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A geological evaluation of the Cinola (specogna) gold deposit, Queen Charlotte Islands, B.C. Champigny, Normand 1981

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A G e o l o g i c a l E v a l u a t i o n of the C i n o l a (Specogna) Gold D e p o s i t , Queen C h a r l o t t e I s l a n d s , B.C. By Normand Champigny B.A.Sc, E c o l e P o l y t e c h n i q u e , 1979. t h e s i s submitted i n p a r t i a l f u l f i l l m e n t of the requirements f o r the degree of master of a p p l i e d s c i e n c e i n The F a c u l t y of Graduate Studi e s Department of G e o l o g i c a l Sciences We accept t h i s t h e s i s as conforming to the r e q u i r e d standard: The U n i v e r s i t y of B r i t i s h Columbia A p r i l 1981 © N o r m a n d Champigny, 1981 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e a n d s t u d y . I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e h e a d o f my d e p a r t m e n t o r by h i s o r h e r r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . D e p a r t m e n t o f /lMXJ^J/1/! The U n i v e r s i t y o f B r i t i s h C o l u m b i a 2075 W e s b r o o k P l a c e V a n c o u v e r , C a n a d a V6T 1W5 n r . I 9 / 7 C H F r o n t i s p i e c e - A r e a l view of the C i n o l a s i t e , l o o k i n g west. The d e p o s i t i s the s m a l l h i l l w i t h many c a t roads i n the foreground. In the background are r o l l i n g h i l l s of the Skidegate P l a t e a u , mainly formed of T e r t i a r y v o l c a n i c r o c k s . i ABSTRACT C i n o l a (Specogna) g o l d d e p o s i t i n the northern Queen C h a r l o t t e I s l a n d s , B r i t i s h Columbia, was f i r s t d i s c o v e r e d i n 1970. I t i s now at the f e a s i b i l i t y stage, with proven r e s e r v e s of 45.4 m i l l i o n s h o r t tons averaging 0.054 oz. Au/s.t. The de-p o s i t i s i n a c l a s t i c sequence c o n s i s t i n g of a lower shale u n i t (Haida Formation, Late Cretaceous) and an o v e r l y i n g conglomerate-sandstone sequence (Skonun Formation, Middle Miocene). Both sedimentary u n i t s are cut by a stock and dykes of r h y o l i t e - p o r p h y r y . Two K-Ar model ages i n d i c a t e m i n e r a l i z -a t i o n and probably r h y o l i t e - p o r p h y r y i n t r u s i o n at about 14 Ma (Middle Miocene). The model ages, together with p l a n t m i c r o f o s -s i l and fauna examination, r e v e a l e d a 17-15 Ma age f o r the f l u -v i a t i l e Skonun sequence, i n which the C i n o l a d e p o s i t o c c u r s . The d e p o s i t i s the f i r s t Canadian C a r l i n - t y p e d e p o s i t to be d e s c r i b e d i n d e t a i l . Gold m i n e r a l i z a t i o n i s widespread, and occurs as m i c r o n - s i z e p a r t i c l e s disseminated i n the sedimentary host rocks and i n quartz v e i n s . P y r i t e and marcasite are the main s u l p h i d e s , and a l t e r a t i o n type i s dominantly a r g i l l i c . The C i n o l a d e p o s i t r e s u l t e d from the development o f a l a r g e geothermal system, the energy f o r which d e r i v e d from the r h y o i i -t i c i n t r u s i o n . Ore f l u i d s o r i g i n a t e d from pore water i n the f l u v i a t i l e host rock, as i n d i c a t e d by f l u i d i n c l u s i o n s t u d i e s . Two temperature regimes centred on 160°C and 270°C e x i s t e d d u r i n g c i r c u l a t i o n of the ore f l u i d s . Depth of m i n e r a l i z a t i o n i i i s estimated between 1.1 and 1.8 km. A g e o s t a t i s t i c a l e v a l u a t i o n of geochemical data from C i n o l a shows t h a t Au, Ag, Hg, As, Sb, and W have syst e m a t i c d i s t r i b u -t i o n p a t t e r n s i n e i t h e r primary or secondary environments, and could be u s e f u l p a t h f i n d e r s f o r e x p l o r a t i o n f o r s i m i l a r types of g o l d d e p o s i t s . A g e o s t a t i s t i c a l study of assay data has shown the d e p o s i t to be p a r t i c u l a r l y amenable to reserve e s t i m a t i o n by k r i g i n g of s e l e c t i o n u n i t s . TABLE OF CONTENTS ABSTRACT I LIST OF TABLES i v LIST OF FIGURES v i i ACKNOWLEDGMENTS x i i . , CHAPTER 1: INTRODUCTION 1 CHAPTER I I : SPECOGNA GOLD DEPOSIT OF CONSOLIDATED CINOLA MINES LIMITED: AN EXAMPLE OF STRUCTURED PROPERTY EXPLORATION 5 CHAPTER I I I : CINOLA GOLD DEPOSIT, QUEEN CHARLOTTE ISLANDS, BRITISH COLUMBIA -A CANADIAN CARLIN-TYPE DEPOSIT 29 CHAPTER IV: FLUID INCLUSION AND SULPHUR ISOTOPE DATA IN RELATION TO GENESIS OF THE CINOLA GOLD DEPOSIT, QUEEN CHARLOTTE ISLANDS, B.C 84 CHAPTER V: NEW EVIDENCE FOR THE AGE OF THE SKONUN FORMATION, QUEEN CHARLOTTE ISLANDS, BRITISH COLUMBIA 104 CHAPTER VI: CINOLA GOLD DEPOSIT, QUEEN CHARLOTTE ISLANDS, B.C. -A GEOCHEMICAL CASE HISTORY 119 CHAPTER V I I : GEOSTATISTICAL STUDY OF THE CINOLA DEPOSIT, QUEEN CHARLOTTE ISLANDS, B.C 161 CHAPTER V I I I : CONCLUSIONS 190 LIST OF TABLES CHAPTER I I : Table 1. General s t r u c t u r e of an e x p l o r a t i o n program. Table 2. S t r u c t u r e of p r o p e r t y e x p l o r a t i o n program. Table 3. Summary of e x p l o r a t i o n h i s t o r y of Specogna g o l d depos-i t . T able 4. Approximate c o s t s i n c u r r e d d u r i n g e x p l o r a t i o n of the Specogna d e p o s i t . CHAPTER I I I : Table 1. Table of G e o l o g i c Formations, Queen C h a r l o t t e I s l a n d s . Table 2. L i t h o f a c i e s and Sedimentary S t r u c t u r e s Observed i n the Skonun Sediments of the C i n o l a Gold Deposit and other B r a i d e d River Systems. Table 3. A n a l y t i c a l Data and K/Ar model ages, C i n o l a g o l d de-p o s i t . Table 4. Opaque M i n e r a l s and T h e i r R e l a t i v e Abundance, C i n o l a Gold D e p o s i t . Trace amounts means l e s s than 0.1%. CHAPTER IV: Table 1. a 3 4 S of p y r i t e sulphur at the C i n o l a d e p o s i t . V CHAPTER VI: Table 1. Summary of means and standard d e v i a t i o n s f o r raw and log-transformed (base 10) l i t h o g e o c h e m i c a l data, C i n o l a d e p o s i t . Table 2. C o r r e l a t i o n matrix f o r log-transformed (base 10) l i -thogeochemical data, C i n o l a d e p o s i t . T a b l e 3. Means and standard d e v i a t i o n s determined g r a p h i c a l l y f o r p a r t i t i o n e d metal p o p u l a t i o n s of l i t h o g e o c h e m i c a l d a t a , C i n o l a d e p o s i t . Table 4. Summary o f means and standard d e v i a t i o n s f o r raw and log-transformed (base 10) s o i l geochemical data, C i n o l a d e p o s i t . Table 5. C o r r e l a t i o n matrix f o r log-transformed (base 10) s o i l geochemical data, C i n o l a d e p o s i t . Table 6. Means and standard d e v i a t i o n s determined g r a p h i c a l l y f o r p a r t i t i o n e d metal p o p u l a t i o n s o f s o i l geochemical d a t a , C i n o l a d e p o s i t . Table 7. Summary of means and standard d e v i a t i o n s f o r raw and log-transformed (base 10) s i l t geochemical data, C i n o l a d e p o s i t . Table 8. C o r r e l a t i o n matrix f o r log-transformed (base 10) s i l t geochemical data, C i n o l a d e p o s i t . Table 9. Means and standard d e v i a t i o n s determined g r a p h i c a l l y f o r p a r t i t i o n e d metal p o p u l a t i o n s of s i l t geochemi-c a l d ata, C i n o l a d e p o s i t . CHAPTER V I I : Table 1. Data types used f o r g e o s t a t i s t i c a l e v a l u a t i o n o f the C i n o l a gold d e p o s i t . Table 2. Summary o f r e g u l a r i z e d s p h e r i c a l models c a l c u l a t e d f o r down-hole assay data of " u n a l t e r e d " and " a l t e r e d " d r i l l h o l e samples and h o r i z o n t a l data o f " u n a l t e r e d " bench composites, C i n o l a d e p o s i t . Table 3. Summary of p o i n t s p h e r i c a l model c a l c u l a t e d for down-hole data of " u n a l t e r e d " d r i l l hole samples, C i n o l a d e p o s i t . Table 4. Summary of p o i n t s p h e r i c a l model f o r h o r i z o n t a l data of " u n a l t e r e d " bench composites, C i n o l a d e p o s i t . V l l LIST OF FIGURES CHAPTER I I : F i g u r e 1. L o c a t i o n of Specogna g o l d d e p o s i t F i g u r e 2. Approximate v a r i a t i o n s i n p r i c e of gold per t r o y ounce (U.S. d o l l a r s ) to pres e n t . F i g u r e 3. S e q u e n t i a l o p t i o n agreements r e l a t i n g to the Specogna d e p o s i t , and shown as a f u n c t i o n of our estimates of the stage of e x p l o r a t i o n . F i g u r e 4. A r b i t r a r y r e l a t i v e i n f o r m a t i o n measures to q u a n t i f y i n f o r m a t i o n during s u c c e s s i v e years of e x p l o r a t i o n , Specogna d e p o s i t . CHAPTER I I I : F i g u r e 1. L o c a t i o n map of the C i n o l a g o l d d e p o s i t , Queen C h a r l o t t e I s l a n d s , B.C. F i g u r e 2. Regional geology, C i n o l a g o l d d e p o s i t ( a f t e r S u t h e r l a n d Brown, 1968). F i g u r e 3. Pr o p e r t y geology, C i n o l a g o l d d e p o s i t . F i g u r e 4. C r o s s - s e c t i o n AA'. v i i i F i g u r e 5. C r o s s - s e c t i o n BB 1. F i g u r e 6. G o l d - s i l v e r s c a t t e r diagram for "low grade" assays from d r i l l c o re, based l a r g e l y on 2 m core l e n g t h s . F i g u r e 7. G o l d - s i l v e r s c a t t e r diagram for "high grade" assays (higher than 0.4 oz. Au/ton) based on 2 m core l e n g t h s . F i g u r e 8. Graphic l o g of diamond d r i l l hole 78-6. F i g u r e 9. P a r a g e n e t i c l i n e diagram for the C i n o l a g o l d d e p o s i t opaque m i n e r a l s . F i g u r e 10. C r o s s - s e c t i o n showing d i s t r i b u t i o n of a l t e r a t i o n m i n e r a ls of the C i n o l a gold d e p o s i t . F i g u r e 11. Schematic sequence i n development of the C i n o l a gold d e p o s i t . CHAPTER IV: F i g u r e 1. Histogram of f i l l i n g temperatures of f l u i d i n c l u -s i o ns i n quartz and c a l c i t e , C i n o l a d e p o s i t . F i g u r e 2. Histogram of f r e e z i n g temperatures of f l u i d i n c l u -s i o ns i n quartz and c a l c i t e , C i n o l a d e p o s i t . i x CHAPTER V: F i g u r e 1. Map showing the area u n d e r l a i n by the Skonun Formation (clashed l i n e ) and l o c a t i o n o f the C i n o l a d e p o s i t . CHAPTER VI: Fi g u r e 1. L o c a t i o n map of the C i n o l a g o l d d e p o s i t . F i g u r e 2. P r o c e d u r a l path i n e v a l u a t i n g C i n o l a geochemical data. F i g u r e 3. Most s i g n i f i c a n t c o r r e l a t i o n s (at the 0.01 l e v e l ) of l o g a r i t h m i c a l l y transformed (base 10) ii t h o g e o c n e m i -c a l d a t a . F i g u r e 4. Lognormal p r o b a b i l i t y p l o t f o r Sb l i t h o g e o c h e m i c a l data p a r t i t i o n e d i n t o upper (A) and lower (B) popu-l a t i o n s . F i g u r e 5. Lognormal p r o b a b i l i t y p l o t f o r Au l i t h o g e o c h e m i c a l data p a r t i t i o n e d i n t o upper (A), median ( A 1 ) , and lower (B) p o p u l a t i o n s . F i g u r e 6. Au (ppm x 100) i n rock. F i g u r e 7. Ag (ppm x 10) i n rock. F i g u r e 8. Hg i n rock (ppb). F i g u r e 9. Sb i n rock (ppb). F i g u r e 10. W i n rock (ppb). F i g u r e 11. P r o b a b i l i t y p l o t f o r Cu i n s o i l s , p a r t i t i o n e d i n t o upper (A) and lower (B) p o p u l a t i o n s . F i g u r e 12. Au (ppm x 100) i n s o i l . F i g u r e 13. Hg i n B h o r i z o n (ppb). F i g u r e 14. Hg i n peat (A horizon) (ppb). F i g u r e 15. Cu i n s o i l (ppm). Fi g u r e 16. P r o b a b i l i t y p l o t f o r Ag i n s i l t s , p a r t i t i o n e d i n t o upper (A) and lower (B) p o p u l a t i o n s . CHAPTER V I I : F i g u r e 1. L o c a t i o n map of the C i n o l a d e p o s i t . F i g u r e 2. G e o l o g i c a l c r o s s - s e c t i o n of the C i n o l a d e p o s i t . F i g u r e 3. P r o b a b i l i t y p l o t f o r g o l d assays of 2 m samples from BX core. x i F i g u r e 4. T h r e s h o l d values versus core sample l e n g t h . F i g u r e 5. Average experimental down-hole semi-variograms (dashed l i n e s ) , r e g u l a r i z e d s p h e r i c a l model ( f u l l l i n e ) , curves for " u n a l t e r e d " and " a l t e r e d " data s e t s , and s p h e r i c a l p o i n t model curve f o r " u n a l t e r e d " data ( d o t s ) . F i g u r e 6. L o c a t i o n s of d r i l l hole c o l l a r s on the C i n o l a depos-i t . F i g u r e 7. Average experimental h o r i z o n t a l semi-variogram (dashed l i n e s ) f o r a l l " u n a l t e r e d " d r i l l hole sam-p l e s , based on 10 m bench composites. F i g u r e 8. Kr i g e d block mean grades f o r 30 x 30 x 10 m blocks at the 110 m l e v e l . ACKNOWLEDGMENTS S p e c i a l thanks are extended to Dr. A.J. S i n c l a i r f o r pro-v i d i n g guidance and encouragement throughout t h i s study. The author a p p r e c i a t e s the f i n a n c i a l support and t e c h n i c a l a s s i s t -ance of C o n s o l i d a t e d C i n o l a Mines L t d . , i n p a r t i c u l a r , t h at of K.G. Sanders, P r e s i d e n t , G. Sanders, V i c e - P r e s i d e n t , S. Lacey and D. Bai n , s t a f f g e o l o g i s t s , and A. M a c K i l l o p , camp manager. T h i s study was a l s o funded i n p a r t by a Canadian N a t u r a l and En g i n e e r i n g Science C o u n c i l s c h o l a r s h i p and a grant from B.C. M i n i s t r y of Energy, Mines, and Petroleum Resources. Thanks are due to M.G. Cruson, c o n s u l t i n g g e o l o g i s t , f o r numerous d i s c u s s i o n s on the genesis of the C i n o l a d e p o s i t . Asger Bentzen provided e x t e n s i v e a s s i s t a n c e i n o b t a i n i n g compu-ter output f o r the g e o s t a t i s t i c a l study. His he l p was g r e a t l y a p p r e c i a t e d . C h a r l e s Henderson completed the f o s s i l i d e n t i f i c a -t i o n and Dr. G.E. Rouse (U.B.C.) conducted the p a l y n o l o g i c a l a n a l y s i s . F l u i d i n c l u s i o n measurements were done by Shen Kun. The d e t a i l and accuracy o f h i s work i s g r a t e f u l l y acknowledged. Model ages were c a l c u l a t e d by J.E. H a r a k a l . Most of the drawings were executed by John Newlands (U.B.C). Thanks to Jan Ashdown, who typed the i n d i v i d u a l papers. The tremendous e f f o r t put f o r t h by Roberta Crosby to type the f i n a l manuscript i s g r e a t l y a p p r e c i a t e d . John Gardiner provided t e c h n i c a l a s s i s t -ance i n the f i e l d . A s p e c i a l mention goes to N i c o l e B a r c e l o s f o r her p e r s o n a l encouragement. 1 CHAPTER 1 I n t r o d u c t i o n 2 C i n o l a (Specogna) g o l d d e p o s i t i s l o c a t e d at l o n g i t u d e 132°13'W, l a t i t u d e 53°32'N i n c e n t r a l Graham I s l a n d , the nor-thernmost of the Queen C h a r l o t t e I s l a n d s , B.C. The d e p o s i t was d i s c o v e r e d i n 1970, but i t was not the f i r s t time that g o l d was found i n the Queen C h a r l o t t e I s l a n d s . The f i r s t few ounces of gold produced by a lode mine i n B r i t i s h Columbia were from the E a r l y B i r d Mine on M i t c h e l l I n l e t i n 1852. Gold occurrences on the i s l a n d s were a l l found by p r o s p e c t i n g . T h i s shows the pro-nounced e f f e c t of p h y s i o g r a p h i c f e a t u r e s such as e l e v a t i o n and v e g e t a t i o n on e x p l o r a t i o n methods. The d e p o s i t went through s e v e r a l e x p l o r a t i o n stages dur i n g the e a r l y 1970's. F e a s i b i l i t y stage was reached i n 1979 by the present o p e r a t o r , C o n s o l i d a t e d C i n o l a Mines L t d . Up to then no r i g o r o u s g e o l o g i c a l e v a l u a t i o n had been done, and there was very l i t t l e understanding of p o s s i b l e ore c o n t r o l s of t h i s high ton-nage - low grade gold d e p o s i t . The f i r s t step of a complete e v a l u a t i o n of the C i n o l a de-p o s i t , which i s a c o l l e c t i o n of f i e l d d ata, was undertaken by the w r i t e r d u r i n g the summer of 1979. D e t a i l e d d r i l l core exam-i n a t i o n and s u r f a c e mapping were completed and new i n f o r m a t i o n was checked on s e v e r a l subsequent v i s i t s to the p r o p e r t y . T h i s t h e s i s i s o r g a n i z e d i n the form of a s e r i e s of papers that are an outgrowth of the w r i t e r ' s f i e l d work. The papers are a r -ranged i n a l o g i c a l sequence, and each one forms a subsequent chapter i n t h i s t h e s i s . A b r i e f d e s c r i p t i o n of each f o l l o w s . 3 Chapter Two shows the s t r u c t u r e d p r o g r e s s i o n of e x p l o r a t i o n of t h i s m i n e r a l d e p o s i t s i n c e d i s c o v e r y , and i s an attempt to q u a n t i f y p r o g r e s s i v e e x p l o r a t i o n of the p r o p e r t y . A r i g o r o u s g e o l o g i c a l d e s c r i p t i o n of the s e t t i n g of the C i n o l a d e p o s i t i s given i n Chapter Three. In the c o n c l u d i n g p a r t of that chapter a g e n e t i c model i s proposed. In Chapter Four a d d i t i o n a l support to the proposed g e n e t i c model i s given from f l u i d i n c l u s i o n s and sulphur isotope data. K-Ar data combined with p a l y n o l o g i c a l and p a l e o n t o l o g i c a l data from the Skonun Formation, which hosts the C i n o l a d e p o s i t , r e s u l t e d i n a r e v i s i o n of the age of t h i s rock u n i t . Chapter F i v e d e t a i l s t h i s age r e v i s i o n . Chapters S i x and Seven are devoted to a s t a t i s t i c a l analy-s i s of e x p l o r a t i o n data. In Chapter S i x rock, s o i l , and s i l t geochemical data from surveys undertaken i n the e a r l y develop-ment of the d e p o s i t are r e - e v a l u a t e d using s t a t i s t i c a l methods. A formal g e o s t a t i s t i c a l approach to ore reserve e s t i m a t i o n i s d e s c r i b e d i n Chapter Seven. The t o t a l amount of d r i l l hole assays were made a v a i l a b l e to the w r i t e r to do g e o s t a t i s t i c a l e s t i m a t i o n s , i n c l u d i n g (1) data e v a l u a t i o n , (2) g e n e r a t i o n of experimental semi-variograms, (3) development of semi-variogram models, and (4) k r i g i n g . G e o l o g i c a l parameters were a l s o taken i n t o account i n t h i s study. 4 General c o n c l u s i o n s are summarized i n Chapter E i g h t . 5 CHAPTER I I S p e c o g n a G o l d D e p o s i t o f C o n s o l i d a t e d C i n o l a M i n e s L i m i t e d : An E x a m p l e o f S t r u c t u r e d P r o p e r t y E x p l o r a t i o n 6 ABSTRACT Specogna g o l d d e p o s i t of C o n s o l i d a t e d C i n o l a Mines L t d . has generated widespread i n t e r e s t s i n c e s h o r t l y a f t e r i t s d i s c o v e r y i n 1980, when i t was d e s c r i b e d as being o f the " C a r l i n - t y p e " , and t h e r e f o r e was thought to have p o t e n t i a l f o r a l a r g e tonnage low grade d e p o s i t . E x p l o r a t i o n s i n c e d i s c o v e r y has been on-going, and has f o l l o w e d a l o g i c a l s t r u c t u r e d p r o g r e s s i o n , with e a r l y emphasis on s u r f i c i a l measurement techniques and l a t e r dominance of subsurface probing by d r i l l i n g . P r o p e r t y e x p l o r a -t i o n phases i n c l u d e : (1) d i s c o v e r y , (2) p r e l i m i n a r y s u r f a c e e v a l u a t i o n , (3)' d e t a i l e d s u r f a c e e v a l u a t i o n , (4) d i r e c t subsur-face e x p l o r a t i o n , and (5) f e a s i b i l i t y . Specogna i s p r e s e n t l y i n the f e a s i b i l i t y phase, and has yet to a t t a i n the development (6) and p r o d u c t i o n (7) phases of e x p l o r a t i o n . The importance of va r i o u s e x p l o r a t i o n methods, with time, can be monitored by a v a r i e t y o f e m p i r i c a l measures of " r e l a t i v e i n f o r m a t i o n g a i n " , the most obvious of which i s t o t a l d r i l l i n g per u n i t time. 7 INTRODUCTION Undiscovered ore d e p o s i t s are hidden resources that common-l y elude a l l but the most thorough search. Even when a m i n e r a l occurrence i s known, a c o n s i d e r a b l e amount of u n c e r t a i n t y clouds an a p p r e c i a t i o n of i t s u l t i m a t e worth. A comprehensive e x p l o r a t i o n program can be d i v i d e d i n t o an o r d e r l y framework of stages, as i l l u s t r a t e d i n Table 1 (Fortesque, 1965). T h i s c l a s s i f i c a t i o n i s somewhat i d e a l i z e d , and assumes a f a r - r e a c h i n g e x p l o r a t i o n program based on substan-t i a l f i n a n c i a l r e s o u r c e s , a s i t u a t i o n that does not always pre-v a i l . N e v e r t h e l e s s , such a scheme i s a u s e f u l conceptual frame-work for c o n s i d e r i n g e x p l o r a t i o n f o r m i n e r a l d e p o s i t s . The un-d e r l y i n g p r i n c i p l e of t h i s i d e a l o u t l i n e i s t h a t , as the s c a l e of examination changes p r o g r e s s i v e l y from g e n e r a l to s p e c i f i c , more and more d e t a i l e d i n f o r m a t i o n i s o b t a i n e d by which t a r g e t s become b e t t e r l o c a l i z e d . In c o n s i d e r i n g a p a r t i c u l a r m i n e r a l p r o p e r t y , however, the framework of Table 1 does not provide a r e a l i s t i c or comprehen-s i v e a p p r e c i a t i o n of the d e t a i l e d and p r o g r e s s i v e nature of ex-p l o r a t i o n , and a more d e t a i l e d sequence of s u b d i v i s i o n s i s war-ran t e d . I t i s o f t e n s a i d tha "mines are made, not found", an e x p r e s s i o n t h a t must not be taken too l i t e r a l l y , but one t h a t emphasizes the e x t r a o r d i n a r y i n s i g h t , c o s t , and e f f o r t g e n e r a l l y i n v o l v e d i n d e f i n i n g an ore body f o r the purpose of e x p l o r a t i o n . 8 There i s l i t t l e q u e s t i o n that the o p t i m a l e x p l o r a t i o n of any m i n e r a l p r o p e r t y i s unique i n d e t a i l , but j u s t as unique o r i g i n s f o r m i n e r a l d e p o s i t s can be grouped i n t o a few p r i n c i p a l c a t e g o r i e s , so can s e q u e n t i a l e x p l o r a t i o n . E a r l y stages i n the e x p l o r a t i o n of many m i n e r a l p r o p e r t i e s depend mainly on the ap-p l i c a t i o n of s u r f i c i a l e v a l u a t i o n techniques; that i s , those methods that are l i m i t e d to d i r e c t o b s e r v a t i o n of s u r f i c i a l ma-t e r i a l or i n d i r e c t measurements of the s u b s u r f a c e . In c o n t r a s t , more advanced stages of an e x p l o r a t i o n program on a p r o p e r t y commonly emphasize subsurface methods that provide d i r e c t obser-v a t i o n s of subsurface m a t e r i a l . T h i s o r d e r l y sequence d e r i v e s mainly from the f a c t that s u r f i c i a l e x p l o r a t i o n methods pr o v i d e r a p i d and cheap i n f o r m a t i o n r e l a t i v e to subsurface methods of i n v e s t i g a t i o n . Thus, i n a staged e x p l o r a t i o n program, s u r f a c e methods serve to c l a r i f y the p r e c i s e c h a r a c t e r of a p o t e n t i a l t a r g e t such that the more c o s t l y subsurface i n v e s t i g a t i o n can be o r g a n i z e d i n an o p t i m a l manner. Of course, i n p r a c t i c e there i s o v e r l a p - l i m i t e d d r i l l i n g may be done e a r l y i n an e x p l o r a t i o n p r o j e c t , or some aspects of s u r f a c e work may be done l a t e i n the program. In other cases, one can imagine that a p a r t i c u l a r l e v e l of e x p l o r a t i o n , dominant i n the e v a l u a t i o n of one p r o p e r t y , might be of n e g l i g i b l e importance i n e v a l u a t i n g another. For example, s u r f a c e e x p l o r a t i o n procedures might be extremely important i n e x p l o r i n g a d e p o s i t that crops out a s u r f a c e , but such t e c h n i -ques may be unnecessary i n e x p l o r i n g a deeply b u r i e d d e p o s i t l o c a t e d from e x i s t i n g underground workings. Despite these problems, the concept of staged e x p l o r a t i o n at the p r o p e r t y l e v e l i s a u s e f u l means by which to plan and d e s c r i b e ongoing e x p l o r a t i o n . Three important l e v e l s serve as b a s i s f o r d i s c u s s i o n : v i z . , s u r f a c e e x p l o r a t i o n , subsurface ex-p l o r a t i o n , and g e n e r a l ongoing e x p l o r a t i o n during e x p l o i t a t i o n . From t h i s p o i n t of view, these can be viewed as a p r o g r e s s i o n from youth to m a t u r i t y , and e v e n t u a l l y to o l d age. A d e t a i l e d documentation of these stages of p r o p e r t y e x p l o r a t i o n i s given i n Table 2. 10 Table I GENERAL STRUCTURE OF AN EXPLORATION PROGRAM STAGE I: STAGE I I : STAGE I I I (modified from Fortesque, 1965) Regional P l a n : General concept of an e x p l o r a t i o n program evolves and t a r g e t areas f o r e x p l o r a t i o n o u t l i n e d . D e f i n i t i o n o f O b j e c t i v e s : A d e t a i l e d approach to an e x p l o r a t i o n p r o j e c t i s designed with a s p e c i f i c ob-j e c t i v e to each p a r t of the p r o j e c t . D e t a i l e d P r o j e c t : T h i s stage of an e x p l o r a t i o n pro-gram i n v o l v e s a p p l i c a t i o n of s p e c i f i c methods to the t a r g e t area and commonly i n v o l v e s three p r i n c i p a l l e v e l s of e x p l o r a t i o n . (a) Regional L e v e l : A broad examination of a r e -g i o n a l t a r g e t area s e l e c t e d i n STAGE I. Purpose i s to d e f i n e sub-areas or l o c a l t a r g e t s that appear to be anomalous o r , i n other words, appear to have a r e l a t i v e l y high m i n e r a l content compared with the r e s t of the r e g i o n a l t a r g e t a r e a . Followup L e v e l : L o c a l t a r g e t areas are ev a l u a -ted by a v a r i e t y of e x p l o r a t i o n methods to i s o l a t e those with g r e a t e s t p o t e n t i a l f o r the occurrence of min e r a l d e p o s i t s . D e t a i l e d L e v e l : E x p l o r a t i o n i s designed to t e s t (b) (c) high p r i o r i t y l o c a l t a r g e t s f o r the presence of m i n e r a l d e p o s i t s with economic p o t e n t i a l . STAGE IV: Development E x p l o r a t i o n : D e t a i l e d e x p l o r a t i o n to prov i d e a thorough i n f o r m a t i o n base f o r e v a l u a t i n g the f e a s i b i l i t y o f m i n e r a l p r o d u c t i o n at a p r o f i t . In p r a c t i c e i t may be d i f f i c u l t to a s c e r t a i n where STAGE I I I ends and STAGE IV begins. Note: Ground a c q u i s i t i o n by c l a i m s t a k i n g , purchase, o p t i o n agreement, or other method i s normally i n i t i a t e d p r i o r to or e a r l y i n Stage I I I , but may continue i n t e r m i t t e n t -l y as i n f o r m a t i o n i s obtained from an e x p l o r a t i o n program. 