甘肃阳山金矿床地质地球化学特征及成矿过程

发布时间：2018-03-09 21:49

本文选题：阳山金矿　切入点：地球化学特征　出处：《中国地质大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：甘肃阳山金矿是西秦岭地区发现的一处超大型金矿床。通过对阳山金矿矿床地质特征、矿床地球化学特征、物质来源与流体演化及成矿年代学的系统研究发现,阳山金矿经历了复杂的构造-岩浆事件,发生了两期成矿作用。第一期矿化形成蚀变岩型矿体,矿化作用范围广、强度弱,受控于逆冲推覆构造体系下的韧性-韧脆性变形,并受到成矿后构造作用影响,使得矿体产状多变、形态规模各异,围岩蚀变以绢云母化、硅化为主,矿体无明显识别标志,金属矿物组合以微细粒黄铁矿和毒砂为主,金以“不可见金”赋存于黄铁矿、毒砂内;第二期矿化形成石英脉型矿体,矿化作用范围小而强度大,受控于陆内造山构造体系下的韧脆性-脆性变形,成矿时间明显晚于第一期蚀变岩型矿体,受构造作用改造较少,矿体产状稳定,没有明显围岩蚀变,仅发育石英-辉锑矿脉,识别简单,金属矿物组合以辉锑矿为主,金以自然金形式赋存于辉锑矿-石英脉中。根据矿床地球化学和同位素示踪研究发现,第一期成矿作用中泥盆系、碧口群、印支晚期酸性岩脉均提供了部分物质,物质来源复杂,流体演化特征显示以变质流体为主,并且发生明显的流体混合作用。第二期成矿作用物质来源相对简单,以岩浆期后热液或岩浆期后热液与变质热液的混合热液为主,成矿流体演化晚期有大气降水的加入。通过蚀变矿物白云母40Ar-39Ar与热液锆石U-Pb同位素年代学研究,显示第一期成矿作用发生于220~179Ma,与印支晚期岩浆活动同期发生并且时间跨度长;第二期成矿作用发生于128~122Ma,对应于早白垩世区域隐伏岩浆活动。
[Abstract]:Yangshan gold deposit is a super large gold deposit discovered in the West Qinling area of Gansu Province. The geological characteristics, geochemical characteristics, material source and fluid evolution and metallogenic chronology of Yangshan gold deposit are systematically studied. The Yangshan gold deposit experienced complex tectonic-magmatic events and had two stages of mineralization. The first stage of mineralization formed altered rock-type orebodies with a wide range of mineralization and weak strength, and was controlled by ductile ductile brittle deformation under the system of thrust nappe tectonics. Due to the influence of post-metallogenic tectonism, the orebodies are variable in occurrence and different in size. The main alteration of surrounding rock is sericite and silicification, and there is no obvious identification mark for orebodies. The metal mineral assemblages are mainly fine-grained pyrite and arsenopyrite. Gold occurs in pyrite and arsenopyrite by "invisible gold", the second stage mineralization forms quartz vein type orebody, the mineralization range is small and strong, controlled by ductile-brittle brittle deformation under intracontinental orogenic tectonic system, The ore-forming time is obviously later than that of the first stage altered rock type orebody, which is less reformed by tectonism, stable in occurrence, no obvious wall rock alteration, only developed quartz-stibnite vein, easy to identify, and mainly composed of stibnite. Gold occurs in the stibnite-quartz vein in the form of natural gold. Based on the geochemical and isotopic tracer studies of the deposit, it is found that the Devonian system, the Bikou Group, and the late Indosinian acid veins all provide some materials during the first stage of mineralization. The material source is complex, the fluid evolution characteristic shows that metamorphic fluid is dominant, and obvious fluid mixing occurs, the second stage metallogenic material source is relatively simple, It is mainly composed of post-magmatic hydrothermal or mixture of post-magmatic hydrothermal and metamorphic hydrothermal, with the addition of meteoric water in the late evolution of ore-forming fluid. The isotopic chronology of altered mineral Muscovite 40Ar-39Ar and hydrothermal zircon U-Pb is studied. It is shown that the first stage of mineralization occurred at 220 ~ 179 Ma, which occurred at the same time as the late Indosinian magmatism, and the second stage occurred at 128 ~ 122 Ma, corresponding to the concealed magmatic activity in the early Cretaceous region.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.51

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