MSI and Earth and Planetary Science Seminar

Deep Earth volatile inventories and the formation of the Moon

Rita Parai

Washington University in St. Louis

The deep Earth is a significant storage reservoir for volatiles, such as water, carbon dioxide and the noble gases. Noble gases in mantle-derived rocks provide unique insights into the evolution of planetary volatile budgets. Volatiles are lost from the mantle in association with volcanism, but are potentially recycled into the mantle via subduction in association with plate tectonics.

We measured noble gas isotopic compositions in a suite of mid-ocean ridge basalts with sufficient precision to demonstrate that atmospheric heavy noble gases are recycled to the deep mantle over time. Although significant atmospheric xenon (Xe) recycling occurs, the Xe isotopic compositions of mantle sources have not been entirely overprinted. Rather, these preserve a record of very early differentiation of the upper mantle from the mantle plume source. I will discuss new constraints from noble gases on the nature of the plume source and upper mantle, volatile cycling between deep Earth and surface reservoirs, and the timing of the Moon-forming giant impact.