Abstract
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.
Highlights
The Seih Syn-tectonic gabbroic intrusion is one of the gabbroic intrusions in southwestern Sinai (Fig. 1)
Higazy and ElGammal (1989) studied the petrography and geochemistry of the gabbros from the northwestern part of the basement rocks in Sinai and considered that the Nesryin gabbroic intrusion is related to the metagabbro–diorite complexes, whereas ElTokhi and Katta (1993) studied the intrusive gabbro–diorite complex around Wadi El Akhdar and Wadi Nesryin, and concluded that the gabbros were intrusive in nature, tholeiitic, and probably represented differentiated mantle-derived magma intruded into an island arc setting
Summary and tectonic evolution The present study revealed the following characteristics: 1. There is no evidence for folding, deformation, and metamorphism, which indicates that the present gabbros are related to late to syn-tectonic stage of the Pan-African orogeny and are not related to the ophiolite suite
Summary
The Seih Syn-tectonic gabbroic intrusion is one of the gabbroic intrusions in southwestern Sinai (Fig. 1). Abdel-Karim (1995) concluded that the metagabbro-diorite complex, southwest Sinai, was derived from subalkaline magma in an island arc setting. Basta (1998) studied the mineralogy and petrology of some gabbroic intrusions in the southern Sinai (e.g., Melhega, Sa’al, and Watier) and in the Eastern Desert He concluded that these rocks were formed from calc-alkaline magma in an active continental margin setting. Higazy and ElGammal (1989) studied the petrography and geochemistry of the gabbros from the northwestern part of the basement rocks in Sinai and considered that the Nesryin gabbroic intrusion is related to the metagabbro–diorite complexes, whereas ElTokhi and Katta (1993) studied the intrusive gabbro–diorite complex around Wadi El Akhdar and Wadi Nesryin, and concluded that the gabbros were intrusive in nature, tholeiitic, and probably represented differentiated mantle-derived magma intruded into an island arc setting. MG varieties exhibit transitional calcalkaline/tholeiite magma types and are comparable to rocks of island arc setting
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