摘要:金岗库矿床位于华北克拉通中部造山带，具有典型的VMS与BIF共生特征。本文对金岗库矿床的地质与地球化学特征进行系统研究，探讨金岗库硫化物矿石与磁铁石英岩的共生特点与成矿动力学模式。研究表明，硫化物矿体受地层及岩性控制，多呈扁豆、层状—似层状赋存于五台绿岩带金岗库组的磁铁石英岩、斜长角闪岩、斜长片岩和云母石英片岩中。矿石中金属矿物组合为黄铁矿—黄铜矿—磁黄铁矿—磁铁矿，矿石主要呈半自形—他形粒状结构和块状、条带状构造，围岩蚀变为绿泥石化和绢云母化。斜长角闪岩的原岩恢复，表明斜长角闪岩的原岩为拉斑玄武岩，可能形成于岛弧环境。LA-ICP-MS锆石U-Pb定年显示变基性火山岩的原岩形成于2 500 Ma，代表了金岗库矿床的成矿年龄。变质流体体系的成分模式为H2O-NaCl-CO2-CH4±N2±H2，变质峰期为中高温（322 ℃～473 ℃）、低盐度（2.2%～6.74%）的热液流体，并叠加少量中高温（290 ℃～470 ℃）、高盐度（37.4%～55.79%）的岩浆热液流体；峰后阶段为中低温（225 ℃～302 ℃）、中低盐度（4.03%～11.81%）的热液流体。金岗库矿床赋存的磁铁石英岩和硫化物矿体紧密共生，具有相同的成矿时代、物质来源和变质变形历史。综合以上研究认为金岗库矿床的成因类型为海相火山喷流沉积—变质热液流体叠加改造型。
关键词: 成矿作用/
VMS/
BIF/
金岗库五台/
华北克拉通
Abstract:Located in the Trans-North China orogen, Jingangku deposit constitutes stratabound VMS and BIF. This paper researches on the geological and geochemical characteristics of Jingangku deposit, and studies the paragenetic association of VMS-BIF as well as metallogenic geodynamic model. The stratiform, stratiform-like and lenticular ore bodies are hosted in the Jingangku Formation of Wutai greenstone belt, with the wall-rock of magnetite quartzite, amphibolite, plagioclase schist and mica-quartz schist. The main metallic minerals in the ore are pyrite-chalcopyrite-pyrrhotite-magnetite, which display hypautomorphic-xenomorphic granular textures, and massive or banded structures. The wall-rock alterationis characterized by chloritization and sericitization. Geochemical analyses indicates that the protolith of amphibolite is tholeiite, probably originating in island arc setting. LA-ICP-MS zircon U-Pb dating shows the protolith of amphibolite formed at 2 500 Ma, representing the formation age of the Jingangku deposit. Through analyses of fluid inclusions from ore-bearing magnetite quartzite, the component of metamorphic fluid is H2O-NaCl-CO2-CH4±N2±H2. The fluid during metamorphic peak has feature of medium-high temperature （322 ℃～473 ℃） and low salinity （2.2%～6.74%）. Little magmatic hydrothermal fluid superimpose on the metamorphic peak, with character of medium-high temperature （290 ℃～470 ℃） and high salinity（37.4%～55.79%）. The fluid after metamorphic peak has feature of low-medium temperature （225 ℃～302 ℃） and low-medium salinity （4.03%～11.81%）. Sulfide orebodies are closely associated with magnetite quartzite, so it is supposed that both sulfide and magnetite quartzite have the same material source and formation age, and underwent the same history of deformation and metamorphism. Consequently, Jingangku deposit were formed from submarine exhalative sedimentation, then superimposed and transformed by metamorphic fluid.
Key words:Mineralization/
VMS/
BIF/
Jingangku Wutai/
North China Craton
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