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A gold-specularite deposit, Unuk River, B.C. 1948

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/- 3 33 ~7 S3 &C C O p> • / A GOLD SPBGULARITE DEPOSIT, UNUK RIVEB, B.C. A t h e s i s submitted i n p a r t i a l f u l f i l m e n t of the requirements f o r the degree of Master of A p p l i e d S o i e n o e i n the Department o f Geology and Geography, UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1948. ROBERT HENRY SEHAPHIM ABSTRACT On the (Jraoey group of claims, Unuk River, B.C., are mesothermal-type quartz veins; (1) with speoularite-gold mineralization, (2) with galena-pyrite-gold mineralization, and (3) with chalcopyrite^pyrite mineralization containing no precious metals. The veins outcrop in a "band of Late Palaeo- zoio(?) andesite tuff t siltstone, a r g i l l i t e , and limestone bordered on the northeast and southwest by Triassic(?) diorite gneiss s i l l s . The main body of Coast Range intrusives out- crops five miles southwest of the property, but several stocks are exposed about five miles east of the property. The regional-type metamorphism, and most of the folding and faulting of the bedded rocks on the property have been caused by orogeny associated with the Coast Range intrusives; but some recrystallization of andesite-tuff can be attributed to thermal metamorphism produoed by the adjacent diorite- gneiss s i l l s . The vein-forming fluids are probably derived from Coast Range intrusive rather than the local s i l l s . In the quartz-galena-pyrite veins anhedral gold fragments are associated with three soft minerals, possibly tellurides, which form inclusions in the galena. In the quartz-specular^- ite-gold veins the gold has been deposited in disruptions between specularite 'cleavage' plates. Both classes of veins contain minor amounts of gold in or near fractures in the quartz. ' ' ' No veins contain both abundant specularite and abundant sulfides. The specularite probably has been deposited earlier than the sulfides but in the same period of mineralization. Specularite does not necessarily indicate hypothermal deposi- tion, but i t is usually one of the f i r s t minerals deposited from hydrothermal solutions. It is formed only under oxid- izing conditions, and i f exposed to later sulfide-bearingi and thus reducing, solutions, i t tends to be reduced to magnetite or an iron-bearing sulfide. AOXUOWLBD (xSMEN US F i e l d work on the Sraoey group was superfcvsed "by D r . D . F , E i d d of L e i t c h Gold M i n e s , and much c r e d i t i s due him f o r h i s sound a d v i c e on some of the f i e l d problems. The w r i t e r i s indebted to D r . H . C . Gunning and D r . K . DeP. Watson f o r a s s i s t a n c e and guidance i n the l a b o r a t o r y work. Dr . H . M . Thompson gave many h e l p f u l sugges t ions on m i n e r a l o g i c a l p r o b - lems. J . A . Donnan gave a d v i c e on p r e p a r a t i o n of t h i n and p o l i s h e d s e c t i o n s . TABLE OF CONTENTS Page MTRODUC TION , 1 PURPOSE OF THESIS 3 METHOD OF INVESTIGATION. 4 LOCATION AND ACCESSIBILITY....................... 6 TOPOGRAPHY. * ............... 7 CLIMATE..., , 8 HISTORY, 8 GENERAL GEOLOGY 9 Structural Correlation - Intrusives...... 10 Structural Correlation - Sedimentary and Volcanic Rooks ,,•>• 10 Lithological Correlation., 11 Mineralization, 13 LO.CAL GEOLOGY. ........................... 14 Rook Types. 16 Limestone 16 Siltstone., , 31 Tuff E l Gneiss of Tuff Origin.................... 24 Intrusive Diorite Gneiss..,.,,. •••• 25 Dykes 26 Coast Range Intrusives (not including Triassic(?J s i l l s ) 29 TABLE OF CONTENTS (CONT'D) Page METAMORPHISM. , 30 STRUCTURE.......................................... 31 Folding. i . . . . 31 Regional Fracture Pattern........ 33 Relation of Veins to S i l l s 35 VEINS. 36 ' General............... 36 Wall Rook Alteration....... 36 Mineralization............................ 40 Chaleopyrite-pyrite Class.............. 40 Galena-pyrite Class....... 41 Specularite Class...................... 46 Significance of Specularite............ 47 Mineralogical Conclusions.....• 58 GENERAL CONCLUSIONS. 60 TABLE OP CONTENTS (CONT'D) PLATE NO. 1. .............................. 2. 3. mm SECTION PHOTOGRAPH NO. 1. 2. .............................. 3. ., 4. 5. 6. 7. • ... 8. 9. ........... POLISHED SECTION PHOTOMICROGRAPH NO. 1. 2. .............................. 3. 4. ............ .............. 5. 6. .............................. 7. 8. .............................. 9 After Page 6 7 7 15 15 21 21 24 24 18 18 17 42 42 42 44 44 44 44 45 45 INTRODUCTION In the 1946 f i e l d season, Thomas M c Q u i l l a n and Fat Onhasy, p r o s p e c t i n g f o r L e i t c h So ld M i n e s , s taked the Graoey group of c l a i m s on the "South F o r k ' of the Unuk R i v e r . Of the e i g h t quar tz v e i n s sampled there by the p r o s p e c t o r s , f i v e gave assays above o n e - h a l f ounce i n g o l d . Four o f these h i g h assays were from samples taken a c r o s s mineable w i d t h s . The w r i t e r was i n charge of open c u t t i n g and i n t e n s i v e p r o s p e c t i n g on the Graoey group d u r i n g the 1947 f i e l d season. The f i v e v e i n s , g i v i n g h i g h assays were named a f t e r the p r o s p e c t o r s 1 sample numbers. (Map Ho. 3 . ) Q-17 v e i n has been t r a c e d f o r f o u r hundred f e e t , and averages f i v e f e e t wide. . A t the west end the quartz p inches out but m i n e r a l i z e d s h e a r i n g c o n t i n u e s . T h i r t y f e e t f a r t h e r west q u a r t z has a g a i n been d e p o s i t e d , f o r m i n g Q-17 west v e i n . This v e i n averages se-een f e e t w i d e , and has been t r a c e d two hundred f e e t to the west , where i t i s covered by deep g l a c i a l d r i f t . Q-22 v e i n i s the probable f a u l t e d e a s t e r n e x t e n s i o n of Q-17 v e i n . Q-22 v e i n has been t r a c e d one thousand f e e t , t o where i t becomes o n l y e i g h t to t en inches wide and assays o n l y t raoes i n g o l d . I t i s suspected t h a t Q-18 sample was out from .a l a r g e b o u l d e r of f l o a t . F l o a t i s abundant i n the a r e a where the sample was t a k e n , but no v e i n was found i n p l a c e , a l t h o u g h the p r o s p e c t o r searohed f o r i t . h i m s e l f . Q-19 v e i n was t r a c e d f o r seven hundred f e e t , but o n l y one s m a l l p o s s i b l e ore shoot was d e l i n e a t e d . Q-24 v e i n i s not of mineable w i d t h , ^ 3 - and i s too i r r e g u l a r to warrant s u r f a c e development under present c o n d i t i o n s . Three a d d i t i o n a l v e i n s , of whioh a t l e a s t one CQ-25) warrants f u r t h e r development, were f o u n d . In the l a t t e r p a r t o f August g e o l o g i c a l mapping of the major showings on a s c a l e o f two hundred f e e t to one i n c h was oommenoed. Inclement weather f o r c e d c e s s a t i o n of work i n e a r l y September, but f u r t h e r e x p l o r a t i o n , i n o l u d i n g diamond d r i l l i n g and g e o l o g i c a l mapping, w i l l be c o n t i n u e d i n the 1948 f i e l d season. G e o l o g i c a l breaks show up i n the l a t e snow.  PURPOSE OF THESIS To d e s c f i b e the l o o a t i o n , a o o e s s i b i l i t y , topography, o l i m a t e , h i s t o r y , and geology of the r e g i o n ; and more p a r t i c u l a r l y to 1 . determine the age of the rooks by s t r u o t u r a l and l i t h o l o g i c a l c o r r e l a t i o n of the geology w i t h t h a t of nearby areas* 2 . determine the host rock of the v e i n s , and the reasons f o r i t s s u s c e p t i b i l i t y to m i n e r a l i z a t i o n . 3. analyse the s t r u c t u r e of the r e g i o n as a guide to f u r t h e r p r o s p e c t i n g and development. 4 . determine the probable source of m i n e r a l i z i n g f l u i d s . 5. determine the m i n e r a l or m i n e r a l s a s s o c i a t e d w i t h g o l d i n the v e i n s as a guide to f u r t h e r development. 6 . determine the s i z e o f g o l d p a r t i c l e s i n the ' o r e 1 , and i t s a s s o c i a t i o n w i t h f r a c t u r i n g , to i n d i c a t e s i z e of g r i n d i n g necessary f o r m i l l i n g . 7. determine the s i g n i f i c a n c e of s p e o u l a r i t e i n the quar tz v e i n s , and i t s a s s o c i a t i o n w i t h the o t h e r m e t a l l i c m i n e r a l s . GRACEY GROUP. - Graoey Creek i n background; South Fork i n v a l l e y on the lower r i g h t ; Graoey c la ims are r i g h t c e n t e r . M E T H O D O F I N V E S T I G A T I O N G e o l o g i c a l mapping c o u l d not be done to best advantage u n t i l A u g u s t , when most of the ground was f r e e o f snow* A c l a i m map was made i n J u l y , u s i n g a Brunton oompass and c h a i n * This map was drawn a t 500 f e e t to the i n o h . The accuracy of the s u r v e y i n g was about one i n a thqusand. Notes of the survey were k e p t , When g e o l o g i c a l mapping was s t a r t e d each c l a i m was drawn a t 200 f t , to the i n c h on a separate shee t . The c l a i m s were then g e o l o g i c a l l y mapped one a t a time u s i n g Brunton compass and c h a i n , as no plane t a b l e was a v a i l a b l e . Traverses were run n o r t h - e a s t and s o u t h - w e s t , i n order to f o l l o w the t r e n d of the o u t c r o p s . ' The c l a i m p o s t s were used f o r ' t i e - i n ' p o i n t s . The s u r v e y o r ' s h e l p e r kept notes of the s u r v e y , i n c l u d i n g topography, and the surveyor kept notes of the geology. A f t e r each f i v e c h a i n s (500 f t . ) , the topography and geology were p l o t t e d on the o l a i m sheet . A c l a i m was mapped i n about two days . The g e o l o g i c a l maps of a l l the c la ims were compiled i n one map (Map N o . 3 i n back p o c k e t ) . Rock specimens c o l l e c t e d d u r i n g mapping were l a b e l l e d n u m e r i c a l l y ; and the number put on the map to show where each specimen was c o l l e c t e d . A s u i t e of specimens was c o l l e c t e d from the w a l l of Q - l ? v e i n ; specimens b e i n g taken a t 8 f t . , 4 f t . i 3 f t . , 2 f t . , !•§• f t . , and £ f t . from the v e i n , and, as c l o s e l y as c o u l d be determined, from the same - 5 - bed. Laok of outcrop made i t d i f f i c u l t to o b t a i n other s u i t e s of a l t e r e d w a l l r o o k . Specimens of " o r e " were c o l l e c t - ed from each important v e i n * Thin s e c t i o n s were made of each of the s i x t y r o c k specimens c o l l e c t e d , and of the ' o r e 1 from s e v e r a l o f the important v e i n s . P o l i s h e d s e c t i o n s were made of the ' o r e ' from each important v e i n . The d e s c r i p t i o n s of a l l s e c t i o n s were kept on indexed cards to f a c i l i t a t e r e f e r e n c e . L i t e r a t u r e was searched f o r i n f o r m a t i o n on the geology of the Unuk and s u r r o u n d i n g a r e a s , and f o r i n f o r m a t i o n on the s i g n i f i c a n c e of the s p e c u l a r i t e i n the quar tz v e i n s . The g e o l o g i c a l s k e t c h map of the Unuk by J . T . Mandy ( B i b l . Ho* 10) has. been reproduced on a l a r g e r s c a l e (Map No. 2 back p o c k e t ) . This map, w i t h maps o f P o r t l a n d Ganal ( B i b l . No . 5 ) , I skut ( B i b l . No* 13) and Southeastern A l a s k a ( B i b l . No* 4) have been compiled (Map No* 1 back p o c k e t ) . r ^ A S u p p l i e s d r o p p i n g a t campsite from plane f l y i n g a t two hundred f e e t . Boxes of dynamite dropped from plane a t camp on South Fork. GRAOEY GROUP - LOCATION AND ACCESSIBILITY The Graoey group i s on the South F o r k of the Unuk R i v e r , t w e n t y - e i g h t m i l e s n o r t h - w e s t of P r e m i e r , B . C . (see map N o . l ) . The n a t u r a l route to the p r o p e r t y i s "by the Unuk R i v e r , whioh d r a i n s i n t o the P a c i f i c a t Burroughs Bayi A l a s k a , s i x t y m i l e s n o r t h of K e t c h i k a n . A wagon road was c o n s t r u c t e d from Burroughs Bay to the i n t e r n a t i o n a l boundary t w e n t y - f i v e m i l e s u p r i v e r , and s i x m i l e s beyond, i n 1903, but has s i n c e f a l l e n i n t o d i s r e p a i r . However, Boundary L a k e , on the i n t e r n a t i o n a l boundary, i s a c c e s s i b l e to s m a l l a i r o r a f t , A good w a l k i n g t r a i l has been mainta ined u p r i y e r from Boundary Lake to La .. Brant Creek on the South F o r k . A t r a i l from La Brant Creek to the Graoey group was s t a r t e d but not completed i n 1947. The t r i p from Boundary Lake to the Graoey group takes two days , but oabins a t G l a c i e r Creek and the mouth o f the South F o r k p r o v i d e good o v e r n i g h t accommodation. An a l t e r n a t e route i s from P r e m i e r , B . C . to B i g M i s s o u r i by r o a d , and thence to Tide Lake by pack t r a i l . From Tide Lake to South F o r k no t r a i l e x i s t s , but Frankmaokie g l a c i e r a f f o r d s a good grade over the summit to Cabin Creek on the South F o r k . (See p l a t e No. 1 ) . T h i s route i s used o n l y by exper ienced mounta ineers . F r a g i l e equipment was back-packed to the camp frpm Boundary L a k e . The b u l k o f s u p p l i e s was w e l l t r u s s e d i n t o about s e v e n t y - f i v e pound bundles and dumped i n t o the snow G l a c i e r pass from South Fork to Bowser-Salmon v a l l e y . P L A T E H O . 