吉林延边东部四道沟钨矿床成矿流体性质、来源及矿床成因

Property and source of the ore–forming fluids and genesis of the Sidaogou scheelite deposit in the eastern Yanbian area,Jilin Province

【研究目的 】四道沟钨矿床位于延边东部Au–Cu–W矿集区,是具代表性的石英脉型白钨矿矿床。本文通过该矿床的成矿流体性质、来源及矿床成因研究,以提升东北地区石英脉型白钨矿矿床的成矿理论认识,并为该类型白钨矿进一步找矿提供理论支撑。【研究方法 】本文开展了主成矿阶段含白钨矿–石英脉流体包裹体岩相学、显微测温和激光拉曼光谱分析,并配合C–H–O同位素和白钨矿稀土元素分析。【研究结果 】流体包裹体岩相学及显微测温相关研究结果显示,主成矿阶段石英中同时分布有富气相、富液相、含石盐子矿物三相以及含CO_(2)三相等类型原生水溶液包裹体,这些不同类型流体包裹体的均一温度大体一致,应属于沸腾流体包裹体。富气端元流体包裹体的最低均一温度为283℃,基本代表了成矿温度。激光拉曼光谱分析结果显示,成矿流体中气相成分以H_(2)O和CO_(2)为主,还有少量N_(2)和CH_(4)。四道沟白钨矿呈现出“驼峰式”的稀土元素配分型式以及弱的负δEu异常。【结论 】四道沟钨矿床的成矿流体为氧化性的、高中温的NaCl–H_(2)O–CO_(2)±CH_(4)±N_(2)的流体。C–H–O同位素分析结果表明,成矿流体主要为岩浆水,还有少量大气降水的加入,而流体中的碳主要来源于五道沟群变质沉积岩系的有机物氧化作用。四道沟钨矿床为中温岩浆热液型钨矿床,流体沸腾作用是白钨矿大规模沉淀的主要机制。

This paper is the result of mineral exploration engineering.Objective Sidaogou deposit is located in the Au–Cu–W ore concentrated area of the eastern Yanbian,and is a typical quartz vein type scheelite deposit.This paper studied the property and source of the ore–forming fluids and genesis of the deposit,to promote the understanding of the quartz vein type scheelite deposit in NE China and further prospecting.Methods This paper presents the petrographic observation,microtemperature measurement and Laser Roman spectral analysis of the fluid inclusion,C–H–O isotope analysis and rare earth element compositions for the Sidaogou scheelite–quartz veins.Results Petrographic observation indicates that the liquid–rich,daughter minerals–bearing,gas–rich,and CO_(2)–bearing inclusions coexisted in the quartz,and all the types of fluid inclusions have similar homogenization temperatures,which indicate that they belong to boiling fluid inclusions.The lowest homogenization temperature of the gas–rich fluid inclusion(283℃)represents the ore−forming temperature.Laser Raman spectral analysis indicates that the gas phases in the fluid inclusions include H_(2)O and CO_(2),as well as minor CH4 and N2.Scheelite grains yield“hump”type REE patterns with weak negativeδEu anomalies.Conclusions The results indicate that the ore–forming fluids of the Sidaogou scheelite deposit are oxidizing NaCl–H_(2)O–CO_(2)±CH_(4)±N_(2) fluids with high–medium temperature.C–H–O isotopic data indicate that the ore–forming fluids were mainly derived from magmatic water,mixed with a little bit of meteoric water,and the carbonaceous material resulted from oxidation of organic material in the sedimentary rocks from the Wudaogou Group.Therefore,Sidaogou scheelite deposit belongs to mesothermal vein type scheelite deposit,and the fluid boiling induced the precipitation of scheelite.