内蒙古边家大院铅锌银多金属矿床的矿物组成及其成因意义

摘要

Located in the southern Daxing'anling metallogenic belt,Bianjiadayuan Pb-Zn-Ag deposit is a new discovery in recent years of higher ore grade lead-zinc-silver polymetallic deposit.Detailed microscopic identifi-cation and electron analysis show that metalliferous minerals of this deposit mainly consist of galena,sphalerite, pyrite,chalcopyrite,pyrrhotite,arsenopyrite and stannine.Silver minerals mainly consist of tetrahedrite, freibergite and pyrrhotite.In addition,we also found a large number of falkmanites in the mine,which are in-timately accompanied by galena,chalcopyrite and tetrahedrite.Falkmanite crystals show as needle,pillar, bunchiness and anhedral grain forms,and their grain sizes commonly vary from 5 to 1 50 μm.Electron micro-probe analysis also shows that its corresponding formula is (Pb4.77Cu0.05Fe0.04Zn0.06)4.92Sb3.91 S11.00,and its sim-plified formula is Pb5Sb4S11 .Falkmanite is generally the product of the late mineralization with a low tempre-ture.The formation of falkmanite may be favored by a low temperature,increasing fS2 and reduced fluid condi-tions in the ore-forming process.%边家大院铅锌银多金属矿床位于大兴安岭成矿带中南段，是近几年来新发现的矿石品位较高的铅锌银多金属矿床。详细的显微镜下鉴定及电子探针分析表明，矿床的金属矿物主要为方铅矿、闪锌矿、黄铁矿、黄铜矿、磁黄铁矿、毒砂、黝锡矿等，含银的矿物主要为银锑黝铜矿、黝锑银矿及深红银矿。此外，矿区还发现大量针硫锑铅矿，与其共生金属矿物主要为方铅矿、黄铜矿、黝锑银矿等。针硫锑铅矿主要呈长柱状、针状、束状和不规则粒状等，粒度变化较大，一般为5～150μm。电子探针分析结果表明，其相应的平均化学分子式为（Pb4.77Cu0.05Fe0.04Zn0.06）4.92Sb3.91 S11.00，简写为Pb5 Sb4 S11。针硫锑铅矿一般是成矿晚期低温作用的产物，边家大院铅锌银多金属矿床中针硫锑铅矿的形成，与成矿温度较低、硫逸度升高以及还原作用等密切相关。