHARACTER OF SILVER MINERALS AND  NATIVE SILVER The writevregards the s i l v e r minerals and the. na t i v e s i l v e r i n S i l b a k Premier ores as of primary, or hypogene, o r i g i n . I n support of t h i s contention the f o l l o w i n g evidence i s o f f e r e d : 1. The majority of the ore-bodies of the B.C,Silver and Sebakwe Sections are o v e r l a i n by Red Porphyry which i s un-mineralized, un-sheared, and q u i t e impervious to the passage of any l a r g e amounts of ground-water. > 2 . Ore-bodies are not known to extend to the surface. 3* JQimonitization, or other signs of supergene a l t e r a t i o n , i s confined to the immediate v i c i n i t y of the few water-courses that do e x i s t . 4. The mineralogy i s of a primary nature: a. Fig.19 shows s i l v e r and p o l y b a s i t e o c c u r r i n g i n intimate a s s o c i a t i o n w i t h primary base metal sulphides b. I n Fig. 2 1 , a r g e n t i t e i s shown f i l l i n g f r a c t u r e s i n p y r i t e . This p i c t u r e -was taken a l i t t l e farther^'along the f r a c t u r e ebLnvfeainlang na t i v e s i l v e r , shown i n Fig.2 0 I f the a r g e n t i t e and s i l v e r are secondary, p y r i t e must also be regarded as secondary. c. Minute grains of a r g e n t i t e i n un-fractured o r i g i n a l s i l i c a are eviden t l y of primary o r i g i n . d. I f p y r a r g y r i t e and p o l y b a s i t e are secondary, then the primary ore should contain the mineral from which they obtained t h e i r antimaony. No such mineral i s present. (56) Galena i s the only apparent source of s i l v e r . I t can carry s i l v e r to the extent of 2 ,5 ounces per ton. To produce secondary s i l v e r ore-bodies of the s i z e and value of thoee of Premier would require the supergene a l t e r a t i o n of somthing over one b i l l i o n tons of primary ore c o n t a i n i n g say, 10% galena, This r i d i c u l o u s f i g u r e i s perhaps the most conclusive argument i n favor of the primary o r i g i n of n a t i v e s i l v e r and s i l v e r minerals. A s i m i l a r occurrence of s i l v e r minerals i n a bonanza-type of deposit i s given i n Appendix G. (57) CHAPTER X3I. FAVORABLE PROSPECTING- AREAS I n estimating the p o s s i b i l i t i e s of the d i s c -overy of new ore-bodies, i t i s w e l l to keep the f o l l o w i n g p o i n t s i n mind: • 1» No major i n t e r s e c t i o n , other than that i n the o l d premier Mine, i s known on the property. 2 . Ore-deposition i s apt to occur where:a s i l i c e o u s shear I n t e r s e c t s s u f f i c i e n t l y competent rocks,such as porphyry or c e r t a i n compact greenstones. 3-. Shear-zones do not n e c e s s a r i l y f o l l o w porphyry-tuff contacts. An example of t h i s i s found below 1304 D r i f t where a hangingwall r o l l of the contact has r e s u l t e d i n the main shear continuing downwards through f o o t w a l l green-stone. I n t h i s case the greenstone was s u f f i c i e n t l y competent to allow the l o c a l l i a a t i o n of IOA, 12A, and 5CE ore-bodies. 4 . The porphyry occurs i n se v e r a l s i l l s d i s t r i b u t e d one above the other. The larg e a r e a l exposure of porphyry i s due to . e r o s i o n more or l e s s p a r a l l e l to the s i l l s . What have been -mapped as pendants may very w e l l be the t u f f separating i n d i v i d u a l s i l l s . 5. E l e v a t i o n above s e a - l e v e l has no s i g n i f i c a n c e as regards the occurrence of e i t h e r gold or electrum, although i t does Urn ii Athe occurrence of s i l v e r minerals. 