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Behaviour of gold in stream sediments, Huai Hin, Loei region, northeastern Thailand 1991

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BEHAVIOUR OF GOLD IN STREAM SEDIMENTS, HUAI HIN LAEP, LOEI REGION, NORTHEASTERN THAILAND by PASAKORN PAOPONGSAWAN B . S c , Khon Kaen U n i v e r s i t y , T h a i l a n d , 1981 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES Department of G e o l o g i c a l Sciences We accept t h i s t h e s i s as conforming t o the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA September 1991 (5) Pasakorn Paopongsawan In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. « Department The University of British Columbia Vancouver, Canada DE-6 (2/88) i i ABSTRACT S t r e a m s e d i m e n t s a m p l i n g f o r g o l d e x p l o r a t i o n h a s e n c o u n t e r e d v a r i o u s p r o b l e m s : t h e s e i n c l u d e l o c a t i o n a n d t y p e o f s a m p l e t o be t a k e n , d e t e r m i n a t i o n o f t h e a p p r o p r i a t e s a m ple s i z e i n v i e w o f g o l d p a r t i c l e s p a r s i t y , a n d t h e a p p a r e n t l y e r r a t i c d i s t r i b u t i o n o f g o l d i n s t r e a m s e d i m e n t s . S t u d y o f t h e b e h a v i o r o f g o l d i n s t r e a m s e d i m e n t s c o u l d h e l p t o s o l v e t h e s e p r o b l e m s and i s needed t o g u i d e s y s t e m a t i c e x p l o r a t i o n f o r g o l d i n T h a i l a n d . The H u a i H i n Laep, an i n t e r m i t t e n t t h i r d o r d e r s t r e a m i n L o e i r e g i o n , n o r t h e a s t e r n T h a i l a n d , d r a i n s a h i l l y a r e a u n d e r l a i n by h i g h l y w e a t h e r e d s a n d s t o n e s , s h a l e s , a n d e s i t e s , a n d t u f f s , b l a n k e t e d by r e s i d u a l l a t e r i t i c a nd p o d z o l i c s o i l s . The s t r e a m r e a c h i s a p p r o x i m a t e l y 8 km l o n g w i t h an a v e r a g e g r a d i e n t o f 0.008. The o r i g i n a l m i x e d e v e r g r e e n f o r e s t h a s been l o g g e d and c l e a r e d f o r a g r i c u l t u r a l p u r p o s e s . A c t i v e s t r e a m s e d i m e n t s a m p l e s c o l l e c t e d f r o m p o i n t b a r s a n d pavements a l o n g t h e s t r e a m r e a c h were p r o c e s s e d t o o b t a i n 8 s i z e f r a c t i o n s . Of t h e s e , f i v e s i z e f r a c t i o n s b e t w e e n 0.42 5 and 0.053 mm were s e p a r a t e d i n t o h e a v y and l i g h t m i n e r a l f r a c t i o n s , and a n a l y z e d f o r g o l d by f i r e a s s a y - a t o m i c a b s o r p t i o n s p e c t r o p h o t o m e t r y . The -0.053 mm s e d i m e n t f r a c t i o n was s p l i t , p u l v e r i z e d and f u r t h e r s p l i t p r i o r t o a n a l y s i s . The c o r r e s p o n d i n g d r y - s i e v e d -0.150 mm s e d i m e n t f r a c t i o n was a l s o p r o c e s s e d and a n a l y z e d f o r g o l d . i i i R e s u l t s show t h a t i n b o t h p o i n t - b a r and pavement s a m p l e s g o l d i s c o n c e n t r a t e d i n t h e h e a v y m i n e r a l f r a c t i o n s , w h e r e a s i n a l l b u t s i x s a m p l e s , t h e c o r r e s p o n d i n g l i g h t f r a c t i o n s and t h e -0.053 mm f r a c t i o n c o n t a i n < 5 ppb g o l d . S i m i l a r l y , t h i r t e e n o u t o f t h e s i x t e e n -0.150 mm s e d i m e n t s a m p l e s c o n t a i n l e s s t h a n 5 ppb g o l d . G o l d c o n t e n t i s t y p i c a l l y h i g h e r a t pavement t h a n a t p o i n t - b a r s i t e s where g o l d c o n c e n t r a t i o n s a r e c l o s e l y c o r r e l a t e d w i t h n a r r o w s t r e a m c h a n n e l , s h a l l o w c h a n n e l d e p t h , h i g h f l o w v e l o c i t y , c o a r s e - g r a i n e d s e d i m e n t t e x t u r e and h i g h bed r o u g h n e s s , i n d i c a t i n g t h a t h i g h e r e n e r g y c o n d i t i o n s f a v o u r a c c u m u l a t i o n s o f g o l d . E s t i m a t e s o f numbers o f f r e e g o l d p a r t i c l e s s u g g e s t t h a t a n a l y s i s o f h e a v y m i n e r a l c o n c e n t r a t e s (between 0.425 and 0.053 mm f r a c t i o n ) f r o m a 40 k g -12 mm f i e l d s a m p l e f r o m e i t h e r p o i n t - b a r o r pavement s i t e h a s a h i g h c h a n c e o f d e t e c t i n g anomalous g o l d . I n c o n t r a s t , t h e p r o b a b i l i t y o f r e l i a b l y d e t e c t i n g g o l d i n a 30 g a n a l y t i c a l s u b s a m p l e i s v e r y low. W i t h r e s p e c t t o m i n e r a l e x p l o r a t i o n , c o n v e n t i o n a l s t r e a m s e d i m e n t s a m p l e s w i l l u s u a l l y f a i l t o d e t e c t t h e g o l d a n o m a ly i n t h e H u a i H i n L a e p . T h i s p r o b a b l y r e s u l t s f r o m t h e d i l u t i o n o f t h e A u - r i c h h e a v y m i n e r a l f r a c t i o n s by t h e b a r r e n l i g h t m i n e r a l s and l a r g e amounts o f s i l t - c l a y . The p r e s e n c e o f anomalous c o n c e n t r a t i o n s o f g o l d w o u l d , however, be r e c o g n i z e d t h r o u g h t h e u s e o f f i e l d p an c o n c e n t r a t e s o r h e a v y m i n e r a l s e p a r a t e s . D u r i n g r e g i o n a l s u r v e y s , s a m p l e s i v f o r t h i s p u r p o s e s h o u l d be c o l l e c t e d f r o m e i t h e r pavement s i t e s o r h i g h e n e r g y p o i n t - b a r s i t e s c h a r a c t e r i z e d by a n a r r o w c h a n n e l , s h a l l o w d e p t h , h i g h f l o w v e l o c i t y a n d l a r g e amount o f c o a r s e g r a i n e d s e d i m e n t a l o n g t h e l o w e r r e a c h e s o f t h e t h i r d o r d e r s t r e a m s . S u b s e q u e n t l y , d e t a i l e d f o l l o w - u p s u r v e y s s h o u l d c o n s i s t o f more d e t a i l e d s a m p l i n g o f e i t h e r 4 0 k g -12 mm s e d i m e n t s o r f i e l d p a n c o n c e n t r a t e s f r o m a t l e a s t 2 0 k g o f s e d i m e n t s a l o n g t h e s t r e a m . A nomalous c o n c e n t r a t i o n s o f g o l d a t t h e l o w e r r e a c h e s o f t h e s t r e a m may r e s u l t f r o m a c c u m u l a t i o n o f g o l d by h y d r a u l i c p r o c e s s e s r a t h e r t h a n t h e l o c a t i o n o f g o l d m i n e r a l i z a t i o n . H i g h g o l d c o n c e n t r a t i o n s a t low e n e r g y s i t e s c h a r a c t e r i z e d by s l o w f l o w v e l o c i t y , low bed r o u g h n e s s and f i n e g r a i n e d s e d i m e n t t e x t u r e may i n d i c a t e p r o x i m i t y t o t h e s o u r c e o f g o l d . V TABLE OF CONTENTS ABSTRACT i i L I S T OF TABLES v i i i L I S T OF FIGURES x i i ACKNOWLEDGEMENTS XV C h a p t e r One: INTRODUCTION 1.1 S t a t e m e n t o f r e s e a r c h p r o b l e m and a p p r o a c h 2 1.2 G o l d i n s t r e a m s e d i m e n t s u r v e y s 5 1.2.1 I n t r o d u c t i o n 5 1.2.2 D i s t r i b u t i o n o f m e t a l a n o m a l i e s i n s t r e a m s e d i m e n t s 6 1.2.3 H y d r a u l i c e f f e c t s 7 1.2.3.1 H y d r a u l i c e q u i v a l e n c e 8 1.2.3.2 E n t r a i n m e n t s o r t i n g 9 1.2.3.3 D i s p e r s i v e o r s h e a r s o r t i n g 11 1.2.3.4 I n t e r s t i c e e n t r a p m e n t o r t r a p p i n g 12 1.2.3.5 T r a n s p o r t e q u i v a l e n c e 14 1.2.4 S a m p l i n g c o n s i d e r a t i o n s 14 1.2.5 F i e l d s t u d i e s o f h e a v y m i n e r a l s i n s t r e a m s 19 C h a p t e r Two: DESCRIPTION OF STUDY AREA 2.1 L o c a t i o n and a c c e s s 24 2.2 B a s i n m o r p h o l o g y and t o p o g r a p h y 24 2.3 S t r e a m l o n g i t u d i n a l p r o f i l e 27 2.4 G e o l o g y 30 2.5 S o u r c e o f g o l d i n t h e H u a i H i n La e p 32 2.6 C l i m a t e , s o i l s , v e g e t a t i o n and l a n d u s e 32 C h a p t e r T h r e e : METHODOLOGY 3.1 F i e l d s a m p l i n g 40 3.2 Sample p r e p a r a t i o n 42 3.2.1 S t r e a m s e d i m e n t s 42 3.2.2 Pan c o n c e n t r a t e s 46 3.3 A n a l y s i s 47 3.3.1 A n a l y s i s o f s e d i m e n t s and h e a v y m i n e r a l s f o r g o l d 47 3.3.2 E x a m i n a t i o n o f he a v y m i n e r a l c o n c e n t r a t e s and g o l d p a r t i c l e s 51 C h a p t e r F o u r : STREAM CHARACTERISTICS AND SEDIMENT PROPERTIES OF THE HUAI HIN LAEP 4 .1 I n t r o d u c t i o n 54 4.2 S t r e a m c h a r a c t e r i s t i c s 56 4.3 S e d i m e n t p r o p e r t i e s 56 4.3.1 S e d i m e n t s i z e d i s t r i b u t i o n s i n p o i n t - b a r and pavement 56 v i 4.3.2 C o m p a r i s o n between t e x t u r e s o f s e d i m e n t s a t p o i n t - b a r and pavement 66 4.3.3 Downstream t r e n d s o f s e d i m e n t t e x t u r e a t p o i n t - b a r and pavement s i t e s 66 4.3.4 C o r r e l a t i o n s between s t r e a m c h a r a c t e r i s t i c s a n d s e d i m e n t p r o p e r t i e s 78 4.4 D i s t r i b u 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 e s 83 4.4.1 Heavy m i n e r a l m o r p h o l o g y and c o m p o s i t i o n s 83 4.4.2 S i z e d i s t r i b u t i o n and abundance o f h e a v y m i n e r a l s 84 4.4.3 Downstream t r e n d s o f h e a v y m i n e r a l c o n c e n t r a t e s i n p o i n t - b a r and pavement d e p o s i t s 84 4.4.4 R e l a t i o n s between h e a v y m i n e r a l a bundance and s t r e a m c h a r a c t e r i s t i c s and s e d i m e n t p r o p e r t i e s 91 4 . 5 Summary 96 C h a p t e r F i v e : GEOCHEMISTRY OF GOLD IN THE HUAI HIN LAEP 5.1 D i s t r i b u t i o n o f g o l d between s i z e and d e n s i t y f r a c t i o n s 98 5.2 G o l d d i s t r i b u t i o n i n t h e H u a i H i n La e p 101 5.2.1 C o m p a r i s o n between Au c o n c e n t r a t i o n s a t p o i n t - b a r and pavement s i t e s 101 5.2.2 Downstream t r e n d s o f Au c o n c e n t r a t i o n s i n p o i n t - b a r and pavement s e d i m e n t s 101 5.2.3 R e l a t i o n s between Au c o n c e n t r a t i o n s , s e d i m e n t t e x t u r e s and s t r e a m g e o m e t r y I l l 5.3 E s t i m a t e d numbers o f g o l d p a r t i c l e s 115 5.4 G o l d g r a i n m o r p h o l o g y and c o m p o s i t i o n s 121 5.4.1 G r a i n m o r p h o l o g y 127 5.4.2 G r a i n c o m p o s i t i o n 129 5.5 Summary 13 6 C h a p t e r S i x : DISCUSSION 6.1 I n t r o d u c t i o n 139 6.2 D i s t r i b u t i o n o f g o l d between s i z e and d e n s i t y f r a c t i o n s 139 6.3 D i s t r i b u t i o n o f g o l d between bed f o r m s 141 6.4 D i s t r i b u t i o n o f g o l d a l o n g t h e s t r e a m ' s l o n g i t u d i n a l p r o f i l e 142 6.5 G o l d g r a i n s h a p e and c o m p o s i t i o n 147 6.6 Recommendations f o r m i n e r a l e x p l o r a t i o n 148 6.6.1 R e g i o n a l s u r v e y 148 6.6.1.1 Sample f r a c t i o n 149 6.6.1.2 Sample l o c a t i o n a t c a t c h m e n t s c a l e 152 6.6.1.3 P r e f e r r e d s a m p l i n g s i t e s a t l o c a l s c a l e 153 6.6.2 F o l l o w - u p s u r v e y 154 v i i C h a p t e r S e v e n : CONCLUSIONS 7.1 C o n c l u s i o n s 157 REFERENCES 160 APPENDIX 168 V l l l L I S T OF TABLES T a b l e 3-1, T a b l e 3-2, T a b l e 4-1, T a b l e 4-2, T a b l e 4-3 T a b l e 4-4 T a b l e 4-5, T a b l e 4-6, D u p l i c a t e a n a l y s e s f o r g o l d c o n c e n t r a t i o n s (ppb) i n l i g h t a nd -0.053 mm s e d i m e n t f r a c t i o n s . The r e p o r t e d d e t e c t i o n l i m i t i s 5 ppb. A n a l y s e s o f g o l d s t a n d a r d samples, 48 ,49 R e s u l t s o f t h e W a l d - w o l f o w i t z t o t a l - n u m b e r - o f - r u n s t e s t (/i) f o r t r e n d s o f s t r e a m c h a r a c t e r i s t i c s a t p o i n t - b a r s i t e s a l o n g t h e e n t i r e r e a c h and between t h e s u p p o s e d s o u r c e o f g o l d and t h e c o n f l u e n c e w i t h t h e H u a i Kho Lo (1,055 and 6,223 m) 58 Summary o f mean g r a i n s i z e ( M Q ) , m e d i a n (D50)/ s e d i m e n t s o r t i n g ( S 0 ) and b e d r o u g h n e s s (055) o f t h e e n t i r e s e d i m e n t a t p o i n t - b a r a n d pavement s i t e s Summary c h a r a c t e r i s t i c s o f c o a r s e g r a i n e d component o f s e d i m e n t f r o m p o i n t - b a r and pavement s i t e s 62 65 S t a t i s t i c a l two-sample t t e s t f o r t h e d i f f e r e n c e between means o f s e d i m e n t c h a r a c t e r i s t i c s f r o m p o i n t - b a r and pavement s e d i m e n t s i n t h e r e a c h between 2,753 and 6,223 m 67 R e s u l t s o f t h e W a l d - w o l f o w i t z t o t a l - n u m b e r - o f - r u n s t e s t (/i) f o r v a r i a t i o n s o f s e d i m e n t t e x t u r e a t p o i n t - b a r and pavement s i t e s a l o n g t h e w h o l e r e a c h and between t h e s u p p o s e d s o u r c e o f g o l d and t h e c o n f l u e n c e w i t h t h e H u a i Kho Lo (1,055 and 6,22 3 m).... 73 R e s u l t s o f t h e W a l d - w o l f o w i t z t o t a l - n u m b e r - o f - r u n s t e s t (/x) and Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t ( r ) f o r downstream t r e n d s o f w e i g h t p e r c e n t s e d i m e n t i n 8 s i z e f r a c t i o n s f r o m p o i n t - b a r and pavement s i t e s a l o n g t h e w h o l e r e a c h and between t h e s u p p o s e d s o u r c e o f g o l d and t h e c o n f l u e n c e w i t h t h e H u a i Kho Lo (1,055 and 6,223 m) 79 i x T a b l e 4-7, T a b l e 4-8 Spearman r a n k 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 s t r e a m g e o m e t r y and s e d i m e n t c h a r a c t e r i s t i c s a l o n g t h e who l e r e a c h and between t h e s u p p o s e d s o u r c e o f g o l d a n d t h e c o n f l u e n c e w i t h t h e H u a i Kho Lo (1,055 and 6,223 m) P r o p o r t i o n (% by volume) o f n o n - m a g n e t i c h e a v y m i n e r a l c o m p o s i t i o n s i n s t r e a m s e d i m e n t 81 86 T a b l e 4-9, R e s u l t s o f t h e W a l d - w o l f o w i t z t o t a l - n u m b e r - o f - r u n s t e s t (/u) and Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t ( r ) f o r downstream t r e n d s o f h e a v y m i n e r a l c o n c e n t r a t e s f r o m p o i n t - b a r and pavement s e d i m e n t s a l o n g t h e whole r e a c h and between t h e s u p p o s e d s o u r c e o f g o l d a n d t h e c o n f l u e n c e w i t h t h e H u a i Kho Lo (1,055 and 6,223 m) 92 T a b l e 4-10. Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t s b etween w e i g h t p e r c e n t h e a v y m i n e r a l c o n c e n t r a t e s and s t r e a m c h a r a c t e r i s t i c s and s e d i m e n t p r o p e r t i e s i n t h e who l e r e a c h and between t h e s u p p o s e d s o u r c e o f g o l d and t h e c o n f l u e n c e w i t h t h e H u a i Kho Lo (1,055 and 6,223 m) 93 T a b l e 5-1. G o l d c o n c e n t r a t i o n s (ppb) i n h e a v y m i n e r a l c o n c e n t r a t e s , -0.150 and -0.053 mm s e d i m e n t f r a c t i o n s 99 T a b l e 5-2. Summary s t a t i s t i c s o f g o l d c o n t e n t (ppb) i n h e a v y m i n e r a l f r a c t i o n s 100 T a b l e 5-3. C a l c u l a t e d g o l d c o n c e n t r a t i o n s ( p p b ) , mean, m e d i a n and r a n g e o f g o l d c o n c e n t r a t i o n s i n s e d i m e n t f r a c t i o n s 102 T a b l e 5-4 T a b l e 5-5, S t a t i s t i c a l two-sample t e s t means o f Au c o n c e n t r a t i o n s (ppb) i n h e a v y m i n e r a l c o n c e n t r a t e s and i n s e d i m e n t s f r o m p o i n t b a r s and pavements i n t h e r e a c h between 2,753 and 6,223 m R e s u l t s o f t h e W a l d - w o l f o w i t z t o t a l - n u m b e r - o f - r u n s t e s t (fi) and Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t ( r ) f o r downstream t r e n d s o f Au c o n c e n t r a t i o n s (ppb) i n p o i n t - b a r and pavement s e d i m e n t s i n t h e H u a i H i n La e p 103 110 X T a b l e 5-6. Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t ( r ) between g o l d c o n c e n t r a t i o n s (ppb) i n s e d i m e n t s a t p o i n t - b a r and pavement s i t e s and s e d i m e n t t e x t u r e s o f t h e H u a i H i n L a e p 112 T a b l e 5-7, Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t ( r ) b etween g o l d c o n c e n t r a t i o n s (ppb) i n s e d i m e n t s a t p o i n t - b a r s i t e s and s t r e a m g e o m e t r y o f t h e H u a i H i n L a e p T a b l e 5-8 E s t i m a t e d numbers o f g o l d p a r t i c l e s i n h e a v y m i n e r a l c o n c e n t r a t e s 114 116 T a b l e 5-9. E s t i m a t e d numbers o f g o l d p a r t i c l e s (n) i n t h e s t a n d a r d i z e d 40 k g (-12 mm) f i e l d s a m p l e s and 30 g a n a l y t i c a l s u b s a m p l e s and p r o b a b i l i t y o f c o n t a i n i n g one o r more g o l d g r a i n s (P>0) 118 T a b l e 5-10. R e s u l t s o f t h e W a l d - w o l f o w i t z t o t a l - n u m b e r - o f - r u n s t e s t (n) and Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t ( r ) f o r downstream t r e n d s o f number o f g o l d p a r t i c l e s i n h e a v y m i n e r a l f r a c t i o n s f r o m p o i n t - b a r and pavement s a m p l e s o f t h e H u a i H i n Laep 124 T a b l e 5-11. Numbers o f g o l d p a r t i c l e s c o u n t e d f r o m pan c o n c e n t r a t e s i n t h e f i e l d and i n l a b o r a t o r y 125 T a b l e 5-12. Summary s t a t i s t i c s o f shape f a c t o r (SF) d a t a 13 0 T a b l e 5-13. R e s u l t s o f e l e c t r o n m i c r o p r o b e a n a l y s e s f o r c h e m i c a l c o m p o s i t i o n s o f t h e c o r e s and r i m s o f 39 g o l d g r a i n s 132 T a b l e 5-14. S t a t i s t i c a l two-sample t t e s t f o r t h e d i f f e r e n c e between means o f Au c o m p o s i t i o n s a t c o r e s o f p r o x i m a l (PP-97) and d i s t a l (PP-69) g o l d g r a i n s 135 T a b l e 6-1. Summary s i g n i f i c a n t c o r r e l a t i o n s between Au c o n c e n t r a t i o n s i n s e d i m e n t s a t p o i n t - b a r s i t e s and s t r e a m c h a r a c t e r i s t i c s and s e d i m e n t p r o p e r t i e s i n t h e r e a c h between t h e s u p p o s e d s o u r c e o f g o l d and t h e c o n f l u e n c e w i t h t h e H u a i Kho Lo 144 x i T a b l e 6-2. Summary s t a t i s t i c s o f median, r a n g e a n d p r o b a b i l i t y o f c o n t a i n i n g one o r more g o l d g r a i n s (P>0) f o r t h e e s t i m a t e d numbers o f g o l d p a r t i c l e s i n t h e s t a n d a r d i z e d 40 k g (-12.0 mm) f i e l d s a m p l e s and 30 g a n a l y t i c a l s u b s a m p l e s 150 x i i L I S T OF FIGURES F i g u r e 1-1. G o l d o c c u r r e n c e s i n T h a i l a n d 3 F i g u r e 1-2. R e l 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 i n w a t e r a t 20°C t o g r a i n d i a m e t e r f o r s p h e r i c a l g r a i n s o f q u a r t z , m o n a z i t e , l e a d and g o l d 10 F i g u r e 1-3. P o i s s o n p r o b a b i l i t i e s o f d e t e c t i n g g o l d p a r t i c l e s 16 F i g u r e 1-4. P o i s s o n p r o b a b i l i t y o f d e t e c t i n g no g o l d p a r t i c l e a s a f u n c t i o n o f g r a i n s i z e a n d s a m p le w e i g h t 18 F i g u r e 1-5. R e l a t i o n s h i p between p a r t i c l e s i z e a n d t h e s i z e o f sample r e q u i r e d t o c o n t a i n t w e n t y g o l d p a r t i c l e s 2 0 F i g u r e 2-1. L o c a t i o n and t o p o g r a p h y o f t h e d r a i n a g e b a s i n o f t h e H u a i H i n L a e p s t u d y r e a c h 2 5 F i g u r e 2-2. T o p o g r a p h y o f t h e H u a i H i n L a e p d r a i n a g e b a s i n 26 F i g u r e 2-3. P r i n c i p a l b e d f o r m s o f t h e H u a i H i n L a e p 28 F i g u r e 2-4. S t r e a m l o n g p r o f i l e , s h o w i n g a v e r a g e g r a d i e n t between 4 00 and 315 m a b o v e s e a l e v e l 29 F i g u r e 2-5. D e t a i l e d g e o l o g y o f t h e H u a i H i n L a e p d r a i n a g e b a s i n 31 F i g u r e 2-6. G r a i n s i z e d i s t r i b u t i o n o f t h e C h o r i z o n s o i l 34 F i g u r e 2-7. S o i l p i t a t t h e h i l l t o p s s h o w i n g A, BC and C h o r i z o n s 35 F i g u r e 2-8. S o i l p i t a t t h e b a s e o f s l o p e s h o w i n g Ap, B, BC and C h o r i z o n s 3 6 F i g u r e 2-9.\Land u s e on t h e H u a i H i n L a e p d r a i n a g e b a s i n s h o w i n g f o r e s t l o g g e d and c l e a r e d f o r a g r i c u l t u r e 37 F i g u r e 3-1. Sample l o c a t i o n s on t h e H u a i H i n L a e p 41 F i g u r e 3-2. F l o w s h e e t f o r sample p r e p a r a t i o n and a n a l y s i s 43 x i i i F i g u r e 3-3. S c a t t e r p l o t f o r d u p l i c a t e Au a n a l y s e s and g o l d s t a n d a r d s a m p l e s 50 F i g u r e 4-1. Downstream t r e n d s o f a) s t r e a m w i d t h , b) s t r e a m d e p t h and c) f l o w v e l o c i t y 57 F i g u r e 4-2. Mean w e i g h t p e r c e n t s o f s e d i m e n t s i z e d i s t r i b u t i o n i n a) p o i n t b a r and b) pavement 60 F i g u r e 4-3. C u m u l a t i v e c u r v e s f o r s e d i m e n t s i z e d i s t r i b u t i o n s 61 F i g u r e 4-4. P r o b a b i l i t y p l o t s f o r s e d i m e n t s i z e d i s t r i b u t i o n s 64 F i g u r e 4-5. Downstream t r e n d s o f a) mean g r a i n s i z e , b) s e d i m e n t s o r t i n g and c) bed r o u g h n e s s 70 F i g u r e 4-6. Downstream t r e n d s o f a) mean g r a i n s i z e and b) s e d i m e n t s o r t i n g o f c o a r s e g r a i n e d s e d i m e n t component 71 F i g u r e 4-7. Downstream t r e n d s o f w e i g h t p e r c e n t s e d i m e n t s 74 F i g u r e 4-8. G r a i n m o r p h o l o g y o f hea v y m i n e r a l c o n c e n t r a t e s 85 F i g u r e 4-9. Mean w e i g h t p e r c e n t o f h e a v y m i n e r a l d i s t r i b u t i o n s .87 F i g u r e 4-10. Downstream t r e n d s o f h e a v y m i n e r a l c o n c e n t r a t e s 88 F i g u r e 5-1. Downstream t r e n d s f o r Au c o n c e n t r a t i o n s i n h e a v y m i n e r a l c o n c e n t r a t e s 105 F i g u r e 5-2. Downstream t r e n d s f o r Au c o n c e n t r a t i o n s i n s e d i m e n t f r a c t i o n s 107 F i g u r e 5-3. Downstream t r e n d s o f t h e e s t i m a t e d numbers o f g o l d p a r t i c l e s i n h e a v y m i n e r a l c o n c e n t r a t e s 122 F i g u r e 5-4. Downstream t r e n d f o r numbers o f v i s i b l e g o l d p a r t i c l e s r e c o v e r e d i n t h e f i e l d p a n - c o n c e n t r a t e s f r o m p o i n t b a r s 126 F i g u r e 5-5. P r o b a b i l i t y p l o t o f shape f a c t o r s (SF) o f v i s i b l e g o l d p a r t i c l e s i n t h e s e l e c t e d f i e l d p a n - c o n c e n t r a t e s 128 x i v F i g u r e 5-6. M o r p h o l o g y o f g o l d g r a i n 131 F i g u r e 5-7. P o l i s h e d g o l d g r a i n s h o w i n g p a t c h y r i m s o f h i g h f i n e n e s s g o l d c o m p o s i t i o n s a l o n g t h e e d g e s 134 X V ACKNOWLEDGEMENTS S p e c i a l t h a n k s a r e due t o Mr. S. S e k t h e r a a n d Mr. M. J a m n o n g t h a i , E c o n o m i c G e o l o g y D i v i s i o n , D e p a r t m e n t o f M i n e r a l R e s o u r c e s , T h a i l a n d , f o r p r o v i d i n g a c c e s s t o i n f o r m a t i o n and f i e l d f a c i l i t i e s . Mr. S. Y e n s a b a i a n d h i s c o l l e a g u e s a r e t h a n k e d f o r t h e i r f i e l d a s s i s t a n c e . A t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , s i n c e r e a p p r e c i a t i o n i s e x p r e s s e d t o D. F e d u i k , J . B o r g e s , S. Paopongsawan and T. P r i e s t f o r l a b o r a t o r y work. W.K. F l e t c h e r p r o v i d e d g u i d a n c e , c r i t i c a l comments and h e l p f u l c r i t i c i s m . A . J . S i n c l a i r and M. C h u r c h c a r e f u l l y r e v i e w e d t h e m a n u s c r i p t . F i n a l l y , I am g r a t e f u l t o Mr. J . Mossop, t h e SNC Group, f o r f u n d i n g t h r o u g h t h e C a n a d i a n I n t e r n a t i o n a l D e v e l o p m e n t A g e n c y ( C I D A ) . 1 CHAPTER ONE INTRODUCTION 2 1.1 S t a t e m e n t o f r e s e a r c h p r o b l e m and a p p r o a c h A l t h o u g h g o l d 1 o c c u r r e n c e s have been r e c o g n i z e d f o r c e n t u r i e s i n many p a r t s o f T h a i l a n d ( F i g . 1-1) a n d p l a c e r g o l d h a s b e e n p a n n e d f r o m s m a l l d e p o s i t s a l o n g r i v e r b a n k s and f r o m s t r e a m s e d i m e n t s , t h e r e was l i t t l e s y s t e m a t i c e x p l o r a t i o n u n t i l 1984 when an e x t e n s i v e 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 was i n i t i a t e d by t h e Department o f M i n e r a l R e s o u r c e s (DMR) w i t h C a n a d i a n I n t e r n a t i o n a l D e v e l o p m e n t A g e n c y (CIDA) s u p p o r t u n d e r t h e M i n e r a l R e s o u r c e s D e v e l o p m e n t P r o j e c t (MRDP) (Kumanchan, 1987). One a s p e c t o f t h i s p r o g r a m was t o i n v e s t i g a t e , and i f a p p r o p r i a t e , a p p l y g e o c h e m i c a l methods t o g o l d e x p l o r a t i o n . However, w i t h t h e e x c e p t i o n o f t h e r e c e n t l y c o m p l e t e d , c o m p l e m e n t a r y s t u d y by Nuchanong ( 1 9 9 1 ) , no d e t a i l e d o r i e n t a t i o n s t u d i e s a r e a v a i l a b l e t o p r o v i d e g u i d e l i n e s f o r d e s i g n and i n t e r p r e t a t i o n o f e x p l o r a t i o n g e o c h e m i c a l s u r v e y s f o r g o l d i n T h a i l a n d . The o b j e c t i v e o f t h i s t h e s i s was t o remedy t h i s s i t u a t i o n . S t u d i e s e l s e w h e r e ( r e v i e w e d l a t e r i n t h i s c h a p t e r ) o f t h e e x p l o r a t i o n g e o c h e m i s t r y o f g o l d i n s t r e a m s e d i m e n t s h a v e shown t h a t : 1) t h e s c a r c i t y o f f r e e g o l d p a r t i c l e s c a n r e s u l t i n d i f f i c u l t y t o o b t a i n r e p r e s e n t a t i v e s t r e a m s e d i m e n t s a m p l e s , 2) t h e d i s p e r s i o n and d i s t r i b u t i o n o f g o l d a s a h e a v y m i n e r a l i s e x t r e m e l y e r r a t i c b e c a u s e o f t h e v a r i a t i o n s o f •'•Gold r e f e r s t o t h e m i n e r a l w h i c h i s an a l l o y o f Au w i t h m i n o r Ag, Cu, Hg e t c . Au r e f e r s t o t h e e l e m e n t o n l y . 3 97 99 101 103 105 Longitude East F i g . 1-1. G o l d o c c u r r e n c e s i n T h a i l a n d ( m o d i f i e d f r o m V u d h i c h a t v a n i c h , 1980; T a t e , 1988). Shaded a r r o w i n d i c a t e s n o r t h d i r e c t i o n . 4 l o c a l h y d r a u l i c c o n d i t i o n s t h a t c a u s e g o l d t o a c c u m u l a t e a t h i g h e n e r g y s i t e s a l o n g t h e s t r e a m bed, and 3) c o n t r a r y t o t h e c o n v e n t i o n a l e x p l o r a t i o n g e o c h e m i c a l d i l u t i o n m o d e l ( P o l i k a r p o c h k i n , 1971; Hawkes, 1 9 7 6 ) , g o l d c o n c e n t r a t i o n s t e n d t o i n c r e a s e downstream away f r o m t h e i r s o u r c e . S p e c i f i c o b j e c t i v e s o f t h i s s t u d y were, t h e r e f o r e , t o : 1) i n v e s t i g a t e b e h a v i o u r o f g o l d i n d i f f e r e n t s i z e a n d d e n s i t y f r a c t i o n s i n o r d e r t o d e t e r m i n e r e p r e s e n t a t i v e s t r e a m s e d i m e n t s a m p l e s , 2) examine t h e r e l a t i o n s between g o l d c o n c e n t r a t i o n s a n d s t r e a m c h a r a c t e r i s t i c s ( i . e . s t r e a m w i d t h , c h a n n e l d e p t h an d f l o w v e l o c i t y ) and s t r e a m s e d i m e n t p r o p e r t i e s ( i . e . mean g r a i n s i z e , s e d i m e n t s o r t i n g , bed r o u g h n e s s and a b u n d a n c e s o f s e d i m e n t f r a c t i o n s ) i n o r d e r t o u n d e r s t a n d t h e h y d r a u l i c e f f e c t s i n f l u e n c i n g t h e e r r a t i c d i s p e r s i o n o f g o l d , a n d 3) e x p l o r e t h e downstream d i s p e r s i o n o f g o l d i n o r d e r t o p r o v i d e an optimum g u i d e l i n e f o r d e s i g n o f e x p l o r a t i o n g e o c h e m i c a l s u r v e y s f o r g o l d i n T h a i l a n d . S e v e r a l a r e a s o f i n t e r e s t were s u g g e s t e d f o r s t u d y by t h e G e o c h e m i c a l S u r v e y D i v i s i o n , D e p a r t m e n t o f M i n e r a l R e s o u r c e s (DMR) . B a s e d on t h e p r e s e n c e o f g o l d i n p a n c o n c e n t r a t e s and s i t e v i s i t s i n J u l y 1989, t h e H u a i 2 H i n L a e p i n L o e i r e g i o n , n o r t h e a s t e r n T h a i l a n d was s e l e c t e d . The c a t c h m e n t , d e s c r i b e d i n g r e a t e r d e t a i l i n C h a p t e r 2, i s a 2 H u a i , i n T h a i , means s t r e a m . 5 t y p i c a l t h i r d o r d e r s t r e a m i n t h i s r e g i o n o f T h a i l a n d w i t h a h i g h s o i l e r o s i o n r a t e as a r e s u l t o f a g r i c u l t u r a l l a n d u s e . C h a p t e r 3 d e s c r i b e s c o l l e c t i o n and a n a l y s i s o f b u l k s t r e a m s e d i m e n t s a m p l e s f r o m t h e H u a i H i n L a e p . S t r e a m c h a r a c t e r i s t i c s and s e d i m e n t p r o p e r t i e s and t h e i r r e l a t i o n s a r e d e s c r i b e d i n C h a p t e r 4 w i t h r e s p e c t t o s t r e a m w i d t h , c h a n n e l d e p t h , f l o w v e l o c i t y and s e d i m e n t t e x t u r e s . I n C h a p t e r 5, v a r i a t i o n s i n g o l d c o n t e n t a r e t h e n p r e s e n t e d i n t e r m s o f t h e p a r a m e t e r s d e s c r i b e d i n C h a p t e r 4. V a r i a t i o n s i n g o l d c o n t e n t a r e t h e n d i s c u s s e d i n C h a p t e r 6 and u s e d a s a b a s i s f o r m a k i n g r e c o m m e n d a t i o n s f o r e x p l o r a t i o n . 