UBC Theses and Dissertations

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UBC Theses and Dissertations

Sampling problems and hydraulic factors related to the dispersion of scheelite in drainage sediments,… Saxby, Donald William 1985

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SAMPLING PROBLEMS AND HYDRAULIC FACTORS RELATED TO THE DISPERSION OF SCHEELITE IN DRAINAGE SEDIMENTS, CLEA PROPERTY, YUKON TERRITORY • By DONALD WILLIAM SAXBY B . S c , W e s t e r n W a s h i n g t o n U n i v e r s i t y , 1980 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES Department o f G e o l o g i c a l S c i e n c e s We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA F e b r u a r y , 1985 © D o n a l d W i l l i a m Saxby, 1985 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y available for reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the head of my department or by h i s or her representatives. I t i s understood that copying or publication of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Donald W. Saxby Department of Geological Sciences The University of B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date HIXVJA. IS > JfaST DE-6 (3/81) i i . ABSTRACT M u l t i f r a c t i o n a l a n a l y s i s f o r s c h e e l i t e (G=5.9-6.1), m a g n e t i t e (G=5.2), h e a v i e s (G>3.3), mediums (3.3<G<2.9), and l i g h t s (G<2.9), i n d r a i n a g e s e d i m e n t s downstream o f the C l e a t u n g s t e n - b e a r i n g s k a r n d e p o s i t , Yukon T e r r i t o r y , r e v e a l e d t h r e e i n t e r d e p e n d e n t p r o b l e m s t h a t c o m p l i c a t e i n t e r p r e t a t i o n o f r e s u l t s o f d r a i n a g e s u r v e y s f o r W: (1) S c h e e l i t e c o n c e n t r a t i o n s i n s t r e a m s e d i m e n t s r e f l e c t , i n p a r t , h y d r a u l i c s o r t i n g r a t h e r t h a n s o u r c e d i s t r i b u t i o n . (2) Low numbers o f s c h e e l i t e g r a i n s i n s t r e a m s e d i m e n t s c a u s e h i g h random s a m p l i n g and s u b s a m p l i n g e r r o r s and p r e s e n t a n a l y t i c a l d i f f i c u l t i e s . (3) S c h e e l i t e / h e a v i e s o r s c h e e l i t e / m e d i u m s r a t i o s may n o t be a p p r e c i a b l y h i g h e r downstream o f s c h e e l i t e - b e a r i n g s k a r n t h a n b a r r e n b e d r o c k , b e c a u s e s c h e e l i t e , h e a v i e s and mediums o c c u r i n i n c r e a s e d amounts i n s k a r n s ( i . e . t h e y c o v a r y i n s o u r c e m a t e r i a l s ) . H y d r a u l i c e f f e c t s r e s u l t i n s y s t e m a t i c c h a n g e s i n m i n e r a l d i s t r i b u t i o n s between h i g h and low e n e r g y e n v i r o n m e n t s ( c h a r a c t e r i z e d by c o a r s e g r a v e l and f i n e g r a v e l t o s a n d , r e s p e c t i v e l y ) . S c h e e l i t e , m a g n e t i t e , h e a v i e s and mediums c o n c e n t r a t i o n s i n minus 10-mesh s e d i m e n t s a r e g r e a t e r i n h i g h t h a n low e n e r g y e n v i r o n m e n t s , and t h i s r e l a t i v e e n r i c h m e n t i n c r e a s e s w i t h I i i . grain size and density (up to one-hundredfold for s c h e e l i t e ) . Using a regression method, developed in this study, h y d r a u l i c a l l y equivalent sizes of magnetite and heavies were empirically determined for finer (3.0-3.5 phi and 3.5-4.25 phi) scheelite s i z e s . Ratioing the weight of scheelite to that of a h y d r a u l i c a l l y equivalent mineral greatly reduces hydraulic v a r i a b i l i t y . Resulting p r o f i l e s of h y d r a u l i c a l l y equivalent scheelite concentrations more c l e a r l y delineate locations of scheelite input to the stream. The rare-grain problem can be reduced at the sampling l e v e l by sampling from high energy environments (thereby exploiting hydraulic effects) and/or by sampling for finer s c h e e l i t e . Heavy mineral separation i s the most e f f e c t i v e means of reducing the rare grain problem at the subsampling and a n a l y t i c a l l e v e l s . The problem of covariance in source materials can best be remedied by rati o i n g to an individual (hydraulically equivalent) heavy mineral which has a constant and ubiquitous d i s t r i b u t i o n in the area of int e r e s t . In this study, magnetite shows promise, but more information on i t s source d i s t r i b u t i o n i s needed. i v . TABLE OF CONTENTS PAGE ABSTRACT i i L I S T OF TABLES v i L I S T OF FIGURES i x ACKNOWLEDGEMENT x i i CHAPTER 1 PROBLEMS ASSOCIATED WITH SAMPLING FOR 1 SCHEELITE INTRODUCTION DISPERSION OF SCHEELITE IN DRAINAGE 2 SEDIMENTS CONCLUSIONS 32 2 DESCRIPTION OF THE STUDY AREA 33 LOCATION AND ACCESS 34 PREVIOUS WORK 34 GEOLOGY 36 R e g i o n a l g e o l o g y 36 L o c a l and p r o p e r t y g e o l o g y 38 PHYSIOGRAPHY 44 CLIMATE 47 SOILS 47 VEGETATION 47 3 METHODS 48 EXPERIMENTAL DESIGN 49 SAMPLING METHODS 51 F I E L D OBSERVATIONS 53 G e n e r a l 53 T e x t u r e s 53 SAMPLE PROCESSING 57 S i e v i n g 57 Heavy m i n e r a l s e p a r a t i o n 60 C o u n t i n g 62 W e i g h t c o n v e r s i o n s 64 4 RESULTS 66 INTRODUCTION 67 DOWNSTREAM PROFILES 68 HYDRAULIC EFFECTS WITHIN SITES 72 S I Z E DISTRIBUTIONS 73 CONCLUSIONS 77 CHAPTER PAGE 5 DETERMINATION OF HYDRAULICALLY 80 EQUIVALENT SIZES INTRODUCTION 81 RITTENHOUSE COEFFICIENT OF 81 VARIATION METHOD CONCENTRATION RATIOS 85 G e n e r a l t r e n d s o f c o n c e n t r a t i o n 85 r a t i o s D e t e r m i n a t i o n o f h y d r a u l i c a l l y 92 e q u i v a l e n t s i z e s u s i n g CR's DISCUSSION 95 6 DISCUSSION 99 INTRODUCTION 100 DEPARTURES FROM HYDRAULIC EQUIVALENCE 100 DOWNSTREAM PROFILES OF HYDRAULICALLY 108 EQUIVALENT CONCENTRATIONS VARIABILITY WITHIN SITES 119 INTERPRETATION OF SOURCE EFFECTS 123 I n t r o d u c t i o n 123 P e l l y R i v e r 124 Omo C r e e k 125 Summary o f i n t e r p r e t a t i o n s o f 126 h y d r a u l i c a l l y e q u i v a l e n t p r o f i l e s APPLICATION TO EXPLORATION 12 7 CONCLUSIONS 137 BIBLIOGRAPHY 139 APPENDIX 1 - RAW DATA 144 APPENDIX 2 - SAMPLE LOCATIONS 151 v i . L I S T OF TABLES TABLE PAGE 1 Sample s i z e t h e o r e t i c a l l y r e q u i r e d t o 6 m a i n t a i n a random s a m p l i n g p r e c i s i o n o f +15%. 2 C l a s s i f i c a t i o n o f heavy m i n e r a l d e p o s i t s 12 b a s e d on t h e b o u n d a r y R e y n o l d s number (R*) and t h e r a t i o (d/BKS) o f heavy m i n e r a l t o b o t t o m g r a i n s i z e ( S l i n g e r l a n d , 1 9 7 7 ) . 3 S i z e d i f f e r e n c e (0) between h y d r a u l i c a l l y 31 e q u i v a l e n t q u a r t z and h i g h e r d e n s i t y m i n e r a l s ( R i t t e n h o u s e , 1 9 4 3 ) . 4 S k a r n a l t e r a t i o n f a c i e s a t C l e a 42 ( D i c k , 1980) . 5 D i s t a n c e s between p a i r e d h i g h and low 52 e n e r g y s a m p l e s and between d u p l i c a t e p a i r s . 6 S t r e a m v e l o c i t i e s ( m e t e r s / s e c o n d ) a t 55 sample l o c a t i o n s . 7 T e x t u r a l r a n k i n g and c l a s s i f i c a t i o n 58 o f s e d i m e n t s . 8 A v e r a g e number o f s c h e e l i t e g r a i n s ( n ) , 63 s t a n d a r d d e v i a t i o n ( s ) , and c o e f f i c i e n t o f v a r i a t i o n (cv) b a s e d on d u p l i c a t e c o u n t s o f s c h e e l i t e g r a i n s . 9 W e i g h t s o f W and s c h e e l i t e i n a s i n g l e 65 g r a i n i n sample 58; f o r c o n v e r s i o n o f s c h e e l i t e g r a i n c o u n t s t o W / s c h e e l i t e c o n c e n t r a t i o n s . 10 Changes i n median d i a m e t e r s o f s c h e e l i t e , 78 m a g n e t i t e , h e a v i e s , mediums and l i g h t s f r o m low t o h i g h e n e r g y e n v i r o n m e n t s a t t h e e i g h t d u p l i c a t e s i t e s . 11 Mean o f median d i a m e t e r s o f s c h e e l i t e , m a g n e t i t e , h e a v i e s , mediums and l i g h t s a t t h e e i g h t d u p l i c a t e s i t e s . 79 v i i . TABLE PAGE 12 C o e f f i c i e n t s o f v a r i a t i o n (%) o f 84 s c h e e l i t e / h e a v i e s w e i g h t r a t i o s -f o u r s a m p l e s per s i t e . 13 G e o m e t r i c means o f c o n c e n t r a t i o n r a t i o s 86 o f m i n e r a l s i n h i g h e n e r g y e n v i r o n m e n t s o v e r low e n e r g y e n v i r o n m e n t s ( c o n c e n t r a t i o n s a r e e x p r e s s e d r e l a t i v e t o s i e v e d s e d i m e n t s i n t h e same s i z e f r a c t i o n ) . 14 G e o m e t r i c means / medians o f c o n c e n t r a t i o n 88 r a t i o s o f m i n e r a l s i n h i g h e n e r g y e n v i r o n m e n t s o v e r low e n e r g y e n v i r o n m e n t s ( c o n c e n t r a t i o n s a r e e x p r e s s e d r e l a t i v e t o minus 10-mesh s e d i m e n t s ) . M e d i a n c o n c e n t r a t i o n r a t i o s o f m i n e r a l f r a c t i o n s w h i c h have GMCR's c o m p a r a b l e t o t h o s e o f s c h e e l i t e a r e i n c l u d e d . 15 C o r r e l a t i o n c o e f f i c i e n t s (r) between l o g 89 CR's o f s c h e e l i t e and o t h e r m i n e r a l s . 16 H y d r a u l i c a l l y e q u i v a l e n t s i z e s i n d i c a t e d 96 by r e g r e s s i o n s o f c o n c e n t r a t i o n r a t i o s ; a l s o , d i a m e t e r r a t i o s o f i n d i c a t e d h y d r a u l i c a l l y e q u i v a l e n t m i n e r a l and s c h e e l i t e . 17 R a t i o s o f p o s i t i v e t o n e g a t i v e l o g CR's 98 f o r i n d i c a t e d s i z e s o f h y d r a u l i c a l l y e q u i v a l e n t m i n e r a l s . 18 D i f f e r e n c e s between r - s q u a r e d v a l u e s o f 101 a d j a c e n t s c h e e l i t e s i z e and h y d r a u l i c a l l y e q u i v a l e n t m i n e r a l . 19 Numbers o f CR's w h i c h i n c r e a s e o r 104 d e c r e a s e when r e c a l c u l a t e d f r o m h a l f - p h i t o minus 10-mesh s e d i m e n t s . 20 Maximum CR's i n h a l f - p h i s i e v e d / minus 105 10-mesh s e d i m e n t s . 21 Mean / median numbers o f s c h e e l i t e g r a i n s 121 i n s e d i m e n t s a m p l e s f r o m t h e P e l l y R i v e r . 22 S a m p l i n g p r e c i s i o n s (%) a s s o c i a t e d w i t h 122 median numbers o f s c h e e l i t e g r a i n s ( T a b l e 21) i n s e d i m e n t s a m p l e s f r o m t h e P e l l y R i v e r . v i i i . TABLE PAGE 23 D e n s i t y f r a c t i o n s i n w h i c h m i n e r a l s 129 i d e n t i f i e d a t t h e C l e a t u n g s t e n p r o p e r t y a r e most l i k e l y t o o c c u r . 24 P r o b a b l e c o n s e q u e n c e s o f v a r i o u s 131 a p p r o a c h e s t o s a m p l i n g f o r s c h e e l i t e . i x . L I S T OF FIGURES FIGURE PAGE 1 T y p i c a l p l a c e r l o c a t i o n s ( c o m p l i e d f r o m 10 M o r i s a w a , 1968; B a l l a n t y n e , 1 9 7 6 ) . 2 CDRep v e r s u s Rep f o r s p h e r e s ; 17 CD = c o e f f i c i e n t o f d r a g and Rep = p a r t i c l e R e y n o l d s number ( Y a l i n , 1 9 7 2 ) . 3 S i e v e s i z e v e r s u s e q u i v a l e n t - s p h e r e f a l l 19 d i a m e t e r ; S.F. = C o r e y ' s shape f a c t o r (Wasp e t a l . , 1977) . 4 E f f e c t o f b o t t o m r o u g h n e s s (BKS) on 22 c r i t i c a l v e l o c i t y (Vc) f o r q u a r t z - d e n s i t y p a r t i c l e s ( S l i n g e r l a n d , 1977) . 5 C a l c u l a t e d c r i t i c a l v e l o c i t y and o b s e r v e d 24 d i s t a n c e moved by q u a r t z and g a r n e t on smooth and ro u g h b a s e s ( S l i n g e r l a n d , 1 9 7 7 ) . 6 E r o s i o n and f a l l v e l o c i t i e s o f r i v e r 25 s e d i m e n t s ( H j u l s t r o m , 1 9 3 5 ) . 7 V a r i a t i o n o f c r i t i c a l s h e a r s t r e s s o f 26 wa t e r w i t h p a r t i c l e s i z e and d e n s i t y ( G r i g g and Ra t h b u n , 1969) . 8 C r i t i c a l v e l o c i t y (Vc) and f a l l v e l o c i t y 27 (Vcs) o f q u a r t z and g a r n e t i n an e q u i g r a n u l a r s e d i m e n t ( S l i n g e r l a n d , 1977) . 9 V a r i a t i o n o f i l m e n i t e / q u a r t z w e i g h t 30 r a t i o s ( h y d r a u l i c r a t i o s ) and t h e c o e f f i c i e n t o f v a r i a t i o n o f t h o s e r a t i o s w i t h g r a i n s i z e o f q u a r t z ( R i t t e n h o u s e , 1943) . 10 L o c a t i o n o f t h e C l e a t u n g s t e n p r o p e r t y , 35 Yukon T e r r i t o r y . 11 R e g i o n a l z o n a t i o n o f s k a r n t y p e s ( m o d i f i e d f r o m D i c k , 1 9 8 0 ) . 37 G e o l o g y n e a r t h e C l e a d e p o s i t ( m o d i f i e d f r o m G o r d e y , 1981) . P a r t i a l s t r a t i g r a p h i c s e c t i o n , C l e a p r o p e r t y ( D i c k , 1 9 8 0 ) . L o c a t i o n s o f s c h e e l i t e - b e a r i n g s k a r n s , C l e a p r o p e r t y ( m o d i f i e d f r o m Tompson, 1978) . L o n g i t u d i n a l p r o f i l e o f C l e a C r e e k and t h e P e l l y R i v e r . L o n g i t u d i n a l p r o f i l e o f Omo C r e e k . Sample l o c a t i o n s . S k e t c h o f s i t e AO. S e d i m e n t c l a s s i f i c a t i o n scheme ( F o l k , 1974) . Sample p r o c e s s i n g . W c o n c e n t r a t i o n s i n s i e v e d s e d i m e n t s , sample 5. W / h e a v i e s c o n c e n t r a t i o n s down t h e P e l l y R i v e r ; (a) 1.5-2.0 p h i (45-60 mesh), (b) 2.0-2.5 p h i (60-80 mesh), (c) 2.5-3.0 p h i (80-120 mesh), (d) 3.0-3.5 p h i (120-170 mesh), (e) 3.5-4.25 p h i (170-270 mesh). W / h e a v i e s c o n c e n t r a t i o n s down Omo C r e e k ; (a) 1.5-2.0 p h i , (b) 2.0-2.5 p h i , (c) 2.5-3.0 p h i , (d) 3.0-3.5 p h i , (e) 3.5-4.25 p h i . W / h e a v i e s c o n c e n t r a t i o n s , v e l o c i t i e s and median s c h e e l i t e s i z e s a t s i t e AO. E n r i c h m e n t o f h i g h r e l a t i v e t o low e n e r g y W / h e a v i e s c o n c e n t r a t i o n s a t s i t e AO. C u m u l a t i v e w e i g h t p e r c e n t a g e s o f minus 10-mesh s i e v e d s e d i m e n t s . 3.5-4.2 5 p h i s c h e e l i t e l o g CR v e r s u s 2.5-3.0 p h i h e a v i e s l o g CR. S l o p e s (b) and y - i n t e r c e p t s ( l o g a) o f s c h e e l i t e v e r s u s h e a v i e s l o g CR r e g r e s s i o n s ; (a) 3.5-4.25 p h i s c h e e l i t e , (b) 3.0-3.5 p h i s c h e e l i t e . S l o p e s (b) and y - i n t e r c e p t s ( l o g a) o f s c h e e l i t e v e r s u s m a g n e t i t e l o g CR r e g r e s s i o n s ; (a) 3.5-4.25 p h i s c h e e l i t e , (b) 3.0-3.5 p h i s c h e e l i t e , (c) 2.5-3.0 p h i s c h e e l i t e . M o d e l f o r f o r m a t i o n o f h e a v i e s - r i c h d e p o s i t s i n h i g h e n e r g y e n v i r o n m e n t s , t h r o u g h s e l e c t i v e r e e n t r a i n m e n t o f c o a r s e l i g h t s . Log CR's o f s e l e c t e d s c h e e l i t e s i z e s down Omo C r e e k . 3.0-3.5 p h i s c h e e l i t e / 1 . 5 - 2 . 0 p h i h e a v i e s on t h e P e l l y R i v e r . 3.5-4.25 p h i s c h e e l i t e / 2 . 0 - 2 . 5 p h i h e a v i e s on t h e P e l l y R i v e r . 3.0/3.5 p h i s c h e e l i t e / 2 . 0 - 2 . 5 p h i m a g n e t i t e on t h e P e l l y R i v e r . 3.5-4.25 p h i s c h e e l i t e / 2 . 5 - 3 . 0 p h i m a g n e t i t e on t h e P e l l y R i v e r . 3.0-3.5 p h i s c h e e l i t e / 1 . 5 - 2 . 0 p h i h e a v i e s on Omo C r e e k . 3.5-4.25 p h i s c h e e l i t e / 2 . 0 - 2 . 5 p h i h e a v i e s on Omo C r e e k . 3.0-3.5 p h i s c h e e l i t e / 2 . 0 - 2 . 5 p h i m a g n e t i t e on Omo C r e e k . 3.5-4.25 p h i s c h e e l i t e / 2 . 5 - 3 . 0 p h i m a g n e t i t e on Omo C r e e k . ACKNOWLEDGEMENT I w i s h t o e x p r e s s my a p p r e c i a t i o n t o D r . W. K. F l e t c h e r , who s u g g e s t e d t h i s p r o j e c t , and t o Dr. W. C. B a r n e s , D r . A. J . S i n c l a i r and Dr. I . Thomson f o r t h e i r h e l p f u l comments. I am a l s o g r e a t f u l t o Mr. T. O'Connel f o r h i s a s s i s t a n c e i n sample c o l l e c t i o n , and t o Ms. M. Soon and Ms. G. K e i m e l f o r t h e i r h e l p i n sample p r o c e s s i n g . F i n a l l y , I would l i k e t o thank P l a c e r D e v e l o p m e n t L i m i t e d f o r f u n d i n g t h i s r e s e a r c h , and t h e Dr. A a r o E. Aho F o u n d a t i o n f o r a d d i t i o n a l s c h o l a s t i c s u p p o r t . 1 . CHAPTER ONE PROBLEMS ASSOCIATED WITH SAMPLING FOR SCHEELITE INTRODUCTION Stre a m s e d i m e n t s a m p l i n g i s b a s e d on t h e p r e m i s e t h a t a s i n g l e sample i s a n a t u r a l c o m p o s i t e o f p r o d u c t s o f w e a t h e r i n g and e r o s i o n i n t h e b a s i n u p s t r e a m o f t h e sample s i t e . Such a sample i s t h e r e f o r e a p a r t i c u l a r l y s u i t a b l e s u b s t r a t e f o r r a p i d , r e l a t i v e l y l o w - c o s t r e g i o n a l m i n e r a l - e x p l o r a t i o n . Hawkes (1976) s u g g e s t e d t h a t anomaly m a g n i t u d e ( m e t a l c o n c e n t r a t i o n ) i s i n v e r s e l y p r o p o r t i o n a l t o d r a i n a g e a r e a u p s t r e a m o f t h e sample s i t e , and s h o u l d s t e a d i l y d e c a y downstream f r o m t h e d e p o s i t due t o d i l u t i o n : A m (Me m - Me. ) M e = _ J 2 S b i + A b a where M e a / Me^ and Me m a r e m e t a l c o n c e n t r a t i o n s i n anomalous s t r e a m s e d i m e n t s , b a c k r o u n d s e d i m e n t s and a t t h e s u r f a c e o f t h e m i n e r a l d e p o s i t , r e s p e c t i v e l y ; A i s d r a i n a g e a r e a above the anomalous s i t e and A m i s t h e m i n e r a l i z e d a r e a . I m p l i c i t a s s u m p t i o n s i n t h i s e q u a t i o n a r e a c o n s t a n t e r o s i o n r a t e and u n i f o r m b a c k g r o u n d m e t a l c o n c e n t r a t i o n s t h r o u g h o u t t h e b a s i n ; no s o r t i n g o r c o m m i n u t i o n o f s t r e a m s e d i m e n t s ; no random s a m p l i n g o r s u b s a m p l i n g e r r o r s ; no a n a l y t i c a l e r r o r s ; and no c h e m i c a l i n t e r a c t i o n between water and s e d i m e n t s . However, e l e m e n t s s u c h as W, Sn, and Au, w h i c h o c c u r as major components o f h i g h - d e n s i t y t r a c e m i n e r a l s (heavy m i n e r a l s ) , c h a r a c t e r i s t i c a l l y d i s p l a y a n o m a l i e s d i s p l a c e d f r o m t h e i r 3. s o u r c e , e r r a t i c s i n g l e - s a m p l e a n o m a l i e s and poor r e p r o d u c i b i l i t y ( Z a n t r o p and N e s p e r e i r a , 1979), r a t h e r t h a n smooth downstream d e c a y o f t h e i r a n o m a l i e s . In s u c h c a s e s , a t l e a s t some o f t h e p a r a m e t e r s o m i t t e d from t h e e q u a t i o n , on t h e a s s u m p t i o n t h a t t h e y a r e c o n s t a n t or z e r o , must, i n f a c t , v a r y s u f f i c i e n t l y t o o b s c u r e d i l u t i o n e f f e c t s r e l a t e d t o i n c r e a s e d d r a i n a g e a r e a . There i s s u b s t a n t i a l e v i d e n c e t h a t s o r t i n g g r e a t l y a f f e c t s t h e l o c a l d i s t r i b u t i o n o f heavy m i n e r a l s i n s t r e a m s e d i m e n t s ( e . g . R i t t e n h o u s e , 1946; Hanson, 1980; G l a d w e l l , 1981; S l e a t h and F l e t c h e r , 1982; F l e t c h e r e t a l . , 198 4 ) . In a d d i t i o n , random s a m p l i n g and s u b s a m p l i n g e r r o r s c a n be s i g n i f i c a n t where s a m p l i n g f o r r a r e g r a i n s ( C l i f t o n e_t a l . , 1969; I n g a m e l l s , 1974). A n a l y t i c a l e r r o r s a l s o become i m p o r t a n t when m e t a l c o n c e n t r a t i o n s a p p r o a c h t h e d e t e c t i o n l i m i t o f t h e method. T h i s s t u d y a t t e m p t s t o a s s e s s , and p r o v i d e p r a c t i c a l methods t o r e d u c e v a r i a b i l i t y c a u s e d by s e l e c t i v e s o r t i n g o f heavy m i n e r a l g r a i n s i n s t r e a m s e d i m e n t s , w i t h p a r t i c u l a r r e f e r e n c e t o d i s p e r s i o n o f W a s s c h e e l i t e . DISPERSION OF SCHEELITE IN DRAINAGE SEDIMENTS S c h e e l i t e (CaW0 4, G=5.9-6.1, H=4.5-5.0) c o n t a i n s 63.8% W by w e i g h t , f l u o r e s c e s b l u e - w h i t e under s h o r t w a v e u l t r a v i o l e t l i g h t , i s r e s i s t a n t t o c h e m i c a l w e a t h e r i n g and i s a major o r e m i n e r a l o f many W d e p o s i t s . P r o b l e m s r e l a t e d t o d i s p e r s i o n o f 4. W i n d r a i n a g e s e d i m e n t s downstream f r o m s u c h a d e p o s i t r e s u l t f r o m : (1) s c h e e l i t e g r a i n s b e i n g r e l a t i v e l y r a r e e v e n i n anomalous s t r e a m s e d i m e n t s ; and (2) h y d r a u l i c f a c t o r s c a u s i n g d i f f e r e n t i a l s o r t i n g o f s c h e e l i t e and o t h e r m i n e r a l s . These p r o b l e m s w i l l be c o n s i d e r e d i n more d e t a i l . The p r i n c i p a l d i f f i c u l t y a s s o c i a t e d w i t h o b t a i n i n g a b s o l u t e e s t i m a t e s o f r a r e s c h e e l i t e g r a i n s i s l a r g e random s a m p l i n g / s u b s a m p l i n g e r r o r s . S a m p l i n g e r r o r s (E) o f r a n d o m l y d i s t r i b u t e d m i n e r a l g r a i n s o c c u r r i n g i n p r o p o r t i o n s o f l e s s t h a n 1:1000 f o l l o w a P o i s s o n d i s t r i b u t i o n and i n c r e a s e w i t h d e c r e a s i n g a v e r a g e number (n) o f r a r e m i n e r a l g r a i n s : E (%) = 100 / n 0 - 5 P r o v i d e d n > 5, random e r r o r s a p p r o x i m a t e l y f o l l o w a n o r m a l G a u s s i a n d i s t r i b u t i o n a b o u t t h e i r mean ( I n g a m e l l s and S w i t z e r , 1973) and p r e c i s i o n ( P n ) a t t h e 95% (two s t a n d a r d d e v i a t i o n s ) c o n f i d e n c e l e v e l becomes: pn = ± 2 ° 0 / n 0 , 5 A v a l u e o f P177 = +15% i n d i c a t e s t h a t i f e q u a l s i z e s u b s a m p l e s o f a w e l l mixed e q u i g r a n u l a r s e d i m e n t c o n t a i n an a v e r a g e o f 177 s c h e e l i t e g r a i n s , s c h e e l i t e (or W) c o n c e n t r a t i o n s i n 19 o u t o f 20 s u b s a m p l e s w i l l v a r y no more t h a n +15% f r o m t h e mean c o n c e n t r a t i o n . P r e c i s i o n s o f +10% t o +15%, w h i c h c o r r e s p o n d t o n=400 and n=177, r e s p e c t i v e l y , a r e c o n s i d e r e d a d e q u a t e f o r most p r o s p e c t i n g p u r p o s e s ( F l e t c h e r , 1 9 8 1 ) . Sample s i z e r e q u i r e d t o m a i n t a i n a p r e c i s i o n o f +15% i n c r e a s e s w i t h i n c r e a s i n g g r a i n s i z e o r d e c r e a s i n g s c h e e l i t e c o n c e n t r a t i o n , and c a n be v e r y l a r g e ( T a b l e 1 ) . R a r i t y o f s c h e e l i t e g r a i n s p r e s e n t s a d i f f e r e n t p r o b l e m a t t h e a n a l y t i c a l l e v e l , i n t h a t W c o n c e n t r a t i o n s i n anomalous s t r e a m s e d i m e n t s c a n be n e a r t h e d e t e c t i o n l i m i t s o f t h e a n a l y t i c a l methods commonly used i n e x p l o r a t i o n (Meyer e_t a l . , 1 9 7 9 ) . P r e c i s i o n a t t h e d e t e c t i o n l i m i t o f an e l e m e n t i s by d e f i n i t i o n +100% ( F l e t c h e r , 1 9 8 1 ) . Two s t u d i e s w h i c h c l e a r l y d e m o n s t r a t e t h e e f f e c t s , o v e r s h o r t d i s t a n c e s i n a s t r e a m , o f s o r t i n g on heavy m i n e r a l c o n c e n t r a t i o n s a r e Hanson (1980) and F l e t c h e r e_t a l . (1984) . Hanson d e m o n s t r a t e d a s i x f o l d d e c r e a s e i n t o t a l heavy m i n e r a l c o n c e n t r a t i o n s and a f i v e f o l d d e c r e a s e i n i l m e n i t e / g a r n e t r a t i o s f r o m t h e head t o t a i l o f a g r a v e l b a r . F l e t c h e r e_t a l . ( i b i d ) , f o u n d t h a t a t t h e same s i t e , c a s s i t e r i t e , w o l f r a m i t e and m a g n e t i t e c o n c e n t r a t i o n s i n minus 80-mesh s e d i m e n t s were s i g n i f i c a n t l y h i g h e r i n samples c o l l e c t e d f r o m c o a r s e t h a n medium s a n d s . In a d d i t i o n , r e l a t i v e e n r i c h m e n t o f c a s s i t e r i t e i n c o a r s e sand i n c r e a s e d w i t h g r a i n s i z e , and was as much as 20 t i m e s g r e a t e r t h a n i n medium s a n d . From t h e f o r e g o i n g , i t c a n be i n f e r r e d t h a t v a r i a b i l i t y i n s c h e e l i t e d a t a , i n t r o d u c e d a t t h e s a m p l i n g , s u b s a m p l i n g and a n a l y t i c a l l e v e l s by r a r e g r a i n e f f e c t s , and a t t h e s a m p l i n g l e v e l by h y d r a u l i c e f f e c t s , i s p o t e n t i a l l y l a r g e enough t o 6. SIEVE PPM W* 5 10 20 50 100 500 10 1100 kg 540 kg 270 kg 110 kg 54 kg U kg 14 400 200 100 40 20 4 18 140 68 34 14 6.8 1.4 25 50 25 12 5 2.5 500 g 35 17 8.6 4.3 1.8 860 g 180 45 5.8 2.9 1.5 580 g 290 58 60 2.2 1.1 540 g 220 110 22 80 800 g 400 g 200 79 40 8 120 260 130 65 27 13 3 170 94 47 23 9 5 1 230 36 18 9 4 2 0.4 *Assumpt i o n s : C u b i c o t h e r g r a i n s ; s p e c i f i c s e d i m e n t s 6.0 and g r a v i t i e s of s c h e e l i t e 2.7, r e s p e c t i v e l y . and a 1 T a b l e 1. Sample s i z e t h e o r e t i c a l l y r e q u i r e d t o m a i n t a i n a random s a m p l i n g p r e c i s i o n of ±15%. o b s c u r e s o u r c e ( i . e . any i n p u t o f s c h e e l i t e o r d i l u t i n g m i n e r a l s t o t h e stream) e f f e c t s . C o n c e p t u a l a p p r o a c h e s t o t h e s e p r o b l e m s a r e t h e s u b j e c t o f t h e r e m a i n d e r o f t h i s c h a p t e r . The f o l l o w i n g c o n d i t i o n s a r e r e q u i r e d t o m i n i m i z e r a r e g r a i n and h y d r a u l i c p r o b l e m s : 1. W (as s c h e e l i t e ) c o n c e n t r a t i o n s must be i n c r e a s e d t o w e l l above d e t e c t i o n l i m i t s o f t h e a n a l y t i c a l method. 2. Numbers o f s c h e e l i t e g r a i n s i n a sample o r subsample must be i n c r e a s e d t o r e d u c e random e r r o r s . 3. C o r r e c t i o n f o r s y s t e m a t i c v a r i a t i o n due t o h y d r a u l i c e f f e c t s must be a p p l i e d . The most e f f e c t i v e means o f r e d u c i n g t h e r a r e g r a i n p r o b l e m a t t h e s u b s a m p l i n g and a n a l y t i c a l l e v e l i s t h r o u g h h e a v y m i n e r a l s e p a r a t i o n . C o n c e n t r a t i o n enhancement b r o u g h t a b o u t by heavy m i n e r a l s e p a r a t i o n depends upon t h e e x t e n t t o w h i c h d i l u t i n g m i n e r a l s a r e removed, w h i c h i n t u r n depends upon t h e n a t u r e o f m i n e r a l i z a t i o n , i t s g e o l o g i c , t o p o g r a p h i c and c l i m a t i c s e t t i n g , and s a m p l i n g and p r e p a r a t i o n methods. In g e n e r a l , c o n c e n t r a t i o n s c a n be i n c r e a s e d by t h r e e o r more o r d e r s o f m a g n i t u d e (Meyer, §_t §_1., 1 9 7 9 ) . 8. Heavy m i n e r a l s c a n be s e p a r a t e d i n t h e l a b o r a t o r y u s i n g motor o r hand d r i v e n m e c h a n i c a l d e v i c e s o r heavy l i q u i d s . Not o n l y c a n l a r g e amounts o f m a t e r i a l be s e p a r a t e d m e c h a n i c a l l y , b u t n a t i v e Au as f i n e as 400-mesh i s r e c o v e r a b l e w i t h a S u p e r p a n n e r i f t h e s e d i m e n t s a r e c l o s e l y g r a d e d (Cook and Rao, 1979) . Van Wees and Sumadiguna (1983) f o u n d t h a t hand p a n n i n g under c o n t r o l l e d l a b o r a t o r y c o n d i t i o n s gave r e l a t i v e l y c o n s i s t e n t r e c o v e r i e s . Heavy l i q u i d s g i v e t h e most c o n s i s t e n t and a c c u r a t e r e s u l t s ( C a r v e r , 1971) b u t sample s i z e i s l i m i t e d by v e r y h i g h c o s t s . P r o v i d e d w a t e r i s a v a i l a b l e , hand o p e r a t e d m e c h a n i c a l d e v i c e s , s u c h a s g o l d p ans o r b a t e a s , c a n be u s e d t o p r o d u c e c o n c e n t r a t e s f r o m l a r g e s a m p l e s a t t h e s i t e , t h e r e b y r e d u c i n g t h e r a r e g r a i n p r o b l e m a t t h e s a m p l i n g l e v e l . However, T h e o b a l d (1957) f o u n d t h a t heavy m i n e r a l s w i t h s p e c i f i c g r a v i t i e s below 4.5 c o u l d n o t be r e c o v e r e d c o n s i s t e n t l y w i t h t h e g o l d p a n , and t h a t r e c o v e r y o f m a g n e t i t e (G = 5.2) i n 13 p a n n i n g s o f t h e same sample by t h e same o p e r a t o r r a n g e d f r o m 16 t o 87 p e r c e n t . L i k e w i s e , Van Wees and Sumadiguma (1983) f o u n d t h a t r e c o v e r i e s o f c a s s i t e r i t e panned by hand i n t h e f i e l d were e r r a t i c and d e c r e a s e d w i t h d e c r e a s i n g s i z e o r i n c r e a s i n g g r a d e . B e c a u s e p a n n i n g h e a v y m i n e r a l s a t t h e s i t e may i n t r o d u c e human e r r o r , a n o t h e r means o f r e d u c i n g random e r r o r s a t t h e s a m p l i n g l e v e l i s p r e f e r r e d . S a m p l i n g n a t u r a l " h y d r a u l i c " c o n c e n t r a t i o n s o f h e a v y m i n e r a l s , and c o l l e c t i n g a s l a r g e a sample as c a n be e c o n o m i c a l l y h a n d l e d o r p r o c e s s e d i s an a l t e r n a t i v e a p p r o a c h . The h y d r a u l i c e f f e c t s w h i c h c o n c e n t r a t e s c h e e l i t e and o t h e r h e a v y m i n e r a l s i n c e r t a i n l o c a t i o n s i n t h e s t r e a m c a n be u s e d a d v a n t a g e o u s l y t o r e d u c e t h e r a r e g r a i n p r o b l e m . O b s e r v a t i o n s by e a r l y p r o s p e c t o r s on t y p i c a l l o c a t i o n s o f g o l d p l a c e r s a l s o a p p l y t o s c h e e l i t e ( F i g u r e 1 ) . G o l d c o n c e n t r a t i o n s have been o b s e r v e d where t h e r e i s an a b r u p t d e c r e a s e i n g r a d i e n t o r w i d e n i n g o f t h e s t r e a m ; a t t h e c o n f l u e n c e w i t h a t r i b u t a r y ; on b e d r o c k i n r i f f l e s , c r a c k s and p o t h o l e s ; i n d eep p o o l s ; and a t t h e head o f b o u l d e r s , b a r s o r o t h e r o b s t r u c t i o n s ( B a l l a n t i n e , 1 9 7 6 ) . S a m p l i n g where h y d r a u l i c e f f e c t s have p r o d u c e d maximum s c h e e l i t e c o n c e n t r a t i o n s r e d u c e s t h e r a r e g r a i n p r o b l e m , b u t i t c a n n o t be e x p e c t e d t h a t h y d r a u l i c e f f e c t s w i l l have a c t e d t o t h e same d e g r e e i n e a c h c a s e . Heavy m i n e r a l s w i t h i n a t y p i c a l p l a c e r d e p o s i t a r e d i s t r i b u t e d e r r a t i c a l l y ( W e l l s , 1 9 7 3 ) , and e x p l o i t i n g n a t u r a l c o n c e n t r a t i o n s may, i n f a c t , i n c r e a s e v a r i a b i l i t y due t o h y d r a u l i c e f f e c t s . One remedy f o r t h i s would be t o q u a n t i t a t i v e l y a s s e s s d i f f e r e n c e s i n h y d r a u l i c e f f e c t s between sample l o c a t i o n s and t o c o r r e c t f o r them. The g e n e r a l method f o r a c c o m p l i s h i n g t h i s s h o u l d be s i m i l a r t o t h a t o f c o r r e c t i n g f o r o t h e r s o u r c e s o f s y s t e m a t i c v a r i a t i o n i n d r a i n a g e s u r v e y s , s u c h as c o r r e c t i n g f o r a d s o r p t i o n o f z i n c on manganese o x i d e s by r a t i o i n g t h e i r c o n c e n t r a t i o n s . U n f o r t u n a t e l y , u n l i k e c o n c e n t r a t i o n s o f manganese o x i d e s , t h e complex h y d r a u l i c e f f e c t s w h i c h l e a d t o . . o : ' a • . • - - N E A R . B A i t O F A U L u v i v j m Figure 1. Typical placer locations, (compiled from Morisawa, 1968; Ballantyne,1976). c o n c e n t r a t i o n o f s c h e e l i t e i n s t r e a m s e d i m e n t s c a n n o t be d i r e c t l y m e a s u r e d . S t r e a m and c h a n n e l p a r a m e t e r s w h i c h m i g h t r e l a t e t o h y d r a u l i c e f f e c t s , s u c h a s s t r e a m g r a d i e n t , d i s c h a r g e , v e l o c i t y , c h a n n e l c o n f i g u r a t i o n and b o t t o m r o u g h n e s s c a n be q u a n t i f i e d , b u t t h e s e have n o t y e t been i n t e g r a t e d i n t o a q u a n t i t a t i v e model t o e x p l a i n h y d r a u l i c e f f e c t s . F u r t h e r m o r e , most o f t h e p a r a m e t e r s a r e measured o v e r d i s t a n c e s o r a r e a s t h a t would be e x p e c t e d t o c o n t a i n s e v e r a l d i f f e r e n t h y d r a u l i c e n v i r o n m e n t s . S i m i l a r l y , i t m i g h t be n e c e s s a r y t o sample s e v e r a l s e d i m e n t a r y l a y e r s , r e p r e s e n t i n g d i f f e r e n t h y d r a u l i c c o n d i t i o n s , t o o b t a i n a l a r g e enough sample. L a s t l y , e c o n o m i c c o n s i d e r a t i o n s l i m i t t h e t i m e t h a t c a n be s p e n t on measurements a t e a c h sample s i t e . S l i n g e r l a n d (1977) d e v e l o p e d a s e m i - e m p i r i c a l c l a s s i f i c a t i o n o f h e a v y m i n e r a l c o n c e n t r a t i o n s ( T a b l e 2) b a s e d on t h e b o u n d a r y R e y n o l d s number (R*) and t h e r a t i o o f h e a v y m i n e r a l t o b o t t o m g r a i n s i z e (d/BKS), and a p p l i e d i t t o beach sands on Lake E r i e . However, a p p l i c a t i o n t o m o u n t a i n s t r e a m s i s l i m i t e d , as v i r t u a l l y a l l s i t e s f a l l i n t o t h e c a t e g o r y R* > 70 and d/BKS < 1, w h i c h p r e d i c t s d e p o s i t s o f low d e n s i t y m i n e r a l s . R e y n o l d s numbers i n s t r e a m s a r e u s u a l l y o v e r 500, and c a n v a r y by s e v e r a l h u n d r e d w i t h v e l o c i t y c h a n g e s o f l e s s t h a n 1 mm/sec (M o r i s a w a , 1 9 6 8 ) . d/BKS = 1 d/BKS < 1 Only trapped or hidden heavy grains R* > 70 remain: Light deposit. Larger grains rolled away and periodic intrusion of turbulence sepa rates rema ining 5 < R* < 70 (equaI-sized) lights and heavies: Very heavy enriched depos i t. Larger grains rolled Approaches settling away leaving equaI-si zed in s t i l l water: lights and heavies: R* < 5 Medium heavy enrichment. Light deposit, of deposit. Table 2. Classification of heavy mineral deposits based on the boundary Reynolds number (R*) and the ratio (d/BKS) of heavy mineral to bottom grain size (Slingerland, 1977) . 1 3 . A n o t h e r a p p r o a c h t o c o r r e c t i n g f o r h y d r a u l i c e f f e c t s would be t o r a t i o s c h e e l i t e w e i g h t s t o t h o s e o f a n o t h e r m i n e r a l w h i c h i s h y d r a u l i c a l l y e q u i v a l e n t . I d e a l l y , s o u r c e c o n c e n t r a t i o n s o f s c h e e l i t e and t h e h y d r a u l i c s t a n d a r d s h o u l d n o t c o v a r y , and t h e s t a n d a r d s h o u l d be u b i q u i t o u s i n t h e a r e a e x p l o r e d . H y d r a u l i c b e h a v i o r o f m i n e r a l g r a i n s d e pends on t h e i r h y d r o d y n a m i c p r o p e r t i e s , o f w h i c h t h e most i m p o r t a n t a r e s i z e , d e n s i t y and shape ( L o w r i g h t e t a l . , 1 9 7 2 ) . I f h y d r o d y n a m i c p r o p e r t i e s o f t h e s t a n d a r d and s c h e e l i t e were i d e n t i c a l , t h e n t h e r a t i o t e c h n i q u e s h o u l d work p e r f e c t l y , In r e a l i t y , h y d r o d y n a m i c p r o p e r t i e s w i l l n e v e r be i d e n t i c a l , and t h e b e s t a v a i l a b l e s t a n d a r d w i l l d i f f e r i n shape and d e n s i t y f r o m s c h e e l i t e . N e v e r t h e l e s s , i t i s p o s s i b l e t o c o n t r o l s i z e f r a c t i o n s a n a l y z e d , and t h i s p r o v i d e s a p o t e n t i a l t o o l f o r c o m p e n s a t i n g f o r shape and d e n s i t y d i f f e r e n c e s . By Rubey's (1933) d e f i n i t i o n , i f two g r a i n s a r e d e p o s i t e d under t h e same h y d r a u l i c c o n d i t i o n s , t h e y a r e h y d r a u l i c a l l y e q u i v a l e n t r e g a r d l e s s o f d i f f e r e n c e s i n s i z e , shape and d e n s i t y . I t f o l l o w s t h a t under g i v e n h y d r a u l i c c o n d i t i o n s , g r a i n s o f a c e r t a i n shape and d e n s i t y a r e h y d r a u l i c a l l y e q u i v a l e n t t o s m a l l e r more d e n s e o r e q u i d i m e n s i o n a l g r a i n s o r t o l a r g e r l e s s d e n s e o r e q u i d i m e n s i o n a l g r a i n s . T h e o r e t i c a l a p p r o a c h e s t o p r e d i c t i n g h y d r a u l i c a l l y e q u i v a l e n t s i z e s w i l l be c o n s i d e r e d f i r s t . Many w o r k e r s have assumed t h a t g r a i n s w h i c h s e t t l e a t t h e same v e l o c i t y i n s t i l l w a t er a r e h y d r a u l i c a l l y e q u i v a l e n t i n 14. f l o w i n g w ater ( e . g . Rubey, 1933; T o u r t e l o t , 1 9 6 8 ) . T h e o r e t i c a l s e t t l i n g v e l o c i t i e s o f s p h e r i c a l p a r t i c l e s depend on t h e f l o w r e g i m e - l a m i n a r o r t u r b u l e n t - a r o u n d them. F l o w a r o u n d p a r t i c l e s , d e s c r i b e d by R e y n o l d numbers, becomes more l a m i n a r a s d i a m e t e r and s e t t l i n g v e l o c i t y d e c r e a s e : R e p = p V d / i Where: Re = p a r t i c l e R e y n o l d s number hr p = f l u i d d e n s i t y (1 gm/cc f o r water) V = s e t t l i n g v e l o c i t y (cm/sec) d = p a r t i c l e d i a m e t e r (cm) i = f l u i d v i s c o s i t y (0.010 g/cm s e c f o r w a t e r a t 20°C) 1 5 . I f Re p < l , flow i s laminar, Stokes law a p p l i e s , and V i s p r o p o r t i o n a l to the square of the diameter: V = 9 ( P s - P) d' 18 i g = 981 cm/sec' p = p a r t i c l e d e n s i t y (g/cm ) If Re > 1000, flow i s t u r b u l e n t , Newton's law a p p l i e s , and V hr i s p r o p o r t i o n a l to the square ro o t o f the diameter: 1/2 g 3.33 (p - p) d V= s Re^ = 1 corresponds to 0.0716 mm and 0.104 mm diameter s c h e e l i t e and quartz d e n s i t y spheres, r e s p e c t i v e l y , and Re = P 1000 corresponds to 1.83 mm and 2.65 mm diameter spheres, r e s p e c t i v e l y . 16. Between t h e r a n g e s o f t h e s q u a r e and s q u a r e r o o t l a w s i s a b r o a d t r a n s i t i o n r e g i o n where s e t t l i n g v e l o c i t y i s i n d i r e c t l y d e t e r m i n e d u s i n g Re and an e m p i r i c a l l y d e r i v e d hr c o e f f i c i e n t o f d r a g ( C D ) : 4 g d 3 (p - p) C D <RV = J " ! E m p i r i c a l l y b a s e d g r a p h s o f C n (Re ) 2 v s Re p r e s e n t e d by Y a l i n ( 1 9 7 2 ) , R a u d k i v i ( 1 9 7 6 ) , and Wasp ejt a l . (1977) a g r e e w e l l . Y a l i n ' s g r a p h i s p r e s e n t e d i n F i g u r e 2. D i a m e t e r r a t i o s o f p a r t i c l e s w i t h t h e same s e t t l i n g v e l o c i t i e s o r " f r e e s e t t l i n g r a t i o s " (Cook and Rao, 1979) w i l l be d i f f e r e n t i n t h e S t o k e s ' s Law and Newton's Law r a n g e s . Thus, q u a r t z / s c h e e l i t e f r e e s e t t l i n g r a t i o s i n c r e a s e f r o m 1.7 i n t h e S t o k e ' s Law r a n g e t o 3.0 i n t h e Newton's Law r a n g e . S i n c e n a t u r a l l y o c c u r r i n g m i n e r a l g r a i n s a r e n o t s p h e r i c a l , e f f e c t s o f g r a i n shape must be c o n s i d e r e d . Durand and Cohen de L a r a ( 1 9 5 3 ) , G r a f and A c a r o g l u (1966) and Baba and Komar (1981) s t u d i e d shape and s e t t l i n g v e l o c i t y o f q u a r t z g r a i n s , and B r i g g s e t a l . (1962) and B r i g g s (1965) c o n d u c t e d s i m i l a r s t u d i e s on a v a r i e t y o f h e a v y m i n e r a l s . P r o v i d e d a, b and c g r a i n a x e s a r e measured and e x p r e s s e d as one o f a number o f p o s s i b l e g e o m e t r i c shape f a c t o r s , e f f e c t s o f shape on s e t t l i n g v e l o c i t y a r e p r e d i c t a b l e . 17. (°--f) O sg f v2 Figure 2; CLRe versus Re for spheres; ° D p p C D=coefficient of drag and Re p=particle Reynolds number (Yalin, 1972). 18. Wasp e_t a l . (1977) used Corey's shape f a c t o r (SF = a/cb; a > b > c) to express s i e v e s i z e versus e q u i v a l e n t - s p h e r e f a l l diameter (Figure 3). From t h i s i t i s c l e a r t h a t g r a i n shape i s much more important f o r l a r g e g r a i n s . For example, 2 mm s c h e e l i t e g r a i n s with shape f a c t o r s of 1.0 and 0.5 are h y d r a u l i c a l l y e q u i v a l e n t to 6 and 2 mm quartz g r a i n s , r e s p e c t i v e l y . Thus a f r e e s e t t l i n g r a t i o of 3 c o u l d t h e o r e t i c a l l y be reduced to u n i t y by shape d i f f e r e n c e s . Conversely, the f r e e s e t t l i n g r a t i o of 1.7 f o r 0.06 mm s c h e e l i t e and 0.1 mm quartz cannot be changed a p p r e c i a b l y by shape v a r i a t i o n s . The p r i n c i p a l o b j e c t i o n to d e f i n i n g h y d r a u l i c e q u i v a l e n c e i n terms of s e t t l i n g v e l o c i t i e s was r a i s e d by Grigg and Rathbun (1969). They showed that although p a r t i c l e s of d i f f e r e n t s i z e and d e n s i t y may s e t t l e together, they w i l l not respond i n the same way to the shear s t r e s s e s i n f l o w i n g water that are r e s p o n s i b l e f o r entrainment of p a r t i c l e s and t h e i r t r a n s p o r t by t r a c t i o n . Numerous examples o f departures from s e t t l i n g e q u i v a l e n c e can be found i n the l i t e r a t u r e (e.g. Rittenhouse, 1943; M c l n t y r e , 1959; B r i g g s , 1965; Hand, 1967; Lowright e t a l . , 1972). 0.05 0.1 1.0 10.0 FALL DIAMETER (mm) Figure 3. Sieve size versus equivalent-sphere f a l l diameter: S.F.=Corey's shape factor (Wasp et a l . , 1977). 2 0 . Sediment entrainment has been studied extensively, but results must be applied with caution to natural systems. Slingerland (1977) developed the most comprehensive semi-emirical equation for predicting entrainment equivalent sizes, based on c r i t i c a l entrainment v e l o c i t y (V ): V c = 5.75 l o g 1 Q (30.2 x y / BKS) B 1 B 2 •[4 d g cos a (p p - P f ) ( t a n tan a) / 3 C D p f ] ' Where: tan 0 = reactive force angle C D = c o e f f i c i e n t of drag x = Einstein correction factor BKS = roughness size a = bed slope in degrees d = grain diameter g = g r a v i t a t i o n a l acceleration Pf = density of f l u i d p = density of p a r t i c l e B^ = turbulent v e l o c i t y f l u c t u a t i o n c o e f f i c i e n t &2 = C o e f f i c i e n t f l u i d - f o r c e application-point 21. However, many s i m p l i f y i n g a s s u m p t i o n s were i n c o r p o r a t e d i n t o h i s a l b e i t complex e q u a t i o n , w h i c h i s v a l i d o n l y f o r n o n - c o h e s i v e , s p h e r i c a l g r a i n s r e s t i n g on a c l o s e p a c k e d bed. L i f t f o r c e s , w h i c h a r e c o n s i d e r e d i m p o r t a n t by some i n v e s t i g a t o r s ( e . g . E i n s t e i n , 1950; H e l l e y , 1969; I n o k u c h i and Takayama, 1973) a r e i g n o r e d as a r e f r i c t i o n a l f o r c e s between g r a i n s . S l i n g e r l a n d assumed t h a t a v i s c o u s l a m i n a r s u b l a y e r a t t h e b o t t o m g r a d e s upward i n t o t h e t u r b u l e n t z o n e , t h a t t h e i n s t a n t a n e o u s v e l o c i t y i n c r e a s e s i n t h e t u r b u l e n t zone w h i c h c a u s e e n t r a i n m e n t a r e t w i c e t h e a v e r a g e v e l o c i t y , and t h a t t h e s e f l u c t u a t i o n s l i n e a r l y d e c r e a s e t o z e r o i n t h e l a m i n a r z o n e . C o n t r a r i l y , o t h e r i n v e s t i g a t o r s d e m o n s t r a t e t h a t t u r b u l e n t f o r c e s a r e n o t e a s i l y d e a l t w i t h ( K a l i n s k e , 1943; E i n s t e i n , 1950; W i l l i a m s and Kemp, 1 9 7 1 ) . M i l l e r e t a l . (1977) n o t e d t h a t e v e n under t h e s i m p l e s t smooth w a l l and bed c o n d i t i o n s , random t u r b u l e n t f o r c e s were a n a l y t i c a l l y i n t r a c t a b l e and f r e q u e n t l y i m p i n g e d upon o r c o m p l e t e l y r e p l a c e d t h e l a m i n a r s u b l a y e r . A l t h o u g h S l i n g e r l a n d 1 s e q u a t i o n i s t o o complex t o a p p l y i n p r a c t i c e t o n a t u r a l s y s t e m s , and, f u r t h e r m o r e , may n o t p r e d i c t e n t r a i n m e n t e q u i v a l e n t s i z e s a c c u r a t e l y due t o f a i l u r e t o a c c o u n t f o r a l l v a r i a b l e s f o u n d i n n a t u r e , s e v e r a l i m p o r t a n t p o s s i b i l i t i e s a r e i n d i c a t e d . In F i g u r e 4, as bed g r a i n s i z e i n c r e a s e s , s m a l l e r g r a i n s s h i e l d e d by l a r g e r g r a i n s become more d i f f i c u l t t o e n t r a i n , i n d i c a t i n g t h a t h y d r a u l i c a l l y e q u i v a l e n t s i z e s s h o u l d v a r y w i t h b o t t o m 100 Figure 4. Effect of bottom roughness (BKS) on c r i t i c a l velocity (Vc) for quartz-density particles (Slingerland, 1 9 7 7 ) . 