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The Neoproterozoic plutonic complex in the Homrit Waggat and El-Yatima areas, central Eastern Desert of Egypt, comprises a deformed calc-alkaline I-type metagabbro-diorite complex and tonalite-granodiorite suite invaded by felsic high level intrusions of A-type characteristics. The metagabbro-diorite complex exhibits petrological and geochemical characteristics of mantle-derived island-are basalts, and its magma was derived possibly from partial melting of a mantle wedge above an early Pan-Af rican subduction zone. The roc ks of the tonalite-granodiorite suite have a wide range of SiO2 (62-71%), and K, Rb and Ba enrichment relative to Nb and Y. Their chemical variations suggest that they are not related to the gabbro-diorite complex, but most probably derived by partial melting of the amphibolitic lower crust in a subduction zone. The A-type granites are mainly syeno- and alkali-feldspar granites characterised by sub- and hyper-solvus textures, late magmatic interstitial biotite and interstitial or vein-fluorite. They are geochemically evolved (SiO2 = 74-78%), metaluminous to mildly peraluminous, enriched in Fe, Y, Nb, Rb, Zr and F, and depleted in CaO, MgO, Ba and Sr. Although they can be classified as A-type and within-plate granites, the least differentiated samples have F, Nb, Y and Rb contents similar to those in the surrounding I-type tonalite-granodiorite suite. This similarity suggests that high concentrations of these elements in the A-type granite are mostly related to unusual fractionation processes rather than to source rock (A-type source). This simply indicates that these granites are I-type and their classification as A-type reflects the process of evolution. A petrogenetic model of dehydration partial melting of an early Pan-African lower crust along major shear zones in a postcollisional environment to produce granodioritic melt seems likely. Fractional crystallisation of this granodioritic melt gave silicic granites, during which a F-rich fluid phase was evolved. Late magmatic F-rich fluid-rock interaction and F complexing played an important role in the evolution and chemical characterisation of the A-type granites. (C) 1999 Elsevier Science Limited. All rights reserved.