【作者】 张长青；

【导师】 毛景文； 余金杰；

【作者基本信息】 中国地质科学院 ， 矿物学、岩石学、矿床学， 2008， 博士

【摘要】 川滇黔交界地区铅锌多金属成矿区位于扬子地台西南缘,是我国重要的铅锌银锗生产基地之一。尽管前人对与该地区做了不少研究工作,但是有关铅锌矿与峨眉山玄武岩关系、矿床成因模型等一些重大问题仍未解决。本文在深入解剖典型矿床的基础上,重点探讨有机质与成矿、成矿流体和成矿时代三个关键科学问题,运用氯仿沥青“A”的提取、有机质族组分、色谱-质谱、岩石地球化学、流体包裹体、扫描电镜、放射性同位素年代学等方法和手段,主要研究了矿床有机质与成矿关系、成矿流体性质和来源、成矿物质来源、成矿年代、成矿模型等内容,取得了如下主要成果:1.川滇黔地区铅锌矿床以厚层碳酸盐岩为容矿岩石,具有明显后生特征,受岩性（岩相）和断层双重控制。矿体形态主要有地层控制型、断裂控制型和古喀斯特控制型三种。2.岩矿微量元素、稀土元素分析表明,铅锌元素的主要富集层位为前震旦系基底、震旦系、石炭系和二叠系地层,矿石和这些地层岩石具有相似的稀土配分特征,表明这些地层为区域铅锌矿床的形成提供了物质基础;矿石和围岩铅、硫、碳、氢、氧同位素组成表明成矿物质具有壳源特征,硫来自碳酸盐岩中硫酸盐的还原,成矿流体主要来自大气降水。3.详细研究赤普铅锌矿床内的有机质成因,认为有机质成熟度较高,矿石和围岩沥青经历了相似的高盐度、强还原过程,有机质主要来自海相页岩和碳酸盐岩,没有陆源有机质的加入;有机质在成矿过程中主要起到还原剂的作用,它可将碳酸盐岩中的硫还原为HS^-或H₂S,为硫化物沉淀提供条件。4.流体包裹体分析表明,川滇黔地区的铅锌矿床主要成矿均一温度为170～270℃,主要盐度为8.0～16.99wt%（NaCl）_eq,属于低温中等盐度矿床。成矿流体组分为NaCl-CaCl₂（MgCl₂） -H₂O体系,金属沉淀机制为含矿热卤水与还原流体（如有机流体）的混合。5.通过高精度超低本底单颗粒闪锌矿Rb-Sr测年技术,精确测定大梁子铅锌矿床的成矿年龄为（366.3±7.7 Ma）。扫描电镜分析表明,高岭石的赋存状态是测年结果成功与否的关键。6.在成矿时代约束下,基于大地构造背景、控矿因素和成矿流体耦合关系的成矿模型为:1)晋宁运动后大规模的海侵,导致初始矿源层沉积:2)加里东期的构造运动导致区域内局部地势抬升,断裂活动广泛发育,沉积盆地中地层水和大气降水在重力驱动下发生运移,萃取矿源层中的成矿物质,逐步演变为含矿热卤水;3)早印支或早燕山期造山构造运动使得川滇黔地区进入陆内发展阶段,并导致了楚雄-西昌边缘前陆盆地的形成。古特提斯俯冲碰撞作用下地壳发生区域性上隆,在造山带内形成测在重力和温度、压力差的驱动下成矿流体再次活化富集、运移;印支期或燕山期运动造山阶段造成逆冲断层的广泛发育;4)印支或燕山运动晚期的造山后的侧向挤压,局部正断层发育,形成局部减压扩容空间,为流体的运移和硫化物沉淀创造条件,流体沿不整合面和断层面快速运移,在减压扩容空间沉淀形成铅锌矿床。7.通过研究区与全球经典MVT矿床的对比,认为川滇黔地区的铅锌矿床是与盆地流体活动有关的MVT矿床。更多还原

