Identifying the principal factors controlling uranium enrichment: Semi-quantitative mineralogy and geochemistry of the sandstone-type Qianjiadian uranium deposit, northeast China
Jun-Ting Qiu, Hong-Xu Mu, Xinqi Yu, Xin-Min Rui, Yanjie Yang, Liang Qiu
Abstract
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.