A post-stishovite SiO2 polymorph in the meteorite Shergotty: implications for impact events.
Transmission electron microscopy and electron diffraction show that the martian meteorite Shergotty, a shocked achondrite, contains a dense orthorhombic SiO2 phase similar to post-stishovite SiO2 with the alpha-PbO2 structure. If an SiO2 mineral exists in Earth's lower mantle, it would probably occur in a post-stishovite SiO2 structure. The presence of such a high-density polymorph in a shocked sample indicates that post-stishovite SiO2 structures may be used as indicators of extreme shock pressures.
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Department of Geology, Arizona State University, Tempe, AZ 85287, USA.
El Goresy
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Wopenka
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Chen
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D003461:Crystallography; D018535:Mars; D019110:Meteoroids; D008854:Microscopy, Electron; D012822:Silicon Dioxide / Q000737:chemistry; D013059:Spectrum Analysis, Raman
D012822:Silicon Dioxide