03 - glaucophane-lawsonite schists - CMP 1980.pdf

8/10/2019 03 - glaucophane-lawsonite schists - CMP 1980.pdf

1/13

Contrib. Mineral. Petrol. 72, 243-255 (1980)

o n t r i b u t i o n s to

i n e ra lo g y an d

P et ro l o g y

9 by Springer-Verlag 1980

M ineralogy Petrology and Phase Relat ions

of G laucophane-Lawsonite Zo ne Blueschists

From the Tavsanh Region Northw est Turkey

A . I . O k a y

Department o f M ineralogy and Petrology, Downing Place, Cambridge CB2 3EW , England

Abstrac t G l a u c o p h a n e - l a w s o n i t e f a c i e s b l u e s c h i s t s

r e p r e s e n ti n g a m e t a m o r p h o s e d s e q u e n c e o f b a s i c ig -

n e o u s r o c k s , c h e r t s a n d s h a l e s h a v e b e e n i n v e s t i g a t e d

n o r t h e a s t o f t h e d i s tr ic t o f T a v s a n l i i n N o r t h w e s t

T u r k e y . S o d i c a m p h i b o l e s a r e r i ch i n m a g n e s i u m r e -

f l e c ti n g t h e g e n e r a l l y h i g h o x i d a t i o n s t a te s o f t h e

b l u es c h is t s. L a w s o n i t e h a s a v e r y u n i f o r m c o m p o s i -

t i o n w i t h u p t o 2 .5 w t . %

Fe203

S o d i c p y r o x e n e s

s h o w a n e x t e n s iv e r a n g e o f c o m p o s i t i o n s w i t h a ll th e

e n d - m e m b e r s r e p r e s en t e d . C h l o r i te s a r e u n i f o r m i n

t h ei r A 1 / ( A I + F e + M g ) r a ti o b u t sh o w v a r ia b l e Fe /

( F e + M g ) r a ti o s . G a r n e t s f r o m m e t a c h e r t s a r e r i ch

i n s p e s s a rt in e ( > 5 0 % ) w h e r e a s t h o s e f r o m m e t a b a -

s i t es a r e l a r g e l y a l m a n d i n e . P i s t a c i t e r ic h e p i d o t e i s

f o u n d i n m e t a c h e r t s c o e x i s t i n g w i t h la w s o n i t e . P h e n -

g i t e s a r c d i s t i n c t l y h i g h e r i n th e i r F e , M g a n d S i

c o n t e n t s t h a n t h o s e f r o m g r e e n s c h i s t f a c ie s . H e m a t i t e s

w i t h l o w T i O z a r e u b i q u i t o u s i n m e t a c h e r t s .

F e 2 + / M g p a r t i ti o n i n g b e t w e e n c h l o r it e a n d s o d ic

a m p h i b o l e i s s t ro n g l y c o n t r o l le d b y t h e c a l c i u m c o n -

t e n t o f t h e s o d i c a m p h i b o l e a n d r a n g e s f r o m 1 .1 f o r

l o w c a l c i u m s u b s t i t u t i o n t o 0 . 8 f o r h ig h e r c a l c i u m

s u b s t i t u t i o n . T h e A 1 / F e 3 + p a r t i t i o n c o e f f i c ie n t b e -

t w e e n s o d i c a m p h i b o l e a n d s o d i c p y r o x e n e is 2 .1 .

A m o d e l s y s t e m h as b e e n c o n s t r u c t e d i n v o l v i n g

p r o j e c t io n s f r o m l a w s o n it e , i r o n - o x i d e a n d q u a r t z

o n t o a t e t r a h e d r o n w i t h N a , A 1 , F e 2 + a n d M g a t

i t s a p i c e s . C a l c i t e i s t r e a t e d a s a n i n d i f f e r c n t p h a s e .

T h e m o d e l s y s t e m i ll u s tr a te s t h e i n c o m p a t i b i l it y o f

t h e s o d i c p y r o x e n e w i t h c h l o r i te i n th e g l a u c o p h a n e -

l a w s o n i t e f a c i e s ; t h i s a s s e m b l a g e i s r e p r e s e n t e d b y

s o d ic a m p h i b o l e .

S o d i c a m p h i b o l e c o m p o s i t i o n s a re p l o t t e d i n

t e r m s o f c o e x i st i n g fe r r o m a g n e s i a n m i n e ra l s . F i v e m a -

j o r a r e a s o n t h e s o d ic a m p h i b o l e c o m p o s i t i o n a l f i e ld

a r e d e l in e a t e d , e a c h a s s o c i a t e d w i t h o n e o f th e f o l l o w -

i n g m i n e r a l s : c h l o r it e , s t i l p n o m e l a n e , t a l c, a l m a n d i n e ,

d e e r i t e .

Introduct i on

I n N o r t h w e s t T u r k e y b l u e s c hi s ts f o r m a c o h e r e n t ,

d i s c o n t in o u s l y e x p o s e d m e t a m o r p h i c b e lt a b o u t

2 0 k m i n w i d t h a n d 3 0 0 k m i n l e n g t h ( F i g . 1 , i n s e t) .

T h e y f l a n k th e n o r t h e r n m a r g i n s o f t h e l a r g e u l tr a m a -

f ic m a s s i f s i n t h e e a s t e r n p a r t o f th e I z m i r - A n k a r a

o p h i o l i t e z o n e ( B r i n k m a n n 1 9 72 ) f o r m i n g a re g i o n a l l y

m e t a m o r p h o s e d e u g e o s y n c l i n a l s e q u e n c e o f b a si c

v o l c a n i c r o c k s , c h e rt s , s h a le s a n d m i n o r g a b b r o i c i n -

t r u s i o n s .

A l t h o u g h t h e e x is t e n c e o f b l u e s c h i s ts i n T u r k e y

h a v e b e e n k n o w n f o r o v e r s e v e n t y y e a r s ( c f . v a n d e r

K a a d e n 1 9 66 ), t h e fi r st d e ta i l e d s t u d y o n t h e i r p e t r o l -

o g y w a s n o t p u b l i s h e d u n t i l 1 96 7 b y C o g u l u . H e

w o r k e d i n t h e e a s te r n p a r t o f th e N o r t h w e s t T u r k i s h

b l u e s c h i s t b e l t i n t h e r e g i o n o f M i h a l l i~ i k , a n d d i s -

t i n g u is h e d t h r e e m e t a m o r p h i c z o n e s : l a w s o n it e , l a w -

s o n i t e -c r o s s i te , a n d e p i d o t e - c r o s s i t e w i t h a n i n c r e a s e

i n g r a d e n o r t h w a r d s . H e a l s o o b t a i n e d a g e s f o r b l u e -

s c h is t m e t a m o r p h i s m o f 6 0 - 8 0 M a ( @ o ~ ul u a n d K r u m -

m e n a c h e r 1 9 6 7 ) . L t i n e l ( 1 9 6 7 ) s t u d i e d a s m a l l a r e a

o f g l a u c o p h a n e - l a w s o n i t e f a c ie s b l u e s c h i s t s s o u t h o f

E s k i s e h i r ( F i g . 1 , i n s e t ) w i t h s p e c i a l r e f e r e n c e t o t h e

b u l k r o c k c h e m i s t r y a n d s t r u c t u r e . K a y a ( 19 7 2 )

w o r k e d o n t h e is o l a t e d s m a l l b lu e s c h i s t o u t c r o p s

s o u t h o f T a v s a n h .

Geo l o g y

Throughout the N W Turkish blueschist/ultramafic belt the out-

crops are separated by an extensive Neogene cover. A large area

(20 to 45 kin ) of blueschists, ultramafics and ma rble s protrudes

from under the N eogene northeast o f the d istrict of Tav~an h (Fig.

1, inset) . During the co urse of the pre sent study, part of this

extensive area (30 to 13 km) of blueschists and ultramafics was

map pcd in d etail and ov er 700 rock specim ens were collected for

petrological investigations. In the studied area glaucophane-lawso-

nite zone blueschists form a coheren t, complexly deform ed regional

O010-7999/80/0072/0243/ 02.60


2/13

244 A.I. Okay: Glaucopha ne-Lawsoni te Zone Blueschists Fro m NW Turkey

t

i

i

i

. , t. 73

s s

~ - 7 2 0

N

. 7 2 1

4 6 0

4 5 9

' v.

