2015 年 25 巻 2 号 p. 172-180
Atomic diffusion rates and transformation mechanims of mantle minelars provide important constraints for understanding many physical and chemical processes in the Earth's interior, including mantle rheology and chemical transportation. Here I introduce two recent experimental studies on the atomic diffusivity and transformation mechanisms of mantle minerals under lower mantle conditions up to 50 GPa using a Kawai-type high-pressure apparatus combined with sintered diamond anvils. Diffusion-controlled growth kinetics of the polycrystalline MgSiO3 bridgmanite enabled us to estimate the grain boundary diffusivity of bridgmanite in the lower mantle. Also, metastability of the deep subducted plate was disscussed based on the mechanism changes through the post-garnet transformation under large over pressure conditions.
