The geological activity at Earth's surface that can so profoundly affect humanity ultimately arises from on-going processes within the deep interior. These large-scale processes are in turn controlled by the properties of the constituent materials of the deep Earth. A mineral's crystal structure is its most fundamental characteristic, from which all other physical and chemical properties follow. Due to the incredibly high pressures (millions of atmospheres) and temperatures (thousands of degrees) of the deep Earth, our knowledge of the crystal structures of minerals residing near the base of Earth's mantle remains far from complete. This region of the Earth is primarily composed of silicate minerals that adopt structures known as perovskite and post perovskite. In this project, the PI will conduct laboratory experiments to probe the basic structural properties of magnesium iron germanates, a class of compounds that serve as close analogs for the silicate minerals of the deep Earth, but which can be studied at lower pressures and temperatures which are more easily attainable in the laboratory. Through this work, he and his team will provide fundamental knowledge of mineral crystal structures and properties that are needed to understand and interpret geophysical observations of the Earth's interior.
The Earth's deep lower mantle is key for understanding the overall structure, dynamics, and evolution of the planet. Seismic evidence indicates this region exhibits considerable chemical heterogeneity as exemplified by features such as large low shear velocity provinces, ultra-low velocity zones, and the complexity of the core-mantle boundary region. The PI will conduct high-pressure X-ray experiments on Fe-bearing compositions in the (Mg,Fe)GeO3 system, an analog for the silicates of the deep mantle. The advantage of this system is that the perovskite to post-perovskite transition occurs at much lower pressure for germanates, allowing the team to avoid or reduce the experimental complications that plague silicate studies at ultrahigh pressures. They will use the laser-heated diamond anvil cell to carry out a series of synchrotron-based studies of the crystal structure, equation of state, electronic configuration, and local environment of iron in germanates with the perovskite and post-perovskite structures. The results will lead to a better understanding of how iron content affects mineralogical behavior in these phases and will directly impact the fields of seismology, petrology, geodynamics, geochemistry, and mineralogy.
