Elemental and Isotopic Systematics in Erosional and Accretionary Subduction Zones, with Implications for Fluid Sources, Pathways, and Fluxes

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Tectonic plate boundaries where ocean crust subducts beneath continental crust are associated not only in the Earth's most active earthquake zones, but also with the largest concentration of land volcanoes. Our understanding of these areas (also called subduction zones) and the processes that cause associated seismic and volcanic hazards is therefore needed for us to be able to better protect coastal communities and prepare effective land use and hazard mitigation strategies. Because both volcanism and earthquakes are affected by, and many times triggered by, fluids and the dehydration of minerals exposed to increasing temperatures and pressures as subduction occurs, our knowledge of how subduction zone fluids change with space, time, and composition across and between subduction zones is critical to our understanding of how these important areas behave and evolve over time. This research completes the geochemical data sets of subduction zones off the northwestern US, Japan, South and Central America, and the Caribbean. It also compiles all relevant laboratory experimental data, pore fluid, and deep sea bore hole fluid data with a focus on synthesizing this voluminous dataset and seeking new insights into how the geochemistry of fluids can reveal processes occurring at depth in the subduction process. Where identified, gaps in the geochemical record of these fluids will be completed, including creating an isotopic dataset for oxygen, deuterium, strontium, lithium, boron. The collective data will be used to examine mass balances of elements, the contribution of subduction fluids to the make-up of present day seawater, the role of compaction and dehydration/hydration reaction on fluid chemistry, and insights on the evolution of pore fluid pressures. Broader impacts of the work include support of a more than 15 year NSF investment in subduction zone characterization and dynamics and support of a PI whose gender is under-represented in the sciences.