Renewal: Chemistry of the Earth's Deep Interior

知识价值。最近发现的（Mg,Fe）SiO3的Cmcm后钙钛矿（ppv）相和铁在下地幔压力-温度条件下的高自旋-低自旋（HS-LS）转变为深部地球研究的新范式奠定了基础。先前支持的研究结果表明，（Mg0.6Fe0.4）SiO3以另一种ppv结构（Pmma）结晶，其铁处于混合自旋状态，并在两个不同的晶体位置有序。因此，地幔矿物学比以前认为的要复杂得多，有几个问题必须解决：下地幔中主要矿物相的晶体结构是什么？压力诱导的电子和磁性转变对下地幔相晶体化学的影响是什么？压强-温度-成分的相关系是什么？主要成分（Fe, Mg, Si）和次要成分（Ca, Al）是如何在不同的固相和熔体相之间以及不同的晶体位置之间分配的？矿物物理学新范式的地球化学和地球动力学后果是什么？高压技术的最新进展使解决这些具有挑战性的问题成为可能。X-DAC和便携式激光加热系统的开发为多功能和坚固的高压-温度环境提供了平台。子- ?Êm x射线探针允许在原地单晶x射线衍射研究与名义上的多晶样品。一组新开发的同步加速器x射线光谱探针，包括NRXS， XES， XANES， XMCD和XRS，可以深入研究铁的氧化态，自旋态和位置占用，以及轻元素（O, Si, Mg, Al）的化学键。这个以成果为基础的项目将解决这些和相关的问题，这些问题是理解大规模过程和现象的基础，包括地球化学储层的性质，深俯冲板块的命运，羽流的起源，核-幔边界的性质，早期地球的分化，以及今天持续的动态地球化学循环。更广泛的影响。本提案中概述的研究将影响地球科学中广泛的学科，包括地震学、地球动力学、大地测量学和构造学，以及岩石学和地球化学。这项工作还将提高对极端条件下材料特性的整体理解，因此，这项研究将照亮地球科学以外的领域：物理学、化学、材料科学、行星科学和生物学。这项研究将提高同步辐射和其他主要国家设施的能力，为更广泛的社区开发新的实验技术，并在这些设施培训新的科学家。一个宽传中？部分参与者将从工作中受益，从实习项目的高中生和本科生，到研究生（博士前研究员），博士后助理和访问研究者。因此，该项目利用现有的基础设施，为青年科学家在学术界、国家实验室和工业界的职业生涯做好准备。与以前的奖项一样，拟议工作的结果和影响将在流行文章和讲座中出现。通过新开发的技术、材料应用的潜力、新科学家的培训和公众教育，推进地球科学的科学前沿，拟议的工作将广泛影响科学和社会。

Intellectual Merit. Recent discoveries of the Cmcm post-perovskite (ppv) phase of (Mg,Fe)SiO3 and the high-spin-low-spin (HS-LS) transition of iron in lower-mantle pressure-temperature conditions have set the stage for a new paradigm in deep Earth research. Previously supported research results reveal that (Mg0.6Fe0.4)SiO3 crystallizes in another ppv structure (Pmma) and its iron is in a mixed spin state and ordered in two distinct crystallographic sites. Thus mantle mineralogy is more complex than previously thought, and several questions must be addressed: What are the crystal structures of the major mineral phases within the lower mantle? What are the effects of pressure-induced electronic and magnetic transitions on the crystal chemistry of lower mantle phases? What are the pressure-temperature-composition phase relations? How do major (Fe, Mg, Si) and minor (Ca, Al) components partition among different solid and melt phases and between different crystallographic sites? What are the geochemical and geodynamic consequences of this new paradigm of mineral physics? Recent progress in high-pressure technology now makes it possible to tackle these challenging questions. The development of X-DAC and portable laser-heating system provide the platform for versatile and robust high pressure-temperature environments. The sub-?Êm x-ray probe allows in situ single-crystal xray diffraction studies with nominally polycrystal samples. A battery of newly developed synchrotron xray spectroscopic probes, including NRXS, XES, XANES, XMCD, and XRS allows in-depth study of the oxidation states, spin states, and site occupancy of Fe, as well as chemical bonding of light elements (O, Si, Mg, Al). This accomplishment-based project will address these and related questions that are fundamental for understanding large-scale processes and phenomena including the nature of geochemical reservoirs, the fate of deeply subducted slabs, the origin of plumes, the nature of the core-mantle boundary, the differentiation of the early Earth, and the continuing dynamic geochemical cycles today. Broader Impacts. The research outlined in this proposal will impact a broad range of disciplines within the Earth sciences, including seismology, geodynamics, geodesy and tectonics, as well as petrology and geochemistry. This work will also improve understanding of material properties as a whole under extreme conditions, and as a consequence the research will illuminate areas beyond the geosciences: in physics, chemistry, materials science, planetary science, and biology. The research will enhance capabilities at synchrotron radiation and other major national facilities with the development of new experimental techniques for the broader community and training of new scientists at these facilities. A wide cross?]section of participants will benefit from the work, from high school and undergraduate students in internship programs, to graduate students (predoctoral fellows), postdoctoral associates and visiting investigators. As such, the project leverages existing infrastructure to prepare young scientists for careers in academia, national laboratories, and industry. The results and implications of the proposed work will be featured in popular articles and lectures, as with previous awards. By advancing the scientific frontiers of geoscience with newly developed techniques, the potential for materials applications, the training of new scientists, and educating the public, the proposed work will broadly impact both science and society.