Projects

(1) The behavior of palladium and silver during core formation and implications for volatile accretion to the Earth:

This project uses metal-silicate partitioning experiments to understand the effect of core-mantle equilibration on the mantle's Pd and Ag contents. Pd is a highly siderophile element and should have been stripped from the mantle by core formation, while silver is a volatile and moderately siderophile element. In addition, 107Pd decays to 107Ag on a timescale of 6.5 million years, making this system a chronometer for early processes in the Earth such as core formation and volatile accretion. Experimental results are combined with core formation models to better understand the evolution of the mantle's Ag isotopic signature.

(2) Equations of state for minor phases in the lower mantle:

Oceanic lithosphere can be subducted as deep as the core-mantle boundary. The increased pressures and temperatures at these depths can lead to phase transitions to mineralogies in the NaAlSiO4-MgAl2O4 system. These minerals can adapt a calcium ferrite or new aluminous phase (NAL) structure and could potentially account for up to 25 volume % of the lower mantle. Some of these phases could also host heat-producing radiogenic elements in the lower mantle and have been linked to low seismic velocity provinces. In order to further understand the fate of subducting slabs, we use X-ray diffraction to study the equations of state of minerals in this system at lower mantle conditions.