1.2 G o l d i n s t r e a m s e d i m e n t s u r v e y s 1.2.1 I n t r o d u c t i o n The b e h a v i o u r o f g o l d i n a c t i v e s t r e a m s e d i m e n t s i s p o o r l y u n d e r s t o o d b e c a u s e o f t h e g e n e r a l s c a r c i t y o f g o l d p a r t i c l e s r e l a t i v e t o c l a s t s o f r o c k s and r o c k f o r m i n g m i n e r a l s , and i t s a p p a r e n t l y e x t r e m e l y e r r a t i c d i s t r i b u t i o n i n s t r e a m s e d i m e n t s . R e c e n t l y , however, s t u d i e s i n B r i t i s h C o l u m b i a , Canada ( e . g . Day and F l e t c h e r , 1986, 1987, 1989 a n d i n p r e s s ; F l e t c h e r , 1990; F l e t c h e r and Day, 1988a, b; F l e t c h e r a n d W o l c o t t , 1989, i n p r e s s ; F l e t c h e r and Zhang, 1989) h a v e shown t h a t v a r i a t i o n s i n g o l d c o n c e n t r a t i o n s on s t r e a m b e d s c a n be u n d e r s t a n d i n t e r m s o f s o r t i n g o f h e a v y m i n e r a l s d u r i n g b e d l o a d t r a n s p o r t o f s e d i m e n t . The f a c t o r s 6 i n v o l v e d a r e b r i e f l y r e v i e w e d i n 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 . 1.2.2 D i s t r i b u t i o n o f m e t a l a n o m a l i e s i n s t r e a m s e d i m e n t s P o l i k a r p o c h k i n (1971) and Hawkes (1976) h a v e p r e s e n t e d t h e d i l u t i o n model o f m e t a l a n o m a l i e s o f s t r e a m s e d i m e n t d ownstream o f t h e m i n e r a l i z a t i o n . The e q u a t i o n i s a s f o l l o w s : M e m A m = ( M e a - M e b ) A t + M e b A m (1-1) where M e m i s t h e m e t a l c o n t e n t o f m i n e r a l i z a t i o n , M e a i s t h e anomalous m e t a l c o n t e n t i n s e d i m e n t , Mejj i s t h e b a c k g r o u n d m e t a l c o n t e n t i n s e d i m e n t , A m i s t h e a r e a o f e x p o s e d m i n e r a l i z a t i o n , and A t i s t h e a r e a o f d r a i n a g e b a s i n . T h i s m o d e l h a s s e v e r a l l i m i t a t i o n s a r i s i n g f r o m t h e f o l l o w i n g a s s u m p t i o n s : 1) e q u a l r a t e o f e r o s i o n 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 ; 2) no c h e m i c a l i n t e r a c t i o n s o f t h e m e t a l i n t h e s t r e a m ; 3) c o n s t a n t g e o c h e m i c a l b a c k g r o u n d v a l u e s f o r t h e m e t a l ; 4) no s a m p l i n g and a n a l y t i c a l e r r o r s ; 5) s i n g l e s o u r c e o f m i n e r a l i z a t i o n i n t h e b a s i n ; 6) no c o n t a m i n a t i o n f r o m any s o u r c e s . A f u r t h e r i m p l i c i t , b u t g e n e r a l l y u n s t a t e d a s s u m p t i o n , i s t h a t w i t h i n any one s i z e f r a c t i o n , t h e v a r i o u s components o f t h e s e d i m e n t s a r e t r a n s p o r t e d a t t h e same r a t e and w i t h o u t 7 s e g r e g a t i o n ( F l e t c h e r , 1990) . T h i s m odel works r e a s o n a b l y w e l l f o r e i t h e r h o m o g e n e o u s l y d i s t r i b u t e d o r r e p r e c i p i t a t e d m i n e r a l s , f o r e x a mple, t h e d i s p e r s i o n o f Cu i n s t r e a m s e d i m e n t a n o m a l i e s d o w nstream f r o m p o r p h y r y - c o p p e r d e p o s i t s (Rose e t a l , 1 9 7 9 ) . However, anomaly d e c a y f o r e l e m e n t s s u c h a s Ba, Au, Sn and W h o s t e d i n h i g h - d e n s i t y r e s i s t a t e m i n e r a l s i s e x t r e m e l y e r r a t i c downstream f r o m t h e s o u r c e and d o e s n o t seem t o f o l l o w t h e Hawkes' model ( e . g . Ba, S l e a t h and F l e t c h e r , 1982; W, Saxby and F l e t c h e r , 1986; Sn, F l e t c h e r e t a l , 1987; Au, Day, 1988, Day and F l e t c h e r , 1987, i n p r e s s , F l e t c h e r , 1990, F l e t c h e r and Day 1988a, b) . M a j o r s o u r c e s o f v a r i a b i l i t y f o r t h e s e e l e m e n t s a r e p l a c e r - f o r m i n g h y d r a u l i c p r o c e s s e s t h a t c r e a t e l o c a l e n r i c h m e n t s o f h e a v y m i n e r a l s on t h e s t r e a m b e d . 1.2.3 H y d r a u l i c e f f e c t s The c o n d i t i o n s c o n t r o l l i n g h e a v y m i n e r a l e n r i c h m e n t a r e ( S l i n g e r l a n d , 1 9 8 4 ) : i ) t h e s e t t l i n g v e l o c i t y d i s t r i b u t i o n s o f t h e l o c a l p o p u l a t i o n s o f h e a v y and l i g h t m i n e r a l s , i i ) t h e l o n g - t e r m h y d r a u l i c f l o w a t t h e s i t e , i i i ) t h e a v e r a g e r o u g h n e s s o f t h e bed and i v ) t h e volume o f m a t e r i a l p r o c e s s e d t h r o u g h t i m e . 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 o c c u r a t p r e f e r r e d s i t e s and a t d i f f e r e n t s c a l e s e . g . b e d ( 1 0 ° m ) , b a r ( 1 0 2 m), and s y s t e m (10 4m) s c a l e s . L o c a t i o n s o f 8 e x t r e m e l y e l e v a t e d 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 ( p l a c e r d e p o s i t s ) i n p r e s e n t - d a y s t r e a m beds a r e s u m m a r i z e d i n S l i n g e r l a n d (1984, T a b l e 1 ) , S l i n g e r l a n d and S m i t h (1986, T a b l e 1) and Day (1988, T a b l e 1-1). Thus, i n e x p l o r a t i o n g e o c h e m i s t r y , s a m p l i n g a s t r e a m a t d i f f e r e n t l o c a t i o n s w i l l p r o d u c e a w i d e r a n g e o f h e a v y m i n e r a l a b u n d a n c e s , p a r t i c u l a r l y a t t h e bed and b a r s c a l e s ( F l e t c h e r , 199 0 ) . 1.2.3.1 H y d r a u l i c e q u i v a l e n c e The t e n d e n c y o f g r a i n s o f d i f f e r e n t m i n e r a l s t o be d e p o s i t e d t o g e t h e r i s d e s c r i b e d by t h e c o n c e p t o f h y d r a u l i c e q u i v a l e n c e , t h a t i s g r a i n s h a v i n g e q u a l f a l l v e l o c i t y t e n d 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 . The c o n c e p t o f h y d r a u l i c e q u i v a l e n c e i s g e n e r a l l y a t t r i b u t e d t o Rubey (193 3) a n d R i t t e n h o u s e ( 1 9 4 3 ) . Use o f t h i s c o n c e p t r e f e r s t o s e t t l i n g v e l o c i t y e q u i v a l e n c e as d e t e r m i n e d by S t o k e s ' law o r m o d i f i c a t i o n s o f i t ( T o u r t e l o t , 1968). T h i s s o r t i n g p r o c e s s r e s u l t s i n s m a l l p a r t i c l e s o f h i g h d e n s i t y b e i n g d e p o s i t e d t o g e t h e r w i t h l a r g e r , l e s s d e n s e m i n e r a l p a r t i c l e s . A l t h o u g h t h e c o n c e p t o f s e t t l i n g e q u i v a l e n c e i s u s e f u l , i t i s n o t s u f f i c i e n t by i t s e l f t o e x p l a i n t h e c o n c e n t r a t i o n o f d e t r i t a l h e a v y m i n e r a l s . I t i s t h e r e f o r e n e c e s s a r y t o c o n s i d e r o t h e r mechanisms i n f l u e n c i n g t h e f o r m a t i o n o f p l a c e r s . 9 1.2.3.2 E n t r a i n m e n t s o r t i n g E n t r a i n m e n t s o r t i n g i s t h e s e p a r a t i o n o f g r a i n s i n t o d i s t i n c t p o p u l a t i o n s o f d i f f e r e n t s i z e , d e n s i t y , a n d s h a p e by d i f f e r e n t i a l p i c k - u p o f f a bed t o p r o d u c e l a g d e p o s i t s ( S l i n g e r l a n d , 1 9 8 4). The c h a r a c t e r i s t i c o f t h i s mechanism i s t h a t l i k e - s i z e and l i k e - s h a p e p a r t i c l e s o f h e a v y m i n e r a l s a c c u m u l a t e t o g e t h e r on t h e bed b e c a u s e t h e l a r g e r l i g h t m i n e r a l p a r t i c l e s p r o t r u d i n g h i g h e r i n t o t h e f l o w a r e more s u s c e p t i b l e t o e n t r a i n m e n t . G r i g g and R a t h b u n (1969) d e f i n e d t h e c r i t i c a l s h e a r s t r e s s f o r t h e i n i t i a l m o t i o n f o r d i f f e r e n t s i z e and d e n s i t y o f s p h e r i c a l p a r t i c l e s o f q u a r t z , m o n a z i t e , l e a d and g o l d i n w a t e r a t 20°C u s i n g S h i e l d s ' c r i t e r i o n a s a f u n c t i o n o f g r a i n d i a m e t e r . The r e s u l t s ( F i g . 1-2) showed t h a t f o r g r a i n d i a m e t e r s f i n e r t h a n 0.10 mm t h e s h e a r s t r e s s r e q u i r e d t o i n i t i a t e m o t i o n i s d i r e c t l y r e l a t e d t o g r a i n d e n s i t y , w h e r e a s f o r l a r g e r g r a i n s t h e c r i t i c a l s h e a r s t r e s s i s a f u n c t i o n o f b o t h g r a i n s i z e and g r a i n d e n s i t y . A d d i t i o n a l l y , R e i d a n d F r o s t i c k (1985) showed t h a t when b e a c h b a r s a r e u n d e r low f l o w s t r e s s e s , e n t r a i n m e n t e q u i v a l e n c e a c t s a s a s o r t i n g mechanism t e n d i n g t o h o m o g e n i z e t h e s i z e d i s t r i b u t i o n o f l i g h t and h e a v y m i n e r a l p a r t i c l e s . T h i s i m p l i e s t h a t s i z e a l o n e i s an i m p o r t a n t f a c t o r c o n t r o l l i n g e n t r a i n m e n t ( S t e i d t m a n n , 1982). S l i n g e r l a n d (1977, 1984) and Komar and Wang (1984) showed t h a t e n t r a i n m e n t s o r t i n g was c o n t r o l l e d by t h e s i z e 10 DIAMETER. IN MILLIMETERS F i g . 1-2. R e l 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 i n w a t e r a t 20 ° C t o g r a i n d i a m e t e r f o r s p h e r i c a l g r a i n s o f q u a r t z , m o n a z i t e , l e a d , a n d g o l d ( f r o m G r i g g and Rathbun, 1969). 11 a n d d e n s i t y o f m i n e r a l s u n d e r d i f f e r e n t R e y n o l d s ' c r i t e r i a and b e d r o u g h n e s s . However, S l i n g e r l a n d and S m i t h (1986) p o i n t e d o u t t h a t t h e s e r e s u l t s a p p l i e d o n l y t o s i m i l a r l y s i z e d s e d i m e n t s on a p l a n e bed. I t was n o t p o s s i b l e t o p r e d i c t f r o m F i g u r e 1-2 w h i c h s i z e s o f d i f f e r e n t - d e n s i t y m i n e r a l s w o u l d be e n t r a i n e d t o g e t h e r f r o m a n a t u r a l b e d . T h e y c o n c l u d e d t h a t winnowing, a r m o r i n g and h i d i n g a r e i m p o r t a n t i n e n t r a i n m e n t s o r t i n g i n m i x e d bed r o u g h n e s s . R e c e n t l y , K u h n l e and S o u t h a r d (1990) e m p i r i c a l l y s t u d i e d i n f l u m e e x p e r i m e n t s t h e r e s p o n s e o f a m i x t u r e o f l i g h t s a n d much f i n e r h e a v i e s t o a r a n g e o f i m p o s e d f l o w s i n a g r a v e l - b e d c h a n n e l . O ver a w i d e r a n g e o f f l o w s and s e d i m e n t f e e d r a t e s , a l a y e r o f h i g h l y c o n c e n t r a t e d h e a v y m i n e r a l s f o r m e d a t t h e b a s e o f t h e a c t i v e l a y e r b e f o r e e q u i l i b r i u m t r a n s p o r t o f t h e h e a v y m i n e r a l s was a t t a i n e d . Once d e p o s i t e d , e n t r a i n m e n t o f f i n e r (< 1 mm) h e a v y m i n e r a l s w o u l d be u n l i k e l y a t any f l o w s t r e n g t h . T h i s a l s o s u g g e s t s t h a t f o r f i n e g r a i n e d s i z e s , d e n s i t y i s an i m p o r t a n t c o n t r o l on t h e e n t r a i n m e n t mechanism. 1.2.3.3 D i s p e r s i v e o r s h e a r s o r t i n g D i s p e r s i v e o r s h e a r s o r t i n g i s a v e r t i c a l f r a c t i o n a t i o n o f p a r t i c l e s i n t o d i f f e r e n t l a y e r s w i t h i n a c o n c e n t r a t e d g r a n u l a r d i s p e r s i o n c a u s e d by d i s p e r s i v e p r e s s u r e s i n a m o v i n g b e d l a y e r o r a g r a i n f l o w ( S l i n g e r l a n d , 1984 a n d S l i n g e r l a n d and S m i t h , 1986). T h i s s o r t i n g mechanism o c c u r s 12 due t o t h e d i s p e r s i v e p r e s s u r e s a r i s i n g f r o m g r a i n c o l l i s i o n s ( S a l l e n g e r , 1979). A s i m i l a r e f f e c t i s p r o d u c e d by k i n e t i c s i e v i n g , w h e r e i n s m a l l e r g r a i n s f a l l b e t w e e n l a r g e r o n e s ( M i d d l e t o n , 1970). B o t h c a s e s p r o d u c e i n v e r s e l y g r a d e d d e p o s i t s ( l a r g e r o r d e n s e r g r a i n s d e p o s i t on t o p ) . I n t h e c a s e o f g r a i n c o l l i s i o n s , S a l l e n g e r (1979) showed t h a t i ) a l o n g any one h o r i z o n o f a g r a i n f l o w composed o f l i g h t and h e a v y g r a i n s o f d i f f e r e n t s i z e s , a h e a v y g r a i n w o u l d be s m a l l e r t h a n an a s s o c i a t e d l i g h t g r a i n a n d i i ) h e a v y m i n e r a l s g e n e r a l l y i n c r e a s e d i n c o n c e n t r a t i o n w i t h d e p t h i n t h e l a m i n a t i o n . I n t h e c a s e o f k i n e t i c s i e v i n g , s m a l l e r o r d e n s e r g r a i n s f a l l downward bet w e e n l a r g e r g r a i n s r e s u l t i n g i n c o a r s e and l e s s h e a v y m i n e r a l s s t a y i n g a b o v e t h e s m a l l e r g r a i n s ( S l i n g e r l a n d , 1984) . N e v e r t h e l e s s , Komar and Wang (1984) s u g g e s t e d t h a t d i s p e r s i v e s o r t i n g was l e s s i m p o r t a n t t h a n e n t r a i n m e n t s o r t i n g . D i s p e r s i v e s o r t i n g may, however, a c t t o f e e d l a r g e r l i g h t m i n e r a l g r a i n s t o t h e t o p o f t h e m o b i l e l a y e r where t h e i r p r o t r u s i o n e n s u r e s t h a t t h e y a r e s u b j e c t t o e n t r a i n m e n t . T h i s l e a v e s a l a g o f s m a l l e r h e a v y m i n e r a l s ( R e i d a n d F r o s t i c k , 1 9 85). 1.2.3.4 I n t e r s t i c e e n t r a p m e n t o r t r a p p i n g I n t e r s t i c e e n t r a p m e n t may be t h e b e s t mechanism t o e x p l a i n 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 a s s o c i a t e d w i t h much c o a r s e r s e d i m e n t s where t h e d i f f e r e n c e between g r a i n s i z e s 13 o f l i g h t and h e a v y m i n e r a l s c a n n o t e f f e c t i v e l y be e x p l a i n e d by 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 . I f g r a i n s a r e a l r e a d y i n m o t i o n , d e n s e r p a r t i c l e s may be t r a p p e d o r s e l e c t e d o u t o f t h e w a n i n g bed l o a d i n p r e f e r e n c e t o l e s s d e n s e p a r t i c l e s b e c a u s e t h e y t e s t t h e bed more o f t e n , and o n c e i n p l a c e a r e n o t r e e n t r a i n e d ( S l i n g e r l a n d a n d S m i t h , 1 9 8 6 ) . A p o s s i b l e p r o c e s s f o r t r a p p i n g i s t h a t t h e l a r g e r f r a mework p a r t i c l e s a r e d e p o s i t e d f i r s t , i m m e d i a t e l y a f t e r e x t r e m e f l o o d e v e n t s , w h i l e t h e h e a v y m i n e r a l s a c c u m u l a t e l a t e r a s p a r t o f a m a t r i x w h i c h s e l e c t i v e l y f i l t e r s i n t o t h e p o r e s o f t h e s t r e a m b e d ( R e i d and F r o s t i c k , 1 9 8 5 ) . T h i s a g r e e s w e l l w i t h r e s u l t s o f a r e c e n t s t u d y by Day a n d F l e t c h e r ( i n p r e s s ) a t H a r r i s C r e e k , s o u t h c e n t r a l B r i t i s h C o l u m b i a , Canada. B e s c h t a and J a c k s o n (1979) and F r o s t i c k e t a l (1984) e m p i r i c a l l y s t u d i e d t h e i n f i l t r a t i o n o f f i n e s e d i m e n t s i n t o a c o a r s e - g r a i n e d s t r e a m b e d . They c o n c l u d e d t h a t f i n e p a r t i c l e s b l o c k e d p o r e s o f t h e n e a r - s u r f a c e c o a r s e - g r a i n e d s t r e a m b e d and p r e v e n t e d f u r t h e r i n t r u s i o n . R e i d and F r o s t i c k (1985) f u r t h e r s u g g e s t e d t h a t c l o g g i n g i n c o a r s e n i n g upwards g r a v e l s p r e v e n t s 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 by e n t r a p m e n t , and t h a t t h e s e a r e u n l i k e l y t o be s i t e s o f p l a c e r f o r m a t i o n . I n c o n t r a s t , where g r a v e l s a r e p r o g r e s s i v e l y f i n e upwards t h e p o r e s t e n d e d t o be p a c k e d u n i f o r m l y , p r o v i d i n g g r e a t e r p o t e n t i a l f o r p l a c e r d e v e l o p m e n t . T h i s t r a p p i n g mechanism a g r e e s w e l l w i t h t h e t r a p p i n g o f a l l u v i a l g o l d i n P r e c a m b r i a n c o n g l o m e r a t i c g o l d d e p o s i t s ( S m i t h and M i n t e r , 14 1980) i n t h e W i t w a t e r s r a n d b a s i n . 1.2.3.5 T r a n s p o r t e q u i v a l e n c e S l i n g e r l a n d ( 1 9 8 4 ) , F l e t c h e r and Day (1988b) and Day and F l e t c h e r ( i n p r e s s ) u s e d t h e m o d i f i e d s t o c h a s t i c b e d l o a d t r a n s p o r t e q u a t i o n o f E i n s t e i n (1950) t o e s t i m a t e t r a n s p o r t e q u i v a l e n c e o f low- and h i g h - d e n s i t y m i n e r a l s i n r e a l s t r e a m s by u s i n g t h e t r a n s p o r t r a t i o s o f l o w - d e n s i t y t o h i g h - d e n s i t y m i n e r a l s (e-g- q u a r t z : m a g n e t i t e a n d q u a r t z : g o l d ) f o r d i f f e r e n t bed r o u g h n e s s c o n d i t i o n s . T h e y f o u n d t h a t f o r b o t h low- and h i g h - d e n s i t y m i n e r a l s , f i n e p a r t i c l e s (< 0.053 mm) be h a v e d v e r y s i m i l a r , b u t t h a t c o a r s e h i g h - d e n s i t y m i n e r a l s t e n d e d t o p r e f e r e n t i a l l y a c c u m u l a t e a t h i g h b e d r o u g h n e s s s i t e s . Day and F l e t c h e r ( i n p r e s s ) f u r t h e r showed t h a t d e c r e a s i n g g r a d i e n t a l o n g a s t r e a m ' s l o n g i t u d i n a l p r o f i l e m i g h t r e s u l t i n i n c r e a s i n g g o l d c o n c e n t r a t i o n s downstream away f r o m t h e s o u r c e . 1.2.4 S a m p l i n g c o n s i d e r a t i o n s The s a m p l i n g d i s t r i b u t i o n o f v e r y r a r e m i n e r a l g r a i n s ( e . g . g o l d , c a s s i t e r i t e , diamond, e t c . ) i n r o c k s , s o i l s a nd s t r e a m s e d i m e n t s c a n be d e s c r i b e d by t h e P o i s s o n d i s t r i b u t i o n (Koch and L i n k , 1970; I n g a m e l l s , 1981) w h i c h i s d e f i n e d a s 15 p ( n ) = M n*e~ M/n! (1-2) where \i i s t h e e x p e c t e d number o f p a r t i c l e s a nd P ( n ) i s t h e p r o b a b i l i t y o f n p a r t i c l e s o c c u r r i n g i n t h e s a m p l e . The c o n f i d e n c e l i m i t a t s i g n i f i c a n c e l e v e l A f o r t h e mean (n) c a n be e s t i m a t e d f r o m t h e c h i - s q u a r e d (X ) d i s t r i b u t i o n ( Z a r , 1984) a s ( * 2 ( l - A / 2 ) ,2N)/2 < M < (* 2(A/2) , 2 ( N + l ) ) / 2 (1-3) where N i s an e s t i m a t e o f /x. The i m p l i c a t i o n s o f t h e above e q u a t i o n s t o s t r e a m s e d i m e n t s a m p l i n g f o r g o l d a r e i l l u s t r a t e d i n t h e f o l l o w i n g e x a m p l e . G o l d i s assumed t o be d i s t r i b u t e d e v e n l y , a s f r e e s p h e r i c a l p a r t i c l e s ( d i a m e t e r 0.175 mm), t h r o u g h o u t t h e s e d i m e n t a t a c o n c e n t r a t i o n o f 200 ppb Au. The g o l d c o n t e n t o f o t h e r m i n e r a l s i s c o n s i d e r e d n e g l i g i b l e . R e p r e s e n t a t i v e s a m p l e s w e i g h i n g 250 g a r e t a k e n f r o m t h e s e d i m e n t . A s s u m i n g t h a t t h e g o l d d e n s i t y i s 15 g/cm 3, t h e e x p e c t e d w e i g h t o f g o l d i s t h e r e f o r e 50 (ig ( b a s e d on b u l k c o n c e n t r a t i o n ) . The mass o f e a c h s p h e r i c a l g o l d p a r t i c l e ( d e n s i t y = 15 g/cm 3, d i a m e t e r = 0.175 mm) i s 42.11 /ig. T h e r e f o r e , t h e e x p e c t e d number o f g o l d p a r t i c l e s (ju) , on a v e r a g e , i s 1.19. U s i n g t h e P o i s s o n d i s t r i b u t i o n e q u a t i o n (1-2) , t h e p r o b a b i l i t y t h a t t h e sample w i l l c o n t a i n no f r e e g o l d (P(o)i n = 0) i s 0.3042. Thus, t h e r e i s a 30.42% c h a n c e t h a t t h e a n o m a l y w i l l go u n d e t e c t e d ( F i g . l - 3 a ) . I f t h e s a m p l e w e i g h s 30 g ( a p p r o x i m a t e l y 1 a s s a y t o n ) , t h e n /x = 0.14 and P(o) = 16 T 1 2 Number of grains F i g . 1-3. P o i s s o n p r o b a b i l i t i e s o f d e t e c t i n g g o l d p a r t i c l e s a) e x p e c t e d number o f g o l d p a r t i c l e s (/x) = 1.19, b) e x p e c t e d number o f g o l d p a r t i c l e s i n 30 g a n a l y t i c a l s a m p le (M) = 0.14. 17 86.94% ( F i g . l - 3 b ) . However, i f a s i n g l e p a r t i c l e o f g o l d h a p p e n s t o be p r e s e n t i n t h e sample ( P ( i ) - 12.17%) t h e n t h e a n a l y s i s w o u l d be 1400 ppb, 7 t i m e s t h e t r u e c o n c e n t r a t i o n o f 200 ppb. T h i s r e s u l t has l e d t o t h e t e r m " n u g g e t e f f e c t " t o d e s c r i b e e r r a t i c a l l y h i g h Au v a l u e s r e s u l t i n g f r o m t h e p r e s e n c e o f a s i n g l e o r v e r y few g o l d p a r t i c l e s i n a s m a l l s a m p l e ( I n g a m e l l s , 1981). V a r i a t i o n i n t h e p a r t i c l e s i z e and sample s i z e u s e d f o r a n a l y s i s w i l l h a v e a d r a m a t i c e f f e c t on t h e r e s u l t o b t a i n e d . Assume t h a t t h e s t r e a m s e d i m e n t c o m p r i s e s f i v e e q u a l l y p r o p o r t i o n e d s i z e f r a c t i o n s (200, 150, 100, 75 and 50 m i c r o n s ) , and e a c h c o n t a i n s 100 ppb Au a s f r e e s p h e r i c a l p a r t i c l e s . A 1000 gram f i e l d sample p r o v i d e s 2 00 grams o f e a c h f r a c t i o n f o r a n a l y s i s . R e p r e s e n t a t i v e 10 and 3 0 gram s u b s a m p l e s s p l i t f r o m e a c h s i z e f r a c t i o n a r e a n a l y z e d f o r Au by FA-AAS. U s i n g e q u a t i o n 1-2, t h e p r o b a b i l i t i e s o f t h e s e s a m p l e s (200, 30, and 10 gram) c o n t a i n i n g no g o l d p a r t i c l e s (P(0) / n = 0) a r e shown i n F i g u r e 1-4. R e s u l t s a r e s t r o n g l y d e p e n d e n t on g r a i n s i z e and sample s i z e . The s c a r c i t y o f g o l d p a r t i c l e s i n c o a r s e s e d i m e n t f r a c t i o n s l e a d s t o a h i g h p r o b a b i l i t y o f Au n o t b e i n g d e t e c t e d , w h e r e a s i n t h e f i n e s i z e f r a c t i o n s t h e r e i s a g r e a t e r c h a n c e o f d e t e c t i n g Au. C l i f t o n e t a l (1969) p o i n t e d o u t t h a t , b a s e d on t h e b i n o m i a l d i s t r i b u t i o n , an a d e q u a t e sample s i z e p r o v i d i n g an a c c e p t a b l e p r e c i s i o n ( r e l a t i v e e r r o r s o f 4-54 and -34% (±44% on a v e r a g e ) , a t t h e 95% c o n f i d e n c e l e v e l ) s h o u l d c o n t a i n a t l e a s t 20 p a r t i c l e s o f g o l d . The r e l a t i o n s b etween p a r t i c l e 200 150 100 50 0 Particle Size (microns) F i g . 1-4. P o i s s o n p r o b a b i l i t y o f d e t e c t i n g no g o l d p a r t i c l e a s a f u n c t i o n o f g r a i n s i z e and sample w e i g h t . 19 s i z e , p a r t i c l e s h a p e and t h e minimum sample s i z e r e q u i r e d t o c o n t a i n 2 0 g o l d p a r t i c l e s a r e p r e s e n t e d i n F i g u r e . 1-5. 1.2.5 F i e l d s t u d i e s o f h e a v y m i n e r a l s i n s t r e a m s R e c e n t l y , s e v e r a l s t u d i e s o f t h e b e h a v i o u r o f h e a v y m i n e r a l s a n d f r e e g o l d p a r t i c l e s i n g r a v e l - b e d s t r e a m s h a v e b e e n c a r r i e d o u t , f o r example, g o l d i n B r i t i s h C o l u m b i a , t u n g s t e n i n Yukon T e r r i t o r y , Canada, and c a s s i t e r i t e i n a m o u n t a i n s t r e a m i n M a l a y s i a . The p u r p o s e o f t h e s e s t u d i e s was t o s o l v e t h e p r o b l e m s o f e x t r e m e l y e r r a t i c and i r r e p r o d u c i b l e r e s u l t s o f s t r e a m s e d i m e n t s u r v e y s f o r r a r e h e a v y m i n e r a l g r a i n s . F l e t c h e r e t a l (1987) u s e d a n a l y s i s o f v a r i a n c e (ANOVA) t o e v a l u a t e r e d u c t i o n o f a m o n g - s i t e / w i t h i n - s i t e v a r i a n c e o f Sn c o n c e n t r a t i o n s i n t h e same s i z e f r a c t i o n a t low and h i g h e n e r g y s i t e s and between s i z e f r a c t i o n s , i n a M a l a y s i a n m o u n t a i n s t r e a m . They f o u n d t h a t l o c a l h y d r a u l i c c o n d i t i o n s c o n t r o l t h e a c c u m u l a t i o n o f c a s s i t e r i t e , and t h a t t h e r e i s no r e l a t i o n between t h e m a g n i t u d e o f an anomaly and p r o x i m i t y t o i t s s o u r c e . S a xby and F l e t c h e r (198 6b) u s e d t h e 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) t o e s t i m a t e l o c a l h y d r a u l i c e f f e c t s on h e a v y m i n e r a l s (W, i n t h i s c a s e ) i n a Yukon T e r r i t o r y s t r e a m . The GMCR i s b a s e d on a n a l y s i s o f t h e same s i z e f r a c t i o n o f p a i r e d s e d i m e n t s a m p l e s f r o m h i g h - a n d l o w - e n e r g y e n v i r o n m e n t s : 20 F i g . 1-5. R e l a t i o n s between p a r t i c l e s i z e and t h e s i z e o f s a m p l e r e q u i r e d t o c o n t a i n t w e n t y g o l d p a r t i c l e s ( a f t e r C l i f t o n e t a l , 1969). 21 n GMCR = a n t i l o g {(Sum l o g 1 0 C R ) f n } (1-4) 1 C R = c h e / c l e where CR = c o n c e n t r a t i o n r a t i o , Cfte = c o n c e n t r a t i o n o f a m i n e r a l f o r h i g h e n e r g y s i t e , C i e = c o n c e n t r a t i o n o f a m i n e r a l f o r low e n e r g y s i t e , n = t h e number' o f p a i r s . T h e y a l s o f o u n d t h a t , l i k e c a s s i t e r i t e ( F l e t c h e r e t a l , 1987) , h y d r a u l i c e f f e c t s a r e d e p e n d e n t on g r a i n s i z e a nd d e n s i t y , a nd a r e r e d u c e d i n f i n e s e d i m e n t f r a c t i o n s . A l t h o u g h l o c a l h y d r a u l i c v a r i a b i l i t y c a n be m i n i m i z e d by u s e o f t h e f i n e s i z e f r a c t i o n s , i t a t t h e same t i m e c a n r e m a i n an i m p o r t a n t s o u r c e o f n o i s e i n d r a i n a g e g e o c h e m i c a l s u r v e y s i f v e r y l a r g e s e d i m e n t s a m p l e s a r e p r o c e s s e d t o o b t a i n r e p r e s e n t a t i v e h e a v y m i n e r a l c o n c e n t r a t e s . I n t h e H a r r i s C r e e k , s o u t h c e n t r a l B r i t i s h C o l u m b i a , Day (1988) and Day and F l e t c h e r (1986) e s t i m a t e d numbers o f g o l d p a r t i c l e s and t h e n u s e d t h e P o i s s o n d i s t r i b u t i o n ( e q u a t i o n 1-2) t o d e t e r m i n e an a d e q u a t e l y r e p r e s e n t a t i v e f i e l d s a m p l e s i z e . They f o u n d t h a t , b e c a u s e o f t h e s c a r c i t y o f g o l d p a r t i c l e s i t was n e c e s s a r y t o f i e l d s c r e e n 60 k g o f -2 mm s e d i m e n t f r o m up t o 2 50 k g o f b u l k s e d i m e n t . Day ( 1 9 8 8 ) , Day and F l e t c h e r (1989) and F l e t c h e r a nd Day (1988b) a l s o u s e d GMCR t o e v a l u a t e downstream d i s p e r s i o n t r e n d s f o r g o l d i n s t r e a m s e d i m e n t and t h e i n f l u e n c e o f h y d r a u l i c e f f e c t s on 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 . They f o u n d t h a t l o c a l h y d r a u l i c p r o c e s s e s r e s u l t e d i n downstream e r r a t i c 22 g e o c h e m i c a l d i s p e r s i o n p a t t e r n s o f g o l d between a s s o c i a t e d h i g h - and l o w - e n e r g y e n v i r o n m e n t s , b u t v a r i a t i o n s were r e d u c e d f o r f i n e g r a i n e d ( e . g . < 0.053 mm) f r a c t i o n s . F u r t h e r i n v e s t i g a t i o n s , Day and F l e t c h e r ( i n p r e s s ) and F l e t c h e r (1990) have shown t h a t g o l d i n t h e H a r r i s C r e e k i s p r e f e r e n t i a l l y a c c u m u l a t e d a t h i g h bed r o u g h n e s s s i t e s a n d a s t h e s t r e a m g r a d i e n t d e c r e a s e s downstream. T h e s e r e s u l t s a r e c o n s i s t e n t w i t h f i e l d o b s e r v a t i o n s (Day and F l e t c h e r , 1989; F l e t c h e r and Day, 1988b) and w i t h b e d l o a d t r a n s p o r t m o d e l s ( S l i n g e r l a n d , 1984; S l i n g e r l a n d and S m i t h , 1 9 8 6 ) . B a s e d on t h e above i t i s a p p a r e n t t h a t 1) l a r g e s e d i m e n t i s r e q u i r e d f o r a r e p r e s e n t a t i v e s a m p l e f o r g o l d a n d 2) t h e d i s p e r s i o n o f g o l d i n s t r e a m s e d i m e n t d e p e n d s m a i n l y on l o c a l h y d r a u l i c p r o c e s s e s and c h a n n e l p h y s i c a l c h a r a c t e r i s t i c s . T h i s s t u d y w i l l i n v e s t i g a t e t h e b e h a v i o u r o f g o l d i n a f l u v i a l e n v i r o n m e n t d i f f e r e n t f r o m t h a t o f t h e H a r r i s C r e e k , B r i t i s h C o l u m b i a . 23 CHAPTER TWO DESCRIPTION OF STUDY AREA 24 2.1 L o c a t i o n and a c c e s s The H u a i H i n L a e p c a t c h m e n t i s i n t h e Na Duang d i s t r i c t (map s c a l e 1:50,000, s e r i e s L 7017, s h e e t s 5444 I I I and 5443 I V ) , a b o u t 50 k i l o m e t r e s e a s t o f L o e i ( F i g . 2 - 1 ) . The s t u d y a r e a i s a c c e s s i b l e by an a l l - s e a s o n h a r d - s u r f a c e r o a d f r o m L o e i . 2.2 B a s i n m o r p h o l o g y and t o p o g r a p h y The c a t c h m e n t o f t h e H u a i H i n L a e p ( F i g . 