23. r o u g h n e s s . A l s o , two d i f f e r e n t s i z e s o f a g i v e n m i n e r a l ( q u a r t z o r g a r n e t ) i n F i g u r e 5 have t h e same c r i t i c a l e r o s i o n v e l o c i t y , and c o u l d t h e r e f o r e be h y d r a u l i c a l l y e q u i v a l e n t t o a g i v e n s i z e o f a n o t h e r m i n e r a l . H j u l s t r o m ' s (1935) e x p e r i m e n t s a l s o r e v e a l e d t h a t two d i f f e r e n t s i z e s o f r i v e r s e d i m e n t s had t h e same c r i t i c a l e r o s i o n v e l o c i t y ( F i g u r e 6 ) , b u t he f o u n d t h a t f i n e t o medium sa n d s were t h e most e a s i l y e n t r a i n e d - t h e o p p o s i t e o f S l i n g e r l a n d 1 s r e s u l t s i n F i g u r e 5. S l i n g e r l a n d a t t r i b u t e s t h e c o n t r a d i c t o r y r e s u l t s t o t h e p r e s e n c e o f c o h e s i v e c l a y s i n H j u l s t r o m ' s s e d i m e n t s . I n a t h i r d example o f c o n f l i c t i n g r e s u l t s , G r i g g and Rathbun (1969) p r e d i c t t h a t , below 0.1 mm, c r i t i c a l s h e a r s t r e s s i s i n d e p e n d e n t o f g r a i n s i z e ( F i g u r e 7 ) ; t h u s , a b r o a d s i z e r a n g e o f one m i n e r a l c o u l d be h y d r a u l i c a l l y e q u i v a l e n t t o a n a r r o w s i z e r a n g e o f a l e s s d e n s e m i n e r a l . A d d i t i o n a l p r o b l e m s a r i s e when s e t t l i n g and e n t r a i n m e n t a r e c o n s i d e r e d t o g e t h e r . F o r example, S l i n g e r l a n d (1977) p r e d i c t s t h a t a 0.1 mm q u a r t z g r a i n and a 0.076 mm g a r n e t g r a i n have s e t t l i n g v e l o c i t i e s o f 20 cm/sec ( F i g u r e 8 ) . The q u a r t z g r a i n i s r e e n t r a i n e d a t 21 cm/sec b u t t h e g a r n e t g r a i n i s n o t r e e n t r a i n e d b e l o w 31 cm/sec. I f , a f t e r d e p o s i t i o n f r o m s u s p e n s i o n , t h e s t r e a m v e l o c i t y i n c r e a s e s t o between 21 and 31 cm/sec, q u a r t z w i l l be e n t r a i n e d , g a r n e t c o n c e n t r a t e d , and t h e i r r a t i o s w i l l no l o n g e r be i n d e p e n d e n t o f h y d r a u l i c c o n d i t i o n s . 2 4 . Figure 5. Calculated c r i t i c a l velocity and observed distance moved bv qusrtz and garnet on smooth and rough bases (Slingerland, 1977). i , 000 100 1 1 V i ^> ^ 1 - X. Erosion y J -ve loc in .— y * ' / J> / T r c j n t p O r i O T i c n i / / S e d i m e n otion / -Fo i l veloc ity 0.001 0.01 0.1 1.0 10 100 1,000 Size, mm Figure 6. Erosion and f a l l velocities of river sediments (Hjulstrom, 1935). Figure 7. Variation of c r i t i c a l shear stress water with size and density (Grigg and Rathbun, 1969). Figure 8. C r i t i c a l velocity (Vc) and f a l l velocity (Vcs) of quartz and garnet in an equigranular sediment (Slingerland, 1977). 28. S e l e c t i v e r e e n t r a i n m e n t o f c o a r s e - g r a i n e d l i g h t s f r o m d e p o s i t s o f s e t t l i n g e q u i v a l e n t l i g h t and h e a v y m i n e r a l s has been p r o p o s e d i n a number o f s t u d i e s t o e x p l a i n h i g h c o n c e n t r a t i o n s o f h e a v y m i n e r a l s ( e . g . Hand, 1964; L o w r i g h t e t a l . , 1972; S l i n g e r l a n d , 1 9 7 7 ) . T h i s has i m p o r t a n t i m p l i c a t i o n s t o s e l e c t i n g h y d r a u l i c a l l y e q u i v a l e n t s t a n d a r d s , p a r t i c u l a r l y where, as i n m o u n t a i n s t r e a m s , d i s c h a r g e f l u c t u a t e s g r e a t l y and m i n e r a l g r a i n s a r e s u b j e c t e d t o d i f f e r e n t f l o w c o n d i t i o n s and t r a n s p o r t modes. The c o n t r a d i c t i o n s and l i m i t a t i o n s o f c u r r e n t t h e o r y on h y d r a u l i c e q u i v a l e n c e r e s u l t i n e m p i r i c a l methods b e i n g p r e f e r r e d f o r d e t e r m i n i n g h y d r a u l i c a l l y e q u i v a l e n t s i z e s under p a r t i c u l a r f i e l d c o n d i t i o n s . One a p p r o a c h i s t o sample a t h i n , d i s c r e t e s e d i m e n t a r y l a y e r , s u c h as a m a c r o l a m i n a ( M c l n t y r e , 1 9 5 9 ) , on t h e a s s u m p t i o n t h a t i t was l a i d down under c o n s t a n t p h y s i c a l c o n d i t i o n s . However, p o o r s o r t i n g o f m o u n t a i n - s t r e a m s e d i m e n t s and t h e n e c e s s i t y o f c o l l e c t i n g l a r g e s a m p l e s p r e c l u d e t h i s a p p r o a c h i n t h e p r e s e n t s t u d y . A d i f f e r e n t e m p i r i c a l method was d e v e l o p e d by R i t t e n h o u s e ( 1 9 4 3 ) , who d e t e r m i n e d h y d r a u l i c a l l y e q u i v a l e n t s i z e s o f q u a r t z t o v a r i o u s m i n e r a l s i n s e d i m e n t s o f t h e R i o G r a n d e . S i x s a m p l e s were c o l l e c t e d a c r o s s t h e r i v e r by f o r c i n g a 2 - i n c h d i a m e t e r p i p e 40 i n c h e s i n t o t h e s e d i m e n t s . He r e a s o n e d t h a t d i f f e r e n c e s i n m i n e r a l c o m p o s i t i o n between s a m p l e s would v a r y w i t h h y d r a u l i c c o n d i t i o n s , b u t r a t i o s o f w e i g h t s o f h y d r a u l i c a l l y e q u i v a l e n t m i n e r a l s w o u l d be c o n s t a n t 29. i n a l l s i x s a m p l e s . The r a t i o o f a g i v e n s i z e o f m i n e r a l t o p r o g r e s s i v e l y l a r g e r s i z e s o f q u a r t z was c a l c u l a t e d f o r e a c h sample, and t h e c o e f f i c i e n t o f v a r i a t i o n (CV) d e r i v e d f o r e a c h s e t o f s i x r a t i o s . On t h i s b a s i s , t h e most c o n s t a n t r a t i o s ( l o w e s t CV) were d e t e r m i n e d g r a p h i c a l l y ( e . g . F i g u r e 9 ) . T a b l e 3 summarizes h i s r e s u l t s . 30. Figure 9. Variation of ilmenite/quartz weight-ratios (hydraulic ratios) and the coefficient of variation of those ratios with grain size of quartz (Rittenhouse, 1943). M i c t n l Magnetite rimenite Zircon Barite Garnet Kyanite Titani ' .e Pyrcacne Hypersthene Diopside (Er) Dioptide ( Q Blue-precn hornblende Crecn hornblende. . . . Brown hornbltnde. . . Apatite Tourmaline Sprcl£c friviry Brd umplcs (Botquc) T n m i t tirapla (Eicbndido) Stic Grade J M K 1 7 J mm. . 1 7 S - . 1 J I mra. . I : J - . O R I mm. -0£$- .061 ir.m. -ITS—.12* ram. .n*- .M) 6 vmitt ^ ..io $ **its 5 . 2 . 9 1 . 2 1 . 0 1 . 0 1.1 1 . 0 4 . 7 . 8 1 . 0 . 9 1 . 0 1.1 . 9 4 . 6 . 8 . 9 .9 4 . 5 . 6 . 4 . 7 . 2 3 . 8 . 8 . 8 . 3 .6 . 5 . 8 3 . 6 . 3 . 5 . 0 3 . 5 . 7 . 4 . 7 . 3 . 3 . 7 3 . 4 . 4 . 7 .1 . 3 . 3 . 3 3 . 4 . 5 . 3 . 4 . . 2 . 3 . 3 3 . 4 . 5 . 2 .1 . 5 3 . 3 . 3 . 4 . 6 • . 4 3 . 2 . 2 . 0 . 0 .1 . 3 . 3 3 . 2 . 4 .1 .1 . 2 . 4 . 2 3 . 2 . 3 . 2 . 0 .0 . 3 . 2 3 . 2 .6 . 5 . 2 . 4 . 4 . 4 3 . 1 . 0 . 0 . 3 . 1 . 3 . 4 Best value 1 . 0 Table 3. Size difference (0) between hydraulically equivalent quartz and higher-density minerals (Rittenhouse, 1943). 32. CONCLUSIONS 1. Rare g r a i n and h y d r a u l i c e f f e c t s c a n i n t r o d u c e v a r i a b i l i t y i n t o s t r e a m s e d i m e n t d a t a f o r W where i t i s d i s p e r s e d a s s c h e e l i t e , and t h i s v a r i a b i l i t y may a d v e r s e l y a f f e c t i n t e r p r e t a t i o n o f g e o c h e m i c a l r e s u l t s f o r m i n e r a l e x p l o r a t i o n . 2. Rare g r a i n p r o b l e m s c a n be r e d u c e d by s a m p l i n g n a t u r a l " h y d r a u l i c " c o n c e n t r a t i o n s i n t h e s t r e a m bed, and by c o n c e n t r a t i n g t h e heavy m i n e r a l f r a c t i o n , e i t h e r by p a n n i n g o r heavy l i q u i d s e p a r a t i o n s . 3. The e x t e n t o f h y d r a u l i c c o n c e n t r a t i o n o f s c h e e l i t e i n a s t r e a m bed a t a g i v e n p o i n t c a n n o t be p r e d i c t e d t h e o r e t i c a l l y . However, i t m i g h t be p o s s i b l e t o use h y d r a u l i c a l l y e q u i v a l e n t m i n e r a l g r a i n s a s a c o n t r o l on h y d r a u l i c v a r i a b i l i t y . 33. CHAPTER TWO DESCRIPTION OF THE STUDY AREA 34. LOCATION AND ACCESS The C l e a t u n g s t e n p r o p e r t y ( F i g u r e 10) i s c e n t e r e d a t l a t i t u d e 62° 47' n o r t h and l o n g i t u d e 129° 52' west (NTS 105-1-13) i n t h e Selwyn M o u n t a i n s , Yukon T e r r i t o r y . The p r o p e r t y i s 270 km n o r t h o f Watson Lake, 20 km s o u t h - s o u t h e a s t o f M a c m i l l a n P a s s , and 9 km west o f t h e N o r t h w e s t T e r r i t o r i e s b o r d e r . A c c e s s i s by h e l i c o p t e r , u s u a l l y f r o m M a c m i l l a n P a s s , w h i c h i s s e r v i c e d by a summer-use g r a v e l r o a d and a y e a r - r o u n d a i r s t r i p . PREVIOUS WORK Low-grade t u n g s t e n m i n e r a l i z a t i o n i n C l e a C i r q u e was d i s c o v e r e d i n 1967 by p r o s p e c t o r s M. MacDonald and G. H o g a r t h J r . . C u r r e n t l y , t h e p r o p e r t y i s j o i n t l y owned by P l a c e r D e v elopment L i m i t e d and U. S. S t e e l . Work t o d a t e i n c l u d e s a number o f diamond d r i l l h o l e s , minor t r e n c h i n g , c h a n n e l s a m p l i n g , and g e o l o g i c a l mapping. eg o oo CO C O C M T- ^ *~ —I I ' N oMacMillan P a s s BRITISH C O L U M B I A 0 50 1 0 0 k m - * J Figure ."10. Location of the Clea tungsten property, Yukon Territory. 36. GEOLOGY R e g i o n a l g e o l o g y The C l e a p r o p e r t y l i e s w i t h i n t h e e a s t e r n m a r g i n o f t h e S e lwyn B a s i n , w h i c h i s a n o r t h w e s t t r e n d i n g t e c t o n i c s u b - p r o v i n c e o f t h e C a n a d i a n C o r d i l l e r a bounded on t h e e a s t and west by t h e c o e v a l M a c k e n z i e and C a s s i a r c a r b o n a t e p l a t f o r m s , r e s p e c t i v e l y ( G a b r i e l s e , 1 9 6 7 ) . B a s i n a l and p l a t f o r m f a c i e s a r e u n d e r l a i n by s h a l e , s a n d s t o n e , g r i t , and l i m e s t o n e o f t h e l a t e P r o t e r o z o i c " G r i t U n i t " (Carne and C a t h r o , 1 9 8 2 ) . The C a m b r i a n t o D e v o n i a n Road R i v e r F o r m a t i o n , o f a t r u e b a s i n a l o r i g i n , c o n s i s t s o f c a r b o n a c e o u s , p e l i t i c , and m i n o r c l a s t i c s e d i m e n t a r y r o c k s . B a s i n a l f a c i e s and t h e i r r e l a t i v e l y t h i c k e r p l a t f o r m c o u n t e r p a r t s a r e o v e r l a i n by t h e D e v o n i a n t o M i s s i s s i p p i a n " B l a c k C l a s t i c G roup" c o m p r i s e d o f t u r b i d i t e s , slump b r e c c i a s , s h a l e and c h e r t d e r i v e d f r o m t h e f a u l t e d and u p l i f t e d Road R i v e r F o r m a t i o n (Carne and C a t h r o , 1 9 8 1 ) . G r a n i t i c b o d i e s , w h i c h g e n e r a l l y change from s t o c k t o b a t h o l i t h s i z e f r o m e a s t t o west i n t h e Selwyn B a s i n ( D i c k , 1 9 8 0 ) , i n t r u d e s e d i m e n t a r y s e q u e n c e s . D i c k (1980) i d e n t i f i e s a r e g i o n a l z o n a t i o n o f s k a r n t y p e s i n and a r o u n d t h e Selwyn B a s i n ( F i g u r e 1 1 ) . Thus, s e v e r a l W-Cu (Zn) s k a r n d e p o s i t s o c c u r i n a n o r t h w e s t - t r e n d i n g a r c u a t e zone on t h e e a s t e r n b o u n d a r y o f t h e Selwyn B a s i n . These 4 S e l w y n N . W . T . C l e a B a s i n 6 2" Y u k o n B . C . 0 100km E a s t e r n M a r g i n a l L E G E N D S k a r n Type." • W - C u ( Z n ) • Z n ( P b ) , Z n ( W ) • W(Mo) Belt . • N 60' '^ fry-Figure 11. Regional zonation of skarn types (modified from Dick, 1980). 38. i n c l u d e t h e C l e a , Mactung, C a n t u n g and Lened d e p o s i t s . T h i s zone i s p a r a l l e l e d on t h e west by a Zn (Pb,W) and W (Mo) s k a r n z o n e . West o f T i n t i n a f a u l t t h e r e a r e t i n - b e a r i n g s k a r n s , W (Mo) s k a r n s and Mo-W s t o c k w o r k s and s k a r n s . L o c a l and p r o p e r t y g e o l o g y In t h e w e s t e r n h a l f o f t h e P e l l y d r a i n a g e a r e a , most o u t c r o p s a r e C a m b r i a n t o O r d o v i c i a n mudstone, s l a t e , l i m e s t o n e and c h e r t ( F i g u r e 1 2 ) . C o n v e r s e l y , i n t h e e a s t e r n h a l f , D e v o n i a n c o n g l o m e r a t e s , a r e n i t e s , wackes, s i l t s t o n e s , s h a l e s , l i m e s t o n e s , and c h e r t s p r e d o m i n a t e . T h r e e C r e t a c e o u s q u a r t z m o n z o n i t e s t o c k s a r e e x p o s e d i n t h e d r a i n a g e a r e a (Gordey, 1 9 8 1 ) . G e o l o g y o f t h e C l e a d e p o s i t has been d e s c r i b e d by Tompson ( 1 9 7 8 ) . Near the c e n t e r o f t h e p r o p e r t y a L a t e C r e t a c e o u s (Godwin e_t aJL. , 1980) q u a r t z m o n z o n i t e s t o c k , 500 m i n d i a m e t e r a t t h e s u r f a c e , has p r o d u c e d a b r o a d a l t e r a t i o n h a l o 5 t o 10 km i n d i a m e t e r i n S i l u r i a n (Tompson, 1978) s e d i m e n t a r y r o c k s . I n t e r b e d d e d a r g i l l a c e o u s , v a r i a b l y mixed a r g i l l a c e o u s and c a l c a r e o u s , and c a l c a e r o u s s e d i m e n t a r y r o c k s were t h e r m a l l y and m e t a s o m a t i c a l l y a l t e r e d t o d i f f e r i n g d e g r e e s , r e s u l t i n g i n complex s e q u e n c e s o f m e t a m o r p h i c r o c k s ( F i g u r e 1 3 ) . In g e n e r a l , b l a c k ( g r a p h i t i c ) , brown ( b i o t i t e - b e a r i n g ) , o r s p o t t e d ( c o r d i e r i t e - b e a r i n g ) d a r k h o r n f e l s g r a d e t h r o u g h p a l e r c o l o r e d c a l c - s i l i c a t e r o c k s t o m a r b l e and s k a r n . 39. uDMps Chert pebble conglomerate; chert-quartz arenites and wackes; shales; s i l t s t o n e s ; slates; chert and shale c l a s t granule to pebble conglomerate muDpt Cherts; s i l i c e o u s shales; s l a t e OSpt Dolomitic s i l t y mudstone; sla t e with interbedded limestone and chert; chert uCIOl Limestone Limit of outcrop Geological boundary: Defined • Approximate Assumed Fault: —-*4-* Defined — — — Approximate • ..... Assumed 60 Cleavage 35 JJedding Figure 12. Geology near the Clea deposit (modified from Gordey, 1981). 40. alternating b i o t i t e and calc s i l i c a t e hornfels limestone alternating b i o t i t e hornfels and limestone .biotite hornfels intermixed black (graphitic) and brown ( b i o t i t i c ) hornfels i skarn I30m^—-^ quartz monzonite Figure 13. Partial stratigraphic section, Clea property (Dick, 1980) A l t h o u g h l i t t l e i s known o f t h e m i n e r a l o g y o f t h e f i n e g r a i n e d m e t a s e d i m e n t s , b i o t i t e , c o r d i e r i t e , p y r r h o t i t e and p y r i t e have been i d e n t i f i e d . The q u a r t z m o n z o n i t e c o n t a i n s q u a r t z , p o t a s s i u m and p l a g i o c l a s e f e l d s p a r s , b i o t i t e , m u s c o v i t e , a p a t i t e , z i r c o n , p y r i t e and c h l o r i t e (Tompson, 1 9 7 8 ) . In a d d i t i o n , i n t r u s i v e and c o u n t r y r o c k s a r e t o u r m a l i n i z e d n e a r f r a c t u r e s and q u a r t z v e i n s . D i c k (1980) d e s c r i b e s f i v e s k a r n a l t e r a t i o n f a c i e s a t C l e a which c a n be mapped on h a n d - s p e c i m e n s c a l e ( T a b l e 4 ) . P y r o x e n e - g a r n e t - v e s u v i a n i t e s k a r n has a b u n d a n t v e s u v i a n i t e and i s most w i d e s p r e a d . S c h e e l i t e , t h e o n l y p l e n t i f u l W - b e a r i n g m i n e r a l , i s most common i n a m p h i b o l e - g a r n e t and b i o t i t e - g a r n e t s k a r n s . S c h e e l i t e c r y s t a l s r a n g e from 2 cm t o l e s s t h a n 0.1 mm a c r o s s . The s c h e e l i t e - b e a r i n g s k a r n s o c c u r i n C l e a and Omo C i r q u e s and on t h e i n t e r v e n i n g a r i t e a s f a r as 1 km f r o m e x p o s e d i n t r u s i v e ( F i g u r e 1 4 ) . G r a d e s i n s u r f a c e o u t c r o p s r a n g e f r o m 6% W0^ o v e r t e n s o f s q u a r e m e t e r s , t o t r a c e amounts r u n n i n g h u n d r e d s o f m e t e r s a l o n g 10 m t h i c k b e d s . Grade and s u r f a c e e x t e n t o f W - m i n e r a l i z a t i o n a r e much g r e a t e r i n C l e a C i r q u e t h a n Omo C i r q u e . FACIES CHARACTERISTIC MINERALS WOLLASTONITE PYROXENE-GARNET-VESUVIANITE PYROXENE-VESUVIANITE AMPHIBOLE-GARNET BIOTITE-GARNET wo I I a s t o n i t e , g a r n e t , v e s u v i a n i t e , c a l c i t e , p y roxene v e s u v i a n i t e , p y r o x e n e , g a r n e t , p y r r h o t i t e v e s u v i a n i t e , c a l c i t e , p y r o x e n e , chaI c o p y r i t e , s c h e e l i t e a m p h i b o l e , s c h e e l i t e , g a r n e t , pyroxene g a r n e t , b i o t i t e , s e r i c i t e , c h l o r i t e , s p h a l e r i t e , q u a r t z , s c h e e l i t e , wo I f r a m i t e T a b l e 4. S k a r n a l t e r a t i o n f a c i e s a t C l e a ( D i c k , 1980) 43. Figure 14! Locations of scheelite-bearing skarns, Clea property (modified from Tompson, 1978). 44. PHYSIOGRAPHY P l e i s t o c e n e a l p i n e g l a c i a t i o n p r o d u c e d t o p o g r a p h i c f e a t u r e s i n t h e s t u d y b a s i n r a n g i n g f r o m c i r q u e s rimmed w i t h j a g g e d h o r n s and aretes t o b r o a d , U-shaped v a l l e y s and g e n t l y r o l l i n g h i l l s . E l e v a t i o n s v a r y f r o m 2177 m a t t h e head o f C l e a c i r q u e t o 1000 m on t h e m a i n - v a l l e y f l o o r . T h i s 9 a p p r o x i m a t e l y 160 km"6 c a t c h m e n t f o r m s t h e h e a d w a t e r s o f t h e P e l l y R i v e r . T r i b u t a r i e s d r o p s t e e p l y f r o m c i r q u e s and h a n g i n g v a l l e y s f o r an a v e r a g e o f 5 km b e f o r e r e a c h i n g t h e main v a l l e y . D r a i n a g e p a t t e r n s a r e r a d i a l t o i n t r u s i v e s b u t d e n d r i t i c e l s e w h e r e . C l e a and Omo C r e e k s f l o w 3.2 and 11 km f r o m t h e i r r e s p e c t i v e c i r q u e s b e f o r e j o i n i n g t h e P e l l y R i v e r ( F i g u r e s 15 and 1 6 ) . C l e a C r e e k i s impeded by two l a k e s o v e r t h e f i r s t 2 km, t h e n d r o p s s t e e p l y o v e r b e d r o c k f o r t h e n e x t 1 km, and i s b r a i d e d f o r t h e l a s t 300 m. Omo C r e e k f l o w s unimpeded down s t e e p b e d r o c k and l e s s s t e e p t i l l and a l l u v i a l s t r e t c h e s f o r the f i r s t 6 km, and t h e n down s t e e p c o n t i n u o u s r a p i d s i n a V - s h a p e d g u l l y f o r t h e f i n a l 5 km. A l o n g t h e P e l l y R i v e r , s t r e t c h e s a l t e r n a t e between s t e e p b e d r o c k f a l l s , meanders i n a l l u v i u m , and r a p i d s i n g l a c i a l t i l l s . 1600 CfcEA CIRaut - C O R R E C T E D ALTIMETER RtADIN* ACO - S A M P L E SITE / ^ B 6 - DUPL ICATE SAMPLE SITE WF - W A T E R F A L L R - R A P I P S A — S — 8 — &ANK M A T E R I A L ALLUV IUM GLAC IAL TILL BEDROCK PREDOMINANT , ALSO PRESENT 10 11 14 K M 16 IS 20 Figure 15. Longitudinal profile of Clea Creek and the Pelly River. 22 z-4 Ln 47. CLIMATE The S t . E l i a s and C o a s t M o u n t a i n Ranges remove most o f th e m o i s t u r e f r o m P a c i f i c s t o r m s and g i v e t h e Yukon T e r r i t o r y a r e l a t i v e l y d r y a l p i n e c o n t i n e n t a l c l i m a t e w i t h an extr e m e t e m p e r a t u r e r a n g e . A t Howards P a s s (1503 m), 45 km s o u t h e a s t o f C l e a i n a c o m p a r a b l e s e t t i n g , t e m p e r a t u r e s o v e r a t h r e e y e a r p e r i o d a v e r a g e d 9°C f r o m mid-June t o mid-September, and -15°C f r o m O c t o b e r t o May ( M o r g a n t i , 1 9 7 9 ) . The C l e a p r o p e r t y i s e s s e n t i a l l y snow f r e e f r o m m i d - J u l y t o m i d - A u g u s t and summer r a i n showers a r e common. SOILS A l t h o u g h p e a t y o r g a n i c m a t e r i a l may e x c e e d 1 m i n t h i c k n e s s , c o l d c l i m a t e , r u g g e d t o p o g r a p h y and r e c e n t g l a c i a t i o n have l i m i t e d d e v e l o p m e n t o f t h e m i n e r a l s o l u m t o 0.5 m o r l e s s ( D o y l e , 1 9 7 2 ) . F r e e l y d r a i n e d s o i l s a r e u s u a l l y r e g o s o l s , and p o o r l y d r a i n e d s o i l s a r e u s u a l l y g l e y s o l s o r o r g a n i c s o i l s ( E a r l e , 1 9 7 5 ) . VEGETATION Dense s t a n d s o f dw a r f w i l l o w ( S a l i x ) , s t a n d s o f s p r u c e ( P i c e a ) , a l d e r ( A l n u s ) , and some a s p e n ( P o p u l u s ) , and boggy meadows f l a n k t h e P e l l y R i v e r . Dwarf w i l l o w becomes l e s s common i n t r i b u t a r y v a l l e y s . Above t h e t r e e l i n e a t a p p r o x i m a t e l y 1,450 m, moss and l i c h e n s p r e d o m i n a t e . CHAPTER THREE METHODS 49. EXPERIMENTAL DESIGN In an e f f o r t t o i s o l a t e , as e f f e c t i v e l y as p o s s i b l e , v a r i a b i l i t y o f s c h e e l i t e and o t h e r m i n e r a l s c a u s e d by h y d r a u l i c f a c t o r s , s e d i m e n t s were sampled f r o m a d j a c e n t h i g h and low s t r e a m - e n e r g y e n v i r o n m e n t s a l o n g s t r e a m s d r a i n i n g t h e C l e a d e p o s i t . S e d i m e n t s i z e was t h e o v e r r i d i n g c r i t e r i o n u s e d t o d i f f e r e n t i a t e e n e r g y e n v i r o n m e n t s , a l t h o u g h s t r e a m v e l o c i t y was m e a s u r a b l y f a s t e r i n h i g h e n e r g y e n v i r o n m e n t s . S i t e s e l e c t i o n was l i m i t e d by s c a r c i t y o f s u i t a b l e low e n e r g y s i t e s , w h i c h t e n d e d t o f o r m o n l y i n t h e l e e o f s h a r p b e n d s , b e d r o c k p r o j e c t i o n s , b o u l d e r s , i s l a n d b a r s and p o i n t b a r s . The b e s t low e n e r g y s i t e s were a t p o i n t b a r s , b u t t h e s e were o n l y f o u n d a l o n g s h o r t s t r e t c h e s o f t h e P e l l y R i v e r . Most h i g h e n e r g y s i t e s were i n t h e t r a n s i t i o n zone f r o m low e n e r g y s i t e s t o t h e m a i n s t r e a m , b e c a u s e t h e m a i n t r e a m was t o o s w i f t . Due t o l i m i t e d s i t e s e l e c t i o n , compromise between b e s t s i t e s and d e s i r e d s a m p l i n g f r e q u e n c y was r e q u i r e d . However, as o r i g i n a l l y i n t e n d e d , d i s t a n c e s between t h e 30 f i n a l s a m p l e -l o c a t i o n s s e l e c t e d i n c r e a s e downstream ( F i g u r e 1 7 ) . S m a l l t r i b u t a r i e s w i t h d r a i n a g e a r e a s a m o u n t i n g t o l e s s t h a n t e n p e r c e n t o f t h e main c a t c h m e n t a t t h e g i v e n j u n c t i o n were n o t s a m p l e d . D u p l i c a t e sample p a i r s were c o l l e c t e d where p o s s i b l e (10 s i t e s ) t o e v a l u a t e v a r i a t i o n by h y d r a u l i c e f f e c t s , l o c a l ( w i t h i n s i t e ) s o u r c e e f f e c t s and d i s t a l (between s i t e s ) s o u r c e Figure 17. Sample locations. 