. 4 5 2 6 4 3

X

3 9 4

. 3 9 3

l / / / / .--,

/ / / / > / / /

/ / / i / ' / /

2-~ / /

\: 5 0 ) w i t h v e r y l o w v a l u e s o f p y r o p e (a v . 1 ) .

G a r n e t s o f th i s t y p e a r e c o m m o n i n t h e F r a n c i s c a n C o m p l e x ( E r n s t

e t a l . 1970) a nd i n N e w Ca l e don i a ( B l a c k 1973) .

T h e s e c o n d a n d m u c h r a r e r t y p e o f g a r n e t is f o u n d i n r o c k s

o f b a si c i g n eo u s c o m p o s i t i o n . T h e s e t e n d t o b e m u c h l a rg e r i n

s i ze ( 1 3 m m ) a n d m o r e s p o r a d i c i n o c c u r r e n c e t h a n t h e f i r s t t y p e .

T h e y c o n s i s t d o m i n a n t l y o f a l m a n d i n e - g r o s s u l a r c o m p o n e n t s w i t h

l e ss e r p y r o p e ( 8 - 1 0 ) a n d s p e s s a rt i n e ( 1 - 5 ) ; a n d a re s i m i la r

i n c o m p o s i t i o n t o t h e g a r n e t s f r o m t y p e I I I m e t a b a s i t e s f r o m t h e

Ca z a de r o a r e a i n Ca l i f o r n i a ( L e e e t a l . 1963) .

G a r n e t s f r o m 1 0 m e t a c h e r t s a n d 5 m e t a b a s i te s a r e p l o t t e d

i n F i g . 6 in t e r m s o f g r o s s u l a r , s p e s s a r t i n e a n d a l m a n d i n e + p y r o p e

e n d - m e m b e r s ; s ix g a r n e t a n a ly s e s , th r e e f r o m m e t a b a s i t es a n d t h r e e

f r o m m e t a c h e r t s , a re s h o w n i n T a b l e 4 . G a r n e t s f r o m t h e D e v l e z

a r e a s h o w c o m p l e t e s o li d s o l u ti o n b e t w e e n a l m a n d i n e a n d s p e s s ar -

t i ne .

Z o n i n g i n t h e s p e s s a r t i n e - r i c h g a r n e t s f r o m t h e m e t a c h e r t s

i s d if f i c u lt to o b s e r v e b e c a u s e o f t h e v e r y s m a l l s i z e o f t h e g r a i n s .

H o w e v e r , a n a l y s e s o f s e p a r a t e g a r n e t g r a i n s i n a s i n g l e th i n s e c t i o n

u s u a l l y r e v e a l v a r i a t io n s i n c o m p o s i t i o n b e t w e e n 2 0 3 0 m o l .

s p e s s a r t i n e - a l m a n d i n e w i t h a f a i rl y c o n s t a n t g r o s s u l a r i t e c o n t e n t .

T h e g r o s s u l a r i t e c o n t e n t s o f a l l a n a l y s e d s p e s s a r t i n e g a r n e t s a r e

r e l a ti v e l y c o n s t a n t ly i n g b e t w e e n 1 0 - 2 0 m o l . ( F i g . 6 ). O n l y g a r -

n e t s f ro m o n e m e t a b a s i t e o u t o f f iv e s h o w e d z o n i n g i n v o l v i n g

a n i n c r e a s e O f a l m a n d i n e t o w a r d s t h e r i m ( F i g . 6 , T a b l e 4 ) .

Epidote

E p i d o t e i s a r a r e m i n e r a l i n t h e a r e a ; i t m a i n l y o c c u r s i n s o m e

m e t a c h e r t s i n a s s o c i a t i o n w i t h h e m a t i t e a n d l a w s o n i t e . T w e n t y -

t h r e e e p i d o t e s fr o m 4 m e t a c h e r t s a n d 3 m e t a b a s i te s w e r e a n a l y s e d

a n d t h e s e a r e s h o w n o n a h i s t o g r a m i n F i g . 7 a . E p i d o t e s f r o m

m e t a c h e r t s a r e i n v a r i a b l y p i s t a c i t e - r i c h ( 2 7 - 3 5 p i s t a c i te ) , a n d

o c c u r i n m u c h l e s s a b u n d a n c e t h a n t h e a c c o m p a n y i n g l a w s o n i t e .

I n m e t a b a s i t e s , e p i d o t e i s u s u a l l y f o u n d a s s m a l l , r o u n d e d i n c l u -

s i o n s in l a w s o n i t e p o r p h y r o b l a s t s , s u g g e s t i n g t h a t i t i s a r e li c t

p h a s e f r o m a s p i l it i c p r o t o l i t h . E p i d o t e s f r o m m e t a b a s i t e s a r e l e s s

p i s t a c i t e - r i c h t h a n t h o s e f r o m m e t a c h e r t s , w i t h p i s t a c i t e c o m -

p o n e n t s o f 2 0 2 8 . A l l e p i d o t e s c o n t a i n s m a l l a m o u n t s o f M n

w h i c h s u b s t i t u t e s f o r C a .

T h e a s s e m b l a g e e p i d o t e -l a w s o n i t e - h e m a t i te , a s f o u n d i n t w o

m e t a c h e r t s ( T a b l e 3 ), is c o m p o s i t i o n a l l y i n v a r i a n t a t c o n s t a n t

P a n d T in t h e s y s t e m C a - A 1 - F e 3 + ; n e g le c t in g s m a l l a m o u n t o f

M n i n e p i d o t e ( 0 .0 7 p e r f o r m u l a u n i t ) a n d T i i n h e m a t i t e ( 0 .0 7

p e r f o r m u l a u n i t ). T h e p i s t ac i t e c o m p o n e n t o f t h e e p i d o t e a n d

t h e f er ri c c o n t e n t o f l a w s o n i te m u s t b e a m a x i m u m f o r t h i s i n v a -

r i a n t a ss e m b l a g e u n d e r t h e p a r t i cu l a r c o n d i t i o n s o f m e t a m o r p h i s m

( F i g . 7 b ) . E p i d o t e s f r o m t h e t w o m e t a c h e r t s h a v e v e r y s i m i l a r

p i s t a c i te c o m p o n e n t s ( 3 1 a n d 3 2 ) ; t h e l a w s o n i t e s h a v e r e l a -

t i v el y h i g h i r o n c o n t e n t s ( a v. 0 . 0 8 p e r f o r m u l a u n i t ) c o n f i r m i n g

t h e i n v a r i a n c e o f t h e s u b a s s e m b l a g e .

Phengite

P h e n g i t e i s t h e o n l y m a j o r K - b e a r i n g p h a s e i n t h e D e v l e z b l u e -

s c h i s t s . I t i s a n i m p o r t a n t c o n s i t u e n t i n t h e m e t a c h e r t s , a n d i s

c o m m o n a s a m i n o r p h a s e i n m e t a b a si t e s. S i x t y - tw o p h e n g i t e a n a l -

y s e s f r o m 1 5 m e t a b a s i t e s a n d 1 1 m e t a c h e r t s a r e s h o w n i n t h e

A 1 - F e - M g d i a g r a m i n F i g . 8 , s ix o f t h e s e a r e g iv e n in T a b l e 4.

T h e D e v l e z p h e n g it e s a r e ri c h e r in F e , M g a n d S i th a n t h o s e o f

t h e g r e e n s c h i s t f a ci e s ( c f. B r o w n 1 9 6 7 ). I n t h o s e f r o m t h e m e t a b a -

s i t e s t h e r e i s n o t e v e n a n o v e r l a p b e t w e e n t h e b l u e s c h i s t a n d g r e e n -

s c h i s t c o m p o s i t i o n s ( F ig . 8 ) . A l l a n a l y s e d p h e n g i t e s s h o w v e r y l i m -

i t e d s o l i d s o l u t i o n t o w a r d s C a - m i c a ( < 1 t o o l . ) a n d n o s o l i d s o l u -

t i o n w i t h p a r a g o n i t e .

Hematite

H e m a t i t e is a n e s s e n t i a l p a r t o f t h e m e t a c h e r t m i n e r a l a s s e m b l a g e .

I t o c c u r s a s a b u n d a n t , s m a l l p l a t e l e t s c l o s e l y a s s o c i a t e d w i t h t h e

o t h e r f e r r o m a g n e s i a n m i n e r a l s i n t h e r o c k ( F i g . 2) . F o u r t e e n a n a -

l y s e d h e m a t i t e s f ro m 9 m e t a c h e r t s a n d 2 m e t a b a s i t e s c o n t a i n u p

t o 4 w t . T i O z a n d 0 . 2 w t . V 2 0 3 .

