EXAMINATION OF TWO GRANITE PHASES ALONG WADI ABU ZAWAL AREA, NORTHEASTERN DESERT, EGYPT

The present work deals with the two granite phases along Wadi Abu Zawal area, North Eastern Desert, Egypt. G. Ad-Dub is located at the northeaster part of the mapped area as an elongate granitoid belt covering collectively about 0.5km², tending NE and shows zonal composition ranging from monzogranite in the outer rim to alkali feldspar granite in the core but it hardly to be traced in the field. G. Hadrabiyyah mass is located in the southwestern part of the mapped area as an elongated body covering collectively about 1.4km²and tending NW and composed of alkali feldspar granite.
Geochemically, the granitoids of the studied area seem to have originated frommetaluminous to peraluminous calc-alkaline magmas with many chemical features similar to I-type granites that developed in volcanic arc tectonic setting in a compressional regime.
The studied granitoids were generated at somewhat intermediate depths of (8-19 km) equivalent to 3-7 kb under temperature ranging from 760ºC to 840ºC. This is consistent with the high k/Rb ratios, and the high k/Ba ratios indicate involvement of ocean sediments in magma generation.
The concentration of U and Th in the granitoid rocks were controlled by magmatic processes which are clear from the positive relation between U and Th and negative relation between U- Th/U. They are also controlled by the presence of some accessory minerals (zircon and apatite) and iron oxides.  Iron oxides and hydroxides are known to absorb U from circulating fluids.