51. e f f e c t s . H y d r a u l i c e f f e c t s were m a x i m i z e d by c o l l e c t i n g n e a r b y h i g h and low e n e r g y s a m p l e s , and l o c a l s o u r c e e f f e c t s were m a x i m i z e d by s a m p l i n g c l o s e l y matched h y d r a u l i c e n v i r o n m e n t s l e s s t h a n 50 m a p a r t . D i s t a n c e s between h i g h and low e n e r g y s a m p l e s a t d u p l i c a t e s i t e s a v e r a g e d 4 m and r a n g e d f r o m 1 t o 12 m, whereas d i s t a n c e s between d u p l i c a t e p a i r s a v e r a g e d 30 m and r a n g e d f r o m 9 t o 50 m ( T a b l e 5 ) . Random s a m p l i n g e r r o r s c o u l d have been e v a l u a t e d by c o l l e c t i n g a b u t t i n g s a m p l e s from i d e n t i c a l e n e r g y e n v i r o n m e n t s , b u t t h i s would have g r e a t l y i n c r e a s e d t h e t o t a l c o s t s and e f f o r t , and has l i t t l e a d v a n t a g e o v e r e s t i m a t i n g e r r o r s f r o m numbers o f s c h e e l i t e g r a i n s . SAMPLING METHODS Samples were s h o v e l l e d o r d i r e c t l y s c o o p e d i n t o a 2.5 6 g a l l o n p a i l , wet s i e v e d t o minus 10-mesh, and s t o r e d i n p l a s t i c b a g s . Sample w e i g h t a v e r a g e d a b o u t 14 kg wet. A p p r o x i m a t e l y e q u i d i m e n s i o n a l p i t s were dug t h r o u g h u n i f o r m l y t e x t u r e d s e d i m e n t s , b u t some t w o - d i m e n s i o n a l s u r f a c e s a m p l e s were r e q u i r e d t o s t a y w i t h i n a p a r t i c u l a r s i z e r a n g e . C o l l e c t i o n t o o k f r o m 15 m i n u t e s f o r t h e e a s i e s t low e n e r g y sample t o 2 h o u r s f o r t h e most d i f f i c u l t h i g h e n e r g y sample. 52. SITE DISTANCES (METERS) BETWEEN SAMPLES BETWEEN LOW / HIGH BETWEEN LOW / HIGH ENERGY PAIR 1 ENERGY PAIR 2 BETWEEN PAIRS SAMPLES METERS SAMPLES METERS METERS G 25 t 1 26 1 7 27 / 28 1 0 20 ZAA 35 / I 36 1 5 37 / 38 2 4 30 . AK 41 , I 42 0 7 43 / 44 1 0 12 AO 45 i I 46 2 2 55 / 56 3 8 9 1234 2 t f 1 2 0 3 / 4 2 1 40 BG 13 / f 14 3 8 15 / 16 4 4 18 CB 47 ) f 48 3 8 49 / 50 11 9 45 CH 71 / f 72 2 1 73 / 74 5 2 50 L 29 j 1 30 1 0 DD 57 t f 58 1 3 CLR 59 / f 60 3 5 BB 11 1 f 12 4 1 CD 61 / f 62 6 6 CE 63 / ^ 64 25 0 CM 79 / ^ 80 7 5 CP 65 t f 66 2 0 T a b l e 5. D i s t a n c e s between p a i r e d h i g h and low energy samples and between d u p l i c a t e p a i r s . 53. F I E L D OBSERVATIONS G e n e r a l Each s i t e was p h o t o g r a p h e d and a number o f g e n e r a l o b s e r v a t i o n s r e c o r d e d ( F i g u r e 18 ) . S k e t c h e s o f s i t e s i n c l u d e d c h a n n e l and b a r c o n f i g u r a t i o n s , sample l o c a t i o n s , and measurements t o 0.1 m o f s t r e a m w i d t h , b r a i d w i d t h , and d i s t a n c e s between s a m p l e s . A l s o , s t r e a m v e l o c i t i e s above sam p l e s and i n t h e m a i n s t r e a m were measured a t 50% d e p t h w i t h a 10 cm d i a m e t e r p r o p e l l o r d r i v e n f i s h ( T a b l e 6 ) . S t r e a m d e p t h s were n o t measured, b u t were g e n e r a l l y l e s s t h a n 15 and 25 cm o v e r low and h i g h e n e r g y s a m p l e s , r e s p e c t i v e l y . T e x t u r e s A w e i g h t e d meter s t i c k was p l a c e d on t h e bed a t e a c h sample l o c a t i o n , and a v e r t i c a l c o l o r p h o t o g r a p h t a k e n f r o m a h e i g h t o f 1.5 m t o c o v e r 1.0 x 0.6 m. These were u s e d t o c l a s s i f y s e d i m e n t t e x t u r e w i t h t h e t r i a n g u l a r d i a g r a m ( F i g u r e •Ip) o f F o l k ( 1 9 7 4 ) . M e d i a n g r a v e l d i a m e t e r was d e f i n e d s u c h t h a t l a r g e r and s m a l l e r d i a m e t e r g r a v e l s c o v e r e d e q u a l a r e a s i n t h e p h o t o . A L L U V I U H T I L L O V E R SHALE B E D R O C K Figure 18. Sketch of site AO. SITE ENERGY ENVIRONMENT LOW ENERGY HIGH ENERGY SAMPLE VELOCITY SAMPLE VELOCITY G 25 0. 08 26 0.32 G 27 0. 05 28 0.28 L 29 <0 05 30 0.24 ZAA 35 <o. 05 36 0.20 ZAA 37 <o. .05 38 0.28 AK 41 <o. .05 42 0.20 AK 43 <0 05 44 0.29 AO 45 <o. 05 46 0.24 AO 55 <0 05 56 0.48 DD 57 <0 05 58 0.38 CLR 59 <0 .05 60 0.10 1234 2 0. .05 1 0.32 1234 3 0, .10 4 0.20 BB 11 0 .09 12 0.37 BG 13 0. 37 14 0.48 BG 15 ? 16 0.30 CB 47 <o. .03 48 0.38 CB 49 0. .08 50 0.21 CD 61 <0. 05 62 0.52 CE 63 <0. 05 64 0.24 CH 71 <o. .05 72 0.32 CH 73 <o. .05 74 0.36 CM 79 <0 .05 80 0.20 CP 65 <0. .12 66 0.62 T a b l e 6. Stream v e l o c i t i e s (meters/second) a t sample l o c a t i o n s . GRA.VEL. f>2 5 , S<*«Jj S, -Tangly Spec 1^ 7 rwtJ.au J' 2* SanJ on[y sG, Saulf c^LUe jr\*e.l CjbM, il^ ***fjr ^ « U r fluj) 1:1 Figure i 9 - e Sediment classification scheme (Folk, 1974) 1 : 1 SAND 57. T e x t u r a l c l a s s i f i c a t i o n and r a n k i n g from c o a r s e s t t o f i n e s t t e x t u r e , a s w e l l a s v e l o c i t i e s a r e l i s t e d i n T a b l e 7. A l l h i g h e n e r g y t e x t u r e s were g r a v e l , whereas low e n e r g y t e x t u r e s r a n g e d from g r a v e l t h r o u g h s l i g h t l y g r a v e l l y s a n d . C r i t e r i a u s e d t o ran k low e n e r g y s a m p l e s a r e , i n d e c r e a s i n g p r i o r i t y , t e x t u r a l c l a s s (g > s > m), median g r a v e l s i z e , and maximum g r a v e l s i z e . H i g h e n e r g y r a n k i n g s were b a s e d on median and maximum g r a v e l s i z e . SAMPLE PROCESSING S i e v i n g Sample p r o c e s s i n g i s shown i n F i g u r e 2.0. Samples were oven d r i e d a t 11 0 ° C , o n e - e i g h t h was s a v e d w i t h a J o n e s s p l i t t e r , and t h e r e m a i n i n g s e v e n - e i g h t h s d r y s i e v e d t h r o u g h 2 s t a c k s o f s i e v e s on a Rot a p f o r 15 m i n u t e s p e r s t a c k . The c o a r s e s i e v e s t a c k c o n t a i n e d US s t a n d a r d s i e v e mesh numbers 10, 14, 18, 25, 35, and 45, and t h e f i n e s i e v e s t a c k numbers 60, 80, 120, 170, and 270. The 500-600 gm and 130-170 gm c h a r g e s were r u n t h r o u g h t h e c o a r s e and f i n e s t a c k s , r e s p e c t i v e l y . E a c h s i z e f r a c t i o n i n c l u d i n g minus 270-mesh was wei g h e d t o t h e n e a r e s t gram. 58. TEXTURAL RANKING* AND CLASSIFICATION OF SEDIMENTS LOW ENERGY HIGH ENERGY SAMPLE R. T. MED. MAX. SAMPLE MED. MAX. 57 1 G 2.0 30 64 1 10 40 13 2 G 2 20 58 2 10 30 15 3 G 2 12 60 3 10 25 27 4 G 2 8 80 3 10 25 37 5 G 2 7 50 4 8 20 29 6 G 2 6 56 4 8 20 43 7 G 1 10 48 5 8 15 41 7 G 1 10 26 6 8 10 2 8 G 1 5 44 7 6 25 3 9 G 1 4 36 8 6 20 49 10 G 0.5 6 72 8 6 20 47 11 msG 2 20 14 9 6 15 11 12 msG 2 8 42 10 5 25 55 13 msG 1 8 16 11 5 15 63 14 msS 1 6 28 11 5 15 45 15 gs 0.5 2 30 12 5 10 73 16 gs 0.5 30 74 13 4 15 59 17 gs 0.5 1 66 14 4 10 65 18 gs 0.5 0.5 12 15 4 8 35 19 gmS 0.5 15 62 16 4 6 71 20 (g)s 0.5 1 4 17 3 10 79 20 (g)s 0.5 1 46 17 3 10 61 21 (g)s 0.5 0.5 38 18 3 8 25 ? ? ? 1 19 2 5 • R a n k i n g (R.) from h i g h e r t o lower energy e n v i r o n m e n t s , i s based on t e x t u r a l c l a s s i f i c a t i o n ( T . ) , from F i g u r e 20, and median (MED.) and maximum (MAX.) g r a v e l s i z e i n low energy e n v i r o n m e n t s , and on median and maximum g r a v e l s i z e i n h i g h energy e n v i r o n m e n t s . T a b l e 7. T e x t u r a l r a n k i n g and c l a s s i f i c a t i o n of s e d i m e n t s . 1/8 s p l i t saved U.S. Standard Sieve Mesh # Millimeters Phi (0) Wentworth Size Class 10 14 18 25 35 45 60 80 120 170 270 2.00 1.41 1.00 0.71 0.50 -1.0 -0.5 0.0 +0.5 1.0 0.35 1.5 -0.25 2.0 0.177 2.5 -0.125 3.0 0.088 3.5 -0.053 4.25 Very coarse sand Coarse sand Medium sand Fine sand Very f i ne sand y Sieved sediments weighed F Size fractions separated in bromoform and methylene iodide: 1.5-2.0* 2.0-2.5 2.5-3.0 3.0-3.5 3.5-4.25 L i ghts,med i urns and heavies wei ghed ScheeIi te gra i ns counted Magnet i te wei ghed Figure 20. Sample processing. 60. Heavy m i n e r a l s e p a r a t i o n R e s p e c t i v e , low and h i g h e n e r g y s a m p l e s 5 and 6 f r o m t h e h e a d w a t e r s o f Omo C r e e k were u s e d as t e s t c a s e s t o d e t e r m i n e i n w h i c h s i z e f r a c t i o n s s c h e e l i t e o c c u r r e d . Twenty f i v e s u b - s a m p l e s o f p u l v e r i z e d s i e v e d m a t e r i a l f r o m sample 5 were a n a l y z e d f o r t u n g s t e n by s o l v e n t e x t r a c t i o n and a t o m i c a b s o r p t i o n (by P l a c e r Development L i m i t e d ) . R e s u l t s i n d i c a t e d t h a t W c o n c e n t r a t i o n s i n s i e v e d s e d i m e n t s were h i g h e s t between 45 and 270-mesh ( F i g u r e 2 1 ) . As a f u r t h e r t e s t , s e l e c t e d s i z e f r a c t i o n s o f sample 6 were s e p a r a t e d i n bromoform (2.71 < G < 2.98) and m e t h y l e n e i o d i d e (3.27 <G < 3.33), and s c h e e l i t e g r a i n s c o u n t e d under a s h o r t w a v e u l t r a v i o l e t l i g h t . T h i s showed t h a t t h e r e were s i g n i f i c a n t c o n c e n t r a t i o n s o f s c h e e l i t e c o a r s e r t h a n 45-mesh.^ However, p r o h i b i t i v e l y l a r g e q u a n t i t i e s o f heavy l i q u i d s were consumed by t h e s i z e a b l e s a m p l e s o f p l u s 45-mesh s e d i m e n t s . Heavy l i q u i d s e p a r a t i o n s were t h e r e f o r e c o n f i n e d t o s i z e f r a c t i o n s between 45 and 270-mesh. Samples were weighed b e f o r e and a f t e r e a c h s e p a r a t i o n e i t h e r t o 0.01 o r 0.0001 gm, d e p e n d i n g on t h e i r s i z e . M a g n e t i t e was removed f r o m t h e h e a v y f r a c t i o n w i t h a hand magnet and weighed t o 0.0001 gm. 10 S e l e c t e d f o r heavy .... I . I 1 m i n e r a l s e p a r a t i o n i . i • * 10 14 18 25 35 45 60 ' 80 120 170 270 SIF-VE. M E S H *t Figure 21. W concentrations i n sieved sediments, sample #5-62. C o u n t i n g T u n g s t e n c o n c e n t r a t i o n s were d e t e r m i n e d by c o u n t i n g s c h e e l i t e g r a i n s i n t h e heavy f r a c t i o n s and t h e n c o n v e r t i n g c o u n t s t o W w e i g h t s . C o u n t i n g was p r e f e r r e d b e c a u s e , a l t h o u g h p r e c i s i o n was unknown, s a m p l e s would be i n t a c t f o r f u r t h e r a n a l y s i s i f n e e d e d . E a c h sample was e v e n l y d i s t r i b u t e d o n t o b l a c k p a p e r marked w i t h a l i g h t - c o l o r e d 2.5 cm g r i d . A f t e r s e v e r a l m i n u t e s f o r v i s i o n t o a d j u s t t o t o t a l d a r k n e s s , s c h e e l i t e g r a i n s were c o u n t e d by s q u a r e s under u l t r a v i o l e t l i g h t . Samples w i t h p r o h i b i t i v e l y l a r g e numbers o f g r a i n s were s p l i t s u c h t h a t a t l e a s t 100 s c h e e l i t e g r a i n s c o u l d be c o u n t e d . Many f a c t o r s i n f l u e n c e d c o u n t i n g . B r i g h t n e s s o f f l u o r e s c e n c e was a f f e c t e d by o x i d e c o a t i n g s , g r a i n o r i e n t a t i o n , b a t t e r y s t r e n g t h , and i n c o n s i s t e n t d a r k n e s s v i s i o n . Thus, i t was d i f f i c u l t t o d i s t i n g u i s h d i m l y f l u o r e s c i n g s c h e e l i t e g r a i n s f r o m lamp r e f l e c t i o n s , a s b o t h were b l u e - w h i t e . A l s o , s c h e e l i t e d u s t a c c o m p a n i e d a l l s i z e f r a c t i o n s and was n o t e a s i l y d i s t i n g u i s h e d f r o m 170 t o 270-mesh g r a i n s . C o u n t i n g e r r o r s were d e t e r m i n e d by r e - c o u n t i n g a l l f i v e s i z e f r a c t i o n s o f 10 r a n d o m l y s e l e c t e d s a m p l e s ( T a b l e 8 ) . C o e f f i c i e n t s o f v a r i a t i o n b o t h o f s p l i t s and whole s a m p l e s a r e g e n e r a l l y b elow 15 p e r c e n t , w i t h o c c a s i o n a l e r r a t i c v a l u e s . SAMPLE SIZE INTERVAL - PHI 1 .5 - 2.0 2 .0 - 2.5 2. . 5 - 3 .0 3 . 0 - 3 .5 3.5 - 4. 25 n* s cv n* s cv n* s cv n* s cv n s cv 1 25 1 0 65 2 0 231 20 9 658 47 7** 1434 37 3* 11 0 0 0 4 3 71 19 8 41 40 20 50 181 22 12 13 11 1 1 11 8 71 37 2 1 164 0 0 422 0 0 43 10 0 0 31 1 0 93 23 24** 243 4 1** 472 165 35* 50 46 4 8 160 41 25 345 28 8** 1090 141 13** 1401 57 5* 58 57 5 9** 291 42 14** 552 6 1** 781 18 3** 1464 79 5* 62 2 7 458 21 1 0 263 0 0** 1631 121 7** 3013 555 18* 63 5 4 79 11 1 13 54 0 20 334 7 2 1304 173 13* 74 6 0 0 90 21 23 700 75 11** 1377 272 20** 1548 60 4 44 14 1 1 45 6 13 108 14 13** 221 7 3** 596 175 29* * - Counts normalized to one gram of sample. ** - Sample was s p l i t f o r counting. Table 8. Average number of s c h e e l i t e g r a i n s (n), standard d e v i a t i o n ( s ) , and c o e f f i c i e n t of v a r i a t i o n (cv) based on d u p l i c a t e counts of s c h e e l i t e g r a i n s . 6 4 . W e i g h t c o n v e r s i o n s C o n v e r s i o n o f s c h e e l i t e c o u n t s t o W c o n c e n t r a t i o n s was done v i a X - r a y f l u o r e s c e n c e a n a l y s i s o f sample 5 8 . Sample 5 8 was c h o s e n b e c a u s e : 1 . I t had t h e l a r g e s t h e a v y m i n e r a l c o n t e n t ; s u f f i c i e n t i n t h e two c o a r s e s t f r a c t i o n s f o r p e l l e t i z i n g w i t h o u t a d d i n g m a t r i x . However, m a t r i x was added t o t h e t h r e e f i n e r f r a c t i o n s and a m a t r i x c o r r e c t i o n made on a l l s i z e s by t h e method o f F e a t h e r and W i l l i s ( 1 9 7 6 ) . 2 . I t c o n t a i n e d many s c h e e l i t e g r a i n s ; 2 0 0 i n 4 5 t o 6 0 mesh and o v e r 8 0 0 i n a l l o t h e r s i z e f r a c t i o n s , and t h e s e had been c o u n t e d t w i c e w i t h c l o s e a greement ( T a b l e 8 ) . In a d d i t i o n , t h e sample came from h a l f w a y down t h e d r a i n a g e , where g r a i n r o u n d i n g s h o u l d be n e a r t h e h a l f w a y p o i n t . Thus t h e b e s t s i n g l e - s a m p l e e s t i m a t e o f W i n an a v e r a g e s c h e e l i t e g r a i n was p r o v i d e d . The r e s u l t s a r e shown i n T a b l e 65. GRAIN S I Z E W AVERAGE NUMBER OF SCHEELITE GRAINS IN DUPLICATE COUNTS WEIGHT OF W IN ONE SCHEELITE GRAIN WEIGHT OF ONE SCHEELITE GRAIN PHI PPM GRAINS/ SAMPLE GRAINS/ GRAM (MICROGRAMS) (MICROGRAMS) 1 .5-2, .0 1,436 431 57 25 .2 39, .4 2. .0-2. .5 3,327 1138 291 11. .4 17. .9 2. .5-3, .0 2,427 1446 552 4 .40 6, .89 3 .0-3. .5 1,861 1375 781 2 .38 3. .74 3. .5-4 .25 570 1873 1464 0 .389 0, .610 T a b l e 9. Weights of W and s c h e e l i t e i n a s i n g l e g r a i n i n sample 58; f o r c o n v e r s i o n of s c h e e l i t e g r a i n c o u n t s t o W / s c h e e l i t e c o n c e n t r a t i o n s . CHAPTER FOUR RESULTS 67. INTRODUCTION R e s u l t s a r e c o n s i d e r e d r e l a t i v e t o downstream p r o f i l e s , b e h a v i o r o f s c h e e l i t e a t s p e c i f i c s i t e s , and c h a n g e s i n median s i z e a s a r e s p o n s e t o h y d r a u l i c e f f e c t s . DOWNSTREAM PROFILES The u s u a l p r o c e d u r e i n a h e a v y m i n e r a l s a m p l i n g p r o g r a m f o r W would be t o e x p r e s s W c o n c e n t r a t i o n s e i t h e r i n heavy m i n e r a l c o n c e n t r a t e s o r i n s i e v e d s e d i m e n t s . I t i s r e a s o n a b l e t o assume t h a t W c o n c e n t r a t i o n s i n h e a v i e s w i l l more e f f e c t i v e l y r e d u c e v a r i a b i l i t y due t o h y d r a u l i c e f f e c t s , b e c a u s e h e a v i e s a r e c l o s e r i n d e n s i t y t o s c h e e l i t e t h a n a r e s i e v e d s e d i m e n t s . T h e r e f o r e , W / h e a v i e s c o n c e n t r a t i o n s down C l e a C r e e k t o t h e l o w e s t sample s i t e on t h e P e l l y R i v e r ( F i g u r e 2 2 ) , and down Omo C r e e k t o s i t e CE, i m m e d i a t e l y b e l o w t h e O m o / P e l l y j u n c t i o n ( F i g u r e 23) were p l o t t e d . T h e r e a r e a number o f s i m i l a r i t e s among p l o t s . D i f f e r e n c e s between h i g h and low e n e r g y s a m p l e s and between sample s i t e s a r e g e n e r a l l y g r e a t e r t h a n between d u p l i c a t e s . In many c a s e s , c o v a r i a n c e o f c o n c e n t r a t i o n s between s i z e f r a c t i o n s and between h i g h and low e n e r g y e n v i r o n m e n t s i s c l e a r l y d i s c e r n a b l e , a l t h o u g h t h e r e a r e e x c e p t i o n s t o t h i s . A l s o , W c o n c e n t r a t i o n s a r e a p p r o x i m a t e l y e q u a l i n h i g h and low e n e r g y e n v i r o n m e n t s n e a r s t r e a m h e a d w a t e r s , b u t downstream, h i g h e n e r g y c o n c e n t r a t i o n s i n c r e a s e o v e r low e n e r g y Figure 22. W/heavies concentrations down the Pelly River; (a) 1.5-2.0 phi (45-60 mesh), (b) 2.0-2.5 phi (60=80 mesh), (c) 2.5-3.0 phi (80-120 mesh).,; .(continued) ... (d) Figure 22. (continued)...(d) 3.0-3.5 phi (120-170 mesh), (e) 3.5-4.25 phi (170-270 mesh). 70. 2000- (a) iooo4 sne : O " T -o AO DO C L R Cf=-X — H I G H E N E R G Y K M Figure 23. W/heavies concentrations down Omo Creek; (a) 1.5-2 0 phi (b) 2.0-2.5 phi, (c) 2.5-3.0 phi...(continued)... 71. Figure 23. (continued)...(d) 3.0-3.5 phi, (e) 3.5-4.25 phi. 72. c o n c e n t r a t i o n s , w i t h t h i s i n c r e a s e b e i n g p r o g r e s s i v e l y more p r o n o u n c e d f o r c o a r s e r s c h e e l i t e s i z e s . F i n a l l y , and o f o b v i o u s c o n c e r n f r o m an e x p l o r a t i o n s t a n d p o i n t , i t i s o n l y i n low e n e r g y s a m p l e s f r o m t h e P e l l y R i v e r t h a t W c o n c e n t r a t i o n s a r e g r e a t e s t n e a r th e C l e a d e p o s i t . HYDRAULIC EFFECTS WITHIN SITE S P a t t e r n s r e l a t e d t o h y d r a u l i c e f f e c t s w i t h i n t h e 8 d u p l i c a t e s i t e s a r e most c o n s i s t e n t , and t h e r e f o r e d e s c r i b e d i n d e t a i l , a t s i t e AO. S i t e AO i s l o c a t e d 5.7 km down Omo C r e e k , a l o n g a s h o r t m e a n d e r i n g s t r e t c h o f r e d u c e d g r a d i e n t i n an a p p r o x i m a t e l y 50 m wide by 50 m h i g h r a v i n e ( F i g u r e 1 8 ) . A t t h i s p o i n t , b r u s h c o v e r s t h e a l l u v i a l f l o o r , and a l o n g t h e t r e e c o v e r e d s l o p e s , s h a l e o u t c r o p s a r e c a p p e d by g l a c i a l t i l l s . On t h e i n s i d e bend o f a meander a r e two embayments, a b o u t 10 m a p a r t . These a r e p o s s i b l y r e m n a n t s o f abandoned c h a n n e l s . Beyond t h e mouth o f e a c h embayment i s a g r a v e l b a r . S e d i m e n t t e x t u r e s g r a d e f r o m f i n e , p a r t l y o r g a n i c muds w i t h i n t h e embayments, t h r o u g h p e b b l e s and c o b b l e s on t h e b a r s , t o p r e d o m i n a n t l y b o u l d e r s i n t h e m a i n s t r e a m . Low e n e r g y d u p l i c a t e s ( s a m p l e s 45 and 55) were t a k e n i n g r a v e l l y sand and muddy sandy g r a v e l , r e s p e c t i v e l y , a t t h e mouths o f e a c h embayment, and h i g h e n e r g y d u p l i c a t e s ( s a m p l e s 46 and 56) were c o l l e c t e d i n 3 and 8 cm m edian g r a v e l s a t t h e head o f e a c h b a r , r e s p e c t i v e l y . D i s t a n c e s between s a m p l e s 45 and 46, 7 3 . between 55 and 56, and between d u p l i c a t e s were a p p r o x i m a t e l y 2 m, 4 m and 10 m, r e s p e c t i v e l y . W / h e a v i e s c o n c e n t r a t i o n s , median s c h e e l i t e s i z e s and s t r e a m v e l o c i t i e s a r e a l l g r e a t e r i n h i g h t h a n low e n e r g y e n v i r o n m e n t s ( F i g u r e 2 4 ) . A l s o , h i g h / l o w e n e r g y c o n c e n t r a t i o n r a t i o s i n c r e a s e w i t h s c h e e l i t e g r a i n s i z e ( F i g u r e 2 5 ) , and r e l a t i v e t o h e a v i e s , c o a r s e s t s c h e e l i t e i s as much as 20 t i m e s more c o n c e n t r a t e d i n h i g h e n e r g y s a m p l e s . R e s u l t s a r e s i m i l a r a t s i t e CB, b u t a t o t h e r d u p l i c a t e s i t e s one o r more o f t h e p a r a m e t e r s d e p a r t f r o m c o n s i s t e n t p a t t e r n s . I n a d d i t i o n , b e c a u s e o f t h e s e i n c o n s i s t e n c i e s , p r e l i m i n a r y i n s p e c t i o n o f t h e d a t a as a whole i n d i c a t e d t h a t no s i m p l e q u a n t i t a t i v e r e l a t i o n s h i p between s t r e a m v e l o c i t i e s , s e d i m e n t t e x t u r e and s c h e e l i t e abundance c o u l d be e x p e c t e d . S I Z E DISTRIBUTIONS Changes i n s i z e d i s t r i b u t i o n s w i t h e n e r g y e n v i r o n m e n t were e v a l u a t e d by c o m p a r i n g median s i z e s o f minus 10-mesh s i e v e d s e d i m e n t s , s c h e e l i t e , m a g n e t i t e , h e a v i e s , mediums and l i g h t s i n p a i r e d h i g h and low e n e r g y s a m p l e s . In 20 o f 24 p a i r s o f c u m u l a t i v e w e i g h t p e r c e n t a g e p l o t s o f minus 10-mesh s e d i m e n t s , h i g h e n e r g y median s i z e s a r e c o a r s e r t h a n low e n e r g y m e d i a n s i z e s ( e . g . F i g u r e 2 6 ) . 