676086 - british columbia · to an absence of documentation and hence,, to the absence of a...
TRANSCRIPT
676086 U o i o c L j Craggy
\\ l vP/ |3
"CORBET-TYPE" VOLCANOGENIC SULPHIDE DEPOSITS,
AND THEIR RELATIONSHIP TO OTHER MAFIC
VOLCANIC-HOSTED MASSIVE SULPHIDE ORES
BY
J. S . FOX
Teck E x p l o r a t i o n s L i m i t e d T o r o n t o , Canada
Paper p r e s e n t e d a t the 86th Annual G e n e r a l M e e t i n g o f the Canadian I n s t i t u t e o f M i n i n g and M e t a l l u r g y ,
Ottawa, A p r i l 1984.
ABSTRACT
A number o f d e p o s i t s have been i d e n t i f i e d i n Canada and
S c a n d i n a v i a which s h a r e many o f the f e a t u r e s o f the C o r b e t
mine, i n Quebec, They are a l l h o s t e d by b a s a l t or a n d e s i t e
o f i s l a n d a r c a f f i n i t y , and are o f t e n accompanied by minor
g r a p h i t i c a r g i l l i t e and/or o r e zone c a r b o n a t e . They have
c o n s i s t e n t l y anomalous Co and N i c o n t e n t s , and are i n c l i n e d
t o g o l d e n r i c h m e n t . The p r e s e n c e of s t o c k w o r k - t y p e
a l t e r a t i o n a t some o f t h e s e s u g g e s t s t h a t d e p o s i t s o f t h i s
t y p e c o n s t i t u t e a p r o x i m a l m e t a l l o g e n i c c l a s s t h a t i s
d i s t i n c t from m a f i c v o l c a n i c - h o s t e d d e p o s i t s of the B e s s h i -
and C y p r u s - t y p e , and from K u r o k o - t y p e d e p o s i t s .
" C o r b e t - t y p e " d e p o s i t s r e p r e s e n t a new e x p l o r a t i o n
o p p o r t u n i t y . The r e c e n t d i s c o v e r y o f the V i s c a r i a d e p o s i t
i n Sweden s u g g e s t s t h a t " w o r l d c l a s s " d e p o s i t s o f t h i s type
remain t o be found i n Canada.
INTRODUCTION
S i g n i f i c a n t base meta l d i s c o v e r i e s , made r e c e n t l y i n
g r e e n s t o n e b e l t s i n Canada and Sweden ( e . g . , C o r b e t ,
Windy Craggy, V i s c a r i a ) , s u ggest t h a t the m a f i c v o l c a n i c
environment may be an i m p o r t a n t , untapped source of economic
s u l p h i d e s i n the Canadian S h i e l d . These r e c e n t d i s c o v e r i e s
a r e m e t a l l o g e n i c a l l y d i s t i n c t from B e s s h i - and C y p r u s - t y p e
d e p o s i t s , which a r e r e l a t i v e l y common i n P r o t e r o z o i c and
P h a n e r o z o i c m a f i c v o l c a n i c t e r r a i n s . I n s t e a d , they seem
t o b e l o n g t o a p r e v i o u s l y u n r e c o g n i z e d c a t e g o r y , t y p i f i e d
by the C o r b e t d e p o s i t i n Quebec, which appears t o have
s i g n i f i c a n t p o t e n t i a l i n the Archean r o c k s of the Canadian
S h i e l d .
A l t h o u g h t he r e c o g n i t i o n o f t h e s e " C o r b e t - t y p e "
d e p o s i t s has g e n e r a t e d a moderate amount o f e x p l o r a t i o n
a c t i v i t y i n S c a n d i n a v i a , l i t t l e i n t e r e s t has been shown
i n them i n Canada, d e s p i t e t h e i r i n c l i n a t i o n t o g o l d -
e n r i c h m e n t . T h i s l a c k o f Canadian a c t i v i t y i s p r o b a b l y due
t o an absence o f documentation and, hence, t o the absence o f
a m e t a l l o g e n i c model. T h i s paper d e s c r i b e s the p r e l i m i n a r y
r e s u l t s o f some r e s e a r c h , which was under t a k e n s p e c i f i c a l l y
t o d e l i n e a t e such m e t a l l o g e n i c g u i d e l i n e s .
- 2 -
MAFIC VOLCANIC-HOSTED MASSIVE SULPHIDE DEPOSITS
U n t i l r e c e n t l y , o n l y two t y p e s o f p r o x i m a l , m a f i c
v o l c a n i c - h o s t e d v o l c a n o g e n i c s u l p h i d e d e p o s i t s have been
r e c o g n i z e d — B e s s h i - and C y p r u s - t y p e s . B e s s h i - t y p e
m i n e r a l i z a t i o n i s c h a r a c t e r i z e d by an a s s o c i a t i o n w i t h
c o n t i n e n t a l l y - d e r i v e d c l a s t i c s e d i m e n t , and w i t h s u b o r d i n a t e
b a s a l t o f o c e a n i c o r i n t r a - p l a t e c h e m i s t r y . D e p o s i t s o f
t h i s t y p e seem t o form i n immature, e p i c o n t i n e n t a l r i f t i n g
e n v i r o n m e n t s (Fox, 1984). C y p r u s - t y p e d e p o s i t s , such as
tho s e c u r r e n t l y f o r m i n g on the E a s t P a c i f i c and Juan de Fuca
R i d g e s , as w e l l as those which a r e thought to have formed i n
b a c k - a r c b a s i n s , c o n s t i t u t e a second c l a s s , are a s s o c i a t e d
w i t h b a s a l t s o f o c e a n i c c h a r a c t e r and have v i r t u a l l y no
accompanying m e c h a n i c a l sediment ( e . g . , Normark, e t a l . ,
1982).
C o r b e t - t y p e d e p o s i t s c o n s t i t u t e a t h i r d , b a s a l t -
r e l a t e d , m e t a l l o g e n i c c a t e g o r y . As w i l l be shown, they are
a s s o c i a t e d w i t h r o c k s s i m i l a r t o th o s e formed d u r i n g
t h e i n i t i a l s t a g e s o f a r c development, which c l e a r l y
c o n t r a s t s w i t h the p e t r o g e n e t i c a s s o c i a t i o n o f B e s s h i - and
C y p r u s - t y p e o r e s .
- 3 -
THE CORBET DEPOSIT
The Cor b e t d e p o s i t i s found i n the A b i t i b i g r e e n s t o n e
b e l t , 7 km n o r t h w e s t of the town of Noranda ( F i g u r e 1 ) . I t
came i n t o p r o d u c t i o n i n 1980, w i t h r e s e r v e s o f 2.7 M t o n n e s ,
g r a d i n g 3.1% Cu, 2.8% Zn, 23 g/tonne Ag and 1 g/tonne Au.
