UC Berkeley

The intrusion ofmagmas can induce hydrothermal convection which in turn enhances the transport of heat and solutes. We use a heat convection model to interpret the temperature evolution documented by organic matter maturation, as recorded by the vitrinite reflectance Rr, in a contact aureole of a 15mthick basaltic sill in the Deep Sea Drilling Project (DSDP) 41-368 hole near Cape Verde Rise, eastern Atlantic. Here there is a pronounced asymmetry of variations of Rr with distance above and below the sill that cannot be explained by heat conduction alone. Neglecting the effects of possible two-phase flow and thermal pressurization from the production of fluids, convection begins to enhance the observed asymmetry for permeabilities greater than about 1md, and the observations can be matched with permeabilities of at least several tens of millidarcies.