德兴朱砂红斑岩型铜(金)矿床流体包裹体研究

朱砂红矿床是德兴铜矿田的3大矿床之一,与铜厂、富家坞矿床呈NW向展布.为了查明该矿床的热液蚀变系统、矿化特征及成矿流体性质,文章选取朱砂红矿区5条勘探线上的21个钻孔,通过详细的岩芯编录和岩相学观察,依据矿物组合、脉体穿切关系及蚀变特征,将该矿区内的脉体分为A脉、B脉、D脉及后期碳酸盐和硫酸盐脉,A、B及D脉为主要的矿化脉,共有14种类型.对各期脉体内石英中的流体包裹体进行了系统的显微测温、气液相成分激光拉曼显微分析(LRM),从而详细示踪了成矿流体演化及蚀变-矿化过程.经研究得知,该矿区流体演化过程包括:成矿早期A脉形成阶段,发育4种脉体类型,其脉体多呈不规则状、顺板理团块状,发育的流体包裹体以富气相和含单子晶或多子晶相(还见有金属硫化物)组合为特点,均一温度为350～550℃,ω(NaCleq)主要集中在52.9％ ～69.9％(含子晶多相包裹体)和2.9％～16.8％(气液两相包裹体)2个区间内,该阶段的流体与早期的钾长石化蚀变关系密切;成矿中期B脉形成阶段,发育5种脉体,以平直为显著特征,发育富气相包裹体和单子晶包裹体,还含有部分富液相包裹体,其均一温度为248～405℃,ω(NaCleq)主要集中在38.6％ ～58.0％和0.9％～10.6％范围内,由于该阶段裂隙发育,成矿流体发生了减压沸腾作用,大量金属发生沉淀,是Cu(Au)、Mo的主要成矿阶段;成矿晚期D脉形成阶段,共有5种脉体类型,以富液相包裹体为主,还有少量富气相包裹体,其均一温度为127～326℃,ω(NaCleq)为0.4％～5.1％,该阶段形成了规模较大的黄铁绢英岩化和绿泥石-水云母化,伴有Mo矿化及少量Cu矿化.朱砂红矿区热液流体的演化总体上是,从早期的高温、中-高盐度的岩浆热液,向成矿晚期中-低温、低盐度的岩浆热液+大气降水混合流体转变.气液相成分激光拉曼显微分析(LRM)结果显示,在朱砂红矿区流体的演化过程中,有少量CO2的参与.此外,该矿床流体包裹体内所发现的多种暗色子矿物还有待进行系统鉴定.

A study of fluid inclusions in Zhushahong copper-gold porphyry deposit, Dexing, Jiangxi

Zhushahong is one of the copper porphyry deposits in the Dexing orefield which is composed of Tongchang,Fujiawu and Zhushahong deposits.These deposits are typical continental porphyry deposits in eastern China.Based on observation of 21 drill holes along five exploration lines in the mining area,the authors determined the order of the formation of mineral veins and the different mineral assemblages.According to systematic microthermometric and LRM analyses of 14 different types of veins,the characteristics of ore-forming fluids of the alteration-mineralization system in the Zhushahong porphyry copper-gold deposit were completely recognized.The characteristics and evolutionary process of ore-forming fluids are as follows:① At the early stage,the four A-type veins were formed when the porphyry rock had not been completely solidified,so that the veins were irregular and unclearly bordered with wall rock or porphyry rock and obvious K-feldspar alteration;Fluid inclusions are mainly LVH(one or more daughter metal minerals or transparent minerals are contained in the fluid inclusions) and VL types,with homogenization temperature being 350～550℃ and w(NaCleq) being 52.9%～69.9% and 2.9%～16.8%;② At the middle stage,the five B-type veins were formed in large quantities.Most of B-type veins are straight along with the chalcopyrite,molybdenite,bornite mineralization.Fluid inclusions in this stage are mainly composed of VL and LV and a few LVH types,with captured temperature being 248～405℃ and w(NaCleq) being 38.6%～58.0% and 0.9%～10.6%;③ At the post-mineralization stage,five D-type veins with or without altered hydromica halo were formed when the mineralization system was opened and meteoric water and underground water were infused into the open fissure with large Py-Qz-Ser alteration.Fluid inclusions of this stage are mainly LV with homogenization temperature being 127～326℃ and w(NaCleq) being 0.4%～5.1%.In conclusion,the characteristics of ore-forming fluid of Zhushahong changed from high temperatures and high salinities at the early stage to low temperatures and low salinities at the later stage.According to the result of laser Raman analysis(LRM),there are still CO2-bearing fluid inclusions in most of A,B and D veins.Some daughter metal minerals and transparent minerals contained in the fluid inclusions are still unidentified.