6. To the northward,: the porphyry s i l l s , e i t h e r terminate somwhere under Sl a t e Mt., or plunge to lower horizons. The Geologic Sections i n d i c a t e the l a t t e r . . (58) P o s s i b i l i t i e s of Discovering; New Ore-bodies at Depth, i n the Mine * i I t was mentioned above th a t the main shear leaves the porphyry below 1304- D r i f t . I n s p e c t i o n of the ' G-eologic Seetion D-D shows that t h i s shear w i l l continue i n d e f i n i t e l y through greenstone unless: (a) another s i l l i s present at depth, or (b) the d i p of the f o o t w a l l s i l l f l a t t e n s s u f f i c i e n t l y to allo w of i n t e r s e c t i o n w i t h the shear at any reasonable depth* The presence of ore-bodies at depth i n t h i s s e c t i o n of the Mine w i l l depend on these contingencies or on the existence of greenstones of s u f f i c i e n t competency to allow of o r e -deposition. A much b e t t e r p o s s i b i l i t y e x i s t s i n the Sebakwe Sec t i o n . Here the porphyry i s much wider on 1350 L e v e l , and the f o o t w a l l contact much f l a t t e r . Producing the shear and the foot?>rall contact on the d i p s i n d i c a t e d on Section" A-A would r e s u l t i n ' t h e i r i n t e r s e c t i o n at a depth of between 200 and 300 f e e t below 135Q Level. At t h i s p o i n t conditions would appear favorable f o r the occurrence of orepbodies. (59) s 3-" p i l.lt :Lgs of Qiscovering Mew Ore-bodies on the Surface: Minor zones i n the footwall., t u f f , such as Cascade F a l l s #3 and the P i c t o u showings, while r e t u r n i n g a few e r r a t i c values, probably would hot c o n s t i t u t e commercial ore-bodies of any dimensions. A small elongate lens of porphyry appears on the surface on Simcoe Claim. This contains several small veins of barren galena and s p h a l e r i t e . S i m i l a r barren sulphide deposits occur i n porphyry on Cascade Forks #6 Claim. These occurrences may i n d i c a t e a n o r t h w e s t e r l y - s t r i k i n g zone i n porphyry s However, examination of these occurrences, and of a weak s i l i c i f l e d zone i n the i n t e r v e n i n g greenstone, f a i l j f e d to i n d i c a t e a shear-zone of any l a r g e dimensions. The showings do not j u s t i f y a large development program, but i t might be advisable to put down a few d r i l l - h o l e s to I n t e r s e c t any p a s s i b l e zone at moderate depth. , A rather p e r s i s t e n t zone s t r i k e s northwest across the B e l l Claim, continuing on i n t o Bush Cobalt ground where i t i s exposed i n a small t u n n e l . I t occurs i n porphyry between the main gra n i t e dyke and an elongate body of t u f f . Although m i n e r a l i z a t i o n i s sc a t t e r e d , the e n t i r e area i s we}l s i l l c i f i e d . This zone i s deserving of some e x p l o r a t i o n , which could be done rather e f f i c i e n t l y by a few d r i l l - h o l e s to moderate depth, d r i l l e d from set-ups along the g r a n i t e . (60) The only other showing of merit i s that area of s i l i c i f i e d porphyry exposed along the M i s s o u r i Road on Cascade Forks #1 Claim. From a rock-cut on the M i s s o u r i Road, the writer/selected a specimen of s i l i c i f i e d porphyry showing r a t h e r s c attered m i n e r a l i z a t i o n of p y r i t e and galena which assayed 0 . 2 5 ounces gold per ton. The w r i t e r i s of the opinion t h a t t h i s area i s the expression of the Northeast Zone i n an upper porphyry s i l l . I t i s deserving of f u r t h e r e x p l o r a t i o n , p o s s i b l y to the extent of open-cutting on top of the b l u f f s immediately east of the Road, or surface d r i l l i n g to i n t e r s e c t a p o s s i b l e zone a t moderate depth. APPENDIX A. MICROPHCTOGRAPHS (61) F i g . I . - I3E stope - El.1400' 4M T h i s photograph i l l u s t r a t e s t he c o n t a c t of o r e - s u l p h i d e s and t h e o r i g i n a l s i l i c a . The d a r k , p i t t e d , o r i g i n a l s i l i c a , which i n p l a c e s c o n t a i n s c h l o r i t e developed p a r a l l e l to the c o n t a c t , i s i n q u i t e sharp c o n t a c t w i t h w i t h t h e o r e - s u l p h i d e s which i n t h i s case c o n s i s t of p y r i t e w i t h secondary q u a r t z , s p h a l e r i t e and g a l e n a f i l l i n g f r a c t u r e s i n i t . There i s a minor development of p y r i t e and c h a l c o p y r i t e , but no g a l e n a o r s p h a l e r i t e , i n the o r i g i n a l s i l i c a . F i g . I - x40 F i g . 