北武夷蔡家坪铅锌矿床硫化物特征、矿床成因类型及成矿时代

北武夷蔡家坪矿床是近年来新发现的一个中型铅锌矿床.矿床赋矿围岩为侏罗系水北组(J1s)、漳平组(J2z)砂岩,铅锌矿体多产在断裂旁侧破碎带及流纹斑岩与砂岩接触带.在野外调查基础上,通过显微镜下观察及电子探针分析,对矿区主要金属硫化物进行了细致研究.初步将成矿过程划分为沉积成矿期、岩浆热液期与表生期,其中岩浆热液期包括中...

Characteristics of sulfide minerals, genetic type and metallogenic epoch of the Caijiaping lead-zinc deposit, North Wuyi Area, Jiangxi Province

The Caijiaping lead-zinc deposit,located in north Wuyi area,Jiangxi Province,is a newfound medium-sized deposit.Sandstones of the Jurassic Shuibei Formation(J1s) and Zhangping Formation(J2z) are wall rocks of orebodies.The lead-zinc orebodies usually occur in the crush belts beside the fractures,and often exist in boundary surfaces of rhyolite porphyries and sandstones.On the basis of field work,by means of observation of microscope and analysis of electron probe,this paper researches main sulfide minerals of the deposit at great length.Ore-forming process is preliminarily divided into sedimentary mineralization period,magmatic hydrothermal period and hypergene period.Magmatic hydrothermal period consists of medium-high temperature pyrite-sphalerite stage,medium-low temperature quartz-polymetallic sulfide stage and carbonate stage.Medium-high temperature pyrite-sphalerite stage is characterized by medium and large-grained hypautomorphic-automorphic pyrite+christophite,which can reflect higher formation temperature.The alteration of this stage is epidotization.Medium-low temperature quartz-polymetallic sulfide stage,which is a major metallogenetic stage,has a major ore mineral association consisting of pyrite+sphalerite+chalcopyrite+galena.The major alteration of this stage is silification,chloritization and sericitization.The data of electron probe indicate that following the mineralization,sulfur was more and more deficient.According to the trace element geochemistry of galena and sphalerite,mineralization mainly resulted from magmatic hydrothermal process superimposed on layer-controlling action and sedimentation-metamorphism,which indicates that the mineralization of this deposit is polygenous.The bedding and incision orebodies we found in the field imply that the origin and the type of the lead-zinc orebodies are not single.Sulfur isotopic analysis indicates that sulfur of the Caijiaping deposit is mainly magmatic sulfur in origin,possibly mixed with mantle-derived magma,and the sulfur isotope was approximately on balance when metallogenic materials were precipitated.The geologic thermometers of chlorite,cadmium and sulfur isotope show that the temperature of mineralization is 292.3—490.6 ℃,which is medium-high temperature and is consistent with the result of the trace element analysis.Additionally,it is found that the fault F4 cuts orebodies in the field,and the potash feldspar selected from felsic vein within F4 yields a 40Ar/39Ar age of 120±4 Ma,implying the mineralization of the Caijiaping deposit should occur before(120±4) Ma.Combining with previous studies,the authors speculate the age of mineralization was 120-138 Ma,corresponding with extensional mineralization stage of the South China area.According to the researches above,the Caijiaping lead-zinc deposit,a medium temperature hydrothermal deposit,mainly resulted from magmatic hydrothermal process.In addition,layer-controlling action and sedimentation-metamorphism also controlled the formation of the deposit.