HYDROLOGICAL DISTURBANCES OF THE CONDUCTIVE HEAT-FLOW IN STABLE CONTINENTAL-CRUST

Geophysical data generally support the presence of free aqueous fluids in the crust to at least the depth of the 700-750-degrees-C isotherm, where granulite facies conditions are reached, which are presumed to have no free water. The fluid phase distribution and transport of fluid in rocks strongly depend on the rheological conditions. In the lithologically heterogeneous crust changes in rheological regime can produce quite complex sandwich-like fluid transport layering, including domains of upward migration, very impermeable layers, or thin reservoirs with nearly horizontal fluid transport. In the present study two, two-dimensional thermal models of the stable continental crust with different spatial configurations of fluid systems have been calculated. The results show that such systems redistribute heat in the crust and give rise to zones of concentrated heat energy storage and transfer. The pattern of the disturbances to the conductive heat flow depends on the arrangement of the fluid systems (which is a function of the crustal structure, temperature and regional stress field) and shows significant lateral and vertical variations. Even at very low velocities of the fluid percolation (a few millimetres per year) the disturbances to the conductive heat flow may reach 30-60%.