## 6 Discussion
### Petrogenesis of the Jabal Al Bayda Granitic Magma
Therefore, we can divide the Jabal al Bayda granitiods into two groups: the high-K calc-alkaline I-type monzogranites, and shoshonite A-type alkali granites and some of monzogranites. The two groups of granites are clearly distinguished in Figure 9b, in which one can also see a trend from older I-types to younger A-types in the studied region. By plotting the CaO/(MgO + FeO\({}_{\text{total}}\)) vs. Al\({}_{2}\)O\({}_{3}\)/(MgO + FeO\({}_{\text{total}}\)) ratios of the studied samples (Figure 9e), it is possible to determine the likely source of the magmas that formed the Jabal Al Bayda granitic rocks. Most of the Jabal Al Bayda granitiods are plotted in metapelite and metagraywackes source fields, supporting a continental crustal source. Tonalite and metasediments as crustal sources were also suggested for numerous alkaline A-type granites in the ANS [43; 71]. According to the information provided, it can be concluded that the 'high-Ca' monzogranite and 'low-Ca' alkali granite at the Jabal Al Bayda have different sources and likely originated from distinct types of protoliths. The 'high-Ca' monzogranite is interpreted to represent partial melts of magma derived from clay-poor, plagioclase-rich greywackes sources, with a contribution of tonalitic source, while the 'low-Ca' alkali granite is inferred to have originated from metapelitic sources (Figure 9e). The distinctive geochemical features observed in the monzogranite suite at the Jabal Al Bayda, including enrichment in Sr and Ba but depletion in Rb with low Rb/Sr ratios (Figure 9f), are consistent with characteristics commonly found in high Ba-Sr granitiods (e.g., [72; 73]). It is evidenced that almost all of the high Ba-Sr granitic intrusions in the world are located on continental margins [74]. On the contrary, the alkali granite shows the lowest strontium and barium values and the highest Rb contents (178 ppm, on average). The variation in Sr, Ba, and Rb contents in the different granitic types can indeed be influenced by the relative contents of feldspars in these rocks. As evidenced by a petrographical study, the monzogranite is enriched in plagioclase, while alkali granite is high in K-feldspar content. Such differences observed in the monzogranites and alkali granites are similar to  
Figure 9: (**a**) Rb/Sr vs. SiO\({}_{2}\) binary diagram. (**b**) I-, S-, M-, and A-type granite discrimination diagram after [68]. (**c**) Zr + Nb + Ce + Y (ppm) versus SiO\({}_{2}\), with division line of A-type granites from [68]. (**d**) Zr vs. SiO\({}_{2}\) discrimination diagram for I-type from A-type granitiod rocks [6]. (**e**) Molar CaO/(MgO + FeO\({}_{\text{total}}\)) vs. Al\({}_{2}\)O\({}_{3}\)/(MgO + FeO\({}_{\text{total}}\)) (After [69]). (**f**) Sr–Rb–Ba ternary plot for the studied granites (modified after [70]). Symbols are as indicated in Figure 6.  
many alkaline intrusions in the ANS (Figure 9f) and can be attributed to a combination of factors, including the composition of the source materials and the conditions under which melting occurs. Ref. [38] studied the isotopic composition of the Jabal az Zuhd granites, in particular, Sr isotopes, and concluded that it was derived from the partial melting of anhydrous metasedimentary lower crust. Ref. [52] investigated the Jabal Sayid granite and interpreted its source to be the result of partial melting of the lower crust of the juvenile AS. Ref. [75] suggested that the source of the Al Ghurayyah granite could be either the mantle or juvenile crust. In Egypt, studies by [33; 43; 48] focused on different areas such as Wadi Um Sidra, Wadi Al-Baroud, and El Fereyid. They concluded that the monzogranite and alkali feldspar granites in these areas were likely the result of the partial melting of metasedimentary sources or pre-existing granitic crustal rocks. From the above discussion, the Neoproterozoic granites from the Jabal Al Bayda area could have resulted from the partial melting of diverse metasedimentary and metagneous sources with variable amounts of metagraywacke, metapelite, and metatonalite source (Figure 9e).