Mössbauer Effect Studies of Taenite Lamellae of an Iron Meteorite Cape York (III. A)

Abstract

Mössbauer spectra have been obtained for 12 taenite lamellae from the iron meteorite Cape York. The spectra show that generally the lamellae contain three phases. A paramagnetic γ-phase, a martensitic α₂-phase and an ordered phase (superstructure) of the composition FeNi and with the structure L10. This superstructure has not previously been detected in meteorites. The ordered phase is concentrated in the outer layers of the lamellae. The outermost layer (1-2 μm) is practically pure superstructure. Mössbauer experiments show that the superstructure breaks down in about 10 hours at a temperature of 732 K. The formation of the ordered structure explains several general features of iron meteorites.