胶东金地球化学背景研究

胶东金矿集区形成于早白垩世构造体制转折期，具有大规模爆发成矿特征，是世界上重要的金矿集中区之一。针对胶东金矿集区成矿物质来源这一科学问题，采用Au元素地球化学分析法系统分析该区地表和深钻样品，揭示该区金的地球化学背景特征，为探讨该区Au元素高强度巨量堆积的成矿作用机制提供地球化学场制约。结果显示：地表胶东群变质岩具有中部高（金丰度均值为1.35×10^-9）、东部及西部低（金丰度均值分别为0.95×10^-9和0.76×10^-9）的地球化学背景场特征；深钻岩石样品的金丰度均值均低于大陆地壳克拉克值及华北地台大陆地壳的金丰度平均值，同样显示亏损地球化学背景场特征。因此，在胶东金矿集区存在金的地球化学亏损场，结合矿区内围岩中普遍存在的热液活动迹象，认为胶东群和中生代花岗岩可能为胶东金矿的形成提供了部分成矿物质。

Study on Geochemical Background Field of the Gold Deposits in Jiaodong，China

Jiaodong gold ore-concentrating area is the third largest gold mining area in the world after the Lande gold mining area in South Africa and Muruntau gold mining area in Uzbekistan，and its proved gold resources exceed 4 500 t.Jiaodong gold ore-concentrating area formed in the Early Cretaceous tectonic regime transition period and has the characteristics of large-scale concentrated mineralization.This area is composed of a lot of super-large，large gold deposits and includes altered rock type，quartz vein type and interlayer fracture zone type gold deposit.The typical altered rock type gold deposits are Sanshandao，Jiaojia，Xincheng，Dayingezhuang，Xiadian and Dongfeng 171 deposits，and so on.The quartz vein type gold deposits include Linglong，Jinqingding and Denggezhuang deposits，and so on.The interlayer fracture zone type gold deposits are represented by the Pengjiakuang gold deposit.These gold deposits are mainly controlled by the regional faults，secondary faults and interlayer slide faults along the northern margin of the Laiyang basin.The gold deposits in Jiaodong mainly occur within the Mesozoic granite，minor whthin Jiaodong Group，Jingshan Group and Mesozoic strata.This paper selects the scientific problem of the source of ore-forming materials，and systematically analyzes the surface and deep-drilling samples sampled from the Jiaodong area by means of Au element geochemical analysis，in order to reveal the geochemical background characteristics of Au element in this area，and provides geochemical field constraints for discussing the metallogenic mechanism of high-intensity massive accumulation of Au element in this area.The results show that the average abundance of Au element (1.10×10^-9) of the Jiaodong group is lower than that of Clark value of continental crust (1.21×10^-9) and the value of continental crust of North China Platform，which shows the characteristic of gold deficit geochemical field.Moreover，the results also show that the gold geochemical background feild of the Jiaodong group is characterized by higher average Au abundance in the central area (1.35×10^-9) and lower average Au abundance in the east and west of the Jiaodong area (0.95×10^-9 and 0.76×10^-9).The average abundance of Au element in the fresh rock samples of different rock types (Jiaodong Group,0.79×10^-9；Mesozoic granites,0.77×10^-9；Gabbro,0.63×10^-9；Lamprophyre,0.93×10^-9；Acidic dykes,0.82×10^-9) from the deep drilling holes is lower than that of Clark value of continental crust and the value of continental crust of North China Platform，which also display the characteristic of gold geochemical deficit field.Therefore，there exists an Au element geochemical deficit field in the Jiaodong ore-concentrating area，combined with the evidence of hydrothermal activities in gold ore areas，we think the Jiaodong Group and the Mesozoic granite might partly provide the source of metallogenic materials for the formation of gold deposits in the Jiaodong area.