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.
