The Host Rock Depositional Facies and Mineralisation of Sandstone-Type Uranium Deposits in North China

摘要

North China has numerous sandstone-type uranium deposits (SUD) in several continental basins along the Tianshan-Xin’an orogenic belt in the study area. From west to east, there are Yili, Turpan-Hami, Bayingebi, Ordos, Erlian and Songliao basins. All uranium deposits are hosted by sandstones deposited in fan-delta, braided-delta and braided river environments. The Helan-Longmen mountain belt, the eastern boundary of Tibetan Plateau, is not only an important boundary of geophysical features like gravity anomaly and crustal thickness, but the geological features like SUD host rock and uranium mineralisation, etc. To the west, the host sandstones are deposited in the fan-braided delta plain and front during J1 - K1 in the Yili, Turpan-Hami and Bayingebi basins. Uranium mineralisation occurs at the southern margin of the Meso-Cenozoic intermontane Yili and Turpan-Hami Basin and the northern margin of Yingejing Subbasin of Bayingebi Basin. Lithologically, all host rocks, deposited from braided channel and front distributary channel, are conglemeratic sandstone and coarse-grained sandstone, containing abundant carbonised plant fragments (CPF). To the east, the host sandstones are deposited in a braided river system during J2-K2 in the Ordos, Erlian and Songliao basins with some CPF. Uranium mineralisation occurs in the coarse-grained sandstones, which are deposited from the braided channel at the centre of the subbasins.