1 •7- from a l o w - f l y i n g plane based a t K e t c h i k a n . Recovery o f dropped s u p p l i e s was w e l l above n i n e t y p e r c e n t . TOPOGRAPHY The topography of the Unuk i s t y p i c a l of the n o r t h e r n Coast Range. Maximum r e l i e f i s seven thousand f e e t . V a l l e y w a l l s i n most p l a c e s are s c a l a b l e . Above t i m b e r l i n e a t t h i r t y - f i v e hundred f e e t , heather s lopes pass upward i n t o domed rock r i d g e s , o r , i n the h i g h e r mounta ins , rough s e r r a t e d peaks out by g l a c i e r s . (See p l a t e Ho. 2). Tongues of g l a c i e r extend from the main i c e f i e l d s i n t o the heads o f the v a l l e y s ; and the main v a l l e y s e x h i b i t the ' U ' shape 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 . P l a t e Ho. 3 shows the headwaters of the Unuk ( a l s o see Map No. 2 ) . Gracey Creek i n the r i g h t foreground oocupies a l o n g s t r a i g h t g l a c i a t e d v a l l e y t r e n d i n g n o r t h - e a s t e r l y . Two m i l e s below i t s j u n c t i o n w i t h the South F o r k , l a Brant Creek enters from the n o r t h , and the v a l l e y swings n o r t h - w e s t e r l y to i t s conf luence w i t h the v a l l e y of Ketohum Creek and the main Unuk R i v e r . The main Unuk R i v e r i s cons idered to be the r i v e r below the j u n c t i o n of Ketohum and S u l f i d e Greeks . I t f l o w s s o u t h - w e s t e r l y , and i s j o i n d d by many t r i b u t a r y streams before f l o w i n g i n t o Burroughs Bay. A l l t r i b u t a r i e s are l aden w i t h g l a c i a l s i l t , much of whioh i s depos i ted i n the lower reaches of the r i v e r . The lower r i v e r c o n s i s t s o f many r e t i c u l a t i n g and c o n s t a n t l y P L A T E N O . 2 M c Q u i l l a n i idge and tha headwaters o f the Unak. PLATS HQ. 3 changing channe ls , except where i t plunges through f o u r narrow panyons. I t has been n a v i g a t e d w i t h f l a t - b o t t o m e d r i v e r b o a t s , but o n l y a t the expense of almost cont inuous l i n i n g . GLLMATB The c l i m a t e Is s i m i l a r to t h a t of P o r t l a n d Oanal a r e a . A l t h o u g h no records o f p r e c i p i t a t i o n are a v a i l a b l e , i t i s est imated t h a t w i n t e r s n o w f a l l would reach twenty f e e t at the p r o p e r t y . Patohes of snow from one season l i n g e r u n t i l i j o i n e d by f r e s h snow of the next season. Above f o u r thousand f e e t e l e v a t i o n snow f l u r r i e s can be expected at any time d u r i n g the summer. The abundance of snow p r o h i b i t s g e o l o g i c a l mapping u n t i l l a t e i n the summer, and i n c e s s a n t r a i n f a l l makes i t d i f f i c u l t even t h e n . H I S T O R Y The f i r s t a c t i v e p r o s p e c t i n g of the Unuk was done i n the e ighteen n i n e t i e s ; but was m a i n l y f o r p l a c e r on S u l f a r e t s Oreek. The Cumberland p r o p e r t y , on S u l f a r e t s Creek, was s taked f o r lode g o l d and s i l v e r about 1900 but has never been developed. The aforementioned wagon road was b u i l t to s e r v i c e t h i s p r o p e r t y . The Globe p r o p e r t y , near the headwaters of the South P o r k , was a l s o staked about 1900. Though a stamp m i l l was e r e c t e d , no g o l d was produced. A f t e r the death on the t r a i l i n 1903 of Ketohum, the owner of the Globe, i n t e r e s t i n the Globe and the Unuk i n Slobe g l a c i e r i n June (above) and i n September (be low) . Rough valley bottom near head of South Fork, Campsite a t t i m h e r l i n e on the Graoey C l a i m s . P l a n * l a n d i n g on Boundary l a k e a t the B r i t i s h C o l u m b i a - A l a s k a boundary to take the orew out i n September. l o o k i n g downriver (south) from M c Q u i l l a n ' s c a b i n at the j u n c t i o n of the South F o r k w i t h the main Unuk. g e n e r a l waned u n t i l the n i n e t e e n t h i r t i e s , when p r o s p e o t p r s from P o r t l a n d Canal entered the r e g i o n . I n 1933 and 1934 Premier i n t e r e s t s diamond d r i l l e d and made open outs on a group of c l a i m s s taked i n 1932 on P r o u t P l a t e a u . In 1946 Canadian E x p l o r a t i o n f u r t h e r developed the showings on these c l a i m s . GENERAL GEOLOGY Very l i t t l e geology has been done i n the Unuk. The o n l y g e o l o g i c a l map i s a s k e t c h (Map N o . .2 i n hack pocket) made i n 1935 by D r . J . T, Mandy of the B r i t i s h Columbia Department of M i n e s . A b r i e f r e p o r t ( B i b l . No. 10) aocompan^ i e s t h i s map. I t was compiled a f t e r a t e n - d a y reconnaissance t r i p , d u r i n g which D r . Mandy had the a d v i c e and guidance of s e v e r a l o f the ' o l d - t i m e 1 p r o s p e o t p r s . D r . Mandy had p r e v - i o u s l y v i s i t e d Prout P l a t e a u ( B i b l . No. 11 ) . He s t a t e s 'The sedimentary and v o l c a n i c rooks composing Prout P l a t e a u are s i m i l a r i n extent and c h a r a c t e r and may p o s s i b l y be c o r r e l a t e d w i t h the Upper Bear R i v e r s e r i e s of J u r a s s i c age. In p l a c e s the exposures of t h i s s e r i e s may p o s s i b l y apprpach the younger Nass s e r i e s h o r i z o n . ' F . E . Wright p u b l i s h e d a s h o r t r e p o r t on the Unuk i n 1905 ( B i b l . No, 8 ) . In an endeavor to determine the age of the format ions i n the Unuk by s t r u c t u r a l and l i t h o l o g i o a l c o r r e l a t i o n , maps from nearby areas have been compi led i n Map No. 1 ( i n back p o c k e t ) . These i n c l u d e 1 ) . The I s k u t R i v e r A r e a , by P.A. K e r r of the G e o l o g i c a l - 1 0 - Survey of Canada. ( B i o l . Ho. 13 . ) 2) . The P o r t l a n d Canal Area by G. Hansen of the G e o l o g i - c a l Survey of Canada. ( B i b l . No. 5 : ) 3) . Southeas tern A l a s k a , by A . E . Buddington and Theodore Chapin of the U n i t e d S ta tes G e o l o g i c a l Survey. ( B i b l . No. 4 . ) S t r u c t u r a l C o r r e l a t i o n - I n t r u s i v e s . The Coast Range i n t r u s i v e s run n o r t h w e s t e r l y through the c o r r e l a t e d areas* The e a s t e r n contac t of the i n t r u s i v e s approx imate ly f o l l o w s the i n t e r n a t i o n a l boundary; but. c o n - t a c t s are i r r e g u l a r i w i t h many s a t e l l i t e s on both f l a n k s . The i n t r u s i v e s show c o n s i d e r a b l e h e t e r o g e n i t y . Buddington r e p o r t s g r a n o d i o r i t e , quar tz monzoni te , q u a r t z d i o r i t e , hornblende b i o t i t e d i o r i t e , monzoni te , h o r n b l e n d l t e , and gabbro from s e c t i o n s a l o n g P o r t l a n d Canal and Chiokamin r i v e r . K e r r r e p o r t s d i o r i t e , o r t h o o l a s e p o r p h y r y , and s y e n i t e , as w e l l as most of the f a e i e s mentioned by Buddington , from the I s k u t onofst ikine s e c t i o n s . The age o f the i n t r u s i v e s i s g i v e n by K e r r as T r i a s s i c to Lower Cretaoeous , and by Buddington as Upper J u r a s s i c to Lower Cretaoftous. The d e s c r i p t i o n s of the T r i a s s i c i n t r u s i v e s g i v e n by K e r r ( B i b l , No. 1) i n d i c a t e they are v e r y s i m i l a r to the d i o r i t e g n e i s s ' s i l l s ' on the Graoey group. S t r u c t u r a l C o r r e l a t i o n - Sedimentary and V o l c a n i c Rocks . The r e g i o n a l t r e n d of the p r e - i n t r u s i v e sedimentary and v o l c a n i c rooks i s n o r t h to n o r t h w e s t , p a r a l l e l tha t o f the - 1 1 - i n t r u s i v e s . This t rend i a p a r t i c u l a r l y marked on the western f l a n k . C o r r e l a t i o n of sediments and v o l o a n i o s of the Unuk area on the east f l a n k w i t h those of Southeastern A l a s k a on the west f l a n k i s d i f f i c u l t because of the i n t e r v e n i n g i n - t r u s i v e s . Of the I s k u t area K e r r s t a t e s "the s t r u c t u r e i s extreme- l y complex; i n t e n s e unsystemat ic f o l d i n g and f a u l t i n g are present everywhere so t h a t the boundaries between format ions are not w e l l d e f i n e d and can be i n d i c a t e d o n l y i n a g e n e r a l w a y . " ( B i b l . Ho. 1 , P» 4 8 ) . S t r u c t u r a l c o r r e l a t i o n w i t h the Unuk i s thus w e l l n i g h i m p o s s i b l e . In P o r t l a n d Canal the s t r u c t u r a l t r e n d of the H a z e l t o n group i s g e n e r a l l y n o r t h to n o r t h w e s t . This t r e n d , i f oon- ' t i n n e d , would b r i n g H a z e l t o n group rocks through a t l e a s t the e a s t e r n p a r t of the Unuk drainage b a s i n . Mandy's o b s e r - v a t i o n s i n the Unuk i n d i c a t e a n o r t h e r l y t rend to the s e d i - mentary and v o l c a n i c r o c k s , and thus s u b s t a n t i a t e c o r r e l a t i o n w i t h P o r t l a n d C a n a l . L i t h o l o g i c a l C o r r e l a t i o n . Mandy has mapped three main types of p r e - i n t r u s i v e bedded rook i n the Unuk; l i m e s t o n e , a r g i l l a c e o u s sediments , and v o l c a n i c s w i t h a s s o c i a t e d h y p a b y s s a l s . The l imes tone i s w h i t e to grey i n c o l o r , and h i g h l y r e c r y s t a l l i z e d . Sec t ions of w e l l over one thousand f e e t are predominant ly l i m e s t o n e , but f o l d i n g or f lowage may g i v e -12- r e p e t i t i o n or e x a g g e r a t i o n of the t r u e t h i c k n e s s . The l i m e - stone i n the I skut (are) t h i r t y m i l e s to the nor th -wes t i s s i m i l a r i n extent and c h a r a c t e r , and has been c a l l e d ' f a i r l y d e f i n i t e l y Permian ' i n age . Limestone i s known i n the H a z e l t o n group of P o r t l a n d C a n a l , but occurs o n l y i n a few l e n s e s o f s e v e r a l f e e t t h i c k n e s s . I n Southeastern A l a s k a l imestone occurs i n s e c t i o n s hundreds of f e e t i n t h i c k n e s s i n P a l a e o z o i c r o o k s , but o n l y i n t h i n l enses i n Mesozoio rooks* The l imes tone of the Unuk R i v e r a r e a i s thus p r o b a b l y P a l a e o z o i o and l i k e l y Permian . A m i l e or two to the west of the l imes tone band the sedimentary and v o l c a n i c rooks are metamorphosed to p h y l l i t e s , s l a t e s , and s c h i s t s . To the east they have undergone l i t t l e metamorphism; the sediments are w e l l bedded and the v o l o a n i o s mass ive . The metamorphism to the west may be a t t r i b u t e d to the g r e a t e r age o f these r o o k s , or to p r o x i m i t y to the main body of Coast Range i n t r u s i v e s . However, metamorphism i s not in tense i n sedimentary and v o l c a n i c rocks that are i n contact w i t h Coast Range i n t r u s i v e s i n P o r t l a n d C a n a l . The metamorphism of the Unuk rooks west of the l imestone, i s then more l i k e l y due to the f a c t tha t they are of g r e a t e r age, and have undergone more d i a s t r o p h i s m than those on the east of the l i m e s t o n e , On the east of the l imestone band, and on P r o u t P l a t e a u , the sedimentary rocks are w e l l bedded a r g i l l i t e s , sandstones , and f i n e conglomerates , and the v o l c a n i o rocks are massive green andesites. The assemblage, as stated by Dr. Mandy, (Bibl. Ho. 11) olosely resembles the Bear River and Hass formations of the Hazelton group in Portland Canal. The struotural and lithological correlation suggests that the Unuk limestone is Permian, the sedimentary and volcanic rocks to the east are Hazelton group (Jurassic?) and those to the west are Pre-.Permian. Ho fossils were found in the limestone and i t is doubtful i f determinable fos s i l s w i l l be found in the. limestone or the rocks to the west because of the metamorphism. Mineralization. Rook exposed on the west flank of the Coast Range i n - trusives has undergone metamorphism of a higher grade than rock exposed on the east flank. Gneisses and schists cut by pegmatite dykes predominate on the west, indicating a deeper-seated type of metamorphism than on the east where a r g i l l i t e s and slates predominate. Erosion has cut down to the zone of flowage on the west, and the rocks exposed now were probably at a high temperature during the period of mineralization and thus not affected markedly by mineralizing fluids. On the other hand, the rocks on the east would frac- ture rather than flow, and the mineralizing fluids would encounter new conditions of temperature and pressure, and deposit much of their load. Mineralization is not pronounced on the western flank of the intrusives, but on the eastern - 1 4 - f l a n k oontaot metamorphic d e p o s i t s and m i