Geological Characteristics And Genesis Of Jiusangou Gold Deposit, Wangqing, Jilin Province

Jiusangou gold deposit was a typically high-sulphidation epithermal golddeposits in Jilin Province. Jiusangou gold deposit is located in the east ofDuhuangzi-Wangqing Mesozoic volcanic rift basin,and the rift basin werecontrolled by EW、NW-trending structures and hydrothermal breccia barrel. Exposedstrata is mainly Early Cretaceous Jingouling formation (K1j) in the mine, lithology isContinental facies Andesitic volcanic. The magmatic rocks are mainly epithermalintrusive which were associated with volcanic activity late Yanshannian.Ore minerals are pyrite, chalcopyrite, chalcocite, tennantite, sphalerite,bismuthinite, arsenopyrite, azurite and gold. Gangue minerals include kaolinite,quartz, sericite. Intense rock alteration, but the type is simple to silicification andkaolinite-based. The main ore rocks are silicon nuclear,which was subjected tointense leaching, Electron microprobe results show that gold is mainly existed inchalcopyrite and pyrite. Bismuthinite and Bi elements in pyrite and chalcopyriteindicate fluid is closely to magma.Ore minerals different levels of a certain amountof Co and Te, suggesting ore fluids from deep sources.Quartz diorite porphyrite of Jiusangou deposite appears dyke or stock involcanic basin, which is closely associated with mineralization in Yanbian. Based onthe studies of geochemistry, zircon LA-ICP-MS U-Pb dating, this discourse mainlydiscusses petrogenesis, magma source, tectonic setting of the quartz diorite porphyrite.Studies show that Jiusangou quartz diorite porphyrite is belonging to calc-alkalineand peraluminous series. The trace elements of quartz diorite porphyrite showenrichment in LILE, more mobile incompatible elements and LREE, relativedepletion of HFSE and HREE.The geochemical dating suggest that the quartz diorite porphyrite was mainly comes from the crust. In the Al2O3-MgO-FeOtdiagrams andR1-R2diagrams, the characteristics of the quartz diorite porphyrite are similar to thoseof arc-type active continental rocks. LA-ICP-MS U-Pb zircon dating of the quartzdiorite porphyrite give weighted average ages of104.2±1.4Ma (MSWD=0.17) andconcordant age of103.7±0.64Ma (MSWD=4.4), which are in the Late Yanshania(Early Cretaceous）. The results of this study suggest that the metallogenicenvironment was the East Asian continent slip extension caused by subduction of thePacific plate during the Late Yanshanian.The fluid inclusion are all air-aqueous two-phase in quartz. It is indicated thatthe ore-forming fluid belongs to H2O-NaCl system and the fluid is characteristic oflow salinity(0.70％~16.72％NaCl) and low density(0.65~0.97g/cm3).The mainmineralization formation temperature ranges from293.4℃to160.4℃. The value ofpressure is from8.17MPa to40.59MPa and the ore-forming depth is from0.8km to4.1km. Hydrogen and oxygen isotope analysis showed Ore-forming fluids mainlyfrom magmatic water mixed partial precipitation.The values of δS34‰in the ore from3.4‰to5.5‰, average3.0‰,sulfurisotopic homogenization completely, the values of δS34‰in quartz dioriteporphyrite,which associated with mineralization, from2.7‰to3.4‰, average4.3‰, Similar to sulfur isotopic in ore, description Jiusangou gold depositsdiagenesis and mineralization have a similar source material, and have a deep sourcecharacteristics.Eastern Jilin epithermal deposits mineralization age are more concentrated in theLate Jurassic-Early Cretaceous, mineralization age was close to the ore-bearingvolcanic and mineralization related to intrusions,indicating that mineralization andvolcanic role of the same geological events. Combine with the results of Jiusangougold ore rocks-quartz diorite porphyry (104.2±1.4Ma), considered Jiusangou golddeposits formed in the late Early Cretaceous.