High-pressure investigations on Piplia Kalan eucrite meteorite using in-situ X-ray diffraction and Fe-57 Mossbauer spectroscopic technique up to 16 GPa

作者：Chandra Usha^*; Pandey K K; Parthasarathy G; Sharma Surinder M

来源：Geoscience Frontiers, 2016, 7(2): 265-271.

DOI：10.1016/j.gsf.2015.05.003

We report here high-pressure investigations on Piplia Kalan eucrite-a member of HED (Howardite-Eucrite-Diogenite) family from asteroid 4-Vesta based on synchrotron X-ray diffraction (up to 16 GPa) and Fe-57 Mossbauer spectroscopy (up to 8 GPa). Dominant with anorthite-rich plagioclase, pigeonite-rich pyroxene and clino-ferrosilite, the sample displayed various phase transitions attaining amorphous character at 16 GPa. These phase transitions of individual components could be explained simultaneously through variations in high-pressure XRD patterns and the Mossbauer parameters. Most prominent P2(1)/c to C2/c transition of pigeonite and ferrosilite was exhibited both as sudden variation in Mossbauer parameters and population inversion of Fe2+ in M1 and M2 sites between 2.9 and 3.8 GPa and variation in intensity profile in XRD patterns at 3.56 GPa. Anorthite seemed to respond more to such impact than other components in the sample. Complete amorphization in anorthite which occurred at lower pressure of similar to 12 GPa implied residual stress experienced due to shock impact. The presence of high pressure (monoclinic) phase of pigeonite and ferrosilite at ambient condition in this eucrite sample confirmed earlier suggestions of an early shock event. This report is an attempt to emphasize the role of anorthite in the determination of the residual stress due to impact process in the parent body thus to understand the behavioral differences amongst HED members.

• 出版日期2016-3