Homrat El-Girigab area located at Northern Eastern Desert which, characterized by abundant intrusion
of calc-alkaline and alkaline/peralkaline granitoids and their associated volcanics. These granitoids have a
particular geodynamic interest as they provide an outstanding opportunity to tell how continental crust of
ANS was formed. Homrat El-Girigab area is covered by Dokhan volcanics (andesite & dacites), which
intruded by alkali-feldspar granites. The chemistry of biotites indicates that, the alkali-feldspar granites
were crystallized from alkaline crustal source under oxidized conditions (i.e. nickel-nickel oxide buffer or
NNO). They were crystallized under conditions including, temperatures range from 700 to 750 °C,
pressures 3 to 4 kbar, depths of emplacement range from 7 to 11 km and under Oxygen fugacity (log fO2)
ranges from -15 to -16. Homrat El-Girigab alkali-feldspar granites (HGAFGs) are alkaline, ferroan
anorogenic (i.e. extensional) A-type granites. They were emplaced during the late post-collisional crustal
extensional stage at which the effect of lithospheric delamination, and thus asthenospheric uprise, likely
diminishes. At this stage the mantle-derived mafic melts start intraplating the lower crustal levels, that
facilitated by the abundance of strike-slip faults and shear zones. This lithospheric intraplating caused
widespread melting producing the alkaline magma of HGAFGs. The studied granites were derived from
lower crustal amphibolitic source and evolved mainly by fractional crystallization.