2-2) i s a s y m m e t r i c a l l y s h a p e d w i t h an a r e a o f a p p r o x i m a t e l y 8 s q u a r e k i l o m e t r e s . T o p o g r a p h i c a l l y , t h e c a t c h m e n t i s u n d u l a t i n g low r e l i e f l y i n g on a p l a t e a u t h a t becomes i n c r e a s i n g l y d i s s e c t e d f r o m n o r t h w e s t t o s o u t h e a s t a t e l e v a t i o n s o f a p p r o x i m a t e l y 400 t o 320 m e t r e s above mean s e a l e v e l . T he H u a i H i n L a e p i s a t h i r d o r d e r (as r e p r e s e n t e d on t h e map s c a l e o f 1:50,000) i n t e r m i t t e n t t r i b u t a r y o f t h e H u a i Kho L o . The s t r e a m i s a p p r o x i m a t e l y 6.5 k i l o m e t r e s l o n g ( m e a s u r e d f r o m t h e t o p o g r a p h i c map) w i t h an a v e r a g e g r a d i e n t o f a p p r o x i m a t e l y 0.01. However, f r o m f i e l d m e asurements, t h e s t r e a m i s a b o u t 8.8 k i l o m e t r e s l o n g . B e c a u s e t h e v a l l e y i s n o t w e l l - d e v e l o p e d , i t i s assumed t h a t v a l l e y l e n g t h e q u a l s s t r e a m l e n g t h f r o m t h e t o p o g r a p h i c map and t h a t c h a n n e l l e n g t h e q u a l s t h e f i e l d measurement (8.8 km). S i n u o s i t y c a n t h e r e f o r e be e s t i m a t e d . By d e f i n i t i o n , s i n u o s i t y i s t h e r a t i o o f c h a n n e l l e n g t h t o v a l l e y l e n g t h ( C h o r l e y e t a l , 25 F i g . 2-1. L o c a t i o n and t o p o g r a p h y o f t h e d r a i n a g e b a s i n o f t h e H u a i H i n L a e p s t u d y r e a c h ( c o n t o u r l i n e s a r e a t 400 m ASL, d o t t e d l i n e s a r e h a r d s u r f a c e r o a d s ; d a s h e d l i n e i s c a t c h m e n t b o u n d a r y ; s h a d e d s t a r s a r e s u p p o s e d b e d r o c k s o u r c e s o f g o l d m i n e r a l i z a t i o n ; s h a d e d a r r o w i n d i c a t e s n o r t h d i r e c t i o n ) . 26 F i g . 2-2. T o p o g r a p h y o f t h e H u a i H i n Laep d r a i n a g e b a s i n . 27 1984 and Schumm, 1985). S t r e a m meanders a r e c o n s t r a i n e d by a d j a c e n t h i l l s l o p e s , so t h e c h a n n e l i s c o n s i d e r e d t o be s t r a i g h t w i t h s i n u o s i t y = 1.35, where t h e d i v i d i n g p o i n t b e t w e e n s t r a i g h t and m e a n d e r i n g c h a n n e l s i s 1.5 ( S e l b y , 1 9 8 5 ) . Pavement r i f f l e s ( F i g . 2 - 3 a ) , p o o l s and p o i n t b a r s ( F i g . 2-3b) a r e t y p i c a l c h a n n e l f o r m s . On a v e r a g e , p a v e m e n t s c o n s i s t p r i m a r i l y o f g r a v e l and c o a r s e s a n d w i t h a b o u t 10% s i l t a nd c l a y . T h ey a r e f o r m e d a t t h e t o p o g r a p h i c h i g h a r e a o f t h e s t r e a m c h a n n e l l o c a t e d between a p a i r o f p o i n t b a r s . P o o l s and p o i n t b a r s a r e p a i r e d , w i t h t h e p o o l s on t h e o u t e r p a r t o f s t r e a m b e n d s . P o i n t b a r s , on t h e i n s i d e o f c h a n n e l b e n d s , a l s o c o n s i s t m a i n l y o f g r a v e l b u t c o n t a i n more s i l t a n d c l a y (" 17%) t h a n pavement. 2.3 S t r e a m l o n g i t u d i n a l p r o f i l e The H u a i H i n L a e p s t u d y r e a c h , between an e l e v a t i o n o f a b o u t 380 m and 315 m above mean s e a l e v e l , i s 7,763 m e t r e s l o n g w i t h t h e a v e r a g e g r a d i e n t o f 0.008 ( F i g . 2 - 4 ) . G r a d i e n t d e c r e a s e s f r o m 0.013 a t t h e s t r e a m h e a d w a t e r t o 0.003 a t t h e c o n f l u e n c e w i t h t h e main s t r e a m , t h e H u a i Kho L o . T h e r e were no m a j o r r a i n f a l l s d u r i n g t h e s a m p l i n g p e r i o d and s t r e a m d i s c h a r g e r e m a i n e d n e a r l y c o n s t a n t . S t r e a m w i d t h a t w a t e r l e v e l r a n g e d f r o m a b o u t 0.5 m a t r i f f l e s t o 6.5 m a t p o o l s , w i t h d e p t h s r a n g i n g f r o m a b o u t 0.5 t o 0.9 m, r e s p e c t i v e l y . F l o w v e l o c i t y v a r i e d f r o m s t a g n a n t t o a b o u t 1 m/second. F i g . 2-3. P r i n c i p a l bedforms of the Huai Hin Laep, a) sandy gravel pavement and b) sandy gravel point bar. 500 F i g . 2-4. Stream l o n g p r o f i l e , s h o w i n g a v e r a g e g r a d i e n t b e t w e e n 380 and 315 m above mean s e a l e v e l . The whole s e c t i o n i s 7,763 m l o n g . A r r o w i n d i c a t e s c o n f l u e n c e w i t h t h e H u a i Kho Lo. 30 2.4 Geolocfv G e o l o g y o f L o e i r e g i o n (Appendix) h a s b e e n s t u d i e d by C h a r o e n p r a v a t e t a l ( 1 9 7 6 ) . The a r e a i s u n d e r l a i n by S i l u r i a n - D e v o n i a n (SD) t o Lower P e r m i a n ( P i ) s e d i m e n t a r y r o c k s a n d P e r m o - T r i a s s i c (PTR) i g n e o u s r o c k s . D e t a i l e d g e o l o g y o f t h e s t u d y a r e a i s shown i n F i g . 2-5. The S i l u r i a n - D e v o n i a n (SD) u n i t c o n s i s t s o f s h a l e s , p h y l l i t i c s h a l e s i n t e r b e d d e d w i t h s a n d y s h a l e s , a c t i n o l i t e s c h i s t , p h y l l i t e , h o r n f e l s i c r o c k s , m e t a - t u f f and s a n d s t o n e s . Q u a r t z v e i n s o c c u r i n f r a c t u r e s . The D e v o n i a n u n i t (D) c o n s i s t s o f s h a l e s i n t e r b e d d e d w i t h g r e y t h i n b e d d e d c h e r t , l i m e s t o n e and v o l c a n i c t u f f s . The C a r b o n i f e r o u s u n i t (C3J c o m p r i s e s g r e y s h a l e s , w e l l - b e d d e d s a n d s t o n e s , c o n g l o m e r a t i c s a n d s t o n e , c o n g l o m e r a t e a n d g r e y l i m e s t o n e . T h e s e t h r e e r o c k u n i t s a r e o v e r l a i n by t h i c k l y b e d d e d t o m a s s i v e P e r m i a n l i m e s t o n e ( P i ) . V o l c a n i c r o c k s (PTR-v) a r e m a i n l y r h y o l i t e p o r p h y r i e s , r h y o l i t i c t u f f s and a n d e s i t e s . A l l r o c k u n i t s have u n d e r g o n e low g r a d e metamorphism, a r e t i g h t l y f o l d e d , and a r e i n t r u d e d by numerous s t o c k s and d y k e s o f h o r n b l e n d e g r a n o d i o r i t e , h o r n b l e n d e d i o r i t e a n d p y r o x e n i t e w h i c h i s p a r t l y a l t e r e d t o s e r p e n t i n i t e . 31 F i g . 2-5. D e t a i l e d g e o l o g y o f t h e H u a i H i n L a e p d r a i n a g e b a s i n (SD = S i l u r i a n - D e v o n i a n ; C± = C a r b o n i f e r o u s ; PTR-v = P e r m o - t r i a s s i c v o l c a n i c r o c k s ; s h a d e d s t a r s a r e s u p p o s e d b e d r o c k s o u r c e s o f g o l d m i n e r a l i z a t i o n ; l a b e l e d r e c t a n g u l a r i n d i c a t e s DMR g r i d s o i l s a m p l i n g a r e a ) . 32 2.5 S o u r c e o f g o l d i n t h e H u a i H i n Laep A l t h o u g h v i s i b l e g o l d i s common i n pan c o n c e n t r a t e s f r o m t h e H u a i H i n Laep, i t s e x a c t b e d r o c k s o u r c e i s n o t known. A n a l y s i s o f B h o r i z o n s o i l s c o l l e c t e d f r o m t h e s u p p o s e d s o u r c e o f g o l d m i n e r a l i z a t i o n ( F i g . 2-5) f a i l e d t o d e t e c t a g o l d anomaly ( Y e n s a b a i and J a m n o n g t h a i , 1 9 9 0 ) . However, b a s e d on s e v e r a l g o l d - q u a r t z v e i n o c c u r r e n c e s r e l a t e d t o p o r p h y r y and s k a r n d e p o s i t s i n t h e L o e i r e g i o n ( F i g . 1-1) [ e . g . Phu Tham P h r a (Kumanchan, p e r s . comm., 1989; Nuchanong, 1988; T a t e , 1988), Phu L o n ( V u d h i c h a t v a n i c h e t a l , 1980; T a t e , 1988), Phu Khum Thong, Phu Khum I a n d Phu Khum I I (Kumanchan, p e r s . comm., 1 9 8 9 ) ] , t h e g o l d i s t h o u g h t ( Y e n s a b a i , p e r s . comm., 1989) t o be a s s o c i a t e d w i t h q u a r t z v e i n f l o a t f o u n d i n two a r e a s n e a r t h e h e a d w a t e r s o f t h e H u a i H i n L a e p . 2.6 C l i m a t e , s o i l s , v e g e t a t i o n and l a n d u s e The L o e i r e g i o n h as a monsoonal c l i m a t e w i t h a l o n g r a i n y s e a s o n f r o m May t o O c t o b e r , w i n t e r s e a s o n f r o m November t o F e b r u a r y , and summer s e a s o n f r o m M a r c h t o A p r i l . A v e r a g e a n n u a l r a i n f a l l i s a p p r o x i m a t e l y 1100 mm, and a v e r a g e a n n u a l t e m p e r a t u r e a b o u t 28°C. S o i l s a r e r e s i d u a l l a t e r i t e s and p o d z o l s d e r i v e d f r o m h i g h l y w e a t h e r e d p a r e n t m a t e r i a l s ( S o i l S u r v e y D i v i s i o n , 1 9 7 5 ) . The e f f e c t o f w e a t h e r i n g h a s been r e c o r d e d t o a d e p t h 33 o f 2 0 t o 90 in a t Phu Tham P h r a 4 0 km w e s t o f t h e s t u d y a r e a ( P h o l p h a n and S i r i r a t a n a m o n g k o l , 1967). F o u r s o i l p i t s i n t h e s t u d y a r e a show t h a t s o i l i s d e v e l o p e d t o a d e p t h o f 80 cm a t h i l l t o p s , i n c r e a s i n g t o 2 m e t e r s a t t h e b a s e o f t h e s l o p e . S o i l s a r e y e l l o w i s h t o r e d d i s h brown and c o n s i s t m a i n l y o f s i l t and c l a y w i t h l e s s t h a n 20% s a n d and c o a r s e r p a r t i c l e s ( F i g . 2 - 6 ) . A t h i l l t o p s i t e s , s o i l p r o f i l e s ( F i g . 2-7) a r e p o o r l y d e v e l o p e d and c o n t a i n numerous q u a r t z and p a r e n t r o c k f r a g m e n t s . A t t h e b a s e o f t h e s l o p e , however, t h e s e f r a g m e n t s a r e a b s e n t ( F i g . 2 - 8 ) . The s o i l p r o f i l e has been m o d i f i e d by c u l t i v a t i o n t o a d e p t h o f a b o u t 30 cm. V e g e t a t i o n i n t h i s r e g i o n was o r i g i n a l l y a m i x e d e v e r g r e e n f o r e s t ( S m i t h e t a l , 1968). However, b e c a u s e o f a r a p i d i n c r e a s e o f p o p u l a t i o n i n t h e p a s t two d e c a d e s , t h e f o r e s t h a s b een l o g g e d and c l e a r e d ( F i g . 2-9) f o r a g r i c u l t u r e . R i d g e s and h i l l t o p s a r e now o c c u p i e d by open bamboo f o r e s t w hereas h i l l s l o p e s and low l a n d s a r e c o n v e r t e d t o c o r n and c o t t o n f i e l d s . P a r t s o f t h e a r e a i n c l u d e a bandoned f a r m l a n d s now o c c u p i e d by s e c o n d g e n e r a t i o n b r u s h and s h r u b s . L o g g i n g and t h e n p l o u g h i n g and t i l l i n g f o r a g r i c u l t u r e h a v e i n c r e a s e d r a t e s o f s o i l e r o s i o n ( L e k h a k u l , 1990) . A l t h o u g h t h e amount o f s o i l e r o s i o n i n t h e s t u d y a r e a i s n o t known, P o o k c h a r o e n and R u a i s o o n g n o e n (1986) h a v e r e p o r t e d t h a t i n Chaiyaphum p r o v i n c e , a b o u t 12 0 km s o u t h o f L o e i , s o i l l o s s e s were 0.86 and 0.56 t o n n e s / h a / y e a r i n a 5 - y e a r 100 90 80 70 60 g> 50 "a> 40 30 20 10 82.63 3.95 5.09 2.6 0.99 0.48 1.72 2.55 Grain Size (mm) F i g . 2-6. G r a i n s i z e d i s t r i b u t i o n o f t h e C h o r i z o n s o i l . y e l l o w b r o w n (7.5 YR 5/6) s i l t y c l a y l o a m c u l t i v a t e d b r o w n (5 YR 4/8) c l a y e y s i l t l o a m r o c k f r a g m e n t s r e d d i s h b r o w n (2.5 YR 4/6) s i l t y c l a y r o c k f r a g m e n t s F i g . 2 - 7 . S o i l p i t a t t h e h i l l t o p s s h o w i n g A, BC a n d C h o r i z o n s . 36 I F : . A P g r e y b r o w n (10 YR 3/2) c l a y e y s i l t l o a m c u l t i v a t e d B y e l l o w b r o w n (10 YR 5/8) s t i c k y c l a y e y s i l t l o a m BC y e l l o w b r o w n (10 YR 6/4) v e r y s t i c k y c l a y e y s i l t l o a m f e w r o c k f r a g m e n t s y e l l o w b r o w n (10 YR 5/6) s t i c k y c l a y e y s i l t l o a m F i g . 2-8. S o i l p i t a t t h e b a s e o f s l o p e s h o w i n g A p , B, BC a n d C h o r i z o n s . 37 F i g . 2-9. L a n d u s e on t h e H u a i H i n L a e p d r a i n a g e b a s i n s h o w i n g f o r e s t l o g g e d and c l e a r e d f o r a g r i c u l t u r e . 38 Acacia auriculaeformis and Leucaena leucocephala p l a n t a t i o n , r e s p e c t i v e l y . I n K a l a s i n p r o v i n c e , a b o u t 200 km e a s t o f L o e i , s o i l l o s s i n c o r n f i e l d was up t o 4.6 t o n n e s / h a / y e a r ( L e k h a k u l , 1 9 9 0 ) . S i m i l a r s i t u a t i o n s o c c u r i n t h e H u a i H i n L a e p b a s i n , where e r o s i o n o f l a r g e amounts o f s i l t a nd c l a y i n t o t h e s t r e a m a p p e a r s t o r e s u l t f r o m t h e p r a c t i c e o f p l o u g h i n g l a t e r i t i c s o i l s t o p l a n t c o r n j u s t b e f o r e t h e o n s e t o f t h e r a i n y s e a s o n . CHAPTER THREE METHODOLOGY 40 3 .1 F i e l d s a m p l i n g F i e l d s a m p l i n g was u n d e r t a k e n i n J u l y - A u g u s t 1989 d u r i n g t h e r a i n y s e a s o n . F o r t u n a t e l y , t h i s was a s h o r t , r e l a t i v e l y d r y p e r i o d t h a t i m p r o v e d a c c e s s i b i l i t y a n d made s a m p l i n g e a s i e r . Where p o s s i b l e , b u l k s a m p l e s o f p o i n t b a r and pavement s e d i m e n t s were o b t a i n e d . I n most l o c a t i o n s , however, o n l y a sample o f e i t h e r p o i n t b a r o r pavement was a v a i l a b l e . A t o t a l o f 101 s t r e a m s e d i m e n t s a m p l e s were c o l l e c t e d f r o m 43 l o c a t i o n s ( F i g . 3 - 1 ) . P a n - c o n c e n t r a t e s a m p l e s were a l s o c o l l e c t e d a t e a c h s i t e . S t r e a m s e d i m e n t s a m p l e s were c o l l e c t e d by s h o v e l l i n g ( w i t h a s l i t t l e w a t e r as p o s s i b l e ) s e d i m e n t on t o a 12 mm w i r e s c r e e n above a 40 l i t e r p l a s t i c t u b (60 cm d i a m e t e r ) . The p l a s t i c t u b was p l a c e d on a s t r o n g p l a s t i c t a r p a u l i n t o p r e v e n t t h e l o s s o f c o a r s e m a t e r i a l s (>12 mm) w h i l e s i e v i n g . A t e a c h s a m p l i n g s i t e , a p p r o x i m a t e l y 65 t o 100 k i l o g r a m s o f s e d i m e n t was p r o c e s s e d t o y i e l d a p p r o x i m a t e l y 40 k g o f m a t e r i a l f i n e r t h a n 12 mm. T h i s was t h e n t r a n s f e r r e d t o s t r o n g p l a s t i c bags and w e i g h e d . The w e i g h t o f m a t e r i a l l a r g e r t h a n 12 mm was a l s o r e c o r d e d p r i o r t o i t b e i n g d i s c a r d e d . I n a d d i t i o n p a n - c o n c e n t r a t e s were o b t a i n e d a t e v e r y s i t e by t a k i n g f o u r s h o v e l - f u l l s o f s e d i m e n t i n t o a s t a n d a r d c o n e - s h a p e d wooden bowl and p a n n i n g . Heavy m i n e r a l s r e t a i n e d i n t h e wooden bowl were examined f o r v i s i b l e g o l d g r a i n s , w h i c h were c o u n t e d u s i n g a h a n d - l e n s , a n d t h e n s t o r e d i n a s m a l l p l a s t i c bag. 41 F i g . 3-1. Sample l o c a t i o n s on t h e H u a i H i n L a e p (open s q u a r e s = p o i n t b a r s ; open t r i a n g l e s = p a v e m e n t s ; s o l i d s q u a r e s = p o i n t b a r and pavement; s o l i d c i r c l e s = s o i l p i t s ; s h a d e d s t a r s = s u p p o s e d b e d r o c k s o u r c e s o f g o l d m i n e r a l i z a t i o n ; s h a d e d a r r o w i n d i c a t e s n o r t h d i r e c t i o n ) . 42 A p l a n s k e t c h was drawn a t e a c h l o c a t i o n t o show a p p r o x i m a t e d i m e n s i o n s and s h a p e s o f c h a n n e l f e a t u r e s ( p o i n t b a r and p a v e m e n t ) , l o c a l bed s e d i m e n t t e x t u r e , s a m ple l o c a t i o n and f l o w d i r e c t i o n . S t r e a m w i d t h was m e a s u r e d a c r o s s t h e w a t e r s u r f a c e and s t r e a m d e p t h by v e r t i c a l l y p l a c i n g a s c a l e t o t h e s t r e a m b e d and r e a d i n g t h e v a l u e a t w a t e r l e v e l . S t r e a m f l o w v e l o c i t y was d e t e r m i n e d by t i m i n g t h e movement o f a f l o a t o v e r a g i v e n d i s t a n c e . O t h e r f i e l d d a t a s u c h a s w a t e r c o l o u r , bank v e g e t a t i o n and e r o s i o n , and l o g - j a m s were a l s o r e c o r d e d and t h e bed p h o t o g r a p h e d . A t o t a l o f 22 s o i l s a m p l e s , i n c l u d i n g 4 p a n - c o n c e n t r a t e s f r o m e a c h C h o r i z o n , were a l s o c o l l e c t e d f r o m f o u r s o i l p i t s a l o n g a n o r t h e a s t t r a v e r s e l i n e o f an e a r l i e r g e o c h e m i c a l s u r v e y by t h e DMR ( F i g . 3 - 1 ) . The s o i l p r o f i l e was s u b d i v i d e d i n t o t h e h o r i z o n s p r e s e n t e d i n s e c t i o n 2.6. E a c h h o r i z o n was t h e n s a m p l e d s y s t e m a t i c a l l y f r o m t h e b o t t o m up i n o r d e r t o a v o i d p o s s i b l e c o n t a m i n a t i o n f r o m o v e r l y i n g h o r i z o n s . 3.2 Sample p r e p a r a t i o n 3.2.1 S t r e a m s e d i m e n t s L a b o r a t o r y p r e p a r a t i o n p r o c e d u r e s f o r s t r e a m s e d i m e n t s a m p l e s a r e i l l u s t r a t e d s c h e m a t i c a l l y i n F i g . 3-2. T h e y were p r e p a r e d i n two p h a s e s w i t h s l i g h t l y d i f f e r e n t p r o c e s s e s b e i n g u s e d i n e a c h . Original sample 10Wt% Coning Quartering 90 Wt% Phase 1 I Dry I Split Weigh Weigh I Dry Sieve I +100 Mesh I Weigh 1 -100 Mesh l Split Store Store 30g FA-AAS Phase 2 i Wet Sieve l +10 Mesh -10+40 Mesh -40+70 Mesh -70+100 Mesh -100+140 Mesh -140+200 Mesh -200+270 Mesh -270 Mesh Dry I Weigh Store +10 Mesh -10+40 Mesh Dry Weigh Store Phase 1 i Wet Sieve -40+70 Mesh -70+100 Mesh -100+140 Mesh -140+200 Mesh -200+270 Mesh Dry I Weigh Phase 2 i Wet Sieve -270 Mesh Dry +10 Mesh -10+40 Mesh -40+70 Mesh -70+270 Mesh Weigh Split Weigh Store 300 g i Grind i Split Dry Weigh Dry I Weigh 30 g FA-AAS Store Heavy Minerals Concentration (Methylene Iodide s.g. 3.3) Light-Mineral Fractions I Weigh Spirt Heavy-Mineral Fractions I Weigh Weigh Store 200 g I Grind Split _ l 30g FA-AAS FA-AAS F i g . 3-2. F l o w s h e e t f o r sample p r e p a r a t i o n and a n a l y s i s . 44 I n t h e f i r s t p h a s e , s i x t e e n s e d i m e n t s a m p l e s f r o m 14 l o c a t i o n s were s e l e c t e d f o r wet s i e v i n g . The e n t i r e wet s e d i m e n t s ample was w e i g h e d and homogenized, by c o n i n g a n d q u a r t e r i n g on a s t r o n g p l a s t i c t a r p a u l i n , t o o b t a i n two p o r t i o n s o f d i f f e r e n t s i z e s . The s m a l l e r p o r t i o n , a m o u n t i n g t o a b o u t t e n p e r c e n t o f t h e e n t i r e wet w e i g h t ( i . e . a b o u t 4 k g ) , was o v e n - d r i e d a t 8 0 ° C , d i s a g g r e g a t e d and w e i g h e d . I t was t h e n f u r t h e r s p l i t , w i t h one h a l f b e i n g m a n u a l l y d r y - s i e v e d t h r o u g h a 0.150 mm s c r e e n and t h e o t h e r h a l f s t o r e d . S e d i m e n t c o a r s e r t h a n 0.150 mm was w e i g h e d and s t o r e d , and t h a t f i n e r t h a n 0.150 mm s p l i t t o o b t a i n a p p r o x i m a t e l y 30 grams f o r g o l d a n a l y s i s . The l a r g e r p o r t i o n was p r o c e s s e d by wet s i e v i n g u s i n g a r e c i r c u l a t i n g w a t e r s y s t e m , w h i c h Day (1988) showed t o be much more e f f e c t i v e t h a n d r y s i e v i n g f o r r e m o v i n g f i n e s f r o m c o a r s e r f r a c t i o n s . E i g h t s i z e f r a c t i o n s were o b t a i n e d : +2.0, -2.0+0.425, -0.425+0.212, -0.212+0.150, -0.150+0.106, -0.106+0.075, -0.075+0.053, and -0.053 mm. The s e v e n s i z e f r a c t i o n s c o a r s e r t h a n 0.053 mm were d r i e d a t 8 0 ° C and w e i g h e d . S e t t l i n g o f t h e -0.053 mm f r a c t i o n was a c c e l e r a t e d by a d d i t i o n o f a few m i l l i l i t e r s o f d i l u t e o r g a n i c f l o c c u l a t i n g a g e n t ( C a t f l o c , C a l g o n L a b o r a t o r i e s ) . A f t e r a few d a y s , t h e c l e a r w a t e r was pumped o f f and d i s c a r d e d . S e d i m e n t was t h e n washed i n t o s e v e r a l s h a l l o w g l a s s t r a y s , d r i e d a t 8 0 ° C and w e i g h e d . The whole p r o c e s s o f wet s i e v i n g was, however, v e r y t i m e consuming, w i t h 4 d a y s t y p i c a l l y b e i n g r e q u i r e d t o p r o c e s s a s i n g l e s a m ple. 45 Heavy m i n e r a l c o n c e n t r a t e s were s e p a r a t e d f r o m t h e f i v e s i z e f r a c t i o n s between 0.425 and 0.053 mm u s i n g m e t h y l e n e i o d i d e ( s p e c i f i c g r a v i t y 3 . 3 ) . A l l f r a c t i o n s were a l l o w e d t o d r y a n d were t h e n w e i g h e d . No f u r t h e r p r e p a r a t i o n was r e q u i r e d f o r t h e -0.425+0.212 ,mm h e a v y m i n e r a l f r a c t i o n p r i o r t o d e t e r m i n a t i o n o f Au. However, b e c a u s e o f t h e i r s m a l l s i z e s , t h e -0.212+0.150 and -0.150+0.106 mm, a n d t h e -0.106+0.075 and -0.075+0.053 mm h e a v y m i n e r a l f r a c t i o n s were c o m b i n e d p r i o r t o a n a l y s i s . L i g h t m i n e r a l f r a c t i o n s g r e a t e r t h a n 200 grams were s p l i t t o o b t a i n a p p r o x i m a t e l y 200 grams w h i c h were t h e n p u l v e r i z e d i n a h a r d e n e d s t e e l r i n g m i l l . A 30 gram s u b s a m p l e o f t h e p u l v e r i z e d m a t e r i a l was t a k e n w i t h a J o n e s r i f f l e s p l i t t e r f o r a n a l y s i s . M i n u s 0.053 mm s a m p l e s were d i s a g g r e g a t e d u s i n g a m e t a l r o l l e r and s p l i t u s i n g a J o n e s r i f f l e s p l i t t e r t o o b t a i n a p p r o x i m a t e l y 250 t o 3 00 grams s a m p l e s . T h e s e were t h e n p u l v e r i z e d i n t h e r i n g m i l l a n d f u r t h e r s p l i t t o o b t a i n 30 gram s u b s a m p l e s f o r a n a l y s i s . Any r e m a i n i n g m a t e r i a l was s t o r e d f o r f u t u r e u s e . A medium s a n d - s i z e d (-0.425+0.212 mm) h e a v y m i n e r a l c o n c e n t r a t e f r o m a s e l e c t e d sample was v i s u a l l y e x a m i n e d u n d e r a b i n o c u l a r m i c r o s c o p e . The sample was t h e n s p l i t s e v e r a l t i m e s ( u s i n g a m i c r o s p l i t t e r ) t o o b t a i n a v e r y s m a l l p o r t i o n w h i c h was mounted on a p o l i s h e d grain-rmount u s i n g a method d e v e l o p e d by J . K n i g h t and Y. Douma a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a . The mount was p o l i s h e d and c a r b o n - c o a t e d f o r s c a n n i n g e l e c t r o n m i c r o s c o p e e x a m i n a t i o n . 46 I n t h e s e c o n d p h a s e , a f t e r o b t a i n i n g Au r e s u l t s o f t h e f i r s t p h a s e , e l e v e n s t r e a m s e d i m e n t s a m p l e s f r o m 7 l o c a t i o n s were s e l e c t e d and p r o c e s s e d u s i n g a s l i g h t l y d i f f e r e n t p r o c e d u r e . The s m a l l e r p o r t i o n was w e t - s i e v e d t o o b t a i n e i g h t s i z e f r a c t i o n s f o r t e x t u r a l a n a l y s i s . The l a r g e r p o r t i o n was a l s o w e t - s i e v e d t o o b t a i n f o u r s i z e f r a c t i o n s : +2.0, -2.0+0.425, -0.425+0.212 and -0.212+0.053 mm. A h e a v y m i n e r a l c o n c e n t r a t e (S.G. > 3.3) was t h e n p r e p a r e d f o r t h e -0.212+0.053 mm f r a c t i o n . The -0.053 mm f r a c t i o n was d i s c a r d e d . 3.2.2 Pan c o n c e n t r a t e s V i s i b l e p a r t i c l e s o f f r e e g o l d were s e p a r a t e d f r o m f i v e f i e l d p a n c o n c e n t r a t e s and c o u n t e d u n d e r a b i n o c u l a r m i c r o s c o p e . The p a r t i c l e s were t h e n p l a c e d on SEM s t u b s c o a t e d w i t h n a i l p o l i s h and immersed i n a c e t o n e v a p o u r f o r a few s e c o n d s a l l o w i n g t h e p a r t i c l e s t o s e t t l e i n t o t h e p o l i s h ( J . K n i g h t , p e r s . comm., 1990). S t u b s were t h e n c a r b o n c o a t e d p r i o r t o SEM e x a m i n a t i o n . S u b s e q u e n t l y , g o l d p a r t i c l e s were removed f r o m t h e s t u b s , u s i n g a c e t o n e , and mounted f o r c r o s s - s e c t i o n p o l i s h i n g . The p o l i s h e d s a m p l e s were c a r b o n - c o a t e d p r i o r t o a n a l y s i s . 3.3 A n a l y s i s 3.3.1 A n a l y s i s o f s e d i m e n t s and h e a v y m i n e r a l s f o r g o l d A t o t a l o f 217 s e d i m e n t s a m p l e s were a n a l y z e d f o r Au by f i r e a s s a y - a t o m i c a b s o r p t i o n s p e c t r o p h o t o m e t r y a t Chemex L a b o r a t o r i e s , N o r t h V a n c o u v e r , B r i t i s h C o l u m b i a . The d e t e c t i o n l i m i t s f o r g o l d i n h e a v y m i n e r a l c o n c e n t r a t e s d e p e n d on t h e w e i g h t o f t h e h e a v i e s , whereas t h e d e t e c t i o n l i m i t f o r g o l d i n l i g h t m i n e r a l and s e d i m e n t f r a c t i o n s i s 5 ppb w i t h a 3 0 g a n a l y t i c a l s u b s a m p l e . D u p l i c a t e s a m p l e s , r a n d o m l y s e l e c t e d f r o m a p p r o x i m a t e l y 10% o f a l l s a m p l e s ( F l e t c h e r , 1981) f r o m l i g h t m i n e r a l and s e d i m e n t f r a c t i o n s , were a n a l y z e d t o g e t h e r w i t h f i v e g o l d s t a n d a r d s a m p l e s a s a q u a l i t y c o n t r o l p r o g r a m . R e s u l t s o f d u p l i c a t e a n a l y s e s a r e l i s t e d i n T a b l e s 3-1 and 3-2. A l l b u t s i x s a m p l e s a r e a t o r below t h e d e t e c t i o n l i m i t (<5 ppb) . T h u s , t h e m i d p o i n t v a l u e (2.5 ppb) i s t a k e n f o r t h o s e b e l o w t h e d e t e c t i o n l i m i t f o r f u r t h e r s t a t i s t i c a l e v a l u a t i o n . A s c a t t e r p l o t o f p r i m a r y and recommended Au v a l u e s v e r s u s d u p l i c a t e and g o l d s t a n d a r d a n a l y s e s i s shown i n F i g . 3-3. The 21 p a i r s o f < 5 ppb g o l d o f d u p l i c a t e s a m p l e s were d i s c a r d e d , and Au v a l u e s f r o m 6 p a i r s o f d u p l i c a t e and 5 f r o m g o l d s t a n d a r d s s a m p l e s were n o r m a l i z e d by m a k i n g t h e l o g t r a n s f o r m a t i o n p r i o r t o r e g r e s s i o n a n a l y s i s . The s q u a r e o f t h e c o r r e l a t i o n c o e f f i c i e n t ( r 2 ) i s 0.896 (n = 11, 48 T a b l e 3-1. D u p l i c a t e a n a l y s e s f o r g o l d c o n c e n t r a t i o n s (ppb) i n l i g h t a nd -0.053 mm s e d i m e n t f r a c t i o n s . The r e p o r t e d d e t e c t i o n l i m i t i s 5 ppb. Sample A n a l y s i s Number F r a c t i o n F i r s t S e c o n d 89-PP-16 -0.150 mm <5 5 89-PP-96 -0.150 mm <5 10 89-PP-94 -0.150 mm <5 5 89-PP-67 -0.150 mm <5 <5 89-PP-68 -0.150 mm <5 <5 89-PP-16 -0.425+0.212 mm <5 <5 89-PP-81 -0.425+0.212 mm <5 <5 89-PP-87 -0.425+0.212 mm <5 <5 89-PP-65 -0.425+0.212 mm <5 <5 89-PP-96 -0.212+0.150 mm 5 15 89-PP-75 -0.212+0.150 mm <5 <5 89-PP-100 -0.212+0.150 mm <5 <5 89-PP-68 -0.212+0.150 mm <5 <5 89-PP-09 -0.150+0.106 mm <5 <5 89-PP-70 -0.150+0.106 mm <5 <5 89-PP-65 -0.150+0.106 mm 35 100 89-PP-94 -0.106+0.075 mm <5 <5 89-PP-67 -0.106+0.075 mm 5 <5 89-PP-68 -0.106+0.075 mm <5 <5 89-PP-96 -0.075+0.053 mm <5 <5 89-PP-10 -0.075+0.053 mm <5 <5 89-PP-89 -0.075+0.053 mm <5 <5 89-PP-64 -0.075+0.053 mm <5 <5 89-PP-16 -0.053 mm <5 <5 89-PP-79 -0.053 mm <5 <5 89-PP-22 -0.212+0.053 mm <5 <5 89-PP-55 -0.212+0.053 mm <5 <5 49 T a b l e 3-2. A n a l y s e s o f g o l d s t a n d a r d s a m p l e s . V a l u e s Sample Number Recommended A n a l y s i s STSD -3 # 5 4 1 6.8 <5 MA-2 2 1860 1810 GTS- l 2 346 360 STSD -1 # 4 3 3 1 8 15 GTS- I 2 346 305 recommended v a l u e s b a s e d on L y n c h (1990) recommended v a l u e s b a s e d on S t e g e r (1986) 1,000 100 CO <D CO >> CO ^ s -° < D_ CD A to 3 ^ < Q 10 0.1 • - • • — • - • • — • : 2 cases -— • o _ 21 cases — • • • • — • = Duplicate samples _ • = Gold standard samples - N = 32 0.1 - l 1—I—r 10 r 100 1,000 Au (ppb) Recommended and First analyses F i g . 3-3. S c a t t e r p l o t f o r d u p l i c a t e Au a n a l y s i s o f t h e l i g h t m i n e r a l f r a c t i o n , -0.053 mm s e d i m e n t f r a c t i o n and v e r s u s recommended v a l u e f o r g o l d s t a n d a r d s a m p l e s . 51 s t a n d a r d e r r o r o f e s t i m a t i o n = 0.349) i n d i c a t i n g t h a t Au v a l u e s o b t a i n e d f r o m t h e d u p l i c a t e and g o l d s t a n d a r d a n a l y s e s a r e c l o s e t o t h e p r i m a r y and recommended v a l u e s . G o l d a n a l y s i s r e s u l t s a r e t h e r e f o r e c o n s i d e r e d t o be s u f f i c i e n t l y p r e c i s e and a c c u r a t e f o r t h e p u r p o s e o f t h i s s t u d y . 