F and Cl in Peridotite Minerals: Analytical Development and Applications to Fluid Cycling in the Earth's Mantle

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Oceanic plates are built in submarine magmatic centers called ridges. Over millions of years, tectonic plates are pushed away from ridges and sink back into the deep Earth via a process called subduction. From birth at a ridge to recycling in a subduction trench, oceanic plates incorporate considerable amounts of seawater, carried into the interior of the Earth during subduction. The presence of fluids at depth dramatically modifies the physical and chemical properties of rocks and trigger melting and formation of arc volcanoes above subducting oceanic plates (e.g., Andes volcanic chain). Unraveling the pathways of fluids inside the Earth is critical to understand how and where arc volcanoes form; yet, elemental cycling of fluids in subduction zones remain poorly understood. This project will take advantage of state-of-the-art micro-analytical facilities at the Woods Hole Oceanographic Institution to develop novel tracers of fluid pathways, fluorine and chlorine, in rocks that were once equilibrated at depth in a subduction zone. In order to accomplish the goals of this study, the team will be furthering the analytical methods to analyze fluid tracers at very low concentrations. The ultimate goal is to advance current analytical techniques and use the distribution of fluorine and chlorine in rock minerals to track global fluid cycling in subduction zone settings.