The role of seamounts in the transport of heat and fluids: Relations among seamount size, circulation patterns, and crustal heat flow

To evaluate the role of seamounts in the transport of heat and fluids, we performed numerical simulations of hydrothermal circulation within and around seamounts that protrude through low-permeability sedimentary layers. A cylindrical flat-top seamount model enables us to take into account crustal heat flow, and the radius and height (i.e., the radius/height ratio) of the seamount. We found that the flow patterns depend primarily on the aspect ratio of the seamount, and secondarily on crustal heat flow. A large seamount, with a radius of several tens of kilometers, cools itself by convection cells that form within the seamount, and this behavior is independent of crustal heat flow. In contrast, a small seamount, with a radius of several hundreds of meters, works as a fluid passageway, either as a fluid exit by discharging hydrothermal fluids at low crustal heat flows, or as a fluid entrance by recharging seawater at high crustal heat flows. The role of a medium-sized seamount varies according to crustal heat flow: it is cooled by a convection cell at low heat flows and works as a fluid entrance at high heat flows. We also found that an increase in crustal heat flow has the same effect on the fluid flow pattern as does an increase in seamount permeability or sediment thickness. ► We classify the role of seamounts in terms of the transport of heat and fluids. ► A seamount with a radius of several tens of kilometers cools the surrounding crust. ► A seamount with a radius of several hundreds of meters works as a fluid passageway.