74. Figure 24., W/heavies concentrations, velocities and median scheelite sizes at site AO. 75. Figure 25. Enrichment of high relative to low energy W/heavies concentrations at site AO. See Figure 24 for key to grain sizes. Figure .26. Cumulative weight percentages of minus 10-mesh sieved sediments. 77. M e d i a n s i z e s o f 1.5 p h i t o 4.25 p h i s c h e e l i t e , m a g n e t i t e , h e a v i e s , mediums and l i g h t s were e s t i m a t e d t o 0.1 p h i f r o m c u m u l a t i v e w e i g h t p l o t s o f t h e 32 s a m p l e s f r o m d u p l i c a t e s i t e s ( T a b l e 10)i H i g h ( v e r s u s low) e n e r g y s c h e e l i t e and h e a v i e s a r e b o t h c o a r s e r i n 13 o f 16 sample p a i r s , b u t t r e n d s o f o t h e r g r o u p s a r e l e s s c l e a r . A l t h o u g h d ependence o f median s i z e v a r i a t i o n on s o u r c e d i s t r i b u t i o n i s p o t e n t i a l l y much g r e a t e r when c o m p a r i s o n s a r e made by d e n s i t y f r a c t i o n r a t h e r t h a n by e n e r g y e n v i r o n m e n t , median s i z e s a r e g e n e r a l l y i n v e r s e l y r e l a t e d t o d e n s i t y ( T a b l e 11). T h u s , f i n e s t t o c o a r s e s t g r o u p s i n b o t h h i g h and low e n e r g y e n v i r o n m e n t s a r e m a g n e t i t e , s c h e e l i t e , h e a v i e s , l i g h t s , and mediums. CONCLUSIONS One c o n c l u s i o n i s t h a t s c h e e l i t e d i s t r i b u t i o n s w i t h i n s i t e s a r e a p p r e c i a b l y i n f l u e n c e d by h y d r a u l i c e f f e c t s . H y d r a u l i c e f f e c t s between s i t e s , i n e i t h e r h i g h o r low e n e r g y e n v i r o n m e n t s must a l s o be p r e s e n t , b u t a r e n o t so e a s i l y a s s e s s e d . As a r e s u l t , downstream i n c r e a s e s i n W c o n c e n t r a t i o n s m i g h t r e p r e s e n t e i t h e r h y d r a u l i c e f f e c t s o r a d d i t i o n a l s o u r c e s o f s c h e e l i t e i n p u t . T h i s i s o f c o n s i d e r a b l e s i g n i f i c a n c e i n a m i n e r a l e x p l o r a t i o n p r o g r a m . The r e m a i n d e r o f t h i s t h e s i s i s t h e r e f o r e d e v o t e d t o u n d e r s t a n d i n g and e l i m i n a t i n g h y d r a u l i c e f f e c t s , s o t h a t s o u r c e e f f e c t s may be b e t t e r i n t e r p r e t e d . 78. CHANGE IN MEDIAN SIZE SCHEELITE MAGNETITE HEAVIES MEDIUMS LIGHTS COARSER 13 7 13 9 4 NO CHANGE 0 4 2 3 10 FINER 3 5 1 4 2 T a b l e 10. Changes i n median d i a m e t e r s o f s c h e e l i t e , m a g n e t i t e , h e a v i e s , mediums and l i g h t s from low t o h i g h energy e n v i r o n m e n t s a t t h e e i g h t d u p l i c a t e s i t e s . 79. ENERGY MEAN OF MEDIAN PHI SIZE ENVIRONMENT SCHEELITE MAGNETITE HEAVIES MEDIUMS LIGHTS HIGH ENERGY 2.3 3.3 2.1 1.9 2.1 LOW ENERGY 2.6 3.4 2.3 1.9 2.0 T a b l e 11. Mean of median d i a m e t e r s of s c h e e l i t e , m a g n e t i t e , h e a v i e s , mediums and l i g h t s a t t h e e i g h t d u p l i c a t e s i t e s . CHAPTER 5 DETERMINATION OF HYDRAULICALLY EQUIVALENT SIZES 81. INTRODUCTION As noted i n Chapter 1, no adequate t h e o r e t i c a l model e x i s t s f o r p r e d i c t i n g h y d r a u l i c e q u i v a l e n c e of m i n e r a l g r a i n s under f i e l d c o n d i t i o n s . Two e m p i r i c a l approaches to determining h y d r a u l i c a l l y e q u i v a l e n t s i z e s have t h e r e f o r e been a p p l i e d . The f i r s t u t i l i z e s the method o f Rittenhouse (1943) as d e s c r i b e d i n Chapter 1. An a l t e r n a t i v e approach, using r a t i o s of c o n c e n t r a t i o n s i n high versus low energy environments was developed s p e c i f i c a l l y f o r t h i s study. RITTENHOUSE COEFFIENT OF VARIATION METHOD Rittenhouse's (1943) e m p i r i c a l c o e f f i c i e n t of v a r i a t i o n (CV) method of determining h y d r a u l i c a l l y e q u i v a l e n t s i z e s was chosen fo r t h i s study because: 1. I t was s u c c e s s f u l l y a p p l i e d by Rittenhouse using one meter deep samples. These would almost c e r t a i n l y have i n c l u d e d sediments d e p o s i t e d under d i f f e r e n t h y d r a u l i c c o n d i t i o n s . 82. 2. D a t a i n c l u d e d w e i g h t s o f i n d i v i d u a l m i n e r a l s and d e n s i t y g r o u p s ( e . g . " l i g h t s " ) . 3. , P r i o r a s s u m p t i o n s a b o u t s e t t l i n g o r e n t r a i n m e n t e q u i v a l e n c e a r e n o t r e q u i r e d T h i s s t u d y d i f f e r e d f r o m R i t t e n h o u s e ' s i n s e v e r a l r e s p e c t s . R i t t e n h o u s e c o n s i d e r e d l i g h t s and a number o f i n d i v i d u a l n o n m a g n e t i c heavy m i n e r a l s i n s i x s a m p l e s f r o m a s i n g l e s i t e a l o n g a mature r e a c h o f t h e R i o Grande R i v e r , New M e x i c o . T h i s s t u d y u t i l i z e d s c h e e l i t e , m a g n e t i t e , h e a v i e s , mediums, and l i g h t s i n f o u r s a m p l e s from e a c h o f e i g h t s i t e s a l o n g immature m o u n t a i n s t r e a m s . P o t e n t i a l l y h y d r a u l i c a l l y e q u i v a l e n t 0.1 p h i s i z e s o f m a g n e t i t e , h e a v i e s , mediums and l i g h t s were c a l c u l a t e d f o r s c h e e l i t e s i z e i n t e r v a l s o f 3.9-4.0, 3.4-3.5, 2.9-3.0, 2.4-2.5, and 1.9-2.0 p h i . The w e i g h t o f e a c h 0.1 p h i s c h e e l i t e sample was d i v i d e d by w e i g h t s i n t h e same and p r o g r e s s i v e l y c o a r s e r 0.1 p h i s i z e i n t e r v a l s o f a g i v e n m i n e r a l g r o u p , t o a maximum o f 1.4 p h i c o a r s e r . C.V.'s o f r a t i o s a t e a c h o f t h e 8 s i t e s were e v a l u a t e d , b u t r e s u l t s were ambiguous and d i f f i c u l t t o i n t e r p r e t . B e c a u s e s i m i l a r r e s u l t s were l a t e r o b t a i n e d u s i n g 0.5 p h i r a t h e r t h a n 0.1 p h i d a t a and 0.5 p h i t a b l e s a r e l e s s e x t e n s i v e , p r o b l e m s common t o a l l r e s u l t s a r e i l l u s t r a t e d u s i n g 0.5 p h i s c h e e l i t e and h e a v i e s d a t a ( T a b l e 1 2 ) . 83. CV's a t i n d i v i d u a l s i t e s v a r y c o n s i d e r a b l y as w e i g h t s o f a g i v e n s c h e e l i t e s i z e a r e r a t i o e d t o w e i g h t s o f d i f f e r e n t h e a v i e s s i z e s , b u t no h y d r a u l i c a l l y e q u i v a l e n t s i z e o f h e a v i e s i s c o n s i s t e n t l y i n d i c a t e d by minimum CV's. F o r example, a t s i t e s G t h r o u g h CH i n T a b l e 12, minimum CV's o c c u r when 3.5-4.25 p h i s c h e e l i t e i s r a t i o e d t o h e a v i e s 0.0, 1.5, 0.0, 1.0, 0.5, 0.0 0.5, and 1.0 p h i c o a r s e r , r e s p e c t i v e l y . I n t e r p r e t a t i o n s a r e f u r t h e r c o m p l i c a t e d by m u l t i p l e CV minima, s u c h as a t s i t e CB, where CV's o f 35% and 37% a r e a s s o c i a t e d w i t h h e a v i e s 0.5 p h i and 1.5 p h i c o a r s e r , r e s p e c t i v e l y . A v e r a g e CV's a r e a l s o d i f f i c u l t t o i n t e r p r e t , i n t h a t c o n s i s t e n t t r e n d s w i t h i n c r e a s i n g s c h e e l i t e s i z e a r e l a c k i n g . P o s s i b l e r e a s o n s f o r t h e f a i l u r e o f t h e CV method a r e t h a t v a r i a t i o n o f CV's i s l a r g e l y due t o : 1. S a m p l i n g a n d / o r a n a l y t i c a l e r r o r s 2. V e r y l o c a l i z e d s o u r c e e f f e c t s 3. H y d r a u l i c e f f e c t s ( i n w h i c h c a s e , none o f t h e m i n e r a l s t e s t e d a r e h y d r a u l i c a l l y e q u i v a l e n t t o s c h e e l i t e ) . However, a n a l y t i c a l e r r o r s c a n be e l i m i n a t e d as t h e s o l e s o u r c e o f v a r i a b i l i t y , b e c a u s e f o r s c h e e l i t e , t h e w o r s t c a s e , a n a l y t i c a l e r r o r s g e n e r a l l y do n o t e x c e e d + 15% (One s t a n d a r d SITE SCHEELITE SIZE INTERVAL (PHI) FROM: 3.5 3.0 2.5 2.0 1.5 TO: 4.25 3.5 3.0 2.5 2.0 SCHEELITE SIZE MINUS HEAVIES SIZE (PHI) 0.0 0.5 1.0 1.5 2.0 0.0 0.5 1.0 1.5 0.0 0.5 1.0 0.0 0.5 0.0 G 1455 31 33 36 51 35 38 39 50 36 55 52 39 48 60 ZAA 44 41 33 29 39 20 14 19 46 36 31 46 25 23 15 AK 19 97 147 122 30 20 76 43 35 24 24 53 41 38 59 AO 37 41 30 50 61 71 57 43 27 85 74 49 85 76 98 1234 103 61 75 67 69 55 75 64 71 32 20 25 55 37 81 BG 19 32 55 60 54 18 35 44 48 54 25 43 94 117 101 CB 50 35 43 37 75 68 49 24 47 90 60 29 92 80 93 CH 47 41 35 40 58 49 44 43 53 66 57 54 101 96 73 MEAN 42 47 56 55 55 42 49 40 47 53 43 44 67 64 73 Table 12. C o e f f i c i e n t s of v a r i a t i o n (5J) of sc h e e I i t e / h e a v i e s weight r a t i o s - f o u r samples per s i t e . Oo 85. d e v i a t i o n ) . F u r t h e r d i s c u s s i o n o f t h i s p r o b l e m i s d e f e r r e d u n t i l C h a p t e r 6. CONCENTRATION RATIOS G e n e r a l t r e n d s o f c o n c e n t r a t i o n r a t i o s F a i l u r e o f t h e CV method t o y i e l d c o n s i s t e n t r e s u l t s l e d t o t h e d e v e l o p m e n t o f a method o f e s t i m a t i n g h y d r a u l i c a l l y e q u i v a l e n t s i z e s b a s e d on c o n c e n t r a t i o n d i f f e r e n c e s , e x p r e s s e d as r a t i o s between h i g h and low e n e r g y e n v i r o n m e n t s . H i g h / l o w e n e r g y c o n c e n t r a t i o n r a t i o s (CR's) a t a s i t e a r e assumed t o p r e d o m i n a n t l y r e f l e c t h y d r a u l i c e f f e c t s . G e o m e t r i c mean c o n c e n t r a t i o n r a t i o s (GMCR's) s h o u l d t h e r e f o r e a l l o w e v a l u a t i o n , w i t h o u t b i a s , o f n e t r e l a t i v e e n r i c h m e n t i n h i g h e n e r g y e n v i r o n m e n t s . F o r example, i f CR's o f t h r e e d i f f e r e n t sample p a i r s a r e 100/10, 50/50 and 10/100, l o g v a l u e s a v e r a g e 0 and y i e l d a GMCR o f u n i t y , t h u s , c o r r e c t l y i n d i c a t i n g no n e t h y d r a u l i c e f f e c t . C o n v e r s e l y , t h e a r i t h m e t i c mean CR o f 3.7 m i s l e a d i n g l y i m p l i e s a n e t e n r i c h m e n t i n h i g h e n e r g y e n v i r o n m e n t s . M i n e r a l c o n c e n t r a t i o n s ' were e x p r e s s e d i n t h e 0.5 p h i s i z e i n t e r v a l s o f t h e s i e v e d s e d i m e n t s ( e . g . 2.5-3.0 p h i s c h e e l i t e / 2 . 5 - 3 . 0 p h i s i e v e d ) t o o b t a i n GMCR's i n T a b l e 13. GMCR's g e n e r a l l y i n c r e a s e w i t h g r a i n s i z e and FRACTION SIZE INTERVAL - PHI 1.5-2.0 2.0-2.5 2.5-3.0 3.0-3.5 3.5-4.25 SCHEELITE 4 .7 5 .1 3. .3 2 .4 1 .7 MAGNETITE 2 .7 2 .0 1 .6 1 .5 1. .5 HEAVIES 2 .1 1 .8 1 .4 1 .3 1 .6 MEDIUMS 1. .2 1 .1 1 .2 1 .2 1 .3 SEIVED/LIGHTS* 1 .0 1 .0 1 .0 1 .0 1. .0 • L i g h t s a r e assumed t o be e q u i v a l e n t t o s i e v e d s e d i m e n t s ; t h e r e f o r e c o n c e n t r a t i o n r a t i o s a r e assumed t o be u n i t y . T a b l e 13. G e o m e t r i c means of c o n c e n t r a t i o n r a t i o s of m i n e r a l s i n h i g h energy e n v i r o n m e n t s over low energy e n v i r o n m e n t s ( c o n c e n t r a t i o n s a r e e x p r e s s e d r e l a t i v e t o s i e v e d s e d i m e n t s i n t h e same s i z e f r a c t i o n ) . 8 7 . d e n s i t y , and a l l m i n e r a l s o f medium o r g r e a t e r d e n s i t y a r e e n r i c h e d (GMCR > 1) r e l a t i v e t o t h e same g i v e n s i z e o f s i e v e d s e d i m e n t s (which a r e e s s e n t i a l l y composed o f l i g h t s ) i n h i g h e n e r g y e n v i r o n m e n t s . C o n c e n t r a t i o n s o f 0.5 p h i i n t e r v a l s o f m i n e r a l s were a l s o r e - e x p r e s s e d r e l a t i v e t o w e i g h t s o f minus 10-mesh s e d i m e n t s t o o b t a i n T a b l e 14 o f GMCR's. E n r i c h m e n t s o f a l l s i z e and d e n s i t y f r a c t i o n s r e l a t i v e t o e a c h o t h e r c a n t h e n be compared, b e c a u s e a common d e n o m i n a t o r ( i . e . minus 10-mesh s e d i m e n t s ) i s u s e d . T r e n d s w i t h s i z e and d e n s i t y a r e unchanged f r o m T a b l e 13, b u t GMCR's a r e u n i f o r m l y l o w e r i n T a b l e 14. I f t h e y were measured w i t h o u t e r r o r , GMCR's o f two p e r f e c t l y h y d r a u l i c a l l y e q u i v a l e n t m i n e r a l s would be e q u a l i n T a b l e 14. On a v e r a g e , c o n c e n t r a t i o n s o f t h e t h r e e c o a r s e r s c h e e l i t e s i z e s a r e 3-5 t i m e s g r e a t e r i n h i g h t h a n low e n e r g y e n v i r o n m e n t s , and o n l y GMCR's o f t h e two f i n e r s c h e e l i t e s i z e s compare w i t h t h o s e o f m a g n e t i t e and and h e a v i e s . GMCR's an d / o r median CR's o f 3.5-4.25 p h i s c h e e l i t e a r e most s i m i l a r t o t h o s e o f 2.0-3.0 p h i m a g n e t i t e and 2.0-2.5 p h i h e a v i e s , and a v e r a g e CR's o f 3.0-3.5 p h i s c h e e l i t e a r e c l o s e s t t o t h o s e o f 1.5-2.0 p h i h e a v i e s . O n l y t h e two c o a r s e s t s i z e s o f s i e v e d s e d i m e n t s , -1.0 t o -0.5 p h i , and -0.5 t o 0.0 p h i , have GMCR's g r e a t e r t h a n 1. Many s t r o n g r e l a t i o n s h i p s e x i s t between l o g CR's o f d i f f e r e n t m i n e r a l s ( T a b l e 1 5 ) . C o r r e l a t i o n s a r e s t r o n g e s t between a d j a c e n t s i z e f r a c t i o n s , w i t h many c o r r e l a t i o n FRACTION SCHEELITE SIZE INTERVAL - PHI (from:to) -1.0:-0.5 -0.5:0.0 0.0:0.5 0.5:1.0 1.0:1.5 1.5:2.0 2.0:2.5 2.5:3.0 3.0:3.5 3.5:4.25 SCHEELITE 4. .2/4 .0 4 .9/4 .7 3 .3/3 .3 2 .2/1.8 1 .5/1.5 MAGNETITE 2. ,5/2. .1 2 .0/1 .5 1 .6/1. .3 1 .4/0.9 1 .2 HEAVIES 1, .9/1 .7 1 .7/1 .4 1 .3/1 .2 1 .2 1 .3 MEDIUMS 1. .1 1 .0 1 . 1 1 .0 1 .1 SIEVED/LIGHTS 1.4/1.3 1 .1 0.9 0.9 0.9 0. ,9 1 .0 1 .0 0 .9 0 .8 Table 14. Geometric means/medians of co n c e n t r a t i o n r a t i o s . Median c o n c e n t r a t i o n r a t i o s of mineral f r a c t i o n s which have GMCR's comparable to those of s c h e e l i t e are i n c l u d e d . 8 9 . MINERAL FRACTION SCHEELITE S I Z E FRACTION - PHI S C H E E L I T E 1 . 5 - 2 . 0 2 . 0 - 2 . 5 2 . 5 - 3 . 0 3 . 0 - 3 . 5 3 . 5 - 4 . 2 5 1 . 5 t o 2 . 0 o 1 . 0 0 2 . 0 t o 2 . 5 0 . 8 2 1 . 0 0 2 . 5 t o 3 . 0 .75 0 . 9 0 1 . 0 0 3 . 0 t o 3 . 5 .68 .79 0 . 9 4 1 . 0 0 3 . 5 t o 4 . 2 5 .47 .57 .76 0 . 8 9 1 .00 MAGNETITE 1 . 5 t o 2 . 0 .77 .69 .67 .61 0 . 5 1 2 . 0 t o 2 . 5 .58 .70 .80 .81 .73 2 . 5 t o 3 . 0 .49 .66 .82 .88 .82 3 . 0 t o 3 . 5 .49 .63 .81 .88 .84 3 . 5 t o 4 . 2 5 .50 .71 .82 .88 .88 HEAVIES 1 . 5 t o 2 . 0 .70 .80 .74 .67 .56 2 . 0 t o 2 . 5 .64 .84 .85 .81 .71 2 . 5 t o 3 . 0 .57 .75 .88 .90 .81 3 . 0 t o 3 . 5 .48 .65 .82 .89 .83 3 . 5 t o 4 . 2 5 .18 .38 .65 .74 .77 MEDIUMS 1 . 5 t o 2 . 0 .33 .44 .43 .47 .56 2 . 0 t o 2 . 5 .45 .54 .57 .65 .62 2 . 5 t o 3 . 0 .33 .50 .69 .79 .81 3 . 0 t o 3 . 5 .21 .34 .56 .67 .68 3 . 5 t o 4 . 2 5 .15 .20 .39 .49 .48 LIGHTS 1 . 5 t o 2 . 0 .37 .42 .45 .52 .57 2 . 0 t o 2 . 5 .25 .40 .59 .68 .70 2 . 5 t o 3 . 0 .13 .30 .56 .65 .68 3 . 0 t o 3 . 5 .12 .34 .62 .72 .76 3 . 5 t o 4 . 2 5 .01 .27 .50 .62 .76 SIEVED - 1 . 0 t o - 0 . 5 .21 .30 .50 .50 .43 - 0 . 5 t o 0 . 0 - . 0 6 - . 1 4 .09 .09 - . 0 3 0 . 0 t o 0 . 5 .00 .09 - . 1 2 - . 2 6 - . 2 8 0 . 5 t o 1 . 0 .17 .09 - . 1 4 - . 2 3 - . 1 9 1 . 0 t o 1 . 5 .15 .37 .28 .21 .29 T a b l e 1 5 . C o r r e l a t i o n c o e f f i c i e n t s between l o g C R ' s o f s c h e e l i t e and o t h e r m i n e r a l s . 9 0 . c o e f f i c i e n t s exceeding 0.9. Also, correlations between adjacent density groups are strong, and magnetite and heavies correlate well with scheelite. The relationships are readily apparent in scatterplots (e.g. Figure 27). Trends of GMCR's and relationships between log CR's indicate that minerals systematically depart from hydraulic equivalence as either their size or density difference increases. Therefore, the assumption that scheelite i s more hy d r a u l i c a l l y equivalent to heavies than to l i g h t s of a given size i s confirmed. For example, in coarsest to f i n e s t size fractions, scheelite i s on average 2.2, 2.9, 2.5, 1.8 and 1.2 times more concentrated than heavies in high energy environments and i s 4.7, 5.1, 3.3, 2.4, and 1.7 times more concentrated than sieved sediments ( l i g h t s ) . However, because GCMR's and relationships between CR's are based on log values, a given high scheelite CR may be exponentially larger than the CR of heavies of the same siz e . Both the decrease in scheelite/heavies CR's r e l a t i v e to scheelite/sieved CR's and the exponential nature of CR's are exemplified in samples 45 and 46 at s i t e AO. CR's of coarsest to f i n e s t scheelite in l i g h t s and heavies respectively decrease from 63, 15, 6.7, 3.9 and 1.9 to 19, 5.4, 3.6, 1.7 and 1.1. Thus very e r r a t i c scheelite/heavies concentrations, p a r t i c u l a r l y in coarser size fractions, can resu l t from hydraulic e f f e c t s . 1.6 1.2 r = .81 at <-> 0.8 <& o O O i 0.<t u r u o o * o.o i o m o o o • o.s. - 1.2--0.5 0.0 O.S 2.3-3.O0f HEAVIE.S uOfr CR 1.0 Figure .27. 3.5-A.25 phi scheelite log CR versus 2.5-3.0 phi heavies log CR. 9 2 . D e t e r m i n a t i o n o f h y d r a u l i c e q u i v a l e n c e u s i n g CR's As m i n e r a l s become more e q u i v a l e n t i n t h e i r h y d r a u l i c b e h a v i o r , e r r a t i c v a l u e s become l e s s l i k e l y . The f o l l o w i n g p r o c e d u r e was t h e r e f o r e d e v e l o p e d t o d e t e r m i n e o p t i m a l h y d r a u l i c a l l y e q u i v a l e n t s i z e s . A ssuming no e r r o r s , r e g r e s s i o n s o f l o g CR's o f p e r f e c t l y h y d r a u l i c a l l y e q i v a l e n t 2 m i n e r a l s would p r o d u c e a s l o p e and r v a l u e o f 1 and a y - i n t e r c e p t o f 0. Hence 1:1 r e l a t i o n s h i p s were s o u g h t . A l l e r r o r s were assumed t o l i e w i t h s c h e e l i t e l o g CR's, t h e d e p e n d e n t v a r i a b l e . M i n e r a l s w i t h GMCR's c o m p a r a b l e t o t h o s e o f s c h e e l i t e , and w i t h s t r o n g r e l a t i o n s h i p s w i t h s c h e e l i t e showed t h e most p r o m i s e as h y d r a u l i c a l l y e q u i v a l e n t s t a n d a r d s . L i g h t and mediums were o m i t t e d f r o m c o n s i d e r a t i o n b e c a u s e o f low GMCR's an d / o r c o r r e l a t i o n c o e f f i c e n t s , and t h e two c o a r s e r s c h e e l i t e s i z e s were o m i t t e d b e c a u s e o f h i g h GMCR's. The t h r e e f i n e r s c h e e l i t e s i z e s were r e g r e s s e d on a l l m a g n e t i t e and h e a v i e s s i z e s . S l o p e s (b) o f r e g r e s s i o n s and y - i n t e r c e p t s ( l o g a) were p l o t t e d a g a i n s t m i d - p o i n t s o f 0.5 p h i i n t e r v a l s , and l o g a was t e s t e d a t t h e 95% c o n f i d e n c e l e v e l f o r s i g n i f i c a n t d e p a r t u r e s from 0. R e s u l t s f o r h e a v i e s and m a g n e t i t e a r e r e s p e c t i v e l y g i v e n i n F i g u r e s 28 and 29. In a l l c a s e s , e x c e p t f o r t h e f i n e s t s c h e e l i t e s i z e v e r s u s m a g n e t i t e ( F i g u r e 2 9 a ) , t h e r e i s one s i z e where b p a s s e s t h r o u g h 1 and l o g a i s n o t 9 3 . Figure 28. Slopes (b) and y-intercepts (log a) of scheelite versus heavies log CR regressions; (a) 3.5-4.25 phi scheelite, (b) 3.0-3.5 phi scheelite. 9 4 . 00 ' • S 2.5 3.0 3.S «.iS <t MAS-. 2 0 2 5 3.0 3.S 4.2S 0 h^fr. Figure 2 9 . Slopes (b) and y-intercepts (log,a) of scheelite versus magnetite log CR regressions; (a) 3.5-4.25 phi scheelite, (b) 3.0-3.5 phi scheelite, (c) 2.5-3.0 phi scheelite. 95. s i g n i f i c a n t l y d i f f e r e n t f r o m 0. In a d d i t i o n , l o g a i s g e n e r a l l y c l o s e s t t o 0 when b = l . S l o p e s i n F i g u r e 29a p a s s t h r o u g h 1 a t 2.25 p h i and 2.75 p h i b u t l o g a p a s s e s t h r o u g h 0 c l o s e s t t o 2.75 p h i . I n d i c a t e d h y d r a u l i c a l l y e q u i v a l e n t s i z e s a r e summarized i n T a b l e 16. D i s c u s s i o n As e x p e c t e d , h y d r a u l i c a l l y e q u i v a l e n t s i z e s ( T a b l e 16) i n c r e a s e w i t h i n c r e a s i n g s c h e e l i t e s i z e , and h y d r a u l i c a l l y e q u i v a l e n t m a g n e t i t e i s g e n e r a l l y f i n e r t h a n h y d r a u l i c a l l y e q u i v a l e n t h e a v i e s . In c o n t r a s t , b a s e d on R i t t e n h o u s e ' s r e s u l t s ( T a b l e 3 ) , i t was n o t e x p e c t e d t h a t t h e p h i - d i f f e r e n c e between s c h e e l i t e and h y d r a u l i c a l l y e q u i v a l e n t m i n e r a l s would be so l a r g e , n o r t h a t i t would d e c r e a s e w i t h i n c r e a s i n g s c h e e l i t e s i z e . R a t i o s o f d i a m e t e r s ( i n mm) o f i n d i c a t e d h y d r a u l i c a l l y e q u i v a l e n t m a g n e t i t e and h e a v i e s t o s c h e e l i t e d e c r e a s e , r e s p e c t i v e l y , f r o m 2.9 t o 1.8 and 2.7 t o 2.4 w i t h i n c r e a s i n g s c h e e l i t e s i z e . T h i s i s i n c o n s i s t e n t w i t h s e t t l i n g t h e o r y , b u t S l i n g e r l a n d ' s (1977) e n t r a i n m e n t f u n c t i o n p r e d i c t s t h a t q u a r t z / g a r n e t d i a m e t e r r a t i o s c a n d e c r e a s e a s w e l l as i n c r e a s e w i t h i n c r e a s i n g s i z e . P r e d i c t e d f r e e s e t t l i n g r a t i o s o f m a g n e t i t e and h e a v i e s t o s c h e e l i t e a r e o n l y 1.1 and 1.2, r e s p e c t i v e l y , a s s u m i n g s p h e r e s w i t h Re = 1. Thus, e n t r a i n m e n t r a t h e r t h a n s e t t l i n g e q u i v a l e n c e i s s u g g e s t e d . HYDRAULICALLY EQUIVALENT SIZES SCHEELITE MAGNETITE HEAVIES DIAMETER DIAMETER RATIO DIAMETER RATIO phi mm phi mm mm/mm phi mm mm/mm 3.9 0.07 2.3 0.20 2.9 2.4 0.19 2.7 3.3 0.11 2.1 0.24 2.2 1.9 0.26 2.4 2.8 0.15 1.9 0.27 1.8 T a b l e 16. H y d r a u l i c a l l y e q u i v a l e n t s i z e s i n d i c a t e d by r e g r e s s i o n s of c o n c e n t r a t i o n r a t i o s ; a l s o , d i a m e t e r r a t i o s o f i n d i c a t e d h y d r a u l i c a l l y e q u i v a l e n t m i n e r a l and s c h e e l i t e . 