Postdoctoral Fellowship: EAR-PF: The origins and role of hydrogen in ocean island lavas.

Although abundant in the form of water near Earth’s surface, hydrogen is only a minor component of Earth’s crust and mantle. When tectonic plates collide, sinking (i.e., subducting) plates transport hydrogen to the deep mantle. Much later, subducted hydrogen may return to Earth’s surface through volcanic hotspots, which form in the middle of tectonic plates. This recycling of hydrogen through the deep Earth can be tracked and provide an understanding of processes deep in the Earth. This project will focus on hydrogen at oceanic volcanic hotspots. This project serves the national interest by informing natural resource management through improved understanding of mantle evolution and the impacts of subduction and by enhancing the science and technology workforce through high school research opportunities. Radiogenic isotope systematics of mantle-derived lavas suggest that long-lived geochemical heterogeneity associated with subducted lithosphere exists in the lower mantle. Hydrogen isotopes provide insights into recycling, core-mantle exchange, diffusion, and degassing processes. The postdoctoral fellow will analyze the abundances of major, trace, and volatile element concentrations, as well as the hydrogen isotopic compositions, of submarine volcanic glasses and olivine-hosted melt inclusions. These melt inclusions represent deeply entrapped melts that are less degassed compared to the submarine glasses. The samples are from localities that tap the geochemical endmembers of the mantle associated with subduction. Many of the samples have elevated helium isotope ratios (3He/4He), which has been attributed to excess primordial helium from ancient mantle domains or the core. This project will constrain the deep cycling of hydrogen through Earth’s interior and facilitate the ability to link high 3He/4He and compositional endmembers to specific processes. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.