CSEDI: Integrated Study of H2O in the mantle

水在地幔和地表之间以及地幔中不同储集层之间的循环是控制地球动力学和地球化学演化的关键过程，影响着从板块构造到宜居性和气候的一切。然而，H2O在地幔中的分布和赋存仍然不确定，主要地幔储集层之间的输运机制还不完全清楚，H2O影响地球关键物质性质的微观机制仍然存在争议。该项目代表了一项多学科的努力，结合了理论矿物物理、实验岩石学和实验岩石物理，以解决关于地幔中H2O的分布和行为的一些关键悬而未决的问题。目前的建议将探讨CSEDI以前资助这一小组所产生的几个广泛问题：1)为了调查在软流圈或410公里以上上地幔深处激发水合熔融所需的条件，我们将进行实验、理论和光谱分析，以确定名义上含橄榄岩的无水矿物中氢替代的机制和限度，重点是石榴石和辉石，并评估软流圈和410公里不连续面上的上地幔水合熔融的条件。2)为了解决我们对橄榄石中氢的取代方式及其对地幔蠕变强度等关键性质的影响的理解上似乎存在的矛盾，我们将结合实验、第一性原理计算和红外光谱来解决结构、化学环境和微量元素取代之间的关系的关键不确定性，这些不确定因素涉及橄榄石、石榴石、石榴石、3)我们将继续努力使用ERDA(弹性反冲检测分析)，以提高FTIR和SIMS对名义上无水矿物中H的测定的准确性。该项目的更广泛影响包括继续进行一项重要的跨部门多学科工作，将最先进的材料理论与岩石学和岩石物理专业知识相结合。这项工作包括三名教员、两名博士后研究人员和一名研究生，并通过定期小组会议促进，以确保我们的重点仍然是多学科方法，并促进所有参与者的跨学科学习。对于Hirschmann、Kohlstedt和Withers来说，拟议的研究与地球科学REU本科生实习生站点(地球中的流体，从表面到核心)非常吻合。Wentzcovitch和Uemoto通过Quantum Epresso项目和相关的研讨会和教程，以及通过暑期实习对本科生进行培训，向更广泛的科学界交流结果和方法。

Cycling of H2O between the mantle and the Earth's surface and between different reservoirs in the mantle are critical processes governing Earth's geodynamical and geochemical evolution, influencing everything from plate tectonics to habitability and climate. However, the distribution and inventory of H2O in the mantle remains uncertain, the mechanisms of transport between principal mantle reservoirs are not fully known, and the microscopic mechanisms by which H2O influences the properties of key Earth materials remain controversial. This project represents a multidisciplinary effort combining theoretical mineral physics, experimental petrology, and experimental rock physics to address some of the key outstanding questions regarding the distribution and behavior of H2O in the mantle. The current proposal will pursue several broad problems that arise from previous CSEDI funding to this group:1) To investigate the conditions required to incite hydrous melting in the asthenosphere or in the deep upper mantle above 410 km, we will conduct experimental, theoretical and spectroscopic studies to determine the mechanism and limits of H substitution in peridotite-saturated nominally anhydrous minerals, with a focus on garnet and pyroxene, and evaluate the conditions for hydrous melting of the asthenosphere and the upper mantle atop the 410 km discontinuity. 2) To resolve seeming contradictions in our understanding of how H substitutes in olivine and how it influences key properties such as mantle creep strength, we will combine experiments, first-principle calculations and infrared spectroscopy to resolve critical uncertainties regarding the connection between structure, chemical environment, and minor element substitution on the mechanisms of incorporation of OH in olivine, garnets, and pyroxene and on the influence of H on diffusivity and creep strength.3) We will continue our efforts to use ERDA (Elastic Recoil Detection Analysis) to improve the accuracy of FTIR and SIMS determinations of H in nominally anhydrous minerals.The broader impacts of this project includes continuation of a significant inter-departmental multidisciplinary effort integrating state-of-the-art materials theory with expertise in petrology and rock physics. The effort includes involving three faculty, two post-doctoral researchers, and one graduate student and is facilitated by regular group meetings to ensure that our focus remains on multidisciplinary approaches and to promote interdisciplinary learning of all of the participants. For Hirschmann, Kohlstedt, and Withers, the proposed research dovetails well with the Earth sciences REU undergraduate intern site (Fluids in the Earth, from the Surface to the Core. Wentzcovitch and Umemoto communicate results and methods to the broader scientific community through the Quantum ESPRESSO project and related workshops and tutorials and in the training of undergraduates through summer internships.