O p a q u e m i n e r a l s a r e m u c h s c a r c e r i n t h e m e t a b a s i t e s . T h e y

t e n d t o b e e i t h e r p y r i t e o r m a g n e t i t e . M a g n e t i t e o f t e n s h o w s l a t e

s t a g e a l t e r a t i o n .

Aragonite Caleite

C a l c i t e o r a r a g o n i t e p a r t i a l l y a l t e r e d t o c a l c i t e o c c u r s i n s o m e

m e t a b a s i t e s a s i n t e r s t i ti a l g r a i n s o r v e i n s . I n s o m e c a s e s it p s e u d o -

m o r p h s l a w s o n i t e . N o o t h e r c a r b o n a t e w a s f o u n d i n t h e a r e a .

I n t h e D e v l e z a r e a o n l y o n e s p e c i m e n ( 3 9 4 / 3 ) w a s f o u n d t o

c o n t a i n

pumpelIyite

i n a l a m e l l a r i n t e r g r o w t h w i t h l a w s o n i t e .

T a / c

T a l c w a s o n l y fo u n d i n o n e o f t h e a n a l y s e d s p e c i m e n s (3 5 6) c o e x i s t -

i n g w i t h c h l o r i t e a n d s o d i c a m p h i b o l e ( T a b l e s 2 a n d 4 ) .

Quartz

Q u a r t z i s th e d o m i n a n t p h a s e i n m e t a c h e r t s a n d i s p r e s e n t i n

s m a l l a m o u n t s i n m a n y m e t a b a s i t e s ( T a b l e s 2 a n d 3 ) .

Albite

A l b i t e i s a v e r y r a r e m i n e r a l . I t w a s o n l y f o u n d i n t w o m e t a b a s i t e s

w h e r e i t i s p u r e a l b i t e w i t h n o d e t e c t a b l e a n o r t h i t e c o m p o n e n t .

I n t h e b l u e s c h i s t f a c i e s s o d i c a m p h i b o l e s a n d p y r o x e n e s t a k e

u p o n l y t r a ce a m o u n t s o f t i t a n i u m ; s u b s e q u e n t l y sphene b e c o m e s

a u b i q u i t o u s a c c e s s o r y m i n e r a l i n m e t a b a s i t e s . It i s l e s s c o m m o n

i n m e t a c h e r t s ( T a b l e 2) w h e r e t i t a n i u m e n t e r s h e m a t i t e i n s t e a d

o f f o r m i n g s p h e n e . S p h e n e o c c u r s a s p o o r l y c r y s t a ll i n e d u s t y b r o w n

a g g r e g a t e s . R u t i l e i s n o t f o u n d i n t h e a r e a . B l u e s c h i s t m i n e r a l s

n o t a b l e i n t h e i r a b s e n c e i n t h e D e v l e z a r e a i n c l u d e s t i l p n o m e l a n e

a n d d e e r i t e . T h e a b s e n c e o f t h e s e t w o m i n e r a l s c a n b e r e l a t e d

t o t h e l a c k o f s u i t a b l e i r o n - r i c h r o c k c o m p o s i t i o n s a n d t o t h e

g e n e r a l ly h i g h o x i d a t i o n s t a t e s o f th e b l u e s c h i s t s . H o w e v e r , a s

stilpnomelane

i s a n i m p o r t a n t m i n e r a l i n t h e m o r e r e d u c e d b l u e -

s c h i s t s , s u c h a s F r a n c i s c a n m e t a c h e r t s , f i v e s t i l p n o m e l a n e - b e a r i n g

m i n e r a l a s s e m b l a g e s w e r e a n a l y s e d : o n e f r o m a m e t a - a c i d i c r o c k

8 k m s o u t h o f t h e a r e a s h o w n i n F i g . 1 , a n d f o u r F r a n c i s c a n

m e t a c h e r t s ( f r o m H e a l d s b n r g , T i b u ra n , P a c h e c o P a s s , a n d P a n o c h e

P a s s ) . T h e e s s e n t i a l m i n e r a l a s s e m b l a g e i n F r a n c i s c a n m e t a c h e r t s

i s ' q u a r t z + s o d i c a m p h i b o l e

c h l o r i te ' a n d i n t h e m e t a -a c i d i c r o c k f r o m T a v s a n l i ' a l b i t e +

s t i l p n o m e l a n e + s o d i c a m p h i b o l e + q u a r t z + i l m e n i t e + l a w s o n i t e ' .

S o d i c a m p h i b o l e s c o e x i s ti n g w i t h s t i lp n o m e l a n e h a v e c o m p o -

s i t i o n s w i t h F e 2 + / F e 2 + + M g r a t i o s g r e a t e r t h a n 0 . 5 ( F i g . 1 2 a )

c h a r a c t e r i s t i c o f r e d u c e d m i n e r a l a s s e m b l a g e s w h i c h r e c r y s t a l li z e d


6/13

248

Table 4. Com pos i t ions of m ine ra l s

A . I . Oka y: G la uc opha ne -La wsoni te Zone B lue sc hi s t s From NW Turke y

Sodic a m phibo le s Sodic pyroxe ne s

357/1 643]2 182 380 381 460 473 33 471 643/2 182 381 395

c ore r im

S iO z 5 7.3 6 5 6 . 7 1 5 5 . 9 9 5 8.2 0 5 7.5 4 5 6 .5 2 5 7 . 9 1 5 8.7 0 5 3 . 4 2 5 3 . 7 5 5 3.5 7 5 5 . 1 3 5 2 . 6 9 5 8.3 7

AI20 ~ 11.00 7.83 6.46 7.72 4.87 3.80 5.72 6.70 4.52 5.58 5.47 8.50 3 _77 19 .59

TiO 2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.19 0.00 0.00 0.00

F e O* 1 0 . 47 1 5 . 1 2 1 6 . 7 1 1 1 . 6 5 1 6 . 5 2 2 3.8 7 1 5 . 0 0 8 .1 8 1 7 . 7 4 1 3 . 8 5 1 4 . 8 8 1 8 . 4 4 2 2.9 7 7 .5 5

M nO 0.00 0.00 0.15 0.20 0.16 0.13 0.27 0.45 0.23 0.30 0.00 0.00 0.00 0.00

Mg O 9 .86 8 .89 8 .79 1 1 .1 6 10 .3 9 6 .57 1 0 .6 7 14 .0 0 4 .00 5 .55 4 .93 0 .91 1 .52 0 .00

Ca O 1.07 0.44 0.72 0.09 0.86 0.22 0.69 0.89 8.10 13 .3 6 9.19 1.92 4.07 0.09

Na 20 6 .72 7 .23 6 .97 7 .76 6 .84 7 .46 7 .22 7 .26 9 .16 6 .36 8 .81 1 3 .1 3 1 1 .5 6 14 .3 8

To ta l 96.48 96.22 95,80 96.79 97.18 98.58 97,49 96.18 97.15 98.75 9 7 .0 3 98,02 96.58 99.97

* Tota l i ron a s Fe O

Si

A1~v

A Iv~

T i

Fe 3 +

Fe 2 +

M n

M g

Num be r of c a t ions pe r 23 oxyge ns Num be r of c a t ions pe r 6 oxyge ns

7.97 8.00 7.99 8.01 8.07 8.03 8.04 8.02 2.01 2.00 2.00 2.01 2.00 2.01

0.03 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

1.77 1.30 1,08 1.25 0.81 0.64 0.94 1.08 0.20 0.25 0.24 0.37 0.17 0.80

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0,00 0.00 0.00

0.22 0.67 0.86 0.70 1.11 1.37 0.95 0.80 0.46 0.21 0.40 0.56 0.68 0.16

1.00 1.11 1.14 0.64 0.83 1.47 0.79 0.13 0.10 0.22 0.07 0.00 0.05 0.06

0.00 0.00 0.02 0.02 0.02 0.02 0.03 0.05 0.01 0.01 0.00 0.00 0.00 0.00

2.04 1.87 1.87 2.29 2.17 1.39 2.21 2,85 0.22 0.31 0.28 0.05 0,09 0.00

~2 5.03 4.95 4.97 4.90 4.94 4.89 4.92 4.92 0.99 1.00 1.00 0.98 0.99 1.02

Ca 0.16 0.07 0.11 0.01 0.13 0.03 0.10 0.13 0.33 0.54 0.37 0.08 0.i7 0.00

N a 1.81 1.98 1.93 2.07 1.86 2.06 1.94 1,92 0.66 0.46 0.64 0.93 0.85 0.96

~2 1.97 2.05 2,04 2.08 1.99 2.09 2.04 2.05 0.99 1.00 1.01 1.01 1.02 0.96

Jd 20 25 2 4 37 17 80

Ac 46 21 40 56 68 20

Au 34 54 36 7 15 0

well within the mag neti te s tabi l i ty f ie ld Okay , in press). W ith

the se c om pos i t ions the who le sodic a m phibole f ie ld , w i th the e xce p-

t ion of a n a re a a round the g la uc op ha ne e nd-m e m be r , c a n be

inferred to be potentia l ly s table in the glaucophane-lawsonite fac ies .

