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

使用核共振非弹性 X 射线散射在同时高 P-T 条件下选定的深层地球相的弹性

• 批准号: 0711542
• 负责人: Jennifer Jackson
• 金额: $ 27.5万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-08-01 至 2010-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0711542&HistoricalAwards=false
• 关键词: Elasticity; Selected; Deep; Earth; Phases

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.

最近观察到的地震复杂性需要新的和更准确的测量候选下地幔物质。 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特性外推到相关的压力-温度（P-T）条件，并将其与地震学确定的压缩波和剪切波速度和密度进行比较来制作的。 然而，深部地幔物质的剪切性质的行为是广泛未知的。 因此，许多外推法要么使用低P-T数据，模拟材料，和/或推断化学复杂矿物的行为与其端元组成相同。 尽管铁方镁石（Mg，Fe）O和铝（Mg，Fe）SiO 3钙钛矿共同构成了地球下地幔的75%以上，但它们大多是光学不透明的，使得它们很难或不可能使用光学散射方法进行研究。为了克服这些挑战，使用已建立的同步加速器微X射线衍射（XRD）和核共振非弹性X射线散射（Nrixs）方法，结合金刚石砧座和激光加热技术，以获得化学复杂的深地球材料在适当但未知的高P-T条件下的状态方程。 通过对这些材料的XRD确定的密度的了解，从Nrixs确定的测量的部分声子态密度确定总压缩和剪切波速度以及绝热体模量和剪切模量。 这些数据允许评价铁和铝对以前未探测的P-T部门的深层地球材料的声速和弹性的影响。 预计这些结果将对地震横向变化和化学成分之间的相关性提供约束。