Abstract:The Longhupao uranium mineralization area, which is located in the north of Longhupao-Da'an terrace and adjacent to Taikang uplift and Western overlap in the west, is one of the important new achievements in northern Songliao Basin based on the secondary development and drilling verification of Daqing Oilfield wells. Based on detailed field work and using experimental means such as polarizing microscope, electron probe energy spectrum, backscattering, chemical analysis and distribution analysis of elements, the authors aimed to explore the relation-ship between the Fe-Ti oxides represented by ilmenite and sandstone-hosted uranium mineralization in Longhupao area. The study shows that the assemblage of altered minerals represented by U-rich Fe-Ti oxide-titanium oxide-pyrite has recorded the important information about ore-forming fluid and metallogenic environment in the process of sandstone-hosted uranium mineralization. The comparative analysis of different occurrences and assemblages for ilmenites and other altered minerals as U-rich Fe-Ti oxide, titanium oxide and pyrite reveals that the uranium mineralization in the Longhupao area was affected by the later oxidative fluid including U/Fe and the reductive fluid including H2S, and the metallogenic environment was strongly reductive. These strongly altered and Mg-rich ilmenites were closely related to the uranium mineralization, and the U-rich Fe-Ti oxides were formed in the redox reaction between these altered ilmenites and the later ore-bearing fluid. The corrosion fissures in these altered ilmenites provided favorable space for further alteration by ore-bearing fluid and uranium precipitation. The altered ilmenite offered a profitable mineral-scale oxidation barrier, and the pyrite offered a reduction barrier for uranium precipitation. During the fluid mixing of ore-forming and H2S-rich fluid, the uranium precipitated near the interface of reduction oxidation between altered ilmenites and pyrites.