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    内蒙古长汉卜罗铅锌银矿床流体包裹体研究

    Fluid inclusions study of the Changhanboluo Pb-Zn-Ag deposit, Inner Mongolia

    • 摘要: 长汉卜罗铅锌银矿床位于华北克拉通北缘,为一隐伏矿床。矿体主要呈脉状、透镜状赋存于石英斑岩、石英二长岩、安山岩及不同岩性接触带内。据各类脉体的穿插关系和矿物组合,可将成矿过程划分为早阶段浸染状矿化,中阶段多金属硫化物脉(该阶段又可分为石英-黄铁矿±黄铜矿±毒砂脉(Ⅰ)和石英-铅锌多金属硫化物脉(Ⅱ)),晚阶段石英-碳酸盐脉。早阶段浸染状矿化石英斑晶中主要发育气液两相水溶液包裹体(W型)和H2O-CO2包裹体(C型),均一温度介于272~349℃,盐度介于1.40%~7.31%NaCleqv.,成矿流体发生了明显的沸腾作用。中阶段主要为W型流体包裹体,其中Ⅰ阶段均一温度介于198~348℃,盐度介于1.40%~5.86%NaCleqv.,该阶段主要沉淀黄铁矿、黄铜矿及毒砂等金属矿物;Ⅱ阶段均一温度为118~199℃,盐度为1.40%~4.80%NaCleqv.,该阶段为铅锌矿的主要成矿阶段;晚阶段均一温度为106~157℃,盐度为0.88%~2.24%NaCleqv.。早阶段浸染状矿化深度为1.8~2.5km,中阶段(Ⅰ)对应的古深度为0.1~1.5km,中阶段(Ⅱ)成矿深度更浅,近于地表。流体包裹体研究结果表明,成矿流体为低温低盐度流体,铅锌矿化主要形成于岩浆流体与天水的混合作用过程。

       

      Abstract: The Changhanboluo Pb-Zn-Ag deposit is located on the northern margin of North China Craton. The concealed orebodies are hosted in quartz porphyry, quartz monzonite, andesite and the contact zone of different lithofacies as lodes and lens. The hydrothermal ore-forming process of the Changhanboluo deposit includes three stages, i.e., the early, middle and late stages: The early stage is disseminated metallogenic stage; the middle stage is lode metallogenic stage which can be divided into quartzpyrite±chalcopyrite±arsenopyrite sub-stage (Ⅰ) and quartz-polymetallic sulfide sub-stage (Ⅱ); the late stage is quartz-carbonate stage. The disseminated metallogenic stage developed NaCl-H2O (W-type) and H2O-CO2 (C-type) fluid inclusions (Fls). The homogeneous temperatures of the W-type and C-type fluids in the disseminated metallogenic stage are mainly 272℃-349℃, with salinities ranging from 1.40% to 7.31% NaCl eqv. The lode metallogenic stage mainly developed W-type fluids. Therefore, fluids of stage 1 mainly have homogenization temperatures between 198 and 348℃, with salinities ranging from 1.40% to 5.86% NaCl eqv.. The stage Ⅱ fluids yield homogenization temperatures of 118℃-199℃ and salinities of 1.40%-4.80% NaCl eqv. In the late stage, the fluids have homogenization temperatures of 106° C-157° C and salinities of 0.88%-2.24% NaCl eqv. The depth of the disseminated mineralization is about 1.8-2.5 km. The mineralization depth of the middle stage (Ⅰ) is possibly at 0.1-1.5 km, while the middle stage (Ⅱ) shows much shallower depth, which is near the surface. The fluid inclusions in the Changhanboluo Pb-Zn-Ag deposit are characterized by low temperatures and low salinities. The mixing of hot magmatic fluids and meteoric water resulted in rapid precipitation of ore-forming materials.

       

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