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: 2243184
• 负责人: Jin Zhang
• 金额: $ 63.33万
• 依托单位: Texas A&M University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-01 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2243184&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着板块构造，从而产生自然灾害，如火山爆发和地震。因此，了解地幔流动具有很强的社会意义。地震学是研究地幔流动的主要工具。地震波速度的差异，称为地震各向异性，反映了地幔岩石的弹性各向异性。这种各向异性的结果，从他们的组成矿物的性质，并从他们的对流变形。在这里，PI将实验测量各种地幔矿物在地球极端压力和温度下的弹性各向异性。根据这些数据，可以计算岩石地震各向异性，并与野外观测结果进行比较。这些实验将在国家同步加速器设施和PI位于新墨西哥州大学（UNM）的激光实验室进行，在那里产生强大的X射线。激光和X射线将被引导到两颗钻石之间加压的小矿物样本上。矿物的弹性性质可以通过量化X射线/激光束与样品之间的相互作用来提取，所述相互作用在矿物中引起弹性波。该项目的结果将提高对地球地幔中三个关键区域的理解，这些区域位于板块边界附近和地表下最初几百公里内。项目成果将纳入对阿尔伯克基（新墨西哥州）高中学生，特别是代表性不足群体的高中学生的教育外展活动，并纳入新墨西哥州大学新的入门课程。该项目还将支持两名早期职业科学家，并为新墨西哥大学的一名研究生提供培训。该提案旨在更好地了解在地球上地幔的三个关键区域观察到的地震各向异性：岩石圈-软流圈边界，中岩石圈不连续性和俯冲带的地幔楔。目的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高温下在金刚石砧室中进行实验。PI激光光谱实验室和国家同步加速器设施Advance Photon Source（IL）的单晶布里渊光谱将允许测量含氢橄榄石和辉石以及闪石和蛇纹石类矿物的弹性常数。将通过聚焦离子束制备样品，并将实施一种新颖的散射几何形状，以确保项目的成功。研究成果将纳入教育和外联活动。PI是一位早期职业女性科学家，她将与阿尔伯克基高中的教师合作，鼓励学生从事STEM研究。一个新的介绍地球科学课程将提供有趣的电影讨论探索风格的学习经验，在新墨西哥州大学。其目标是在早期阶段让更多的女性和学生从代表性不足的群体进入地球科学职业。该项目还将支持一名博士后助理，并为UNM的一名研究生提供培训。该奖项反映了NSF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。