【Abstract】 The boundaries area of Sichuan-Yunnan-Guizhou province is located on the southwestern margin of Yangtze craton,which is the most important Zn-Pb metallogenic belt in China.Although many work and study have been done there,many problems still exist,such as the genesis of deposits and the relationship between Pb-Zn deposits and Emeishan basalt.Based on the Dissecting the representative deposits in detail,this thesis focused on the three key problems of the relationship between Pb-Zn deposits and organic matter,ore-forming fluid and the geochronology of deposit. By employing many methods to study mainly on the organic matters and metallogenesis,inclusion fluid,source of metal,geochronology and deposits model,such as extract the Chloroform bitumen "A",Group component of organic matters,Chromatogram-mass spectrum,Petrogeochemistry, Fluid inclusion,Scanning electron microscope（SEM） and radioactive isotopic geochronology.The main conclusions that we got are as follows:1.The Pb-Zn deposits of Chuan-Dian-Qian area have not the direct connection with magmatism, whose host by thick carbonate rocks and are the clear post-sedimentary deposits.They controlled by both lithology（lithofacies） and faults.There are three types of orebodies’ shape, namely like bedded controlled by strata,vein controlled by faults and anomaly shape controlled by palaeokarst.2.The analysis of the trace and rare element in the ore and country rock suggests that the main strata of Pb and Zn elements are basement rock,Dengying Formation of Sinian, Carboniferous and Permian.Both of them have the same characteristics of rare elements distribution.These strata supply the metals for the formation of Pb-Zn deposits.The analysis of Pb,S,C,H and O isotopes indicate that the metals of deposits were form upper crust, sulfurs came from the reducing of sulfate in carbonate rocks,and ore fluids came form atmospheric water.3.Through particular studying on the genesis,the organic matters in the ore and country rock of Chipu Pb-Zn deposit have the high maturity and come through the same process of high salinity and strong reduction.The source of organic matters is the shale and carbonate rock from the sea environment,and not from the continent environment.The organic matters can reduce the sulfate to HS^- or H₂S and play the key role in the precipitation of metal sulfides.4.The measures on fluid inclusion obtained the homogenization temperatures of 170～270℃and the salinity of 8.0～16.99 wt%（NaCl）_eq from Pb-Zn deposits in Chuan-Dian-Qian area.These data suggested that the Pb-Zn deposits belong to low temperature and middle salinity deposits. The components of fluid inclusion are NaCl-CaCl₂（MgCl₂） -H₂O system.The precipitation of metal sulfides is from the mixing between hot metalliferous brine and reducing fluid.5.By employing the high precision ultra-low procedural blank Rb-Sr method,the age of 166.3±.7.7 Ma is obtained by dating on single grains（2～5mg） of sphalerite from Daliangzi deposit.The SEM analysis implies that the occurrence of Kaolinite is the key factor for getting the isochrone age or not.6.Based on the constraints of geotectonics setting,geochronology and the coupling of controlling factors and ore-forming fluid,the genetic model is as follows:1) the source beds settled be accompanying by the activities of contemporaneous faults at extensive ingression after the movement of Jinning.2) Locally topography uplift and comprehensive fracture developed during the Caledonian tectonic movement.Formation water and atmospheric water descended along strata and faults at the driving of gravity.The descending fluid extracted the mineral substance and gradually grew into hot metalliferous brine.The early stage Pb-Zn ore precipitated at the open space when the condition of brine changed.3) The orogenesis,which occurred at lndosinian or Yanshanian,brought large-scale quantity of heat and made the ore-forming fluid reactivation and movement again.4) Lateral compression developed the locally normal faults and released the pressure,then formed the dilation spaces for the movement and sulfide deposit.The metalliferous brine flow rapidly along the surface of unconformity or fault surface and settled down at the low pressure and open dilation spaces.7.By compared the Pb-Zn deposits in Chuan-Dian-Qian area with the classic MVT deposits,the Pb-Zn deposits in research district are belong to MVT deposits and are associated to the basin fluid.They are the results of post orogenesis process.更多还原