内蒙古西拉沐伦成矿带羊场石英脉型钼矿床成矿流体地球化学特征研究  

Ore-forming fluid geochemistry of Yangchang quartz vein molybdenum deposit in Xilamulun molybdenum metallogenic belt,Inner Mongolia

作　　者：张作伦[1,2] 刘建明[2] 褚少雄[2] 

机构地区：[1]中铁资源集团中铁资源地质勘查有限公司,北京100039 [2]中国科学院地质与地球物理研究所矿产资源研究重点实验室,北京100029

出　　处：《岩石学报》2012年第2期391-400,共10页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(40972065);全国危机矿山接替资源找矿综合研究项目(20089931);中国中铁股份有限公司2010年度重点科技开发计划(2010-04;2010-07)联合资助

摘　　要：内蒙古羊场钼矿床产于华北克拉通北缘西拉沐伦钼多金属成矿带内,矿体主要以石英脉形式产于燕山期黑云母二长花岗岩内,受NW、NNW向断裂构造控制。成矿过程包括石英大脉阶段(Ⅰ)、石英-黄铁矿亚阶段(Ⅱ-1)、石英-黄铁矿-辉钼矿-黄铜矿-方铅矿-闪锌矿亚阶段(Ⅱ-2)、碳酸岩化阶段(Ⅲ)。流体包裹体研究发现,按照气相比不同可将包裹体分为WL型(<50%)、WV型(50%～90%)、G型(100%)。Ⅰ、Ⅱ-1、Ⅱ-2阶段包裹体均一温度分别为173～280℃、180～467℃、151～366℃,不具有继承演化关系,可能是成矿作用过程中加入有岩浆热液的结果;盐度分别为4.03%～10.61%NaCleqv、2.07%～10.36%NaCleqv和2.41%～9.98%NaCleqv。各阶段流体成分均以H2O为主(>94.39mol%),含少量挥发份CO2、N2、CH4、C2H6、Ar、H2S等还原性气体,阳离子以Na+为主,阴离子以HS-、Cl-为主,属含少量CO2的NaCl-H2O体系;各阶段石英氢、氧同位素δ18OH2O介于-0.08‰～1.90‰、δD介于-119.66‰～-98.79‰。上述特征说明该矿床的成矿流体是岩浆热液与古大气降水混合而成。不同来源、不同性质的流体混合作用是造成羊场辉钼矿沉淀成矿的主要原因。The Yangchang Mo deposit is located in the Xilamulun molybdenum metallogenic belt on northern margin of North China Craton,Inner Mongolia.The mineralization is occurred within the NW-to NNW-trending faults and fractures hosted by the Yanshanian biotite monzogranite.The ore-forming hydrothermal process can be subdivided into four stages：quartz vein stage（Ⅰ） ,quartz-pyrite stage（Ⅱ-1） ,quartz-pyrite-molybdenite-chalcopyrite-galena-sphalerite stage（Ⅱ-2） and carbonate stage（Ⅲ） .Three types of fluid inclusions are observed in quartz crystals,i.e.liquid-rich（VH2O50%） inclusion,gas-rich（VH2O=50%～90%） inclusion and vapor inclusions.Homogenization temperatures of Ⅰ,Ⅱ-1,Ⅱ-2 stages are 173～280℃,180～467℃,151～366℃,respectively.From Ⅰ stage to Ⅱ-1 stage the temperatures become higher,suggesting the magmatic water was introduced into the mineralizing system.Salinities of Ⅰ,Ⅱ-1,Ⅱ-2 stages are in the range of 4.03%～10.61% NaCleqv,2.07%～10.36% NaCleqv,2.41%～9.98% NaCleqv,respectively.The composition of the hydrothermal fluids at different stages are mainly H2O（94.39mol%） ,with minor CO2,N2,CH4,C2H6,Ar,H2S,and Na＋,HS-,Cl-ions.These suggest the Yangchang Mo deposit was formed in reduction condition and the ore-forming fluids were of the NaCl-H2O±CO2 system.Hydrogen and oxygen isotopes of fluid inclusions in various mineralization stages are-119.66‰～-98.79‰ and-0.08‰～1.90‰ respectively,indicating that the ore-forming fluids were the mixture of magmatic water and meteoric water.It is suggested that the mixing of different fluids with distinct natures might be responsible for the precipitation of molybdenite.

关 键 词：流体包裹体 氢氧同位素 羊场 西拉沐伦 

分 类 号：P618.65[天文地球—矿床学]