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Hot brines and recent heavy metal deposits in the Red Sea
Chemical Geology - Elsevier Publishing Company. Amsterdam Printed in The Netherlands
Book Reviews H o t B r i n e s and R e c e n t Heavy M e t a l D e p o s i t s in the R e d Sea. E . T . D e g e n s a n d D.A. R o s s ( E d i t o r s ) , S p r i n g e r , New Y o r k , N.Y., 1969, 600 pp., 220 i l l u s . , DM 1 2 8 . - .
B e t w e e n the t i m e of the o p e n i n g of the Suez C a n a l in 1869 and its c l o s i n g a l m o s t 100 y e a r s l a t e r , p o s s i b l y 100 o r m o r e o c e a n o g r a p h i c r e s e a r c h v e s s e l s t r a v e r s e d the Red Sea without r e a l i z i n g that they w e r e p a s p a s s i n g w i t h i n a few t h o u s a n d feet of what is now r e c o g n i z e d a s one of the g r e a t p o t e n t i a l o r e d e p o s i t s of the e a r t h . In 1948, i n a r o u t i n e h y d r o g r a p h i c s a m p l i n g o p e r a t i o n , a n o m a l o u s b o t t o m w a t e r t e m p e r a t u r e s w e r e noted by o c e a n o g r a p h e r s of the Swedish v e s s e l % l b a t r o s s " . E l e v e n y e a r s l a t e r the b o t t o m w a t e r in the a r e a of the high t e m p e r a t u r e s w a s found to be a b n o r m a l l y s a l i n e . B e t w e e n 1963 and 1967 eight e x p e d i t i o n s w e r e m o u n t e d to i n v e s t i g a t e this u n u s u a l o c e a n o g r a p h i c e n v i r o n m e n t i n the Red Sea. In O c t o b e r , 1966, the R.V. "Chain" with 25 s c i e n t i s t s r e p r e s e n t i n g s e v e n d i f f e r e n t o r g a n i z a t i o n s m a d e about 100 t r a v e r s e s of the r i f t v a l l e y in the hot b r i n e a r e a of the R e d Sea, t a k i n g o v e r 200 w a t e r and s e d i m e n t s a m p l e s . T h e d a t a c o l l e c t e d on t h o s e c r u i s e s a n d s u b s e q u e n t i n v e s t i g a t i o n s of the d a t a a l l o w e d the p r e p a r a t i o n of s o m e 50 p a p e r s by 75 d i f f e r e n t a u t h o r s of s e v e r a l n a t i o n s which have b e e n c o l l e c t e d and r e c e n t l y p u b l i s h e d in t h i s 600-page volume. T h i s v o l u m e is i m p o r t a n t for s e v e r a l r e a s o n s . It r e p r e s e n t s a v e r y high d e g r e e of c o o p e r a t i o n by s c i e n t i s t s v e r s e d in m a n y d i s c i p l i n e s ; it d e s c r i b e s a geologic p r o c e s s which i s now r e c o g n i z e d to be f u n d a m e n t a l i n the f o r m a t i o n of the c o n t i n e n t s a n d i n c o n t r o l l i n g m a n y of the e a r t h ' s c r u s t a l p h e n o m e n a ; and it d e s c r i b e s p r o c e s s e s p r e s e n t l y in o p e r a t i o n , which m a y be f u n d a m e n t a l in the f o r m a t i o n of s o m e of the e a r t h ' s g r e a t ore deposits. T h e Red Sea was o r i g i n a l l y a m a s s i v e f a u l t s y s t e m in the P r e c a m b r i a n r o c k s of the Red Sea B a s i n . In the L a t e C r e t a c e o u s the A r a b i a n P e n i n s u l a w a s thought to b e g i n to d r i f t n o r t h e a s t w a r d r e l a t i v e to A f r i c a and to r o t a t e c o u n t e r c l o c k w i s e with p e r i o d s of m a x i m u m m o t i o n . o c c u r r i n g in M i o c e n e a n d R e c e n t t i m e s . T o d a y , the m a i n body of the Red Sea i s about 1,800 k m i n length and a v e r a g e s about 300 k m in width. T h e l a t e s t p a l e o m a g n e t i c m e a s u r e m e n t s i n d i c a t e that the f l o o r of the Red Sea i s s p r e a d i n g at the r a t e of 1.6 c m p e r y e a r . T h e hot b r i n e a r e a of the R e d Sea l i e s a l m o s t e x a c t l y at its m i d p o i n t . In t h i s a r e a t h r e e b a s i n s have b e e n l o c a t e d a n d s t u d i e d : D i s c o v e r y D e e p , C h a i n Deep and A t l a n t