内蒙古二道河子铅锌矿矿床地质特征与矿床成因

发布时间：2018-09-13 10:36

【摘要】：二道河子铅锌矿位于额尔古纳地块与兴安地块的结合部位,得耳布干断裂北西侧,大兴安岭得耳布干成矿带中部上护林-西吉诺成矿亚带内。该带成矿地质条件优越,矿产资源丰富,现己发现多处大中型铅锌矿床。矿区出露的地层主要为中侏罗统塔木兰沟组火山岩地层和第四系残坡积物、冲洪积物。火山岩地层产状平缓,主要由有安山岩、流纹岩、晶屑凝灰岩、凝灰岩、沉凝灰以及火山角砾岩组成,此外还发育有熔结的岩屑晶屑凝灰岩、砂岩和砾岩等。区域NE向得耳布干深断裂从矿区东南部通过,其次级构断裂构成矿区的主要构造格局,其中北西向断裂发育密集,在矿区内形成三条断裂破碎带,控制了铅锌矿体的产出,北东向断裂对矿体有一定的破坏作用,断裂均具有多期活动的特征。矿床主要由三个矿带构成,矿体主要呈脉状、网脉状、透镜状产出于塔木兰沟组晶屑凝灰岩、安山岩的北西向断裂破碎带中。矿体形态严格受控于断裂构造,产状稳定,局部具有膨大收缩的特征,断裂交汇处矿体厚大。二道河子铅锌矿床的主要金属矿物有方铅矿、闪锌矿、黄铁矿、黄铜矿等,而脉石矿物主要有石英、方解石、绢云母、绿泥石等。交代溶蚀结构、半自形粒状结构、固溶体分离结构等是二道河子铅锌矿主要的矿石结构,矿石构造主要有脉状-网脉状构造、浸染状构造、块状构造等。围岩蚀变主要有硅化、绢云母化、碳酸盐化、绿泥石化等,其中硅化与铅锌矿化较为密切。成矿过程可划分为热液期与表生期,其中热液期又可划分为石英一黄铁矿阶段、石英一多金属硫化物阶段与石英-碳酸盐阶段。地球化学研究表明,矿区安山岩可分为碱性系列和高钾钙碱性系列,流纹岩和火山碎屑岩属于高钾钙碱性系列,而脉岩多属钾玄岩系列。矿区火山岩轻、重稀土分异明显,强烈富集大离子亲石元素,亏损高场强元素,结合前人同位素资料研究表明中酸性火山岩主要来源于地幔,并有地壳物质的混染,而酸性火山岩是来源于地壳部分熔融,矿区火山岩可能形成于大陆板内构造环境。二道河子铅锌矿床流体包裹体主要有富气相和富液相两种类型,石英包裹体均一温度在77℃~384℃,大至集中在250℃~270℃和310℃~330℃,闪锌矿的均一温度为254℃,因此240℃~280℃基本代表主成矿阶段温度范围。成矿流体总体上为一套中温、低盐度、低密度流体,流体压力在17.85 Mpa~31.15 Mpa,成矿深度为0.66 km~1.15 km。成矿流体具有多期次的特征。流体包裹体成分测试表明成矿流体为CO2-H2O-NaCl体系,并且富含深源气体,结合区域S、Pb、H、O同位素特征,推测成矿物质主要来源于深部,成矿流体为岩浆水和大气降水组成的混合流体。综合研究认为二道河子铅锌矿床成因类型为断裂控制的与火山—次火山热液有关的浅成中低温热液型铅锌矿床,形成于燕山晚期大陆板内伸展构造环境。
[Abstract]:Erdaohezi lead-zinc deposit is located in the joint part of Erguna block and Xingan block, the north west side of Deerbugan fault, and the upper protection forest- Xijinuo metallogenic subzone in the middle of Daxing'anling Deerbugan metallogenic belt. There are many large and medium-scale lead-zinc deposits found in this belt because of its superior geological conditions and rich mineral resources. The exposed strata of the mining area are the volcanic strata of the middle Jurassic Tamulangou formation and the Quaternary residual slope deposits and alluvial deposits. The volcanic strata are flat, mainly composed of andesite, rhyolite, crystalline tuff, sedimentary tuff and volcanic breccia, in addition, there are clastic tuff, sandstone and conglomerate, etc. The regional NE trending Deerbugan deep fault passes through the southeast of the mining area, and the next gradation fault constitutes the main tectonic pattern of the mining area, in which the NW trending faults are densely developed, and three fracture zones are formed in the mining area, which control the production of the lead-zinc orebody. NNE faults have a certain destructive effect on orebodies, and the faults have the characteristics of multi-stage activity. The ore deposit is mainly composed of three ore belts, the orebody is mainly vein-like and reticulate, and lenticular occurs in the grain tuff of the Tamulangou formation and the NW-trending fracture zone of the andesite. The shape of the orebody is strictly controlled by the fault structure, the occurrence is stable, the part has the characteristic of expanding and shrinking, and the orebody at the fault junction is thick. The main metal minerals of Erdaohezi Pb-Zn deposit are galena sphalerite pyrite chalcopyrite and so on while gangue minerals mainly include quartz calcite sericite chlorite and so on. Metasomatic dissolution structure, semi-automorphic granular structure and solid solution separation structure are the main ore structures of Erdaohezi lead-zinc deposit. The ore structures mainly include vein-reticulate structure, disseminated structure, block structure and so on. The main alteration of surrounding rock is silicification sericite carbonization green mud fossilization and so on among which silicification and lead-zinc mineralization are very close. The metallogenic process can be divided into hydrothermal period and epigenetic stage, in which hydrothermal period can be divided into quartz-pyrite stage, quartz-polymetallic sulfide stage and quartz-carbonate stage. Geochemical studies show that the andesite can be divided into alkaline series and high-potassium calc-alkaline series, rhyolite and pyroclastic rocks belong to high-potassium calc-alkaline series, and dike rocks belong to kaliacite series. The volcanic rocks in the mining area are characterized by light, heavy rare earth elements, strong enrichment of large ion lithophile elements and depletion of high field strength elements. Combined with previous isotopic data, it is shown that the intermediate-acid volcanic rocks are mainly derived from the mantle and are mixed with crustal materials. The acidic volcanic rocks are derived from partial melting of the crust, and the volcanic rocks in the mining area may be formed in the continental intraplate tectonic environment. The fluid inclusions of Erdaohezi lead-zinc deposit are mainly gas-rich and liquid-rich. The homogenization temperature of quartz inclusions is from 77 鈩，

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