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Geology of the Rain Gold Deposit, Elko County, Nevada
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SEDIMENT-HOSTED PRECIOUS METAL DEPOSITS Application of Rank Sum Analysis to Soil Geochemistry at the Dee Gold Mine, Elko County, Nevada W.C. B A G B Y , W.J. P I C K T H O R N , R. G O L D F A R B a n d R.A. H I L L
Western Mining Resources Branch, U.S. Geological Survey, 345 Middlefield Road, M.S. 901, Menlo Park, CA 94025, U.S.A. T h e Dee m i n e is a s e d i m e n t - h o s t e d , d i s s e m i n a t e d gold d e p o s i t in t h e R o b e r t s M o u n tains a l l o c h t h o n o f n o r t h c e n t r a l Nevada. Soil samples were collected f r o m t h e C - h o r i z o n in u n d i s t u r b e d areas over t h e deposit in o r d e r to investigate t h e usefulness o f soil g e o c h e m i s t r y in i d e n t i f y i n g this t y p e o f deposit. T h e d e p t h o f s a m p l i n g varied b e t w e e n 1 2 " a n d 1 6 " , d e p e n d i n g u p o n soil d e v e l o p m e n t . E a c h s a m p l e was sieved t o - - 8 0 m e s h a n d a n a l y z e d q u a n t i t a t i v e l y for Au, Ag, As, Sb, Hg, T1 a n d s e m i - q u a n t i t a t i v e data for a n a d d i t i o n a l 31 e l e m e n t s . Individual e l e m e n t plots d e l i n e a t e k n o w n ore z o n e s w i t h variable success. F a c t o r analysis o f t h e q u a n t i t a t i v e data is n o t useful for ore z o n e identif i c a t i o n using t h e t o t a l d a t a set. However, r a n k s u m analysis is successful for t h e Au, Ag, As, Sb, Hg, T1 suite, even t h o u g h b e d r o c k geology is disregarded. This m e t h o d involves d a t a t r a n s f o r m a t i o n i n t o a t o t a l e l e m e n t s i g n a t u r e b y r a n k i n g t h e d a t a in ascending o r d e r a n d s u m m i n g t h e e l e m e n t r a n k s for each sample. T h e r a n k sums are t h e n divided into percentile groups a n d p l o t t e d . T h e r a n k s u m p l o t for t h e Dee soils u n e q u i v o c a l l y identifies t h r e e of f o u r k n o w n ore zones. T h e success of this statistical m e t h o d for t h e Dee m i n e area indicates t h a t it can serve as a p o w e r f u l e x p l o r a t i o n t o o l for this t y p e o f d e p o s i t w h e r e o u t c r o p is sparse a n d b e d r o c k is largely u n k n o w n .
Geology of the Rain Gold Deposit, Elko County, Nevada G A L E C. K N U T S E N
Newmont Exploration Limited, P.O. Box 368, Elko, NV89801, U.S.A. T h e 6 8 6 , 0 0 0 o u n c e R a i n ore b o d y is a n e p i t h e r m a l , s e d i m e n t - h o s t e d , d i s s e m i n a t e d gold d e p o s i t l o c a t e d a l o n g a n a l i g n m e n t of deposits t h a t includes t h e Carlin gold mine. T h e R a i n d e p o s i t lies largely w i t h i n siltstones o f t h e Mississippian Webb F o r m a t i o n a n d is associated w i t h a high angle reverse fault w h i c h is a m a j o r e l e m e n t o f t h e h y d r o t h e r m a l p l u m b i n g . R a i n , a n essentially b l i n d ore b o d y , e x h i b i t s similarities to t h e Alligator Ridge gold m i n e in White Pine C o u n t y , Nevada, i n c l u d i n g a j a s p e r o i d a l surface expression.
