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    Sr-Nd isotopes and geochemistry of granite-gneiss complexes from the Meatiq and Hafafit domes, Eastern Desert, Egypt: No evidence for pre-Neoproterozoic crust

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    Authors
    Liégeois, J.P.
    Stern, R.J.
    Discipline
    Earth and related Environmental sciences
    Subject
    Geodynamics and mineral resources
    Audience
    Scientific
    Date
    2010
    Publisher
    Elsevier
    Metadata
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    Description
    Neoproterozoic gneisses at Meatiq and Hafafit in the Eastern Desert of Egypt give Rb-Sr and U-Pb zircon ages of 600-750 Ma. These gneisses are interpreted by different workers to represent deeper levels of juvenile Neoproterozoic crust or Archaean/Palaeoproterozoic crust that was remobilized during Neoproterozoic time. Geochemical and Sr-Nd isotope compositions for these gneisses reported here are remarkably homogeneous: Initial 87Sr/86Sr (0.70252 ± 0.00056) and eNd (+6.4 ± 1.0). These values are best explained as reflecting derivation from depleted asthenospheric mantle sources during Neoproterozoic time, consistent with mean Nd model ages of 0.70 ± 0.06 Ga. The increasing recognition of old, xenocrystic zircons in juvenile ANS igneous rocks can be explained in several different ways. The participation of ancient crust is allowed as one of the explanations, but it is the isotopic composition of radiogenic elements such as Sr and Nd for whole-rock specimens that are the most reliable indicators of whether or not a given crustal tract is juvenile or reworked older crust. These isotopic data indicate that the protolith for the Meatiq and Hafafit gneisses were juvenile Neoproterozoic igneous rocks and sediments derived from them. There is no support in the isotopic data for any significant contribution of pre-Neoproterozoic crust in these two sections of Eastern Desert crustal infrastructure
    Citation
    Liégeois, J.P.; Stern, R.J. (2010). Sr-Nd isotopes and geochemistry of granite-gneiss complexes from the Meatiq and Hafafit domes, Eastern Desert, Egypt: No evidence for pre-Neoproterozoic crust. , Journal of African Earth Sciences, Vol. 57, 31-40, Elsevier, DOI: 10.1016/j.jafrearsci.2009.07.006.
    Identifiers
    uri: https://orfeo.belnet.be/handle/internal/779
    doi: http://dx.doi.org/10.1016/j.jafrearsci.2009.07.006
    Type
    Article
    Peer-Review
    Yes
    Language
    eng
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