11 Table 2 STRUCTURE OF PROPERTY EXPLORATION PROGRAM PHASE OF EXPLORATION 1. D i s c o v e r y 2. P r e l i m i n a r y s u r f a c e e v a l u a t i o n 3. D e t a i l e d s u r f a c e e v a l u a t i o n 4. Subsurface e v a l u a t i o n 5. F e a s i b i l i t y GENERAL DESCRIPTION OF WORK Di s c o v e r y may r e s u l t from a staged ex-p l o r a t i o n program, p r o s p e c t i n g , w i l d c a t i n v e s t i g a t i o n s , or a c c i d e n t . T h i s stage i n c l u d e s i n i t i a l ground c o n t r o l by s t a -k i n g , o p t i o n , e t c . L i m i t e d s u r f i c i a l examination, i n c l u d -ing c onceptual g e o l o g i c a l a p p r a i s a l , l i m i t e d geochemical and/or g e o p h y s i c a l responses are measured, sampling f o r assay and m i n e r a l o g i c a l s t u d i e s , l i m i t e d t e s t p i t s , and s t r i p p i n g . T h i s i s the i n i t i a l r a p i d a p p r a i s a l or " s c o u t i n g " stage of many major companies. T h i s stage g e n e r a l l y begins with the l a y i n g out of a r e g u l a r g r i d on areas of i n t e r e s t , to serve as a ase f o r de-t a i l e d geochemical and g e o p h y s i c a l surveys and g e o l o g i c a l mapping. L i m i t e d s t r i p p i n g , t r e n c h i n g , and d r i l l i n g are common at t h i s stage, as a guide to de-velopment of g e o l o g i c a l t h e o r i e s . Systematic sampling. Subsurface e v a l u a t i o n i n v o l v e s v a r i o u s types of d r i l l i n g , g e n e r a l l y i n a more-or-less sys t e m a t i c manner, and i n i -t i a l l y with a r e l a t i v e l y wide spacing of h o l e s . Other methods, such as s i n k i n g e x p l o r a t o r y s h a f t s or d e c l i n e s and d r i -v i n g a d i t s and other workings, are l e s s common now than i n the pas t . The f e a s i b i l i t y l e v e l begins when a conscious d e c i s i o n i s made to mount a d e t a i l e d program to examine the p o s s i b i -l i t y of ec o n o m i c a l l y v i a b l e p r o d u c t i o n . E x p l o r a t i o n at t h i s stage i n v o l v e s d e l i -m i t i n g a m i n e r a l d e p o s i t i n some d e t a i l by an ex t e n s i v e r e g u l a r g r i d o f d r i l l h o l e s , bulk sampling procedures, and p i l o t p l a n t m i l l i n g t e s t s . S e v e r a l stages of f e a s i b i l i t y s t u d i e s may be i n v o l v e d , and w i l l i n c l u d e a thorough e v a l u a t i o n of ore grade and tonnage. 6. Development Normally r e p r e s e n t s a h a l t i n e x p l o r -a t i o n e f f o r t s while the d e p o s i t i s pre-12 pared f o r p r o d u c t i o n . 7. Production An on-going e x p l o r a t i o n program i s com-mon du r i n g the p r o d u c t i v e l i f e o f a min-e r a l p r o p e r t y . Here both s u r f a c e and subsurface techniques are used as needs a r i s e . Work can be focussed on exten-d i n g l i m i t s o f known ore bodies or sea r c h i n g f o r new d i s c r e t e ore zones. 13 Table 3 SUMMARY OF EXPLORATION HISTORY OF SPECOGNA GOLD DEPOSIT Year ( D e s c r i p t i o n ) iy70 D i s c o v e r y i n e a r l y 1SJ70 by E. Specogna and J . T r i c o . 17 claims (BABE group) l o c a t e d and recorded i n March 1970. Optioned to Kennco L t d . i n December 1970. 1971 P r o p e r t y optioned by Kennco L t d . Twenty-seven claims and seven f r a c t i o n s added to o r i g i n a l group. Four bulk samples (23 kg each) taken and assayed f o r Cu, Mo, Zn, Pb, N i , Co, Au, Hg, Ag, As, and Sb. F i f t e e n hundred s o i l samples c o l l e c t e d at 60 m i n t e r v a l s on c l a i m boun-d a r i e s . A - horizon samples analyzed f o r Hg and B-horizon fo r Cu, Mo, Zn, Pb, N i , Co, Au, Hg, and Ag. Large Hg and Au anomalies l o c a t e d . Two packsack holes d r i l l e d (56 m), and core assayed f o r Au, Ag, and Hg. P r o p e r t y dropped at the end of 1971. 1972 Canex A e r i a l E x p l o r a t i o n i n v e s t i g a t e d p r o p e r t y from January to May 1972 and conducted l i m i t e d s o i l sampling (125 samples), with a n a l y s i s f o r Au and Ag. Cominco L t . took over i n the summer of iy72. 6960 m of l i n e were cut; 105 s o i l samples were analyzed for Au. A i r photo i n t e r p r e t a t i o n r e v e a l i n g the F o o t w a l l f a u l t . 26 trenches and 502 m of diamond d r i l l i n g (9 v e r t i c a l h o l e s ) . Ore p i c t u r e was 20 to 40 m i l l i o n tons of .035 oz Au/ton. P r o p e r t y dropped at the end of 1972. 1973 S i l v e r Standard Mines L t d . optioned the p r o p e r t y . Very l i m i t e d amount of s u r f a c e work was done. A d d i t i o n a l ground was staked. Marino Specogna found new showing with v i s i b l e g o l d . A s i x - t o n sample assayed from 2.7 to 16.5 oz Au/ton and 1.5 to 6.7 oz Ag/ton. 1974 Quintana M i n e r a l s Corp. assumed 90% of S i l v e r Standard o p t i o n c o n t r a c t on May 1, 1974. Two nundred and e i g h t y -one 1.5 m c h i p samples weighing from 9 to 14 kg each taken from a c l i f f face .57 m of pack sack d r i l l i n g (4 holes) and 604 m (18 d r i l l holes) of p e r c u s s i o n d r i l l i n g were performed. Core assayed f o r Au. Ore r e s e r v e s were e s t a b l i s h e d at 13 m.t. of .046 oz Au/ton, with a cut o f f of .025 oz Au/ton. E x t e n s i v e nature of the m i n e r a l i z -a t i o n v e r i f i e d . 1975 Quintana M i n e r a l s Corp. d r i l l e d 5 diamond holes (720 m, BQ s i z e ) . S t a k i n g of 34 a d d i t i o n a l u n i t s . Two metal-l u r g i c a l t e s t s were conducted. Assay d i s c r e p a n c i e s round i n assays of Quintana and a l s o p r e v i o u s assays by Kennco. Unacceptable g o l d r e c o v e r i e s (50%) and p o l i t i -c a l c l i m a t e f o r c e d the company to drop the p r o s p e c t . Ore r e s e r v e s gave 13.8 m.t. at .058 oz Au/ton using a .03 oz/ton c u t o f f and a depth of 30 m. 14 1976 No r e p o r t e d work. 1977 C o n s o l i d a t e d C i n o l a Mines L t d . optioned the p r o p e r t y from E. Specogna (44 f u l l c l a i m s and 7 f r a c t i o n s ) . D r i l l i n g s t a r t e d i n J u l y , using a 30 x 30 m g r i d . 697 m of diamond d r i l l i n g (13 v e r t i c a l holes) with BQ c o r e . Core assayed f o r g o l d and p a r t f o r s i l v e r . iy78 E i g h t v e r t i c a l h oles t o t a l l i n g 1253 m were d r i l l e d f o l -lowing a 40 m g r i d . Bottom of 78-6 hole assayed 0.86 oz/ton and re-assayed 1.15 oz Au/ton, with 0.43 Ag oz/ton over an i n t e r v a l of 24 m. T h i s changed the p i c -ture as to m i n e r a l p o t e n t i a l of the d e p o s i t . A g r e s s i v e d r i l l i n g program was proposed f o r the next year. C i n o l a purchased the claims at the end o f 1978. 1979 From January to August, 3041 m of diamond d r i l l i n g (15 holes using BQ and NQ s i z e ) were performed by C i n o l a . D r i l l i n g extended the m i n e r a l i z a t i o n down depth (up to 315 m). Core assayed f o r gold and some f o r s i l v e r . S t a r t of j o i n t venture with Energy Reserves Group i n August ±979. From August to end of year, 5127 m of d i a -mond d r i l l i n g completed (33 h o l e s ) . I n i t i a l m e t a l l u r g i c a l t e s t i n g completed. 1980 F i r s t quarter diamond d r i l l i n g of 32 holes t o t a l l e d 3544 m. A d d i t i o n a l 10,000 m of d r i l l i n g planed, as i s under-ground examination, bulk sampling, and a p i l o t m i l l program to process 10,000 s h o r t tons. I n d i c a t e d r e -serves f o r the southern p a r t of the m i n e r a l i z e d system are 28.6 m.t., averaging 0.064 oz Au/ton. 15 SPECOGNA (BABE) DEPOSIT Specogna d e p o s i t of C o n s o l i d a t e d C i n o l a Mines L t d . i s an i n t e r e s t i n g example to examine as an e x p l o r a t i o n case h i s t o r y , because i t was d i s c o v e r e d r e l a t i v e l y r e c e n t l y , and i n f o r m a t i o n concerning s e q u e n t i a l e x p l o r a t i o n i s r e a d i l y a v a i l a b l e . The p r o p e r t y i s c e n t r a l l y l o c a t e d on Graham I s l a n d , the northern of the two l a r g e s t Queen C h a r l o t t e I s l a n d s (Figure 1), and i s ac-c e s s i b l e by about 18 km of good q u a l i t y l o g g i n g road south from the town o f Port Clements. The o r i g i n a l showing, a p r o s p e c t i n g d i s c o v e r y by E. Specogna and J . T r i c o , was staked i n 1970 and subsequently was optioned s u c c e s s i v e l y to s e v e r a l major e x p l o r a t i o n com-panies. I n t e r e s t was maintained i n the snowing because of an ex t e n s i v e s i l i c i f i e d zone c a r r y i n g low g o l d v a l u e s , and e x p l o r a -t i o n d e c i s i o n s d u r i n g the decade the p r o p e r t y has been examined have been a f f e c t e d by the dramatic v a r i a t i o n s i n the p r i c e of gold (Figure 2). E x p l o r a t i o n methodology has been guided by p h y s i o g r a p h i c f e a t u r e s such as e l e v a t i o n , overburden, and v e g e t a t i o n cover. Specogna p r o p e r t y l i e s i n the border zone between the r e l a t i v e l y low and f l a t Queen C h a r l o t t e Lowlands to the east and the h i g h -e r , more rugged Skidegate P l a t e a u to the west. These two phy-s i o g r a p h i c p r o v i n c e s are separated by a major n o r t h w e s t e r l y t r e n d i n g f a u l t zone, the Sandspit F a u l t , of r e g i o n a l e x t e n t , that u n d e r l i e s much of the p r o p e r t y . A major s p l a y of t h i s 16"' f a u l t , s t r i k i n g 157° and d i p p i n g about 50°E, cuts the western p a r t of the p r o p e r t y and marks the f o o t w a l l of the main m i n e r a l -i z e d zone. Outcrop i s sparse on the p r o p e r t y , and i s concen-t r a t e d mainly along the scarp of t h i s F o o t w a l l f a u l t . The o r i g -i n a l d i s c o v e r y s i t e i s an i n t e n s e l y s i l i c i f i e d p a r t of the f o o t -w a l l m a t e r i a l along t h i s s c a r p . Two small h i l l s , with e l e v a -t i o n s 217 m and 180 m, are the main p h y s i o g r a p h i c f e a t u r e s of the p r o p e r t y . T o t a l r e l i e f i s about 100 m. A d e s c r i p t i o n of the geology of the p r o p e r t y and r e f e r e n c e to e a r l i e r works i s given by Champigny and S i n c l a i r (1980). In b r i e f , the d e p o s i t has been c l a s s e d as C a r l i n - t y p e (Richards e_t a l . , 1976), and i s c h a r a c t e r i z e d by a g o l d - b e a r i n g s i l i c i f i e d zone at the c o n t a c t between two host rocks, a Miocene r h y o i i t e (14 Ma) and o l d e r coarse c l a s t i c sediments of the Miocene Skonun Formation. The s i l i c i f i e d and m i n e r a l i z e d zone i s now known to • underly an area of at l e a s t 1.3 km2. S e v e r a l stages of s i l i c i -f i c a t i o n are r e c o g n i z e d , a l l of which have a s s o c i a t e d "micron" g o l d . A s s o c i a t e d s u l p h i d e s are mainly p y r i t e and m a r c a s i t e , with very small amounts of s p h a l e r i t e , c h a l c o p y r i t e , p y r r h o t i t e , and v i s i b l e g o l d as much as t r a c e amounts of other m i n e r a l s , galena, c i n n a b a r . Most of the p r o p e r t y i s covered by g l a c i a l overburden, ap-p a r e n t l y t i l l , with v a r i a b l e t h i c k n e s s , but commonly about 1.5 m t h i c k . The v e g e t a t i o n cover i s p r i n c i p a l l y t h i c k stands of r e -l a t i v e l y small second growth c o n i f e r s , mainly s i t k a spruce, wes-te r n hemlock, and red cedar. A major r i v e r , the Yakoun, l i e s 133° 132° 131° J 1 _ J _ F i g u r e . 1 . L o c a t i o n o f S p e c o g n a g o l d d e p o s i t . 18 7973 7<i 75 ?6 77 7& 7 9 80 F i g u r e 2. A p p r o x i m a t e v a r i a t i o n s i n p r i c e o f g o l d p e r t r o y o u n c e (U.S. d o l l a r s ) t o p r e s e n t . j u s t to the south of the c l a i m s , and s e v e r a l streams d r a i n the pr o p e r t y , f l o w i n g south i n t o Yakoun R i v e r . E x p l o r a t i o n on the p r o p e r t y has been ongoing s i n c e o r i g i n a l p r o s p e c t i n g i n iy 7 0 , with the ex c e p t i o n of ly 7 6 , when l i t t l e a c t i v e work was done. U n t i l very r e c e n t l y , p r o p e r t y work has been c o n f i n e d mainly to summer e x p l o r a t i o n seasons, d e s p i t e the r e l a t i v e l y m i l d , i f r a i n y (average annual r a i n f a l l at nearby Masset of 140 cm), c l i m a t e compared to the more extreme c l i m a t e throughout much of B r i t i s h Columbia. A d e t a i l e d summary of pro-g r e s s i v e e x p l o r a t i o n of the p r o p e r t y i s given i n Table 3, and i n d i c a t e s the c o n t i n u i n g accumulation of i n f o r m a t i o n on which s u c c e s s i v e e x p l o r a t i o n d e c i s i o n s were made. General sequence o f these major d e c i s i o n s i s i l l u s t r a t e d i n F i g u r e 3, where i n d i v i -dual blocks with company names are organized with r e s p e c t to year and our e v a l u a t i o n as to l e v e l of corresponding p r o p e r t y e v a l u a t i o n . Each company name i m p l i e s e x i s t e n c e o f a formal agreement to conduct e x p l o r a t i o n , with an o p t i o n on eve n t u a l purchase. These o p t i o n s were dropped s u c c e s s i v e l y u n t i l out-r i g h t purchase of the p r o p e r t y i n 1978 by C o n s o l i d a t e d C i n o l a Mines L t d . The data of Table 3 i n d i c a t e a predominance of su r f a c e mea-surement techniques i n the e a r l y years of e x p l o r a t i o n , with d r i l l i n g much more important i n the l a t t e r y e ars. P r i n c i p a l s u r f a c e work c o n s i s t e d o f sampling s u r f a c e showings f o r assay and s o i l sampling. A l l companies i n v o l v e d i n e v a l u a t i n g the p r o p e r t y rechecked p r e v i o u s sampling and assaying r e s u l t s . 20 Thus, the emphasis on s u r f a c e e x p l o r a t i o n can be i l l u s t r a t e d by examining these f o r e g o i n g types of work. A rough measure of the r e l a t i v e i n f o r m a t i o n obtained from v a r i o u s s o i l sampling p r o j e c t s must consider number of samples, number of elements analyzed f o r , and geographic area covered by a survey. Here we ignore the area aspect and adopt an a r b i t r a r y method of t a k i n g i n t o account the number of samples and the number of elements determined f o r each sample as a means of i n -d i c a t i n g r e l a t i v e i n f o r m a t i o n o b t a i n e d . Our procedure i s to k c a l c u l a t e a q u a n t i t y l y = n ^ I ^ d / j ) , where j i s the element to a maximum of 6, n i s the number of samples, and l y i s the r e l a t i v e i n f o r m a t i o n gain f o r a given time p e r i o d (one year, i n our c a s e ) . T h e r e f o r e , f o r the 1500 s o i l samples taken i n 1971 and analyzed f o r 11 elements, we c a l c u l a t e a r e l a t i v e i n f o r m a t i o n T.71 of 1500 x (i+i+l+l+l+I) = 3675. The comparable f i g u r e for 7 1 1 5^6 1972 when 125 samples were analyzed f o r Au and Ag and 105 sam-p l e s were analyzed f o r Au i s 293. In an analogous manner, we estimate r e l a t i v e i n f o r m a t i o n gain f o r rock sampling as a func-t i o n of t o t a l sample weight per year, m u l t i p l i e d by the number of c l a i m s from which samples were assayed. R e l a t i v e i n f o r m a t i o n from d r i l l i n g can be approximated by t o t a l l ength d r i l l e d per u n i t of time to provide a r e l a t i v e i n f o r m a t i o n measure of the l a t e r stages of e x p l o r a t i o n . These three r e l a t i v e i n f o r m a t i o n measures cannot be compared one to the o t h e r , but i l l u s t r a t e the changing emphasis with time to i n d i v i d u a l e x p l o r a t i o n proce-dures. F i g u r e 4 shows the changing emphasis of p r i n c i p a l e v a l u -a t i o n techniques as e x p l o r a t i o n on the Specogna p r o p e r t y pro-P H A S E O F P R O P E R T Y E X P L O R A T I O N 1 D I S C O V E R Y P R E L I M . S U R R j D E T . S U R F . S U B S U R F . F E A S I B I L I T Y 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 S P E C O G N A + T R I C O K E N N C O C A N E X C O M I N C O S I L V E R S T A N D A R D Q U I N T A N A C O N S . C I N O L A C I N O L A +• E N E R . R E S . F i g u r e 3, S e q u e n t i a l o p t i o n a g r e e m e n t s r e l a t i n g t o t h e S p e c o g n a d e p o s i t , an shown as a " f u n c t i o n " " o f " a n e s t i m a t i o n o f '£he s t a g e o f e x p l o r a t i o n . 22 6000 O 4500 LL Z . 3000 UJ a 1500 PI 71 72 73 74 F i g u r e 4 . A r b i t r a r y r e l a t i v e i n f o r m a t i o n m e a s u r e s t o q u a n t i f y i n f o r m a t i o n d u r i n g s u c c e s s i v e y e a r s o f e x p l o r a t i o n , S p e c o g n a d e p o s i t . A: R e l a t i v e i n f o r m a t i o n f r o m s o i l s a m p l i n g B: R e l a t i v e i n f o r m a t i o n f r o m r o c k s a m p l e s C: R e l a t i v e i n f o r m a t i o n f r o m d i a m o n d d r i l l i n g See t e x t f o r f u r t h e r e x p l a n a t i o n r e g a r d i n g r e l a t i v e i n f o r m a t i o n m e a s u r e s . 23 gressed. Of course, i n a g e n e r a l way a s i n g l e parameter such as funds expended per u n i t time can be used to monitor the g e n e r a l i n t e n s i t y of e x p l o r a t i o n on a p r o p e r t y . Consequently, we i n -clude here a summary of annual expenditures (Table 4) estimated by us from r e p o r t s d e s c r i b i n g the nature of work performed; that i s , the work summarized i n Table 3. These c o s t s do not i n v o l v e o f f i c e overhead, and are not s t a n d a r d i z e d to a s i n g l e r e f e r e n c e year. C o r r e c t i o n s f o r both overhead and i n f l a t i o n would serve o n l y to f u r t h e r exaggerate the obvious trend of d r a m a t i c a l l y i n c r e a s i n g expenditures as phase o f p r o p e r t y e v a l u a t i o n pro-gresses . 24 T a b l e 4. A p p r o x i m a t e c o s t s i n c u r r e d d u r i n g e x p l o r a t i o n o f t h e S p e c o g n a d e p o s i t . Y e a r E x p l o r a t i o n E x p e n d i t u r e s ($) A n n u a l C u m u l a t i v e 1970 5,000 5,000 1971 40,000 45,000 1972 50,000 95,000 1973 20,000 115,000 1974 60,000 175,000 1975 75,000 250,000 1976 0 250,000 1977 80,000 330,000 1978 750,000 1,080,000 1979 800,000 1,949,000 25 CONCLUSIONS 1. E x p l o r a t i o n and e v a l u a t i o n of a mi n e r a l p r o p e r t y can be d i -v i d e d c o n v e n i e n t l y i n t o l o g i c a l pnases that d e s c r i b e the ge n e r a l framework of an e v a l u a t i o n program, v i z . (a) d i s c o -very, (b) p r e l i m i n a r y s u r f a c e , (c) d e t a i l e d s u r f a c e , (d) subs u r f a c e , (e) f e a s i b i l i t y , (f) development, and (g) produ-c t i o n phases. 2. E a r l y phases of p r o p e r t y e x p l o r a t i o n are dominated by s u r f i -c i a l techniques that i n c o r p o r a t e d i r e c t examination of su r -f i c i a l m a t e r i a l on the p r o p e r t y and i n d i r e c t examination o f subsurface m a t e r i a l . 3. Later phases of p r o p e r t y e x p l o r a t i o n i n v o l v e techniques that probe the subsurface d i r e c t i o n , p r i n c i p a l l y a v a r i e t y o f d r i l l i n g procedures, but i n c l u d i n g e x p l o r a t o r y underground workings. 4. Specogna d e p o s i t of C o n s o l i d a t e d C i n o l a Mines L t d . i s an exemplary i l l u s t r a t i o n of the s t r u c t u r e d aspect o f p r o p e r t y e x p l o r a t i o n and e v a l u a t i o n . 5. As e x p l o r a t i o n proceeds, the r e l a t i v e importance of a par-t i c u l a r e x p l o r a t i o n method can be monitored approximately by a r b i t r a r y measures of in f o r m a t i o n gained per u n i t time (com-monly, per y e a r ) . In the case o f Specogna d e p o s i t , e m p i r i -c a l methods are presented f o r measuring r e l a t i v e i n f o r m a t i o n 26 fo r both s o i l geochemical data and rock sample a n a l y s e s . For s o i l samples, the number of samples, number of elements determined, and survey area are used to estimate r e l a t i v e i n f o r m a t i o n . For assayed samples, we consider number and s i z e of samples and area sampled to be gen e r a l i n d i c a t o r s of r e l a t i v e i n f o r m a t i o n g a i n . In the case of d r i l l i n g , t o t a l l e n g t h of bedrock i n t e r s e c t e d i s accepted as a rough e s t i -mate o f i n f o r m a t i o n gained. 6. These estimates of " r e l a t i v e i n f o r m a t i o n " are o b v i o u s l y crude at bes t , but pr o v i d e a u s e f u l means o f mon i t o r i n g the g e n e r a l importance of v a r i o u s e x p l o r a t i o n procedures through the course o f ongoing p r o p e r t y e v a l u a t i o n . Consequently, such s e l e c t i v e measures provide a convenient b a s i s f o r d i s -c u s s i n g e x p l o r a t i o n case h i s t o r i e s , p a r t i c u l a r l y i f i t i s borne i n mind that some f l e x i b i l i t y i s necessary i n d e t e r -mining a p p r o p r i a t e measures of r e l a t i v e i n f o r m a t i o n gain f o r a given p r o p e r t y . 27 ACKNOWLEDGMENTS Mr. A. M c K i l l o p has aided immeasureably i n p r o v i d i n g p e r s -p e c t i v e on some of the e a r l y phases o f e x p l o r a t i o n on the Specogna p r o p e r t y . D i s c u s s i o n with G.G. Richards and W.K. L i v i n g s t o n e , who had c o n s i d e r a b l e involvement with the pro-p e r t y i n the past, c l a r i f i e d some aspects of the e a r l y e x p l o r a -t i o n . 28 REFERENCES Champigny, N., and A.J. S i n c l a i r , 1980, Progress r e p o r t on the geology of the Specogna (Babe) gold d e p o s i t ; B.C. M i n i s t r y of Energy, Mines and Petroleum Resources, Paper 1980-1, pp. 158-1/0. Fortesque, J . , 1965, E x p l o r a t i o n a r c h i t e c t u r e , i n Neale, E.R.W. (Ed.), Some guides to m i n e r a l e x p l o r a t i o n ; G e o l o g i c a l Survey of Canada Paper 65-6, pp. 4-14. R i c h a r d s , G.G., J.S. C h r i s t i e , and M.R. Wolfhard, 1976, Specogna: A C a r l i n - t y p e gold d e p o s i t , Queen C h a r l o t t e I s l a n d s , B r i t i s h Columbia ( a b s t r a c t ) , Canadian I n s t i t u t e of Mining and M e t a l l u r g y B u l l e t i n , v. 69, no. 773, p. 64. CHAPTER I I I C i n o l a Gold De p o s i t , Queen C h a r l o t t e I s l a n d s , B r i t i s h Columb A Canadian C a r l i n - t y p e Deposit 30 ABSTRACT C i n o l a g o l d d e p o s i t i n the northern Queen C h a r l o t t e I s l a n d s , B r i t i s h Columbia, i s i n a c l a s t i c sequence c o n s i s t i n g of a lower shale u n i t (Haida Formation, Late Cretaceous) and an o v e r l y i n g interbedded sequence of pebble conglomerate and coarse g r a i n e d sandstone (Skonun Formation, Middle Miocene). Both u n i t s are i n t r u d e d by a stock and dykes of r h y o l i t e - p o r p h y r y . Two K-Ar model ages i n d i c a t e m i n e r a l i z a t i o n and probably r h y o l i t e - p o r p h y r y i n t r u s i o n at about 14 Ma (Middle Miocene). A s p l a y of the Sandspit f a u l t system c o n s t i t u t e s the f o o t w a l l on the west of the d e p o s i t and marks a sharp c o n t a c t with adjacent rocks to the west, p r i n c i p a l l y Haida s h a l e s . The C i n o l a d e p o s i t can be c l a s s e d as C a r l i n - t y p e , based on f e a t u r e s such as (1) small p a r t i c l e s i z e f o r g o l d , (2) T e r t i a r y age of m i n e r a l i z a t i o n , (3) geochemistry (e.g. high Hg), (4) a l -t e r a t i o n (dominantly a r g i l l i c ) , (5) s t r u c t u r a l s e t t i n g ( a s s o c i a -t i o n with major f a u l t s ) , (6) p o r o s i t y of the host rock, and (7) s p a t i a l and p o s s i b l y g e n e t i c a s s o c i a t i o n with f e i s i c i n t r u s i o n s . Gold m i n e r a l i z a t i o n i s widespread and occurs mainly as minute g r a i n s (<0.5 v) i n s i l i c i f i e d sediments, and i n quartz v e i n s . L o c a l l y coarse (>100 y) p a r t i c l e s of n a t i v e g o l d occur i n quartz v e i n s , e s p e c i a l l y i n h i g h l y b r e c c i a t e d r h y o l i t e - p o r p h y r y . Ore m i n e r a l s are mainly p y r i t e and m a r c a s i t e , but i n c l u d e small amounts of c h a l c o p y r i t e , s p h a l e r i t e , galena, p y r r h o t i t e , c i n n a -bar, tiemmanite (HgSe), r u t i l e , magnetite, hematite, and l i -monite, i n a d d i t i o n to n a t i v e gold and electrum. No s i l v e r min-,31 e r a l s have been found, but s i l v e r was found i n g o l d p a r t i c l e s i n amounts v a r y i n g from 6.2 to 76.4 weight percent. A l t e r a t i o n products are s e r i c i t e , i l l i t e , k a o l i n i t e , and c h l o r i t e , with abundant quartz of s e v e r a l stages. Host r o c k s , s p e c i f i c a l l y the Skonun Formation, formed as an a l l u v i a l p l a i n f a c i e s i n a braided r i v e r system d i s c h a r g i n g i n t o a marine b a s i n i n e a r l y Middle Miocene time. During Middle Miocene t h i s sequence was i n t r u d e d by a r h y o l i t i c stock. The h i g h l y porous and permeable Miocene c l a s t i c sequence a p p a r e n t l y provided an optimum s e t t i n g f o r development of a l a r g e geother-mal system, the energy for which probably d e r i v e d from the rhyo-l i t e stock. M i n e r a l d e p o s i t i o n f o l l o w e d a w e l l - d e f i n e d para-g e n e s i s , which from o l d e s t to youngest i s : (1) p r e c i p i t a t i o n of i r o n s u l p h i d e s , and e a r l y q u a r t z , (2) s e v e r a l