Pyrite Re–Os Geochronology of the Erlian Uranium District: an Alternative Dating Method for Sandstone-type Uranium Deposits.

Owing to the lack of precise and reliable mineralization ages, the origins of some sandstone-type U deposits (STUDs) are still debated. The unusual texture of U ore (commonly uraninite) and the difference between the chemical characteristics of U and its radiogenic daughter isotopes make U–Pb dating unsuitable for STUDs. However, STUDs are commonly rich in Re; therefore, Re–Os dating may be an alternative. Re–Os dating of two groups of pyrite samples from U ores in the Erlian sandstone-type U district yields two similar ages: 52.5 ± 4.7 and 53.3 ± 3.5 Ma. These ages are consistent with previous U–Pb ages (56.5 ± 7.5 and 63 ± 22 Ma) and demonstrate the reliability of sulfide Re–Os dating of STUDs. The pyrite Re–Os ages suggest that the Erlian STUDs formed at ~53 Ma, corresponding to the regional uplift of the Erlian basin during the Late Cretaceous–Early Eocene and the humid environment in the region during the Early Eocene Climatic Optimum. [ABSTRACT FROM AUTHOR]