Reworked Neoproterozoic sub-arc lithosphere beneath the Eastern Desert (Egypt): Evidence from geochemistry and geochronology of metabasites and granitoid gneisses, Gabal Um Gunud area

Mohamed A. Abd El-Wahed, Mohamed M. Hamdy, Kamal A. Ali, Ahmed E. Ayad, Armin Zeh, Basem Zoheir, Minghua Ren, Petros Koutsovitis

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

High-grade granitoid gneisses (740–710 Ma) and elongate bodies of amphibolite and hornblende schist with cm-scale layers of garnet pyroxenite form an overturned fold in the Gabal Um Gunud area, South Eastern Desert of Egypt. Whole-rock geochemical data combined with zircon U-Pb-Hf isotope data suggest that the metabasites represent relics of oceanic crust with an N-MORB affinity, which has been derived from partial melting (2.0–1.4 GPa; ~65- ~ 45 km depth) of a depleted mantle source beneath an intra-oceanic, spreading forearc basin. Such increment of melting degree resulted in small basaltic melt batches with transitional tholeiitic to boninitic affinities. Progressive slab subduction and partial melting of the tholeiitic amphibolite produced high-Al and low HREE melts for trondhjemite at av. T = 854°C and low-Al and high HREE melts for tonalite at higher temperatures (av. 949°C). The low Mg# of the trondhjemite-tonalite rocks may be attributed to limited contamination of subduction components, as evidenced by the weak lanthanide tetrad effects (TE1,3~1) and near-chondritic Zr/Hf, Nb/Ta, and Y/Ho ratios, while the garnet pyroxenite was the residuum produced in equilibrium with the trondhjemite-tonalite melts.

Original languageEnglish
Pages (from-to)702-733
Number of pages32
JournalInternational Geology Review
Volume66
Issue number3
DOIs
Publication statusPublished - 2024

Keywords

  • Amphibolites
  • Arabian-Nubian Shield (ANS)
  • Gneisses
  • Mantle-derived N-MORB
  • Sub-arc
  • Trondhjemite-tonalite (TT)

ASJC Scopus subject areas

  • Geology

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