The Luhai uranium deposit is a large-scale uranium deposit newly discovered in recent years through comprehensive prospecting methods. It is located in the Basaiqi Paleochannel Uranium metallogenic belt of the Erlian Basin and is characterized by its shallow burial and large scale. This paper provides new data on the genetic processes of sandstone-type uranium mineralization through sedimentological and geochemical environmental indicators (such as Fe³⁺/Fe²⁺, organic carbon, total sulfur, etc.), analysis of C-O isotopes of carbonate cements and H-O isotopes of groundwater, and geochemical and mineralogical studies of uranium minerals, iron–titanium oxides (involving backscatter analysis, micro-area chemical composition determination, and elemental surface scanning), and organic matter. Sedimentological analysis shows that the ore- bearing layer in the upper member of the Saihan Formation developed a braided channel within floodplain subfacies, which control the distribution of uranium ore bodies. Uranium mineralogical observations, geochemical environmental indicators, and organic geochemical data indicate that the main reducing agents related to mineralization are pyrite, terrestrial plants, and deep-sourced oil and gas. The δD values of groundwater in the ore-bearing layer range from −95.34‰ to −90.68‰, and the δ¹⁸O values range from −12.24‰ to −11.87‰. For calcite cements, the δ¹⁸O_V-PDB values range from −24‰ to −11.5‰, and the δ¹⁸_OV-SMOW values range from 6.2‰ to 19‰. It was determined that the ore-forming fluid is mainly surface fresh water that entered the strata during the tectonic uplift stage, with local mixing of deep-sourced brine. Based on these data, the main modes of uranium mineralization in the paleochannel were obtained as follows: (1) Redox mineralization occurs due to the reducing medium within the sand body itself and the reduction caused by deep- sourced oil and gas generated from the Tengge’er and Arshan Formations. (2) Mineralization is achieved through the mixing of fluids from different sources. Furthermore, a genetic model related to uranium mineralization in the paleochannels of the Luhai area has been established: favorable uranium reservoirs were formed during the sedimentary period, and during the post-sedimentary stage, reverse structures promoted redox reactions and fluid-mixing-induced mineralization. The research findings can provide guidance for the exploration of paleochannel sandstone-type uranium deposits in other areas of the Erlian Basin.

《地球科学》(ISSN 1000-2383;CN42-1874/P) (原刊名《地球科学——中国地质大学学报》ISSN 1000-2383;CN42-1233/P)，创刊于1957年，是由教育部主管、中国地质大学主办的综合性地学学术理论期刊，月刊，2015年改名为《地球科学》,她以反映中国地质大学教学与科研最新的、高水平的基础地质、应用地质、资源与环境地质及地学工程技术研究成果为主要任务。

To reveal the uranium enrichment mechanism in the Daqing Placanticline area, northern Songliao Basin, this study collected a total of 41 samples of three geological types, namely uranium ore, uranium-mineralized sandstone and host rock from the Upper Cretaceous Sifangtai Formation. Combined with 109 geochemical datasets from exploration, systematic analyses were performed on major elements, trace elements, rare earth elements (REE), total organic carbon (TOC), total sulfur and other key geochemical parameters. The results indicate that uranium ore and mineralized sandstone are generally characterized by high TOC, high total sulfur, low Th/U and low Fe₂O₃/FeO ratios, while host rocks show the opposite geochemical assemblage, suggesting uranium enrichment took place in a strongly reducing sedimentary environment. The ore-forming system is significantly enriched in trace elements including U, Pb, Mo, Ba, Zn and Y, and depleted in Cu, Co, Ni, Cr, Sr, Nb, Ta, Zr and Hf. Among these elements, Mo and Pb have an extremely close relationship with uranium mineralization and can be used as effective ore-forming indicator elements. Uranium ore, mineralized sandstone and host rock exhibit consistent REE distribution patterns, implying that the strata in the study area share uniform provenance, sedimentary environment and tectonic setting. Some high-grade uranium ores are obviously enriched in heavy rare earth elements (HREE), demonstrating fluid modification during the late mineralization stage. Combined with regional tectonic evolution and hydrocarbon migration features, this study concludes that sandstone-type uranium deposits in the Daqing Placanticline mainly underwent two stages of mineralization: supergene fluid mineralization and superimposed reworking by deep hydrocarbon-bearing reducing fluids.