Geological features and dating of uraninite in serpentinized dolomite marbles of the Dashiqiao Formation in eastern Liaoning Province

In this study, the authors analyzed the geological features and ore-forming ages of the newly found uranium mineralization in serpentinized dolomite marbles to infer their regional metallogenic significance. The uranium mineralization in serpentinized dolomite marbles occurs as uraninite breccias imprinted by later sulfide mineralization such as molybdenite, pyrite. The U-Pb isotopic dating indicates that the uraninite was formed in 1763~1794Ma. The in situ EPMA U-Th-Pb chemical dating of uraninite implies a thermal reworking event on uraninite at 1512±20Ma, which is synchronous to a regional magmatic event. The eastern Liaoning Province underwent significant geological evolution in Paleo-Proterozoic, from early rifting to collisional orogenesis and post orogenic extension. The newly found uranium mineralization in serpentinized dolomite marbles and the uranium mineralization in the Lianshan-guan U deposit and in the Fe-B-U deposits in the Wengquangou area were all formed in a post orogenic/unorogenic extensional environment possibly related to the mantle plume activity in regional extensional tectonic setting.