Petrogenesis, Depth Storage and Intensive Physico‐Chemical Parameters of Gulf of Suez Rift‐Related Oligo‐Miocene Basaltic Magmas

ABSTRACT Basaltic volcanism associated with the onset of Gulf of Suez rifting at the end of the Oligocene produced fissure‐fed dykes, sills, and minor lava flows dominated by dolerites and olivine basalts. They crystallised under relatively uniform redox conditions close to the fayalite–magnetite–quartz (FMQ) buffer and show comparable liquidus temperatures (1183°C–1153°C ± 51°C). Thermobarometric estimates indicate magma storage over a broad pressure range (9.3–6 kbar; ~34.9–21.9 km), just above the estimated Moho (~35 km), consistent with episodic cooling and crystallisation. Magma ascent to subvolcanic and near‐surface crustal levels was controlled by neutral buoyancy within the crystalline upper crust. Upon encountering a density barrier, the magmas propagated through the overlying sedimentary succession via mechanical intrusion along fracture systems. Crystallisation followed a sequence from cotectic plagioclase–olivine to eutectic plagioclase–olivine–augite, with late Fe–Ti oxides. Geochemically, the basalts are tholeiitic high Ti–P varieties enriched in high‐field‐strength elements (HFSE) and large‐ion lithophile elements (LILE) and exhibit moderate Mg# values (50–46) together with low Cr and Ni contents. Their mantle source corresponds to an enriched ocean island basalt (OIB)‐like reservoir. Modelling indicates derivation from ~12% to 16% partial melting of a garnet lherzolite, reflecting significant adiabatic decompression from a fertile deep‐mantle source to the conductive thermal boundary layer beneath a thin lithosphere.