n e r a l i z e d v e i n s are r e l a t i v e l y abundant. LOCAL GEOLOGY The Graoey Group i s on the mountain between Graeey Greek and the South Fork (see P l a t e No. 3 and map No. 2 ) . This mountain i s composed of l i m e s t o n e , t u f f , s i l t s t o n e , a r g i l l i t e , and d i o r i t e g n e i s s . The sediments , i n c l u d i n g t u f f , t rend n o r t h - w e s t e r l y , and d i p 40 to 60 degrees n o r t h e a s t . They grade i n t o . o n e another , and are i n p l a c e s i n t i m a t e l y i n t e r - - bedded, i n d i c a t i n g p r a c t i c a l l y s imultaneous d e p o s i t i o n d u r i n g some p e r i o d s . The abundance of l imes tone shows marine d e - $ p o s i t i o n . The beds o f the e l a s t i c s range from a f r a o t i o n o f an i n c h to s e v e r a l f e e t i n t h i c k n e s s . The main band of l i m e - stone has an apparent t h i c k n e s s of w e l l over one thousand f e e t . The sediments are i n t r u d e d by d i o r i t e gne i ss s t o c k s and s i l l ; l i k e b o d i e s , and a p l i t e , lamprophyre , and s y e n i t e dykes . The mountain as a whole has not been mapped g e o l o g i c a l l y , but an outorop map was made c o v e r i n g the most important m i n e r a l showings (Map No. 3 ) . The most important v e i n s l i e i n a thousand- foot -wide sedimentary b e l t t r e n d i n g n o r t h w e s t e r l y . The b e l t i s bounded on the n o r t h - e a s t and south-west by s i l l l i k e bodies of d i o r i t e g n e i s s . The ' l o w e r s i l l ' , on the n o r t h e a s t , i s about three hundred f e e t wide and has been t r a c e d f o r three thousand f e e t . The 'upper s i l l ' , on the - 1 5 - southwest, is more irregular and not as well delineated, but is estimated to be several hundred to one thousand feet wide. Veins occur in the sediments outside the s i l l s , but, though similar in mineralization and attitude, have shown neither the widths nor the gold content-of the veins in the central band of sediments. In some parts of the mapped area the sediments show olose folding and crenulation. The tuffs have in places been recrystallized to a fine-grained gneiss. The gneissic struc- ture strikes northwest, parallel to the strike of the beds and the axes of the folds. To the west high angle shearing with a westerly strike is widespread. Discontinuous shears are abundant throughout most of the mapped area. No major faults were proven, but one of about one thousand feet hori- zontal offset, striking northerly, may occur west of Ptarmi- gan H i l l . x 80 THIN SECTION PHOTOGRAPH NO. 1 Quartz and oalcite have recrystallized side by side, without formation of sili c a t e s . Serioite is also present. THIN SECTION PHOTOGRAPH NO. 2 Near the contact with i n t r u s i v e gneiss the f i n e laminae i n the sediments are c r e n u l a t e d . l i i n e r a l a are q u a r t z , c h l o r i t e a n d s e r i o i t e . -16- BOCK TYPES Limestone. fhe main band of limestone l i e s northeast of the lower s i l l , outside the mapped area, but a few beds l i e in the central band of sediments. A l l the limestone i s highly re- orystallized. Thin sections show an interlocking mosaic of grains up to three mm. in diameter. Many grains show strong twin-gliding. Chemical tests prove a traoe of magnesium in the limestone. Knobby protrusions up to one foot in diameter have formed from differential erosion where the limestone contains quartz. The alignment of these protrusions is parallel to the con- tacts of the bed and this alignment could be caused by flow- age of the limestone, or may be indicative of the original bedding, or both. The quartz grains in the knobs range from .05 to .15 mm, in diameter. The larger grains are strongly fractured, strain shadowed, sutured, and intergrown. Isolated quartz grains in the limestone are of smaller average size, about .05 mm. and are strongly strain shadowed. The quartz in the limestone could have originated as wind blown s i l t , water transported s i l t , or oherJb_nodules. If wind or water transported, the quartz would possibly be accompanied by feldspars and/or serioite. A l i t t l e serioite does occur with quartz in the limestone. Chert nodules, on reerystalliza- tion would have quartz grains of considerable size variation. 17 The grains here show a markedly small variation in size (.05 to .i5 mm.) in spite of the recrystallization they have under- gone. Ho beds of ohert have been found in the area, but beds of siltstone, in places composed almost entirely of quartz, and in other places grading into a r g i l l i t e and tuff, are abundant. The quartz in the limestone i s of the same average grain size as that in the siltstone, a r g i l l i t e , and tuff. The quartz i s thus probably wind or water transported, or both. According to Tweahofel (Bibl. Ho. 14) more grains tend to be rounded, and rounding occurs down to a smaller grain size (.03 mm.) in wind transported s i l t , than in water transported s i l t (.1 to .05 mm.). Recrystallization, however, has changed the size and shape of the grains so much that these c r i t e r i a are no longer applicable. Aeolian s i l t , however, tends to be better sorted than water-transported s i l t , and as this s i l t shows l i t t l e variation in grain size and i s predominantly quartz i t is l i k e l y aeolian. The irregular knotty aggregates have formed from a 'rolling up' of the grains during the lime- stone flowage. Other impurities in the limestone are serioite, tremolite, chlorite, and opaque metallios. These minerals are in minute amounts in some beds, but are abundant in others where the limestone grades into a r g i l l i t e s and tuffs. The tremolite occurs as a few fibers replacing quartz and carbonate in a bed of si l i c i o u s limestone close to the lower diorite gneiss s i l l . x 25 THIN SECTION PHOTOGRAPH NO.9. Irregular contact of twin-glided carbonate with fine-grained tuff. Aotinolite 3hreds have developed in the carbonate. .18- Several beds of limestone about five feet thick which outcrop twelve hundred feet north of Ptarmigan H i l l are intercalated with beds of tuff, and contain inequidimensional fragments of green andesite tuff up to several inches in diameter. These fragments are probably thin lenses of tuff which have 'rolled up' in the limestone during i t s flowage. The essential minerals in the tuff fragments are horn- blende and plagioclase (oligoolase to andesine) in about equal proportions. Grains of these average .15 mm. in dia- meter. Sphene, pyrite, and apatite are minor, forming about one percent of the total. In the interiors of the tuff fragments the hornblende grains are ragged, slightly poikiloblastic, and altered in part (about one-third) to chlorite. The plagioclase is kaolinized, particularly in the centers of the grains, and shows very l i t t l e twinning. Titanite is clouded with leucox- ene. One or two small epidote grains are present. The carbonate five or ten millimeters away from the tuff fragments has recrystallized to grains several millimeters in diameter, and these grains are strongly twin-?glided. Highly strain shadowed, fractured, sutured, and intergrown quartz grains up to .7.5 mm. in diameter are present in one or two knots in the limestone. They have probably originated in the same way as the knotty aggregates of quartz previously discussed. At the contacts of the tuff fragments with the limestone x 80 THIN SECTION PHOTOGRAPH NO. 7. P y r i t e oube wi t h i n c l u s i o n of diopside and another replaced by a c t i n o l i t e at oontact of t u f f fragment w i t h limestone. x 80 THIN SECTION PHOTOGRAPH NO. 8. P l a g i o c l a s e ( l i g h t grey) with o r i e n t e d inclusions of fibrous a c t i n o l i t e (white). - 1 9 - reactiona between the minerala of the t u f f and the carbonate have produced diopside,-tremolite, and a c t i n o l i t e . Some r a d i a l aggregates of a fibrous c h l o r i t e are pseudomorphous aft e r a pyroxene, possibly diopside, and others, with assoc- iated magnetite, replace a c t i n o l i t e . A few t i t a n i t e grains Shi;.owing much a l t e r a t i o n to leucoxene are isolated i n the carbonate. One pyrite grain has an i n c l u s i o n of diopside, and others are replaced by a c t i n o l i t e (Thin seotion photo- graph No. 7 ) . No py r i t e i s found i n the carbonate away from the t u f f fragments. The pyr i t e has thus formed before some of the metamorphic s i l i c a t e s , and i s probably not from l a t e r hydrothermal a c t i v i t y . The diopside, tremolite, and a c t i n o l i t e grains are most abundant i n a band seven or eight millimeters wide at the contacts of the t u f f fragments and limestone. They are not found i n the central portions of the t u f f fragments. A rough zoning has taken place. A c t i n o l i t e has formed f o r several millimeters on both sides of the contacts. Tremolite, showing no green pleochroism, and diopside have formed only i n the carbonate several millimeters away from the contacts. Plagioclase has r e c r y s t a l l i z e d at the contact. The grains are four or f i v e times the diameter of those i n the t u f f , and i n one place contain oriented inclusions of actino- l i t e (Thin section photograph No. 8), thus must have replaced the a c t i n o l i t e . Some of the feldspar was probably o r i g i n a l l y coarse as i t occurs i n bands angling away from the contact. - 2 0 - The coarse plagioclase has the same composition as that in the tuff (oligoclase to andesine), and thus has undergone no chemical change. No metasomatism was necessary to produce the alteration at the contacts. The iron i s provided by the hornblende and pyrite of the tuff, the s i l i c a by the hornblende of the tuff, and/or the quartz inclusions in the carbonate. The magnesium comes from the hornblende or i t s chlorite alteration in the tuff, and from the slightly magnesian carbonate. The oalcium comes from the carbonate and from the hornblende in the tuff. The titanite may be a primary constituent of the tuff, or may have i t s titanium derived from titaniferous magnetite or ilmenite in the tuff, The rough zoning of the silicates.supports the hypothesis that alteration is purely metamorphic. Calcium and magnesium and s i l i c a need not migrate far as they are present in both limestone and tuff. Iron, which i s present only in the tuff» has not migrated far from the contacts. Ferriferous actinolite at the contact gives way to the non-ferriferous tremolite and diopside several millimeters away from the contacts. Tuff near Q-25 vein contains disseminated carbonate grains, and no reaction has taken place here between tuff minerals and carbonate. However, the carbonate is less abundant, the rock has undergone shearing rather than flowage. The shearing may have prevented the formation of the new metamorphic minerals, particularly diopside, Siltstone. . The siltstone i s very thinly bedded, white to grey and green in color, and composed predominantly of quartz. Some beds contain abundant feldspar and chlorite, and grade into tuff. The quartz grains in the siltstone have diameters up to •3 mm., but in most thin sections the maximum is .1 mm. Grains are strain shadowed, sutured, and intergrown to form a fine- grained quartzite. No evidence of aocretionary growth was noted. Serioite,. chlorite, and caloite f i l l interstices, and andesine forms minute laminae in the siltstone. The feldspar is probably both volcanic and detri t a l . The siltstones grade into andesite tuffs, containing andesine but some bands in the siltstone that are high in feldspar contain no mafic minerals, and are thus l i k e l y detrital rather than volcanic in origin. The feldspar in these bands is of the same grain size as the associated quartz. The r e c r y s t a l l i - zation prevents determining whether the s i l t is water transport- ed or aeolian. Tuff Thin bedded, green to grey, water-lain andesite-tuff forms the bulk of the central band of 'sediments\ Predomin- ant minerals are andesine and hornblende. Biotite i s a minor constituent. The grains average .15 mm. in diameter, and show markedly l i t t l e variation is size in any one bed, and even in different beds. The original fragments have been well compacted and recrystallized; no fragmental outlines were x 80 THIN SECTION PHOTOGRAPH NO. 3 Hornblende forme 'feather-amphibole' i n the r e g i o n a l l y metamorphosed t u f f a . The other m i n e r a l i a andeaine p l a g i o c l a s e . x 25 THIN SECTION PHOTOGRAPH NO. 4 The dark band c r o a a - c u t t i n g the hornblende l i n e a t i o n i s caused by a l t e r a t i o n of f e l d s p a r to o l a y - minerala. I t may represent the o r i g i n a l bedding. - 2 2 - seen in the f i e l d or in thin section. Fine ohloritic material i n t e r s t i t i a l to the plagioolase and hornblende is probably devitrified ash or glass. Aooessory magnetite, pyrite, hema- tite and sphene are associated with the mafio minerals. Although quartz i s present in many of the specimens, i t is considered to be detrital rather than volcanic The rela- tive amount of quartz varies greatly in different beds. The tuffs grade into siltstone. The quartz