GEOLOGY, GEOCHEMISTRY AND POTENTIALLITY OF RADIOACTIVE MINERALIZATIONS AT UM SAFI AREA, CENTRAL EASTERN DESERT, EGYPT.

Abstract

The present thesis deals with the geological, structural, petrographical, geochemical and radiometrical studies of the basement rocks of Um Safi area which is located in the Central Eastern Desert, Egypt between Long. 34° 03' and 34° 14' E, Lat. 25° 15' and 25° 24' 20" N. The basement rock units in the study area can be chronologically arranged beginning with the oldest as follows:- allochthonous ophiolitic assemblage (dismembered ophiolitic rocks and melange), arc assemblage [metavolcanics (meta-andesites), volcaniclastic and volcano-sedimentary association, older granitoids, volcanic rocks (rhyolite and pyroclastics)), molasse sediments, younger gabbros (noritic troctolite, normal gabbro and hornblende gab bro), younger granites (biotite granite, perthite leucogranite and muscovite leucogranite), post granite dykes and veins and trachyte plugs. The granitoid rocks of Um Safi area have been subdivided into three categories, (based on field relationships, petrography and geochemical characteristics) termed magmatic cycles emplaced during successive tectonic events. Granites of the first magmatic cycle ( diorite, quartz diorite, tonalite and gneissic granodiorite) have calc-alkaline, metaluminous, I-type character and emplaced during pre-plate collision to post collision uplift regime under a high water vapour pressured (5-10 k- bar) and high temperature (800-840 °C). Biotite granite and perthite leucogranite represent the second magmatic cycle, they characterized by calc-alkaline, metaluminous magma and emplaced during late-orogenic regime. Granites of the third magmatic cycle are mainly peraluminous muscovite leucogranite in composition, crosscutting all other rock types in the region and were emplaced during syn-collision regime. The latter two magmatic cycles were emplaced at moderate water-vapour pressure (2-5 k-bar) and temperature (760-800 °C).