Renewal-Experimental Studies of Elasticity, Rheology, Volume, and Texture of Materials at Pressure-Temperature Conditions of the Earth's Mantle and Core

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Geophysical observations of the Earth's mantle and core present us with a rich array of large-scale processes and phenomena that are not yet fully understood. Minerals that make up the bulk of the deep interior are subject to enormous pressures and temperatures that drastically altered the minerals properties. This award will support the investigators to extend their pressure-temperature capability of in-laboratory simulations to the extreme conditions of the inner core. They will develop new techniques using national x-ray facilities to investigate the altered properties of the compressed minerals, and will use the new data to help interpreting the geophysical observations. The proposed experiments will also shed light on how the liquid iron core separated from the rocky mantle during the Earth's formation.In addition to the continuation of data acquisition up to the P-T range of the outer core using a battery of newly available synchrotron analytical probes that the team has developed with prior support, they propose to extend mineral physics investigations to inner core P-T conditions (330-360 GPa, 5000-6000 K), and to enable elasticity and deformation measurements of sub-micron single crystals, direct volume determinations of non-crystalline materials, and investigations of complex intergranular textures of rocks. These new capabilities will be accomplished by integration of diamond-anvil cells with the state-of-the-art nano-focusing hard x-ray beam, 3D x-ray tomography with full-field nanoscope objective, and a new-generation, laser-heating system supported by a NSF-MRI grant. Using the new and existing techniques, the investigators propose to study elasticity, rheology, volume, and texture of the mantle silicates, oxides, and sulfides, and core metals and alloys along the geotherm P-T conditions. The results will be used to address major geophysical issues, including mantle-core separation beyond the magma ocean, drainage or trapping of liquid iron from silicate and oxide grain boundaries in the mantle, mass transport of fluids, seismic profiles and anomalies in the deep mantle and core, liquid density of Fe and alloys in the outer core, inner core mineralogy, growth, and rheology, and nature of the proposed innermost inner core.