2 - H a n g i n g - w a l l 13D stope T h i s photograph shows a v e i n l e t o f p y r i t e and q u a r t z i n j e c t e d i n t o a f r a c t u r e i n the o r i g i n a l s i l i c a . T h i s i s the dominent method of s u l p h i d e emplacement - i n j e c t -i o n of o r e - s o l u t i o n s a l o n g f r a c t u r e s i n o r i g i n a l s i l i c a ( p o s s i b l y accompanied by some s o l u t i o n of s i l i c a ) , f o l l o w e d by r e - f r a c t u r i n g and p r o g r e s s -i v e c r y s t a l l i z a t i o n of the v a r i o u s s u l p h i d e s . F i g . 2 - x40 (62) jENERAL FEATURES F i g . F i g . 3 - x40 1315 D r i f t . The r e l a t i o n s h i p o f q u a r t z to l a t e r s u l p h i d e s - a c r y s t a l i of ( t e r n a r y ) q u a r t z has dev e l o p e d i t s o u t l i n e a t the expense of b o t h g a l e n a and secondary q u a r t z . T h i s p r o b a b l y r e p r e s e n t s the f i n a l s t a g e o f s i l i c a d e p o s i t i o n . Note the m i c r o - b r e c c i a t l o n of p y r i t e - a t y p i c a l f e a t u r e o f low-grade s u l p h i d e b o d i e s . - I3B stope - E1.1400' An example of replacement of p y r i t e by s p h a l e r i t e . G-alena i n the lo w e r p a r t of the photograph i s p r o b a b l y s l i g h t l y l a t e r t h a n the s p h a l e r i t e . F i g . 4 - x250. (63) TEXTURAL C0MARI50NS OF LOW/ AND HIGH-GRADE ORES * ~~ Fig. 5 - 5CE Stope - El.1220. P y r i t e texture t y p i c a l of barren sulphide bodies -P y r i t e massive, micro-brecclated, w i t h f r a c t u r e s very narrow and e i t h e r u n f i l l e d or f i l l e d only w i t h quartz and c h a l c o p y r i t e . Fig.5 - xl40 Fig.6 - I5A stope - El.1550 1 P y r i t e texture t y p i c a l of ore. P y r i t e i s f r a c t u r e d , and the fr a c t u r e s have been f i l l e d by galena, s h h a l e r i t e and quartz. Other examples of t h i s type of p y r i t e texture are i l l u s t r a t e d by F i g s , showing the occurrence of electrum. Fig.6 - xl40 (64) TEXTURAL COMPARISONS, cont. F i g . 7 - Low-grade from 1558 Dr. F i g , 7 x l 4 0 Another t y p i c a l s t r u c b a r r e n s u l p h i d e b o d i e the p y r i t e o c c u r s i n rounded g r a i n s w i d e l y w i t h the i n t e r s t i c e s by q u a r t z and massive o r s p h a l e r i t e . I n t h i m a t e r i a l g a l e n a and s a r e found i n l a r g e , i masses - never i n t i m a a s s o c i a t e d t u r e of s -s m a l l , s e p a r a t e d f i l l e d g a l ena s type of p h a l e r i t e s o l a t e d t e l y F i g . 8 xI50 Fig.8 - 1670 Lev. under I00IA Rse. A r e l a t i o n s h i p commonly seen i n o r e s o f medium t o h i g h grade-p y r i t e , g a l e n a and s p h a l e r i t e a r e i n t i m a t e l y a s s o c i a t e d . C a l c i t e i s t y p i c a l l y p r e s e n t . J u s t to the r i g h t of f i e l d , a f r a c t u r e i n i s seen t o bS f i l l e d g a l e n a , s p h a l e r i t e , and e l e c t r u m see f i g . 1 4 . t h i s p y r i t e by C a l c i t e , (65) THE OCCURRENCE OF FREE GOLD F i g . 9 x2430 F i g . 9 - 1814 XC - E l . 1830' Th i s photograph i l l u s t r a t e s t h e o c c u r r e n c e of g o l d as I s o l a t e d g r a i n s i n u n - f r a c t u r e d o r i g i n a l q u a r t z . T h i s p a r t i c l e i s about 6 m i c r o n s l o n g . Qf*. QtZ. F i g . 