The Wadi Khashab area in the southern Nubian Shield of Egypt records the transition from subduction-related to post-collisional magmatism, representing a major phase in the evolution of the Arabian-Nubian Shield. Understanding the geochemistry of uranium (U) and thorium (Th) is crucial for tracking magmatic and post-magmatic processes, as these radioactive elements provide valuable insights into crustal evolution. This study integrates field observations, petrography, whole-rock geochemistry, and gamma-ray spectrometric analyses of U and Th to clarify the petrogenesis and geodynamic setting of the granitic rocks. Two distinct magmatic pulses were identified: an older calc-alkaline suite (quartz diorite, tonalite, granodiorite) with low high-field-strength elements (HFSE: Nb = 8-20 ppm, Zr ∼200 ppm) and I-type characteristics, formed in a volcanic arc; and a younger suite of A-type biotite granites and altered varieties (albitized and greisenized), characterized by high SiO2 and enrichment in incompatible elements. Geochemical modeling suggests that the older suite originated from the hybridization of mantle-derived melts with mafic lower crust, while the younger suite was derived from partial melting of the crust. U-Th geochemistry indicates that magmatic fractionation was overprinted by hydrothermal fluids, leading to significant uranium enrichment in the altered granites, with average contents of 16.2 ppm in albitized and 13.6 ppm in greisenized varieties. These altered granites are classified as uraniferous, with U and Th mainly hosted in resistant accessory minerals. This study links U-Th mobility to specific post-emplacement alteration events, providing new insights into post-accretionary fluid-driven processes in the Nubian Shield and highlighting the area's potential for uranium mineralization.
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