The mantle source of fluids for the U-bearing Na-metasomatites of the central-ukrainian uranium province inferred from Pb, Sr and Nd isotope composition

Abstract

The results of the determination of Sr, Nd and Pb isotope composition in U-bearing Na-metasomatites of the Central-Ukrainian Uranium Province are reported. In total, 23 samples representing 5 deposits, were studied. The obtained results reveal the similarity of the Sr and Nd isotope composition between the metasomatic rocks and their host rocks. However, metasomatic rocks in general have a lower 87Sr/86Sr ratio that indicates a presence of a more “primitive” juvenile component in their composition. The constructed Pb-Pb isochron has yielded an age of 1810 ± 17 Ma, in good agreement with the previously obtained results. This age confirms the simultaneity of the formation of Na-metasomatites and the emplacement of the numerous mafic dykes widely distributed in the area. Apparently, metasomatic fluids were generated in the upper mantle and their ore potential was inherited from the mantle source. The formation of the huge volumes of the mantle-derived fluids is linked to the establishment of the Prutivka-Novogol large igneous province and emplacement of the large anorthosite-mangerite-charnockite-granite plutonic complexes (Korosten and Korsun-Novomyrhorod complexes) that also belong to the province.