3.3.2 E x a m i n 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 e s and g o l d p a r t i c l e s S e l e c t e d h e a v y m i n e r a l c o n c e n t r a t e s were e x a m i n e d u n d e r t h e b i n o c u l a r m i c r o s c o p e t o o b t a i n g r a i n m o r p h o l o g y . P o l i s h e d s e c t i o n s o f t h e g r a i n s were t h e n e x a m i n e d u s i n g a SEMCO NANOLAB 7 s c a n n i n g e l e c t r o n m i c r o s c o p e (SEM) o p e r a t i n g a t 15 kV, e q u i p p e d w i t h a K e v e c U n i s p e c S ystem 7000 e n e r g y d i s p e r s i v e s y s t e m , t o i d e n t i f y h e a v y m i n e r a l c o m p o s i t i o n s . M o unted g o l d p a r t i c l e s were a l s o e x a m i n e d u n d e r t h e SEM. E a c h g o l d g r a i n was p h o t o g r a p h e d w i t h b a c k s c a t t e r s e c o n d a r y e l e c t r o n i m a g i n g t o o b t a i n g r a i n m o r p h o l o g y . Two a x i a l d i m e n s i o n s (a and b axes) o f e a c h p a r t i c l e were e s t i m a t e d f r o m t h e SEM p h o t o g r a p h s . The t h i r d (c) a x i s was e s t i m a t e d u n d e r a r e f l e c t e d l i g h t m i c r o s c o p e . P o l i s h e d s e c t i o n s o f g o l d p a r t i c l e s were q u a n t i t a t i v e l y a n a l y z e d f o r Au, Ag, Cu and Hg u s i n g an SX-50 Cameca e l e c t r o n m i c r o p r o b e and o p e r a t i n g c o n d i t i o n s m o d i f i e d f r o m K n i g h t and M c T a g g a r t ( 1 9 8 6 ) . C u r r e n t was 100 nA on a l u m i n i u m 52 w i t h an a c c e l e r a t i n g p o t e n t i a l o f 20 kV. C o u n t i n g t i m e f o r b a c k g r o u n d was 10 s e c o n d s on e a c h s i d e o f t h e p e a k s a n d 30 s e c o n d s on t h e p e a k s . D a t a were r e d u c e d u s i n g t h e p h i - r h o - x i d a t a r e d u c t i o n method ( J . K n i g h t , p e r s . comm., 1 9 9 0 ) . D e t e c t i o n l i m i t s f o r Au and Ag were 0.05% ( K n i g h t a n d M c T a g g a r t , 1986), Cu 0.025% and Hg 0.65% ( K n i g h t , p e r s . comm., 1 9 9 0 ) . Where p o s s i b l e , e a c h p a r t i c l e was a n a l y z e d 3 t i m e s - o n c e i n t h e c o r e and t w i c e a t o p p o s i t e p a r t s o f t h e o u t e r e d ge. 53 CHAPTER FOUR STREAM CHARACTERISTICS AND SEDIMENT PROPERTIES OF THE HUAI HIN LAEP 54 4.1 I n t r o d u c t i o n A s r e v i e w e d i n C h a p t e r 1, s t u d i e s i n t h e H a r r i s C r e e k , B r i t i s h C o l u m b i a , h a ve shown t h a t a c c u m u l a t i o n s o f g o l d i n s t r e a m s a r e r e l a t e d t o p h y s i c a l c h a r a c t e r i s t i c s o f t h e s t r e a m and s t r e a m s e d i m e n t s a t b o t h b a r and r e a c h s c a l e s (Day a n d F l e t c h e r , 1986, 1989, i n p r e s s ; F l e t c h e r , 1990; F l e t c h e r and Day, 1988b; F l e t c h e r and W o l c o t t , 1989, i n p r e s s ) . The p u r p o s e o f t h e p r e s e n t s t u d y was t o d e t e r m i n e i f t h e same, o r s i m i l a r , f a c t o r s c o n t r o l l e d d i s t r i b u t i o n o f g o l d i n t h e H u a i H i n Laep, a t y p i c a l s t r e a m i n n o r t h e a s t e r n T h a i l a n d . S p e c i f i c a l l y , i t was i n t e n d e d t o e v a l u a t e 1) g o l d c o n c e n t r a t i o n s i n d i f f e r e n t s i z e and d e n s i t y f r a c t i o n s t o d e t e r m i n e c r i t e r i a f o r a r e p r e s e n t a t i v e f i e l d s ample f o r g o l d , 2) a c c u m u l a t i o n o f g o l d i n d i f f e r e n t e n v i r o n m e n t s , and 3) d i s p e r s i o n and d i s t r i b u t i o n o f g o l d a l o n g t h e H u a i H i n L a e p . W i t h r e s p e c t t o 2) and 3) , r e l a t i o n s b e t w e e n g o l d c o n c e n t r a t i o n s and p r o p e r t i e s o f e i t h e r t h e s t r e a m c h a n n e l ( i . e . s t r e a m w i d t h , c h a n n e l d e p t h and f l o w v e l o c i t y ) o r s e d i m e n t s ( i . e . mean g r a i n s i z e , s e d i m e n t s o r t i n g , b e d r o u g h n e s s and abundance o f s e d i m e n t ) a r e o f b o t h t h e o r e t i c a l i n t e r e s t and p r a c t i c a l s i g n i f i c a n c e f o r d e s i g n and i n t e r p r e t a t i o n o f s t r e a m s e d i m e n t s u r v e y s f o r g o l d . The f i r s t p a r t o f t h i s c h a p t e r t h e r e f o r e d e s c r i b e s a n d t e s t s s t r e a m c h a r a c t e r i s t i c s and s e d i m e n t p r o p e r t i e s f o r any 55 s y s t e m a t i c r e l a t i o n s t h a t m i g h t i n f l u e n c e d i s t r i b u t i o n o f g o l d . D i s t r i b u t i o n o f hea v y m i n e r a l s i s a l s o d e s c r i b e d w i t h r e s p e c t t o s t r e a m and s e d i m e n t p r o p e r t i e s . I n o r d e r t o a v o i d i ) b i a s f r o m t h e s i n g l e g o l d - r i c h a n o m a l o u s sample n e a r t h e s u p p o s e d s o u r c e o f g o l d , and i i ) t h e e f f e c t s o f c o n t a m i n a t i o n o f s e d i m e n t d r a i n i n g f r o m t r i b u t a r i e s a t t h e s t r e a m h e a d w a t e r and d i l u t i o n by s e d i m e n t f r o m t h e H u a i Kho Lo, r e l a t i o n s between s t r e a m c h a r a c t e r i s t i c s and s e d i m e n t p r o p e r t i e s a r e p r i m a r i l y e x a m i n e d i n t h a t p a r t o f t h e r e a c h between t h e s u p p o s e d s o u r c e o f g o l d and t h e c o n f l u e n c e w i t h t h e H u a i Kho Lo (1,055 t o 6,223 m) . However, r e l a t i o n s a l o n g t h e e n t i r e r e a c h a r e a l s o p r e s e n t e d f o r p u r p o s e s o f c o m p a r i s o n a n d t o i n d i c a t e p o s s i b l e outcomes o f r o u t i n e g e o c h e m i c a l s u r v e y s . Where s t a t i s t i c a l t e s t s , s u c h as W a l d - w o l f o w i t z t o t a l - n u m b e r - o f - r u n s t e s t ( B r a d l e y , 19 6 8 ) , Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t and two-sample t t e s t 1 ( S n e d e c o r and C o c h r a n , 1 9 8 9 ) , a r e u s e d t h e 90% (P r j . i o ) c o n f i d e n c e l e v e l i s u s e d t o e v a l u a t e t h e outcome. T h i s r a t h e r low l e v e l o f s i g n i f i c a n c e i s u s e d on an e x p l o r a t o r y b a s i s t o e n s u r e t h a t m e a n i n g f u l r e l a t i o n s between p a r a m e t e r s w i l l n o t be o v e r l o o k e d . t w o - s a m p l e t t e s t i s u s e d t o t e s t t h e d i f f e r e n c e b e t w e e n t h e means o f two i n d e p e n d e n t s a m p l e s when t h e two p o p u l a t i o n v a r i a n c e s a r e n o t e q u a l . 56 4.2 S t r e a m c h a r a c t e r i s t i c s T h e r e was no r a i n f a l l d u r i n g t h e s a m p l i n g p e r i o d a n d s t r e a m d i s c h a r g e a p p e a r e d t o r e m a i n c o n s t a n t . S t r e a m g e o m e t r y d a t a ( i . e . w i d t h a t w a t e r s u r f a c e , c h a n n e l d e p t h , a n d f l o w v e l o c i t y ) f o r p o i n t - b a r s i t e s a r e p l o t t e d w i t h r e s p e c t t o d i s t a n c e downstream i n F i g . 4-1. A l t h o u g h s t r e a m w i d t h ( F i g . 4 - l a ) and c h a n n e l d e p t h ( F i g . 4 - l b ) v a r y q u i t e e r r a t i c a l l y , s t r e a m w i d t h seems t o s y s t e m a t i c a l l y d e c r e a s e b e t w e e n 2,500 and 5,500 m w h i l e f l o w v e l o c i t y ( F i g . 4 - l c ) i n c r e a s e s . B a s e d on t h e W a l d - w o l f o w i t z t o t a l - n u m b e r - o f - r u n s t e s t ( T a b l e 4 - 1 ) , t h e s e v a r i a t i o n s a r e n o t s i g n i f i c a n t . However, a l o n g t h e e n t i r e r e a c h t h e r e a r e t o o few segments ( r u n s ) f o r v a r i a t i o n i n s t r e a m w i d t h and f l o w v e l o c i t y , r e l a t i v e t o m e d i a n c u t - o f f v a l u e s , t o be e n t i r e l y random. 4.3 S e d i m e n t p r o p e r t i e s 4.3.1 S e d i m e n t s i z e d i s t r i b u t i o n s i n p o i n t - b a r and pavement D r y w e i g h t s o f e i g h t s i z e f r a c t i o n s o b t a i n e d f r o m wet s i e v i n g o f s e d i m e n t s i n t h e l a b o r a t o r y a r e u s e d t o s t u d y s e d i m e n t s i z e d i s t r i b u t i o n . S e d i m e n t s i z e s l a r g e r t h a n 12 mm a r e e x c l u d e d i n o r d e r t o a v o i d b i a s f r o m r e j e c t i o n o f l a r g e c o b b l e s ( i . e . l a r g e r t h a n a b o u t 30 cm) d u r i n g f i e l d s a m p l i n g . 57 F i g . 4-1. Downstream t r e n d s o f a) s t r e a m w i d t h , b) s t r e a m d e p t h and c) f l o w v e l o c i t y a t p o i n t - b a r s i t e s . 58 T a b l e 4-1. R e s u l t s o f t h e W a l d - w o l f o w i t z t o t a l - n u m b e r - o f - r u n s t e s t (/i) f o r t r e n d s o f s t r e a m c h a r a c t e r i s t i c s a t p o i n t - b a r s i t e s a l o n g t h e e n t i r e r e a c h and between s u p p o s e d s o u r c e o f g o l d a n d t h e c o n f l u e n c e w i t h t h e H u a i Kho Lo (1,055 and 6,223 m). F r a c t i o n / N S o u r c e o f C u t p o i n t n^ r\2 M P(M) V a r i a t i o n (median) (+) (-) Whole r e a c h P o i n t b a r (N = 19) W i d t h 1.70 10 9 7 0.0500* D e p t h 0.25 12 7 9 0.3339 V e l o c i t y 0.12 10 9 7 0.0500 Between s u p p o s e d s o u r c e o f g o l d m i n e r a l i z a t i o n a n d t h e c o n f l u e n c e w i t h t h e H u a i Kho Lo (1,055 and 6,223 m) P o i n t b a r (N = 12) W i d t h 2.55 6 6 7 0.5000 D e p t h 0.37 6 6 8 0.2724 V e l o c i t y 0.10 6 6 5 0.1129 N = t o t a l number o f sa m p l e s n i = number o f s a m p l e s above median n.2 = number o f s a m p l e s below median \i = t o t a l number o f r u n s above and below t h e m e d i a n * = s t a t i s t i c a l l y s i g n i f i c a n t a t 95% c o n f i d e n c e l e v e l 59 G r a i n s i z e d i s t r i b u t i o n s , u s i n g mean v a l u e s f o r p o i n t - b a r (n = 19) and pavement (n = 7) s a m p l e s , a r e p l o t t e d on h i s t o g r a m s ( F i g . 4-2) and s e m i - l o g a r i t h m i c g r a p h p a p e r ( F i g . 4 - 3 ) . The h i s t o g r a m o f p o i n t - b a r s e d i m e n t s ( F i g . 4-2a) shows a s t r o n g l y b i m o d a l d i s t r i b u t i o n c o n s i s t i n g m a i n l y o f g r a v e l a n d c o a r s e - s a n d (" 8 0 % ) , and s i l t and c l a y (" 1 7 % ) . Medium and f i n e - s a n d s i z e s a r e s c a r c e (" 3%) . The c e n t r a l t e n d e n c i e s o f g r a i n s i z e d i s t r i b u t i o n a r e a r i t h m e t i c mean (M) = 3.65 mm, m e d i a n ( D 5 0 ) = 1.80 mm. S o r t i n g (S Q) i s c a l c u l a t e d f r o m s 0 = ( Q 3 / Q i ) 1 / 2 (4-1) where Q3 i s t h e t h i r d q u a r t i l e ( t h a t d i a m e t e r w h i c h h a s 75% o f t h e d i s t r i b u t i o n s m a l l e r and 25% l a r g e r t h a n i t s e l f ) , a n d 0,! i s t h e f i r s t q u a r t i l e ( t h a t d i a m e t e r w h i c h h a s 25% o f t h e d i s t r i b u t i o n s m a l l e r and 75% l a r g e r t h a n i t s e l f ) . I t h a s a v a l u e o f 2.89 i n d i c a t i n g n o r m a l l y s o r t e d s e d i m e n t ( T r a s k i n K r u m b e i n a n d P e t t i j o h n , 1938). I t s h o u l d be n o t e d t h a t v a l u e s o f t h e median ( D 5 0 ) and s o r t i n g ( S Q ) , o b t a i n e d f r o m t h e c u m u l a t i v e c u r v e ( F i g . 4-3), a r e s l i g h t l y d i f f e r e n t f r o m t h o s e o b t a i n e d f r o m s t a t i s t i c a l e s t i m a t i o n ( l i s t e d i n T a b l e 4-2) . Pavement s e d i m e n t s a l s o have a s t r o n g l y b i m o d a l s i z e d i s t r i b u t i o n ( F i g s . 4-2b, and 4-3) and a g a i n c o n s i s t m a i n l y o f g r a v e l and c o a r s e - s a n d (" 89%) and s i l t - c l a y (" 9%) w i t h o n l y m i n o r amounts (" 2%) o f medium and f i n e s a n d . D i s t r i b u t i o n p a r a m e t e r s o f pavement s e d i m e n t s a r e mean (M) = 4.70 mm, m e d i a n ( D 5 0 ) = 3.20 mm and s o r t i n g (Sg) = 2.52 60 75 50 g> 25 Point bar N = 19 46.76 29.72 16.9 3.93 0.83 0.62 0.54 0.67 3.09 '"I 0.6 0.41 0.27 0.36 0. 21 2 0. 15 0 0. 10 6 0. 07 5 0 05 3 -0 .4 25 + + CJ CJ 9 Grain + size (mm) -0 .1 06 + -0 .0 75 + F i g . 4-2. Mean weight percents of sediment s i z e d i s t r i b u t i o n i n a) p o i n t bar (n = 19) and b) pavement (n = 7). F i g . 4 - 3 . C u m u l a t i v e c u r v e s f o r sediment s i z e d i s t r i b u t i o n s u s i n g mean w e i g h t p e r c e n t f o r p o i n t - b a r ( s o l i d square) and pavement ( s o l i d t r i a n g l e ) s h o w i n g d e t e r m i n a t i o n p o i n t s f o r Q1 - f i r s t q u a r t i l e , Q 3 - t h i r d q u a r t i l e a n d D 5 0 - m edian. 62 T a b l e 4-2. Summary o f mean g r a i n s i z e (M 0) , m e d i a n ( D 5 0 ) , s e d i m e n t s o r t i n g (S Q) and bed r o u g h n e s s ( D 5 5 ) o f t h e e n t i r e s e d i m e n t a t p o i n t - b a r and pavement s i t e s . Mean (mm) M e d i a n (mm) S o r t i n g D 5 5 (mm) Sample (M 0) (D 5 0) ( S 0 ) P o i n t - b a r (n = 19) PP-22 4.46 2.60 2 .11 4 PP-16 4.67 2.80 1.93 4 PP-96 1.58 0.11 8.37 1 PP-98 1.45 0.14 8.37 5 PP-09 3.88 2.00 2.48 3 PP-08 3.99 2.10 2 .47 3 PP-06 3.46 1.70 2 . 63 2.5 PP-94 2.89 1.30 12.45 15 PP-10 4 .72 3.00 2 .28 2 PP-89 2.87 1.25 1.81 5 PP-81 4.38 2.50 2.29 20 PP-75 4.40 2.50 2.13 15 PP-73 3.11 1.60 1. 82 10 PP-70 4.08 2.40 3.16 70 PP-67 4 . 68 3.50 2.99 15 PP-64 4 .36 2 . 60 2 .40 10 PP-59 3.15 1.30 2.48 5 PP-55 3.15 1.30 2 . 85 35 PP-56 4.11 2 .30 2 .73 35 Mean 3.65 1.95 3 . 57 13.66 S t d 0.98 0.90 2 . 88 17. 02 Pavement (n = 7) PP-2 3 4 . 52 2.70 2 .19 10 PP-87 5.58 4.30 1.79 30 PP-100 5.07 3.60 2.00 15 PP-79 4.74 3.00 2.10 15 PP-68 3 .92 2.15 3 .16 30 PP-65 4.42 2.80 2 . 37 50 PP-58 4.66 3.00 2.25 50 Mean 4.70 3 . 08 2 . 27 28 . 57 S t d 0.52 0.69 0.44 16.51 63 i n d i c a t i n g w e l l s o r t e d s e d i m e n t s . Summaries o f t h e a r i t h m e t i c mean (M), m e d i a n ( D 5 0 ) / s o r t i n g ( S Q ) and bed r o u g h n e s s ( D g s ) a r e g i v e n i n T a b l e 4-2. (Bed r o u g h n e s s ( D 5 5 ) i s e s t i m a t e d f r o m p h o t o g r a p h t a k e n a t e a c h s i t e b e f o r e sample c o l l e c t i o n and t h e r e f o r e i n c l u d e s t h e s e d i m e n t f r a c t i o n l a r g e r t h a n 12 mm). B e c a u s e t h e d i s t r i b u t i o n o f s e d i m e n t s f r o m b o t h p o i n t - b a r a n d pavement s i t e s i s b i m o d a l , p r o b a b i l i t y p l o t s ( F i g . 4 - 4 ) , u s i n g t h e method o f S i n c l a i r ( 1 9 7 6 ) , h a v e b e e n u s e d t o i d e n t i f y t h e two component p o p u l a t i o n s . R e s u l t s show, f o r example, t h a t f o r p o i n t - b a r s e d i m e n t 89-PP-94 two p o p u l a t i o n s c a n be d i s t i n g u i s h e d by an i n f l e c t i o n p o i n t o f t h e c u r v e a t a b o u t 0.07 mm ( 6 8 % ) . S i m i l a r l y , f o r pavement s e d i m e n t 89-PP-100 t h e c u t p o i n t i s a t a b o u t 0.07 mm ( 9 3 % ) . The c e n t r a l t e n d e n c i e s o f t h e c o a r s e g r a i n e d component o f p o i n t - b a r s e d i m e n t s a r e mean (M c) = 2.66 mm and s o r t i n g (SQ) = 2.16, i n d i c a t i n g w e l l s o r t e d s e d i m e n t . D i s t r i b u t i o n p a r a m e t e r s o f c o a r s e g r a i n e d pavement s e d i m e n t s a r e mean (M c) = 3.80 mm and s o r t i n g ( S c ) = 2.38, a l s o i n d i c a t i n g w e l l s o r t e d s e d i m e n t . Summary s t a t i s t i c s f o r c o a r s e g r a i n e d s e d i m e n t c h a r a c t e r i s t i c s f r o m p o i n t - b a r and pavement s i t e s a r e l i s t e d i n T a b l e 4-3. I t i s s e l f - e v i d e n t t h a t s o r t i n g (SQ) o f t h e c o a r s e g r a i n e d s e d i m e n t , p a r t i c u l a r l y a t p o i n t - b a r s i t e s , i s b e t t e r t h a n s o r t i n g (S Q) o f t h e e n t i r e s e d i m e n t . 64 \ \ \ 99.9 99 90 50 10 1 0.1 Cumulative weight % F i g . 4-4. P r o b a b i l i t y p l o t s f o r s e d i m e n t s i z e d i s t r i b u t i o n s o f 89-PP-94 ( p o i n t b a r , s o l i d s q u a r e ) and o f 89-PP-100 (pavement, s o l i d t r i a n g l e ) . The s t r a i g h t l i n e s a r e p a r t i t i o n e d l o g - n o r m a l l y d i s t r i b u t e d c o a r s e - g r a i n e d p o p u l a t i o n s ( c f . S i n c l a i r , 1976). 65 T a b l e 4-3. Summary c h a r a c t e r i s t i c s o f c o a r s e g r a i n e d component o f s e d i m e n t f r o m p o i n t - b a r and pavement s i t e s . P r o p o r t i o n Mean (mm) S o r t i n g Sample (%) (M c) ( S c ) P o i n t - b a r (n = 19) PP-22 91 3.00 2 . 03 PP-16 93 2 .80 1. 65 PP-96 50 1.25 2 . 38 PP-98 50 1.25 1.98 PP-09 84 2 . 50 1.91 PP-08 83 2.90 2 . 22 PP-06 79 2.25 1.85 PP-94 68 2 .30 2 . 08 PP-10 91 3.65 2.24 PP-89 74 1.75 1.99 PP-81 87 3 . 20 2.16 PP-75 90 2.90 2.03 PP-73 90 1. 60 1.70 PP-70 85 3.20 2 . 65 PP-67 85 6.70 3 .32 PP-64 88 3.30 2.10 PP-59 92 1. 50 2 .14 PP-55 87 1.70 2 .15 PP-56 91 2 . 80 2.49 Mean 82.11 2.66 2.16 S t d 12.84 1.23 0. 37 Pavement (n = 7) PP-23 90 3 . 50 2 .44 PP-87 95 5.20 2.10 PP-100 93 4.50 2.44 PP-79 93 3.40 2 .19 PP-68 84 2 .90 2 . 66 PP-65 90 3 .40 2 . 49 PP-58 91 3.70 2.35 Mean 90.86 3 . 80 2 .38 S t d 3.53 0. 78 0.19 C o a r s e g r a i n e d component o f s e d i m e n t i s s e p a r a t e d a t t h e i n f l e c t i o n p o i n t ( F i g . 4-4) f o r an i n d i v i d u a l s a m p l e , f o r example, 89-PP-94 a t 0.07 mm and 89-PP-100 a t 0.07 mm. 66 4.3.2 C o m p a r i s o n between t e x t u r e s o f s e d i m e n t s a t p o i n t - b a r and pavement C o m p a r i s o n s o f s e d i m e n t t e x t u r e between p o i n t - b a r and pavement a r e c a r r i e d o u t u s i n g a two-sample t t e s t ( a t t h e 90% (Po.io) c o n f i d e n c e l e v e l ) t o examine t h e d i f f e r e n c e s b e t w e e n mean g r a i n s i z e (M Q ) , s e d i m e n t s o r t i n g ( S Q ) , mean g r a i n s i z e (M c) and s o r t i n g (SQ) o f c o a r s e g r a i n e d component, bed r o u g h n e s s (Dg5) and abundance o f s e d i m e n t f r a c t i o n . T h e s e p a r a m e t e r s a r e e v a l u a t e d i n t h e p a r t o f t h e r e a c h between 2,753 and 6,223 m b e c a u s e o f : 1) t h e a b s e n c e o f pavement s i t e s i n t h e u p p e r p a r t o f t h e r e a c h , a n d 2) p o s s i b l e s t a t i s t i c a l b i a s r e s u l t i n g f r o m i n c l u s i o n o f s e d i m e n t a t s i t e s downstream o f t h e c o n f l u e n c e w i t h t h e H u a i Kho L o . R e s u l t s ( T a b l e 4-4) show t h a t o n l y t h e w e i g h t p e r c e n t s o f g r a v e l and s i l t - c l a y d i f f e r s i g n i f i c a n t l y , w i t h g r a v e l b e i n g more abu n d a n t i n pavement and s i l t - c l a y (-0.053 mm) i n p o i n t - b a r s e d i m e n t s . 4.3.3 Downstream t r e n d s o f s e d i m e n t t e x t u r e a t p o i n t - b a r and pavement s i t e s Downstream t r e n d s i n mean g r a i n s i z e (Mg), s e d i m e n t s o r t i n g ( S Q ) and bed r o u g h n e s s (055) f r o m p o i n t - b a r and pavement s i t e s a r e shown i n F i g . 4-5. The c o r r e s p o n d i n g p a r a m e t e r s , mean g r a i n s i z e (MQ) and s o r t i n g (SQ) ) f o r t h e c o a r s e g r a i n e d component a r e shown i n F i g . 4-6. I n t h e 67 T a b l e 4-4. S t a t i s t i c a l two-sample t t e s t f o r t h e d i f f e r e n c e b e t w e e n means o f s e d i m e n t c h a r a c t e r i s t i c s f r o m p o i n t - b a r and pavement s i t e s i n t h e r e a c h between 2,753 and 6,223 m. N u l l h y p o t h e s i s : M Wt% s e d i m e n t i n p o i n t - b a r _ M Wt% s e d i m e n t i n pavement F r a c t i o n / S o u r c e o f N Mean S S e D e g r e e s o f V a r i a t i o n F reedom Mean g r a i n s i z e (M Q ) P o i n t - b a r Pavement 7 5 3.9829 4.7460 T c a l c = -1-79 T ( 9 f 0 . 1 0 ) = S o r t i n g ( S 0 ) P o i n t - b a r 7 2.3714 Pavement 5 2.2840 0.7035 0.6303 0.3954 9 1.833 N u l l h y p o t h e s i s a c c e p t e d 0.5306 0.5323 T c a l c : Mean ( M Q ) P o i n t - b a r Pavement 0.3111 9 0.28 T ( 9 , 0.10) = 1-833 N u l l h y p o t h e s i s a c c e p t e d 7 5 3.2357 3.8800 T C a l c = - ° - 8 4 T ( 1 0 , 0.10) S o r t i n g (S Q ) P o i n t - b a r 7 2.2786 Pavement 5 2.3760 T C a l c = - ° - 4 2 T ( 9 , 0.10) = Bed r o u g h n e s s (Dg 5) P o i n t - b a r 7 20.7143 Pavement 5 28.0000 T C a l c = - ° - 69 T ( 1 0 , 0 . 1 0 ) 1.6834 0.9418 0.8394 10 : 1.812 N u l l h y p o t h e s i s a c c e p t e d 0.5398 0.2283 0.2590 9 1.833 N u l l h y p o t h e s i s a c c e p t e d 22.2539 14.4049 11.4164 10 = 1.812 N u l l h y p o t h e s i s a c c e p t e d T a b l e 4-4. ( c o n t i n u e d ) . F r a c t i o n / S o u r c e o f N Mean S S e D e g r e e s o f V a r i a t i o n Freedom W e i g h t % s e d i m e n t -12.0+2.0 mm P o i n t - b a r Pavement 7 51.5886 5 63.5700 11.6471 9.6571 6.3793 10 T C a l c = " I * 9 4 T ( 1 0 , 0.10) = 1-812 N u l l h y p o t h e s i s r e j e c t e d -2.0+0.425 mm P o i n t - b a r Pavement 7 29.4543 5 23.2760 T c a l c = I - 3 9 T ( 8 , 0.10) = -0.425+0.212 mm P o i n t - b a r 7 3.2843 Pavement 5 2.944 0 10.9667 3.5941 5.1490 8 1.860 N u l l h y p o t h e s i s a c c e p t e d 1.5434 1.7384 0.9510 8 T C a l c = 0.35 T ( 8 , 0.10) = I * 8 6 0 N u l l h y p o t h e s i s a c c e p t e d -0.212+0.150 mm P o i n t - b a r 7 0.7429 Pavement 5 0.6160 T c a l c = 0 - 4 7 T ( 7 , 0.10) = -0.150+0.106 mm P o i n t - b a r 7 0.4914 Pavement 5 0.4 060 T C a l c = ° - 4 4 T ( 7 , 0.10) = -0.106+0.075 mm P o i n t - b a r 7 0.3257 Pavement 5 0.2580 0.3742 0.5085 0.2535 7 1.895 N u l l h y p o t h e s i s a c c e p t e d 0.2597 0.3739 0.1818 7 1.895 N u l l h y p o t h e s i s a c c e p t e d 0.1306 0.2321 0.1044 T c a l c = 0 - 5 9 T ( 6 , 0.10) - 1.943 N u l l h y p o t h e s i s a c c e p t e d 69 T a b l e 4-4. ( c o n t i n u e d ) . F r a c t i o n / S o u r c e o f N Mean S S e D e g r e e s o f V a r i a t i o n Freedom -0.075+0.053 mm P o i n t - b a r 7 0.4986 0.1737 Pavement 5 0.3660 0.3192 0.1421 6 T ( 6 , 0.10) = 1-943 N u l l h y p o t h e s i s a c c e p t e d T C a l c = ° - 8 4 -0.053 mm P o i n t - b a r 7 13.6114 4.4919 Pavement 5 8.5620 3.7784 2.4716 10 T f j a l c = 2.11 T ( 1 0 , 0.10) = 1-812 N u l l h y p o t h e s i s r e j e c t e d N = number o f s a m p l e s S = s t a n d a r d d e v i a t i o n Mean = p o p u l a t i o n mean S e = s t a n d a r d e r r o r o f d i f f e r e n c e F i g . 4-5. Downstream t r e n d s o f a) median g r a i n s i z e (M) , b) s e d i m e n t s o r t i n g ( S 0 ) and c) bed r o u g h n e s s ( D 6 5 ) o f p o i n t b a r ( s o l i d s q u a r e ) and pavement ( s o l i d t r i a n g l e ) s e d i m e n t s . 71 Distance Downstream (m) F i g . 4 -6 . Downstream t r e n d s o f a) mean g r a i n s i z e (MQ) a n d b) s e d i m e n t s o r t i n g (S^) o f c o a r s e g r a i n e d s e d i m e n t component f r o m p o i n t - b a r ( s o l i d s q u a r e ) and pavement ( s o l i d t r i a n g l e ) . 7 2 s e l e c t e d r e a c h (between 1 , 0 5 5 and 6 , 2 2 3 m) , no s y s t e m a t i c t r e n d i n mean g r a i n s i z e ( b o t h MQ and M ^ ) o f p o i n t - b a r s e d i m e n t s i s a p p a r e n t . However, mean g r a i n s i z e ( b o t h MQ and MQ) o f pavement s e d i m e n t s a p p e a r s t o d e c r e a s e s l i g h t l y b e t w e e n 3 , 0 0 0 and 6 , 0 0 0 m and t h e n i n c r e a s e s a g a i n . S e d i m e n t s o r t i n g (S Q) o f p o i n t - b a r s e d i m e n t s i n t h e u p p e r p a r t o f t h e s t r e a m i s v e r y e r r a t i c w i t h v e r y p o o r s o r t i n g a t 82 0 and 1 , 5 0 0 m. S o r t i n g (SQ) o f pavement s i t e s i n c r e a s e s ( p o o r l y s o r t e d ) s l i g h t l y f r o m 2 , 7 5 3 t o 5 , 5 0 0 m and t h e n d e c r e a s e s ( b e t t e r s o r t e d ) a g a i n . S e d i m e n t s o r t i n g (SQ) o f c o a r s e g r a i n e d component o f b o t h p o i n t - b a r and pavement s e d i m e n t s i s r o u g h l y c o n s t a n t t h r o u g h o u t t h e r e a c h . Bed r o u g h n e s s a t p o i n t - b a r s i t e s shows a v e r y e r r a t i c t r e n d , b u t a p p e a r s t o i n c r e a s e a t pavement s i t e s f r o m 3 , 6 0 0 m t o w a r d s t h e c o n f l u e n c e w i t h t h e H u a i Kho L o . R e s u l t s o f t h e W a l d - w o l f o w i t z t o t a l - n u m b e r - o f - r u n s t e s t ( T a b l e 4 - 5 ) , s u g g e s t t h a t t h e s e t r e n d s a r e s i g n i f i c a n t f o r s e d i m e n t s o r t i n g (S Q ) a n d b e d r o u g h n e s s ( D ^ ) a t p o i n t - b a r s i t e s , a nd f o r mean g r a i n s i z e (MQ) and s e d i m e n t s o r t i n g ( S 0 ) a t pavement s i t e s . The d i s t r i b u t i o n s o f s e d i m e n t f r a c t i o n s f i n e r t h a n 1 2 . 0 mm a r e shown i n F i g . 4 - 7 . I n t h e r e a c h between 1 , 0 5 5 and 6 , 2 2 3 m, v a r i a t i o n s i n g r a v e l and c o a r s e s a n d (between 1 2 . 0 a n d 0 . 2 1 2 mm) c o n t e n t o f p o i n t b a r s a r e e r r a t i c a nd no s y s t e m a t i c t r e n d s a r e a p p a r e n t . However, t h e a b u n d a n c e s o f s e d i m e n t f r a c t i o n s f i n e r t h a n 0 . 2 1 2 mm seem t o d e c r e a s e b e t w e e n 1 , 5 0 0 and 4 , 5 0 0 m and t h e n i n c r e a s e a g a i n f u r t h e r d ownstream. G r a v e l c o n t e n t o f pavements d e c r e a s e s between T a b l e 4-5. R e s u l t s o f t h e W a l d - w o l f o w i t z t o t a l - n u m b e r - o f - r u n s t e s t (/i) f o r v a r i a t i o n s o f s e d i m e n t t e x t u r e s a t p o i n t - b a r and pavement s i t e s a l o n g t h e whole r e a c h and bet w e e n t h e s u p p o s e d s o u r c e o f g o l d and t h e c o n f l u e n c e w i t h t h e H u a i Kho Lo (1,055 and 6,223 m). F r a c t i o n / N S o u r c e o f C u t p o i n t n^ ri2 M P ( M ) V a r i a t i o n (median) (+) (-) Whole r e a c h P o i n t b a r (N = 19) Mean (MQ) S o r t i n g ( S 0 ) Mean (MQ) S o r t i n g ( S c ) Bed r o u g h n e s s Pavement (N = 7) Mean (MQ) S o r t i n g ( S 0 ) Mean (Mc) S o r t i n g (SQ) Bed r o u g h n e s s Between t h e s u p p o s e d s o u r c e o f g o l d and t h e c o n f l u e n c e w i t h t h e H u a i Kho Lo (1,055 and 6,223 m) P o i n t b a r (N = 12) Mean (MQ) S o r t i n g (SQ) Mean (Mc) S o r t i n g ( S c ) Bed r o u g h n e s s 3 . 99 10 9 11 0. 4016 2 . 48 10 9 8 0. 1207 2. 80 10 9 11 0. 4016 2. 14 9 10 12 0. 2349 5. 00 12 7 6 0. 0251* 4 . 66 4 3 4 0. 3580 2. 19 4 3 3 0. 1126 3. 50 4 3 4 0. 1126 2 . 44 4 3 6 0. 0911* 30. 00 4 3 4 0. 3580 Pavement (N = 5) Mean (M 0) S o r t i n g ( S 0 ) Mean (Mc) S o r t i n g ( S c ) Bed r o u g h n e s s 3 0.00 4 . 04 6 6 6 0.2724 2.44 6 6 4 0.0346* 2.90 7 5 8 0.2331 2.09 6 6 8 0.2724 10.00 7 5 4 0.0384* 4.74 3 2 2 0.0633* 2 .10 3 2 2 0.0633* 3.40 4 1 3 0.2071 2.44 3 2 4 0.2563 3 2 3 0.3313 N = t o t a l number o f s a m p l e s n i = number o f s a m p l e s above median ri2 = number o f s a m p l e s below median /x = t o t a l number o f r u n s above and below t h e m e d i a n * . . . . = s t a t i s t i c a l l y s i g n i f i c a n t a t h i g h e r t h a n 90% c o n f i d e n c e l e v e l . 74 F i g . 4-7. Downstream t r e n d s o f w e i g h t p e r c e n t s e d i m e n t s a t p o i n t b a r s ( s o l i d s q u a r e s ) and pavements ( s o l i d t r i a n g l e s ) i n a) -12.0+2.0 mm f r a c t i o n , b) -2.0+0.425 mm f r a c t i o n , 75 in w o -0.425+0.212 mm Point-bar Pavement Selected reach CO CM CM CO -| , | i | , | t - -| - . -| i —] i 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 D io m o - -0.212+0.150 mm Selected reach E co CO 1,000 2,000 3,000 4,000 5,000 6,000 Distance Downstream (m) 7,000 8,000 F i g . 4-7. ( c o n t i n u e d ) c) -0.425+0.212 mm f r a c t i o n , d) -0.212+0.150 mm f r a c t i o n , 76 E 8" 1,000 -0.106+0.075 mm Selected reach 2,000 3,000 4,000 5,000 Distance Downstream (m) 6,000 7,000 8,000 F i g . 4-7. ( c o n t i n u e d ) e) f ) -0.106+0.075 mm f r a c t i o n , -0.150+0.106 mm f r a c t i o n , 77 i 1 1 1 1 1 1 1 1 1 r 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 10 i ~ H -0.053 mm in in o Selected reach CO i CM 1 CM 1,000 2,000 3,000 4,000 5,000 Distance Downstream (m) 6,000 7,000 8,000 F i g . 4-7. ( c o n t i n u e d ) h) -0.053 mm f r a c t i o n . g) -0.075+0.053 mm f r a c t i o n a nd S t a r i n d i c a t e s t h e s u p p o s e d s o u r c e o f g o l d m i n e r a l i z a t i o n . A r r o w i n d i c a t e s t h e c o n f l u e n c e w i t h t h e H u a i Kho L o . 78 3,000 and 6,000 m whereas c o n t e n t o f s e d i m e n t f i n e r t h a n 2.0 mm i n c r e a s e s . The W a l d - w o l f o w i t z t o t a l - n u m b e r - o f - r u n s t e s t a n d Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t s s u g g e s t o n l y t h e c h a n g e s i n t e x t u r e o f pavement w i t h d i s t a n c e a l o n g t h e s e l e c t e d r e a c h a r e s i g n i f i c a n t ( T a b l e 4 - 6 ) . 4.3.4 C o r r e l a t i o n s between s t r e a m c h a r a c t e r i s t i c s and s e d i m e n t p r o p e r t i e s R e l a t i o n s between s t r e a m w i d t h , c h a n n e l d e p t h , f l o w v e l o c i t y , mean g r a i n s i z e (MQ and M C ) , s e d i m e n t s o r t i n g ( S 0 and SQ) and bed r o u g h n e s s , b a s e d on Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t s , a r e summarized i n T a b l e 4-7. I n t h e r e a c h between 1,055 and 6,22 3 m, s t r e a m w i d t h i s p o s i t i v e l y c o r r e l a t e d w i t h d e p t h , b u t n e g a t i v e l y c o r r e l a t e d w i t h f l o w v e l o c i t y and s e d i m e n t s o r t i n g (S Q) a t p o i n t - b a r s i t e s . S t r e a m d e p t h i s a l s o n e g a t i v e l y c o r r e l a t e d w i t h s e d i m e n t s o r t i n g ( S Q ) • T h e s e r e l a t i o n s i n d i c a t e t h a t a s s t r e a m w i d t h and d e p t h i n c r e a s e , f l o w v e l o c i t y d e c r e a s e s (as i t must t o m a i n t a i n c o n t i n u i t y ) and s e d i m e n t s o r t i n g ( S 0 ) i m p r o v e s . A d d i t i o n a l l y , mean g r a i n s i z e ( b o t h MQ and MQ) a r e p o s i t i v e l y c o r r e l a t e d w i t h s o r t i n g (SQ) s u g g e s t i n g t h a t w i t h i n c r e a s i n g g r a i n s i z e t h e c o a r s e component o f t h e p o i n t - b a r s e d i m e n t becomes moor p o o r l y s o r t e d . Bed r o u g h n e s s i s p o s i t i v e l y c o r r e l a t e d w i t h d i s t a n c e downstream i n d i c a t i n g t h a t i t i n c r e a s e s downstream. T a b l e 4-6. R e s u l t s o f t h e W a l d - w o l f o w i t z t o t a l - n u m b e r - o f - r u n s t e s t (/it) and Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t ( r ) f o r downstream t r e n d s o f w e i g h t p e r c e n t s e d i m e n t i n 8 s i z e f r a c t i o n s f r o m p o i n t - b a r and pavement s i t e s a l o n g t h e w h o l e r e a c h and between t h e s u p p o s e d s o u r c e o f g o l d and t h e c o n f l u e n c e w i t h t h e H u a i Kho Lo (1,055 and 6,223 m). F r a c t i o n / N S o u r c e o f C u t p o i n t n^ ri2 M P(M) Spearman's V a r i a t i o n (median) (+) (-) r v a l u e s Whole r e a c h P o i n t - b a r (n = 19) -12.0+2.0 mm 51.93 9 10 9 0.2426 0 . 