江西彭山矿田张十八铅锌矿地质特征与成矿物质来源研究

【作者】 卢树东；

【导师】 杜杨松；

【作者基本信息】 中国地质大学（北京） ， 矿物学、岩石学、矿床学， 2005， 硕士

【摘要】 彭山矿田是一个以锡、铅、锌为主的大型矿田。各类矿床以岩体为中心,呈“晕圈式”分布。从内到外,由高温矿种过渡为低温矿种。张十八铅锌矿位于“晕圈”的中低温地带。本文重点探讨了张十八铅锌矿的地质地球化学特征、成矿流体来源、以及成矿机制。 良好的区域成矿背景是张十八铅锌矿形成的重要前提。研究表明,九瑞地区呈交叉状的基底深断裂在中生代发生活化,在断裂交汇处形成了岩浆上升的通道。由岩体侵位所形成的穹窿构造体系是本区含矿热液运移的重要场所。张十八铅锌矿床明显受穹窿体系控制,主要赋存在震旦系硐门组顶部与陡山沱组的层间滑动断裂体系内,形成时间大致为燕山晚期,属于中低温热液型矿床。成矿作用可分为三个阶段:石英—黄铁矿阶段、石英—闪锌矿、方铅矿(多硫化物)阶段、少硫化物的石英—碳酸盐阶段。 通过对矿床中流体包裹体及氢氧同位素的系统研究,认为形成本矿床的成矿流体属于中温低盐度流体,矿质从含矿流体中析出时流体并非完全处于均一状态。在成矿过程中明显有外来流体(可能为下渗的大气降水)的混入,流体可能发生了沸腾。本矿区的氢、氧同位素数据显示,主成矿阶段的成矿热液既有岩浆水又有大气降水成分,且随着温度降低(350℃→150℃),大气降水比重逐渐增大,最终占主导地位。 矿区各类地质体的微量元素、铅及硫同位素的分析结果表明矿床铅不是单一来源的正常铅,而是混合型、多来源的异常铅,主要富上地壳铅的特征,并具有少量深源铅。硫同位素与稀土元素分析结果表明矿体与彭山岩体之间存在同源性,均具有壳源特征,成矿作用与燕山晚期的花岗岩浆作用关系密切,由此推测彭山岩体是矿质的主要提供者。 文章最后对影响成矿的因素,包括岩浆岩条件、围岩条件以及构造条件等进行了分析,并对成矿动力学系统、矿液运移通道和方式以及成矿机理和过程等进行了讨论。更多还原

【Abstract】 The Pengshan orefield is a huge orefield predominated by Sn,Pb and Zn deposits.These are distributed as a halo pattern with transition from a high-temperature mineral assemblage in inner zone to a low-temperature mineral assemblage in outer zone.The Zhangshiba Pb-Zn deposit is located in the middle zone of pattern with a middle-low temperature mineral assemblage.This paper presents some new geochemical analyses and fluid inclusion measurements,and provides some new insights into geochemical characteristics,ore-forming fluid source,and metallogenic mechanism of the deposits.A suitable regional metallogenic background is an important precondition for formation of the Zhangshiba Pb-Zn deposit.It is shown that the activation of deep basement faults in Mesozoic Era is responsible for formation of pathways for magma uplifting along some cross zones of the faults,and the dome tectonic system resulted from magma emplacement acts as important locations for migration of ore-forming hydrothermal fluids.The Zhangshiba Pb-Zn deposit is obviously controlled by the dome tectonic system.The orebodies are found mainly in the sliding fault system deposit possibly formed in the late Yanshanian period belongs to a type of middle-low temperature hydrothermal deposit.The formation process of the deposit can be divided into three stages including quartz-pyrite,quartz-sphalerite/galena(multi-sulfide),and quartz-carbonate(little sulfide)stages.The fluid inclusion measurements as well as hydrogen and oxygen isotope analyses indicate that ore-forming fluids with middle temperature and low salinity were not homogeneous when ore minerals crystallied from them.It is shown that evident addition of some introduced fluids possibly from infiltating atmospheric water into the ore-forming fluids and their ebullition occur during the metallogenic process.The hydrogen and oxygen data support deriation of the ore-forming fluids at the major metallogenic stage from mixture of magmatic water with atmospheric water,and are consistent with increasing of atmospheric water with decreasing of temperature rom 35℃ to 150 ℃ and its final predomination in the ore-forming fluids.The trace element as well as lead and sulfur isotope analyses on the samples collected from various geological bodies of the mine provide evidence for derivation of lead in ores not from a single normal source ,but from abnormal multi-source with mixture of much upper crust component with less mantle component.Meanwhile,the sulfur isotope and rare earth element analyses support evident concordance in material source of crust composition between the orebodies and Pengshan pluton and close relation of metallogeny to Yanshanian granite magmatism,which leads to inference that the ore-forming materials are mainly from Pengshan pluton.An analysis has been also carried out on the factors of influence on metallogeny such as magmatic rocks,wall rocks and structures,and a discussion had on metallogenic dynamic system,pathways for ore-forming fluid migration ,and metallogenic process.更多还原