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.

H2O在地幔和地球表面之间以及地幔中不同储层之间的循环是控制地球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可居住性和气候的一切。然而，H2O在地幔中的分布和库存仍然不确定，主要地幔储层之间的传输机制还不完全清楚，H2O影响地球关键物质性质的微观机制仍然存在争议。该项目代表了一个多学科的努力，结合理论矿物物理学，实验岩石学和实验岩石物理学，以解决一些关键的突出问题，有关H2O在地幔中的分布和行为。 目前的建议将继续研究CSEDI以前对该小组的资助所产生的几个广泛问题：1）为了调查在软流圈或410公里以上的上地幔深部引发含水熔融所需的条件，我们将进行实验，理论和光谱研究，以确定橄榄岩饱和的名义上无水矿物中H取代的机制和限制，重点是石榴石和辉石，并评估软流圈和上地幔在410公里不连续面顶部的含水熔融条件。2)为了解决我们在理解橄榄石中的H如何取代以及它如何影响地幔蠕变强度等关键性质方面的矛盾，我们将结合联合收割机实验，第一性原理计算和红外光谱来解决关于结构，化学环境和微量元素取代之间联系的关键不确定性，这些不确定性对橄榄石，石榴石，以及氢对扩散率和蠕变强度的影响。3）我们将继续努力使用ERDA（弹性反冲检测分析），以提高名义上无水矿物中H的FTIR和西姆斯测定的准确性。最先进的材料理论与岩石学和岩石物理学的专业知识。 这项工作包括涉及三名教师，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本科实习生网站（地球中的流体，从表面到核心。 Wentzcovitch和Umemoto通过量子ESTEGO项目和相关的研讨会和教程以及通过暑期实习培训本科生，向更广泛的科学界传达结果和方法。