Abstract
U-bearing syenitic rocks cropping at the Mbanga massif in the South Region of Cameroon were geochemically and mineralogially charactarized, before the determination of their radiometric data, and processing of their uranium ores by H2SO4 acid leaching. The syenitic rocks are alkaline syenite, high-K syenite, and alkaline quartz syenite, with the first two rocks being metaluminous and the third, peraluminous. Both rocks show a compositional difference in uranium abundances (133–447 ppm) and those of other elements (exàmples of SiO2 : 61.6–66.6 wt.% and Al2O3 : 16.9–17.9 wt.%). The trace and rare earth element’s suites show the predominance of Sr (157.1–999 ppm) and Zr (111-599.7 ppm). The ƩLREE (37.3–168 ppm), ƩHREE (8.7–22.2 ppm), ƩLREE/ ƩHREE (1.6–13.8), and Eu/Eu* < 0.4 are variable. Found U-ore minerals (uraninite, uranophane, autunite, carnotite, torbernite, and/or coffinite) and other ore minerals (U-rich titanium oxide, zircon, magnetite, and/or ilmenite) are in a gangue made up of chlorite, calcite, quartz, alkaline feldspars, plagioclase, and/or biotite. The uranium contents (< 465 ppm) in the studied U-bearing syenites classify them within low grade ores; suggested to have formed with the aid of circulating hydrothermal fluids source of the precipitated OH, H2O, and OH-H2O bearing uranium ore minerals. The measured raw radiometric values range from 3542–6600 c/s and U3O8, from 0.33–0.59 wt.%. The presence of some minerals in the studied ores and the use of oxidant such as manganese dioxide during the H2SO4 acid leaching, provided elements which positively impact the process by increasing the U extraction with a total recovery of 80–90%. The maximum leaching temperatures 40–60 oC were less, compared to those used to process some other low grade uranium ores.