Sound Velocities and Elastic Moduli of Minerals Mantle Pressures and Temperatures with Laser Heating

该项目的重点是在地球深部实际压力和温度（P和T）条件下对氧化物矿物的声速和弹性模量进行实验室测量。该项目包括几个相关的活动：1）在超高P-T条件下测量声速的仪器的开发。该装置将基于CO2激光加热的样品，而他们在金刚石砧室加压。声速将通过布里渊散射测量。我们的目标是测量矿物的速度高达T=2500 K和P=50 GPa，其跨越P-T条件到~1300 km的深度。2)仅在高压、仅在高温和同时P-T条件下使用连续加热的金刚石压砧室（温度适中但准确已知）进行速度测量。这将确定P和T对速度的单独影响，并有助于表征激光加热条件。 3)利用同步辐射x射线测量热膨胀。最初的实验将涉及MgO，一种下地幔成分。我们将评估测量的精度和准确度，热应力和压力介质中的偏应力。然后，我们将研究可能构成地球的地幔，选自：橄榄石及其高压多晶型β-和γ-（镁，铁）2SiO 4，镁橄榄石石榴石固溶体，辉石，镁硅酸盐钙钛矿，和含水相。将我们的结果与地震学确定的地球速度进行比较，将有助于我们更好地了解地球内部的化学和热状态。

BassEAR-0003383The focus of this project is laboratory measurements of sound velocities and elastic moduli of oxide minerals under the actual pressure and temperature (P and T) conditions of the Earth's deep interior. This project involves several related activities: 1) The development of an apparatus to measure sound velocities at ultra-high P-T conditions. The apparatus will be based on CO2 laser heating of samples while they are pressurized in a diamond anvil cell. Sound velocities will be measured by Brillouin scattering. Our goal is to measure the velocities of minerals up to T=2500 K and P=50 GPa, which spans the P-T conditions to a depth of ~1300 km. 2) Velocity measurements at high pressure only, at high temperature only, and at simultaneous P-T conditions using a resistively-heated diamond-anvil cell (where the temperature is moderate but accurately known). This will identify the separate effects of P and T on velocities, and help characterize conditions under laser heating. 3) Thermal expansion measurements using synchrotron x-radiation. Initial experiments will involve MgO, a lower mantle constituent. We will assess the precision and accuracy of the measurements, thermal stresses, and deviatoric stresses in the pressure medium. We will then study likely constituents of the Earth's mantle, chosen from: olivine and its high pressure polymorphs beta- and gamma-(Mg,Fe)2SiO4, majorite-garnet solid solutions, pyroxenes, magnesium-silicate perovskites, and hydrous phases. Comparisons of our results with seismologically-determined velocities for the Earth will be used to improve our understanding of the chemical and thermal state of the Earth's interior.