1 0 - 1070 Lev. a t I00IA Rse. Thsi photograph was t a k e n under c r o s s e d n l c o l s t o r e v e a l the f r a c t u r e s i n which the p y r i t e ' and c h a l c o p y r i t e o c c u r and the u n - f r a c t u r e d n a t u r e of the o r i g i n a l q u a r t z s u r r o u n d i n g the p a r t i c l e o f g o l d . Gold i s found o n l y i n t h i s q u a r t z and as i n c l u s i o n s i n p y r i t e c r y s t a l s . I t bears no r e l a t i o n t o the l a t e r s u l p h i d e s . The l a r g e s t g r a i n o f g o l d seen was about 25 m i c r o n s i n d i a m e t e r , w h i l e the s m a l l e s t p o s i t i v e l y i d e n t i f i e d was somewhat l e s s t h a n a m i c r o n . F i g . 1 0 x775 (66) Fig. 1 1 - x l 5 0 THE OCCURRENCE OF ELECTRUM I n these micro-photographs: electrum i s colored yellow, galena l i g h t grey, and s p h a l e r i t e l i g h t brown. P y r i t e i s i d e n t i f i e d by i t s higher r e l i e f and p i t t e d sufifac Fig.11 - 1814 XC. - E1.1830 1 Electrum f i l l i n g a f r a c t u r e -zone i n p y r i t e i n t i m a t e l y a s s o c i a t e d with galena and s p h a l e r i t e . The dark grey m a t e r i a l a t the top of the f i e l d and that f i l l i n g the dark c i r c u l a r f r a c t u r e i s c a l c i t e . A dark i n c l u s i o n i n p y r i t e i n the lower l e f t - h a n d corner i s an etched p a r t i c l e of gold 20 microns i n diameter. Fig,12 -18B stope - El. 1 8 7 0 ' Electrum f i l l i n g a f r a c t u r e i n p y r i t e with galena. The dark m a t e r i a l i n the lower part of the f i e l d i s s p h a l e r i t e . I t i s not as i n t i m a t e l y associated with electrum as galena. Fig. 1 2 x l 5 0 (67) OCCURRENCE OF ELECSRUM, cont. F i g . 1 3 X150 F i g . 13 - 16C stope - El. 1 7 0 0 ' A g r a i n of electrum bounded by grains of a r g e n t i t e ( p a r i a l l y etched). Galena occurs nearer the fracture-* zone which i s f i l l e d by c a l c i t e (etched) This i s the only example seen i n which electrum was even remotely associated w i t h aggentite and ife i s here regarded as only a chance a s s o c i a t i o n Fig.14 - 1556 D r i f t - E l . 1530' An e x c e l l e n t example of electrum deposited i n a p y r i t e 'corrosion i n l e t ' w i t h galena and s p h a l e r i t e . The apparent replacement of p y r i t e by galena i s contrary to the chemistry of the problem. However, se v e r a l such cases were noted - i t seems that such a c o n d i t i o n can o b t a i n only when s p h a l e r i t e i s also present -the excess i r o n could be accounted f o r by t h i s mineral. F i g . 14 x l 5 0 The 'un-supported n u c l e i i i " p y r i t e are galena. i n (68) OCCURRENCE OF ELECTRUM, c o n t . F i g . 15 x570 Fig. 1 5 - 13B stope - E l .1400' E l e c t r u m f i l l i n g en e c h e l o n f r a c t u r e s i n o r i g i n a l q u a r t z . T h i s i s not a common mode o f o c c u r r e n c e ; i n the few examples seen t h e f r a c t u r e s were r e l a t i v e l y l o n g but not o v e r t e n micr o n s wide (the f r a c t u r e shown i s about 4 micr o n s wide) Fig.16 x l 5 0 Fig.16 - 13A stope - E1.1400' A r a t h e r u n u s u a l o c c u r r e n c e o f e l e c t r u m w i t h g a l e n a i n t h a t no p y r i t e o c c u r s i n the immediate v i c i n i t y . The dark grey etched m i n e r a l i s a r g e n t i t e , the l i g h t grey m i n e r a l w i t h h i g h r e l i e f i s q u a r t z , w h i l e the b l a c k a r e a s a re c a l c i t e d e e p l y etched w i t h HC1. The g a l e n a - c a l c i t e boundary i n d i c a t e s r e - s o l u t i o n of galena and a r g e n t i t e w i t h d e p o s i t i o n i n t h e i r p l a c e s of c a l c i t e . (69) OCCURRENCE O.F_ELECTRIIMf cont, F i g . 