The relative effects of deformation and thermal advection on fluid pathways in basin-related mineralization

Abstract

The migration of basinal brines into basement material has been proposed as a means of scouring or leaching metals for subsequent ore deposition. Here we address this issue by numerically examining competing processes, namely deformation, fluid flow and thermal gradients, to describe potential fluid pathways leading to enrichment of metals and ore deposition. Stable convective fluid patterns may be established across the cover/basement interfaces if permeability contrasts are minimized, however, at the onset of extensional deformation these convective patterns quickly collapse. On cessation of the deformation, convection cells again develop, which are oscillatory with time. Input to the thermal budget from a radiogenic heat source suggests that basinal fluids can be drawn down around the margins of granite intrusions and fluid mixing processes may take place due to small and localised convective patterns. Fluid migration from basin into basement and back is highly likely given the right conditions, however, the rate and extent of fluid flow are determined by thermal and deformation processes.