Abstract:The selection of economical, efficient, lightweight and non-destructive analysis techniques is a practical requirement for the green exploration and research of sandstone-type uranium deposits. By the means of portable colorimeter, X-ray fluorescence (XRF) and hyperspectrum, this work comprehensively investigated the geological and geochemical characteristics of the red-variegated strata of the Huanhe Formation in the Telaaobao deposit, northwest of the Ordos Basin. The quantitative chromaticity interval standard was constructed to characterize the different colors of sandstone. It was found that the red sandstone underwent differential oxidation that included stronger original oxidation with a crimson and the relatively extensive epigenetic oxidation with brown (or purple) red color. The taupe gray and gray-green sandstones in the transition zone, were usually characteristic with a slight weak oxidation. The redness (a) curves of the sandstones displayed several gradual transition boundaries, indicating that some redox geochemical interfaces were located within the interior of the ore belt. As a result multiple coassociated enrichment of some variable valence elements includes uranium-molybdenum-vanadium-niobium. The above evidence suggests that redox was the main uranium mineralization mechanism in the study area. The green reduced sandstones owned the lowest value of redness, and they were transformed by the late alkaline and reducing fluids before uranium mineralization. Fluid activity event also resulted in the chloritization, ferric-iron reduction, local carbonation and other alterations of the Huanhe Formation. This study provides a case and important reference for the rapid and multi-scale evaluation on the metallogenic environment of uranium-bearing formations with different geochemical properties in sedimentary basins.
