Abstract
Transformations of mantle minerals have a great effect on the dynamics of the descending oceanic plate through metastable reactions and changes in the microstructures of the transformed minerals. High pressure and temperature in situ X-ray observation experiments have been performed in order to reveal the mechanisms and kinetics of the olivine-spinel transformation. In the interior of cold slabs, the depth of transformation of olivine mainly depends on the growth rate of spinel. The determination of the growth rate suggests that olivine survives metastably at a depth of∼600km in cold slabs. Water, strain energy due to the transformation, and intracrystalline transformation have significant effects on both the depth and width of the field of metastable olivine.
