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

地幔中的热对流驱动板块构造，从而产生自然灾害，如火山爆发和地震。因此，理解地幔流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，称为地震各向异性，反映了地幔岩石的弹性各向异性。这种各向异性是由它们的本构矿物的性质和它们在对流流动下的变形造成的。在这里，PI将实验测量在地球上普遍存在的极端压力和温度下各种地幔矿物的弹性各向异性。根据这些数据，可以计算出岩石地震各向异性，并与现场观测结果进行比较。实验将在国家同步加速器设施和PI在新墨西哥大学（UNM）的激光实验室进行，该设施产生强大的x射线。激光和x射线将被引导到压在两颗钻石之间的小矿物标本上。通过量化x射线/激光束与样品之间的相互作用，可以提取矿物的弹性特性，从而在矿物中产生弹性波。这个项目的结果将提高对地幔中三个关键区域的理解，它们位于板块边界附近和地表以下几百公里内。该项目的成果将被纳入对阿尔伯克基（新墨西哥州）高中生的教育外展活动，特别是来自代表性不足群体的学生，以及新墨西哥大学的一门新的入门课程。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。本研究旨在更好地理解在岩石圈-软流圈边界、岩石圈中不连续和俯冲带的地幔楔这三个地球上地幔关键区域观测到的地震各向异性。目标是将各向异性与相关矿物的弹性特性联系起来。PI将在地幔中普遍存在的高压和高温下在钻石砧细胞中进行实验。PI的激光光谱实验室和国家同步加速器先进光子源（IL）的单晶布里渊光谱将允许测量含氢橄榄石和辉石以及角闪洞和蛇纹石群中的矿物的弹性常数。样品将通过聚焦离子束制备，新的散射几何将被实施，以确保项目的成功。研究成果将纳入教育和推广活动。PI是一名早期职业女性科学家，她将与阿尔伯克基高中的老师合作，鼓励学生从事STEM研究。新墨西哥大学的一门新的地球科学入门课程将提供有趣的电影-讨论-探索式学习体验。目标是在早期阶段让更多来自代表性不足群体的女性和学生参与到地球科学事业中来。该项目还将支持一名博士后，并为新墨西哥大学的一名研究生提供培训。该奖项反映了美国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。

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.