## 4 Results and Discussion
### Analysis of Radionuclides  
Gamma-ray spectrometry is a powerful, non-destructive analytical tool for the qualitative and quantitative determination of gamma emitters [20]. The specific activity (activity per unit mass) is the number of atomic decays per unit time per unit mass. It is used to describe the radionuclide contents of rocks and building materials [23] and is expressed in becquerel per kilogram (Bq kg\({}^{-1}\)), where 1% K = 313 Bq kg\({}^{-1}\), 1 ppm U = 12.35 Bq kg\({}^{-1}\) and 1 ppm Th = 4.06 Bq kg\({}^{-1}\) as recommended by [24]. The calculated activity values of \({}^{238}\)U, \({}^{226}\)Ra, \({}^{232}\)Th and \({}^{40}\)K radionuclides, expressed in Bq kg\({}^{-1}\), are given in Table 1 for the twenty-nine different samples of Aswan granites investigated in this work. The average values of the radioelements worldwide are 33 Bq kg\({}^{-1}\) for \({}^{238}\)U, 45 Bq kg\({}^{-1}\) for \({}^{232}\)Th, and 412 Bq kg\({}^{-1}\) for \({}^{40}\)K ([PERSON], 2008). The activity concentration values for the studied samples ranged from 12 to 148 Bq kg\({}^{-1}\) for \({}^{238}\)U. About seventeen samples exceeded the worldwide average specific activity of \({}^{238}\)U, and the samples with the highest value were Red Nefertiti (123.5 Bq kg\({}^{-1}\)), Gandolla (111.2 Bq kg\({}^{-1}\)), Light Rose (86.45 Bq kg\({}^{-1}\)), and Forsan (74.1 Bq kg\({}^{-1}\)). The P-factor of the investigated granitic samples was calculated (Table 1). It is clear that most values of the P-factor of the studied samples are more than one, referring to a possible loss of radon or radium, which can be indicated by a U/Ra average value up to 1.9. The U/Th ratio varied from 0.2 to 9.1 with an average of up to 1.4 and higher than the range commonly recorded for granites (0.08-0.50) [25,26]. This high ratio may reflect the enrichment of the studied granites with some accessory minerals, such as uranophane, autunite, monazite, zircon, and xenotime. Th/U ratio varied from 0.1 to 6.6 with 1.9 as the average content (Table 1). The crustal average content of Th/U ratio was nearly 3; in these granitic rocks, the wide range of Th/U ratio (0.1 and 6.6) suggests that the enrichment of uranium and thorium is related to hypogene fluids, which cause the enrichment of uranium and thorium by the same ratio. The disturbance of the Th/U ratio (less than 3) indicates that the uranium enrichment is higher than that of thorium, due to the greater stability of thorium than uranium in the secondary environment. Figure 4: Photomicrographs for Aswan granite showing: (**a**) Deformed crystal of zircon associating biotite, hornblende and quartz, CN; (**b**) euhedral crystal of zircon in BI, CN; (**c**) zoned crystal of metamict allanite associating perthite, plagioclase, and opaque, CN; (**d**) well-formed crystals of titanite with prismatic and sphenoidal forms (sphene), CN; (**e**) well-formed crystals of titanite with sphenoidal forms (sphene) associating antiperthite, CN; (**f**) secondary epidote associating plagioclase and quartz, CN. The activity concentration values of \({}^{232}\)Th ranged from 4 to 97 Bq kg\({}^{-1}\). Comparing the activities of \({}^{232}\)Th of the studied samples with the average worldwide data [27], it appears that nineteen samples exceeded the value of 45 Bq kg\({}^{-1}\), and the highest values are for Dark Rosa (75.11 Bq kg\({}^{-1}\)), Red Aswan (71.73 Bq kg\({}^{-1}\)), Gandolla and Forsan (69.02 Bq kg\({}^{-1}\)). As far as the specific activities of \({}^{40}\)K are concerned, the Royal, Red Aswan, Red Nefertiti, Forsan, and Gandolla samples displayed the highest average values (1305, 1271, 1246, 1199, and 1178 Bq kg\({}^{-1}\), respectively) and exceeded the average granite value for \({}^{40}\)K, which is 1104 Bq kg\({}^{-1}\)[28]. The activity concentrations of \({}^{226}\)Ra for the studied granite samples ranged from 11 to 89 Bq kg\({}^{-1}\) within an average value of 32 Bq kg\({}^{-1}\).