Evolution of hematite and/or magnetite iron phases with thermal heating in ordinary chondrites: A generic characteristic

We used 57Fe Mössbauer spectroscopic measurements on untreated and controlled thermally treated Ararki, Didwana, and Bhawad ordinary chondritic meteorites to understand the evolution of different iron phases with temperature. The samples were subjected to different heating temperatures and room temperature Mössbauer spectra were collected after cooling down these samples. The untreated meteorite samples showed the presence of olivine, pyroxene, troilite, and Fe–Ni alloy (kamacite/taenite) minerals. The decomposition of such iron based minerals started at or above 600°C towards hematite iron phase for all these meteorites. More interestingly, at about 1000°C or above, all initial mineral phases got converted into either hematite and/or magnetite. The present study provides a clue to understand the mechanism of conversion of minerals in ordinary chondrites.