Chemical Compositions of Natural Uraninite
The chemical compositions of uraninites from five major deposit types (tabular, unconformity, vein, metasomatic, and igneous), measured by electron microprobe and LA-ICP-MS, underline the extreme chemical variation of natural uraninite, due to different formation conditions prevailing at each deposit type.
Apart from the major elements always analyzed in uraninite (U, Th, Y, REE, Pb, as well as Si, Ca, and Fe), several additional elements are present in uraninite to a significant degree: Mn (overall median value of 6088 ppm), V (4528 ppm), Na (2365 ppm), As (2251 ppm), W (1811 ppm), Mg (441 ppm), Sb (286 ppm), Sr (261 ppm), Ti (235 ppm), Mo (133 ppm), Bi (125 ppm), and Ba (118 ppm).
Uraninites from different deposit types have distinct chemical compositions: tabular-type uraninites have the lowest Th, Y, and REE and the highest trace elements, in particular Mg, Mn, and V; sandstone-hosted unconformity-related uraninites have the lowest Y and the highest Fe, Na, Cu, Ni, and Ni; basement-hosted unconformity-related uraninites have the lowest Ca and Fe and the highest Ti, Ni, and W; metasomatism-related uraninites have the lowest Y and the highest Th and Si; and igneous uraninites have the lowest trace elements and the highest Th, Y, REE, Zr, and Hf. The vein-type uraninites have the most variable chemical compositions. In addition to the REE spectra, with only the igneous uraninites displaying a negative Eu anomaly, the chemical compositions of uraninites can be used with high confidence as provenance indicators. (Read More)