Multi-scale visualization of uranium-rich domains dispersed in U-Zr mineralization of sandstone-type (Břevniště, Czech Republic)

Abstract

Multi-level visualization of U-Zr mineralization in sandstones is discussed, aiming at the identification of mineral phases, imaging of their distribution using 2D and 3D projections, and quantification of the presence of U-rich domains. For this purpose, uranium-bearing sediments with anomalous concentrations of Zr, Nb ± Fe, Sr were studied (Břevniště deposit, Czech Republic). The applied multi-instrumental approach included selection of the most suitable areas in core samples (highest U and Zr concentrations) using X-ray fluorescence analysis (XRF). The presence of numerous detrital and authigenic accessories, hardly discernible using optical methods, was confirmed with the use of automated mineralogical analysis (TIMA). Hydrozircon and metacolloidal mixed phases were shown to be the carriers of uranium. Their close relationship to sulfides, Fe oxyhydroxides and clay minerals was documented using phase distribution maps. X-ray micro-computed tomography (μCT) was used for the visualization of internal structures of uranium-bearing sandstones. Based on a series of thresholding of μCT data, segmentation of selected samples was performed with subsequent visualization of selected mineral phases. The combination of TIMA and μCT analysis allowed for an effective discrimination of U-rich areas and quantification of their volume. This approach provides new possibilities in imaging elementary complex disseminated uranium mineralizations.