l e m e n t P a r t i t io n i n g

T h e v a r i a b l e f e r r o m a g n e s i a n r a t i o s o f p h e n g it e s a n d

s o d i c p y r o x e n e s w i t h i n a s i n g le s e c t i o n a n d t h e i r

r e s t r i c t e d r a n g e d o n o t a l l o w r e l i a b l e d i s t r i b u t i o n

c o e f f i c i en t s b e t w e e n t h e m a n d o t h e r m i n e r a l s t o b e

d e t e r m i n e d . D i s c u s s i o n o n e l e m e n t p a r t i t i o n i n g i s

c o n s e q u e n t l y r e s t r ic t e d to t h e F e Z + / M g d i s t r i b u t i o n

b e t w e e n c h l o r i t e a n d s o d i c a m p h i b o l e a n d A 1 / F e 3 +

d i s t r ib u t i o n b e t w e e n s o d i c a m p h i b o l e a n d s o d i c p y -

r o x e n e ,

Chlorite Sodic Amphibole

F e 2 + / M g r a t i o s f o r s e v e n t e e n c o e x i s t in g h o m o g e n -

e o u s s o d i c a m p h i b o l e s a n d c h l o r i t e s a r e s h o w n i n

F i g . 9 a . T h i r t e e n o f t h e p a ir s c o m e f r o m D e v l e z ,

2 f r o m G f i m e l e L i i n e l 19 6 7) , o n e f r o m M i h a l l i c i k

~ o g u l u 1 9 67 ) a n d o n e f r o m P a n o c h e P a s s , C a l i f o r -

n i a . T h e m a i n e r r o r s i n t h e d e t e r m i n a t i o n o f t h e p a r t i -

t i o n c o e f f i c i e n t K D a r is e f r o m t h e u n c e r t a i n t y o f f e r r i c /

f e r r o u s r e c a l c u l a t i o n i n s o d i c a m p h i b o l e m i c r o p r o b e

a n a l y s e s a n d t h e m i n o r u n d e t e r m i n e d f e rr i c i o n i n

c h l o r i t e ,

T h e F e a + / M g d i s t r i b u t i o n c o e f f i c i e n t i s s t r o n g l y

d e p e n d e n t o n t h e c a l c i u m c o n t e n t o f t h e s o d ic a m p h i -

b o l e a n d r a n g e s f r o m 1 .1 f o r l o w c a l c i u m s u b s t i t u t i o n

0 . 0 0 < C a / C a + N a < 0 . 0 3 ) t o 0 .8 f o r i n c r e a s e d c a l-


7/13

A . I . O k a y : G l a u c o p h a n e - L a w s o n i t e Z o n e B l u es c h is t s F r o m N W T u r k e y

T a b l e 4 C o n t i n u e d )

2 4 9

C h l o r i t e s T a l c G a r n e t s

2 7 3 3 3 5 6 1 8 2 3 5 6 3 5 7 / 1 4 7 1 3 8 0 4 6 0 4 7 3

c o r e r i m

S i O / 2 7 . 7 5 2 7 . 6 8 2 8 . 7 7 2 9 . 1 7 6 1 . 2 8 3 8 . 1 4 3 7 . 8 5 3 7 . 8 7 3 6 . 9 9 3 7 . 2 5 3 7 . 5 7

A 1 2 0 3 1 7 . 5 8 1 7 . 5 6 1 8 , 5 2 2 0 . 3 9 0 . 0 0 2 1 . 9 9 2 1 . 3 1 2 1 . 3 8 1 9 . 7 4 2 0 . 7 7 2 0 . 1 9

T i O 2 0 . 0 0 0 . 0 0 0 . 0 0 0 . 0 0 0 . 0 0 0 . 2 0 0 . 0 0 0 . 0 0 0 . 2 5 0 . 3 3 0 . 2 8

F e O * 2 2 . 9 9 2 1 . 6 2 1 8 . 2 8 1 0 . 7 7 8 . 1 8 2 8 . 4 0 1 5 . 3 4 2 2 . 3 4 9 . 4 9 7 . 4 0 2 . 9 8

M n O 0 . 6 9 1 . 2 3 0 , 3 2 0 . 5 2 0 . 0 0 0 . 8 4 1 3 . 7 t 7 , 2 9 2 6 . 1 7 3 0 . 6 4 3 3 . 8 5

M g O 1 7 . 6 7 1 9 . 1 9 2 1 . 4 7 2 5 . 1 2 2 5 . 7 2 2 . 2 5 0 . 0 0 0 . 3 2 0 . 2 7 0 . 2 7 0 . 2 9

C a O 0 . 0 9 0 . 0 0 0 . 0 8 0 . 0 0 0 . 0 0 9 . 0 8 1 3 . 1 2 1 1 . 7 8 7 . 3 3 5 . 7 4 0 , 5 6

T o t a l 8 6 . 7 7 8 7 . 2 6 8 7 . 4 4 8 6 . 1 1 9 5 . 1 9 1 0 0 . 8 9 1 0 1 . 3 4 1 0 0 , 9 7 1 0 0 . 2 5 1 0 2 . 3 0 1 0 1 . 7 2

N u m b e r o f c a t io n s p e r :

2 8 o x y g e n s 2 2 o x y g e n s 8 o x y g e n s

S i 5 . 8 5 5 , 7 8 5 . 8 4 5 . 7 8 8 , 0 4 2 , 9 9 2 . 9 8 3 . 0 0 2 , 9 9 2 . 9 6 3 . 0 0

A 1 ~ 2 , 1 5 2 . 2 2 2 . 1 6 2 . 2 2 0 . 0 0 0 . 0 1 0 . 0 2 0 . 0 0 0 . 0 1 0 . 0 4 0 . 0 0

A1 v l 2 . 2 2 2 . 1 0 2 . 2 7 2 . 5 4 0 . 0 0 2 . 0 2 1 . 9 6 2 . 0 0 1 . 8 7 1 .9 1 1 . 9 0

F e 3 . . . . . 0 .0 0 0 . 0 4 0 .0 0 0 .1 3 0 .0 9 0 .1 0

F e 2 + 4 . 0 5 3 . 7 8 3 . 1 0 1 . 7 8 0 . 9 0 1 . 8 5 0 . 9 7 1 .4 8 0 . 5 1 0 . 4 0 0 . 1 0

T i 0 . 0 0 0 . 0 0 0 , 0 0 0 . 0 0 0 . 0 0 0 . 0 1 0 . 0 0 0 . 0 0 0 . 0 1 0 . 0 1 0 . 0 2

M n 0 . 1 2 0 . 2 2 0 . 0 6 0 . 0 9 0 . 0 0 0 . 0 6 0 . 9 2 0 . 4 9 1 . 7 9 2 . 0 6 2 . 2 9

M g 5 . 5 5 5 . 9 7 6 . 5 0 7 . 4 1 5 . 0 3 0 . 2 6 0 . 0 0 0 . 0 4 0 . 0 3 0 . 0 3 0 . 0 3

C a 0 . 0 2 0 . 0 0 0 . 0 2 0 . 0 0 0 . 0 0 0 . 7 6 1 . 11 1 . 0 0 0 . 6 4 0 . 4 9 0 . 5 6

T o t a l 1 9 . 9 7 2 0 . 0 6 1 9 . 9 5 1 9 . 8 4 1 3 . 9 7 7 . 9 8 8 . 0 0 8 . 0 1 8 . 0 0 8 . 0 0 8 . 0 0