061 -2.0+0.425 mm 28.09 9 10 12 0.2349 0 .090 -0.425+0.212 mm 3.20 9 10 8 0.1207 0 .448 -0.212+0.150 mm 0.66 10 9 6 0.0171* 0 . 317 -0.150+0.106 mm 0.61 9 10 4 0.0011* 0 . 161 -0.106+0.075 mm 0.35 10 9 7 0.0500* -0 .037 -0.075+0.053 mm 0. 60 10 9 8 0.12 07 0 . 057 -0.053 mm 12.92 9 10 7 0.0500* -0 .316 Pavement (n = 7) -12.0+2.0 mm 62.14 4 3 4 0.3580 -0 .429 -2.0+0.425 mm 24 . 53 4 3 2 0.0196* 0 . 643 -0.425+0.212 mm 3 .13 3 4 4 0.3580 0 .250 -0.212+0.150 mm 0. 53 3 4 4 0.3580 0 . 393 -0.150+0.106 mm 0.43 3 4 4 0.3580 0 . 393 -0.106+0.075 mm 0.27 4 3 3 0.1126 0 . 607 -0.075+0.053 mm 0.30 4 3 3 0.1126 0 . 607 -0.053 mm 8.54 4 3 3 0.1126 0 .429 B etween t h e supp o s e d s o u r c e i o f a o l d and t h e c o n f l u e n c e wit] t h e H u a i Kho Lo (1,055 and 6 ,223 m) P o i n t - b a r (n = 12) -12.0+2.0 mm 53.04 6 6 6 0.2724 0 . 371 -2.0+0.425 mm 27.73 6 6 6 0.2724 -0 .357 -0.425+0.212 mm 2.37 6 6 8 0.2724 0 . 196 -0.212+0.150 mm 0.65 6 6 7 0.5000 0 .231 -0.150+0.106 mm 0.43 6 6 5 0.1129 0 . 277 -0.106+0.075 mm 0.34 6 6 5 0.1129 -0 .270 -0.075+0.053 mm 0.59 6 6 5 0.1129 -0 . 084 -0.053 mm 14.48 6 6 6 0.2724 -0 .490 T a b l e 4-6. ( c o n t i n u e d ) . F r a c t i o n / N S o u r c e o f C u t p o i n t ^2 ^ p(M) Spearman's V a r i a t i o n (median) (+) (-) r v a l u e s Pavement (n = 5) -12 .0+2.0 mm 63. 08 3 -2. 0+0.425 mm 24. 90 3 -0. 425+0.212 mm 2. 91 3 -0. 212+0.150 mm 0. 38 3 -0. 150+0.106 mm 0. 26 3 -0. 106+0.075 mm 0. 16 3 -0. 075+0.053 mm 0. 21 3 -0. 053 mm 7. 92 3 2 2 0.0633* -0.900* 2 2 0.0633* 0.900* 2 2 0.0633* 0.900* 2 4 0.2563 0.800 2 4 0.2563 0. 800 2 4 0.2563 0.800 2 4 0.2563 0.800 2 2 0.0633* 0.900* N = t o t a l s a m p le number n^ = number o f s a m p l e s above median ri2 = number o f s a m p l e s below median /x = t o t a l number o f r u n s above and below t h e m e d i a n r = Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t N o t e : n = 5; r 0 . i o = 0.90 n = 12; r 0.1 0 = °•50 n = 7; r 0 ! i o = 0.71 n = 19; r 0 ] 1 0 = 0.39 * , , . . . = s t a t i s t i c a l l y s i g n i f i c a n t a t 90% c o n f i d e n c e l e v e l T a b l e 4 - 7 . Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t s between s t r e a m geometry a n d s e d i m e n t c h a r a c t e r i s t i c s a l o n g t h e whole r e a c h and between t h e s u p p o s e d s o u r c e o f g o l d a n d t h e c o n f l u e n c e w i t h t h e H u a i Kho Lo ( 1 , 0 5 5 and 6 , 2 2 3 m) . D i s t a n c e W i d t h Depth V e l o c i t y M 0 M C & 6 5 Whole r e a c h P o i n t - b a r (n = 1 9 ) D i s t a n c e W i d t h D e p t h V e l o c i t y Mean s i z e (MQ) S o r t i n g ( S 0 ) Mean (MQ) S o r t i n g (SQ) D 6 5 0 0 0 3 6 2 3 0 3 2 4 0 - 0 6 7 0 . 1 0 0 - 0 . 1 4 9 0 . 4 4 7 * 0 . 7 0 4 * - 1. 0, 0, 0, 0, 1 . 0 0 0 0 . 6 0 4 1 . 0 0 0 0 . 5 1 7 - 0 . 3 0 5 1 . 0 0 0 0 . 1 4 3 0 . 0 5 3 0 . 243 1 . 0 0 0 0 . 4 7 1 - 0 . 4 7 7 * 0 . 024 - 0 . 3 7 0 1 . 0 0 0 0 . 3 0 9 0 . 2 5 1 - 0 . 0 6 7 0 . 8 7 4 * - 0 . 2 0 6 0 . 0 6 8 0 . 1 1 1 - 0 . 062 0 . 2 4 8 0 . 4 5 9 0 . 0 0 4 0 . 047 0 . 3 4 7 0 . 0 7 1 0 . 1 9 3 1 . 0 0 0 0 . 4 2 5 1 0 . 2 0 7 1, 0, 0 0 0 3 2 1 1 . 0 0 0 Pavement (n = 7 ) D i s t a n c e 1 . 0 0 0 W i d t h D e p t h V e l o c i t y Mean s i z e ( M 0 ) - 0 . 4 2 9 S o r t i n g (S Q ) 0 . 6 4 3 Mean (M c) - 0 . 3 9 6 S o r t i n g ( S c ) 0 . 2 8 8 D 6 5 0 . 8 2 6 1 1 1 . 0 0 0 • 0 . 9 6 4 * 1 . 0 0 0 0 . 8 4 7 * - 0 . 8 1 1 ' - 0 . 8 4 7 - 0 . 2 3 9 0 . 7 9 3 0 . 4 4 1 1 . 0 0 0 • 0 . 6 5 5 • 0 . 0 7 4 1 . 0 0 0 0 . 1 2 0 1 . 0 0 0 T a b l e 4 - 7 . ( c o n t i n u e d ) . D i s t a n c e Width Depth V e l o c i t y M 0 s 0 M C s c D 6 5 Between t h e s u p p o s e d s o u r c e o f g o l d and 1 t h e c o n f l u e n c e w i t h t h e H u a i Kho i Lo f l . 0 5 5 and 6 . 2 2 3 m) P o i n t - b a r (n = = 1 2 ) D i s t a n c e 1 . 0 0 0 W i d t h 0 . 0 7 0 1 . 0 0 0 D e p t h 0 . 3 2 2 0 . 6 2 9 * JL 1 . 0 0 0 V e l o c i t y 0 . 1 7 5 - 0 . 8 0 9 - 0 . 4 5 5 1 . 0 0 0 Mean s i z e (MQ) 0 . 3 7 1 0 . 1 1 2 - 0 . 1 6 8 0 . 0 7 0 1 . 0 0 0 S o r t i n g (S Q ) - 0 . 1 0 5 - 0 . 6 5 7 * - 0 . 6 0 1 * 0 . 2 7 7 0 . 0 0 0 1 . 0 0 0 Mean (MQ) 0 . 4 2 5 0 . 1 3 3 - 0 . 1 5 4 - 0 . 1 2 8 0 . 8 9 1 0 . 2 6 0 1 . 0 0 0 S o r t i n g (SQ) 0 . 343 JL 0 . 0 0 0 - 0 . 1 3 3 - 0 . 1 6 1 0 . 8 6 7 * 0 . 3 7 7 0 . 8 6 7 * 1 . 0 0 0 D 6 5 0 . 6 0 1 - 0 . 4 2 4 - 0 . 1 3 8 0 . 2 9 0 0 . 1 2 7 0 . 2 5 8 0 . 2 1 1 0 . 3 3 9 1 . 0 0 0 Pavement (n = 5) D i s t a n c e 1 . 0 0 0 W i d t h - - D e p t h - - - V e l o c i t y JL - - - Mean s i z e (MQ) - 0 . 9 0 0 JL - - - 1 . 0 0 0 S o r t i n g (S Q ) 0 . 9 0 0 - - - • 1 . 0 0 0 JL 1 . 0 0 0 Mean (MQ) - 0 . 8 2 1 - - - 0 . 9 7 5 - 0 . 9 7 5 * 1 . 0 0 0 S o r t i n g ( S c ) 0 . 8 0 0 - - - • 0 . 9 0 0 0 . 9 0 0 * - 0 . 8 2 1 1 . 0 0 0 D 6 5 0 . 5 2 7 — •0 . 3 6 9 0 . 3 6 9 - 0 . 1 8 9 0 . 3 6 9 1 . 0 0 0 N o t e : n = 5 ; R 0 . 1 0 = 0 . 9 0 n = 1 2 ; R 0 . 1 0 = 0 . 5 0 * n = 7 ; r 0 . i o = 0 . 7 1 n = 1 9 ; r 0 . i o = 0 . 3 9 = s t a t i s t i c a l l y s i g n i f i c a n t a t 90% c o n f i d e n c e l e v e l M = mean g r a i n s i z e ; SQ = sediment s o r t i n g ; D 5 5 = bed r o u g h n e s s 83 A t pavement s i t e s , mean g r a i n s i z e ( b o t h MQ and M c) i s n e g a t i v e l y c o r r e l a t e d w i t h d i s t a n c e , b u t p o s i t i v e l y c o r r e l a t e d w i t h s o r t i n g (SQ) i . e . pavement g r a i n s i z e becomes f i n e r and s o r t i n g p o o r e r downstream. U n l i k e p o i n t - b a r s i t e s , s o r t i n g i m p r o v e s ( n e g a t i v e c o r r e l a t i o n ) w i t h i n c r e a s i n g a v e r a g e g r a i n s i z e ( b o t h MQ and MQ). 4.4 D i s t r i b u 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 e s D i s t r i b u t i o n o f h e a v y m i n e r a l s i s d e s c r i b e d w i t h r e s p e c t t o s t r e a m and s e d i m e n t p r o p e r t i e s b e c a u s e i ) b e h a v i o u r and d i s t r i b u t i o n o f h e a v y m i n e r a l s i n s t r e a m s may be s i m i l a r t o t h a t o f g o l d , and p r o v i d e a method o f c o r r e c t i n g g o l d d a t a f o r h y d r a u l i c e f f e c t s (Day and F l e t c h e r , 1986, 1989, i n p r e s s ; F l e t c h e r , 1990; F l e t c h e r and Day, 1988b), and i i ) h e a v y m i n e r a l s a r e o f t e n s a m p l e d and a n a l y z e d f o r g o l d i n g e o c h e m i c a l e x p l o r a t i o n programmes. 4.4.1 Heavy m i n e r a l m o r p h o l o g y and c o m p o s i t i o n s Q u a l i t a t i v e c o m p o s i t i o n s o b t a i n e d f r o m SEM-EDS show t h a t h e a v y m i n e r a l c o n c e n t r a t e s c o n t a i n l i m o n i t e , h e m a t i t e , i l m e n i t e , m a g n e t i t e , z i r c o n , g a r n e t , s p i n e l and b a r i t e . C l a y m i n e r a l s c a n a l s o be o b s e r v e d i n t h e h e a v y m i n e r a l s b e c a u s e t h e y c o a t o r a d h e r e t o t h e s u r f a c e o f h e a v y - m i n e r a l g r a i n s a n d a r e n o t s e p a r a t e d d u r i n g t h e c o n c e n t r a t i o n p r o c e s s . H eavy m i n e r a l g r a i n s a r e s u b a n g u l a r t o w e l l - r o u n d e d w i t h 84 i r r e g u l a r t o s p h e r i c a l s h a p e s ( F i g . 4 - 8 ) . T h e y c o m p r i s e a p p r o x i m a t e l y 15% m a g n e t i c and 85% n o n - m a g n e t i c m i n e r a l s . A f t e r m a g n e t i c m i n e r a l s were removed, t h e n o n - m a g n e t i c f r a c t i o n was e x amined w i t h a b i n o c u l a r m i c r o s c o p e t o e s t i m a t e t h e p r o p o r t i o n (by volume) o f e a c h m i n e r a l . R e s u l t s a r e p r e s e n t e d i n T a b l e 4-8. 4.4.2 S i z e d i s t r i b u t i o n and abundance o f h e a v y m i n e r a l s Mean w e i g h t p e r c e n t s o f h e a v y m i n e r a l c o n c e n t r a t e s i n f i v e s i z e f r a c t i o n s between 0.425 and 0.053 mm o f p o i n t - b a r and pavement s i t e s a r e p l o t t e d i n F i g . 4-9. I n b o t h t y p e s o f s e d i m e n t , t h e f o u r s i z e f r a c t i o n s between 0.425 and 0.075 mm c o n t a i n a p p r o x i m a t e l y 1% h e a v y m i n e r a l s , w h e r e a s t h e v e r y f i n e s a n d (-0.075+0.053 mm) f r a c t i o n c o n t a i n s a p p r o x i m a t e l y 0.2%. A l o n g t h e r e a c h between 2,7 53 and 6,22 3 m, a b u n d a n c e o f h e a v i e s i n t h e two c o a r s e r s a n d (between 0.425 and 0.150 mm) f r a c t i o n s a t pavement s i t e s i s s l i g h t l y g r e a t e r t h a n a t p o i n t b a r s . However, s t a t i s t i c a l r e s u l t s (two-sample t t e s t ) show t h a t t h e d i f f e r e n c e i s n o t s i g n i f i c a n t . 4.4.3 Downstream t r e n d s o f h e a v y m i n e r a l c o n c e n t r a t e s i n p o i n t - b a r and pavement d e p o s i t s Downstream t r e n d s o f h e a v y m i n e r a l c o n c e n t r a t e s a r e shown i n F i g . 4-10. The d i s t r i b u t i o n i s somewhat e r r a t i c . N e v e r t h e l e s s , i n t h e r e a c h between 1,055 and 6,22 3 m, h e a v y F i g . 4 - 8 . G r a i n morpho logy o f heavy m i n e r a l c o n c e n t r a t e s . 86 T a b l e 4-8. P r o p o r t i o n (% by volume) o f n o n - m a g n e t i c h e a v y m i n e r a l c o m p o s i t i o n s i n s t r e a m s e d i m e n t . P r o p o r t i o n M i n e r a l (% by volume) L i m o n i t e 40 H e m a t i t e 25 I l m e n i t e 25 Z i r c o n 5 G a r n e t 3 B a r i t e 1 S p i n e l 1 87 Ui o I <£ 1 CO "53 Point bar - N = 11 0.91 0.92 - 0.82 0.80 0.21 -CU25+0.212 -0.212+0.150 -0.150+0.106 -0.108+0.075 -0.075+0.053 B Ui CD I C D I CO "53 (N = 5) 0.91 (N = 5) (N = 4) 1.00 1.00 (N = 4) 0.84 Pavement (N = 5) 0.25 -0.425+0.212 -0.212+0.150 -0.150+0.108 -0.108+0.075 -0.075+0.053 Grain Size (mm) F i g . 4-9. Mean w e i g h t p e r c e n t o f h e a v y m i n e r a l d i s t r i b u t i o n s i n a) p o i n t - b a r (n = 11) and b) pavement (n = 5) s e d i m e n t s . 88 (A CD I CD I to CD > CO CD I -0.425+0.212 mm Point-bar Pavement A r 1 1 1 1 1 1 1 1 1 r 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 B -0.212+0.150 mm Selected reach co CM CM CO X i 1 i 1 i 1 i 1 i 1 i 1 i 1 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 Distance Downstream (m) F i g . 4-10. Downstream trends of heavy mineral concentrates at point-bar ( s o l i d square) and pavement ( s o l i d triangle) s i t e s f o r a) -0.425+0.212 mm f r a c t i o n , b) -0.212+0.150 mm f r a c t i o n , 89 co CD I CD I co CD i CD I i n : i n ; o " -0.150+0.106 mm Selected reach Point-bar Pavement • co CM CM CO "1 ' 1 1 1 ' 1 1 1 1 I 1 I 1 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 D -0.106+0.075 mm Selected reach CO CM CM CO — i ' 1 1 1 1 i 1 i 1,000 2,000 3,000 4,000 5,000 6,000 Distance Downstream (m) 7,000 8,000 F i g . 4-10. ( c o n t i n u e d ) c) -0.150+0.106 mm d) -0.106+0.075 mm f r a c t i o n and f r a c t i o n , 90 F i g . 4-10. ( c o n t i n u e d ) e) -0.075+0.053 mm f r a c t i o n . S t a r i n d i c a t e s t h e s u p p o s e d s o u r c e o f g o l d m i n e r a l i z a t i o n . A r r o w i n d i c a t e s t h e c o n f l u e n c e w i t h t h e H u a i Kho L o . 91 m i n e r a l c o n t e n t o f c o a r s e s a n d (-0.425+0.212 mm) f r a c t i o n f r o m p o i n t b a r s a p p e a r s t o d e c r e a s e s l i g h t l y downstream. C o n v e r s e l y , f o r t h e two f r a c t i o n s between 0.150 and 0.075 mm c o n c e n t r a t i o n s seem t o i n c r e a s e e r r a t i c a l l y downstream. Abundance o f h e a v i e s i n t h e f i n e s t f r a c t i o n d e c r e a s e s f r o m 1,500 t o 3,300 m and t h e n i n c r e a s e s a g a i n . T h e r e a r e no o b v i o u s s y s t e m a t i c t r e n d s i n t h e abundance o f h e a v y m i n e r a l s a t pavement s i t e s . S t a t i s t i c a l e v a l u a t i o n s b a s e d on t h e W a l d - w o l f o w i t z t o t a l - n u m b e r - o f - r u n s t e s t and Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t s ( T a b l e 4-9) s u g g e s t t h a t t r e n d s f o r d e c r e a s e i n abundance o f c o a r s e g r a i n e d h e a v i e s downstream v e r s u s i n c r e a s e d abundance o f t h e -0.150+0.106 mm h e a v i e s may be r e a l . 4.4.4 R e l a t i o n s between h e a v y m i n e r a l a b u n d a n c e and s t r e a m c h a r a c t e r i s t i c s and s e d i m e n t p r o p e r t i e s Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t s ( T a b l e 4-10) a r e e v a l u a t e d t o examine t h e r e l a t i o n s between t h e a b u n d a n c e o f h e a v y m i n e r a l s and s t r e a m c h a r a c t e r i s t i c s and s e d i m e n t p r o p e r t i e s i n t h e s e l e c t e d r e a c h . R e s u l t s i n d i c a t e t h a t a t p o i n t - b a r s i t e s o n l y s t r e a m w i d t h and s o r t i n g ( S 0 ) a r e s i g n i f i c a n t l y c o r r e l a t e d w i t h abundance o f h e a v i e s , and t h e n o n l y i n two f i n e s t s i z e f r a c t i o n s . However, i t i s n o t a b l e t h a t h e a v y m i n e r a l c o n t e n t s i n a l l s i z e f r a c t i o n s a r e n e g a t i v e l y c o r r e l a t e d w i t h s t r e a m w i d t h a n d d e p t h , a n d p o s i t i v e l y c o r r e l a t e d w i t h f l o w v e l o c i t y and bed r o u g h n e s s . 92 T a b l e 4-9. R e s u l t s o f t h e W a l d - w o l f o w i t z t o t a l - n u m b e r - o f - r u n s t e s t (/i) and Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t ( r ) f o r downstream t r e n d s o f he a v y m i n e r a l c o n c e n t r a t e s f r o m p o i n t - b a r a n d pavement s e d i m e n t s a l o n g t h e wh o l e r e a c h and betw e e n t h e s u p p o s e d s o u r c e o f g o l d and t h e c o n f l u e n c e w i t h t h e H u a i Kho Lo (1,055 and 6,223 m). F r a c t i o n / N S o u r c e o f C u t p o i n t n± n 2 M P(M) Spearman's V a r i a t i o n (median) (+) (-) r v a l u e s Whole r e a c h P o i n t - b a r (n = 11) -0.425+0. 212 mm 0. 74 6 5 8 0. 1607 -0. 409 -0.212+0. 150 mm 0. 88 5 6 8 0. 1607 -0. 109 -0.150+0. 106 mm 0. 95 6 5 4 0. 0577* 0. 164 -0.106+0. 075 mm 0. 85 5 6 4 0. 0577* 0. 145 -0.075+0. 053 mm 0. 18 5 6 5 0. 1754 0. 436 Pavement (n = = 5) -0.425+0. 212 mm 1. 04 2 3 3 0. 3313 0. 100 -0.212+0. 150 mm 1. 04 3 2 5 0. 0404* -0. 100 -0.150+0. 106 mm 1. 08 2 2 4 0. 1103 0. 800 -0.106+0. 075 mm 0. 91 2 2 2 0. 1103 0. 800 -0.075+0. 053 mm 0. 29 3 2 3 0. 3313 -0. 200 Bewteen t h e s u p p o s e d s o u r c e o f g o l d and t h e c o n f l u e n c e w i t h t h e H u a i Kho Lo (1,055 and 6,223 m) P o i n t - b a r (n = 9) -0. 425+0. 212 mm 0. 74 5 4 6 0. 3440 -0. * 667 -0. 212+0. 150 mm 0. 81 5 4 6 0. 3440 -0. 117 -0. 150+0. 106 mm 0. 95 5 4 3 0. 0386* 0. 393 -0. 106+0. 075 mm 0. 68 5 4 7 0. 1304 0. 567 -0. 075+0. 053 mm 0. 20 4 5 5 0. 3740 -0. 150 Pavement (n = 5) a s above N = t o t a l s a m p le number n^ = number o f s a m p l e s above median n 2 = number o f s a m p l e s below median ju = t o t a l number o f r u n s above and below t h e m e d i a n r = Spearman's c o r r e l a t i o n c o e f f i c i e n t N o t e n = 5; *"(0.10) "' 0.90 n = 9 / ' r ( o!lO) = ° - 6 0 n = 11; r ( 0 . 1 0 ) = 0.54 * . . . . . . = s t a t i s t i c a l l y s i g n i f i c a n t a t 90% c o n f i d e n c e l e v e l T a b l e 4-10. Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t s b e t w e e n w e i g h t p e r c e n t h e a v y m i n e r a l c o n c e n t r a t e s and s t r e a m c h a r a c t e r i s t i c s and s e d i m e n t p r o p e r t i e s i n t h e w h o l e r e a c h and b e t w e e n t h e supposed s o u r c e o f g o l d and t h e c o n f l u e n c e w i t h t h e H u a i Kho Lo (1,055 and 6,223 m). Width Depth V e l o c i t y M 0 S 0 D65 M C S C Whole r e a c h P o i n t - b a r (n = 11) -0.425+0.212 mm -0.212+0.150 mm -0.150+0.106 mm -0.106+0.075 mm -0.075+0.053 mm -0.164 -0.333 -0.209 -0.319 -0.269 -0.288 -0.664* -0.196 -0.023 •0.108 0.319 0.446 0.609' 0.405 0.378 0.064 0.218 0.397 •0.109 0.407 •0.145 •0.418 ,434 245 362 •0, 0, 0, 0.257 0.202 0.447 0.202 0.379 -0.100 0.073 0.293 -0.087 0.544 1 -0.500 -0.282 -0.064 0.445 0.371 Pavement (n = 5) -0.425+0.212 mm -0.212+0.150 mm -0.150+0.106 mm (n=4) -0.106+0.075 mm (n=4) -0.075+0.053 mm 0.229 0.229 -0.424 -0.990 0.000 -0.229 -0.229 0.424 0.990 0. 000 0.567 0.000 0.674 0.674 0.567 0.310 0. 000 -0.467 •0.934 0.232 •0.381 •0. 686 -0.076 0.680 0. 000 Between t h e supposed s o u r c e o f g o l d and t h e c o n f l u e n c e w i t h t h e H u a i Kho Lo (1,055 and 6,223 m) P o i n t - b a r (n = 9) -0.425+0.212 mm -0.217 -0.250 -0.100 -0.500 0.367 0.067 -0.418 -0.233 -0.212+0.150 mm -0.300 -0.217 0.167 -0.267 0.000 0.136 -0.167 0.067 -0.150+0.106 mm -0.427 -0.192 0.477 0.075 -0.084 0.460 0.130 0.360 -0.106+0.075 mm -0.600* -0.083 0.583 0.033 0.183 0.526 0.109 0.433 -0.075+0.053 mm -0.527 -0.318 0.544 0.268 0.661* 0.187 0.412 0.586 Pavement (n = 5) as above Table 4 - 1 0 . (continued). Note: n = 4 ; r 0 . i o = 1 . 0 0 n = 9 ; r 0 . i o = 0 . 6 0 n = 5 ; T Q ] i o = 0 • 9 0 n = 1 1 ; r o . i o = 0 . 5 4 = s t a t i s t i c a l l y s i g n i f i c a n t at 90% confidence l e v e l MQ = mean grain s i z e of the entire sediment SQ = sediment sorting of the entire sediment Dg5 = bed roughness Mc = mean grain s i z e of coarse grained sediment component Sc = sorting of coarse grained sediment component 95 T h e s e r e l a t i o n s s u g g e s t t h a t a b u ndances o f h e a v y m i n e r a l s a t p o i n t - b a r s i t e s i n c r e a s e where r e d u c t i o n i n c h a n n e l w i d t h a n d d e p t h c a u s e s f l o w v e l o c i t y and bed r o u g h n e s s t o i n c r e a s e . 96 4.5 Summary 1) I n t h e H u a i H i n Laep s e d i m e n t s f r o m p o i n t - b a r and pavement s i t e s h a v e s t r o n g l y b i m o d a l d i s t r i b u t i o n s . T h ey c o n s i s t m a i n l y o f g r a v e l and s i l t - c l a y w i t h o n l y m i n o r amounts o f s a n d . 2) Pavement s e d i m e n t s c o n t a i n s i g n i f i c a n t l y more g r a v e l b u t l e s s s i l t - c l a y t h a n p o i n t b a r s e d i m e n t s . 3) T r e n d s i n s e d i m e n t t e x t u r e and mean g r a i n s i z e a t p o i n t - b a r s i t e s a l o n g t h e r e a c h between 1,055 and 6,223 m a r e v e r y e r r a t i c , whereas bed r o u g h n e s s i n c r e a s e s and s o r t i n g i m p r o v e s downstream. However, a t pavement s i t e s mean g r a i n s i z e i n c r e a s e s and s e d i m e n t s o r t i n g d e c r e a s e s downstream. A t p o i n t - b a r s i t e s s e d i m e n t s o r t i n g i s n e g a t i v e l y c o r r e l a t e d w i t h s t r e a m w i d t h and d e p t h . 4) Abundance o f h e a v y m i n e r a l s a t p o i n t - b a r and pavement s i t e s i s s i m i l a r , a p p r o x i m a t e l y 1%. A t p o i n t - b a r s i t e s t h e i r abundance g e n e r a l l y i n c r e a s e s i n z o n e s o f c o n v e r g e n t f l o w (narrow c h a n n e l w i d t h ) c h a r a c t e r i z e d by h i g h e r f l o w v e l o c i t i e s , i n c r e a s e d bed r o u g h n e s s a n d p o o r e r s o r t i n g . CHAPTER FIVE GEOCHEMISTRY OF GOLD IN THE HUAI HIN LAEP 98 5.1 D i s t r i b u t i o n o f g o l d between s i z e and d e n s i t y f r a c t i o n s G o l d c o n c e n t r a t i o n s i n h e a v y m i n e r a l c o n c e n t r a t e s , and -0.150 mm and -0.053 mm s e d i m e n t f r a c t i o n s a r e l i s t e d i n T a b l e 5-1. C o n c e n t r a t i o n s i n hea v y m i n e r a l c o n c e n t r a t e s r a n g e f r o m <15 ppb t o a maximum o f 198,000 ppb, b u t a r e t y p i c a l l y i n t h e s e v e r a l t h o u s a n d s o f ppb r a n g e . Of t h e c o r r e s p o n d i n g l i g h t m i n e r a l f r a c t i o n s a l l b u t s i x c o n t a i n l e s s t h a n 5 ppb g o l d (Appendix) . I n a l l c a s e s , Au c o n c e n t r a t i o n s i n t h e -0.053 mm s e d i m e n t f r a c t i o n a r e l e s s t h a n 5 ppb ( T a b l e 5-1) . S i m i l a r l y , e x c e p t f o r 85 ppb i n a s i n g l e p o i n t - b a r sample and two v a l u e s o f 80 and 95 ppb a t pavement s i t e s , Au c o n c e n t r a t i o n s i n t h e -0.150 mm s e d i m e n t f r a c t i o n a r e a t o r l e s s t h a n 5 ppb. T h e s e low v a l u e s i n t h e l i g h t s , t h e -0.150 mm and t h e -0.053 mm s e d i m e n t f r a c t i o n s c o n t r a s t s t r o n g l y w i t h t h e h i g h v a l u e s i n t h e h e a v y m i n e r a l f r a c t i o n s . Summary s t a t i s t i c s a r e shown i n T a b l e 5-2. The d a t a f o r Au c o n c e n t r a t i o n s i n h e a v y m i n e r a l c o n c e n t r a t e s ( T a b l e 5-1) were c o n v e r t e d t o Au c o n c e n t r a t i o n s i n t h e w h o l e c o r r e s p o n d i n g s e d i m e n t f r a c t i o n u s i n g t h e e q u a t i o n : A U T O T A L = ( A u H x W t H ) / W t T o T A L (5-1) where A u r r i O T A I j i s t h e Au c o n c e n t r a t i o n (ppb) i n t h e s e d i m e n t f r a c t i o n , AUJJ i s t h e Au c o n c e n t r a t i o n (ppb) i n h e a v y m i n e r a l c o n c e n t r a t e s , Wtjj i s t h e w e i g h t (g) o f t h e h e a v y m i n e r a l f r a c t i o n , a nd W t r p O T A L i s t h e combined w e i g h t (g) o f h e a v y m i n e r a l and s e d i m e n t f r a c t i o n , and a s s u m i n g t h a t Au 99 T a b l e 5-1 . G o l d c o n c e n t r a t i o n s (ppb) i n h e a v y m i n e r a l c o n c e n t r a t e s , -0.150 and -0.053 mm s e d i m e n t f r a c t i o n s . Heavy m i n e r a l f r a c t i o n (mm) S e d i m e n t (mm) Sample 425+.212 -.212+.106 .106+.053 -.150 .053 P o i n t - b a r PP-16 <15 14700 <200 <5 <5 PP-96 185000 86300 7540 <5 <5 PP-09 380 <25 930 <5 <5 PP-94 3080 <30 4000 <5 <5 PP-10 <20 2290 11000 <5 <5 PP-89 3260 1465 3500 <5 <5 PP-81 14800 46000 18700 <5 <5 PP-75 <30 <75 21300 5 <5 PP-70 28900 28400 11800 85 <5 PP-67 29200 58500 36100 <5 <5 PP-64 25 1790 14200 <5 <5 Pavement PP-87 90 55400 38200 95 <5 PP-100 58800 46000 11300 <5 <5 PP-79 800 23000 15200 <5 <5 PP-68 26700 37800 18800 <5 <5 PP-65 72000 198000 67200 80 <5 * = I n a l l b u t s i x s a m p l e s t h e c o r r e s p o n d i n g l i g h t f r a c t i o n s c o n t a i n < 5 ppb g o l d . R e p o r t e d Au d e t e c t i o n l i m i t s d e p e n d on w e i g h t o f h e a v y m i n e r a l c o n c e n t r a t e s . 100 T a b l e 5-2. Summaries s t a t i s t i c s o f g o l d c o n t e n t (ppb) i n h e a v y m i n e r a l f r a c t i o n s . S i z e f r a c t i o n (mm) -0.425+0.212 -0.212+0.106 -0.106+0.053 B a r (n = 11) Mean 24060 21775 11745 M e d i a n 3080 2290 11000 Range (<15-185000) (<25-86300) (<200-36100) Pavement (n = 5) Mean 31678 72040 30140 M e d i a n 26700 46000 18800 Range (90-72000) (23000-198000) (11300-67200) 101 c o n c e n t r a t i o n i n t h e l i g h t m i n e r a l f r a c t i o n s i s l e s s t h a n 5 ppb. R e s u l t s ( T a b l e 5-3) show t h a t c a l c u l a t e d Au c o n c e n t r a t i o n s i n a l l t h r e e c o r r e s p o n d i n g s e d i m e n t f r a c t i o n s a r e g r e a t e r t h a n t h o s e i n t h e -0.150 and -0.053 mm s e d i m e n t f r a c t i o n s . 5.2 G o l d d i s t r i b u t i o n i n t h e H u a i H i n L a e p 5.2.1 C o m p a r i s o n between Au c o n c e n t r a t i o n s a t p o i n t b a r and pavement s i t e s I n a l l t h r e e s i z e f r a c t i o n s mean and m e d i a n g o l d c o n c e n t r a t i o n s a t pavement s i t e s e x c e e d t h e s e f o r p o i n t - b a r s i t e s ( T a b l e s 5-2 and 5 - 3 ) . However, v a l u e s a r e e x t r e m e l y e r r a t i c , w i t h a v e r y w i de r a n g e o f g o l d c o n c e n t r a t i o n s , and a s t a t i s t i c a l c o m p a r i s o n o f c o n c e n t r a t i o n s shows none o f t h e d i f f e r e n c e s a r e s i g n i f i c a n t a t 90% c o n f i d e n c e l e v e l ( T a b l e 5-4) . 5.2.2 Downstream t r e n d s o f Au c o n c e n t r a t i o n s i n p o i n t - b a r and pavement s e d i m e n t s G o l d v a l u e s i n h e a v i e s f r o m p o i n t - b a r and pavement s i t e s a r e p l o t t e d a g a i n s t t h e d i s t a n c e downstream f o r f o u r s i z e f r a c t i o n s i n F i g . 5-1. C o r r e s p o n d i n g g o l d v a l u e s r e c a l c u l a t e d f o r s e d i m e n t s a r e shown i n F i g . 5-2. B e c a u s e s e d i m e n t t e x t u r e r e m a i n s r e a s o n a b l y c o n s t a n t t h r o u g h o u t t h e T a b l e 5-3. C a l c u l a t e d g o l d c o n c e n t r a t i o n s ( p p b ) , mean, m e d i a n and r a n g e o f g o l d c o n c e n t r a t i o n s i n s e d i m e n t f r a c t i o n s . S i z e f r a c t i o n (mm) Sample -0.425+0.212 -0.212+0.106 -0.106+0.053 P o i n t - b a r PP-16 <1 180 <1 PP-96 1050 340 40 PP-09 5 <1 5 PP-94 25 <1 15 PP-10 <1 20 40 PP-89 25 15 15 PP-81 130 395 30 PP-75 <1 <1 95 PP-70 220 435 85 PP-67 190 555 275 PP-64 <1 10 45 Mean 150 180 60 M e d i a n 25 20 40 Range <1-1050 <l-555 <l-275 Pavement PP-87 <1 625 190 PP-100 410 330 25 PP-79 10 270 55 PP-68 185 360 120 PP-65 770 2160 410 Mean 275 750 160 M e d i a n 185 360 120 Range <l-770 270-2160 25-410 * = c a l c u l a t e d f r o m d a t a i n T a b l e 5-1, v a l u e s l e s s t h a n t h e d e t e c t i o n l i m i t were t a k e n a t m i d - p o i n t . 103 T a b l e 5-4. S t a t i s t i c a l two-sample t e s t means o f Au c o n c e n t r a t i o n s (ppb) i n h e a v y - m i n e r a l c o n c e n t r a t e s a n d i n s e d i m e n t s f r o m p o i n t b a r s and pavements i n t h e r e a c h b e t w e e n 2,753 and 6,223 m. N u l l h y p o t h e s i s : M Au i n i p o i n t - b a r - M Au i n pavement F r a c t i o n / S o u r c e o f V a r i a t i o n N Mean S S e D e g r e e s o f Freedom Au i n h e a v i e s -0.425+0.212 mm P o i n t - b a r Pavement 6 5 12700. 31678. 00 00 13782.44 32929.85 14676.77 5 T C a l c = -1-20 T (5, 0.10) = 2. 015 N u l l h y p o t h e s i s a c c e p t e d -0.212+0.106 mm P o i n t - b a r Pavement 6 5 22698. 72040. 75 00 25529.44 71411.12 31045.16 5 T c a l c = "1-45 T (5, 0.10) = 2. 015 N u l l h y p o t h e s i s a c c e p t e d -0.106+0.053 mm P o i n t - b a r Pavement 6 5 17600. 30140. 00 00 10965.04 23157.89 10577.66 5 T c a l c = " L H T (5, 0.10) = 2. 015 N u l l h y p o t h e s i s a c c e p t e d -0.212+0.053 mm P o i n t - b a r Pavement 6 5 21623. 62147. 22 76 20904.51 58446.43 25410.57 5 T C a l c = -1-47 T (5, 0.10) = 2. 015 N u l l h y p o t h e s i s a c c e p t e d Au i n s e d i m e n t s -0.425+0.212 mm P o i n t - b a r Pavement 6 5 93. 274. 90 61 98.75 323.69 138.06 5 T C a l c = "1-20 T (5, 0.10) = 2. 015 N u l l h y p o t h e s i s a c c e p t e d T a b l e 5-4. ( c o n t i n u e d ) . F r a c t i o n / S o u r c e o f N Mean S S e D e g r e e s o f V a r i a t i o n Freedom -0.212+0.106 mm P o i n t - b a r Pavement 6 5 235. 748. 94 31 253.85 800.22 342.75 5 T c a l c = -1-38 T ( 5 , 0 .10) = 2. 015 N u l l h y p o t h e s i s a c c e p t e d -0.106+0.053 mm P o i n t - b a r Pavement 6 5 90. 160. 36 76 94.75 152.85 75.08 6 T C a l c = - ° - 9 0 T ( 6 , 0 .10) = 1. 943 N u l l h y p o t h e s i s a c c e p t e d -0.212+0.053 mm P o i n t - b a r Pavement 6 5 174. 521. 57 41 182.15 554.82 238.59 5 T C a l c = "1-34 T ( 5 , 0 .10) = 2. 015 N u l l h y p o t h e s i s a c c e p t e d * . . . = v a l u e s l o w e r t h a n d e t e c t i o n l i m i t s were t a k e n a t m i d - p o i n t . N = number o f s a m p l e s Mean = p o p u l a t i o n mean S = s t a n d a r d d e v i a t i o n S e = s t a n d a r d e r r o r o f d i f f e r e n c e 105 200,000 150,000 Q. S 100,000 < 50,000 -0.425+0.212 mm Point-bar Pavement Selected reach + i — i r 1 — 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 200,000 150,000 J3 CL 3 100,000 < 50,000 -0.212+0.106 mm Selected reach B y — f =1 i |~ r - | | i p 1,000 2,000 3,000 4,000 5,000 6,000 + 7,000 8,000 Distance Downstream (m) F i g . 5-1. Downstream tren d s f o r Au c o n c e n t r a t i o n s i n heavy m i n e r a l c o n c e n t r a t e s a t p o i n t bars ( s o l i d squares) and pavements ( s o l i d t r i a n g l e s ) f o r a) -0.425+0.212 mm f r a c t i o n , b) -0.212+0.106 mm f r a c t i o n , 106 200,000 150,000 o. 3 100,000 < 50,000 E 1 8- -0.106+0.053 mm Selected reach Point-bar Pavement — i 1 1 1 1 j 1 - | 1 — 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 200,000 150,000 Q. S 100,000 3 50,000 -0.212+0.053 mm Selected reach 1,000 2,000 3,000 4,000 5,000 6,000 Distance Downstream (m) D 7,000 8,000 F i g . 