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Science 3 July 1998:
Vol. 281. no. 5373, pp. 85 - 87
DOI: 10.1126/science.281.5373.85
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Reports

Effects of Water on the alpha -beta Transformation Kinetics in San Carlos Olivine

Tomoaki Kubo, * Eiji Ohtani, Takumi Kato, Toru Shinmei, Kiyoshi Fujino

In experiments at 13.5 gigapascals and 1030°C, the growth rate of wadsleyite, which forms from transformation of olivine, was substantially enhanced by the presence of water. Wadsleyite had a low dislocation density and subgrain boundaries in wet runs. Water enhanced the dislocation recovery in wadsleyite and therefore caused inelastic relaxation of the localized pressure drop associated with the transformation, resulting in an increase of the growth rate in wet runs. These results imply that even a small amount of water of 0.05 weight percent can weaken wadsleyite in the mantle.

T. Kubo and E. Ohtani, Institute of Mineralogy, Petrology, and Economic Geology, Faculty of Science, Tohoku University, Sendai 980-8578, Japan. T. Kato, Institute of Geoscience, University of Tsukuba, Tsukuba 305-0006, Japan. T. Shinmei and K. Fujino, Division of Earth and Planetary Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
*   To whom correspondence should be addressed.

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