滇西北羊拉铜矿床深部锑矿体的成矿时代及成因研究

The Yangla copper deposit is a typical large scale ore deposit in Jinshajiang tectonic belt. Recently, antimony was newly discovered in the depth of Yangla copper deposit, which is never reported in Jinshajiang copper polymetallic belt, the minerlization age, ore genesis and metallogenic model of antimony has become a new scientific problem to study the genesis and mineralization of Yangla copper deposit. In this proposal, the newly discovered antimony will be as the research object. Spatial distribution, shape attitude, ore-controlling factors, ore structures and textures, mineral species, mineral association and mineral generates sequence of antimony will be studied, through tunnel mapping , detailed observations of typical antimony and rock mineral identification. Fluid inclusions in gangue minerals (eg. quartz) and stibnite will be studied by using microthermometric technique, infrared microthermometric technique and micro-Raman spectrometry. Calcite (fluorite) Sm-Nd dating, Rb-Sr dating of quartz-stibnite fluid inclusions and pyrite Re-Os isotopic dating will be used to research the minerlization age of stibnite, association with element geochemistry and C-H-O-S-Pb isotopic, the minerlization and the source of ore-forming material and fluid of antimony will be discussed in this project, while the genesis relationships between antimony mineralization and copper mineralization will be further revealed. Research results can not only rich the oregenesis and metallogenic model of antimony, and can provide evidence for the deep and periphery prospecting prediction of antimony in the Yangla copper deposit.

云南羊拉铜矿床为金沙江成矿带内的典型矿床，近期在其深部新发现锑矿体，在金沙江铜多金属成矿带内未见报道，锑矿体的成矿时代、成因及其与铜矿体的联系便成为亟待解决的新科学问题。本申请拟以羊拉铜矿床新发现的锑矿体为研究对象，通过坑道编录、典型矿体的精细解剖以及镜下鉴定，研究锑矿体的空间分布、形态产状、控矿因素以及矿物种类、矿物组合和矿物生成顺序；利用红外光显微测温、可见光显微测温及激光拉曼光谱，研究辉锑矿及共生脉石矿物（石英）中的成矿流体性质和演化；采用方解石（萤石）Sm-Nd同位素、石英-辉锑矿流体包裹体Rb-Sr同位素和黄铁矿Re-Os同位素精确厘定锑矿体的成矿时代；结合微量元素地球化学和H-O、C-O、S、Pb同位素组成，探讨锑矿体的成矿物质来源及成因，进一步揭示锑矿体与铜矿体之间的成因联系；构建羊拉矿床的铜锑成矿模式，并为羊拉矿区深部和外围的锑矿找矿预测提供依据。

滇西北羊拉矿床为金沙江成矿带内的典型矿床，近期在其深部新发现锑矿体，在金沙江铜多金属成矿带未见报道，锑矿体的成矿时代、成因及其与铜矿体的成因联系便成为亟待解决的科学问题。本项目以羊拉矿床新发现的锑矿体为研究对象，重点研究了其成矿时代和成因，得到如下结论：①羊拉矿床锑矿体主要呈似层状、不规则脉状和团块状产出于大理岩内，严格受NE向断裂控制。锑矿体具明显的矿化蚀变分带，围岩蚀变主要为碳酸盐化、黄铁矿化和硅化。锑矿石矿物组合简单，矿石矿物主要为辉锑矿，脉石矿物主要为方解石和石英。②燕山期北东向断裂为锑矿体的控矿构造，矿田构造研究显示锑矿体形成于北东向断裂之后，表明锑矿体可能形成于燕山期-喜马拉雅期，推测锑矿体可能是中低温热液成矿作用的产物。③锑矿石成矿流体属中低温、中低盐度、中低密度的NaCl-H2O体系，降温冷却和不等温混合作用可能是锑沉淀富集的主要机制。④C-O同位素显示锑成矿流体中的碳和氧可能源于围岩碳酸盐岩的溶解作用，S、Pb同位素表明硫来源于赋矿地层、铅源于上地壳。⑤羊拉矿床锑矿体为热液成因，与辉锑矿共生的方解石Sm-Nd同位素年龄为154.9±7.6Ma，结合矿田构造及白钨矿原位U-Pb年龄，厘定锑矿体的成矿年代为燕山期和喜马拉雅期。羊拉矿床锑矿体与铜矿体并无直接的成因联系，两者在地质特征、成矿时代、成因及成矿机制等方面存在显著差异，为不同期成矿作用的产物。⑥建立了羊拉矿床的铜锑成矿模式，认为羊拉矿床经历了三期成矿作用，印支期矽卡岩-斑岩Cu-Pb-Zn成矿作用、燕山期构造热液Sb成矿作用、喜马拉雅期热液W-Sb-Pb-Zn-Ag成矿作用，并提出了四个找矿方向。本项目研究成果不仅丰富了羊拉矿床的成矿模式，而且为探讨金沙江成矿带的成矿作用演化提供重要支撑。目前羊拉矿床已累计探获锑资源量达中型矿床规模，同时深部发现了铅锌矿体、钨矿体，为矿山企业带来了显著的经济效益。