黔东南天柱—锦屏地区石英脉型金矿床成矿作用研究

发布时间：2018-12-14 05:16

【摘要】：黔东南天柱-锦屏地区作为贵州省两大金矿集区之一,开采历史悠久。区内金矿床密集,成矿地质条件良好,有较好的找矿前景。但由于黔东南地区金矿的勘查较采掘滞后,研究工作更多地是针对单个矿床进行,致使区域的成矿机理不清,且在成矿物质来源、流体来源等方面一直存在着较大的争议。研究区位于江南造山带的西南端,是湘-黔金矿带的重要组成部分。地史上经历了武陵运动、雪峰运动、加里东运动和印支-燕山等多期构造运动,为洋壳向陆内转换的造山带。区内构造复杂,发育有多种类型的构造组合,整体的构造格架为北东向及北北东向,其次为近东西向及北西向。具体到各个金矿床,矿体主要受控于北东向背斜及其与之斜交的断裂构造。矿体产出形态分为顺层含金石英脉及穿层剪切破碎带石英脉。矿物组合类型相对简单,常见矿石矿物有自然金、自然银、黄铁矿、毒砂、黄铜矿、方铅矿及闪锌矿等,脉石矿物主要有石英、方解石、菱铁矿等。区内围岩蚀变发育,主要蚀变类型有黄铁矿化、毒砂化、硅化、绿泥石化、绢云母化,与金矿化关系密切。本文通过对研究区区域地质特征、大地构造演化背景、各典型矿床地质特征及成矿作用地球化学的研究,结合成矿系统理论基本框架和前人的研究成果,初步探讨了研究区金矿的成矿机理,分析了其成矿物质来源及流体来源,以期为下一步矿产地质工作提供理论依据。取得了以下认识:总结了黔东南天柱-锦屏地区的宏观找矿标志。并从岩相学、地球化学的角度解释了找矿标志的判别依据,并建立了金的迁移、沉淀机制,认为金在成矿流体中主要以Au(HS)2-的形式进行迁移,在硫化作用的影响下沉淀出来;揭示了有机质(炭质)与金矿化的关系,认为有机质(炭质)的物理性质及化学性质可对金矿化产生有利的影响。同时,分析了韧性剪切带的演化对金成矿的影响,认为研究区金矿的成矿过程符合Sibson提出的“断层阀模式”。应用四级杆型电感耦合等离子体质谱(Q-ICP-MS)对黔东南天柱地区各典型金矿床含金石英脉及近矿围岩的微量、稀土元素进行系统的测定,结果表明:其微量、稀土分布曲线与区域变质岩基本一致,表明部分成矿物质来源于浅部区域绿片岩相地层。部分石英脉样品的稀土配分模式为“平坦型”,轻重稀土分馏不明显,更接近上地幔或下地壳的稀土组成特征,深部低绿片岩相地层在逐渐向低角闪岩相转变的过程中,绿泥石和白云石转变为角闪石和斜长石,并释放出3%-5%的水,并演变成为成矿流体。同时,黄铁矿中的金和砷被分解出来,进入流体中形成含金变质热液,反映成矿物质具有深部来源的特征。结合Y/Ho、Th/U的研究结果:成矿流体主要为变质热液,部分矿床可能有大气降水的混入。综合分析认为:该区金矿床的成矿流体与成矿物质具多来源特征。
[Abstract]:Tianzhu-Jinping area in the southeast of Guizhou province is one of the two gold mining areas in Guizhou Province, with a long history of mining. The gold deposits in the area are dense, and the geological conditions are good. However, since the exploration of gold deposits in the southeast of Guizhou province is lagging behind, the research work is more focused on a single deposit, which leads to unclear metallogenic mechanism in the region, and there has always been a great controversy in the source of ore-forming materials and fluid sources. The study area, located at the southwest end of the Jiangnan orogenic belt, is an important part of the Hunan-Guizhou gold belt. In the history, Wuling Movement, Xuefeng Movement, Caledonian Movement and Indosinian Yanshanian tectonic Movement are the orogenic belts that transform the oceanic crust to the intracontinental crust. There are many types of tectonic assemblages in this area. The whole tectonic framework is NNE and NNE, followed by NW and NW. The ore bodies are mainly controlled by the NE anticline and its fault structure. The ore bodies are divided into gold bearing quartz veins and quartz veins in shear fracture zone. The mineral assemblages are relatively simple. The common ore minerals are natural gold, natural silver, pyrite, arsenopyrite, chalcopyrite, galena and sphalerite, etc. The gangue minerals are mainly quartz, calcite, siderite and so on. The main alteration types are pyrite, arsenopyrite, silicification, green mud fossilization and sericite, which are closely related to gold mineralization. In this paper, the regional geological characteristics, the tectonic evolution background, the geological characteristics of typical deposits and the geochemistry of mineralization in the study area are studied, combined with the basic framework of metallogenic system theory and the previous research results. The metallogenic mechanism of gold deposits in the study area is discussed preliminarily, and the source of ore-forming materials and fluids are analyzed in order to provide theoretical basis for further mineral geological work. The main conclusions are as follows: the macroscopic prospecting marks of Tianzhu-Jinping area in southeast Guizhou are summarized. From the viewpoint of petrography and geochemistry, this paper explains the discriminant basis of prospecting markers, and establishes the mechanism of gold migration and precipitation. It is considered that the gold in ore-forming fluid is mainly migrated in the form of Au (HS) _ 2-. Precipitate under the influence of vulcanization; The relationship between organic matter (carbonaceous) and gold mineralization is revealed. It is considered that the physical and chemical properties of organic matter (carbonaceous) can have a beneficial effect on gold mineralization. At the same time, the influence of ductile shear zone evolution on gold mineralization is analyzed. It is concluded that the metallogenic process of gold deposits in the study area is in line with the fault valve model proposed by Sibson. The trace and rare earth elements of gold bearing quartz vein and surrounding rock near the gold deposit in Tianzhu area of southeast Guizhou Province were systematically determined by four-step inductively coupled plasma mass spectrometry (Q-ICP-MS). The results show that the trace elements are trace. The REE distribution curve is basically consistent with that of the regional metamorphic rocks, indicating that some of the ore-forming materials are derived from the shallow regional greenschist facies. The rare earth distribution pattern of some quartz vein samples is "flat", and the fractionation of light and heavy rare earths is not obvious, which is closer to the REE composition characteristics of upper mantle or lower crust, and the deep low-greenschist facies is gradually changing to low-amphibolite facies. Chlorite and dolomite were transformed into amphibole and plagioclase, and 3- 5% of water was released and developed into ore-forming fluid. At the same time, the gold and arsenic in pyrite are decomposed and entered into the fluid to form a metamorphic hydrothermal solution containing gold, which shows that the ore-forming material has the characteristics of deep source. Combined with the research results of Y / Hoi Th-U, the ore-forming fluids are mainly metamorphic hydrothermal fluids, and some deposits may be mixed with precipitation. It is concluded that the ore-forming fluid and ore-forming material of the gold deposit in this area are characterized by multiple sources.
【学位授予单位】：贵州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.51

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