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

我们的实验室研究将量化铁-镁的扩散速度与橄榄石和镁辉石这两种重要的地幔矿物中的水含量的关系。我们实验的一个目标是在明确的热化学条件下建立阳离子扩散系数与水/羟基浓度之间的关系。对于许多名义上的无水矿物来说，少量的水显著增强了扩散相关的性质。然而，这些观察只是定性的：水的存在是否会导致特定过程的动力学增强……是还是不是？橄榄石和镁铁矿的扩散系数与水/羟基含量之间的定量关系尚未确定。这些结果将被用在点缺陷热力学的背景下，以获得对水影响离子扩散和电导率等输运性质的机制的基本理解(S)。所得到的理论框架对于可靠地将实验室结果外推到地幔环境，以及利用实验观测建立地球S内部的动力学行为和地球化学演化模型是必不可少的。

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.