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.

最近观测到的地震复杂性需要对候选下地幔物质进行新的、更准确的测量。 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，地球深处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，深部地幔材料的剪切特性的行为却广为人知。 因此，许多外推使用低 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成分相同。 尽管方镁石 (Mg,Fe)O 和铝 (Mg,Fe)SiO3 钙钛矿合计占地球下地幔体积的 75% 以上，但它们大多是光学不透明的，这使得使用光学散射方法对其进行研究变得困难或不可能。为了克服这些挑战，使用已建立的同步加速器方法微 X 射线衍射 (Xrd) 和核共振非弹性 X 射线散射 (Nrixs) 与金刚石砧池和激光加热技术相结合，以获得状态方程在适当但未知的高 P-T 条件下化学复杂的地球深部材料。 知道了这些材料的 Xrd 密度后，压缩波和剪切波的总速度以及绝热体积模量和剪切模量可根据 Nrixs 所测得的部分声子态密度来确定。 这些数据可以评估铁和铝对先前未探索的 P-T 区域中地球深部材料的声速和弹性的影响。 预计结果将为地震横向变化与化学成分之间的相关性提供约束。