CSEDI: Integrated Study of H2O in the mantle

CSEDI：地幔中 H2O 的综合研究

• 批准号: 1161023
• 负责人: Marc Hirschmann
• 金额: $ 76万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-05-15 至 2017-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1161023&HistoricalAwards=false
• 关键词: CSEDI; Integrated; Study; H2O; mantle

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.

地幔与地球表面之间以及地幔中不同储层之间的H2O循环是管理地球地球动力学和地球化学进化的关键过程，从而影响了从板块构造到可居住性和气候的一切。但是，H2O在地幔中的分布和清单仍然不确定，主要地幔储层之间的运输机制尚不完全清楚，并且H2O会影响关键地球材料的性质的微观机制。该项目代表了将理论矿物质物理学，实验性岩石学和实验岩石物理学结合在一起的多学科工作，以解决有关H2O在地幔中H2O的分布和行为的一些关键问题。 当前的提案将提出几个广泛的问题，这些问题是从以前的CSEDI资金到这一组引起的：1）调查在小圈中或高于410 km的深层上层中煽动含水所需的条件，我们将进行实验，理论和光谱学研究以确定橄榄石饱和的名义上无水矿物质中H取代的机制和限制，重点是石榴石和辉石，并评估了410 km不连续性的研究，小动植物层和上层地幔的含水条件。 2）解决似乎矛盾的是我们对橄榄石中H替代品的理解及其如何影响关键特性（例如地幔蠕变强度），我们将结合实验，第一原则计算和红外光谱，以解决有关结构，化学之间的联系，化学的关键不确定性的关键不确定性环境和次要元素替代了OH在橄榄石，石榴石和辉石的掺入机制，以及H对H扩散性和蠕变强度的影响。3）我们将继续努力使用ERDA（弹性后坐力检测分析）来改善FTIR和SIMS在名义无水矿物质中的H和SIMS确定的准确性。该项目的更广泛影响包括继续进行大部分跨部门的多学科努力，将先进的材料理论与岩石学和岩石物理学的专业知识相结合。 这项工作包括涉​​及三个教职员工，两名博士后研究人员和一名研究生，并通过常规小组会议促进，以确保我们的重点保留在多学科方法上，并促进所有参与者的跨学科学习。对于Hirschmann，Kohlstedt和Withers，拟议的研究与地球科学REU本科生实习地很好地吻合（地球上的流体，从表面到核心。项目和相关的研讨会和教程以及通过暑期实习的本科生培训。