grains are in many places in bands and lenses rather than disseminated. The diorite s i l l s are the intrusives nearest in age and in dis- tance to the. tuff. The s i l l s and the tuff may represent early igneous activity associated with the Ooast Range intrusives. If so, the s i l l s , though younger than the tuff, are probably derived from the same magma as the tuff. The later s i l l s contain no quartz, and, as late differentiates of the same magmatic facies are usually more sil i c i o u s than earlier differentiates i t is doubtful that the earlier tuff would contain quartz. In places the tuff grades into limestone, and here carbonate i s local l y abundant in the tuff. Where oarbonate grains are disseminated in the tuff no reaction between tuff and carbonate has occurred, although, as described under limestone, in some places fragments of tuff in limestone were altered on the borders to diopside, tremolite, and actinolite. In one or two areas, and in particular i n the outcrop on the north side of Ptarmigan H i l l , the feldspar in the tuff has -23- "been saussuritized. Here epidote is very abundant, forming over f i f t y percent of the rook. It is mostly in patches associated with plagioclase, but also occurs in irregular microscopic veinlets and lenses cutting a l l other minerals. Albite, untwinned and with abundant inclusions, has formed in irregular masses probably replacing andesine, although andesine could not be. proven. Calcite grains are disseminated through- out the slides, "kaolins' cloud the feldspars, and small zoisite grains form inclusions in the feldspars. C h l o r i t i - zation of the hornblende acoompanies the saussuritization of the feldspar, but some of the chlorite has been replaced by the abundant epidote. Alteration is not confined to the tuff near the chlorite gneiss s i l l s . Areas several hundred feet from intrusive outcrops have abundant epidote. Some of the tuff beds near the s i l l s show crenulation, particularly where the s i l l s cut across the bedding, but thin sections show no reoonstitution of the minerals. In some areas the tuff shows no bedding, and i s indis- tinguishable from fine-grained intrusive diorite gneiss. These areas have been mapped as massive greenstone. Since the outcrops l i e on strike of tuff beds rather than on strike of diorite gneiss s i l l s , and since most thin sections contain quartz, which does not occur in the intrusives, the rock i s undoubtedly 'sedimentary' in origin. Marked lineation of hornblende 'feather amphibole1 (Thin Section photograph No. 3) -24- indieates dynamic metamorphism was stronger here than in Surrounding areas. In one thin section (see Thin Section photograph No. 4) a band of kaolinio alteration orosses the amphibole lineation, and may represent the original bedding. Why dynamic metamorphism has been more intense in these areas has not been determined. The areas are not particularly close to exposed intrusives, the bedded rooks on their margins are not severely folded, and they are too irregular to be associated with concealed faulting. The gneissic structure in them is parallel to the regional folding and foliation. Gneiss of Tuff Origin. Where the sedimentary rocks are silioious the contact with the diorite gneis3 s i l l s are sharp, but where andesite tuff i s the main sediment the tuff has recrystallized, bedding is obscured, and the contact with the s i l l is indistinguish- able. Some of the rock mapped as diorite gneiss has undoubt- edly formed by recrystallization of tuff under dynamic meta- morphism. The gneiss in several outcrops shows bands of coarser and finer grain size and lighter and darker grey-green colors. These bands may be from multiple intrusion, but are more li k e l y original bedding in tuff. The gneissio structure In these bands is parallel to that in the s i l l s and to the regional lineation. This paragneiss contains the same minerals as the orthogneiss. Andesine and hornblende predominate; biotite, pyrite, magnetite, sphene, and specularite are minor x 85 THIH SECTION PHOTOGRAPH IO. 5 Gneisaic s t r u c t u r e from lensey aggregations of hornblende c r y s t a l s . Andesine comprises mo3t of the r e s t of the s l i d e but c h l o r i t e epidote, 3 e r i c i t e and carbonate are a l s o present. x 80 THIN SECTION PHOTOGRAPH i*0. 6 F r e s h andesine i n r e c r y s t a l l i z e d t u f f . Hornblende, quartz, c h l o r i t e , a e t i n o l i t o , and epidote are present. -25 forming about one percent of the rock. The average grain size is .2 mm. A few of the,specimens contain quartz, and thus are probably sedimentary rather than intrusive. The gneissic structure is produced by aggregation of hornblende grains to parallel lenses. Andesine has been kaolinized and sericitized, and hornblende chloritized. Minute grains of epidote (.05 mm. in diameter) are associated with the kao- li n i o alteration of plagioclase. Gneiss has been formed by recrystallization of the andes- ite tuff for twenty or thirty feet on each wall of the acid dykes. The gneiss shows no addition of material, but is coarser in grain size than the tuff. The gneissic structure has been produoed by segregation of hornblende into parallel lenses. The structure i s not parallel to the walls of the dykes, but is parallel to the regional fol i a t i o n . The dykes must thus have been intruded before or during the orogenio period. Intrusive Diorite Gneiss. 'The intrusive gneiss, like that formed from tuff, is composed predominantly of andesine and hornblende, but i t contains no quartz. Apatite, titanite, and ilmenite or titaniferous magnetite are accessory minerals. Euhedral crystals of hornblende up to a millimeter in diameter occur in parallel lenses in a groundmass of subhedral andesine grains of about .5 millimeters diameter. (Thin Section photo- - 2 6 - graph No. 5) At sharp contacts with the sediments the gneiss i s fine grained from c h i l l i n g , and in places cuts the sediments at a small angle, At one exposure the sediments have been crenulated and shattered at the contact (Thin Section photo- graph No. 2.)* Angular fragments found in boulders of gneiss may be xenoliths of tuff or autpliths. The gneiss has undergone similar alteration to the tuff. Feldspars have been saussuritized with the production of albite, epidote, clinozoisite, and olay minerals, and have been serioitized. Hornblende has altered to chlorites and to epidote. Ilmenite or titaniferous magnetite i s rimmed by titanite, and the two are altered in part to leucoxene. Four c r i t e r i a have been found to distinguish the ortho- gneiss from paragneiss. Quartz, probably detrital in origin, is in places disseminated and in minute lenses and bands in the paragneiss, but has not been found in orthogneiss. In places vague banding, probably bedding, can be traced into paragneiss. The orthogneiss contains xenoliths of tuff or autoliths. The orthogneiss, although s i l l - l i k e , in places crosscuts the bedding of the sediments. Dykes. Sediments and gneiss are cut by aplite, lamprophyre and syenite dykes. The aplite dykes are composed of about equal proportions J -27-, of aubhedral orthoclase, quartz and albite in grains up to five millimeters in diameter. Muscovite, chlorite, and anorthoolase are minor constituents, forming less than one percent of the dykes. One or two grains of garnet and pyrite were noted. Parts of some orthoclase grains have recrystallized, probably because of stress. Parallel laths, arranged en echelon and in places joined, are a l l of the same optic orientation, but of a different orientation than the host crystal. The laths are clearer than the rest of the crystal. In places orthoclase grains are replaced on the borders by anorthoolase. Pine flamboyant quartz grains, .1 mm. in diameter, f i l l irregular fractures in orthoolase and albite. The aplite dykes have undergone l i t t l e alteration. Serioite flakes replace the orthoclase, and clay minerals cloud the plagioclase. Ghlorite has completely replaced the few grains of mafic originally present. The aplite dykes have irregular walls, stringers of aplite forming retioulating veinlets in the wall-rock. The andesite tuff wall-rock has recrystallized to diorite gneiss, as discussed under 'Gneiss of Tuff Origin'. Several lamprophyre dykes also cut both sedimentary rocks and diorite gneiss. Thin sections were made of two of these dykes. One,, a kersantite, contains twenty percent biotite in flakes averaging .2 mm. in diameter. The biotite forms -28- inolusions in labradorite laths and part i a l l y f i l l s inter- stices between laths. Augite, in phenocrysts .5 mm, in diameter, makes up two or three percent of the rock. Labra- dorite laths, up to 1 mm, long and forming seventy peroent of the rock, have a sub-parallel disposition, giving the rock a trachytoid texture. Two or three percent of quartz in grains .15 mm. in diameter is present with biotite in the interstices between the labradorite and augite crystala. Minute graina of opaque, probably magnetite, are present. The other, a spesaartite, has sixty-five percent euhedral hornblende phenocrysts up to 2 mm, long. One percent of biotite is scattered through the slide both in hornblende phenocrysts and their intersticea. Andesine in grains up to ,5 mm., forms the groundmass. Minor apatite is scattered throughout the groundmasa and in one place forms an aggregate of a dozen or more crystals. Both rooks are quite fresh, augite and hornblende showing only slight alteration to chlorite, and feldspar a l i t t l e clouding by clay minerals. One outcrop of a syenite dyke was found. This dyke contains sixty to seventy percent albite laths of random orientation ranging in size from several microns to several millimeters; and thus giving the rook a seriate texture. Hornblende grains, mostly twinned and very acicular, up to •5 mm. long, form inclusions in some of the large albite grains, and are scattered through the rock with the fine -29-* albite laths. Chlorite and magnetite pseudomorph pyroxene, apatite and magnetite are aooessory minerals. Coast Range Intrusives (not inoluding Trlassio? s i l l s ) . The eastern contact of the main bodfc of Coast Range intrusives is about five miles southwest of the property, but several stocks outcrop in the sedimentary and volcanic rocks east of the property. Specimens were taken from one of these stocks, about four miles east. The rock is a medium-grained granite. Zoned oligoolase- albite forms f i f t y percent of the rock, orthoclase thirty percent, quartz ten percent, and biotite and hornblende ten percent. Some of the orthoclase enveloped the plagioclase and quartz, giving the rock a p o i k i l i t i o texture. Sphene and ilmenite or titaniferous magnetite are accessory minerals. Alteration is slight; plagioclase i s somewhat clouded by clay minerals, orthoclase contains a few flakes of serieite, and hornblende shows ohloritization. Sphene and the opaque mineral are bordered by leuooxene. - 3 0 - MB TAMORPHISM Sedimentary rocks have undergone minor contact metamorph- ism where they are intruded by diorite s i l l s , but both sedi- ments and s i l l s have undergone regional metamorphism. Where the contacts of diorite s i l l s are close to s i l i c i o u s limestone minor tremolite has formed, and where s i l l s intrude andesite tuff the tuff has recrystallized to diorite gneiss. Where calcareous tuff i s intruded a few garnets have formed, but these are localized within a few feet of the contact. Uo large skarn zones are found. The diorite must have been low in volatiles, and transmitted l i t t l e heat to the country rock. Dynamic metamorphism has produoed a regional fo l i a t i o n . The gneissic structure in both the s i l l s and the r e c r y s t a l l i z - ed tuff trends northwesterly. Hornblende has the feathery poikiloblastic form typical of dynamic metamorphism. Limestone is recrystallized; the carbonate grains show twinrgliding from flowage, but have not reacted with inclusions of quartz. Quartz grains in a l l rocks except the acid dykes show strain shadowing. Quartz inclusions in the limestone are aligned from flowage. Most of the metamorphism is regional, from orogenic movements associated with the coast range intrusives; but some local contact metamorphism has been produoed by the diorite s i l l s . - 3 1 - STHUGTUBE F o l d i n g . The c e n t r a l band of sediments has been f o l d e d i n t o n o r t h - w e s t e r l y - t r e n d i n g d i s c o n t i n u o u s a n t i o l i n e s , s y n c l i n e s and monocl ines p l u n g i n g to the nor thwest . Some of t h i s f o l d i n g may be due to the i n t r u s i o n o f the s i l l s , f o r i t becomes l e s s in tense away from the s i l l s . However* the s i l l s are cons idered to have undergone some deformat ion w i t h the sediments because: they have s u f f e r e d s i m i l a r metamorphism to the sediments , the g n e i s s i c s t r u c t u r e i n them i s p a r a l l e l to the r e g i o n a l f o l i a t i o n ( a l t h o u g h a pr imary f lowage s t r u c t u r e would have the same t rend s i n c e the s t r i k e of the s i l l s i3 p a r a l l e l the r e g i o n a l f o l i a t i o n , i t would not be as marked a s