Organic matter maturation in the contact aureole of an igneous sill as a tracer of hydrothermal convection

E-ISSN： 2169-9356|120|6|4102-4112

ISSN： 2169-9313

Source： JOURNAL OF GEOPHYSICAL RESEARCH: SOLID EARTH, Vol.120, Iss.6, 2015-06, pp. : 4102-4112

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Abstract

AbstractThe intrusion of magmas 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 15 m thick 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 1 md, and the observations can be matched with permeabilities of at least several tens of millidarcies.