Abstract
Diffusion experiments of mantle minerals are important for understanding the rheological properties of the Earth's mantle and subducting slab, because the atomic diffusion in the crystals controls plastic deformation in silicate minerals. Wadsleyite is a major constituent mineral in the mantle transition zone. Hence experimental examination of the diffusion rates is essential for debating the rheology of mantle transition zone. In this study, Si self-diffusion rates in wadsleyite were measured at 18 GPa, 1703-1903 K and the viscosity of wadsleyite deformed by diffusion creep was calculated. Our results imply some portions in cold subducting slabs, where the grain size reduces to less than 1 micron after the olivine-spinel transformation, become weaker than the surrounding mantle.
