Elasticity of High Pressure Phases of Mantle Minerals

地震学研究提供了有关地球内部声波速度的最准确信息。同时在高压和高温下对矿物中的声速进行实验室测量，使这些地震数据能够从化学成分、矿物学和温度方面进行解释。该项目将包括对地幔中矿物弹性性质的实验测定。在过去十年中，在美国国家科学基金会地球科学部的支持下，已开发出超声波干涉技术，以便与多锤、高压设备和能源部国家实验室的同步辐射X辐射设备结合使用。这项研究计划还利用了石溪高压实验室的多砧座、大容量设施和石溪大学矿物物理研究所的辅助分析设施提供的特殊研究机会。其中一些设备是在1991年至2002年期间由美国国家科学基金会高压研究科学技术中心[CHiPR]赞助开发的。这些实验将使用安装在布鲁克海文国家实验室国家同步辐射光源(NSLS)超导摇摆器光束线上的高压多砧座设备进行；该设备在NSLS的操作得到地球科学材料性质研究联盟(COMPRES)的支持。其他实验将利用Argonne国家实验室高级光子源的GeoSoilEnviroCARS[GSECARS]运营的多锤设备进行。目前正在研究的特殊矿物包括：(1)斜方辉石，上地幔岩石中第二丰富的矿物。以前的实验表明，当这种矿物转变为单斜结构时，在高压下会出现异常的弹性行为。辉石中的这种相变可能有助于解释在地球深处200-300公里处观察到的地震速度的不连续性。(2)钙钛矿结构的矿物，其成分为CaTiO_3和CaSiO_3。在这些矿物的混合物中，存在着从正交对称性到四方对称性的转变，并伴随着弹性性质的变化。(3)铁方镁石是地球下地幔中第二丰富的矿物。为了与该地区的地震模型进行比较，以前在高压和常温下的研究正在扩展到高温和高压。

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.