Relationship between architecture of uranium reservoirs and mineralization: A case study from the northern Songliao Basin, China

Abstract

Using a large volume of drilling data, this study aims to characterize the geometry and architecture of the uranium reservoir of the Lower Sifangtai Formation in the northern Songliao Basin on the basis of core observation, polarized light microscope, scanning electron microscopy (SEM), elemental analysis (EA) and sedimentary mapping. Following that, the effects of the geometry and architecture of uranium reservoirs on the uranium metallogenetic mechanism were discussed. The average thickness of the uranium reservoir of the Lower Sifangtai Formation in the southern Daqing area is 20.62 m, and the average ratio of the sandstone and strata is 41.02 %, with high value zones mainly distributed in the west, northeast and central-south of the study area. The average thickness of the impermeable beds is 30.15 m, and the average number of impermeable beds is 3, with high value zones mainly developed in the central-north, northwest and southwest of the study area. The average thickness of oxidized sandstones is 4.28 m, and the average ratio is 15.68 %. Oxidized zones are mainly developed in the northeast of the study area and on the north of the southern denudation zone, where the uranium reservoir thickness is 15–30 m, the ratio of the sandstone and strata is over 60 %, the thickness of the impermeable beds is less than 20 m and the number of impermeable beds is less than 2. Uranium mineralization is mainly developed near the transitional zone with the uranium reservoir thickness of 10–20 m, the ratio of the sandstone and strata of 20 %–80 %, the impermeable beds thickness of 10–40 m and the number of impermeable beds of 2–8. This study indicates that the geometry and architecture of uranium reservoir have a controlling effect on formation of the interlayer oxidized zone, which hence restricts uranium mineralization. The results have unveiled the restrictive mechanism of uranium reservoir architecture on uranium mineralization, laying a foundation for the study of regional uranium metallogenic regularities.