Geophysics of Iron in the Earth's D" Layer and Core

地球 D" 层和地核中铁的地球物理学

• 批准号: 0738873
• 负责人: Wendy Mao
• 金额: $ 31.59万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-01-01 至 2011-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0738873&HistoricalAwards=false
• 关键词: Geophysics; Iron; Earth; Layer; Core

The Earth?s core and core-mantle boundary play a central role in the evolution and dynamic processes within the Earth. Seismological observations provide detailed descriptions of this most remote region in our planet, but interpretations of the many enigmatic seismic features await in-depth understanding of the mineral physics of iron and iron-rich compounds at extreme pressure-temperature (P-T) conditions where in-situ measurements are challenging. This project takes advantage of recent advances in high pressure synchrotron x-ray technology, pushes the envelope of current experimental capabilities, and integrates multiple in-situ probes in order to measure key properties and address fundamental geophysical questions surrounding the Earth?s core and D? layer. The experiments focus on taking an integrated approach in determining the high P-T elasticity of iron and iron-rich silicates. For iron, the equation of state, aggregate compressional and shear wave velocities, velocity anisotropy and lattice preferred orientation, and elastic tensor will be determined in-situ in a diamond anvil cell using a suite of complementary synchrotron x-ray techniques: hydrostatic x-ray diffraction (XRD), radial XRD, nuclear-resonant inelastic x-ray scattering, and phonon inelastic x-ray scattering. The results will address major issues such as inner core seismic anisotropy and will establish a benchmark for pure iron for constraint of theoretical calculations and comparison with iron alloys. For the core-mantle boundary, this project focuses on the elasticity of iron-bearing silicate post-perovskite. Although the significance of the discovery of silicate ppv at D? conditions is well recognized, due to experimental challenges, the amount of data on the properties of silicate post-pervoskite has been scarce. In-situ high P-T radial XRD measurements will be applied to this phase to provide the experimental foundation for understanding the unusual characteristics of the Earth?s D? layer, including the sharp discontinuity at the top of this layer, its lateral velocity variations, its seismic anisotropy, its VP-VS anti-correlation, and its ultralow-velocity zones.

地球的核心和核心-地幔边界在地球内部的演化和动态过程中发挥着核心作用。地震观测提供了对地球上这个最偏远地区的详细描述，但对许多神秘地震特征的解释有待深入了解铁和富铁化合物在极压-温度（P-T）条件下的矿物物理，而现场测量具有挑战性。该项目利用高压同步加速器 X 射线技术的最新进展，突破了当前实验能力的极限，并集成了多个原位探测器，以测量关键特性并解决围绕地核和 D 的基本地球物理问题。层。实验重点是采用综合方法来确定铁和富铁硅酸盐的高 P-T 弹性。对于铁，状态方程、聚集压缩波和剪切波速度、速度各向异性和晶格择优取向以及弹性张量将使用一套互补的同步加速器 X 射线技术在金刚石砧室中原位确定：静水 X 射线衍射 (XRD)、径向 XRD、核共振非弹性 X 射线 散射和声子非弹性 X 射线散射。研究结果将解决内核地震各向异性等重大问题，并将为纯铁建立一个基准，用于理论计算的约束以及与铁合金的比较。对于核幔边界，该项目重点研究含铁硅酸盐后钙钛矿的弹性。 尽管在 D 处发现硅酸盐 ppv 的意义是什么？条件已得到广泛认可，但由于实验挑战，有关硅酸盐后钙钛矿特性的数据量一直很少。原位高 P-T 径向 XRD 测量将应用于这一阶段，为了解地球 D 的不寻常特征提供实验基础。层，包括该层顶部的急剧不连续性、其横向速度变化、其地震各向异性、其VP-VS反相关性以及其超低速区。