Thesis for the Doctor’s degree in Geology on speciality 04.00.11 – geology of metallic and non-metallic mineral resources.M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation, National Academy of Sciences of Ukraine, State Institution «Institute of Environmental Geochemistry, National Academy of Sciences of Ukraine», Kyiv, 2018.
The research results on geological structure of ore fields and deposits; chemical and mineral composition of wallrock alkaline sodium metasomatites and ore albitites of the Precambrian ore assemblageοfuranium (ore-bearing) sodium metasomatites of the of the Central Ukrainian (uranium) ore district of the Kirovograd metallogenic region of theMetallogenic Province of theUkrainian Shield are presented. It was proved that in the time of ore-bearing albitite formation, there had been additional deposition of not only uranium but also thorium.Correlation of uranium and thorium in ore albitites is classified as of high level as these elements are included into thorium-uranium minerals of pneumatolytic-hydrothermal origin. The association of uranium and thorium in thorium-uranium ore albitites was recognized as paragenetic. Change in degree of oxidation of uranium forms able to migrate in ore-forming fluids was reconstructed: in high-temperature (actinolite-diopsidefacie) U4+ (along withTh4+), U6+ (uranyl ion compounds) –in mediumtemperature (riebeckite-aegirine and chlorite-epidote facies). The “vertical” orezoningmanifestedinthorium-uraniumoreondeephorizonsandinuraniumoresonupperhorizonswasrecognizedthrough the example of the Partyzan thorium-uraniumdeposit. This fact substantiated the regional "vertical" ore zoning of the uranium sodium metasomatitesformation in general.Thorium-uranium ores are located in the lower (deep) part of the pneumatolytic- hydrothermal column while uranium ores – in the upper part of it, thus reflecting changes over time and section of physical and chemical parameters.Change (increase) of oxygen volatility in ore-forming system was considered to be the main factor in separation of geochemical history of uranium and thorium in the process of ore albitites forming. It was shown for the first time that thorium-uranium ore albitites of the Novooleksiivske ore manifestation were distinguished by high concentration of niobium while corresponding anomalies calcium, titanium, yttrium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, but tantalum were not fixed. This is considered as an additional criterion of deep-seated origin of magmatogenic ore-forming fluids. Based on generalized data, a complete rethink of geological and genetic model for ore assemblage of deep magmatic origin fluids was developed. Forming of pneumatolytic and hydrothermal uranium, thorium-uranium, scandium-uranium, and uranium-thorium-rear-earth-phosphorus ores in sodium metasomatites of deep-fault zones is considered as a result of long-term evolution of a subregionalmagmatic-pneumatolytic-hydrothermal column.The initial factors of the column formation were processes of matter differentiation in deep magmatic reservoir, which led to the formation of A-type granites. The metallogenic tectonic and magmatic factor of the Precambrian ore assemblage of uranium (ore-bearing) sodium metasomatites in the zones of deep faults had been reasoned - the presence of A-type granite massifs in geological structure of regions of tectonic and magmatic protoactivation.The formation of ore assemblage of uranium (ore-bearing) sodium metasomatites is considered as a consequence of matter differentiation in large deep-bottomed magmatic cells of regions of tectonic and magmatic protoactivation.Pneumatolytic and hydrothermal exhalates of those formed the assemblage of uranium (ore-bearing) sodium metasomatites, magmatic differentiates, in particular, anorogenic granites in the Ingul megablock ofthe Ukrainian shield - A-type granites of the anorthosite-rapakivi-granite Korsun-Novomyrgorodskyi Pluton. The search petrophysical criterion (favorable values of the coefficient of correlation between density and magnetic susceptibility of rocks - <0.3) was used as an additional one to the estimation of Zlinkivska area perspective on uranium mineralization.
Key words: uranium, thorium, ore albitite, ore zoning, deposit, genesis, Central Ukrainian Uranium Ore District, Ukrainian Shield.
