Research

Chemical cycling at subduction zones

Subduction zones mediate long-term chemical exchange between the Earth’s mantle and surface reservoirs. Detailed assessments of the loss or retention of specific slab components in subduction zone environments are critical to our understanding of the recycling of volatiles such as water and carbon to the deep Earth. We published a study that used H2O mass balance and constraints on sea level change to set limits on the amount of water subducted beyond depths of magma generation. We have ongoing projects looking into the cycling of volatiles through subduction zones based on new stable isotope tracers.

Diagram of mantle-exosphere volatile fluxes

The nature of heterogeneity in Earth's mantle

Earth's silicate mantle is heterogeneous on a variety of lengthscales, and these heterogeneities reflect the integrated history of mantle convection over 4.5 billion years of Earth history. Noble gas isotopes provide a powerful set of linked radiogenic systems (e.g., U-Th-He, U-Xe, Pu-Xe, I-Xe) that can be leveraged to examine the generation of mantle heterogeneity on a variety of timescales.

Cook-Austral He and Ne and the nature of the HIMU mantle source

Southwest Indian Ridge mid-ocean ridge basalts and heterogeneous recycling of atmospheric gases

An examination of systematic differences in the Xe isotopic signatures of mid-ocean ridge basalt sources and plume mantle sources

The timing of lunar formation

A violent accretion process established the Earth’s inventory of volatile compounds. The extent and timescale of volatile loss during terrestrial accretion, particularly in association with the Moon-forming giant impact, are not well-constrained. The Moon-forming giant impact triggered the last catastrophic degassing event on the early Earth. Degassing fractionates lithophile radioactive species from their atmophile radiogenic daughter species. We use a pair of short-lived radionuclide systems (I-Xe and Pu-Xe) to better constrain the timing and nature of volatile loss from the early Earth.