THERMOBAROGEOCHEMICAL EXPLORATION AND ASSESSMENT CRITERIA OF GOLD MINERALIZATION OF THE BALKA SHYROKA DEPOSIT (MIDDLE DNIEPER REGION)

Abstract

A scheme of the staging and thermobaric regime of the formation of the Balka Shyroka deposit gold mineralization (Middle Dnieper megablock of the Ukrainian Shield) was constructed, and the sequence and thermobaric intervals of ore formation were determined. Mineral paragenesises are combined into four mineral associations that form a series of mineral complexes: pre-productive magnetite-quartz, productive polysulphide, which includes two productive gold-bearing associations (arsenopyrite-pyrite-quartz with gold and gold-sulphosalt) and post-productive carbonate (quartz-calcite mineral association). Gold-producing associations were formed in a rather narrow range of temperature and pressure changes of the ore-forming environment specific to its composition and aggregate-density state. This affected the phase typomorphism of the respective families of fluid inclusions. Carbon dioxide-water inclusions with different phase ratios are common: Г—РСО2—РН2О, РСО2—Г—РН2О, РСО2—РН2О, Г—РСО2. The most optimal temperature for homogenization of gas-liquid inclusions (according to the first type) is 210-290 °С. In minerals, there are families of two-phase and one-phase CO2 fluid inclusions with wide variations in its density (from 0.65 to 0.87 g/cm3) and homogenization into the liquid phase. These typomorphic features are thermobarogeochemical search criteria and evaluation signs of gold mineralization. Equally important is the definition of the paleotemperature gradient and the spatial extrapolation of its change with depth, which makes it possible to calculate the vertical extent of mineralization, the level of its erosional section, and the depth of thinning out.