SEM-CL Study of Quartz Containing Fluid Inclusions in Wangjiazhuang Porphyry Copper (-Molybdenum) Deposit, Western Shandong, China

The Wangjiazhuang porphyry copper(-molybdenum)deposit is located at Zouping volcanic basin in Shandong Province,East China and hosted in the Wangjiazhuang intrusive complex emplaced along a late volcanic conduit.There are two types of ores in this deposit:early disseminated and stockwork ores in the ore-bearing intrusion,and late massive sulfide-quartz veins above brecciated quartz monzonite.The ore minerals are mainly pyrite,chalcopyrite,and subordinately magnetite,tennantite,molybdenite with minor bornite,enargite,galena and sphalerite,etc.,and gangue minerals including K-feldspar,biotite,quartz,muscovite-sericite,chlorite and calcite.Combined with fluid inclusion study,the scanning electron microscope-cathodoluminescence(SEM-CL)study of quartz in the deposit and wall rocks shows significant differences between the two types of quartz in the ores.In addition,four types of primary-pseudosecondary fluid inclusions in the quartz have been recognized.They are one-or two-phase aqueous inclusions with vapor/liquid ratios less than 30%to 40%(type Ⅰ);gas-rich inclusions with vapor/liquid ratios more than 50%(type Ⅱ),some of which contain some small opaque minerals,probably chalcopyrite;multiphase fluid inclusions with daughter minerals of halite±anhydrite±opaque(chalcopyrite)±sylvite±hematite±unknown crystal(type Ⅲ);and mica-bearing fluid inclusions(type Ⅳ).Quartz containing abundant muscovite-bearing and halite-bearing fluid inclusions in the mineralized quartz monzonite with potassic-silicic alteration,have better oscillatory growth zoning with CL-colors from bright in the core to darker in the rim,indicating variations of element concentrations in the fluid media from which quartz grew during the later period of magmatic-hydrothermal process.In contrast,the quartz in the sulfide-quartz veins contains mainly fluid inclusions of low-to-medium salinities and does not show oscillatory zoning,indicating that there was less fluctuation in composition and element concentrations of the hydrothermal fluids.However,the quartz containing halite-bearing fluid inclusions and being associated with copper-molybdenum mineralization in the sulfide-quartz veins shows zoning in its rims,indicating variations in composition and element concentrations of the hydrothermal fluids.