EAR-PF: Hydrogen in the Earth's transition zone: Merging experimental and theoretical approaches

Elizabeth C. Thompson博士获得美国国家科学基金会EAR博士后奖学金，在西北大学开展研究和教育计划。该研究将确定含铝超含水硅酸盐镁矿物的压力和温度稳定场。这项研究的结果将有助于限制地球过渡带和地幔（410-660公里深）中水的数量和位置，这是地球上一个比地壳大100倍的区域。该教育计划将侧重于指导、编写教材和讲座以及推广。汤普森博士还将与日本爱媛大学的科学家合作。本项目利用几种互补技术，包括：(1)第一性原理计算，(2)基于同步加速器的红外光谱，(3)拉曼光谱和(4)单晶衍射，对高压超水B相中的铝取代进行了评估。这些发现将在广泛意义上影响地球深部的地球化学，因为富铝的超水相B要么将氢引入过渡带，进入下地幔，要么分解，根据其P-T稳定性释放H2O。超水相B分解产生的熔体会在地幔中产生化学非均质性。此外，由于氢对熔融温度和粘度的影响，脱水熔体可能潜在地影响板块构造。本研究还将探索al取代对超水相B中压力诱导氢键对称的影响，这一现象先前被报道对矿物的体材料性质（包括体模量及其压力导数）有重大影响。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。

Dr. Elizabeth C. Thompson has been granted an NSF EAR Postdoctoral Fellowship to carry out research and education plans at Northwestern University. The investigation will determine the pressure and temperature stability field for aluminum-bearing super hydrous magnesium silicates minerals. The results of this study will help constrain the quantity and location of water in the Earth's transition zone and mantle (410-660 Km depth), a region of the Earth ~100 times more massive than the Earth's crust. The education plan will focus on mentoring, developing teaching materials and lectures, and outreach. Dr. Thompson will also collaborate with scientists at Ehime University in Japan.This project evaluates aluminum substitution in high-pressure superhydrous phase B, using several complementary techniques, including: (1) first-principles calculations, (2)synchrotron-based infrared spectroscopy, (3) Raman spectroscopy and (4) single crystal diffraction. These findings will impact deep Earth geochemistry in a wide-ranging sense, as Al-rich superhydrous phase B either ushers hydrogen through the transition zone and into the lower mantle or decomposes, releasing H2O depending on its P-T stability. Fluxed melts resulting from the decomposition of superhydrous phase B would produce chemical heterogeneities in the mantle. Additionally, dehydration melts may potentially influence plate tectonics due to the effect of hydrogen on melting temperatures and viscosity. This study will also explore the effect of Al-substitution on pressure-induced hydrogen bond symmetrization in superhydrous phase B, a phenomenon previously reported to have a significant influence on a mineral's bulk material properties including bulk modulus and its pressure derivative.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.