i s II Deep. A l l of t h e s e b a s i n s a r e e n c l o s e d by the 2 , 0 0 0 - m depth c o n t o u r and they a r e s e p a r a t e d by s h a l l o w s i l l s . In the D i s c o v e r y Deep~ a 44°C l a y e r of b r i n e o v e r l i e s i r o n - r i c h s e d i m e n t s which a r e thought, f r o m s e i s m i c p r o b e d a t a j to r e a c h a m a x i m u m t h i c k n e s s of 200 m . In the C h a i n D e e p a 36°C l a y e r of b r i n e o v e r l i e s s e d i m e n t s with a m a x i m u m t h i c k n e s s of a b o u t 50 m . In the A t l a n t i s II D e e p the s e d i m e n t s a r e o v e r l a i n by a 56°C b r i n e which i n t u r n is o v e r l a i n by a 30 m t h i c k l a y e r of 44°C b r i n e . T h e m a x i m u m s e d i m e n t t h i c k n e s s i n this b a s i n is e s t i m a t e d to be about 100 m j but a s in the o t h e r b a s i n s the a v e r a g e Chem. Geol., 7 (1971) 149-152
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t h i c k n e s s a p p e a r s to be about 25 m. Only in the A t l a n t i s II Deep have the s e d i m e n t s been noted to contain high q u a n t i t i e s of heavy m e t a l s such as c o p p e r and zinc. The g e n e r a l l y a c c e p t e d t h e o r y c o n c e r n i n g the f o r m a t i o n of the hot b r i n e s is that they a r e fed by a s e a - f l o o r s p r i n g within the A t l a n t i s II Deep. The w a t e r supply for this s p r i n g i s thought to be at the s o u t h e r n end of the Red Sea. T h e r e w a t e r c i r c u l a t e s downward through e v a p o r i t e s e d i m e n t s w h e r e it d i s s o l v e s s a l t s , b e c o m e s m o r e d e n s e and t h e r e b y d e v e l o p s a d r i v i n g m e c h a n i s m . In m o v i n g through 400 km of r o c k f i s s u r e s between the s o u t h e r n Red Sea and the hot b r i n e a r e a s , the flowing w a t e r t a k e s into solution many of the heavy m e t a l s found t h e r e i n and a r e h e a t e d by the host r o c k s . A f t e r i s s u i n g at the ocean floor~ the hot b r i n e with its heavy m e t a l content m i x e s with the o v e r l y i n g Red Sea w a t e r and the p r e c i p i t a t i o n of v a r i o u s m i n e r a l s occurs. C o r e s to a m a x i m u m depth of about 10 m have been taken of the s e d i m e n t s u n d e r l y i n g the hot b r i n e s . T h e s e c o r e s show a n u m b e r of s e d i m e n t f a c i e s with i r o n m o n t m o r i l l o n i t e being found n e a r the s e d i m e n t s u r f a c e , u n d e r l a i n by a g o e t h i t e l a y e r and then a sulphide l a y e r . I n t e r s p e r s e d in t h e s e s e d i m e n t l a y e r s in v a r i o u s p l a c e s a r e a m a n g a n i t e f a c i e s and d e t r i t a l m i n e r a l f a c i e s . Changes in the r a t e of flow and c o m p o s i t i o n of the i s s u i n g b r i n e and changes in the c h e m i c a l e n v i r o n m e n t of the o v e r l y i n g w a t e r with t i m e a r e thought to c a u s e the p r e c i p i t a t i o n of the d i f f e r e n t m i n e r a l s at varying times. F r o m an e c o n o m i c standpoint, only the A t l a n t i s II Deep a p p e a r s to c a r r y i n t e r e s t i n g m e t a l v a l u e s . A v e r a g e a s s a y s of m e t a l s in the s e d i m e n t s of this deep a r e : i r o n , 29%; zinc, 3.4%; copper~ 1.3%; s i l v e r , 54 p . p . m . ; and gold 0.5 p . p . m . T h e s e d i m e n t s contain f r o m 55% to 96% of i n t e r s t i t i a l b r i n e , but a v e r a g e about 85%. The t o t a l b r i n e - f r e e s e d i m e n t in the upper 10 m of the A t l a n t i s II Deep is e s t i m a t e d to be about 50 m i l l i o n tons. J.L. MERO (La Jolla, Calif. i
A d v a n c e s in O r g a n i c G e o c h e m i s t r y , 1966. G.D. Hobson and G.C. S p e e r s ( E d i t o r s ) , P e r g a m o n , Oxford, 1970, 577 pp., £8.0.0.
