Identifying the principal factors controlling uranium enrichment: Semi-quantitative mineralogy and geochemistry of the sandstone-type Qianjiadian uranium deposit, northeast China

The Qianjiadian deposit is the first late Mesozoic-Cenozoic sandstone-type uranium deposit discovered in the Songliao Basin, northeast China. It remains uncertain whether high-temperature hydrothermal fluid or low temperature groundwater dominated the mineralization process that led to uranium enrichment in this deposit. We investigated the gamma ray intensity and semi-quantitative mineralogical and geochemical characteristics of drill cores from the Qianjiadian deposit. A total of 60 gamma ray anomalies were identified; most of these anomalies are associated with negative Fe2O3 and Fe3+/Fe2+ anomalies, four are associated with positive total organic carbon (TOC) anomalies, and none are associated with positive carbonate (calcite + dolomite) anomalies. The absence of positive carbonate anomalies, together with low kaolinite crystallinities, rules out the influence of high-temperature fluid on uranium enrichment. The dominant negative Fe2O3 and Fe3+/Fe2+ anomalies and the occurrence of pyrite in thin section and gray-red sandstone and native sulfur in some U-rich drill cores indicate that redox reactions in low-temperature groundwater may have been the principal control on uranium enrichment. In addition, two gamma ray anomalies are associated with positive TOC, Fe2O3, and Fe3+/ Fe2+ anomalies and another two are associated only with positive kaolinite anomalies, suggesting that carbonaceous debris and kaolinite could also cause limited uranium enrichment.

Automated summary

The Qianjiadian deposit is the first late Mesozoic-Cenozoic sandstone-type uranium deposit discovered in the Songliao Basin, northeast China. The study of gamma ray intensity and mineralogical and geochemical characteristics suggests that low-temperature groundwater redox reactions were the main control on uranium enrichment.