Grain Boundary Diffusion in the Mantle: An Integrated Theoretical and Experimental Study of MgO

原子沿着矿物颗粒之间的边界传输是一个基本的但知之甚少的过程，它在许多重要的地质现象中起着重要的作用，从地震产生的地震能量的衰减到与地幔对流和板块构造相关的许多变形和化学传输过程。本项目支持对地球深部地幔主要成分MgO的晶界扩散进行理论和实验相结合的研究。本研究结果将提高对地球深部晶界化学输运速率及相关地球物理和地球化学性质的估计能力。实验与理论相结合的研究项目将专门针对晶界扩散的原子水平机制，以及压力、化学杂质和晶界结构对元素迁移率的影响。晶界扩散系数及其对温度、压力和钙硅存在的依赖关系将通过扩散偶实验、第一性原理和经典分子动力学模拟来确定。理论模拟将提供有关扩散机制、晶界输运与晶界结构的关系以及与地球有关的高压的晶界扩散数据外推的关键信息。最深的地幔。

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.