Impact related changes in mineral properties: Ti-magnetite from basaltic rocks at Lonar crater, India
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Samples from vesicular Lonar impactite have been investigated by Mössbauer spectroscopy and SEM in combination with elemental analysis. Observation reveal the new-formation of oxide minerals have occurred with nucleation in particular at the walls of the vesicles interpreted as having formed from condensation of the gas phase having caused the vesicles to form in the first place. Elemental analysis of Ti-magnetites gives very similar compositions irrespective of the oxides grains being vesicle or matrix associated (Fe/Ti ratios approximately 3). The room temperature spectra of the oxides show magnetically ordered components due to A, B, and C sites in the substituted spinel. The occurrence of these ordered components are not in accordance with expectations from the bulk chemical compositions, suggesting the presence of fine scaled intergrowth of Ti-oxide and Ti-magnetite.
Key wordsTi-magnetite impactite Lonar crater vesicles gas condensation growth
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