## 5 Discussion
### Magnatic Evolution  
With respect to the magmatic sources of A-type granites, scholars have previously drawn the following four main conclusions: (1) A-type granites are formed by the separa  
Figure 9: Discrimination diagrams of genetic types for granites in the western Kendewula region (**a**) 10,000 \(\times\) Ga/Al vs. (Na\({}_{2}\)O + K\({}_{2}\)O)/CaO diagram; (**b**) 10,000 \(\times\) Ga/Al vs. Nb diagram; (**c,d**) analysis of A-type granite sub-class diagram [33, 44]. tion and crystallization of mantle-derived alkaline basaltic magma [67]; (2) A-type granites are formed by mixing crustal and mantle-derived magma [68]; (3) A-type granites are formed by the direct partial melting of silicate middle-upper crust [69]; and (4) A-type granites are formed by the partial melting of continental lower crust caused by mantle-derived magma underthrusting [70]. The granites and the moyites are not associated with many basic or intermediate rocks and are covered by a large area of granite in the study area. Many basic magmatic rocks have been found; thus, the A-type granite in this area is unlikely to have formed by the separation and crystallization of mantle-derived alkaline basaltic magma. Moreover, partial melting of mantle-derived material can only form mafic magma or intermediate magma, making it impossible to directly produce granite magma. Second, the content of SiO\({}_{2}\) in the A-type granite studied in this paper is extremely high (72.45-78.96), and the ratio of trace rare earth elements is close to the reference value of crustal rocks but quite different from the corresponding ratio of the mantle. These characteristics indicate that the magma source of the A-type granite studied in this paper is the crust rather than the mantle. Combined with the view that the formation of A-type granites proposed by [PERSON] [4] is independent of the source rock and related only to pressure, the formation of A-type granites can occur only in the lower crust. In addition, the partial melting of silicate-rich middle-upper crust materials occurs in a shallow and low-pressure environment. The required temperature is not high, and the lowest zircon saturation temperature of the A-type granites studied here is 800 \({}^{\circ}\)C, which is obviously inconsistent with this environment. In the \(\varepsilon\)Hf(t)-age diagram (Figure 5), almost all samples are plotted between the depleted mantle and chondrite evolution lines. These lines are even closer to the chondrite uniform reservoir evolution line. The Hf model ages (tDM2 = 1.0\(\sim\)1.4 Ga \(\varepsilon\)Hf(t) = -4.3\(\sim\)3.69 (Table S1)) and the \(\varepsilon\)Hf(t) values of most samples are positive and relatively low in value. Rocks with low and positive \(\varepsilon\)Hf(t) values indicate that their magma source areas probably involve mantle-derived materials [71; 72] and the average value of Ba/La is 10.67, which is slightly greater than the reference value of the crust (9.6) [73; 74]. A higher zircon saturation temperature (800-900 \({}^{\circ}\)C) supports the contribution of mantle-derived materials during diagenesis, and the two most common methods for mantle-derived materials to participate in the rock-forming process are as follows: (1) mixing with the generated felsic mag in the deep crust and (2) first intruding into the crustal basal rocks to form the primary crust and then undergoing partial melting by dehydration. The A-type granite formed by mantle-derived materials through the second method mostly shows quasi-aluminous characteristics [67], which are different from the weakly over-aluminous characteristics of the A-type granites studied in this work. Abnormal silicon, which is rich in alkalis and significantly depleted in Ca, Mg, Nb, Ta, P, Ti, Eu and other elements shown in this study, indicate that such materials have undergone differentiation evolution [75].