Elasticity of Mantle Minerals at High Pressures and Temperatures

在地球表面如此引人注目的地质活动最终源于内部深处的过程。为了提高我们对地球内部动力学和结构的认识，有必要将联合收割机的地球物理观测（如地震学观测）与有关地质材料物理性质的直接实验测量结合起来。这项研究的目的是测量矿物在高压下的声速，并将测量结果与地震数据结合起来，建立地球上地幔成分和结构的改进模型。 使用布里渊光谱，我们将进行新的测量的高压弹性性质的主要阶段的上地幔，包括橄榄石及其高压多晶型。矿物的弹性性质对于解释地球的地震数据是必不可少的。体模量和剪切模量沿着与密度一起确定压缩波和剪切波速度，其可以直接与地震数据进行比较。结合我们以前对含水橄榄石多晶型物的研究，这些研究将产生新的理解，铁和氢如何影响上地幔主要相的弹性性质。特别是，我们的研究将揭示我们以前的工作中观察到的含水和无水镁橄榄石之间的速度交叉新的光。该项目的另一个目标是开发和应用利用外部加热金刚石砧室在同时高压和高温（高达600 ℃）下进行布里渊光谱学的技术。这项工作将提供第一个实验约束的高P-T弹性张量的一些关键地幔矿物。最后，我们将全面综合我们目前对矿物弹性性质的化学和结构控制及其对解释地震数据的重要性的理解。

The geological activity that manifests itself so dramatically at the Earth's surface ultimately originates from processes in the deep interior. To improve our understanding of the interior dynamics and structure of the Earth, it is necessary to combine geophysical observations such as those from seismology with direct experimental measurements of the physical properties of the relevant geological materials. The aim of this study is to measure the sound velocities of minerals at high pressure and to use the results in combination with seismic data to construct improved models of the composition and structure of the Earth's upper mantle. Using Brillouin spectroscopy we will carry out new measurements of the high-pressure elastic properties of major phases of the upper mantle including olivine and its high-pressure polymorphs. The elastic properties of minerals are essential for the interpretation of seismic data for the Earth. The bulk and shear moduli along with density determine compressional and shear wave speeds which can be directly compared to seismic data. In combination with our previous work on hydrous olivine polymorphs, these studies will yield new understanding of how iron and hydrogen affect the elastic properties of the major phases of the upper mantle. In particular, our studies will shed new light on the velocity crossover between hydrous and anhydrous forsterite observed in our previous work. Another goal for this project is to develop and apply techniques for Brillouin spectroscopy at simultaneous high pressures and temperatures (to as high as 600oC) using an externally heated diamond anvil cell. This work will provide the first experimental constraints on the high P-T elastic tensor for some key mantle minerals. Lastly, we will undertake a comprehensive synthesis of our current understanding of chemical and structural controls on mineral elastic properties and their importance for interpreting seismic data.