Elastic properties of carbonates at high pressures and temperatures

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The objectives of the continuation project remain to determine elastic wave velocity data for carbonates at high pressure and temperature conditions that can be used to assess the detectability of carbonated assemblages in the mantle. The first three years of the project were focused on carbonates with the calcite-type structure that are stable from the crust down to the mid part of the lower mantle. The second three years of the project will be focused on the new high-pressure carbonates that are stable above 75 GPa and 1400 K, hence potentially in the lower part of the lower mantle. The scientific questions that will be addressed by the project are the following: (1) What is the effect of oxygen fugacity on the stability of the high-pressure iron carbonates? Are these phases stable at the reduced conditions expected in the deep Earth? (2) What is the solubility of Mg in the high-pressure iron carbonates? (3) What is the effect of pressure, temperature and composition on the compressional and shear wave velocities of polycrystalline forms of the new iron-containing high-pressure carbonates at pressures and temperatures relevant for the deep Earth? The answers to these questions will be used to quantify the detectability of carbon in the deep Earth's interior.