This book is c o m p r i s e d of p a p e r s p r e s e n t e d at the T h i r d I n t e r n a t i o n a l Meeting on O r g a n i c G e o c h e m i s t r y which was held in London in S e p t e m b e r , 1966, u n d e r the a u s p i c e s of the E u r o p e a n B r a n c h of the O r g a n i c G e o c h e m i c a l Division of the G e o c h e m i c a l Society. P r o f e s s o r Hobson and Mr. S p e e r s , e d i t o r s , the a u t h o r s , and the m e e t i n g o r g a n i z e r s a r e to be c o m m e n d e d f o r an e x c e l l e n t book and the m e e t i n g that l e d to i t s publication. The book c o n s i s t s of 27 p a p e r s w r i t t e n in English, 4 p a p e r s in F r e n c h , and 3 a b s t r a c t s . Although the p u b l i c a t i o n of the book p o s t d a t e s the p r e s e n t a tion of the p a p e r s by m o r e than t h r e e y e a r s , the book contains a w e a l t h of i n f o r m a t i o n on a n a l y t i c a l m e t h o d s and r e s u l t s a s well a s i m p o r t a n t t h e o r e t i cal concepts that r e m a i n of g r e a t v a l u e to o r g a n i c g e o c h e m i s t s . The book d e a l s with the i s o t o p i c , c o m p o s i t i o n a l , and e n v i r o n m e n t a l s t u d i e s of o r g a n i c m a t e r i a l s , h y d r o g e n i s o t o p i c f r a c t i o n a t i o n in w a t e r s p a s s i n g through t r e e s , c r u d e oil c o r r e l a t i o n s , diffusion of light h y d r o c a r b o n s 150
Chum= Geol., 7 (1971) 149-152
Book Reviews H o t B r i n e s and R e c e n t Heavy M e t a l D e p o s i t s in the R e d Sea. E . T . D e g e n s a n d D.A. R o s s ( E d i t o r s ) , S p r i n g e r , New Y o r k , N.Y., 1969, 600 pp., 220 i l l u s . , DM 1 2 8 . - .
B e t w e e n the t i m e of the o p e n i n g of the Suez C a n a l in 1869 and its c l o s i n g a l m o s t 100 y e a r s l a t e r , p o s s i b l y 100 o r m o r e o c e a n o g r a p h i c r e s e a r c h v e s s e l s t r a v e r s e d the Red Sea without r e a l i z i n g that they w e r e p a s p a s s i n g w i t h i n a few t h o u s a n d feet of what is now r e c o g n i z e d a s one of the g r e a t p o t e n t i a l o r e d e p o s i t s of the e a r t h . In 1948, i n a r o u t i n e h y d r o g r a p h i c s a m p l i n g o p e r a t i o n , a n o m a l o u s b o t t o m w a t e r t e m p e r a t u r e s w e r e noted by o c e a n o g r a p h e r s of the Swedish v e s s e l % l b a t r o s s " . E l e v e n y e a r s l a t e r the b o t t o m w a t e r in the a r e a of the high t e m p e r a t u r e s w a s found to be a b n o r m a l l y s a l i n e . B e t w e e n 1963 and 1967 eight e x p e d i t i o n s w e r e m o u n t e d to i n v e s t i g a t e this u n u s u a l o c e a n o g r a p h i c e n v i r o n m e n t i n the Red Sea. In O c t o b e r , 1966, the R.V. "Chain" with 25 s c i e n t i s t s r e p r e s e n t i n g s e v e n d i f f e r e n t o r g a n i z a t i o n s m a d e about 100 t r a v e r s e s of the r i f t v a l l e y in the hot b r i n e a r e a of the R e d Sea, t a k i n g o v e r 200 w a t e r and s e d i m e n t s a m p l e s . T h e d a t a c o l l e c t e d on t h o s e c r u i s e s a n d s u b s e q u e n t i n v e s t i g a t i o n s of the d a t a a l l o w e d the p r e p a r a t i o n of s o m e 50 p a p e r s by 75 d i f f e r e n t a u t h o r s of s e v e r a l n a t i o n s which have b e e n c o l l e c t e d and r e c e n t l y p u b l i s h e d in t h i s 600-page volume. T h i s v o l