Petrogenesis and tectonic evolution of ophiolitic mafic rocks from the Eastern Desert of Egypt: new insights from mineral and whole-rock geochemistry

Faculty Science Year: 2026
Type of Publication: ZU Hosted Pages: 655–678
Authors:
Journal: Journal of Iberian Geology Springer Nature Link Volume:
Keywords : Petrogenesis , tectonic evolution , ophiolitic mafic rocks    
Abstract:
Since ophiolites are remnants of ancient oceanic crust, which are later emplaced along convergent plate boundaries, they provide key insights into the magmatic and tectonic processes linked to mid-ocean ridges (MOR) and subduction zones, particularly in the Arabian Nubian Shield (ANS). This study presents an integrated mineralogical and geochemical inves- tigation of ophiolitic metagabbros (MG) and metabasalts (MB) from two tectonically distinct regions of the Egyptian Eastern Desert: W. Um Qarati in the Central Eastern Desert (CED) and G. Gerf in the Southern Eastern Desert (SED). The Um Qarati rocks form part of a dismembered ophiolite thrust over an island arc assemblage, whereas the Gerf rocks preserve one of the most intact ophiolite sequences in the ANS. The primary mineral phases (plagioclase, hornblende, and clinopyroxene) are variably overprinted by greenschist to amphibolite facies metamorphism, as evidenced by secondary actinolite and chlorite. Plagioclase compositions in metagabbros range from oligoclase to labradorite with minor albite, exhibiting normal zoning in Um Qarati and reversed zoning in G. Gerf. Hornblende thermobarometry yields crystalliza- tion temperatures of ~ 800–870°C and pressures of ~ 3.99‒5.78 kbar. The presence of interstitial quartz, alongside apatite, and ilmenite points to a high degree of magma evolution. The studied metagabbros and metabasalts seem to represent a transitional stage between mid-ocean ridge (MOR) and island-arc tholeiitic (IAT) magmas. Their chondrite-normalised LREE patterns and HFSE ratios (Nb/Yb = 0.41–5.97 in MG and 0.74–11.47 in MB) suggest derivation from heterogeneous mantle sources ranging from depleted MORB-like to enriched OIB-like compositions. However, the negative Nb anoma- lies and high Th/Yb ratios in the metagabbros, point to metasomatic enrichment by slab-derived fluids and melts. The concentrations of immobile elements (Ti, V, Zr, Nb, and Y), along with structural features, including sheeted dykes and deformed pillow basalts, support a subduction initiation setting. In this context, early-stage extension and mantle upwell- ing generated MORB-type magmas, followed by progressive subduction-related input, yielding IAT-like compositions. The transitional geochemical character of the studied ophiolites closely resembles that of globally recognized subduction- initiation complexes, such as the Izu-Bonin-Mariana forearc and the Balkan Tethyan belt. These findings highlight the role of the Egyptian ophiolites as valuable analogues for understanding crustal generation during Neoproterozoic subduction initiation and early arc development.
   
     
 
       

Author Related Publications

  • Waheed Ibrahim Alwan, "Experimental and modeling investigations of cesium and strontium adsorption onto clay of radioactive waste disposal. Applied Clay Science, 132-133, 391-401.", Applied Clay Science, 2016 More
  • Waheed Ibrahim Alwan, "Balasy, M.R. Abd Allah, Sh.E., Waheed Elwan (2008) Geochemistry of North Wadi Hawashia Granitoid Rocks, North Eastern Desert, Egypt", Alexandria University, 2008 More
  • Waheed Ibrahim Alwan, "Waheed I. Elwan & Lotfy Abdel-Salam 2008. Petrographical characteristics and physical testing of El-Tarr albitites and their suitability for ceramic industry", Faculty of Science, Al Azhar University, 2008 More
  • Waheed Ibrahim Alwan, "Spinels, Fe–Ti oxide minerals, apatites, and carbonates hosted in the ophiolites of Eastern Desert of Egypt: mineralogy and chemical aspects. Arabian Journal of Geosciences", Springer, 2013 More
  • Waheed Ibrahim Alwan, "Mineralogical and geochemical aspects of mica, amphibole, pyroxene and zircon from some granitoid rocks, South Sinai, Egypt.", Zagazig University, 2001 More

Department Related Publications

  • Osama Mohamed Abdelmoneim Elbadry, "El-Badry, O. Abul Enein & Moursi, : Surface Triassic of Arif El Naga, Sinai, Egypt: A Petrologic study: M.E.R.C., Ain ¬Shams Univ., Earth Sci. Ser., V. 11, p. 51 67. (1997)", لايوجد, 1900 More
  • Osama Mohamed Abdelmoneim Elbadry, "Gadallah, Abdel-Shafi, Abdel Razek, and El-Badry, O. : “Reservoir Evaluation of Nukhul Clastics, South Gulf of Suez, Egypt”. GRMENA-1, First International Conference on Georesources in the Middle East and North Africa. (2005).", لايوجد, 1900 More
  • Osama Mohamed Abdelmoneim Elbadry, "Hassaan, El-Badry, O. Atawiyaa & Zalat, : Sedimentology and Chemistry of Eocene Rocks, Maadi Area, Egypt : Science Research Series, Ain Shams Univ., Cairo, V. IV. (1984)", لايوجد, 1900 More
  • Osama Mohamed Abdelmoneim Elbadry, "El-Badry, O. : Contribution on the stratigraphy of Ras Banas, Egypt : Science Research Series, Ain Shams Univ., Cairo V. III, p. 85 95. (1983)", لايوجد, 1900 More
  • Osama Mohamed Abdelmoneim Elbadry, "El Badry, O. & El Sheimi : Sedimentology of Upper Cretaceous Lower Tertiary Rocks, Sinn El Kaddab Scarp, Upper¬ Egypt : Science Research Series, Ain Shams Univ., Cairo, V. III, p. 117 138. (1983)", لايوجد, 1900 More
Tweet