## 3 Analytical Procedures  
### Molybdenum Re-Os Isotopic Analyses  
Four typical gold-bearing ore samples were crushed with the grains being 40-60 mesh so as to separate the molybdenites, which were handpicked subsequently with a binocular microscope in order to obtain >99% purity. Then, the molybdenite mineral samples selected were carried out for Re-Os isotopic analyses at the Re-Os Laboratory in the National Research Center of Geoanalysis, Chinese Academy of Geological Sciences, Beijing. The procedures of Re-Os chemical separation and mass spectrometry measurement have been summarized in [50; 51; 52; 53; 54] in detail, which are described briefly as follows.  
The molybdenite mineral sample weighed accurately, followed by the mixed \({}^{185}\)Re and \({}^{190}\)Os spike solution with an appropriate amount of ultrapure HCl by a thin-necked long funnel, was loaded into the bottom of a Carius tube, which was placed in the vacuum cup containing an ethanol-liquid nitrogen slush with a temperature of \(-\)50--80 \({}^{\circ}\)C. Subsequently, 3 mL 10 mol/L HCl was added into the same Carius tube, and 5 mL 16 mol/L HNO\({}_{3}\) was also added only after the HCl was completely frozen. Then, the Carius tube was sealed and heated in an oven at 200 \({}^{\circ}\)C for 24 h to decompose the molybdenite sample. After decomposition, the Carius tube was again chilled and then was opened in the abovementioned vacuum cup. After the opened tube was tempered in an ice bath, the Milli-Q water with a volume of about 1.5 times that of the sample solution was added.  
Figure 4: **(a)** Photograph of representative fine-grained granite sample for LA-ICP-MS zircon U–Pb dating. **(b–d)** Subhedral to anhedral quartz, K-feldspar, plagioclase and biotite, **(e,f)** representative metallic minerals of pyrite, galena and molybdenite. Mineral abbreviations: Pl: plagioclase, Qtz: quartz, Kfs: K-feldspar, Bt: biotite, Py: pyrite, Mot: molybdenite, Ga: galena.  
Next, the Os was separated from the Carius tube by distillation in a steam bath at 100 \({}^{\circ}\)C for 60 min and trapped by Milli-Q water. The resulting solution of OsO\({}_{4}\) liquid was used for Os isotope measurements. Re was extracted from the remaining Re-bearing solution with 10 mL acetone in the 10 mL 5 mol/L NaOH solution.  
Lastly, the Os-Re isotopic composition of molybden was determined using a TJA X-series ICP-MS (Thermo Jarrell Ash Corporation, Franklin, Boston, MA, USA). The total blanks for this technique are 4 pg for Re, 0.0002 pg for common Os and 0.09 pg for \({}^{187}\)Os. The certified reference standard material GBW04435 (HLP) (National Geological Testing Center; Beijing, China, 2022) [50], with a measured model Re-Os age of 222.2 \(\pm\) 3.4 Ma, which corresponds to the recommended 221.4 \(\pm\) 5.6 Ma [50], was used to monitor the analytical reliability. The equation [t = ln(\({}^{187}\)Os/\({}^{187}\)Re + 1)/\(\lambda\)] with a decay constant (\(\lambda\)) of 1.666 \(\times\) 10\({}^{-11}\) a\({}^{-1}\) (\(\pm\)1.02%) [55] was used to calculate the model Re-Os age. The analytical uncertainties on the Re and Os contents of molybden include those in the calibration of spike solutions, the weighting of samples and spike solutions, fractionation correction in the mass spectrometry measurement and the measurement of the isotopic ratio of the sample analyzed. The Re-Os model age uncertainty stems from the decay constant of \({}^{187}\)Re. All uncertainties are shown at a confidence level of 95%. The isochronal and weighted average ages were obtained using Isoplot 3.75 software [56].