Unraveling the Genesis of Highly Fractionated Rare-Metal Granites in the Nubian Shield via the Rare-Earth Elements Tetrad Effect, Sr-Nd and Mineral

Sami M., Monsef M. A. E., Abart R., TOKSOY KÖKSAL F., Abdelfadil K. M.

ACS EARTH AND SPACE CHEMISTRY, cilt.6, sa.10, ss.2368-2384, 2022 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 6 Sayı: 10
  • Basım Tarihi: 2022
  • Doi Numarası: 10.1021/acsearthspacechem.2c00125
  • Dergi Adı: ACS EARTH AND SPACE CHEMISTRY
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Geobase
  • Sayfa Sayıları: ss.2368-2384
  • Anahtar Kelimeler: tetrad effect, Sr-Nd isotopes, rare-metal granites, magmatic-hydrothermal fluids, Nb-Ta-Sn mineralization, Abu Dabbab, A-TYPE GRANITES, GEOCHEMICAL CONSTRAINTS, MAGMATIC FRACTIONATION, PERALUMINOUS GRANITES, ELECTRON-MICROPROBE, TOPAZ-BEARING, NANLING RANGE, ORE DISTRICT, TA, CHINA
  • Orta Doğu Teknik Üniversitesi Adresli: Evet

Özet

The rare-metal granites of the Nubian Shield are commonly associated with Nb-Ta and Sn mineralization. The magmatic and hydrothermal evolution of these granites and their relation to the Nb-Ta and Sn mineralization need further investigations. This study reports new mineral chemistry, whole rock geochemical, and Sr-Nd isotopic data for the Abu Dabbab granites in the Central Eastern Desert of Egypt to provide new insights into the formation mechanisms of the granites and their associated rare-metal mineralization. The granites consist mainly of albite, orthoclase, quartz, and Li-phengite, with accessory minerals including cassiterite, columbite, tantalite, wodginite, and Hf-zircon. Geochemically, they are peraluminous with high SiO2, alkalis, Rb, Nb, Ta, Sn, F, and low contents of MgO, CaO, and P2O5. The granites are characterized by distinct rare-earth element tetrad effects (TE1,3 = 1.8-2.5), with strongly negative Eu anomalies and are extremely depleted in Ba, Sr, P, and Ti. These features imply that they are typical muscovite peraluminous highly evolved granites. Isotopically, they display positive epsilon Nd(t) values (+1.11 to +8.32) and two-stage Nd depleted model ages (tDM2) between 0.68 and 1.13 Ga, suggesting a juvenile magma source of the Neoproterozoic age. The Abu Dabbab granites could be formed by dehydration melting of muscovite-rich crustal materials followed by extensive fractional crystallization with a significant role of magmatic-hydrothermal fluids during the transitional orogenic stage of the Nubian Shield.