## 5 Discussion
### Tectonic Setting and Geological Significance  
Many Middle and late Triassic granites [3; 24; 25; 53] in the Western Kunlun orogen are predominantly distributed along both sides of the Mazha-Kangxiwa Fault. The Late Triassic granite belt of the Western Kunlun area is related to the closure of the Paleo-Tethys Ocean. An LA-ICP-MS zircon U-Pb age of 231.4 Ma was previously obtained for the Mushitage pluton [25], while the SHRIMP age was 230.3 Ma [53]. This pluton was the  
Figure 8: S- and I-type granite discrimination diagram for the Dahongliutan pluton samples (according to [PERSON], et al. [48]). A = n (Al\({}_{2}\)O\({}_{3}\) – Na\({}_{2}\)O – K\({}_{2}\)O); C = n (CaO – 3.33 P\({}_{2}\)O\({}_{5}\)); F = n (FeO + MgO + MnO). product of a transition from a mainly collisional compressive tectonic setting to a back arc extensional setting [40], and of the detachment of the subducted slab in a post-collisional tectonic setting [53]. Isotopic ages ranging from 213 to 225 Ma have been obtained for the Akaraz Shan granite [22; 23; 24; 26], which has been postulated to have formed in post-collisional, subduction, and syn-collisional settings [23; 24; 26]. Studies of the Middle and Late Triassic Yuqikapa, Taer, Mazha, Shengliqiao, and Qitaidaban plutons indicate that they are related to the subduction and closure of the Paleo-Tethys Ocean and subsequent continental collisional orogen [22; 27; 28; 53]. Zircon U-Pb dating of metamorphic rocks in the Kangsiwa Fault zone and fission track dating of detrital zircons in areas adjacent to the Western Kunlun region indicate that strong compressive uplift occurred between 235 and 267 Ma in the Western Kunlun region. This uplift was closely related to the subduction and collision of the Paleo-Tethys Ocean [1; 7; 54]. [PERSON], et al. [55] also found that the Western Kunlun region lacks sedimentary records from the late Permian to the Middle Triassic, which is likely related to the orogenic event that occurred during this period. Before the late Permian, predominantly marine sedimentation occurred; after the Middle Triassic, sediment was composed of continental material, which may indicate the end of the collisional event [55]. Thus, as the Paleo-Tethys Ocean retreated northward until it closed in the Late Triassic [30; 56], continental collision occurred along both sides of the Kangsiwa Fault zone. This collision resulted in crustal thickening and large-scale re-melting under a compressive setting, which led to strong magmatism that formed the Dahongliutan pluton on the southern edge of the Kangsiwa Fault zone. The Dahongliutan pluton is located in the Hoh Xil-Songpan foreland basin, and its long axis trends NW-SE. The pluton is controlled by fault structures consistent with the regional tectonic direction. The steep surrounding rocks were affected by the lateral compression of the pluton, indicating that magma actively expanded and pushed the surrounding rock outward during emplacement. The pluton then expanded further through structural expansion and magmatic encroachment. During the Late Triassic, the study area underwent large-scale crustal uplift, and heat flow values increased accordingly. The melting layer moved upwards and Al-rich granitic magma was produced through the partial melting of the crust. The pluton was emplaced and along a structurally weak zone in the uplift. As the magma ascended through the crust, the viscosity increased, owing to crystallization, and the speed of ascent slowed. When ascent stopped, the magma expanded laterally through tectonic expansion (i.e., along the fault zone). Magma encroachment occurred into the surrounding rock and produced xenoliths in the pluton. The Dahongliutan pluton therefore had a composite emplacement mechanism that was dominated by active expansion supplemented by tectonic expansion and magma intrusion mechanisms. On a R1-R2 diagram (Figure 9), the data are predominantly in Zone 6 during the same collision period.