Si and O self-diffusion in hydrous forsterite and iron-bearing olivine from the perspective of defect chemistry.

We discuss the experimental results of silicon and oxygen self-diffusion coefficients in forsterite and iron-bearing olivine from the perspective of defect chemistry. Silicon diffusion is dominated by V-associated V″″, whereas oxygen diffusion is dominated by hopping of V under anhydrous conditions, and by (OH) under hydrous conditions. By considering the charge neutrality condition of [(OH)] = 2[V″] in hydrous forsterite and iron-bearing olivine, we get D ∝ ( $$C_{{{\text{H}}_{2} {\text{O}}}}$$ ) and D ∝ ( $$C_{{{\text{H}}_{2} {\text{O}}}}$$ ), which explains the experimental results of water effects on oxygen and silicon self-diffusion rates (Fei et al. in Nature 498:213-215, ; J Geophys Res 119:7598-7606, ). The $$C_{{{\text{H}}_{2} {\text{O}}}}$$ dependence of creep rate in the Earth's mantle should be close to that given by Si and O self-diffusion coefficients obtained under water unsaturated conditions. [ABSTRACT FROM AUTHOR]