河南王坪西沟铅锌矿床流体包裹体特征和矿床成因类型

Fluid inclusion features and genetic type of the Wangpingxigou Pb-Zn deposit,Henan province.

王坪西沟铅锌矿床隶属于东秦岭外方山钼铅锌多金属成矿区,位于车村—鲁山断裂北侧。矿床赋存于中元古代熊耳群鸡蛋坪组火山岩系中,受断裂控制,呈脉状产出;矿石主要由金属硫化物,少量石英和碳酸盐组成;成矿过程分为早、中、晚三个阶段,分别以石英—黄铁矿组合、金属硫化物和碳酸盐为标志。流体包裹体研究表明,成矿流体为 CO_2-H_2O-NaCl±CaCl_2体系,石英或闪锌矿中可见 CO_2-H_2O 型、含子晶型和水溶液型三类包裹体,CO_2-H_2O 型包裹体集中在早阶段产出。早、中、晚阶段流体包裹体均一温度分别为280～386℃、180～350℃和120～230℃,从早到晚逐渐降低;盐度分别集中在3%～7%NaCl eqv.、3.55%～17.43% NaCl eqv.和3.06%～13.51%NaCl eqv.。含子晶型流体包裹体主要出现在中阶段,子晶为方解石,该阶段为成矿主要阶段,可见 CO_2-H_2O 型包裹体与富液相水溶液包裹体共存,均一温度相近,指示流体沸腾, 发生 CO_2的逃逸,成矿物质快速沉淀。总之,王坪西沟铅锌矿床地质特征与造山型矿床一致,成矿机理可由碰撞成岩成矿与流体作用(CMF)模式所解释。

The Wangpingxigou Pb-Zn deposit in Henan Province is located to the north of the Checun-Lushan fault along the southern margin of North China Craton. The deposit is a fault-controlled vein-type deposit, hosted in Mesoproterozoic strata. The ores mainly consist of sulfides, quartz and carbonate minerals. Ore-forming process includes three stages marked by three kinds of parageneses： An early quartz-pyrite stage, an intermediate polymetallic sulfide ore stage and a late barren carbonate stage. Microthermometric data of fluid inclusions indicate that ore-forming fluids are CO2-H2O-NaCl ＋ CaCl system. In hydrothermal quartz and sphalerite three types of fluid inclusions can be observed. They are CO2-H2O type, daughter mineral-bearing and NaCl-H2O solution. However, the CO2-H2O type fluid inclusions are mainly observed in the early stage. From early to late stages, homogenization temperatures of fluid inclusions decrease from 280 -386℃, through 180 -350℃, to 120 -230℃ ; Salinities change from 3% -7% NaCl eqv., through 3.55% -17.43% NaCl eqv., to 3.06% -13. 51% NaCl eqv. In the middle stage, Pb and Zn are mainly mineralized and the calcite daughter minerals in fluid inclusions can be recognized. The CO2 -H2O fluid inclusions coexist with the vapor and liquid-rich fluid inclusions. Fluid inclusions with contrasting salinities are homogenized to divergent＂ phase at similar temperature. These phenomena strongly suggest that fluid-boiling occurred in the middle stage and resulted in CO2-release and rapid precipitation of ore-forming material. All the above suggest that the Wangpingxigou deposit is a typical case of orogenic-type Pb-Zn lodes formed during transition from collisional compression to extension and can be genetically addressed using the tectonic model for collisional orogeny, metallogeny and fluid flow （CMF model）.