stages o f quartz veins with d e p o s i t i o n of s p h a l e r i t e succeeded by galena, c h a l c o -p y r i t e , and v i s i b l e g o l d . M i c r o n - s i z e gold was p r e c i p i t a t e d throughout these two stages of m i n e r a l d e p o s i t i o n . A r g i l l i t i z a -t i o n of the host rocks probably c o i n c i d e d i n p a r t with the min-e r a l i z a t i o n and continued during c o o l i n g of the geothermal c e l l . In s i t u r e s e r v e s have been estimated at 45.4 m i l l i o n short tons, averaging 0.054 oz Au/s.t., using a c u t o f f of .025 oz Au/s.t. 32 Resume" d'auteur Le gisement C i n o l a (Specogna) e s t l o c a l i s e dans une se-quence de muastones (Formation Haida, Cretace s u p e r i e u r ) et une sequence de conglomerats a c a i l l o u x i n t e r l i t g s avec des gres g r o s s i e r s (Formation Skonun, Miocene Moyen). Un stock de rhyo-l i t e porphyrique f a i t i n t r u s i o n a t r a v e r s l e s deux sequences. Deux d a t a t i o n s par l a metnode potassium-argon i n d i q u e n t un age d ' i n t r u s i o n et de m i n e r a l i s a t i o n d 1 e n v i r o n 14 Ma. (Miocene Moyen). Une f a i l l e p a r a l l e l e a l a f a i l l e r e g i o n a l e Sandspit c o n s t i t u e l'eponte ouest du gisement et marque un c o n t a c t abrupte avec l a sequence de mudstones. Le gisement C i n o l a peut e t r e c l a s s i f i e du type C a r l i n s u i -vant l e s c r i t e r e s communs s u i v a n t s : (1) p e t i t e t a i l l e des p a r t i -c u l e s d'or, (2) age de l a m i n e r a l i s a t i o n ( T e r t i a i r e ) , (3) g6o-chimie (anomalie en mercure par exemple), (4) a l t e r a t i o n (sur-tout a r g i l l i q u e ) , (5) contexte s t r u c t u r a l ( a s s o c i a t i o n des f a i l l e s majeures), (6) p o r o s i t e des roches notes, (7) a s s o c i a -t i o n s p a t i a l e e t genetique avec des i n t r u s i o n s f e l s i q u e s . La m i n e r a l i s a t i o n a u r i f e r e e s t etendue et c o n s i s t e en des p a r t i -c u l e s sub-microscopiques (<0.5u) dans des sediments s i l i c i f i e s , et dans l e s veines de q u a r t z . Localement des g r a i n s g r o s s i e r s (>100y) d'or sont observes ans l e s veines de quartz specialement dans l e s r h y o i i t e s porphyriques brechiques. Les mineraux opaques observes sont presqu 1exclusivement l a p y r i t e et l a mar-c a s i t e . De f a i b l e s q u a n t i t e s de c h a l c o p y r i t e , s p h a l e r i t e , ga-l e n e , p y r r h o t i t e , c i nnabar, tiemmanite (HgSe), r u t i l e , magne-33 t i t e , hematite, et l i m o n i t e sont a u s s i presentes en p l u s de l ' o r n a t i f et de l ' e l e c t r u m . Aucun mineral d 1 a r g e n t a ete i d e n t i f i e , de 1"argent e s t contenu dans l e s p a r t i c u l e s d'or dans des pro-p o r t i o n s qui v a r i e n t de 6.2 a 76.4 pourcentage p o i d s . Les mineraux d 1 a l t e r a t i o n sont l a s e r i c i t e , l ' i l l i t e , l a k a o l i n i t e , et l a c h l o r i t e . Le quartz e p i t h e r m a l e s t t r e s abondant. Les sediments m i n e r a l i s e s d'age Miocene Moyen ont ete de-poses par un f l e u v e possedant un drainage t r e s s e q u i se de-c h a r g e a i t dans un b a s s i n marin. L ' i n t r u s i o n du stock de rhyo-l i t e porphyrique au Miocene Moyen a cree une immense c e l l u l e geothermale, l ' e n e r g i e de c e l l e - c i etant d e r i v e e de l ' i n t r u s i f . La m i n e r a l i s a t i o n a u r i f e r e s'est p r o d u i t e s u i v a n t l a para-genese s u i v a n t e (du p l u s vieux au p l u s jeune): (1) p r e c i p i t a t i o n des s u l f u r e s de f e r et d'une premiere g e n e r a t i o n de q u a r t z , (2) p l u s i e u r s episodes de veines de quartz accompagnes par l a depo-s i t i o n de l a s p h a l e r i t e s u i v i e par l a galene, l a c h a l c o p y r i t e , et l ' o r v i s i b l e . L ' a l t e r a t i o n de type a r g i l l i q u e a probablement debute pendant l a m i n e r a l i s a t i o n et s'est continuee durant l e r e f r o i d i s s e m e n t de l a c e l l u l e geothermale. Le m i n e r a i prouve a ete estime a 45.4 m i l l i o n s de tonnes avec une teneur moyen en or de .054 once Au/tonne courte en u t i i i s a n t une teneur de coupure de .025 once Au/tonne c o u r t e . 34 INTRODUCTION C i n o l a g o l d d e p o s i t , known a l s o as Babe and Specogna depos-i t , i s c e n t r a l l y l o c a t e d on Graham I s l a n d , the northern of the two l a r g e s t Queen C h a r l o t t e I s l a n d s (Figure 1). I t i s acces-s i b l e by about 18 km of l o g g i n g road south from the town o f Po r t Clements. F i v e companies optioned the p r o p e r t y s u c c e s s i v e l y from 1971 to 1975 (Champigny et a l . , 1980). C o n s o l i d a t e d C i n o l a Mines L t d . a c q u i r e d the c l a i m s by o p t i o n i n 1977 and purchased them i n 1978. Since August 1979 Energy Reserves Group and C o n s o l i d a t e d C i n o l a Mines L i m i t e d have undertaken a 50-50% j o i n t e v a l u a t i o n venture on the p r o p e r t y . I n d i c a t e d open p i t reserves are estimated at 45.4 m i l l i o n s h o r t tons grading .054 oz. Au/s.t., using a c u t o f f of .025 oz. Au/s. t . T h i s i n c l u d e s 10% d i l u t i o n from the w a l l s of the orebody and from i n c l u d e d waste. S i l v e r grade i s about the same as g o l d . Sutherland Brown and Schroeter (iy75) were the f i r s t to d e s c r i b e the show-ings f o r m a l l y and produced a g e n e r a l i z e d g e o l o g i c a l c r o s s - s e c -t i o n of the d e p o s i t . Richards et a l . (1976, 1979) c l a s s i f i e d the d e p o s i t as C a r l i n - t y p e and p u b l i s h e d the r i r s t K-Ar age de-t e r m i n a t i o n . Champigny and S i n c l a i r (1980) p u b l i s h e d a more d e t a i l e d d e s c r i p t i o n of the geology based on p r e l i m i n a r y i n t e r -p r e t a t i o n of s u r f a c e and d r i l l hole data obtained to the end of August i y 7 9 . T h i s account i s based on g e o l o g i c a l examination of 5506 m o f diamond d r i l l core and l i m i t e d s u r f a c e exposure d u r i n g the summer of 1979 f o l l o w e d by l a b o r a t o r y s t u d i e s at the U n i v e r s i t y 35 F i g u r e 1. L o c a t i o n ^ m a p i t o f t h e C i n o l a g o l d d e p o s i t , Queen C h a r l o t t e I s l a n d s , B.C. ,36 o f B r i t i s h Columbia. Computer-oriented core l o g g i n g techniques (GEOLOG System) were used as a b a s i s f o r the f i e l d work (Blanchet and Godwin, 1972; Godwin, Hendson and Blanchet, 1977). 37 REGIONAL GEOLOGY The Queen C h a r l o t t e I s l a n d s form p a r t of the I n s u l a r T e c t o n i c B e l t o f the Canadian C o r d i l l e r a and are composed o f rocks ranging i n age from Late T r i a s s i c to Recent (Sutherland Brown, 1968) (Table 1 ) . Three major p e r i o d s of volcanism are recognized that separate four p r i n c i p a l episodes of sedimenta-t i o n . PIutonism seems to be c o n f i n e d to two main p e r i o d s . Bodies of hornblende d i o r i t e to quartz d i o r i t e composition were emplaced i n the Middle to Late J u r a s s i c and a more v a r i e d se-quence of q u a r t z d i o r i t e to a l k a k i n e g r a n i t i c rocks was i n t r u d e d i n the E a r l y to Middle T e r t i a r y . C r u s t a l f r a c t u r i n g (mainly major n o r t h w e s t e r l y s t r i k i n g f a u l t s ) has had a pronounced e f f e c t on volcanism, sedimentation, i n t r u s i o n and secondary f o l d i n g (Sutherland Brown, 1968). The g e n e r a l area about the C i n o l a g o l d d e p o s i t i s u n d e r l a i n by three main rock u n i t s , Haida Formation of Late Cretaceous age, Masset Formation of E a r l y to Middle T e r t i a r y age and Skonun Formation o f Middle Miocene age (Figure 2). These rocks are cut by the Sandspit f a u l t system of r e g i o n a l extent (Sutherland Brown, 1968). Sandspit f a u l t system separates the two main phy-s i o g r a h i c p r o v i n c e s o f the area, Queen C h a r l o t t e Lowlands on the east and the Skidegate P l a t e a u to the west. The f a u l t zone s t r i k e s about 143 degrees and seems to represent a l a r g e v e r t i -c a l movement. Southwest of the d e p o s i t the Haida Formation i s mainly composed of s h a l e s . Skonun Formation o v e r l i e s the Haida Formation unconformably and i s composed of conglomerate with 38 coarse pebbles to small c o b b l e s , coarse sandstone and minor s i l t s t o n e or s h a l e . West of the gold prospect v o l c a n i c rocks of the Masset Formation mark the beginning of the Skidegate P l a t e a u . Near C i n o l a d e p o s i t Masset v o l c a n i c rocks are mainly o l i v i n e b a s a l t . P L E I S T O C E N E - R E C E N T g l a c i a l and i n t e r g l a c i a l s e d i m e n t s LATE T E R T I A R Y E A R L Y TO MIDDLE TERTIARY L A T E C R E T A C E O U S Q U E E N CHARLOTTE 6 R 0 U P S K O N U N F M : mar ine and n o n - mar ine s a n d s . M A S S E T F M : a l ka l i basalt f loods and sodic rhyol i te ash f lows / S K I D E 6 A T E - F M ' - mar ine sandstones and s i l t s tones H O N N A F M : conglomerates H A I D A FM-' mar ine sandstones, and shales E A R L Y C R E T A C E O U S U P P E R T R I A S S I C TO L A T E J U R A S S I C V A N C O U V E R GROUP L O N G A R M FM". mar ine l i th ic wackes and ca lcareous siltstones / YAKOUN F M ( M . J U R A S S I C ) : explosive andesit ic volcanics MAUDE F M ( L . J U R A S S I C ) : mar ine shales and sandstones KUNGA F M ( L . J U R A S S I C A N D U P P E R TRIASSIC): l imestones . K A R M U T S E N FM<U.TRIASSIC) \ maf ic vo lcan ics T a b l e 1. T a b l e o f G e o l o g i c " F o r m a t i o n s , Queen C h a r l o t t e I s l a n d s . 40 M A S S E T INLET f ~ ~ l Y A K O U N F M ( J U R A S S I C ) E 2 3 H A I D A F M ( C R E T A C E O U S ) ETTT1 M A S S E T F M ( P A L E D . - E O C E N E ) 0 1 2 3 4 5 6 k m E l S K O N U N F M ( M I D - M I O C E N E ) F i g u r e 2. Regional geology,' C i n o l a g o l d d e p o s i t ( a f t e r S u therland Brown, 196 8). 41 STRATIGRAPHY The d e p o s i t u n d e r l i e s a small h i l l (210 m above sea l e v e l ) i n the t r a n s i t i o n zone between the Skidegate P l a t e a u and the Queen C h a r l o t t e Lowlands. A shale u n i t (Haida Formation) and an o v e r l y i n g interbedded sequence of pebble conglomerate and coarse sandstone (Skonun Formation) are both i n t r u d e d by an elongate stock o f r h y o l i t e - p o r p h y r y (Figure 3). A t h i n cover o f g l a c i a l t i l l and sand o v e r l i e s the area and outcrops are scarce i n the v i c i n i t y o f the d e p o s i t . Shale Sequence - (Haida Formation, Late Cretaceous) T h i s formation u n d e r l i e s an area from the T e r t i a r y v o l -c a n i c s on the west s i d e of the d e p o s i t to the o v e r l y i n g coarse c l a s t i c sequence to the e a s t . Thickness of the shale sequence at the C i n o l a d e p o s i t i s unknown - a maximum t h i c k n e s s o f 34 m was penetrated i n one d r i l l h o l e . The u n i t i s mainly dark grey to b l a c k , p o o r l y c o n s o l i d a t e d and t h i n l y bedded c a l c a r e o u s s h a l e . Minor sandy l a y e r s are prese n t . Near the c o n t a c t with the r h y o l i t e - p o r p h y r y , the shale sequence becomes an a r g i l i i t e or h o r n f e l s due mainly to intense s i l i c i f i c a t i o n . On the ba s i s o f l i t h o l o g y t h i s shale sequence appears to c o r r e l a t e with the upper member of the Haida Formation. 42 F i g u r e 3. P r o p e r t y g e o l o g y , C i n o l a g o l d d e p o s i t . T o p o -g r a p h i c c o n t o u r s i n m e t r e s a . m . s . l . a r e shown o n l y on t h e e a s t s i d e o f t h e F o o t w a l l F a u l t w h i c h s e p a r a t e s s h a l e f r o m t h e o t h e r two u n i t s AA' and BB' a r e l o c a t i o n s o f c r o s s s e c t i o n s i n F i g u r e s 4 a n d 5 43 Conglomerate - Sandstone Sequence (Skonun Formation, Miocene) A c o a r s e - g r a i n e d sedimentary sequence o v e r l i e s the shale sequence and extends eastward to the Sandspit f a u l t (Figure 3 ) . The c o n t a c t between the two u n i t s has not been observed c l e a r l y i n d r i l l core because of p e r v a s i v e s i l i c i f i c a t i o n and i n t r u s i o n o f the r h y o l i t e - porphyry (Figures 3, 4 and 5). Thickness o f the sequence throughout the d r i l l e d area v a r i e s from 0 to 300 m. S t r i k e changes from n o r t h w e s t e r l y to n o r t h e a s t e r l y with most of the values around 015°. S t r a t a c o n s i s t e n t l y d i p 15° to 25° to the e a s t . Thickness of i n d i v i d u a l conglomerate, sandstone or s i l t s t o n e l a y e r s range from 0.1 to 30 m, with a 2 m average. The sequence c o n t a i n s about 62 percent conglomerate, 26 percent coarse sandstone, 7 percent i n t e r c a l a t e d sandstone and s i l t s t o n e with r a r e shale i n t e r beds and 5 percent matrix supported con-glomerate. B a s a l c o n t a c t s of rock u n i t s are g e n e r a l l y sharp but ra r e t r a n s i t i o n a l c o n t a c t s are a l s o observed. M a f i c v o l c a n i c , p e b b l e - r i c h conglomerate, interbedded sandstone and shal e y s i l t -stone and some sandstone have been used s u c c e s s f u l l y f o r s t r a t i -g r a p h i c c o r r e l a t i o n among d r i l l holes as i s apparent i n F i g u r e s 4 and 5. The p r i n c i p a l rock type i s a medium grey to pa l e brown p o l y m i c t i c conglomerate with w e l l rounded to subangular l a r g e pebbles and small c o b b l e s . Graded bedding and load c a s t s t r u c -t u r e s are abundant. The coarse f r a c t i o n t o t a l s 70 percent o f the rock with an average fragment diameter of 3 cm. P a r t i c l e s are moderately s o r t e d and s p h e r i c i t y i s low to i n t e r m e d i a t e . 44 Most of the conglomerate u n i t s are pebble supported. Pebble and cobble i i t h o l o g i e s are 60 percent f e l s i c v o l c a n i c rock, 20 per-cent mafic v o l c a n i c rock, 10 percent g r a n i t e , 5 percent a r g i l -l i t e and shale and 5 percent conglomerate, sandstone, s i l t s t o n e and c h l o r i t e s c h i s t . A c i d v o l c a n i c c l a s t s i n c l u d e massive and oanded r h y o l i t e , r h y o l i t e - p o r p h y r y , quartz and r a r e p y r o c l a s -t i c s , c h e r t and h e m a t i t i c r h y o l i t e - p o r p h y r y . M a f i c v o l c a n i c pebbles are mostly dark green p o r p h y r i t i c a n d e s i t e with p l a g i o -c l a s e and hornblende phenocrysts commonly a l t e r e d to c h l o r i t e and e p i d o t e . G r a n i t i c fragments c o n s i s t of a q u a r t z - f e l d s p a r mosaic with about 10 percent disseminated b i o t i t e or c h l o r i t e . Rare wood fragments are intermixed with the coarse and f i n e f r a c t i o n s . The matrix of these conglomerates occupies 30 per-cent of the volume of the rock and c o n s i s t s of sand-sized par-t i c l e s of q u a r t z and rock fragments. D i s t i n g u i s h i n g quartz cement from quartz c l a s t s i s d i f f i c u l t i n most of the samples due to the poor d e f i n i t i o n of quartz c l a s t boundaries. The mosaic and sutured c o n t a c t s suggest that r e c r y s t a l l i z a t i o n d u r i n g m i n e r a l i z a t i o n may have destroyed many o r i g i n a l c l a s t boundaries. Sandstone u n i t s are medium grey to dark brown and medium to coarse g r a i n e d with bedding and graded bedding commonly ap-parent. Quartz and v o l c a n i c rock fragments comprise most of the g r a i n s . Two to 15 percent wood fragments are present commonly a l i g n e d p a r a l l e l to bedding. Leaves have been found i n sand-stone u n i t s . One small outcrop of sandstone c o n t a i n s abundant w e l l preserved pelecypods. The s h e l l s are r e l a t i v e l y t h i c k and 4 5 C R O S S - SECTION A A' DDH 77-8 1 DDH 77-9" DDH 77-l2~| A ELEVATION DDH (METRES) 78-5 -| .200 10 20 30 40 50 METRES .180 1160 1140 .1120 1100 80 160 140 120 F i g u r e 4 . C r o s s - s e c t i o n AA' - L o c a t i o n shown on f i g u r e 3 . See f i g u r e 5 f o r l e g e n d . 46 F i g u r e 5." C r o s s - s e c t i o n -BB 1 . 47 most of them are f l a t l y i n g . One s p h e r o i d a l c o n c r e t i o n was ob-served i n a sandstone bed. Minor but p e r s i s t e n t medium to pale grey interbedded sand-stone and s i l t s t o n e - shale u n i t s are found throughout the de-p o s i t . They show bedding, graded bedding, c r o s s - b e d d i n g , r i p p l e marks and rare convolute bedding and flame s t r u c t u r e s . Massive, matrix-supported conglomerate u n i t s are found l o -c a l l y . These u n i t s c o n s i s t of angular fragments of sandstone and conglomerate i n a matrix of s i l t y mud. S i m i l a r l i t h o l o g i e s and types of c l a s t s , abundance of c a r -bonaceous m a t e r i a l and r e g i o n a l s t r a t i g r a p h i c s e t t i n g suggest that t h i s sedimentary sequence c o r r e l a t e s with the b a s a l p a r t of the Skonun Formation of Middle Miocene age found i n the lower p a r t of the Tow H i l l w e l l (Sutherland Brown, 1968, p. 120) to the n o r t h e a s t . The d e s i g n a t i o n of t h i s coarse c l a s t i c sequence as p y r o c l a s t i c m a t e r i a l by p r e v i o u s g e o l o g i s t s i s m i s l e a d i n g i n the l i g h t o f our d e t a i l e d megascopic and m i c r o s c o p i c s t u d i e s . An e p i c l a s t i c v o l c a n i c component does occur with other fragment types. No r e l i c t t e x t u r e s were seen which would i n d i c a t e the presence of a p r e - e x i s t i n g pumice or r h y o l i t e as r e p o r t e d by Cruson and Limbach (personal communication, 1980). 48 ENVIRONMENT OF DEPOSITION AND AGE OF SKONUN SEDIMENTS The coarse nature of the sediments, t h e i r p o l y m i c t i c char-ac t e r and e r o s i o n a l c o n t a c t s between conglomerate and sandstone u n i t s s t r o n g l y suggest a f l u v i a t i l e environment of d e p o s i t i o n f o r the Skonun sediments, e i t h e r as meandering r i v e r d e p o s i t s or braided r i v e r d e p o s i t s ( B l a t t e t a l . , 1972, p. 199). In s e d i -ments de p o s i t e d by meandering r i v e r s framework conglomerates are uncommon and occur o n l y as l o c a l i z e d l a g c o n c e n t r a t e s . In con-t r a s t framework conglomerate dominate sediments d e p o s i t e d i n modern braided r i v e r s . Framework conglomerate i s the dominant l i t h o f a c i e s at the C i n o l a d e p o s i t and acc o r d i n g to Rust (±y78) i s evidence f o r d e p o s i t i o n by a braided r i v e r system. Rust (1978), M i a l l (1978), and Vondra and B u r g g r a f f (1978) d e s c r i b e d d i s t a l b r a ided r i v e r s and a l l u v i a l p l a i n s sequences very s i m i -l a r to the Skonun sediments present at the C i n o l a d e p o s i t . Table 2 i s a l i s t of the l i t h o f a c i e s and sedimentary s t r u c t u r e s both observed at the C i n o l a d e p o s i t and i n recognized d i s t a l b r a i ded r i v e r s and a l l u v i a l p l a i n d e p o s i t s . Conglomerate and sandstone u n i t s make up 85-90% of the t o t a l sediment volume, the remainder c o n s i s t i n g o f s i l t y mud-stone and minor s h a l e . Conglomerate-sandstone u n i t s are i n t e r -p r e t e d as d e p o s i t s o f the a c t i v e t r a c t , whereas muostone and p l a n t fragments accumulated on i n a c t i v e areas. The a c t i v e t r a c t migrated across the f l o o d p l a i n ; the area e v e n t u a l l y became i n a c -t i v e and accumulation of mud and support v e g e t a t i o n began, a l -though minor channels s t i l l remained to t r a n s p o r t sand d u r i n g 49 f l o o d p e r i o d s . Much of the d e t r i t u s found i n the f l u v i a t i l e sequence i s most l i k e l y to have been d e r i v e d and t r a n s p o r t e d eastward from the E a r l y to Middle T e r t i a r y v o l c a n i c rocks of the Masset Formation. The coarse c l a s t s are mostly r h y o i i t e , q u a r t z - f e l d -spar porphyry and p o r p h y r i t i c a ndesite a l l of which except por-p h y r i t i c a n d e s i t e , are very common i n exposures o f Masset Formation. J u r a s s i c a n d e s i t i c agglomerates, Upper Cretaceous s h a l e s and i n t r u s i o n s could be the sources f o r c h l o r i t i z e d ande-s i t i c , a r g i l l i t e and g r a n i t i c c l a s t s r e s p e c t i v e l y . Rust (1972) found framework g r a v e l 50 km from the r i v e r ' s source i n a comparable f l u v i a t i l e sequence. Occurence o f b o u l d e r - s i z e d rock fragments, presence o f some d e b r i s flow u n i t s and p r o x i m i t y o f the probable source area suggest a d i s t a n c e o f t r a n s p o r t much shorter than 50 km, although most of the Skonun rocks appear d i s t a l . A sample of carbonaceous s i l t s t o n e with abundant p y r i t e was c o l l e c t e d by the authors i n the ea s t e r n p a r t o f the d e p o s i t ( d r i l l hole 79-14) and submitted f o r p a l y n o l o g i c a l a n a l y s i s . In a d d i t i o n , three samples of s h e l l y sandstone were c o l l e c t e d on a su r f a c e t r e n c h . The p l a n t m i c r o f o s s i l assemblage and fauna r e v e a l an e a r l y Middle Miocene age (17-15 Ma) f o r the d e p o s i t i o n of the Skonun (Champigny, Henderson and Rouse, 1981). The sug-gested environment of d e p o s i t i o n i s that of near shore, p o s s i b l y an e s t u a r i n e environment which i s i n accord with the sedimento-T a b l e 2 . L i t h o f a c i e s and S e d i m e n t a r y S t r u c t u r e s O b s e r v e d i n t h e Skonun S e d i m e n t s o f t h e C i n o l a G o l d D e p o s i t a n d o t h e r B r a i d e d R i v e r . S y s t e m s . APPROX. % TOT. SED. VOL LITHOFACIES SEDIMENTARY STRUCTURES OBSERVED INTERPRE -TATION 62 M A S S I V E OR C R U D E L Y B E D D E D F R A M E W O R K C O N G L O M E R A T E - G R A D E D B E D D I N G - R A R E H O R I Z O N T A L B E D D I N G C H A N N E L D E P O S I T S 26 S A N D S T O N E , M E D I U M T O V E R Y C O A R S E , MAY B E P E B B L Y - H O R I Z O N T A L L A M I N A T I O N - W O O D F R A G M E N T S C H A N N E L D E P O S I T S 7 S A N D , SILT, M U D - F I N E L A M I N A T I O N - C R O S S L A M I N A T I O N - R I P P L E M A R K S - P E L E C Y P O D S O V E R B A N K O R W A N I N G F L O O D D E P O S I T S 5 M A S S I V E MATRIX S U P P O R T E D C O N G L O M E R A T E N O N E D E B R I S F L O W D E P O S I T S 51 l o g i c a l i n t e r p r e t a t i o n proposed here. 52 RHYOLITE-PORPHYRY - MIDDLE MIOCENE An elongate stock of r h y o l i t e - p o r p h y r y and a s s o c i a t e d dykes crop out s p a r s e l y east and west of the F o o t w a l l f a u l t . The i n -t r u s i o n cuts both the shale and conglomerate-sandstone sequence. L o c a l l y the c o n t a c t with the coarse sedimentary rocks i s sharp but i n many pla c e s a t r a n s i t i o n zone e x i s t s . The c o n t a c t zone i s composed of a mixture of h i g h l y deformed conglomerate, sand-stone and r h y o l i t e fragments i n an a p h a n i t i c white to b l u i s h -grey s i l i c e o u s m a t r i x . The t h i c k n e s s of the r h y o l i t e - p o r p h y r y mass decreases to the east (Figures 4 and 5). The rock i s pale grey and c o n t a i n s 1 to 3 percent b l u i s h - g r e y subrounded q u a r t z -eyes 0.1 to 4 mm i n diameter and 5 to 8 percent white subhedral to euhedral f e l d s p a r phenocrysts, 0.1 to 5 mm l o n g . P l a g i o c l a s e phenocrysts (mainly a l b i t e ) are more abundant than potassium f e l d s p a r phenocrysts. The r h y o l i t e i s b r e c c i a t e d i n many p l a c e s with angular fragments of r h y o l i t e and shale con-t a i n e d i n a very f i n e g r a i n e d matrix of dark grey to black s i l i -c i f i e d s h a l e . In the conglomerate u n i t s c l o s e to the i n t r u s i v e mass, angular fragments r e p r e s e n t i n g broken pebbles are v i s i b l e . These b r e c c i a s are probably r e l a t e d to the i n t r u s i o n of the r h y o l i t e - p o r p h y r y . Recent K-Ar data on the T e r t i a r y v o l c a n i c s (Masset Formation) compiled by Young and Chase (19 76) r e s u l t e d i n a r e -v i s i o n of t h e i r age. Sutherland Brown's (1968) i n t e r p r e t a t i o n and h i s s i n g l e K-Ar a n a l y s i s gave a Paleocene to Eocene age. 53 Nineteen recent whole rock K-Ar analyses provide ages ranging from 11 to 84 Ma. At l e a s t two i n t e r p r e t a t i o n s are p o s s i b l e from these data: (1) there i s more than one T e r t i a r y v o l c a n i c c y c l e or (2) the younger dates are r e s e t from E a r l y T e r t i a r y ages. I f we accept the f i r s t i n t e r p r e t a t i o n then the r h y o l i t e -porphyry i n t r u s i o n c o u l d represent a p l u t o n i c phase a s s o c i a t e d with a Late T e r t i a r y v o l c a n i c c y c l e . The Sandspit f a u l t system probably a l s o played an important r o l e i n the l o c a l i z a t i o n and form of the r h y o l i t e - p o r p h y r y stock. 