西秦岭金矿带南亚带印支期造山型金成矿系统

发布时间：2018-04-04 09:33

本文选题：印支期造山型金成矿系统　切入点：多样性与连续性　出处：《中国地质大学(北京)》2016年博士论文

【摘要】：西秦岭金矿带内印支期造山型金矿床分布地域广泛、产出空间各异、矿化类型多样,但其成矿时代、成矿地球动力学背景和成矿流体性质等特征一致。论文选择了位于南亚带内的阳山、铧厂沟与马脑壳三个造山型金矿床作为研究对象,聚焦于区域及矿区尺度三个矿床地质特征的异同与其成因,通过系统的矿床地质与矿床地球化学工作,获得了如下主要成果。(1)区域尺度上,矿床的地质特征显示出连续性:金成矿事件发生于221~200 Ma,与区域变质作用峰期同时或略滞后,成矿作用发生于后碰撞伸展环境;受控于勉略构造带及其二、三级断裂构造系统,赋存于(低)绿片岩相变质地体,矿化样式有浸染型和石英脉型两种,金矿化与硫化、硅化、碳酸盐化蚀变密切相关;初始成矿流体为中低温、低盐度的变质流体。(2)矿区尺度上,矿床的地质特征显示出多样性:铧厂沟、阳山、马脑壳分别为大型、超大型与大型金矿床,主要赋矿围岩依次为细碧岩、千枚岩、板岩等;矿石矿物共生组合依次为黄铁矿,黄铁矿、毒砂、辉锑矿与黄铁矿、毒砂、辉锑矿、雄(雌)黄等。(3)LA-ICP-MS微区原位分析显示,三个矿床成矿早、主阶段黄铁矿、毒砂强烈富集Au、As和Te,不同程度富集Sb、Bi和Ag,不富集Cu和Zn,Pb、Co和Ni接近背景值;阳山及马脑壳金矿床中辉锑矿呈略微富集Au、较强富集Ag的特征。这些特征表明成矿流体可能是来自区域变质作用过程中变质脱挥发分形成的含金变质流体。矿床尺度硫化物微量元素的差异,是在不同成矿深度/环境下,成矿流体对元素运移的差异及不同的沉淀机制所致。(4)Sr-Nd-Pb同位素研究表明,深部中下地壳结晶基底与浅部就位环境中赋矿围岩共同为金成矿提供了成矿物质。(5)构建了区域金成矿模式:晚三叠世后碰撞伸展环境下,区域大范围的壳幔作用及广泛的岩浆活动,引起岩石圈尺度地热梯度上升,驱动中下地壳物质变质脱挥发分形成的含金流体进入地壳尺度的断裂系统,在不同成矿深度/环境通过围岩硫化、相分离或流体混合等,形成了一系列造山型金矿床。
[Abstract]:The Indosinian orogenic gold deposits in the West Qinling gold belt are widely distributed, have different occurrence space and various types of mineralization, but their metallogenic geodynamic background and ore-forming fluid properties are consistent in the metallogenic age.In this paper, three orogenic gold deposits, Yangshan, Huachanggou and Manaokou, which are located in the South Asian belt, are selected as the research objects, focusing on the similarities and differences of the geological characteristics and the genesis of the three ore deposits in the regional and mining scale.Based on the systematic geological and geochemical work of ore deposits, the following main achievements have been obtained: on the regional scale, the geological characteristics of the deposits show continuity: the gold mineralization event occurred at 221 ~ 200 Ma and was at the same or slightly behind the peak stage of regional metamorphism.Mineralization occurred in the post-collision extensional environment, controlled by the Mianluo tectonic belt and its secondary and tertiary fault systems, and occurred in the (low) greenschist phase change textures, with mineralization patterns of disseminated and quartz vein types, gold mineralization and sulfidation, silicification,Carbonate alteration is closely related; the initial ore-forming fluid is metamorphic fluid with medium and low temperature and low salinity. On the scale of the ore area, the geological characteristics of the deposit show diversity: the Huachanggou, Yangshan and Manaohou are large, super large and large gold deposits, respectively.The main ore-bearing rocks are in turn acrylite, phyllite, slate, etc. The ore mineral symbiotic assemblages are pyrite, pyrite, arsenopyrite, stibnite and pyrite, arsenopyrite, stibnite, male (female) yellow, etc. The in-situ analysis shows that the ore mineral symbiotic assemblage is pyrite, pyrite, arsenopyrite, stibnite, androgenite, etc.The three deposits are characterized by early mineralization, major stage pyrite and arsenopyrite, enrichment of SB, Bi and Ag to varying degrees, and no enrichment of Cu and ZnPbPb Co and Ni close to the background value, while in Yangshan and Manaoheng gold deposits, stibnite is slightly enriched in Auand strongly enriched in Ag.These characteristics suggest that the ore-forming fluid may be derived from the gold metamorphic fluid formed by metamorphic devolatilization during the regional metamorphism.The difference of trace elements in the scale of the deposit is due to the difference of the migration of elements in the ore-forming fluid and the different precipitation mechanism under different ore-forming depth / environment.The crystalline basement of the deep middle and lower crust and the ore-bearing surrounding rock in the shallow emplacement environment together provide the ore-forming material. 5) the regional gold metallogenic model is constructed: in the late Triassic post-collision extensional environment.The extensive crust and mantle action and extensive magmatic activity in the region cause the lithospheric geothermal gradient to rise, driving the gold-bearing fluid formed by metamorphic and devolatilized matter in the middle and lower crust into the crustal scale fracture system.A series of orogenic gold deposits were formed in different ore-forming depth / environment by surrounding rock vulcanization, phase separation or fluid mixing.
【学位授予单位】：中国地质大学(北京)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P618.51

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