* T o t a l i r o n a s F e O

A i m . 6 3 3 2 4 9 1 7 1 3 3

Spe ss . 2 31 17 60 69 76

Pyr . 9 0 1 1 1 1

G r o s s . 2 6 3 7 3 3 2 2 1 7 1 9

P h e n g i t e s

3 3 3 5 7 / 1 3 8 0 4 6 0 4 7 3 3 9 5

S i O 2 5 1 . 4 3 5 1 . 7 1 5 2 . 2 0 5 2 . 1 5 5 1 . 5 0 4 7 . 7 5

A 1 / O 3 2 2 . 5 0 2 2 . 9 5 2 3 . 0 0 2 3 . 2 7 2 4 . 9 6 3 0 . 0 4

T i O 2 0 . 0 0 0 . 2 0 0 . 2 2 0 . 0 0 0 . 1 4 0 . 0 0

F e O * 4 . 9 5 3 . 9 3 4 . 5 0 4 . 4 5 2 . 7 8 3 . 9 3

M n O 0 . 0 0 0 . 0 0 0 . 1 8 0 . 1 2 0 . 1 3 0 . 3 4

M g O 3 . 7 5 3 . 7 8 3 . 8 8 3 . 8 3 3 . 7 1 0 . 9 4

C a O 0 . 0 0 0 . 1 6 0 . 0 0 0 . 0 0 0 , 0 0 0 . 0 0

N a 2 0 0 . 0 0 0 , 0 0 0 . 0 0 0 . 0 0 0 , 0 0 0 . 0 0

K 2 0 1 0 . 8 3 1 0 . 8 0 1 0 , 8 6 1 0 . 8 1 1 0 , 5 0 1 0 . 0 5

T o t a l

9 3 . 4 5 9 3 . 5 2 9 4 . 8 4 9 4 . 6 4 9 3 , 7 2 9 3 . 0 5

N u m b e r o f c a t i o n s p e r 2 2 o x y g e n s

33 357 /1 380 460 4 73 395

S i 7 . 1 0 7 . 1 0 7 . 0 9 7 . 0 9 6 . 9 9 6 . 5 7

A1 v 0 .90 0 .90 0 .91 0 .91 1 ,01 1 .43

A W 2 . 7 6 2 . 8 1 2 . 7 7 2 . 8 2 2 . 9 9 3 . 4 4

T i 0 . 0 0 0 . 0 2 0 . 0 2 0 . 0 0 0 . 0 1 0 . 0 0

Fe 2+ 0 .57 0 .45 0 .51 0 .51 0 .32 0 .45

M n 0 . 0 0 0 . 0 0 0 . 0 2 0 . 0 1 0 . 0 2 0 . 0 4

M g 0 . 7 7 0 . 7 7 0 . 7 9 0 . 7 8 0 . 7 5 0 . 1 9

4 . 1 0 4 . 0 6 4 . 1 1 4 . 1 2 4 , 0 9 4 . 1 2

C a 0 . 0 0 0 . 0 2 0 . 0 0 0 , 0 0 0 , 0 0 0 . 0 0

N a 0 . 0 0 0 . 0 0 0 , 0 0 0 . 0 0 0 , 0 0 0 . 0 0

K 1 .91 1 .89 1 .88 1 ,87 1 .82 1 .76

T o t a l 1 4 . 0 l 1 3 . 9 7 1 3 . 9 9 1 3 , 9 9 1 3 . 9 1 t 3 . 8 8

* T o t a l i r o n a s F e O


8/13

2 5 0 A . I . O k a y : G l a u c o p h a n e - L a w s o n i t e Z o n e B l u e s ch i s ts F r o m N W T u r k e y

c

o o c~

o o o 9

0 o

u Jd

Fi g . 4 . C o mp o s i t i o n s o f so d i c p y ro x e n e s p l o t t e d o n a c mi t e - j a d e i t e -

a u g i t e d i a g r a m . S o d i c p y r o x e n e s f r o m m e t a c h e r t s , f i l l e d c i r c l e s ;

f r o m m e t a b a s i t e s , o p e n c i r c l e s ; f r o m m e t a k e r a t o p h y r e s , f i l l e d

s q u a r e s

O 4

X _

O . 2

I I I I l l

o o . 0 . 2 o . 3 o 4 o ~ o . 6

Fe/Fe Mg Mn

F i g . 5 . C o m p o s i t i o n o f c h l o r i t e s f r o m N o r t h e a s t T a v s a n h p l o t t e d

i n t e r m s o f t h e i r F e / ( F e + M g + M n ) a n d A 1 /( A 1 + F e + M g + M n )

ra t i o s

9 - . . o ~ o = o o ; \

.

oO 9 9 - 9 ~ 9

/

V V V V

" - /

v ,.]

Sp lm

Fi g . 6 . Ga rn e t c o m p o s i t i o n s p l o t t e d o n sp e ssa r t i n e -g ro ssu l a r - (a l -

m a n d i n e d i a g r a m ; a l l p y r o p e c o n t e n t s b e l o w 9 . G a r -

n e t s f r o m m e t a c h e r t s f i l l e d c i rc l e s; f r o m m e t a b a s i t es , o p e n c i r c l e s

a Mo t. Ea2Fe3Si3012(OH)

_>.

~ 3

~

E a A t

Fi g . 7 . a C o mp o s i t i o n s o f 23 e p i d o t e s f ro m 7 b l u e sc h i s t s p l o t t e d

i n t e rms o f t h e i r p i s t a c it e c o m p o n e n t s , b Th e c o m p o s i t i o n a l l y i n v a -

r i a n t e p i d o t e - l a w so n i t e -h e m a t i t e a s se mb l a g e i n th e C a - Fe 3+ - A1

s y s t em f r o m t w o m e t a c h e r t s ( 38 0 a n d 4 5 9 )

L

~

e g

F i g . 8 . P h e n g i t e c o m p o s i t i o n s p l o t t e d o n A 1 - F e - M g d i a g r a m .

P h e n g i t e s f r o m m e t a c h e r t s ,

f i l l e d c i r c l e s ;

f r o m m e t a b a s i t e s ,

o p e n

circles.

C o m p o s i t i o n a l f i e ld o f p h e n g i t e s f r o m E a s t e r n O t a g o

g re e n sc h i s t s (B ro wn 1 9 6 7 ) a re sh o wn b y

d a s h e d l i n e s

c i u m s u b s t i t u t i o n 0 .0 3 < X c a < 0 .1 0 ) i n s o d i c a m p h i -

bo le . A decrease in the par t i t ion coeff ic ien t , wi th in -

creas ing ca lc ium con ten t in sod ic am phibo le , i s to

be expe c ted as the KD fo r ac t ino l i t e /ch lo r i t e pa i rs i s

0 .58 Ka wa ch i 1975 ; Co om bs e t a l. 1976) .


9/13

A.I. Okay: Glaucophan e-Lawsonite Zone Blueschists Fro m NW Turkey 251

1.6

~.2

OA

0 0

0 0

' o i ~ o 1 8 1 : 2 ' 6

F e / M g ) c h l o r i t e

1 6

,~I,2

=

~

0B

0.0

o . o o o 1 8 1 . (

b (At/Fe3 ]sodic.,

y r o x e n e

Ok,

Fig. 9. a Fe 2 +/Mg ratios in coexisting sodic amphib ole an d chlorite,

where Fe =to tal Fe, Sodic amphiboles with Xca< 0.03, o p e n c i r -

c l e s ; sodic amphibo les with 0.03 < Xca < 0.1, i l l e d c i r c le s b A1/Fe 3+

ratios in coexisting sodic amphibole and sodic pyroxene

T h e C o m p o s i t i o n o f t h e F l u i d P h a s e a n d t h e S t a t u s

o f C 2

The abundance of hydrous bluescbist minerals, such

as lawsonite and/or sodic amphibole, in the initially

anhydrous basic igneous rocks is prima facie evidence

for the presence of fluid phase during the regional

metamorphism. The lack of graphite in the blueschists

suggests that the two main components of the fluid

phase were H20 and CO2. The common occurrence

of lawsonite-quartz and phengite-sphene subassem-

blages indicate that the fluid was dominated by H20

Xco2


10/13

252 A.I. Okay: Glaucophan e-Lawsonite Zone Blueschists Fro m NW Turkey

a A t

/ / ~

* Q u o r t z

/ / \ +Lo.wsonife

/ / ~ +Iron-oxide

1 \

A l b i f e L / \

A ~ to /:: ~ / L 6 - - - : - - - ~

A[bil'e

Jadeite

. t

0.2

AcmiteN

AI9

~ S Quartz

9Lowsonite

*Iron-oxide

*H20

[orite

f i l p n o m e l o n e

R/MR

0 4

Ornphacite

F i g 10. a NAFM projection of mineral

compositions from quartz, lawsonite

and iron-oxide hematite) onto the

tetrahedra Na- AI *- Fe 2+ -M g. Only

some of the tie lines are indicated.

