## 4 Results
### Zircon U-Pb Ages and Trace Elements  
Twelve zircon grains from the biotite schist sample were analyzed for LA-ICP-MS U-Pb dating and trace element analysis (Tables 1 and 2). These spots have relatively medium Th (129-2018 ppm) and U (391-1133 ppm) contents with high Th/U ratios of 0.21-1.78, and most of the ratios are greater than 1 (Figure 5). Twelve spot analyses conducted on the zircons resulted in nearly concordant \({}^{206}\)Pb/\({}^{238}\)U ages, spanning from 206 Ma to 225 Ma, with a weighted mean age of 214.6 \(\pm\) 3.6 Ma (MSWD = 5.1). When compared to chondrite patterns, most of the spots display flat heavy rare earth element (HREE) patterns, marked by a positive Ce anomaly and an absence of a notable negative Eu anomaly. In contrast, a single spot has enrichment in HREE (Figure 6). Therefore, the crystallization age of the anatectic zircon may be indicated by 215 Ma. Figure 5: Th/U values versus U–Pb ages of analyzed zircons from biotite schist and granitic genesis in the Sulu orogenic belt. Figure 6: **(A,B)** Zircon U-Pb Concordia diagrams and Chondrite-normalized REE patterns of biotite schist from the Sulu orogenic belt; **(C,D)** Zircon U-Pb Concordia diagrams and Chondrite-normalized REE patterns of granitic genesis from the Sulu orogenic belt. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline
**Spot** & **La** & **Ce** & **Pr** & **Nd** & **Sm** & **Eu** & **Gd** & **Tb** & **Dy** & **Ho** & **Er** & **Tm** & **Yb** & **Lu** \\ \hline
1 & 4.95 & 236.64 & 12.51 & 122.31 & 88.83 & 39.38 & 152.70 & 27.62 & 207.56 & 40.73 & 131.71 & 22.04 & 218.45 & 24.23 \\
2 & & 7.32 & 0.04 & 1.12 & 1.43 & 0.99 & 6.21 & 1.36 & 13.63 & 3.61 & 17.80 & 3.91 & 48.74 & 7.28 \\
3 & 5.33 & 155.54 & 9.89 & 94.69 & 64.72 & 31.28 & 129.52 & 29.12 & 263.18 & 64.76 & 261.05 & 50.61 & 543.83 & 64.26 \\
4 & 1.24 & 96.84 & 37.5 & 40.55 & 38.24 & 20.36 & 100.07 & 25.41 & 255.18 & 67.79 & 283.70 & 56.08 & 615.67 & 77.01 \\
5 & 0.34 & 30.84 & 0.81 & 9.68 & 10.19 & 5.31 & 27.72 & 6.70 & 71.30 & 19.23 & 78.86 & 14.94 & 169.05 & 21.49 \\
6 & 0.13 & 32.87 & 0.73 & 9.69 & 8.83 & 4.93 & 24.23 & 4.40 & 34.09 & 7.19 & 24.79 & 4.30 & 48.12 & 6.26 \\
7 & 0.83 & 34.36 & 1.86 & 19.07 & 13.68 & 5.39 & 24.16 & 4.33 & 34.92 & 4.77 & 31.16 & 6.17 & 73.93 & 11.17 \\
8 & 1.67 & 78.25 & 3.96 & 41.91 & 37.66 & 19.15 & 89.41 & 23.02 & 224.30 & 59.54 & 253.94 & 50.44 & 553.63 & 69.30 \\
9 & 1.19 & 48.06 & 2.70 & 28.05 & 23.81 & 11.44 & 52.38 & 12.57 & 211.96 & 31.61 & 131.90 & 26.04 & 282.78 & 36.22 \\
10 & 0.07 & 12.10 & 0.22 & 2.32 & 2.87 & 1.67 & 9.41 & 2.29 & 26.04 & 7.80 & 36.98 & 7.62 & 90.26 & 13.18 \\
11 & 1.15 & 65.39 & 3.77 & 37.95 & 32.82 & 15.26 & 61.85 & 12.71 & 99.09 & 20.80 & 76.80 & 14.03 & 149.85 & 18.72 \\
12 & 5.66 & 141.07 & 9.57 & 86.20 & 56.68 & 26.03 & 98.34 & 19.56 & 160.69 & 35.22 & 129.37 & 22.91 & 232.40 & 26.60 \\ \hline \end{tabular}
\end{table} 
Table 2: LA–ICP–MS trace element analyses of zircons for the biotite schist. The U-Pb dating results and trace element data for ten zircon spots, derived from granitic gneiss and analyzed using LA-ICP-MS, are presented in Tables 3 and 4, respectively. Four-spot analyses conducted on Type 1 samples showed moderate concentrations of Th, ranging between 64 and 203 ppm, low levels of U, varying from 115 to 208 ppm, and high Th/U ratios, which were between 0.56 and 1.45 (Figure 5). The spot analyses yielded a concordant range of \({}^{206}\)Pb/\({}^{238}\)U ages, spanning from 746 to 796 Ma, with a weighted mean age of 774 \(\pm\) 32 Ma (MSWD = 5.7) (Figure 6). When compared to chondrite patterns, the zircons display enrichment in HREE, accompanied by a notable negative Eu anomaly and a positive Ce anomaly, both indicative of an igneous origin (Figure 6) [47,48]. The analysis of six spots from zircon type 2 showed moderate concentrations of Th, ranging from 66 to 123 ppm, and significantly higher concentrations of U, spanning from 1633 to 3463 ppm, resulting in very low Th/U ratios of 0.03 to 0.05 (Figure 5).