Sami, Mabrouk, Sanislav, Ioan V., Kumar, Avish A., Abukhadra, Mostafa R., Kamaunji, Vandi Dlama, and Alhejji, Suhail S. (2025) Crystal-Chemical Evolution of Muscovite and Nb–Ta–Y–REE-Bearing Minerals in the Wadi Al-Baroud Granite–Pegmatite System. Minerals, 15 (11). 1206.

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Abstract

The Wadi Al-Baroud granite–pegmatite system in the Eastern Desert of Egypt displays a progressive rare-metal enrichment evident in the crystal chemistry of muscovite mica and associated Nb–Ta–Y–REE oxide minerals. EMP analyses demonstrate that pegmatite-hosted muscovite is systematically enriched in Si, Fe, Mg, and fluorine compared to its granitic counterpart, reflecting crystallization from volatile-rich, highly evolved melts. Columbite group minerals exhibit pronounced fractionation trends, with pegmatitic columbite showing Ta and Mn enrichment and a low Nb/Ta ratio, indicative of late-stage F- and H2O-rich melt evolution and advanced magmatic differentiation. Y–Nb–Ti oxides, especially fergusonite-Y and euxenite-Y, record exceptional enrichment in high-field-strength elements (HFSEs) and heavy rare earth elements (HREEs), further driven by structural focusing and fluid-mediated alteration. These crystal-chemical trends record an extreme fractional crystallization and magmatic–hydrothermal transition, wherein F-rich fluids modified early magmatic minerals and promoted the incorporation of Y, REEs, Th, and U into late-stage oxides. The data indicate a two-stage evolutionary model, in which rare-metal mineralization first occurred through primary magmatic crystallization within the granite, followed by fluid-driven re-equilibration in the pegmatites. This integrated mineral-chemical approach provides a clearer understanding of rare-metal enrichment processes in granite–pegmatite systems and offers refined criteria for identifying exploration targets for Nb, Ta, Y, and HREEs.

Item ID:	89658
Item Type:	Article (Research - C1)
ISSN:	2075-163X
Copyright Information:	© 2025 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
Date Deposited:	19 Nov 2025 02:28
FoR Codes:	37 EARTH SCIENCES > 3705 Geology > 370505 Mineralogy and crystallography @ 40% 37 EARTH SCIENCES > 3705 Geology > 370508 Resource geoscience @ 30% 37 EARTH SCIENCES > 3705 Geology > 370503 Igneous and metamorphic petrology @ 30%
SEO Codes:	28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280107 Expanding knowledge in the earth sciences @ 100%
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