International Journal of Earth Sciences

, Volume 101, Issue 7, pp 1705–1722

Composition, age, and origin of the ~620 Ma Humr Akarim and Humrat Mukbid A-type granites: no evidence for pre-Neoproterozoic basement in the Eastern Desert, Egypt

Authors

    • Department of Mineral Resources and Rocks, Faculty of Earth SciencesKing Abdulaziz University
    • Geosciences DepartmentUniversity of Texas at Dallas
  • Abdel-Kader M. Moghazi
    • Department of Mineral Resources and Rocks, Faculty of Earth SciencesKing Abdulaziz University
    • Department of Geology, Faculty of ScienceAlexandria University
  • Ayman E. Maurice
    • Geology Department, Faculty of ScienceBeni Suef University
  • Sayed A. Omar
    • Nuclear Material Authority
  • Qiang Wang
    • State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of GeochemistryChinese Academy of Sciences
  • Simon A. Wilde
    • Department of Applied GeologyCurtin University
  • Ewais M. Moussa
    • Nuclear Material Authority
  • William I. Manton
    • Geosciences DepartmentUniversity of Texas at Dallas
  • Robert J. Stern
    • Geosciences DepartmentUniversity of Texas at Dallas
Original Paper

DOI: 10.1007/s00531-012-0759-2

Cite this article as:
Ali, K.A., Moghazi, A.M., Maurice, A.E. et al. Int J Earth Sci (Geol Rundsch) (2012) 101: 1705. doi:10.1007/s00531-012-0759-2

Abstract

The Humr Akarim and Humrat Mukbid plutons, in the central Eastern Desert of Egypt, are late Neoproterozoic post-collisional alkaline A-type granites. Humr Akarim and Humrat Mukbid plutonic rocks consist of subsolvus alkali granites and a subordinate roof facies of albite granite, which hosts greisen and Sn–Mo-mineralized quartz veins; textural and field evidence strongly suggest the presence of late magmatic F-rich fluids. The granites are Si-alkali rich, Mg–Ca–Ti poor with high Rb/Sr (20–123), and low K/Rb (27–65). They are enriched in high field strength elements (e.g., Nb, Ta, Zr, Y, U, Th) and heavy rare earth elements (La n /Yb n  = 0.27–0.95) and exhibit significant tetrad effects in REE patterns. These geochemical attributes indicate that granite trace element distribution was controlled by crystal fractionation as well as interaction with fluorine-rich magmatic fluids. U–Pb SHRIMP zircon dating indicates an age of ~630–620 Ma but with abundant evidence that zircons were affected by late corrosive fluids (e.g., discordance, high common Pb). εNd at 620 Ma ranges from +3.4 to +6.8 (mean = +5.0) for Humr Akarim granitic rocks and from +4.8 to +7.5 (mean = +5.8) for Humrat Mukbid granitic rocks. Some slightly older zircons (~740 Ma, 703 Ma) may have been inherited from older granites in the region. Our U–Pb zircon data and Nd isotope results indicate a juvenile magma source of Neoproterozoic age like that responsible for forming most other ANS crust and refute previous conclusions that pre-Neoproterozoic continental crust was involved in the generation of the studied granites.

Keywords

U–Pb zircon dating A-type granite Neoproterozoic Nd isotopes Arabian-Nubian Shield

Supplementary material

531_2012_759_MOESM1_ESM.pdf (46 kb)
Supplementary material 1 (PDF 47 kb)

Copyright information

© Springer-Verlag 2012