【作者】 石得凤；

【导师】 张术根；

【作者基本信息】 中南大学 ， 矿物学、岩石学、矿床学， 2012， 博士

【副题名】Mechanism and Regularities of Dingjiashan Pb-Zn Ore District

【摘要】 丁家山铅锌矿区地处闽中地区南部,东南地洼区浙闽地穹系绍广地洼列南平地洼内。受区域环境内多类型沉积建造、多期次构造、岩浆活动及多类型变质作用的影响,区内地质情况较为复杂。目前关于研究区矿床成因类型存在接触交代变质型和与双峰式火山岩有关的块状硫化物矿床(VMS型)两种截然不同的认识,双方争议焦点集中在矿区赋矿围岩原岩类型、成矿作用类型、成矿时代、成矿物质来源、控矿因素等关键性问题上。矿区主要赋矿围岩为上元古界马面山群龙北溪组上段石榴子石透辉石绿帘石系列变质岩,综合变质岩产状、主要造岩矿物的组构及分布特征、岩石化学、岩相学、稀土元素化学等方面的系统化原岩恢复表明其原岩为形成于新元古代的浅(滨)海陆棚相—浅海台地相的粉砂质泥岩、钙质泥质粉砂岩、泥质钙质粉砂岩及泥灰岩等富钙质沉积岩类,而不是以往研究中认为的双峰式火山岩类。精细化矿物场填图结果显示赋矿围岩内石榴子石、透辉石、绿帘石等造岩矿物和矿体内主要金属矿物具有切层分布特征,各类矿物富集中心沿NE、NW向排布,矿物体积百分数等值线整体沿NE向展布,与研究区西部燕山期串珠状花岗岩岩株体分布走向一致,说明矿区成岩、成矿热源——燕山期钙碱性—碱性重熔型钾长花岗岩自矿区中部NE、NW向断层交叉处(Ⅲ-1、Ⅲ-2号矿体交汇处)侵入后,主要沿规模较大的NE向断层向SW方向运移。同成矿期石英流体包裹体Rb-Sr等时线证实矿区成矿时代为(146.15±3.95)Ma,属侏罗纪晚期,为燕山运动早期第三阶段；Pb、 S、H、O同位素及岩体、矿体、围岩稀土元素组成系统化研究证明成矿物质具有多来源特征。其中Pb、Zn由燕山期花岗岩和上元古界马面山群龙北溪组地层共同提供,而S主要由燕山期花岗岩提供,成矿流体由大气降水和岩浆水混合组成。成矿期石英内原生流体包裹体均一法测温结果、闪锌矿-方铅矿矿物对地质温度计计算结果及磁黄铁矿成因矿物学研究结果显示矿区成矿温度在200℃-350℃之间；闪锌矿(六方磁黄铁矿+黄铁矿)地质压力计计算结果显示矿区成矿压力在0.197～0.409GPa之间,与燕山期花岗岩Q-Ab-Or温度压力三相图投影得出的侵入压力0.2-0.3GPa基本一致。以上证据综合证实矿区内与成矿直接相关的变质作用为发生在燕山早期第三阶段的钙碱性—碱性重熔型钾长花岗岩与上元古界马面山群龙北溪组上段经加里东期区域变质的粉砂质泥岩、钙质泥质粉砂岩、泥质钙质粉砂岩及泥灰岩等富钙质岩间的接触交代变质作用。矿区成矿受燕山期钙碱性-碱性重熔型钾长花岗岩、上元古界马面山群龙北溪组富钙质地层和断层、背斜褶皱及角度不整合等构造因素联合控制。其中岩体和地层是发生接触交代变质作用的基本物质条件,为成矿提供Pb、Zn、S等物质和部分成矿流体；断层、背斜褶皱及角度不整合等构造因素为岩体的侵入、成矿热液的运移和矿物质卸载、沉淀开辟空间,其中北东向断层的控矿意义更为关键。丁家山矿区成矿系统结构要素与VMS型矿床和SEDEX型矿床截然不同,属于挤压构造成矿系统(大类)下属的与燕山期花岗质岩浆有关的接触交代变质成矿系统类。位于上元古界马面山群龙北溪组上段、上侏罗统长林组及二者间角度不整合接触面上的矿体为同一成矿系统在不同矿化网络节点上的产物。更多还原