97. I n d i c a t e d h y d r a u l i c a l l y e q u i v a l e n t s i z e s were r o u n d e d t o the n e a r e s t 0.5 p h i i n t e r v a l f o r c o n v e n i e n c e i n c a l c u l a t i n g h y d r a u l i c a l l y e q u i v a l e n t c o n c e n t r a t i o n s . F o r example, 3.0-3.5 p h i s c h e e l i t e i s assumed t o be h y d r a u l i c a l l y e q u i v a l e n t t o 1.5-2.0 p h i h e a v i e s (1.5 p h i c o a r s e r ) r a t h e r t h a n h e a v i e s 1.3 p h i c o a r s e r . The two f i n e s t h y d r a u l i c a l l y e q u i v a l e n t m a g n e t i t e s i z e s were r o u n d e d f i n e r , and c o a r s e s t m a g n e t i t e and b o t h h e a v i e s s i z e s were r o u n d e d c o a r s e r . I f two h y d r a u l i c a l l y e q u i v a l e n t m i n e r a l s a r e r a t i o e d , t h e n p o s i t i v e and n e g a t i v e l o g CR's s h o u l d o c c u r w i t h a p p r o x i m a t e l y e q u a l f r e q u e n c y , and t h i s p r o v i d e s a means o f v e r i f y i n g r e s u l t s . Numbers o f p o s i t i v e and n e g a t i v e l o g CR's ( T a b l e 17: ) a r e a p p r o x i m a t e l y e q u a l f o r a l l r o u n d e d h y d r a u l i c a l l y e q u i v a l e n t s i z e s e x c e p t 2.5-3.0 p h i s c h e e l i t e / 1 . 5 - 2 . 0 p h i m a g n e t i t e . I n t h e l a t t e r c a s e , t h e r a t i o o f 15/9 s u g g e s t s " u n d e r c o m p e n s a t i o n " by m a g n e t i t e . The a p p a r e n t u n d e r e s t i m a t i o n o f t h e m a g n e t i t e s i z e w h i c h i s h y d r a u l i c a l l y e q u i v a l e n t t o 2.5-3.0 p h i s c h e e l i t e m i g h t be due t o a p o o r f i t o f t h e f u n c t i o n t o t h e r e g r e s s i o n m o d e l . U s i n g t h e D u r b i n Watson s t a t i s t i c ( d ) , t h e n u l l h y p o t h e s i s (H Q) t h a t a u t o c o r r e l a t i o n i s a b s e n t was t e s t e d a t t h e 0.05 s i g n i f i c a n c e l e v e l . H Q was i n c o n c l u s i v e and r e j e c t e d f o r r e g r e s s i o n s o f 2.5-3.0 p h i s c h e e l i t e on 1.5-2.0 p h i and 2.0-2.5 p h i m a g n e t i t e , and was n o t r e j e c t e d f o r a l l o t h e r r e g r e s s i o n s . T h u s , as i s s u p p o r t e d by i t s r e l a t i v e l y h i g h GMCR o f 3.3, 2.5-3.0 p h i s c h e e l i t e i s h y d r a u l i c a l l y e q u i v a l e n t t o none o f t h e s i z e s o f o t h e r m i n e r a l s a n a l y z e d . INDICATED HYDRAULICALLY EQUIVALENT SIZE ROUNDED RATIO OF TO NEAREST HALF-PHI POSITIVE/NEGATIVE INTERVAL LOG CR'S 2.5-3.0 PHI SCHEELITE/ 1 5 / 9 1.5-2.0 PHI MAGNETITE 3.0-3.5 PHI SCHEELITE/ 13 / 11 2.0-2.5 PHI MAGNETITE 3.5-4.25 PHI SCHEELITE/ 11 / 13 2.5-3.0 PHI MAGNETITE 3.0-3.5 PHI SCHEELITE/ 13 / 11 1.5-2.0 PHI HEAVIES 3.5-4.25 PHI SCHEELITE/ 12 / 12 2.0-2.5 PHI HEAVIES T a b l e 17. R a t i o s o f p o s i t i v e t o n e g a t i v e l o g CR's f o r i n d i c a t e d s i z e s of h y d r a u l i c a l l y e q u i v a l e n t m i n e r a l s . CHAPTER 6 DISCUSSION 100. INTRODUCTION On t h e b a s i s o f t h e p r e c e d i n g C h a p t e r s , h y d r a u l i c b e h a v i o r o f m i n e r a l s i s d i s c u s s e d w i t h r e f e r e n c e t o d e p a r t u r e s from h y d r a u l i c e q u i v a l e n c e , downstream p r o f i l e s o f h y d r a u l i c a l l y e q u i v a l e n t c o n c e n t r a t i o n s , i n t e r p r e t a t i o n o f s o u r c e e f f e c t s , and a p p l i c a t i o n t o e x p l o r a t i o n . DEPARTURES FROM HYDRAULIC EQUIVALENCE V a r i a t i o n o f 3.0-3.5 p h i and 3.5-4.25 p h i s c h e e l i t e l o g CR's e x p l a i n e d by l o g CR's o f a d j a c e n t s c h e e l i t e s i z e s i s 88% and 79%, r e s p e c t i v e l y . L e s s v a r i a t i o n i s e x p l a i n e d by l o g CR's o f t h e c l o s e s t h y d r a u l i c a l l y e q u i v a l e n t m i n e r a l s . By i n f e r e n c e f r o m raw w e i g h t s o f m i n e r a l s ( A p p e n d i x 1 ) , numbers o f s c h e e l i t e g r a i n s a r e much l e s s t h a n t h o s e o f o t h e r m i n e r a l s , and, h e n c e , t h e o r e t i c a l s a m p l i n g e r r o r s o f s c h e e l i t e a r e much g r e a t e r t h a n t h o s e o f o t h e r m i n e r a l s . T h e r e f o r e , 2 d i f f e r e n c e s between r v a l u e s o f t h e most s t r o n g l y c o r r e l a t i v e a d j a c e n t s c h e e l i t e s i z e and o f h y d r a u l i c a l l y e q u i v a l e n t s t a n d a r d s must r e p r e s e n t e i t h e r v e r y l o c a l i z e d s o u r c e e f f e c t s o r u n e x p l a i n e d h y d r a u l i c v a r i a t i o n . However, t h e s e d i f f e r e n c e s i n c r e a s e w i t h g r a i n s i z e ( T a b l e 1 8 ) , and, b a s e d on p r e v i o u s o b s e r v a t i o n s ( e . g . T a b l e 1 4 ) , as g r a i n s i z e i n c r e a s e s , h y d r a u l i c e f f e c t s s h o u l d a c c o u n t f o r r e l a t i v e l y more o f t h e t o t a l v a r i a t i o n t h a n s o u r c e e f f e c t s . Thus, much o f t h e u n e x p l a i n e d v a r i a t i o n i s due t o d e p a r t u r e s f r o m R-SQUARED VALUES OF ADJACENT SCHEELITE SIZES 3.5-4.25 PHI SCHEELITE/ 7955 3.0-3.5 PHI SCHEELITE 3.0-3.5 PHI SCHEELITE/ 88% 2.5-3.0 PHI SCHEELITE R-SQUARED VALUE OF HYDRAULICALLY EQUIVALENT MINERALS 3.5-4.25 PHI SCHEELITE/ 6755 3.0-3.5 PHI MAGNETITE 3.0-3.5 PHI SCHEELITE/ 665? 2.5-3.0 PHI MAGNETITE 3.5-4.25 PHI SCHEELITE/ 4555 2.0-2.5 PHI HEAVIES 3.0-3.5 PHI SCHEELITE/ 5055 1.5-2.0 PHI HEAVIES DIFFERENCE BETWEEN R-SQUARED VALUES OF ADJACENT SCHEELITE SIZE AND HYDRAULICALLY EQUIVALENT MINERAL 1255 2255 3455 3855 Table 18. D i f f e r e n c e between r-squared values of adjacent s c h e e l i t e s i z e and h y d r a u l i c a l l y e q u i v a l e n t m i n e r a l . 102. h y d r a u l i c e q u i v a l e n c e , and t h e s e d e p a r t u r e s i n c r e a s e w i t h s i z e as w e l l a s s i z e and d e n s i t y d i f f e r e n c e . U n d e r l y i n g r e a s o n s f o r d e p a r t u r e f r o m h y d r a u l i c e q u i v a l e n c e must be examined. The most d r a m a t i c d e p a r t u r e from h y d r a u l i c e q u i v a l e n c e i s e v i d e n t between 3.5 t o 4.25 p h i s c h e e l i t e and -1.0 p h i t o -0.5 p h i s i e v e d s e d i m e n t s , w h i c h have s i m i l a r GMCR's o f 1.5 and 1.4 ( T a b l e 1 4 ) , r e s p e c t i v e l y , b u t a c o r r e l a t i o n c o e f f i c i e n t o f o n l y 0.29. Much c a n be s u r m i s e d o f t h e h y d r a u l i c b e h a v i o r o f s i e v e d s e d i m e n t s f r o m t h e c a l c u l a t i o n s used t o p r o d u c e T a b l e s 13 and 14. I n d i v i d u a l CR's i n minus 10-mesh s e d i m e n t s ( C R 1 Q ) were r e c a l c u l a t e d f r o m CR's i n h a l f - p h i s i e v e d s e d i m e n t s ( C R - ^ ) u s i n g t h e f o l l o w i n g c o r r e c t i o n f a c t o r : n p l O " I r p 10 ~ c " K l / 2 L U 10. . S-, ' h i l o where 1 0 ^ Q , 1 0 ^ , S ^ Q and a r e w e i g h t s o f minus 10-mesh s e d i m e n t s i n low and h i g h e n e r g y e n v i r o n m e n t s and o f a g i v e n 0.5 p h i s i z e i n t e r v a l o f s e i v e d s e d i m e n t s i n low and h i g h e n e r g y e n v i r o n m e n t s , r e s p e c t i v e l y . However, c o a r s e l i g h t s c o m p r i s e t h e b u l k o f , and a r e e f f e c t i v e l y r e p r e s e n t e d by minus 10-mesh s e d i m e n t s , whereas 1.5-2.0 p h i t h r o u g h 3.5-4.25 p h i s i e v e d s e d i m e n t s r e p r e s e n t f i n e l i g h t s . Thus, c h a n g e s i n GMCR's f r o m h a l f - p h i s i e v e d s e d i m e n t s ( T a b l e 13) t o minus 10-mesh s e d i m e n t s ( T a b l e 14) a r e e n t i r e l y due t o v a r i a t i o n s i n r e l a t i v e s i z e d i s t r i b u t i o n s o f s i e v e d s e d i m e n t s between h i g h 1 0 3 . and low e n e r g y e n v i r o n m e n t s . GMCR's a r e t h e r e f o r e l o w e r i n minus 10-mesh s e d i m e n t s ( T a b l e 14) t h a n h a l f - p h i s i e v e d s e d i m e n t s ( T a b l e 1 3 ) , b e c a u s e c o a r s e l i g h t s a r e e n r i c h e d r e l a t i v e t o f i n e l i g h t s i n h i g h e n e r g y e n v i r o n m e n t s , t h e r e b y d i l u t i n g h i g h e n e r g y c o n c e n t r a t i o n s o f o t h e r m i n e r a l s . As would be a n t i c i p a t e d , i n d i v i d u a l CR's g e n e r a l l y f o l l o w t h e GMCR's i n d e c r e a s i n g i n minus 10-mesh compared t o h a l f - p h i s i e v e d s e d i m e n t s . T h e r e a r e , however, e x c e p t i o n s ( T a b l e 1 9 ) . In g e n e r a l , low CR's i n h a l f - p h i s e d i m e n t s d e c r e a s e i n minus 10-mesh s e d i m e n t s , whereas h i g h CR's i n c r e a s e . Thus, a l t h o u g h GMCR's a r e l o w e r i n minus 10-mesh t h a n h a l f - p h i s e d i m e n t s , maximum CR's i n c r e a s e , w i t h o u t e x c e p t i o n ( T a b l e 2 0 ) . F o r example, i n t h e most ex t r e m e c a s e , t h e maximum 2.5-3.0 p h i s c h e e l i t e CR i n c r e a s e s f r o m 26 t o 100. In a d d i t i o n , t h r e e o f the n e x t f o u r h i g h e s t 2.5-3.0 p h i s c h e e l i t e CR's i n c r e a s e f r o m 12, 11 and 9 t o 27, 29 and 25, r e s p e c t i v e l y . These u n u s u a l i n c r e a s e s i n CR's p r o v i d e e v i d e n c e a s t o some o f t h e f a c t o r s i n v o l v e d i n d e p a r t u r e s f r o m h y d r a u l i c e q u i v a l e n c e . H i g h e s t CR's become g r e a t e r i n minus 10-mesh s e d i m e n t s b e c a u s e , i n t h e s e few c a s e s , c o a r s e / f i n e l i g h t s r a t i o s a r e l o w e r i n h i g h t h a n low e n e r g y s a m p l e s . C o n t r o l l i n g f a c t o r s c o u l d l i e w i t h c o a r s e o r f i n e l i g h t s o r h i g h o r low e n e r g y s a m p l e s . However, h i g h e s t CR's c o r r e s p o n d t o h i g h e s t h i g h - e n e r g y and n o t t o l o w e s t l o w - e n e r g y c o n c e n t r a t i o n s . F o r example, t h e f i v e h i g h e s t 2.5-3.0 p h i s c h e e l i t e / 2 . 5 - 3 . 0 p h i s i e v e d CR's c o r r e s p o n d t o SIZE INTERVAL - PHI 1.5-2.0 2.0-2.5 2.5-3.0 3.0-3.5 3.5-4.25 INCREASE: 8 10 8 7 8 DECREASE: 16 14 16 17 16 T a b l e 19. Numbers of CR's which i n c r e a s e or d e c r e a s e when r e c a l c u l a t e d from h a l f - p h i t o minus 10-mesh s e d i m e n t s . FRACTION GRAIN SIZE - PHI 1.5-2.0 2.0-2.5 2.5-3.0 3.0-3.5 3.5-4.25 SCHEELITE MAGNETITE HEAVIES MEDIUMS 63 / 76 36 / 41 9.2 / 24 1.9 / 4.8 40 / 85 6.2 / 18 7.1 / 21 2.1 / 6.1 26 / 100 6.9 / 18 3.0 / 9.4 2.0 / 5.2 15 / 52 9.4 / 19 2.3 / 9.4 3.5 / 14 9.6 / 20 6.3 / 12 6.2 / 8.0 22 / 26 T a b l e 20. Maximum CR's i n h a l f - p h i s i e v e d / minus 10 mesh-sediments. 106. f o u r o f t h e f i v e h i g h e s t h i g h - e n e r g y c o n c e n t r a t i o n s . T h e r e i s l i t t l e r e a s o n t o s u s p e c t t h a t f i n e l i g h t s were more e a s i l y d e p o s i t e d t h a n c o a r s e l i g h t s o n l y i n v e r y h i g h e n e r g y e n v i r o n m e n t s . More p r o b a b l y , t h e few f i n e l i g h t s d e p o s i t e d r e m a i n e d b e c a u s e t h e y were s h i e l d e d , w h i l e c o a r s e l i g h t s were r e e n t r a i n e d t o p r o d u c e a h e a v i e s - r i c h d e p o s i t ( F i g u r e 3 0 ) . S h i e l d i n g o f f i n e by c o a r s e g r a i n s has o f t e n been d e s c r i b e d ( e . g . B r a d y and J o b s o n , 1 9 7 3 ) . I f c o a r s e l i g h t s were s e l e c t i v e l y r e e n t r a i n e d , t h e n t h e y would no l o n g e r be h y d r a u l i c a l l y e q u i v a l e n t t o f i n e r s c h e e l i t e g r a i n s w h i c h r e m a i n e d b e h i n d . T h i s may a l s o e x p l a i n t h e p r o g r e s s i v e l y s m a l l e r d e p a r t u r e s f r o m h y d r a u l i c e q u i v a l e n c e o f h e a v i e s and m a g n e t i t e f r o m s c h e e l i t e . S i m i l a r d e p a r t u r e s f r o m h y d r a u l i c e q u i v a l e n c e s h o u l d n o t o c c u r and a r e n o t o b s e r v e d i n low e n e r g y e n v i r o n m e n t s , b e c a u s e winnowing i n s u c h e n v i r o n m e n t s i s m i n i m a l . I t i s t h e r e f o r e p o s s i b l e t h a t , i n low e n e r g y e n v i r o n m e n t s , s c h e e l i t e g r a i n s may be h y d r a u l i c a l l y e q u i v a l e n t t o much c o a r s e r mediums o r l i g h t s . U n f o r t u n a t e l y , t h e d a t a a r e i n s u f f i c i e n t t o t e s t t h i s h y p o t h e s i s . H y d r a u l i c v a r i a b i l i t y i n low e n e r g y e n v i r o n m e n t s must, i n l a r g e p a r t , be r e l a t e d t o t h e r e l a t i v e amounts o f v a r i o u s s i z e s o f m i n e r a l s t r a n s p o r t e d i n t o s l o w i n g w a t e r . In t h e most e x t r e m e example, numbers o f 2.0-2.5 p h i s c h e e l i t e g r a i n s a r e 0 and 388 i n low and h i g h e n e r g y s a m p l e s 71 and 72, r e s p e c t i v e l y . S c h e e l i t e g r a i n s between 1.5 and 2.0 p h i a r e 107. T U R B U L E N T I N T E R S T I C E , B E T W E E N BOVJLOCai OR. COtSOLCS WTDE. b!7.E. RftN(a-a OF M I N E R A L S DE.POilTE.0 IN INTERSTICE-I H E A V Y Q . U A R T Z - D E . r t S I T Y W I T H E A C H P R O T R U D I N G C O A R S E . L I G H T — M I N E R A L R £ M O V E D , T H E H E A V Y / L I G H T W E I G H T - R A T I O G R E A T L Y I N C R E A S E S . Figure 30. Model for formation of heavies-rich deposits in high energy environments, through selective reentrainment of coarse lights. 108. a l s o a b s e n t f r o m sample 71. Thus, e i t h e r no c o a r s e s c h e e l i t e g r a i n s were t r a n s p o r t e d i n t o sample l o c a t i o n 71, o r , on a v e r a g e , v e r y few s u c h g r a i n s were c a r r i e d i n w i t h e v e r y 10 kg ( i . e . t h e a p p r o x i m a t e w e i g h t o f sample 71) o f minus 10-mesh s e d i m e n t s . In e i t h e r c a s e , s c a r c i t y o f c o a r s e s c h e e l i t e i n a few v e r y low e n e r g y e n v i r o n m e n t s may be a n a l a g o u s t o s c a r c i t y o f c o b b l e s i n most low e n e r g y e n v i r o n m e n t s . J u s t a s t h e s t r e a m c l e a r l y l a c k s t h e e n e r g y t o t r a n s p o r t c o b b l e s i n t o low e n e r g y s i t e s , i t may a l s o l a c k e n e r g y t o c a r r y c o a r s e s c h e e l i t e i n t o l o w e s t e n e r g y s i t e s . In t h e ext r e m e c a s e , n e a r - s t a g n a n t embayments c o n t a i n i n g o r g a n i c muds a r e p r o b a b l y d e v o i d o f e v e n r e l a t i v e l y f i n e s c h e e l i t e . Thus, i n low e n e r g y e n v i r o n m e n t s , d e p o s i t i o n a l f a c t o r s have a major i n f l u e n c e on s c h e e l i t e c o n c e n t r a t i o n s , and v e r y low as w e l l as v a r i a b l e c o n c e n t r a t i o n s may r e s u l t . C o n v e r s e l y , i n h i g h e n e r g y e n v i r o n m e n t s , e r o s i o n a l f a c t o r s become more i m p o r t a n t , and, a l t h o u g h s c h e e l i t e g r a i n s a r e more a b u n d a n t , t h e p o t e n t i a l f o r h y d r a u l i c v a r i a b i l i t y becomes g r e a t e r . DOWNSTREAM PROFILES OF HYDRAULICALLY EQUIVALENT CONCENTRATIONS CR's i n c r e a s e down Omo C r e e k ( F i g u r e 31) and t h e P e l l y R i v e r , i n d i c a t i n g t h a t s o r t i n g i s o n g o i n g w i t h t r a n s p o r t d i s t a n c e . T h i s o f f e r s a f u r t h e r means t o v e r i f y t h a t 110. i n d i c a t e d s i z e s a r e h y d r a u l i c a l l y e q u i v a l e n t . A l t h o u g h a p p r o x i m a t e l y e q u a l numbers o f h i g h v e r s u s low e n e r g y h y d r a u l i c a l l y e q u i v a l e n t c o n c e n t r a t i o n s a r e h i g h e r i n T a b l e 17, r a d i c a l d e p a r t u r e s f r o m h y d r a u l i c e q u i v a l e n c e t h r o u g h u n d e r c o m p e n s a t i o n o r o v e r c o m p e n s a t i o n s h o u l d r e s u l t i n p r o g r e s s i v e l y h i g h e r o r l o w e r c o n c e n t r a t i o n s , r e s p e c t i v e l y , i n h i g h t h a n low e n e r g y e n v i r o n m e n t s downstream. Thus downstream p l o t s o f h y d r a u l i c a l l y e q u i v a l e n t c o n c e n t r a t i o n s must be i n s p e c t e d f o r s u c h t r e n d s . P r o f i l e s down t h e P e l l y R i v e r and Omo C r e e k o f h y d r a u l i c a l l y e q u i v a l e n t c o n c e n t r a t i o n s a r e shown i n F i g u r e s 32 t o 35 and F i g u r e s 36 t o 39, r e s p e c t i v e l y . Compared t o s c h e e l i t e / h e a v i e s p l o t s i n F i g u r e s 22 and 23, h i g h and low e n e r g y h y d r a u l i c a l l y e q u i v a l e n t c o n c e n t r a t i o n s show much c l o s e r a g r e e m ent, and s y s t e m a t i c d e p a r t u r e s downstream a r e n o t e v i d e n t . In F i g u r e 22, f o r example, a v e r a g e c o n c e n t r a t i o n s o f h i g h e n e r g y d u p l i c a t e s a r e much h i g h e r t h a n t h o s e o f low e n e r g y d u p l i c a t e s a t t h e two l o w e r s i t e s , CB and CH. C o n v e r s e l y , i n F i g u r e 32, a l l h i g h e n e r g y d u p l i c a t e s a r e b r a c k e t e d by low e n e r g y d u p l i c a t e s , and s i m i l a r a v e r a g e c o n c e n t r a t i o n s a r e e s t i m a t e d , i n s p i t e o f g r e a t d i s p a r i t i e s i n e n e r g y environments.. In a d d i t i o n , d i f f e r e n c e s between h i g h and low e n e r g y c o n c e n t r a t i o n s a t s i n g l e sample s i t e s CD and CP a r e much g r e a t e r i n F i g u r e 23 t h a n F i g u r e 32. Figure 32. 3.0-3.5 phi/1.5-2.0 phi heavies on the Pelly River. 10 /oo * - HIGH ENERGY O - LOW ENERGY A k M Figure 33. 3.5-4.25 phi scheelite/2.0-2.5 phi heavies on the Pelly River. 11.4. 00 o 119. A l t h o u g h t h e r e i s no s y s t e m a t i c d i v e r g e n c e f r o m h y d r a u l i c e q u i v a l e n c e w i t h t r a n s p o r t d i s t a n c e , t h e r e i s a l a r g e d i s c r e p a n c y between low and h i g h e n e r g y s a m p l e s 79 and 80, r e s p e c t i v e l y , a t s i t e CM on t h e P e l l y R i v e r . The r e a s o n f o r t h i s i s o l a t e d d i s c r e p a n c y i s unknown, b u t t h e s a m p l e s a r e u n u s u a l i n t h a t t h e y were c o l l e c t e d f r o m a l o n g n a r r o w b r a i d a r o u n d an i s o l a t e d g r a v e l b a r , due t o a l a c k o f s u i t a b l e s i t e s a l o n g s e v e r a l k i l o m e t e r s o f t h e main c h a n n e l . VARIABILITY WITHIN SITES F o r e g o i n g CV r e s u l t s ( C h a p t e r 5) show t h a t v a r i a b i l i t y w i t h i n many d u p l i c a t e s i t e s i s n o t r e d u c e d u s i n g h y d r a u l i c a l l y e q u i v a l e n t c o n c e n t r a t i o n s . S i n c e h y d r a u l i c e f f e c t s a r e r e d u c e d as c o r r e l a t e d l o g CR's o f m i n e r a l s become s i m i l a r i n m a g n i t u d e , much o f t h e t o t a l v a r i a b i l i t y w i t h i n d u p l i c a t e s i t e s must be due t o s a m p l i n g e r r o r s , uncompensated h y d r a u l i c v a r i a t i o n , a n d / o r l o c a l s o u r c e e f f e c t s . These c a u s e s o f v a r i a t i o n must be examined t o b e t t e r i n t e r p r e t s o u r c e e f f e c t s between s i t e s . G r e a t e r s p r e a d o f low t h a n h i g h e n e r g y d u p l i c a t e s i n downstream p r o f i l e s o f h y d r a u l i c a l l y e q u i v a l e n t c o n c e n t r a t i o n s d e m o n s t r a t e s t h e h i g h e r s a m p l i n g e r r o r s a s s o c i a t e d w i t h fewer s c h e e l i t e g r a i n s . A b s o l u t e numbers o f s c h e e l i t e g r a i n s ( A p p e n d i x 1) show t h a t s a m p l e s f r o m t h e P e l l y R i v e r g e n e r a l l y c o n t a i n fewer s c h e e l i t e g r a i n s t h a n s a m p l e s from Omo C r e e k . 120. T h e r e f o r e , s c h e e l i t e s a m p l i n g e r r o r s a l o n g t h e P e l l y R i v e r a r e examined as a w o r s t c a s e . Mean and median numbers o f s c h e e l i t e g r a i n s i n P e l l y R i v e r s a m p l e s a r e summarized i n T a b l e 21. H i g h e n e r g y samples c o n t a i n s e v e r a l t i m e s more g r a i n s t h a n low e n e r g y s a m p l e s , and c o a r s e r s i z e s c o n t a i n fewer g r a i n s . Mean and median v a l u e s i n d i c a t e t h a t r e s u l t s a r e p o s i t i v e l y skewed, and t h a t a l a r g e number o f s a m p l e s c o n t a i n r e l a t i v e l y few g r a i n s . T h e o r e t i c a l s a m p l i n g p r e c i s i o n s o f P e l l y R i v e r s a m p l e s ( T a b l e 2 2 ) , b a s e d on t h e i r median numbers o f s c h e e l i t e g r a i n s , were e s t i m a t e d u s i n g t h e e q u a t i o n on page 4. P r e c i s i o n i s p o o r e r i n low e n e r g y e n v i r o n m e n t s and becomes worse w i t h i n c r e a s i n g g r a i n s i z e . F o r example, p r e c i s i o n o f 3.0-3.5 p h i s c h e e l i t e i s 10% and 30% i n h i g h and low e n e r g y s a m p l e s , r e s p e c t i v e l y . T h i s i s c o n s i s t e n t w i t h o b s e r v e d r e s u l t s . H i g h s a m p l i n g e r r o r s f o r s c h e e l i t e i n low e n e r g y e n v i r o n m e n t s may p a r t l y e x p l a i n why CR's a r e n o t a l w a y s l o w e r f o r h y d r a u l i c a l l y e q u i v a l e n t s i z e s . Thus, i f h i g h e n e r g y d u p l i c a t e s a r e b r a c k e t e d by w i d e l y s e p a r a t e d low e n e r g y d u p l i c a t e s , r e d u c t i o n o f h y d r a u l i c e f f e c t s c a n r e s u l t i n b e t t e r a g r e e m e n t o f a v e r a g e c o n c e n t r a t i o n s o f d u p l i c a t e s , w i t h o u t a s i g n i f i c a n t r e d u c t i o n o f t h e CV. F o r example, low e n e r g y d u p l i c a t e s a t s i t e CH a c c o u n t f o r most o f t h e v a r i a b i l i t y o f b o t h 3.0-3.5 p h i s c h e e l i t e / 3 . 