The d e p o s i t o c c u r s i n the m a f i c v o l c a n i c s o f the
Archean B l a k e R i v e r Group and, i n p a r t i c u l a r , i n the
F l a v r i a n A n d e s i t e , which l i e s at the base o f one o f the
m a f i c t o f e l s i c e r r u p t i v e c y c l e s r e c o g n i z e d i n the c e n t r a l
p a r t o f the Group. Most of the K u r o k o - t y p e m i n e r a l i z a t i o n
i n t h e Noranda camp i s found a t the t o p o f t h e same c y c l e ,
1,000 m s t r a t i g r a p h i c a l l y above the Corb e t o r e s (Knuckey and
W a t k i n s , 1982; W a t k i n s , 1980 - F i g u r e 2 ) .
The F l a v r i a n A n d e s i t e i n the v i c i n i t y o f C o r b e t
c o n s i s t s of b a s a l t and a n d e s i t e , and i s c h a r a c t e r i z e d by a
d i f f e r e n t i a t i o n t r e n d t h a t s t r a d d l e s the boundary between
c a l c - a l k a l i n e and t h o l e i i t i c on an AFM p l o t . Dimroth et
a l . (1982) b e l i e v e t h e s e r o c k s t o r e p r e s e n t p r i m i t i v e a r c
l a v a s , e x t r u d e d d u r i n g the p r e - c a l d e r a phase of the Noranda
s t r a t o v o l c a n i c complex. G e l i n a s et a l . (1984) b e l i e v e them
t o have formed as a r e s u l t of c o n t i n e n t a l r i f t i n g , and deep-
mantle c r u s t a l f u s i o n .
- 4 -
The F l a v r i a n A n d e s i t e i s composed of m a s s i v e , p i l l o w e d
and l o c a l a m y g d a l o i d a l f l o w s , and minor h y a l o c l a s t i t e .
C o a r s e , v e s i c u l a r m a f i c p y r o c l a s t i c r o c k s are i m p o r t a n t
c o n s t i t u e n t s o f t h i s u n i t i n the v i c i n i t y o f C o r b e t .
I s o p a c h maps o f the a n d e s i t e r e v e a l the p r e s e n c e o f a
p a l e o t o p o g r a p h i c h i g h i n the v i c i n i t y o f the d e p o s i t . These
f e a t u r e s suggest m a f i c v o l c a n i c doming w h i c h , a c c o r d i n g t o
Knuckey and W a t k i n s (1982), was l o c a l i z e d by the f o o t w a l l
M cDougall and D e s p i n a f a u l t s ( F i g u r e 3 ) .
The main o r e zone at C o r b e t i s a l e n s o i d , s t r a t i f o r m
body which i s d i r e c t l y u n d e r l a i n by a s m a l l but d i s t i n c t
s t o c k w o r k a l t e r a t i o n p i p e . The a l t e r a t i o n i s c h a r a c t e r i z e d
m a i n l y by Fe- and Mg-enr ichment and by S i - , Ca- and Na
d e p l e t i o n (Knuckey and W a t k i n s , 1982), but s p o r a d i c
Na-enrichment at the o u t e r edge of t h e a l t e r a t i o n e n v e l o p e
may a l s o be p r e s e n t . T h i s a l t e r a t i o n has been superimposed
on an e a r l i e r e v e n t o f s p i l i t i z a t i o n and e p i d o t i z a t i o n
(H. G i b s o n , p e r s . comm., 1984).
M i n e r a l i z a t i o n i n the main ore zone c o n s i s t s of massive
t o semi-massive p y r r h o t i t e , p y r i t e , c h a l c o p y r i t e , s p h a l e r i t e
and m a g n e t i t e , and a t t a i n s a t h i c k n e s s of up t o 70 m above
the a l t e r a t i o n s t o c k w o r k . The main o r e l e n s e e x h i b i t s the
hanging w a l l t o f o o t w a l l Cu t o Zn z o n i n g t y p i c a l o f o t h e r
v o l c a n o g e n i c d e p o s i t s i n the r e g i o n .
- 5 -
OTHER "CORBET-TYPE" DEPOSITS
A number o f o t h e r C o r b e t - t y p e d e p o s i t s can be
i d e n t i f i e d from the l i t e r a t u r e w i t h a moderate degree o f
c e r t a i n t y , e.g., H a v e r i (Kahkonen et a l . , 1981), Pahtavuoma
( I n k i n e n , 1979), B i d j o v a g g e (Hagen, 1982; H o l l a n d e r , 1979)
and C o r o n a t i o n ( F r o e s e , 1969 - T a b l e 1 ) . Other d e p o s i t s
which may b e l o n g i n t h i s c a t e g o r y a r e New I n s c o and Magusi
w h i c h , l i k e C o r b e t , appear t o be h o s t e d by a n d e s i t e o c c u r i n g
low i n the B l a k e R i v e r sequence ( L a r s o n , 1983), and the
l a r g e , newly d i s c o v e r e d Windy Craggy d e p o s i t i n B r i t i s h
C o l u m b i a . However, the Maybrun and V i s c a r i a d e p o s i t s
i l l u s t r a t e t h e main f e a t u r e s o f t h i s group p a r t i c u l a r l y
w e l l , and are b r i e f l y d e s c r i b e d below.
(a) Maybrun
The Maybrun Cu-Au d e p o s i t i s l o c a t e d i n the m a f i c
v o l c a n i c s o f the Wabigoon g r e e n s t o n e b e l t , 70 km southwest
o f Dryden ( F i g u r e 4 ) . I t c o n t a i n s i n d i c a t e d r e s e r v e s o f
2.8 M tonnes g r a d i n g 1.1% Cu and 3 g/tonne Au, and i s
t h e l a r g e s t of s e v e r a l s i m i l a r d e p o s i t s i n the a r e a
( S e t t e r f i e l d , 1980; S e t t e r f i e l d e t a l . , 1983).
- 6 -
The d e p o s i t o c c u r s i n r o c k s p r o b a b l y e q u i v a l e n t t o the
Archean Populus V o l c a n i c s , a sequence t h a t i s dominated by
m a f i c v o l c a n i c f l o w s , but which a l s o c o n t a i n s minor
a n d e s i t e , m a f i c p y r o c l a s t i c s , g r a p h i t i c a r g i l l i t e and
c h e r t . South o f Maybrun, i n the v i c i n i t y o f the Cameron
Lake g o l d d e p o s i t , the Populus V o l c a n i c s may be u n d e r l a i n by
a sequence o f t h o l e i i t i c t o c a l c - a l k a l i n e m a f i c t o
i n t e r m e d i a t e f l o w s and p y r o c l a s t i c s . A t Rowan Lake, t h e s e ,
i n t u r n , a r e u n d e r l a i n by e x t e n s i v e magnesian t h o l e i i t i c
v o l c a n i c s o f p r o b a b l e o c e a n i c a f f i n i t y ( D a v i e s , 1973;
T r o w e l l e t a l . , 1980; B l a c k b u r n , p e r s . comm., 1984).
