摘要:
提要：岔路口超大型斑岩钼矿床位于大兴安岭北部，是目前中国东北地区最大的钼矿床，矿体赋存于中酸性杂岩体及侏罗系火山-沉积岩内，其中花岗斑岩、石英斑岩、细粒花岗岩与钼矿化关系密切。流体包裹体研究表明，岔路口矿床主要发育富液两相包裹体、富气两相包裹体和含子矿物多相包裹体。花岗斑岩石英斑晶中流体包裹体的形成温度集中在230 ~ 440℃和470 ~ 510℃两个温度区间，盐度分别介于0.7％ ~ 53.7％ NaCl eqv和6.2％ ~ 61.3％ NaCl eqv两个区间；成矿早阶段钾长石-石英-磁铁矿脉中流体包裹体的形成温度集中在320 ~ 440℃、盐度介于4.2％ ~ 52.3％ NaCl eqv；成矿中阶段石英-辉钼矿脉和角砾岩中流体包裹体的形成温度集中在260 ~ 410℃、盐度介于0.4％ ~ 52.3％ NaCl eqv；成矿晚阶段石英-萤石-方铅矿-闪锌矿脉中流体包裹体的形成温度集中在170 ~ 320℃、盐度介于0.5％ ~ 11.1％ NaCl eqv。成矿流体具高温、高盐度及高氧逸度的特征，总体上属于富F的H2O–NaCl±CO2体系。成矿流体的δ18OW值为-4.5‰ ~ 3.2‰，δDW值为-138‰ ~ -122‰，表明成矿流体为岩浆水与雨水的混合流体。金属硫化物的δ34S值介于-1.9‰ ~ +3.6‰，均值为+1.6‰，表明成矿物质主要来自深源岩浆。多期次的流体沸腾作用是该矿床的主要成矿机制。
Abstract:
Abstract：The superlarge Chalukou porphyry Mo deposit, located in northern Da Hinggan Mountains, is the biggest Mo deposit in Northeast China. Its ore bodies are mainly hosted in the intermediate-acid complex and Jurassic volcanic sedimentary rocks, of which granite porphyry, quartz porphyry and fine grained granite are closely associated with Mo mineralization. Three types of fluid inclusions are distinguished based on petrographic and microthemometric criteria, namely liquid-rich two-phase, gas-rich two-phase and daughter mineral-bearing multiphase fluid inclusions. Fluid inclusions in quartz phenocrysts of granite porphyry are mainly liquid-rich two-phase, gas-rich two-phase and daughter mineral-bearing multiphase fluid inclusions, their homogenization temperatures vary from 230 to 440℃ and from 470 to 510℃, and salinities vary from 0.7％ to 53.7％ NaCl eqv and from 6.2％ to 61.3％ NaCl eqv, respectively. Fluid inclusions of the ore-forming early stage K-feldspar-quartz-magnetite vein are mainly composed of liquid-rich two-phase, gas-rich two-phase and daughter mineral-bearing multiphase fluid inclusions, and their homogenization temperatures and salinities vary from 320°C to 440°C and from 4.2% to 52.3% NaCl eqv, respectively. Fluid inclusions of the ore-forming middle stage quartz-molybdenite vein and breccia are mainly composed of liquid-rich two-phase, gas-rich two-phase and daughter mineral-bearing multiphase fluid inclusions, and their homogenization temperatures and salinities vary from 260°C to 410°C and from 0.4% to 52.3% NaCl eqv, respectively. Fluid inclusions of the ore-forming late stage quartz-fluorite-galena-sphalerite vein are mainly liquid-rich two-phase fluid inclusions, and their homogenization temperatures and salinities vary from 170°C to 320°C and from 0.5% to 11.1% NaCl eqv, respectively. The ore-forming fluid of the Chalukou deposit is characterized by high temperature, high salinity and high oxygen fugacity, roughly belonging to the H2O-NaCl±CO2 system enriched in F. The δ18OW values of the ore-forming fluid vary from -4.5‰ to 3.2‰, and δDW values vary from -138‰ to -122‰, indicating that the ore-forming fluid was derived mainly from magmatic fluid mixed with meteoric water. The δ34S values of metallic sulfides range from -1.9‰ to +3.6‰, with an average of +1.6‰, suggesting that the ore-forming materials came mainly from deep magma. The multi-stage boiling action of the ore-forming fluid seems to have been the dominant factor for metallic sulfide deposition.
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