江西德兴斑岩铜钼矿床流体包裹体子矿物SEM-EDS研究及其对成矿流体性质的制约  

SEM-EDS investigation of daughter minerals of fluid inclusions at the Dexing porphyry Cu-Mo deposit,Jiangxi Province,China

作　　者：刘玄[1] 范宏瑞[1] 胡芳芳[1] 胡保根[2] 朱小云[2] 

机构地区：[1]中国科学院地质与地球物理研究所矿产资源重点实验室,北京100029 [2]江西铜业股份有限公司德兴铜矿,德兴334200

出　　处：《岩石学报》2011年第5期1397-1409,共13页Acta Petrologica Sinica

基　　金：中国科学院知识创新工程重大项目(KZCX1-YW-15-3)资助

摘　　要：江西德兴斑岩铜钼矿床Q+Py±Cp±Cc脉、(黄铁)绢英岩和Q+Py+Mo±Cp脉中发育大量多相(透明、暗色子矿物)包裹体。本文以详细的显微观察和流体包裹体岩相学观察为基础,利用SEM-EDS(扫描电镜-X射线能谱仪)对多相包裹体内的子矿物进行了系统的鉴定。分析结果表明,Q+Py±Cp±Cc脉石英中发育的透明子矿物包括绢云母、石盐、水氯镁石、白云石、铁氯化物、磷灰石和含稀土元素磷酸盐;暗色子矿物包括赤铁矿、铁氧化物和黄铜矿。(黄铁)绢英岩石英和黄铁矿中透明子矿物包括石盐、(硬)石膏、绢云母、硫酸镁、菱镁矿、六水泻盐和(Fe、Cu、Mg)碳酸盐和硫酸盐,暗色子矿物包括磁铁矿、赤铁矿、金红石和黄铜矿;Q+Py+Mo±Cp脉石英包裹体中发育的子矿物相对较少,透明子矿物包括石盐、菱铁矿和钾长石;暗色矿物为赤铁矿。它们中发育种类繁多的子矿物,表明热液的化学成分非常复杂,多种盐类以及高氧化态子矿物出现指示流体具有高盐度-高氧化态的特征。此外,还鉴别出了黄铜矿、赤铁矿和磁铁矿等金属矿物,这表明热液含有丰富的成矿物质,这些成矿物质随物理化学条件的变化以黄铜矿等金属矿物从热液中沉淀下来,形成了矿床内的主要矿体。结合蚀变矿物组成观察,我们认为Q+Py±Cp±Cc脉、(黄铁)绢英岩和Q+Py+Mo±Cp脉中子矿物组成很可能不代表原始流体的化学成分,因为它们在很大程度上受到了热液蚀变作用的影响,围岩矿物由于水-岩反应被分解,同时释放出Na、Ca、Mg、Fe等元素进入热液,形成了上述种类多样的子矿物。通过流体包裹体岩相学观察发现,(黄铁)绢英岩和中Q+Py+Mo±Cp脉含石盐多相包裹体通常与富气包裹体或者CO2包裹体紧密共生,这表明热液在被捕获前发生了相分离(或沸腾)作用,而这一过程必然会导致富液包裹体盐度的升高,因此不能排除这些高盐包裹体是�A large number of daughter mineral-bearing fluid inclusions formed in Q＋Py±Cp±Cc veins,phyllic rocks and Q＋Py＋Mo±Cp veins at the Dexing porphyry copper-molybdenum deposit,SE China.On the basis of microscopic investigation of the vein（and rock）mineral assemblages and fluid inclusion petrology,Scanning Electron Microscopy and X-ray Energy Dispersive Spectrum（SEM-EDS）were employed in identification of the solid phases in fluid inclusions.Our results suggest that（1）transparent daughter minerals in Q＋Py±Cp±Cc veins include sericite,halite,bischofite,dolomite,iron-bearing chlorides,apatite and Ce-bearing phosphates,and opaque phases consist of hematite,iron-bearing oxides and chalcopyrite;（2）transparent daughter minerals in phyllic rocks include halite,anhydrite,gypsum,sericite,magnesium sulfate,magnesite,magnesium chloride,（Fe,Cu,Mg）carbonate and sulfate,while opaque phase include hematite,magnetite,rutile and chalcopyrite;and（3）daughter minerals in Q＋Py＋Mo±Cp veins are far less developed,which include halite,siderite and K-feldspar for the transparent daughters and hematite for the opaque ones.Various types of daughter minerals in Q＋Py±Cp±Cc veins,phyllic rocks and Q＋Py＋Mo±Cp veins indicate that hydrothermal fluids responsible for their formation are significantly complex in composition and appear to be hypersaline,oxidized and ore minerals enriched.However,detailed alteration mineral observation suggests that Na,Ca,Mg,Fe,which appear in those solid phases are probably contributions from the preexisting minerals（plagioclases,hornblendes,biotites and possibly phosphates）by water/rock reaction in the wall rocks.Furthermore,fluid inclusion petrology indicates that those hypersaline fluid inclusions in the phyllic rocks and Q＋Py＋Mo±Cp veins are likely to be generated from low-or moderate-salinity fluids by fluid-vapor phase separation,which are evidenced by coexistence of daughter mineral-bearing inclusions and vapor-rich inclusions or CO2-rich inclusions.Finall

关 键 词：德兴斑岩铜钼矿 SEM-EDS 含稀土子矿物 热液蚀变 流体体系 

分 类 号：P618.41[天文地球—矿床学] P618.65[天文地球—地质学]