Sound Velocities and Elasticity of Deep-Earth Materials at High Pressures and Temperatures

高压和高温下地球深部材料的声速和弹性

• 批准号: 0738871
• 负责人: Jay Bass
• 金额: $ 58万
• 依托单位: University of Illinois at Urbana-Champaign
• 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 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0738871&HistoricalAwards=false
• 关键词: Sound; Velocities; Elasticity; Deep; Earth

The investigators are carrying out a three-year program to determine the elastic properties of a wide range of Earth materials at high pressures (P) and temperatures (T) by Brillouin scattering measurements of sound velocities. Their goal is to measure the velocities of the most important materials comprising the transition zone of the Earth (from 410-660 km depth), the lower mantle, subducting tectonic plates and the adjacent upper mantle. The motivation for this work stems from seismological studies of Earth?s deep interior, which provide the velocities of longitudinal (VP) and shear (Vs) sound waves as a function of depth, and the lateral variations of velocity relative to global average models. These seismic results are the most direct information on the in-situ properties of Earth?s mantle, thus providing strong constraints on chemical, mineralogical, thermal, and geodynamic models of the deep interior, and evolution of the Earth through time. The sound velocity measurements are critical for fully utilizing the seismic data, and they are making these measurements under high pressure and high temperature conditions that closely mimic the actual conditions in the Earth at great depth. The investigators are pursuing two broad classes of activities: 1) Measurements of velocities and elastic properties at high pressures up to the 100 GPa region (at room T), and high temperature measurements at normal pressure. The first priority is measurements on what are believed to be the most abundant solid phases in the Earth?s mantle (to 2900 km depth). They are attempting to measure how changes in the electronic state of iron in these minerals affect on the sound velocities, and are performing some preliminary measurements on hydrous phases that carry hydrogen (or water) into the deep earth in subducting tectonic plates and store it there. 2) The team is continuing to develop an apparatus to measure the sound velocities of minerals at the actual pressure-temperature conditions of the mantle. This is being done by Brillouin measurements on samples compressed in a diamond anvil cell (DAC) and heated with an infrared laser. They expect to measure velocities on minerals at conditions of at least T=2500 K and P50 GPa, spanning the likely range of P-T conditions that exist in the Earth at depths of about 1300 km. Lower-temperature measurements are being made with an electrically-heated DAC.The results of these experiments will provide far stronger constraints than are currently available on the chemical composition and temperature of the Earth?s interior. The community will be positioned to more fully exploit the potential of detailed seismic information for understanding the structure of the Earth and its heterogeneity at depth. These experiments are also pushing forward the technology of experimental velocity measurements at elevated P-T conditions, into a regime that has previously been the realm of theory alone. The expected findings are of benefit to the entire spectroscopy community (chemistry, physics, materials sciences, etc.) interested in experiments under extreme conditions. This research involves the training of graduate and undergraduate students. These students have a unique opportunity to be involved in cutting-edge experimental research and be trained in some of the most advanced experimental techniques in this field.

研究人员正在进行一项为期三年的计划，通过声速的布里渊散射测量来确定各种地球材料在高压 (P) 和高温 (T) 下的弹性特性。他们的目标是测量最重要物质的速度，包括地球过渡带（深度为 410-660 公里）、下地幔、俯冲构造板块和邻近的上地幔。这项工作的动机源于对地球深层内部的地震学研究，该研究提供了作为深度函数的纵向（VP）和剪切（Vs）声波的速度，以及相对于全球平均模型的速度的横向变化。这些地震结果是有关地幔原位特性的最直接信息，从而为深层内部的化学、矿物学、热学和地球动力学模型以及地球随时间的演化提供了强有力的约束。声速测量对于充分利用地震数据至关重要，他们是在高压和高温条件下进行这些测量，非常接近地球深处的实际情况。 研究人员正在开展两大类活动：1）在高达 100 GPa 区域（在 T 室）的高压下测量速度和弹性特性，以及在常压下进行高温测量。 首要任务是测量地幔（深度 2900 公里）中被认为最丰富的固相。他们正在尝试测量这些矿物中铁的电子态变化如何影响声速，并对水相进行一些初步测量，这些水相将氢（或水）带入俯冲构造板块的地球深处并将其储存在那里。 2）该团队正在继续开发一种装置，用于测量地幔实际压力-温度条件下矿物的声速。这是通过对在金刚石砧座 (DAC) 中压缩并用红外激光加热的样品进行布里渊测量来完成的。他们期望在至少 T=2500 K 和 P50 GPa 的条件下测量矿物的速度，跨越地球深度约 1300 公里的 P-T 条件的可能范围。较低温度的测量正在使用电加热 DAC 进行。这些实验的结果将提供比目前对地球内部的化学成分和温度更严格的限制。该社区将能够更充分地利用详细地震信息的潜力，以了解地球的结构及其深度的异质性。这些实验也将提高 P-T 条件下的实验速度测量技术推向了一个以前仅属于理论领域的领域。预期的发现对于对极端条件下的实验感兴趣的整个光谱学界（化学、物理、材料科学等）都有好处。这项研究涉及研究生和本科生的培训。这些学生有独特的机会参与前沿实验研究，并接受该领域一些最先进实验技术的培训。