Hydrothermal uranium mineralization in the Tuyukan ore field (Northern Transbaikal region): time of formation of pitchblende mineralization and age of the source of the matter

Based on the study of local volumes of minerals using classical methods of isotope dilution and thermal ionization mass spectrometry (U–Pb ID TIMS), an isotopic study of pitchblende and galena was carried out at the Natali uranium ore occurrence (Northern Transbaikalia). For the first time, it was shown that pitchblende mineralization at the ore occurrence is Late Silurian (422±4 million years) age. Its formation is associated with early-mid Paleozoic collisional tectogenesis in the area of the Tonod uplift, accompanied by increased fluid activity. The results of analyzing the Pb isotopic composition in galena associated with pitchblende showed that it is enriched in the radiogenic isotopes 206Pb and 207Pb, the source of which was ancient (Precambrian) concentrations of uranium.