The sandstone-type Uranium mineralization mechanism in the Western Kuche Depression, Northwest China, A case study of Ridalike Uranium deposite

The Kuche Depression, is an E-W trending foreland basin located at the South margin of the Tianshan Orogenic Belt. The Ridalike uranium deposit is located in the western Qiulitage fold-and-thrust belt of the Kuche Depression, and the uranium ore bodies are mainly preserved in the sandstones of the Pliocene Kuche Formation (N₂k). The Kuqa Formation is a set of yellow oxidized sandstone layers formed in a semi-arid climate, but the grey layer is developed in Qiulitage fold-and-thrust belt, and uranium mineralization mainly deposit on the grey fluvial sandstone. According to the characteristics of the growth strata and the spatial cutting relationship between the strata in the Kuche Formation in the Qiulitage area, we conclude that the deformation age of the western Qiulitage anticline is between 5 ~ 2.5Ma and during the deposition of the upper part of Kuche Formation (N₂k) and Early Pleistocene. Two stages of structure deformation can be identified in Ridalike area: type 1 is mainly composed of the fold-related faults, which developed between Paleogene and the early Pleistocene. The general strike of the axial plane of the type 1 fold and the related faults is near the E-W direction, and the local direction is slightly changed to NEE or SWW direction, which reflects the maximum principal compressive stress in approximately N-S direction. The type 2 structural deformation was mainly developing in the Early Pleistocene Xiyu conglomerate, and the outcrop appeared as a geomorphic escarpment. The surface outcrops of type 2 structure deformation can be observed in the Xiyu conglomerate on the North area of the Ridalik deposit, showing a series of fault escarpment, and normal faults with their associated reverse faults. According to the field structural deformation characteristics, it is inferred that the active age of the fault occurred after the early Pleistocene, which is a late tectonic event in the region. In the central and western Qiulitage fold-and-thrust belt, field investigation of the Kuche Formation (N₂k) revealed "reversed" interlayer oxidation zones and "inverted roll" orebodies.  The interlayer oxidation zone is widely developed from the Southern Tianshan Mountains along the Muzhaerte River basin to the southeast direction. The oxidized containing uranium fluid infiltrates into the target sandstone band of the Kuche Formation through the surface outcrops or the Windows under the loose quaternary sandstone, and the flow distance is approximately 50~60km, and the scale of the interlayer oxidation zone is large-scale. During this process, an oxidation zone containing uranium-containing fluid flowed through the Kuche depression and reached Qiulitage area. After surface denudation, the oxidation zone partially uplifted out of the surface, forming the present form of an "inverted" interlayer oxidation zone. The uranium ore body controlled by the interlayer oxidation zone has a normal rolled ore body, an inverted rolled ore body, and a double rolled ore body. In the NW direction of Ridalike uranium deposit, the Meso-Cenozoic fault system is scanty, which did not obstruct the flow of groundwater. Therefore, this study supported the genetic model of Ridalike uranium deposit as a "Trans-basin metallogenic model".