AI* = A1-2 Ca) . b Projection of

mineral compositions from quartz,

lawsonite, HzO and iron-oxide

hematite) onto the plane

Na -A I* - Fe z+, Mg). The jadeite and

augite contents of sodie pyroxenes are

also indicat ed. A1 * = A1 - 2Ca)

assemblages may be recognizable. However, the es-

tablishment of the ideal phase compatibilities at dif-

ferent P- T -X va lu es is important in understanding

the evolution of mineral assemblages through meta-

morphism. Phase relations established from equili-

brated mineral assemblages can then be used to un-

derstand the nature of frozen reactions and zoning

in minerals.

Metamorphic minerals are assumed to have

reached equilibrium in equigranular, schistose meta-

cherts (see Fig. 2) and metabasites. Rocks with reac-

tion textures involving replacement of sodic pyroxene

by sodic amphibole are interpreted to be in disequili-

brium.

At

/ / ~ * Q u a r t z

/ \ +Lawsonife

/ \ +Iron-oxide

A[bite~ ~ .1"120

(Jnd e i f e ) ~ . . . _ ..~ ~ i r e

Fig. 11. Model phase relations in the gla ucophane-lawson ite facies

for moderat e Fe2 +/F e2+ +Mg values 0.30-0.50) in the rock,

shown on a NAF diagram. Sodic pyroxene field is s t i pp l e

h a s e R e l a t io n s

The minerals considered in this study can be rep-

resented to a first approximation in the system

Na20 - K2 0 - CaO - MgO - FeO - MnO - Fe203

-A1203-TiO2-SiO2-H20. K20, MnO and TiOa

are assumed to affect only the formation of the

phases phengite, spessartine and sphene respectively.

By considering quartz-bearing assemblages SiO2 is

regarded as an excess component, and H20 is

taken as a perfectly mobile component. The chemo-

graphic relationships are further simplified by pro-

jecting from lawsonite for CaO and from hematite

for Fe203 into the system Na20-MgO-FeO-

AlzO3 (NAFM). All projections are made from hema-

tite although part of the sodic amphibole field, as

well as almandine and stilpnomelane are only stable

with magnetite. However, projecting from magnetite

will only slightly alter the coordina tes of sodic pyrox-

enes and amphiboles in the NAFM system but will

not have any effect on the topology. The algebraic

procedure used for projecting phases is that given

by Greenwood (1975).

Phase relations in the glaucophane-lawsonite

facies between the minerals sodic amphibole,

chlorite, albite, sodic pyroxene, almandine, stilpno-

melane and talc are shown in Fig. 10 a. In the NA FM

diagram sodic pyroxenes project into an open ended

beak shaped volume with the calcic end-members

plotting below the A1 -F e 2 + - M g plane. The posi-

tions of different sodic pyroxene end-members are

shown in a NAF triangular diagram (Fig. 10 b) where

Fe 2 + and Mg are treated as a single component . The

advantage of the NAF diagram lies in the precision

with which actual sodic pyroxene and sodic amphi-

bole compositions can be plotted.

Figure 11 shows an NAF diagram for moderate

Fe2+ /Fe2++Mg values (0.3-0.5), where chlorite is

the stable ferromagnesian phase. Here, the important,

compositionally invariant assemblage is albite

(jadeite)-chlorite-sodic amphibole plus the projected

phases. Such assemblages are found in Northwest

Turkey, in New Caledonia (Black 1973, p. 224) and

in many other areas.

At lower Fe2+/Fe2++Mg values (0.55) stillp-


11/13

A.I. O kay: G laueophane-LawsoniteZone Blueschists From NW Turkey 253

. . . . . .

R

u

e

o o o S T I L P N O H E L N E

i / l l / / / i / / / / / / , / / / / / / /~r~l~}//I//////11///11/i////////;,,, . . . , , , ,

9 : , ~ ' : : " 9 ~ , l l , , , ~ l l , , 7 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ~ ' i l , 'l l ll / # l l ,, i ll i l, I / ,v / I / l l

I l l l

i l l I I ~ O I "

m m 9 ~ m 9 m m 9

o

: , 9 #

9

_

o ~ . . . . . , . ~ : . : J , - - , .

' ; / i / tt / l i, i D ; : i ' ll t i, , Y i

T L E

I I I I _ _ I I ~ i

t _ _ I ~ ]

I I . . . . 1 | | I - I I . 1

M R M R

Fig. 12. a So dic amphibole composition n re lation to the mineral assemblage. Sodic amphibole with ch lorite, solid squares; with stilpnome~

lane, open squares; wi th chlorite and stilpnomelane, half-filled squares; with almandine,open circles; with talc and chlorite, open trzkmgles.

ll Phase relations o f sod ic amphibo le in the glaucophane-lawsonite facies. Sodic amphibo le compositions which may coexist with two

ferromagnesian minerals are ruled. Iron-o xides most probably can coexist with all so dic amp hibole compositions. Albite is restricted

to glaucophane-ferroglalscophane olid solution

n o m e l a n e a r e t h e s t a b l e f e r r o m a g n e s i a n m i n e r a l s

c o e x i s t in g w i t h s o d i c a m p h i b o l e . T h e c h a n g e f r o m

o n e f e r r o m a g n e s i a n m i n e r a l t o a n o t h e r o c c u r s a t a p -

p r o x i m a t e l y c o n s t a n t F e 2 + / F e z + + M g a n d t h e r e f o r e

c a n n o t b e s u c c e s sf u l ly il l u s tr a t e d o n t h e N A F d i a -

g r a m .

A p e c u l i a r p r o b l e m i n t h e D e v l e z a r e a i s t h e p r e s -

e n c e o f a l m a n d i n e g a r n e ts w i t h 2 5 - 3 5 g r o s su l a r

c o m p o n e n t c o e x i s ti n g w i t h A l - r ic h a m p h i b o l e s . W h e n

p r o j e c t e d f r o m l a w s o n i te f o r C a o n t h e N A F p l a n e,

t h e g a r n e t s p l o t n e a r t h e F e 2 + , M g ( F ) a p e x ; s i nc e

c h l o r i t e c o e x i s t s w i t h c o m p a r a t i v e l y A l - p o o r s o d i c

a m p h i b o l e , g a r n e t - a m p h i b o l e a n d c h l o r i te - a m p h i b o l e

t i e l ines c ros s .

T h e r e i s n o t e x t u r a l e v i d e n c e f o r a n y d i s e q u i l i -

b r i u m b e t w e e n c o e x i s t in g l a w s o n i t e a n d g a r n e t . F u r -

t h e r m o r e g a r n e t s f r o m t h e C a z a d e r o a r e a m e t ab a s it e s,

c o e x i s t i n g w i t h l a w s o n i t e a n d a l m n i n o u s s o d i c a m p h i -

b o l e ( C o l e m a n a n d P a p i k e 1 9 6 8 , p . l 1 1 ), h a v e s i m i l a r

g r o s s u l a r c o m p o n e n t s ( 2 5 - 3 0 ; L e e e t a l. 1 96 3 ,

p . 4 7 2 ) . I t s e e m s t h a t t h e b l u e s c h i s t s o f t h e D e v l e z

a r e a r e c r y s t a l li z e d a t t h e c r i ti c a l P - T c o n d i t i o n s c o r -

r e s p o n d i n g t o t h e c h l o r i t e - g a r n e t t r a n s i t i o n .

