滇黔交界地区玄武岩铜矿流体包裹体地球化学特征

为了探讨玄武岩铜矿成矿流体的特征,对滇黔交界地区峨眉山玄武岩铜矿3个成矿期次铜矿石中石英和方解石的气液包裹体进行了激光拉曼成分研究和均一温度、盐度测定,对古石油包裹体通过荧光显微镜进行了成分鉴定。结果表明：第1、2期次成矿流体主要为盆地卤水,其气液包裹体气液比小（一般5%～10%）,w（NaCl）为8%～22%,气相为甲烷,液相为水,无子晶及液相CO2,均一温度为80℃～260℃;第2期次成矿流体除盆地卤水外,还有以古石油为代表的有机流体,古石油包裹体由液态烃、固体沥青和气相组成,均一温度变化大（30℃～290℃）,液态烃以荧光性强的芳烃为主;第3期次成矿流体具有大气降水成因,其气液包裹体气液比一般为5%～10%,w（NaCl）〈4%,无子晶及液相CO2,均一温度140℃～270℃,但以小于200℃为主。从第1期次到第3期次,成矿流体盐度逐渐降低,特别是第3期次的盐度非常低,但温度变化不明显。本区最重要的自然铜沉淀富集成矿是第2期次不同性质成矿流体混合或成矿流体与有机流体混合、有机质的还原的结果。

Geochemistry of Fluid Inclusions of the Basalt Copper Deposits in Adjacent Area of Northeastern Yunnan and Western Guizhou,China

In order to understand the characteristics of ore-forming fluids of the Emeishan basalt copper mineralization in adjacent area of northeastern Yunnan and western Guizhou,studies on the composition,homogenization temperature and salinity of the fluid inclusions and palaeo-petroleum inclusions in quartz and calcite of three metallogenic stages have been carried out by means of laser Ramman microprobe,fluorescent microscope and micro-thermometry.The results show that the ore-forming fluids of the first and the second metallogenic stages are of basinal saline fluids,which are composed of liquid H2O and gas CH4 with the ratios of gas to liquid 5%-10%,salinity of 8%-22%（mass fraction of NaCl）,and homogenization temperatures range from 80 ℃ to 260 ℃,without liquid CO2 or daughter minerals.Besides,there also are palaeo-petroleum inclusions that are composed of liquid hydrocarbon dominating of fluorescent aromatic hydrocarbon,solid bitumen and gas phase with homogenization temperature from 30 ℃ to 290 ℃ in the second metallogenic stage.The ore-forming fluids in the third metallogenic stage are of meteoric source,which is composed of liquid and vapor H2O with the ratios of gas to liquid 5%-10%,lower salinity than 4%（mass fraction of NaCl）,and homogenization temperatures mainly range from 140 ℃ to 200 ℃,without liquid CO2 or daughter minerals.The salinity of the ore-forming fluids decreases from the first stage to the third stage,especially low in the third stage,while the homogenization temperature changes slightly.The main ore depositions are developed in the second stage,which may resulted from the mixing of different ore-forming fluids,or mixing of ore-forming fluids and organic fluids with reduction of organic matter.