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

作者：Golubev V N^*; Chernyshev I V; Chugaev A V; Eremina A V; Baranova A N; Krupskaya V V

来源：Geology of Ore Deposits, 2013, 55(6): 399-410.

DOI：10.1134/S1075701513060044

The isotopic (U-Pb, U-238-U-235, U-234-U-238) and chemical study of whole-rock samples and finegrained fractions of rocks in a vertical section of the terrigenous sequence at the Dybryn uranium deposit in the Khiagda ore field shows that a wide U-Pb isotopic age range (26.9-6.5 Ma) is caused by oxidation and disturbance of the U-Pb isotopic system in combination with protracted uranium ore deposition. The oxidation of rocks resulted in the loss of uranium relative to lead and eventually to an overestimated Pb-206/U-238 age at sites with a low U content. The U-238/U-235 ratios in the studied samples are within the range of 137.74-137.88. Samples with a high uranium content are characterized by a decreasing U-238/U-235 ratio with a decrease in Pb-207/U-235 and Pb-206/U-238 ages. A nonequilibrium U-234/U-238 ratio in most studied samples furnishes evidence for young (< 1.5 Ma) transformation of the Miocene uranium ore, which is responsible for uranium migration and its redeposition.

• 出版日期2013-11