滇中前震旦纪地层内铅锌矿床硫、铅同位素特征及对成矿物质来源指示  

Characteristics of Sulfur and Lead Isotopes in a Pre-Sinian Lead-Zinc Deposit in Central Yunnan and their Implications for Origin of Ore-Forming Material

作　　者：陈欣彬 高建国[1] 刘岩[1] 王文元[1] 侬阳霞 

机构地区：[1]昆明理工大学,国土资源工程学院,云南昆明650093

出　　处：《地质与勘探》2017年第2期227-236,共10页Geology and Exploration

基　　金：国家自然科学基金项目(编号41272111)资助

摘　　要：滇中前震旦系主要位于扬子地块西南缘,元谋-绿汁江断裂以东、普渡河-滇池断裂以西,岩浆活动强烈导致该区地壳结构复杂,具有"多层结构"的特点。据统计,赋存在昆阳群中的铅锌矿床(点)有近20处,其赋矿地层主要为:大龙口组(Pt_2d)、黑山头组(Pt_2hst)、鹅头厂组(Pt_2e)。本文优选大笑、热水塘硫铅同位素进行系统分析对比,总结指示成矿流体与指示物质来源。研究结果显示:赋存在前震旦纪铅矿矿床^(34)S值变化范围在6.33‰~14.99‰,成矿流体的总硫同位素值(δ^(34)SΣS)12.17‰。由此可见,赋存在前震旦纪地层中铅锌矿床硫化物主要为混合硫来源,硫同位素的来源具有多源性的特点。东川大笑铅锌矿:^(206)Pb/^(204)Pb变化范围为18.282~18.391,^(207)Pb/^(204)Pb变化范围为15.491~15.515,208Pb/204Pb变化范围为38.287~38.326,主要分布于地幔、造山带演化线。热水塘铅锌矿:^(206)Pb/^(204)Pb变化范围17.702~18.512,^(207)Pb/^(204)Pb变化范围15.626~15.72,^(208)Pb/^(204)Pb变化范围37.504~38.528,主要分布在造山带演化线附近。μ、ω值的变化范围表明所分析样品铅同位素均属于异常铅,说明其成矿物质多来源。因此,铅同位素主要来自地幔、上地壳和造山带,暗示成矿物质来源具有多源型特点。The Pre-Sinian System of central Yunnan is largely located in the southwestern margin of the Yangtze block, east of the Yuanmou-Luzhijiang fault and west of the Puduhe-Dianchi fault, where the crustal structure is complex with a multiple-layer structure associated with intense magma activity. Statistics shows nearly twenty lead-zinc deposits （ore occurrences） in the Kunyang group, including the Dalongkou Formation （Pt2d）, Heishantou Formation （Pt2hst）, and Etouchang Formation （Pt2e）. This work selected the sulfur and lead isotopes from Daxiao and Reshuitang as targets of analysis comparison to reveal the indicators of ore-forming fluid and material sources. Research results show that the Pre-Sinian lead ore deposit has 34 S values ranging from 6.33‰ to 14.99 ‰, with a total sulfur isotope value of ore-forming fluid （34 S ΣS） 12.17 ‰. It means that the sulfide is mainly from a mixed sulfur source for the Kunyang group deposit in central Yunnan, and the sulfur isotope has multiple sources. For the Daxiao, Dongchuang lead zinc deposits, 206Pb/204Pb varies in 8.282~18.391, 207Pb/204Pb varies in 15.491~15.515, and 208Pb/204Pb changes in 38.287~38.326, primarily distributed around the evolution lines of mantle and the orogenic belt. For the Reshuitang lead-zinc deposit, 206Pb/204Pb ranges 17.702~18.512, 207Pb/204Pb 15.626~15.72, and 208Pb/204Pb 37.504~38.528, distributed around the evolution line of the orogenic belt. The variations of μ and ω values show the lead isotope analysis samples are attributed to abnormal lead, implying its minerals came from multiple sources. Therefore, the lead isotope, mainly from the mantle and the crust and orogenic belts, suggests the ore-forming material is characterized by multiple sources.

关 键 词：硫同位素 铅同位素 成矿物质来源 滇中 前震旦纪 

分 类 号：P591[天文地球—地球化学]