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

这个项目的重点是研究橄榄石的力学性质，橄榄石是地球上地幔中的一种主要矿物。该项目的目标是研究单个滑移系统在不同压力和含水环境下的流动特性。该项目的成功将有助于解释地球内部条件下上地幔这一主要组成部分(橄榄石)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，这项研究将从矿物物理的角度提供实验证据，以了解在约200公里深的上地幔观测到的地震各向异性的衰减，这种衰减的原因一直是地球科学界长期关注的问题之一。该项目将利用国家实验室同步加速器设施中高压变形实验的最新技术发展。形变-DIA(D-DIA)装置和同步辐射X射线源将是实验研究的主要仪器。该装置将研究骨料样品的压力范围扩大到10 Gpa以上。为了研究单个滑移系统的特性，该项目将使用单晶作为修改后的电池组件中的变形样品。A滑移系统(010)[100]和c滑移系统(010)[001]的流动特性将被单独和比较地研究。在对比研究中，两个取向分别为(010)[100]和(010)[001]滑移的样品将在实验过程中按顺序同时变形。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。变形实验后回收的样品将用傅里叶变换红外光谱(FTIR)和透射电子显微镜(TEM)进行检测，以确定样品的水分含量和微观结构。该项目将增强国家同步加速器光源X17B2光束线高压装置的实验能力。该设施服务于大量来自地球科学界的普通用户。该项目将促进与传统变形领域的专家/先驱的合作，以验证新技术的有效性。此外，来自代表性不足群体(妇女/拉美裔)的学生将在项目期间被吸引、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.