Physicochemical models of formation of gold–silver mineralization at the Rogovik deposit (Northeastern Russia)

Abstract

The T,X-parameters of the main ore-forming stages of the Rogovik epithermal gold-silver deposit (northeastern Russia) were determined using microthermometric techniques on fluid inclusion assemblages. On the basis of these data we carried out thermodynamic calculations that model the formation conditions of three types of ore mineral assemblages: gold-silver – at the early volcanic stage, silver-polymetallic and silver-gold-polymetallic – at the late volcanoplutonic stage. The silver-gold-polymetallic mineralization is located at the sites where silver-polymetallic and gold-silver zones overlap. The calculations were made using the “Selektor-C” software within a complex geochemical multicomponent system. Several scenarios of formation of gold-silver mineralization at an early volcanic stage were considered: 1) boiling of a hydrothermal solution; 2) interaction of residual aqueous solution with host rocks; 3) mixing of an ore-bearing gas phase with meteoric waters. For the late volcanoplutonic stage, we modeled formation of “silver mineralization” using an ore-forming solution genetically related to a deep-seated granite massif and its interaction with host rocks and gold-silver zones of early volcanic stage. These physicochemical models substantially improve our understanding of formation of the three types of mineral assemblages at the Rogovik deposit and can be applied to other epithermal deposits with similar mineralization styles.