WEI Shuai-chao^1,2, ZOU Niu-niu^1*, FU Yong¹, Li Jian-guo³, Tang Chao³, Wei Jia-lin³

(1. School of Resources and Environments, Guizhou University, Guiyang 550025, China;
2.Institute of Hydrogeology and Environment Geology, Chinese Academy of Geological Sciences, Shijiazhuang 050061, China;
3.Tianjin Center, China Geological Survey, Tianjin 300170, China.)

Abstract: In order to discuss the geochemical characteristics of trace elements and uranium enrichment regularity of the U-rich bed in Sifangtai Formation in the Songliao Basin, the field geological investigation and systematic sampling have been carried out. Samples of non-mineralized and uranium mineralized sandstones of Sifangtai Formation, systematically selected from drill cores of 4 EW-striking profiles in the study area, have been studied in petrology, mineralogy, and trace element geochemistry. The results show that uranium is mainly enriched in feldspar lithic sandstones. The rock types of strata closing to the U-rich bed are changed regularly in both horizontal and vertical directions. The North American Shale standardized REE distribution patterns of wallrocks, uranium mineralized sandstones, and uranium-rich sandstones are all right-inclined, with the LREE enrichment feature and relatively weak internal fractionation of the LREE comparing to that of the HREE. The uranium-rich sandstones have positive Eu anomalies, which may be caused by high contents of plagioclase, but have no or slightly negative Ce anomalies. The Grant equipotential line analysis of trace elements in uranium-rich stratum sandstones shows that most trace elements, especially whole rare earth elements, are migrated into the sandstone in the primary uranium enrichment process whereas trace elements were gradually migrated out, especially the REE were wholly migrate out, in the second uranium enrichment process, reflecting the difference of hydrolysis intensity between two uranium enrichment processes, with the relatively weak hydrolysis intensity for the later process.

Keywords: the Songliao Basin; geochemistry; sandstone; uranium-rich stratum; rare earth elements (REE)

ACTA MINERALOGICA SINICA Vol. 39, No. 6, 2019, page 697-708