Geochemical characteristics of thorium and their sedimentary environment indication of Engeriyin uranium deposit in Sunid Left Banner, Inner Mongolia

Located in the Sunid Left Banner, the Engeriyin deposit is a newly discoveried sandstone–type uranium deposit. Though summarized the geochemical characteristics and distribution of thorium contents in 278 samples from 31 boreholes in Engeriyin area of Manite depression in Erenhot Basin, this paper analyzed the influencing factors and indicating significance of thorium content. The findings indicate that the thorium level in this region is higher than that of the volcanic rocks to the south of the Manite depression, ranging from 3 × 10⁻⁶ to 99.9 × 10⁻⁶ with a weighted average of 24.03 × 10⁻⁶. The primary determinants of thorium content in rock samples, as determined by data processing and analysis, are the source of the sediment, the distance and sorting of transportation, the granularity, the water permeability, and the adsorption strength of sedimentary rock, all of which affect the migration and differentiation of thorium−bearing minerals. Additionally, there is no discernible relationship with the uranium concentration, the redox reaction, sample depth, or newly generated thorium−bearing minerals during the deposition process. Numerical characterization and spatial distribution of Thorium in sedimentary rocks along the margins of terrestrial basins are useful for locating sedimentary sources within sedimentary basins, creating isochronous stratigraphic grids, defining sedimentary phases and sand connectivity, figuring out the direction of palaeocurrents, and reestablishing palaeochannel spreads.