首页|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

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

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  • NSTL
  • Elsevier
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 postDokhan 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 similar to 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 similar to 660 Ma for the subduction-related Dokhan andesite and dacite, reflecting a magmatic arc lifespan longer than previously considered. The change of setting from subduction to post-collisional was accompanied by an increased role of crustal sources in the generation of the felsic magmas, resulting in differentiation of the accreted arc crust.

NeoproterozoicSubductionMature island arcDokhan volcanicsFelsitesEastern Desert of Egypt

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

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Helwan Univ, Fac Sci, Geol Dept, Cairo 11795, Egypt

Curtin Univ, Sch Earth & Planetary Sci, POB U1987, Perth, WA 6845, Australia

United Arab Emirates Univ, Coll Sci, Dept Geol, Abu Dhabi, U Arab Emirates

Elmergib Univ, Fac Sci, Geol Dept, Elmergib, Libya

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2021

10.1016/j.precamres.2021.106148

Precambrian Research

Precambrian Research

SCI
ISSN：0301-9268
年,卷(期)：2021.358
  • 6
  • 93