Simulation of magmatic and metamorphic fluid production coupled with deformation, fluid flow and heat transport

A methodology for simulating magmatic and metamorphic fluid production coupled with mechanical deformation, fluid flow and heat transport is presented. The methodology is implemented in FLAC3D, a lagrangian finite difference code designed for simulation of coupled deformation, fluid flow and heat transport in porous media. The rate of metamorphic fluid production is governed by the rate of temperature change and an approximation of the variation in bound water content of appropriate lithologies with temperature. Magmatic fluid production is governed by the rate of cooling and the variation in free water content of a mafic granitic magma with temperature. Changes in porosity and fluid pressure due to fluid production, deformation, and thermal expansion are taken into account. Dilation associated with thermal expansion and fluid production leads to rotation of the principal stresses around fluid source regions. Fluid properties are calculated using an equation of state for pure water. The methodology has been applied to examples representing aspects of Archaean gold mineralisation in Western Australia, providing insight into the role of magmatic and metamorphic fluids in mineralisation, and effects arising from interactions between deformation, heat transport and fluid production.