Elasticity of Selected Deep Earth Phases Under Simultaneous High P-T Conditions Using Nuclear Resonant Inelastic X-ray Scattering

最近观测到的地震复杂性要求对候选下地幔物质进行新的、更准确的测量。努力了解这些地震复杂性的起源是现代跨学科研究的一个活跃领域。通常，地球深部的模型是通过将矿物性质外推到相关的压力-温度(P-T)条件，并将它们与地震学确定的纵波和横波速度和密度进行比较来建立的。然而，深部地幔物质的剪切特性的行为是广泛未知的。因此，许多外推要么使用低P-T数据，要么使用类似的材料，和/或推断化学上复杂的矿物与其端元组成具有相同的行为。尽管镁铁方镁矿和铝钙钛矿(镁，铁)钙钛矿的体积占地球下地幔体积的75%以上，但它们大多是光学不透明的，因此很难或不可能用光学散射方法进行研究。为了克服这些挑战，利用已建立的同步加速器显微X射线衍射方法和核共振非弹性X射线散射方法，与金刚石顶压室和激光加热技术相结合，在适当但尚未绘制图表的高P-T条件下，获得了化学上复杂的地球深部材料的状态方程。在知道了由XRd确定的这些材料的密度后，根据由Nrixs确定的部分声子态密度确定了聚集的纵波速度和横波速度，以及绝热体积和剪切模数。这些数据可以评估铁和铝对地球深处物质的声速和弹性的影响，这些材料位于以前未被勘探的P-T部门。这一结果有望对地震横向变化与化学成分之间的相关性提供约束。

Recently observed seismic complexities require new and more accurate measurements of candidate lower mantle materials. The effort to understand the origin of these seismic complexities is an active area of modern cross-disciplinary research. Typically, models of the deep Earth have been made by extrapolating mineral properties to relevant pressure-temperature (P-T) conditions and comparing them with seismological determined compressional- and shear-wave velocities and density. However, the behavior of the shear properties of deep mantle materials is widely unknown. As a result, many extrapolations use either low P-T data, analogue materials, and/or infer that the chemically complex minerals behave the same as their end-member compositions. Even though ferropericlase (Mg,Fe)O and aluminous (Mg,Fe)SiO3 perovskite together make up more than 75% by volume of Earth's lower mantle, they are mostly optically opaque, making them difficult or impossible to study using optical scattering methods. In an effort to overcome these challenges, the use of established synchrotron methods of micro x-ray diffraction (Xrd) and nuclear resonant inelastic x-ray scattering (Nrixs) is engaged with diamond anvil cell and laser heating technology to obtain equations of state for chemically complex deep Earth materials under appropriate, yet uncharted, high-P-T conditions. With knowledge of the density determined from Xrd for these materials, the aggregate compressional and shear wave velocities, as well as the adiabatic bulk and shear moduli, is determined from the measured partial phonon density of states determined from Nrixs. These data permit the evaluation of the effects of iron and aluminum on the sound velocities and elasticity of deep Earth materials in a previously unexplored P-T sector. The results are expected to provide constraints on the correlation between seismological lateral variations and chemical composition.