## 5 Discussion
### Genetic Types and Source Material  
The LILE contents of the Dahongliutan pluton indicate Rb enrichment and Sr depletion. The HFSE contents indicate Th enrichment and strongly indicate Ta and Nb depletions. The total REE contents are 65.5 \(\times\) 10\({}^{-6}\) to 293.09 \(\times\) 10\({}^{-6}\) and zircons have inherited cores that share similarities with Himalayan leucogranites [40]. Leucogranites are metasedimentary rocks formed by the dehydration and melting of hydrous minerals [41; 42] and are regarded as representative S-type and syn-collisional granites [40]. The Zr contents of the Dahongliutan pluton are relatively low (65.51 \(\times\) 10\({}^{-6}\) to 354 \(\times\) 10\({}^{-6}\)). Even at low temperatures, zircon crystallization also requires Zr contents of \(\sim\)100 \(\times\) 10\({}^{-6}\)[26]. Therefore, the pluton has experienced zircon fractional crystallization. Only four samples (D3801 GS01, P6-06 XT01, P22-39 XT01, and P7-65 XT03) have Zr/Hf ratios of \(>\)40; the other 19 samples have low Zr/Hf ratios (17.85-39.85), which supports this conclusion, as zircons have high Zr/Hf ratios (\(>\)40). The fractional crystallization of zircon leads to lower Zr/Hf ratios in the residual magma. The presence of inherited cores indicates that the initial magma was Zr-saturated during the formation of the pluton. According to Zr-saturation thermometer calculations, the zircon saturation temperature of the Dahongliutan pluton was 724-872 \({}^{\circ}\)C [43; 44]. This is similar to the emplacement temperature of I-type granites (750-850 \({}^{\circ}\)C). Among the sample, two (P22-71 GS and P21-08 GS) had Zr-saturation temperatures of \(>\)800 \({}^{\circ}\)C; the remaining 21 samples had Zr-saturation temperatures that were substantially lower than the emplacement temperature of A-type granite (\(>\)800 \({}^{\circ}\)C), which is the upper limit for the initial magma temperature [45]. However, given that zircon fractional crystallization requires higher temperatures and lower viscosity, the actual temperature of the magma may have been higher [40]. On an S- and I-type granite discrimination diagram (Figure 8) most of the Dahongliutan pluton samples plot in the S-type granite region, and some plot in the I-type granite region. The A/CNK of the pluton is 1.01-1.43 (average = 1.21), which is greater than 1.1 and belongs to the peraluminous granite region. The presence of biotite and Al-rich minerals such as muscovite and garnet is consistent with S-type granites. Dark elliptical or irregular diorite xenoliths of different sizes are common, but are unevenly distributed. The boundaries between the xenoliths and the surrounding rock are clear. Some boundaries have clear condensation edges, indicating that the xenoliths had a magmatic origin. Such boundaries are the result of mixing between relatively more basic and acidic magmas. In summary, the magma that formed the Dahongliutan pluton mainly originated from the crust and was an S-type granite. However, a small amount of upper mantle material was involved in the early stages of magma formation, as reflected by the I-type granite characteristics. The Dahongliutan pluton samples are enriched in LREEs and depleted in HREEs (La/Yb\({}_{\rm N}\) = 7.05-49.9), except for three samples (P26-88 GS, P21-32 XT01, and P21-08 GS). One sample has an \(\delta\)Eu value of \(>\)1, with a pronounced negative Eu anomaly, low Y (\(\sim\)34.4 \(\times\) 10\({}^{-6}\)) and Yb (\(\sim\)3.83 \(\times\) 10\({}^{-6}\)) contents, and a high Sr/Y ratio (\(\sim\)38.97). This is similar to adakite, and indicates that garnet was present during magma formation. The other 20 samples have \(\delta\)Eu values of 0.34-0.94, relatively pronounced negative Eu anomalies, and insignificant Sr losses, which indicates that no plagioclase residue was present in the source. Given the lower pressure limit of rutile stability (1.5 GPa), the formation pressure of the Dahongliutan pluton was likely 1-1.5 GPa. Biotite and polysilicon muscovite have stronger affinities for Nb than Ta [46] in granitic magmas.