摘要
河南省栾川县南泥湖超大型钼钨矿床形成于秦岭造山带的燕山期大陆碰撞体制,流体成矿过程包括早、中、晚3个阶段,分别以石英+钾长石±辉钼矿±黄铁矿、石英+多金属硫化物±碳酸盐和石英+碳酸盐+萤石组合为标志,矿石矿物主要沉淀于中阶段。早、中阶段石英中可见纯CO_2包裹体、CO_2-H_2O型包裹体、水溶液包裹体和含子晶多相包裹体,但晚阶段萤石中只发育水溶液包裹体。早阶段流体包裹体均一温度集中于350～460℃,盐度为5.68 wt%～17.87 wt%NaCl.eqv。中阶段包裹体均一温度集中在250～380℃,盐度为3.00 wt%～38.16 wt%NaCl.eqv;中阶段多相包裹体中常见石盐、黄铜矿和未知种类的子矿物,指示流体具有沸腾所致的还原性、过饱和特征;盐度相差悬殊的含子晶多相包裹体、富气相水溶液包裹体和富液相水溶液包裹体共存,在相近温度下异相均一,表明流体沸腾的存在。晚阶段流体包裹体均一温度集中在115～265℃,盐度介于0.53 wt%～1.23、wt%NaCl.eqv之间。估算早、中阶段流体捕获压力分别为70～300MPa和30～150MPa,推测成矿深度约为3km。总之,成矿流体具高温、高盐度、高氧逸度、富CO_2的特征;流体沸腾导致CO_2逃逸,氧化性降低,成矿物质沉淀。
The Nannihu Mo-W deposit, Luanchuan County, Henan Province is a giant porphyry Mo-W deposit formed in the Yanshanian continental collision regime in the Qinling orogenic belt. The hydrothermal ore-forming process includes the early, middle and late stages, characterized by mineral assemblages of quartz + potassic feldspar +/- molybdenite +/- pyrite, quartz + polymetal +/- carbonate and quartz + carbonate + fluorite, respectively. Ore minerals were mainly precipitated in the middle stage. The hydrothermal quartz formed in the early and middle stages contain four types of fluid inclusions (FIs), i.e. pure CO(2), NaCl-H(2)O, CO(2)-H(2)O and daughter mineral-bearing fluid inclusions; while the late-stage minerals, Such as fluorite, contain only NaCl-H(2)O fluid inclusions. The homogeneous temperatures of the early stage FIs are mainly 350 similar to 460 degrees C, with salinities ranging from 5.68 wt% to 17.87 wt% NaCl. eqv. The middle stage FIs yield homogeneous temperatures of 250 similar to 380 degrees C and salinities of 3.00 wt% similar to 38.16 wt% NaCl. eqv. Daughter minerals, such as halite, chalcopyrite and some unknown minerals, are frequently present in the middle stage, which probably represents a reducing and oversaturated fluid-system resulted from fluid-boiling. Fluid-boiling is evidenced by coexistence of daughter mineral-bearing, and vapor-and liquid-rich NaCl-H(2)O FIs; and by divergent-phase homogenizations of FIs with contrasting salinities at similar temperatures. FIs of late stage are homogenized at temperatures of 115 to 265 degrees C, yielding salinities of 0.53 w% to 1.23 wt% NaCl eqv. The estimated pressures range from 70 similar to 300MPa in the early stage to 30 similar to 150MPa in the middle stage, respectively, corresponding to depth of 3km. In a word, the ore-fomring fluids are characterized by high temperature, high salinity, high f(02) and high CO(2) content; and fluid-boiling resulted in CO(2) release, f(02) decrease and ore minerals precipitation.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2009年第10期2550-2562,共13页
Acta Petrologica Sinica
基金
国家973项目(2006CB4035008课题)
国家自然科学基金项目(编号40730421和40425006)
国家危机矿山项目(编号 20089934)
中国科学院百人计划项目的资助