The P o p u l u s V o l c a n i c s i n the v i c i n i t y o f Maybrun
e x h i b i t a r e s t r i c t e d , i r o n - r i c h t h o l e i i t i c magmatic t r e n d on
an AFM p l o t . B l a c k b u r n (1980) and L a n g f o r d and Morin (1976)
have emphasized t h e a r c - l i k e g e o c h e m i c a l and m o r p h o l o g i c a l
n a t u r e of p o s s i b l y e q u i v a l e n t r o c k s e l s e w h e r e i n the r e g i o n ,
such as the Upper Wabigoon V o l c a n i c s .
M i n e r a l i z a t i o n at Maybrun c o n s i s t s o f p y r r h o t i t e ,
c h a l c o p y r i t e , minor s p h a l e r i t e and, l o c a l l y , c a r b o n a t e i n
p i l l o w i n t e r s t i c e s a t the tops o f t h r e e s t r a t i g r a p h i c a l l y
s e p a r a t e b a s a l t i c f l o w s . In each o f t h e s e , s h a r p c o n t a c t s
are o b s e r v e d between m i n e r a l i z e d p i l l o w e d f l o w s and
o v e r l y i n g m a s s i v e f l o w s (H. Matthews, p e r s . comm., 1984).
- 7 -
Bedded s u l p h i d e s have not been f o u n d , and t h i s i n d i c a t e s
t h a t a l t h o u g h t h e Maybrun o r e s a r e v o l c a n o g e n i c and
s t r a t a b o u n d , t h e y are not e x h a l a t i v e . S i m i l a r i n t e r - p i l l o w
m i n e r a l i z a t i o n i s p r e s e n t l o c a l l y a t C o r b e t , and p r o b a b l y
r e f l e c t s a m u l t i - p h a s e e v o l u t i o n o f the r e l e v a n t
h y d r o t h e r m a l c e l l ( v i z . , s u b s u r f a c e m i x i n g w i t h c o o l
s e a w a t e r ) .
Three d i s t i n c t f l o w u n i t s have been r e c o g n i z e d on the
mine p r o p e r t y , and c o n s i s t o f a p h y r i c , p l a g i o c l a s e - p h y r i c
and c a r b o n a t i z e d a p h y r i c b a s a l t . Lenses of v e s i c u l a r m a f i c
l a p i l l i t u f f a r e l o c a l l y i n t e r c a l a t e d w i t h t h e s e f l o w s . The
b u l k of the known Cu-Au o r e o c c u r s near the c o n t a c t between
the p l a g i o c l a s e - p o r p h y r i t i c and the c a r b o n a t i z e d a p h y r i c
b a s a l t i c u n i t s (H. Matthews, p e r s . comm., 1984 - F i g u r e 5 ) .
The b a s a l t s a s s o c i a t e d w i t h the m i n e r a l i z a t i o n have been
m o d e r a t e l y d e p l e t e d i n Ca and Na, and e n r i c h e d i n Fe, Mg
and K ( S e t t e r f i e l d , 1980; S e t t e r f i e l d e t a l . , 1983).
(b) V i s c a r i a
The V i s c a r i a d e p o s i t i s l o c a t e d o n l y 3 km west o f the
i r o n o re complex at K i r u n a , Sweden. I t i s a "world c l a s s "
d e p o s i t , h a v i n g gone i n t o p r o d u c t i o n i n 1983 w i t h e s t i m a t e d
r e s e r v e s of 24 M tonnes g r a d i n g 2.0% Cu t o 400 m i n t h r e e
- 8 -
s t r a t i g r a p h i c a l l y s e p a r a t e zones. P o s s i b l e r e s e r v e s exceed
50 M t o n n e s , and g rades i n c r e a s e t o t h e 4-5% Cu range w i t h
d e p t h . A l t h o u g h the Zn and p r e c i o u s m e t a l c o n t e n t s of the
o r e are low near s u r f a c e , t h e r e i s some i n d i c a t i o n t h a t the
l a t t e r i n c r e a s e i n grade at depth ( L . G o d i n , p e r s . comm.,
1984; M i n i n g Magazine, 1983).
The d e p o s i t o c c u r s i n t h e K i r u n a G r e e n s t o n e Group, a
sequence of e a s t - f a c i n g subaqueous v o l c a n i c s composed o f
b a s a l t i c f l o w s , m a f i c t u f f and s u b o r d i n a t e g r a p h i t i c
a r g i l l i t e and d o l o m i t i c l i m e s t o n e ( F i g u r e 6 ) . To the e a s t ,
the K i r u n a g r e e n s t o n e s are u n c o n f o r m a b l y o v e r l a i n by the
P r o t e r o z o i c a n d e s i t e , r h y o l i t e and t r a c h y t e o f the K i r u n a
P o r p h y r y Group, i n which the K i r u n a i r o n o r e s are found.
The K i r u n a G r e e n s t o n e Group i s thought t o be c o e v a l w i t h the
Archean K i t t i l a g r e e n s t o n e complex o f n o r t h e r n Norway and
F i n l a n d , i n which s i m i l a r " C o r b e t - t y p e " d e p o s i t s o c c u r
( e . g . , B i d j o v a g g e , Pahtavuoma - F o r s e l l and G o d i n , 1980;
Hagen, 1982 ; Lundberg and S m e l l i e , 1979 ; G a a l et a l . , 1978 ;
I n k i n e n , 1979 - F i g u r e 7 ) .
The K i r u n a G r e e n s t o n e s i n the v i c i n i t y o f V i s c a r i a
e x h i b i t a r e s t r i c t e d t h o l e i i t i c d i f f e r e n t i a t i o n t r e n d on an
AFM d i a g r a m . A l t h o u g h no t e c t o n i c or p e t r o g e n e t i c m o d e l l i n g
has p r e v i o u s l y been attempted f o r t h e s e r o c k s , the p resence
- 9 -
o f an o l d e r g r a n i t i c s u b s t r a t u m , the abundance of d i s t a l
m a f i c p y r o c l a s t i c r o c k s and a s s o c i a t e d f i n e - g r a i n e d c l a s t i c
s e d i m e n t , and the absence of o p h i o l i t e - e q u i v a l e n t i n t r u s i v e
r o c k s suggest an a r c - l i k e e nvironment o f d e p o s i t i o n .
M i n e r a l i z a t i o n a t V i s c a r i a i s c o n f i n e d t o b a s a l t - h o s t e d
zones o f g r a p h i t i c a r g i l l i t e and l i m e s t o n e ( F i g u r e 8 ) .
