Effect of Water on Fe-Mg Interdiffusion in Mantle Minerals: Implications for Geodynamical Processes

9805419 Kohlstedt我们的实验室研究将量化两种重要的地幔矿物橄榄石和镁橄榄石中Fe-Mg扩散速率对水浓度的依赖性。 我们的实验的一个目标是在定义明确的热化学条件下，阳离子扩散率和水/羟基浓度之间的关系。 对于许多名义上的无水矿物，少量的水显着增强扩散依赖性。然而，这些观察只是定性的：水的存在是否会导致特定过程动力学的增强？是不是？ 扩散率和水/羟基含量之间的定量关系尚未确定的橄榄石或镁橄榄石。结果将用于点缺陷热力学的背景下，以获得水影响传输性能，如离子扩散和电导率的机制（S）的基本理解。 由此产生的理论框架是必不可少的可靠外推实验室结果地幔环境和利用实验观测，以开发地球内部的动力学行为和地球化学演化模型。

9805419KohlstedtOur laboratory study will quantify the dependence of the rate of diffusion of Fe-Mg on water concentration in olivine and magnesiowstite, two important mantle minerals. One goal of our experiments is to develop relationships between cation diffusivity and water/hydroxyl concentration under well-defined thermochemical conditions. For many nominally anhydrous minerals, a small amount of water significantly enhances diffusion-dependent properties. However, these observations are only qualitative: Does the presence of water result in an enhancement in the kinetics of a specific process ... yes or no? Quantitative relationships between diffusivity and water/hydroxyl content have not been determined for either olivine or magnesiowstite. The results will be used in the context of point defect thermodynamics to gain a fundamental understanding of the mechanism(s) by which water influences transport properties such as ionic diffusion and electrical conductivity. The resulting theoretical framework is essential for reliably extrapolating laboratory results to mantle environments and for utilizing experimental observations to developmodels of the dynamic behavior and geochemical evolution of Earth s interior.