Rare-metal granites of Nuweibi and Abu Dabbab,
central Eastern Desert of Egypt, have mineralogical and geochemical
specialization. These granites are acidic, slightly
peraluminous to metaaluminous, Li–F–Na-rich, and Sn–Nb–
Ta-mineralized. Snowball textures, homogenous distribution
of rock-forming accessory minerals, disseminated mineralization,
and melt inclusions in quartz phenocrysts are typical
features indicative of their petrographic specialization.
Geochemical characterizations are consistent with low-P-rare
metal granite derived from highly evolved I-type magma in
the late stage of crystallization. Melt and fluid inclusions were
studied in granites, mineralized veins, and greisen. The study
revealed that at least two stages of liquid immiscibility played
an important role in the evolution of magma–hydrothermal
transition as well as mineral deposition. The early stage is
melt/fluid case. This stage is represented by the coexistence of
type-B melt and aqueous-CO2 inclusions in association with
topaz, columbite–tantalite, as well as cassiterite mineral inclusions.
This stage seems to have taken place at the late magmatic
stage at temperatures between 450 °C and 550 °C. The
late magmatic to early hydrothermal stage is represented by
vapor-rich H2O and CO2 inclusions, sometimes with small
crystallized silicic melt in greisen and the outer margins of the
mineralized veins. These inclusions are associated with beryl,
topaz, and cassiterite mineralization and probably trapped at
400 °C. The last stage of immiscibility is fluid–fluid and
represented by the coexisting H2O-rich and CO2-rich inclusions.
Cassiterite, wolframite ± chalcopyrite, and fluorite are
the main mineral assemblage in this stage. The trapping temperature
was estimated between 200 °C and 350 °C. The latest
phase of fluid is low-saline, low-temperature (100–180 °C),
and liquid-rich aqueous fluid.