Heat and Fluid Flux through Sediment on the Western Flank of the Mid-Atlantic Ridge - a Hydrogeological Study of North Pond

A comprehensive survey of heat flow, sediment thickness and bathymetry in a large intermontane sediment pond on the western flank of the Mid-Atlantic Ridge (North Pond) shows that only 20 to 25% of the heat escaping from the lithosphere flows through the sediments in the pond even though they completely cover a 70 km2 area of the seafloor. Three in situ pore-pressure gradient measurements gave values that were negative relative to hydrostatic, indicating that there is drawdown of water through the sediment at rates of 1 to 5 mm/yr. North Pond is a recharge zone for hydrothermal circulation that is probably driven by lateral pressure gradients produced by topographic relief.