THE KINETICS OR REDUCTION OF CARBONACEOUS METEORITES : MÖSSBAUER STUDY

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THE KINETICS OR REDUCTION OF

CARBONACEOUS METEORITES : MÖSSBAUER STUDY

T. Malysheva

To cite this version:

T. Malysheva. THE KINETICS OR REDUCTION OF CARBONACEOUS METEORITES : MÖSSBAUER STUDY. Journal de Physique Colloques, 1980, 41 (C1), pp.C1-405-C1-406.

�10.1051/jphyscol:19801156�. �jpa-00219642�

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JOURNAL DE PHYSIQUE Colloque Cl , supplgment au n ^O1, Tome 41, janvier 1980, page C 1-405

M E KINETICS OR REDUCTION OF CAREIONACEOUS METEORITES : I%SSBAUER STUDY

T .V. Malysheva

V . I . Vernadsky I n s t i t u t e o f Geochemistry and AnaZyticaZ Chemistry, USSR Academy o f S c i e n c e s , Moscow, USSR.

The experimental simulation of formation of e n s t a t i t e chondrites from car-

bonaceous ones is the purpose of t h i s work. The e n s t a t i t e chondrites consist

largely of almost pure ens t a t i te MgSi03, nickel-iron and t r o i l i t e PeS (1 ). The whole mineralogy of the e n s t a t i t e chond- r i t e s suggests t h a t they were formed i n very reduced conditions (2). The reduc-

t i o n k i n e t i c s of the carbonaceous chond- r i t e s Orgueil C 1 , Cold Bokkeveld C2 and Allende C3(V) studied by means of Mgssba- n e r spectroscopy w a s investigated i n

temperature range 7C+1300°C with the run duration 5 min t o several days.

Reducing condltions were obtained by means of a buffer system Ti-TiO, &hat provides the equilibrium f a t m

(T=1230°C). O2

The i r o n phase d i s t r i b u t i o n i n natu- ral simples of carbonaceous chondrites is given i n the Fable. Montmorillonite, magnetite

,

c h l o r i t e , o l i v i n e and pentlan- d i t e a r e i d e n t i f i e d . Metal-iron, t r o i l i t e and o l i v i n e have been detected i n the i n t e m e d i a t e products of react;ions

.

^By

means of X-ray phase a n a l y s i s the exist-

The i r o n d i s t r i b u t i o n among the mineral phases demonstrates that isomorphous exchange of pe2+, Mg between ferrogeneous o l i v i n e and e n s t a t i t e does not occur i n any case; the t r o i l i t e amount goes through a maximum and does not depend on the reducing temperature but only on the sulphur amount i n the chondrite: -3C@

( C I ) ; 420% (C2) and -10% (C3V). On the Fig. the t y p i c a l change of Blf6ssbauer s p e c t r a with increasing heating time from 5 min t o 40 min i s shown. The amount of m e t a l l i c i r o n increases and of ~ e ~ +

i r o n i n olivine decreases with increasing time. Solne i r o n is formed i n the super- paramagnetic s t a t e . The amount of taoi- l i t e has i t s maximum a f t e r a 10 min heating. Por i r o n t o be reduced t o the point a t which t h e amount of t r o i l i t e is a maximum high temperatures (> 1300°C) during s h o r t period of time ( 4 5 min) a r e necessary. Such conditions may be r e a l i - zed i n impacts between the parent bodies along with the process of chondrules formation. Such s h o r t heating time requi- r e s cm-size parent bodies.

enoe of e n s t a t i t e was established (7).

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19801156

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C1-406 ^JOURNAL^DE^PHYSIQUE

Fig. M'dssbauer s p e c t r a of the carbonaceous chondrite Cold Bolrkeveld reduced a t the temperature l l O O ° C during time:

a ) 5 min; b) 1 0 min; c ) 20 min; d ) 40 min.

Table Parameters of ~bijksbaner s p e c t r a and i r o n phase d i s f r i b u t i o n of n a t u r a l carbonaceous chondrite: IS, QS, T 20.02 mm/s;

S+%;

-

^He,,+5 ^koe

Meteorite pe2+

2 . Cold Bok-1.20 2.59 0.41 0.52 36.2

keveld C2

3. Allende 3.28. 2.95 0.35 0.39 82-87 c3(v) 0.40.5 0.-0.3 0.45-0.82 13-18

IS '-left h g h t S mineral 1. 0.52 0.68 0.48 0.48 50.6 montmo-

r i l l o n i t e (3)

2. 0.53 0.73 0.52 0.66 63.8 c h l o r i t e (4) 3.

- ^- ^- - -

o l i v i n e

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References

1. Mason B e y Geochim. Cosmochim Acta 30, (1962), 23.

2. Larimer J.W. ,Buseck P.R., Geochim.

Cosmochim, Acta 38 (1974), 471.

3. Malysheva T.V.,Grachev V.I.,Malyshev 1 Geochimia No1 (19771, 17.

4, Malysheva T.V.,Satarova L.M,,Polyakova - N.P., Geochimia No8 (1977), 1136.

5. W y s h e v a T.V., 6 s s b a u e r E f f e c t in geochemis G r y and cosmochemist rg

.

Nauka, 1975.

6. Goncharov G.P. ,Tomilov C.B., ZVMO, 104. (1975) 233.

7. Malysheva T.V. e t al., Lunw Planet,.

Sci. X (1979)s 775.

- - ^-- ^- -

^pentlan-

d i t e (6)