Abstract

The metamorphosed sandstones exposures occur in two locations in Wadi Sikait. The exposed rocks in this area are ophiolitic mélange, metamorphosed sandstones, porphrytic granites invaded by post-granite dykes (lamprophyres) and quartz-fluorite veins. The uranium contents measured radiometrically range from 3 to 41.97 ppm, with an average of 12 ppm, while the chemically measured are in the range from 20 to 100 ppm and averaging 50.83 ppm. High uranium contents are mainly attributed to the presence of secondary uranium minerals (uranophane and autonite), accessory minerals (monazite, zircon, allanite and xenotime) and U-bearing minerals (muscovite, biotite, chlorite, iron oxides and clays). P- and D-factors indicate disequilibrium in U-decay due to addition of uranium in these rocks. Since radioactive secular equilibrium of the young age deposits have not yet reached, therefore, the activity ratios (AR) of ²³⁰Th/²³⁴U in the studied rocks is very small and ranges from 0.43 to 1.3. Radon exhalation rates of the studied rocks were also measured using ‘‘Sealed Can technique” and indicated the presence of subsurface and surface uranium anomaly which confirms the previous results.

Key words: Metamorphosed sandstones, uranium, minerals, Wadi Sikait.