Source identification of the geochemical anomaly from the fine-grained soil survey in the Nuheting sandstone-type uranium deposit, Erlian Basin, north China

Sedimentary basins in the arid areas of northern China have great potential to aid the discovery of new sandstone-type uranium deposits. A fine-grained (<75 μm) soil survey covering an area of approximately 6400 km2 has been undertaken to explore the concealed sandstone-type uranium deposit in Erlian Basin, north China. Displaying an obvious geochemical anomaly, the Nuheting (NHT) sandstone-type uranium deposit has been chosen for detailed studies of the source of geochemical anomaly, using lead (Pb) isotopic tracing and nanoparticle observation. Fine-grained soils are divided into three groups according to their spatial distance to the NHT uranium deposit which are soils above deposit, proximal soils and distal soils. Using analysis of variance (ANOVA), Pb isotope ratios of these soils show significant difference between proximal and distal samples. Deep mineralization and regional faults may give rise to the difference of radiogenic Pb isotopes. In addition, the widely observed Mo-bearing nanoparticles provide evidence that fine-grained soils contain signature of deep uranium ore. The characteristics of Pb isotope and nanoparticles indicate that accumulation of radiogenic Pb isotopes in the fine-grained soils is resulted from the concealed NHT uranium deposit. The transport and evaporation of groundwater has led to the vertical migration of geochemical signature from the deep to the surface. The fine-grained soil survey shows promise as an effective exploration technique for the sandstone-type uranium deposit in arid areas.