Natural (Mg,Fe)SiO3-Ilmenite and -Perovskite in the Tenham Meteorite
Abstract
The minerals (Mg,Fe)SiO3-ilmenite and -perovskite were identified in the shock-induced veins in the Tenham chondritic meteorite. Both phases are inferred to have transformed from pyroxene at high pressures and temperatures by shock metamorphism. Columnar-shaped ilmenite grains, one of two types of morphologies, have a topotaxial relationship with neighboring pyroxene grains, indicating shear transformation. Granular-shaped perovskite grains showed a diffraction pattern consistent with orthorhombic perovskite, but these grains were not stable under the electron beam irradiation and became amorphous. The higher iron concentration in both phases compared with those experimentally reported may suggest their metastable transition from enstatite because of shock compression.
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We thank Y. Syono and N. Miyajima for helpful comments and T. Kuwajima and R. Tanaka for technical assistance. Supported by a Grant-in-Aid for Research (no. 06402019) from the Ministry of Education, Science, and Culture of the Japanese Government.
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Science
Volume 277 | Issue 5329
22 August 1997
22 August 1997
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Received: 15 April 1997
Accepted: 11 July 1997
Published in print: 22 August 1997
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- Naotaka Tomioka,
- Kiyoshi Fujino
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