GEOLOGY AND RADIOACTIVITY OF MUSCOVITE LEUCOGRANITES AT NORTH WADI ABU RUSHEID AREA, SOUTH EASTERN DESERT, EGYPT

The study area is located at north Wadi Abu Rusheid and is composed of ophiolitic mélange
(the oldest), cataclastic rocks, biotite granites and muscovite leucogranites (the youngest). The muscovite
leucogranites are found as dyke like body intruded between ophiolitic mélange and cataclastic rocks.
Petrographically, the muscovite leucogranites are composed mainly of quartz, plagioclase of albitic
composition, potash feldspare and muscovite. Zircon, thorite, uranophane and opaques as accessories.
Geochemically, the muscovite leucogranites are peraluminous in nature, crystallized from relatively
sodic rich magma and related to calc-alkaline series. The muscovite leucogranites are belong to A-type,
emplaced during within plate tectonic setting and intruded in a continental crust with thickness < 20 km.
The muscovite leucogranites have high contents of Zr, Y, Pb and Nb and moderate contents of Zn,
Ba, Cu, Sr and Rb. The mineralogical study of the muscovite leucogranites is characterized by presence of
radioactive minerals (uranophane and thorite) and zircon. From radioactivity point of view the muscovite
leucogranites up to 250 ppm eU and 1146 ppm eTh and related to magmatic origin. The muscovite
leucogranites lose some of their uranium contents which migrated towards the cataclastic rocks along
bedding planes and re-deposited on their fracture planes.