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The Nuweibi area (7.5 km2) is located towards NW Marsa Alam City, central Egyptian Nubian Shield. It constitutes ophiolite assemblages (serpentinites, metagabbros), Tuffaceous metasediments, granodiorite–tonalite, and Late Ediacaran albite granite. The present study mainly focuses on determination of the concentrations of specific elements and their interrelationships to 238U, 232Th, and 40K for the granitic rocks. The radiometric measurements have been performed using a high-purity germanium (HPGe) detector and a portable RS-230 γ-ray spectrometer in combination with chemical analysis using ICP-MS. The radionuclide values measured with a ground gamma-ray detector are more than twice those recorded using both HPGe spectroscopic and chemical analysis methods. On the other hand, the chemical data given by many correlations between U, Th, and K as well as selected major, trace, and rare earth elements suggest the occurrence of the magmatic process followed by Na-metasomatic albitization in albite granite. This process caused redistribution and remobilization of U, as follows the facts that eTh/eU exceeds 3 and the average eTh/eU ratio of albite granites exceeds the Clark's value (3.5). On the other hand, the higher eTh contents of the albite granites reflect additional contribution from Th-bearing minerals, and in most sampling sites the 232Th/226Ra activity ratios are higher than the natural equilibrium ratio, 1.1, indicating possible enrichment process of these radionuclides as a result of alkali metasomatism. [ABSTRACT FROM AUTHOR]

The North Abu Rusheid area in Egypt is a well-known high background natural radiation area (HBNRA) due to the existence of naturally occurring radioactive materials (NORMs) in mylonitic rocks. In this study, 27 rock samples were selected for dose estimation studies. 238 U and 232 Th were measured using inductively coupled plasma mass spectrometry (ICP-MS) and 40 K was measured using sodium iodide (thallium) gamma-ray spectroscopy. The ranges of activity concentrations (Bq/kg) of 238 U, 232 Th and 40 K in the samples varied from 270 ± 2 to 2120 ± 29, 350 ± 2 to 1840 ± 27 and 20 ± 2 to 1390 ± 35 with mean values of 980 ± 349, 770 ± 351, and 640 ± 402 Bq/kg, respectively. The radiological hazard parameters were estimated from activity concentrations of 238 U, 232 Th and 40 K and compared to United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) values. The present study revealed that the hazard parameters were several times higher than the worldwide averages. The U/Th concentration ratio ranged from 0.7 to 3 and could be attributed to the presence of kasolite, uranothorite, zircon, and columbite in mylonitic rocks. From the radiological protection viewpoint, it is necessary to monitor natural radionuclides in these rocks prior to their use in residential and commercial construction materials., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)