Natural radioactivity of granitoid rocks in a case study from the Northern Egyptian basement complex: insights from gamma ray spectrometry.

Authors

Eman Saad, Mohamed A Soliman, Sobhi M Ghoneim

Published in

Environmental monitoring and assessment. Volume 198. Issue 7. Jul 02, 2026. Epub Jul 02, 2026.

Abstract

This study investigates some granitoid intrusions in the North Eastern Desert of Egypt, specifically at Gabal Gharib area. Image processing of the remote sensing ASTER satellite data enabled updating the geological map of the study area, successfully identifying five distinct granitoid varieties (riebeckite arfvedsonite alkaline granite, alkali feldspar granite, monzogranite, tonalite-granodiorite, and gabbro-diorite association), and guiding the fieldwork and sampling. A total of 14 representative samples were analyzed using gamma ray spectrometry to determine the activity concentrations (Bq/kg) of ⁴⁰K, ²²⁶Ra, ²³²Th, and ²³⁸U. The results show that alkali granite samples exhibit the highest concentrations levels of all four radionuclides, followed by monzogranite, granodiorite, tonalite, and diorite which showed the lowest levels. The elevated radioactivity is primarily attributed to K-bearing minerals (e.g., alkali feldspars and mica minerals) and accessory minerals (e.g., apatite, sphene, zircon, and allanite) whose flexible structure and crystal lattice readily incorporate uranium and thorium. Most of the measured rock samples exceed global average safety limits for all radionuclides, especially ⁴⁰K, with only minor exceptions. We estimated five parameters: radium equivalent (Ra_eq), absorbed dose rate (D), external hazard index (H_ex), internal hazard index (H_in), and radioactivity concentration index (Iγ) to further estimate the possibility of these granitoid rocks to be used as a building material. It is found that the granitoids of Gabal Gharib area generally fall outside the internationally recommended safety limits for construction and building materials. Notably, only the diorite variety is suitable for unrestricted use for indoor or outdoor construction and decorative purposes, whereas alkali granite and tonalite varieties failed to meet the safety requirements for such applications.

PMID:
42387060
Bibliographic data and abstract were imported from PubMed on 02 Jul 2026.

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