0 - 3 . 5 p h i h e a v i e s ( F i g u r e 2 2 ) , w h i c h a r e n o t h y d r a u l i c a l l y e q u i v a l e n t , and 3.0-3.5 p h i s c h e e l i t e / 1 . 5 - 2 . 0 p h i h e a v i e s ( F i g u r e 3 2 ) , which 121. ENERGY SIZE INTERVAL - PHI ENVIRONMENT 1.5-2.0 2.0-2.5 2.5-3.0 3.0-3.5 3.5-4.25 HIGH 43 / 35 133 / 99 361 / 278 692 / 352 757 / 463 LOW 6 / 4 1 3 / 5 5 6 / 2 1 190 / 43 346 / 83 T a b l e 21. Mean / median numbers of s c h e e l i t e g r a i n s i n sediment samples from t h e P e l l y R i v e r . 122. ENERGY SIZE INTERVAL - PHI ENVIRONMENT 1.5-2.0 2.0-2.5 2.5-3.0 3.0-3.5 3.5-4.25 HIGH 34 20 12 10 10 LOW 100 90 44 30 22 T a b l e 22. S a m p l i n g p r e c i s i o n s ( %) a s s o c i a t e d w i t h median numbers of s c h e e l i t e g r a i n s ( T a b l e 21) i n s e d i m e n t samples from t h e PeI Iy R i v e r . 123. a r e h y d r a u l i c a l l y e q u i v a l e n t . S c h e e l i t e s a m p l i n g e r r o r s , however, c l e a r l y do n o t e x p l a i n a l l o f t h e v a r i a t i o n o f W o r s c h e e l i t e c o n c e n t r a t i o n s , and h e n c e , o f CV's. I n t h o s e c a s e s where CV's a r e h i g h l y v a r i a b l e , b u t a r e n o t m i n i m i z e d a t t h e h y d r a u l i c a l l y e q u i v a l e n t s i z e , d e p a r t u r e s f r o m h y d r a u l i c e q u i v a l e n c e may be a c o n t r i b u t i n g f a c t o r . I n a d d i t i o n , downstream p l o t s o f CR's ( F i g u r e 30) show t h a t s o u r c e e f f e c t s p r e v a i l u p s t r e a m , and a r e g r a d u a l l y s u p e r c e d e d downstream by h y d r a u l i c e f f e c t s . V a r i a b l e s c h e e l i t e c o n c e n t r a t i o n s n e a r h e a d w a t e r s s u g g e s t t h a t t h e s e immature s t r e a m s e d i m e n t s a r e n o t a w e l l mixed c o m p o s i t e o f p r o d u c t s o f w e a t h e r i n g u p s t r e a m o f t h e sample s i t e . INTERPRETATION OF SOURCE EFFECTS I n t r o d u c t i o n R e d u c t i o n o f h y d r a u l i c e f f e c t s and a s s e s s m e n t o f v a r i a b i l i t y w i t h i n s i t e s f a c i l i t a t e i n t e r p r e t a t i o n o f s o u r c e e f f e c t s w i t h i n s i t e s . However, i t s h o u l d be n o t e d t h a t t h e a s s o c i a t i o n o f heavy m i n e r a l s w i t h s c h e e l i t e a t t h e C l e a d e p o s i t may c o m p l i c a t e i n t e r p r e t a t i o n s . Due t o b e t t e r p r e c i s i o n o f h i g h t h a n low e n e r g y c o n c e n t r a t i o n s , e m p h a s i s i s p l a c e d on t h e f o r m e r . 124. P e l l y R i v e r The P e l l y R i v e r , where p r o f i l e s o f s c h e e l i t e c o n c e n t r a t i o n s which a r e h y d r a u l i c a l l y e q u i v a l e n t ( F i g u r e s 32 t o 35) and a r e n o t h y d r a u l i c a l l y e q u i v a l e n t ( F i g u r e 22) a r e s u b s t a n t i a l l y d i f f e r e r e n t , i s e v a l u a t e d f i r s t . As a l r e a d y n o t e d , s c h e e l i t e / h e a v i e s c o n c e n t r a t i o n s i n h i g h e n e r g y e n v i r o n m e n t s ( F i g u r e 22) a r e l o w e s t n e a r e r t h e C l e a d e p o s i t . C o n v e r s e l y , e x c e p t i n g sample 80 a t s i t e CM, h y d r a u l i c a l l y e q u i v a l e n t s c h e e l i t e c o n c e n t r a t i o n s a r e h i g h e s t n e a r e s t t h e C l e a d e p o s i t , a t s i t e 1234 ( F i g u r e s 32 t o 3 5 ) . D i s t i n c t p e a k s a r e o b s e r v e d a t t h r e e s i t e s i n most p r o f i l e s o f h y d r a u l i c a l l y e q u i v a l e n t s c h e e l i t e c o n c e n t r a t i o n s i n h i g h e n e r g y e n v i r o n m e n t s , a l t h o u g h t h e s e p e a k s d i f f e r i n m a g n i t u d e between p l o t s . The p e a k s o c c u r a t s i t e 1234 on C l e a C r e e k , s i t e CD above the Omo o u t l e t , and f a r downstream a t s i t e CM. The h i g h s c h e e l i t e c o n c e n t r a t i o n i n C l e a Creek i s c l e a r l y due t o t h e C l e a d e p o s i t . GSC Open F i l e R e p o r t 20 (1981) , r e l e a s e d d u r i n g t h i s s t u d y , r e v e a l s a n o m a l o u s l y h i g h W c o n c e n t r a t i o n s i n t h e s t r e a m marked W i n F i g u r e 12, and P l a c e r D e velopment L i m i t e d h a s t r a c e d t h i s anomaly t o s c h e e l i t e - b e a r i n g f l o a t b o r d e r i n g t h e C r e t a c e o u s q u a r t z m o n z o n i t e t o t h e e a s t ( I . Thomson, p e r s . comm., 1 9 8 4 ) . On t h i s b a s i s , i t i s i m p o r t a n t t o n o t e t h a t i n the o r i g i n a l s c h e e l i t e / h e a v i e s d a t a ( F i g u r e 2 2 ) , W c o n c e n t r a t i o n s a t s i t e CD a r e a p p a r e n t l y low, p a r t i c u l a r l y i n t h e c o a r s e r 125. s i z e f r a c t i o n s ( i . e . t h e anomalous s o u r c e i n s t r e a m W would n o t have been r e c o g n i z e d by s a m p l i n g t h e P e l l y R i v e r u n l e s s h y d r a u l i c a l l y e q u i v a l e n t s t a n d a r d s were u s e d ) . The peak a s s o c i a t e d w i t h h i g h e n e r g y sample 80 a t s i t e CM r e m a i n s i n e x p l i c a b l e , b u t i s n o t b e l i e v e d t o be s i g n i f i c a n t due t o t h e l a c k o f s i m i l a r r e s p o n s e by sample 79 and t h e u n u s u a l s i t e l o c a t i o n . In s p i t e o f s c h e e l i t e i n p u t f r o m Omo C r e e k , h y d r a u l i c a l l y e q u i v a l e n t c o n c e n t r a t i o n s a r e l o w e r a t s i t e CE t h a n s i t e CD, r e s p e c t i v e l y , b elow and above t h e O m o / P e l l y j u n c t i o n ( F i g u r e s 32 t o 3 5 ) . A p o s s i b l e e x p l a n a t i o n i s t h a t a b s o l u t e amounts o f s c h e e l i t e c o n t r i b u t e d f r o m Omo C r e e k a r e i n s u f f i c i e n t t o i n c r e a s e c o n c e n t r a t i o n s h i g h e r t h a n t h e a l r e a d y h i g h v a l u e s a t s i t e CD. H y d r a u l i c a l l y e q u i v a l e n t c o n c e n t r a t i o n s a r e 1.3-1 . 4 t i m e s h i g h e r a t s i t e CLR (on l o w e r Omo C r e e k ) t h a n s i t e CD, b u t t h e e n t i r e Omo d r a i n a g e a r e a i s o n l y o n e - f i f t h as l a r g e a s t h e d r a i n a g e a r e a above CD. Omo C r e e k H y d r a u l i c a l l y e q u i v a l e n t c o n c e n t r a t i o n s i n a l l h i g h and most low e n e r g y p l o t s i n i t i a l l y d r o p and t h e n i n c r e a s e down Omo C r e e k ( e . g . F i g u r e 3 6 ) , and o n l y 3.0-3.5 p h i s c h e e l i t e / 2 . 0 - 2 . 5 p h i m a g n e t i t e c o n c e n t r a t i o n s a r e g r e a t e s t a t t h e h e a d w a t e r s ( F i g u r e 3 8 ) . The downstream i n c r e a s e i n most h y d r a u l i c a l l y e q u i v a l e n t p r o f i l e s i s 126. r e l a t i v e l y s t e a d y , s u g g e s t i n g c o n s t a n t i n p u t o f s c h e e l i t e . The s i m p l e s t e x p l a n a t i o n i s t h a t s c h e e l i t e m i g h t be a b u n d a n t , r e l a t i v e t o h y d r a u l i c a l l y e q u i v a l e n t s t a n d a r d s , i n g l a c i a l t i l l s a l o n g t h e banks o f Omo C r e e k and i t s t r i b u t a r i e s . Summary o f i n t e r p r e t a t i o n s o f h y d r a u l i c a l l y e q u i v a l e n t  p r o f i l e s In summary, two s c h e e l i t e s i z e f r a c t i o n s , e a c h r a t i o e d t o two h y d r a u l i c a l l y e q u i v a l e n t s t a n d a r d s , and d u p l i c a t e s a m p l i n g p r o v i d e a d e q u a t e c o n t r o l on v a r i a t i o n w i t h i n s i t e s . R e s u l t i n g d i s p e r s i o n p r o f i l e s a r e complex, and do n o t f o l l o w s i m p l e d i l u t i o n c u r v e s . Samples a l o n g t h e P e l l y R i v e r d e m o n s t r a t e t h a t W a n o m a l i e s a r e more r e a d i l y t r a c e d t o t h e i r s o u r c e s by u s i n g h y d r a u l i c a l l y e q u i v a l e n t s t a n d a r d s , and, f u r t h e r m o r e , t h a t t h e s e a n o m a l i e s may p e r s i s t f o r l o n g d i s t a n c e s , b u t f a i l u r e o f s c h e e l i t e c o n c e n t r a t i o n s t o i n c r e a s e below t h e O m o / P e l l y j u n c t i o n u n d e r s c o r e s t h e l a c k o f s e n s i t i v i t y o f s a m p l i n g l a r g e d r a i n a g e b a s i n s . As t h e o b j e c t i v e o f t h i s s t u d y was n o t t o o b t a i n a c o m p l e t e r e p r e s e n t a t i o n o f the 2 s c h e e l i t e d i s t r i b u t i o n i n t h e 160 km d r a i n a g e b a s i n , h i g h e r d e n s i t y s a m p l i n g i s r e q u i r e d t o r e s o l v e a n o m a l i e s a l o n g t h e P e l l y R i v e r . L i k e w i s e , t h e s t e a d y i n c r e a s e o f h y d r a u l i c a l l y e q u i v a l e n t c o n c e n t r a t i o n s down Omo C r e e k i s p r o b a b l y due t o s c h e e l i t e i n p u t f r o m g l a c i a l t i l l s , b u t t h i s c a n o n l y be c o n f i r m e d by f o l l o w u p s a m p l i n g o f t i l l s . 127. APPLICATION TO EXPLORATION M e r i t s o f a l t e r n a t i v e a p p r o a c h e s t o s a m p l i n g f o r W d i s p e r s e d as s c h e e l i t e c a n be i n f e r r e d f r o m t h e p r o b l e m s i d e n t i f i e d i n t h i s s t u d y . In a d d i t i o n , i t i s r e a s o n a b l e t o e x p e c t t h a t many o f t h e s e p r o b l e m s , and h e n c e , t h e i r r e m e d i e s , a l s o a p p l y , t o o t h e r e l e m e n t s d i s p e r s e d as r a r e , r e s i s t a t e h e a v y - m i n e r a l s i n s t r e a m s e d i m e n t s . P a r t i c u l a r l y i m p o r t a n t p r o b l e m s t o c o n s i d e r a r e random s a m p l i n g e r r o r s , h y d r a u l i c e f f e c t s , and s o u r c e d i s t r i b u t i o n o f t h e s t a n d a r d . Random s a m p l i n g e r r o r s a r e r e d u c e d by i n c r e a s i n g t h e number o f s c h e e l i t e g r a i n s i n t h e sample. T h i s c a n be a c c o m p l i s h e d by u t i l i z i n g h e a v y m i n e r a l c o n c e n t r a t e s , by s a m p l i n g f o r f i n e r s c h e e l i t e , and by s a m p l i n g f r o m h i g h e n e r g y e n v i r o n m e n t s . A l s o , s a m p l i n g s m a l l e r d r a i n a g e b a s i n s r e d u c e s t h e r e l a t i v e c o n t r i b u t i o n o f d i l u t i n g m i n e r a l s from b a r r e n a r e a s , and t h e r e b y i n c r e a s e s t h e number o f s c h e e l i t e g r a i n s i n a g i v e n s i z e o f sample. H y d r a u l i c v a r i a b i l i t y , w h i c h i s p r e s e n t w i t h i n b o t h h i g h and low e n e r g y e n v i r o n m e n t s , c a n be r e d u c e d by s a m p l i n g low e n e r g y e n v i r o n m e n t s , where winnowing i s l e s s a f a c t o r , by u t i l i z i n g h y d r a u l i c a l l y e q u i v a l e n t s t a n d a r d s , a n d / o r by s a m p l i n g f o r f i n e r s c h e e l i t e . P o s s i b l y , h y d r a u l i c e f f e c t s become n e g l i g i b l e f o r minus 270-mesh s c h e e l i t e , w h i c h was n o t a n a l y z e d i n t h i s s t u d y . The h y d r a u l i c p r o b l e m c a n a l s o be r e d u c e d by s a m p l i n g s m a l l e r d r a i n a g e b a s i n s , b e c a u s e s o r t i n g i s m i n i m a l a l o n g t h e f i r s t 3-4 km o f an immature s t r e a m 128. ( F i g u r e 3 1 ) . A l t h o u g h s a m p l i n g from g r o s s l y mismatched h y d r a u l i c e n v i r o n m e n t s c a n u n d o u b t e d l y a g g r a v a t e t h e h y d r a u l i c v a r i a b i l i t y p r o b l e m , s i z e , shape and c o m p o s i t i o n a l d i f f e r e n c e s o f t h e b e d l o a d between s i t e s make i t i m p o s s i b l e t o sample i d e n t i c a l h y d r a u l i c e n v i r o n m e n t s , and s u c h s a m p l i n g i s n o t c o n s i d e r e d a v i a b l e remedy t o t h e h y d r a u l i c p r o b l e m . I d e a l l y , t h e s t a n d a r d t o w h i c h r e l a t i v e abundance o f s c h e e l i t e i s compared s h o u l d : Have a w i d e s p r e a d d i s t r i b u t i o n i n t h e d r a i n a g e b a s i n , so t h a t downstream d i l u t i o n o f an anomaly c a n o c c u r ; have a c o n s t a n t d i s t r i b u t i o n , so t h a t unwanted v a r i a b i l i t y i s n o t i n t r o d u c e d i n t o t h e d a t a ; and n o t c o v a r y w i t h s c h e e l i t e i n s o u r c e r o c k s , so t h a t a f l a t r e s p o n s e i s n o t o b t a i n e d downstream f r o m a s c h e e l i t e - b e a r i n g d e p o s i t . U n f o r t u n a t e l y , h e a v y m i n e r a l s , as a g r o u p , a l w a y s o c c u r i n s c h e e l i t e - b e a r i n g s k a r n d e p o s i t s ( T a b l e 2 3 ) . C o n v e r s e l y , s i e v e d s e d i m e n t s , composed m a i n l y o f r o c k f r a g m e n t s , q u a r t z and f e l d s p a r s ( i . e . l i g h t m i n e r a l s ) , meet a l l o f t h e above c r i t e r i a . More i n f o r m a t i o n i s r e q u i r e d on t h e s o u r c e d i s t r i b u t i o n o f m a g n e t i t e , as w e l l as o t h e r i n d i v i d u a l heavy m i n e r a l s . From t h e f o r e g o i n g , i t i s c l e a r t h a t r e m e d i e s t o t h e v a r i o u s p r o b l e m s a s s o c i a t e d w i t h s a m p l i n g f o r s c h e e l i t e a r e n o t i n d e p e n d e n t o f one a n o t h e r , and t h a t a remedy t o one p r o b l e m may a c c e n t u a t e a n o t h e r p r o b l e m . F o r example, u s i n g s i e v e d s e d i m e n t s r a t h e r t h a n h e a v y m i n e r a l s as a s t a n d a r d d e c r e a s e s t h e p r o b l e m o f s o u r c e d i s t r i b u t i o n s , b u t i n c r e a s e s 129. DENSITY FRACTIONS IN MINERALS WHICH OCCUR WHICH MINERALS ARE MOST IN SKARNS AT THE SPECIFIC LIKELY TO OCCUR CLEA TUNGSTEN DEPOSIT GRAVITY q u a r t z 2 .65 LIGHTS ca1c i t e 2 .7 c h1o r i t e 2 .6-2 .9 wo 11aston i t e 2 .8-2 .9 amph i bo 1e 2 .8-3 .5 MEDIUMS b i o t i t e 2 .8-3 .2 s e r i c i t e 2 .8-3 .1 f 1 u o r i t e 3 .2 pyroxene 3. .2-3 .5 vesuv i an i t e 3 .4-3 .5 g a r n e t 3. .4-4 .3 HEAVIES spha1er i t e 3. .9-4 .1 cha1 c o p y r i t e 4, .1-4 .3 p y r r h o t i t e 4. .6-4 .7 s c h e e 1 i t e 5. .9-6 .1 wo 1f ram i t e 7. .0-7 .5 T a b l e 23. D e n s i t y f r a c t i o n s i n which m i n e r a l s i d e n t i f i e d i n s k a r n s a t t h e C l e a t u n g s t e n p r o p e r t y a r e most l i k e l y t o o c c u r . 130. t h e h y d r a u l i c p r o b l e m . Thus, compromise may be r e q u i r e d t o a c h i e v e t h e o p t i m a l a p p r o a c h t o s a m p l i n g , o r , i n t h o s e c a s e s where t h e r e i s u n c e r t a i n t y as t o t h e o p t i m a l a p p r o a c h , i t may be b e s t t o t r y more t h a n one a p p r o a c h ( s u c h as e x p r e s s i n g s c h e e l i t e c o n c e n t r a t i o n s r e l a t i v e t o b o t h h e a v i e s and s i e v e d s e d i m e n t s ) . C o n s e q u e n c e s o f v a r i o u s a p p r o a c h e s t o s a m p l i n g a r e summarized i n T a b l e 24. Mediums, a l t h o u g h n o t i n c l u d e d i n T a b l e 24, would make t h e l e a s t d e s i r a b l e s t a n d a r d s , b e c a u s e t h e y have t h e w o r s t a t t r i b u t e s o f b o t h h e a v i e s and s i e v e d s e d i m e n t s - t h a t i s , t h e y a l w a y s o c c u r i n s c h e e l i t e - b e a r i n g s k a r n s ( T a b l e 23) and a r e n o t a p p r e c i a b l y more h y d r a u l i c a l l y e q u i v a l e n t t o s c h e e l i t e t h a n a r e s i e v e d s e d i m e n t s ( T a b l e 1 4 ) . The o p t i m a l a p p r o a c h t o s a m p l i n g d e p e n d s , i n p a r t , upon t h e o b j e c t i v e o f t h e e x p l o r a t i o n p r o g r a m , w h i c h , among o t h e r s , c o u l d be t o d e t e c t t h e mere p r e s e n c e o f W o r s c h e e l i t e , t o d i s t i n g u i s h between anomalous and b a c k g r o u n d W c o n c e n t r a t i o n s i n d r a i n a g e b a s i n s , o r t o t r a c e a W anomaly t o i t s s o u r c e . I f t h e o b j e c t i v e were m e r e l y t o d e t e c t t h e p r e s e n c e o f W o r s c h e e l i t e ( i . e . any amount i s c o n s i d e r e d a n o m a l o u s ) , t h e n s a m p l i n g f r o m h i g h e n e r g y e n v i r o n m e n t s where s c h e e l i t e i s c o n c e n t r a t e d n a t u r a l l y would be b e s t . A l t h o u g h t h i s n a t u r a l c o n c e n t r a t i o n enhancement i s g r e a t e r f o r c o a r s e r s c h e e l i t e , i t may n o t n e c e s s a r i l y be b e s t t o sample f o r c o a r s e r s c h e e l i t e . F o r example, i n most h i g h e n e r g y s a m p l e s a l o n g t h e P e l l y R i v e r , s c h e e l i t e / h e a v i e s c o n c e n t r a t i o n s a r e h i g h e s t i n t h e 3.0-3.5 p h i s i z e f r a c t i o n ( F i g u r e 2 2 ) , i n s p i t e o f g r e a t e r IS PROBLEM SUFFICIENT TO ADVERSELY APPROACH TO SAMPLING FOR SCHEELITE AFFECT INTERPRETATION? ENERGY ENVIRONMENT SCHEELITE SIZE SAMPLED FOR i STANDARD* USED RARE GRAIN HYDRAULIC COVARIANCE IN SOURCE h i gh coarse se i ved poss i b1y yes no h i gh coarse heav i es poss i b1y yes probab 1y h i gh coarse magneti te poss i b1y yes p o s s i b l y h i gh f i ne se i ved no no no high f i ne HE heavies no no probab 1y h i gh f i ne HE magnetite no no poss i b1y 1 ow coarse s i eved yes probab1y no 1 ow coarse heav i es yes poss i b 1y probab1y 1 ow coarse magnet i te yes poss i b 1y poss i b1y 1 ow f i ne s i eved no poss i b 1 y no 1 OW f i ne HE heavies no no probab1y 1 ow f i ne HE magnetite no no poss i b1y • H y d r a u l i c a l l y e q u i v a l e n t (HE) heavies and magnetite assumed i f sampling f o r 3.0-3.5 or 3.5-4.25 phi s c h e e l i t e , but not i f sampling f o r s c h e e l i t e c o a r s e r than 3.0 ph i . Table 24. Probable consequences of v a r i o u s approaches to sampling f o r s c h e e l i t e . 132. h y d r a u l i c c o n c e n t r a t i o n o f c o a r s e r s c h e e l i t e s i z e s ( T a b l e 1 4 ) . In a d d i t i o n t o h y d r a u l i c e f f e c t s , o t h e r f a c t o r s w h i c h may be o f i m p o r t a n c e i n d e t e r m i n i n g t h e optimum s c h e e l i t e s i z e f o r w h i c h t o sample a r e : The s i z e d i s t r i b u t i o n o f s c h e e l i t e r e l a t i v e t o t h a t o f t h e s t a n d a r d i n s o u r c e m a t e r i a l s t h r o u g h o u t t h e d r a i n a g e b a s i n ( i . e . n o t s i m p l y i n t h e s c h e e l i t e - b e a r i n g m a t e r i a l s ) ; and, p o s s i b l y , c o m m i n u t i o n o f s c h e e l i t e w i t h downstream t r a n s p o r t ( a l t h o u g h s u c h c o m m i n u t i o n c o u l d n o t be c o n f i r m e d i n t h i s s t u d y ) . I f , as i n many e x p l o r a t i o n s i t u a t i o n s , t h e s e a d d i t i o n a l f a c t o r s c o u l d n o t be r e a d i l y a s s e s s e d , d e t e c t i o n o f s c h e e l i t e c o u l d b e s t be a s s u r e d by s a m p l i n g f o r a wide r a n g e o f s c h e e l i t e s i z e f r a c t i o n s from h i g h e n e r g y e n v i r o n m e n t s . However, i n some e x p l o r a t i o n s i t u a t i o n s , an o r i e n t a t i o n s u r v e y downstream o f a known W d e p o s i t i n o r n e a r t h e a r e a t a r g e t e d f o r e x p l o r a t i o n would be f e a s i b l e . U s i n g s u c h an o r i e n t a t i o n s u r v e y , t h e optimum s c h e e l i t e s i z e f r a c t i o n f o r w h i c h t o sample m i g h t be d e t e r m i n e d w i t h g r e a t e r c e r t a i n t y , and a s u b s t a n t i a l s a v i n g s t h e r e b y r e a l i z e d . R e g a r d l e s s o f t h e s i z e r a n g e s e l e c t e d , sample s i z e s h o u l d be s u f f i c i e n t t o e n s u r e t h a t s e v e r a l s c h e e l i t e g r a i n s would be i n c l u d e d , i f p r e s e n t , b u t g e n e r a l l y , s a m p l i n g e r r o r s o r h y d r a u l i c v a r i a b i l i t y would n o t be o f c o n c e r n . I f t h e o b j e c t i v e were t o d i s c r i m i n a t e between anomalous and b a c k g r o u n d W c o n c e n t r a t i o n s , t h e n i t must be e n s u r e d t h a t t h e d i f f e r e n c e between t h o s e v a l u e s w i l l be r e c o g n i z e d a s 133. s i g n i f i c a n t . One i m p o r t a n t c o n s i d e r a t i o n i s t h a t t h e m a g n i t u d e o f t h i s d i f f e r e n c e i s d e t e r m i n e d b o t h by g e o l o g i c a l f a c t o r s and t h e s i z e o f t h e d r a i n a g e b a s i n s s a m p l e d . Based on Hawke's (1976) e q u a t i o n f o r anomaly d i l u t i o n (see page 1 ) , s a m p l i n g s m a l l e r b a s i n s s h o u l d i n c r e a s e t h e d i f f e r e n c e between anomalous and b a c k g r o u n d c o n c e n t r a t i o n s . A n o t h e r i m p o r t a n t c o n s i d e r a t i o n i n r e c o g n i z i n g s i g n i f i c a n t d i f f e r e n c e s i s t h e r e l i a b i l i t y a s s o c i a t e d w i t h W c o n c e n t r a t i o n s - as r e l i a b i l i t y i m p r o v e s , more s u b t l e d i f f e r e n c e s c a n be r e c o g n i z e d . R e l i a b i l i t y c a n be i m p r o v e d most e f f e c t i v e l y by r e d u c i n g s a m p l i n g and h y d r a u l i c v a r i a b l i t y w i t h i n s i t e s . However, the e x t e n t t o w h i c h improvement i s p o s s i b l e i s l i m i t e d by s o u r c e e f f e c t s w i t h i n s i t e s , and by t h a t h y d r a u l i c v a r i a b i l i t y w h i c h i s n o t a c c o u n t e d f o r by t h e use o f