On the cratonization of the Arabian-Nubian Shield: Constraints from gneissic granitoids in south Eastern Desert, Egypt

The Shaitian granite complex (SGC) spans more than 80 Ma of crustal growth in the Arabian–Nubian Shield southeast Egypt. It is a voluminous composite intrusion (60 km2) comprising host tonalite massif intruded by subordinate dyke-like masses trondhjemite, granodiorite and monzogranite. tonalite, turn, encloses several, fine-grained amphibolite enclaves. U-Pb zircon dating indicates wide range crystallization ages within SGC (800 ± 18 for tonalites; 754 3.9 trondhjemite; 738 3.8 granodiorite; 717 3.2 monzogranite), suggesting independent magma pulses. high positive ?Ndi (+6–+8) indicate that melting sources were dominated juvenile material without any significant input from older crust. Application saturation geothermometry increasing temperatures during generation melts 745 31 °C to 810 25 840 10 868 pressure partial loosely constrained be below stability residual garnet (<10 kbar) as inferred almost flat HREE pattern ((Gd/Lu)N = 0.9–1.1), but >3 kbar amphibole significantly lower NbN TaN compared with LREEN sub-chondrite Nb/Ta ratios exhibited granitic phases. inverse relation between estimates granitoid lithologies argue against role fractional crystallization. major trace element contents emplacement subduction zone setting. lacks distinctive features melt derived subducted slab (e.g. Sr/Y (La/Yb)N ratios), relatively low MgO Ni all phases suggest crust an island arc overlying mantle wedge. Comparison produced experiments basaltic composition best candidate source trondhjemite magmas whereas monzogranite most consistent fusion protolith. Given overlapping Sm-Nd isotope well several samples, it reasonable renewed underplating may have caused SGC. potassic (monzogranite) subsequent Na-rich granites (tonalite-trondhjemite-granodiorite) likely suggests thickening prior collision amalgamation into over thickened proto-crust Arabian-Nubian shield. Eventually, after complete consolidation, whole was subjected regional deformation, probably accretion Saharan Metacraton (arc–continent collisions) late Cryogenian -Ediacaran times (650–542 Ma).