The FeNi metal equilibrium temperature of the unequilibrated Chainpur LL 3 . 4 chondrite

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.