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Science 20 December 1996:
Vol. 274. no. 5295, pp. 2052 - 2054
DOI: 10.1126/science.274.5295.2052
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Reports

Grain Growth Rates of MgSiO3 Perovskite and Periclase Under Lower Mantle Conditions

Daisuke Yamazaki, * Takumi Kato, Eiji Ohtani, Mitsuhiro Toriumi

The grain growth rates of MgSiO3 perovskite and periclase in aggregates have been determined at 25 gigapascals and 1573 to 2173 kelvin. The average grain size (G) was fitted to the rate equation, and the grain growth rates of perovskite and periclase were G10.6 = 1 × 10-57.4 t exp(-320.8/RT) and G10.8 = 1 × 10-62.3 t exp(-247.0/RT), respectively, where t is the time, R is the gas constant, and T is the absolute temperature. These growth rates provide insight into the mechanism for grain growth in minerals relevant to the Earth's lower mantle that will ultimately help define the rheology of the lower mantle.

D. Yamazaki and M. Toriumi, Geological Institute, Faculty of Science, University of Tokyo, Bunkyo, Tokyo 113, Japan.
T. Kato, Institute of Geoscience, University of Tsukuba, Tsukuba, Ibaragi 305, Japan.
E. Ohtani, Institute of Mineralogy, Petrology and Economic Geology, Tohoku University, Sendai 980-77, Japan.
*   To whom corresponce should be addressed. E-mail: daisuke{at}geol.s.u-tokyo.ac.jp

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