17 x300 F i g . 1 7 - 12B stope - E l . 1 2 7 0 ' Electrum i n c a l c i t e (grey) i n a wide fracture-zone i n p y r i t e . Galena i s i n t i m a t e l y a s s o c i a t e d w i t h the electrum and a small amount of s p h a l e r i t e i s a l s o present. A l i t t l e quartz with the c a l c i t e i s i d e n t i f i e d by i t s higher r e l i e f . F i g . 1 8 - 1 0 7 0 Lev. at I 0 0 I A Rse Galena and electrum i n a f r a c t u r e i n p y r i t e . Note close adherence to p y r i t e surfaces. The dark m a t e r i a l at e i t h e r end of the f r a c t u r e i s c a l c i t e (etched). A few small grains of electrum occur i n the c a l c i t e . Fig.18 x l 5 0 . ( 7 0 ) THE 0CCURRENCE_pF SILVER MYNERALS~&~NATIVE STIVER F i g . 1 9 - 13H stope - El.1450' T h i s photograph i l l u s t r a t e s the i n t i m a t e p r i m a r y a s s o c i a t i o n o f n a t i v e s i l v e r , p o l y b a s i t e , g a l e n a and s p h a l e r i t e a g a i n s t an i r r e g u l a r p y r i t e s u r f a c e . F i g . 1 9 x325 Fig.20 x l 5 0 Fig.20 - 13H stope - El.1450' A v e i n l e t o f n a t i v e s i l v e r and a r g e n t i t e accompanied by c a l c i t e (grey w i t h low r e l i e f ) i n o r i g i n a l q u a r t z . Note the i n t i m a t e a s s o c i a t i o n of s i l v e r w i t h i t s s u l p h i d e . The p r i m a r y c h a r a c t e r of t h i s v e i n l e t i s not e v i d e n t i n the photograph, but f u r t h e r a l o n g the f r a c t u r e i s a l s o f i l l e d by gal e n a The c o l o r s o b t a i n e d by f i l m i n g are somewhat b r i g h t e r t h a n those shown. (71) Fig.2 1 x l 5 0 13H stope Fig.23 x570 13A stope - El.1420 Fig.22 x l 5 0 17A stope El.1 7 4 0 " THE OCCURRENCE OF ARGENTITE Figs.2 1 & 22 sfeow f i l m e d a r g e n t i t e i n f r a c t u r e s i n p y r i t e . Fig.2 1 i s taken f u r t h e r along the f r a c t u r e shown i n f i g . 2 0 . Some galena i s a l s o present with the a r g e n t i t e i n f i g . 2 2 . Fig.23 i l l u s t r a t e s a t y p i c a l occurrence fofi a r g e n t i t e f i l l i n g a f r a c t u r e i n o r i g i n a l quartz, surrounding p y r i t e and i n a s s o c i a t i o n with s p h a l e r i t e . The hulk of evidence i s that a r g e n t i t e i s somewhat l a t e r than s p h a l e r i t e . A r g e n t i t e also occurs as blebs i n o r i g i n a l quartz so minute as to be only p o s i t i v e l y i d e n t i f i e d by f i l m i n g . A P P E N D I X B MINERALOG-IC EXAMINATION OF S I L B A K P REMIER ORE BY MEANS OF THE HAULTAIN ' I N F R A - S I Z E R ' AND 1 SUBER-PANNER ' Two t e s t s , a rough p r e l i m i n a r y one and a more d e t a i n e d one, are given to show the value of t h i s apparatus i n a t t a c k i n g a m i n e r a l o g i c a l problem. Altho the ordinary mineralogic r e l a t i o n s can be worked out from microscopic examination, i n t h i s case, the composition of electrum and the presence of fre e gold could only be determined by the use of t h i s apparatus. 6 (72) 'GOLD DEPOSITS RESEARCH', DEPT. OF GEOLOGY & GEOGRAPHY-/ UNIVERSITY OF BRITISH COLUMBIA, Mar.A9 3 8 . THE RELATION OF SILVER TO GOLD IN SILBAK PREMIER ORES ' : This i n v e s t i g a t i o n was undertaken more to t e s t the new H a u l t a i n 'Super-panner' on a mineralogic problem than to o b t a i n any p o s i t i v e r e s u l t s . The object was to o b t a i n some i d e a of the r e l a t i o n of s i l v e r to gold i n S i l b a k ores. Two samples from d i f f e r e n t e l e v a t i o n s i n the Mine were screen-s i z e d and the s i z e d products panned to ob t a i n s e v e r a l more or l e s s pure mineral products. C e r t a i n r e s u l t s were rather i n t e r e -- s t i n g and are tabulated on the next page. From examination of these r e s u l t s the f o l l o w i n g conclusions may be set down: •1. Grinding has caused a r e - d i s t r i b u t i o n of s i l v e r . This i s because the bulk of s i l v e r i s present afe s i l v e r minerals such as a r g e n t i t e and ruby s i l v e r s . The presence of these minerals i s r e f l e c t e d i n the increased ' S i l v e r - G o l d r a t i o s i n the f i n e r products. 