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Element fluxes within crust and across ocean floor

To assess the variability in seawater composition and global biogeochemical cycling, we will first estimate the influence of water circulation in the oceanic basement on ocean-floor element fluxes. For each geodynamic context, we will develop a module of subseafloor fluid-flow circulation using Darcy-type porous flow. An important innovation will be to take into account the thermodynamics and kinetics of fluid-rock reactions along the fluid-flow path, which strongly control ocean-floor element fluxes. The catabolic energy resulting from these interactions and available for fueling microbial life will be calculated, and first-order estimations of biomass amount and its implications for the carbon cycle will be made. In areas where fluid flow is influenced by tectonic activity (e.g., at rifted margins or ultra-slow spreading centers), we will couple these modules to a model of seafloor tectonic deformation.