Radioanalytical Assessment and Mineral Chemistry Investigations in the Pegmatites of Eastern Desert, Egypt: Implications for Mining and Radiation Protection

This study is carried out to investigate the radiological characteristics and mineralogical controls of natural radioisotopes (238U, 226Ra, 232Th, and 40K) in granitic pegmatites from Abu Zawal Area (AZA) in the Eastern Desert of Egypt. The analyzed pegmatites, containing thorite, zircon, monazite, ferrocolumbite, and fergusonite, exhibit exceptionally high radioactivity concentrations of 238U ≤ 568; 232Th ≤ 674; 226Ra ≤ 170 (Bq kg−1), significantly exceeding the world average permissible limits (35, 30, 30, and 400 Bq kg−1 for 238U, 226Ra, 232Th, and 40K, respectively). Comprehensive radiological assessment reveals severely elevated radiological impact associated with Raeq ≤ 1243 (Bq kg−1) and hazard indices (Hex≤ 3.36; ELCR ≤ 12.2 × 10−3) surpassing international safety thresholds (Hex ≤ 1; ELCR ≤ 1 × 10−3). The observed disequilibrium between 238U and 226Ra (with 226Ra activities approximately half those of 238U) is attributed to the geochemical mobility of radium and potential selective leaching during late-stage hydrothermal alteration, while the overall enrichment of the uranium series over the thorium series is linked to the predominance of uranium-bearing minerals like zircon and fergusonite in these pegmatites. Mineralogical analysis demonstrates distinct radiation patterns: thorite and monazite dominate Th-derived gamma radiation and radon/thoron exhalation, while zircon and fergusonite control U enrichment and decay chain disequilibrium. Notably, nominally low-activity minerals like ferrocolumbite contribute to localized radiation hotspots through U/Th co-concentrations. The calculated absorbed dose rates ranged from 182 to 978 (nGy h−1) and annual effective doses show extreme spatial variability correlated with Th-rich mineral assemblages.