吉林省大横路钴铜矿床地质特征及成矿流体来源讨论

摘要

大横路钴铜矿床为大型铜伴生钴矿床,矿体主要赋存于大栗子组中段含碳绢云千枚岩之中.矿床经历了海底喷流沉积、变质改造、热液叠加及表生氧化4期成矿作用.热液叠加期形成脉状与浸染状矿石并对层状矿体起到了局部改造的作用,可进一步划分为Ⅰ石英-黄铁矿阶段、Ⅱ石英-方铅矿阶段.流体包裹体岩相学、显微测温及C、H、O同位素研究,表明Ⅰ阶段石英中发育气液两相流体包裹体,均一温度为178~229℃,盐度为6.0%~11.8% NaCleqv,属于中温、低盐度的H2O-NaCl体系.流体包裹体的δDH2O约为-82.3‰~-84.8‰,δ18OH2O为5.5‰~6.4‰,δ13CPDB为-9.7‰~-5.1‰,反应成矿流体主要来自岩浆水.Ⅱ阶段石英中也以气液两相包裹体为主,均一温度为113~169℃,盐度为3.0%~8.5% NaCleqv,属于低温、低盐度的H2O-NaCl体系.流体包裹体的δD为-96.3‰~-90.7‰,δ18OH2O为1.2‰~2.5‰,δ13CPDB为-20.7‰~-16.7‰,反映成矿流体具有岩浆水与大气水混合的特点.%The Dahenglu Cu-Co deposit is a large Cu deposit with associated Co.The ore bodies mainly occur in the carbonaceous sericite phyllite from the Dalizi Formation.This deposit has experienced four stages of mineralization: submarine exhalative origin, metamorphic reformation, hydrothermal superimposition and supergenetic oxidation.The vein and disseminated ores were formed in the hydrothermal superimposition stage, which were subjected to the local transformation for the layered ore bodies.And this stage can be divided into 2 sub-stages: quartz-pyrite sub-stage (I) and quartz-galena sub-stage (Ⅱ).In this paper, the petrography, microthermometry of fluid inclusions, as well as C, H and O isotopes have been studied.The results show that, the quartz-pyrite sub-stage (I) mainly contains aqueous inclusions, their homogenization temperatures are 178~229℃, whereas their salinities range from 6.0% NaCleqv to 11.8% NaCleqv, suggesting the characteristics of the medium temperature and low salinity H2O-NaCl system.The δ DH2O, δ18OH2O and δ13CPDB of fluid inclusions from this sub-stage vary from-82.3‰ to-84.8‰, from 5.5‰ to 6.4‰ and from-9.7‰ to-5.1‰ respectively, showing that the ore-forming fluid mainly sourced from magmatic water.The quartz-galena sub-stage (Ⅱ) are also dominated by aqueous inclusions, with the homogenization temperatures are 113~169℃, whereas the salinities are 3.0%~8.5% NaCleqv, which belong to the low temperature and low salinity H2O-NaCl system.For the fluid inclusions from this sub-stage, the δDH2O, δ18OH2O and δ13CPDB range from-96.3‰ to-90.7‰, from 1.2‰ to 2.5‰ and from-20.7‰ to-16.7‰ respectively, showing the features of magmatic water mixed with atmospheric water.