54 STRUCTURE The major s t r u c t u r a l f e a t u r e on the C i n o l a g o l d d e p o s i t i s the F o o t w a l l f a u l t which s t r i k e s 180 to 157 degrees and d i p s 53 degrees to the east (Figures 4 and 5). The F o o t w a l l f a u l t p a r a l l e l s the Sandspit f a u l t system and probably i s a p a r t o f that system. In the d r i l l core the F o o t w a l l f a u l t i s recognized by: (1) an abrupt cnange from s i l i c i f i e d s hale to s o f t , f r e s h shale and (2) s l i c k e n s i d e s i n a l t e r e d r h y o l i t e - p o r p h y r y and s i -l i c i f i e d s h a l e . In the northwestern p a r t o f the d e p o s i t , an outcrop c a l l e d the Marino showing exposes the f a u l t c o n t a c t . A l s o on s u r f a c e the f a u l t i s v i s i b l e as a f a u l t s carp near the southwest boundary of the d e p o s i t (Figure 3). The r h y o l i t e - p o r p h y r y i s observed both beneath and above the F o o t w a l l f a u l t . Thus, f a u l t i n g o c c u r r e d at l e a s t i n p a r t a f t e r i n t r u s i o n o f the r h y o l i t e - p o r p h y r y . Absence of Middle Miocene sediments on the west s i d e of the F o o t w a l l f a u l t , and d i s p l a c e d geochemical anomalies and drainage p a t t e r n s suggest a d e x t r a l f a u l t with some r e l a t i v e downward movement of the east b l o c k . T h i s i s the same movement p i c t u r e observed f o r the Sandspit f a u l t system (Sutherland Brown, iy68, p. 153). Tow H i l l w e l l d r i l l e d on the eas t e r n block of the Sandspit f a u l t i n the l a t e ±y50's shows the base of a conglomerate-sand-stone sequence at 1800 m b.m.s.l. (Sutherland Brown, 1968). The Skonun sediments are exposed on the west s i d e o f the Sandspit f a u l t system at the C i n o l a d e p o s i t at a minimum e l e v a t i o n near 55 -200m. G r a v i t y measurements by Young and Chase (1976) give a d i p f o r the Sandspit f a u l t of 50 to 70 degrees east and a v e r t i -c a l displacement of approximately 1500 metres (east block down). T h i s compares w e l l with a v e r t i c a l d i f f e r e n c e o f 1600 metres between the Skonun sediments of the C i n o l a d e p o s i t and Tow H i l l w e l l . The F o o t w a l l f a u l t on the C i n o l a gold d e p o s i t has been a c t i v e a f t e r the i n t r u s i o n of the r h y o l i t e - p o r p h y r y / that i s , a l t e r 14 Ma. S i m i l a r s t r i k e , d i p and movement p i c t u r e s o f the Fo o t w a l l f a u l t and the Sandspit f a u l t s t r o n g l y suggest that the two r e s u l t from the same s t r e s s p a t t e r n . 56 FORM AND SETTING OF CINOLA DEPOSIT The C i n o l a d e p o s i t extending over an area of at l e a s t 1.3 K2 appears to terminate a b r u p t l y a g a i n s t the F o o t w a l l f a u l t on the west and disappears g r a d u a l l y to the north and east (Figure 3). Depth extent i s unknown but i s at l e a s t 350 m. In s i z e and shape the m i n e r a l i z e d system r i v a l s small porphyry systems. The m i n e r a l i z i n g system i s c h a r a c t e r i z e d by a prominent zone of s i -l i c i f i c a t i o n with a few percent of p y r i t e and m a r c a s i t e . Gold and s i l v e r values are widespread over the same area. Gold values range between .01 and 4.55 oz. Au/short ton. High grade gold values ( i . e . , higher than 0.20 oz. Au/short ton) are found i n q uartz veins s p o r a d i c a l l y throughout the d e p o s i t and i n quartz v e i n l e t s at the c o n t a c t zone between the r h y o l i t e - p o r -phyry and the Skonun conglomerates (Figure 8). The rocks are h i g h l y anomalous i n mercury and a r s e n i c and l e s s anomalous i n antimony and tungsten. Intense s i l i c i f i c a t i o n c h a r a c t e r i z e s the host r o c k s . The degree of s i l i c i f i c a t i o n i n c r e a s e s i n a general way towards the r h y o l i t e - p o r p h y r y body. S e v e r a l generations of veins and s t r i n -gers c r o s s - c u t the host rock. Large veins up to s e v e r a l metres width s t r i k e 020+20 de-grees and d i p 60° to 90° i n e i t h e r d i r e c t i o n . I n c r e a s i n g spa-t i a l d e n s i t y of quartz veins near m i n e r a l i z e d r h y o l i t e s has been measured q u a n t i t a t i v e l y i n most d r i l l h o l e s (Figure 8). I n d i v i d u a l veins present c l e a r a c c r e t i o n a r y f e a t u r e s such as 57 c r u s t i f i c a t i o n , c h a l c e d o n i c quartz and development of w e l l -formed quartz and c a l c i t e c r y s t a l s r e a c h i n g 2 cm i n s i z e with coxcomb tex t u r e i n drusy c a v i t i e s . Banding i n the veins i s com-mon; s e v e r a l c o l o u r e d bands of quartz show the d i f f e r e n t e p i -sodes of v e i n i n g . M i c r o v e i n s and s t r i n g e r s commonly pervade wood fragments, producing a chess-board t e x t u r e on a hand s p e c i -men s c a l e . C r o s s - c u t t i n g r e l a t i o n s h i p s support the f o l l o w i n g sequence of v e i n i n g i n order o f de c r e a s i n g age: a) black to grey c h a l c e d o n i c q u a r t z , b) h e m a t i t i c q u a r t z , c) massive milky quartz d) c l e a r euhedral quartz and e) c a l c i t e . Wall rock s i l i c i f i c a t i o n i s common and i n many pla c e s con-glomerate c l a s t s are b r e c c i a t e d and i n c o r p o r a t e d w i t h i n a quartz v e i n . T h i s i s seen o n l y with black and grey quartz v e i n s . I t i s o f t e n d i f f i c u l t to d i s t i n g u i s h between v e i n m a t e r i a l and host r o c k s . DRILL HOLE 7 8 - 6 E L E V A T I O N A u ( o z . / T o n ) F i g u r e 8. G r a p h i c l o g o f d i a m o n d d r i l l S U L F I D E S ( % ) F R A C T U R E C O U N T Q U A R T Z V E I N S ( % ) P E R M E T R E 0 5 10 0 10 30 50 0 25 50 >50 h o l e 78-6. See F i g u r e 5 f o r l o c a t i o n a n d l e g e n d . 59 WALLROCK ALTERATION A l t e r a t i o n m i n e r als i d e n t i f i e d i n the d r i l l core and t h i n s e c t i o n s i n c l u d e i n de c r e a s i n g order of abundance; q u a r t z , i l -l i t e , k a o l i n i t e , s e r i c i t e and c h l o r i t e . Iron hydroxides are a l s o present near the s u r f a c e . Quartz i s the predominant m i n e r a l and i s present i n two generations ; (1) a f i r s t g e n e r a t i o n o f c r y p t o c r y s t a l l i n e quartz cement b i n d i n g pebbles and smaller c l a s t s o f the o r i g i n a l s e d i -ment and (2) a second g e n e r a t i o n o f blocky c l e a r c r y s t a l s , U . l mm to 2 cm i n diameter o c c u r r i n g as v o i d f i l l i n g s , vugs and v e i n s . T h i s l a t t e r g e n e r a t i o n corresponds to the sequence of m i n e r a l i z a t i o n d e s c r i b e d elsewhere i n t h i s account. T h i s second ge n e r a t i o n o f quartz i s c l e a r l y r e l a t e d to gold m i n e r a l i z a t i o n . Thus, two p e r i o d s of s i l i c i f i c a t i o n have a f f e c t e d the o r i g i n a l sediment. Quartz cement has corroded p a r t s of l i t h i c c l a s t s and pro-duced quartz overgrowth. Cementation destroyed the c l a s t boun-d a r i e s which l o c a l l y are reduced to an i r o n oxide rim. Quartz cement commonly rims p y r i t e g r a i n s and carbonaceous fragments. In q uartz v e i n s , coxcomb s t r u c t u r e i s common. In numerous v e i n s , t h i n selvages o f quartz are coated with p y r i t e , which i n turn i s covered with drusy quartz c r y s t a l s p r o j e c t i n g to the i n t e r i o r o f the v e i n where they are encased i n p y r i t e c r y s t a l s . T h i s common text u r e shows that quartz d e p o s i t i o n i n p a r t pre-60 ceded formation of a l l opaque minerals and continued to some extent d u r i n g d e p o s i t i o n o f opaque m i n e r a l s . P l a g i o c l a s e pheno-c r y s t s of the p o r p h y r i t i c r h y o l i t e are r e p l a c e d i n many pla c e s by q u a r t z . A r g i l l i c a l t e r a t i o n i s e x t e n s i v e . I l l i t e and k a o l i n i t e are the two c l a y minerals i d e n t i f i e d by X-ray d i f f r a c t i o n . These c l a y s seem to be the r e s u l t s of hydrothermal a l t e r a t i o n based on t h e i r random o r i e n t a t i o n and f i b r o u s h a b i t i n the m i n e r a l i z e d r o c k s . I l l i t e and k a o l i n i t e occur; (1) with quartz cement i n the matrix of r h y o i i t e s , conglomerates, sandstones and s i l t -stones (2) as v o i d and v e i n f i l l i n g , commonly c o a t i n g quartz c r y s t a l s and (3) as a l t e r a t i o n o f f e l d s p a r phenocrysts. C l u s t e r s of idiomorphic p y r i t e c r y s t a l s are found i n c l a y -a l t e r e d r o c k s . At the c o n t a c t zone between the Miocene s e d i -ments and the r h y o l i t e - p o r p h y r y a r g i l l i c a l l y a l t e r e d sediments are s i l i c i f i e d with very f i n e g r a i n e d q u a r t z . T h i s superimposed s i l i c i f i c a t i o n on a r g i l l i c a l t e r a t i o n has been r e f e r r e d to as an advanced a r g i l l i c a l t e r a t i o n i n porphyry-copper d e p o s i t s by McMillan and Panteleyev (1980). These o b s e r v a t i o n s suggest that i l l i t i z a t i o n and k a o l i n i z a t i o n took plac e d u r i n g and a f t e r q u a r t z and s u l p h i d e d e p o s i t i o n . T a y l o r and Fryer (1980) ob-served that p h y l l i c o v e r p r i n t i n g a f f e c t e d a l l primary m i n e r a l s except quartz and p y r i t e which i s a l s o the case with the a r g i l -l i c a l t e r a t i o n at C i n o l a . A zone of a r g i l l i c a l t e r a t i o n ( i n which more than 30% of 61 the g o l d - b e a r i n g rock i s composed of c l a y s ) c o n s t i t u t e s the e a s t e r n boundary of the m i n e r a l i z a t i o n (Figure 10). T h i s a r g i l -l i z e d zone d i p s s t e e p l y to the west and, i n g e n e r a l , g o l d values are l e s s than .01 oz. Au/short ton. S e r i c i t i c a l t e r a t i o n i s found mainly as f i n e l y disseminated g r a i n s on f e l d s p a r s pnenocrysts of conglomerate pebbles and of the r h y o l i t e - p o r p h y r y . Small amounts a l s o occur i n the matrix of r h y o i i t e s , conglomerates, f i n e g r a i n e d sediments and i n s i l i -c i f i e d s h a l e s . An e a r l i e r p h y l l i c zone c o u l d have been present around the i n t r u s i o n but the p e r v a s i v e nature of the a r g i l l i c a l t e r a t i o n makes r e c o g n i t i o n of any e a r l y a l t e r a t i o n stage very d i f f i c u l t i f not i m p o s s i b l e . Except fo r a l t e r a t i o n of phenocrysts i n a n d e s i t i c pebbles i n conglomerate u n i t s , c h l o r i t e occurrences seem to be l i m i t e d to the c o n t a c t zone of the r h y o l i t e - p o r p h y r y where the m i n e r a l i s f i n e l y disseminated with q u a r t z , i l l i t e and k a o l i n i t e . C h l o r i t e might r e p r e s e n t , (1) an a l t e r a t i o n product of a g l a s s y c h i l l e d margin of the r h y o l i t e i n t r u s i o n or (2) a m i n e r a l phase r e l a t e d to e a r l y nyorothermal a l t e r a t i o n . Iron hydroxides are present on s u r f a c e exposures and up to 20 m i n depth i n d r i l l h o l e s . They form pale yellow to r e d d i s h -brown f i n e - g r a i n e d earthy m a t e r i a l f i l l i n g and l i n i n g boxwork c a v i t i e s and v e i n l e t s . They r e s u l t from o x i d a t i o n of p r e - e x i s -t i n g s u l p h i d e s , p r i n c i p a l l y p y r i t e and m a r c a s i t e . 77-5- 77-4" 77-3—| 78-4" = > f t : ; OVERBURDEN ~^E3 SHALE RHYOLITE PORPHYRY ADV. ARGILLIC ALT'N SILIC1FICATION ± SERICITIZATION ARGILLIC ALT'N. UNALTERED SEDIMENTS ELEVATION (metres) r 2 0 0 h-150 s O 20 40 60 80 100metres \ N \ \ L100 U50 kSL k-100 L-150 ON NO 63 F i g u r e 10. C r o s s - s e c t i o n s h o w i n g d i s t r i b u t i o n o f a l t e r a t i o n m i n e r a l s o f t h e C i n o l a g o l d d e p o s i t . A r g i l l i c a l t e r a t i o n i n d i c a t e s t h a t t h e s e d i m e n t i s composed o f more t h a n 30% c l a y s ( i l l i t e a n d k a o l i n i t e ) . G r a d e s i n t h e a r g i l l i c a l t e r a t i o n zone a r e l e s s t h a n .01 o z . A u / t o n . A d v a n c e d a r g i l l i c a l t e r a t i o n s i g n i f i e s t h a t s i l i f i c a t i o n i s s u p e r i m p o s e d on ;: a r g i l l i c a l t e r a t i o n . The r h y o l i t e - p o r p h y r y a nd t h e s h a l e w i t h i n a f e w m e t r e s o f t h e f a u l t c o n t a c t a r e s i l i c i f i e d , s e r i c i t i z e d a n d g o l d - b e a r i n g . 64 ORE MINERALOGY Opaque minerals r e c o g n i z e d i n the C i n o l a d e p o s i t are l i s t e d i n Table 4 with an i n d i c a t i o n of t h e i r approximate abundances i n 60 specimens examined i n d e t a i l . M i n e r a l i z e d rock contained from 0.5 to 10 percent opaque minerals with an average o f about 3% (by volume). Two g e n e r a l m i n e r a l a s s o c i a t i o n s are present i n the d e p o s i t (Figure 9 ) : p y r i t e - m a r c a s i t e i n s i l i c i f i e d nost rocks and p y r i t e - m a r c a s i t e - s p h a l e r i t e - c h a l c o p y r i t e - g a l e n a - n a t i v e gold i n quartz v e i n s . P y r i t e and marcasite are the most common m e t a l l i c m i n e r a l s . Four g e n e r a t i o n s of p y r i t e are pr e s e n t . In order o f d e c r e a s i n g age they are; (1) " r a s p b e r r y - l i k e " p y r i t e , r a r e l y observed and p o s s i b l y o f sedimentary o r i g i n , (2) f i n e g r a i n e d m e l n i k o v i t i c p y r i t e o c c u r r i n g as c o a t i n g s and f i s s u r e f i l l i n g s i n pebbles o f conglomerates, (3) w e l l developed s i n g l e c r y s t a l s or c r y s t a l c l u s t e r s i n the coarse f r a c t i o n and cement of the s i l i c i f i e d sediments and (4) p y r i t e i n quartz veins and vugs where i t i s disseminated or forms l a y e r s i n c r y p t o c r y s t a l l i n e q u a r t z . P y r i t e and marcasite occur i n d i v i d u a l l y or together. I n d i v i d u a l g r a i n s range from .01 to 4 mm. Sulphide rims around pebbles i n the conglomeratic host c o n s i s t o f disseminated p y r i t e g r a i n s (.001 to .05 mm). M a r c a s i t e commonly forms groups of small lath-shaped c r y s t a l s and i n p l a c e s shows the c h a r a c t e r i s t i c cox-comb form. Quartz, p y r i t e and marcasite have f i l l e d spaces i n wood fragments. G r a p h i t e was observed r a r e l y with the o r g a n i c matter. In conglomerate u n i t s p y r i t e and marcasite are d i s t r i -65 buted through both the matrix and pebbles i n d i c a t i n g a d e p o s i -t i o n subsequent to the formation of the sediment. No d e f i n i t e c o r r e l a t i o n can be obtained between s u l p h i d e content and g o l d values (Figure 8). I n c l u s i o n s of p y r r h o t i t e , hematite and r a r e l y magnetite and r u t i l e were observed i n p y r i t e g r a i n s . F i v e p y r i t e - m a r c a s i t e g r a i n s were analyzed with the e l e c t r o n microprobe and i n one g r a i n 1.1 weight percent a r s e n i c was measured. No a r s e n o p y r i t e has been i d e n t i f i e d i n the d e p o s i t and the high a r s e n i c content can probably be a t t r i b u t e d to s o l i d s o l u t i o n of a r s e n i c i n p y r i t e and/or m a r c a s i t e . R u t i l e occurs as lath-shaped disseminated g r a i n s or aggre-gates. G r a i n s are r e l a t i v e l y s m a l l ; around .02 mm. No other m e t a l l i c m i n e r a l s are i n c o n t a c t with r u t i l e apart from abundant p y r i t e . R u t i l e c o u l d have been a primary m i n e r a l as i t i s not found i n quartz v e i n s . Small amounts of p y r r h o t i t e are found as i n c l u s i o n s from .01 to .03 mm i n diameter i n p y r i t e and m a r c a s i t e . Hematite occurs as f i n e l y disseminated g r a i n s (<.005 mm) i n quartz veins g i v i n g a brownish-red colour to the q u a r t z . Trace amounts of hematite are found as i n c l u s i o n s (.01 to 0.1 mm) i n p y r i t e or m a r c a s i t e . Magnetite i s very r a r e and was found as anhedral to euhedral g r a i n s from .02 to .3 mm i n s i z e i n c l u d e d i n p y r i t e and on one sample as an i n c l u s i o n i n c i n n a b a r . Mercury minerals (cinnabar and tiemmanite, HgSe) were observed i n one quartz v e i n MINERAL SILICIFIED HOST ROCK QUARTZ VEINS PYRITE 75 75 MARCASITE 22 22 RUTILE 2 — PYRRHOTITE 0-5 0-5 HEMATITE 0-5 2-5 MAGNETITE TR TR SPHALERITE — TR CHALCOPYRITE — TR GALENA — TR GOLD NOT VISIBLE TR CINNABAR — TR TIEMMANITE TR T a b l e 4. Opaque M i n e r a l s a n d T h e i r R e l a t i v e A b u n d a n c e , C i n o l a G o l d D e p o s i t . T r a c e amounts means l e s s t h a n 0.1%. 6 7 TIME PYRITE <Z 5 RUTILE MARCASITE PYRRHOTITE HEMATITE MAGNETITE SPHALERITE CHALCOPYRITE GALENA GOLD IRON HYDROXIDE SILICIFIED HOST ROCKS QTZ. SURF and QUARTZ VEINS VEINS OXD. F i g u r e 9. P a r a g e n e t i c l i n e d i a g r a m f o r t h e C i n o l a g o l d d e p o s i t opaque m i n e r a l s . 68 sample. Cinnabar i s present as .01 to .05 mm disseminated patches i n q u a r t z . " F r a m b o i d a l - l i k e " p y r i t e i s a s s o c i a t e d with cinnabar i n s e v e r a l p l a c e s . S p h a l e r i t e i s present o n l y r a r e l y but i s the most abundant s u l p h i d e a f t e r p y r i t e and m a r c a s i t e . I t i s encountered o n l y i n q uartz veins g e n e r a l l y i n c o n t a c t with p y r i t e , m a r c a s i t e , c h a l -c o p y r i t e , galena and g o l d . G r a i n s are g e n e r a l l y i r r e g u l a r and t h e i r s i z e vary from .01 to .02 mm. S p h a l e r i t e has been ob-served with i n c l u s i o n s of p y r i t e , c h a l c o p y r i t e , galena and q u a r t z , but many g r a i n s are c l e a r of i n c l u s i o n s . M o lecular per-cent FeS i n s p h a l e r i t e o b t a i n e d from seven e l e c t r o n microprobe analyses range from 11 to 25 molecular percent i n d i c a t i n g that s p h a l e r i t e i n the C i n o l a d e p o s i t i s i r o n - r i c h . C h a l c o p y r i t e i s l e s s abundant than s p h a l e r i t e and occurs c l o s e l y a s s o c i a t e d with s p h a l e r i t e e i t h e r as i n c l u s i o n s i n s p h a l e r i t e or as simple com-p o s i t e s u l p h i d e g r a i n s or monominerallic g r a i n s . G r a i n s i z e i s comparable to s p h a l e r i t e . A l l c h a l c o p y r i t e g r a i n s are i r r e g u -l a r . T h i n v e i n l e t s of c h a l c o p y r i t e were observed c r o s s - c u t t i n g s p h a l e r i t e g r a i n s . Rounded i n c l u s i o n s of n a t i v e gold i n c h a l c o -p y r i t e were observed i n a few p l a c e s . Galena i s very rare and i s observed i n p o l y m i n e r a l l i c aggregates with s p h a l e r i t e , c h a l -c o p y r i t e and g o l d , g r a i n s are .01 to 0.1 mm i n s i z e . One v e i n -l e t of galena c r o s s - c u t t i n g a s p h a l e r i t e g r a i n was found. From 20 to 23 molecular percent Se was recorded i n three e l e c t r o n microprobe analyses of galena g r a i n s , so the m i n e r a l i s a c t u a l l y i n the s o l i d s o l u t i o n s e r i e s g a l e n a - c l a u s t h a l i t e . Native g o l d occurs i n three p r i n c i p a l ways (1) micron-gold (<0.5u) i n a l l 69 the rock types that have undergone s i l i c i f i c a t i o n (quartz veins i n c l u d e d ) , (2) as monominerallic g r a i n s i n quartz veins and (3) i n c l u d e d i n c h a l c o p y r i t e i n quartz v e i n s . The t h i r d a s s o c i a t i o n i s o n l y found l o c a l l y . The v i s i b l e gold g r a i n s (>10y) are h i g h l y i r r e g u l a r with some as l a r g e as 500y. I n c l u s i o n s of g o l d i n c h a l c o p y r i t e are 10U on average and are more-or-less rounded. Eleven v i s i b l e g o l d g r a i n s (>100u) o c c u r i n g i n quartz veins were analyzed with the e l e c t r o n microprobe. A l l the gold con-t a i n s s i l v e r ranging from 6.2 to 76.4 weight percent. C a l c u l a t e d Au/Ag r a t i o s vary from 0.2 to 15.1 with an average and standard d e v i a t i o n of 6.3 and 4.9 r e s p e c t i v e l y . These r e -s u l t s c o n t r a s t somewhat with g o l d - s i l v e r s c a t t e r diagrams f o r assays from d r i l l core (Figures 6 and 7) which on average show about twice as much gold as s i l v e r . N e v e r t h e l e s s , we conclude that (1) v i r t u a l l y a l l the s i l v e r i s t i e d up i n s o l i d s o l u t i o n with gold and (2) s i l v e r m i n e r a ls other than g o l d - s i l v e r s o l i d s o l u t i o n are u n l i k e l y to occur, none have been found to date. The t r a c e amount of galena present may c o n t a i n some s i l v e r . One g o l d a n a l y s i s showed 9.8 weight percent Te i n a g r a i n abnormally e n r i c h e d i n s i l v e r (wt. % Ag = 76.4). OA 0.3-Au. (oz/ion) 02H o.H 1 r "oT 0.2 Ag.(oz/ton) 0.3 0.4 F i g u r e 6. G o l d - s i l v e r s c a t t e r - d i a g r a m f o r " l o w g r a d e " a s s a y s f r o m d r i l l c o r e , b a s e d l a r g e l y on 2 m c o r e l e n g t h s . 2.5 2.0-1.5-Au. (oz/ton) 1.0-0.5-N = 273 ~ai~ 1.0 Ik Ag.(oz / ton) F i g u r e 7 . - i - G o . l d v j s i l v e n . s c a t t e r - d i a g r a m f o r - "-high 1 g r a d e " a s s a y s ( h i g h e r t h a n 0.4 o z . A u / t o n ) b a s e d on 2 m c o r e l e n g t h s . 72 AGE OF MINERALIZATION I n t r u s i o n of r h y o l i t e - p o r p h y r y and g o l d m i n e r a l i z a t i o n are c l o s e l y r e l a t e d i n space, time and perhaps g e n e s i s . Quartz veins of the m i n e r a l i z i n g system cut the r h y o l i t e - p o r p h y r y near i t s e a s t e r n margin i n d i c a t i n g that at l e a s t some m i n e r a l i z a t i o n took plac e a f t e r the emplacement of the f e l s i c p l u g . Two samples of g o l d - b e a r i n g s i l i c i f i e d p o r p h y r i t i c r h y o l i t e and one sample of gold bearing s i l i c i f i e d s hale were dated by the K/Ar method and a n a l y t i c a l data and model ages are given i n Table 3. A l l three samples contained about 1% disseminated p y r i t e . A 17.4 Ma model age was obtained f o r s i l i c i f i e d s hale adjacent to the r h y o l i t e - p o r p h y r y and r e p r e s e n t s a r e s e t or par-t i a l l y r e s e t age of the Late Cretaceous s h a l e . Thus, the model age appears to be a maximum p o s s i b l e age of emplacement of the r h y o l i t e - p o r p h y r y , a c o n c l u s i o n i n accord with the e a r l y Middle Miocene age i n d i c a t e d by palynology f o r the Skonun Formation which i s cut by the r h y o l i t e - p o r p h y r y (Champigny, Henderson and Rouse, i y 8 I ) . The two 14 Ma model ages f o r s i l i c i f i e d and s e r i -c i t i z e d r h y o l i t e - p o r p h y r y almost c e r t a i n l y r e p r e s e n t the age o f m i n e r a l i z a t i o n as w e l l as minimum age of emplacement of the r h y o l i t e - p o r p h y r y . These data i n d i c a t e that both i n t r u s i v e and m i n e r a l i z i n g events were c o n f i n e d to a maximum i n t e r v a l of about 3 m i l l i o n y e a r s . We favour an i n t e r p r e t a t i o n i n which 14 Ma r e p r e s e n t s the time of both i n t r u s i o n and m i n e r a l i z a t i o n , and the 17.4 Ma model age was not completely r e s e t by heat from the r h y o l i t e - p o r p h y r y and/or the m i n e r a l i z i n g f l u i d s . T a b l e 3. A n a l y t i c a l d a t a a nd m o d e l a g e s , C i n o l a g o l d d e p o s i t . S a m p l e I d e n t i f i c a t i o n Rock Type %K+ab A r ( r a d ) 40 A r ( t o t a l ) 40 * u A r ( r a d ) ( 1 0 " 7 c m 3 STP/g) A p p a r e n t Age ( M a ) c 22065 M a S i l i c i f i e d R h y o l i t e P o r p h y r y :.1.19 + 0. 04 .532 6 .522 14.0+0.6 7906 D01 S i l i c i f i e d R h y o l i t e P o r p h y r y 5.31-0.12 .440 29.22 14.1+0.6 7805 D01 S i l i c i f i e d S h a l e ( H a i d a . F o r m a t i o n ) 2.91+0.04 .505 14.85 17.4+0.5 a R e s u l t s p r o v i d e d c o u r t e s y o f N.C. C a r t e r a n d G.G. R i c h a r d s b e r r o r i s one s t a n d a r d d e v i a t i o n ( l a b o r a t o r y m e a s u r e m e n t e r r o r ) c c o n s t a n t s u s e d f o r m o d e l age c a l c u l a t i o n s : = 0.581x 10 y e a r Xa = 4.96 x 1 0 ~ 1 0 y e a r " p 4 0 K / K = 1.167 x 1 0 ~ 4 74 CLASSIFICATION OF THE CINOLA DEPOSIT Richards e t a l . (1976) consider the d e p o s i t to be of the C a r l i n type, a c o n c l u s i o n supported by the authors o b s e r v a t i o n s . Features i n common with the g o l d d e p o s i t s of n o r t h - c e n t r a l Nevada ( C a r l i n , C o r t e z , G e t c h e l l and Gold Acres) are (1) s m a l l p a r t i c l e s i z e for most of the g o l d (<0.5y), (2) T e r t i a r y age of m i n e r a l i z a t i o n (14 Ma i n case of the C i n o l a d e p o s i t ) , (3) t r a c e element geochemistry, i n p a r t i c u l a r high Hg, As and Sb, (4) a r -g i l l i c a l t e r a t i o n , (5) a s s o c i a t i o n with major high angle f a u l t s , (6) high p o r o s i t y and p e r m e a b i l i t y of the host rock (mostly un-cemented conglomerate and sandstone at C i n o l a ) , (7) c l o s e spa-t i a l a s s o c i a t i o n with f e l s i c i n t r u s i o n s , and (8) low s i l v e r con-t e n t . 7 5 GENETIC MODEL A g e n e r a l model for the e v o l u t i o n of host rocks and genesis of the C i n o l a gold d e p o s i t i n c l u d e s three main events (Figure 11) : (1) i n the Middle T e r t i a r y , e x t r u s i o n of Masset v o l c a n i c rocks over Haida s h a l e s and a c t i v a t i o n o f , or c o n t i n u a t i o n o f , movement along the Sandspit f a u l t , (2) i n the e a r l y Middle Miocene, u p l i f t and e r o s i o n o f Masset v o l c a n i c and o l d e r rocks and subsequent d e p o s i t i o n of Skonun conglomerates, sandstones and s i l t s t o n e s , and (3) at 14 Ma, i n t r u s i o n o f the r h y o l i t e - p o r -phyry stock along the F o o t w a l l f a u l t , f o l l o wed by the develop-ment of a f r a c t u r e system that provided s t r u c t u r a l c o n t r o l o f m i n e r a l i z a t i o n and p h y s i c a l l i m i t s to the m i n e r a l i z i n g system. The p r e - m i n e r a l i z a t i o n Skonun Formation i s viewed as a per-meable, wa t e r - s a t u r a t e d p i l e o f c l a s t i c sediments. I n i t i a t i o n of f a u l t i n g along the F o o t w a l l f a u l t , a p a r t o f the Sandspit f a u l t system, c o n t r o l l e d emplacement of an elongate stock of r h y o l i t e - p o r p h y r y at about 14 Ma. T h i s event upset the pre-ex-i s t i n g thermal regime, and i n i t i a t e d the development of convec-t i o n c e l l s i n pore water i n the Skonun Formation. As m i n e r a l i z -a t i o n proceeded and f i l l e d channels, i n t e r m i t t e n t movement on the F o o t w a l l f a u l t l e d to f r a c t u r i n g i n a d j o i n i n g rocks with r e s u l t a n t i n c r e a s e s i n p e r m e a b i l i t y f o r ore f l u i l d s t r a n s p o r t . M i n e r a l d e p o s i t i o n i n the system followed a w e l l d e f i n e d p a r a g e n e t i c sequence with a p p a r e n t l y s p o r a d i c abrupt decreases i n temperature of the ore f l u i d . As d e p o s i t i o n continued tern-76 MIDDLE TERTIARY w E EARLY MIOCENE 300 m H o o SL I--100 -300 + • + + + + + + -z^*^^^^ ^ S ^ o ^ o V p a V57N J?OJ£orJr^°o.r\ SL 14 Ma (MIDDLE MIOCENE) + • + + + SYSTEM ^^m^^fmm SL = 3 HAIDA + + +! + + + + + +» MASSET SKONUN RHYOLITE-PORPHYRY 77 F i g u r e 1 1 . S c h e m a t i c s e q u e n c e i n d e v e l o p m e n t o f t h e C i n o l a g o l d d e p o s i t . E r o s i o n o f t h e H a i d a s h a l e s d u r i n g E a r l y M i o c e n e i s s p e c u l a t i v e . E m p l a c e m e n t o f r h y o l i t e -p o r p h y r y i s t h o u g h t t o h a v e i n i t i a t e d t h e r m a l c o n v e c -t i o n o f p o r e w a t e r f r o m t h e S k o n u n F o r m a t i o n and l e d t o d e v e l o p m e n t o f t h e m i n e r a l i z e d s y s t e m . See t e x t f o r d e t a i l s . 