I n s t a b i l i ty o f S o d i c P y r o x e n e C h l o r i te

S o d i c p y r o x e n e s c o n t a i n p r o p o r t i o n a t e l y h i g h er

a m o u n t s o f N a + C a t h a n s o d i c a m p h i b o l e s , c o n s e -

q u e n t l y t h e y a r e r e s t r i c t e d t o t h e s o d i u m - r i c h c o r n e r

o f t h e N A F M d i a g ra m . T h e y a re s e p a ra t e d f r o m t h e

f e r r o m a g n e s i a n m i n e r a l s b y t h e i n t e r v e n i n g s o d i c a m -

p h i b o l e c o m p o s i t i o n a l f i e l d a n d a l b i t e -s o d i c a m p h i -

b o l e t i e l i n e s ( F i g . 1 0 a ) . T h u s a c m i t e - a n d j a d e i t e - r i c h

s o d i c p y r o x e n e s c a n n o t c o e x i s t w i t h f e r r o m a g n e s i a n

m i n e r a l s, i n s t e a d s o d i c a m p h i b o l e i s t h e s t a b le p h a s e .

O b v i o u s l y s o d i c p y r o x e n e c a n c o e x i s t s t a b ly w i t h s o -

d i c a m p h i b o l e i n a s s e m b l a g e s f r e e o f a n y f e r r o m a g n e -

s i a n m i n e r a l s , a s i n t h e s o d i u m - r i c h m e t a c b e r t 3 8 1

(Table 3 ) .

T h e c o e x i s t e n c e o f s o d i c p y r o x e n e w i t h c h l o r i t e

a n d s o d i c a m p h i b o l e i n m a n y b l u e s c h i s t m e t a b a s i t e s

f r o m t h e D e v l e z a r e a is d u e t o a n i m c o m p l e t e p r o -

g r a d e s o d i c a m p h i b o l e p r o d u c i n g r e a c t i o n i n v o l v i n g

s o d i c p y r o x e n e a n d c h l o r i t e ( O k a y i n p r e p a r a t i o n ) .

T h e C o m p o s i ti o n o f S o d i c A m p h i b o l e

i n R e l a t i o n t o M i n e r a l A s s e m b l a g e

A l l p h a s e s i n t h e N A F M s y s t e m h a v e t ie l in e s e x t e n d -

i n g t o t h e s o d ic a m p h i b o l e f i e ld ; t h e r e f o r e t h e c o m p o -

s i t i o n a l f i e l d o f s o d i c a m p h i b o l e s c a n b e u s e d a s a

p l a n e o n w h i c h o t h e r p h a s e s a r e p r o j e c t e d i n t e r m s

o f a c tu a l s o d i c a m p h i b o l e c o m p o s i t i o n s ( B r o w n

1974).

I n q u a r t z - b e a r i n g r o c k s , s o d i c a m p h i b o l e c a n b e


12/13

254 A.I. Ok ay: Glaucophane-Lawsonite Zone Blueschists Fro m NW Turkey

r e g a r d e d a s c o n s is t in g o f fi ve m a j o r c o m p o n e n t s

( N a 2 0 , M g O , F e O , A 1 2 03 , F e 2 O a ) , c o n s e q u e n t l y a n y

t h r ee p h a s es in t h e N A F M d i a g r a m p l u s ir o n - o x i d e

s h o u l d c o e x i s t w i t h a s i n gl e c o m p o s i t i o n o f s o d i c a m -

p h i b o l e . S o d i c a m p h i b o l e c o e x i s t i n g w i t h t w o o t h e r

p h a s e s i n t h e N A F M d i a g r a m p l u s i ro n - o x i d e s h o u l d

b e c o m p o s i t i o n a l l y u n i v a r i a n t; t h e c o m p o s i t i o n

s h o u l d v a r y a l o n g a l in e o n t h e M i y a s h i r o d i a g r a m .

I n F i g . 1 2 a s o d i c a m p h i b o l e s a r e s h o w n i n t e r m s

o f c o e x i s t in g m i n e r a l s ; t h e f i g u r e in c l u d e s s o d i c a m -

p h i b o l e s f r o m G t i m e l e ( L f i n e l 1 9 67 ) a n d f r o m s t i lp n o -

m e l a n e - b e a r i n g F r a n c i s c a n m e t a c h e r t s , a s w e l l a s so -

d i c a m p h i b o l e s f r o m t h e D e v l e z a r ea . T h e s o d i c a m -

p h i b o l e c o m p o s i t i o n a l f i e ld is d i v i d e d i n t o f o u r m a j o r

r e g i o n s e a c h a s s o c i a t e d w i t h o n e o f t h e f o l l o w i n g f e r -

r o m a g n e s i a n m i n e r a l s : c h l o r i te , a l m a n d i n e , t a l c a n d

s t i l p n o m e l a n e ; a f i ft h d e e r i t e r e g i o n i s p r e s e n t

a r o u n d t h e r i eb e c k it e e n d - m e m b e r ( M u i r W o o d 1 97 7,

p . 256 ) .

S p e s s a r t i n e - r i c h g a r n e t s a r e s t a b l e w i t h a l l s o d i c

a m p h i b o l e c o m p o s i t i o n s a s a n ex t r a M n - b e a r i n g

p h a s e ; o n l y a l m a n d i n e w i t h n e g l i g ib l e s p e s s a r ti n e

c o m p o n e n t i s r e s t r ic t e d t o g l a u c o p h a n e (s.1 .) b e a r i n g

a s s e m b l a g e s ( 3 5 7 / 1 a n d 5 3 6 ) . H o w e v e r , a s d i s c u s s e d

e a r li e r, a l m a n d i n e m i g h t r e p r e s e n t a h i g h e r g r a d e o f

m e t a m o r p h i s m . S o d i c p y r o x e n e s a re n o t s h o w n a s

t h e y d o n o t c o e x i s t s t a b l y w i t h th e o t h e r f e r r o m a g n e -

s i a n m i n e r a ls , l y i n g o n t h e o p p o s i t e s id e o f t h e s o d i c

a m p h i b o l e c o m p o s i t i o n a l f ie l d ( F i g . 1 0 a ).

T h e p o s i t io n o f u n i v a r i a n t l in e s o n t h e s o d i c a m -

p h i b o l e f i e l d w i ll d e p e n d t o s o m e e x t e n t o n t h e c a l -

c i u m c o n t e n t o f t h e s o d ic a m p h i b o l e w h i c h h a s a n

i m p o r t a n t e f fe c t o n t h e F e Z + / M g p a r t i ti o n i n g b e -

t w e e n s o d i c a m p h i b o l e a n d o t h e r m i n e r al s . V a r i a ti o n s

i n t h e c a lc i u m c o n t e n t o f so d i c a m p h i b o l e a n d u n c e r -

t a i n t i e s i n t h e f e r r i c / f e r r o u s r e c a l c u l a t i o n w i l l r e s u l t

i n c o m p o s i t i o n a l b a n d s , r a t h e r t h a n l i n es , o n t h e s o d i c

a m p h i b o l e f i el d , m a r k i n g t h e c o e x i s te n c e o f t w o f e r r o -

m a g n e s i a n m i n e r a l s (F i g . 1 2 b ).

B r o w n ( 1 9 7 4 ) f i rs t r e l a t e d s o d i c a m p h i b o l e c o m -

p o s i t i o n t o c o e x i s t in g m i n e r a l s i n t h e b l u e s c h is t s f r o m

S h u k s a n . T h e m a i n d i ff e re n c e b e t w e e n t h e d i a g r a m

h e r e a n d B r o w n s d i a g r a m ( 1 9 74 , F i g . 1 1) i s i n t h e

t r e a t m e n t o f i r o n - o x id e s ; a s m a n y o f B r o w n s a m p h i -

b o l e a s s e m b l a g e s l a c k e d ir o n - o x i d e s , h e a s s u m e d t h a t

i r o n -o x i d e s w e r e n o t s t ab l e w i t h f e r r o g l a u c o p h a n e

a n d g l a u c o p h a n e c o m p o s i t i o n s . H o w e v e r , s o d i c a m -

p h i b o l e c o m p o s i t i o n s f r o m N o r t h w e s t T u r k e y d e -

m o n s t r a t e t h a t t h i s i s n o t t h e c a s e ( O k a y , i n p r e s s );

t h e a b s e n c e o f i r o n - o x i d e s i n s o m e a s s e m b l a g e s i s

p o s s i b l y d u e t o l o w a m o u n t s o f fe r r ic i o n i n th e r o c k

g i v in g i n c re a s e d c o m p o s i t i o n a l f r e e d o m .

Acknowledgements I thank S .O . Ag rell , E.H. Brown, G.T.R.