5 - 1 . ( c o n t i n u e d ) c ) - 0 . 1 0 6 + 0 . 0 5 3 mm f r a c t i o n a n d d) i d e a l l y c o m b i n e d - 0 . 2 1 2 + 0 . 0 5 3 mm f r a c t i o n . S t a r i n d i c a t e s t h e s u p p o s e d s o u r c e o f g o l d m i n e r a l i z a t i o n . A r r o w i n d i c a t e s t h e c o n f l u e n c e w i t h t h e H u a i Kho L o . 107 3,000 2,500 2,000 a & 1,500 < 1,000 500 -0.425+0.212 mm Selected reach A Point-bar Pavement 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 F i g . 5-2. Downstream trends sediment f r a c t i o n s a t p o i n t pavements ( s o l i d t r i a n g l e s ) f o r b) -0.212+0.106 mm f r a c t i o n , f o r Au c o n c e n t r a t i o n s i n bars ( s o l i d squares) and a) -0.425+0.212 mm f r a c t i o n , 108 3,000 2,500 -0.106+0.053 mm Point-bar Pavement 2,000 n 31,500 < 1,000 Selected reach 500 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 3,000 2,500 i i | 1 1 1 1 1 r 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 Distance Downstream (m) F i g . 5-2. ( c o n t i n u e d ) c) -0.106+0.053 mm f r a c t i o n a nd d) i d e a l l y c o m b i n e d -0.212+0.053 mm f r a c t i o n . S t a r i n d i c a t e s t h e s u p p o s e d s o u r c e o f g o l d m i n e r a l i z a t i o n . A r r o w i n d i c a t e s t h e c o n f l u e n c e w i t h t h e H u a i Kho L o . 109 r e a c h , downstream d i s t r i b u t i o n p a t t e r n s o f Au c o n c e n t r a t i o n s i n h e a v y m i n e r a l c o n c e n t r a t e s and i n s e d i m e n t s a r e s i m i l a r , e x c e p t t h a t Au c o n c e n t r a t i o n s i n h e a v i e s a r e a p p r o x i m a t e l y 100 t i m e s h i g h e r t h a n t h o s e i n s e d i m e n t s . I t i s n o t a b l e t h a t t h e r e i s a s i n g l e h i g h g o l d v a l u e i n a l l s i z e f r a c t i o n s o f t h e p o i n t - b a r sample a t 820 m n e a r t h e s u p p o s e d b e d r o c k s o u r c e o f t h e m i n e r a l i z a t i o n , where t h e s e d i m e n t (PP-96, A p p e n d i x ) c o n t a i n s m a i n l y o f s i l t a nd c l a y (> 46%) and m i n o r g r a v e l (~ 1 8 % ) . G o l d c o n c e n t r a t i o n s a t t h i s s i t e d e c r e a s e w i t h d e c r e a s i n g g r a i n s i z e . I n t h e r e a c h d o w n stream f r o m t h i s s i t e , t r e n d s i n g o l d c o n c e n t r a t i o n s i n a l l t h r e e f r a c t i o n s a r e e r r a t i c b u t show s i m i l a r i t i e s w i t h h i g h g o l d v a l u e s a t 3,250 and 5,750 m. E s p e c i a l l y i n t h e v e r y f i n e s a n d (-0.106+0.053 mm) and combined -0.212+0.053 mm f r a c t i o n s , g o l d c o n c e n t r a t i o n s a p p e a r t o i n c r e a s e d ownstream a s f a r a s t h e c o n f l u e n c e w i t h t h e H u a i Kho L o . The W a l d - w o l f o w i t z t o t a l - n u m b e r - o f - r u n s t e s t a n d Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t s ( T a b l e 5-5) s u g g e s t t h a t t h e t r e n d o f Au c o n c e n t r a t i o n s i n t h e s e two f r a c t i o n s i s s i g n i f i c a n t . T h e r e a r e t o o few r e s u l t s f o r pavement s e d i m e n t s t o i d e n t i f y downstream t r e n d s . N e v e r t h e l e s s , i t s h o u l d be n o t e d t h a t t h e h i g h e s t c o n c e n t r a t i o n o f Au i s f o u n d a t 6,223 m ( i . e . a p p r o x i m a t e l y 5 k i l o m e t e r s downstream o f t h e s u p p o s e d b e d r o c k s o u r c e o f g o l d ) . T a b l e 5-5. R e s u l t s o f t h e W a l d - w o l f o w i t z t o t a l - n u m b e r - o f - r u n s t e s t (n) and Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t ( r ) f o r downstream t r e n d s o f Au c o n c e n t r a t i o n s (ppb) i n p o i n t - b a r a nd pavement s e d i m e n t s i n t h e H u a i H i n L a e p . F r a c t i o n / C u t p o i n t N S o u r c e o f (median) n± n 2 M P(M) Spearman's V a r i a t i o n (ppb) (+) (-) r v a l u e s Whole r e a c h P o i n t - b a r (n = 11) -0.425+0. 212 mm 23. 53 6 5 9 0. 0512 0. 009 -0.212+0. 106 mm 17. 98 5 6 6 0. 3853 0. 255 -0.106+0. 053 mm 39. 27 6 5 6 0. 3853 0. 782* -0.212+0. 053 mm(n=18) 28. 20 9 9 9 0. 3135 0. 201 Pavement (n = = 5) -0.425+0. 212 mm 184. 24 2 3 4 0. 2563 0. 700 -0.212+0. 106 mm 360. 71 3 2 3 0. 3313 0. 300 -0.106+0. 053 mm 120. 35 3 2 3 0. 3313 0. 400 -0.212+0.053 mm(n=7) 268.35 4 3 4 0.3580 -0.321 Between s u p p o s e d s o u r c e o f m i n e r a l i z a t i o n a nd c o n f l u e n c e w i t h H u a i Kho Lo (1,055 and 6,223 m) P o i n t - b a r (n = 9) -0.425+0.212 mm 23.53 5 4 7 0.1304 0.283 -0.212+0.106 mm 14.94 4 5 7 0.1304 0.567  94 40.24 4 5 2 0. 0064* 36.70 5 6 5 0. 1754 -0.106+0.053 mm " 0.800* 0.536* n^ = number o f s a m p l e s above median n 2 = number o f s a m p l e s below median ju = t o t a l number o f r u n s above and below t h e m e d i a n * = s t a t i s t i c a l l y s i g n i f i c a n t a t 90% c o n f i d e n c e l e v e l N o t e : n = 5, r ( 0 < 1 0 ) = 0.90 n = 11, r ( 0 . i o ) = 0-54 n = 1> r ( 0 . 1 0 ) = ° - 7 1 n = r ( 0 . 1 0 ) = ° - 4 6 n = 9> r ( 0 . 1 0 ) = ° - 6 0 n = 1 8 / r ( 0 . 1 0 ) = ° - 4 0 I l l 5.2.3 R e l a t i o n s between Au c o n c e n t r a t i o n s . s e d i m e n t t e x t u r e s and s t r e a m g e o m e t r y R e l a t i o n s between Au c o n c e n t r a t i o n s i n s e d i m e n t s and s e d i m e n t t e x t u r e s ( i . e . mean g r a i n s i z e , s e d i m e n t s o r t i n g , b e d r o u g h n e s s and w e i g h t p e r c e n t o f s e l e c t e d s e d i m e n t f r a c t i o n s ) and s t r e a m g e o m e t r y ( i . e . s t r e a m w i d t h , d e p t h and f l o w v e l o c i t y ) were examined u s i n g Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t s . R e s u l t s ( T a b l e 5-6) show t h a t a t p o i n t - b a r s i t e s a l o n g t h e s e l e c t e d r e a c h , Au c o n c e n t r a t i o n s a r e p o s i t i v e l y c o r r e l a t e d w i t h mean g r a i n s i z e (M Q), b e d r o u g h n e s s ( D g s ) , mean g r a i n s i z e (MQ) and p o o r e r s o r t i n g (SQ) o f t h e c o a r s e g r a i n e d component o f t h e bed, and a l s o w i t h g r a v e l c o n t e n t , b u t n e g a t i v e l y c o r r e l a t e d w i t h c o a r s e s a n d c o n t e n t . The r e l a t i o n s w i t h g r a v e l c o n t e n t , KQ, SQ, b e d r o u g h n e s s (DQ$) and c o a r s e s a n d c o n t e n t a r e most p r o m i n e n t . A t pavement s i t e s t h e o n l y s i g n i f i c a n t c o r r e l a t i o n i s b e t w e e n Au c o n c e n t r a t i o n s i n t h e two f i n e f r a c t i o n s and b e d r o u g h n e s s . T h e s e r e l a t i o n s a l l i n d i c a t e t h a t g o l d i s p r e f e r e n t i a l l y a c c u m u l a t e d w i t h r e l a t i v e l y c o a r s e g r a i n e d s e d i m e n t s . B e c a u s e s t r e a m g e o m e t r y d a t a a t pavement s i t e s a r e n o t a v a i l a b l e , r e l a t i o n s between Au c o n c e n t r a t i o n s and s t r e a m g e o m e t r y a r e shown o n l y f o r p o i n t - b a r s i t e s i n T a b l e 5-7. I n t h e r e a c h between 1,055 and 6,223 m, Au c o n c e n t r a t i o n s i n a l l s i z e f r a c t i o n s a r e n e g a t i v e l y c o r r e l a t e d w i t h s t r e a m w i d t h , and p o s i t i v e l y c o r r e l a t e d w i t h f l o w v e l o c i t y . T a b l e 5-6. Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t (r) between g o l d c o n c e n t r a t i o n s (ppb) i n s e d i m e n t s a t p o i n t - b a r and pavement s i t e s and se d i m e n t t e x t u r e s o f t h e H u a i H i n L a e p . W e i g h t % s e d i m e n t F r a c t i o n (mm) M 0 S 0 D 6 5 M c S c -12.0 -2.0 -0.425 -0.053 +2.0 +0.425 +0.212 Whole r e a c h P o i n t b a r (n = 11) -0.425+0.212 -0.509 0.545* 0.248 -0.273 0.518 -0.382 -0.500 0.773* 0.682* -0.212+0.106 0.300 0.073 0.248 0.415 0.682* 0.400 -0.664* 0.336 -0.100 -0.106+0.053 0.363 0.245 0.422 0.629* 0.745* 0.355 -0.645* 0.164 -0.127 -0.212+0.053 (n=18) 0.495 0.140 0.247 0.358 0.507 0.348 -0.474* -0.121 0.057 Pavement (n = 5) -0.425+0.212 -0.100 0.500 0.316 -0.359 0.700 -0.500 0.600 0.500 0.500 -0.212+0.106 0.500 0.100 0.949* 0.103 0.200 -0.100 0.100 0.100 0.100 -0.106+0.053 0.200 0.200 0.949*-0.051 0.100 -0.200 0.300 0.200 0.200 -0.212+0.053 (n=7) -0.179 0.036 0.092 -0.018 0.252 -0.179 0.000 -0.107 0.179 Between s u p p o s e d s o u r c e o f m i n e r a l i z a t i o n and t h e c o n f l u e n c e w i t h H u a i Kho Lo (1,055 a n d 6,223 m) P o i n t b a r (n = 9) -0.425+0.212 -0.283 0.467 0.695* 0.000 0.417 -0.083 -0.417 0.717* 0.517 -0.212+0.106 0.483 0.000 0.373 0.661* 0.817* 0.600* -0.750* 0.367 -0.267 -0.106+0.053 0.683* 0.100 0.458 0.695* 0.700* 0.683* -0.567 -0.133 -0.517 -0.212+0.053 ( n = l l ) 0.518 0.164 0.520* 0.548* 0.574* 0.600* -0.545* 0.045 -0.309 T a b l e 5.6. ( c o n t i n u e d ) . n = 5; r 0 . i o = ° - 9 0 n = 9'" ^"0.10 = ° - 6 0 n = 7; r 0 * i o = 0.71 n = 11; r 0 * i o = 0.52 n = 18; r g ' i o = 0.40 * = s t a t i s t i c a l l y s i g n i f i c a n t a t 90% c o n f i d e n c e l e v e l MQ = mean g r a i n s i z e o f t h e e n t i r e s e diment SQ = s o r t i n g o f t h e e n t i r e s e d i m e n t Mrj = mean g r a i n s i z e o f c o a r s e g r a i n e d s e d i m e n t component Sc = s o r t i n g o f c o a r s e g r a i n e d s e d i m e n t component D 6 5 = b e d r o u g h n e s s 114 T a b l e 5-7. Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t ( r ) b e t w e e n g o l d c o n c e n t r a t i o n s (ppb) i n s e d i m e n t s a t p o i n t - b a r s i t e s a n d s t r e a m g e o m e t r y o f t h e H u a i H i n L a e p . F r a c t i o n (mm) W i d t h D e p t h V e l o c i t y Whole r e a c h (n = 11) -0.425+0.212 -0.518 -0.068 0.091 -0.212+0.106 -0.345 -0.005 0.292 -0.106+0.053 0.100 0.191 0.132 -0.212+0.053 (n=18) -0.202 0.053 -0.014 Between s u p p o s e d s o u r c e o f crold and t h e c o n f l u e n c e w i t h t h e H u a i Kho Lo (n = 9) -0.425+0.212 -0.633* -0.167 0.417 -0.212+0.106 -0.167 0.133 0.283 -0.106+0.053 -0.317 -0.100 0.600* -0.212+0.053 ( n = l l ) -0.345 -0.045 0. 369 n = 9; r o . i o = ° - 6 0 n = 11; r g . i o = 0.52 n = 18; r 0 ] 1 0 = 0.40 * = s t a t i s t i c a l l y s i g n i f i c a n t a t 90% c o n f i d e n c e l e v e l 115 However, o n l y t h e c o r r e l a t i o n s between Au c o n c e n t r a t i o n s i n t h e medium s a n d (-0.425+0.212 mm) f r a c t i o n and s t r e a m w i d t h , and Au c o n c e n t r a t i o n s o f t h e v e r y f i n e s a n d (-0.106+0.053 mm) f r a c t i o n and f l o w v e l o c i t y a r e s t a t i s t i c a l l y s i g n i f i c a n t . 5.3 E s t i m a t e d numbers o f g o l d p a r t i c l e s The numbers o f g o l d p a r t i c l e s i n h e a v y m i n e r a l c o n c e n t r a t e s were c a l c u l a t e d b a s e d on t h e a s s u m p t i o n t h a t 1) g o l d o c c u r s a s f r e e s p h e r i c a l p a r t i c l e s , 2) t h e s i e v e d i a m e t e r o f p a r t i c l e s i s t h e g e o m e t r i c m i d p o i n t o f t h e b o u n d i n g s i e v e o p e n i n g s , and 3) t h e d e n s i t y o f t h e p a r t i c l e s i s 15 g/cm 3. D e p e n d i n g on t h e a c t u a l s h a p e o f t h e g o l d p a r t i c l e s and t h e i r s i z e d i s t r i b u t i o n w i t h i n e a c h s i e v e f r a c t i o n , t h e s e e s t i m a t e s c o u l d be t o o h i g h o r t o o low by a f a c t o r o f a b o u t f i v e . The t o t a l number o f g o l d p a r t i c l e s i n a l l t h r e e s i z e f r a c t i o n s (-0.425+0.053 mm) was o b t a i n e d by summing t h e numbers o f g o l d p a r t i c l e s i n e a c h s i z e f r a c t i o n , a n d a l s o i n t h e two s i z e f r a c t i o n s (-0.212+0.053 mm). R e s u l t s o f t h e e s t i m a t e s ( T a b l e 5-8) s u g g e s t t h a t i n most s a m p l e s t h e number o f g o l d p a r t i c l e s i n t h e -0.425+0.212 mm f r a c t i o n f r o m p o i n t - b a r s i t e s i s f e w e r t h a n one (median = 0. 1 2 ) . However, t h e number o f g o l d p a r t i c l e s i n c r e a s e s w i t h d e c r e a s i n g g r a i n s i z e . F o r example, a t p o i n t - b a r s i t e s m e d i a n numbers o f g o l d p a r t i c l e s i n c r e a s e f r o m 0.12, t o 0.21 t o 2.83. C o r r e s p o n d i n g v a l u e s f o r pavement s i t e s a r e 1.26, 116 T a b l e 5-8. E s t i m a t e d numbers o f g o l d p a r t i c l e s i n h e a v y m i n e r a l c o n c e n t r a t e s . F r a c t i o n s (mm) T o t a l Sample -0.425 -0.212 -0.106 -0.425 -0.212 +0.212 +0.106 +0.053 +0.053 +0.053 P o i n t - b a r (n = 11) PP-16 0.00 1.15 0. 00 1.15 1.15 PP-96 6.90 10.46 11.94 29.30 22.40 PP-09 0.02 0.00 0.33 0.35 0.33 PP-94 0.12 0.00 2.83 2.95 2.83 PP-10 0. 00 0.20 2.59 2 . 79 2 .79 PP-89 0.20 0.21 1. 07 1.48 1.28 PP-81 0.40 3 . 08 2.47 5.95 5.55 PP-75 0. 00 0. 00 3.21 3 .21 3 .21 PP-70 1.94 9 . 09 9.45 20.48 18.54 PP-67 0.95 12.78 28.23 41.96 41.01, PP-64 0. 00 0.20 5.00 5.20 5.20 Mean 0.96 3 . 38 6.10 10.44 9.48 M e d i a n 0.12 0.21 2.83 3.21 3.21 Range 0. 00-6.90 0.00-12.78 0.00-28.23 0 .35-41.96 0.33-41.01 S c o r e 3 5 9 10 10 Pavement (n = 5) PP-87 0.00 1.19 1.92 3 .11 3 .11 PP-100 1.26 2 . 46 0.99 4.71 3.45 PP-79 0. 04 1.85 1.62 3.51 3.47 PP-68 1.48 10. 01 17.01 28.50 27 . 02 PP-65 3 . 65 30.78 28.92 63 . 35 59.70 Mean 1.29 9.26 10.09 20.64 19. 35 M e d i a n 1.26 2.46 1.92 4.71 3 . 47 Range 0. 00-3.65 1.19-30.78 0.99-28.92 3 .11-63.35 3.11-59.70 S c o r e 3 5 5 5 5 * = e s t i m a t e d f r o m d a t a i n T a b l e 5-1. S c o r e = number o f s a m p l e s c o n t a i n i n g one o r more g o l d p a r t i c l e s 117 2.46 a n d 1.92 p a r t i c l e s . B a s e d on t h e above r e s u l t s , t h e e s t i m a t e d numbers o f g o l d p a r t i c l e s were s t a n d a r d i z e d t o 40 k g (-12.0 mm) f i e l d s a m p l e s and 3 0 g a n a l y t i c a l s u b s a m p l e s . The p r o b a b i l i t y ( f r o m t h e P o i s s o n d i s t r i b u t i o n , e q u a t i o n 1-2) o f r e c o v e r i n g one o r more p a r t i c l e s o f g o l d (P>0) i n a random s a m p l e was t h e n e s t i m a t e d ( T a b l e 5 - 9 ) . Of t h e 40 k g f i e l d s a m p l e s , o n l y t h r e e o u t o f e l e v e n s a m p l e s c o n t a i n more t h a n one g o l d p a r t i c l e i n t h e -0.425+0.212 mm f r a c t i o n o f p o i n t - b a r s e d i m e n t , w h e r e a s i n t h e f i n e s t (-0.106+0.053 mm) f r a c t i o n t h e r e a r e n i n e o u t o f e l e v e n s a m p l e s t h a t c o n t a i n more t h a n one g o l d p a r t i c l e . The median o f t h e s t a n d a r d i z e d number o f g o l d p a r t i c l e s i n c r e a s e s f r o m 0.15 t o 3.54, w i t h a c o r r e s p o n d i n g i n c r e a s e i n t h e p r o b a b i l i t i e s o f o b t a i n i n g one o r more g o l d g r a i n s f r o m 21% t o 97%. A t pavement s i t e s t h r e e o u t o f f i v e s a m p l e s o f t h e -0.425+0.212 mm and a l l o f t h e f i n e r f r a c t i o n s c o n t a i n one o r more g o l d p a r t i c l e s . The median number o f g o l d p a r t i c l e s i n c r e a s e s f r o m 1.61 t o 3.13 and 2.88 and t h e c o r r e s p o n d i n g p r o b a b i l i t y o f o b t a i n i n g one o r more g o l d g r a i n s i n c r e a s e s f r o m 80 t o 96 and 94%, r e s p e c t i v e l y . I n t h e c a s e o f 30 g a n a l y t i c a l s u b s a m p l e s , o n l y t h e m e d i a n o f t h e s t a n d a r d i z e d number o f g o l d p a r t i c l e s i n t h e f i n e s t (-0.106+0.053 mm) f r a c t i o n f r o m pavement s i t e s i s g r e a t e r t h a n one p a r t i c l e w i t h a c o r r e s p o n d i n g p r o b a b i l i t y o f f i n d i n g one o r more g o l d p a r t i c l e s o f 68%. T a b l e 5-9. E s t i m a t e d numbers o f g o l d p a r t i c l e s (n) i n t h e s t a n d a r d i z e d 40 kg (-12.0 mm) f i e l d samples and 30 g a n a l y t i c a l s u b s a m p l e s and p r o b a b i l i t y o f c o n t a i n i n g one o r more g o l d g r a i n s (P>0). F r a c t i o n s (mm) Sample -0. 425+0 .212 -0. 212 + 0 .106 -0. 106+0.053 n P>0 n P>0 n P>0 40 k a f i e l d samples P o i n t b a r PP-16 0.00 0.00 1.48 0.77 0.00 0.00 PP-96 11.38 1.00 17.63 1.00 19.70 1.00 PP-09 0.02 0.02 0.00 0.00 0.43 0.35 PP-94 0.15 0.14 0.00 0.00 3.54 0.97 PP-10 0.00 0.00 0.24 0.21 3.08 0.95 PP-89 0.23 0.21 0.23 0.21 1.21 0.70 PP-81 0.51 0.40 3.98 0.98 3.19 0.96 PP-75 0.00 0.00 0.00 0. 00 4.53 0.99 PP-70 2.47 0.92 14.99 1.00 12.04 1.00 PP-67 1.22 0.71 16.36 1.00 36.45 1.00 PP-64 0.00 0.00 0.25 0.22 6.22 1.00 Mean 1.45 0.31 5.01 0.49 8.22 0.81 M e d i a n 0.15 0.21 0.25 0.22 3.54 0.97 Range 0. 00-11.38 0.00' -1.00 0.00-17.63 0. 00 -1.00 0.00-36.45 0.00-1.00 S c o r e 3 3 5 5 9 9 T a b l e 5-9. ( c o n t i n u e d ) . F r a c t i o n s (mm) Sample -0.425+0.212 -0.212+0.106 -0.106+0.053 n P>0 n P>0 n P>0 Pavement PP-87 0. 00 0. ,00 1. ,37 0. ,75 2. ,88 0. ,94 PP-100 1. 61 0. .80 3 . ,13 0. ,96 1. ,27 0. ,72 PP-79 0. 05 0. ,05 2. ,33 0. ,90 2. ,04 0. ,87 PP-68 2. 01 0. ,87 13. ,61 1. ,00 23. ,16 1. ,00 PP-65 4. 87 0. ,99 41. ,40 1. ,00 38. ,70 1. ,00 Mean 1. 71 0. ,54 12. ,37 0. ,92 13. .61 0. ,91 M e d i a n 1. 61 0. ,80 3. ,13 0. ,96 2. .88 0. ,94 Range 0.00-•4. 87 0.00-1. ,00 1.37-41. ,40 0.75-1. ,00 1.27-38. .70 0.72-1. ,00 S c o r e 3 3 5 5 5 5 30 a a n a l y t i c a l . s u b s a m p l e s P o i n t b a r PP-16 0. 00 0. ,00 0. ,20 0. ,19 0. .00 0. .00 PP-96 0. 15 0. , 14 0. ,39 0. ,33 0. .37 0. .31 PP-09 0. 00 0. ,00 0. .00 0. ,00 0, .02 0. .02 PP-94 0. 00 0. .00 0. .00 0. ,00 0, .16 0. .15 PP-10 0. 00 0. .00 0. .02 0. ,02 0. .38 0. .32 PP-89 0. 00 0. .00 0. .02 0. ,02 0. .12 0. . 11 PP-81 0. 02 0. .02 0. .46 0. ,37 0. .30 0. .26 PP-75 0. 00 0. , 00 0. ,00 0. ,00 0. .87 0. .58 PP-7 0 0. 03 0, .03 0. . 50 0. .40 0, .80 0. .55 PP-67 0. 03 0, .03 0. .64 0. .47 2. .58 0, .92 PP-64 0. 00 0, .00 0. .01 0. .01 0, .44 0. .36 T a b l e 5-9. ( c o n t i n u e d ) . F r a c t i o n s (mm) Sample -0.425+0.212 -0.212+0.106 -0.106+0.053 n P>0 n P>0 n P>0 Mean 0.02 0.02 0.20 0.16 0.55 0.33 M e d i a n 0.00 0.00 0.02 0.02 0.37 0.31 Range 0.00-0.15 0.00-0.14 0.00-0.64 0.00-0.47 0.00-2.58 0.00-0.92 S c o r e 0 0 0 0 1 1 Pavement PP-87 0.00 0.00 0.72 0.51 1.81 0.84 PP-100 0.06 0.06 0.38 0.31 0.25 0.22 PP-79 0.00 0.00 0.31 0.27 0.52 0.40 PP-68 0.03 0.03 0.42 0.34 1.13 0.68 PP-65 0.11 0.11 2.49 0.92 3.86 0.98 Mean 0.04 0.04 0.86 0.47 1.51 0.62 M e d i a n 0.03 0.03 0.42 0.34 1.13 0.68 Range 0.00-0.11 0.00-0.11 0.31-2.49 0.27-0.92 0.25-3.86 0.22-0.98 S c o r e 0 0 2 2 3 3 S c o r e = number o f sam p l e s c o n t a i n i n g one o r more g o l d p a r t i c l e s 121 Downstream t r e n d s o f t h e e s t i m a t e d numbers o f g o l d p a r t i c l e s i n h e a v y m i n e r a l f r a c t i o n s a r e shown i n F i g . 5-3. As e x p e c t e d downstream t r e n d s o f t h e number o f Au p a r t i c l e s i n a l l f r a c t i o n s o f b o t h e n v i r o n m e n t s behave s i m i l a r l y t o Au c o n c e n t r a t i o n s ( F i g s . 5-1 and 5 - 2 ) . B a s e d on t h e W a l d - w o l f o w i t z t o t a l - n u m b e r - o f - r u n s t e s t ( T a b l e 5-10) t h e numbers o f g o l d p a r t i c l e s i n t h e combined -0.212+0.053 mm f r a c t i o n a r e c l u s t e r e d , w i t h s i t e s c o n t a i n i n g g r e a t e r t h a n t h e m e d i a n number o f p a r t i c l e s a l l i n t h e l o w e r p a r t o f t h e r e a c h . S t a t i s t i c a l l y , t h i s i s h i g h l y s i g n i f i c a n t . S i m i l a r l y , s p e a rman r a n k c o r r e l a t i o n c o e f f i c i e n t s show t h a t t r e n d s f o r t h e e s t i m a t e d numbers o f g o l d p a r t i c l e s i n t h e -0.106+0.053 mm and t h e combined -0.212+0.053 mm f r a c t i o n s i n c r e a s e s i g n i f i c a n t l y downstream. T h i s a l s o o c c u r s a t pavement s i t e s . 5.4 G o l d g r a i n m o r p h o l o g y and c o m p o s i t i o n s The numbers o f v i s i b l e g o l d g r a i n s c o u n t e d i n t h e f i e l d p a n - c o n c e n t r a t e s a r e l i s t e d i n T a b l e 5-11 and p l o t t e d a g a i n s t d i s t a n c e ( F i g . 5 - 4 ) . The d i s t r i b u t i o n o f v i s i b l e g o l d g r a i n s f r o m p o i n t - b a r s i t e s a l o n g t h e e n t i r e r e a c h i s r o u g h l y s i m i l a r t o t h e d i s t r i b u t i o n o f Au c o n c e n t r a t i o n s ( F i g s . 5-1 and 5-2) and t h e e s t i m a t e d numbers o f g o l d p a r t i c l e s ( F i g . 5 - 3 ) . F i v e s e l e c t e d pan c o n c e n t r a t e s s a m p l e s were r e c o u n t e d f o r v i s i b l e g o l d g r a i n s i n t h e l a b o r a t o r y p r i o r t o f u r t h e r s t u d y . I t i s n o t a b l e t h a t , e x c e p t i n one 122 60 50 - o Q. 8)30 CD •| 20 10 -0.425+0.212 mm Point-bar Pavement Ei 8 . or Selected reach T 1 1 —" f • i1 1 1 r - — 1 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 60 50 - co 0) g 40 co a. 8) 30 CD •| 20 10 B -0.212+0.106 mm Selected reach 1,000 2,000 3,000 4,000 5,000 Distance Downstream (m) 6,000 7,000 8,000 F i g . 5-3. Downstream t r e n d s o f t h e e s t i m a t e d numbers o f g o l d p a r t i c l e s i n h e a v y m i n e r a l c o n c e n t r a t e s a t p o i n t b a r s ( s o l i d s q u a r e s ) and pavements ( s o l i d t r i a n g l e s ) f o r a) -0.425+0.212 mm f r a c t i o n , b) -0.212+0.106 mm f r a c t i o n , 123 60 50 co o % 40 Q. 8) 30 CD •g 20 3 10 -0.106+0.053 mm Selected reach Point-bar Pavement i 1 i 1 1—'—' "n ' — 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 60 50 co o o 1 4 0 Q. o O)30 -0.212+0.053 mm Selected reach 0 1,000 2,000 3,000 4,000 5,000 6,000 Distance Downstream (m) 7,000 D 8,000 F i g . 5-3. (continued) c) -0.106+0.053 mm f r a c t i o n and d) i d e a l l y combined -0.212+0.053 mm f r a c t i o n . Star indicates the supposed source of gold mineralization. Arrow indicates the confluence with the Huai Kho Lo. T a b l e 5-10. R e s u l t s o f t h e W a l d - w o l f o w i t z t o t a l - n u m b e r - o f - r u n s t e s t (/i) and Spearman r a n k c o r r e l a t i o n c o e f f i c i e n t ( r ) f o r downstream t r e n d s o f number o f g o l d p a r t i c l e s i n h e a v y m i n e r a l f r a c t i o n s f r o m p o i n t - b a r and pavement s a m p l e s o f t h e H u a i H i n L a e p . F r a c t i o n / N S o u r c e o f C u t p o i n t n^ ri2 M P(M) Spearman's V a r i a t i o n (median) (+) (-) r v a l u e s Whole r e a c h P o i n t b a r (n = 11) -0.425+0.212 mm 0.12 6 5 9 0.0512 -0.212+0.106 mm 0.21 6 5 6 0.3853 -0.106+0.053 mm 2.83 6 5 6 0.3853 -0.212+0.053 mm 3.21 6 5 4 0.0577* Pavement (n = = 5) -0.425+0.212 mm 1.26 3 2 4 0.2563 -0.212+0.106 mm 2.46 3 2 4 0.2563 -0.106+0.053 mm 1.92 3 2 3 0.3313 -0.212+0.053 mm 4 .10 3 2 3 0.3313 0. 051 0.147 0.555* 0.536* 0.900 0.900* 0.700 1.000* Between s u p p o s e d s o u r c e o f m i n e r a l i z a t i o n and c o n f l u e n c e w i t h H u a i Kho Lo (1,055 and 6,223 m) P o i n t b a r (n = 9) -0. 425+0. 212 mm 0. 12 5 4 7 0. 1304 -0. 212+0. 106 mm 0. 20 6 3 4 0. 2071 -0. 106+0. 053 mm 2 . 83 5 4 4 0. 1482 -0. 212+0. 053 mm 3 . 21 5 4 2 0. 0064* 0.186 0.579 0.800* 0.800* N = t o t a l s a m p le number n-i = number o f s a m p l e s above median r\2 = number o f s a m p l e s below median \i = t o t a l number o f r u n s above and below t h e m e d i a n * = s t a t i s t i c a l l y s i g n i f i c a n t a t 90% c o n f i d e n c e l e v e l n = 5; r 0 . i o = 0.90 n = 9; r 0 . i o = 0.60 n = 6; r 0 ] i o = 0.83 n = 11; r 0 ] 1 0 = 0.52 125 T a b l e 5-11. Numbers o f g o l d p a r t i c l e s c o u n t e d f r o m p a n c o n c e n t r a t e s i n t h e f i e l d and i n l a b o r a t o r y . Number o f g o l d p a r t i c l e s Sample D i s t a n c e Number (m) F i e l d L a b o r a t o r y P o i n t b a r PP-17 550 3 PP-97 820 25 27 PP-03 1055 20 PP-95 1513 0 PP-12 2458 17 25 PP-90 2753 0 PP-82 3303 5 PP-76 4423 2 PP-71 5423 11 PP-69 5823 14 12 PP-66 6223 10 15 Pavement PP-88 3013 5 PP-101 3608 3 6 PP-80 4068 0 = s a m p l e n o t p r o c e s s e d i n l a b o r a t o r y . 126 30 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 Distance Downstream (m) F i g . 5-4. Downstream t r e n d f o r numbers of v i s i b l e g o l d p a r t i c l e s r e c o v e r e d i n the f i e l d pan-concentrates from p o i n t b a r s . S t a r i n d i c a t e s the supposed source o f g o l d m i n e r a l i z a t i o n . Arrow i n d i c a t e s the confluence w i t h the Huai Kho Lo. 127 c a s e , t h e number o f g o l d p a r t i c l e s c o u n t e d i n t h e l a b o r a t o r y ( T a b l e 5-11) i s g r e a t e r t h a n t h a t c o u n t e d i n t h e p a n . 5.4.1 G r a i n m o r p h o l o g y Shape o f g o l d p a r t i c l e s was o b t a i n e d u s i n g t h e m o d i f i e d C o r e y s h a p e f a c t o r e q u a t i o n ( C o r e y , 1949): SF = ( D s * D L ) 1 / 2 / D I where DQ, D J and D L a r e t h e s m a l l e s t , i n t e r m e d i a t e and l o n g e s t d i a m e t e r s , r e s p e c t i v e l y (Day, 1 9 8 8 ) . An SF v a l u e o f 1 r e p r e s e n t s a s p h e r i c a l g r a i n , g r e a t e r t h a n 1 a l o n g c y l i n d r i c a l g r a i n , and l e s s t h a n 1 a t a b u l a r p a r t i c l e ( f l a k e ) . E s t i m a t i o n o f p o p u l a t i o n d i s t r i b u t i o n o f 85 g o l d g r a i n s u s i n g a p r o b a b i l i t y p l o t ( F i g . 5-5) i n d i c a t e s t h a t a t l e a s t two p o p u l a t i o n s o f g r a i n s h a p e s a r e p r e s e n t . P o p u l a t i o n 1 h a s a mean SF o f 0.748 ( s t a n d a r d d e v i a t i o n = 0.106) and c o m p r i s e s 65% o f t h e g r a i n s . T h i s c o r r e s p o n d s t o a t a b u l a r g r a i n o r " f l a k e " w i t h d i a m e t e r t o t h i c k n e s s r a t i o o f 1.79. P o p u l a t i o n 2 a c c o u n t s f o r 35% o f t h e g r a i n s and h a s a mean SF = 1.052 ( s t a n d a r d d e v i a t i o n = 0.105), c l o s e t o a s p h e r i c a l s h a p e w i t h d i a m e t e r t o t h i c k n e s s r a t i o o f 0.90. Between t h e 52nd and 7 0 t h p e r c e n t i l e s , t h e r e i s an o v e r l a p b e t w e e n t h e two p o p u l a t i o n s i n t h e r a n g e o f SF v a l u e s b e t w e e n 0.842 and 0.960. T h i s i n d i c a t e s a t r a n s i t i o n o f g r a i n s h a p e f r o m a s l i g h t l y f l a t t e d t o n e a r l y s p h e r i c a l s h a p e . Summary o f shape f a c t o r d a t a o f i n d i v i d u a l s a m p l e i s COREY SHAFE FACTOR ANALYSIS ARITHMETIC UALUES F R D E i i E I L I T V P L O T 1.50 1.2? 1 .05 ~ 0 .62 ~ 0 .to 99 9$ VARIABLE = SF UNIT = N s {5 N CI = JO P O P U L A T I O N S Pop. Mean Std.Dev. > 0 .7*? 1.052 0 .10S «S.O 0.105 35.0 USERS UISUfiL PARAMETER ESTIMATES F i g . 5-5. P r o b a b i l i t y p l o t o f shape f a c t o r s (SF) o f v i s i b l e g o l d p a r t i c l e s (n = 85) i n t h e s e l e c t e d f i e l d p a n - c o n c e n t r a t e s s howing i n f e r r e d component n o r m a l p o p u l a t i o n s . to CO 129 g i v e n i n T a b l e 5-12. I t i s a p p a r e n t t h a t t h e p r o x i m a l s a m ple (PP-97) c o n s i s t s 86% o f n e a r l y s p h e r i c a l and c y l i n d r i c a l g o l d g r a i n s ( F i g . 5-6a) whereas t h e d i s t a l s a m p l e s (PP-12 t o PP-66) c o n t a i n g r e a t e r t h a n 65% o f t h e t a b u l a r ( f l a k e ) g o l d g r a i n s ( F i g . 5 - 6 b ) . 5.4.2 G r a i n c o m p o s i t i o n E l e c t r o n m i c r o p r o b e a n a l y s i s o f 39 p o l i s h e d g o l d g r a i n s ( T a b l e 5-13) shows t h a t most o f t h e g o l d g r a i n s h a v e p a t c h y r i m s ( F i g . 5-7) o f h i g h f i n e n e s s g o l d . The r i m s a r e v e r y t h i n (" 2 t o 5 m i c r o n s ) . G o l d c o m p o s i t i o n v a r i e s w i d e l y , r a n g i n g between 42.02 and 83.44% a t c o r e s and 72.62 and 100.17% a t r i m s . Mean f i n e n e s s ( r a t i o o f Au/(Au+Ag) * 1000) f o r t h e 39 g r a i n c o r e s i s 622.56 ( s t a n d a r d d e v i a t i o n = 1 1 2 . 4 9 ) , w h e r e a s mean f i n e n e s s f o r 10 r i m s i s 967.98 ( s t a n d a r d d e v i a t i o n = 2 9 . 9 4 ) . C o n c e n t r a t i o n s o f Cu a n d Hg a r e g e n e r a l l y a t o r l e s s t h a n t h e d e t e c t i o n l i m i t s and t h e r e f o r e c a n n o t be c o n s i d e r e d r e l i a b l e . The d i f f e r e n c e o f Au c o m p o s i t i o n s i n c o r e b etween p r o x i m a l a n d d i s t a l s a m p l e s i s s t a t i s t i c a l l y e x a m i n e d i n T a b l e 5-14. R e s u l t shows no s i g n i f i c a n t d i f f e r e n c e b etween Au c o m p o s i t i o n s o f c o r e s o f d i s t a l g r a i n s (mean = 65.87) and p r o x i m a l g r a i n s (mean = 5 9 . 6 2 ) . 130 T a b l e 5-12. Summary s t a t i s t i c s o f shape f a c t o r (SF) d a t a . SF Sample D i s t a n c e Number P o p u l a t i o n s (%) Number Downstream Au G r a i n s 1 2 PP-97 820 27 14 86 PP-12 2458 25 67 33 PP-101 3608 6 80 20 PP-69 5823 12 75 25 PP-66 6223 15 65 35 T o t a l 85 65 35 P o p u l a t i o n 1 = f l a t g r a i n P o p u l a t i o n 2 = n e a r l y s p h e r i c a l and c y l i n d r i c a l g r a i n 131 F i g . 