【Abstract】 Dingjiashan Pb-Zn ore district in central Fujian province is located in Southeast tiwa region, Zhemin geodome system, Shaoguang tiwa series. Geological conditions in study area are very complex because of heavily influenced from many types of sedimentary formation, many times of structural activity, magmatism and metamorphism.There are two views on metallogenesis, one is contact metasomatic metamorphism ore deposit and the other one is massive sulfide ore deposit related to bimodal volcanic rocks (VMS). The focus of contention is original rock types of wall rock, metallogenesis type, mineralogenetic epoch, metallogenic material sources, controlling factors, and so on.Main wall rock in Dingjiashan Pb-Zn ore district is metamorphic rock composed by garnet, diopside, and epidote in Neoproterozoic Mamianshan formation Longbeixi group upper. Synthesis studies is used to recover the original rock of wall rock inclouding metamorphic rock attitude, mineral association, texture and structure, characteristic of distribution, petrochemistry, petrography, REE chemistry, and so on. The result confirms that wall rock of Pb-Zn ore body in study area are pararocks, original rock of them are calcareous rocks, like silty mudstones, calcium shale siltstone, shale calcium siltstone, marlstone and so on, but not bimodal volcanic rocks mentioned in previous research. These rocks are neritic (littoral) shelf facies-neritic platform facies.The result of Mineral mapping reveals that essential rock-forming minerals in wall rock and essential metallic minerals in ore body are all cut stratums, enrichment points of them distribute along Northeast and Northwest. The overall disposition of minerals volume percentage contour lines is northeast, which is consistent with the trend of Yanshanian granite in Upper Jurassic Changlin group. It confirms that the heat source of diagenesis and metallogenesis is Yanshanian calc alkalic-alkalic remelted granite. It intruded into the junction of NE fault and NW fault (the junction of ore body Ⅲ-1and Ⅲ-2) in the central of Dingjiashan Pb-Zn district and flowed to SW along NE fault. Rb-Sr isochron of fluid inclusion in quartz indicates the mineralogenetic epoch is (146.15±3.95) Ma, it was late Jurassic and third stage of early Yanshanian. It is found that there are many metallogenic material sources through systematic research on isotope like Pb, S, H and O, REE composition of granite, ore body and wall rock. Pb and Zn is supplied by Yanshanian granite and Neoproterozoic Mamianshan formation Longbeixi group. S is supplied by Yanshanian granite. Ore-forming fluid is composed by magmatic water and atmospheric water. Ore-forming temperature is200℃～350℃, which is confirmed by gas-liquid inclusions homogenization temperature, the result of sphalerite-galena geothermometer and pyrrhotite genetic mineralogy. Ore-forming pressure get from sphalerite (hexagonal pyrrhotite+pyrite) geobarometer is0.197～0.409GPa, which is close to0.2～0.3Gpa, the pressure of Yanshanian granite get from Q-Ab-Or temperature and pressure three phase diagram. There are many differences between Dingjiashan Pb-Zn ore district and VMS and SEDEX ore deposits. The metamorphism which is directly bound up with metallogenesis is contact metasomatic metamorphism between Yanshanian granite and the regional metamorphiced calcareous rock in Neoproterozoic Mamianshan formation Longbeixi group upper.There are three control factors to ore body, Yanshanian calc alkalic-alkalic remelted granite, calcareous rock in Neoproterozoic Mamianshan formation Longbeixi group upper and many kinds of structures like fault, anticline and angular unconformity. Yanshanian granite and calcareous rock in Neoproterozoic Mamianshan formation Longbeixi group upper supply material to contact metasomatic metamorphism, like Pb, Zn, S and a part of ore-forming fluid. Structures open up roads to granite and ore-forming fluid. Finally, these structures become to the spaces for ore bodies. NE faults are the most important ore-controlling structures.It is entirely different between VMS, SEDEX type ore deposits to Dingjiashan Pb-Zn ore district metallogenic system elements. Dingjiashan Pb-Zn ore district is contact metasomatic metamorphism metallogenic system related to Yanshanian granite, which belongs to compression structure metallogenic system. Ore bodies in Neoproterozoic Mamianshan formation Longbeixi group upper, Upper Jurassic Changlin group and angular unconformity between them are products of one metallogenic system but on different Mineralization network points.更多还原