Geology and Geochemistry o f t h e Q u i t o P r o s p e c t R O B E R T N. W H I T T E M O R E a n d R.S. C O W A R T
FMC Corporation, Natural Resources Operation, 5011 Meadowood Way, Suite 200, Reno, NV89502, U.S.A. T h e Q u i t o p r o s p e c t is l o c a t e d a b o u t 10 miles s o u t h o f t h e t o w n of A u s t i n in t h e T o i y a b e Range. L i t e r a t u r e research in early 1 9 7 9 i n d i c a t e d t h e f a v o r a b l e p o t e n t i a l of t h e area, w h i c h was s u p p o r t e d b y a field e x a m i n a t i o n later in t h e year. A f t e r a successful g e o c h e m i c a l s a m p l i n g p r o g r a m , land a c q u i s i t i o n b e g a n in 1 9 8 0 . E x t e n s i v e surface s a m p l i n g in 1 9 8 0 was successful in o u t l i n i n g t w o m a j o r gold a n o m a l i e s a n d n u m e r o u s i n d i c a t o r - e l e m e n t anomalies. S u b s e q u e n t investigation has i d e n t i f i e d a d d i t i o n a l a n o m alous areas. Drilling was i n i t i a t e d in 1981 a n d has c o n t i n u e d to t h e present. To date, o n e ore b o d y h a s b e e n discovered; w i d e s p r e a d w e a k gold m i n e r a l i z a t i o n occurs in several
SEDIMENT-HOSTED PRECIOUS METAL DEPOSITS Application of Rank Sum Analysis to Soil Geochemistry at the Dee Gold Mine, Elko County, Nevada W.C. B A G B Y , W.J. P I C K T H O R N , R. G O L D F A R B a n d R.A. H I L L
Western Mining Resources Branch, U.S. Geological Survey, 345 Middlefield Road, M.S. 901, Menlo Park, CA 94025, U.S.A. T h e Dee m i n e is a s e d i m e n t - h o s t e d , d i s s e m i n a t e d gold d e p o s i t in t h e R o b e r t s M o u n tains a l l o c h t h o n o f n o r t h c e n t r a l Nevada. Soil samples were collected f r o m t h e C - h o r i z o n in u n d i s t u r b e d areas over t h e deposit in o r d e r to investigate t h e usefulness o f soil g e o c h e m i s t r y in i d e n t i f y i n g this t y p e o f deposit. T h e d e p t h o f s a m p l i n g varied b e t w e e n 1 2 " a n d 1 6 " , d e p e n d i n g u p o n soil d e v e l o p m e n t . E a c h s a m p l e was sieved t o - - 8 0 m e s h a n d a n a l y z e d q u a n t i t a t i v e l y for Au, Ag, As, Sb, Hg, T1 a n d s e m i - q u a n t i t a t i v e data for a n a d d i t i o n a l 31 e l e m e n t s . Individual e l e m e n t plots d e l i n e a t e k n o w n ore z o n e s w i t h variable success. F a c t o r analysis o f t h e q u a n t i t a t i v e data is n o t useful for ore z o n e identif i c a t i o n using t h e t o t a l d a t a set. However, r a n k s u m analysis is successful for t h e Au, Ag, As, Sb, Hg, T1 suite, even t h o u g h b e d r o c k geology is disregarded. This m e t h o d involves d a t a t r a n s f o r m a t i o n i n t o a t o t a l e l e m e n t s i g n a t u r e b y r a n k i n g t h e d a t a in ascending o r d e r a n d s u m m i n g t h e e l e m e n t r a n k s for each sample. T h e r a n k sums are t h e n divided into percentile groups a n d p l o t t e d . T h e r a n k s u m p l o t for t h e Dee soils u n e q u i v o c a l l y identifies t h r e e of f o u r k n o w n ore zones. T h e success of this statistical m e t h o d for t h e Dee m i n e area indicates t h a t it can serve as a p o w e r f u l e x p l o r a t i o n t o o l for this t y p e o f d e p o s i t w h e r e o u t c r o p is sparse a n d b e d r o c k is largely u n k n o w n .
Geology of the Rain Gold Deposit, Elko County, Nevada G A L E C. K N U T S E N
Newmont Exploration Limited, P.O. Box 368, Elko, NV89801, U.S.A. T h e 6 8 6 , 0 0 0 o u n c e R a i n ore b o d y is a n e p i t h e r m a l , s e d i m e n t - h o s t e d , d i s s e m i n a t e d gold d e p o s i t l o c a t e d a l o n g a n a l i g n m e n t of deposits t h a t includes t h e Carlin gold mine. T h e R a i n d e p o s i t lies largely w i t h i n siltstones o f t h e Mississippian Webb F o r m a t i o n a n d is associated w i t h a high angle reverse fault w h i c h is a m a j o r e l e m e n t o f t h e h y d r o t h e r m a l p l u m b i n g . R a i n , a n essentially b l i n d ore b o d y , e x h i b i t s similarities to t h e Alligator Ridge gold m i n e in White Pine C o u n t y , Nevada, i n c l u d i n g a j a s p e r o i d a l surface expression.
Geology and Geochemistry o f t h e Q u i t o P r o s p e c t R O B E R T N. W H I T T E M O R E a n d R.S. C O W A R T
FMC Corporation, Natural Resources Operation, 5011 Meadowood Way, Suite 200, Reno, NV89502, U.S.A. T h e Q u i t o p r o s p e c t is l o c a t e d a b o u t 10 miles s o u t h o f t h e t o w n of A u s t i n in t h e T o i y a b e Range. L i t e r a t u r e research in early 1 9 7 9 i n d i c a t e d t h e f a v o r a b l e p o t e n t i a l of t h e area, w h i c h was s u p p o r t e d b y a field e x a m i n a t i o n later in t h e year. A f t e r a successful g e o c h e m i c a l s a m p l i n g p r o g r a m , land a c q u i s i t i o n b e g a n in 1 9 8 0 . E x t e n s i v e surface s a m p l i n g in 1 9 8 0 was successful in o u t l i n i n g t w o m a j o r gold a n o m a l i e s a n d n u m e r o u s i n d i c a t o r - e l e m e n t anomalies. S u b s e q u e n t investigation has i d e n t i f i e d a d d i t i o n a l a n o m alous areas. Drilling was i n i t i a t e d in 1981 a n d has c o n t i n u e d to t h e present. To date, o n e ore b o d y h a s b e e n discovered; w i d e s p r e a d w e a k gold m i n e r a l i z a t i o n occurs in several