辽东猫岭金矿床流体包裹体特征和成矿时代研究

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

    • 摘要: 猫岭金矿位于华北克拉通胶-辽-吉活动带,赋存于辽河岩群盖县岩组. 该矿床具有规模大、品位低、成因复杂的特点,其成矿流体特征与成矿时代存在争议. 为此,本研究对含金硫化物石英脉中的石英开展了流体包裹体分析,并对猫岭岩体进行了锆石U-Pb定年. 结果表明,成矿流体以水溶液包裹体和含CO2包裹体为主,均一温度介于104.7~288.5℃,冰点温度为-2.2~-14.2℃,盐度为3.53%~17.96%,密度为0.84~0.99 g/cm3,成矿压力为5.65~50.89 MPa,平均成矿深度约10.5 km.激光拉曼光谱显示包裹体气相成分以H2O、CO2为主,含少量CH4,表明成矿流体属中低温、中低盐度、中低密度的NaCl-H2O-CO2±CH4体系. 锆石U-Pb定年结果指示猫岭岩体形成于181±1 Ma,岩体侵入于盖县岩组二段地层中产生矿化,蚀变二长花岗岩Au含量0.2×10-6,猫岭岩体与猫岭金矿成矿密切相关. 推测猫岭金矿成矿作用发生在猫岭金矿侵位之后,即晚于早侏罗世.

       

      Abstract: 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.

       

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