Linking mineral chemistry and radiological risk in rare-metal-bearing monzogranite in Egypt

Abstract

Abstract This study aims to define the mineralogical controls on natural radioactivity and its associated hazards in the El Fereyid monzogranite, Egypt. Integrated petrographic, microchemical, and radiometric analyses identify thorite (containing ≤ 66.1 wt% ThO 2 ), monazite-(Ce) (≤ 10.0 wt% ThO 2 ), and zircon (≤ 1.4 wt% UO 2 ) as the primary carriers of radioactivity. These minerals are responsible for 232 Th and 238 U activities that significantly exceed global averages. Multivariate statistics confirm strong correlations (r > 0.8) between these Th-bearing phases and elevated gamma dose rates. We conclude that the primary magmatic crystallization and subsequent hydrothermal alteration of these accessory minerals create substantial radiological heterogeneity. Although mean radiological hazard indices remain within international safety limits, localized concentrations generate annual effective doses up to 0.7 mSv and annual gonadal dose equivalents of up to 0.9 mSv, necessitating targeted occupational precautions. This work establishes a direct petrogenetic link between rare-metal enrichment and radioactivity, providing a crucial model for resource potential and radiological risk assessment in analogous granitic terrains worldwide.