Chemistry and Structure of Grain and Phase Boundaries: Importance for Trace Element Storage and Transport in the Mantle

这项工作试图回答的问题，“什么是地幔岩石中的不相容元素的晶粒和相边界的存储容量？在地幔中，颗粒-颗粒界面的偏析如何影响颗粒间扩散？“最近发现，Mg-Fe橄榄石晶粒之间的边界富含Ca、Al、Cr、K和Ti等元素。的浓度系统地变化的浓度在粮食内部，在某些情况下，以下的经典热力学模型的元素分配。这项研究涉及这些过程的系统分析和实验研究，以及由此产生的影响在地球地幔的扩散运输。研究结果将为地球深部的地球化学演化和行为提供约束。 这一建议的更广泛的影响来自本科生的教育，研究生和博士后的专业发展，以及建立新的实验技术。 (1)地质和地球物理系是NSF资助的REU网站，用于研究地球从表面到核心的流体。 因此，本科生每年夏天都会获得实践经验，进行与本文件中提出的研究直接相关的实验。 (2)本提案中概述的研究是作为最近一个博士研究金项目的一部分启动的一个项目的继续，现在将由一名一年级研究生和一名年轻的博士后科学家继续进行，从而促进他们的专业发展。 (3)作为拟议研究的一部分，将开发新的实验技术，这些技术在建立固体地球科学研究基础设施方面发挥重要作用。

This work seeks to answer the questions, "What is the storage capacity of grain and phase boundaries for incompatible elements in mantle rocks?" and "How does segregation to grain-grain interfaces affect intergranular diffusion in the mantle?" It was recently discovered that boundaries between grains of Mg-Fe olivine are enriched in elements such as Ca, Al, Cr, K and Ti. The concentrations vary systematically with the concentrations in the grain interiors, in some cases following classic thermodynamic models for elemental partitioning. This study involves systematic analytical and experimental investigation of these processes and the resultant effects on diffusive transport in Earth's mantle. The results will provide constraints on the geochemical evolution and behavior of Earth's deep interior. The broader impacts of this proposal emerge from education of undergraduates, professional development of a graduate student and a postdoctoral associate, and establishment of new experimental techniques. (1) The Department of Geology and Geophysics is an NSF-funded REU site for studies of Fluids in the Earth from Surface to Core. As such, undergraduates gain hands-on experience each summer carrying out experiments that are direct outgrowths of and intimately related to the research proposed in this document. (2) The research outlined in this proposal is a continuation of a project that was initiated as part of a recent doctoral fellowship project and will now be carried forward by a first-year graduate student and a young postdoctoral scientist, thus contributing to the professional development of both. (3) As part of the proposed research, new experimental techniques will be developed, which play an important part in building the research infrastructure in the solid-earth sciences.