Genesis and Geochemical Evolution of the Beryl Mineralization in the Igla Tin Mine, Central Eastern Desert, Egypt: Insights from Geochemistry and Raman Spectroscopy

The Igla Tin Mine in the Central Eastern Desert of Egypt hosts significant beryl mineralization associated with zoned granitic pegmatites and greisenized granites of the Arabian-Nubian Shield (ANS). The investigated beryl preserves a complete record of magmatic, transitional, and hydrothermal processes associated with the evolution of rare-metal A-type granites. Integrated EPMA, LA-ICP-MS, SIMS, and Raman spectroscopy reveal systematic core-rim chemical and structural variations that constrain the origin and modification of beryl and its relationship to cassiterite-wolframite mineralization. Trace-element variations (Fe²⁺/Fe³⁺, V³⁺, and alkali contents) account for the observed color range from pale green to white and yellowish brown. Raman spectroscopy further supports these variations, showing that color changes correspond to lattice distortions, trace-element substitutions, and fluid inclusion effects acquired during late-magmatic to hydrothermal evolution. Magmatic cores are characterized by low Fe, Mg, Cs, and H2O and minimal Raman band displacement, indicating crystallization from a moderately evolved, low- H2O leucogranitic melt. Transitional zones show progressive increases in Fe, Mg, Cs, Sc, and estimated H2O, together with subtle Raman shifts that reflect fluid exsolution and incipient greisenization. Hydrothermal rims exhibit the highest Fe³⁺, Cs, and H2O contents, incorporation of fluid-mobile elements (V, Sc), and diagnostic Raman features consistent with low-temperature alteration. Multivariate elemental relationships (Li-Cs, Mg/Mg+Fe-Fe, Cs-Na) demonstrate clear fractionation trends, incompatible-element enrichment, and fluid-rock interaction along pegmatite and greisen pathways. Genetically, beryl crystallized early from the granitic melt, was modified during Sn-bearing fluid exsolution, and underwent late overprinting by oxidizing W-bearing hydrothermal fluids. The combined chemical, spectroscopic, and textural evidence defines a robust genetic model linking beryl evolution to the magmatic-hydrothermal transition of rare-metal granites and clarifies the timing relationships between Be, Sn, and W mineralization at Igla. Compared with other Egyptian beryl deposits (Abu Dabbab, Nuweibi, Wadi Sikait), Igla is distinguished by its association with Sn mineralization and very low Cr levels, whereas globally it shares features with Ural and Madagascar pegmatites but exhibits its own distinct trace-element and fluid evolution signatures.