THERMODYNAMIC MODELLING OF PHYSICOCHEMICAL CONDITIONS OF FORMATION FOR THE RICH GOLD DEPOSITS.

The purpose of this study is thermodynamic simulation modelling of physicochemical conditions of the high-grade gold ore formation in the hydrothermally altered host rocks at different levels of erosion. In modelling, equilibrium mineral assemblages in the ores were obtained by minimizing the Gibbs free energy of chemical processes. The thermodynamic modelling of gold deposition was based on mineralogical-petrographic volumetric mapping and quantitative phase analysis of the ore and host rock samples. The high-grade gold ore genesis is associated with volcanic apparatus and occurs at 10- 12 km depth, at a temperature of 600-500°C and pressure of 500-300 MPa in hydromica-quartz and dolomite-quartz-illite metasomatites. The high temperature of gold formation can be confirmed by the presence of sanidine, a high-temperature monoclinic polymorph of potassium feldspar that remains stable up to 900°C; while the depth of formation can be confirmed by the gold content of 78 g/t at more than 9 km depth in the Kola Superdeep Borehole. [ABSTRACT FROM AUTHOR]