Physicochemical modeling of the coupled behavior of gold and silver in hydrothermal processes: Gold fineness, Au/Ag ratios and their possible implications

Data on the physicochemical conditions of Au-Ag mineralization and mineralogical-geochemical characteristics of pyritic ores of hydrothermal gold deposits of different types are summarized. Wide ranges of gold fineness and low (Au/Ag)ore ratios of Au-Ag epithermal, Au-Cu-porphyry and Au-Cu-skarn deposits are related to the participation of acid or near-neutral high- or medium chloride ore-forming solutions (types I-III). High fineness gold and high values of (Au/Ag)ore ratio of Au-Te, Au-As, Au-Sb, Au orogenic and Carlin-type deposits are explained by participation of alkaline (type IV) or low chloride (type V) sulphide solutions. Gold fineness and (Au/Ag)ore ratios in the sulphide ores may be characteristics that determine the type of ore solution and its evolution in the process of hydrothermal deposit formation.