Elasticity of High Pressure Phases of Mantle Minerals

地震学调查产生了关于地球内部声波速度的最精确的信息。 在实验室同时测量高压和高温下矿物中的声速，使这些地震数据能够从化学成分、矿物学和温度方面加以解释。 这个项目将包括实验测定地球地幔矿物的弹性性质，在过去十年中，在国家科学基金会地球科学司的支助下，开发了超声波干涉测量技术，以便与多砧高压仪器结合使用，并与能源部国家实验室的同步加速器X射线设施结合使用。 该研究计划还利用了斯托尼布鲁克高压实验室的多砧大容量设施和斯托尼布鲁克大学矿物物理研究所的相关分析设施提供的特殊研究机会。 其中一些装置是在美国国家科学基金会高压研究科学技术中心（CHiPR）的赞助下于1991- 2002年研制的。这些实验将使用高压、多砧装置进行，安装在布鲁克海文国家实验室的国家同步加速器光源（NSLS）的超导摇摆器光束线上;在NSLS的该装置的操作由地球科学中的材料性质研究联合会（COMPRES）支持。 其他实验将使用在阿贡国家实验室高级光子源的GeoSoilEnviroCARS [GSECARS]操作的多砧设施进行。目前正在研究的具体矿物包括：（1）斜方辉石，上地幔岩石中第二丰富的矿物。 以前的实验已经揭示了这种矿物在高压下转变为单斜结构时的异常弹性行为。 辉石中的这种相变可能有助于解释在地球内部200-300公里深处观察到的地震速度的不连续性。(2)钙钛矿结构矿物，成分为CaTiO 3和CaSiO 3。 在这些矿物的混合物中，存在从正交对称到四面体对称的转变，这伴随着弹性性质的变化。(3)铁长石是地球下地幔中第二丰富的矿物。 以前在高压和室温下的研究正在扩展到高温和高压，以便与该地区的地震模型进行比较。

Seismological investigations yield the most precise information on the velocities of sound waves in the Earth's interior. Laboratory measurements of the sound velocities in minerals at simultaneous high pressures and temperatures enable these seismic data to be interpreted in terms of chemical composition, mineralogy and temperature. This project will include experimental determinations of elastic properties of minerals in the Earth's mantle.Over the past decade, with the support of the NSF Division of Earth Sciences, ultrasonic interferometric techniques have been developed for use in combination with multi-anvil, high-pressure apparatus and in conjunction with synchrotron X-radiation facilities at the national laboratories of the Department of Energy. This research program also takes advantage of the special opportunities for research that are provided by the multi-anvil, large-volume facilties of the Stony Brook High Pressure Laboratory and the associate analytical facilities of the Mineral Physics Institute at Stony Brook University. Some of these facilities were developed under the auspices of the NSF Science and Technology Center for High Pressure Research [CHiPR] from 1991-2002.These experiments will be conducted using high-pressure, multi-anvil apparatus, installed on the superconducting wiggler beamline at the National Synchrotron Light Source (NSLS) of the Brookhaven National Laboratory; the operation of this apparatus at NSLS is supported by the Consortium for Materials Properties Research in Earth Sciences (COMPRES). Other experiments will be performed using the multi-anvil facilities operated by GeoSoilEnviroCARS [GSECARS] at the Advanced Photon Source of the Argonne National Laboratory.Specific minerals which are currently being studied include :(1) Orthopyroxene, the second most abundant mineral in upper mantle rocks. Previous experiments have revealed anomalous elastic behavior at high pressures when this mineral transforms to the monoclinic structure. Such phase transformations in pyroxenes may help to explain discontinuities in seismic velocities observed at depths of 200-300 kilometers inside the Earth.(2) Perovskite-structure minerals with compositions CaTiO3 and CaSiO3. In mixtures of these minerals, there are transitions from orthorhombic to tetragonal symmetry which are accompanied by changes in the elastic properties.(3) Ferropericlase is the second most abundant mineral in the lower mantle of the Earth. Previous studies at high pressure and room temperature are being extended to high temperatures and pressures for comparison with seismic models in this region.