u m e is i m p o r t a n t for s e v e r a l r e a s o n s . It r e p r e s e n t s a v e r y high d e g r e e of c o o p e r a t i o n by s c i e n t i s t s v e r s e d in m a n y d i s c i p l i n e s ; it d e s c r i b e s a geologic p r o c e s s which i s now r e c o g n i z e d to be f u n d a m e n t a l i n the f o r m a t i o n of the c o n t i n e n t s a n d i n c o n t r o l l i n g m a n y of the e a r t h ' s c r u s t a l p h e n o m e n a ; and it d e s c r i b e s p r o c e s s e s p r e s e n t l y in o p e r a t i o n , which m a y be f u n d a m e n t a l in the f o r m a t i o n of s o m e of the e a r t h ' s g r e a t ore deposits. T h e Red Sea was o r i g i n a l l y a m a s s i v e f a u l t s y s t e m in the P r e c a m b r i a n r o c k s of the Red Sea B a s i n . In the L a t e C r e t a c e o u s the A r a b i a n P e n i n s u l a w a s thought to b e g i n to d r i f t n o r t h e a s t w a r d r e l a t i v e to A f r i c a and to r o t a t e c o u n t e r c l o c k w i s e with p e r i o d s of m a x i m u m m o t i o n . o c c u r r i n g in M i o c e n e a n d R e c e n t t i m e s . T o d a y , the m a i n body of the Red Sea i s about 1,800 k m i n length and a v e r a g e s about 300 k m in width. T h e l a t e s t p a l e o m a g n e t i c m e a s u r e m e n t s i n d i c a t e that the f l o o r of the Red Sea i s s p r e a d i n g at the r a t e of 1.6 c m p e r y e a r . T h e hot b r i n e a r e a of the R e d Sea l i e s a l m o s t e x a c t l y at its m i d p o i n t . In t h i s a r e a t h r e e b a s i n s have b e e n l o c a t e d a n d s t u d i e d : D i s c o v e r y D e e p , C h a i n Deep and A t l a n t i s II Deep. A l l of t h e s e b a s i n s a r e e n c l o s e d by the 2 , 0 0 0 - m depth c o n t o u r and they a r e s e p a r a t e d by s h a l l o w s i l l s . In the D i s c o v e r y Deep~ a 44°C l a y e r of b r i n e o v e r l i e s i r o n - r i c h s e d i m e n t s which a r e thought, f r o m s e i s m i c p r o b e d a t a j to r e a c h a m a x i m u m t h i c k n e s s of 200 m . In the C h a i n D e e p a 36°C l a y e r of b r i n e o v e r l i e s s e d i m e n t s with a m a x i m u m t h i c k n e s s of a b o u t 50 m . In the A t l a n t i s II D e e p the s e d i m e n t s a r e o v e r l a i n by a 56°C b r i n e which i n t u r n is o v e r l a i n by a 30 m t h i c k l a y e r of 44°C b r i n e . T h e m a x i m u m s e d i m e n t t h i c k n e s s i n this b a s i n is e s t i m a t e d to be about 100 m j but a s in the o t h e r b a s i n s the a v e r a g e Chem. Geol., 7 (1971) 149-152
149
t h i c k n e s s a p p e a r s to be about 25 m. Only in the A t l a n t i s II Deep have the s e d i m e n t s been noted to contain high q u a n t i t i e s of heavy m e t a l s such as c o p p e r and zinc. The g e n e r a l l y a c c e p t e d t h e o r y c o n c e r n i n g the f o r m a t i o n of the hot b r i n e s is that they a r e fed by a s e a - f l o o r s p r i n g within the A t l a n t i s II Deep. The w a t e r supply for this s p r i n g i s thought to be at the s o u t h e r n end of the Red Sea. T h e r e w a t e r c i r c u l a t e s downward through e v a p o r i t e s e d i m e n t s w h e r e it d i s s o l v e s s a l t s , b e c o m e s m o r e d e n s e and t h e r e b y d e v e l o p s a d r i v i n g m e c h a n i s m . In m o v i n g through 400 km of r o c k f i s s u r e s between the s o u t h e r n Red Sea and the hot b r i n e a r e a s , the flowing w