78 p e r a t u r e s ranged from 300°C to 130°C as i n d i c a t e d by p r e l i m i n a r y f l u i d i n c l u s i o n geothermometry data (Shen, Champigny and S i n c l a i r , 1981). I n c l u s i o n data a l s o i n d i c a t e low s a l i n i t i e s ; thus the ore f l u i d i s thought to have o r i g i n a t e d as pore water w i t h i n the Skonun Formation. Metals are b e l i e v e d by the authors to have been d e r i v e d from the Skonun Formation, i n p a r t by a l t e r a t i o n of v o l c a n i c fragments and i n p a r t by d i s s o l u -t i o n o f neavy m i n e r a l s . I t appears l i k e l y t h a t p r e c i p i t a t i o n of g o l d was to some extent promoted by the abundant o r g a n i c ma-t e r i a l w i t h i n the Skonun Formation. 79 ACKNOWLE DGMENTS The f i n a n c i a l support of C o n s o l i d a t e d C i n o l a Mines L t d . f o r our study has been g r a t i f y i n g . In p a r t i c u l a r the c o o p e r a t i o n and a s s i s t a n c e of K.G. Sanders, P r e s i d e n t and A. M a c K i l l o p , camp manager, i s acknowledged with thanks. The l a b o r a t o r y work was funded i n p a r t by a N.S.E.R.C. S c h o l a r s h i p to Champigny and a grant from the B.C. M i n i s t r y o f Energy, Mines and Petroleum Resources. H.J. Mah, P.H. Blanchet and T. Chen ( I n t e r n a t i o n a l Geosysterns Corp.) advised on the use of the GEOLOG system. Mr. John Gardiner provided t e c h n i c a l a s s i s t a n c e i n the f i e l d . D i s -c u s s i o n s with Dr. A. Sutherland Brown and a v i s i t with him to the type of l o c a l i t y of the Skonun Formation were extremely b e n e f i c i a l to t h i s study. 80 REFERENCES Bla n c h e t , P.H., and Godwin, C.I., 1972, 'Geolog System 1 f o r com-puter and manual a n a l y s i s o f g e o l o g i c data from porphyry and other d e p o s i t s ; Econ. Geol., v. 67, pp. 796-813. B l a t t , H., Mi d d l e t o n , G.V., and Murray, R., 1972, O r i g i n of sed-imentary rocks; P r e n t i c e - H a l l Inc., Englewood C l i f f s , N.J., 634 p. Champigny, N., and S i n c l a i r , A.J., 1980, Progress r e p o r t on the geology of the Specogna (Babe) gold d e p o s i t ; B.C. M i n i s t r y of Energy, Mines and Petroleum Res., Paper 1980-1, pp. 158-170. Champigny, N., S i n c l a i r , A .J., and Sanders, K.G., 1980, Specogna gold d e p o s i t o f C o n s o l i d a t e d C i n o l a Mines, an example of s t r u c t u r e d p r o p e r t y e v a l u a t i o n ; Western Miner, v. 53, n. 6, pp. 35-44. Champigny, N., Henderson, C , and Rouse, G.E., 1981, New e v i -dence f o r the age of the Skonun Formation; Queen C h a r l o t t e I s l a n d s , B.C., to be submitted to Can. Jour . E a r t h S c i e n c e s . Godwin, C.I., Hendson, R.E., and Blanchet, P.H., 1977, GEOLOG: A computer-based scheme f o r d e t a i l e d a n a l y s i s of s t r a t i g r a p h y , e s p e c i a l l y as a p p l i e d to data from d r i l l holes i n c o a l ex-p l o r a t i o n or development; Can. I n s t . Min. M e t a l l . , B u l l . , v. 81 70, pp. 123-132. Mc M i l l a n , W.J., and Panteleyev, A., 1980, Ore Deposit Models I. Porphyry copper d e p o s i t s ; Geoscience Canada, v. 7, n. 2, pp. 52-63. M i a l l , A.D., 1978, L i t h o f a c i e s types and v e r t i c a l p r o f i l e models i n b raided r i v e r d e p o s i t s : a summary; in A.D. M i a l l ( E d i t o r ) , Can. Soc. Petroleum G e o l , Memoir 5, F l u v i a l Sedimentology, pp. 507-604. Rich a r d s , G.G., C h r i s t i e , J.S., and Wolfhard, M.R., 1976, Specogna: A C a r l i n - t y p e Gold D e p o s i t . Queen C h a r l o t t e I s l a n d s , B r i t i s h Columbia ( a b s t r a c t ) ; Can. I n s t . Min. M e t a l l . B u l l . , v. 69, n. 773, pp. 64 Ri c h a r d s , G.G., C h r i s t i e , J.S., and L i v i n g s t o n e , K.W., 1979, Some gold d e p o s i t s of the Queen C h a r l o t t e I s l a n d s ( a b s t r a c t ) ; Can. I n s t . Min. M e t a l l . B u l l . , v. 72, n. 809, pp. 64. Rust, B.R., 1978, D e p o s i t i o n a l models f o r braided a l l u v i u m ; _in A.D. M i a l l ( E d i t o r ) , Can. Soc. Petroleum G e o l . , Memoir 5, F l u v i a l sedimentology, pp. 605-625. Rust, B.R., 1972, S t r u c t u r e and process i n a braided r i v e r ; Sedimentology, v. 18, pp. 221-246. 82 Shen, K., Champigny, N., and S i n c l a i r , A.J., 1981, Ge n e t i c im-p l i c a t i o n s o f f l u i d i n c l u s i o n s t u d i e s , C i n o l a gold d e p o s i t , Queen C h a r l o t t e I s l a n d s , B.C.; B.C. M i n i s t r y o f Mines and Pet. Res., Paper 1981-1 ( i n p r e s s ) . Sutherland Brown, A., 1968, Geology of the Queen C h a r l o t t e I s l a n d s , B r i t i s h Columbia, B.C. M i n i s t r y o f Energy, Mines & Pet. Res., B u l l . 54. Sutherland Brown, A., and S c h r o e t e r , T.G., 1975, Report on the Babe Gold P r o s p e c t , Queen C h a r l o t t e I s l a n d s ; B.C. M i n i s t r y of Energy, Mines & Pet. Res., G e o l o g i c a l Fieldwork, 1975, pp. 71-75. Sutherland Brown, A., and S c h r o e t e r , T.G., 1977, Babe Gold Prospect; B.C. M i n i s t r y o f Energy, Mines and Pet. Res., Geology i n B.C., 1975, pp. G73-G77. T a y l o r , R.P., and F r y e r , B.J., 1980, M u l t i p l e stage hydrothermal a l t e r a t i o n i n porphyry copper systems i n northern Turkey: the temporal i n t e r p l a y o f p o t a s s i c , p r o p y l i t i c , and p h y l l i c f l u i d s ; Can. J . E a r t h Sc., v. 17, No. 7, pp. 901-926. Vondra, C.F., and Burggraf, D.R., J r . , 1978, F l u v i a l f a c i e s o f the P l i o - P l e i s t o c e n e K o o l i Fora Formation, K a r a r i Ridge, East Lake Turkana, Kenya; in M i a l l , A.D. ( e d i t o r ) , Can. Soc. Petroleum G e o l . , Memoir 5, F l u v i a l sedimentology, pp. 511-529. 83 Young, I.F., and Chase, R.L., 1976, G r a v i t y and s e i s m i c p r o f i l e s over the Sandspit F a u l t , Queen C h a r l o t t e I s l a n d s , B.C.; B.C. Dept. of of Mines and Pet. Res., G e o l o g i c a l Fieldwork, 1976, pp. 59-64. CHAPTER IV F l u i d I n c l u s i o n and Sulphur Isotope Data R e l a t i o n To Genesis of the C i n o l a Gold D e p o s i t , Queen C h a r l o t t e I s l a n d s , B.C. 85 ABSTRACT F l u i d i n c l u s i o n s t u d i e s from the C i n o l a d e p o s i t i n d i c a t e low s a l i n i t i e s and low C O 2 contents of the ore f l u i d . T h i s sup-p o r t s a suggestion that the m i n e r a l i z i n g f l u i d s o r i g i n a t e d from pore water i n the f l u v i a t i l e host rock (mid-Miocene Skonun Formation). Bimodal d i s t r i b u t i o n of f i l l i n g temperatures sug-gests the e x i s t e n c e of at l e a s t two temperature regimes c e n t r e d on 160°C and 270°C duri n g m i n e r a l d e p o s i t i o n . Independent age and s t r a t i g r a p h i c evidence i n d i c a t e that depth of m i n e r a l i z a t i o n i s between 1.1 and 1.8 k, corresponding to a h y d r o s t a t i c load between 110 and 170 bars. 86 RESUME D'AUTEUR Les donnees sur l e s i n c l u s i o n s f l u i d e s du gisement C i n o l a i n d i q u e n t de basses s a l i n i t e s et basses teneurs en C0 2- C e c i confirme que l e s f l u i d e s m i n e r a l i s a n t s ont ete d e r i v e s de l'eau i n t e r s t i t i e l l e p r i s e dans l e s sediments f l u v i a t i l e s notes. La d i s t r i b u t i o n bimodale des temperatures d'homogenisation implique 1'existence de deux regimes de temperature concentrees vers o o 160 C et 270 C pendant l a m i n e r a l i s a t i o n . La profondeur a l a -q u e l l e l e gisement s ' e s t forme e s t evaluee d'etre 1.1 e t 1.8 k a p a r t i r d ' i n f o r m a t i o n s s t r a t i g r a p h i q u e s independantes: c e c i c o r -respond a des p r e s s i o n s h y d r o s t a t i q u e s de 110 a 170 bars. 87 INTRODUCTION At the C i n o l a g o l d d e p o s i t , a shale sequence (Late Cretaceous) and a coarse c l a s t i c sequence o f f l u v i a t i l e o r i g i n (Middle Miocene) were int r u d e d by a Middle Miocene stock o f q u a r t z - f e l d s p a r porphyry (Champigny and S i n c l a i r , 1980b). The m i n e r a l i z e d system c o n s i s t s o f an i n t e n s i v e l y s i l i c i f i e d zone with l a t e stage veins and stockwork both superimposed on the r h y o l i t i c i n t r u s i o n and the adjacent sedimentary sequence. Thus, two pe r i o d s o f s i l i c i f i c a t i o n have a f f e c t e d the host r o c k s . S i l i c i f i e d host rocks and veins c o n t a i n about 3% d i s s e -minated p y r i t e and m a r c a s i t e , with sub-microscopic gold and r a r e v i s i b l e g o l d . Other ore minerals are s p h a l e r i t e , c h a l c o p y r i t e , galena, p y r r h o t i t e , c i n n a b a r , tiemmanite, r u t i l e , hematite, and magnetite, but they are r a r e l y observed. The veins are d i v i d e d i n t o four s u c c e s s i v e p a r a g e n e t i c events on the b a s i s o f form and c r o s s - c u t t i n g r e l a t i o n s h i p s . These a r e , with d e c r e a s i n g age, black to grey c h a l c e d o n i c quartz ( e a r l i e s t ) , h e m a t i t i c q u a r t z , massive milky q u a r t z , c l e a r euhedral q u a r t z , and c a l c i t e (youngest). Quartz d e p o s i t i o n i n p a r t preceded formation o f a l l s u l p h i d e s (mainly p y r i t e ) and n a t i v e g o l d , and continued during d e p o s i t i o n o f these opaque m i n e r a l s . Veins at C i n o l a e x h i b i t c r u s t i f i c a t i o n , ribbon t e x t u r e , and development of drusy vugs, and some c a l c i t e c r y s t a l s a t t a i n 2 cm i n l e n g t h . W a l l rock a l -t e r a t i o n i s dominantly a r g i l l i c and s e r i c i t i c . The authors sug-gest t h a t the r h y o l i t e - p o r p h y r y i n t r u s i o n i n i t i a t e d the develop-ment of a l a r g e geothermal system from which g o l d m i n e r a l i z a t i o n took p l a c e . F l u i d i n c l u s i o n s t u d i e s o f f r a c t u r e - c o n t r o l l e d , 88 g o l d bearing veins and sulphur isotope analyses of p y r i t e were performed to estimate the ore f l u i d composition and to b e t t e r d e f i n e a g e n e t i c model f o r the C i n o l a d e p o s i t . Samples f o r t h i s study were c o l l e c t e d from d r i l l core d u r i n g the summer of 1979. 89 FLUID INCLUSION DATA Bl a c k , grey, h e m a t i t i c , and c h e r t y quartz are mostly too p o o r l y c r y s t a l l i z e d f o r f l u i d i n c l u s i o n s s t u d i e s . Consequently, a t t e n t i o n was d i r e c t e d mainly to l a t e stage milky quartz and rare occurrences o f c a l c i t e . S i x specimens of quartz and one o f c a l c i t e were s e l e c t e d to provide p r e l i m i n a r y i n s i g h t i n t o the a p p l i c a t i o n o f f l u i d i n c l u s i o n data to the development of a ge-n e t i c model f o r the d e p o s i t . The specimens c o l l e c t e d r epresent a l a r g e a r e a l coverage o f the C i n o l a m i n e r a l i z e d system. F l u i d i n c l u s i o n s range from 5 to 47 microns i n t h e i r l o n g e s t dimen-s i o n , and a l l have two phases: a l i q u i d phase and a vapour phase that t o t a l s from 1 to 15 volume percent but commonly i s about 5 volume pe r c e n t . The i n c l u s i o n s were found mostly along c r y s t a l growth zones, and i n some cases from c r y s t a l s developed i n vugs or as c r u s t i f o r m l a y e r i n g with no evidence o f deformation. Thus, we f e e l r e l a t i v e l y c o n f i d e n t that i n c l u s i o n s s t u d i e d are primary. 90 HOMOGENIZATION DATA Homogenization temperatures by vapour disappearance were recorded From 38 i n c l u s i o n s (Figure 1). They show a bimodal p o p u l a t i o n with a low temperature mode between 150°and 160°C and a higher temperature mode between 270°and 280°C. These two pop-u l a t i o n s o f f i l l i n g temperatures can be i n t e r p r e t e d as at l e a s t two episodes of mi n e r a l d e p o s i t i o n and m i n e r a l i z a t i o n w i t h i n the l a t e stage white quartz and c a l c i t e v e i n s . From seven measure-ments above 275°C f f i v e were from t r a n s l u c e n t quartz cement g r a i n s b i n d i n g pebbles and matrix i n a conglomerate u n i t . T h i s i s i n accord with an e a r l y stage of d e p o s i t i o n o f quartz cement observed by Champigny and S i n c l a i r (1980b). Our l i m i t e d data fo r f i l l i n g temperature f o r i n c l u s i o n s i n c a l c i t e suggests t h a t c a l c i t e d e p o s i t i o n i s p a r t of the low temperature (160°) minera-l i z i n g stage. T h i s agrees with c a l c i t e ' s p o s i t i o n i n the para-g e n e t i c sequence (Champigny and S i n c l a i r , 1980b). 100 150 200 250 300 350 F i g u r e ' 1. H i s t o g r a m o f f i l l i n g t e m p e r a t u r e s o f f l u i d i n c l u s i o n s i n q u a r t z a n d c a l c i t e , C i n o l a d e p o s i t . C a l c i t e m e a s u r e m e n t s a r e shown i n b l a c k . H a t c h e d p a t t e r n i s f o r ( e a r l y ) q u a r t z cement. 92 FREEZING DATA Most f r e e z i n g temperatures measured from 41 i n c l u s i o n s are between 0 . 0 and - 0 . 9 ° C (Figure 2). Recorded temperatures from 2.5 to 4 . 9 2 c are considered evidence f o r the presence o f d i s -s o l v e d CO2 ( c l a t h r a t e s ) i n the aqueous s o l u t i o n ( C o l l i n s , 1 9 7 9 ) . M e l t i n g p o i n t s of these c l a t h r a t e s range from 3 . 0 to 3 . 4°C and 2.5 to 4 . 9 ° C f o r the two samples where they were observed. Double f r e e z i n g , a c h a r a c t e r i s t i c phenomenon of c l a t h r a t i o n , was very d i f f i c u l t to observe because of the small s i z e of the i n -c l u s i o n s and gas bubbles. S a l i n i t y estimates of the i n c l u s i o n f l u i d s were obtained using the formula of P o t t e r e t a l . ( 1 9 7 8 ) . NaCl e q u i v a l e n t i n s o l u t i o n v a r i e s from 0 to 1.5 weight p e r c e n t , with an average of 0.5 weight percent. The presence of small amounts of C 0 2 i n the trapped ore f l u i d i s p o s s i b l e , but would not s i g n i f i c a n t l y change the estimated s a l i n i t i e s ( C o l l i n s , 1 9 7 9 , F i g u r e 5 ) . ro F i g u r e 2. H i s t o g r a m o f f r e e z i n g t e m p e r a t u r e s o f f l u i d i n c l u s i o n s i n q u a r t z a n d c a l c i t e , C i n o l a d e p o s i t . C a l c i t e m e a s u r e m e n t s a r e shown i n b l a c k . H a t c h e d p a t t e r i s f o r ( e a r l y ) q u a r t z cement. 94 PRESSURE CORRECTIONS The homogenization data are uncorrected for the e f f e c t s of p r e s s u r e . Host rocks at C i n o l a are mainly conglomerates which are c o r r e l a t e d with the base of the Skonun Formation as found to the east (Tow H i l l W e l l , Sutherland Brown, 1968). Skonun s e d i -ments are weakly cemented and h i g h l y porous where exposed at Skonun P o i n t , 65 km to the n o r t h e a s t . T h i s , combined with the ext e n s i v e f r a c t u r i n g i n the m i n e r a l i z e d zone, suggested that pressure during d e p o s i t i o n was h y d r o s t a t i c . Average t h i c k n e s s of the Skonun sediments from f i v e d r i l l e d w e l l s i s about 1200 m, and 1760 m of s t r a t a are present i n Tow H i l l . H y d r o s t a t i c p r e s -sures of approximately 117 and 172 bars correspond to these depths. From t h i s , pressure c o r r e c t i o n s o f 15°C or l e s s , f o r a s o l u t i o n o f 1 percent NaCl e q u i v a l e n t , c o u l d apply ( P o t t e r , 1977); that i s , a c t u a l temperatures of d e p o s i t i o n probably are no more than 15°C h i g h e r , on average, than the f i l l i n g tempera-tur e s r e p o r t e d here. 95 SULPHUR ISOTOPE DATA Sulphur isotope analyses were obtained f o r s i x samples of p y r i t e from C i n o l a d e p o s i t (Table 1). In a l l cases p y r i t e oc-curre d as disseminated r a i n s i n s i l i c i f i e d sediments. The s u l -phur i s ' l i g h t ' , and the range i s s m a l l , from -3.58 to -u.52%. The most negative ( l i g h t e s t ) value i s from dark brown m e l n i k o v i -t i c p y r i t e , whereas the other a3ks values are from p y r i t e - m a r c a -s i t e g r a i n s c o n t a i n i n g small i n c l u s i o n s of p y r r h o t i t e . A v a r i e -t y o f o r i g i n s o f sulphur i s c o n s i s t e n t with these sulphur i s o -tope data, i n c l u d i n g the g e n e t i c model presented by Champigny and S i n c l a i r (1980a) and o u t l i n e d i n d e t a i l elsewhere i n t h i s volume. T a b l e 1 - a S o f p y r i t e s u l p h u r a t t h e C i n o l a D e p o s i t D r i l l h o l e D e p t h a 3 4 S No. ( M e t r e s ) o o 78-2 95 -0.52 78-5 27 -3.58 79-6 123 -0.82 79-9 137 -0.73 79-10 130 -1.82 79-11 139 -1.28 97 DISCUSSION From the homogenization and f r e e z i n g data, i t i s apparent that m i n e r a l i z i n g f l u i d s at C i n o l a had a r e l a t i v e l y low and o n l y s l i g h t l y v a r i a b l e s a l i n i t y , c o n t a i n i n g very minor amounts of NaCl e q u i v a l e n t and C 0 2 . Low s a l i n i t i e s such as estimated f o r the C i n o l a d e p o s i t are c h a r a c t e r i s t i c o f go l d quartz veins and C a r l i n - t y p e d e p o s i t s (Nash, 1972), and are c o n s i s t e n t with a meteoric o r i g i n f o r the ore f l u i d s . In the present case, heated pore waters o f the Skonun sediments are a l i k e l y source o f m i n e r a l i z i n g f l u i d s . The sedimentary host rocks at C i n o l a are of f l u v i a t i l e o r i g i n , and t h e r e f o r e pore waters should have low NaCl and CO2 c o n t e n t s , i n agreement with the i n d i c a t i o n s from f r e e z i n g data f o r f l u i d i n c l u s i o n s . Textures i n d i c a t i v e o f open space f i l l i n g and the absence of c o e x i s t i n g vapour-dominated i n c l u s i o n s at C i n o l a suggest t h a t b o i l i n g d i d not occur or that the b o i l i n g "top" of the system has been removed by e r o s i o n . For maximum f i l l i n g temperatures of 300°C and a s a l i n i t y of 0.5 percent NaCl e q u i v a l e n t s o l u t i o n , a h y d r o s t a t i c p r essure e q u i v a l e n t to a depth o f 1100 m below su r f a c e i s necessary to prevent the system from b o i l i n g (Haas, 1971). T h i s depth i s considered a minimum for m i n e r a l d e p o s i t i o n , i n that p a r t o f the system a v a i l a b l e f o r study because o f the absence o f t e x t u r a l and other evidence i n d i c a t i v e o f b o i l i n g . The maximum p o s s i b l e depth of m i n e r a l i z a t i o n appears to be 1.8 98 k, based on the t o t a l maximum t h i c k n e s s o f the o v e r l y i n g s t r a t i -g r a p hic s e c t i o n to the east (Sutherland Brown, 1968). C l a t h r a t i o n , observed i n two samples, i n d i c a t e s the pre-sence of small amounts of CO 2 , and i t i s p o s s i b l e that a very s m a l l amount of CO 2 does occur i n i n c l u s i o n s where c l a t h r a t i o n was not re c o g n i z e d . The Skonun Formation i s a p l a u s i b l e source f o r t h i s CO 2-L o c a l s h e l l - r i c h l a y e r s are a c h a r a c t e r i s t i c f e a t u r e of the Skonun Formation and are w e l l exposed at the type l o c a l i t y at Skonun P o i n t , on the noth shore o f Graham I s l a n d (Sutherland Brown, 1968). S i m i l a r l a y e r s have been i d e n t i f i e d i n d r i l l core at the C i n o l a d e p o s i t (Champigny and S i n c l a i r , 1980b). At the type o f l o c a l i t y o f the normally f r i a b l e Skonun, sandstones and conglomerates are cemented by c a l c i t e f o r as much as 10-30 cm from s h e l l - r i c h l a y e r s that are normally o n l y a few cen t i m e t e r s wide. 99 CONCLUSIONS Although the s t u d i e s r e p o r t e d here are f a r from comprehen-s i v e , they provide important c o n s t r a i n t s on a g e n e t i c model f o r the C i n o l a d e p o s i t . The low s a l i n i t i e s and low C0 2 contents o f the ore f l u i d are c o n s i s t e n t with the suggestion that the f l u i d d e r i v e d from pore water i n the f l u v i a t i l e Skonun Formation. F i l l i n g temperatures and the absence of t e x t u r e s r e s u l t i n g from b o i l i n g suggest a minimum depth of formation of about 1.1 k, whereas s t r a t i g r a p h i c i n f o r m a t i o n suggests a maximum depth of formation of about 1.8 k. The two major peaks of f i l l i n g temperatures suggest that two p r i n c i p a l temperature regimes may have e x i s t e d d u r i n g the d e p o s i t i o n a l h i s t o r y . These peaks i n d i c a t e an e a r l y p e r i o d of high temperature d e p o s i t i o n and a l a t e p e r i o d o f lower tempera-ture d e p o s i t i o n . Our very l i m i t e d f i l l i n g temperature data for p a r a g e n e t i c a l l y l a t e c a l c i t e are comparable to the l a t e q uartz p o p u l a t i o n , and i n d i c a t e that c a l c i t e veins are probably an i n -t e g r a l p a r t o f the m i n e r a l i z i n g episode rather than a l a t e r un-r e l a t e d and superimposed event. Both the e a r l i e s t and some of the l a t e s t quartz i n the pa r a g e n e t i c sequence have f l u i d i n c l u s i o n f i l l i n g temperatures i n the "high" temperature p o p u l a t i o n of F i g u r e 1. T h i s may i n -d i c a t e that most d e p o s i t i o n o c c u r r e d under the high temperature regime, and that o n l y the l a t e s t p a r t o f the youngest quartz and contemporaneous and younger c a l c i t e were de p o s i t e d under the low 100 temperature regime. Our p r e l i m i n a r y sulphur isotope data are c o n s i s t e n t with the views presented here, but are too sparse to p r o v i d e evidence r e l a t i n g to a s p e c i f i c g e n e t i c model. 101 ACKNOWLE DGMENTS F i n a n c i a l support f o r t h i s study was provided by C o n s o l i d a t e d C i n o l a Mines L t d . and an N.S.E.R.C. s c h o l a r s h i p to Champigny. 102 REFERENCES Champigny, N., and S i n c l a i r , A.J., 1980a, C i n o l a (Specogna) g o l d d e p o s i t , Queen C h a r l o t t e I s l a n d s , B r i t i s h Columbia - A Canadian C a r l i n - t y p e d e p o s i t ( a b s t r a c t ) ; Can. I n s t . Min. M e t a l l . B u l l . 75, v. 73, p. 62. Champigny, N., and S i n c l a i r , A.J., 1980b, Progress r e p o r t on the geology o f the Specogna (Babe) gold d e p o s i t ; B.C. M i n i s t r y of Energy, Mines and Petroleum Resources, Paper 1980-1, pp. 158-170. Champigny, N., Henderson, C , and Rouse, G.E., 1981, New e v i -dence f o r the age of the Skonun Formation, Queen C h a r l o t t e I s l a n d s , B.C.; to be submitted to Can. Jour. E a r t h S c i e n c e s . C o l l i n s , P.L.F., 1979, Gas hydrates i n C 0 2 - b e a r i n g f l u i d i n c l u -s i o n s and the use of f r e e z i n g data f o r the e s t i m a t i o n of s a l i n i t y ; Econ. Geol., v. 74, pp. 1435-1444. Haas, J.L. J r . , 1971, The e f f e c t of s a l i n i t y on the maximum thermal g r a d i e n t o f a hydrotnermal system at h y d r o s t a t i c p r e s s u r e ; Econ. Geol., v. 66, pp. 940-946. Nash, J.T., 1972, F l u i d i n c l u s i o n s t u d i e s o f some g o l d d e p o s i t s i n Nevada; U.S.G.S. P r o f . Paper 800-C, pp. C15-19. P o t t e r , R.W., 1977, Pressure c o r r e c t i o n for f l u i d i n c l u s i o n 103 homogenization temperatures based on the v o l u m e t r i c proper-t i e s o f the system NaCl-H^O; J . of Research, U.S.G.S., v. 5, pp. 603-607. P o t t e r , R.W., C l y n e , M.A., and Brown, D.L., 1978, F r e e z i n g p o i n t depression o f aqueous sodium c h l o r i d e s o l u t i o n s ; Econ. Geol., v. 73, pp. 284-285. Sutherland Brown, A., 1968, Geology of the Queen C h a r l o t t e I s l a n d s , B r i t i s h Columbia; B.C. M i n i s t r y o f Energy, Mines and Pet. Res., B u l l . 54. CHAPTER V Evidence for the Age of the Skonun Formation, Queen C h a r l o t t e I s l a n d s , B r i t i s h Columbia 105 ABSTRACT Recent p a l y n o l o g i c a l , macrofaunal, and i n t r u s i v e evidence from a low s e c t i o n o f the Skonun Formation on the C i n o l a d e p o s i t on Graham I s l a n d i n d i c a t e s that i t i s of Middle Miocene age, that the whole formation i s most probably of the same age, and that i t c o r r e l a t e s with s e v e r a l Middle Miocene s e r i e s of the P a c i f i c northwest. 106 RESUME D'AUTEUR Une etude recente des assemblages de palynomorphes et de mollusques combinee aux donnees radiometriques d'une s e c t i o n i n f e r i e u r e de l a Formation Skonun sur l e gisement C i n o l a (Graham Island) indique (1) un age Miocene Moyen, (2) que toute l a Formation Skonun e s t probablement du meme age, et (3) que l a Formation Skonun peut e t r e c o r r e l e e avec p l u s i e u r s autres s e r i e s du Miocene Moyen sur l a cote nord-ouest du P a c i f i q u e . 