Rheology of hydrous melt-bearing dunite

Abstract

Deformation experiments on hydrous melt-bearing dunite were conducted under upper mantle conditions, in order to explore the effect of intergranular fluids on the plastic flow of olivine in Earth's upper mantle. The creep strength of hydrous melt-bearing dunite was about 2 times lower than the dislocation creep strength of hydrous olivine under these experimental conditions. The strain rate was proportional to differential stress to the 2.1 power, and the differential stress markedly increased with increase in grain size. These observations show that grain boundary sliding dominated the deformation of olivine (i.e., superplasticity). Superplasticity is the dominant creep mechanism of olivine in fluid-bearing fine-grained peridotites under low-temperature and high-stress conditions