Study Of Geological Characteristics And Ore-forming Fluids For Gold Deposits In The Northern Zhaoping Fault Zone, Jiaodong Peninsula

The zhaoping fault zone is located in the Northwest of Jiaodong Peninsula withdominant ore-forming geological conditions and abundant gold resources. So far,there are13large scale and super-large scale gold deposits have been discovered inthe region, including Linglong,Taishang, Dayingezhuang, Xiadian and Fushan golddeposits. Based on previous research results, we chose Jiuqu, Fushan and Damoqujiagold deposits to undertake system study from ore deposit geological characteristics,fluid inclusion, source and evolution of ore-froming fluids. The main advanceachievements from this study area are as followings.Ore deposit geological characteristics and mineralography indicate that depositsin the study area are controlled by NE-NNE trending tectonic faults, and gold orebodies occurred in the Linglong type granite, Guojialing type granodiorite andLuanjiahe type granite or contact zone between granites. The orebodise for Jiuqu golddeposit occurred as vein or lentoid, and metallogenic stage can be divided intoⅠpyrite-quartz stage, Ⅱquartz-pyrite stage, Ⅲpolymetallic sulfides stage andⅣcarbonate stage. The metallogenic stage for Fushan gold deposit can be devidedinto Ⅰpyrite-quartz stage, Ⅱquartz-polymetallic sulfides stage and Ⅲquartz-carbonate stage. The metallogenic stage for Damoqujia gold deposit can be dividedintoⅠpyrite-quartz stage, Ⅱquartz-pyrite stage, Ⅲquartz-polymetallic sulfides stage and Ⅳcarbonate stage.The mineral fluid inclusions reveal that types of fluid inclusions formed in Jiuquand Fushan gold deposit mainly are aqueous two-phase inclusions，CO2-bearingthree-phase and minor gas-rich fluid inclusions. The types of fluid inclusions formedin the Damoqujia gold deposit mainly are aqueous two-phase inclusions,CO2-bearingthree-phase and CO2-rich fluid inclusions. The homogenization temperature for fluidinclusions from Jiuqu gold deposit is range from133.4℃to325.6℃, andhomogenization temperature for main metallogenic stage is range from222.1℃to315℃. The homogenization temperature of the main metallogenic stage for fluidinclusions of Fushan gold deposit ranges from152.3~328.5℃. The homogenizationtemperature for fluid inclusions from Damoqujia gold deposit is range from111.6℃to443.6℃, and homogenization temperature for main metallogenic stage is rangefrom188.6℃to306.1℃. The salinity of ore-forming fluid are range from0.41%to17.81%NaCl,3.19%to18.45%NaCl and0.35%to15.8%NaCl, respectively. Thefluid density are range from0.63to1.03g/cm3,0.69to0.98g/cm3and0.6~1.1g/cm3,respectively.Research on gas phase composition analysis for fluid inclusions, H-O and Cisotope show that ore-forming fluid for gold deposit in the northern Zhaoping faultzone are NaCl-H2O-CO2fluid system. The ore-forming fluid in the main metallogenicstage are mainly from magmatic hydrothermal, and mixed with meteoric water in thelater stage, so we preliminary concluded that ore-forming fluid undergo immiscibilityThe ore-forming fluid for gold deposits developed in the northern Zhaoping faultzone is NaCl-H2O-CO2hydrothermal system of medium and low temperature, lowsalinity. The gold deposits formed in the late period of Yanshan, and mineralization isrelated to intrusion activity of the Guojialing type granodiorite.