论石英脉型与矽卡岩型钨矿床成矿流体的差异性  

The differences of the ore-forming fluid between the vein-type and skarn type tungsten deposits

作　　者：祝新友[1,2] 王京彬[1,2] 王艳丽[3] 陈细音 傅其斌 田野[1] 

机构地区：[1]北京矿产地质研究院,北京100012 [2]中色地科矿产勘查有限公司,北京100012 [3]有色金属矿产地质调查中心,北京100012 [4]紫金矿业集团有限公司,福州364200

出　　处：《岩石学报》2015年第4期941-953,共13页Acta Petrologica Sinica

基　　金：国家科技支撑计划(2011BAB04B08);国土资源部公益性行业科研专项(201411024);全国危机矿山接替资源找矿项目(20089927)联合资助

摘　　要：石英脉型与矽卡岩型是最重要的两类钨矿床,二者间存在密切的成因联系,均经历了同源碱长花岗岩岩浆分异演化至晚期形成的浆液过渡态流体,进而演化至热液阶段,但二者成矿地质特征不同,成矿流体的差异性明显。通过对湖南瑶岗仙石英脉型钨矿与杮竹园矽卡岩型钨锡多金属矿的对比性研究,发现这种差异性自岩浆晚期阶段就开始了,热液阶段差异性更加显著。脉型钨矿成矿物质和成矿流体具有较单一岩浆来源,无明显外来流体的加入。与花岗岩相比,云英岩中的熔流包裹体气液部分含量更高,逐渐向流体包裹体演化。钨矿化石英脉的流体包裹体均一温度主要集中于350-150℃,盐度2%-8%NaCleqv,变化范围小;流体富CO2,Na^＋/K^＋〉1,成矿环境偏酸性。除岩浆至热液演化过程外,热液阶段的演化进程不明显,没有经历明显的沸腾和系统的降温过程。包括花岗岩、蚀变岩、石英脉等,石英的δ18O值相似,成矿体系的水/岩比值较低。矽卡岩型钨矿的成矿花岗岩浆受碳酸盐岩同化混染的影响,Ca、S含量增高。与多成矿阶段相对应,成矿流体温度、盐度跨度大,均一温度550-100℃,盐度35%-2%NaCleqv。岩浆晚期阶段及矽卡岩阶段,发生于岩浆固结之前大规模隐爆作用,引起成矿流体的沸腾,进而导致流体的高盐度、低CO2、Na^＋/K^＋〈1。CO2的逸失提高了体系的pH值,弱碱性环境下发生广泛钾长石化,流体属岩浆水性质。退变质氧化物阶段,均一温度450-250℃,盐度〈15%NaCleqv,大气降水参与成矿体系导致温度、盐度迅速降低。流体中高度富含Ca^2＋,是导致大规模白钨矿沉淀富集的主要机制。硫化物阶段,均一温度〈250℃,盐度〈10%NaCleqv,成矿流体中来自大气降水比例进一步增加,导致温度、盐度进一步降低,成矿环境向弱酸性转变。引起两类钨矿成矿流体差异性的主要原因包括：岩浆性质略有�The quartz vein and skarn,who have closely genetic relationship,are the most important types of W-bearing deposits.Although both the two type deposits formed during the magma differentiation process from the alkali feldspar granite magma to the transition fluid,then to the magmatic hydrothermal fluid,they are different in geologic characteristics and the ore-forming fluid. Based on the studies of geology and fluid inclusion of Yaogangxian quartz-vein type and Shizhuyuan skarn type W-bearing deposits,it is recognized that the ore-forming process of the two types of deposits differs since the late stage of magmatic differentiation,and is more significant in the magmatic hydrothermal stage. In the vein type tungsten deposit,ore material and fluid has a single magmatic origin,which means no external fluid and material take part in the ore-forming system. Compared to the granite,the content of the gas and liquid in the fluid inclusion in greisen is higher. The homogenization temperature and salinity of fluid inclusion in quartz are about 350- 150℃ and 2% - 8% NaCleqv respectively. The fluid riches in CO2,Na^＋/ K^＋ratio 〉1,and the environment biased toward acidic.In addition to the evolution from magma to magmatic-hydrothermal stage,there are no multi-hydrothermal stages,no obvious boiling and systematic cooling process. The quartzes from the granite,greisen and quartz vein have a similar narrow range of δ^18O value,which shows that the water / rock ratio of the metallogenic system is low. As the assimilation of the carbonate wall rocks,the alkali feldspar granite magma in the skarn type tungsten deposit riches in Ca and S. The wide ranges of homogenization temperature of 550 - 100℃and salinity of 2% - 35% NaCleqv correspond to multiple mineralization stages. In the late stage of magmatic differentiation and prograde stage,the magma cryptoexplostion,which occurred before magma solidification,leads to the boiling of the fluid and causes the high salinity,poor CO2 and Na^＋/ K^＋ratio 〈1. The escape of the

关 键 词：钨矿 石英脉型 矽卡岩型 成矿流体 流体包裹体 湖南省 

分 类 号：P618.67[天文地球—矿床学]