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Jean-Paul Liégeois
Earth Sciences
Geodynamics and mineral resources
Geodynamics and mineral resources
Publication details
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 57: 31-40. Amsterdam : Elsevier. DOI: 10.1016/j.jafrearsci.2009.07.006. I.F. 1.219.
Article in a scientific Journal / Article in a Journal
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