碧口地体区域成矿系统

发布时间：2018-05-02 18:35

  本文选题：岩石地球化学 + U-Pb年代学与Hf同位素　； 参考：《中国地质大学(北京)》2016年博士论文

【摘要】：本文围绕碧口地体构造演化与区域成矿作用关系,通过对碧口地体与邻区出露的岩石建造以及不同类型矿床(新太古代BIF型铁矿床、新元古代VMS型铜多金属矿床、泥盆纪沉积型硅矿床、三叠纪造山型金矿床)开展了详细的野外地质观测、岩石地球化学分析、成岩成矿年代学、锆石Lu-Hf同位素、金属矿物电子探针与原位LA-ICP-MS分析,获得以下主要认识。(1)新太古代鱼洞子群与侵入其中的花岗岩构成了碧口地体新太古代陆核。鱼洞子群海相火山-沉积岩系在~2.6 Ga遭受了区域变质作用,并形成了以条带状铁建造(BIF)为赋矿围岩的BIF型铁矿床。结合矿床地质特征、磁铁矿电子探针和原位LA-ICP-MS分析,明确鱼洞子铁矿床为BIF型铁矿床。(2)新元古代为碧口地体地壳增生期,洋陆俯冲背景下的弧前盆地浊积岩、弧后裂谷盆地与陆缘弧火山岩、侵入岩构成了碧口地体主体。双峰式火山岩与该区VMS矿床成因关系密切。别子型VMS铜矿床产于基性火山岩(细碧岩)中,黑矿型VMS矿床产于中性-中酸性火山岩(角斑岩-石英角斑岩)中。黄铜矿原位LA-ICP-MS分析显示黑矿型比别子型含更多Pb、Bi和Ag,且黄铁矿Co/Ni1。(3)古生代碧口地体北缘处于陆缘裂陷构造背景。勉略构造带内硅质岩的岩石学、地球化学、碎屑锆石U-Pb年代学及Hf同位素表明,大量来自华南板块(尤其碧口地体)的新元古代岩浆岩与沉积岩碎屑向北运移至陆缘裂陷,并与来自裂陷深部的富硅流体一起沉淀下来,在勉略构造带内形成了该区不同时代的硅质岩,这些不同时代硅质岩反映碧口地体北缘的裂陷作用东部早于西部。此外,这些硅质岩岩层具经济价值,构成了沉积型硅矿床。(4)印支期随着中国华南、华北板块的碰撞拼合,该区随即进入陆内造山阶段,构造体制由南北向的挤压碰撞转为应力松弛,表现为区域性的左行剪切走滑。在这种构造背景下,该区形成了后碰撞板片断离花岗岩。并在勉略构造带内形成了以变质流体作为成矿流体来源的不同深度造山型金矿床,如文县阳山浅成造山型金矿床和略阳铧厂沟中浅成造山型金矿床等。
[Abstract]:Based on the relationship between the tectonic evolution of the Bikou terrane and regional metallogenesis, the rock formations and different types of deposits (NeoArchean BIF iron ore deposit, Neoproterozoic VMS type copper polymetallic deposit) in the Bikou terrane and adjacent areas are studied in this paper. Devonian sedimentary silicon deposits and Triassic orogenic gold deposits) have been developed for detailed field geological observation, petrogeochemical analysis, diagenetic geochronology, zircon Lu-Hf isotopes, electron probe analysis of metallic minerals and in situ LA-ICP-MS analysis. The main understanding is as follows. 1) the NeoArchean fishhole subgroup and the intrusive granite formed the NeoArchean continental nucleus of the Bikou terrane. The marine volcanic-sedimentary rock series of the Yudong subgroup suffered from regional metamorphism at 2.6Ga and formed a BIF type iron deposit with banded iron formations as host rocks. Combined with the geological characteristics of the deposit, electron probe analysis of magnetite and in situ LA-ICP-MS analysis, it is clear that the Yudongzi iron deposit is a BIF type iron deposit.) the Neoproterozoic is the turbidite of the Pikou terrane during the crustal accretion period and the oceanic subduction setting. Back-arc rift basin and continental margin arc volcanic rocks, intrusive rocks constitute the main body of Bikou terrane. Bimodal volcanic rocks are closely related to the genesis of VMS deposits in this area. The peer-type VMS copper deposit occurs in the basic volcanic rocks and the black type VMS deposits occur in the neutral and intermediate acid volcanic rocks (hornblene-quartz keratophytes). The in-situ LA-ICP-MS analysis of chalcopyrite shows that the black ore type contains more PBO Bi and Ag than the subtype, and the Paleozoic Bikou terrane north margin is located in the continental margin rifting tectonic setting. The petrology, geochemistry, U-Pb chronology of clastic zircon and HF isotopes of siliceous rocks in the Mianliao tectonic belt indicate that a large number of Neoproterozoic magmatic and sedimentary rocks from the South China plate (especially the Bikou terrane) migrated northward to the continental margin rift. Together with silicon-rich fluids from deep rifting, siliceous rocks of different ages were formed in the Mianliao structural belt, which reflected that the rifting in the northern margin of the Bikou terrane was earlier than that in the west. In addition, these siliceous rock formations are of economic value and form sedimentary silicon deposits. The Indosinian epoch followed the collision and assembly of the South China and North China plates, and the area immediately entered the intracontinental orogenic stage. The tectonic system changed from the compression collision in the south to north direction to the stress relaxation, which is characterized by regional left shear strike-slip. In this tectonic setting, the post-collision plate fragment is formed in this area. Different depth orogenic gold deposits with metamorphic fluids as the source of ore-forming fluids have been formed in the Mianliao structural belt, such as the metamorphic fluids in Wenxian County, Yangshan superficial orogenic type gold deposits and Lueyang Huachanggou medium and superficial orogenic gold deposits, etc.
【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】：P612
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本文编号：1835022