t r u c t u r e , and would more l i k e l y be caused by o r i e n t a t i o n o f i s o l a t e d g r a i n s , r a t h e r than a g g r e g a t i o n of g r a i n s i n t o l e n s e s sueh as has occurred h e r e ) , f r a c t u r e s , i n c l u d i n g those m i n e r a l i z e d are cont inuous from sedimentary rocks i n t o s i l l s , no dykes of d i o r i t e from the s i l l s out i n t o the sediments . The time of i n t r u s i o n of the s i l l s i s i m p o r t a n t . I f the s i l l s were i n t r u d e d w h i l e the sediments were s t i l l r e l a t i v e l y f l a t - l y i n g , they would r a i s e the o v e r l y i n g sediments , but would p r o b a b l y not cause f o l d i n g i n them. On the other hand, i f they were i n t r u d e d a f t e r the sediments had been f o l d e d or t i l t e d so t h a t they dipped at moderate or h i g h a n g l e s , 32 folding (or further folding) in the sediments between s i l l s would more li k e l y take place. If, on the basis of the correlation discussed previously, the sediments are consider- ed to be Palaeozoic, and the s i l l s Triassic, the problem of the conformity of Palaeozoic rocks to Triassic rocks is s t i l l to be solved, to determine the amount of folding before intrusion of the s i l l s . In the Iskut area the contact be- tween Permian and Triassic is unconformable; and in South- eastern Alaska i t is suspected of being perhaps angularly unconformable, but not markedly so (a variation of twenty degrees in dip but no change in strike i s reported in one place). On the whole, there does not seem to be much orogeny before Triassic time, which would indicate that the Triassic? s i l l s were intruded into relatively undisturbed strata, and thus would produce l i t t l e further disruption in them. On the basis of the available f i e l d information, the upper and lower are not considered to be parts of the one trough-like body which contains a shallow basin of sediments, for the following reasons: at the contacts the s i l l s do not dip under the sediments consistently, the regional dip is f a i r l y steep, about sixty degrees northeast, the sediments between the s i l l s , though folded and fractured, contain no dykes of diorite. The relation of the s i l l s to the sedimentary rocks is important because, although veins continue from sedimentary rocks into diorite, they diminish from about five feet to one -33 - foot in width. Samples taken on surface indioate a decrease in gold content where diorite is the host rook. Apparently the diorite is unfavourable to mineralization. Regional Fracture Pattern. A l l the dykes strike from forty to sixty degrees east of north and dip vertically. The irregularity of the dykes» especially the aplite» indicate the fractures they occupy are tensional. The quartz veins, including those outside the central band of sedimentary rooks, are closely parallel, striking south sixty-five degrees east, and dipping eighty degrees north. A zone of abundant shearing with specularite mineraliza- tion is exposed in the outcrop north of Ptarmigan H i l l . The shears vary forty degrees in strike, but those of most abun- dant go#ge strike northerly. Dips are vertica l . Bands of limestone several hundred feet wide on the east of this broken zone are not found on strike*on the west of the zone. A band of limestone to the north, outside the mapped area, may be the continuation. A right-hand fault of over one thousand feet horizontal offset is suspected. The presence of specularite in stringers several inches wide in the zone * indicates the faulting was In part pre--mineralization. Q-17 and Q-E3 vein are each offset several feet by l e f t - hand faults, and a fault cutting off the west end of Q-22 vein has the same strike, north fifteen degrees east, indicate ing Q-17 and Q-22 are the same vein, offset by a left-hand fault. If the structures, excluding the post-vein left-hand faults, are assumed to have resulted from one set of forces, they may be fitted into the strain ellipsoid diagram as follows: y<-̂  reborn?/ /o/ci/nf c?nd /o/'af/o/t -/T7/f>erc7//zccS /ace// of /c?r-ye cS'J/s/'&cr/z'esz/ fe/n f/'//e</ rjS?c<»- aortas The veins are known to have formed on shear zones, because the wall-rock, particularly the hang-wall, has abun- dant gouge, and where the quartz pinches out between Q-17 and Q-17 west veins sheared rock persists. The folding, with regional f o l i a t i o n parallel the axes of the folds, indicates the stress oausing the deformation was pressure. From the strain ellipsoid diagram above, this pressure was from the southwest or northeast. The two evident sources of pressure are the local s i l l s , trending northwest, and the main body of Coast Range i n - trusives, also trending northwest. The metamorphism is -35* regional, thus l i k e l y produced by the orogeny associated with* the Coast Range intrusives. If the fractures are_ produced by the same stress, they must be regional also, but a larger area w i l l have to be mapped to verify this. Relation of Veins to S i l l s . The veins show no direct spatial relation to the s i l l s . Q-19 vein, Q-25 vein, and several veins outside the mapped area, are well over one thousand feet from s i l l outcrops. Ho marked ohange i s noted in the mineralogy in tracing the veins away from the s i l l s . Vein fraotures occur well into the s i l l s rather than just on the borders. Many other mineral deposits, including one reported to contain specu- l a r i t e , have been found in the Unuk. Thus the mineralizing fluids probably were not derived from the diorite s i l l s , but probably were derived from the main Coast Range intrusive or i t s satellites. 36- V E I N S . general. The quartz veins have formed in shear zones, as indicated "by gouge on the walls, but no movement along the zones has been proven. The veins continue from sediments into diorite but diminish in width and gold content in the diorite. The veins contain about ten percent of metallios. In order of abundance these are galena, pyrite, specularite, chalcopyrite, sphalerite, magnetite, three soft minerals^ possibly tellurides, and gold. Q-17 vein Is by far the most interesting, both economically and mineralogically. Most of the surface devel- opment has been done on i t . In one place i t outcrops con- tinuously for over one hundred feet. Wall Rook Alteration. Fairly fresh samples were obtained from Q-17 vein to de- termine the nature of the wall rock alteration. Specimens were taken, as-closely as could be determined, from the same bed, and at 8 f t . , 4 f t . , 3 f t . , 2 f t . , 1̂ - f t . , and & f t . from the vein. A specimen was taken from the shear zone between Q-17 and Q-17 west veins. At eight feet from the vein the wall rock shows no altera- tion that can be attributed to hydrothermal activity. It is metamorphosed, but the metamorphism is similar to that in most tuff specimens taken from the mapped area. The andesine is in part well twinned, and although altered to clay minerals, is not more so than in tuff outcrops away from the veins. - 3 7 * E p i d o t e and c h l o r i t e have developed as a l t e r a t i o n of p l a g i o - c l a s e and hornblende , but these m i n e r a l s are a l s o p r e s e n t i n t u f f and gne iss i n most o ther p a r t s of the a r e a . Four f e e t from the v e i n the w a l l rock s t i l l shows no change; andesine i s w e l l twinned , hornblende s t i l l the •fea ther -amphibole ' type of the m a j o r i t y of the t u f f specimens, e p i d o t e , c h l o r i t e , and k a o l i n s are m i n o r . However q u a r t z , which i s u s u a l l y d isseminated or i n t h i n bands i n the t u f f , occurs as t h i n i n t r o d u c e d v e i n l e t s i n the t h i n s e c t i o n . The next s e o t i o n , taken at three f e e t from the v e i n , shows c o n s i d e r a b l e a l t e r a t i o n . Many o f the p l a g i o c l a s e g r a i n s have been comple te ly r e p l a c e d by s e r i o i t e . Only the l a r g e r s e r i o i t e f l a k e s show the maximum b i r e f r i n g e n c e of normal ( .03 mm. t h i c k ) s e c t i o n s ; most f l a k e s are about .01 mm. t h i o k , and thus low i n b i r e f r i n g e n c e . The c l a y m i n e r a l s are here abundant, but not as abundant as the s e r i o i t e . Quartz v e i n l e t s are more numerous, forming three or f o u r percent of the s e o t i o n . The few f e l d s p a r s tha t are f r e s h enough to show t w i n n i n g have t w i n l a m e l l a e of g r e a t e r e x t i n c t i o n angles ( l a b r a d o r i t e i n s t e a d of a n d e s i n e ) ; and one or two g r a i n s have two se t s of t w i n l a m e l l a e a t r i g h t a n g l e s . I t i s d o u b t f u l , however, tha t t h i s more c a l c i c f e l d s p a r has been i n t r o d u c e d , f o r i t shows the same haz iness as the andesine f u r t h e r away from the v e i n , and shows no v e i n i n g r e l a t i o n s to i n d i c a t e replacement . At two f e e t from the v e i n the f e l d s p a r has almost completer - 3 8 - l y disappeared; and hornblende has a l t e r e d i n e n t i r e t y to, c h l o r i t e . The w a l l rock i s here composed of quartz and one or two vague p l a g i o c l a s e r e s i d u a l s i n a f i n e grained groundmass of s e r i e i t e , c h l o r i t e , and c l a y m i n e r a l s . A few f r a c t u r e s across the t h i n s e c t i o n are bordered by f a i r l y coarse (.1 mm.) f l a k e s of s e r i e i t e . The next s e c t i o n was taken one and one-half f e e t from the v e i n , i n an area where there are few f r a c t u r e s or v e i n l e t s . I t showed s u r p r i s i n g l y l i t t l e a l t e r a t i o n when compared to the s e c t i o n taken two f e e t from the v e i n . About h a l f the f e l d - spar has been s e r i c i t i z e d ; the remainder i s f a i r l y f r e s h and i s w e l l twinned, andesine i n composition. Hornblende i s only i n part (about h a l f ) replaced by c h l o r i t e . Disseminated quartz, probably r e s i d u a l , i s s t r a i n shadowed and r e c r y s t a l l - i z e d * but t h i s deformation occurs i n a l l the sedimentary quartz. At one h a l f a f o o t from the v e i n a l l minerals except the quartz are r e c o n s t i t u t e d to a f i n e p u l v u r u l e n t mass of s e r i e i t e , c h l o r i t e , and k a o l i n s . Some Of the 3 e r i c i t e has grown to p o i k i l o b l a s t i c muscovite, p a r t i c u l a r l y near f r a c - t u r e s . Several r e g u l a r v e i n l e t s of a l b i t e , c l e a r but w i t h p o o r l y developed twinning, t r a n s e c t the s e c t i o n . The next s e c t i o n was taken from the shear zone between Q-17 and Q-17 west v e i n s , and i s not from the same bed as the sec t i o n s described above. The o r i g i n a l rock, however, was s i m i l a r andesite or d a c i t e t u f f . An assay of t h i s sheared -39- rook gave several tenths of an ounce of gold per ton. Serio- ite shreds, constituting about thirty peroent of the slide, and chlorite (five peroent) show a marked parallelism to lens- es of carbonate and to the direction of elongation of the albite grains. Carbonate lenses form about thirty percent of the slide, and albite, poorly twinned and partly s e r i o i t - ized, forms about thirty-five peroent. Highly strained quartz is present in disseminated grains and lenses. Eu- • hedral pyrite crystals are present in the carbonate lenses, and in polished seotion the pyrite is seen to be rimmed and replaced by marmatitio sphalerite. A few subhedral grains, possibly apatite, are too small to identify. Ghost-like inclusions of wall rock were found in the vein in many places. The fragments are completely altered to a soft pale green s e r i c i t i o material too friable to permit making thin sections. Wall rock alteration is thus confined to narrow limits, having progressed only three or four feet into the walls. Serioite, clay minerals, and chlorite have formed by altera-? tion of the plagioclase and hornblende. Quartz and albite have been introduced in veinlets a fraction of a millimeter in width; and in the shear zone i t s e l f , carbonate, pyrite and sphalerite have been introduced. The hydrothermal additions needed to produce this alteration are potash, soda* (probably introduced as albite molecule as the albite occurs in definite veinlets), zinc, and sulphur. The quartz, c a l - 40 c i t e , and pyrite i n the shear zone are probably hydrothermal as they occur i n v e i n l e t s and lenses. The wall rook a l t e r a - t i o n i s t y p i c a l of that accompanying mesothermal veins. Mineralization. The quartz veins may be c l a s s i f i e d as follows: (1) those with ohalcopyrite and p y r i t e with or without magnetite, (2) those with galena and p y r i t e , and (3) those with speeu- l a r i t e . The f i r s t class was found to contain only traces of precious metals, irresp e c t i v e of the amount of metallies, but the l a s t two classes give good assays i n gold, p a r t i c u l a r l y where metallies are abundant. In a l l veins found the quartz has c r y s t a l l i z e d i n grains up to several millimeters i n diameter. One