P y r r h o t i t e and c h a l c o p y r i t e a r e the most abundant s u l p h i d e s ,
but s p h a l e r i t e and m a g n e t i t e a r e a l s o common. No e v i d e n c e
o f f o c u s s e d h y d r o t h e r m a l a l t e r a t i o n has y e t been f o u n d ,
a l t h o u g h s c a t t e r e d a reas of s c a p o l i t i z a t i o n , and p e r v a s i v e
s p i l i t i z a t i o n , and e p i d o t i z a t i o n a r e known i n t h e
s u r r o u n d i n g b a s a l t s ( L. G o d i n , p e r s . comm., 1984).
BASALT GEOCHEMISTRY
S i g n i f i c a n t c o m p o s i t i o n a l o v e r l a p e x i s t s between i s l a n d
a r c b a s a l t ( I A B ) , "normal" m i d - o c e a n i c b a s a l t (N-MORB) and
b a s a l t from back a r c b a s i n s (BABB), d e s p i t e t h e i r d i f f e r e n t
p a r e n t a g e . As a r e s u l t , many c o n v e n t i o n a l g e o c h e m i c a l
d i s c r i m i n a n t s , such as those which use e l e m e n t a l r a t i o s o f
h i g h f i e l d s t r e n g t h c a t i o n s , o f t e n g i v e u n a c c e p t a b l e
p e t r o g e n e t i c s e p a r a t i o n ( e . g . , P e r f i t et a l . , 1980; Hawkins,
1980). I n c o n c l u s i v e r e s u l t s o f t h i s s o r t were o b t a i n e d f o r
- 10 -
a n a l y s e s of r e l a t i v e l y u n a l t e r e d h o s t b a s a l t and b a s a l t i c
a n d e s i t e from C o r b e t , Maybrun and V i s c a r i a , when p l o t t e d on
P i e r c e and Cann's (1973) T i - Z r and Zr-Y d i a g r a m s ( F i g u r e 9 ) .
A somewhat b e t t e r magma-type c a t e g o r i z a t i o n was
o b t a i n e d w i t h P i e r c e ' s (1976) major element d i s c r i m i n a n t ,
which showed these r o c k s t o have IAB a f f i n i t y . The
c a t e g o r i z a t i o n a c h i e v e d i s r e m a r k a b l y c o n s i s t e n t ,
p a r t i c u l a r l y i n v i e w of the s u s c e p t i b i l i t y o f the h e a v i l y
w e i g h t e d d i s c r i m i n a t i n g v a r i a b l e s ( K 2 O , MgO, SiC>2, A I 2 O 3 ) t o
h y d r o t h e r m a l a l t e r a t i o n and w e a t h e r i n g .
G e o l o g i c a l l y younger IAB are c o n s i s t e n t l y d e p l e t e d i n
some t r a n s i t i o n m e t a l s , and n o t a b l y e n r i c h e d i n some a l k a l i
m e t a l s w i t h r e s p e c t t o b a s a l t s formed at c o n s t r u c t i v e p l a t e
m argins (Hawkins, 1980; G a r c i a , 1980). T h i s r e f l e c t s the
c o n t r a s t i n g c l i n o p y r o x e n e - o l i v i n e - and p l a g i o c l a s e - o l i v i n e -
dominant c o n t r o l s on f r a c t i o n a t i o n shown by IAB and N-MORB,
r e s p e c t i v e l y ( Saunders, 1984; P e r f i t et a l . , 1980; T a y l o r
e t a l . , 1980; Rhodes and Bence, 1980). In t h i s r e g a r d ,
N i , Cr and Ba appear t o be p a r t i c u l a r l y u s e f u l p e t r o g e n e t i c
i n d i c a t o r s , s i n c e they are m o d e r a t e l y i n e r t . These
d i s c r i m i n a n t s have been used t o c o n f i r m the IAB a f f i n i t y f o r
the C o r b e t , Maybrun and V i s c a r i a r o c k s t h a t was s uggested by
the major element d a t a ( F i g u r e 1 0 ) .
- 1 1 -
The r a r e e a r t h elements (REE) are a l s o s e n s i t i v e t o
magmatic p r o c e s s e s , and can be used t o c o n s t r a i n
p e t r o g e n e t i c models ( H a s k i n , 1984; Hanson, 1980).
C h o n d r i t e - n o r m a l i z e d p l o t s o f t h e C o r b e t , Maybrun and
V i s c a r i a b a s a l t a n a l y s e s show the f l a t t o m o d e r a t e l y l i g h t
R E E - e n r i c h e d abundance p a t t e r n s common to g e o l o g i c a l l y young
IAB ( e . g . , P h i l p o t t s e t a l . , 1971; Dixon and B a t i z a , 1979;
P e r f i t e t a l . , 1980 - F i g u r e 11). The Maybrun and V i s c a r i a
b a s a l t s have REE abundance p a t t e r n s which are s i m i l a r i n
shape t o t h a t shown by T a y l o r e t a l . ' s (1980) IAB r e f e r e n c e
s u i t e , but the y are r i c h e r i n t o t a l REE. The REE p a t t e r n
f o r t he F l a v r i a n A n d e s i t e shows t h a t i t i s somewhat more
e v o l v e d than the r o c k s o f the r e f e r e n c e s u i t e . S i g n i f i c a n t
Eu a n o m a l i e s a r e absent i n a l l o f the b a s a l t s a n a l y z e d , as
i s the case f o r most a p h y r i c IAB (Con d i e and B a r a g a r , 1974;
T a y l o r e t a l , 1980), and t h i s can a l s o be a t t r i b u t e d t o
the absence o f l i q u i d u s phase p l a g i o c l a s e i n p r i m i t i v e
IAB f r a c t i o n a t i o n (Hanson, 1980; Rhodes and Bence, 1980).
The absence o f an Eu anomaly i s i n c o n t r a s t w i t h r e c e n t
o b s e r v a t i o n s made f o r o r e - a s s o c i a t e d f e l s i c v o l c a n i c r o c k s
(Campbell e t a l . , 1982).
These I A B - l i k e REE p a t t e r n s can be compared w i t h those
c h a r a c t e r i z i n g N-type MORB. About 75% o f the o c e a n i c c r u s t
i s "normal" (Kay and Hubbard, 1978), and b a s a l t s o f t h i s
- 12 -
type appear t o h o s t most o f the a c t i v e C y p r u s - t y p e
m e t a l l i f e r o u s systems t h a t have r e c e n t l y been r e p o r t e d on,
f o r example, the E a s t P a c i f i c R i s e ( S c h e i d i g g e r and C o r l i s s ,
1981). In c o n t r a s t t o the I A B - l i k e b a s a l t s t h a t h ost
C o r b e t - t y p e d e p o s i t s , N-MORB shows c o n s i s t e n t LREE d e p l e t i o n
(La/Sm are u s u a l l y <1.0) and, when m o d e r a t e l y e v o l v e d ,
e x h i b i t n e g a t i v e Eu an o m a l i e s (Rhodes and Bence, 1980).
