Study On Genesis And Geological And Geochemical Characteristics Of Banmiaozi Gold Deposit In Baishan City, Jilin Province

Banmiaozi gold deposit, a large deposit, which is currently under exploration and islocated5km～8km to the north of Baishan city.Strata is consist of Gaoling group and Qingbaikouan Group in mining area. F102is animportant ore-controlling structure, F100is an important ore-bearing fault. Ore mineralsconsist of native gold, limonite, arsenopyrite, hematite, pyrite and pyrogelite. Ore texturehas edge and crack filling ones, ore structure are composed of brecciated, disseminatedcolloform stages and star point ones. The wall rock is silicified structural breccias.Metallogenic stages can be divided into quartz-gold-pyrite, quartz-gold-disseminatedpyrite section, Barite-chalcedony-gold-hematiten and pyrite-marcasite epochs.Petrochemistry and geochemistry indicate that the middle Jurassic porphyry granitediorite related to Banmiaozi deposit contains corundum content of6.30～8.73, Al2O3of17.27%～17.85%, A/CNK of1.49～1.81, belonging to strongly peraluminous granites. Ithas Na2O+K2O of5.32%～5.60%, with an average of5.44%, Rittmann Index σ of1.13～1.29(＜3.3), indicating calc-alkaline rocks, with δEu of1.01～1.06(＞1), It has positiveEu anomaly showing plagioclase is rich in source, with δCe of0.72～0.82(average0.76)，＜1. It has negative Ce anomaly, and LFSE Rb, Ba are relatively enriched but Sr isdepleted, HFSE P, U, Sm, Th are enriched with a depletion of Ti and K, Ti is relativelydepleted, indicating the rocks are S stype granite in orogenic belts. It may be located in thevolcanic arc environment and has a close relationship with plate subduction.Two-phase aqueous fluid inclusions are mostly circular and oval, with diameters of2μm～12μm and2μm～5μm are in the majority. Homogenization ranges from140.0℃～243.3℃,with an average of190.4℃,showing a low-temperature fluid.The densities variyfrom0.82g/cm3to0.93g/cm3,with an average of0.91g/cm3,belonging to low-density fluidThe main metallogenic pressures range from9.64Mpa to17.91Mpa, with an average of 12.51Mpa. Salinities vary from1.7%to3.4%, with an average of2.81%, showing it islow-salinity fluid. Mineralizing depth are of0.96km～1.80km, with an average of1.25km,indicating it is a epithermal deposit. Analysis from S isotopic indicate that S isfrom marine evaporate.Comprehensive study shows that the Banmiaozi deposit is an epithermal golddeposittype gold deposit assiciated with the orogeny in Yanshan period.