or two small vugs were noted, and these are bordered by the coarsest grains of quartz. Exoept f o r the rare vugs, vein f i l l i n g shows none of the features of open space deposition, and thus was probably deposited at moderate depth. Chalcopyrite - p y r i t e Class. Pour veins containing ohaloppyrlte-pyrite mineralization were found on the claims, but none gave an assay above a few hundredths of an ounoe i n gold. In these veins the p y r i t e occurs i n cubes up to several millimeters across, and, where magnetite i s present, forms inclusions i n the magnetite. Chalcopyrite, where abundant, veins and replaces quartz, and, where sparse, i s found only as inclusions i n p y r i t e . Ho -41- definite paragenetic relations, other than that the sulfides were later than the quartz, could he established. Q-23 vein is rather a zone of quartz stringers than a true vein. Associated with the quartz is a dark green chlorite, which in thin seotion shows the anomalous blue birefringence of penninite. The quartz contains aggregations of serioite, and is clouded by clay minerals. Magnetite constitutes five to ten percent of the polished sections. The footwall side of Q-25 vein contains quartz-chalcopyrite mineralization, and the hangwall quartz-galena-pyrite mineral- ization. Gold assays in the footwall side were very low, but in the hangwall side were very encouraging. No fracture or selvage separates the two classes of mineralization. Galena Pyrite Glass. The galena pyrite veins usually carry good values in gold. The gold is generally proportional to the amount of sulfides, but may continue into sulfide-poor quartz. However, two veins found outside the central band of sedimentary rocks contain fifteen or twenty percent galena with minor pyrite, but gave assays as low as one or two tenths of an ounce per ton. The small possible ore shoot in Q-19 vein contained very l i t t l e galena but did contain a few disseminations and lenses of coarse (up to a centimeter in diameter) pyrite. The pyrite grains are oxidized oh the rims' so that they f a l l out o f the quartz, • .Some were collected and mounted in a polished -48- section. Although inclusions of chalcopyrite and sphalerite are abundant, no gold was found in the pyrite. One small free particle of gold was found in the section, l i k e l y a remnant after oxidation of the pyrite, or a particle that was deposit- ed in quartz near pyrite. Q-17 and Q-17 west veins are on the same shear zone, separated by thirty feet that is barren of quartz. As afore-? mentioned, the sheared rock between these two quartz veins i s mineralized with pyrite and sphalerite, and gave gold assays of several tenths of an ounce per ton. Q-17 west vein is mineralized with five to ten percent of galena and pyrite but contains no specularite. Q-17 vein i s mineralized with about five percent specularite but contains no sulfides. The signi- ficance of this marked change in mineralization is discussed later. The mineralization of Q-17 west vein was studied in de- t a i l as i t afforded some interesting specimens. In thin section the quartz grains are found to be strongly strain shadowed and fractured, and the coarser grains (5 mm.) are cut by many veinlets of small (.1 mm.) flamboyant grains. Pyrite and galena occur in these veinlets, and replace the coarser quartz in their walls. Coarse quartz i s clouded by clay minerals. Polished sections show the pyrite to be markedly free of fractures and inclusions. The galena, however, has inclusions of gold and three other soft metallio minerals. The soft x 700 Intergrowth i n galena of gold w i t h i s o t r o p i c white m i n e r a l (No. 1) and i s o t r o p i c grey mineral (No. 2). POLISHED SECTION PHOTOMICROGRAPH NO. 1 (see Appendix f o r photographic data.) x 700 POLISHED SECTION PHOTOMICROGRAPH NO. 2 x 700 POLISHED SECTION PHOTOMICROGRAPH NO. 3 Lensey fractures in galena, with no relation to galena cleavage, contain intergrowths of gold, isotropic white, (No. 1) and isotropic grey (No. minerals. -43- minerals are in places found singly, but in most places are in aggregations of two or more (see Polished Section photo- micrographs Nos. 1,2,3,4 and 5). The three soft metallios other than gold have not been identified owing to their small size. They can be seen under medium power (8 ocular, 3b objective), only when sections have been well polished. Their reaotions to tests are as follows: No.l Ho.2 No. 3 Color lighter white a very l i t t l e moderately darker than galena darker grey than galena with than galena a tint of brown Hardness no r e l i e f no r e l i e f softer than from galena from galena galena Anisotropism n i l n i l moderate with a brownish birefring- ence M 0 3 negative negative slight etoh to neg. HCl negative negative negative KCN negative negative quick blaok etch PeClg dark brown, negative darker brown than stronger than galena galena -44. No, 3 moderate brown s t a i n KOH some remain c l e a r n e g a t i v e n e g a t i v e and others t u r n brown, even i n same reagent drop A speot rographio a n a l y s i s on minute amounts i n c l u d i n g some galena i n d i c a t e d the presence o f : N o . l No ,2 N.o.g Ag medium medium medium Cu weak weak weak Pb present but known i n ga lena i n o l u d e d Te t raoe traoe t r a c e As s t r o n g n e g a t i v e n e g a t i v e These r e a c t i o n s d i d not conform to those of any o f the - m i n e r a l s l i s t e d i n ' S h o r t ' ( B i b l . No. 15).. The fragments are so s m a l l tha t on e t c h i n g the reagent drop o v e r l a p s onto the g a l e n a , and r e a c t i o n s cannot be taken as d i a g n o s t i c . Speotrographio ana lyses were taken on minute amounts, and thus may not be e n t i r e l y r e l i a b l e . The m i n e r a l s are h e r e a f t e r r e f e r r e d to by t h e i r number i n the above t a b l e . The l o n g s t r i n g e r - l i k e form o f some of the aggregat ions (see P o l i s h e d S e c t i o n Photomicrographs Nos . 2 and 3) suggests N o . l No. 2 HgClp n e g a t i v e negat ive w \ 7 i y / i / i—> i L i / I I m x 700 POLISHED SECTION PHOTOMICROGRAPH NO. 4 Gold f i l l i n g a minute x 570 POLISHED SECTION PHOTOMICROGRAPH NO. 5 Gold i n a n i s o t r o p i c grey mineral (No. 3) i n galena. x 204 POLISHED SECTION PHOTOMICROGRAPH NO. 6 x 204 POLISHED SECTION PHOTOMICROGRAPH NO. 7 The gold remains i n p i t s formed hy the o x i d a t i o n of p y r i t e and galena. -46- they are of later age than the galena. They do not show any relation to cleavage directions in the galena. Besides occurring as blebs and minute veinlets both alone and with the other soft minerals in the galena, gold was found in pits where galena has oxidized (see Polished Section photo- micrographs Nos. 6 and 7), and in or near fractures in the quartz. Q-22 vein, the probable faulted eastern extension of Q-17 vein, i s mineralized with galena and pyrite, but not as abundantly as Q-17 west vein. Polished sections show irregu- l a r l y walled veinlets of galena cutting into pyrite grains. Chalcopyrite and sphalerite form lens-like inclusions, l i k e l y replacements, in the pyrite, and rounded grains with no appar- ent paragenetic relations in the galena. One small fragment of gold was found in the oxidized material at the edge of galena. A veinlet of specularite a fraction of an inch wide was noted in one trench across the vein, but the trench contained no other metallics. The galena-pyrite mineralization in Q-25 vein i s , as found in polished section examination, accompanied by minor sphal- erite, chalcopyrite, the soft mineral No. 1 and gold. Galena, in irregularly walled veinlets, replaces pyrite, and contains rounded inclusions of sphalerite and chalcopyrite. The gold was found as a small stringer in fresh galena, Paragenetic relations in the galena-pyrite type of min- eralization are (1) pyrite, (2). sphalerite and chalcopyrite, x 204 POLISHED SECTION PHOTOMICROGRAPH NO. 8 x 204 POLISHED SECTION PHOTOMICROGRAPH NO. 9 The gold in the quartz specularite shoot occurs mostly in disruptions between specularite'cleavage*plates, but in a few places forms lenses between plates. -46- (3) galena, (4) soft minerals Including gold. Specularite Glass. Only one vein, Q-17, containing abundant specularite mineralization was found on the property, although one small veinlet of specularite was noted in one of the pits on Q-22 vein. However, the presence of other quartz specularite veins is suspected because of abundant float in one or two d r i f t covered areas. Thin section shows the specularite to be associated with fractures in the quartz, but replacing quartz on the edges of the fractures. Plates of the specularite cut well into quartz grains, and even traverse several grains. The quartz i s clouded by fine clay minerals, and in places includes masses of serieite which are l i k e l y altered fragments of wall rock. Polished sections show the specularite 'cleavage' flakes to be markedly twisted and folded. In the open spaces or weak- nesses produced by the deformation gold has been deposited. In no place was gold observed to cut across the 'cleavage' plates, and replace the speoularite. It has been deposited as lenses between parallel plates, but most is found where the cleavage'is disrupted, leaving angular openings. (See Polish- ed Section photomicrographs Nos. 8 and 9). A few small frag- ments of gold were noted in or near fractures in the quartz. Significance of Speoularite. Although speoularite in places comprises as much as ten percent of the vein f i l l i n g , and sulfides in places comprise fifteen percent, in no place was 3 p e c u l a r i t e found in contact with the sulfides. Speoularite i s the only metallic, except for gold, in Q-17 vein, and yet none i s found in Q-17 west vein, which is in the same 'hreai:1 with only a thirty-foot length that is barren of quartz intervening. Both speoularite and sulfides are found in the eastern part of Q-32 vein, but they are neither abundant nor in contact. -48- Speoularite, though f a i r l y common in the 'contaot meta- morphic' type of deposits, i s not a common vein mineral. This discussion w i l l .be primarily on the significance of'hydro- thermal hematite in veins, Most, but not a l l , hematite of hydrothermal origin occurs as speoularite rather than "as earthy-lustered hematite. iindgren (Bibliography No. 25) presents speoularite as a characteristic mineral in 'ore deposits of deap-seated orir gin*. Aooording to Lindgren, in these deposits i t is found in the oassiterite veins, where i t is commonly associated with cassiterite, arsenopyrite, pyrite, tourmaline, etc., and in the gold and silver-bearing veins, where i t is commonly assoc- iated with gold, pyrrhotite, ilmenite, magnetite, galena, zincklende, eto. The structure and the wall rock alteration of the specular- ite-bearing veins in the Unuk suggested the veins were formed under mesothermal conditions, rather than hypothermal. The literature was searched for examples of deposits containing speoularite (or hydrothermal hematite) to see i f they are consistently hypothermal, and at the same time to see what the relations are between the hematite and sulfides. Before examples of deposits are considered, some discussion concerning the chemical relations of hematite to sulfides w i l l give more significance to the mineralogical associations in _ the deposits. In the f i r s t place, sulfides are deposited only under reducing conditions, and hematite, including the weather- -49- ing product, only under oxidizing conditions. In the second place, i f hematite, FeO , containing trivalent (ferric) iron, 2, 3 is subjected to reducing conditions, i t should be reduced to magnetite, Fe o0 .FeO, containing trivalent (ferric) iron and divalent (ferrous) iron or, of sulphur i s abundant, to pyrite. Pyrite, according to Partington (Bibliography l o , 34) is supposed to contain divalent iron. Hematite thus should not be deposited from the same solutions as sulfides., and i f after deposition i t is exposed to later sulfide-bearing solutions, i t should be reduced to magnetite or pyrite. Gilbert (Bibliog- raphy) No. 27) mentions several deposits in whioh hematite has been replaced by magnetite, and magnetite by hematite, and mentions that both replacements are found in the same mineral deposit. He attributes the replacements to changes from oxid- izing to reducing conditions and vice versa. In another paper . (Bibliography No. 32) he mentions that the replacement of magnetite by hematite is most vigorous in ores that are sul- phur poor. Reducing conditions connected with sulfides would inhibit the oxidation of the magnetite. According to Van Hise (Bibliography No. 33) hematite is reduced by hydrogen sulfide as follows: F e2°3 * 2 H 2 S * G 02 F e S 2 F e 0 0 3 * 2 H2° to form pyrite. Hematite can form, however, by the action of alkaline carbonates on pyrite as follows: 8 FeSg 15 Na200g — 4 FegOg *• 14 NagS * H a g S 2 0 g + 15 GOg The latter reaction has been carried out in the laboratory. - 5 0 Hydrogen sulfide and alkaline carbonates are both possible constituents of hydrothermal solutions. There seems to be l i t t l e possibility of a solid solution of magnetite and hematite. Broderick (Bibliography