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ON THE POSSIBILITY OF APPLYING THE Fe57 ISOTOPE TO GEOCHRONOLOGY
K. Amirkhanov, L. Anokhina, R. Chalabov
To cite this version:
K. Amirkhanov, L. Anokhina, R. Chalabov. ON THE POSSIBILITY OF APPLYING THE Fe57 ISOTOPE TO GEOCHRONOLOGY. Journal de Physique Colloques, 1980, 41 (C1), pp.C1-413-C1- 414. �10.1051/jphyscol:19801160�. �jpa-00219647�
JOURNAL DE PHYSIQUE Colloque Cl , supplkment au n " 1, Tome 41, janvier 1980, page C1-413
ON W E POSSIBI L I P OF APPLY I NG W E Fe I SOTOPE TO GEOCHRONOLOGY K.I. Amirkhanov, L.K. Anokhina, R.I. Chalabov
I n s t i t u t e of Physics, t h e Dagheskm Branch of the Acadew of Sciences of the USSR, Makhachkak, 367003
Q h i l e i n v e s t i g a t i n g d i f f e r e n t - a g e nine- rals by b l ~ s s b a u e r spectroscopy it h a s been f o m d t h a t t h e Fe i s o t o p e can s e r v e a s 57 i n d i c a t o r . o f t h e n a t u r a l ageing of a mine- r a l /1,2/. It has been e s t a b l i s h e d t h a t t h e change of i ~ g s s b a u e r p a r a ~ e t e r s w i t h age i s due t o t h e s u p e r p o s i t i o n of such f a c t o r s as r a d i a t i o n and t h e r a s l e f f e c t s which a r e c o n s t a n t l y i n a c t i o n .
3 a d i a t i o n e f f e c t a show t h e i r presence a t t h e decay of r a d i o a c t i v e i s o t o p e s which can be found i n a l l t h e natura-l ~ l i n e r a l s . During t h e g e o l o g i c a l t i a e t h e r e t a k e s p l a c e an i n c r e a s e i n t h e c o n c e n t r a t i o n of daughter products i n a mineral, e.g. such
ones a s r a d i o g e n i c argon and calcium-40 t h a t g e t formed v l t h potassium-40 deca,y/3/.
The appearance of neer e l e z e n t s mith d i f f e - r e n t i o n i c r a d i i d i s t o r t s t h e sy:.lmetrg of t h e l a t t i c e . Thus, f o r example, b i g potas- sium c a t i o n s t o l e r a t e t h e maximum s t r e t c h - ing of t h e o c t a h e d r a l s i t e i n t h e "abw p l a n e , which p r e v e n t s t e t r a h e d r o n s from t u r n i n g . i i h i l e coming i n t o b e i n g of t h e daughter calcium w i t h a s m a l l i o n i c r a d i u s s i v e s r i s e t o a n a x i m u ~ t u r n i n g of t e t r a - hedrons p o s s i b l e and, according-, a mini- 3wn s t r e t c h i n g pf t h e o c t a h e d r a l s i t e i n t h e l a y e r plane. T h i s r e c i p r o c a l a d a p t a t i - on of o c t a h e d r a l and t e t r a h e d r a l s i t e s :.lhich is achieved a t t h e expense of t e t r a - hedrons being t u r n e d and octahedrons being thickened o r f l a t t e n e d i s ~ a p a b l e of pro- n o t i n g s y m e t r y d i s t o r t i o n . And, l a s t l y , t h e el-aergence of argon w i t h t h e i o n i c ra- d i u s 1.93 n o t only deforms t h e i n t e r - s t i c e s b u t a l s o weakens t h e t i e s w d l e s s - e n s t h e e n e r g of t h e l a t t i c e /4/. The .
daughter elements can r e n a i n i n t h e i n t e r - packet space o r , breaking t h e t i e s , g e t
g i v i p g r i s e t o t h e d e f e c t s of t h e F r e n k e l t y p e
The degree of t h e order-disorder around t h e i r o n atoms changes depending on t h e c o n c e n t r a t i o n of t h e d e f e c t s which a r e a f u n c t i o n of terneperature. The number oY
c: ef e c t s d e c ~ e a s e s i ~ i t h t i n e , but t h i s or- r:ering n r o c e s s is extre:2ely i n s i p i f i c a n t and proceeds on t h e g e o l o g i c a l time s c a l e . The value of 3FG
-
"q"-
nay be c a l l e d a f u n c t i o n of t h e number of d e f e c t s t h a t a r e p r e s e n t a t a ziven aoment i n t h e f i r s t , t h e second, t h e t h i r d , e t c , coozdination spheres; it aay be a l s o c a l l e d a f e a s i b l e"couxiternof g e o l o g i c a l e f f e c t s /5/. Zadi- a t i o n cad therlaal e f f e c t s i n minerals d i s - turb t h e balanca of charges, v ~ h i c h i s ax- ways compensated ,by bhe o x i d a t i o n of some ye2+ 60 I?e3+ /6/.
I n t h e geochronological s c a l e s e c u l a r v a r i a t i o n s of @ a r e observed, determined, n o s t l i k e l y , by a change i n t h e thermo- dynaaic regime.
