The current contribution goal is to measure the distribution of the radionuclide within the exposed rock units of southwestern Sinai, Seih-Sidri area, and assess the radiological risk. Gneisses, older granites, younger gabbro, younger granites, and post granitic dikes (pegmatites) are the main rock units copout in the target area. Radioactivity, as well as radiological implications, were investigated for forty-three samples from gneisses (seven hornblende biotite gneiss and seven biotite gneiss), older granites (fourteen samples), and younger granites (fifteen samples of syenogranites) using NaI (Tl) scintillation detector. External and internal hazard index (H_ex, H_in), internal and external level indices (Iα, Iγ), absorbed dose rates in the air (D), the annual effective dose equivalent (AED), radium equivalent activity (Ra_eq), annual gonadal dose (AGDE), excess lifetime cancer risk (ELCR), and the value of Upper Continental Core ²³²Th/²³⁸U mass fractions were determined from the obtained values of ²³⁸U, ²³²Th and ⁴⁰K for the examined rocks of Seih-Sidri area. The average ²³⁸U mg/kg in hornblende biotite gneiss and biotite gneiss, older granites, and syenogranites is 2.3, 2.1, 2.7, and 8.4 mg/kg, respectively, reflecting a relatively higher concentration of uranium content in syenogranites. The results suggest that using these materials may pose risks to one’s radiological health.

Variable single and/or swarms of post-granitic dikes are widespread at Gabal Serbal, Southwestern Sinai, Egypt. The present article aims to identify and discriminate these multiphase dikes through detailed geological, petrographical, and geochemical examinations. These dikes are classified into two subphases: (1) acidic dikes (porphyritic dacite, microgranite, granophyre, and alkaline granophyre dikes); and (2) basic dikes (basalt and dolerite dikes). They range from vertical or steeply inclined bodies, 0.5–15 m wide, pink to black color, and NE–SW to N–S directions. Acidic dikes with different mineralogical constituents have medium to high k-characters, originating from calc-alkaline magma and extruded in a volcanic arc environment. In contrast, basic dikes have medium k-characters, originating from tholeiitic magma and developing within a plate environment. Basic dikes are enriched with opaque minerals, where the basaltic dike contains iron oxides (magnetite and hematite), such as apatite in addition to copper minerals. Dolerite dike comprises magnetite, titanomagnetite, and pyrite.

High-level natural radioactivity, geochemical, geological, and radiological hazard assessment of the poorly investigated Wadi Gebeiy Dokhan volcanics rocks are discussed. Wadi Gebeiy Dokhan volcanics are located in Southwestern Sinai, Egypt, covering an area of ~1.3 km². Dokhan volcanics rocks are represented by porphyritic dacite. Geochemically, they have medium-k characters and originate from calc-alkaline magma within a volcanics arc environment. Along the fault plane striking NNE-SSW, and at its intersection with the NW-SE fault plane, altered Dokhan volcanics occur with high radioactive anomalies. Radiological parameters (absorbed dose rate, radium equivalent, activity annual effective dose, external and internal hazard indices) are used to evaluate their suitability as an ornamental stone. Except for the absorbed dose rate, all the radiological hazard indices show that unaltered Dokhan volcanics can be used as an ornamental stone. Controversially, the applied radiological indices reveal that altered Dokhan volcanics have a higher content than the recommended values of UNSCEAR, reflecting their risk on human organs.

Beryl mineralization represents one of the most significant gemstones. The radioactive concentrations of ²³⁸U, ²³²Th, and ⁴⁰K in beryl-bearing rocks in South Sinai, Central and South Eastern Desert, Egypt were measured using a portable RS230 gamma spectrometer. ²³⁸U (40 ± 14), ²³²Th (51 ± 19), and ⁴⁰K (1176 ± 277 Bq/kg) are recorded for Ghazala, 54 ± 16, 36 ± 12, and 921 ± 243 Bq/kg for Sedri, 39 ± 15, 27 ± 12, and 842 ± 356 Bq/kg for Igla, 69 ± 16, 34 ± 3, and 1572 ± 83 Bq/kg for Homrit-Akarem, 89 ± 21, 130 ± 16, and 1439 ± 175 Bq/kg for Homrit-Mikpid, and 35 ± 13, 21 ± 12, and 940 ± 645 Bq/kg for Zabara-Um Addebaa. Radiological risk assessment parameters (e.g., annual effective dose, radium equivalent activity) were estimated to deduce the radiation effects on human organs. The obtained results are within acceptable limits.

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.