2 , Electrum has a constant composition of about 1:1 over the range i n v e s t i g a t e d og 470' . About 80% of the electrum i s over 25 microns i n s i z e . 3 . Galena, when pure, c a r r i e d very l i t t l e s i l v e r . A rough c a l c u l a t i o n from 'tip'A i n d i c a t e s a maximum content of 2 . 5 ounces of s i l v e r per ton of pure galena. (73) FEED ANALYSIS S A M P L E . :;• v - J S a l g r ^ • ' M ' • S 5 R E E ¥ ~ ! " ^ = _ ^ _ ^ _ _ ^ A ¥ . . /AG-. AU SIZEg AU ~~Aa" AU••- ~ SPM#1. A -70/100 16.90 51.0 3 < 0 39 1 0 I3E s t . B r r o o / i 5 o 12.8S 80.6 6 , 2 30 .94 9.6 10 , . . E l . 1350' C - I50/2OO 5 . 5 7 5 2 . 5 9.6 _ 13 11_ L - 1 - - I L _ _ " 2 0 ° 8 » 1 6 314.0 37. 18 64 SPM#32 B» -IOO/15O 7 . 5 7 241.0 3 2 . 26 9 1.88 100.6 53 " 1802 Dr. C'~ -150/200 7.64 424.0 55 . 26 17 £1.1820' D' . 2 0 0 14.20 1879.0130 . 48 74 PANNER PRODUCT ANALYSTS PbS /. t i p (Au-AgJ/ FeS2 cone. SlOp / s i . sulph, NO/ CONTENT nig.{ AG l CONTENT mg8? AG y CONTENT mg..1 AG ' TOTALS^ w ; ; / : A G A U • : R A U I• M A G , R " ' A U ' A U ; 1 •• A G A U ^ A I T m \ A 4 . 7 0 9.68 2.08 2.25 9.24 3.6 0.12 4.4 36.7 89 99 B 2.45 6.76 2.43 0.80 8.26 10.7 0.14- 4.7 34.0 82 88 C 2.02 7.16 3.54 0 . 5 0 7.05 20,4 0 . 0 3 3.0 1 0 0 . 0 9 8 92 D 1.20 8.62 7*20 0 , 3 0 .9.10 35»5 0,11 6 . 3 57.3 98 92 18 .8 1 . 3 4 141. 1 0 5 . 0 85 8 3 5 0 . 0 2,04 185 v 92 .0 7 9 80 95.5.. 1 .35 1 5 1 . 111.0 77 79 Space does not permit the complete Table to be given. Two other products, a s p h a l e r i t e m i d d l i n g and a slime product are omitted. However t h i s does not a l t e r the e s s e n t i a l p i c t u r e • although the o r i g i n a l ores d i f f e r e d widely, the Ag/Au r a t i o s of the ' t i p ' products are s i m i l a r i n d i c a t i n g approach to a mineral of constant composition - electrum. (74) gPQSITS RESEARCH' , DEPT. OF GEOLOGY, UNIVERSITY OF B.C., JAN. 1939. MECHANICAL ANALYSES OF SPECIMENS OF SILBAK PREMIER ORE WITH THE HAULTAIN 'INFRA-SIZER' & 'SUPER-PANNER' Although i t s primary f i e l d , i s that of t a i l i n g a n a l y s i s , the Haul t a i n equipment has "been found of use i n the m i n e r a l o g i c a l .analysis of ores. The polysulphide deposits of Si l b a k Premier^ and s i l v e r , the l a t t e r o c c u r r i n g as a const!t--uent of electrum and as various s i l v e r s u l p h o - s a l t s . By i n f r a -- s i z i n g ground samples of the ore and panning the products, I t was hoped to o b t a i n i n f o r m a t i o n regarding the r e l a t i o n of gold to s i l v e r , the composition of electrum, and any progressive change i n mineralogy which might p r e d i c t the v e r t i c a l range of ore-deposition. Five samples were chosen f o r the analyses which were reasonably r e p r e s e n t a t i v e of t h e i r r e s p e c t i v e ore-bodies. The procedure was to g r i n d them to -200 mesh., i n f r a -s i z e and wfefegh, assay, and f i n a l l y pan the var i o u s s i z e r products to o b t a i n a m e t a l l i c ' t i p ' . Losses were q u i t e low -weight about h%, gold l e s s than 1%, and s i l v e r from 3 to 5$ -and have been corrected f o r i n the Tables. When the m e t a l l i c p a r t i c l e s of the 'Panner' ' t i p were examined under an 'Ultro-Pak' microscope i t was a t once evident that both electrum and gold were, present. The electrum