Quantifying heat and chemical fluxes between the oceans and ocean crust

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A significant global geochemical cycle throughout most of geological time involves the creation, alteration, and recycling of the oceanic crust. This cycle brings mantle components into the crust and oceans, and seawater components into the mantle through subduction zones. As the largest aquifer on earth, the entire volume of the ocean is cycled through the ocean crust on timescales of 100 to 1000 kyr. This flow of seawater-derived fluids through the crustal aquifer extracts ~30% of the lithospheric heat and promotes chemical exchange between the ocean crust and oceans that moderates seawater chemistry and the subsurface biosphere. My research program has two interrelated themes. First, we will investigate global-scale geochemical cycles related to fluid flow and low temperature exchange in the ridge flank environment (e.g., where ocean crust is > 1 Myr). We will use a two pronged approach, hydrogeological modeling to explore how seawater flows through the ocean crust, and between the ocean crust and the oceans, and field and geochemical studies to quantify how the chemistry of the crust is modified by different styles of fluid flow. We will also investigate secular changes in the chemistry of the oceans and ocean crust, with a focus on the natural sequestration of CO2 in the ocean crust. Second, we will examine the chemical and heat fluxes associated with high temperature, hydrothermal systems at mid-ocean ridges on a range of timescales, ranging from 10 kyr to hours. We will use samples recovered by remotely operated vehicles, manned submersible and an international drillship, and data streaming in from a novel ocean observing network.