Droop, J.G. Spray, and R. Muir Wood for reviewing the manu-

script. Probe facili t ies were provided by the Department of M ineral-

ogy and Petrology in Camb ridge. This work was carried out w hile

in receipt of a grant from the Mineral Research and Exploration

Institute of Turkey (M.T.A.), w hich is gratefully acknowledged.

eferences

Black, P.M .: Mineralogy of New Caledonian m etamorphic rocks

I. Garnets fro m the Ouego a district. Contrib. M ineral. Petrol.

38, 221-235 (1973)

Black, P.M .: M ineralogy of New Caledonian m etamorphic rocks

IV. Shee t si licates from th e Ouegoa district . Contrib. Mineral.

Petrol. 49, 269-284 (1975)

Brinkmann, R. : Mesozoic troughs an d crustal structure in An ato-

lia. Bull. Geol. S oc. Am . 83, 819-82 6 (1972)

Brown, E.H .: The greenschist facies in part of Eastern Otago,

New Zealand. Contrib. M ineral. Petrol. 14, 259 ~92 (1967)

Brown, E.H.: Com parison o f the mineralogy and phase relations

of b lueschist s f rom the Nor th Cascades , Washington and

greenschists from O tago, New Zealand. B ull . Geol. So c. Am .

85, 333-344 (1974)

~o~u lu, E. : Etude p6 trographique de la r6gion de M ihalli~qik (Tur-

quie). Schweiz. Mineral. Petrogr. Mitt. 47, 683 824 (1967)

~o~ulu, E. , Krummenacher, D. : Probl6mes g6ochronom6triques

dans la patt ie NW de l Anatolie Centre (Turquie). Schweiz.

Mineral. Petrogr. Mitt. 47, 825 831 (1967)

Coleman, R.G. , Lee , D.E . : Glaucophane-bearing m etamorphic

types of the Cazed oro area, C alifornia. J. Petrol. 4, 260-301

(1963)

Coleman, R.G. , Papike, J.J. : Alkali amphiboles from the blue-

schists of Cazadero, California. J. P etrol. 9, 105-1 22 (1968)

Coombs, D.S., Nakamura, Y., Vuagnat, M. : Pumpellyite-actinolite

facies schists of the Taveyanne Formation near Loeche, Valais,

Switzerland. J. Petrol. 17, 440-471 (1976)

Cooper, A .F. : Progressive metamorphism of metabasic rocks from

the Ha ast S chist Gro up of Southern N ew Zealand. J. Petrol.

13, 457-492 (1972)

Ernst, W.G. , S eki, Y. , Onuki, H. , Gilbert , M .C.: Com parative

study of low-grade metamorphism in the California C oast

Ranges and the outer metamorphic belt of Japan. Geol. Soc.

Am., Me re. 124, 259 (1970)

Essene, E.J. , Fyfe, W.S. : Om phacite in Californian metamorphic

rocks. Contrib. Mineral. Petrol. lfi, 1 23 (1967)

Greenwood, H.J. : Thermodynamically valid projections of exten-

sive phase relationships. Am . M ineral. 60, 1-8 (1975)

Hsu, L.C. : Se lec ted phase re lat ionships in the sys tem A 1 - M n -

F e - S i - O ; a model for garnet equil ibr ia . J . Pet ro l . 9 , 40-83

(1968)

Hun t, J.A. , Kerrick, D.M. : The stabili ty of sphene: experimental

redetermination and geological implications. Geochim. C osmo-

chim. Acta 41, 279~88 (1977)

Kaaden, G.v.d. : The significance and distribution of glaucophane

rocks in Turkey . Bull. M iner. Res . Explor. Inst. Tu rk. 67, 37-67

(1966)

Kawachi, Y. : Pum pellyite-actinolite and contiguous facies meta-

morphism in part of upper Wakatipu district , South Island,

New Zealand. N.Z.J. Geol. Geophys. 18, 401-441 (1975)

Kaya, O. : Aufbau un d Geschichte einer anatolischen Opiolith-

Zone. Z. Deutsch. Geol. G es. 123, 491-501 (1972)

Kaya, O. : Outlines of the ophioli te question in the Tavsanli region

(in Turkish). Bu ll. Geo l. Soc. Turk. 15, 26-108 (1972)

Lee, D.E. , Coleman, R.G. , E rd, R.C. : Garnet types from the C a-

zadero area, California. J. Petrol. 4, 460M92 (1963)

Lfinel, T. : Geolo gy o f Stibren-Karaalan area, Eski~eh ir county


13/13

A . I . O k a y : G l a u c o p h a n e - L a w s o n i t e Z o n e B l u e s ch i s ts F r o m N W T u r k e y 2 55

Tu rk e y ) . Ph . D Th e s i s u n p u b l i sh e d ) , U n i v e rs i t y o f B r i s to l

1967

M a d e n T e t k i k v e A r a m a E n s t . : G e o l o g i c a l m a p s o f T u r k e y ; A n -

k a ra sh e e t 1 9 6 3 ; I s t a n b u l , Zo n g u l d a k , I z mi r sh e e t s . A n k a ra :

M .T .A . Pu b l i c a t i o n s 1 9 6 4

M i y a sh i ro , A . : Th e c h e mi s t ry , o p t i c s a n d g e n e s is o f t h e a l k a l i

am phibo les . J . Fac . Sci . , Un iv . Tokyo , Sect . 2 11 , 57-83 1957)

M u i r W o o d , R . : Th e i ro n - r i c h b l u e sc h i s t f a c i e s mi n e ra l s : I D e e r i t e .

M i n e ra l . M a g . 4 3 , 2 5 1 ~ 5 9 1 9 79 )

N i t s c h, K . H . : D a s P - T - X c o ~ S t a b i li t at s f ie l d y o n L a w s o n i t . C o n -

t r ib . Minera l . Pet ro l . 34 , 116 134 1972)

O k a y , A . I . : So d i c p y ro x e n e s f ro m me t a b a s i t e s i n th e e a s t e rn M e d i -

t e r ra n e a n . C o n t r i b . M i n e ra l . Pe t ro l . 6 8, 7 -1 1 1 9 78 )

O k a y , A . I . : So d i c a mp h i b o l e s a s o x y g e n fu g a c i t y i n d i c a t o r s i n

me t a mo r p h i sm . J . G e o l . i n p re s s )

O n u k i , H . , E rn s t , W.G . : C o e x i s t i n g so d i c a m p h i b o l e s a n d so d i c

p y ro x e n e s f ro m b l u e sc h i s t fa c i e s me t a m o rp h i c ro c k s . M i n e ra l .

Soc , Am ., Spec . Pap . 2 , 241-25 0 1969)

R o e v e r , E .W.F . , d e : B l u e a mp h i b o l e -a l b i t e -c h l o r i t e a s se mb l a g e s

f r o m F u s c a l d o S o u t h e r n I ta l y ) a n d t h e r o l e o f g l a u c o p h a n e

i n me t a mo r p h i sm . C o n t r i b . M i n e ra l . Pe t ro l . 5 8 , 2 2 1 -2 3 4 1 9 76 )

S t a t h a m , P . J . : A c o m p a ra t i v e s t u d y o f t e c h n i q u e s fo r q u a n t i t a t i v e

a n a l y s i s o f t h e X - ra y sp e c t ra o b t a i n e d w i t h a S i L i ) d e t e c t o r .

X -R a y Sp e c t ro m. 5 , 1 6 -2 8 1 9 7 6 )

Sw e a t m a n , R .R . , Lo n g , J .V .P . : Q u a n t i t a t i v e e l e c t ro n p ro b e mi c ro -

a n a l y s i s o f ro c k fo rmi n g mi n e ra l s . J . Pe t ro l . 1 0 , 3 3 2 -3 7 9 1 9 69 )

Ze n , E -A n . : P re h n i t e a n d p u mp e l l y i t e b e a r i n g mi n e ra l a s se mb l a g e s

w e s t s i d e o f t h e A p p a l a c h i a n m e t a m o r p h i c b e l t , P e n n s y l v i n i a

t o N e w fo u n d l a n d . J . Pe t ro l. 1 5 , 1 97 -2 4 2 1 9 74 )

R e c e i v e d D e c e mb e r 2 1 , 1 9 7 9 ; A c c e p t e d Fe b ru a ry 7 , 1 9 8 0

03 - glaucophane-lawsonite schists - CMP 1980.pdf

Documents

Transcript of 03 - glaucophane-lawsonite schists - CMP 1980.pdf