No. 19) shows that specimens of an iron oxide that were described as solid solutions of magnetite are in reality mechanical mix- tures. The components of the mixture are visible in polished sections studied under the microscope. The relative temperatures of crystallization of fe r r i c oxide, ferrous oxide, and sulfides of iron may also have a bearing on the apparent antipathy of hydrothermal hematite to sulfides. Butler (Bibliography No. 23) has, on empirical evi- dence, constructed a chart showing the relative temperatures of formation of oxides and sulfides of the common ore metals. The temperature zones shown on this chart are f a i r l y well in harmony with Emmons*1 zonal theory and with the zoning implied by Lindgren's olassifieation of ore deposits. Ferric oxides and silicates are very largely confined to the. high tempera- ture zone. Ferrous minerals are formed at high temperatures, and continue to form, though in less abundance, to the low temperature zone. Sulfides do not form above the intermediate temperature zone, but. continue to form in the low temperature zone. Thus.unless a low temperature type of mineralization i s superimposed upon a high temperature t y p f , or vice versa, hematite v^ould not be l i k e l y to occur with sulfides. The zoning suggests a gradual change in the nature of the deposit- 51- ing f l u i d , from oxidizing during i t s early, higher-temperature stages to reducing during i t s late, lower-temperature stages. The influence of pressure may also be important in some cases. In the Ouray d i s t r i c t of Colorado (Bibliography No. 35) laccoliths and sills^have associated veins containing hematite, magnetite, chalcopyrite, and pyrite. Most of the magnetite was deposited before hematite. A decrease in pres- sure on the depositing liquids after they deposited magnetite is evident from the forma'tion of f i l l e d fissures cutting mag- netite-bearing lodes. The liquid is presumed to have v o l a t i l - ized to some extent, owing to this decrease In pressure. FeClg, being quite volatile, probably formed. This f e r r i c iron has been deposited in fissures as hematite. The oxida- tion of ferrous to ferric iron provides considerable heat, and so the hematite was not necessarily deposited at a lower temperature than the magnetite,•though i t was deposited later in the period of mineralization. Examples that are relavant to the above discussion are now given, tabulated according to their probable temperature of : formation. Epithermal deposits. Some copper deposits in Tertiary sediments and voloanfca in Japan are 'often intricately cut by veins and veinlets of quartz and micaceous speoularite', 'The speoularite is decid- edly primary in origin*. Its formation in Tertiary rocks, thus at shallow depth, was considered by Takeo Koto (Bibllog- -52- raphy No. 26) to "be worthy of comment as i t r e f u t e s the gener- a l o p inion that s p e c u l a r i t e i s a hypothermal m i n e r a l . On Iro n Mountain, at the j u n c t i o n of the Coldwater and N i c o l a R i v e r s , veins of s p e c u l a r i t e are found i n T e r t i a r y ( ? ) v o l c a n i c s ( B i b l i o g r a p h y No. 26). I f the deposits are Ter- t i a r y they must have been deposited at shallow depths. At K a t l m a i , A l a s k a , s p e c u l a r i t e was observed as an i n r o r u s t a t i o n formed by fumaroles; thus here i t formed under atmospheric pressure. At Hickey's Pond, f i v e m i l e s west of the head of P l a c e n t i a Bay, i n Southeastern Newfoundland, are deposits of s p e o u l a r i t e a s s o c i a t e d w i t h abundant a l u n i t e . ( B i b l i o g r a p h y No. 2L) The deposits are i n a s i l i c i f i e d zone at the contact of granodior- i t e and v o l c a n i c s c h i s t . S p e c u l a r i t e , a l u n i t e , and quartz i n the zone are i n p a r a l l e l bands g i v i n g a g n e i s s i c s t r u c t u r e to the dep o s i t . The s p e c u l a r i t e occurs i n ragged masses or i n d i v i d u a l g r a i n s and blades, l i n e a t e d p a r a l l e l to the g n e i s s i c s t r u c t u r e . Small amounts of p y r i t e occur only i n the s p e c u l a r i t e - p o o r s i l i c i f i e d s c h i s t . The presence of a l u n i t e suggests the deposit i s epithermal. In the same l o c a l i t y are s p e c u l a r i t e - b e a r i n g quartz v e i n s c o n t a i n i n g a few grains of a l u n i t e . The sequence of d e p o s i t i o n i s (1) quartz, (2) s p e c u l a r i t e , (3) p y r i t e and a l u n i t e , In one or two places p y r i t e cubes replace s p e c u l a r i t e . No r e d u c t i o n of s p e c u l a r i t e to magnetite i s reported. However, the abundance of a l u n i t e (KgO.3Al2Og.6H2O.4SO3), -53- indicates sulfur rloh solutions in the later stages of de- position, and the pyrite may have formed from the reduction of speeularite rather than from introduction of pyrite as such. The reactions may he as follows: F e2°3 2 H 2 ° ^ 2Pe(0H)3 2fe(-0H) 3 + 3HgS 2FeS f S t 6Hg0 27eS ^ 23 Fe s3 4 (pyrite) Only HgS and S need he added in aqueous solution to cease the replacement, but they would be reducing, and a later change back to oxidizing conditions is necessary for the formation of alunite. The deposit may then be an example of reduction of hematite to pyrite by sulfur rich solutions introduced at a late stage. The alunite, introduced at a s t i l l later stage, may have formed at much lower temperature than the speeular- it e . Mesothermal deposits. An example of replacement of hematite by magnetite during the introduction of sulfides is found in the George Copper deposit of Portland Canal, B.^. (Bibliography No. 28). In this deposit the paragenetic sequence is given as (1) wall rock alteration (2) pyrite (3) arsenopyrite (4) quartz (5) speoularite (6) magnetite (replacing speoularite§(7) fithal- copyrite. The deposition of quartz midway in the deposition of the metallic minerals suggests a change in conditions, sinoe i t Is usually the f i r s t mineral deposited in a vein, and the -54- speoularite indicates this change was to oxidizing conditions. The replacement of hematite hy magnetite before the deposition of chalcopyrite indicates a renewal of the reducing conditions necessary for the deposition of sulfides. The deposit was considered to have formed under inter- mediate temperatures at a depth approximating eight thousand feet. In the large quartz veins of Great Bear Lake, N.W.T. Bibliography No. 29) specularite has been deposited earlier than other .metallics. It is not stated whether or not the hematite and later.sulfides are in contact. The veins are considered formed at 'not very elevated temperatures'. At the Eldorado mine, Great Bear Lake, N.W.T., hematite is associated with deposits of pitchblende (Bibliography No. 22 and No. 30). The hematite in the 'veins' was deposited after pitchblende, and before the sulfides. Sulfides that are in contact with hematite include pyrite and chalcopyrite, and these iron bearing sulfides have formed by reduction of hematite. The temperature of formation of this deposit is d i f f i c u l t to establish as the deposit shows several f a i r l y distinct periods of mineralization. Hypothermal deposits. At Kalgoorlie, Western Australia, specularite is found in the "deep vein zone' with quartz, magnetite, and ilmenite (Bibliography No. 36). These are cut by the later telluride -55- bearing quartz veins. In the Virgilina D i s t r i c t , North Carolina and Virginia, primary bornite and chalcocite in quartz veins have minor associated speoularite. No relation is given between the sulfides and the oxide. The veins are considered to belong to the 'deeper vein zone 1. On Tipella Mountain, near Harrison Lake, B.C. micaceous hematite oocurs in a zone of lens-like bodies. Highly altered rocks on the contact of granite, and in places the granite i t s e l f i s the host rock. (Bibliography No. 16.) If the speoularite is derived from the granite, i t s de- position in the granite indicates formation under high tempera- ture. Lindgren (Bibliography No. 25) states 'at many contacts of intrusive rocks not characterized by pegmatites, quartz vein- lets abound and often carry crystallized speoularite 1. Other Deposits. It is perhaps noteworthy that speoularite occurs without other associated metallics in many veins, and these hematite veins are probably more abundant than the literature indicates, for, since they are seldom economic, they receive l i t t l e pub- l i c i t y . The veins at Tipella Mountain are apparently barren of sulfides. Others in which no indication of temperature of formation i s given occur at Finger Lake, near Vanderhoof, B.C., and. on Iron Range Mountain, near Kitchener, B.G.(Bibliography No. 16). The Kitchener deposits have been called sedimentary -56 - in origin (Bibliography Io. 17), but later work shows the zone of mioaoeous and earthy hematite crosscuts the bedding. A small amount of magnetite occurs but as a rule l i t t l e or no pyrite or other sulfide is visible. Hydrothermal hematite i s much more common in the 'contact metamorphic' deposits, but i s seldom associated with sulfides in these deposits. The hematite is always in parts of the deposit that contain l i t t l e sulfide, and the -sulfides in parts that contain l i t t l e hematite. The almost complete lack of hematite in pyrrhotite bearing deposits has been attributed to the fact that pyrrhotite is a stronger reducing agent than most other sulfides. Since both pyrrhotite and hematite are commonly deposited in the 'deep vein zone' they would normally be associated. If an iron oxide is found with pyrrhotite i t is invariably magnetite rather than hematite (Bibliography Io. 27). Further evidence of the tendency of hematite to be reduced to magnetite and/or pyrite is found in some deposits in which the hematite was probably originally sedimentary or a product of weathering. Reduction of hematite to magnetite and pyrite is considered to have occurred in the iron deposits of Michigan* Veins of pyrite indicate the presence of a reducing agent which could be organic acids (Bibliography Io. 20). At Mesabi, 'graphite in considerable amounts associated with the magne- • * t i t e , and siderite, indicate the former presence of reduoing material which would convert the higher oxides of iron into -57- magnetite' (Bibliography No. 31). Oxidation by hematite solu- tions carrying copper and sulfur is presumed to have caused deposition of native copper rather than copper sulfides in parts of the Michigan Copper Deposits (Bibliography No. 38). Bleaching of hematite from the wall rock of ore zones attests the the participation of hematite in the reactions producing deposition. In summary, though hydrothermal hematite is commonly de- posited under hyp.othermal conditions,- i t has formed in. veins which appear to be mesothermal and epithermal, and in fumarole incrustations. The hematite is usually one of the f i r s t min- erals to be deposited from vein-forming solutions. Where hydrothermal hematite was formed after hydrothermal (or mag- matic) magnetite, an accompanying inorease in temperature has li k e l y occurred. Hematite is deposited under oxidizing con- ditions. If sulfur bearing, and thus reducing, solutions in contact-with hematite, the hematite tends to be replaced by magnetite, or i f the solutions are very rich in sulfur, pyrite or perhaps some other iron bearing sulfide. Abundant hematite thus should not occur with abundant sulfides becasue of.their chemioal incompatibility, and geologic evidence substantiates this theory. Thus the sulfides of Q-17 west vein, and the speoularite of Q-17 vein, could not be deposited from the same solution at the same time. Bo marked shearing of the quartz has taken place in either lens, thus reopening of the main 'break' by -58- continued movement after the formation of vein i s improbable. The mineralization of the two veins more li k e l y occurred at different times in the same general period of mineralization, that of Q-17 vein occurring f i r s t under oxidizing conditions and that of Q-17 west vein occurring later under reducing conditions. According to Schwartz (Bibliography No. 39, p. 371) the association of gold with specularite has no particular signi- ficance. He states 'A few examples of association of gold with specularite have been described. This occurrence does not seem significant except as an indication of f a i r l y high tem- perature of formation at an early stage i n formation of the veins'. Mineralogical Conclusions. In the galena-jayrite type of mineralization most of the gold is associated with three soft minerals which may be t e l l u r i t e s . These minerals ocour as individual grains and aggregations in the galena. Minor amounts of gold are present in and near fractures in the quartz. The gold particles are up to 50 microns long, but are mostly irregular and much narrower than this. In the specularite type of mineralization the gold occurs in disruptions between specularite 'cleavage' plates, and in minor amounts in and near fractures in the quartz. The gold particles are f a i r l y equidimensional, and up to f i f t y microns -59 in diameter. The granularity of the quartz, and the