Rare metals bearing pegmatites in the Nubian Shield: A case study of Ras Al-Baroud area, Eastern Desert of Egypt

Matta, Marian G.; Azer, Mokhles K.; Darwish, Mahmoud H.

doi:10.21608/nujbas.2024.259338.1020

Rare metals bearing pegmatites in the Nubian Shield: A case study of Ras Al-Baroud area, Eastern Desert of Egypt

Document Type : Original papers

Authors

¹ Geology Department, Faculty of Science, New Valley University, 72511 El-Kharga, Egypt

² Geological Sciences Department, National Research Centre, 12622 Dokki, Cairo, Egypt

10.21608/nujbas.2024.259338.1020

Abstract

Abstract
This study documents the geochemical evolution of rare-metal mineralized granitic pegmatite of Ras Al-Baroud using mineral chemistry and whole rock chemistry. Pegmatite occurs as sheet-like bodies, pockets along the edges of the Ras Al-Baroud post-collisional granite, or within fault zones. Pegmatites at the outer margins of Ras Al-Baroud granites show gradational boundaries. In a few outcrops, the Ras Al-Baroud pegmatites are affected by intense metasomatic-hydrothermal alteration resulting in albitization and greisenization: especially close to the contact with the host rocks. Nb-Ta oxides are the most important rare metals in the Ras Al-Baroud pegmatite and are represented mainly by columbite and less amount of tantalite. They are commonly zoned, exhibiting a wide range of chemical compositions and are characterized by partial digestion and late-stage overgrowth due to the effecting of magmatic and hydrothermal processes in the granite-pegmatite system. Ras Al-Baroud pegmatite is considered to mainly crystallize late from a pegmatite-forming melt that resulted from a combination of magmatic and hydrothermal processes. Extended fractional crystallization in Ras Al-Baroud granites eventually produced saturated, late-magmatic magmatic fluids. These fluids migrated towards the apex of the magma chamber, reacting with still-hot but subsolidus granite and becoming increasingly focused into distinct channels and veins. This upward and outward mode of fluid migration led to pegmatites with gradational boundaries.

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