GRANITES OF GABAL EL-DOB AREA AND ASSOCIATED PEGMATITES, CENTRAL EASTERN DESERT, EGYPT: GEOCHEMISTRY AND SPECTROMETRY

The late Pan-African El-Dob granites in the Egyptian Central Eastern Desert are small and circular
bodies from older and younger granites. The older granitoids are represented by granodiorites and tonalites
and they are intruded by the younger gabbros and younger granites with sharp contacts. The younger
granites are represented by alkali feldspar granites cropping out in the central part of the studied area
forming Gable El-Dob. The older and younger granites are cut by pegmatite and quartz veins. El-Dob
granites are peraluminous and I-type granites. The older granites belong to volcanic arc granites (VAG),
while the younger granites belong to within plate granites (WPG). Pegmatite veins possess high contents
of important elements as Zn, Y and Cu. The El-Dob granites have relatively high uranium and thorium
contents. The average equivalent uranium is 19.2 ppm for the older granites and 32.5 ppm for the younger
granites, the average eTh is 55.4 ppm with the average eTh/ eU = 3.1 for the older granites and the average
eTh is 86 ppm with the average eTh/ eU = 2.8 for the younger granites. These radiometric measurements
are higher than the Clark values, i. e uraniferous granites. In pegmatites, the average eU content is 32.5
ppm and the average of eTh content is 86 ppm. Most of the radioactive anomalies are associated with the
pegmatites.