Neoproterozoic granites of Sharm El-Sheikh area, Egypt: mineralogical and thermobarometric variations
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ORIGINAL PAPER
Neoproterozoic granites of Sharm El-Sheikh area, Egypt: mineralogical and thermobarometric variations Mohamed F. Ghoneim & Mohamed Th. S. Heikal & Bothina T. El Dosuky & Tamer S. Abu-Alam & Mahmoud I. Sherif
Received: 4 August 2013 / Accepted: 4 November 2013 # Saudi Society for Geosciences 2013
Abstract Calc-alkaline and alkaline intrusions of the late Neoproterozic form essential part of the Arabian–Nubian Shield. They were formed during the collision between Eastand West-Gondwana. Sharm El-Sheikh area, Sinai, includes wide compositional array of these intrusions that can be considered as a case study. Variations in both tectonic and thermobarometric condition for granitic intrusions are studied. Four mappable granitic types are recognized namely monzogranite, syenogranite, alkali feldspar granites, and riebeckite-bearing granites. The monzogranite and the syenogranite of the study area are mostly I-type, whereas the alkali feldspar granite and the riebeckite-bearing granite belong to A-type granitoid. The calc-alkaline intrusions were formed in compressional setting due to decompressional melting of mafic lower crust. Partial melting and anatexing of crustal rocks are suggested to explain the protolith of the alkaline intrusions. The transition from the calc-alkaline magma to the alkaline one occurred as a result of the tectonic transition from compression regime to tectonic relaxation (extension setting) during the last stage of the Pan-African Orogeny. The amphiboles of the studied granites are classified as calcicand alkali-amphiboles. The calcic-amphiboles are ferroElectronic supplementary material The online version of this article (doi:10.1007/s12517-013-1182-0) contains supplementary material, which is available to authorized users. M. Th. T. S.S.Heikal Heikal::B. B.T.T.ElElDosuky Dosuky:: M. F. Ghoneim (*) :M. T. S. Abu-Alam : M. I. Sherif Geology Department, Faculty of Science, Tanta University, Tanta 31527, Egypt e-mail: [email protected] T. S. Abu-Alam Institut für Erdwissenschaften, Universität Graz, Universitätsplatz 2, 8010 Graz, Austria T. S. Abu-Alam Egyptian Institute of Geodynamic, Cairo, Egypt
edenite while the alkali-amphiboles are typically riebeckite. Both amphibole types are of magmatic nature. Coexisting amphiboles and plagioclases are used to estimate the physicochemical parameters of magma crystallization. The syenogranite underwent temperature and pressure of formation range of 520–730 °C,
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