Estimation of heat and chemical fluxes from a seafloor hydrothermal vent field using radon measurements

Abstract

The circulation of seawater through newly formed ocean crust at mid-ocean ridge spreading centres is important in the oceanic heat and chemical budgets. The heat transfer in submarine hydrothermal systems accounts for ˜25% of the total global heat loss¹. The transfer of mass resulting from basaltic alteration affects the geochemistry of seawater² and is responsible for the formation of ore deposits on and beneath the seafloor³. Various geophysical techniques have been employed in efforts to determine the heat output from hydrothermal vent fields^4–9; however, the magnitudes of the heat and chemical fluxes through these systems remain uncertain. Here we introduce a geochemical approach for estimating the flux from a vent field based on radon (²²²Rn) measurements in the overlying effluent plume. This method was applied successfully in September 1986 during a 23-day expedition to an active vent field on the 170-km Endeavour segment of the Juan de Fuca Ridge (Fig. la). We estimate the heat flux from this site to be l–5×l0⁹ W.