This 2-year research project focuses on investigating the fate of oceanic crust and tectonic plates that dive into Earth's interior at subduction zones. Earth's convecting mantle transports the former crust to the deep interior, and eventually back up to the surface. This work specifically seeks to understand the chemistry, structure, and dynamics of oceanic crust in Earth's lower mantle. Plate tectonics and thus subduction-currents carrying crust into the deep mantle are an ongoing process; thus better understanding the distribution of, the dynamics of, and chemistry of deeply transported crust uniquely provides a window into the chemical and dynamical evolution of Earth's mantle as a whole. Past work clearly establishes how the mantle might convect, viable deep mantle minerals, and that there are seismically detected heterogeneities. This work builds upon these ideas by seeking to connect them via studying a known input into the system of unique chemistry: the oceanic crust. This work has broad impact, since the mantle's evolution ultimately plays a role in the chemical and thermal evolution of the oceans and atmosphere.
A multidisciplinary approach is adopted for this project, since (a) high pressure mineral physics in the diamond anvil cell can investigate the properties of former crust and sediments (e.g., melt) at conditions 1000's of km deep in Earth's mantle; (b) how former crust interacts with convective flow and structures, including deep compositional reservoirs, hot mantle plumes, and deep mantle chemistries can be explored with state-of-the-art numerical convection experiments; and (c) former oceanic crust may relate to structures observed with modern array seismology methods that have unknown mineralogy, including thin ultra low seismic wave speed zones at the bottom of the mantle, as well as massive continent-sized zones of low shear wave velocities beneath the Pacific and Atlantic Oceans. The multidisciplinary proposed work will include a strong co-mentoring approach among the team of PIs for the graduate student and postdoctoral researchers.
