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

Kamal A. Ali, Abdel Kader M. Moghazi, Ayman E. Maurice, Sayed A. Omar, Qiang Wang, Simon A. Wilde, Ewais M. Moussa, William I. Manton, Robert J. Stern

Research output: Contribution to journalArticlepeer-review

66 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)1705-1722
Number of pages18
JournalInternational Journal of Earth Sciences
Volume101
Issue number7
DOIs
Publication statusPublished - Oct 2012
Externally publishedYes

Keywords

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

ASJC Scopus subject areas

  • General Earth and Planetary Sciences

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