On the basis of the geological and petrological investigations, the Pan-African granitoid rocks of Wadi Fatirah area are differentiated into two distinct assemblages, viz. the older granites and younger granites. The older granitoids comprise quartz diorite, tonalite and granodiorite, arranged in accordance to their sequence of emplacement. The older granites are calc-alkaline in character and of I-type and were emplaced under compressional tectonic regime. The normalized chemical data indicate that the older granites are generally enriched in LIL elements and depleted in HFS elements. The normalized values of the trace elements are consistent throughout the quartz diorite, tonalite and granodiorite reflecting their comagmatic parentage.
The younger granites, on the other hand, comprise monzogranite, syenogranite and alkali feldspar granite exhibiting sub- and hyper-solvus textures. They are alkaline to mildly peralkaline in nature, with a restricted content of SiO2 (72-76%) and were formed under an extensional tectonic regime. The normalized chemical values of these rocks indicate that they are more or less similar to the average continental crust but they are depleted in Sr, P and Ti. The matter which is attributed to the fractionation of plagioclase, apatite and Fe-Ti oxides. Generally, the younger granite assemblage are low in Al2O3, CaO and MgO whereas they show higher concentrations of SiO2, alkalies (Na2O+K2O) and Ga, a characteristic feature of A-type granite. They probably originated by partial melting of deplted crustal I-type tonalite to granodiorite. Variation of U and Th among the studied younger granites, examined by plotting eU against eTh content, displays their enrichment by means of magmatic rather than secondary processes and consequently they can be classified as uraniferous granites.