A11 t h e above mentioned f a c t o r s c o n t r i - b u t e t o t h e v a l u e of &; r a d i a t i o n e f f e c t s and t h e p r o c e s s of d i f f u s i o n m a y be c a l l e d g e r p e t u a l l y a c t i n g f a c t o r s , and.thernody- namic e f f e c t s t h e p e r i o d i c ones. The per- i o d i c i t y of ;2S i n t i n e p e r n i t s t o d a t e r o c k s only i n one s e c t i o n of t h e s c a l e w i t h coorStinating t h e r e l a t i v e o r a b s o l u t e age /7,8/.
While s t u d y i n g b i o t i t e s and p h l o g o p i t e s chosen from a l l over t h e ~ e o c h r o n o l o g i c a l s c a l e , beginning with t h e Caizonoic and ending up w i t h t h e pre-Cambrian, it was found t h a t t h e r e l a t i o n of cis-coordinated
i r o n
-
~ e ~ + ~-
c o r r e l a t e s w i t h ~ ~ / ~ e ~ + ~ ~ ~ ~ ~ t h e age of minerals. The v a l u e of t h i si n t o t h e i n t e r s t i c e s of t h e packet t h u o
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19801160
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The d e c r e a s e i n t h e i n t e n s i v i t i e s of t h e p e a k s of I?eL+ 3 and t h e i n c r e a s e of t h e l i n e se?liv;.idth w r e c o n d i t i o n e d by an ir- z e p l a r i t y o f t h e i n t e r a c t i o n o f p e 2 + i o n s -!ith t h e l i g a n d s i n t h e n e a r e s t c o o r d i n a t - i o n s p h e r e s . The a-dthors /9/ a t t r i b u t e it t o t h e l o c a l i z a t i o n of t h e $ e f e c t s mainly i n t h e v i c t n i t g of t h e s e p o s i t i o n s and t o t h e o x i d a t i o n of i r o n i n t r a n s - o c t a h e d - r o n s . And the presence of a d i s t i n c t i v e q u a d r u p o l e d-ov-blet ye,? i n t h e s p e c t r a of
?re-Sanbrian m i n e r a l s and i t s i n t e n s i v i t y t e s t i f y t o a d o s e of r a d i o a c t i v e i r r a d i - a t i o n r e c e i v e d by t h e a i n e r a l . P i 5 , 7 shows Kgssbauer s p e c t r a of ??e2+ in b i o - t i k e s : ( a ) f o r t h e b i o t i t e d a t e d by t h e
1 , a i z o n o i c , ( b ) f 9 r t h e b i o t i t e d a t e d by t h e ?re-Car~brbrban. I n t h e s ? e c t r a ( a , b ) t h e d . o ~ b l e t T e T c h a r a c t e r l . n t i c of t h e t e t r a h e d r a l Lron i s p r e s e n t ; i n t h e spec- t r a ~ ( b ) t h e r e aDpeprs t h e d o u b l e t 7eZ+
o x i d i z e d i n t r a n s - o z t a h e d r o n s and c h a r a c - t e r i s t i c of t h g s a n p l e s t h a t g o t a d o s e of i r r a d i a t i o n .
The r e s u l t s c b t a i n e d f o r h i o t i t e s m d g h l o ~ o p i t e s a r e i r , s a t i s f a c t o r y agree:lent w i t h t h e d a t a f o r t g u r d a l i n e s ob.tained by t h e a u t h o r s
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and &i one c a n d a t e n f n e r a l s i n v e s t i g a t e d and nake known c a u s e s dis- t o r t i n g t h e i r t n ~ e age.2 7; -3 2
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/ I / K h . I . A a i ~ k h m o v , L.K..Anokhira, J.S.
S a r d a r o v . C o l l e c k i o n of P a p e r s , D,2U, Kakbaohkala, (1967) , 2 3 .
/2/ Ph.I.Anirkhanov, L.K.Anokhina, S.S.
L a r d a r o v . T h e s e s of P a p e r s f o r t h e XVIth S e s s i o n of t h e So;z;:ission f o r C e f i s i u g A b s o l u t e Age. Xauka P u b l i s h - e r s , 1.; (1969) 103. ,
/3/ Kh. I . h i r k h m o v , d .E . B r a n d t , F .N.
B a r t n i t s l v . T a d i o g e n i c Argon i n Kin- e r a l s and P;ountain liocks. I:akhachkala, (1960) 136.
/4/ V.A.Drits, B .E .Zviagin, S.V.Sobolev.
C h r i s t q l l o c h i m i a ,
2 ,
P u b l i s h - e r s , .BI. (1974) 232./5/
L.?S.Anokhina. A u t h o r ' s P a p e r o f Cmd.T h e s i s . ii;akhacE?kala, (1 970).
/6/ T.V.k;alysheva. "u&sbauer E f f e c t i n Geochemistry axd.Cosmocherni$try. Bau- k a P u b l i s h e r s , L. (1975) 83.
/7/ Kh.I.Ainirkhanov, L.K.Anokhina. Dokla- dy Akademii Wauk SSSB (VdSR),
218,
(1974) 319.
/8/ Kh.I.Amirkhanovt L.K,Anokhina. Dok- l a d y A k a d e p i i liauk S8SR (USSR),
&
(1375) 659.
/9/ V.P.Ivqnitsky, I.V.lJatyash, E.V,Pol- s h i q , F .I .Rakovich. Kiev,
.
(1 974)./lo/
J.Da.non e t a l . .Pyoc . L n t , Conf . ~ E s s b .Spec. (1977) 217.