The o p h i o l i t e s u i t e s i n which many o l d e r C y p r u s - t y p e
d e p o s i t s are found are now thought t o r e p r e s e n t m a t e r i a l
from b a c k - a r c s p r e a d i n g c e n t r e s , r a t h e r than from mature,
m i d - o c e a n i c r i f t s ( e . g . , Smewing e t a l . , 1975; P i e r c e ,
1975). However, from the p o i n t o f v i e w o f b a s a l t
g e o c h e m i s t r y , and p a r t i c u l a r l y REE, C y p r u s - t y p e BABB and
N-MORB are i n d i s t i n g u i s h a b l e (Hawkins, 1980). Both a r e
s i g n i f i c a n t l y d i f f e r e n t g e o c h e m i c a l l y from the IAB-type
r o c k s w i t h which " C o r b e t - t y p e " d e p o s i t s are found ( F i g u r e
12a,b). I t sh o u l d be noted t h a t many back a r c - t y p e
o p h i o l i t e s u i t e s c o n t a i n IAB h i g h i n t h e i r s t r a t i g r a p h i c
s u c c e s s i o n ( e . g . , Luzon-Hawkins, 1980; P i n d o s , Greece
C a p e d r i et a l . , 1980), and some of t h e s e IAB host massive
s u l p h i d e d e p o s i t s which are i n many ways s i m i l a r t o Corbet
( e . g . , S k o u r i o t i s s a , Cyprus - C o n s t a n t i n o u , 1980).
- 13 -
The f l a t REE p a t t e r n s f o r b a s a l t s h o s t i n g the
B e s s h i - t y p e G o l d s t r e a m and Ore Knob d e p o s i t s ( F o x r 1984)
are s i m i l a r t o tho s e o f the t h r e e C o r b e t - t y p e d e p o s i t s ,
a l t h o u g h they can e a s i l y be d i f f e r e n t i a t e d on the b a s i s o f
o t h e r g e o l o g i c a l and g e o c h e m i c a l c r i t e r i o n . For example,
S l a c k ( 1983) and G a i r and S l a c k ( 1983) have d i s c u s s e d the
h i g h C r , N i , V and T i c o n t e n t s o f the MORB-like b a s a l t s
h o s t i n g t h e B e s s h i - t y p e E l i z a b e t h d e p o s i t , and the d e p o s i t s
o f t he G r e a t Gossan Lead. The REE p a t t e r n s shown i n
F i g u r e 12c are a l s o s i m i l a r t o t h o s e e x h i b i t e d by the
" t r a n s i t i o n a l " (T-MORB) b a s a l t s o f some slow s p r e a d i n g r a t e
o c e a n i c r i d g e segments ( e . g . , G a l a p a g o s , G u l f o f Aden -
e.g., Rhodes and Bence, 1980; S c h i l l i n g , 1971) to which t h e y
may be more c l o s e l y r e l a t e d , g e n e t i c a l l y .
ORE GEOCHEMISTRY
The Co, N i , Au c o n t e n t s o f seven " C o r b e t - t y p e " d e p o s i t s
are compared w i t h those o f o t h e r v o l c a n o g e n i c s u l p h i d e o r e s
i n T a b l e 2. A l t h o u g h the d a t a a r e i n c o m p l e t e , t h e r e i s
a c l e a r i n d i c a t i o n t h a t the C o r b e t - t y p e o r e s have an
i n c l i n a t i o n t o g o l d e n r i c h m e n t . Two o f th e s e d e p o s i t s ,
Maybrun and H a v e r i , appear t o be near economic at c u r r e n t
p r i c e s on the b a s i s o f t h e i r g o l d c o n t e n t a l o n e . A l l known
" C o r b e t - t y p e " d e p o s i t s are l e a d - p o o r .
- 14 -
C o r b e t - t y p e d e p o s i t s are a l s o r e l a t i v e l y r i c h i n N i and
Co, and t h i s c l e a r l y d i s t i n g u i s h e s them from Kuroko-type
o r e s , w i t h which they have been compared i n the p a s t . The
mean Co c o n t e n t s o f a l l t h r e e m a f i c - h o s t e d m e t a l l o g e n i c
t y p e s appear t o be s i m i l a r , but C o r b e t - t y p e o r e s seem t o
have N i c o n t e n t s which are an o r d e r o f magnitude g r e a t e r
t h a n t h o s e of B e s s h i - and C y p r u s - t y p e d e p o s i t s .
DISCUSSION
M o d e r a t e l y e v o l v e d b a s a l t and b a s a l t i c a n d e s i t e ,
s i m i l a r t o those h o s t i n g C o r b e t , Maybrun and V i s c a r i a , and
r i c h e r i n t o t a l REE than T a y l o r e t a l . ' s (1980) IAB
r e f e r e n c e s u i t e , are found i n a number o f i s l a n d a r c s i n the
s o u t h w e s t e r n P a c i f i c , i n c l u d i n g F i j i ( F i g u r e 13). The
F i j i a n IAB, which are c o n t a i n e d i n the Wainamala Group and
which are o v e r l a i n by c a l c - a l k a l i n e and s h o s h o n i t i c r o c k s ,
were formed as a r e s u l t of the s u b d u c t i o n o f the P a c i f i c
p l a t e under the I n d o - A u s t r a l i a n p l a t e i n the l a t e Miocene
(Lawrence and Savage, 1976; E g u c h i , 1984 - F i g u r e 1 4).
A number of s m a l l v o l c a n o g e n i c m a s s i v e s u l p h i d e
d e p o s i t s are found i n the Wainamala m a f i c v o l c a n i c s
( e . g . , T h o l o - i - S a v a , W a i n a l e k a - Lawrence and Wood, 1980).
These d e p o s i t s are l e a d - p o o r , l o c a l l y g o l d - e n r i c h e d , a r e
a s s o c i a t e d w i t h c h l o r i t i c and s i l i c i c a l t e r a t i o n ( C o l l e y and
- 15 -
Greenbaum, 1980), and c o n t r a s t m e t a l l o g e n i c a l l y w i t h the
l e a d - r i c h m a s s i v e s u l p h i d e and v e i n - t y p e g o l d d e p o s i t s found
i n the o v e r l y i n g v o l c a n i c s u i t e s . A l t h o u g h d e t a i l e d
d e s c r i p t i o n s a r e l a c k i n g , t h e s e d e p o s i t s may prove to be
g e o l o g i c a l l y young analogues o f t h e P r e c a m b r i a n
" C o r b e t - t y p e " o r e s .
