Abstract: Based on the borehole core, logging curve and sample tess and analytical data, the sedimentary facies, sedimentary system and uranium mineralization characteristics of the Lower Cretaceous Shahezi Formation in the southeastern margin of the Songliao Basin are analyzed. From the aspects of uranium source, structure, sedimentation, paleoclimate, and rock geochemistry, the uranium ore-forming conditions are analyzed. In addition, the potential of the Lower Cretaceous uranium mineralization in the southeastern margin of the basin was evaluated. The results show that the sedimentary environment of the upper part of Shahezi, i.e., the ore-bearing target layer, is mainly the micro-facies between the subaqueous distributary channel and the distributary channel in the fan delta front. The uranium mineralization was mainly developed in the fan delta subaqueous distributary channels or near the interface between subaqueous distributary channels and subaqueous interdistributary channel microfacies. The uranium mineralization rock types are sandstone and mudstone, with an average thickness of 0.30 m, an average grade of 0.0259% , an average content of 0.0775 kg/m² of uranium, an average 0.99 radium balance coefficient, and a plate shape of the uranium mineralization layer. The study area is rich in uranium resources, moderate in structural conditions, favorable lithology suitable in paleoclimate, strong in reducing capacity and adsorption capacity of ore-bearing rocks, and large in mineralization potential of sandstone-type uranium deposits. This study provides a
basis for enriching and expanding new areas of uranium prospecting in the basin.

Key words: Southeastern Songliao Basin, Lower Cretaceous, uranium mineralization characteristics, metallogenic conditions;
metallogenic potential