Wadi Sodmein area lies to the northwest of Quseir town on the Red Sea. The studied volcanic rocks are
distinguished into Dokhan Volcanics and felsites. The Dokhan Volcanics are subdivided into two rock
units, an older unit of andesite-dacite composition and a younger unit of rhyolite, rhyolitic tuffs and
ignimbrite. They have petrographical and geochemical features similar to calc-alkaline, subduction-related magmas of active continental margins. The rhyolitic members of the upper unit contain slightly
higher contents of alkalis and some incompatible elements than those of typical active continental margins due to crustal contamination. The Dokhan Volcanics at Wadi Sodmein evolved from an andesitic magma resulting from the partial melting of the subducted oceanic slab. This magma underwent a complex interplay of partial melting, contamination and fractional crystallization processes.
On the basis of field and chemical data, the younger rhyolitic volcanics were generated fromthe same andesitic magma, but was separated by a considerable time gap (period ofmagmatic quiescence). Plagioclase was the main fractionating phase, while fractionation of mafics, apatite and Fe-Ti oxides played a minor role.
The felsites at Wadi Sodmein were intruded after the extrusion of the Dokhan Volcanics comprising lava flows and pyroclastic layers. Geochemically, they are alkaline and contain normative acmite which are
characteristic properties of within-plate A-type magma. Therefore, the studied felsites are not equivalent
to the high silica Dokhan Volcanics as previously thought, but represents the extrusive member of the A-type granite magma in the Eastern Desert and Sinai. In other words, they are comparable to the alkaline
Atalla felsite in the central Eastern Desert and Katherina Volcanics in South Sinai. The emplacement of
the studied felsites has most probably occurred along Pan-African fractures that have been re-activated
by relaxation after the terminationof the Pan-African orogeny.