The Study On Metallogenic Time Limit And Geological Characteristics Of Songjiagou Gold Deposit In Jiaodong

Songjiagou gold deposit lies in the northeast margin of Jiaolai Basin,in Shandong Province.This deposit is situated at the junction of Zhu-Dian fault and Tanjia detachment fault.When the Pacific Plate subducted to the Eurasian Plate,in the late of Mesozoic,the extrusion stage changed to the extension stage.Meanwhile,The deposit was manufactured.There are some uncovered rock stratas,which includes Precambrian,Mesozoic,as well as Quaternary.The Cretaceous Laiyang group is the primary strata of the gold deposits.There are some kinds of Magmatic rocks,which chiefly includes Linglong Granite,Weide mountain Granite,Laoshan Granite and involves a number of basic and medium basic dikes.This area has many structures,and these structures’direction primarily are NE or NNE.There is no obvious boundary between ore body and surrounding rock.The junction of ore body and surrounding rocks is hazy.And the average content of the ore is 1.69×10^-6.The major metal minerals involve pyrite,chalcopyrite,sphalerite,natural gold,etc.and the non-metal minerals contain quartz,orthoclase,plagioclase,muscovite,sericite,calcite,etc.The ore structures principally involve granular,interstitial,veinlet,lump,as well as disseminated.The alteration of country rock principally involves pyritization-sericitization,silicification,carbonatization.Moreover,there are three metallogenic stages:Quartz-sericite-pyrite,quartz-polymetallic-sulfide,carbonatite,and the ruling metallogenic phases are the first phase and the second phase.According to these studies of dike rock of Songjiagou gold deposit,which involves petrography,petrochemistry,isotopic geochronology,the research results exhibit that the pre metallogenic dike rocks are diabase and the post metallogenic dike rock are diorite,as well as,theΣREE content is comparatively luxurious.The LREE/HREE ratio of the pre metallogenic dike rocks are 12.76～15.52,and the LREE/HREE ratio of the post metallogenic dike rock is 18.72,which reveal two characteristics that are enrichment of LREE and deficit of HREE.The pre metallogenic dike rocks and the post metallogenic dike rock carry same characteristics that are enrichment of LILE and deficit of HFSE,and it is extraordinarily key that point the distinction of intraplate basalt polluted by crustal ingredients.According to the geochronological study,we acquire some data that point the pre metallogenic dike rock’s age of zircon U-Pb are 518～802Ma,whereas the post metallogenic dike rock’s age of zircon U-Pb already 121±5Ma.Integrated with the past investigations which the Laiyang group’s age is 130±2 Ma,we think that Songjiagou gold deposit is formed from 121Ma to 130Ma.And According to the studies of the crystal shape of pyrite and the thermoelectricity of pyrite,we deem that the gold deposit has no high temperature.The ranges of thermoelectric coefficient of pyrite is from-168.6μV/°C^-1 to 334.4μV/°C^-1,which points that these pyrites conductive types largely are cavity type,and the P-type rate accounts for more than 85%.And the exploration and mining depth index of the ore body is estimated to be about 40.71%.Integrated with these studies,which contain the analysis of crystal shape of pyrite and the thermoelectricity of pyrite,as well as previous work results,it is considered that the Songjiagou gold deposit has prospecting potential in or around the depth.