【作者】 王兴安；

【导师】 刘正宏； 徐仲元；

【作者基本信息】 吉林大学 ， 构造地质学， 2014， 博士

【摘要】 华北板块北缘中段作为中亚造山带的核心部位，经历和记录了古亚洲洋构造域的形成、发展和消亡，是研究中亚造山带地质演化历史问题的关键部位。本文以板块构造和大陆动力学理论为指导，在野外地质调查基础上，利用锆石U-Pb同位素LA-ICP-MS定年技术和岩石地球化学测试等手段，深入探讨了华北板块北缘中段早古生代-泥盆纪期间的构造演化历史。1．早古生代俯冲-增生杂岩带华北板块北缘早古生代期间发生洋内俯冲作用，形成了一套由温都尔庙蛇绿岩组合、超基性岩块、德言其庙斜长角闪岩和奥长花岗岩组成的俯冲增生杂岩，为古亚洲洋大洋板块俯冲消减的残留和岛弧岩浆活动的产物，其形成演化到最终构造侵位从寒武纪一直持续到中志留世。温都尔庙蛇绿岩组合为SSZ型（俯冲带）蛇绿岩，为古亚洲洋大洋板块俯冲消减的残留；德言其庙斜长角闪岩原岩为中基性岩浆岩，是岛弧岩浆活动的产物，晚奥陶世期间受后期热流体作用影响发生高温角闪岩相变质作用；晚奥陶世奥长花岗岩属于低钾拉斑系列，具有较高的Sr含量和明显的Sr、Eu正异常及Nb负异常，为大洋斜长花岗岩与埃达克质岩浆之间的过渡类型，形成于岛弧的构造环境；温都尔庙群高压变质带中的蓝片岩为B型蓝片岩，形成于洋壳俯冲碰撞带的构造环境。早古生代期间古亚洲洋板块的自北向南俯冲作用，在温都尔庙群地层中形成了三期褶皱构造和一期韧性变形带。早期小型层间倒转-平卧褶皱为岩石塑性流动变形的产物；中期近东西向褶皱规模巨大，形态多样，为南北向俯冲挤压作用的产物；晚期褶皱的主应力方位发生改变，受东西向挤压作用，叠加改造中期褶皱。在褶皱带南部的温都尔庙群地层中发育伸展韧性变形带，带内岩石线理发育，形成大量L构造岩和L＞S型构造岩，线理统计分析显示存在一期南东东向的伸展作用，为南北向俯冲挤压折返作用的产物。2．早古生代岛弧岩浆活动带白乃庙岛弧岩浆活动带内早古生代火山沉积地层和侵入岩发育。白乃庙群火山岩下部以酸性火山岩为主，上部则主要为基性火山岩，其源区性质为受俯冲流体交代的地幔源区，同时受到一定程度地壳物质混染，属于安第斯型活动大陆边缘火山岩。晚寒武世石榴石白云母花岗岩由于强烈的热液蚀变而发生稀土元素四分组效应，具有平坦的稀土元素配分型式和强烈的负Eu异常，类似于四分组效应的“M”型配分曲线，为经历了强烈热液蚀变的高分异I型花岗岩，是早期俯冲作用的产物；晚奥陶世石英闪长岩具有相对富钠、贫钾和准铝质的特征，轻稀土元素富集，重稀土元素亏损，无明显的Eu异常，强烈亏损高场强元素Nb、P、Ti，反映了俯冲带岛弧或大陆边缘弧火山岩的特征，为白乃庙岛弧岩浆活动的产物。3．早古生代弧后盆地沉积白乃庙岛弧岩浆岩带南部分布着一套中上志留统徐尼乌苏组复理石沉积，其物源为白乃庙岛弧岩浆岩，在粒度上具有明显的韵律性，可分为6个大的沉积旋回，每个旋回都是由底向顶粒度逐渐变细，属于复理石建造下部的粗复理石沉积，代表了水动力条件较强的沉积环境，而远离岛弧带的晒勿苏组地层则为相对稳定的浅海相沉积环境。不整合覆盖在徐尼乌苏组和晒勿苏组之上的顶志留统西别河组与四道杖棚组地层为一套磨拉石建造，地层层序具明显的韵律性，可分为多个沉积旋回，每个旋回都是以砾岩开始，向上粒度变细，反映出其沉积时有大量的陆源碎屑物质和地壳频繁波动的沉积环境。西别河组磨拉石建造属于造山带前陆盆地堆积的磨拉石沉积，形成于挤压的前陆盆地的构造环境，说明在志留纪末期白乃庙岛弧与华北板块发生弧-陆碰撞，形成了西别河组前陆盆地磨拉石建造，标志着华北板块北缘中段在早古生代期间完成了沟-弧-盆体系的构造演化。4．泥盆纪碰撞后伸展华北板块北缘在志留纪末期经历了与白乃庙岛弧的弧-陆碰撞事件后，发生了区域性的大规模伸展，在固阳、商都、张家口及赤峰一带形成了早-中泥盆纪的岩浆活动。其中赤峰-解放营子地区发育的中泥盆世A型花岗岩，属于A2型花岗岩，形成于后碰撞或后造山的环境，表明在泥盆纪期间华北板块北缘进入了碰撞后的伸展阶段，年代学数据显示该期伸展作用可能持续了整个泥盆纪。更多还原

