## 4 Results
### LA-ICP-MS Zircon U-Pb Age  
The obtained LA-ICP-MS zircon U-Pb concentrations and isotopic compositions from the two fine-grained granite samples (XWL4 ZK1B2 and XWL5 ZK4B3) of the Xiawolong gold deposit are given in Table 2, as well as the U-Pb age normal distribution histograms and Concordia diagrams associated with the typical zircon cathodoluminescence (CL) images; the weighted average \({}^{206}\)Pb/\({}^{238}\)U ages are illustrated in Figures 6 and 7. \begin{table}
\begin{tabular}{l c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Sample No.**} & \multirow{2}{*}{**Oe Style**} & \multirow{2}{*}{**Sample Weight (g)**} & \multicolumn{2}{c}{**Re (ppm)**} & \multicolumn{2}{c}{**Common Os (ppb)**} & \multicolumn{2}{c}{**187e (ppm)**} & \multicolumn{2}{c}{**187**Os (ppb)**} & \multicolumn{2}{c}{**Model Age (Ma)**} \\ \cline{3-13}  & & **Measured** & **Error** & **Measured** & **Error** & **Measured** & **Error** & **Measured** & **Error** & **Measured** & **Error** \\ \hline XWL-g1 & stockwork-style & 0.00019 & 192.6 & 1.3 & 0.7217 & 0.6775 & 121.1 & 0.8 & 234.72 & 2.39 & 116.26 & 1.84 \\ XWL-g4 & disseminated-style & 0.00241 & 107.2 & 0.8 & 8.1377 & 0.1126 & 67.39 & 0.49 & 133.26 & 0.81 & 118.57 & 1.62 \\ XWL-g2 & stockwork-style & 0.0025 & 33.85 & 0.34 & 0.1431 & 1.2672 & 21.28 & 0.21 & 41.30 & 0.54 & 116.40 & 2.24 \\ XWL-g9 & disseminated-style & 0.00129 & 79.72 & 0.52 & 0.0043 & 0.0976 & 50.11 & 0.33 & 99.93 & 0.67 & 119.59 & 1.62 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Molybdenum Re-Os abundance and isotopic compositions for gold-bearing cores from the Xiawolong gold deposit. For sample XWL4 ZK1B2, forty zircon spots have \({}^{206}\)Pb/\({}^{238}\)U ages between 106 \(\pm\) 3 and 725 \(\pm\) 19 Ma (Table 2; Figure 6a), except for two slightly older grains that have \({}^{206}\)Pb/\({}^{238}\)U ages of 128 \(\pm\) 4 Ma and 129 \(\pm\) 4 Ma, and two older grains that have \({}^{206}\)Pb/\({}^{238}\)U ages of 635 \(\pm\) 22 Ma and 725 \(\pm\) 19 Ma, which are considered to be inherited zircon from the Late Yanshanian granitoids and the Precambrian basement in Sulu terrane [15], respectively; the other grains form two populations (Figure 6b). One population has 24 grains and records \({}^{206}\)Pb/\({}^{238}\)U ages of 114 \(\pm\) 3 Ma and 126 \(\pm\) 4 Ma, with a weighted average age of 118 \(\pm\) 2 Ma (2\(\sigma\), MSWD = 0.8) (Figure 6c,d), which is used to estimate the crystallization age of the magma; the other has 12 grains and gives \({}^{206}\)Pb/\({}^{238}\)U ages of 106 \(\pm\) 3 Ma to 113 \(\pm\) 3 Ma, with the weighted average age of 110 \(\pm\) 2 Ma (2\(\sigma\), MSWD = 0.48) (Figure 6e,f), probably recording the thermal disturbance by the emplacement of younger disks, which are widely present in the area (Figure 2) [15]. Figure 6: The diagrams of LA-ICP-MS zircon U–Pb Concordia age (**a**–**c**,**e**) and weighted average age (**d**,**f**) of fine-grained granite sample XWL4 ZK1B2 in Xiawolong deposit. The insets show the typical zircon CL images with U–Pb apparent age and the corresponding histogram. For sample XWL5 ZK4B3, forty-four zircon spots produce \({}^{206}\)Pb/\({}^{238}\)U ages of 98 \(\pm\) 3-126 \(\pm\) 4 Ma (Table 2; Figure 7a), except for two younger grains that show \({}^{206}\)Pb/\({}^{238}\)U ages of 98 \(\pm\) 3 Ma and 102 \(\pm\) 3 Ma, likely resulting from a later thermal disturbance. The other grains also form two populations (Figure 7a,b), similar to those of sample XWL4 ZK1B2 (Figure 6b). One population has 16 grains and gives \({}^{206}\)Pb/\({}^{238}\)U ages of 113 \(\pm\) 3 Ma and 126 \(\pm\) 4 Ma, with a weighted average age of 117 \(\pm\) 2 Ma (2\(\sigma\), MSWD = 1.15) (Figure 7c,d), and the other has 26 grains and shows \({}^{206}\)Pb/\({}^{238}\)U ages of 106 \(\pm\) 3 Ma to 112 \(\pm\) 3 Ma, with a weighted average age of 109 \(\pm\) 1 Ma (2\(\sigma\), MSWD = 0.32) (Figure 7e,f).