## 5 Discussion
### Retrograde Metamorphism and Anatexis During the Late Triassic  
For an extended period, the investigation of UHP metamorphism and anatexis within the Sulu orogenic belt has garnered considerable interest. Previous studies of the China Continental Scientific Drilling Project (CCSD) eclogite and granitic gneiss have found petrology and zircon evidence of partial melting, such as mineral intergranular melt, garnet, and accessory minerals (zircon) appeared in felsic multiphase solid inclusions [63]. Substantial microscopic evidence of partial melting, including petrological features (e.g., intergranular melt, felsic multiphase solid inclusions in garnet) and zircon characteristics, has been identified in both eclogites and granitic gneiss [64; 65; 66]. The origin of the late Triassic ultra-alkaline intrusion rocks emerging from the Shidao area in the northeast Sulu orogenic zone is also related to the dehydration and melting of the UHP rocks [67]. The magmatic activity that occurred synchronously with exhumation, exemplified by these exposed potassium-rich granites, signifies the dehydration and melting processes experienced by the UHP metamorphic rocks during their exhumation [15; 68]. The syn-exhumation granites (218-216 Ma) emerging from Mibai Mountain in the Lanshan area in the middle of the Sulu orogenic zone are also thought to be the product of decompression and melting of subduction continental crust during the ex \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline  
1 & 746 & 0.28197 & 0.00002 & 0.00245 & 0.00005 & 0.09219 & 0.28193 & \(-\)28.5 & \(-\)13.3 & 0.8 & 1879 & 3216 & 31 & 2487 \\
2 & 771 & 0.28213 & 0.00001 & 0.00113 & 0.00000 & 0.03869 & 0.28211 & \(-\)22.8 & \(-\)6.4 & 0.5 & 1590 & 2622 & 20 & 2075 \\
3 & 796 & 0.28213 & 0.00002 & 0.00209 & 0.00001 & 0.07121 & 0.28210 & \(-\)22.8 & \(-\)6.3 & 0.6 & 1631 & 2635 & 24 & 2091 \\ \hline \multicolumn{12}{c}{Metamorphic} \\ zircon & & & & & & & & & & & & & & & & & \\ \hline
1 & 211 & 0.28225 & 0.00001 & 0.00157 & 0.00001 & 0.03929 & 0.28224 & \(-\)18.6 & \(-\)14.2 & 0.4 & 1439 & 2954 & 18 & 2144 \\
2 & 210 & 0.28224 & 0.00001 & 0.00121 & 0.00001 & 0.02983 & 0.28224 & \(-\)18.8 & \(-\)14.3 & 0.4 & 1433 & 2968 & 17 & 2153 \\
3 & 211 & 0.28225 & 0.00001 & 0.00148 & 0.00010 & 0.03553 & 0.28225 & \(-\)18.4 & \(-\)14.0 & 0.4 & 1429 & 2937 & 16 & 2132 \\
4 & 216 & 0.28227 & 0.00001 & 0.00177 & 0.00001 & 0.04218 & 0.28226 & \(-\)17.8 & \(-\)13.3 & 0.4 & 1414 & 2878 & 17 & 2092 \\
5 & 211 & 0.28223 & 0.00001 & 0.00097 & 0.00000 & 0.02509 & 0.28223 & \(-\)19.2 & \(-\)14.7 & 0.5 & 1440 & 3000 & 19 & 2176 \\
6 & 209 & 0.28227 & 0.00002 & 0.00141 & 0.00001 & 0.03613 & 0.28226 & \(-\)17.9 & \(-\)13.5 & 0.6 & 1405 & 2893 & 22 & 2100 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: LA–MC–ICP–MS zircon Lu-Hf isotopic data of the granitic gneiss. human stage [69]. Both experimental petrological evidence and micro- to macro-scale observations of partial melting in natural samples affirm that extensive anatexis has occurred in the metamorphic rocks of the Sulu orogenic zone. This phenomenon offers an exemplary opportunity to investigate melt/fluid dynamics during the process of continental collision orogen. Chronost stratigraphic analyses further indicate that the UHP metamorphic rocks within the Sulu orogenic zone underwent multiple episodes of anatexis during both the exhumation phase and the post-collisional period. [PERSON] et al. (2016) [64] studied the magmatic in the Weihai area and identified that the anatexis of the UHP metasdepositional rocks occurred at 230-227 Ma, while the anatexis of the underlying UHP metamorphic granite occurred at 218-214 Ma, both of which were caused by the dehydration and decomposition of water-bearing minerals such as phengite. [PERSON] et al.