Geochemical Characteristics And Genesis Of Panzijain Gold Deposit In Jiaodong Peninsula,China

The Panzijian gold deposit locates in Qixia City,Shandong Province.Tectonically,it is located at south of Qixia-Penglai metallogenic belt,Jiaobei Uplift,east of North China plate.The Panzijian gold deposit is a typical quartz vein type gold deposit in Jiaodong area,with high gold grade.On the basis of detailed petrographic observation and mineralogical research,this work further carried out micro temperature measurement experiment of quartz fluid inclusions,laser Raman component analysis test,H-0 isotope analysis test of quartz single mineral,He-Ar isotope of rare gas analysis test of pyrite inclusions and Pb isotope analysis test of pyrite single mineral,and obtained the following results research findings:(1)The phase states of fluid inclusions in the ore-bearing quartz vein of Panjian gold mine can be divided into three types:three-phase fluid inclusions containing CO2,gas-liquid two-phase fluid inclusions and single-phase fluid inclusions,The ore-forming fluid is a CO2-H2O-NaCl system fluid with medium low temperature(172 ??341 ?),low salinity(1.57?10.49 wt%NaCl)and low density(0.79?0.96 g/cm3).The ore-forming pressure is 78.04?130.13 MPa,and the estimated ore-forming depth is 7.12?9.5 1 km.(2)The results of H-O isotope analysis(?D value range is-79.8?65.1 ‰,?18O water value range is 1.33?2.63 ‰)indicate that the ore-forming fluid is mainly from the enriched mantle source area,and the effect of atmospheric precipitation on the mineralization is limited.(3)The results of He-Ar isotope analysis(3He/4He value range is 0.81?1.20 Ra,40Ar/36Ar value is between 896.3 and 1724.1),indicating that the ore-forming fluid is dominated by enriched lithosphericmantle,and the crustal fluid also participates in the mineralization,with the characteristics of crust mantle mixing.(4)The results of Pb isotopic analysis of pyrite(206Pb/204Pb value is between 16.06?16.943,207Pb/204Pb value is between 15.337?15.858,208Pb/204Pb value is between 37.143?38.081),indicating that the ore-forming material mainly comes from the deep underground In the lower crust and upper mantle of the Jiaodong Group,only a small amount of ore-forming minerals may be extracted during the upwelling of ore-forming hydrothermal fluid,which is not the main source of ore-forming minerals.In conclusion,combined with the tectonic background of Jiaodong area,the metallogenic process of Panjian gold deposit is inferred as follows:Under the background of the tectonicmovement of the subduction of the paleo Pacific plate to the North China plate in the Mesozoic era,the magmatic activity was intense,the lithosphere was thinned,the lithosphere mantle was upwelling,the tectonic stress environment changed from the early compressive stress to the extension stress,the ore-forming fluid was decompressed and boiling,and gold was deposited and gathered along the faults and other favorable structural parts.