The Mesozoic Gold Polymetallic Regional Metallogeny In Qipengfu Ore Concentration Area,Jiaodong Peninsula

Qixia-Penglai-Fushan ore concentration area is an important Au-Cu-Mu-Pb-Zn and other polymetallic metallogenic region in Jiaodong region and even in the whole country.Large-scale magmatism and mineralization occurred in Late Jurassic-Early Cretaceous,continental collision between North China and Yangtze Craton and subduction of Pacific plate to North China Craton provided dynamic environment for diagenesis and mineralization in this area.In this paper,the deposit geochemistry and isotopic chronology are used to study the Majayao gold deposit,Dujiaya gold deposit,Xiangkuang copper-lead-zinc deposit and other typical intrusive rocks in the area,and the diagenetic and metallogenic ages are obtained,the ore-controlling factors are analyzed,the metallogenic regularity is summarized,and the metallogenic prediction is carried out.Gain the following understanding:The types of gold-polymetallic deposits in the study area are mainly medium-low temperature hydrothermal vein type,porphyry-skarn type and interlayer detachment zone type deposits.The study of fluid inclusions shows that the ore-forming fluid of the mid-low temperature hydrothermal vein type gold deposit belongs to a reductive hydrothermal system with medium-low temperature,medium-low salinity,low density and rich CO2.According to the comprehensive analysis of the temperature and pressure conditions of fluid inclusions,the ore-forming depth of the gold deposit is concentrated in 3.5?8km.The results of hydrogen and oxygen isotopes of quartz reveals that porphyry-skarn polymetallic deposits are dominated by magmatic fluids.Medium-low temperature hydrothermal vein type and interlayer detachment zone type gold deposits,the initial fluid is magmatic fluid,and the later stage is mixed with atmospheric water.In-situ sulfur isotope research results show that the ore-forming materials of porphyry-skarn deposit have mantle-derived magma characteristics.However,the mid-low temperature hydrothermal vein type and interlayer detachment zone type deposits have the characteristics of crust-mantle mixed source.Lead isotope results show that the mid-low temperature hydrothermal vein type and porphyry type polymetallic deposits have the attribute of crust-mantle mixed source.Lead in the interlayer detachment zone type gold deposits mainly comes from the upper crust and orogenic belts.Helium and argon isotope results show that the mantle fluid of the medium-low temperature hydrothermal vein type gold deposit has the highest proportion of mineralization,followed by porphyry type polymetallic deposit,and the interlayer detachment zone type gold deposit has the lowest proportion.The metallogenic ages of Majiayao gold deposit,Daliuhang gold deposit,Yangjiakuang gold deposit and Xiangkuang copper-lead-zinc deposit are accurately obtained for the first time by using Rb-Sr isotopic dating of pyrite and Sm-Nd isotopic dating of carbonate minerals,which are 123.4 ± 2.9 Ma,117.6±0.1 Ma,123.5 ± 8.1 Ma and 125.8 ± 3.8 Ma,respectively.The Yanshanian period in this area developed three stages of magmatic activities,namely,Late Jurassic(160?145Ma),Early Early Cretaceous(130-126Ma)and Late Early Cretaceous(118?110Ma),accompanied by three stages of large-scale metallogenic events.Among them,gold deposits are mainly concentrated in the early Early Cretaceous(123.5?117.6 Ma).The mineralization of nonferrous polymetallic deposits can be divided into three stages:skarn-type tungsten-molybdenum deposit of Late Jurassic(Xingjiashan tungsten-molybdenum deposit,158Ma);Porphyry Pb-Zn deposit(Xiangkuang Cu-Pb-Zn deposit,125.8 Ma)in the early Early Cretaceous;The middle-low temperature hydrothermal vein copper deposit(Wangjiazhuang copper deposit,116.1 Ma)in the late Early Cretaceous.The results of apatite fission track study show that since 110Ma,the denudation depth of Mesozoic rock mass in the study area is about 3.27-3.52 km,which is far less than the mineralization depth of the deposit,indicating that the deposit has been well preserved after formation.At present,the mining depth of the deposit in the study area is generally shallow and there is still great prospecting potential in the deep part.