5 - 6 . M o r p h o l o g y o f a) p r o x i m a l and b) d i s t a l g o l d g r a i n r e l a t i v e t o t h e s u p p o s e d b e d r o c k s o u r c e o f g o l d . T a b l e 5-13. R e s u l t s o f e l e c t r o n m i c r o p r o b e a n a l y s e s f o r c h e m i c a l c o m p o s i t i o n s o f t h e c o r e s and r i m s o f 39 g o l d g r a i n s . G r a i n C o r e C o r e Rim-1 Rim-2 Rim-1 Rim-: Number Au Ag Au Au Ag Ag PP-97-01 57.18 42.41 96.67 97.48 3.04 2.42 PP-97-02 49.17 49.66 - - - - PP-97-03 82.83 17.13 - - - — PP-97-04 68.34 31.69 - - - - PP-97-05 65.71 33.48 91.79 - 5.84 - PP-97-06 60.78 38.83 - - — — PP-97-07 72.27 25.66 - - - — PP-97-08 65.17 34.16 - - - — PP-97-09 53.87 45.07 - - - — PP-97-10 53.61 45.53 - - - - PP-97-11 48.21 50.76 - - - — PP-97-12 62 .56 36.21 - - - — PP-97-13 52 . 31 46.51 - - - — PP-97-14 61. 67 37.60 - - - - PP-97-15 55.41 43.43 - - — — PP-97-16 55.03 43.96 - - - — PP-97-17 63 .97 34.60 97.98 97.79 1.29 1. 65 PP-97-18 65.30 33.73 - - - — PP-97-19 76.82 22.77 - - - - PP-97-20 57.3 3 , 41.45 - - - — PP-97-21 43 .15 55.86 - - - — PP-97-22 54 .93 44.08 - - - - PP-97-23 73.32 26.15 - - - — PP-97-24 50.38 49.19 - - - - PP-97-25 47.55 52 .16 - - - — PP-97-26 65.82 33.55 - - - — PP-97-27 46.93 52 .30 - - - — T a b l e 5-13. ( c o n t i n u e d ) G r a i n C o r e Core Rim-1 • Rim-2 Rim-1 Rim-2 Number Au Ag Au Au A g Ag PP-97 ( c o n t i n u e d ) Mean 59.61 39.55 95.48 97.63 3.39 2.03 M e d i a n 57.33 41.45 96.67 97.63 3.04 2.03 Range 43.15-82.83 17.13-55.86 72.62-97.98 97.48-97.79 1.29-17.46 1.65-2.42 PP-69-01 PP-69-02 PP-69-03 PP-69-04 PP-69-05 PP-69-06 PP-69-07 PP-69-08 PP-69-09 PP-69-10 PP-69-11 PP-69-12 74.60 55.69 61.76 78.76 72.12 45.29 83.44 77.58 71.18 69.25 42.02 58.73 24.13 43.05 37.18 20.48 27.17 53.24 16.03 21.98 27.77 21.06 56.01 40.11 89.57 98.77 98.63 95.23 100.17 10. 63 1.41 0. 67 4.66 0.27 Mean M e d i a n Range 65.87 74.38 42.02-83.44 32.35 27.47 16.03-56.01 95.66 98.63 89.57-98.77 97.70 97.70 95.23-100.17 4.24 1.41 67-10.63 2.46 2.46 0.27-4.66 F i g . 5-7. P o l i s h e d g o l d g r a i n s h owing p a t c h y r i m o f h i g h f i n e n e s s g o l d c o m p o s i t i o n s a l o n g t h e e d g e s f o r a) p r o x i m a l and b) d i s t a l r e l a t i v e t o t h e s u p p o s e d b e d r o c k s o u r c e o f g o l d . 135 T a b l e 5-14. S t a t i s t i c a l two-sample t t e s t f o r t h e d i f f e r e n c e b e tween means o f Au c o m p o s i t i o n s a t c o r e s o f p r o x i m a l (PP- 97) and d i s t a l (PP-69) g o l d g r a i n s . N u l l h y p o t h e s i s : P Au c o m p o s i t i o n s i n p r o x i m a l = M Au c o m p o s i t i o n s i n d i s t a l F r a c t i o n / S o u r c e o f N Mean S S e D e g r e e s o f V a r i a t i o n Freedom C o r e s P r o x i m a l 27 59.615 9 .858 D i s t a l 12 65.868 13 .247 3.808 17 T c a l c = "1-47 T ( 1 7 , 0.10) = 1 - 740 N u l l h y p o t h e s i s a c c e p t e d N = number o f s a m p l e s Mean = p o p u l a t i o n mean S = s t a n d a r d d e v i a t i o n S e = s t a n d a r d e r r o r o f d i f f e r e n c e 136 5.5 Summary 1) G o l d c o n c e n t r a t i o n s i n h e a v y m i n e r a l c o n c e n t r a t e s a r e t y p i c a l l y i n t h e s e v e r a l t h o u s a n d ppb r a n g e , v e r s u s < 5 ppb i n most o f t h e c o r r e s p o n d i n g l i g h t and s e d i m e n t f r a c t i o n s . 2) I n t h e r e a c h between 2,753 and 6,223 m, g o l d c o n c e n t r a t i o n s i n a l l s i z e f r a c t i o n s a r e s l i g h t l y g r e a t e r a t p avement t h a n a t p o i n t - b a r s i t e s . However, d i f f e r e n c e s a r e n o t s t a t i s t i c a l l y s i g n i f i c a n t . 3) S t r o n g l y anomalous c o n c e n t r a t i o n s o f g o l d a r e f o u n d i n a l l t h r e e s i z e f r a c t i o n s o f a s i n g l e s a m ple c l o s e t o t h e s u p p o s e d s o u r c e o f g o l d . Downstream f r o m t h i s p o i n t c o n c e n t r a t i o n s o f g o l d a r e e r r a t i c b u t a p p e a r t o i n c r e a s e downstream, p a r t i c u l a r l y i n t h e f i n e s t s a n d (-0.106+0.053 mm) and t h e combined -0.212+0.053 mm f r a c t i o n s o f p o i n t b a r s . 4) G o l d c o n c e n t r a t i o n s i n s e v e r a l s i z e f r a c t i o n s f r o m p o i n t - b a r s i t e s a r e p o s i t i v e l y c o r r e l a t e d w i t h g r a v e l c o n t e n t , mean g r a i n s i z e (M Q ) , mean g r a i n s i z e (MQ) and d e c r e a s e d s o r t i n g (S^) o f c o a r s e g r a i n e d component o f s e d i m e n t , and bed r o u g h n e s s ; and n e g a t i v e l y c o r r e l a t e d w i t h c o a r s e s a n d c o n t e n t . 5) The e s t i m a t e d numbers o f g o l d p a r t i c l e s i n h e a v y m i n e r a l c o n c e n t r a t e s i n c r e a s e w i t h d e c r e a s i n g g r a i n s i z e . I n a 40 k g f i e l d sample, numbers o f g o l d p a r t i c l e s i n t h e f i n e s t f r a c t i o n f r o m p o i n t - b a r and a l l t h r e e s i z e f r a c t i o n s 137 f r o m pavement p r o v i d e a r e a s o n a b l e c h a n c e o f c o n t a i n i n g f r e e g o l d , w h e r e a s a 30 g a n a l y t i c a l s u b s a m p l e i s u n r e l i a b l y t o c o n t a i n e v e n a s i n g l e g o l d g r a i n . 6) The number o f g o l d p a r t i c l e s i n p o i n t - b a r and pavement d e p o s i t s , p a r t i c u l a r l y t h e two f i n e f r a c t i o n s , i n c r e a s e s downstream. 7) G o l d p a r t i c l e s a r e n e a r l y s p h e r i c a l n e a r t h e i r s o u r c e b u t a r e more f l a t t e n e d downstream. They h a v e t h i n , p a t c h y r i m s o f h i g h f i n e n e s s g o l d . CHAPTER SIX DISCUSSION 139 6.1 I n t r o d u c t i o n B a s e d on r e s u l t s p r e s e n t e d i n C h a p t e r 5, g o l d c o n t e n t i s g r e a t e s t i n h e a v y m i n e r a l f r a c t i o n s , w h e r e a s , w i t h a few e x c e p t i o n s , c o n c e n t r a t i o n s i n t h e c o r r e s p o n d i n g l i g h t m i n e r a l , -0.150 mm and -0.053 mm s e d i m e n t f r a c t i o n s a r e a t o r b e l o w t h e d e t e c t i o n l i m i t . The a v e r a g e c o n c e n t r a t i o n o f Au i n h e a v y m i n e r a l and i n s e d i m e n t f r a c t i o n s f r o m pavement i s s l i g h t l y g r e a t e r t h a n f r o m p o i n t - b a r s i t e s , b u t Au c o n c e n t r a t i o n s i n s e d i m e n t f r o m p o i n t - b a r s i t e s i n c r e a s e w i t h i n c r e a s i n g f l o w v e l o c i t y and bed r o u g h n e s s where c h a n n e l w i d t h and d e p t h d e c r e a s e . T h e s e c o n t r o l s r e s u l t i n Au c o n c e n t r a t i o n s i n c r e a s i n g downstream, away f r o m t h e s o u r c e , t o w a r d s t h e c o n f l u e n c e w i t h t h e H u a i Kho L o . 6.2 D i s t r i b u t i o n o f g o l d between s i z e and d e n s i t y f r a c t i o n s H i g h c o n c e n t r a t i o n s o f g o l d ( T a b l e 5-1) a r e t y p i c a l l y p r e s e n t i n h e a v y m i n e r a l f r a c t i o n s (between 0.425 and 0.053 mm) . T h i s c o n t r a s t s w i t h t h e a b s e n c e o f g o l d (< 5 ppb) i n t h e c o r r e s p o n d i n g l i g h t m i n e r a l f r a c t i o n s , o n l y s i x o f w h i c h ( A p p e n d i x ) c o n t a i n g o l d v a l u e s g r e a t e r t h a n t h e d e t e c t i o n l i m i t . T h e s e s i x s a m p l e s , w h i c h w i t h one e x c e p t i o n c o n t a i n l e s s t h a n 50 ppb g o l d , p r o b a b l y r e p r e s e n t c a s e s o f i n c o m p l e t e s e p a r a t i o n d u r i n g p r e p a r a t i o n o f t h e h e a v y m i n e r a l c o n c e n t r a t e . Low Au v a l u e s i n t h e l i g h t m i n e r a l f r a c t i o n s i n d i c a t e t h a t e i t h e r 1) g o l d d o e s n o t o c c u r a s 140 i n c l u s i o n s i n low d e n s i t y m i n e r a l s , o r 2) g o l d may o c c u r a s i n c l u s i o n s i n low d e n s i t y m i n e r a l s b u t i t s c o n c e n t r a t i o n s a r e d i l u t e d by l a r g e amounts o f b a r r e n l i g h t m i n e r a l s . C o n c e n t r a t i o n s o f g o l d i n t h e c o r r e s p o n d i n g -0.150 mm and s i l t - c l a y (-0.053 mm) f r a c t i o n s ( T a b l e 5 - 1 ) , w i t h e x c e p t i o n o f 85 ppb f r o m one p o i n t b a r and 80 a n d 95 ppb f r o m two pavement s i t e s , a r e a l s o a t o r below t h e d e t e c t i o n l i m i t . The -0.150+0.053 mm h e a v y m i n e r a l s ( T a b l e 5-1) and t h e c o r r e s p o n d i n g s e d i m e n t f r a c t i o n s ( T a b l e 5-3) c o n t a i n c o n s i d e r a b l e amounts o f g o l d . F a i l u r e t o d e t e c t g o l d i n t h e -0.150 mm f r a c t i o n o f s e d i m e n t s must t h e r e f o r e r e s u l t f r o m i t s d i l u t i o n by l a r g e amounts o f b a r r e n s e d i m e n t . T h i s d i l u t i o n g r e a t l y r e d u c e s t h e p r o b a b i l i t y o f e v e n a s i n g l e g r a i n o f g o l d b e i n g e n c o u n t e r e d i n a 30 g a s s a y s a m p l e ( T a b l e 5 - 9 ) . I t seems u n l i k e l y t h a t t h e r e i s an a b r u p t c u t o f f i n g o l d p a r t i c l e s i z e a t 0.053 mm f r a c t i o n . A b s e n c e o f g o l d f r o m t h e -0.053 mm s e d i m e n t f r a c t i o n t h e r e f o r e p r o b a b l y a l s o r e s u l t s f r o m d i l u t i o n by l a r g e amounts o f b a r r e n s i l t a n d c l a y . Nuchanong and N i c h o l (1990) a l s o r e p o r t e d h i g h Au c o n c e n t r a t i o n s i n f i e l d pan c o n c e n t r a t e s f r o m t h e H u a i H i n L a e p v e r s u s low v a l u e s i n t h e s i l t - c l a y (-0.063 mm) s e d i m e n t f r a c t i o n . Low g o l d c o n t e n t o f t h e H u a i H i n L a e p s e d i m e n t s ( a s o p p o s e d t o t h e h e a v y m i n e r a l c o n c e n t r a t e s ) t h u s seems t o r e s u l t f r o m d i l u t i o n o f f r e e g o l d by l a r g e q u a n t i t i e s o f f i n e s e d i m e n t d e r i v e d f r o m e r o s i o n o f t h e l a t e r i t i c s o i l s t h a t c o n s i s t m a i n l y o f s i l t and c l a y ( F i g . 2 - 6 ) . 141 The b i m o d a l d i s t r i b u t i o n o f s e d i m e n t s i n t h e H u a i H i n L a e p , w i t h l a r g e amounts o f s i l t and c l a y (~ 1 0 % ) , c o n t r a s t s w i t h o n l y 0.8% o f t h e s e s i z e f r a c t i o n s f o u n d i n a M a l a y s i a n s t r e a m a l s o d r a i n i n g l a t e r i t i c s o i l s , c o n t a i n i n g more t h a n 60% s i l t a n d c l a y , i n a m a t u r e r u b b e r p l a n t a t i o n ( S i r i n a w i n e t a l , 1 9 8 7 ) . I n t h i s c a s e w innowing o f f i n e s e d i m e n t s f r o m t h e s t r e a m b e d e n h a n c e d t h e Sn ( c a s s i t e r i t e ) c o n c e n t r a t i o n s i n t h e s e d i m e n t s r e l a t i v e t o c o n c e n t r a t i o n s i n s o i l s . I n t h e H u a i H i n L a e p t h e s u b s t a n t i a l amounts o f s i l t a nd c l a y a p p e a r t o r e s u l t f r o m l a n d c l e a r i n g and i n p a r t i c u l a r t h e p r a c t i c e o f p l o u g h i n g t o p l a n t c o r n j u s t b e f o r e t h e o n s e t o f t h e r a i n y s e a s o n . A s i m i l a r c i r c u m s t a n c e was a l s o f o u n d i n c o r n f i e l d s i n K a l a s i n p r o v i n c e ( L e k h a k u l , 1 9 9 0 ) . However, t h e e f f e c t s o f s o i l e r o s i o n and l a n d u s e on s t r e a m s e d i m e n t g e o c h e m i s t r y r e q u i r e f u r t h e r s t u d y . 6.3 D i s t r i b u t i o n o f g o l d between bed f o r m s The s i z e d i s t r i b u t i o n o f b o t h p o i n t - b a r and pavement s e d i m e n t s i n t h e H u a i H i n Laep i s s t r o n g l y b i m o d a l ( F i g s . 4-2 a n d 4 - 4 ) . However, pavement c o n t a i n s s i g n i f i c a n t l y more g r a v e l and l e s s s i l t - c l a y t h a n do p o i n t b a r s . T h i s i s c o n s i s t e n t w i t h pavement s i t e s b e i n g h i g h e r e n e r g y e n v i r o n m e n t s where f i n e s e d i m e n t s a r e e i t h e r n o t d e p o s i t e d o r t h e y a r e winnowed more e f f e c t i v e l y t h a n f r o m p o i n t - b a r s i t e s . The r e m o v a l o f f i n e s e d i m e n t m i g h t a c c o u n t f o r t h e somewhat h i g h e r h e a v y m i n e r a l and Au c o n c e n t r a t i o n s a t 142 pavement t h a n a t p o i n t - b a r s i t e s . However, t h e c o a r s e r g r a i n s i z e and l o w e r abundance o f s i l t - c l a y m i g h t a l s o p r o m o t e a c c u m u l a t i o n o f g o l d and h e a v y m i n e r a l s by i t s p r e f e r e n t i a l d e p o s i t i o n and t r a p p i n g i n v o i d s . Once p r e f e r e n t i a l l y t r a p p e d i n t h e pavement, winnowing o f f i n e l i g h t m i n e r a l s c o u l d f u r t h e r i n c r e a s e 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 a n d g o l d . 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 a t i o n s e l s e w h e r e o f p r e f e r e n t i a l a c c u m u l a t i o n o f h e a v y m i n e r a l s a t h i g h e n e r g y s i t e s ( 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 , 1987; S a xby an d F l e t c h e r , 1987; F l e t c h e r and Day, 1988b; Day and F l e t c h e r , 1989) . The p r e f e r e n t i a l a c c u m u l a t i o n o f h e a v y m i n e r a l s and g o l d a t s u c h s i t e s i s a l s o c o n s i s t e n t w i t h p r e d i c t i o n s o f t h e i r b e h a v i o u r b a s e d on b e d l o a d t r a n s p o r t m o d e l s p r o p o s e d by S l i n g e r l a n d ( 1 9 8 4 ) , S l i n g e r l a n d a n d S m i t h (1986) and Day and F l e t c h e r ( i n p r e s s ) . 6.4 D i s t r i b u t i o n o f g o l d a l o n g t h e s t r e a m ' s l o n g i t u d i n a l p r o f i l e When c o n s i d e r i n g t h e d i s t r i b u t i o n o f g o l d a l o n g t h e s t r e a m ' s l o n g i t u d i n a l p r o f i l e , t h e e f f e c t s o f s e d i m e n t s u p p l y and c h a n g e s i n s t r e a m c h a r a c t e r i s t i c s must be t a k e n i n t o a c c o u n t . A l t h o u g h t h e s u p p o s e d b e d r o c k s o u r c e ( s ) o f g o l d i s p r o b a b l y l o c a t e d i n t h e s t r e a m h e a d w a t e r s ( F i g . 2-5) , i t i s n o t p o s s i b l e t o d e m o n s t r a t e t h a t t h i s i s t h e s o u r c e o f t h e g o l d i n t h e H u a i H i n L a e p w i t h o u t a c o m p r e h e n s i v e programme o f bank s o i l a n a l y s i s : t h i s was 143 b e y o n d t h e s c o p e o f t h i s t h e s i s . However, a n o m a l o u s Au c o n c e n t r a t i o n s a r e f o u n d i n t h e H u a i H i n La e p n e a r , b u t n o t u p s t r e a m f r o m , t h e s u p p o s e d b e d r o c k s o u r c e o f t h e g o l d ( F i g s . 5-1 and 5 - 2 ) . I t i s t h e r e f o r e assumed t h a t t h i s s i t e i s a t o r c l o s e t o t h e e n t r y p o i n t o f g o l d i n t o t h e s t r e a m . The a b n o r m a l l y h i g h Au c o n c e n t r a t i o n a t t h e p o i n t - b a r s i t e n e a r t h e s u p p o s e d s o u r c e o f g o l d ( F i g s . 5-1 and 5-2) p r o b a b l y r e s u l t f r o m t h e s e d i m e n t a t t h i s s i t e b e i n g d i r e c t l y d e r i v e d f r o m anomalous s o i l s . T h i s i s c o n s i s t e n t w i t h t h e u n u s u a l t e x t u r e o f t h e s e d i m e n t (PP-96, A p p e n d i x ) w h i c h c o n t a i n s g r e a t e r t h a n 46% s i l t and c l a y b u t o n l y 18% g r a v e l . A t t h e n e x t s i t e downstream, Au c o n c e n t r a t i o n s a r e much l o w e r , p r o b a b l y a s a r e s u l t o f l a r g e amounts o f b a r r e n l i g h t m i n e r a l s d e r i v e d f r o m u p s t r e a m s e d i m e n t s t h a t d i l u t e t h e c o n c e n t r a t i o n o f g o l d . I n c r e a s e d Au c o n c e n t r a t i o n s a t p o i n t - b a r s i t e s f u r t h e r d o wnstream c o n t r a s t w i t h t h e downstream d i l u t i o n m o d e l p r e s e n t e d by P o l i k a r p o c h k i n (1971) and Hawkes ( 1 9 7 6 ) . However, i t i s c o n s i s t e n t w i t h o b s e r v a t i o n s e l s e w h e r e t h a t c o n c e n t r a t i o n s o f c a s s i t e r i t e ( F l e t c h e r e t a l , 1986, 1987) s c h e e l i t e (Saxby and F l e t c h e r , 1986) and g o l d ( F l e t c h e r and Day, 1988b; F l e t c h e r , 1990 and Day and F l e t c h e r , i n p r e s s ) c a n i n c r e a s e downstream f r o m t h e i r s o u r c e i n r e s p o n s e t o c h a n g i n g h y d r a u l i c c o n d i t i o n s . I n t h i s s t u d y , c o n c e n t r a t i o n s o f g o l d a t p o i n t - b a r s i t e s a r e most f r e q u e n t l y p o s i t i v e l y c o r r e l a t e d ( T a b l e 6-1) w i t h s e d i m e n t p r o p e r t i e s s u c h as mean g r a i n s i z e (M c) and T a b l e 6-1. Summary s i g n i f i c a n t c o r r e l a t i o n s between Au c o n c e n t r a t i o n s i n s e d i m e n t s a t p o i n t - b a r s i t e s and stre a m c h a r a c t e r i s t i c s and s e d i m e n t p r o p e r t i e s i n t h e r e a c h between t h e s u p p o s e d s o u r c e o f g o l d m i n e r a l i z a t i o n and t h e c o n f l u e n c e w i t h t h e H u a i Kho L o . wt s e d i m e n t F r a c t i o n (mm) w M C Mo  s 0 D 6 5 - 1 2 . 0 - 2 . 0 - 0 . 4 2 5 - 0 . 0 5 3 + 2 . 0 + 0 . 4 2 5 + 0 . 2 1 2 P o i n t - b a r (n = 9) -0.425+0.212 -0.212+0.106 -0.106+0.053 -0.212+0.053 ( n = l l ) S c o r e -1 + + + + + + + + + + 2 + + + + -2 w = s t r e a m w i d t h ; d = c h a n n e l d e p t h ; v = f l o w v e l o c i t y Mc = mean g r a i n s i z e o f c o a r s e g r a i n e d s ediment component SQ = s o r t i n g o f c o a r s e g r a i n e d s e d i m e n t component MQ = mean g r a i n s i z e o f sediment S Q = s o r t i n g o f se d i m e n t D 6 5 = k e d r o u g h n e s s S c o r e = t o t a l numbers o f s i g n i f i c a n t c o r r e l a t i o n s between g o l d c o n c e n t r a t i o n s i n s e d i m e n t f r a c t i o n s s t r e a m c h a r a c t e r i s t i c s and s e d i m e n t p r o p e r t i e s - = n e g a t i v e l y s i g n i f i c a n t c o r r e l a t i o n + = p o s i t i v e l y s i g n i f i c a n t c o r r e l a t i o n 145 p o o r s o r t i n g (SQ, i . e . i n c r e a s i n g ) o f t h e c o a r s e g r a i n e d s e d i m e n t component, and g r a v e l c o n t e n t . T hey a r e a l s o p o s i t i v e l y c o r r e l a t e d w i t h o t h e r p a r a m e t e r s s u c h a s b e d r o u g h n e s s , mean g r a i n s i z e (M Q ) , abundance o f medium s a n d (-0.425+0.212 mm) and f l o w v e l o c i t y , b u t n e g a t i v e l y c o r r e l a t e d w i t h abundance o f c o a r s e s a n d (-2.0+0.425 mm) and c h a n n e l w i d t h . Thus, abundance o f Au i s p o s i t i v e l y c o r r e l a t e d w i t h t h o s e s e d i m e n t p r o p e r t i e s t h a t i n d i c a t e h i g h e n e r g y e n v i r o n m e n t s and r e m o v a l o f f i n e s e d i m e n t . As w o u l d be e x p e c t e d t h e s e p a r a m e t e r s a r e p o s i t i v e l y c o r r e l a t e d w i t h f l o w v e l o c i t y and n e g a t i v e l y c o r r e l a t e d w i t h c h a n n e l w i d t h . A c c u m u l a t i o n o f g o l d a t p o i n t - b a r s i t e s i s t h u s a s s o c i a t e d w i t h f l o w c o n v e r g e n t zones where d e c r e a s e d c h a n n e l w i d t h r e s u l t s i n i n c r e a s e d f l o w v e l o c i t y , i n c r e a s e d b e d r o u g h n e s s a n d d e c r e a s e d ( p o o r ) s o r t i n g . I t w o u l d be u s e f u l t o e s t a b l i s h a m o d e l f o r c o n c e n t r a t i o n s o f g o l d i n s e d i m e n t f r a c t i o n s i n t e r m s o f e a s i l y m e a s u r e d f i e l d p a r a m e t e r s , s u c h a s s t r e a m w i d t h , d e p t h a n d f l o w v e l o c i t y , and e s t i m a t e s o f s e d i m e n t t e x t u r e s s u c h a s mean g r a i n s i z e , s e d i m e n t s o r t i n g and amount o f g r a v e l . T h e s e c a n be done by l i n e a r r e g r e s s i o n s o f t h e f o r m : A U ( _ 0 . 4 2 5 + 0 . 2 1 2 mm) = ° - 2 9 " 4 0 w + 3 6 8 d + 5 9 4 v ( r 2 = .675, Se = 64.138) A u ( - 0 . 2 1 2 + 0 . 1 0 6 mm) = " 1 3 ° " 7 8 w + 9 2 0 d +2053v ( r 2 = .671, Se = 167.931) 146 A U ( _ o .106+0.053 mm) = "158 + 24w + 60d + 1353V ( r 2 = .939, Se = 26.033) where w = s t r e a m w i d t h (m), d = c h a n n e l d e p t h (m), v = f l o w v e l o c i t y (m/sec) and Se = s t a n d a r d e r r o r o f e s t i m a t i o n , and: A U ( - 0 . 4 2 5 + 0 . 2 1 2 mm) = 925 - 1440M 0 + 2 D 6 5 - 1 5 S 0 + 93G ( r 2 = .890, Se = 41.746) A u ( - 0 . 2 1 2 + 0 . 1 0 6 mm) = 2396 - 3974M 0 + 3 D 6 5 - 4 0 S 0 + 263G ( r 2 = .804, Se = 144.775) A u ( - 0 . 1 0 6 + 0 . 0 5 3 mm) = 9 6 8 ~ 1673M 0 - D 6 5 - 1 3 S 0 + 112G ( r 2 = .764, Se = 57.257) where MQ = mean g r a i n s i z e (mm) , D 5 5 = bed r o u g h n e s s (mm) , S Q = s e d i m e n t s o r t i n g and G = w e i g h t p e r c e n t g r a v e l . G o l d c o n c e n t r a t i o n s ( F i g s . 5-1 and 5-2) t e n d t o i n c r e a s e downstream a s t h e s l o p e o f t h e H u a i H i n L a e p ( F i g . 2-3) d e c r e a s e s f r o m 0.013 i n t h e h e a d w a t e r s t o 0.003 a t t h e c o n f l u e n c e w i t h t h e H u a i Kho L o . A l t h o u g h s t a t i s t i c a l c o r r e l a t i o n s between s l o p e and h e a v y m i n e r a l and g o l d c o n c e n t r a t i o n s were n o t c a r r i e d o u t , 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 a t i o n s e l s e w h e r e (Day, 1988; F l e t c h e r , 1990; Day and F l e t c h e r , i n p r e s s ) t h a t as s l o p e d e c r e a s e s a b u n d a n c e o f g o l d i n c r e a s e s . 147 6.5 G o l d g r a i n s h a p e and c o m p o s i t i o n The p r o p o r t i o n o f n e a r l y s p h e r i c a l t o f l a t g o l d g r a i n s i n f i e l d p a n c o n c e n t r a t e s d e c r e a s e s f r o m 86:14 c l o s e t o t h e s o u r c e , t o 35:65 downstream ( T a b l e 5 - 12). T h u s , g o l d g r a i n s e i t h e r t e n d t o become more f l a t t e n e d d u r i n g t h e i r t r a n s p o r t d o w n stream o r f l a t t e n e d g r a i n s a r e s e l e c t i v e l y t r a n s p o r t e d . 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 a t i o n s by G i u s t i (1986) and P o l i n g (1987) t h a t t h e more f l a t t e n e d , t h e more e a s i l y t h e g o l d g r a i n s a r e t r a n s p o r t e d by s t r e a m c u r r e n t . Use o f c h a n g e s o f g o l d g r a i n shape i n e s t i m a t i n g t h e p r o x i m a l o r d i s t a l ( r e l a t i v e t o s o u r c e ) o c c u r r e n c e o f g o l d m i g h t be a p p l i c a b l e i n t h e H u a i H i n L a e p . C o m p o s i t i o n o f p l a c e r g o l d p a r t i c l e s h a s b e e n e x t e n s i v e l y s t u d i e d . The p r e s e n c e o f h i g h f i n e n e s s g o l d h a s b e e n i n t e r p r e t e d t o i n d i c a t e e i t h e r l e a c h i n g o f s i l v e r ( D e s b o r o u g h , 1970; Mann, 1984; F r e y s s i n e t e t a l , 1989; Grimm and F r i e d r i c h , 1990 ) o r p r e c i p i t a t i o n o f p u r e g o l d (Mann, 1984; W e b s t e r and Mann, 1984; W i l s o n , 1984; F r e y s s i n e t e t a l , 1990; G r o e n e t a l , 1990 ) . I n t h e H u a i H i n L a e p , h i g h f i n e n e s s r i m s a r e p r e s e n t on o n l y a few g o l d g r a i n s a n d a r e v e r y p a t c h y and i n c o m p l e t e ( F i g . 5 - 7 ) . T h i s s u g g e s t s t h a t , d e s p i t e t h e l a t e r i t i c w e a t h e r i n g e n v i r o n m e n t , w h i c h h a s b e e n a s s o c i a t e d w i t h h y d r o m o r p h i c m o b i l i t y o f g o l d i n A u s t r a l i a (Mann, 1984; W e b s t e r and Mann, 1984), d i s p e r s i o n o f g o l d i s p r i n c i p a l l y m e c h a n i c a l r a t h e r t h a n c h e m i c a l . Nuchanong and N i c h o l (1990) r e a c h e d a s i m i l a r c o n c l u s i o n . 148 6.6 Recommendations f o r m i n e r a l e x p l o r a t i o n S e v e r a l g o l d o c c u r r e n c e s were v i s i t e d d u r i n g p r e l i m i n a r y s i t e s e l e c t i o n . The H u a i H i n L a e p was c h o s e n t o r e p r e s e n t a t y p i c a l s m a l l s t r e a m i n an a r e a o f d e f o r e s t e d a g r i c u l t u r a l l a n d u s e i n n o r t h e a s t e r n T h a i l a n d . The f o l l o w i n g r e c o m m e n d a t i o n s s h o u l d be a p p l i c a b l e t o s i m i l a r s t r e a m s c o n t a i n i n g r e l a t i v e l y c o a r s e , s a n d s i z e , g o l d p a r t i c l e s . 6.6.1 R e g i o n a l s u r v e y The p u r p o s e o f a r e g i o n a l r e c o n n a i s s a n c e s u r v e y i s t o r e l i a b l y d e t e c t p r e s e n c e o r a b s e n c e o f g o l d i n l a r g e s u r v e y a r e a s u s i n g t h e minimum number o f s a m p l e s , i . e . a low s a m ple d e n s i t y . T h i s u s u a l l y r e s t r i c t s s a m p l i n g t o r e l a t i v e l y l a r g e d r a i n a g e c a t c h m e n t s . I n s u c h c a s e s , t h e p r o b a b i l i t y t h a t a s i n g l e s a m p l e , i n an a r e a o f known g o l d m i n e r a l i z a t i o n , w i l l f a i l t o d e t e c t t h e p r e s e n c e o f g o l d must be c o n s i d e r e d . Recommendations f o r t h i s s u r v e y i n g s t a g e s h o u l d c o n s i d e r : i ) r e p r e s e n t a t i v e f i e l d sample s i z e , i i ) s a m ple l o c a t i o n a l o n g t h e s t r e a m r e a c h , and i i i ) p r e f e r r e d s a m p l i n g s i t e s o r t y p e s o f s a m p l e . 149 6.6.1.1 Sample f r a c t i o n T he p r e s e n c e o f g o l d i n t h e H u a i H i n L a e p i s r e a d i l y d e t e c t e d i n h e a v y m i n e r a l f r a c t i o n s t h a t c o n t a i n Au c o n c e n t r a t i o n s up t o 100 t i m e s g r e a t e r t h a n t h o s e i n i n d i v i d u a l s e d i m e n t f r a c t i o n s . The h i g h g o l d c o n t e n t o f t h e h e a v y m i n e r a l f r a c t i o n s i n d i c a t e s t h a t t h e s e w i l l be much more e f f e c t i v e t h a n c o n v e n t i o n a l s e d i m e n t s a m p l e s i n d e t e c t i n g g o l d i n t h e H u a i H i n L a e p . T h u s , b a s e d on e s t i m a t e s o f t h e numbers o f f r e e g o l d p a r t i c l e s l i k e l y t o be p r e s e n t i n 40 k g o f -12 mm f i e l d s a m p l e s and i n 30 g a n a l y t i c a l s u b s a m p l e s ( T a b l e s 5-9 and 6-2), t h e m e d i a n o f t h e t o t a l numbers o f g o l d p a r t i c l e s i n a h e a v y m i n e r a l c o n c e n t r a t e f r o m a 40 k g p o i n t - b a r sample i s a b o u t 3 g r a i n s . The c o r r e s p o n d i n g P o i s s o n p r o b a b i l i t y o f d e t e c t i n g one o r more g o l d g r a i n s i s v e r y h i g h - 95%. S i m i l a r l y , f o r pavement s a m p l e s , t h e m e d i a n o f t h e t o t a l numbers o f g o l d p a r t i c l e s i s a b o u t 5 g r a i n s w i t h a p r o b a b i l i t y o f d e t e c t i n g one o r more g o l d g r a i n s o f 99%. T h e s e r e s u l t s i n d i c a t e t h a t a n a l y s i s o f h e a v y m i n e r a l c o n c e n t r a t e s f r o m a 4 0 k g f i e l d s a m p l e o f e i t h e r p o i n t - b a r o r pavement s e d i m e n t s w i l l h a v e v e r y h i g h c h a n c e o f d e t e c t i n g t h e p r e s e n c e o f a n o m a l o u s c o n c e n t r a t i o n s o f g o l d . T h i s a l s o e x p l a i n s why u s e o f t r a d i t i o n a l f i e l d pan c o n c e n t r a t e s i s a v e r y e f f e c t i v e method i n t h e H u a i H i n L a e p . Use o f t h e -2.0 mm s e d i m e n t f r a c t i o n w o u l d r e d u c e t h e f i e l d sample s i z e , l i k e t h a t o f t h e H a r r i s C r e e k , s o u t h c e n t r a l B r i t i s h C o l u m b i a (Day, 150 T a b l e 6-2. Summary s t a t i s t i c s o f median, r a n g e and p r o b a b i l i t y o f c o n t a i n i n g one o r more g o l d g r a i n s (P>0) f o r t h e e s t i m a t e d numbers o f g o l d p a r t i c l e s i n t h e s t a n d a r d i z e d 40 k g (-12.0 mm) f i e l d s a m p l e s and 30 g a n a l y t i c a l s u b s a m p l e s . F r a c t i o n s (mm) T o t a l -0.425 +0.212 -0.212 +0.106 -0.106 +0.053 -0.425 +0.053 40 k g f i e l d s a m p l e s P o i n t b a r (n = 11) M e d i a n Range P>0 0.15 0.00-11.38 0.14 0.25 0.00-17.63 0.22 3.54 0.00-36.45 0.97 3.21 0.35-41.96 0.96 Pavement (n = 5) M e d i a n Range P>0 1. 61 0.00-4.87 0.80 3.13 1.37-41.40 0.96 2.88 1.27-38.70 0.94 4.71 11-59.70 0.99 30 g a n a l y t i c a l s u b s a m p l e s P o i n t b a r M e d i a n Range P>0 0.00 0.00-0.15 0.003 0.02 0.00-0.64 0.02 0.37 0.00-2.58 0.31 0.45 0.02-3.25 0.36 Pavement M e d i a n Range P>0 0.03 0.00-0.11 0.03 0.42 0.31-2.49 0. 34 1.13 0.25-3.86 0.68 1.58 0.69-6.46 0.79 S t a t i s t i c a l d a t a a r e b a s e d on d a t a i n T a b l e s 5-8 and 5-9. 