Suppression and Stimulation of Hydrothermal Convection by Serpentinization

The effect of serpentinization on hydrothermal convection is explored using a dynamic 2D numerical model. Serpentinization is a highly exothermic mineral hydration process that consumes large quantities of water. The reaction is ubiquitous in the oceanic crust and is generally associated with hydrothermal activity. In this study, the thermal and hydration effects are incorporated into conservation equations describing fluid flow and heat transfer in hydrothermal systems. Simulations of convection with and without serpentinization demonstrate that mineral alteration can have a profound effect on hydrothermal flow patterns and vent temperatures. Differences in peak vent temperatures between the standard convective case and that with serpentinization were found to be as high as 170°C. Two parameters determine the behaviour of the system: (1) the temperature of the bottom boundary (Tb), and (2) the dimensionless Rayleigh number (Ra). For values of Tb ≤ 170°C, serpentinization has only a minor effect on vent temperatures and flow patterns. Although the effect of serpentinization peaks at around Ra = 50-100, vent temperatures remain strongly influenced at Ra = 350, closer to the values expected in hydrothermal systems. Simulations at higher values of Ra are required in order to fully assess the effect of serpentinization on seafloor venting.