Petrogenesis and tectonic implications of Seih Syn-tectonic gabbroic intrusion, South Sinia, Egypt: Insights from whole-rock geochemistry, mineral chemistry and P-T estimate

The present work deals with the gabbroic intrusion in the Wadi Seih area as a part of the Neoproterozoic Pan-African basement in the southwestern part of Sinai, Egypt. It comprises as small plutons intruded into Seih metamorphic belt. The intrusions comprise hornblende gabbros, Anorthositic gabbros and sometimes occur as coarse-grained gabbros (appetites). These plutons belong to what is known throughout Egypt as Younger Gabbros. The present study includes petrography, whole-rock geochemistry, mineral chemistry, and geothermobarometry. Geochemically, the gabbroic intrusions are derived from tholeiitic magma with minor calc-alkaline affinity. They have a chemical signature of subduction-related arc magmatism formed at an active convergent plate margin by 15– 30% of partial melting of a garnet lherzolite and to a minor extent of spinel-garnet lherzolite sources, modified by fluids related to a subducting slab. Mineral chemistry indicates that the gabbroic rocks crystallize at a pressure between 2.9 and 4.4 Kb and temperature between 590 °C to 700°C.