Debate s t i l l e x i s t s r e g a r d i n g the n a t u r e o f p l a t e
t e c t o n i c s i n the P r e c a m b r i a n , s p e c i f i c a l l y i n terms of the
p r e s e n c e o r absence o f subduct i o n - r e l a t e d phenomena i n e a r l y
c r u s t a l h i s t o r y , and t h i s p r e v e n t s a d i r e c t comparison o f
the F i j i a n and o t h e r g e o l o g i c a l l y younger IAB e n v i r o n m e n t s
w i t h those h o s t i n g C o r b e t , Maybrun and V i s c a r i a . Whatever
the t e c t o n i c p r o c e s s i n v o l v e d , however, the d i s t i n c t i v e
c h e m i s t r y o f the P r e c a m b r i a n I A B - l i k e b a s a l t s which h o s t the
t h r e e " C o r b e t - t y p e " d e p o s i t s i s i n d i c a t i v e o f s o u r c e magmas
which must have been d i f f e r e n t from those r e s p o n s i b l e f o r
the a n c i e n t a n a l o g u e s o f c o n s t r u c t i v e m a r g i n a l b a s a l t s
( e . g . , N a l d r e t t and S m i t h , 1980; C o n d i e , 1982). A n c i e n t
IAB c h e m i s t r y i s c o n s i s t e n t w i t h hydrous m e l t i n g o f mantle
m a t e r i a l , and w i t h amphibole-and/or g a r n e t - c o n t r o l l e d
f r a c t i o n a t i o n , as i s the case f o r younger IAB.
Carbonate i s an i m p o r t a n t o r e - h o r i z o n c o n s t i t u e n t i n
many C o r b e t - t y p e d e p o s i t s ( e . g . , V i s c a r i a , Pahtavuoma,
- 16 -
Bidgovagge, Maybrun). T h i s i s a f e a t u r e which i s a l s o
t y p i c a l o f B e s s h i - t y p e d e p o s i t s , but which i s r a r e i n
C y p r u s - and Kuroko-type o r e s . The l a t t e r two, i n
c o n t r a s t , o f t e n c o n t a i n o r e - h o r i z o n s u l p h a t e (Rona, 1984,
C o n s t a n t i n o u , 1980).
I t i s t e m p t i n g t o a p p e a l t o t h e d i f f e r i n g c h e m i c a l
c h a r a c t e r i s t i c s o f o r o g e n i c and a n o r o g e n i c b a s a l t t o e x p l a i n
t h i s phenomenon, as w e l l as the i n c l i n a t i o n t o g o l d - and
n i c k e l - e n r i c h m e n t apparent f o r " C o r b e t - t y p e " o r e s . For
example, g e o l o g i c a l l y young IAB are known t o have
s i g n i f i c a n t l y h i g h e r c o n t e n t s o f C O 2 (up t o 0.44 wt.%)
and CI (up t o 0.24 w t . % ) , as w e l l as h i g h e r H 2 O and F than
N-MORB ( P e r f i t e t a l . , 1980; H a g g e r t y , 1980). These
v o l a t i l e s p e c i e s are known t o enhance the m o b i l i t y o f Au,
as w e l l as N i , d u r i n g metasomatism ( e . g . , H a g g e r t y , 1973;
K e r r i c h and F y f e , 1981).
F l u i d h i s t o r y may have a l s o had an i n f l u e n c e on the
d i f f e r e n t o r e h o r i z o n l i t h o l o g i e s . For example, r o c k -
dominated h y d r o t h e r m a l systems, i n v o l v i n g b a s a l t - s e a w a t e r
i n t e r a c t i o n , a r e known t o be c h a r a c t e r i z e d by s i g n i f i c a n t
C a - m o b i l i z a t i o n and by r e l a t i v e l y complete S O 4 2 - r e d u c t i o n
( M o t t l e and H o l l a n d , 1978; Hajash and A r c h e r , 1980).
Research may show t h a t "Corbet t y p e " d e p o s i t s form from
m i n e r a l i z i n g f l u i d s h a v i n g lower w a t e r - r o c k r a t i o s t h a n i s
the case f o r C y p r u s - t y p e d e p o s i t s .
- 17 -
I A B - l i k e r o c k s are common i n the P r e c a m b r i a n ( e . g . ,
J a h n , 1974; Condie and B a r a g a r , 1974), and t h i s s u g g e s t s
t h a t C o r b e t - t y p e d e p o s i t s may a l s o be r e l a t i v e l y abundant.
However, a n c i e n t magnesian and F e - r i c h t h o l e i i t e s i n some
ways analogous t o o c e a n i c b a s a l t a r e a l s o known ( e . g . ,
Ludden and G e l i n a s , 1982) and, by a n a l o g y w i t h t h e i r younger
e q u i v a l e n t s , s h o u l d a l s o c o n t a i n v o l c a n o g e n i c s u l p h i d e
d e p o s i t s .
The P o t t e r mine near Timmins, from which 500,000 t o n s
o f Cu-Zn or e were e x t r a c t e d between 1 967 and 1972, may be
one such example of an Archean C y p r u s - t y p e d e p o s i t (Coad,
1976). The mine o c c u r s i n a sequence o f low-K t h o l e i i t i c
b a s a l t s and k o m a t i i t e s which make up N a l d r e t t and Smith's
(1980) " p i e r i t e - t h o l e i i t e " s e r i e s , and which are u n d e r l a i n
by a body of d i f f e r e n t i a t e d g a b b r o - p e r i d o t i t e ( F i g u r e 15).
The h o s t t h o l e i i t e s f a l l i n the f i e l d o f o c e a n i c b a s a l t on
P i e r c e ' s (1976) major element d i s c r i m i n a n t d i a g r a m , and are
a l s o s i m i l a r t o N-MORB i n terms of t h e i r h i g h N i and Cr
c o n t e n t s ( F i g u r e 16). In c o n t r a s t w i t h the Cyprus Lower
La v a s , however, these t h o l e i i t e s show moderate LREE
enri c h m e n t ( N a l d r e t t and S m i t h , 1980), and i n t h i s r e s p e c t ,
as w e l l as i n terms of t h e i r t e c t o n i c s e t t i n g , they seem t o
be c l o s e r t o i n t r a p l a t e b a s a l t s .
- 18 -
The d i s t i n c t i v e n e s s o f " C o r b e t - t y p e " d e p o s i t s , and the
p e t r o g e n e t i c environment i n which they o c c u r , has been
emphasized. However, i t may a l s o be p o s s i b l e t o t h i n k o f
t h e s e i n terms o f a m e t a l l o g e n i c l i n k between b a c k - a r c
C y p r u s - t y p e d e p o s i t s and K u r o k o - t y p e o r e s . The c l o s e
t e m p o r a l and s p a t i a l r e l a t i o n s h i p t h a t e x i s t s between
S k o u r i o t i s s a and the Lower L a v a - h o s t e d o r e s on Cyprus may
be i n s t r u c t i v e i n t h i s r e g a r d , as may be the p e t r o g e n e t i c
convergence o f some g e o l o g i c a l l y young IAB. and BABB ( e . g . ,
Lau b a s i n - G i l l , 1976; Japan - Masuda and A o k i , 1978), and
the p o s s i b i l i t y t h a t many K u r o k o - t y p e d e p o s i t s may have
formed i n f a i l e d b a c k - a r c r i f t s ( e . g . , C a t h l e s e t a l . ,
1983). A l i n k a g e may a l s o e x i s t w i t h b a s a l t - h o s t e d ,
v o l c a n o g e n i c g o l d d e p o s i t s such as A g a s s i z and Detour Lake.