107 INTRODUCTION The Skonun Formation i s a s e r i e s of sandstones (marine and non-marine), s h a l e s , l i g n i t e s t r i n g e r s , and conglomerates under-l y i n g the Queen C h a r l o t t e Lowlands of e a s t e r n Graham I s l a n d (Figure 1). Named and d e s c r i b e d by MacKenzie (1916), the Skonun Formation was d e s c r i b e d most r e c e n t l y and thoroughly by Sutherland Brown (1968). Skonun sediments onlap v o l c a n i c rocks of the Masset Formation (Paleocene-Eocene?), and are cut by the Tow H i l l s i l l s o f l a t e P l i o c e n e - e a r l y P l e i s t o c e n e age (Sutherland Brown, 1968). P l e i s t o c e n e marine d r i f t , outwash d e p o s i t s , and t i l l o v e r l y the Skonun unconformably to conformab-l y . Although exposures of Skonun sediments are very l i m i t e d because of t h e i r f r i a b l e nature and e x t e n s i v e e r o s i o n , a t o t a l t h i c k n e s s of the formation has been determined from d r i l l holes from 107 to 1812 m. Quoting the p a l y n o l o g i c a l study by M a r t i n and Rouse (1966), Sutherland Brown concluded that the Skonun sediments had accumulated i n an e s t u a r i n e - l i k e b a s i n , p o s s i b l y c o n t r o l l e d by the r e g i o n a l Sandspit f a u l t system. Although they had no f i r m evidence at that time as to the age of the Skonun, M a r t i n and Rouse (1966) suggested that d e p o s i t i o n probably oc-c u r r e d between the l a t e Miocene and e a r l y P l i o c e n e . Based on assemblages of m o l l u s c s , A d d i c o t t (1978) i n d i c a t e d an e a r l y Late Miocene age and a shallow marine to b r a c k i s h water d e p o s i t i o n a l environment for the marine sands of the formation. At the C i n o l a g o l d d e p o s i t on c e n t r a l Graham I s l a n d (Figure 1), conglomerate and coarse sandstone u n i t s comprise 85 to 90% 108 o f the t o t a l Skonun Formation, with the remainder c o n s i s t i n g of s i l t y mudstone and minor s h a l e . T h i s c l a s t i c sequence appears to have been de p o s i t e d by a braided r i v e r system d i s c h a r g i n g i n t o a marine b a s i n (Champigny and S i n c l a i r , 1980, 1981). De-t a i l e d g e o l o g i c a l examination of d r i l l core by Champigny, com-bined with K-Ar dates, p a l y n o l o g i c a l a n a l y s i s , and molluscan fauna, have prompted us to r e v i s e the age of the Skonun forma-t i o n over the p r e v i o u s e s t i m a t e s . 109 F i g u r e 1. Map s h o w i n g t h e a r e a u n d e r l a i n b y t h e S k o n u n F o r m a t i o n ( d a s h l i n e s ) a nd l o c a t i o n o f t h e C i n o l a d e p o s i t . 110 RESULTS K-Ar Data: A stock of p o r p h y r i t i c r h y o l i t e and a s s o c i a t e d dykes cut the conglomerate-sandstone sequence at the C i n o l a gold de-p o s i t . Whole-rock K-Ar age determinations on two samples of r h y o l i t e - p o r p h y r y i n d i c a t e d ages o f 14.0 and 14.1 Ma. (Champigny and S i n c l a i r , 1980, 1981). Hence, d e p o s i t i o n of Skonun s e d i -ments o c c u r r e d p r i o r to 14 Ma, or Middle Miocene, a c c o r d i n g to Berggren and van Couvering (1974). Palynology : A d r i l l - c o r e sample of carbonaceous s i l t s t o n e with abundant p y r i t e , from the e a s t e r n p a r t of the C i n o l a d e p o s i t , was c o l l e c t e d f o r p a l y n o l o g i c a l a n a l y s i s and processed using HC1, HF, a c e t o l y s i s , b l e a c h , and ZnBr . Palynomorph r e c o v e r y and p r e s e r v a t i o n were e x c e l l e n t , a l l o w i n g f o r r e l a t i v e l y good r e c o n s t r u c t i o n s . The C i n o l a palynoassemblage i s dominated by c o n i f e r p o l l e n , p a r t i c u l a r l y those o f Pinus ( p i n e ) , Tsuga h e t e r o p h y l l i t e s (hemlock), P i c e a g r a n d i v e s c i p i t e s (spruce), Pseudotsuga (Douglas f i r ) , Sequoia (redwood), and other taxodiaceous p o l l e n . Other main elements are p o l l e n of the Cyperaceae (sedges), Quercus sp. (oak), and Fagus (beech), and spores of Osmunda, L a e v i g a t o s p o r i t e s , and Polypodiaceae ( f e r n s ) . Other p o l l e n occur i n l e s s e r amounts, v i z . Alnus ( a l d e r ) , Carya ( h i c k o r y ) , I l e x ( h o l l y ) , G r a m i n i d i t e s ( g r a s s ) , and Cedrus p e r i a l a t a ( c e d a r ) . I l l The palynoassemblage i s s i m i l a r to that r e p o r t e d by M a r t i n and Rouse (1966) f o r s t r a t i g r a p h i c a l l y higher s t r a t a of the Skonun Formation on Graham I s l a n d , northeast of the C i n o l a de-p o s i t . In the present assemblage, however, we found p o l l e n of both Nyssa and Liquidambar p r e v i o u s l y unrecorded by M a r t i n and Rouse (1966). In A l a s k a Wolfe and Leopold (1967) r e p o r t e d both Nyssa and Liquidambar i n the younger of two S e l d o v i a n f l o r a s of e a r l y - m i d Miocene age. These authors (p. 203) r e p o r t that both genera are summer-temperature s e n s i t i v e , and a p p a r e n t l y became e x t i n c t i n A l a s k a by the l a t e S e l d o v i a n (Middle Miocene), i n response to a r a p i d d e c l i n e i n summer temperatures. From t h i s , we conclude that the Skonun assemblange from the C i n o l a s i t e i s no younger than the e a r l y p a r t of the mid-Miocene, c o r r e l a t i n g c l o s e l y with the younger S e l d o v i a n f l o r a o f A l a s k a , i . e . no younger than mid-Barstovian i n the North American mammalian stage s c a l e , or c l o s e to 15 Ma (Berggren and van Couvering, 1974). Other c l o s e l y c o r r e l a t i v e Miocene f l o r a s from the P a c i f i c Northwest are the M a s c a l l of Oregon (K-Ar - 15.4 Ma), the R o c k v i l l e o f Idaho (16.7 Ma), and the F r a s e r Bend Formation near Quesnel, B.C., estimated r e c e n t l y by Rouse and Mathews (1979) to be between 17 and 13.7 Ma. The F r a s e r Bend assemblage, however, l a c k s p o l l e n of Nyssa, and hence may be s l i g h t l y younger than the C i n o l a assembly. A l t e r n a t i v e l y , the absence of Nyssa might r e f l e c t a more i n l a n d and/or upland l o c a t i o n r e l a t i v e to the other f l o r a s of s i m i l a r a g e f l o r i s t i c composition. Based on the c o l l e c t i v e evidence, a reasonable estimate of the age of the 112 Cinola-Skonun assemblage i s between 17-15 Ma, e a r l y Middle Miocene, or e a r l y to mid B a r s t o v i a n on the North American mamma-l i a n stage sequence (Berggren and van Couvering, 1974). The presence of Nyssa and Liquidambar i n the C i n o l a assemb-lage supports a c o n c l u s i o n that the conglomerate-sandstone se-quence at C i n o l a i s o l d e r than the other s e c t i o n s of the Skonun Formation to the north and e a s t , and hence s t r a t i g r a p h i c a l l y lower (Champigny and S i n c l a i r , 1981). I t a l s o suggests that the higher s e c t i o n s of the Skonun, i n outcrops to the north and e a s t , are younger, but s t i l l w i t h i n the Middle Miocene, judging by the presence of p o l l e n of Fagus, Quercus, and J u g l a n s , which became e x t i n c t i n the l a t e S e l d o v i a n (Middle Miocene) i n A l a s k a (Wolfe and Leopold, 1967). T h i s apparent range i n age for the Skonun Formation on Graham I s l a n d c o u l d l i k e l y be confirmed by a d d i t i o n a l p a l y n o l o g i c a l and i n v e r t e b r a t e s t u d i e s of w e l l s i n e a s t e r n and northern Graham I s l a n d . In s i x w e l l s d r i l l e d by R i c h f i e l d (now A t l a n t i c R i c h f i e l d ) O i l C o r p o r a t i o n (Sutherland Brown, 1968, p. 123, f i g u r e 20), what appears to be Skonun e q u i -v a l e n t v a r i e s from about 1760 m i n the Tow H i l l w e l l to zero t h i c k n e s s i n the Masset w e l l . In the Tow H i l l w e l l , the lower 750 m i s mainly conglomerate with some sandstone, resembling the l i t h o l o g y of the C i n o l a d e p o s i t . The f a c i e s of the upper p a r t of Tow H i l l w e l l , by c o n t r a s t , ranges from c o a l , s h a l e , s i l t -stone to sandstone, e s s e n t i a l l y the same as i n the outcrops s t u -died by M a r t i n and Rouse (1966) and A d d i c o t t (1978). To see i f we c o u l d c o r r o b o r a t e the suggested c o r r e l a t i o n , 113 f i v e core samples from the Tow H i l l w e l l were analyzed for pa-lynomorphs. The upper two samples, at 187 and 649 m, e s s e n t i a l -l y contained assemblages i d e n t i c a l to those of the outcrops r e -ported by M a r t i n and Rouse (1966); both lacked Liquidambar and Nyssa. However, the assemblage at 762 m contained one Liquidambar, but no Nyssa. The lower two samples from the coarse f a c i e s c o ntained too few and r e l a t i v e l y p o o r l y p r eserved palynomorphs to be u s e f u l i n c o r r e l a t i o n . Although the presence o f a s i n g l e g r a i n of Liquidambar i s i n s u f f i c i e n t evidence, i t i s tempting to s p e c u l a t e that i t may rep r e s e n t the uppermost p a r t of the lower coarse f a c i e s o f the Skonun Formation. 114 FAUNAL EXAMINATION Three samples o f p o o r l y s o r t e d , coarse g r a i n e d , s i l i c i f i e d sandstone with abundant d i s a r t i c u l a t e d b i v a l v e s were c o l l e c t e d on a su r f a c e trench at the C i n o l a d e p o s i t . The pelecypods are preserved as i n t e r n a l and e x t e r n a l molds without any t r a c e o f o r i g i n a l s h e l l m a t e r i a l . The i d e n t i f i e d taxa i n c l u d e : S p i s u l a (Mactromeris) sp. (Miocene-Recent i n Western North America), Chione ( S e c u r e l l a ) sp. (Oligocene-Pliocene i n Northwestern North America), and ? Macoma (Eocene-Recent). The specimen o f the subgenus S e c u r e l l a bears a strong resemblance to S. e n s i f e r a (Dall) which, a c c o r d i n g to Moore (1963) ( f i d e E t h e r i n g t o n , 1931), d i d not occur beyond the Middle Miocene. However, the p r e s e r v a t i o n ( e x t e r n a l mold) i s not s u f f i c i e n t to make a de-f i n i t e s p e c i f i c i d e n t i f i c a t i o n . T h i s b i v a l v e assemblage compares with other western North American Miocene fauna ( A d d i c o t t , 1973), i n p a r t i c u l a r those o f the Miocene C l a l l a m and A s t o r i a Formations ( A d d i c o t t , 1976; Moore, 1963). The assemblage, together with the immature char-ac t e r o f the sandstone and the c o q u i n o i d nature o f the molds, suggests d e p o s i t i o n i n a beach to near-shore marine environment. 115 CONCLUSIONS With the three independent l i n e s o f evidence, we conclude that most of the Skonun Formation was de p o s i t e d d u r i n g the e a r l y p a r t o f the mid-Miocene (17 to 15 Ma), probably c o i n c i d i n g with an i n t e r v a l d u r i n g which the Sandspit f a u l t system was very a c t i v e (Sutherland Brown, 1968). The environment of d e p o s i t i o n i s mainly non-marine, but r e l a t i v e l y c l o s e to sea, and i n c l u d e s e s t u a r y , swamp, and beach. A d d i t i o n a l evidence for the age of the Skonun has been pro-vided by Shen et al. (1981) i n a study o f f l u i d i n c l u s i o n s at C i n o l a . They estimated a minimum sedimentary cover o f 1100 m at the time o f i n t r u s i o n and a s s o c i a t e d m i n e r a l i z a t i o n , suggesting that a l l o f the Skonun was de p o s i t e d p r i o r to 14 Ma. 116 ACKNOWLEDGMENTS We thank Jane Shepperd ( G e o l o g i c a l S c i e n c e s , U.B.C.) f o r the p a l y n o l o g i c a l sample p r e p a r a t i o n . F i n a n c i a l support was provided by N.S.E.R.C. through a post-graduate s c h o l a r s h i p (N.C.) and by C o n s o l i d a t e d C i n o l a Mines L t d . 117 REFERENCES A d d i c o t t , W.O., 1973, Neogene marine molluscs of the P a c i f i c Coast o f North America: An annotated b i b l i o g r a p h y , 1797-1969; U.S.G.S. B u l l . 1362, 201 p. A d d i c o t t , W.O., 1976, Molluscan p a l e o n t o l o g y of the Lower Miocene C l a l l a m Formation, northwestern Washington; U.S.G.S. P r o f . Paper 196, 44 p., 9 p l a t e s . A d d i c o t t , W.O., 1978, Late Miocene molluscs from the Queen C h a r l o t t e I s l a n d s , B r i t i s h Columbia, Canada; Jou r . Res. USGS, v. 6, no. 5, pp. 677-690. Berggren, W.A., and van Couvering, J.A., 1974, The Late Neogene; Paleogeog. P a l e o c l i m . P a l e o e c o l . , v. 16, no. 1/2, 216 p. Champigny, N., and S i n c l a i r , A.J., 1980, C i n o l a (Specogna) g o l d d e p o s i t , Queen C h a r l o t t e I s l a n d s , B r i t i s h Columbia - A C a r l i n - t y p e d e p o s i t ( a b s t r a c t ) ; Can. I n s t . Min. M e t a l l . B u l l 75, v. 73, p. 62. Champigny, N., and S i n c l a i r , A.J., 1981, C i n o l a g o l d d e p o s i t , Queen C h a r l o t t e I s l a n d s , B r i t i s h Columbia - A Canadian C a r l i n - t y p e d e p o s i t ; Can. I n s t . Min. M e t a l l . Spec. V o l . ( i n p r e s s ) . Mackenzie, J.D., 1916, Geology of Graham I s l a n d , B.C.; Geol. 118 Surv. Canada, Mem. 88. M a r t i n , H.A., and Rouse, G.E., 1966, Palynology of Late T e r t i a r y sediments from Queen C h a r l o t t e I s l a n d s , B r i t i s h Columbia; Can. J . Botany, v. 44, pp. 171-208, 12 p l a t e s . Moore, E . J . , 1963, Miocene marine molluscs from the A s t o r i a Formation i n Oregon; U.S.G.S. P r o f . Paper 419, 109 p., 32 p l a t e s . Rouse, G.E., and Mathews, W.H., 1979, T e r t i a r y geology and pa-l y n o l o g y of the Quesnel area, B r i t i s h Columbia; B u l l . Can. P e t r o l . Geology, v. 27, no. 4, 418-445. Shen, K., Champigny, N., and S i n c l a i r , J.A., 1981, G e n e t i c im-p l i c a t i o n s of f l u i d i n c l u s i o n s t u d i e s , C i n o l a gold d e p o s i t , Queen C h a r l o t t e I s l a n d s , B.C.; B.C. M i n i s t r y of Mines and Pet. Res. Paper 1981-1 ( i n p r e s s ) . Sutherland Brown, A., 1968, Geology of the Queen C h a r l o t t e I s l a n d s , B r i t i s h Columbia; B*C. M i n i s t r y o f Energy, Mines, and Pet. Res., B u l l . 54. Wolfe, J.A., and Leopold, E.B., 1967, Neogene and e a r l y Quaternary v e g e t a t i o n of northwestern North America and n o r t h e a s t e r n A s i a ; in The B e r i n g Land B r i d g e , D.M. Hopkins (ed.), S t a n f o r d U n i v e r s i t y P r e s s , pp. 193-206. 119 CHAPTER VI C i n o l a Gold D e p o s i t , Queen C h a r l o t t e I s l a n d s , B.C. A Geochemical Case H i s t o r y 120 ABSTRACT C i n o l a d e p o s i t , a l a r g e tonnage, low grade C a r l i n - t y p e g o l d d e p o s i t on Graham I s l a n d (Queen C h a r l o t t e I s l a n d s ) , was s u b j e c t to e x tensive geochemical e x p l o r a t i o n s h o r t l y a f t e r i t s d i s c o v e r y i n 1970. We have reviewed the a v a i l a b l e rock, s o i l , and s i l t multi-element geochemical data from t h i s e a r l y e x p l o r a t i o n stage i n a r i g o r o u s , s y s t e m a t i c manner, and i n the l i g h t o f substan-t i a l g e o l o g i c a l i n f o r m a t i o n about the d e p o s i t . Some s p e c i f i c c o n c l u s i o n s from our study are: 1. Ag l i t h o g e o c h e m i c a l data d e f i n e s the known m i n e r a l i z e d zone b e t t e r than does Au. T h i s i s ap p a r e n t l y due to a more con-tinuous primary d i s p e r s i o n of Ag r e l a t i v e to g o l d . 2. Cu, N i , Co, Pb, Zn, and Mo i n rocks, s o i l s , or s i l t s do not provide c l e a r cut p a t t e r n s or high enough abundance l e v e l s f o r use i n e x p l o r a t i o n . 3. Hg i n s o i l and Hg i n peat show a pronounced secondary d i s -p e r s i o n p a t t e r n , a p p a r e n t l y due to f l u i d t r a n s p o r t eastward from the main centre of m i n e r a l i z a t i o n at the C i n o l a depos-i t . 4. Threshold s e l e c t i o n using p r o b a b i l i t y graphs i s a u s e f u l p r a c t i c a l approach to evaluate s p a t i a l d i s t r i b u t i o n p a t t e r n s of subpopulations i n geochemical data s e t s . 121 INTRODUCTION C i n o l a g o l d d e p o s i t , c e n t r a l l y l o c a t e d on Graham I s l a n d , o f f the west coast of B r i t i s h Columbia (Figure 1), has been de-s c r i b e d g e o l o g i c a l l y by Champigny and S i n c l a i r (1980a, 1981). The d e p o s i t i s l a r g e , more than 45 m i l l i o n tons, with an average of .054 oz. Au/s.t, and has many of the c h a r a c t e r i s t i c s of a C a r l i n - t y p e d e p o s i t (Richards et a l . , 1976; Champigny and S i n c l a i r , 1980b, 1981). G e o l o g i c a l f e a t u r e s c h a r a c t e r i s t i c of the d e p o s i t i n c l u d e (1) small p a r t i c l e s i z e f o r g o l d ( l e s s than 0. 5 u ) , (2) mid-Miocene age of m i n e r a l i z a t i o n , (3) p r o x i m i t y with a major f a u l t system, (4) a r g i l l i c a l t e r a t i o n , (5) p o r o s i t y of the host rock, and (6) s p a t i a l and p o s s i b l y g e n e t i c a s s o c i a -t i o n with a r h y o l i t e - p o r p h y r y i n t r u s i o n . S u r f i c i a l d e p o s i t s are g l a c i a l t i l l s ranging i n t h i c k n e s s from 0 to 35 m, with an average o f 3 m. G l a c i a l movement f o l l o w e d a southwest-northeast d i r e c t i o n i n the area (Sutherland Brown, 1968). The area i s h e a v i l y f o r e s t e d , due to a m i l d and r a i n y c l i m a t e , and outcrops are absent except along f a u l t s c a r p s . Three c o n t i n u a l l y f l o w i n g creeks and one r i v e r d r a i n the m i n e r a l i z e d zone. T h i s work forms p a r t of a comprehensive study which empha-s i z e s the a p p l i c a t i o n of g e o l o g i c a l s t u d i e s f o r e x p l o r a t i o n and e v a l u a t i o n of the C i n o l a d e p o s i t . A s y s t e m a t i c e v a l u a t i o n of e x p l o r a t i o n geochemical data was done to: 1. provide a r i g o r o u s e v a l u a t i o n of multi-element geochemical data f o r a Canadian " C a r l i n - t y p e " gold d e p o s i t ; 122 2. evaluate c r i t i c a l l y the primary and secondary d i s p e r s i o n haloes of elements represented i n the v a r i o u s data s e t s a v a i l a b l e to us; and 3. i l l u s t r a t e the advantage of a r i g o r o u s but simple s t a t i s t i -c a l approach as an e v a l u a t i o n procedure f o r geochemical data. 122a A\SA^7 %BR,TISH GRAHAM I C H A R L O T T E * ^ „ n l l l l l m > \ . t £ > F^<-JPORT/ ISLANOSjA ^COLUMBIA V X- -O CLEMENTS 1 V ISLAND CjT <^\jU SKATLA "jlTLELL I \ CINOLA > C . N O L T U S & GOLD DEP0SIT>^^^^rDSP,T GOLD DEPOSIT ^ MORESBY T ~ y M ^ V ISLAND ^K>^3 j SCALE ' ^  ^ l^V? 1 s o ,o 2OM,LES P h y s i o g r o p h i c Boundary M 133° 132° 131° 1 1 1 F i g u r e 1. L o c a t i o n map o f t h e C i n o l a d e p o s i t . 123 THE DATA Multi-element geochemical data were a v a i l a b l e f o r rock, s o i l , and s i l t samples taken d u r i n g r o u t i n e e x p l o r a t i o n o f the C i n o l a p r o p e r t y i n the e a r l y and middle 1970's (see Champigny, S i n c l a i r , and Sanders, 1980). These data are a v a i l a b l e i n as-sessment r e p o r t s f i l e d with the B r i t i s h Columbia government, but were pr o v i d e d to us by G.G. Richards of J.M.T. S e r v i c e s Corp. and R.W. Stevenson of Kennco E x p l o r a t i o n L t d . A b r i e f d e s c r i p t i o n of the nature of each data type f o l l o w s . L i t h o g e o c h e m i c a l d a t a : f i f t y - n i n e grab samples from l i m i t e d s u r -face exposures were analyzed f o r a l l or some of Au, Ag, Hg, As, Sb, and W. Gold content was measured by f i r e assay. Ag and Hg were determined by atomic a b s o r p t i o n spectrophotometry. The As and W analyses were obtained by c o l o r i m e t r i c methods. No i n f o r -mation r e g a r d i n g a n a l y t i c a l method was a v a i l a b l e f o r Sb. S o i l d a ta: four hundred and e i g h t y - s i x s o i l samples were taken more-or-less r e g u l a r l y over the C i n o l a p r o p e r t y , mainly along c l a i m l i n e s . Most were B-horizon samples that were analyzed f o r Au, Ag, Hg, Mo, Cu, Pb, Zn, N i , and Co. A - h o r i z o n samples were anayzed for Hg. A second s o i l survey over the m i n e r a l i z e d zone added 158 more samples that were analyzed f o r g o l d . The -80 mesh f r a c t i o n was used f o r a l l the a n a l y s e s . Determination of a l l elements was by atomic a b s o r p t i o n spectrophotometry. S i l t : F i f t y - e i g h t s i l t samples were c o l l e c t e d from three creeks 124 and a r i v e r i n the v i c i n i t y o f the m i n e r a l i z e d area. The sam-p l e s were analyzed f o r a l l or some of Au, Ag, Mo, Cu, Pb, Zn, N i , Co, and As, with the same a n a l y t i c a l procedures as were used f o r the s o i l samples. As content was measured by a c o l o r i m e t r i c method. 125 DATA EVALUATION PROCEDURE Our g e n e r a l procedure (Figure 2) f o r c r e a t i n g each of the f o r e g o i n g data groups i n v o l v e d (1) coding and e d i t i n g , (2) pro-d u c t i o n of c o r r e l a t i o n matrixes for raw and log-transformed data, (3) c o n s t r u c t i o n of a c o r r e l a t i o n diagram, (4) t h r e s h o l d s e l e c t i o n from p r o b a b i l i t y p l o t s of i n d i v i d u a l elements, (5) drawing o f machine-constructed maps showing d i s t r i b u t i o n s o f v a r i o u s sub-populations for each element i n each data group, and (6) i n t e g r a t i o n of r e s u l t s f o r the three separate data s e t s , and i n t e r p r e t a t i o n i n a g e o l o g i c a l c o ntext. The method of t h r e s h o l d s e l e c t i o n i s that d e s c r i b e d by S i n c l a i r (1SJ74, 1976) , i n which multi-modal d i s t r i b u t i o n s are p a r t i t i o n e d on p r o b a b i l i t y graphs i n t o two or more components, which i n g e n e r a l appear to be lognormal i n form. 126 F i g u r e 2. P r o c e d u r a l p a t h i n e v a l u a t i n g C i n o l a g e o c h e m i c a l d a t a . GEOCHEMICAL DATA ± COMPUTER F I L E (SAMPLE LOCATION AND CHEMICAL ANALYSIS) REARRANGED COMPUTER F I L E (LOG TRANSFORMED VALUES) CORRELATI AND SCATTE ON MATRIX R DIAGRAMS y f CORRELATION DIAGRAMS PROBABI PLOT L I T Y S > SELECTION OF THRESHOLDS COMPUTER MAPS OF VALUES ABOVE THRESHOLDS INTERPRETATION 127 LITHOGEOCHEMISTRY A summary o f means and standard d e v i a t i o n s f o r raw and l o g -transformed l i t h o g e o c h e m i c a l data i s given i n Table 1, and a c o r r e l a t i o n matrix f o r log-transformed v a r i a b l e s i s given i n Table 2. The c r i t i c a l f e a t u r e s of the c o r r e l a t i o n matrix are summarized i n the c o r r e l a t i o n diagram of F i g u r e 3. These r e -s u l t s are of i n t e r e s t because they demonstrate c l e a r l y t h a t among the elements s t u d i e d a simple, d i r e c t r e l a t i o n s h i p i n v o l -v i n g gold e x i s t s with s i l v e r , a r s e n i c , and antimony. Mercury and tungsten have s i g n i f i c a n t i n t e r - c o r r e l a t i o n s , but do not c o r r e l a t e s i g n i f i c a n t l y with gold at the 0.01 l e v e l . P r o b a b i l i t y graphs of a l l v a r i a b l e s were examined i n de-t a i l . Ag, Hg, Sb, and W can be i n t e r p r e t e d without d i f f i c u l t y as combinations of two, and i n the case of g o l d , three lognormal p o p u l a t i o n s . Two of these graphs are reproduced i n f i g u r e s 4 and 5. Both i l l u s t r a t e the ease with which t h r e s h o l d s can be s e l e c t e d u sing the method of S i n c l a i r (1974). Such t h r e s h o l d s have been used as a b a s i s for c o n t o u r i n g the data to separate geographic areas u n d e r l a i n by "high" and "low" valued popula-t i o n s so that t h e i r d i s t r i b u t i o n s c o u l d be examined i n r e l a t i o n to the m i n e r a l d e p o s i t as o u t l i n e d by e x t e n s i v e diamond d r i l -l i n g . R e p r e s e n t a t i v e examples are shown i n F i g u r e s 6, 7, 8, 9, and 10, and i n d i c a t e : 1. the c l o s e s p a t i a l c o r r e l a t i o n of areas of c e r t a i n "high" element c o n c e n t r a t i o n s and t h e i r r e l a t i o n s h i p to the gold d e p o s i t ; 128 T a b l e 1. Summary o f means a n d s t a n d a r d d e v i a t i o n s f o r raw a n d l o g - t r a n s f o r m e d ( b a s e 10) l i t h o g e o c h e m i c a l d a t a , C i n o l a d e p o s i t . A r i t h m e t i c v a l u e s a r e a l l i n ppm e x c e p t Hg w h i c h i s i n ppb. NAME NO.OOF ARITHMETIC LOGARITHMIC VALUES MEAN STD.DEV. MEAN STD.DEV. Au 59 0.2954 0.6060 -1.362 0.9675 Hg 48 2158. 2572. 2.944 0.7064 Ac? 45 1.509 1.307 0.1243E-01 0.3971 As 45 127.8 200.0 1.508 0.9118 Sb 45 63.91 61.84 1.499 0.6151 W 45 40.02 37.10 1.280 0.6817 129 T a b l e 2. C o r r e l a t i o n matrix f o r log-transformed (base 10) l i -thogeochemical data, C i n o l a d e p o s i t . Au Hg Ag As Sd Hg .31 Ag .50 .32 As .56 .63 .30 Sb .50 .34 .36 .12 W .40 .49 .07 .36 .49 The c o r r e l a t i o n c o e f f i c i e n t s are based on 45 p a i r e d o b s e r v a t i o n s between Hg, Ag, As, and Sb, 29 p a i r e d o b s e r v a t i o n s between Au and Ag, As, Sb, and W, and 31 p a i r e d o b s e r v a t i o n s between Au and Hg. 2. a high s i l v e r p o p u l a t i o n that c l e a r l y d e f i n e s the centre o f the gold d e p o s i t . Parameters o f p a r t i t i o n e d p o p u l a t i o n s are given i n Table 3. The geographic d i s t r i b u t i o n o f gold values above t h r e s h o l d i s not s u r p r i s i n g (Figure 6). Diamond d r i l l i n g has i n d i c a t e d that g o l d m i n e r a l i z a t i o n decreases p r o g r e s s s i v e l y to the north and e a s t . Sporadic occurrences of Au highs probably a r i s e from the wides-pread nature o f m i n e r a l i z a t i o n combined with i t s l o c a l v a r i a b i -l i t y , a v a r i a b i l i t y that would be enhanced by the small s i z e o f the l i t h o g e o c h e m i c a l samples. S i l v e r i s about as abundant as go l d at C i n o l a , and i s known to be present i n s o l i d s o l u t i o n i n gold p a r t i c l e s (Champigny and S i n c l a i r , 1980b, 1981). A low s i l v e r content i n the bedrock produces a much lower geochemical c o n t r a s t of s i l v e r r e l a t i v e to g o l d , and t h e r e f o r e a smaller area of s i l v e r "high" (Figure 7). Cinnabar and tiemmanite (HgSe) occur i n the C i n o l a ore and are the obvious sources f o r mercury. S p h a l e r i t e , r a r e l y ob-130 served, i s a l s o a p o s s i b l e source of Hg. F r a c t u r e systems through the p o o r l y l i t h i f i e d Skonun sediments east o f the ore body probably c o n t r i b u t e d to the d i f f u s i o n of mercury (Figure 8) . Disseminated p y r i t e occurs o u t s i d e the l i m i t o f economic m i n e r a l i z a t i o n and e l e c t r o n microprobe a n a l y s i s has shown l o c a l -l y a high As content (1.1%) i n p y r i t e (Champigny and S i n c l a i r , 1981). No a r s e n i c and antimony minerals have been i d e n t i f i e d i n the d e p o s i t . As and Sb l i t h o g e o c h e m i c a l highs can probably be a t t r i b u t e d to s o l i d s o l u t i o n o f a r s e n i c and antimony i n p y r i t e and/or m a r c a s i t e , as rep o r t e d i n other g o l d d e p o s i t s by Boyle (1979, p. 144-145). The tungsten anomaly (Figure 10) may be caused by the pre-sence of t r a c e amounts o f s c h e e l i t e , which i s not repo r t e d at C i n o l a but i s a common t r a c e m i n e r a l i n g o l d d e p o s i t s (Boyle, 1979, p. 195). T a b l e 3. Means and s t a n d a r d d e v i a t i o n s d e t e r m i n e d g r a p h i c a l l y f o r p a r t i t i o n e d m e t a l p o p u l a t i o n s o f l i t h o g e o c h e m i c a l d a t a , C i n o l a d e p o s i t . E l e m e n t Cone. U n i t . Q, ."'