occurred as f l a t t e n e d p a r t i c l e s of pale yellow c o l o r , the extreme size-range of which was 100 to 50 microns; while the gold appeared as r o l l e d dark yellow grains none of which were l a r g e r than 25 microns. Unfortunately a q u a n t i t a t i v e estimate of the p r o p o r t i o n of f r e e gold to electrum was not feasable. However, although a l l samples contained some fre e gold* I t appeared to be more p l e n t i f u l I n #2-38, from IOA stope* As the electrum p a r t i c l e s s e l e c t e d f o r assay were q u i t e clean, the composition given i n Table 2 I s very nearly c o r r e c t . Knowing the p h y s i c a l p r o p e r t i e s of a mineral i t s r e a c t i o n to g r i n d i n g may be p r e d i c t e d : thus gold or electrum would remain unaffected, a r g e n t i t e , being s o f t but s e c t i l e , would be p a r t i a l l y comminuted, while the s o f t , b r i t t l e , minerals of the ruby s i l v e r f amily would s u f f e r maximum comminution. Examination of Table I . d i s c l o s e s a r e - d i s t -- r i b u t i o n of s i l v e r , the s i l v e r - g o l d r a t i o i n c r e a s i n g I n the f i n e r s i z e s . Thsi i n f e r s that the bulk of the s i l v e r i s present as s i l v e r minerals. Nos. 31-37 & 29-3$, w i t h a p r o g r e s s i v e l y i n c r e a s i n g . r a t i o , probably c o n t a i n a greater p r o p o r t i o n of ruby s i l v e r s ; while those with h i g h r a t i o s i n the intermediate s i z e s may c o n t a i n more a r g e n t i t e . (75) SUMMARY AMD CONCLUSIONS No progressive change occurs i n the composition of electrum Ehe average composition i s : Gold, 65%; S i l v e r , 35%« Size of electrum p a r t i c l e s v a r i e s between 50 and 10.0 microns Free gold i s present i n a l l samples examined. Maximun p a r t i c l e s i z e i s 25 microns. There i s a p o s s i b i l i t y that f r e e gold i s more abundant on the lower l e v e l s . The greater p a r t of the s i l v e r occurs as s i l v e r sulpho-sal^s The quantity of s i l v e r minerals decreases w i t h depth. (76) TABLE I . S A M P L E " PRODUCT (Size Mic) AG AU ; DISTRIBUTION '%~~ -WEIGHT AU . AG 5P£BLE 2, SAMPLE NO. LOCATION ELEVATION ^Au. i n ELECTRUM 31-37 s i l l I8B 1820"™" 24-37 s i l l I6A 1670 70 29-37 I 5 A 1550 61 2-38 I OA 1160 68 Av. tS% Au. 35% Ag. APPENDIX G OTHER OCCURRENCES OF ELECTRUM IN B.C. THE OCCURRENCE OF PRIMARY SILVER MINERALS AT THE DOLLY VARDEN MINE, ALLICE ARM, B.C. (77) THE OCCURRENCE OF ELECTRUM IN BRITISH COLUMBIA * •. During the past year, research a t the U n i v e r s i t y has d i s c l o s e d the presence of electrum i n several B r i t i s h Columbian Mines. ' . The f o l l o w i n g account of the occurrence of electrum was k i n d l y supplied by Mr.Jim Mc.Gammon, graduate student of geology: "Electrum was found i n four mines from the Sheep Creek Mining Gamp. These mines were Reno, Gold B e l t , Kootenay B e l l e , and Sheep Creek. I n every case the electrum was as s o c i a t e d w i t h the mineral galena, and occurred i n f r a c t -ures i n the other minerals present; thus i n d i c a t i n g t h a t galena and electrum were the l a t e s t minerals to s o l i d i f y . Analyses of electrum from the va r i o u s mines: ^ S i l v e r ^Gold Reno 3 0 . 2 4 6 9 .¥6 Kootenay B e l l e 27.28 72.72 Gold B e l t 17.47 82.53 Sheep Creek 11.69 88.31 I n a Geology^ Report on Reno, submitted to the Dept of Geology & Geography, Mr. E.A.Schmidt has, t h i s to say: "Electrum i s found i n every s e c t i o n of ore. .. I t i s apparently the l a t e s t mineral to be introduced and occurs mainly w i t h galena i n small f r a c t u r e s i n quartz. During e a r l y examination of the p o l i s h e d s e c t i o n s , I thought that there were two types o f - g o l d present. These I c a l l e d ' l i g h t gold' and 'dark gold. SeparationoSf the two types under the Ultro-Pac and assaying gave the f o l l o w i n g r e s u l t s : ^ S i l v e r ^Gold L i g h t Gold 33 . 