Transport of atoms along the boundaries between mineral grains is a fundamental but poorly understood process that plays an important role in many important geological phenomena, from the attenuation of seismic energy produced by earthquakes to the many deformation and chemical transport processes associated with mantle convection and plate tectonics. This project supports a combined theoretical and experimental study of grain boundary diffusion in MgO, a major component of Earth's deep mantle. The results of this study will improve the ability to estimate grain boundary chemical transport rates and related geophysical and geochemical properties of the deep Earth.
The combined experimental and theoretical research program will specifically target the atomic-level mechanisms involved in grain boundary diffusion, and the influence of pressure, chemical impurities and grain boundary structure on element mobility. Grain boundary diffusion coefficients, and their dependence on temperature, pressure and the presence of calcium and silicon, will be determined using diffusion couple experiments, and first-principles and classical molecular dynamics simulations. The theoretical simulations will provide critical information on the diffusion mechanism(s), the relation of grain boundary transport to grain boundary structure, and the extrapolation of grain boundary diffusion data to the high pressures relevant to Earth?s deepest mantle.
