## 6 Discussion
### The Petrogenesis of the Jabal Sayid and Dayheen Granitoids
#### 6.2.3 Post-Orogenic or Anorogenic Granitoids  
After a collision, significant amounts of high-K calc-alkaline granitoids are often emplaced, primarily as batholiths [44]. The isotopic ratios of Nd are often used as tracers to identify the sources of magmatic rocks. However, in the case of the ANS, the possible crustal materials for post-orogenic or anorogenic magmatism were themselves relatively young and had not undergone enough geological processes to develop distinctively crustal Nd isotope signatures, making it difficult to apply Nd isotope ratios as a reliable tracer in this context [45; 46]. In that case, we can go to other evidence to identify the source of the Jabal Sayid and Dayheen parental peralkaline magmas. The Nb/Ta ratio and Y/Nb ratio are geochemical signatures that can provide valuable information about the source of magmas. These ratios are particularly useful in differentiating between mantle-derived and crustal-derived magmas. The Nb/Ta ratios in the Jabal Sayid and Dayheen peralkaline granites and pegmaties propose that these rocks crystallized from magmas derived from crustal sources rather than mantle-derived sources. The average Nb/Ta ratios are 12.94 for peralkaline granites and 11.72 for pegmaties in the case of Jabal Sayid and 12.98 for peralkaline granites and 13.08 for pegmaties in the case of Dayheen (Tables 2 and 3). These values fall within the range typically observed for crustal materials, which is generally lower than the Nb/Ta ratios observed in mantle-derived rocks. The typical Nb/Ta ratios for the continental crust range from 8 to 14, as reported by [PERSON] and [PERSON] (2013). In contrast, the chondritic ratio, which represents the composition of the Earth's primitive mantle, is approximately 19.9 \(\pm\) 0.6 [47]. Moreover, the Nb/Ta ratios in ocean island basalts typically fall around 15.9 \(\pm\) 0.6 [48]. The Y/Nb ratio is another geochemical parameter commonly used to distinguish between different sources of magma. The average Y/Nb ratios reported for the peralkaline granites and pegmaties of Jabal Sayid (2.87 and 5.06, respectively, Table 3) and the peralkaline granites and pegmaties of Dayheen (1.34 and 1.33, respectively, Table 2) are higher than the typical Y/Nb ratios observed in mantle-derived sources, which are often less than 1.2 [33]. In terms of Rb/Sr ratios, mantle-derived materials typically have low Rb/Sr ratios, ranging from 0.1 to 0.01 [49], whereas lower and middle continental crust tends to be enriched in Rb relative to Sr [50]. Based on the Rb/Sr ratios observed in the studied granitoids, it is reasonable to conclude that the granodiorite-diorite association was formed from mantle material where lower Rb/Sr ratios between 0.03 and 0.1 were observed (Figure 13a). However, the higher Rb/Sr ratios in the monzogranites and peralkaline granites compared to typical mantle values suggest a significant contribution from sources other than the mantle, such as crustal materials. The use of the ternary discrimination diagram developed by [38] provides further evidence supporting the conclusion that the Jabal Sayid and Dayheen peralkaline granites  
Figure 13: (**a**) Rb/Sr ranges of the studied granitoid and associated pegmaties. (**b**) The Nb-Y-3 Ga ternary diagram of [33]. Symbols as in Figure 6.  
have a metasedimentary source (Figure 12d). Similarly, most of the Jabal Sayid and Dayheen peralkaline granites are plotted in the metapeitic source field, indicating a continental crustal source (Figure 12f). This further supports the idea that the peralkaline granitoids in the study area have a continental crustal source and are consistent with the broader geological context of the ANS. This is in agreement with the highest rubidium values and the lowest strontium and barium contents of the Jabal Sayid and Dayheen peralkaline granites (Figure 12e). The petrographical study indicating that the Jabal Sayid and Dayheen peralkaline granites are high in K-feldspar content is consistent with the observed variations in the Sr, Ba, and Rb contents in these rocks.