U-Pb systems and U isotopic composition of the sandstone-hosted paleovalley Dybryn uranium deposit, Vitim uranium district, Russia

Post-Ore Processes of Uranium Migration in the Sandstone-Hosted Type Deposits: 234U/238U, 238U/235U and U–Pb Systematics of Ores of the Namaru Deposit, Vitim District, Northern Transbaikalia

“…5). Taking into account the relatively young age of uranium mineralization (about 12 Ma, Golubev et al, 2013), this agreement, gives reason to consider that the ore body mainly preserved the outlines acquired at the early stage of its formation. At the same time, the U-Pb isotopic age values of samples selected from different boreholes and at dif-ferent levels of the vertical section span a wide range (see Table 3).…”

“…13-15), the K 234/238 values are greater than 1, and the U-Pb ages (8.0, 10.4, and 12.1 Ma) are smaller less (sample nos. 13 and 15) or close (samples 14) to the age of the main phase of uranium mineralization in the KhOF (Golubev et al, 2013). A possible source of excess 234 U and common U in this part of the section could have been material from the underlying part of the terrigenous sequence, in which, as the results of studying sample no.…”

“…The smallest of the obtained values is significantly younger than the age of the main stage of uranium mineralization of the KhOF (ca. 12 Ma (Golubev et al, 2013)), and the maximum is 9 Ma older than the onset of deposition of rocks of the Dzhilinda Formation (Kochkin et al, 2017b) hosting the uranium mineralization. Variations in the U-Pb age and 234 U/ 238 U ratio characteristic in the ores of the Namaru deposit indicate the uranium migration that took place in the ore body of the deposit after its formation, as well as a possible change in the uranium concentrations.…”

“…In a recent review (Andersen et al, 2017), numerous summarized determinations of this ratio in various natural environments have shown that 238 U/ 235 U data can be used as information about the formation processes of natural objects. The study of 238 U/ 235 U variations in sandstone-type uranium deposits has made it possible to conclude that a change in redox conditions with the successive advancement of the uranium deposition front causes significant fractionation of 238 U and 235 U, both in the uranium ores themselves (Golubev et al, 2013;Murphy et al, 2014) and in migrating waters in ore-hosting rocks (Murphy et al, 2014;Basu et al, 2015;Placzek et al, 2016). These studies contributed additional information on the formation conditions of sandstone-type uranium deposits.…”

“…These studies contributed additional information on the formation conditions of sandstone-type uranium deposits. Golubev et al (2013), in studying the U-Pb isotope systems and isotopic composition of uranium samples from a borehole drilled in the productive sequence of the Dybryn uranium deposit in the Khiagda ore field (KhOF) of the VUD, demonstrated the possibility of using these data to assessing the postore redistribution of uranium. This paper presents the results of studying the U-Pb isotope systems and isotopic composition of uranium ( 234 U/ 238 U and 238 U/ 235 U) of a set of samples collected in different zones of a cross section through ore body no.…”