Pressure and water influences on alternating active slip systems of single crystal olivine at the upper mantle pressures

该项目的重点是研究地球上地幔中的主要矿物橄榄石的力学性质。本计画之目的在于研究不同压力及含水环境下个别滑移系之流动特性。该项目的成功将有助于解释在地球内部条件下上地幔主要成分（橄榄石）的晶格择优取向（LPO）的形成/变化。由于LPO被认为是引起地震各向异性的原因，本研究将从矿物物理学的角度为理解上地幔200 km深度处地震各向异性的衰减提供实验证据，这种衰减的原因一直是地球科学界长期以来的问题之一。该项目将利用国家实验室同步加速器设施高压变形实验方面的最新技术发展。形变-DIA（D-DIA）装置与同步加速器X射线源一起将是实验研究的主要仪器。该装置将骨料样品的研究压力范围扩大到10 GPa以上。为了研究单个滑移系的性质，本项目将使用单晶作为修改后的单元组件中的变形试样。a滑移系（010）[100]和c滑移系（010）[001]的流动特性将分别进行比较研究。在比较研究中，两个样品分别在（010）[100]和（010）[001]滑动的方向上取向，在实验期间将同时顺序变形。当确定这两个滑移系统中的哪一个在给定的压力/温度/化学条件下被激活时，这将使实验误差最小化。将使用FTIR和TEM检查变形实验后回收的样品，以确定样品的水浓度和微观结构。该项目将提高国家同步加速器光源X17 B2光束线高压设施的实验能力。该设施为地球科学界的大量普通用户提供服务。该项目将促进与传统变形领域的专家/先驱的合作，以使新技术有效。此外，来自代表性不足群体（妇女/西班牙裔）的学生将在项目期间受到吸引、参与和培训。

This project focuses on study of mechanical properties of olivine, a dominant mineral in Earth's upper mantle. The objectives of this project include studies of the flow properties of individual slip system under different pressures and water containing environments. Success of the project will help to explain formation/variation of lattice preferred orientation (LPO) of this major constitution (olivine) of the upper mantle under the conditions of Earth's interior. As the LPO is believed to give rise to seismic anisotropy, this study will supply experimental evidence, from the mineral physics point of view, to understand the attenuation of seismic anisotropy observed at about 200km depth in the upper mantle, the cause of this attenuation has been one of the long standing issues for Earth science community. The project will take advantage of state-of-the-art technical developments in high-pressure deformation experiments at synchrotron facilities of national laboratories. The deformation-DIA (D-DIA) apparatus in conjunction with a synchrotron x-ray source will be the major instrument for the experimental investigation. This apparatus has extended the pressure range for studying aggregate samples beyond 10 GPa. To study properties of individual slip systems, this project will use single crystals as the deformation specimens in a modified cell assembly. Flow properties of a-slip system, (010)[100], and c-slip system, (010)[001] will be studied individually and comparatively. In the comparative study, two samples oriented in such directions that active (010)[100] and (010)[001] slip, respectively, will be deformed simultaneously in sequence during the experiment. This will minimize the experimental error when determination of which of these two slip systems is activated at given pressure/temperature/chemical conditions. Samples recovered after deformation experiments will be examined using FTIR and TEM to determine the water concentration and microstructure of the sample. The project will enhance the experimental capability of the high pressure facility at the X17B2 beamline of the National Synchrotron Light Source. This facility serves a large number of general users from Earth science community. The project will promote collaborations with experts/pioneers in the traditional deformation field to valid the new technology. In addition, students from underrepresented groups (women/Hispanics) will be attracted, engaged, trained during the project.