Fluid inclusion characteristics and metallogenic age of Maoling gold deposit in eastern Liaoning Province

The Maoling gold deposit, situated within the Jiao-Liao-Ji mobile belt of North China Craton, is hosted in Gaixian Formation of Liaohe Group. The deposit is characterized by large scale, low grade, and complex genesis, with ongoing debates surrounding the characteristics of its ore-forming fluids and metallogenic age. To address these issues, this study conducts the fluid inclusion analysis on quartz from auriferous sulfide-quartz veins and performs zircon U-Pb dating on Maoling pluton. The results indicate that the ore-forming fluids are dominated by aqueous and CO₂-bearing inclusions, with the homogenization temperatures of 104.7-288.5 ℃, final ice-melting temperatures from -2.2 to -14.2 ℃, salinity of 3.53%-17.96%, density of 0.84-0.99 g/cm³, trapping pressures of 5.65-50.89 MPa, and the average mineralization depth of 10.5 km approximately. Laser Raman spectroscopy reveals that the vapor phase of the inclusions is primarily composed of H₂O and CO₂, with minor CH₄, indicating that the ore-forming fluid represents an epimesothermal, low-moderate salinity, and low-moderate density NaCl-H₂O-CO₂±CH₄ system. The zircon U-Pb dating yields an emplacement age of 181±1 Ma for Maoling pluton. The intrusion of this pluton into the second member of Gaixian Formation induced mineralization, with the altered monzogranite containing 0.2×10^-6 of Au, suggesting a close genetic relationship between Maoling pluton and gold mineralization. It is inferred that the mineralization of Maoling gold deposit occurred after the emplacement of the pluton, that is, later than the Early Jurassic.