CONCLUSIONS
I t has been shown t h a t " C o r b e t - t y p e " d e p o s i t s
c o n s t i t u t e a c l a s s o f p r o x i m a l , v o l c a n o g e n i c o r e s w h i c h ,
by v i r t u e o f t h e i r a r c - l i k e h o s t r o c k g e o c h e m i s t r y , a r e
d i s t i n c t from o t h e r m a f i c v o l c a n i c - h o s t e d o r e s , such as
C y p r u s - and B e s s h i - t y p e d e p o s i t s . T h e i r f r e q u e n t a s s o c i
a t i o n w i t h m a f i c p y r o c l a s t i c r o c k s , v e s i c u l a r b a s a l t , and
w i t h s u b o r d i n a t e f i n e c l a s t i c s e d i m e n t , a l l of which a r e
r a r e i n the o c e a n i c environment ( G a r c i a , 1980), p r o v i d e s
- 19 -
f u r t h e r d i s c r i m i n a t i o n , as does t h e i r commonly o b s e r v e d
s t r a t i g r a p h i c l o c a t i o n a t the base of a r c - l i k e m a f i c t o
f e l s i c v o l c a n i c sequences. " C o r b e t - t y p e " d e p o s i t s a r e
d i s t i n g u i s h e d from o t h e r v o l c a n o g e n i c m a s s i v e base m e t a l
s u l p h i d e d e p o s i t s by t h e i r a p p a r e n t i n c l i n a t i o n t o g o l d
e n r i c h m e n t ( T a b l e 3 ) .
The abundance o f I A B - l i k e r o c k s i n t h e S h i e l d s u g g e s t s
t h a t d e p o s i t s o f t h i s type c o u l d a l s o be r e l a t i v e l y abundant
i n Canada. Moreover, the r e c e n t d i s c o v e r y o f the l a r g e
V i s c a r i a d e p o s i t s u g g e s t s t h a t a d d i t i o n a l " w o r l d - c l a s s "
d e p o s i t s o f t h i s t y p e remain t o be found. The 350 M t o n
Windy Craggy d e p o s i t , w i t h i t s a r c - l i k e h o s t b a s a l t s ,
o r e - z o n e c a l c a r e o u s and g r a p h i t i c a r g i l l i t e , h i g h Co c o n t e n t
and l o c a l Au en r i c h m e n t ( J . Gammon, p e r s . comm., 1984) may
be a n o t h e r c a s e i n p o i n t . From a l l of t h i s , i t must be
con c l u d e d t h a t " C o r b e t - t y p e " d e p o s i t s r e p r e s e n t an i m p o r t a n t
new e x p l o r a t i o n o p p o r t u n i t y f o r the Canadian m i n i n g
i n d u s t r y .
Q JSF-119/ef Apr 13/8 4
- 20 -
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Smewing, J.C., Cimonian, K.O. and Gass, I.G., 1975. M e t a b a s a l t s from the Troodos m a s s i f , C y prus: G e n e t i c i m p l i c a t i o n s deduced from p e t r o g r a p h y and t r a c e elements g e o c h e m i s t r y . C o n t r i b . M i n e r a l . P e t r o l . , V. 51, pp. 49-64.
Spence, C D . , and de Rosen-Spence, A.F., 1 975. The p l a c e o f s u l p h i d e m i n e r a l i z a t i o n i n the v o l c a n i c sequence at Noranda, Quebec. Econ. G e o l . 70, pp.90-101.
T a y l o r , S.R., A r c u l u s , R. and P e r f i t , M.R., 1980. I s l a n d a r c b a s a l t s . I n : B a s a l t i c v o l c a n i s m s t u d y p r o j e c t . Pergamon P r e s s , pp. 193-213.
T r o w e l l , N.F., B l a c k b u r n , C.E., and Edwards, G.R., 1980. P r e l i m i n a r y g e o l o g i c a l s y n t h e s i s o f the Savant Lake-Crow Lake m e t a v o l c a n i c - m e t a s e d i m e n t a r y b e l t . O.D.M. MP. 89.
W a t k i n s , J . J . , 1980. The g e o l o g y o f the Corbet Cu-Zn d e p o s i t and the environment of ore d e p o s i t i o n i n the c e n t r a l Noranda a r e a . M.Sc. T h e s i s , Queen's U n i v .
Whitmore, D.R.E., 1969. Geology o f the C o r o n a t i o n Copper D e p o s i t . I n : B y e r s , A.R. ( e d . ) . Symposium on the g e o l o g y o f the C o r o n a t i o n mine, Saskatchewan, G.S.C pap. 68-5, pp. 37-54.
Yamaoka, K., 1962. S t u d i e s on the bedded c u p r i f e r o u s i r o n s u l p h i d e d e p o s i t s o c c u r i n g i n the Sanbagawa metomorphic zone. Sec. Rept. Tohoku, U n i v . , V. 8, pp. 1-68.
Q JSF-119
- 27 -
FIGURES
1. Geology o f the Noranda r e g i o n , a f t e r Spence and de Rosen-Spence (1975).
2. S c h e m a t i c c r o s s s e c t i o n t h r o u g h the B l a k e R i v e r Group i n the Noranda a r e a , showing the s t r a t i g r a p h i c l o c a t i o n o f t he Corbet d e p o s i t w i t h r e s p e c t t o the o t h e r v o l c a n o g e n i c s u l p h i d e d e p o s i t s i n the r e g i o n (from Knuckey and W a t k i n s , 1982).
3. Schematic c r o s s s e c t i o n t h r o u g h the Corbet d e p o s i t (from Knuckey and W a t k i n s , 1982).
4 . Geology o f the A t i k w a Lake r e g i o n , n o r t h w e s t e r n O n t a r i o ( s i m p l i f i e d from T r o w e l l et a l . , 1980).
5. G e o l o g i c a l p l a n o f the Maybrun d e p o s i t (from H. Matthews, p e r s . comm. 1984).
6. Geology o f t h e K i r u n a - V i s c a r i a r e g i o n (from L. G o d i n , p e r s . comm., 1983).
7. Geology o f n o r t h e r n S c a n d i n a v i a , showing the l o c a t i o n o f t h e K i r u n a and K i t t i l a g r e e n s t o n e b e l t s (from Hagen (1982).
8. Schematic c r o s s s e c t i o n t h r o u g h the V i s c a r i a d e p o s i t (from L. G o d i n , p e r s . comm., 1983).
