Subduction-related mafic-silicic magmatism in the Nubian Shield: Tectono-magmatic implications of ensialic island arc association at Central Eastern Desert, Egypt

• Published in: Journal of African earth sciences (1994) Vol. 212; p. 105204
• Main Authors: Radwan, Abdelhady, H Younis, Mohammed, Hassan, Mohamed A., Abbas, Hassan
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-04-2024
• Subjects: Island arc plutonism; Mafic to silicic magmatism; Metagabbro-diorite complex; Wadi El Mayet; Metagabbro-diorite complex; Mafic to silicic magmatism; Wadi El Mayet; Island arc plutonism
• ISSN: 1464-343X; 1879-1956
• DOI: 10.1016/j.jafrearsci.2024.105204

For the Wadi El Mayet, the metagabbro-granodiorite-tonalite intrusive complex (MIC) occupies the eastern sector of famous wadi Mubarak–Dabr complex which considered as the largest intrusion in the Egyptian Eastern Desert. The basement associations in the area include volcano-sedimentary rocks, metavolcanics, and ultramafics. The whole successions were intruded by MIC, and granites. The (MIC) comprises multifarious gabbroic varieties namely: olivine, pyroxene, hornblende, uralitized gabbros and rare amphibolites, while silicic portion includes tonalite and granodiorite. Microprobe analytical chemistry of gabbros and granites refers that: the amphiboles are calcic magnesio hornblende formed at low pressure conditions. Chlorites have corundophillite composition. Plagioclase range between labradorite, andesine and oligoclase. Biotite is mainly siderophylite. Muscovite minerals are mainly cheladonite. Geothermo-barometers calculations reveal crystallization temperatures of 550 °C and 860 °C for granites and metagabbros respectively. The (MIC) cover a wide silica range (44.5–74.5 wt %). It has transitional tholeiitic to calc-alkaline magmas. The gabbroic rocks show distinct fecundity with LILE (e.g. Rb, Ba, U and Th), but show observed shortage in most HFSE (e.g. Zr, Nb, Ta). The REE patterns show enrichment in light REE and posse variably positive Eu. It is suggested that, the gabbroic units were likely generated by fractional crystallization of mafic magmas produced through partial melting of metasomatized mantle within island-arc environments. Tonalite - granodiorite (TG) suite show calc-alkaline magmas of I-type settings. They also exhibit enrichment in Ba, Zr, Hf, Rb, U and Th, while P, Nb, Ta and Sr are depleted. Such reductions are harmonious with fractionation of K-feldspar phases. The (TG) show enrichment of (LREE) compare to (HREE) this proposes either the existence of persistent garnet or LREE fertile magma sources. The (TG) is believed to be formed through dehydration melting processes at lower crust settings. Based on the field, geochemistry and structure elements, the investigated mafic and silicic suites are not linked to a single magma origin. The (MIC) can be comparable with intrusions formed in ensialic island-arcs settings. At subduction zone integration between mantle (basaltic suites) and silicic magmas from lower crust forming the early stages of (MIC) crystallization. The whole association was suffered by insignificant fractionation processes and addition of crustal materials during the final stages of (MIC) emplacement.
•Wadi El Mayet rocks association represents a good example of Mafic-silicic magmatism in Egypt.•The mafic-silicic rocks of Wadi El Mayet are ensialic island arc suites formed at subduction setting.•The geochemical and structural aspects of wadi El Mayet rocks prove different magma sources.•Five deformational events (D1 – D5) are designated for the formation of area comprise wadi El Mayet intrusive complex.