Petrographic composition and ore potential of low-temperature metasomatites of the Middle-Dniprean mega-block of the Ukrainian Shield

Abstract

Purpose. To substantiate the formation conditions, distribution patterns and metallogenic specialization of low-temperature metasomatites of the Middle Dnipro megablock of the Ukrainian Shield based on the research results obtained. Methodology. The authors used a set of field and laboratory methods. Petrographic, mineragraphic, petrochemical studies were carried out. Interpretation of the results of chemical, laser microspectral, X-ray diffraction, scintillation spectral, thermal analyses is carried out. Findings. A generalized petrological description of low-temperature metasomatites of the Middle Dnipro megablock of the Ukrainian Shield is carried out, taking into account the composition of the original rocks, characteristics of newly formed mineral parageneses, metallogenic specialization and patterns of distribution of metasomatic formations. The study on occurrences of vertical and horizontal metasomatic zoning within the greenstone structures of the Middle-Dniprean region was carried out. The composition of telescoped metasomatites spatially related to the intersection of deep faults is characterized. The metallogenic specialization of low-temperature metasomatic formations is determined and the process of formation of ore concentrations of complex composition in the nodes of intersection of deep faults has been characterized. Based on the results of studies on the composition and ore content of metasomatites, an insignificant level of erosional truncation of vertical ore-metasomatic columns within greenstone structures is substantiated. Originality. The aspects of petrology and ore content of the group of low-temperature metasomatic formations of the Middle Dnipro megablock of the Ukrainian Shield have been revealed. The spatial relationship of the metasomatic areas with the systems of deep faults has been substantiated, which justifies using the identified metasomatic formations as geological indicators of deep fault zones. The features of ore content of low-temperature metasomatic formations of the Middle Dnipro megablock are characterized. It is shown that formations of telescoped metasomatites with a complex composition of mineralization are spatially associated with the intersection of deep faults. Practical value. The metallogenic specialization of low-temperature metasomatic formations has been determined, which can be used as a search criterion for various types of deposits of metallic and non-metallic minerals within the Ukrainian shield.