3 66.7 Dark Geld 23.9 76.1 The r e s u l t s i n d i c a t e that the c o l o r d i f f e r e n c e " i s due to a va r y i n g p r o p o r t i o n of gold to s i l v e r (although each type has an i n v a r i a b l e composition). I n subsequent microscopic examination both types reacted w i t h H g C l 2 to confirm electrum". The occurrence of electrum i n these Mesothermal d e p o s i t s , i n d i c a t e s that i t i s not confined to the epithermal Zone. I t tends to l i n k the metalogenic province of Portland- Canal w i t h t h a t of Southern B r i t i s h Columbia. (78) THE OCCURRENCE OF PRIMARY SILVER MINERALS AT THE DOLLY VARDEN I n a Geology 24 Report to the Dept. of Geology & Geography, Mr.C.E.Gordon Brown, Graduate student, a r r i v e d at a conclusion that the a r g e n t i t e and p y r a r g y r i t e i n the Dolly TVarden Mine, A l i c e Arm, B.C., are of primary hypogene o r i g i n . He concludes that t h i s i s a bonanza type of deposit of the low-to-medium.temperature zone. A few po i n t s of s i m i l a r i t y to the h i g h - s i l v e r deposits of S i l b a k Premier are noted: 1. A r g e n t i t e has a mode of occurrence s i m i l a r to that of S i l b a k Premier.'Black Quartz' containing minute j grains of a r g e n t i t e , gave.comarable assays from the outcrop and from 100 f e e t below. : 2. Veining of base metal sulphides by a r g e n t i t e and p y r a r g y r i t e . Intimate r e l a t i o n s are u s u a l . 3. Some 'un-supported n u c l e i ' of a r g e n t i t e and p y r a r g y r i t e occur i n p y r i t e . Mr. Brown considers these to i n d i c a t e replacement of p y r i t e by the s i l v e r minerals. 4. I f the deposit i s of secondary o r i g i n , the low-grade, m a t e r i a l below the productive horizons should represent the primary ore, and should contain the minerals from which the p y r a r g y r i t e obtained i t s : antimany. No such minerals are present. -This deposit i n general i s s i m i l a r to the s i l v e r element of S i l b a k Premier ores. I t supports the cbHtention t h a t the l a t t e r i s a primary bonanza type of deposit. T 0 E2000 E4000 E 6 0 0 0 E8000 ElOOOO E1ZOOO E14000 N 1 8 0 0 0 N16000 N 1 4 - 0 0 0 N I 2 0 0 0 N I O O O O N800O N 6 0 0 0 N 4 0 0 0 N 2 0 0 0 0 N I 8 0 O O NI6000 NIOOOO D o u b l e 0 0 F r o c hi o f ; ? 8 4 4 N 8 0 0 0 N 6 0 0 0 N 4 0 0 O fig Tuff*(BR, N 2 0 0 0 L e g e n d R o a . d e Sr B u i l d i n q s T r a i I s Streams A- Lakes N o s , A. ft- 13 5 0 L e v e l s Nos 1,6, 175 O 8r 2080 Levels N o * 2 Sr 1820 Levels N o - , 3 £k- 16 7 0 L e v e l s N o s 5 «Hr- 1 0 7 0 L e v e l s N o & 14-50 £r 1525 L e v e l s B o u n d a r i e s 8*- C l a i m Po«>ts P i p e L i n e s 0 E 1 4 0 0 0 0 E20r E 4 0 0 0 H 6 0 0 0 E S O O O EIOOOO E i e o o o S I L B A K P R E M I E R M I N E S L T P P R E M I E R B.C. M A P o f P R O P E R T Y S C A L E - - I I N . 4 0 0 F T . C O R (3 E C T : A E Gordon D A T F J A N . D R A W I N G NO. 2000 M I N E F I L E - 0-2OOO \ / 1 1 1 < \ J I I I ' ' // ' ': G E O L O G I C P L A N O F 1 3 5 0 L E V E L & V E R T I C A L SECTIONS O N N 4 5 W S C A L E : ) m. a* BOOft L E G E N D P R E M I E R P O R P H Y R Y R E D P O R P H V R V G R E E N T U F F * P U R P L E T U F F G R A N O D I O R I T E STORES M I N E R A L I S A T I O N F A U L T S * P o s i t i o n p r o j e c t e d f r o m S e c t i o n Z O O f e e t H.E. o f S e c t ton A A on ta s t r i k e of M 4 5 E <5» d . *> 2£*W C o r», r , I c oi t h r u t h e . c o u r t e » j o f S . l U a K P r e m i t i - M m e i . U d 

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