Geochemical mobility of Au and Ag during hydrothermal transfer and precipitation: Thermodynamic simulation

The thermodynamic simulation of the geochemical mobility of Au and Ag during their hydrothermal transfer and precipitation was conducted with regard for the formation of continuous nonideal Au-Ag solid solutions (or AuXAg1-X) alloys) and with the analysis of the effects of principal physicochemical parameters (temperature, pH, redox potential, and the concentrations of sulfide sulfur and chloride ions) on the solubility of Au-Ag alloys of various composition. Predominant Au and Ag complexes and the types of solutions were identified, which are characterized by different extractive ability with respect to these metals. A tendency in the variations in the Au/Ag ratio in the solid phase during the evolution of the hydrothermal process was revealed with regard for various conditions under which Ag sulfides can occur. The possible effect of the AuXAg1-X/solution ratio on the composition of the Au-Ag mineralization was demonstrated, and tendencies in the variations in the composition (fineness) of the alloys during their redeposition were identified.