Mineralogical and Geochemical Characterization of Beryl-Bearing Granitoids, Eastern Desert, Egypt: Metallogenic and Exploration Constraints

Mineral chemistry and geochemical characteristics of beryl-bearing granitoids in Eastern Desert of Egypt, were examined in order to identify the metallogenetic processes of the host granitoids. The investigated Be-bearing granitoids and type occurrences are classified into two groups: (i) peraluminous, Ta ≥ Nb + Sn + Be ± W-enriched, Li-albite granite (e.g. Nuweibi and Abu Dabbab); and (ii) metasomatized, Nb >> Ta + Sn + Be ± W ± Mo-enriched alkali feldspar granite (i.e. apogranite; e.g. Homr Akarem, Homr Mikpid and Qash Amir). In these two groups, beryl occurs as stockwork greisen veins, greisen bodies, beryl-bearing cassiterite ± wolframite quartz veins, dissemination, and miarolitic pegmatites. Beryl of the Be-granitoids, particularly those of miarolitic pegmatites, contains appreciable contents of Fe, Na, and H₂O. An important feature of the Be-apogranites is the occurrence of white mica as the sole mafic mineral in the unaltered alkali feldspar granite in lower zones. Presence of white mica as volatile-rich pockets suggests that the melt underwent disequilibrium crystallization, rapid nucleation rates, and exsolving and expulsion of volatiles.