mineralogic assem- blage point to deposition under moderate temperature and pres- sure. Under Lindgfen's classification the veins would be mesothermal. The difference in mineralogy between Q-17 west vein and Q-17 vein is probably the result of deposition at different times during one general period of mineralization. The hema- tite of Q-17 vein was probably deposited f i r s t under oxidiz- ing conditions, and the sulfides of Q-17 west vein deposited later under reducing conditions. -60- GENERAL CONCLUSIONS The limestone of the Unuk Area is probably Permian, the sedimentary and volcanic rocks to the west of the limestone Pre-Permian, and those to the east Triassic and Jurassic (Hazelton). The host rock of the veins is a dynamo-thermal metamorph- osed water-lain dacite tuff, or andesite tuff containing detrital quartz. The veins do cut intrusive diorite gneiss, but diminish in both size and grade in the intrusive. The intrusive diorite has caused recrystallization of tuff on i t s contacts, forming paragneiss which is d i f f i c u l t to distinguish from the intrusive orthogneiss. L i t t l e or no skarn has developed in siliceous limestone beds near the intrusive diorite. Actinolite, tremolite, and dippside have formed, l i k e l y by metamorphism rather than metasomatism, in bands of a few millimeters' width rimming tuff fragments in limestone. Epidote is abundant in most andesitic and d i o r i t i c rocks, both intrusive and extrusive. The area has undergone regional metamorphism of medium grade. The quartz veins show a marked parallelism in attitude, striking 115 degrees, and dipping 80 degrees northeast, with the exception of Q-19 vein, which dips only twenty to forty degrees north-east. They have been intruded along 'breaks' caused by shearing forces. Mineralized faults, dyke-filled tension fractures, the vein 'breaks', folding, and regional -61- f o l i a t i o n can be f i t t e d i n t o a s t r a i n - e l l i p s o i d p a t t e r n which i n d i c a t e s the deforming pressure came from the southwest and/ or n o r t h e a s t . The source of t h i s pressure could be orogeny a s s o c i a t e d w i t h the coast range i n t r u s i v e s , or the l o c a l d i o r i t e gneiss s i l l s , but i s more l i k e l y the former. The most, prom-* . i s i n g v e i n s occur i n a band of sediments between two s i l l s , but the evidence i n d i c a t e s the v e i n - f o r m i n g f l u i d s were der i v e d from Ooast Range I n t r u s i v e s r a t h e r than the T r i a s s i c ( . ? ) s i l l s . The w a l l - r o c k a l t e r a t i o n produced by the v e i n - f o r m i n g f l u i d s has penetrated o n l y a few f e e t i n t o v e i n w a l l s . S e r i - o i t e , k a o l i n , c h l o r i t e , p y r i t e , a l b i t e , and quartz have formed by replacement and f r a c t u r e - f i l l i n g . . T h i s a l t e r a t i o n i s t y p i c a l of v e i n s of the mesothermal c l a s s . Quartz v e i n s are d i v i d e d i n t o three c l a s s e s on the b a s i s of t h e i r mineralogy. (1) C h a l c o p y r i t e , p y r i t e , magnetite ve i n s devoid of p r e c i o u s metals (2) Galena p y r i t e v e i n s w i t h minor s p h a l e r i t e , c h a l c o p y r i t e , three s o f t m i n e r a l s which may be t e l l u r i d e s , and g o l d . The gold occurs i n i r r e g u l a r v e i n - l e t s and s e g r e g a t i o n s , u s u a l l y a s s o c i a t e d w i t h one or more of the s o f t m i n e r a l s as i n c l u s i o n s i n galena; and as i n d i v i d u a l g r a i n s i n or near f r a c t u r e s i n the q u a r t z . (3) S p e o u l a r i t e v e i n s , c o n t a i n i n g l i t t l e or no s u l f i d e s . The gold occurs i n i r r e g u l a r i t i e s between s p e o u l a r i t e 'cleavage' f l a k e s , and i n or near f r a c t u r e s i n the q u a r t z . C l a s s e s (2) and (3) give good assays i n g o l d . -62 The gold grains in olass (2) are quite irregular, up to 50 microns long and about ten microns wide. Those in class (3) are more equidimensional, and up to 50 microns in dia- meter. Extraction of gold should not be d i f f i c u l t . Speoularite is deposited under oxidizing conditions, and thus cannot be deposited from the same fl u i d at the same time as sulfides, which require reducing conditions for deposition. No geologic evidence for two periods of mineralization was found, so the speoularite and sulfides are considered to be deposited at slightly different times, the speoularite f i r s t , in the one general period of mineralization. The metallic minerals in the veins are members of the mod- erate to high temperature type of mineralization. The quartz grains are f a i r l y coarse (several millimeters in diameter) thus not of the epithermal type. The lack of banding and other structures diagnostic of open^space deposition, except for a few vugs, indicate deposition at moderate pressure. Vein f i l l i n g , wall rock alteration, and the regularity and contin- uity of the 'breaks' a l l indicate a mesothermal deposit. The veins show good promise of continuing to depth. Theoretical sequence of events in the region i s (1) De- position of sediments - limestone, quartz siltstone, a r g i l l i t e , and tuff, in marine environment, at times practically simul- taneously, during late Palaeozoic time. (2) Uplift, erosion, and probably some t i l t i n g or slight folding during the Appal- achian Revolution. (3) Depression of the area, and continued -63- sedimentation of t u f f and probably minor limestone. I n t r u s - i o n o f d i o r i t e ' s i l l s ' , p r o b a b l y as separate bodies, perhaps causing some f o l d i n g i n the i n t r u d e d sediments d u r i n g T r i a s s i c time. (4) S l i g h t u p l i f t and d e p o s i t i o n of shallow water sediments as a r g i l l i t e , and v o l c a n i c s (Hazelton) d u r i n g J u r - a s s i c time, g i v i n g f a i r l y deep b u r i a l of the P a l a e o z o i c s e d i - ments. (5) I n t r u s i o n of the Coast Range composite b a t h o l i t h d u r i n g Jura-Cretaceous time, producing f u r t h e r f o l d i n g , r e g i o n a l metamorphism, f a u l t i n g , and u p l i f t of the bedded rocks, f o l l o w e d and accompanied by m i n e r a l i z a t i o n . (6) E r o - s i o n , i n p a r t by g l a o i a t i o n , t i l l today P a l a e o z o i c rocks are a g a i n exposed. BIBLIOGRAPHY No. 1. P.A.Kerr ...... "Preliminary Report on Iskut River Area» B.O,' G.S.C. Summ. Rept. 1929, Part A. 2. P.A. Kerr 'Preliminary Report on Stikine River Area,*. B.O.-' G.S.G. Summ. Rept. 1926, Part A. 3. P.A. Kerr....... 'Second Preliminary Report on Stikine River Area, B.C.' G.S.C, Summ. Rept. 1928, Part A. 4. A.P. Buddington and 0?. Chapin ...'Geology and Mineral Deposits of Southeastern Alaska' B u l l e - t i n 800, U.S.G.S. /929 5. G. Hanson....... 'Portland Canal Area, B r i t i s h Columbia' G.S.C. Mem. 175. /93S 6. P.A. Kerr....... 'Defining the Mineral Zones of Northern B r i t i s h Columbia' C.I.M.M. TRANS. Vol. 34, pp. 68 - 72. '93/ 7. P.A. Kerr. 'The Relationships of Mineral Deposits i n the Skeena River D i s t r i c t , B r i t i s h Columbia* Be. Geol. Vol. 33, No.4, pp. 428 - 439. '9*8 8. P.B. Wright..... 'The Unuk River Mining Region of B r i t i s h Columbia' G.S.C, Summ. Rept. 1905, pp. 46 - 53. BIBLIOGRAPHY (CONT'D) NO. 9. A.F. Buddington... 'Types of Mineralization and of Coast Range Intrusives', Eo. Geol. Vol. 22, •a. No. 2, pp. 158-179. / « 7 10. J i T . Mandy 'Unuk River Area', Annual Rept. of Minister of Mines, 1935. Pp. B 7- B 12. 11. J.T, Mandy........ 'Unuk River Seotion - Northwestern District No. 1',Annual Rept. of Min- ister of Mines, 1934. 12. L.V. Pirrson 'Microscopical Character of Volcanio Tuffs', American Journal of Science, 4th series, Vol. 40, 1915. pp. 191- . 211, 13. P.A. Kerr... 'Map 311A South Sheet, Stikine River Area, Cassiar District*, G.S.C., 1935. 14. Twenhofel........, 'Principles of Sedimentation*. 15. M.N. Short......,, 'Microscopic Determination of the Ore Minerals', U.S.G.S, Bull. 914. s*40 16, G.A. Ypung and W.L. Uglow...'The Iron Ores of Canada, Vol. 1, British Columbia and Yukon*, G,S,C. Ec. Geol. Series No. 3. /&6 17. S.J. Schofield.... 'The Ore Deposits of British Columbia*, Trans, Can. Inst. Min. and Met. Vol. 24, 1922. p. 86. BIBLIOGRAPHY (CONT'D) NO. 18. G.M. Dawson 'Preliminary Report on the Physical and Geological Features of the South- ern Portion of the Interior of Bri t - ish Columbia,' G.S.C, Rept. of Prog. 1877-78, p. 122B. 19. T.M, Broderiok 'Some of the Relations of Magnetite and Hematite', Be. Geol. Vol. 14, August, 1919. 20. Van Hise and Leith. 'The Geology of the Lake Superior Re- gion', U.S.G.S. Monograph No. 52./?// 21. A.L. Howland........ 'iSpecularite-alunite Mineralization at Hickey's Pond, Newfoundland', American Mineralogist, Vol. 25, 1940. P. 34. 22. Eldorado Mine Staff...'The Eldorado Enterprise', C.I,M.M, Bull. 413, Sept., 1946, p. 423. 23. B.S. Butler........ 'Some Relations between Oxygen Miner- als and Sulfur Minerals in Ore Depos- i t s ' , Ec. Geol. Vol. 22, No. 3, p.233. 24. H.A. Tableman and J.A. Potter... A.I.M.E. Bull. 146, p. 485. 25. W. Lindgren, 'Ore Deposition and Physical Condit- ions', Ec. Geol. Vol. 2, p. 105. /907 26. Editor, Ec. Geol... Editorial , Ec. Geol. Vol. 18, 1923, p. 695." BIBLIOGRAPHY (CONT'D) No. 27. G. Gilbert 'Significance of Hematite in Certain Ore Deposits', Ec.Geol. Vol. 22, No.6, p. 560. /927 28. W.V. Smitheringale.. 'Mineral Associations of the George Gold Copper Mine, Stewart, B.C.', Ec. Geol. Vol. 23, pp. 193. /s*8 29. G.M. Furnival...... 'The Large Quartz Veins of Great Bear Lake, Canada', Ec, Geol. Vol. 30, p. 843, SS3S- 30. D.P. Kidd and M.H. Haycook... 'Mineragraphy of the Ores of Great Bear Lake', G.S.A. Bull. Vol. 46, pp. 879-960. 31. J.W. Gruner,,.,... 'Paragenesis of Martite Ore Bodies and. Magnetite of the Mesabi Range*, Eo. Geol. Vol, 17, No. 1, p. 1. /92z 32. G, Gilbert........ 'Some Magnetite-Hematite Relations', Ec. Geol. Vol. 20, 1925, pp. 587-596. 33. Van Hise *A Treatise on Metamorphism', U,S,G.S. Monograph 47. /so* 34. Partington........ 'Textbook of Inorganic Chemistry*. 35. W.S. Burbank 'A Source of Heat Energy in the Cryst- al l i z a t i o n of Granodiorite Magma, and Some Related Problems of Vulcanismf, Am. Geophys, anion. 'Trans. 17th, 1936, p. 236. BIBLIOGRAPHY (CONT'D) No. 36. W. lindgren....,.. 'Metasomatic Processes in the Gold Deposits of Western Australia', Ec. Geol. Vol. 1, p. 530. /s?&s 37. F . B . Laney 'The Relation of Bprnite and Chaloo- cite in the Copper Ores of the Vir- gilina District of North Carolina and Virginia', Ec. Geol. Vol. 6, p. 399. 38. G.M. Schwartz,.... 'The' Host Minerals of Native Gold', Ec. Geol. Vol. 39, 1944. POLISHED.SECTION PHOTOGRAPHS NO. Micro- scope Oo. Obj. Mag. Time F i l t e r Niool Section No. 1. H.V.W. x8 l/7a 700 not 8 sec. dark blue(#2) crossed #1 2. it n i i 300 sec. none #10 3. it it it 10 sec. none #2 4, it 1! i i 15 sec. none #2 5. i i 6a 570 8 sec. dark blue(#2) " #1 6. n 3b 204 13 sec. none #15 7. i i 6a 570 10 sec. none #19 8, i i 3b 204 15 sec. light blue " #11 9. ti 3b 204 THIN 15 See. light blue " SECTION PHOTOGRAPHS #6 No. Micro- scope Oo. Obj . Mag. Time Light Niool Sectioi No. 1. Leitz 331223 x8 3B 80 600 sec. Lamp- box crossed Q-51 2. tt rt 32 25 15 sec* it not crossed Q-25 3 « ti n 3B 80 840 sec. i i not crossed Q-40 4. i i i i 32 25 17 sec. n not crossed Q-40 5. " rt 32 25 15 sec, n not crossed Q-22 6, n n 3B 80 840 sec. ti crossed Q-53 7. n i i 3B 80 600 see. n crossed Q-26 8. it i i 3B 80 600 sec. ti crossed Q-26 9. tt t i 32 25 60 sec. i i orossed Q-26 N A T I O N A L T O P O G R A P H I C SERIES S U R V E Y S A N D E N G I N E E R I N G B R A N C H HYDROGRAPHIC AND MAP SERVICE S H E E T 104 S.E W Aerial photography j ^ ^ j Contours (approximate) ^~30o0 Contours are shown at, 500, 1000,2000, 3000 4000 6000 and 8000feet above mean sea level ' Price 25 cents 132° 128° Index to adjacent sheets SHEET 104 S.E. / ) M i les L E G E N D R e c e n t l a v a f l o w s • U n c o n s o l i d a t e d d e p o s i t s ( S a n d a n d g r a v e l ) C o a s t R a n g e I n t r u s i v e s . g r a n i t e , g r a n o d i o r i t e , q u a r t z d i o r i t e , e t c I—-I M a i n l y s e d i m e n t s , a r g i 1 1 1 t e , s a n d s t o n e , q u a r t z i t e , s o m e t u f f g g g ] L i m e s t o n e vv-/i M a i n l y i g n e o u s r o c k s : Y'/t/A v o l c a n i c t u f f s a n d f l o w s , : some sediments n e d o x i r \yy\ B e d d i n g ( i n c l i n e d , v e r t i c a l ) \ ~ ~ \ G e o l o g i c a l b o u n d a r y ( d e f i n e d ) ( a p p r i m a t e ) T r a i l G l a c i e r C o n t o u r s (500 feet) D C D e p a r t m e n t o f M i n e s . 1 9 3 5 Geological Sketch-map of Unuk River Area. :.-'-V" CRACEV- SWANSEA CROUP UA/UK R/VER Ou/c~op hound'city /> e d d tne/ a/ft/tide g/?e/65/c hand/no- contour //ncs jjgjjj C/Uo.rf'z l/c/r/d ^Z7\* cfmAlP con-facts ttn 200 ft. L eyencl as <//////e j tp // cl/Or-/ he g-n e/ss mossrise greens/one 'cimprophyrc dyke Op/the dyke QNo\ /oc<jf/on of ^pectmcn "r i 0-0 0-33 • • — .40* ' ' (c- Q-53 v — • - \ ) s \ \ ,^0« 'i \ \ i — £ L

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