【作者】 赵珍；

【导师】 胡道功；

【作者基本信息】 中国地质科学院 ， 构造地质， 2013， 硕士

【摘要】 冈底斯造山带经历了从特提斯俯冲阶段到陆陆碰撞阶段的多阶段复杂的构造运动和岩浆演化作用,并且发育了多阶段、多类型、多矿种的成矿作用,形成了规模巨大的成矿带。本论文以位于冈底斯南缘的、紧邻雅鲁藏布江缝合带的泽当矿田为研究对象,通过野外地质调查,结合各种同位素测年、岩石地球化学测试、ESR测试等技术,对泽当矿田构造特征、岩浆作用类型、矿床特征和成矿作用等进行详细调查研究,分析从特提斯洋俯冲阶段、主碰撞造山阶段、晚碰撞转换阶段以及后碰撞伸展阶段,泽当矿田的构造岩浆演化与成矿作用的关系,深化对泽当矿田成矿母岩、控矿构造以及成矿作用的认识,探讨泽当矿田成矿潜力和成矿规律,取得了以下成果和认识：1、特提斯俯冲阶段：泽当地块中斜长花岗岩的锆石U-Pb年龄为152.5-156Ma,具有埃达克质,可能与洋内弧环境下板片俯冲熔融有关；安山质玄武岩具有岛弧岩浆岩特征,微量元素上显示IAB型特征。说明泽当地区在晚侏罗世可能发生了一期洋内俯冲。晚白垩世发育具有埃达克特征的岩浆侵入活动,岩体时代为94.1Ma,埃达克岩可能来自俯冲板片,并在上升过程中与幔源物质发生了混染。这期埃达克岩形成了桑布加拉矽卡岩矿床,含矿辉钼矿的Re-Os年龄为(93.3±4.1)Ma；2、碰撞造山阶段：主碰撞阶段侵入岩的时代为50～63Ma,地球化学特征为具有大陆边缘弧特征的I型高钾钙碱性岛弧岩浆岩。这类岩浆具有成矿的优势条件,在泽当矿田外围发现有成矿作用,但是泽当矿田目前尚未有相关成矿作用的报导；在大竹卡组内部发现了火山岩夹层,获得锆石U-Pb年龄集中在49.6-52.6Ma之间,通过对砂岩ESR测试,年龄为19.8-28.5Ma。重新厘定了大竹卡组的时代,将下限提前到始新世早期,地层时限为E2-N1。说明至少在52Ma之前,泽当地区特提斯洋已经完全闭合,陆陆碰撞造成的山脉隆升作用已经发生；3、晚碰撞阶段：泽当矿田最主要的成矿阶段,主要为矽卡岩型矿床,矿体受侵入岩与围岩的接触边界控制。成矿母岩的时代集中在29.88-31.64Ma之间,与含矿辉铝矿的Re-Os时代同期。成矿母岩具有两种类型,一种具有埃达克特征,一种具有岛弧岩浆岩特征。说明泽当矿田在该阶段的成矿母岩来源具有多样性,反应不同的构造环境导致的不同的岩浆来源；4、后碰撞阶段：冈底斯反冲断层和冈底斯逆冲断层相向对冲到大竹卡组之上,因此两期断层的下限至少要晚于19.8Ma。两期断层破坏了早期的成矿作用,是主要的破坏性构造。除了大规模的断层活动外,泽当矿田广泛发育与逆冲推覆和裂谷相关的北东、北西、南北向节理、裂隙,被热液充填,发生矿化现象。单一规模虽然不大,但是某些节理密集或是断层活动强烈处,也能成为较为可观的矿化现象。更多还原

【Abstract】 From the Tethys subduction to the continental collision, the Gangdese orogenic belt has expericnecd complex evolution and development about tectonism, magmatism and metallization, which forming a gaint metallogenic belt with great varieties of stage,type and mineral.In this thesis,we regard Zetang orefield,located in the southern margin of the Gangdese ore belt and adjacent to the Yarlung Zangbo suture zone,as the research object. We undertake inverstigation and research about the structure feature, magma types,deposit characteristics and metallization based on field geological survey and testing methods,including isotope dating,lithogeochemical testing and Electron Spin Resonance method and so on. Our study was divided into four stages, correspongding to the orogenetic process,namely Tethys subduction stage, main collisional orogenic stage,late-collisional transformation stage and post-collisional extension.According to the research about each stage,summarize the relationship between tectonic evolution and mineralization.It is propitious to strengthen the understanding of ore host rock,ore-controlling structural and metallization,besides,it is also in favor of investigating the metallogenic potential and metallogenic regularities. The achievements are as follows.1.Tethys subduction stage:Plagioclase granite from Zetang terrane has the Zicon U-Pb ages from152.5Ma to156Ma,and show the adakite character. The source of host rock maybe come from the melt plate subduction, associated with the intra-oceanic arc environment. Moreover, the andesite basalt also has the characteristics of magmatic arc, its trace element display IAB type character. All the results suggest that, it was exist a intra-oceanic subduction in Late Jurassic. At the subduction late stage, like-adakite magma had intruded, with94.1Ma age of Zicon U-Pb. The adakite maybe come from subduction plate, and mixed with mantle material. This period adakite intrude wall rock, forming the Sangbujiala deposit. The Re-Os age of molydenite in Sangbujiala deposit is (93.3±4.1) Ma, in Late Cretaceous.2.Main collisional orogenic stage:The age of this period intrusive rock is50-63Ma.and the geochemical characteristics indicate they are island arc magmatic rocks with Ⅰ type, high calc-alkaline,potassium and continental margin arc characters. This kind of magmatic has an advantage of mineralization. Researchers have found this period mineralization nearby Zetang but not in Zetang orefield. Zicon U-Pb ages of the volcano rock interlayer in Dazhuka group are between49.6Ma with52.6Ma. and the ESR ages of the sandstone are from19.8Ma to28.5Ma.We redefine the Dazhuka group age with these results, from early Eocene to Miocene. The age of Dazhuka group illustration the Tethys ocean had closed completely and the mountains caused by collision has been uplifting before52Ma, in Zetang.3.Late-collisional transformation stage:It is the main metallogenic stage of Zetang orefield.The deposits are skarn and the ore bodies are controlled by the contact boundary of intrusive rocks and wall rocks. The era of mother rocks concentrated at29.88-31.64Ma, in accordance with the Re-Os age of molydenite in deposits. The ore-forming mother rock has two types, one with adakitic features and the other with arc magmatic features. Suggesting that the mother rock has diversity sources and resulting in different tectonic environment.4.Post-collisional extension:Gangdese Thrust(GT) and Great Counter Thrust(GCT) thrust upon Dazhuka group in opposite direction, thus the two thrust systems at least later than19.8Ma. Besides, they are become the most important structure destructing the early mineralization. In addition to these faults, Zetang orefield widely developed north-east, north-west and north-south trend joints and cracks, which were filled by hydrothermal, and developmented weak mineralization.更多还原