Homret Ghannam Post‐collisional Granites in the Eastern Desert of Egypt: Petrogenesis, Geodynamic Evolution, and Rare‐metal Significance

Abstract

Abstract Homret Ghannam alkali feldspar granite (HGAFG) in the central Eastern Desert (CED) of Egypt represents a distinctive example of late Neoproterozoic magmatism in the Arabian‐Nubian Shield (ANS). This study integrates field observations, petrography, mineral chemistry (EMPA), and whole‐rock geochemistry to investigate its petrogenesis, geodynamic evolution, and rare‐metal potential. HGAFG comprises two cogenetic varieties, alkali feldspar granite and riebeckite‐bearing granite, hosting rare‐metal minerals such as zircon, fluorite, columbite and apatite. HGAFG exhibits diagnostic A‐type geochemical characteristics, including high SiO 2 contents (73.81–77.86 wt%), metaluminous to mildly peralkaline composition (ASI: 0.92–1.03), enrichment in HFSE (Zr ≈ 791.80 ppm, Nb ≈ 68.12 ppm, Y ≈ 90.81 ppm) and ΣREE (103.40–475.57 ppm), and pronounced negative Eu anomalies (Eu/Eu * = 0.07–0.20). Zircon saturation thermometry yields high crystallization temperatures ( T Zr ≈ 908.87°C) and low emplacement pressures (1.46 kbar) under reducing conditions (ƒO 2 ≈ –11.5). The mineralogical and geochemical results reveal that HGAFG originated from a hybrid, fluorine‐rich magma generated by anatexis of lower crust, followed by extensive fractional crystallization, during late post‐collisional extension associated with lithospheric delamination. The reduced nature and fluorine enrichment of HGAFG magma promoted the mineralization of Nb–Ta–REE phases, highlighting its significance as a fertile, high‐temperature product of the terminal magmatic stage in ANS evolution.