西秦岭厂坝-李家沟铅锌矿床流体包裹体特征及成因意义

Characteristic and genetic significance of fluid inclusions in the Changba Zn-Pb Deposit,Qinling orogen,China

厂坝-李家沟铅锌矿床位于秦岭造山带西段的西成盆地内,是秦岭泥盆系铅锌成矿带中规模最大的铅锌矿床.由于矿床经历了三叠纪的秦岭造山过程,使得矿床的原始流体的记录全部被消除,现存的包裹体仅记录了后期造山过程中产生的变质流体活动的信息.本次通过对矿床块状和条带状矿石中石英内流体包裹体详尽的包裹体岩相学、显微测温学和拉曼光谱学研究,鉴定出矿床中的包裹体类型主要为H2O-NaCl型包裹体、H2O-NaCl-CH4-CO2型包裹体和CH4-CO2型碳质流体包裹体三类,矿床的包裹体的典型特征是富含CH4和CO2.测温结果显示,H2O-NaCl型包裹体和富气的H2O-NaCl-CH4-CO2型包裹体的均一温度范围基本一致,说明该变质流体经历了不混溶过程.拉曼探针分析结果显示,流体包裹体的主要成分为盐水溶液和以CH4和CO2为主的碳质流体.厂坝-李家沟铅锌矿的流体包裹体特征表明这种碳质流体为代表的变质流体对矿床存在改造作用.

The Changba-Lijiagou lead-zinc deposit,located in the Xicheng basin,the western Qinling orogen,Gansu Province,is the largest and most economically reserves and resource of zinc and lead in lead-zinc metallogenic belt of the Devonian system in the Qinling orogen.The records of original ore-forming fluid were erased by Triassic Qinling orogeny but the information of the metamorphic fluids formed in the process of Qinling orogeny was preserved.The fluid inclusions in quartz associated with massive and bedded ores was studied by fluid inclusions petrography,microthermometry and Raman spectrometry.Three types of fluid inclusions are identified,which are H2O-NaCl,H2O-NaCl-CH4-CO2 and CH4-CO2 carbonic inclusions.Microthermometric results show that the range of homogenization temperature of H2O-NaCl inclusions is equal to that of volatile-rich H2O-NaCl-CH4-CO2 inclusions,implying the ore-forming fluids experience a process of fluid immiscibility.The Laser-Raman micro-spectroscopy results show that the compositions of fluid inclusions are rich in CH4and CO2.The fluid inclusions features of Changba-Lijiagou lead-zinc deposit argues that the later metamorphic fluid characterized by carbonic fluid reworked the deposit.