Geochemical characteristics and evolution paths of the superficial brines in the Llamara Salar (Chile).

The geochemical evolution of the superficial brines in the 'Salar de Llamar a' saline system is studied in this paper. Systematic sampling of saline so lutions and sediments has pointed out the continuous equilibrium state of b rines with respect to calcite and gypsum along the evaporative path. The hi gh evaporation rate causes a progressive increasing in the concentration of brines, up to ionic strengths near 6 molal. From the mineralogical analysi s of solid saline samples and the physicochemical treatment of solutions, a process of glauberite precipitation has been identified during the final s tages. The formation of glauberite is associated with the partial simultane ous dissolution of the previously precipitated gypsum. The thermodynamic vi ability of this process has also been confirmed through the theoretical sim ulation of the evaporation process performed with the geochemical code PHRQ PITZ.