The Fe-Ni metal equilibrium temperature of the unequilibrated Chainpur LL3.4 chondrite

Nassima MEFTAH; Albert JAMBON; Smail MOSTEFAOUI; El Habib GUEDDA

Nassima MEFTAH Univ Ouargla, Faculté des Mathématiques et Sciences de la Matière, Dépt. de Physique, Ouargla 30 000, Algeria, 4Fac. Sciences Exactes, Université d'El Oued, B. P. 789, El Oued 39000, Algeria.
Albert JAMBON Sorbonne Universités ISTEP UMR 7193, 4 Place Jussieu, UPMC, 75252 Paris Cedex 05, France
Smail MOSTEFAOUI Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie (IMPMC). Sorbonne Université. Muséum National d’Histoire Naturelle, 57 rue Cuvier. 75005 Paris.
El Habib GUEDDA Fac. Sciences Exactes, Université d'El Oued, B. P. 789, El Oued 39000, Algeria.

Keywords: Fe-Ni, ordinary chondrite, temperature, metamorphism, chemical equilibrium

Abstract

We report electron microprobe analyses of Fe, Ni and Co abundances in the associated α and γ phases in the Fe-Ni metal grains in unequilibrated ordinary chondrite Chainpur (type LL3.4). Our elemental measurements of five grains in chondrule and two grains in the matrix show that Co preferentially partitions into Kamacite relative to teanite, however the Co/Ni ratio in both phases is non-solar. The correlation of Co/Ni concentrations between associated kamacite and taenite in different metal grains emphasizes a common thermal event that established chemical equilibrium among individual metal grains and suggests that this chemical equilibrium of the metal grains could have been reached subsequent to chondrule formation events. Using the experimental study of Widge and Goldstein, the equilibrium temperature of these grains is 486±28°C; such a temperature is consistent with a post-accretion thermal metamorphism.