Mineralogical and natural radioactivity investigations of Wadi El Reddah stream sediments

Abstract

ABSTRACT Wadi El Reddah (valley), Central Eastern Desert, Egypt extends in North-South direction, it represents a semi-closed basin with only one outlet in its northern tip. Wadi El Reddah is mainly surrounded by scattered exposures in a sequence of metagabbro-diorite and metavolcanics complex in addition to wide sector of Hammamat sedimentary rocks, monzongranites of Gabal El Reddah, perthitic leucogranites of Gabal Gattar as well as swarms of post-granitic dykes. The studied sediments showed wide variation in their Uranium, Thorium, Radium (eU) and potassium (K%) contents. Uranium ranges from 5 to 51 ppm, with an average of 17.33 ppm, Th contents between 16 and 141 ppm, with 32.47 ppm as an average. Ra (eU) varies between 5 and 26 ppm with an average of 9.56 ppm. While potassium falls between 2.19% and 4.41% with an average of 3.19%. The disequilibrium conditions in the stream sediments under investigation indicated that they are mostly recent which is due to the fact that most of the radiometric measurements are lower than the chemical measurements. eTh/eU ratio values of old uranium deposits in the studied sediments suggested mineralisation in an environment of rapid deposition of rock detritus and poor weathering with the dominance of detrital radioactive minerals like thorite, samarskite, euxenite and xenotime.