The occurrence and chemical implications of geothermal convection of seawater in continental shelves

Geothermal convection is an important driving force for fluid flow and diagenesis in carbonate platforms, and the similar shape of continental shelves in general suggests that geothermal convection could occur in continental shelves around the world. Numerical models based on seven transects of the shelf off the east coast of North America were developed to bracket possible fluxes. Simulations assuming relatively permeable sediments (medium-grained carbonates) failed to produce significant thermal variations, suggesting that chemical tracers will be required to detect this flow in the field. Fluxes calculated assuming lower permeabilities (fine grained carbonates) between Cape Fear and the Savannah River were approximately 3 orders of magnitude smaller than river discharge for the area, a difference similar to that between global river discharge and hydrothermal convection at mid-ocean ridges. Sediment diagenesis during geothermal convection in continental shelves thus has the potential to affect ocean chemical budgets, including potassium, calcium, and magnesium.