X-ray diffraction, Mössbauer spectroscopic and electrical resistivity studies on Lohawat meteorite under high-pressure up to 9 GPa

The physical properties of the extraterrestrial materials, meteorites, though important but are not well studied. We present here structural and electrical properties of Lohawat meteorite under high-pressure up to 9 GPa, using in situ high-pressure powder X-ray diffraction, 57Fe Mössbauer spectroscopic and electrical conductivity techniques. The studied meteorite sample fell at Lohawat (Rajasthan) India is classified as a Howardite based on geochemical and mineralogical studies. Electron Probe Microanalysis (EPMA) indicates that Lohawat meteorite composed mainly of orthopyroxene (Fs0.65En0.34Wo0.09) and plagioclase (An.946Ab.053). All the three experimental studies independently confirm pressure-induced structural changes of Lohawat meteorite at ∼2.8 GPa and at 5.6 GPa representing irreversible amorphization and reversible crystallization respectively. The observed experimental results are explained based on the high-pressure behavior of orthopyroxene and anorthite, which are dominant mineral phases of the Lohawat meteorite. The observation of structural phase transition at lower pressure for the meteorite sample compared to their analogous pure end member mineral indicates that the meteorite sample preserved a residual stress in the sample. The present study, therefore, may help in estimating the residual peak metamorphic shock pressure experienced by the parent body transforming into differentiated achondrite meteorite.