A new and fast method to determine mixing and conductive cooling of thermal waters in carbonate-evaporite environments

A method is proposed, for low-temperature geothermal systems, for calculating the aquifer temperature and relative proportions of mixed thermal and shallow groundwaters from carbonate-evaporite environments. The fluid is assumed to be in chemical equilibrium with anhydrite and chalcedony in the aquifer, and mixed with diluted waters during its ascent. An attempt has been made to establish a relationship between reservoir temperature, the aqueous sulfate and silica contents of the mixed fluid, the proportion of the thermal end-member and the temperature of the adiabatic mixture. The method calculates mineral solubilities in the field context, calibrated on representative thermal springs. The method also considers the effects of conductive cooling.