151 1988) . However, b e c a u s e o f t h e l a r g e amounts o f s i l t and c l a y i n t h e H u a i H i n L a e p s e d i m e n t , t h e d i f f i c u l t y may a r i s e when t h e s e s e d i m e n t f r a c t i o n s b l o c k t h e s c r e e n o p e n i n g p r e v e n t i n g s a n d s i z e d p a r t i c l e s t o p a s s t h r o u g h i t , and t h e n t h e f i e l d s i e v i n g p r o c e s s becomes v e r y t i m e c o n s u m i n g . T h e s e f i n d i n g s a r e c o n s i s t e n t w i t h t h o s e o f Nuchanong and N i c h o l (1990) who a l s o f o u n d t h a t r e l a t i v e l y h i g h Au c o n c e n t r a t i o n s were p r e s e n t i n f i e l d p an c o n c e n t r a t e s 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 i n t h e H u a i H i n L a e p . However, t h e r e a r e some p o t e n t i a l d i s a d v a n t a g e s t o u s e o f f i e l d p a n c o n c e n t r a t e s a m p l e s i n m i n e r a l e x p l o r a t i o n , f o r example, d i f f e r e n c e s i n g o l d r e c o v e r y by d i f f e r e n t i n d i v i d u a l s and s u b s t a n t i a l l o s s e s o f f i n e g r a i n e d g o l d (Wang and P o l i n g , 1983; G i u s t i , 1986 and P o l i n g , 1987). To i m p r o v e r e c o v e r y o f f i n e g o l d p a r t i c l e s , m e t h y l e n e i o d i d e h e a v y l i q u i d c a n be e m p l o y e d t o p r e p a r e t h e c o n c e n t r a t e s . However, t h e d i s a d v a n t a g e s o f t h i s a r e 1) t h e h i g h c o s t o f s a m ple t r a n s p o r t a t i o n and l a b o r a t o r y p r e p a r a t i o n and 2) i n a b i l i t y t o s e p a r a t e g o l d o r h e a v y m i n e r a l s f i n e r t h a n a b o u t 0.053 mm f r a c t i o n . Compared t o numbers o f g o l d p a r t i c l e s i n h e a v y m i n e r a l c o n c e n t r a t e s p r e p a r e d f r o m 40 k g f i e l d s a m p l e s , t h e m e d i a n number o f g o l d p a r t i c l e s i n a l l s i z e f r a c t i o n s o f a 30 g s u b s a m p l e i s o n l y a b o u t 0.15 g r a i n s f o r p o i n t - b a r s a m p l e s and 0.53 g r a i n s f o r pavement s a m p l e s . The c o r r e s p o n d i n g p r o b a b i l i t i e s o f d e t e c t i n g one o r more g o l d g r a i n s a r e 14 a n d 41%, r e s p e c t i v e l y . I n a d d i t i o n , t h e i n a b i l i t y o f 152 c o n v e n t i o n a l s e d i m e n t s a m p l e s t o r e l i a b l y d e t e c t a n omalous c o n c e n t r a t i o n s i s c o n f i r m e d by Au c o n c e n t r a t i o n s i n t h e -0.150 mm and -0.053 mm s e d i m e n t f r a c t i o n s b e l o w t h e d e t e c t i o n l i m i t ( T a b l e 5 - 1 ) . A b s e n c e o f Au f r o m t h e -0.053 mm f r a c t i o n s i m p l i e s t h a t a n a l y s i s o f 30 g s e d i m e n t s a m p l e s w i l l h a v e e v e n l o w e r p r o b a b i l i t i e s o f d e t e c t i n g t h e p r e s e n c e o f g o l d t h a n i n d i c a t e d by p r o b a b i l i t i e s b a s e d on e s t i m a t e s o f numbers o f g o l d p a r t i c l e s . Thus, c o n v e n t i o n a l s t r e a m s e d i m e n t s a m p l e s w i l l f a i l t o r e l i a b l y d e t e c t t h e p r e s e n c e o f a g o l d anomaly i n t h e H u a i H i n L a e p . 6.6.1.2 Sample l o c a t i o n a t c a t c h m e n t s c a l e I n a l a r g e s c a l e s t r e a m s e d i m e n t s u r v e y , i t i s n e c e s s a r y t o c o n s i d e r t h e d i s p e r s i o n p a t t e r n o f a nomalous s e d i m e n t a l o n g t h e d r a i n a g e . W i t h t h e anomaly d i l u t i o n m o del o f P o l i k a r p o c h k i n (1971) and Hawkes (1976) , t h e a n o maly d e c r e a s e s e x p o n e n t i a l l y f r o m t h e s o u r c e , i n p r o p o r t i o n t o c a t c h m e n t b a s i n a r e a , as a c o n s e q u e n c e o f d i l u t i o n by b a r r e n s e d i m e n t . To d e t e c t s u c h an anomaly i t may be n e c e s s a r y t o do d e t a i l e d s e d i m e n t s a m p l i n g a l o n g t h e e n t i r e s t r e a m r e a c h . However, w i t h Au c o n c e n t r a t i o n s i n c r e a s i n g d ownstream i n r e s p o n s e t o c h a n g i n g s t r e a m and s e d i m e n t p r o p e r t i e s , d i s p e r s i o n o f g o l d i n t h e H u a i H i n L a e p d o e s n o t f o l l o w t h i s c o n v e n t i o n a l m o d e l . I t f o l l o w s t h a t c o l l e c t i o n o f s e d i m e n t s a m p l e s a l o n g t h e l o w e r r e a c h e s o f t h i r d o r d e r s t r e a m s may be c a p a b l e o f d e t e c t i n g t h e p r e s e n c e o f a s o u r c e o f c o a r s e 153 g o l d much f u r t h e r u p s t r e a m . Thus, p r o v i d i n g t h a t h e a v y m i n e r a l c o n c e n t r a t e s a r e p r e p a r e d f r o m b u l k s e d i m e n t s a m p l e s o f s u f f i c i e n t s i z e (" 40 k g ) , r e l a t i v e l y low d e n s i t y r e g i o n a l s u r v e y s s h o u l d be e f f e c t i v e i n e x p l o r a t i o n f o r g o l d d e p o s i t s c o n t a i n i n g c o a r s e g o l d . 6.6.1.3 P r e f e r r e d s a m p l i n g s i t e s a t l o c a l s c a l e G o l d c o n c e n t r a t i o n s i n s e d i m e n t s a r e s l i g h t l y g r e a t e r a t pavement t h a n a t p o i n t b a r s i t e s . The e n t i r e 40 k g o f -12 mm s e d i m e n t o r f i e l d pan c o n c e n t r a t e s h o u l d t h e r e f o r e be t a k e n f r o m pavement s i t e s where p o s s i b l e . Where t h i s i s n o t p o s s i b l e p o i n t - b a r s c h a r a c t e r i z e d by n a r r o w i n g o f t h e s t r e a m c h a n n e l and i n c r e a s e d bed r o u g h n e s s and f l o w v e l o c i t y s h o u l d be c h o s e n . B e c a u s e g o l d c o n c e n t r a t i o n s a r e c l o s e l y r e l a t e d t o s e d i m e n t p r o p e r t i e s t h a t c a n e a s i l y be e v a l u a t e d d u r i n g s a m p l e c o l l e c t i o n , i t i s i m p o r t a n t t o r e c o r d t h i s i n f o r m a t i o n a s a g u i d e t o s u b s e q u e n t i n t e r p r e t a t i o n . P a r a m e t e r s t o be r e c o r d e d i n c l u d e 1) c h a n n e l w i d t h and d e p t h a t t h e w a t e r l e v e l where v e r y e a s i l y m e a s u r e d i n t h e f i e l d , 2) f l o w v e l o c i t y by t i m i n g a f l o a t o v e r a known d i s t a n c e , and 3) s e d i m e n t t e x t u r e , p a r t i c u l a r l y t h e amount o f g r a v e l a n d b e d r o u g h n e s s e s t i m a t e d i n t h e f i e l d . T h e s e p a r a m e t e r s must be r e c o r d e d p r i o r t o sample c o l l e c t i o n : a s c a l e d p h o t o g r a p h o f t h e bed p r o v i d e s a u s e f u l r e c o r d o f bed t e x t u r e . 154 6.6.2 F o l l o w - u p s u r v e y The p u r p o s e o f t h e f o l l o w - u p s u r v e y i s t o l o c a t e t h e s o u r c e o f g o l d i n t h e d r a i n a g e b a s i n . S i n c e t h e a u r i f e r o u s c a t c h m e n t h a s b een i d e n t i f i e d , t h e f o l l o w - u p s u r v e y s h o u l d c o n s i s t o f more d e t a i l e d s a m p l i n g o f e i t h e r t h e 40 k g o f -12 mm s e d i m e n t o r f i e l d pan c o n c e n t r a t e s a l o n g t h e s t r e a m c h a n n e l . A p a n sample s h o u l d be s u f f i c i e n t l y l a r g e ( i . e . p a n n e d f r o m 8 s h o v e l s - f u l l o r a t l e a s t 20 k g o f s e d i m e n t ) t o d e t e c t t h e p r e s e n c e o f v e r y r a r e g o l d p a r t i c l e s . T o g e t h e r w i t h s t r e a m s e d i m e n t s a m p l i n g , s o i l s a m p l e s s h o u l d be c o l l e c t e d f r o m b o t h s i d e s o f t h e s t r e a m b a n k s t o i d e n t i f y t h e p o i n t o f e n t r y o f g o l d i n t o t h e s t r e a m . B e c a u s e o f t h e p o s s i b i l i t y o f g o l d c o n c e n t r a t i o n s i n c r e a s i n g downstream away f r o m t h e s o u r c e a s a f u n c t i o n o f s t r e a m c h a r a c t e r i s t i c s and s e d i m e n t t e x t u r e s , g o l d a n o m a l i e s a l o n g t h e l o w e r r e a c h e s o f s t r e a m s h o u l d n o t be i n t e r p r e t e d a s b e i n g i n t h e i m m e d i a t e v i c i n i t y o f g o l d m i n e r a l i z a t i o n . A n o m a l o u s c o n c e n t r a t i o n s o f g o l d must t h e r e f o r e be c a r e f u l l y e v a l u a t e d i n r e l a t i o n t o s t r e a m c h a r a c t e r i s t i c s and s e d i m e n t t e x t u r e s , f o r example, p o s s i b l y u s i n g r e g r e s s i o n e q u a t i o n s s i m i l a r t o t h o s e i n s e c t i o n 6.4. H i g h g o l d c o n c e n t r a t i o n s a t l o c a t i o n s where t h e c h a n n e l n a r r o w s and f l o w v e l o c i t y and b e d r o u g h n e s s i n c r e a s e may i n d i c a t e a l o c a l a c c u m u l a t i o n o f g o l d i n r e s p o n s e t o t h e s e c o n d i t i o n s . C o n v e r s e l y , h i g h c o n c e n t r a t i o n s o f g o l d a t s i t e s n o t f a v o u r a b l e t o i t s a c c u m u l a t i o n a r e more l i k e l y t o i n d i c a t e p r o x i m i t y t o a 155 s o u r c e . I t must be e m p h a s i z e d t h a t t h e s e r e c o m m e n d a t i o n s a p p l y o n l y t o e x p l o r a t i o n f o r c o a r s e s a n d s i z e d g o l d i n s t r e a m s l i k e t h e H u a i H i n L a e p . They a r e p r o b a b l y n o t a p p l i c a b l e t o e x p l o r a t i o n f o r d e p o s i t s o f f i n e g r a i n e d g o l d o f t h e t y p e d e s c r i b e d by Nuchanong and N i c h o l (1990) i n t h e L o e i r e g i o n . CHAPTER SEVEN CONCLUSIONS 7.1 C o n c l u s i o n s 1) S e d i m e n t s o f t h e H u a i H i n Laep h ave a s t r o n g l y b i m o d a l d i s t r i b u t i o n w i t h l a r g e amounts o f g r a v e l and s i l t - c l a y b u t l i t t l e s a n d . Pavement s e d i m e n t s c o n t a i n g r e a t e r amounts o f g r a v e l b u t l e s s s i l t and c l a y t h a n p o i n t - b a r s e d i m e n t s . A b n o r m a l l y h i g h s i l t and c l a y p r o b a b l y r e s u l t s f r o m i n c r e a s e d s o i l e r o s i o n t h a t r e s u l t s f r o m t h e p r a c t i c e o f p l o u g h i n g t h e l a t e r i t i c s o i l s t o p l a n t c o r n j u s t b e f o r e t h e o n s e t o f t h e r a i n y s e a s o n . 2) Downstream t r e n d s i n s e d i m e n t t e x t u r e a t p o i n t - b a r s i t e s a r e v e r y e r r a t i c b u t s e d i m e n t s o r t i n g and f l o w v e l o c i t y a r e n e g a t i v e l y c o r r e l a t e d w i t h s t r e a m w i d t h and d e p t h . T h a t i s , s e d i m e n t s o r t i n g a t p o i n t - b a r s i t e s becomes p o o r e r i n t h e c o n v e r g e n t z o n e s c h a r a c t e r i z e d by h i g h f l o w v e l o c i t y , n a r r o w c h a n n e l and s h a l l o w d e p t h . 3) Heavy m i n e r a l c o n t e n t o f s e d i m e n t s f r o m p o i n t - b a r and pavement s i t e s i s a p p r o x i m a t e l y 1%. A t p o i n t - b a r s i t e s , h e a v y m i n e r a l c o n t e n t i n c r e a s e s i n h i g h e n e r g y c o n v e r g e n t z o n e s . 4) G o l d c o n c e n t r a t i o n s i n t h e h e a v y m i n e r a l f r a c t i o n s (SG > 3.3) a r e t y p i c a l l y s e v e r a l t h o u s a n d ppb r a n g i n g up t o 198,000 ppb. I n c o m p a r i s o n , c o n c e n t r a t i o n s i n l i g h t m i n e r a l f r a c t i o n s and w h o l e s e d i m e n t s a r e g e n e r a l l y l e s s t h a n 5 ppb. 158 5) G o l d c o n c e n t r a t i o n s i n a l l t h r e e s i z e f r a c t i o n s a t pavement s i t e s a r e s l i g h t l y h i g h e r t h a n a t p o i n t - b a r s i t e s . A t p o i n t - b a r s i t e s g o l d i s p r e f e r e n t i a l l y a c c u m u l a t e d where n a r r o w s t r e a m c h a n n e l , s h a l l o w d e p t h , h i g h f l o w v e l o c i t y l e a d s t o h i g h bed r o u g h n e s s and c o a r s e s e d i m e n t t e x t u r e . C h a n g e s o f t h e s e s t r e a m c h a r a c t e r i s t i c s and s e d i m e n t o l o g i c a l c o n d i t i o n s c a u s e c o n c e n t r a t i o n s o f g o l d t o i n c r e a s e d o w n stream away f r o m t h e s u p p o s e d s o u r c e . 6) The e s t i m a t e d numbers o f g o l d p a r t i c l e s i n h e a v y m i n e r a l c o n c e n t r a t e s f r o m t h e 40 k g f i e l d s a m p l e s and t h e c o r r e s p o n d i n g l y h i g h p r o b a b i l i t i e s o f d e t e c t i n g t h e g o l d a n o m a l i e s s u g g e s t t h a t a n a l y s i s o f h e a v y m i n e r a l c o n c e n t r a t e s f r o m l a r g e b u l k s e d i m e n t s h a s v e r y h i g h c h a n c e o f d e t e c t i n g t h e p r e s e n c e o f anomalous c o n c e n t r a t i o n s o f g o l d . 7) The e s t i m a t e d numbers o f g o l d p a r t i c l e s i n t h e 3 0 g s e d i m e n t s a m p l e s g i v e a low p r o b a b i l i t y o f d e t e c t i n g t h e p r e s e n c e o f g o l d w i t h s u c h s a m p l e s . T h i s r e s u l t s f r o m d i l u t i o n o f A u - r i c h h e a v y m i n e r a l s by l a r g e amounts o f l i g h t a n d s i l t - c l a y f r a c t i o n s . 8) W i t h r e s p e c t t o m i n e r a l e x p l o r a t i o n f o r c o a r s e g r a i n e d g o l d s i m i l a r t o t h a t f o u n d i n t h e H u a i H i n L a e p , b e c a u s e g o l d c o n c e n t r a t i o n s i n c r e a s e downstream, a t t h e r e g i o n a l 159 s u r v e y s t a g e b u l k s e d i m e n t s a m p l e s ( i . e . 40 k g o f -12 mm) o r f i e l d p a n c o n c e n t r a t e s ( i . e . a t l e a s t 20 k g o f s e d i m e n t ) c a n be t a k e n a l o n g t h e l o w e r p a r t o f t h i r d o r d e r s t r e a m s . T o g e t h e r w i t h sample c o l l e c t i o n , d a t a r e g a r d i n g s t r e a m c h a r a c t e r i s t i c s and s e d i m e n t p r o p e r t i e s s h o u l d be r e c o r d e d . 9) A t t h e f o l l o w - u p s u r v e y s t a g e , more d e t a i l e d s a m p l e s o f e i t h e r b u l k s e d i m e n t s o r f i e l d pan c o n c e n t r a t e s s h o u l d be t a k e n f r o m h i g h e n e r g y p o i n t - b a r s i t e s a l o n g t h e s t r e a m c h a n n e l , t o g e t h e r w i t h bank s o i l s a m p l e s t o i d e n t i f y t h e p o i n t o f e n t r y o f g o l d i n t o t h e s t r e a m . B e c a u s e g o l d c o n c e n t r a t i o n s i n c r e a s e downstream, g o l d a n o m a l i e s a t t h e l o w e r r e a c h o f t h e s t r e a m may n o t be t h e v i c i n i t y o f g o l d m i n e r a l i z a t i o n . H i g h g o l d c o n c e n t r a t i o n s a t s i t e s n o t f a v o u r a b l e t o i t s a c c u m u l a t i o n may i n d i c a t e p r o x i m i t y t o a s o u r c e . 160 REFERENCES 161 R e f e r e n c e s B e s c h t a , R.L. and J a c k s o n , W.L. 1979. The i n t r u s i o n o f f i n e s e d i m e n t s i n t o a s t a b l e g r a v e l bed. J . F i s h . R e s . B o a r d Can. 36: 204-210. B r a d l e y , J.V. 1968. D i s t r i b u t i o n - f r e e s t a t i s t i c a l t e s t s . P r e n t i c e - H a l l , I n c . Englewood C l i f f s , N . J . 388 p a g e s . C h a r o e n p r a v a t , A., Wongwanich, T., T a n t i w a n i t , W and T h e e t i p a r i v a t r a , U. 1976. R e g i o n a l g e o l o g i c a l s u r v e y , s c a l e 1 : 250,000, Changwat L o e i , map s h e e t NE 47-12. G e o l o g i c a l S u r v e y D i v i s i o n , D e p a r t m e n t o f M i n e r a l R e s o u r c e s , Bangkok, T h a i l a n d ( i n T h a i ) . C h o r l e y , R . J . , Schumm, S.A. and Sugden, D.E. 1984. G e o m o r p h o l o g y . Methuen & Co. L t d , London. 605 p a g e s . C l i f t o n , H.E., H u n t e r , R.E., Swanson, F . J . and P h i l l i p s , R.L. 1969. Sample s i z e and m e a n i n g f u l g o l d a n a l y s i s . U.S. G e o l . S u r v . P r o f . P a p e r 625 C, pp. C1-C17. C o r e y , A.T. 1949. I n f l u e n c e o f shape on t h e f a l l v e l o c i t y o f s a n d g r a i n s . Unpub. M.Sc. t h e s i s , C o l o r a d o A & M c o l l e g e , 102 p a g e s . Day, S . J . 1988. S a m p l i n g s t r e a m s e d i m e n t s f o r g o l d i n m i n e r a l e x p l o r a t i o n , s o u t h e r n B r i t i s h C o l u m b i a . Unpub. M.Sc. t h e s i s , The U n i v e r s i t y o f B r i t i s h C o l u m b i a , 232 p a g e s . Day, S . J . and F l e t c h e r , W.K. 1986. 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S c i . , V o l . 14: 113-147. S m i t h , H.H., B e r n i e r , D.W., Bung, F.M., R i n t z , F.C., S h i n n , R. and T e l e k i , S. 1968. A r e a handbook f o r T h a i l a n d . 558 p a g e s . S m i t h , N.D. and M i n t e r , W.E.L. 1980. S e d i m e n t o l o g i c a l c o n t r o l s o f g o l d and u r a n i u m i n W i t w a t e r s r a n d p a l e o p l a c e r s . E c o n . G e o l . 75: 1-14. 167 S n e d e c o r , G.W. and C o c h r a n , W.G. 1989. S t a t i s t i c a l M e t h o d s . Iowa S t a t e U n i v e r s i t y P r e s s / AMES. 503 p a g e s . S o i l S u r v e y D i v i s i o n , 1975. D e t a i l e d r e c o n n a i s s a n c e s o i l map o f L o e i p r o v i n c e . P r o v i n c e S e r i e s : No. 10., S o i l S u r v e y D i v i s i o n , D e p a r t m e n t o f L a n d Development, Bangkok, T h a i l a n d . S t e g e r , H.F. 1986. C e r t i f i e d r e f e r e n c e m a t e r i a l s . CM84-14E ( r e v i s e d e d i t i o n ) : E n e r g y , M i n e s and R e s o u r c e s Canada. 42 p a g e s . S t e i d t m a n n , J.R. 1982. S i z e - d e n s i t y s o r t i n g o f s a n d - s i z e s p h e r e s d u r i n g d e p o s i t i o n f r o m b e d l o a d t r a n s p o r t and i m p l i c a t i o n s c o n c e r n i n g h y d r a u l i c e q u i v a l e n c e . S e d i m e n t o l o g y . 29: 877-883. T a t e , N.M. 1988. S t y l e s and d i s t r i b u t i o n o f g o l d d e p o s i t s i n T h a i l a n d ( u n p u b l i s h e d p a p e r ) . 15 p a g e s . T o u r t e l o t , H.A. 1968. H y d r a u l i c e q u i v a l e n c e o f g r a i n s o f q u a r t z and h e a v i e r m i n e r a l s , and i m p l i c a t i o n s f o r t h e s t u d y o f p l a c e r s . U.S. G e o l . S u r v . , P r o f . P a p e r 594-F, pp. F1-F13. V u d h i c h a t v a n i c h , S., V i c h i t , P. and S u v a n v e s , B. 1980. G o l d . E c o n o m i c G e o l o g y B u l l e t i n , no. 25. E c o n o m i c G e o l o g y D i v i s i o n , D e p a r t m e n t o f M i n e r a l R e s o u r c e s ( i n T h a i ) , 99 p a g e s . Wang, W. and P o l i n g , G.W. 1983. Methods f o r r e c o v e r i n g f i n e p l a c e r g o l d . C a n a d i a n I n s t i t u t e M i n i n g M e t a l l u r g y B u l l e t i n , 76: 47-56. W e b s t e r , J.G. and Mann, A.W. 1984. The i n f l u e n c e o f c l i m a t e , g e o m o r p h o l o g y and p r i m a r y g e o l o g y on t h e s u p e r g e n e m i g r a t i o n o f g o l d and s i l v e r . J . Geochem. E x p l o r . , 22: 21-42. W i l s o n , A.F. 1984. O r i g i n o f q u a r t z f r e e g o l d n u g g e t s a n d s u p e r g e n e g o l d f o u n d i n l a t e r i t e s and s o i l s . A r e v i e w o f some new o b s e r v a t i o n s . A u s t . J . E a r t h S c i . , 31: 303- 316. Y e n s a b a i , S. and J a m n o n g t h a i , M. 199 0. R e p o r t on d e t a i l e d g e o c h e m i c a l s u r v e y o f t h e H u a i H i n L a e p a r e a , Ban Nong Khan, Amphoe Na Duang, Changwat L o e i . E c o n o m i c G e o l o g y R e p o r t , A u g u s t , 1990. Economic G e o l o g y D i v i s i o n , D e p a r t m e n t o f M i n e r a l R e s o u r c e s ( i n T h a i ) . 34 p a g e s . Z a r , J.H. 1984. B i o s t a t i s t i c a l a n a l y s i s . P r e n t i c e - H a l l I n c . 718 p a g e s . 168 APPENDIX 169 Summary o f s t r e a m c h a r a c t e r i s t i c s o f t h e H u a i H i n L a e p . Sample W i d t h D e p t h V e l o c i t y Number (m) (m) (m/sec) P o i n t - b a r (n = 19) PP-22 1.45 .34 0.50 PP-16 0.70 .9 0.45 PP-96 1.00 .20 0. 03 PP-98 1.40 .5 0. 03 PP-09 2.80 . 10 0.05 PP-08 3.30 . 38 0.00 PP-06 1.20 .30 0.36 PP-94 1.50 .20 0.11 PP-10 5.40 .55 0.03 PP-89 5. 00 .61 0. 02 PP-81 2 .30 .50 0. 08 PP-75 1.90 .18 0.17 PP-73 2.85 .92 0.14 PP-70 1.30 .36 0.12 PP-67 1.70 . 15 0.27 PP-64 6.50 .70 0. 00 PP-59 2 . 00 .25 0.30 PP-55 1.60 .25 1. 00 PP-56 1. 60 .25 1. 00 Mean 2.39 .34 0.25 S t d 1. 60 . 29 0.31 Pavement (n = 3) PP-23 — — — PP-87 2 .40 . 15 0. 50 PP-100 2.80 .8 0.40 PP-79 2.00 . 11 0.33 PP-68 - - - PP-65 - - - PP-58 - - - Mean S t d 2.40 0. 40 . 11 .35 0.41 0. 09 W e i g h t (g) o f s e d i m e n t s i n each s i z e f r a c t i o n o f p o i n t - b a r and pavement s a m p l e s . F r a c t i o n s (mm) Sample -12.0 -2.0 -0.425 -0.212 -0.150 -0.106 -0.075 -0.053 +2.0 +0.425 +0.212 +0.150 +0.106 +0.075 +0.053 P o i n t - b a r (n = 19) pp- 22 2769 .50 1382 .50 106 .60 26 .80 17 .20 8 .70 10 .30 409 .89 pp- 16 19172 .00 9530 .00 287 .60 99 .50 69 .50 47 .00 54 .70 2010 .58 pp- 96 4411 .00 5431 .00 1354 .00 386 .45 427 .29 411 .21 558 .23 11293 .16 pp- 98 520 .40 923 .20 138 .00 37 .60 51 .80 86 .70 64 .30 1518 .65 pp- 09 15364 .00 8979 .00 811 .89 203 .03 229 .00 187 .81 222 .01 4659 .60 pp- 08 2202 .90 1187 .80 88 .30 25 .50 19 .70 21 .80 25 .60 670 .75 pp- 06 2070 .80 1558 .50 71 .10 30 .60 9 . 60 15 .40 15 .50 978 .93 pp- 94 11601 .00 8770 .00 1021 .02 300 .51 193 . 60 190 .35 329 .38 9542 .20 pp- 10 21174 .00 8379 .00 693 .60 174 .76 114 . 32 76 .41 129 . 18 2901 .90 pp- 89 12162 .00 12695 .00 1702 .54 227 .40 130 .09 102 .62 164 .56 8054 .80 pp- 81 17910 .20 8199 .10 635 .37 131 .76 70 .06 67 .89 178 .56 3794 .10 pp- 75 16363 .00 8373 .00 529 .97 111 .30 56 .68 42 . 10 68 .32 2868 .10 pp- 73 997 .70 1390 .80 91 .80 15 .80 10 .81 8 .08 8 .18 274 .08 pp- 70 17004 .00 7013 .30 1827 .20 442 .43 260 . 12 165 .24 190 .17 4533 .60 pp- 67 19992 .60 4771 .30 1025 .72 342 .42 250 .78 140 . 34 190 .72 4543 .60 PP- 64 18482 .00 8659 .60 605 .30 217 .26 198 .52 112 .95 226 .05 3642 .60 PP- 59 2367 .10 2675 .10 632 .00 102 .30 45 . 00 23 .90 17 .30 503 .62 PP- 55 1751 .90 1654 .20 458 .90 45 .90 28 . 10 19 . 30 29 .30 591 .55 PP- 56 3026 .80 1589 .40 416 .70 55 .50 39 .70 19 .50 34 .50 476 .27 W e i g h t (g) o f s e d i m e n t s ( c o n t i n u e d ) . F r a c t i o n s (mm) Sample -12.0 +2.0 -2.0 +0.425 -0.425 +0.212 -0.212 +0.150 -0.150 +0.106 -0.106 +0.075 -0.075 +0.053 -0.053 Pavement (n = 7) PP-23 3438.00 PP-87 26664.00 PP-100 21555.00 PP-79 20056.80 PP-68 15082.70 PP-65 17458.50 PP-58 2825.40 1397.90 6189.00 6776.00 8225.00 7321.00 7867.80 1115.40 216.40 325.08 638.39 925.10 1649.60 970.56 142.20 32.80 49. 66 118.33 115.24 419.54 230.09 23.90 25.10 22.89 80.99 63.36 300.94 142.46 19.40 15.70 18 .83 51.74 37.09 186.30 98.69 14.10 17.30 41.24 65.75 57.29 263.60 126.78 17.80 571.95 1491.90 2167.64 2317.80 4182.40 3028.30 388.27 172 W e i g h t p e r c e n t s e d i m e n t i n e a c h s i z e f r a c t i o n o f p o i n t - b a r and pavement s a m p l e s . F r a c t i o n s (mm) Sample -12.0 -2.0 -0.425 -0.212 -0.150 -0.106 -0.075 -0.053 +2.0 +0.425 +0.212 +0.150 +0.106 +0.075 +0.053 P o i n t - b a r (n = 19) PP-22 58.53 29 .22 2 .25 0 .57 0 .36 0 . 18 0 .22 8 . 66 PP-16 61. 31 30 .48 0 .92 0 . 32 0 .22 0 . 15 0 . 17 6 .43 PP-96 18.17 22 .38 5 .58 1 .59 1 .76 1 . 69 2 . 30 46 .53 PP-98 15.58 27 .64 4 .13 1 . 13 1 .55 2 .60 1 .92 45 .46 PP-09 50.12 29 .29 2 .65 0 .66 0 .75 0 .61 0 .72 15 .20 PP-08 51.93 28 .00 2 .08 0 .60 0 .46 0 .51 0 . 60 15 .81 PP-06 43 . 59 32 .81 1 .50 0 .64 0 .20 0 .32 0 .33 20 .61 PP-94 36.31 27 . 45 3 .20 0 .94 0 . 61 0 . 60 1 .03 29 . 87 PP-10 62 .94 24 .91 2 .06 0 .52 0 .34 0 .23 0 . 38 8 .63 PP-89 34.51 36 .03 4 .83 0 .65 0 .37 0 .29 0 .47 22 .86 PP-81 57.80 26 .46 2 .05 0 .43 0 .23 0 .22 0 . 58 12 .24 PP-75 57.59 29 .47 1 .87 0 .39 0 .20 0 . 15 0 . 24 10 . 09 PP-7 3 35.67 49 .72 3 .28 0 . 56 0 . 39 0 .29 0 .29 9 . 80 PP-70 54 . 09 22 . 31 5 .81 1 .41 0 .83 0 . 53 0 . 60 14 .42 PP-67 63.96 15 .26 3 .28 1 .10 0 .80 0 .45 0 . 61 14 .54 PP-64 57.50 26 .94 1 .88 0 .68 0 .62 0 .35 0 .70 11 .33 PP-59 37.18 42 . 02 9 .93 1 . 61 0 .71 0 .38 0 .27 7 .91 PP-55 38.26 36 .12 10 .02 1 .00 0 .61 0 .42 0 . 64 12 .92 PP-56 53.49 28 . 09 7 .36 0 .98 0 .70 0 .34 0 .61 8 .42 Mean 46.76 29 . 72 3 .93 0 . 83 0 .62 0 .54 0 . 67 16 .93 S t d 14.42 7 .52 2 .70 0 .39 0 . 42 0 . 60 0 .56 11 .76 Pavement (n = 7) PP-23 60.16 24 .46 3 .79 0 .57 0 .44 0 .27 0 . 30 10 .01 PP-87 76.61 17 .78 0 .93 0 .14 0 . 07 0 . 05 0 . 12 4 .29 PP-100 68.53 21 .54 2 .03 0 .38 0 .26 0 . 16 0 .21 6 .89 PP-79 63 . 08 25 .87 2 .91 0 .36 0 .20 0 . 12 0 . 18 7 .29 PP-68 51. 29 24 .90 5 . 61 1 .43 1 . 02 0 .63 0 .90 14 . 22 PP-65 58 . 34 26 .29 3 . 24 0 .77 0 .48 0 . 33 0 .42 10 . 12 PP-58 62 .14 24 .53 3 .13 0 . 53 0 .43 0 .31 0 .39 8 .54 Mean 62 . 88 23 . 62 3 .09 0 . 60 0 .41 0 .27 0 . 36 8 .77 S t d 7.99 2 .99 1 .45 0 .42 0 .31 0 . 19 0 .26 3 .13 173 W e i g h t (g) o f h e a v y m i n e r a l c o n c e n t r a t e s i n e a c h s i z e f r a c t i o n f r o m p o i n t - b a r and pavement s a m p l e s . F r a c t i o n s (mm) Sample -0.425 -0.212 -0.150 -0.106 -0.075 +0.212 +0.150 +0.106 +0.075 +0.053 P o i n t - b a r (n = 11) PP-16 7.28 1.10 PP-96 7.68 1.60 PP-09 10.32 1.88 PP-94 7.80 2.05 PP-10 4.67 1.29 PP-89 12.59 2.33 PP-81 5.54 1.07 PP-75 3.18 0.77 PP-70 13.82 4.78 PP-67 6.71 3.02 PP-64 3.72 1.31 Pavement (n = 5) PP-87 3.42 0.57 PP-100 4.42 0.85 PP-79 9.59 1.37 PP-68 11.38 3.77 PP-65 10.42 2.41 0.94 0.40 0.09 1.56 4.86 0.20 2.02 0.80 0.34 1.18 1.29 0.98 0.98 0.45 0.29 1.30 0.78 0.23 0.67 0.35 0.07 0.54 0.37 0.12 3.51 2.03 0.52 2.66 1.37 1.13 1.58 0.73 0.41 0.17 0.55 0.21 0.08 0.72 0.30 0.05 3.10 2.09 0.81 1.63 1.01 0.37 174 W e i g h t p e r c e n t h e a v y m i n e r a l c o n c e n t r a t e s f r a c t i o n f r o m p o i n t - b a r and pavement s a m p l e s . i n e a c h s i z e S i z e F r a c t i o n s (mm) Sample -0.425 -0.212 -0.150 -0.106 -0.075 Number +0.212 +0.150 +0.106 +0.075 +0.053 P o i n t - b a r (n = 11) PP-16 2.53 1.21 1.35 0.85 0.16 PP-96 0.57 0.41 0.36 1.19 0.04 PP-09 1.27 0.93 0.88 0.43 0.16 PP-94 0.76 0.68 0.61 0. 68 0.30 PP-10 0.67 0.74 0.86 0.59 0.23 PP-89 0.74 1.02 1.00 0.75 0.14 PP-81 0. 87 0.81 0.95 0.52 0.04 PP-75 0. 60 0. 69 0.95 0.88 0.18 PP-70 0.76 1.08 1.35 1.23 0. 28 PP-67 0.65 0.88 1.06 0.98 0.59 PP-64 0. 61 0.60 0.80 0. 65 0.18 Mean 0.91 0.82 0.92 0.80 0.21 S t d 0. 54 0.22 0.27 0.25 0.14 Pavement (n = 5) PP-87 1.05 1.14 — — 0.42 PP-100 0. 69 0.75 0. 68 0.41 0. 13 PP-79 1.04 1.19 1.13 0.80 0.08 PP-68 0. 69 0.90 1. 03 1.12 0.31 PP-65 1.07 1. 04 1.14 1. 02 0.29 Mean 0.91 1. 00 1. 00 0.84 0.25 S t d 0.18 0.16 0.19 0.27 0.12 G o l d c o n c e n t r a t i o n s (ppb) i n l i g h t m i n e r a l f r a c t i o n s , L i g h t m i n e r a l f r a c t i o n s (mm) 175 Sample -0.425 +0.212 -0.212 +0.150 -0.150 +0.106 -0.106 +0.075 -0.075 +0.053 P o i n t - b a r PP-16 PP-96 PP-09 PP-94 PP-10 PP-89 PP-81 PP-75 PP-70 PP-67 PP-64 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 5 <5 <5 <5 <5 <5 <5 160 <5 <5 <5 10 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 Pavement PP-87 PP-100 PP-79 PP-68 PP-65 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 35 <5 <5 <5 <5 45 <5 <5 <5 <5 A x i a l measurements ( m i c r o n s ) o f e a c h v i s i b l e g o l d g r a i n a n d i t s C o r e y s h a p e f a c t o r (SF) . Sample L - a x i s I - a x i s S - a x i s SF PP-97-1-1 180 150 80 0.80 PP-97-1-2 225 189 95 0.77 PP-97-1-3 156 137 80 0.82 PP-97-1-4 544 380 255 0.98 PP-97-1-5 246 138 100 1.14 PP-97-1-6 309 267 95 0.64 PP-97-1-7 686 554 415 0.96 PP-97-1-8 274 260 200 0.90 PP-97-1-9 442 328 210 0.93 PP-97-1-10 266 240 145 0.82 PP-97-1-11 262 238 145 0.82 PP-97-1-12 714 566 320 0.85 PP-97-1-13 321 180 140 1. 18 PP-97-1-14 261 183 130 1. 01 PP-97-1-15 342 220 160 1.06 PP-97-1-16 153 114 80 0.97 PP-97-1-17 324 228 130 0.90 PP-97-1-18 442 272 175 1. 02 PP-97-1-19 270 207 80 0.71 PP-97-1-20 266 218 160 0.95 PP-97-1-21 394 394 190 0. 69 PP-97-1-22 528 410 175 0.74 PP-97-1-23 1200 864 290 0. 68 PP-97-1-24 442 218 145 1.16 PP-97-1-25 550 350 270 1.10 PP-97-1-26 336 272 175 0.89 PP-97-1-27 237 146 95 1. 03 PP-12-1-1 975 758 190 0.57 PP-12-1-2 189 96 65 1.15 PP-12-1-3 180 93 65 1.16 PP-12-1-4 207 207 95 0.68 PP-12-1-5 246 156 65 0.81 PP-12-1-6 346 230 110 0.85 PP-12-1-7 330 218 80 0.75 PP-12-1-8 234 126 95 1.18 PP-12-1-9 895 736 175 0.54 PP-12-1-10 195 135 50 0.73 PP-12-1-11 432 214 120 1. 06 PP-12-1-12 650 310 130 0.94 PP-12-1-13 279 255 95 0.64 PP-12-1-14 321 234 145 0.92 PP-12-1-15 153 78 55 1.18 PP-12-1-16 294 165 50 0.73 PP-12-1-17 198 99 50 1. 01 PP-12-1-18 432 336 145 0.75 PP-12-1-19 358 278 110 0.71 A x i a l measurements ( c o n t i n u e d ) . Sample L - a x i s I - a x i s S - a x i s SF PP-12-1 -20 210 180 110 0.84 PP-12 -1 -21 330 294 145 0.74 PP-12-1-22 132 99 50 0.82 PP-12-1-23 111 96 30 0.60 PP-12-1-24 114 84 30 0.70 PP-12-1 -25 272 246 95 0.65 PP-101-1 -1 216 129 80 1.02 PP-101-1-2 576 362 175 0.88 PP-101-1-3 165 126 30 0.56 PP-101-1-4 168 108 50 0.85 PP-101-1 -5 325 234 120 0.84 PP-101-1 -6 348 219 80 0.76 P P - 6 9 - 1 - 1 214 180 140 0.96 PP-69-1 -2 297 156 65 0.89 PP-69 -1 -3 311 153 115 1.24 PP-69-1 -4 239 197 95 0.77 P P - 6 9 - 1 - 5 347 311 95 0.58 P P - 6 9 - 1 - 6 343 251 110 0.77 P P - 6 9 - 1 - 7 237 159 80 0.87 PP-69 -1 -8 357 270 95 0.68 P P - 6 9 - 1 - 9 203 90 55 1.17 PP-69-1 -10 548 314 130 0.85 PP-69 -1 -11 256 176 110 0.95 PP-69-1-12 272 180 80 0.82 P P - 6 6 - 1 - 1 713 298 175 1.19 PP-66 -1 -2 604 305 110 0.85 PP-66 -1 -3 436 156 65 1.08 PP-66 -1 -4 404 196 110 1.08 P P - 6 6 - 1 - 5 218 138 50 0.76 P P - 6 6 - 1 - 6 287 200 95 0.83 P P - 6 6 - 1 - 7 444 218 110 1.01 P P - 6 6 - 1 - 8 633 298 80 0.76 P P - 6 6 - 1 - 9 240 185 40 0.53 PP-66-1 -10 302 229 50 0.54 PP-66 -1 -11 189 138 65 0.80 PP-66-1-12 335 207 65 0.71 PP-66-1 -13 165 149 65 0.70 PP-66-1-14 149 147 95 0.81 PP-66-1 -15 75 75 30 0.63 L = l o n g e s t , I = i n t e r m e d i a t e and S = s m a l l e s t a x i s . 178 10f45' 102W R e g i o n a l g e o l o g y o f L o e i r e g i o n , n o r t h e a s t e r n T h a i l a n d ( a f t e r C h a r o e n p r a v a t e t a l , 1976). SD = S i l u r i a n - D e v o n i a n ; D = D e v o n i a n ; C l r C 2 = C a r b o n i f e r o u s ; = P e r m i a n ; PTR-gr = P e r m o - t r i a s s i c g r a n i t e ; PTR-v = P e r m o - t r i a s s i c v o l c a n i c r o c k s ; Q = Q u a t e r n a r y . Shaded a r r o w i n d i c a t e s n o r t h d i r e c t i o n .

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