【作者】 王强；

【导师】 和钟铧；

【作者基本信息】 吉林大学 ， 构造地质学， 2021， 硕士

【摘要】 研究区处于大兴安岭中南段典型的锡-钨-铜-铅-锌-银多金属成矿带,其内广泛分布有中基性侵入岩,特别是闪长玢岩（含细晶闪长岩）岩脉及岩墙等,这些脉岩多沿北东—北北东向断层而贯入,少数呈北西向及近南北向展布,其规模不大,一般只有几米宽,长约几十米至几百米,它们大多数切穿了晚侏罗世-早白垩世火山岩层,表明其时代应属早白垩世及以后,为燕山运动晚期的产物。本文在区域地质调查的基础上,查明了研究区侵入岩的空间产出状态及与围岩之间的接触关系,确定了中基性侵入岩的岩石类型,并通过对中基性侵入岩年代学、地球化学的分析和研究,探讨了其成因和形成构造背景,所获认识不仅是对“兴蒙造山带”构造-岩浆演化的完善和补充,而且对于寻找与中基性岩石相关的铜等金属矿均有一定意义。（1）研究区早白垩世中基性侵入岩岩性主要为辉绿岩、辉绿玢岩、闪长岩、闪长玢岩和石英闪长岩,多呈岩株和岩脉产出,其中岩脉多受北东—北北东向和北西向断层控制,空间上呈“之”型延伸,显示张扭性断层控制的特点;（2）LA-ICP-MS锆石U-Pb和全岩K-Ar的测年结果表明研究区中基性岩形成于早白垩世,并具有多期活动的特征,且显示随时代变新,岩石愈基性化的特点。（3）研究区中基性侵入岩具有低Si O₂、高Al₂O₃、高Na₂O/K₂O、弱或无Eu负异和轻稀土富集及重稀土亏损的特点,显著富集Rb、Ba、U、Sr、K等元素,亏损Ta、Nb、Ti等高场强元素和P元素,这些地球化学特征可能继承了岩浆源区特点而显示弧岩浆岩的性质。岩石全岩地球化学及锆石Hf同位素揭示其源区主要来自于基性下地壳物质再熔融,并且具有幔源和壳幔岩浆混合特征;（4）研究区中基性侵入岩形成于早白垩世伸展构造背景,与蒙古—鄂霍茨克洋的闭合碰撞作用有关,是蒙古—鄂霍茨克洋闭合碰撞之后加厚陆壳的拆沉、幔源岩浆底侵作用的结果。更多还原

【Abstract】 The research area is located in the typical tin-tungsten-copper-lead-zinc-silver polymetallic metallogenic belt in the middle and southern part of the Great Xing’an Range,in which there are widely distributed intermediate-basic intrusive rocks,especially diorite porphyrite（containing fine crystal diorite）dikes and veins,These vein rocks are mostly along the NE,NNE-trending fault and penetrate,a few are NW and nearly NS-trending distribution,the scale is not large,generally only a few meters wide,about tens of meters to hundreds of meters long.Most of them cut through the Late Jurassic to Early Cretaceous volcanic strata,indicating that their age should belong to the Early Cretaceous and later,and is the product of the late Yanshanmovement.On the basis of regional geological survey,it is ascertains the spatial occurrence state of intrusive rocks in the study area and the contact relationship between intrusive rocks and surrounding rocks,determines the rock types of intrusive rocks.Through the analysis and study of the chronology and geochemistry of the intermediate basic intrusive rocks,the origin and tectonic setting of the intrusive rocks are discussed.The understanding not only complements the tectono-magmatic evolution of the Xingmeng-Mongolia orogenic belt,but also has certain significance for the exploration of copper and other metallic deposits related to theintermediate-basic rocks.（1）The lithology of the Early Cretaceous intermediate-basic intrusive rocks in the research area is mainly diabase,diabase porphyrite,diorite,diorite porphyrite and quartz diorite,most of them are produced in the form of dikes and veins,in which the veins are controlled by NE,NNE-trending and NW-trending faults and extend in type of―z‖in space,it is shows the characteristics of tension fault control.（2）LA-ICP-MSZircon U-Pb and K-Ar dating results indicate that the intermediate-basic intrusive rocks in the research area were formed in the Early Cretaceous.It has the characteristics of multi-phase activities,and shows that the rocks change with the time and become more basic.（3）The intermediate basic intrusive rocks in the research area is characterized bylow Si O₂,high Al₂O₃ and Na₂O/K₂O,and weak or no negative Eu,it is enrichment of LREE and depletion of HREE.These geochemical characteristics may inherit the characteristics of the magma source area and indicate the properties of arc magmatic rocks.The whole rock geochemistry and zircon Hf isotopic characteristics reveal that the source area is mainly derived from the remelting of basic lower crustal materials,and has the characteristics of mantle-derived and crust-mantle magmatic mixing.（4）The intermediate-basic intrusive rocks in the research area were formed in the extensional tectonic setting of the Early Cretaceous,which is related to the closed collision of the Mongolian Okhotsk Ocean,it is the result of the bottom invasion of the Delaminationmantle-derived magma of the thickened continental crust after the closed collision of the Mongolian Okhotsk Ocean.更多还原