a h y d r a u l i c a l l y e q u i v a l e n t s t a n d a r d . Thus, a b a l a n c e must be a t t a i n e d between t h e c o s t s o f h i g h e r d e n s i t y s a m p l i n g , t h e c o s t s o f c o l l e c t i n g and p r o c e s s i n g t h e l a r g e s a m p l e s needed t o r e d u c e s a m p l i n g e r r o r s and h y d r a u l i c e f f e c t s , and t h o s e l i m i t s p l a c e d on r e l i a b i l i t y w h i ch a r e beyond c o n t r o l . A l t h o u g h t h e a b o v e m e n t i o n e d b a l a n c e w i l l v a r y w i t h t h e s i t u a t i o n , t h i s s t u d y i n d i c a t e s t h a t , p r o v i d e d 120-mesh t o 170-mesh and 170-mesh t o 270-mesh W / s i e v e d c o n c e n t r a t i o n s a r e e q u a l t o o r g r e a t e r t h a n 10 ppm and 3 ppm, r e s p e c t i v e l y , 100 g o f minus 120-mesh s e d i m e n t s o r 20 g o f minus 170-mesh s e d i m e n t s a r e needed t o m a i n t a i n a random s a m p l i n g p r e c i s i o n o f + 15% i n t h o s e r e s p e c t i v e s i z e f r a c t i o n s ( c a l c u l a t i o n s a r e 134. f r o m raw d a t a i n A p p e n d i x 1 ) . R e l a t i v e s i z e d i s t r i b u t i o n s o f s i e v e d s e d i m e n t s ( e . g . F i g u r e 26) i n d i c a t e t h a t such p r e c i s i o n i n t h e f i n e r (minus 120-mesh) s e d i m e n t s c o u l d a l s o be m a i n t a i n e d by c o l l e c t i n g 10 kg o f minus 10-mesh o r 1 kg o f minus 45-mesh s e d i m e n t s . A c k n o w l e d g i n g t h e p r o b a b i l i t y o f more t h a n one s c h e e l i t e s o u r c e , t h i s p r e c i s i o n would be m a i n t a i n e d by s a m p l i n g h i g h e n e r g y s e d i m e n t s f r o m t h e l o w e s t s i t e on t h e P e l l y R i v e r , s i t e CP, w hich has a c o r r e s p o n d i n g 2 d r a i n a g e b a s i n o f 160 km . Such p r e c i s i o n would a l s o be m a i n t a i n e d by s a m p l i n g e i t h e r h i g h o r low e n e r g y s e d i m e n t s 2 f r o m t h e mouth o f C l e a C r e e k (7 km b a s i n ) , w h i c h p r e s u m a b l y has o n l y one s o u r c e o f s c h e e l i t e . Note t h a t t h e u s u a l minus 80-mesh s i e v e d s e d i m e n t s a m p l e s , w h i c h a r e r e l a t i v e l y s m a l l by c o n v e n t i o n , would be g r o s s l y i n a d e q u a t e f o r m a i n t a i n i n g a c c e p t a b l e p r e c i s i o n . M a i n t a i n i n g low random s a m p l i n g e r r o r s i s o f l i t t l e h e l p i f s y s t e m a t i c h y d r a u l i c v a r i a b i l i t y i s t o o g r e a t . I f s m a l l e r 2 (7 km ) b a s i n s a r e t o be s a m p l e d , h y d r a u l i c v a r i a b i l i t y may n o t be a p r o b l e m , due t o l a c k o f s o r t i n g s o c l o s e t o t h e h e a d w a t e r s . C o n v e r s e l y , i f l a r g e r (160 km ) b a s i n s a r e t o be s a m p l ed, h y d r a u l i c e f f e c t s must be r e d u c e d e i t h e r w i t h h y d r a u l i c a l l y e q u i v a l e n t s t a n d a r d s , o r , p o s s i b i l y , by u s i n g o n l y v e r y f i n e (minus 270-mesh) s c h e e l i t e . I t must be c a u t i o n e d , however, t h a t improvements i n p r e c i s i o n b r o u g h t a b o u t by u s i n g f i n e r g r a i n s i z e s c o u l d be o f f s e t i f t h e g i v e n d e p o s i t d o e s n o t c o n t a i n a r e l a t i v e abundance o f t h o s e f i n e r 135. s i z e s . A t h i r d o b j e c t i v e i n s a m p l i n g f o r s c h e e l i t e m i g h t be t o t r a c e an anomaly t o i t s s o u r c e by d e f i n i n g i t s d i l u t i o n c u r v e . A g a i n , d i f f e r e n c e s i n W c o n c e n t r a t i o n s between s i t e s become i m p o r t a n t . Most l i k e l y , t h e s i z e o f t h e d r a i n a g e b a s i n would be s u c h t h a t r e l a t i v e l y l a r g e s a m p l e s and h y d r a u l i c c o r r e c t i o n s would be r e q u i r e d t o m a i n t a i n a d e q u a t e r e l i a b i l i t y . P r o b l e m s a s s o c i a t e d w i t h s a m p l i n g f o r s c h e e l i t e must a l s o be a s s o c i a t e d w i t h many o t h e r m i n e r a l s o f i n t e r e s t i n e x p l o r a t i o n ; W, Sn and Au, among o t h e r e l e m e n t s , t e n d t o be d i s p e r s e d s o l e l y as r a r e , r e s i s t a t e h e a v y m i n e r a l s . In a d d i t i o n , s u l p h i d e s , w h i c h a r e e x t r e m e l y i m p o r t a n t i n m i n e r a l e x p l o r a t i o n , may be d i s p e r s e d p r i m a r i l y as h e a v y m i n e r a l s i n a r e a s where m e c h a n i c a l w e a t h e r i n g e x c e e d s c h e m i c a l w e a t h e r i n g , s u c h as i n m o u n t a i n o u s t e r r a i n s i n c o l d o r a r i d c l i m a t e s . S e v e r i t y o f t h e t h r e e m a j o r p r o b l e m s ( r a r e g r a i n , h y d r a u l i c and s o u r c e d i s t r i b u t i o n ) d i s c u s s e d i n t h i s s t u d y w i l l v a r y w i t h t h e i n d i v i d u a l m i n e r a l , and e a c h p r o b l e m c o u l d be l e s s , e q u a l l y o r more s e v e r e w i t h a g i v e n m i n e r a l t h a n w i t h s c h e e l i t e . F o r e xample, use o f h e a v i e s as a s t a n d a r d would be l e s s o f a p r o b l e m i f t h e m i n e r a l o f i n t e r e s t o c c u r r e d i n q u a r t z - v e i n r a t h e r t h a n s k a r n d e p o s i t s , b e c a u s e , i n g e n e r a l , s o u r c e d i s t r i b u t i o n s o f h e a v i e s a r e r e l a t i v e l y l e s s d e p e n d e n t on t h e d i s t r i b u t i o n o f q u a r t z v e i n s t h a n o f s k a r n s . In a d d i t i o n , m i n e r a l s w i t h a p p r o x i m a t e l y s i m i l a r n a t u r a l 136. a b u n d a n c e s and s p e c i f i c g r a v i t i e s , s u c h a s s c h e e l i t e (G=5.9-6.1), w o l f r a m i t e ((Fe,Mn)W0 4, G=7.0-7.5) and c a s s i t e r i t e ( S n 0 2 , G=6.8-7.1) s h o u l d be s i m i l a r l y a f f e c t e d by r a r e g r a i n and h y d r a u l i c p r o b l e m s . C o n v e r s e l y , r a r e g r a i n and h y d r a u l i c p r o b l e m s must be much more s e v e r e w i t h n a t i v e g o l d (G=19) t h a n w i t h s c h e e l i t e , b a s e d on t h e ext r e m e s c a r c i t y o f g o l d , and on e x t r a p o l a t i o n o f t h e o b s e r v e d t r e n d o f g r e a t l y i n c r e a s i n g h y d r a u l i c e f f e c t s w i t h i n c r e a s i n g d e n s i t y . CONCLUSIONS 138. IONS Rare g r a i n and h y d r a u l i c e f f e c t s c a n i n t r o d u c e v a r i a b i l i t y i n t o s t r e a m s e d i m e n t d a t a f o r W d i s p e r s e d a s s c h e e l i t e , and t h i s v a r i a b i l i t y may a d v e r s e l y a f f e c t i n t e r p r e t a t i o n o f g e o c h e m i c a l r e s u l t s f o r m i n e r a l e x p l o r a t i o n . R a r e - g r a i n p r o b l e m s c a n be r e d u c e d a t t h e s a m p l i n g l e v e l by e x p l o i t i n g n a t u r a l " h y d r a u l i c " c o n c e n t r a t i o n s , by s a m p l i n g f o r f i n e r s i z e s a nd/or by s a m p l i n g s m a l l e r c a t c h e m e n t s . The b e s t means o f r e d u c i n g r a r e - g r a i n p r o b l e m s a t t h e s u b s a m p l i n g and a n a l y t i c a l l e v e l s i s by c o n c e n t r a t i n g t h e heavy m i n e r a l f r a c t i o n , e i t h e r by p a n n i n g o r heavy l i q u i d s e p a r a t i o n . The h y d r a u l i c p r o b l e m c a n be r e d u c e d by u t i l i z i n g h y d r a u l i c a l l y e q u i v a l e n t m i n e r a l s as s t a n d a r d s , by s a m p l i n g f o r f i n e r s i z e s , a n d / o r by s a m p l i n g s m a l l e r c a t c h m e n t s . F u r t h e r s t u d y i s r e q u i r e d on h y d r a u l i c b e h a v i o r and s o u r c e d i s t r i b u t i o n s o f i n d i v i d u a l h eavy m i n e r a l s w h i c h m i g h t be us e d as h y d r a u l i c a l l y e q u i v a l e n t s t a n d a r d s . BIBLIOGRAPHY Baba, J . and Komar, P.D., 1981. Measurement and a n a l y s i s o f s e t t l i n g v e l o c i t i e s o f n a t u r a l q u a r t z sand g r a i n s . J . o f Sed. P e t . , v. 51, no. 2, pp. 631-642. B a l l a n t y n e , V.H., 1976. How and Where t o F i n d G o l d ;  S e c r e t s o f t h e ' 4 9 e r s . A r c o , 124 pp. B r a d y , L . L . and J o b s o n , H.E., 1973. 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Theobald, A s s o c i a t i o n o f E x p l o r a t i o n Geochemists. pp. 329-336 APPENDIX 1 RAW DATA SITE SAMPLE SIZE - PHI 1.5-2.0 2.0-2 .5 2.5-3.0 3-0-3.5 3.5-4.25 G 25 5/ 5 23/ 23 45/ 45 114/ 114 133/ 133 G 26 89/ 89 187/ 187 441/ 154 1083/ 95 1078/ 109 G 2T 329/ 113 408/ 208 1302/ 198 1664/ 571 1885/ 618 G 28 33/ 33 127/ 70 234/ 121 627/ 239 806/ 267 L 29 210/ 210 45/ 45 246/ 246 307/ 73 165/ 46 L 30 307/ 307 195/ 195 131/ 131 150/ 150 202/ 202 ZAA 35 137/ 137 214/ 110 555/ 184 823/ 257 1049/ 295 ZAA 36 136/ 136 275/ 126 494/ 183 521/ 179 692/ 114 ZAA 37 163/ 163 182/ 182 377/ 377 511/ 193 742/ 191 ZAA 38 139/ 139 151/ 151 198/ 198 417/ 417 286/ 286 AK 41 124/ 124 160/ 160 208/ 208 432/ 108 637/ 131 AK 42 122/ 122 180/ 180 326/ 118 442/ 119 676/ 144 AK 43 66/ 66 121/ 121 343/ 112 586/ 204 933/ 268 AK 44 87/ 87 155/ 155 247/ 120 379/ 74 735/ 134-AO 45 3/ 3 21/ 21 41/ 41 81/ 81 162/ 162 AO 46 228/ 125 382/ 181 317/ 149 376/ 112 299/ 299 AO 55 20/ 20 54/ 54 134/ 134 123/ 123 141/ 141 AO 56 302/ 139 427/ 168 587/ 245 474/ 216 385/ 318 DD 57 134/ 134 409/ 121 850/ 196 1290/ 216 1946/ 181 DD 58 399/ 168 1021/ 295 1431/ 194 1563/ 183 1803/ 162 CLR 59 8/ 8 18/ 18 64/ 64 201/ 201 415/ 103 CLR 60 111/ 111 147/ 147 365/ 153 670/ 107 1129/ 136 1234 1 19/ 19 30/ 30 104/ 104 257/ 169 478/ 245 1234 2 9/ 9 39/ 39 131/ 131 294/ 81 528/ 172 1234 3 4/ 4 43/ 43 104/ 104 605/ 115 530/ 142 1234 4 9/ 9 59/ 59 81/ 81 139/ 139 27/ 27 BB 11 0/ 0 3/ 3 9/ 9 6/ 6 13/ 13 BB 12 1/ 1 7/ 7 8/ 8 13/ 13 43/ 43 BG 13 5/ 5 2/ 2 13/ 13 35/ 35 66/ 66 BG 14 52/ 52 91/ 91 86/ 86 73/ 73 102/ 102 BG 15 4/ 4 13/ 13 22/ 22 26/ 26 43/ 43 BG 16 6/ 6 15/ 15 20/ 20 18/ 18 29/ 29 CB 47 1/ 1 3/ 3 30/ 30 34/ 34 87/ 87 CB 48 73/ 73 265/ 98 702/ 135 561/ 116 545/ 121 CB 49 18/ 18 37/ 37 231/ 231 830/ 167 1769/ 240 CB 50 88/ 88 172/ 172 248/ 109 446/ 97 448/ 98 CD 61 0/ 0 0/ 0 3/ 3 29/ 29 78/ 78 CD 62 16/ 16 46/ 46 313/ 120 1201/ 115 1205/ 131 CE 63 18/ 18 14/ 14 71/ 71 267/ 267 792/ 91 CE 64 124/ 124 186/ 186 509/ 106 707/ 155 658/ 263 CH 71 0/ 0 0/ 0 20/ 20 18/ 18 30/ 30 CH 72 45/ 45 388/ 177 623/ 166 631/ 218 586/ 157 CH 73 8/ 8 7/ 7 35/ 35 68/ 68 71/ 71 CH 74 25/ 25 106/ 106 307/ 97 187/ 91 143/ 143 CM 79 5/ 5 3/ 3 10/ 10 51/ 51 110/ 110 CM 80 48/ 48 222/ 222 1286/ 167 4019/ 342 4734/ 174 CP 65 0/ 0 0/ 0 5/ 5 25/ 25 42/ 42 CP 66 5/ 5 13/ 13 52/ 52 70/ 70 85/ 85 Numbers of scheelite grains i n : total sample/sample or subsample in which scheelite grains were actually counted. SITE SAMPLE SIZE - PHI 1.5-2.0 2.0-2.5 2.5-3.0 3.0-3.5 3.5-4.25 G 25L 0.0015 0.0010 0.0024 0.0425 0.1690 G 26H 0 . 0 0 9 2 0.0101 0 . 0389 0.7423 0.4672 G 27L 0.0112 0 . 0 0 6 9 0.0624 1.2367 0.7494 G 28H 0.0044 0.0038 0.0219 0.4314 0.3160 L 29L 0.0108 0.0041 0.0046 0.0452 0.0317 L 30H 0.0123 0.0054 0.0052 0.0386 0.0302 ZAA 35L 0 . 0 2 1 2 0.0118 0 . 0 2 1 8 0.3680 0.3013 ZAA 36H 0.0370 0.0106 0 . 0122 0.2053 • 0.2002 ZAA 37L 0.0310 0.0099 0 . 0180 0.2261 0.1941 ZAA 38H 0.0290 0 . 0108 0.0114 0.1304 0 . 1 2 8 8 AK 41L 0 . 0 1 8 8 0.0048 0.0000 0.1156 0.1444 AK 42H 0.0338 0.0147 0.0141 0.0932 0.1031 AK 4 3 L 0.0352 0.0197 0.0317 0 . 2012 0.1753 AK 44H 0 . 0 3 4 5 0.0163 0.0147 0.1214 0.1074 AO 45L 0.0059 0 . 0 0 2 9 0.0042 0.0161 0.0299 AO 46H 0 . 0 2 1 2 0 . 0 0 9 5 0.0075 0 . 0556 0.0647 AO 55L 0.0133 0.0061 0.0047 0.0395 0.0468 AO 56H 0.0239 0 . 0 0 7 4 0.0055 0.0582 0.0615 DD 57L 0.0341 0.0155 0.0146 0.1248 0.1354 DD 58H 0.0300 0 . 0 2 0 6 0.0170 0.1105 0.1212 CLR 59L 0.0079 0.0063 0.0058 0 . 0720 0 . 0 8 8 9 CLR 60H 0 .0181 0.0084 0 . 0081 0.0696 0.0913 1234 1H 0.0070 0.0048 0 . 0062 0.0849 0 . 0721 1 2 3 1 2L 0.0060 0 . 0 0 3 5 0 . 0069 0 . 1354 0.1215 1234 3L 0.0043 0.0022 0.0054 0 .1335 0.0271 1234 4H 0.0036 0 . 0 0 2 1 0.0036 0.0551 0.0052 BB 11L 0 . 0096 0.0040 0.0036 0.0476 0.0526 BB 12H 0.0104 0 . 0 0 3 2 0 . 0 0 3 2 0.0493 0.0532 BG 13L 0 .0069 0 .0031 0.0045 0.0646 0.0620 BG 14H 0.0196 0.0055 0.0051 0.0606 0 . 0810 BG 15L 0.0149 0.0033 0.0023 0.0265 0 . 0 3 4 5 BG 16H 0 . 0102 0 . 0029 0.0031 0.0177 0.0195 CB 47L 0 . 0 0 3 0 0 . 0017 0 .0017 0.0173 0.0179 CB 48H 0.0482 0.0178 0 . 0081 0.0552 0.0607 CB 49L 0.0257 0.0213 0.0259 0.3605 0.2431 CB 50H 0.0242 0 . 0 1 3 5 0.0087 0.0680 0.0603 CD 61L 0.0013 0 . 0012 0.0015 0.0126 0.0153 CD 62H 0.0451 0.0195 0 . 0123 0.1158 0.1126 CE 63L 0 . 0199 0.0110 0 . 0130 0 .1821 0 . 2328 CE 64H 0.0477 0.0159 0 . 0105 0 .0997 0 . 0 9 3 7 CH 71L 0 . 0 0 9 1 0.0025 0 .0013 0.0063 • 0.0074 CH 72H 0.0457 0.0172 0.0085 0 . 0730 0.0891 CH 73L 0.0062 0 .0021 0.0011 0.0080 0 . 0 0 9 3 CH 74H 0.0197 0.0046 0 . 0037 0.0214 0.0252 CM 79L 0 . 0078 0.0046 0.0030 0 . 0 3 3 4 0.0330 CM 80H 0 . 0 1 8 9 O.O325 0 . 0332 0.4879 0.3963 CP 65L 0 .0029 0 . 0019 0 . 0013 0 . 0103 0.0104 CP 66H 0 . 0083 0.0042 0.0024 0.0149 0.0204 Weights (grams) of magnetite in samples from high and low energy environments (suffix H and L, respectively). SITE SAMPLE SIZE - PHI 1.5-2.0 2.0-2.5 2.5-3.0 3.0-3.5 3-5-4.25 G 25L 3.1958 1.6127 0.8421 0.6503 0.1753 G 26H 7.6965 5.0329 3.2626 2.4537 1.1971 G 27L 16.05 9.23 8.88 5.45 2.87 G 28H 3.82 3.07 2.17 1.56 1.02 L 29L 7.27 2.26 1.25 0.82 0.62 L 30H 7.44 2.54 1.24 0.71 0.84 ZAA 35L 7.58 4.61 4.34 3.59 1.93 ZAA 36H 10.58 3.86 2.5658 1.7151 0.9934 ZAA 37L 9.81 4.20 3.51 2.65 1.67 ZAA 38H 8.71 3.29 2.31 1.78 1.17 AK 41L 3.50 1.72. 1.52 1.40 1.23 AK 42H 6.78 3.14 2.20- 1.55 1.23 AK 43L 6.89 4.12 3.12 2.44 1.55 AK 44H 6.46 3.27 2.51 1.75 1.02 AO 45L 1.06 0.54 0.61 0.48 0.44 AO 46H 3.52 1.64 1.10 1.05 0.58 AO 55L 2.92 1.40 0.91 0.65 0.50 AO 56H 4.56 1.43 0.91 0.57 0.43 DD 57L 5.96 3.47 2.66 2.09 1.00 DD 58H 7.57 3.91 2.62 1.76 1.28 CLR 59L 1.87 1.15 1.13 0.79 0.68 CLR 60H 2.78 1.52 1.31 0.94 0.83 1234 1H 0.97 0.52 0.62 0.41 0.34 1234 2L 1.63 0.92 0.83 0.61 0.43 1234 3L 0.8615 0.4726 0.3414 0.3740 0.0896 1234 4H 0.9762 0.3807 0.2218 0.2232 0.0430 BB 11L 1.02 0.63 0.37 0.33 0.23 BB 12H 1.41 0.97 0.58 0.39 0.21 BG 13L 0.80 0.40 0.45 0.40 0.42 BG 14H 1.66 1.08 0.54 0.40 0.34 BG 15L 1.24 0.60 0.49 0.19 0.20 BG 16H 1.11 0.41 0.25 0.22 0.27 CB 47L 0.2680 0.1561 0.1556 0.2110 0.2453 CB 48H 3.48 1 .4630 0.7844 0.4381 0.3556 CB 49L 2.0991 2.0630 2.4255 1.7912 0.8730 CB 50H 2.1465 1.1734 0.7495 0.5247 0.3697 CD 61L 0.28 0.13 0.40 0.36 0.15 CD 52H 6.06 2.35 1.21 0.70 0.46 CE 63L 2.61 1.52 1.11 0.95 0.67 CE 64H 5.71 1.98 1.09 0.58 0.22 CH 71L 1.58 0.4236 0.1651 0.0927 0.0545 CH 72H 10.4929 3.1558 1.0754 0.5490 0.3775 CH 73L 1.0097 0.4062 0.1721 0.0756 0.0416 CH 74H 4.6757 1.4658 0.4753 0.1971 0.1444 CM 79L 1.4819 0.8185 0.4154 0.2258 0.1239 CM 80H 3.8669 • 6.1534 4.7248 2.5512 1.1708 CP 65L 0.9746 0.4192 0.2047 0.1151 0.0625 CP 66H 2.4133 0.9882 0.4999 0.1870 0.1120 Weights (grams) of high-density minerals (heavies). SITE SAMPLE SIZE - PHI 1.5-2.0 2.0-2.5 2.5-3.0 3.0-3.5 3.5-4.25 G 25L 23.4709 5.4318 3 . 0362 2.3714 0 . 2 0 0 3 G 26H 52.99 22.66 14.28 11.34 4 .71 G 27L 59.70 24.96 16.70 18.46 6 .43 G 28H 31.17 14.30 8.62 7.75 3.51 L 29L 19.03 4.84 2.52 2.26 0 .88 L 3 OH 27.78 6.64 2.98 1.97 0.89 ZAA 35L 45.19 23.37 16.30 10.30 4.71 ZAA 36H 50.60 18.44 12.66 7.34 3.45 ZAA 3 7 L 3 9 . 8 8 16.24 11.41 7.58 2.51 ZAA 38H 34.92 12.14 7 .62 5.04 2.59 AK 41L 28.60 17.04 6.72 4.92 1.70 AK 42H 22.00 5.65 3.91 2 .86 1.78 AK 4 3 L 24.71 10.80 7.11 5.22 1.65 AK 44H 28.96 10.75 6.55 4.11 1.66 AO 45L 13.69 4.86 3.10 1.12 0 .39 AO 46H 17.71 6.52 3.25 1.72 0 .69 AO 55L 16.40 4.44 2.47 1.36 0 .61 AO 56H 12.44 4.56 2.71 1.77 0.78 DD 57L 23.80 9.47 4.70 3 .02 0.87 DD 58H 23-09 9.52 5.66 3.31 1.34 CLR 59L 18.33 8.68 4.99 3 .81 1.62 CLR 60H 11.30 6.20 3.71 2.25 1.12 1234 1H 14.41 6.91 4.28 2.59 1.39 1234 2 L 23.02 10.33 6.56 3.77 2.00 1234 3 L 18.6575 6.1051 4.1261 2 . 3101 0 . 2 3 8 4 1234 4H 8 . 3 1 8 8 3.2148 2.4603 2.3077 0.2776 BB 11L 9 .81 4.15 2.14 1.52 0.71 BB 12H 11.70 3.81 2.16 1.20 0.63 BG 13L 10.57 4.68 4.31 2.57 0.95 BG 14H 12.47 4.33 2.75 1.80 0.63 BG 15L 10.52 3.08 1.53 0.96 0.55 BG 16H 7.51 1.99 1.10 0 .81 0 .23 CB 47L 6.4383 2.2560 1.5714 1.3839 0.4210 CB 48H 26.80 8.1498 3.7843 1.6312 0.6261 CB 49L 43.00 22.63 11.6010 5.4755 0.5766 CB 50H 23.5624 7.4398 3.3689 1 .4952 O .3668 CD 61L 5.44 1.38 0 .82 0.62 0.20 CD 62H 24.32 7.38 3.10 1.81 0.58 CE 6 3 L 28.15 12.03 3 . 1 3 26.67 6 . 5 3 CE 64H 21.47 6.97 3.26 1.82 0.38 CH 71L 14.60 2.69 0.7988 0.3886 0.1586 CH 72H 22.9116 7.3571 2.4069 1.3404 0.2937 CH 7 3 L 11.7979 2.3927 0.9033 0.4533 0.1161 CH 74H 15.5791 3.6556 1.5511 0.7692 0.3505 CM 79L 23.1265 6.6725 2.5008 1.1147 0.3299 CM 8 OH 26.51 22.44 12.73 19.2490 0.9318 CP ' 65L 10.6077 2.3119 0.9185 0.4086 0 . 1 3 3 4 CP 66H 13.9894 3.3090 1 .4208 0.5532 0.2016 Weights (grams) of medium-density minerals (mediums). SITE SAMPLE SIZE - PHI 1.5-2.0 2.0-2.5 2.5-3.0 3.0-3.5 3.5-4.25 G 25L 201.22 58.95 47.20 45.36 58.79 G 26H 403.75 158.67 102.67 75.91 58.30 G 27L 476.71 191.87 141.32 111.06 91.35 G 28H 252.08 103.39 70.98 57.86 48.70 L 29L 192.22 54.15 33.09 24.75 26.06 L 30H 178.19 45.91 24.54 16.80 19.04 ZAA 35L 585.25 260.99 163.32 96.60 67.59 ZAA 36H 409.00 152.95 100.87 64.55 46.16 ZAA 37L 381.49 153.13 98.43 58.16 38.49 ZAA 38H 289.25 108.04 68.88 45.44 33.13 ' AK 41L 343.30 140.10 115.38 88.84 17.87 AK 42H 257.87 104.79 76.04 55.62 40.25 AK 43L 468.68 214.21 160.08 117.02 83.63 AK 44H 344.00 141.93 100.87 66.65 45.52 AO 45L 168.36 63.88 51.05 37.77 32.56 AO 46H 160.21 69.00 49.49 34.78 24.37 AO 55L 175.25 62.82 43.98 30.76 22.84 AO 56H 160.85 62.65 43.89 28.60 20.16 DD 57L 382.36 160.99 105.53 68.39 41.93 DD 58H 356.82 139.69 92.30 55.94 36.99 CLR 59L 448.01 177.07 118.98 64.95 38.45 CLR 60H 212.17 99.86 75.01 44.80 27.17 1234 1H 143.96 66.19 40.39 23.76 18.19 1234 2L 274.41 115.85 69.49 41.47 32.07 1234 3L 221.06 82.23 61.25 56.93 46.37 1234 4H 102.17 46.58 34.70 25.29 5.78 BB 11L 412.50 147.58 83.29 46.84 27.75 BB 12H 404.87 144.74 87.20 47.86 29.56 BG 13L 361.56 152.47 91.50 49.24 29.47 BG 14H 260.52 105.57 74.30 46.51 29.75 BG 15L 275.59 86.29 47.30 27.20 17.04 BG 16H 199.73 56.32 31.53 18.37 12.46 CB 47L 140.50 50.59 45.45 57.54 69.15 CB 48H 453.26 144.66 81.64 52.49 38.40 CB 49L 983.35 438.34 252.92 137.55 85.03 CB 50H 441.76 157.55 91.60 56.78 37.19 CD 61L 158.42 49.12 32.13 22.21 16.31 CD 62H 358.44 123.29 63.29 33.38 18.52 CE 6 3 L 617.04 283.06 195.05 88.71 53.84 CE 64H 283.92 104.70 62.55 34.70 24.01 CH 71L 367.66 56.39 20.56 11.77 8.45 CH 72H 359.16 97.76 55.17 36.36 23.55 CH 73L 140.73 33.44 19.07 12.54 10.06 CH 74H 220.8 52.74 27.55 16.14 11.70 CM 79L 568.13 150.35 67.49 33.93 20.71 CM 80H 495.02 487.23 306.82 152.05 86.96 CP 65L 233.18 58.04 23.02 11.29 7.29 CP 66H 249.26 61.81 29.50 12.03 7 .32 Weights (grams) of low-density minerals (lights). 150 . SITE SAMPLE SIZE - PHI -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.25 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.25 OR FINEF G 25L 1003 1482 1729 1321 722 247 85 69 66 77 241 G 26H 1260 1192 1112 840 685 483 205 138 113 88 226 G 27L 2108 1773 1563 1124 898 575 250 190 159 124 335 G 28H 1819 1439 1064 639 476 311 143 104 89 75 200 L 29L 1308 2207 2742 1660 567 245 86 61 51 52 134 L 30H 2321 2085 1764 1144 554 238 79 53 44 45 91 ZAA 35L 1448 1550 1654 1375 983 666 317 210 135 97 196 ZAA 36H 1734 1689 1759 1463 950 497 200 143 99 74 131 ZAA 37L 1974 1869 1693 1267 837 457 198 138 92 68 133 ZAA 38H 2394 2156 1846 1245 616 361 149 105 77 62 114 AK 41L 1636 1595 1401 964 661 401 204 165 133 107 170 AK 42H 2322 2069 1671 1044 612 314 139 105 85 69 99 AK 43L 1995 1885 1647 1182 825 511 250 191 146 107 198 AK 44H 2032 1870 1611 1088 710 400 175 129 91 67 109 AO 45L 1185 2284 2590 1332 593 207 92 77 63 56 106 AO 46H 2278 2185 1472 866 207 201 101 77 60 49 70 AO 55L 2812 2427 1670 827 498 217 91 70 55 47 62 AO 56H 2789 2318 1612 750 448 201 91 70 53 44 51 DO 57L 1574 1781 1636 1520 365 436 198 136 96 66 88 DD 58H 2370 2434 1993 1604 335 411 176 123 83 62 83 CLR 59L 1565 2216 2292 1438 957 492 210 148 93 64 82 CLR 60H 2661 2243 1405 690 431 250 131 104 71 51 61 1234 IH 2211 1843 1108 546 316 186 101 72 52 46 104 1234 2L 1609 1487 1189 805 573 325 153 103 71 59 144 1234 3L 1610 1380 2408 884 645 252 96 71 68 55 89 1234 4H 2273 2144 1971 567 334 118 56 44 35 14 80 BB 11L 2157 2048 1813 1180 834 450 178 112 74 54 72 BB 12H 1695 1900 1939 1256 847 444 174 114 74 54 73 BG 13L 2970 2627 1839 915 607 398 183 121 77 53 63 BG 14H 2694 2631 2092 1126 617 301 137 105 74 56 68 BG 15L 1915 2094 2079 1245 744 312 114 74 53 42 51 BG 16H 2060 2050 1908 1080 620 234 83 57 44 37 45 CB 47L 2859 2924 2503 1034 450 161 64 56 71 79 82 CB 48H 1971 1922 2063 1656 1109 495 164 98 67 51 63 CB 49L 2066 1684 1342 944 1086 1035 475 281 156 97 100 CB 50H 2259 1925 1866 1233 978 478 78 110 69 48 75 CD 61L 1268 2791 3181 1924 741 190 76 58 48 42 56 CD 62H 1999 2236 2104 1486 961 417 160 94 63 46 54 CE 63L 1702 2042 1924 1307 1040 673 324 231 144 87 97 CE 64H 2696 2676 2162 1125 697 338 140 93 62 50 47 CH 71L 293 966 3928 2942 1617 398 71 33 23 20 30 CH 72H 1510 1988 3126 1979 1156 403 119 70 49 36 43 CH 73L 1553 2384 2149 1133 488 169 49 32 26 22 31 CH 74H 3278 2439 1767 961 653 251 71 42 30 25 31 CM 79L 585 972 2268 2713 1710 602 169 80 51 33 48 CM 80H 1768 1646 2364 1697 1874 1089 530 334 189 105 111 CP 65L 1046 2127 2748 1694 861 256 72 36 22 19 26 CP 66H 2330 2493 2098 1338 797 293 92 57 39 33 35 Weights (grams) of sieved sediments. APPENDIX 2 SAMPLE LOCATIONS 152. 1234 2,J.;3,4.-4 7,8: BF 9,10. BB 11,12. B 23,24. G 25,26;27 ,28.-L 29,30. Q 31,32; V 33,34. ZAA 35,36;37,38 AE 39,40. AK 41,42;43,44; AO 45,46;55,56. DD 57,58 CLR 59,60 CE 63,64; CF 69,70. CH 21,72;73,74. CI 75,76. CM 79,80. CO 77,78. CP 65,66;67,68.-E » - 1 sample each from high _ Duplicate samples and low energy c a k e n from high and low environments energy environments 0 5 k m Appendix 2. Sample locations. Designations are as follows: SITE low energy sample #1, high energy sample #1; low energy sample #2, high energy sample #2. Samples which were processed (Figure 20) are underlined. 

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