Renewal: Chemistry of the Earth's Deep Interior

本项目旨在确定地球深部相关条件下下地幔和地核物质的化学性质，以获得地球内部化学组成、形成和演化的直接实验约束。到目前为止，固体地球中的大部分矿物都隐藏在高压(P)和高温(T)下的很深的地方。这些矿物决定了地球的形成、演化、现状和目的地。最近对地球深处的地球化学研究向我们展示了大量尚未完全了解的大规模过程和现象。这些问题包括深俯冲板块的命运、地幔柱的起源、地核-地幔边界层的反应、形成当今地壳、地幔和地核的元素分化、微量元素的分布、以及地球历史过程中挥发物的吸收和再循环。解决这些问题需要详细了解相关材料的化学性质，这些材料在高P-T下发生了深刻的变化，导致新的和不可预见的反应发生，并引起近地表环境中矿物系统中未观察到的结构、电子和磁性转变。该项目利用了许多使能技术的最新发展，包括高P-T金刚石砧细胞、新的中子衍射设施和仪器、先进的x射线衍射和光谱、电子显微镜和聚焦离子束方法。铁和铁合金的关键高P-T晶体结构，在核心-地幔边界P-T条件下的后钙钛矿晶体学，后尖晶石结构以及使用中子衍射的致密水相晶体结构都将采用最先进的技术进行研究。将对氧化物、硅酸盐、碳酸盐、硼酸盐和硝酸盐的高压键合性能进行k边x射线拉曼光谱分析。三维元件的压力诱导自旋对跃迁和压力诱导磁矩变化的电子和磁跃迁也将被研究。将对下地幔和地核物质中的相关系、熔融和铁-镁分配进行选定的测量。虽然将使用广泛的技术，但所测量的性质将相互关联，为测量提供重要的交叉检查，并为地球深层内部的化学模型提供关键输入。

The proposed project aims to determine the chemical properties of lower mantle and core materials at relevant deep Earth conditions in order to obtain direct experimental constraints on the chemical composition, formation, and evolution of the planet's interior. By far the major fraction of minerals in the solid Earth are hidden at great depth under high pressures (P) and temperatures (T). These minerals dictate the formation, evolution, present state, and destination of the planet. Recent geochemical studies of the Earth's deep interior present us with a rich array of large-scale processes and phenomena that are not fully understood. These range from the fate of deeply subducting slabs, the origin of plumes, the reactions at the core-mantle boundary layer, the differentiation of elements to form the present day crust, mantle, and core, the distribution of trace elements, and the uptake and recycling of volatiles over the course of the Earth's history. Resolving these questions requires a detailed understanding of the chemistry of the relevant materials that are profoundly altered at high P-T, causing new and unforeseen reactions to occur and giving rise to structural, electronic, and magnetic transitions not observed in mineral systems in the near-surface environment. The project takes advantage of recent developments in a number of enabling technologies, including high P-T diamond anvil cells, new neutron diffraction facilities and instrumentation, advanced in x-ray diffraction and spectroscopy, and electron microscopy and focused ion beam methods. Key high P-T crystal structures of iron and iron alloys, post-perovskite crystallography at the P-T conditions of the core-mantle boundary, post-spinel structures, and crystal structures of dense hydrous phases using neutron diffraction will all be studied with state-of-the-art techniques. K-edge x-ray Raman spectroscopy of the high-pressure bonding properties of oxides, silicates, carbonates, borates, and nitrates will be conducted. Electronic and magnetic transitions of pressure-induced spin pairing transitions of 3d elements and pressure-induced magnetic moment changes will also be pursued. Selected measurements of phase relations, melting, and Fe-Mg partitioning in lower mantle and core materials will be carried out. Although a broad range of techniques will be used, the properties measured will be interrelated to provide important cross checks on the measurements as well as critical input for chemical models of the Earth's deep interior.