The effects of pressure on the high-temperature dislocation creep of (Mg,Fe)2SiO4 (olivine) aggregates were determined under both water-poor (dry) and water-saturated (wet) conditions. New experimental data were obtained, at pressures of 1 to 2GPa, under dry and wet conditions; using a newly developed high-resolution dislocation density

measurement technique to estimate the creep strength. These data were compared with previous data for lower and higher pressures in order to determine the pressure-dependence of high-temperature dislocation creep in such aggregates. It was found that the creep strength under dry conditions increased monotonically with increasing pressure, whereas the creep strength under wet conditions changed with pressure in a non-monotonic fashion. That is, it first decreased rapidly with increasing pressure and then became less sensitive to pressure above 1GPa. The data for wet conditions were consistent with a model in which the creep-rate was controlled by the motion of positively charged jogs involving the diffusion of Si via an interstitial mechanism.

Effects of Pressure on High-Temperature Dislocation Creep in Olivine. S.Karato, H.Jung: Philosophical Magazine, 2003, 83[3], 401-14