CAREER: Upper mantle anisotropy: the effect of pressure, temperature and hydration

职业：上地幔各向异性：压力、温度和水合作用的影响

• 批准号: 1847707
• 负责人: Jin Zhang
• 金额: $ 63.33万
• 依托单位: University of New Mexico
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-07-01 至 2022-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1847707&HistoricalAwards=false
• 关键词: CAREER; Upper; mantle; anisotropy; effect

Thermal convection in the Earth's mantle drives plate tectonics which generates natural hazards, such as volcanic eruptions and earthquakes. Understanding mantle flows has, thus, strong societal relevance. Seismology is a major tool when investigating mantle flows. Differences in seismic velocities, called seismic anisotropy, reflect the elastic anisotropy of mantle rocks. This anisotropy results from the properties of their constitutive minerals and from their deformation by convective flows. Here, the PI will experimentally measure the elastic anisotropy of various mantle minerals at the extreme pressures and temperatures prevailing in the Earth. From the data, rock seismic anisotropies can be calculated and compared with field observations. The experiments will be carried out at a national synchrotron facility, where powerful X-rays are generated, and in the PI's laser laboratory at University of New Mexico (UNM). The lasers and X-rays will be guided toward small mineral specimens pressurized in-between two diamonds. Mineral elastic properties can be extracted by quantifying the interaction between X-ray/laser beams and specimens which induces elastic waves in the minerals. Results from this project will improve the understanding of three critical zones in the Earth's mantle, located near plate boundaries and within the first few hundred kilometers underneath the surface. The project outcomes will be integrated into educational outreaches towards high-school students in Albuquerque (NM), notably from under-represented groups, as well as in a new introductory course at UNM. The project will also support two early-career scientists and provide training to one graduate student at UNM.This proposal aims at better understanding the seismic anisotropy observed in three critical regions of the Earth's upper mantle: the lithosphere-asthenosphere boundary, the mid-lithosphere discontinuity and the mantle wedge in subduction zones. The goal is to link the anisotropy to the elastic properties of the relevant minerals. The PI will perform experiments in the diamond-anvil cell at the high pressures and temperatures prevailing in the mantle. Single-crystal Brillouin spectroscopy at PI's laser spectroscopy laboratory and a national synchrotron facility, the Advance Photon Source (IL), will allow measuring the elastic constants of hydrogen-bearing olivine and pyroxenes and minerals from the amphibole and serpentine groups. Specimens will be prepared by focused ion beam and a novel scattering geometry will be implemented to ensure the success of the project. The research outcomes will be integrated into educational and outreach activities. The PI, an early-career female scientist, will work with teachers from Albuquerque high schools to encourage students to pursue STEM studies. A new introductory geoscience course will provide fun movie-discussion-exploration style learning experiences at University of New Mexico. The objective is to engage at an early stage more female and students from underrepresented groups into Earth Sciences careers. The project will also support a postdoctoral associate and provide training to one graduate student at UNM.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

地幔中的热对流驱动板块构造，从而产生自然灾害，如火山喷发和地震。因此，了解地幔流动具有很强的社会相关性。地震学是研究地幔流动的主要工具。地震速度的差异被称为地震各向异性，反映了地幔岩石的弹性各向异性。这种各向异性是由其构成矿物的性质和由对流引起的变形造成的。在这里，PI将实验测量各种地幔矿物在地球上普遍存在的极端压力和温度下的弹性各向异性。根据这些数据，可以计算出岩石的地震各向异性，并与现场观测结果进行比较。这些实验将在国家同步加速器设施中进行，在那里产生强大的X射线，并在新墨西哥大学(UNM)的PI激光实验室进行。激光和X射线将被引导到两颗钻石之间加压的小矿物样品。可以通过量化X射线/激光与在矿物中诱导弹性波的样品之间的相互作用来提取矿物的弹性性质。该项目的结果将提高对地幔中三个临界区的理解，这三个临界区位于板块边界附近和地表下最初几百公里内。项目成果将被纳入针对阿尔伯克基(新墨西哥州)高中生的教育外展，特别是来自代表性不足群体的教育外展，以及在新墨西哥州大学的一门新的入门课程。该项目还将支持两名职业生涯初期的科学家，并为联合国苏丹特派团的一名研究生提供培训。这项提议旨在更好地了解在地球上地幔的三个关键区域观测到的地震各向异性：岩石圈-软流圈边界、岩石圈中期不连续和俯冲带中的地幔楔形。目标是将各向异性与相关矿物的弹性性质联系起来。PI将在地幔中普遍存在的高压和温度下，在钻石顶压室中进行实验。派的激光光谱学实验室和国家同步加速器设施先进的光子源(IL)上的单晶布里渊光谱学将允许测量含氢橄榄石和辉石以及角闪石和蛇纹石类矿物的弹性常数。样品将由聚焦离子束制备，并将实施一种新的散射几何结构，以确保项目的成功。研究成果将纳入教育和外联活动。PI是一位职业生涯早期的女科学家，她将与阿尔伯克基高中的老师合作，鼓励学生学习STEM。一门新的地球科学入门课程将在新墨西哥大学提供有趣的电影讨论式探索学习体验。其目标是在早期阶段吸引更多的女性和来自代表性不足群体的学生进入地球科学的职业生涯。该项目还将支持一名博士后助理，并为联尼特派团的一名研究生提供培训。这一奖励反映了国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Effect of structural water on the elasticity of orthopyroxene

• DOI: 10.2138/am-2021-7843
• 发表时间: 2022-03
• 期刊: American Mineralogist
• 影响因子: 3.1
• 作者: M. Hou;Wencai Zhou;M. Hao;Florian Tian-Siang Hua;J. Kung;Dongzhou Zhang;P. Dera;Jin S. Zhang

The Water-Fe-Pressure dependent single-crystal elastic properties of wadsleyite: Implications for the seismic anisotropy in the upper Mantle Transition Zone

瓦兹利石的水-铁-压力依赖性单晶弹性特性：对上地幔过渡带地震各向异性的影响

• DOI: 10.1016/j.epsl.2021.116955
• 发表时间: 2021
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Zhou, Wen-Yi;Ren, Zhiyuan;Zhang, Jin S.;Chen, Bin;Hao, Ming;Ohuchi, Tomohiro;Miyagi, Lowell;Zhang, Dongzhou;Alp, Esen E.;Lavina, Barbara
• 通讯作者: Lavina, Barbara