Geochronology and petrogenesis of the Cryogenian Sukari granite intrusion, Central Eastern Desert, Egypt: Inferences from whole rock geochemistry, zircon U-Pb-Hf isotopes and trace elements

Document Type : Research article

Authors

1 Geology Department, Faculty of Science, Alexandria University

2 Sukari Gold Mine Ltd

Abstract

The Sukari granite intrusion is a trondhjemite-granodiorite-granite suite in the Central Eastern Desert of Egypt. Its rocks are calc-alkaline and slightly metaluminous to peraluminous. On variation diagrams, general trends of decreasing Al2O3, TiO2, Fe2O3t, MgO, CaO, and Sr and increasing Th are observed. The REE patterns are slightly fractionated {(La/Yb)N = 1.89–2.24} with moderate negative Eu (Eu/Eu* = 0.33 – 0.58) anomalies. On primitive-mantle trace element diagrams, the granites are depleted in Nb, Ta, Sr, and Ti. These geochemical traits suggest that the Sukari granites were evolved by fractional crystallization of plagioclase and ferromagnesian minerals in a subduction-related tectonic environment. Zircons separated from the Sukari granites are characterized by HREE enrichment, positive Ce- and negative Eu- anomalies, and crystallization temperatures in the range of 606 - 819°C, which are typical of magmatic zircons. Zircon U–Pb-Hf analyses of the Sukari granite reveals an emplacement age of 676.5 ± 1.3 Ma, positive ɛHf(t) ( +10.7 to +16.2), single-stage Hf model age (TDM) of 608-838 Ma, and two-stage Hf model age (TDMc) of 574 - 920 Ma. The positive ɛHf(t) and the Hf-TDMc ages, which are close to the U–Pb crystallization ages, in addition to the absence of zircon inheritance indicate that the protolith of the Sukari granite was juvenile. A combined examination of the whole rock geochemistry and isotope signatures suggests that the parent magma of the Sukari granite was formed by partial melting of a depleted mantle source with lower crustal contribution in a subduction-related tectonic environment.

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