Petrology of the Sandstone-Type Uranium Target Layer and Its Uranium Existence Form in the Telaaobao Mineral Area, Ordos Basin.

In recent years, the Telaaobao Mineral Area in the Northwestern Ordos Basin has been newly discovered as a uranium mineralization area with its ore-bearing target layer located within the Lower Cretaceous Huanhe Formation, belonging to a new area and a new layer, and has great uranium deposit formation potential. In order to deeply study the issues of the ore-bearing target in this area, such as the petrology, mineralogy, and uranium mineralization of the ore-bearing sandstone, based on the data from field geological investigation and drill core logging, the petrological characteristics of the ore-bearing sandstone of the target layer are preliminarily interpreted using a polarizing microscope and a scanning electron microscope, and the uranium mineral composition, uranium occurrence state, and uranium deposit mineralization are investigated through the electron probe microanalysis technique in this paper. The results show that the target layer sandstone in the study area has the characteristics of proximal deposit and has undergone significant epigenetic alteration and transformation, producing favorable conditions for uranium- and oxygen-containing water transportation and uranium mineralization. The uranium minerals are dominated by the independent coffinite with the UO content ranging from 40.93 to 60.45%, followed by the titanium-uranium oxides. The uranium minerals occur in various forms, mainly in the edge or fissure of the debris particles, in the edge of the framboidal pyrite, around the biotite or within its cleavage fissures, and on the surface of the chlorite. In addition, a preliminary uranium mineralization model was also established in the Telaaobao Mineral Area. The uranium mineralization in the Telaaobao Mineral Area results from the combined action of the infiltrating and ascending fluids. The uranium- and oxygen-containing fluids from the source area infiltrate downward into the target sandstone layer and meet the ascending reducing fluids from the depth, producing a redox barrier in Huanhe Formation, within which U is reduced to U for precipitation, leading to the formation of uranium mineralization.