> ro ' 1 A p o p u l a t i o n b b+SL b-SL B p o p u l a t i o n b b+SL b-SL T h r e s h o l d ( s ) Au ppm 11 1.6 2.0 1.2 55 0.01 0.03 0.006 0.05 a n d 34 0.13 0.30 0.06 0.85 ppm Ag ppm 29 3.3 4.2 2.5 71 ".0.7 1,35 0.36 2.5 Hg ppb 5 8 3630 5750 1950 42 178 355 85 800 As ppm 100 36 260 4.8 Sb ppm 45 129 170 98 55 13 26 5.8 70 W ppm 56 61 110 36 44 7.5 13.5 4.3 23 G r a p h s b a s e d on 59 v a l u e s f o r Au, 48 v a l u e s f o r Hg a n d 45 v a l u e s f o r A g , A s , Sb and W c u m u l a t e d i n d i v i d u a l l y . b = a n t i l o g o f mean o f l o g t r a n s f o r m e d d a t a b+SL = a n t i l o g o f mean p l u s one s t d . d e v . o f l o g t r a n s f o r m e d d a t a b-SL = a n t i l o g o f mean m i n u s one s t d . d e v . o f l o g t r a n s f o r m e d d a t a F i g u r e 3. M o s t s i g n i f i c a n t c o r r e l a t i o n s ( a t t h e 0.01 l e v e l ) o f l o g a r i t h m i c a l l y t r a n s f o r m e d (base 10) l i t h o g e o c h e m i c a l d a t a . to 133 5 20 40 60 80 95 CUMULATIVE PERCENT F i g u r e 4 . Lognormal p r o b a b i l i t y p l o t f o r Sb l i t h o g e o c h e m i c a l data p a r t i t i o n e d i n t o upper (A) and lower (B) p o p u l a t i o n s . Black dots are o r i g i n a l data. 134 5 20 40 60 80 y s B B — m — i — g — i 1 9 CUMULATIVE PERCENT F i g u r e 5 . L o g n o r m a l p r o b a b i l i t y p l o t f o r Au l i t h o g e o c h e m i c a l da.ta p a r t i t i o n e d i n t o u p p e r ( A ) , m e d i a n (A') a n d l o w e r ( B ) 1 p o p u l a t i o n s . B l a c k d o t s a r e o r i g i n a l d a t a . i 135 F i g u r e 6. Au (ppm X 100) i n r o c k . T r i a n g l e s a r e h i g h p o p u l a t i o n ; p l u s s i g n s a r e l o w p o p u l a t i o n . H a c h u r e d a r e a r e p r e s e n t s r e l a t i v e l y h i g h g r a d e zone o f C i n o l a d e p o s i t . P r i n c i p a l f a u l t s a r e shown as f o l l o w s : FF = F o o t w a l l F a u l t , SF = S a n d s p i t F a u l t . 136 F i g u r e 7. Ag (ppm X 10) i n r o c k . See F i g u r e 6 f o r e x p l a n a t i o n , o f s y m b o l s . 137 F i g u r e 8 . Hg i n r o c k ( p p b ) . s y m b o l s . See F i g u r e 6 f o r e x p l a n a t i o n o f 138 F i g u r e 9. Sb i n rock (ppb). symbols. See F i g u r e 6 f o r e x p l a n a t i o n of 139 F i g u r e 10. W i n r o c k , ( p p b ) . s y m b o l s . See F i g u r e 6 f o r e x p l a n a t i o n o f 140 SOIL GEOCHEMISTRY A s i m i l a r method of data a n a l y s i s was used f o r s o i l data as fo r l i t h o g e o c h e m i c a l data. A summary of means and standard de-v i a t i o n s i s given i n Table 4 and a c o r r e l a t i o n matrix of l o g -transformed values i s provided i n Table 5. The c o r r e l a t i o n matrix i n d i c a t e s the presence of three groups of elements. Group I (Au, Hg, Hg i n peat, Ag). would appear to r e l a t e most d i r e c t l y to the m i n e r a l i z a t i o n p r o c e s s . Group II elements (Cu, N i , Co, Zn, Pb) have high i n t r a g r o u p c o r r e l a t i o n s , but c o r r e l a t e o n l y i n a l i m i t e d manner with Group I elements. I t would appear that these two groups are fundamentally d i f f e r e n t . Group I I I c o n s i s t s o n l y of Mo, about which l i t t l e can be s a i d , because of the narrow range of values and poor a n a l y t i c a l p r e c i s i o n . P r o b a b i l i t y graphs of a l l elements i n groups I and II can be p a r t i t i o n e d i n t o two or three lognormal sub-populations and t h r e s h o l d s chosen with ease (Figure 11 and Table 6). As with l i t h o g e o c h e m i c a l data, we produced contoured p l o t s , u s ing t h r e s h o l d s as the o n l y contour v a l u e s . Four examples are shown i n F i g u r e s 12, 13, 14, and 15 f o r Au, Hg, Hg i n peat, and Cu r e s p e c t i v e l y . The example f o r copper c l e a r l y i l l u s t r a t e s the s p o r a d i c d i s t r i b u t i o n of high values throughout the p r o p e r t y , a r e s u l t that we found to be c h a r a c t e r i s t i c of a l l elements of Group I I . These e r r a t i c s o i l geochemical highs are e a s i l y ex-p l a i n e d i n the cases of z i n c , copper, and l e a d , because of t r a c e amounts of s p h a l e r i t e , c h a l c o p y r i t e , and galena o c c u r i n g very s p o r a d i c a l l y i n the C i n o l a d e p o s i t . 141 On the other hand, Group I elements, exce p t i n g s i l v e r , have a p p r e c i a b l y more r e g u l a r d i s t r i b u t i o n p a t t e r n s . Most r e g u l a r are the comparable p a t t e r n s shown by Hg i n B-horizon and Hg i n A-horizon s o i l s . The p a t t e r n i s pronouncedly a r c u a t e , concave to the west but d r a m a t i c a l l y removed to the east of the C i n o l a d e p o s i t , i n a manner suggestive o f secondary e a s t e r l y d i s p e r s i o n (Figures 13 and 14). T h i s d i s p e r s i o n was probably chemical rather than p h y s i c a l , because gold which i s i n i m a t e l y r e l a t e d i n the d e p o s i t has s o i l highs i n p a r t d i r e c t l y over the C i n o l a de-p o s i t (Figure 12), suggesting r e l a t i v e l y l i t t l e secondary d i s -p e r s i o n . The e r r a t i c s p a t i a l d i s t r i b u t i o n of s i l v e r highs probably r e s u l t s from the low abundance l e v e l i n s o i l s i n combination with poor a n a l y t i c a l p r e c i s i o n . I t i s a l s o p o s s i b l e that no background c o r r e c t i o n was a p p l i e d d u r i n g spectrophotometrie a-n a l y s i s . 142 T a b l e 4. Summary o f means a n d s t a n d a r d d e v i a t i o n s f o r raw a n d l o g - t r a n s f o r m e d ( b a s e 10) s o i l g e o c h e m i c a l d a t a , C i n o l a d e p o s i t . A r i t h m e t i c v a l u e s a r e a l l i n ppm e x c e p t Hg and Hg i n p e a t (HgP) w h i c h a r e i n ppb. NAME NO. OF ARITHMETIC LOGARI THMIC VALUES MEAN STD.DEV. MEAN STD.DEV. Au 644 0.3781E-01 0.8178E-01 -1.729 : 0.4126 Hg 474 590.0 1227. 2.519 0.4034 Ag 486 0.6926 0.5865 -0.2677 0.3262 MO 480 1.077 0.3484 0.1945E-01 0.9844E-01 CO 483 10.22 5.578 0.9285 0.2892 Pb 484 10.18 3.629 0.9723 0.1958 Zri 483 29.74 19.46 1. 358 0.3504 N i 483 9.673 18.66 0.8245 0.3496 Co 483 7.077 5.184 0.6898 0.4212 HgP 457 675. 3 1248. 2.621 0.3458 p 143 T a b l e 5. C o r r e l a t i o n m a t r i x f o r l o g - t r a n s f o r m e d ( b a s e 10) s o i l g e o c h e m i c a l d a t a , C i n o l a d e p o s i t . Dash l i n e s r e p r e s e n t c o r r e l a t i o n c o e f f i c i e n t s t h a t a r e n o t s i g n i f i c a n t a t t h e 1% l e v e l . GROUP ELEMENT Au Hg p e a t Hg Ag Cu N i Co Zn Pb I Hg p e a t .30 Hg .24 .63 Ag .19 - .23 Cu - - .29 .71 N i - - . .14 .63 .72 I I Co - - .17 .73 .78 .79 Zn - - - .69 .78 .82 .86 Pb - - - . 38 .26 .35 . 30. .38 I I I Mo - - .15 .16 - .15 -The c o r r e l a t i o n c o e f f i c i e n t s a r e b a s e d o n a b o u t 480 p a i r e d o b s e r v a t i o n s b e t w e e n a l l e l e m e n t s e x c e p t i n g p a i r s w i t h Au a n d Hg i n p e a t w h i c h a r e b a s e d o n 4 38 a n d 340 p a i r e d o b s e r v a t i o n s r e s p e c t i v e l y . T a b l e 6. Means and s t a n d a r d d e v i a t i o n s d e t e r m i n e d g r a p h i c a l l y f o r p a r t i t i o n e d m e t a l p o p u l a t i o n s o f s o i l g e o c h e m i c a l d a t a , C i n o l a d e p o s i t . ELEMENT CONC. UNIT g. *o A b p o p u l a t i o n b+SL b-SL Q, B p o p u l a t i o n b b+SL b-SL T h r e s h o l d s A u ppm 4 0.26 0.29 0.23 91 0.015 0.030 0.008 0.20 a n d 0.07 ,\ • 5 0.11 0.15 0.09 Ag ppm 5 1.6 2.0 1.3 80 0.78 1.1 0.56 ,1.3 a n d 0.3 15 0.05 0.18 0.02 Hg ppb 10 2100 3600 1300 90 240 500 120 1000 Hg p e a t ppb 7 3200 4700 2200 93 350 620 195 1350 Mo' ppm 100 1.1 1.5 0.8 Cu ppm 65 13 17 9.4 35 4.2 6.4 2.8 8 Pb ppm 96 10 13 8.0 4 2.1 3.0 1.4 5 Zn ppm 70 35 54 23 30 8.8 15 5.0 23 N i ppm 15 14 17 12 85 7.0 11 4.2 35 a n d 16• Co ppm 70 8.4 13 5.4 30 1.5 2.3 1.0 3.5 G r a p h s b a s e d o n 644 v a l u e s f o r Au, 486 v a l u e s f o r A g , 484 v a l u e s f o r P b , 483 v a l u e s f o r Zn, N i a n d Co, 480 v a l u e s f o r Mo, 474 v a l u e s f o r Hg and 457 v a l u e s f o r Hg i n p e a t . S y m b o l s u s e d a r e t h e same a s T a b l e 3. 146 F i g u r e 12. Au (ppm X 100) i n s o i l . S y m b o l s a s i n F i g u r e 6. S a m p l i n g g r i d m o s t l y f o l l o w s c l a i m b o u n d a r i e s . 147 F i g u r e 13. Hg i n B h o r i z o n ( p p b ) . S y m b o l s as i n F i g u r e 6. 148 149 F i g u r e 15. Cu i n s o i l (ppm)." S y m b o l s a s i n F i g u r e 6 150 SILT GEOCHEMISTRY An i d e n t i c a l s t a t i s t i c a l a n a l y s i s was done f o r stream s e d i -ment data as f o r the rock and s o i l data. P l o t t i n g and con-t o u r i n g of the data were not done i n t h i s case, because the s i l t survey covered o n l y a very s m a l l p o r t i o n of the p r o p e r t y . Table 7 c o n t a i n s the means and standard d e v i a t i o n s of the nine e l e -ments that were analyzed. Groupings of elements from the c o r r e -l a t i o n matrix f o r s i l t data (Table 8) are very s i m i l a r to groups d e f i n e d from the c o r r e l a t i o n matrix f o r s o i l data. Group I f o r s i l t samples i n c l u d e Au, As, and Ag. Group II elements (Cu, N i , Co, Zn, and Pb) elements are h i g h l y i n t e r c o r r e l a t e d , e s p e c i a l l y Zn, N i , and Co, which have c o r r e l a t i o n c o e f f i c i e n t s higher than 0.8. C o r r e l a t i o n s of Group II to Group I elements are r e s -t r i c t e d to Ag and As; no s i g n i f i c a n t c o r r e l a t i o n o f Group II elements e x i s t s with g o l d . Mo has a very narrow range of va-l u e s , and i s the o n l y v a r i a b l e i n c l u d e d i n Group I I I . For both s o i l and s i l t c o r r e l a t i o n m a t r i x e s , Group I and Group II are e a s i l y d i s t i n g u i s h e d . Group I i s c e r t a i n l y r e l a t e d to m i n e r a l i z a t i o n , but such a r e l a t i o n s h i p i s not apparent f o r Group I I . Bimodal lognormal d i s t r i b u t i o n s were observed f o r most v a r i a b l e s o f Groups I and II of the s i l t data. S e l e c t i o n o f t h r e s h o l d s was done without d i f f i c u l t y . P a r t i t i o n i n g o f upper and lower p o p u l a t i o n s i s shown f o r Ag i n F i g u r e 16 and sum-marized f o r a l l v a r i a b l e s i n Table 9. A r s e n i c and copper data 151 seem to r e p r e s e n t s i n g l e lognormal d i s t r i b u t i o n s . 152 T a b l e 7. Summary o f means a n d s t a n d a r d d e v i a t i o n s f o r raw a n d l o g - t r a n s f o r m e d ( b a s e 10) s i l t g e o c h e m i c a l d a t a , C i n o l a d e p o s i t . A r i t h m e t i c v a l u e s a r e a l l i n ppm. NAME NO. OF ARITHMETIC LOGARITHMIC VALUES MEAN STD.DEV. MEAN STD.DEV. Au 58 0.1845E-01 0.1412E-01 -1.838 0.33059 Ag. 58 0.7293 0.2728 -0.1813 0.2214 M6 58 0.7241 1.121 -0.3443 0.4656 Cu 58 9.138 3.390 0.9339 0.1556 Z.n 58 70.90 48.98 1.744 0.3279 Pb 58 10.48 3.803 0.9900 0.1690 N i 58 14.53 5.823 1.120 0.2046 ct> 58 35.50 60.55 1.220 0.5782 A s : 57 141.9 191.3 1.855 0.5050 153 T a b l e 8. C o r r e l a t i o n m a t r i x f o r l o g - t r a n s f o r m e d ( b a s e 10) s i l t g e o c h e m i c a l d a t a , C i n o l a d e p o s i t . Dash l i n e s r e p r e s e n t c o r r e l a t i o n c o e f f i c i e n t s t h a t a r e n o t s i g n i f i c a n t a t t h e 1% l e v e l . GROUP ELEMENT Au Ag As Cu N i Co Zn Pb I Ag .57 As .45 .43 Cu - .38 -N i - .65 .60 .57 I I CO - .60 .52 .57 .89 Zn - .54 .54 .54 .94 .84 Pb - .48 - .63 .63 .61 .54 I I I Mo - - .50 - .45 - .45 -C o r r e l a t i o n c o e f f i c i e n t s b a s e d on 58 p a i r e d o b s e r v a t i o n s . T a b l e 9. Means and s t a n d a r d d e v i a t i o n s d e t e r m i n e d g r a p h i c a l l y f o r p a r t i t i o n e d m e t a l p o p u l a t i o n s o f s i l t g e o c h e m i c a l d a t a , C i n o l a d e p o s i t . ELEMENT CONC. UNIT \ Q. ~o A p o p u l a t i o n b b+t b - t % B p o p u l a t i o n b b + t b - t T h r e s h o l d ( s ) Au ppm 30 .037 .048 .029 70 .007 .011 .005 0.02 . Ag ppm 83 0.80 1.00 0.66 17 0.25 0.32 0.17 0.48 As ppm 100 63 250 15 Cu ppm 100 8.4 11.6 6.2 Zn ppm 20 125 180 88 51 83 112 62 110 a n d 40 29 20 27 15 Pb ppm 30 16 17 15 70 8.2 10.5 -J 6 5 14 N i ppm 71 18 24 14 29 6.8 8.4 5.5 11 Co ppm 6 133 174 108 94 23 39 12 83 Mo ppm 100 0.72 1.84 0 G r a p h s b a s e d o n 58 v a l u e s f o r a l l e l e m e n t s a p a r t f r o m A s w h i c h i s b a s e d on 57 v a l u e s . S y m b o l s u s e d a r e t h e same a s T a b l e 3. 5 20 40 60 80 D i 1 ! 1 1 5 e i r 2 10 30 50 70 90 CUMULATIVE PERCENT F i g u r e 16. P r o b a b i l i t y p l o t f o r Ag i n s i l t s p a r t i t i o n e d i n u p p e r (A) a n d l o w e r (B) p o p u l a t i o n s . 156 CONCLUSIONS Th i s simple s t a t i s t i c a l e v a l u a t i o n of geochemical data from the C i n o l a d e p o s i t has l e d to the f o l l o w i n g c o n c l u s i o n s : 1. S i g n i f i c a n t but moderate c o r r e l a t i o n c o e f f i c i e n t s between Au on the one hand and Hg, Ag, As, Sb, and W on the other hand i n d i c a t e t hat a l l were p a r t of the primary m i n e r a l i z i n g pro-cess at C i n o l a . 2. S p a t i a l c o r r e l a t i o n of sub-populations determined by p a r t i -t i o n i n g p r o b a b i l i t y graphs of each v a r i a b l e i s a more u s e f u l method f o r e v a l u a t i n g l i t h o g e o c h e m i c a l data than i s a matrix of s i n g l e l i n e a r c o r r e l a t i o n c o e f f i c e n t s . 3. A high s i l v e r l i t h o g e o c h e m i c a l p o p u l a t i o n d e f i n e s the C i n o l a d e p o s i t b e t t e r from an e x p l o r a t i o n viewpoint than does a high g o l d p o p u l a t i o n . High p o p u l a t i o n s of Hg, Sb, and W i n rocks are as much d i s p e r s e d as i s g o l d . 4. A c o r r e l a t i o n matrix f o r multi-element s o i l data deads to r e c o g n i t i o n of two groups of elements. Group I elements (Au, Hg, and Ag) are shown to have more-or-less sys t e m a t i c d i s p e r s i o n p a t t e r n s i n s o i l s r e l a t i v e to the C i n o l a ore body. Group II (Cu, N i , Co, Zn, and Pb) are very e r r a t i c a l -l y d i s p e r s e d i n s o i l s , and the absence of a s y s t e m a t i c pat-t e r n makes them l e s s u s e f u l i n an e x p l o r a t i o n sense. 157 Groups of elements from the c o r r e l a t i o n matrix f o r s i l t data are very s i m i l a r to the groups f o r the s o i l data. T h i s sug-ge s t s that Group I elements i n s i l t (Au, Ag, As) can be con-s i d e r e d as good i n d i c a t o r s of the p r o x i m i t y of C i n o l a - t y p e g o l d c o n c e n t r a t i o n s . S i g n i f i c a n t c o r r e l a t i o n s between (1) Au and (2) Ag, Hg, and As and comparable d i s t r i b u t i o n s of these elements i n rock, s o i l , and s i l t are a f e a t u r e of the C i n o l a data. Thus Au, Ag, Hg, and As are p o t e n t i a l elements to be analyzed f o r i n geochemical e x p l o r a t i o n f o r s i m i l a r l a r g e tonnage, low grade C a r l i n - t y p e gold d e p o s i t s . I n s u f f i c i e n t data were a v a i l a b l e to f u l l y e v a l u a t e the e x p l o r a t i o n p o t e n t i a l f o r Sb and W, although high l i t h o g e o c h e m i c a l p o p u l a t i o n s of each of these two elements showed syst e m a t i c d i s t r i b u t i o n p a t t e r n s . In c o n t r a s t , the more abundant elements, such as Cu, Pb, and Zn, are shown to be much l e s s u s e f u l because t h e i r s p o r a d i c occurrence i n geochemical samples seems to r e f l e c t t h e i r minor and s p o r a d i c occurrence i n the m i n e r a l i z e d system comprising the C i n o l a d e p o s i t . S i m i l a r l y , Mo, Co, and N i are of l i t t l e p r a c t i c a l use, i n t h i s case because of t h e i r very low l e v e l s of abundance. 158 ACKNOWLEDGMENTS Var i o u s maps and r e p o r t s s u p p l i e d to us by G.G. Richards and R.W. Stevenson made the job of data c o m p i l a t i o n e a s i e r than i t otherwise would have been. Mrs. Z o f i a Radlowski a s s i s t e d c h e e r f u l l y i n the tedious task of data coding. We a p p r e c i a t e the r a p i d i t y with which an abundance of computer output was ob-ta i n e d f o r us by Mr. Asger Bentzen. Cost of the study was borne by an N.S.E.R.C. grant to A.J. S i n c l a i r and funds s u p p l i e d by C o n s o l i d a t e d C i n o l a Mines L t d . 159 REFERENCES Boyle, R.W., 1979, The geochemistry o f g o l d and i t s d e p o s i t s ; G e o l . Surv. of Canada, B u l l . 280. Champigny, N., and S i n c l a i r , A.J., 1980a, Progress r e p o r t on the geology of the Specogna (Babe) gold d e p o s i t ; B.C. M i n i s t r y of Energy, Mines and Pet. Res., Paper 1980-1, pp. 158-170. Champigny, N., and S i n c l a i r , A.J., 1980b, C i n o l a (Specogna) g o l d d e p o s i t , Queen C h a r l o t t e I s l a n d s , B r i t i s h Columbia - A Canadian C a r l i n - t y p e d e p o s i t ( a b s t r a c t ) ; Can. I n s t . Min. M e t a l l . B u l l . 75, v. 73, p. 62. Champigny, N., and S i n c l a i r , A .J., 1981, C i n o l a gold d e p o s i t , Queen C h a r l o t t e I s l a n d s , B r i t i s h Columbia - A Canadian C a r l i n - t y p e d e p o s i t ; Can. I n s t . Min. M e t a l l . , Spec. V o l . ( i n p r e s s ) . Champigny, N., S i n c l a i r , A .J., and Sanders, K.C., 1980, Specogna gold d e p o s i t of C o n s o l i d a t e d C i n o l a Mines, an example of s t r u c t u r a l p r o p e r t y e v a l u a t i o n ; Western Miner, v. 53, no. 6, pp. 35-44. R i c h a r d s , G.G., C h r i s t i e , U.S., and Wolfhard, M.R., 1976, Specogna: A C a r l i n - t y p e gold d e p o s i t , Queen C h a r l o t t e I s l a n d s , - B r i t i s h Columbia ( a b s t r a c t ) ; Can. I n s t . Min. M e t a l l . B u l l . , v. 69, no. 773, pp. 64. 160 S i n c l a i r , A .J., 1974, S e l e c t i o n of t h r e s h o l d s i n geochemical data using p r o b a b i l i t y graphs; Jour. Geochem. E x p l . , v. 3, p. 129-149. S i n c l a i r , A .J., 1976, A p p l i c a t i o n s of p r o b a b i l i t y graphs i n min-e r a l e x p l o r a t i o n ; Assoc. E x p l o r . Geochemists, Spec. V o l . 4, 95 p. Sutherland Brown, A., 1968, Geology of the Queen C h a r l o t t e I s l a n d s , B r i t i s h Columbia; B.C. M i n i s t r y o f Energy, Mines & Pet. Res., B u l l . 54. CHAPTER VII G e o s t a t i s t i c a l Study of the C i n o l a D e p o s i t , Queen C h a r l o t t e I s l a n d s , B.C. 162 ABSTRACT The C i n o l a g o l d d e p o s i t , owned by C o n s o l i d a t e d C i n o l a Mines L t d . , i s at the f e a s i b i l i t y stage of e v a l u a t i o n . Ore r e s e r v e e s t i m a t i o n by a g e o s t a t i s t i c a l approach o u t l i n e d here i s based on d r i l l hole assays from a g r i d of v e r t i c a l diamond d r i l l h o l e s spaced at i n t e r v a l s of approximately 40 m. Separate g e o s t a t i s -t i c a l models are developed fo r u n a l t e r e d ore and e x t e n s i v e l y a r g i l l i c a l l y a l t e r e d ground. The d e t a i l e d model f o r " u n a l t e r e d " gold c o n c e n t r a t i o n i s used to i l l u s t r a t e the p r a c t i c a l a p p l i c a -t i o n of g e o s t a t i s t i c s i n producing grade and e r r o r e s t i m a t e s . Blocks ( s e l e c t i o n u n i t s ) that were estimated are measuring 30 x 30 x 10 m3 where 10 m i s the expected bench l e v e l of open p i t mining. One of the most s t r i k i n g r e s u l t s of t h i s study has been the r e c o g n i t i o n of unusual u n i f o r m i t y of gold grade d i s t r i b u t i o n compared with many other gold d e p o s i t s . The r e s u l t s show that a g e o s t a t i s t i c a l approach to ore reserve e s t i m a t i o n i s a v i a b l e and u s e f u l procedure. 163 INTRODUCTION Ore reserve e s t i m a t i o n o f go l d d e p o s i t s i s probably one of the most d i f f i c u l t problems faced by g e o l o g i s t s and eng i n e e r s . The a p p a r e n t l y e r r a t i c d i s t r i b u t i o n of go l d i n many ore bodies i s the main reason f o r the tremendous d i f f i c u l t y i n making con-f i d e n t e s t i m a t i o n s o f mean grades f o r s e l e c t i o n u n i t s (mining b l o c k s ) . T h i s paper documents a r i g o r o u s g e o s t a t i s t i c a l ap-proach to grade e s t i m a t i o n at the C i n o l a g o l d d e p o s i t , based on a r e l a t i v e l y uniform and dense d i s t r i b u t i o n of sampled diamond d r i l l h o l e s . The mathematical concepts used i n t h i s a n a l y s i s have been d e s c r i b e d i n numerous p u b l i c a t i o n s , such as C l a r k (1980), J o u r n e l and H u i j b r e g t s (1978), and David (1977). C i n o l a d e p o s i t i s a l a r g e tonnage, low grade g o l d d e p o s i t i n c e n t r a l Graham I s l a n d , Queen C h a r l o t t e I s l a n d s , B.C. (Figure 1). About 50 m i l l i o n tons of low grade m a t e r i a l were i n f e r r e d on the b a s i s o f l i m i t e d d r i l l i n f o r m a t i o n e a r l y i n the e x p l o r a -t i o n h i s t o r y o f the occurrence (Richards et a l . , 1976). I t was not u n t i l 1980 that the present o p e r a t o r , C o n s o l i d a t e d C i n o l a Mines L t d . , proved by diamond d r i l l i n g 45.4 m i l l i o n tons at an average grade of .054 oz. Au/s.t., using a c u t o f f o f .025 oz. Au/s.t. The g o l d d e p o s i t i s contained i n a c o a r s e - g r a i n e d , c l a s t i c , sedimentary sequence of Middle Miocene age which i s cut by a r h y o l i t e - p o r p h y r y body (Figure 2) (Champigny and S i n c l a i r , 1980, 1981). The sequence i s composed of interbedded conglomerate and 164 F i g u r e - 1. L o c a t i o n map o f t h e G i n o l a d e p o s i t . CROSS-SECTION BB' B B O 10 20 30 40 50 METRES 166 F i g u r e 2. G e o l o g i c a l c r o s s - s e c t i o n o f t h e C i n o l a d e p o s i t . The m i n e r a l i z e d zone i s l o c a l i z e d a t t h e m a r g i n and t o t h e e a s t o f t h e r h y o l i t e - p o r p h y r y . 167 sandstone u n i t s d i p p i n g g e n t l y (15°) to the e a s t . Upper Cretaceous s h a l e s are i n f a u l t c o n t a c t with the r h y o l i t e i n t r u -s i o n on the west and c o n s t i t u t e the f o o t w a l l of the d e p o s i t . These three u n i t s are cut by s e v e r a l generations of quartz v e i n s that l o c a l l y c o n t a i n high grade values (higher than 0.20 oz. A u / s . t . ) . Gold i s a l s o disseminated through the s i l i c i f i e d c o a r s e - g r a i n e d sediments, to a l e s s e r extent i n the r h y o l i t e -porphyry and r a r e l y i n the s h a l e s . P y r i t e and marcasite are the most abundant s u l p h i d e s , and g o l d p a r t i c l e s are mainly of sub-m i c r o s c o p i c s i z e . A s t e e p l y c l i p p i n g envelope of a r g i l l i c a l -t e r a t i o n a b r u p t l y t r u n c a t e s the economic m i n e r a l i z a t i o n on the e a s t . The u l t i m a t e g o a l of t h i s study was to c a l c u l a t e mean grade and e r r o r f o r blocks measuring 30 x 30 x 10m3 where 10 m i s the bench h e i g h t proposed f o r open-pit mining. An important product of the g e o s t a t i s t i c a l approach i n c l u d e s t e s t i n g whether the d r i l l hole s p a c i n g , commonly about 40 m at C i n o l a , i s c l o s e enough to p r o v i d e reasonable estimates f o r 30 x 30 x 10 m3 b l o c k s . To answer these q u e s t i o n s we proceeded i n four stages as f o l l o w s : (1) data e v a l u a t i o n , (2) g e n e r a t i o n of experimental semi-variograms, (3) development of semi-variogram models, and (4) k r i g i n g . Over 20,000 m of assayed d r i l l core form the data set f o r t h i s study. C a l c u l a t i o n i n v o l v i n g t h i s q u a n t i t y o f data must be done i n the computer. In a d d i t i o n , e x t e n s i v e care must be taken i n e d i t i n g data so that e r r o r s are not b u i l t i n t o subsequent 168 expensive computer runs. Data C o n t r o l Borehole g o l d assays obtained d u r i n g a l l e x p l o r a t i o n phases of the d e p o s i t s i n c e d i s c o v e r y were made a v a i l a b l e by C o n s o l i d a t e d C i n o l a Mines L t d . S e v e r a l data types make up the data set and are l i s t e d i n Table 1. Nea r l y a l l h o l e s are v e r t i -c a l , and the core was analyzed i n continuous sample l e n g t h s o f 1.5, 2, or 3 m. Check assays from at l e a s t one other a n a l y t i c a l T able 1 Data Types Sample le n g t h % Core s i z e (m) of t o t a l data P e r c u s s i o n 3.0 1.4 Diamond AX 1.5 0.3 BX 1.5 6.0 BX 2.0 40.5 BX 3.0 2.5 NX 3.0 49.3 l a b o r a t o r y were provided f o r the f i v e c a t e g o r i e s o f data. No assay d i s c r e p a n c i e s were re c o g n i z e d . G e o l o g i c a l d e s c r i p t i o n by the w r i t e r s o f most of the d r i l l c o r e, combined with o b s e r v a t i o n s of other g e o l o g i s t s on the r e -mainder o f the d r i l l c o r e , allowed us to s e t t l e on a simple one-l e t t e r coding system f o r host rock of each sample assayed f o r g o l d . The three p r i n c i p a l host rock c a t e g o r i e s are; (1) 169 conglomerate-sandstone, (2) r h y o l i t e - p o r p h y r y , and (3) s h a l e . E a r l y i n the study i t appeared that a l l rock types c o u l d not be taken i n t o account because of the s m a l l p r o p o r t i o n of both r h y o l i t e - p o r p h y r y and s h a l e . A l l assays of s h a l e are below the .025 oz. Au/s.t. c u t o f f , and are excluded from the study. P r o b a b i l i t y graphs were c o n s t r u c t e d f o r assays f o r each of three d i f f e r e n t core l e n g t h s , 1.5, 2, and 3 m. An example, f o r sample le n g t h of 2m, i s shown on F i g u r e 3. Two lognormal popu-l a t i o n s are apparent i n each case, and a t h r e s h o l d s e p a r a t i n g them was s e l e c t e d using the p a r t i t i o n i n g procedure d e s c r i b e d by S i n c l a i r (1976). The t h r e s h o l d s r e p r e s e n t optimum s e p a r a t i o n o f a high-grade p o p u l a t i o n from a low-grade p o p u l a t i o n . A l i n e a r r e l a t i o n s h i p i s apparent between the t h r e s h o l d values and the core sample l e n g t h , and i s i l l u s t r a t e d i n F i g u r e 4. Longer and t h e r e f o r e bigger core samples are l e s s v a r i a b l e i n t h e i r g o l d values than are s h o r t e r samples. We have reco g n i z e d two p o p u l a t i o n s i n the d r i l l core as-says; a "high-grade" p o p u l a t i o n which t o t a l s 3.5 percent of the data and i s assumed to be d i s t r i b u t e d randomly throughout the d e p o s i t , and a "low-grade" p o p u l a t i o n which comprises the bulk of the data and whose d i s t r i b u t i o n i s more continuous. The values above t h r e s h o l d s , that i s , the "high-grade" p o p u l a t i o n , were d e l e t e d f o r mathematical mod e l l i n g of the "low-grade" popu-l a t i o n . 