## 6 Discussion
### Geodynamic Implications  
Refs. [82; 83; 84; 85] interpreted the evolution of the AS in terms of three main stages of development: (1) The Hijaz orogenic cycle occurred from about 950 to 680 Ma, and involved plate subduction, leading to the formation of the volcanic and associated plutonic rocks in the southern AS. (2) The Nabitah orogen, occurring from 680 to 630 Ma, represents a significant stage in the tectonic evolution of the AS. During this period, smaller tectonic plates within the AS underwent convergence and collision, leading to the formation of mountain belts and associated intense deformation, and metamorphism of the rocks involved. (3) The Najd orogen stage occurred from 630 to 550 Ma and involved a period of tectonic deformation and magmatism within the AS. Based on geochemistry and strontium isotope initial ratios, ref. [84] concluded that the volcanic and plutonic rocks in the southern AS were developed during the Hijaz orogenic cycle. These rocks were formed within intraoceanic island arcs that were associated with northeast-dipping subduction zones. The collision and accretion of the Hijaz and Asir arcs along the Bir Umq suture represent the last stage of the northeast-dipping subduction and collision process. A different model that interprets the development of the AS during the Pan-African period was proposed by [85]. It was based on three stages as follows: (1) the accretion of oceanic island arcs stage (950-680 Ma), where the development of the Nabitah mobile belt occurred, is considered a suture zone resulting from west-dipping subduction between two allochthonous plates: the western Hijaz-Asir province and the eastern Afif province; (2) a compressional orogen stage, during the time frame of 680-630 Ma, which occurred as a result of the collision between the Hijaz-Asir and Afif crustal blocks, as well as between the Afif and Ar Rayn crustal blocks; and (3) the final orogenic phase, which occurred from 620 to 550 Ma in the northern Arabian Shield; this phase is characterized by several key geological processes, including extensive molassic sedimentation, granitic plutonism, and the development of the Najd faulting. In the context of the Jabal Al Bayda area, it is crucial to understand the geodynamic transition that occurred between the termination of subduction-controlled magmatism during the late stages of the East African Orogen and the appearance of post-orogenic granitic magmas. Geochemical similarities between the studied monzogranites and the alkaline stage I (609-602 Ma) of [45] and the 620-600 Ma Idah Suite of [86] suggest a late-orogenic magmatism producing the Jabal Al Bayda monzogranites that occurred at this time. On the other hand, geochemical similarities between the Jabal Al Bayda alkali granites and the 572-556 Ma Feinan A-type granites of [41], the 608-578 Ma alkaline stage II granites of [45], and the 564 \(\pm\) 140 Ma Jabal az Zuhd granite of [38] suggest a post-orogenic magmatism producing the Jabal Al Bayda Alkali granites that occurred at this time. Based on the regional geology and magmatic evolutionary history, it is suggested that the Jabal Al Bayda monzogranite was formed through the partial melting of a metagraywacke source within a subduction setting (Figure 10A). This late-orogenic magmatism is believed to have occurred in the range of 620-600 Ma, corresponding to the post-collision stage 3 of the ANS evolution. It follows the accretion of juvenile arc terranes and the formation of volcanic and stratigraphic successions associated with the Al Ays group (745-700 Ma) and the Furayh group (660-630 Ma). The high Ba-Sr signatures of the monzogranite are in agreement with an enriched source related to the partial melting of metagraywackes and metatonalites in a subduction zone. The Jabal Al Bayda A2-type alkali granite shows low Ba-Sr signatures and high Rb content, suggesting a different source and tectonic setting.