SHRIMP U–Pb age and geochemistry of hydrothermal xenotime and monazite from the Huachanggou gold deposit, Qinling orogen, northern China

• Hydrothermal xenotime and monazite are identified at Huachanggou and linked to gold mineralization. • SHRIMP U–Pb dating of xenotime and monazite constrains gold mineralization to the Late Triassic (ca. 210–207 Ma). • The Huachanggou gold deposit is an orogenic gold system, formed during the final collision between the South Qinling and Yangtze blocks. The genesis of the Huachanggou gold (Au) deposit in the Qinling orogenic belt has been controversial due to the absence of direct geochronological constraints. To resolve this, we investigated hydrothermal xenotime and monazite occurring in Au-bearing quartz–albite veins and alteration halos, which are texturally and paragenetically coeval with gold mineralization. LA-ICP-MS analyses reveal that these phosphates are MREE–HREE enriched, have low U and Th concentrations, and exhibit subdued Eu anomalies–all diagnostic of a hydrothermal origin. SHRIMP U–Pb dating yields weighted mean 206 Pb/ 238 U ages of 208.8 ± 2.2 Ma and 210.4 ± 2.4 Ma for xenotime, consistent with the 206.9 ± 4.0 Ma age for monazite, tightly constraining the gold mineralization to the Late Triassic (ca. 210–207 Ma). This age coincides with a regional compressional event attributed to the final collision between the South Qinling and Yangtze blocks. Our results demonstrate that hydrothermal xenotime–monazite U–Pb chronometry provides a robust and high-temperature geochronometer for orogenic gold systems, overcoming limitations of low-temperature isotopic systems (e.g., Ar–Ar on mica or fuchsite). This approach refines the timing and tectono-metallogenic framework of orogenic gold deposits in the Qinling belt and similar collisional settings.