邹平王家庄铜矿床成矿地球化学及成因探讨

The Mineralization Geochemistry of the Wangjiazhuang Copper Deposit in Zouping County,Shandong Province,and a Discussion on Its Genesis

王家庄铜矿床的矿化脉石英中流体包裹体均一温度介于116~566℃之间,均值为289℃;盐度介于7.2%~63.2%NaCleq,均值为21.1%NaCleq。流体的气相成分主要为H2O和CO2。在均一温度为240~440℃区间内,出现了富气相的两相水溶液包裹体、富液相的两相水溶液包裹体和含子晶的三相水溶液包裹体共存现象,以及加温后富气相包裹体均一到气相和同期富液相包裹体均一到液相的特征,表明成矿流体曾发生过沸腾作用;其中第一次发生于360~400℃,主要形成高温、高盐度含子晶的三相水溶液包裹体和高温、中盐度富液相的两相水溶液包裹体及高温、低盐度富气相的两相水溶液包裹体;第二次发生于240~320℃,主要形成高—中温、高盐度的含子晶的三相水溶液包裹体和高—中温、中盐度富液相的两相水溶液包裹体及高—中温、低盐度富气相的两相水溶液包裹体;之后主要形成富液相的两相水溶液包裹体,具有中低温和中盐度的特征。矿化脉石英中的δ18OH2O介于-1.14‰~1.79‰之间,均值为0.94‰;δD介于-63.70‰^-56.50‰之间,均值为-59.8‰;说明王家庄铜矿床的成矿流体主要来源于岩浆,后期混入大气降水。矿石矿物的δ34S变化于-8.80‰^-2.80‰之间,均值为-6.33‰。矿石矿物的n(206Pb)/n(204Pb)介于18.1684~18.3637之间,均值为18.2892;n(207Pb)/n(204Pb)介于15.5546~15.6342之间,均值为15.5777;n(208Pb)/n(204Pb)介于38.1286~38.4840之间,均值为38.2780。说明矿石具有贫重硫和富放射性成因铅的特征,硫、铅主要来源于深部,后期可能受到地壳物质或大气降水的混染。

This paper presents a comprehensive study on the mineralization geochemistry and the oreforming mechanisms of the Wangjiazhuang copper deposit in Zouping County, Shandong Province. The homogenization temperature of primary fluid inclusions in the mineralized quartz veins of the Wangjiazhuang copper deposit ranges from 116 ℃ to 566 ℃ with an average value of 289 ℃, while the salinity ranges from 7.2% to 63.2% NaCleq with an average of 21.1% NaCl eq. The Raman spectra indicate that H,O and CO2 are the dominating components in the inclusions. When the homogenization temperature ranges from 240℃ to 440℃, a phenomenon was observed that the vapor-rich inclusions, the liquid-rich inclusions and the three-phase inclusions containing daughter minerals coexisted, meanwhile, vapor-rich inclusions homogenized to a single vapor phase and liquid-rich ones homogenized to liquid phase, which indicates that the fluid has once been boiling. The first boiling event occurred at about 360 ℃ to 400 ℃, resulting in the formation of the three-phase inclusions containing daughter minerals with high temperature and high salinity, the liquid-rich inclusions with high temperature and moderate salinity, and the vaporrich inclusions with high temperature and low salinity. The second boiling event, which occurred at about 240 ℃ to 320 ℃, caused the formation of the three-phase inclusions containing daughter minerals with medium to high temperature and high salinity, the liquid-rich two-phase fluid inclusions with medium to high temperature and medium salinity, and the vapor-rich two-phase fluid inclusions with medium to high temperature and low salinity, The inclusions formed after two boiling events are mainly liquid-rich fluid inclusions characterized by low to medium temperature and medium salinity. The δ^18OH2O values range from --1. 14‰ to 1.79‰ with an average value of 0.94‰, while δD range from --63.70‰ to --56.50‰ with average of --59.80‰. It is deduced that the ore-forming fluid was mainly derived from the magmatic fluids and mixed with meteoric water in the late stage. The ore-mineral are poor in heavy sulfur isotopes and rich in radiogenic lead isotopes, The values of δ^34S of ore-minerals range from --8.80‰ to --2.20‰ with an average of -6. 33‰. The values of n（^206Pb）/n（^204pb） range from 18. 1684 to 18. 3637 with an average of 18. 2892. n（^207Pb）/n（^204pb） ranges from 15. 5546 to 15. 6342 with an average of 15. 5777. n（^208Pb）/ n（^204Pb） ranges from 38. 1286 to 38.4840 with an average of 38. 2780. It is indicated that sulfur and lead originated from deeper crust or mantle and were influenced by the mixture from the wall rocks and meteoric water in the late ore-forming stage.