Cryogenian accretion of the Northern Arabian-Nubian shield: Integrated evidence from central Eastern Desert Egypt
Peng Peng, Mohamed Metwaly ABU ANBAR, Xiao‐Fang He, Xu Liu, Zhaoyuan Qin
Abstract
Accretionary geology of the Arabian-Nubian shield (ANS) is critical in deciphering the Neoproterozoic global tectonics. Multidiscipline investigation of ophiolites, sediments, and igneous units of central Eastern Desert Egypt results in a revisited tectono-magmatic scenario. The first baddeleyite U-Pb age (ca. 687 Ma ) of the ANS ophiolites is obtained from the layered gabbro of the Wadi Ghadir ophiolite, which limits the back-arc spreading age. Significant Archean-Paleoproterozoic detrital zircon age spectrum, similar to those of the Saharan-Congo craton, is identified from a conglomerate of the Atud turbidites, indicating the existence of craton basement in the shield. Significant ca. 840 Ma and ca. 750 Ma detrital zircon ages with a mixing of juvenile and ancient Hf isotope features approve the provenances to be arc(s) with craton basement. Two episodes of calc-alkaline units represented by the Umm Rus complex (URC) and the El Sibai complex (ESC) are dated at ca. 680 Ma and ca. 660 Ma , respectively. They were both originated from juvenile sources ( in situ zircon ɛHf t = +6.1 ∼ +12.2) with depleted high-strengthen field elements (e.g., Nb, Ta, Zr, Hf) but enriched large ion lithophile (e.g., Ba, Sr) and radiogenic elements (e.g., Th, U). The Ti-in-zircon temperature of the ESC granitoids (696 ± 16 °C ) is lower than that of the older URC (749 ± 21 °C ), as well as the inferred ca. 840 Ma and ca. 750 Ma arcs; and this reconciles an increased hydrous melting during the final Gondwana assembly. The older plutons represented by the URC show an E-W elongated distribution consistent with the alignment of the regional imbricated thrusting; whereas the elongation of the younger generation represented by the ESC is N-NE to S-SW and is coherent with the axis of the core complexes and the major strike-slip faults of the region. This possibly coincides a direction-change of paleo-subduction. In summary, the Northern ANS likely represents a superimposed arc accreted at 680–660 Ma during the closure of the Mozambique ocean.