a t e r t a k e s into solution many of the heavy m e t a l s found t h e r e i n and a r e h e a t e d by the host r o c k s . A f t e r i s s u i n g at the ocean floor~ the hot b r i n e with its heavy m e t a l content m i x e s with the o v e r l y i n g Red Sea w a t e r and the p r e c i p i t a t i o n of v a r i o u s m i n e r a l s occurs. C o r e s to a m a x i m u m depth of about 10 m have been taken of the s e d i m e n t s u n d e r l y i n g the hot b r i n e s . T h e s e c o r e s show a n u m b e r of s e d i m e n t f a c i e s with i r o n m o n t m o r i l l o n i t e being found n e a r the s e d i m e n t s u r f a c e , u n d e r l a i n by a g o e t h i t e l a y e r and then a sulphide l a y e r . I n t e r s p e r s e d in t h e s e s e d i m e n t l a y e r s in v a r i o u s p l a c e s a r e a m a n g a n i t e f a c i e s and d e t r i t a l m i n e r a l f a c i e s . Changes in the r a t e of flow and c o m p o s i t i o n of the i s s u i n g b r i n e and changes in the c h e m i c a l e n v i r o n m e n t of the o v e r l y i n g w a t e r with t i m e a r e thought to c a u s e the p r e c i p i t a t i o n of the d i f f e r e n t m i n e r a l s at varying times. F r o m an e c o n o m i c standpoint, only the A t l a n t i s II Deep a p p e a r s to c a r r y i n t e r e s t i n g m e t a l v a l u e s . A v e r a g e a s s a y s of m e t a l s in the s e d i m e n t s of this deep a r e : i r o n , 29%; zinc, 3.4%; copper~ 1.3%; s i l v e r , 54 p . p . m . ; and gold 0.5 p . p . m . T h e s e d i m e n t s contain f r o m 55% to 96% of i n t e r s t i t i a l b r i n e , but a v e r a g e about 85%. The t o t a l b r i n e - f r e e s e d i m e n t in the upper 10 m of the A t l a n t i s II Deep is e s t i m a t e d to be about 50 m i l l i o n tons. J.L. MERO (La Jolla, Calif. i
A d v a n c e s in O r g a n i c G e o c h e m i s t r y , 1966. G.D. Hobson and G.C. S p e e r s ( E d i t o r s ) , P e r g a m o n , Oxford, 1970, 577 pp., £8.0.0.
This book is c o m p r i s e d of p a p e r s p r e s e n t e d at the T h i r d I n t e r n a t i o n a l Meeting on O r g a n i c G e o c h e m i s t r y which was held in London in S e p t e m b e r , 1966, u n d e r the a u s p i c e s of the E u r o p e a n B r a n c h of the O r g a n i c G e o c h e m i c a l Division of the G e o c h e m i c a l Society. P r o f e s s o r Hobson and Mr. S p e e r s , e d i t o r s , the a u t h o r s , and the m e e t i n g o r g a n i z e r s a r e to be c o m m e n d e d f o r an e x c e l l e n t book and the m e e t i n g that l e d to i t s publication. The book c o n s i s t s of 27 p a p e r s w r i t t e n in English, 4 p a p e r s in F r e n c h , and 3 a b s t r a c t s . Although the p u b l i c a t i o n of the book p o s t d a t e s the p r e s e n t a tion of the p a p e r s by m o r e than t h r e e y e a r s , the book contains a w e a l t h of i n f o r m a t i o n on a n a l y t i c a l m e t h o d s and r e s u l t s a s well a s i m p o r t a n t t h e o r e t i cal concepts that r e m a i n of g r e a t v a l u e to o r g a n i c g e o c h e m i s t s . The book d e a l s with the i s o t o p i c , c o m p o s i t i o n a l , and e n v i r o n m e n t a l s t u d i e s of o r g a n i c m a t e r i a l s , h y d r o g e n i s o t o p i c f r a c t i o n a t i o n in w a t e r s p a s s i n g through t r e e s , c r u d e oil c o r r e l a t i o n s , diffusion of light h y d r o c a r b o n s 150
Chum= Geol., 7 (1971) 149-152