Chemical cycles in the oceanic crust

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Hydrothermal circulation in the oceanic crust plays a critical role in controlling the compositions of the world's oceans, provides energy and nutrients for extremophile organisms and generates ore deposits of economic importance. Heat and mass are exchanged between the lithosphere and oceans throughout the lifecycle of an ocean plate, from its creation at mid-ocean ridges to its recycling back into the mantle at subduction zones. My proposed research program focuses on understanding what drives this exchange, both at mid-ocean ridges where high temperature hydrothermal systems are active and in the off-axis where seafloor weathering dominates. In both environments, we integrate geological constraints with insights from geochemical tracers to assess what environmental conditions control chemical reactions and element mobility. For the mid-ocean ridge setting, we will examine the conditions and consequences of seawater ingress into the lower ocean crust by studying drill cores recovered by a novel deep-sea drill. We will also analyze the real-time data stream from instruments recording high temperature fluid properties from active hydrothermal systems at the Endeavour segment of the Juan de Fuca Ridge through the NEPTUNE network. Our focus in the off-axis environment is to advance our understanding of how seafloor weathering responds to external forcing by exploring linkages with seawater chemistry and climate. We will conduct an in depth study of the products of seafloor weathering using the extensive core collection of international drilling programs and basin-scale datasets to develop predictive models that assess the relative importance of crustal age versus climate state and seawater chemistry for seafloor weathering geochemical fluxes.