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Science 6 March 1992:
Vol. 255. no. 5049, pp. 1238 - 1240
DOI: 10.1126/science.255.5049.1238
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Articles

Diffusion Creep in Perovskite: Implications for the Rheology of the Lower Mantle

SHUN-ICHIRO KARATO 1 and PING LI 1

1 Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455

High-temperature creep experiments on polycrystalline perovskite (CaTiO3), an analog of (Mg,Fe)SiO3 perovskite of the lower mantle, suggest that (grain size-sensitive) diffusion creep is important in the lower mantle and show that creep rate is enhanced by the transformation from the orthorhombic to the tetragonal structure. These observations suggest that grain-size reduction after a subducting slab passes through the 670-kilometer discontinuity or after a phase transformation from orthorhombic to tetragonal in perovskite will result in rheological softening in the top portions of the lower mantle.

Submitted on October 8, 1991
Accepted on January 3, 1992


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