Subduction to post-collisional volcanism in the Northern Arabian-Nubian shield: Genesis of Cryogenian/Ediacaran intermediate-felsic magmas and the lifespan of a Neoproterozoic mature island arc

Ayman E. Maurice, Moustafa E. Gharib, Simon A. Wilde, Kamal A. Ali, Madiha S.M. Osman

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

The Neoproterozoic intermediate-felsic volcanic rocks in the Wadi Ambagy area, Eastern Desert of Egypt, comprise three units: Dokhan intermediate-felsic volcanics, post-Dokhan felsic volcanics and felsites. The Dokhan lavas are generally porphyritic and composed of andesite and dacite with subordinate basalt, whereas the post-Dokhan felsic volcanics are represented by phyric and aphyric rhyolites. The medium-K calc-alkaline nature, LILE enrichment, Ta-Nb anomalies and LREE-enriched patterns of the Dokhan volcanic rocks are consistent with development in a subduction setting. Arc crustal thickness estimation using average (La/Yb)n is ~ 32 km, indicating that these rocks were generated in a Neoproterozoic island arc with thick crust. The subduction magmas were generated by hydrous mantle melting and they evolved by fractional crystallization. In contrast, the post-Dokhan felsic volcanics and felsites have medium- to high-K and shoshonitic affinities, respectively. They are highly silicic with weak to absent Ta-Nb anomalies and significant Nb, Zr, Hf and REE enrichment, which increases from the post-Dokhan felsic volcanics to the felsites. These geochemical features suggest generation in a post-collisional to within-plate tectonic setting by partial melting of mafic or intermediate arc crustal sources. SHRIMP U-Pb zircon dating indicates a crystallization age of ~ 660 Ma for the subduction-related Dokhan andesite and dacite, reflecting a magmatic arc lifespan longer than previously considered.

Original languageEnglish
Article number106148
JournalPrecambrian Research
Volume358
DOIs
Publication statusPublished - Jun 15 2021

Keywords

  • Dokhan volcanics
  • Eastern Desert of Egypt
  • Felsites
  • Mature island arc
  • Neoproterozoic
  • Subduction

ASJC Scopus subject areas

  • Geology
  • Geochemistry and Petrology

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