Flow patterns of dolomitizing solutions in a buried carbonate ramp - The Benicassim case study (Maestrat Basin, NE Spain)

Geometric, petrographic, and geochemical observations suggest that sub-stratiform dolomitization in a Lower Cretaceous Benicassim ramp (Maestrat Basin, E Spain) was due to the circulation of high temperature brines through faults and high permeability layers. In this study, fluid and heat flow numerical simulations are applied to investigate the controls on hydrothermal flow in this area, depending on the tectonic activity at the time of dolomitization. The results indicate that flow caused by rapid release of overpressured fluids below seals in recurrent pulses through large-scale faults may drive enough fluid for dolomitization, but not enough heat. Thermal conduction dominates advection over large-time scale. However, long-term fluid circulation, due to differences in pressure and temperature within the basin, can pump dolomitizing fluids at high temperature during long periods of time if the system is open. Moreover, a permeability contrast of two orders of magnitude is required to have lateral flow preferentially in some layers and to form relatively sharp, sub-stratiform dolomitization fronts.