9. Geochemical v a r i a t i o n d iagrams f o r the C o r b e t , Maybrun and V i s c a r i a h o s t b a s a l t s and b a s a l t i c a n d e s i t e s .
a ) , b) P i e r c e ' s (1976) major element d i s c r i m i n a n t d i a g r a m s , where:
F t = +0.088 S i 0 2 - 0.0774 T i 0 2 + 0.0102 A 1 2 0 3 + 0.0066 FeO - 0.0017 MgO - 0.0143 CaO - 0.0155 Na 20 -0.007 K 2 0 ;
F 2 = -0.0130 S i 0 2 - 0.185 T i 0 2 - 0.0129 A 1 2 0 3 - 0.0134 FeO - 0.0300 MgO - 0.0204 CaO - 0.0481 Na 20 + 0.0715 K 2 0 ; and
F 3 = -0.0221 SiO 2-0.0532 TiO 2-0.0362 A1 20 3-0.0016 FeO -0.0310 MgO -0.0237 CaO -0.0614 Na 20 -0.0289 K 20
OFB = ocean f l o o r b a s a l t , LKT = low-K t h o l e i i t e , CAB = c a l c - a l k a l i b a s a l t , SHO - s h o s h o n i t e , WPB = w i t h i n p l a t e b a s a l t c ) , d) P i e r c e and Cann's 1973) Zr-Y and T i - Z r d i s c r i m i n a n t d i a g r a m s .
- 28 -
10. T i - C r f Ni-Y and T i - ( B a / L a ) g e o c h e m i c a l v a r i a t i o n d i a g rams ( P i e r c e , 1 975 ; P e r f i t et a l . , 1 9 8 0 ) , f o r the h o s t b a s a l t s from C o r b e t , Maybrun and V i s c a r i a .
11. C h o n d r i t e n o r m a l i z e d r a r e e a r t h element abundance diagrams f o r the C o r b e t , Maybrun and V i s c a r i a b a s a l t s . The shaded a r e a c o r r e s p o n d s t o T a y l o r et a l . ' s (1980) i s l a n d a r c b a s a l t r e f e r e n c e s u i t e .
12. C h o n d r i t e - n o r m a l i z e d r a r e e a r t h element abundance diagrams f o r "normal" o c e a n i c b a s a l t , i n which most of the a c t i v e m i n e r a l i z i n g systems on the East P a c i f i c r i s e a r e found, f o r the Lower Lavas on Cyprus and f o r b a s a l t s h o s t i n g two B e s s h i - t y p e o r e s .
13. Geology o f V i t i L evu, F i j i ( a f t e r G i l l , 1970).
14. Geochemical v a r i a t i o n d iagrams f o r the i s l a n d a r c b a s a l t s o f the W a i n i m a l a Group, F i j i ( d a t a from G i l l , 1970) .
15. S u r f a c e p l a n o f the P o t t e r Mine near Timmins, O n t a r i o (from Coad, 1976 ).
16. Geochemical v a r i a t i o n d iagrams f o r the b a s a l t s h o s t i n g the P o t t e r o r e s . The r a r e e a r t h element d a t a i s from N a l d r e t t and Smith (1980).
Q JSF-119
TABLE 1
CORBET-TYPE DEPOSITS
D e p o s i t
CANADA Corbe t New Hosco (?) Maybrun Coronat i o n Cuprus Windy Craggy (?)
Age
Archean Archean Archean P r o t e r o z o i c P r o t e r o z o i c T r i a s s i c
Tonnage x 10^
2.7 2.2 2.8 1.5 0.5
3 50 (approx)
Cu %
3.1 1.4 1.1 4.2 3.3 1.5
Zn %
2.8 1 .1
6.4
Oz/t Ag
0.68 0. 1 1
0.5
SCANDINAVIA V i s c a r i a
H a v e r i B i d j o v a g g e
Pahtavuoma
Archean
P r o t e r o z o i c A rchean
Archean
50
1.5 3
4.4
1.6¬5.0 0.4 1.8
1.0
0.3
0.1
0.1
0.5
0.63
AUSTRALIA C a d i a (?) O r d o v i c i a n 43 0.7 0.20
Q JSF-119
TABLE 2
METAL CONTENTS OF VOLCANOGENIC MASSIVE SULPHIDE ORES
Deposit Type Au Ni Co
"Corbet"<1> 1.8 +1.0 393+300 445+300
Besshi* 2) 0.5 + .3 2 7 + ? 5 3 0 ^ ?
Cyprus (oceanic) <3) 0.09^ .04 11 ± 10 500 ± 25 Cyprus (back-arc) <4) - 53 ± 25 57 ± 25
Kuroko (Canada) <5) 0.5 ± .5 Kuroko (Japan) <6) 1.1 ± 0.5 20 ± 1 0 25 ± 10
(1) Corbet, V i s c a r i a , Maybrun, Pahtayuoma, Bidjovagge, Coronation, Haveri (Fox, unpubl.; Makela, 1980; Inkenen, 1979; Whitmore, 1969)
(2) F i f t e e n Sanbagawa be l t mines, including Besshi (Yamaoka, 1962)
(3) EPR, A t l a n t i s II Deep, Red Sea (Rona, 1984; B i s c h o f f et a l . , 1983; Scott, per comm 1983)
(4) Mathiati, Agokipian, Kokkinoyia (Constantinou and Govett, 1973)
(5) 72 deposits (Assad and F a v i n i , 1980)
(6) Kosaka, Hanoka, Kano (Shimazaki, 1974)
Q JSF-119
TABLE 3
CHARACTERISTICS OF BASALT-HOSTED VOLCANOGENIC DEPOSITS
B e s s h i - t y p e " C o r b e t - t y p e " C y p r u s - t y p e
P o s s i b l e environment
E p i c o n t i n e n t a l r i f t E a r l y a r c O c e a n i c , b a c k - a r c r i f t s
Host r o c k s T-MORB, IP B ( ? ) c o n t i n e n t - d e r i v e d s ed.
IAB v o l c a n o g e n i c sed.
N-MORB, T-MORB(?)
Tenor Cu-Zn (±Co) Cu-Zn-Au (±Co, N i ) Cu-Zn (±Co)
A c c e s s o r y o r e h o r i z o n 1 i t h o l o g i e s
I r o n fmn., l i m e s t o n e , a r g i l l i t e
L i m e s t o n e , a r g i l l i t e S u l p h a t e
Age range P r o t e r o z o i c - r e c e n t Archean-Eocene (?) A r c h e a n ? - r e c e n t
Recent examples
Guaymas b a s i n T h o l o - i - S u v a (?) EPR-21°N, -20°S, Juan de Fuca , e t c .
A n c i e n t examples
B e s s h i Ducktown Trondheim
C o r b e t V i s c a r i a Maybrun
Cyprus B e t t s Cove P o t t e r
Q JSF-119
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N O R T H W E S T R H Y O L I T E
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X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X
X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X
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X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X
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