Heavy metals in oils and formation of bitumen-hydrothermal associations in the rocks of the Dnieper-Donetsk paleorift

Abstract

Formulation of the problem of the article. The problem of common finding of hydrocarbons and heavy metals in the geological space is very interesting from the point of view of theoretical and practical meaning. It was discussed in many works of domestic and foreign scientists from different positions, stipulated by the absence of ambiguity in the explanation of this fact. It is important that heavy metals are present not only in oils, but also in bitumen of bituminous-hydrothermal mineral associations of ore fields in the region. The main aim of the article is to research the genetic, spatial and temporal correlation of heavy metals and hydrocarbons. Research Methods. The processes adducting to the accumulation of heavy metals in oils and the formation of bituminous-hydrothermal associations in rocks have been researched. In particular, the definition of heavy metals in oils from various deposits of the Dnieper-Donetsk basin was performed using the X-ray fluorescence method and the definition of the isotopic composition of carbon of solid bitumen - by mass spectrometric methods. Results. The processes adducting to the accumulation of heavy metals in oils and the formation of bituminous-hydrothermal associations in rocks have been researched. These processes are associated with ascending heat and mass transfer, which adduct to the unloading of fluid streams, which contained a variety of chemical elements, including compounds of carbon dioxide, methane, mercury vapor, and complexes of heavy metal. Spatially, that process coincides with the anticlannel structures which accompany the zones of deep faults. It has been found that the concentrations of heavy metals in oils are associated with the peculiarities of deposits formation within different geological structures. Physical-chemical conditions for the formation of hydrocarbon-hydrothermal fluid systems, which involve both biogenic and abiogenic (synthesized) hydrocarbons, were determined. The established geochemical regularity of increasing concentrations of heavy metals with the depth of oil occurrence is associated with high contents of sulfur compounds in the form of hydrothermal sulfide minerals, which are actively hydrolyzed at high temperatures and lead to leaching of metals and their entry into fluid`s systems where stable sulfur complexes are formed. Scientific novelty and practical importance. The formation of hydrocarbon-heavy metal systems within the Dnieper-Donetsk basin occurs with the participation of synthesized and organic hydrocarbons, as well as mantle exhalates and hydrothermal vent. The result is cooling of these systems. Hydrocarbon fractions (oil) are enriched with heavy metals, and hydrothermal vents are enriched with bitumen-forming naphthides. The practical importance of this research is increase in the efficiency of forecasting and prospecting of hydrocarbon deposits at the expense of theoretical modeling of the bituminous-hydrothermal mineral associations formation in ore fields.