【Abstract】 The central segment of the northern margin of the North China Plate as a corepart of the Central Asian Orogenic Belt, is a key part of the study of geologicalevolution in the Central Asian Orogenic Belt, which experience and records theformation, development and demise of the Palao Asian tectonic domain. In this paper,based on field geological survey, explore the tectonic evolution of the northern marginof the North China Plate from Early Paleozoic to Devonian using geochronology andgeochemistry research, which is guided by the theory of plate tectonics andcontinental dynamics.1．Early Paleozoic subduction-accretion complex beltThe subduction-accretion complex consisting of the Ondor Sum ophiolite,ultrabasic rock, Deyanqimiao amphibolite and trondhjemite formed in intra-oceanicsubduction in the the central segment of the northern margin of the North China Plate,which is the product of the residual Paleoasian Ocean Plate and arc magmatism, itsformation, evolution and tectonic emplacement from the Cambrian until the middleSilurian. The Ondor Sum ophiolite is a typic SSZ(subduction belt) ophiolite suite,which formed forearc in the subduction belt. Deyanqimiao amphibolite original rockis mafic igneous rocks, which is affected by the hydrothermal fluid, experienced ahigh temperature amphibolite facies metamorphism in the late Ordovician. The lateOrdovician trondhjemite belonged low potassium tholeiitic sreies, positive anomaliesin Sr, Eu and negative anomalies in Nb, which is a transitional type between oceanplagiogranite and adakitic magmatic rock, formed in arc tectonic environment. TheB-type blue schist in Ondor Sum group high-pressure metamorphic belt is formed in the environment of the oceanic subduction-collision zone.The Paleoasian Ocean Plate subducted from north to south in early Palaeozoic, inOndor Sum group formed three fold and a ductile deformation zone. The early interlaminar overturned-recumbent fords formed in the plastic flow defermation of rocks.The middle fords are huge and diverse, trace nearly east-west axis, which are theproducts of north-south compressional deformation. The late fords’ maxumumprincipal stress orientation changes to east-west compressional deformation. There arelots of L-type and L>S type tectonites in the ductile deformation zones which islocated in the southern of the fords belt, lineation statistical analysis showed asoutheast-east stretch which is the tectonic deformation in the deeper levels of thefords belt.2．Early Paleozoic arc magmatic active beltEarly Palaezoic volcanic and intrusive rocks in Bainaimiao arc magmatic activebelt are commonly. The acidic volcanic rocks are in the lower of Bainaimiao Group,but the basic volcanic rocks of the upper, its nature of the source regions are thesubduction fluid metasomatism of the mantle source region, at the same time to acertain extent crustal material contamination, similar to Anden-type active continentalmargin volcanic rocks. The Late Cambrian garnet muscovite granite which issubjected to the occurrence of hydrothermal alteration of REE tetrad effect, has a flatREE pattern and strong negative Eu anomaly, similar to the “M” type distributionpattern of the tetrad effect, is experiencing a strong hydrothermal alteration of I-typegranites, which is an early produce of subduction of oceanic crust. The lateOrdovician quartz diorite has the characteristics of rich Na, poor K, LREE enrichmentand HREE loss, there is no obvious Eu anomaly and strongly depleted in high fieldstrength elements Nb, P, Ti in the quartz diorite, which is similar to arc subductionzone and continental margin arc volcanic rocks, is a produce of Bainaimiao arcmagmatism.3．Early Paleozoic back-arc basinThe Mid-Upper Silurian Xuniwusu Group is the lower coarse flysch formation inthe south of Bainaimiao arc magmatic rocks, its provenance comes from Bainaimiao arc magmatic rocks. The Xuniwusu Group has obvious rhythmic, which can bedevided into six major depositional cycles and each cycle is from the bottom to thetop of granularity tapering, belong to the lower of the coarse flysch formation,represents a strong hydrodynamic conditions sedimentary environment, but theShaiwusu Group which stay away from Bainaimiao arc reflect relatively stableshallow marine depositional environment. The Upper Silurian Xibiehe andSidaozhangpeng Group which is a set of molasse formation, have obvious rhythmic,they are devided into many sedimentary cycles and each cycle begins withconglomerate, tapering upward granularity, reflecting the large number of terrigenousmaterial and frequent fluctuatuons in the crust sedimentary environment. XibieheGroup belongs to orogen foreland basin molasse formation, which is formed in theextrusion of tectonic environment. It shows that Bainaimiao island arc and the NorthChina Plate happened arc-continent collision in the Late Silurian, which marks thetrench-arc-basin tectonic evolution fanished in early Paleozoic in the middle of thenorthern margin of the North China Plate.4．Devonian post-collision extensionAfter Bainaimiao island arc-continent collision in the late Silurian, begin to largescale regional extension, which formed early-middle Devonian magmatism in theGuyang, Shangdu, Zhangjiakou and Chifeng area. The middle Devonian A-typegranites in the Chifeng Jiefangyingzi and its southern regions are belong toA2-type(post-collision or post-orogenesis), which show that the northern margin ofthe North China Plate entered post-collision extension stage in the Devonian, andgeochrononlogy data show that the extension is likely to continue throughout thewhole Devonian.更多还原