170 0 2 5 10 20 30 40 50 60 70 80 C U M U L A T I V E P E R C E N T F i g u r e 3. P r o b a b i l i t y p l o t f o r g o l d a s s a y s o f 2 m s a m p l e s f r o m BX c o r e . F u l l c i r c l e s a r e c u m u l a t e d f r e q u e n c i e s o f raw d a t a . Open c i r c l e s a r e p a r t i t i o n i n g p o i n t s u s i n g a m e t h o d d e s c r i b e d by S i n c l a i r ( 1 9 7 6 ) . 171 F i g u r e 4 . T h r e s h o l d v a l u e s versus core sample l e n g t h . Thresholds were determined from p r o b a b i l i t y graphs. 172 R e l a t i v e Semi-Var iograms The semi-variogram (h) i s a measure of the d i f f e r e n c e be-tween the grades of samples separated by a d i s t a n c e h. An ex-pe r i m e n t a l semi-variogram i s c a l c u l a t e d using the equation: Y((h) = ^ E [g(x) - g(x+h) ] 2 where g i s the grade, x i n d i c a t e s the l o c a t i o n of one sample i n the p a i r , and x+h i n d i c a t e s the l o c a t i o n of the o t h e r . The t o t a l number of p a i r s f o r each s p a c i n g , h, i s given by n. Y (h) has u n i t s o f grade squared, that i s , (oz. A u / s . t . ) 2 i n our case, and i s c a l c u l a t e d f o r a maximum number of d i f f e r e n t values o f h. R e l a t i v e semi-variograms are obtained by d i v i d i n g y (h) values by the squared mean grade of a l l samples used i n c a l c u l a t i n g the semi-variogram. A l l the semi-variograms reproduced here are r e l a t i v e semi-variograms. C o n s t r u c t i o n of "down-hole" r e l a t i v e semi-variograms i s simple i n the case of d r i l l h o l e s , s i n c e we have one long l i n e of r e g u l a r l y spaced samples, g e n e r a l l y with no gaps. At C i n o l a these one dimensional semi-variograms d e f i n e the s t r u c t u r e o f grades i n a v e r t i c a l d i r e c t i o n . S t r u c t u r e i s examined h o r i z o n -t a l l y by c o n s t r u c t i n g experimental semi-variograms i n four d i -r e c t i o n s i n a h o r i z o n t a l f i e l d — f o r example, using bench l e v e l composites from a s i n g l e bench or from a l l benches. 173 Down-Hole Semi-Variograms Down-hole semi-variograms were generated by computer sepa-r a t e l y f o r each d r i l l h o l e , and average semi-variograms were produced f o r each data support (Table 1). The purpose of ge n e r a t i n g these i s to compare the v a r i a b i l i t y o f gold v a l u e s from the d i f f e r e n t c a t e g o r i e s of data. Such a comparison may l e a d t o : (1) grouping c e r t a i n data types with s i m i l a r v a r i a b i l i -t y , and (2) r e c o g n i z i n g data supports that have d i s t i n c t l y d i f -f e r e n t l e v e l s of v a r i a b i l i t y . E xperimental semi-variograms from very l i m i t e d data s e t s f o r AX and p e r c u s s i o n d r i l l h o les are markedly d i f f e r e n t from those f o r other data types, and these two data types were ex-cluded from the study because of the l i k e l i h o o d of a l a r g e sampling-type e r r o r . A l l the semi-variograms f o r BX d r i l l h o les are very s i m i l a r r e g a r d l e s s of the sample l e n g t h s (1.5 m, 2m, and 3 m) (Figure 5). S i m i l a r curves based on NX d r i l l h o les are d i v i d e d i n t o two groups: one group has semi-variograms comparable to those f o r BX core samples, whereas a second NX data set has a much higher nugget e f f e c t . T h i s second group of semi-variograms was c a l c u -l a t e d from d r i l l h o les l o c a t e d i n zones of e x t e n s i v e a r g i l l i c a l t e r a t i o n , whereas those with a lower l e v e l o f v a r i a b i l i t y , as w e l l as a l l the semi-variograms based on BX c o r e , d e r i v e from the r e l a t i v e l y u n a l t e r e d p a r t of the C i n o l a d e p o s i t (Figure 6 ). F i g u r e 5. A v e r a g e e x p e r i m e n t a l d o w n - h o l e s e m i - v a r i o g r a m s ( d a s h e d l i n e s ) , r e g u l a r i z e d s p h e r i c a l m o d e l ( f u l l l i n e ) c u r v e s f o r " u n a l t e r e d " a n d " a l t e r e d " d a t a s e t s and s p h e r i c a l p o i n t m o d e l c u r v e f o r " u n a l t e r e d " d a t a ( d o t s ) . . " U n a l t e r e d " v a r i o g r a m c u r v e s a r e f o r BX 1.5 ( 2 ) , 2 (4) and 3m (3) and some NX 2m (5) d r i l l h o l e s . " A l t e r e d " v a r i o g r a m c u r v e s a r e f o r some o f t h e NX 2 m d r i l l h o l e s (1) . 175 Consequently, the f o l l o w i n g two simple g e o l o g i c a l groups are d e f i n e d f o r g e o s t a t i s t i c a l purposes, " u n a l t e r e d " samples i n c l u d i n g BX and NX d r i l l holes and " a l t e r e d " samples comprising o n l y p a r t of the NX d r i l l h o l e s . From t h i s we conclude that a l t e r a t i o n , as opposed to core s i z e , d i c t a t e s the behaviour of experimental down-hole semi-variograms at C i n o l a . U n a l t e r e d rocks c o n s t i t u t e the main min-e r a l i z e d zone. A l t e r e d rocks have grades l e s s than .025 oz. Au/s.t. F i g u r e 6 i l l u s t r a t e d the mapped d i s t r i b u t i o n of e x t e n s i v e a r g i l l i c a l t e r a t i o n i n d r i l l h o l e s . The remainder o f our study i s c o n f i n e d to a g e o s t a t i s t i c a l e v a l u a t i o n of the " u n a l t e r e d " group of sample data. H o r i z o n t a l Semi-Variograms D r i l l core assays from the u n a l t e r e d holes were averaged i n t o 10 m composites, 10 m being the proposed bench h e i g h t at C i n o l a . For each bench l e v e l , h o r i z o n t a l semi-variograms were generated f o r four d i r e c t i o n s ; north-south, east-west, northwest-southeast, and southwest-northeast. In a d d i t i o n , an average i s o t o p i c semi-variogram f o r each l e v e l and a weighted average i s o t r o p i c semi-variogram f o r a l l l e v e l s were produced. Experimental semi-variograms f o r the four d i r e c t i o n s were s i m i -l a r f o r a given l e v e l and were a l s o s i m i l a r to the grand average semi-variograms f o r a l l l e v e l s , as reproduced i n F i g u r e 7. T h i s i m p l i e s i s o t r o p y i n the d i s t r i b u t i o n of g o l d assays i n a h o r i -z o n t a l plane. A A A A A A A A A A A A A A A A A A A A A A A A A A A \ A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A . A A A A A A A A A A A A A A A A A A A A A ^ A , A J ' A A A ' A A , A A A A A A A 21 " A " A A A A A A A A 177 F i g u r e 6. L o c a t i o n s of d r i l l hole c o l l a r s on the C i n o l a d e p o s i t . The p r i n c i p a l g o l d c o n c e n t r a t i o n extends from the F o o t w a l l f a u l t (FF) to the AA 1 l i n e . D r i l l h o les w i t h i n the orebody are grouped i n the " u n a l t e r e d " data s e t . A s t e e p l y d i p p i n g zone of a r g i l l i c a l t e r a t i o n extends e a s t of the AA 1 l i n e and c a r r i e s no economic m i n e r a l i -z a t i o n . D r i l l h o l e s i n the a l t e r a t i o n zone are grouped i n the " a l t e r e d " data s e t . F i g u r e 7. A v e r a g e e x p e r i m e n t a l h o r i z o n t a l s e m i - v a r i o g r a m ( d a s h e d l i n e ) f o r a l l " u n a l t e r e d " d r i l l h o l e s a m p l e s b a s e d o n 10 m b e n c h c o m p o s i t e s . T h e -r e g u l a r i z e d s p h e r i c a l m o d e l c u r v e ( f u l l l i n e ) a n d p o i n t s p h e r i c a l m o d e l c u r v e ( d o t s ) a r e a l s o s h o w n . 0 . 5 _ 0.4 L 0 I i i i i i i ; 1 — 0 5 0 100 150 2 0 0 2 5 0 3 0 0 3 5 0 L A G (meters) 4 0 0 r-> CO 179 M o d e l l i n g Experimental semi-variograms shown i n F i g u r e s 5 and 7 are saw-tooth curves that can be approximated by smooth mathematical models. The most common model that a p p l i e s to experimental semi-variograms i s the s p h e r i c a l model d e f i n e d as f o l l o w s : Y ( h ) = C Q + C x < § | - | ( | ) 3 ) f o r h<a "y (h) = c 0 + c i f o r h^- a where C Q i s the nugget e f f e c t , C 1 i s the s i l l o f the s p h e r i c a l model, a i s the range, and h i s any sample s e p a r a t i o n . The range of i n f l u e n c e o f a sample (a) i s the d i s t a n c e at which sam-p l e s become independent. The s i l l , , r e p r e s e n t s the s t r u c -tured p a r t of the v a r i a b i l i t y , whereas the nugget e f f e c t i s a random component and i n d i c a t e s the presence o f one or more smal-l e r s c a l e s t r u c t u r a l components ( i . e . smaller than the momentum sample spacing o f about 30 m), each with i t s own s i l l and range. The experimental down-hole semi-variograms f o r u n a l t e r e d and a l t e r e d d r i l l h o les were each f i t t e d with a s p h e r i c a l model curve. A f a i r l y good f i t was o b t a i n e d , as shown i n F i g u r e 5. Parameters f o r these models are summarized i n Table 2. Both data s e t s have a r e l a t i v e l y s h o r t range (22 and 18 m), and the s p h e r i c a l model f o r a l t e r e d data has a s i l l 1.8 times higher than the s i l l o f u n a l t e r e d data. A s p h e r i c a l model was a l s o f i t t e d to bench composites to provide an i s o t r o p i c model i n 180 h o r i z o n t a l d i r e c t i o n s (Figure 7). Experimental down-hole semi-variograms are based on 1.5, 2, and 3 m core sample l e n g t h s , whereas h o r i z o n t a l semi-variograms are based on sample lengths of 10 m. The down-hole models are s a i d to have " r e g u l a r i z e d " over 1.5, 2, and 3 m, and the h o r i -z o n t a l model i s r e g u l a r i z e d over 10 m. We cannot reasonably expect the grade smoothed over 2 m of core to have the same be-haviour as the grade smoothed over 10 m of co r e . In order to compare h o r i z o n t a l and down-hole models, one must c a l c u l a t e the r e s p e c t i v e p u nctual s p h e r i c a l models. The mathematical manipu-l a t i o n s i n v o l v e d i n determining the punctual s p h e r i c a l model are d e s c r i b e d by H u i j b r e g t s (1971), David (1977, p. 130), and C l a r k (1980, chapter 3). Tables 3 and 4 summarize the p o i n t s p h e r i c a l models c a l c u l a t e d f o r h o r i z o n t a l and down-hole data s e t s . The h o r i z o n t a l data have been approximated with a mixture of two s p h e r i c a l models (Figure 7). The f i r s t component i s the down-hole p o i n t s p h e r i c a l model (a = 16 m), to which i s added a second component with a long range (240 m). The nugget e f f e c t i s the same f o r both down-hole and h o r i z o n t a l data i f c a l c u l a t e d fo r the same sample l e n g t h . The long range s t r u c t u r e may be present on down-hole variograms, but d r i l l l e n g t h s are too s h o r t to be c e r t a i n . I t i s p o s s i b l e that the g e o s t a t i s t i c a l s t r u c t u r e i s i s o t r o p i c i n three dimensions. The long range of 240 m d e f i n e d by the h o r i z o n t a l p o i n t s p h e r i c a l model makes d r i l l spacing of v e r t i c a l h o l e s l e s s c r i -t i c a l . A spacing o f 40 m i s c e r t a i n l y a c c e p t a b l e at the present 181 T a b l e 2. Summary o f r e g u l a r i z e d s p h e r i c a l m o d e l s c a l c u l a t e d f o r d o w n - h o l e a s s a y d a t a o f " u n a l t e r e d " a n d " a l t e r e d " d r i l l h o l e s a m p l e s a nd h o r i z o n t a l d a t a o f " u n a l t e r e d " b e n c h c o m p o s i t e s , C i n o l a d e p o s i t . C n C x A 1(m) C^ A 2 (m) Down-hole ( r e g u l a r i z e d o v e r 2 m s a m p l e s ) a l t e r e d .54 .37 22 u n a l t e r e d .30 .20 18 H o r i z o n t a l ( r e g u l a r i z e d o v e r 10 m c o m p o s i t e s ) u n a l t e r e d .06 .20 18 .12 250 T a b l e 3. Summary o f p o i n t s p h e r i c a l m o d e l c a l c u l a t e d f o r d o w n - h o l e d a t a o f " u n a l t e r e d " d r i l l h o l e s a m p l e s , C i n o l a d e p o s i t . b h a ( m ) ( 1 / C 1 ) v £ ( h ) C 0 + Y £ ( h ) 0 0 0 .31 4 2 . 31 . 38 8 4 .63 .44 12 6 .75 .47 16 8 .95 .51 20 10 .95 .51 a h i s s a m p l e s p a c i n g ; I i s l e n g t h o v e r w h i c h g r a d e s a r e a v e r a g e d b v a l u e o b t a i n e d f r o m H u i j b r e g t s ( 1 9 7 1 ) . 182 T a b l e 4. Summary o f p o i n t s p h e r i c a l m o d e l f o r h o r i z o n t a l d a t a o f " u n a l t e r e d " b e n c h c o m p o s i t e s , C i n o l a d e p o s i t . h a ( m ) h / f ( 1 / C ^ y M h ) C Q + Y £ (h) 0 0 0 .06 25 2.5 .16 .28 50 5 .31 .30 75 7.5 .45 .33 100 10 .59 .35 150 15 .82 .38 200 20 .96 • .40 250 25 .98 .41 a h i s s a m p l e s p a c i n g ; I i s l e n g t h o v e r w h i c h g r a d e s a r e a v e r a g e d b v a l u e o b t a i n e d f r o m H u i j b r e g t s (1971). 183 l e v e l o f e x p l o r a t i o n , as i t w i l l become c l e a r e r from k r i g i n g estimates that are co n s i d e r e d i n a subsequent s e c t i o n . K r i g i n g K r i g i n g i s a weighted average procedure f o r e s t i m a t i n g l o c a l mean grade, and i s o p t i m a l i n the sense that the estima-t i o n v a r i a n c e i s minimized. Procedures are summarized by va r i o u s authors, and w i l l not be o u t l i n e d here. The low s i l l l e v e l and long range f o r the h o r i z o n t a l semi-variograms at C i n o l a suggest t h a t two-dimensional k r i g i n g with a p o i n t i s o t r o -p i c model f i t t e d to the experimental data w i l l p rovide r e a -sonable block e s t i m a t i o n f o r blocks of 30 x 30 x 10m 3. Because the e f f e c t o f the short range s t r u c t u r e w i l l be minimal, the model adopted f o r two-dimensional k r i g i n g i s a simple s p h e r i c a l model f i t t e d to the experimental semi-variogram of F i g u r e 7 and having the f o l l o w i n g parameters: C 0 = .24 C i = .38 a = 250 m For the 110 m l e v e l we attempted to k r i g e 352 blocks a r -ranged i n a r e c t a n g u l a r a r r a y measuring 22 blocks by 16 b l o c k s . I n d i v i d u a l b l o c k s are k r i g e d o n l y i f : (1) four or more assays (bench h e i g h t composites) are found w i t h i n the search r a d i u s o f 80 m from the center of the square to be k r i g e d , or (2) there i s one or more bench composite w i t h i n the block to be k r i g e d . These r e s t r i c t i o n s g ive estimates f o r o n l y one aureole of blocks 184 beyond the l i m i t o f a v a i l a b l e d r i l l data. Kriged grades f o r the 100 m l e v e l are shown on F i g u r e 8. These estimated grades con-s i s t of two components combined i n a manner developed by Giroux and S i n c l a i r (personal communications, 1981). Each block e s t i -mate c o n s i s t s o f a k r i g e d component and a t o t a l random com-ponent. The two components are present i n the p r o p o r t i o n o f 96.5 and 3.5 percent f o r the low grade and high grade propor-t i o n s r e s p e c t i v e l y . For each block the estimated grade i s de-termined as f o l l o w s : m = (1-p) m + pm m = .965 m + .035 m The high grade random component has a mean value of .235 oz. Au/s.t., or a c o n t r i b u t i o n o f 0.008 oz. Au/s.t. f o r each b l o c k . E r r o r estimates on mean grades of i n d i v i d u a l b l o c ks range from 15 percent r e l a t i v e e r r o r to 56 percent, with a l a r g e number near 20 percent. Such values are remarkably low f o r gold d e p o s i t s and r e f l e c t the c o n t i n u i t y o f m i n e r a l i z a t i o n at C i n o l a . C o n c l u s i o n s T h i s study has provided a syst e m a t i c procedure f o r geosta-t i s t i c a l ore reserve e s t i m a t i o n o f a l a r g e tonnage, low grade g o l d d e p o s i t . The procedure i n c l u d e s : 1. c a r e f u l e d i t i n g o f the data, 2. c o n s t r u c t i o n of p r o b a b i l i t y p l o t s to p a r t i t i o n e d "high" grade and "low" grade p o p u l a t i o n s , I I < .025 HH .04-.05 TTTTTTTl .025-.04 |jT] >.os 110 L E V E L - A u (oz/s.t.) 186 F i g u r e 8. K r i g e d b l o c k mean g r a d e s f o r 30 X 30 X lOm"' b l o c k s a t t h e 110 m l e v e l . The a p p r o x i m a t e t r a c e o f t h e F o o t w a l l f a u l t (FF) a t t h e 110 m l e v e l a n d t h e AA' l i n e mark t h e e x t e n t o f t h e p r i n c i p a l g o l d c o n c e n t r a -t i o n . E a s t o f AA 1 t h e r o c k s a r e s e v e r e l y a l t e r e d B l o c k s t h a t w e r e k r i g e d w e s t o f t h e F o o t w a l l f a u l t , w e r e e x c l u d e d b e c u a s e o f t h e a b r u p t t e r m i n a t i o n o f m i n e r a l i z a t i o n on t h e F o o t w a l l f a u l t . 187 3. genera t i o n of experimental down-hole and h o r i z o n t a l r e l a t i v e semi-variograms and development of a three-d i m e n s i o n a l p o i n t model, and omission of u n r e l i a b l e subsets of data, and 4. block k r i g i n g . Although not co n s i d e r e d here, a l o g i c a l e x tension of the study would be to produce grade/tonnage curves. S p e c i f i c r e -s u l t s f o r the C i n o l a g o l d d e p o s i t are summarized as f o l l o w s : 1. Core s i z e (NX, BX) and core l e n g t h from 1.5 to 3 m do not a p p r e c i a b l y change the behaviour of experimental s e m i - v a r i o -grams. 2. A r g i l l i c a l t e r a t i o n has a pronounced e f f e c t on the behaviour of experimental semi-variograms, by i n c r e a s i n g the r e l a t i v e v a r i a b i l i t y . 3. A remarkable homogeneity i n the d i s t r i b u t i o n o f g o l d values at C i n o l a i s shown by the two-dimensional i s o t r o p i c nature of the assay data and r e l a t i v e l y low e r r o r s o f k r i g e d block means. Consequently, a d r i l l s pacing of 40 m i s reasonable f o r e v a l u a t i o n of ore grades and tonnages at the present f e a s i b i l i t y stage. Acknowledgments The a s s i s t a n c e of Asger Bentzen and G.H. Giroux i n ob-t a i n i n g computer output f o r t h i s study i s acknowledged with thanks. F i n a n c i a l support was obtained from C o n s o l i d a t e d C i n o l a Mines L t d . and the N a t u r a l Sciences and E n g i n e e r i n g Research C o u n c i l of Canada (N.S.E.R.C.). 188 REFERENCES Champigny, N., and S i n c l a i r , A .J., 1980, C i n o l a (Specogna) gold d e p o s i t , Queen C h a r l o t t e I s l a n d s , B.C. - A Canadian C a r l i n -type d e p o s i t ( a b s t r a c t ) ; Can. I n s t . Mining M e t a l l . B u l l . 75, v. 73, p. 62. Champigny, N., and S i n c l a i r , A.J., 1981, C i n o l a gold d e p o s i t , Queen C h a r l o t t e I s l a n d s , B.C. - A Canadian C a r l i n - t y p e de-p o s i t ; Can. I n s t . Mining M e t a l l . Spec. V o l . (in p r e s s ) . C l a r k , F., 1980, P r a c t i c a l G e o s t a t i s t i c s ; A p p l i e d Science P u b l i s h e r s , London, 129 p. David, M., 1977, G e o s t a t i s t i c a l ore reserve e s t i m a t i o n ; Developments i n Geomathematics 2, E l s e v i e r , Amsterdam, 364 P-H u i j b e r g t s , C , 1971, R e c o n s t i t u t i o n du variogramme p o n c t u e l a p a r t i r d'un variogramme experimental r e g u l a r i s e ; Report N-244, Centre de Morphologie Mathematique, F o n t a i n e b l e a u , 22 p. and three graphs. J o u r n e l , A.G., and H u i j b r e g t s , C , 1978, Mining G e o s t a t i s t i c s ; Academic P r e s s , 600 p. R i c h a r d s , G.G., C h r i s t i e , J.S., and Wolfhard, M.R., 1976, Specogna: A C a r l i n - t y p e gold d e p o s i t , Queen C h a r l o t t e 189 I s l a n d s , B r i t i s h Columbia ( a b s t r a c t ) ; Can. I n s t . Min. M e t a l l . B u l l , v. 69, no. 773, p.64. S i n c l a i r , A .J., 1976, P r o b a b i l i t y graphs i n m i n e r a l e x p l o r a t i o n ; Assoc. E x p l . Geochem., Spec. V o l . 4, 95 p. CHAPTER VIII C o n c l u s i o n s 191 E x p l o r a t i o n data f o r C i n o l a d e p o s i t have been organized i n a manner that c l e a r l y i l l u s t r a t e s the changing emphasis i n ex-p l o r a t i o n method as the occurrence evolved from a raw prospect to a d e p o s i t of p o t e n t i a l economic worth undergoing a thorough f e a s i b i l i t y study. E a r l y e x p l o r a t i o n emphasized s o i l ' and s i l t geochemical methods, fo l l o w e d by a g r e a t e r weight on rock geo-chemis t r y . Diamond d r i l l i n g became p r o g r e s s i v e l y more important as e x p l o r a t i o n continued to the f e a s i b i l i t y stage. D e t a i l e d g e o l o g i c a l mapping was c o n f i n e d l a r g e l y to core l o g g i n g by a r i g o r o u s computer based system (GEOLOG). F i e l d data and m i n e r a l o g i c a l s t u d i e s l e d to development of a g e n e t i c model f o r the d e p o s i t . A Middle T e r t i a r y (17-15 Ma) coarse g r a i n e d c l a s t i c sequence, the Skonun Formation i s the p r i n c i p a l m i n e r a l i z e d u n i t , and i s cut by a 14 Ma r h y o l i t e - p o r p h y r y . T h i s i n t r u s i o n i s thought to represent a heat source that set up a r e l a t i v e l y near s u r f a c e c i r c u l a t i n g geothermal system that d e r i v e d i t s f l u i d from i n t e r s t i t i a l or pore f l u i d o f the Skonun sediments. As m i n e r a l i z a t i o n proceeded and f i l l e d channels, i n t e r m i t t e n t movement on the F o o t w a l l f a u l t l e d to f r a c t u r i n g i n a d j o i n i n g rocks, with r e s u l t a n t i n c r e a s e s i n p e r m e a b i l i t y f o r ore f l u i d t r a n s p o r t . F l u i d i n c l u s i o n s t u d i e s support the g e n e t i c model and showed that (1) the m i n e r a l i z i n g f l u i d s were probably d e r i v e d from pore water of the f l u v i a t i l e host rock, and (2) m i n e r a l d e p o s i t i o n o c c u r r e d at temperatures ranging from 300°C to 130°C and at a depth between 1.1 and 1 . 8 k. 192 A 17 to 15 Ma age f o r the Skonun Formation i s proposed from three independent sources of evidence: K-Ar data, p a l y n o l o g i c a l a n a l y s i s , and fauna examination of s p e c i f i c a l l y c o l l e c t e d sam-p l e s at C i n o l a . Primary and secondary d i s p e r s i o n haloes of Au, Ag, Hg, As, and W are e v i d e n t from s t a t i s t i c a l a n a l y s i s of rock, s o i l , and s i l t geochemical data. Ag i n rock best d e f i n e d the a r e a l extent of the C i n o l a orebody. On the other end, base metals (Cu, PB, and Zn), with N i , Co, and Mo i n a d d i t i o n , have low values and show an e r r a t i c d i s t r i b u t i o n . The uniform d i s t r i b u t i o n of g o l d at C i n o l a i s remarkable fo r a gold d e p o s i t . T h i s i s shown by the two-dimensional i s o -t r o p i c nature of d r i l l hole assay data and r e l a t i v e l y low e r r o r estimates on mean grades of k r i g e d b l o c k s . 193 REFERENCES A d d i c o t t , W.O., 1973, Neogene marine molluscs of the P a c i f i c Coast of North America: An annotated b i b l i o g r a p h y , 1797-1969; U.S.G.S. B u l l . 1362, 201 p. A d d i c o t t , W.O., 1976, Molluscan p a l e o n t o l o g y of the Lower Miocene C l a l l a m Formation, northwestern Washington; U.S.G.S. P r o f . Paper 196, 44 p., 9 p l a t e s . A d d i c o t t , W.O., 1978, Late Miocene molluscs from the Queen C h a r l o t t e I s l a n d s , B r i t i s h Columbia, Canada; Jour. Res. U.S.G.S., v. 6, no. 5, pp. 677-690. Berggren, W.A., and van Couvering, J.A., 1974, The Late Neogene; Paleogeog. P a l e o c l i m . P a l e o e c o l . , v. 16, no. 1/2, 216 p. Blanche t , P.H. and Godwin, C.I., 1972, 'Geolog System* f o r com-puter and manual a n a l y s i s of g e o l o g i c data from porphyry and other d e p o s i t s ; Econ. G e o l . , v. 67, pp. 796-813. B l a t t , H., Mi d d l e t o n , G.V., and Murray, R., 1972, O r i g i n of sed-imentary rocks; P r e n t i c e - H a l l Inc., Englewood C l i f f s , N. J . , 634 p. Boyle, R.W.,1979, The geochemistry of go l d and i t s d e p o s i t s ; G e o l . Surv. o f Canada, B u l l . 280. 194 Champigny, N., and S i n c l a i r , A.J., 1980a, C i n o l a (Specogna) g o l d d e p o s i t , Queen C h a r l o t t e I s l a n d s , B r i t i s h Columbia - A Canadian C a r l i n - t y p e d e p o s i t ( a b s t r a c t ) ; Can. I n s t . Min. M e t a l l . B u l l . 75, v. 73, p. 62. 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