Gabal Hamrat Al Jirjab area is located in the northern part of Esh El Melaha range, north Eastern
Desert. The area is covered mainly by Dokhan volcanic rocks (andesite, dacite and their pyroclastics)
intruded by alkali feldspar granites of G. Hamrat Al Jirjab with some dyke swarms of various composition,
felsic dykes (granophyres and rhyolite), intermediate dykes (andesite) and basic dykes (dolerite).
The studied Dokhan volcanics are considered as medium-K rocks originated from calc-alkaline
magma in island arc to active continental margin environment. On the other hand, the studied granites are
classified as alkali feldspar granites and considered as I-type, originated from peraluminous calc-alkaline
highly fractionated magma. They are post-orogenic and formed under an extensional regime suggesting
crystallization during relaxation stage that following collision. They are intruded in a crust of thickness> 30
Km and crystallized at temperature < 800oC.
Alkali feldspar granites of G. Hamrat Al Jirjab can be described as uraniferous granite. The average
values (16 ppm eU and 32 ppm eTh) are attributed to the presence of U and Th bearing accessory minerals
namely; thorite, uranothorite, monazite, zircon, fluorite and allanite.
Stream sediments of G. Hamrat Al Jirjab area exhibit mixture of detritus components, represented by
pebble, granules, sand and sizes less than very coarse silt. These sediments are considered the natural trap
for the accessory and some radioactive minerals for the surrounding country rocks.