THE ROLE OF ENDOGENOUS FACTORS IN HYDROGENIC ORE FORMATION

Abstract

Processes in hydrogenic ore formation by groundwater and does not explicitly associated with the magmatism, possible participation of deep fluids and thermal solutions are of endogenous origin, which is the cause of non-equilibrium physico-chemical condition of the host rocks, mineralization of underground waters and their transformation into ore-forming solutions. The ore-bearing fluid has a predominantly aqueous composition. The behavior of hydrocarbons in hydrothermal solutions of vadose origin obeys the laws of joint solubility of H2O, CO2, CH4 and liquid bitumoids at various pressures and temperatures. Epiplatform activation of geotectonic structures of different ages and types that have a sedimentary cover leads to a combination of ore-forming processes in time and often in space caused by descending infiltration waters and ascending hydrothermal solutions. Such ore-forming processes on the territory of Ukraine can be traced in the Don-Dnipro structural-metallogenic zone and the Volyn-Podolsk metallogenic region. In the Don-Dnipro structural-metallogenic zone during the Cimmerian metallogenic epoch (late Triassic – early Cretaceous), fault zones and tectonically complicated salt-dome anticlines served as discharge centers for both ascending hydrothermal solutions and pressure infiltration waters. As a result, a group of polygenic deposits of uranium-bitumen-mercury composition was formed, including the Adamovskoye uranium-bitumen deposit and the Slavyanskoye mercury ore occurrence, located within the same structure. On the territory of the Volyn-Podilsky metallogenic region, Cimmerian-era ore occurrences are formed by ascending low-temperature carbon dioxide-hydrocarbon chloride solutions of deep (metamorphic or metagenetic) origin, which were diluted by underground meteor waters before the completion of ore formation. This led to the redistribution of uranium and associated ore elements during the lithogenesis of sedimentary rocks and regeneration during the late Paleozoic-early Mesozoic tectonic activation involving both exogenous and endogenous processes. The result was the formation of hydrothermal-regenerative uranium ore occurrences, which are characterized by their proximity to zones of discontinuous faults, veined-interspersed mineralization, its presence not only in sedimentary rocks, but also in zones of foundation fracturing, association of uranium minerals (coffinite, nasturane) with the release of solid black bitumen and ore occurrences of the barite-fluorite-polymetallic formation.