【作者】 欧阳征健；

【导师】 周鼎武；

【作者基本信息】 西北大学 ， 构造地质学， 2006， 博士

【摘要】 新疆地处亚洲大陆腹地,是中亚大陆造山带在中国区域内的重要组成部分,为研究大陆地质、探索大陆动力学新理论提供了最佳野外实验地区。新疆北部古生代构造作用既是研究中亚大陆造山带构造演化的关键,又可能为全球大陆地质和动力学研究提供具有普遍性和特殊性的范例。 新疆北部地区现今的复杂地质结构构造面貌,主要是经历了古生代以板块汇聚、碰撞作用为特点的主造山期构造作用,又遭受中、新生代板内强烈构造作用的叠加改造所致,但涉及古生代造山作用及造山期后方式、过程和特点的研究至今仍存在较大分歧。因而,本文选择新疆北东部的克拉麦里蛇绿混杂岩、博格达山、巴音沟蛇绿混杂岩带、萨日达拉韧性剪切带与南天山库米什榆树沟高压麻粒岩地体作为解剖对象,采用宏观与微观、定性与定量和多种测试方法相配套,岩石学、构造地质学与地球化学等多学科相结合,研究与构造作用密切相关的岩浆作用、沉积响应、变质作用与构造变形等,进而探讨新疆北东部地区晚古生代构造作用的方式、特点及其形成演化过程。 通过对新疆北东部地区不同构造区带构造作用的方式、过程和特点的研究,确定:①南天山榆树沟高压麻粒岩地体的正变质原岩是一个基本完整的蛇绿岩套,其经历了俯冲至下地壳的高压麻粒岩相、构造抬升至深地壳麻粒岩相以及快速构造折返至角闪岩相的变质过程,代表了南天山洋壳俯冲、变质、随后折返的过程,并首次确定了变质过程的PTt轨迹;②奥陶纪末期中天山北缘发生洋盆俯冲、地体增生作用,此时萨日达拉地区处于岛弧活动带;中石炭世晚期中天山小型洋盆关闭,准噶尔地块与伊犁—中天山板块斜向对接随后发生脆韧性质近水平高温低速右行走滑剪切;③根据巴音沟地区不构成蛇绿岩套有效成分的硅质岩具有与活动大陆边缘密切相关的地球化学特征以及洋中脊玄武岩显示其岩浆源区受到消减带流体交代作用的影响,结合区域地质资料,首次提出巴音沟蛇绿岩带所代表的洋盆古构造环境为弧后盆地,并于早石炭世至中石炭世末期间,经历了扩张、收缩和闭合过程;④首次在克拉麦里蛇绿混杂岩带中分解出具有N-MORB、T-MORB与OIB三种不同类型的火山岩岩石组合,反映了洋盆俯冲更多还原

【Abstract】 Xinjiang Uygur Autonomous Region locates in the hinterland of Asia, which is one of the important part of the Central Asia continental orogenic zone in China. It is the best field laboratory of researching and explorating of new theories of the continental geology and dynamics. Researching Paleozoic tectonic process in North Xinjiang is not only the key to study structural evolution of the Central Asia continental orogenic zone, but also likely to offer an universal and particular example to study the global continental geology and dynamics.Physiognomy of complex geological frame and structure nowadays in North Xinjiang was caused by suffering superposition and alteration of the tectonic process which were the tectonization that was typical of the plate convergence and collision during the main stage of the orogenesis in Paleozoic and the intense tectonic process within the plate in Mesozoic and Cenozoic. However, relating to investigate the modes, courses and characteristics of the orogenetic process in Paleozoic and after orogenetic process, the cognitive divergence have still occurred. So, the Kelamaili ophiolitic melange, Bogeda Mountain, Bayingou ophiolitic melange, Saridala ductile shear zone and Yushugou terrane of high-pressure granulite facies in Kumishi area, Southern Tianshan are selected for subjects and many ways, for example, macroscopic and microscopic methods, qualitative and quantitative analysis are applied to this systemic research on magmatism, response of deposition, metamorphism, tectonic deformation and so on that are closely related to tectonic process and discuss furthermore the modes, characteristics and evolution of the tectonic process in Late Paleozoic in Northeast Xinjiang by means of lithology, tectonics and geochemistry.According to what is researched above, it is confirmed that, ① the protolith of Yushugou terrane of high-pressure granulite facies in south Tianshan is a basic ophiolite suite which was underwent complicated process of metamorphosing. To begin with, the suite had subducted lower crust and gone through metamorphism of high-pressure granulite facies, later due to the tectonic uplifting that had made the terrane get into the environment of deep crust, the terrane suffered metamorphism of mid-pressure granulite facies, subsequently it had underwent fast tectonic uplift and occurred metamorphism of amphibolite facies. It is indicated that the plate of southTianshan oceanic crust underwent subduction, metamorphism and uplifting in succession through studying of the metamorphism process of the suite, and for the first time, the PTt track of the metamorphism process is ascertained in this research;?Oceanic basin-subducting and terrane-accreting occurred in late Ordocician at the northern margin of the Middle Tianshan Belt where was an arc active belt.In Late Middle-Carboniferous, the small Middle Tianshan oceanic basin was closed, what came next was slant abutment between Zhungar plot and Yili-Middle Tianshan plot and later occurred brittle-ductile ductile shearing with nearly level, high temperature, low speed and right lateral strike-slipping.?Based on the geochemical characteristics with close relations to active continental margin of sillcalite at Bayingou which is not one part of an ophiolite suite and MORB in Bayingou ophiolitic melange which its magma source was influenced by input of the subduction components and according to areal geological data, one new idea is brought forward for the first time that the Bayingou ophiolitic melange standing for Paleo-structural setting of oceanic basin is bank-arc basin that occurred spreading and gradually closed between Early Carboniferous and late middle carboniferous epoch;(4) Three different volcanic rock associations of N-MORfk T-MORB and OIB are decomposed in Kelamaili ophiolitic melange and it is implied that different plots occurred accreting during ocean basin-subducting, which approved that Kelamaili ophiolitic melange is a suture zone between Siberia Plate and Kazakhsta Plate;?Slump-deposition structure, extending molasse formation of and basite which is related to continental rift and pullapart zone or primary rift in continent, that it is suggested that there was an extensional setting after orogeny in early Permian in Northeast Xinjiang.Colligating many predecessors’ results and this research, a mode of tectonic process evolution is constructed in Northeast Xinjiang and compartmentalized four stages as follows: € -O2 , oceanic basin-expanding stage;O3-S-D , oceanic basin-subducting, terrane-montage and accreting stage;D-C2 oceanic basin-closed in southern Tianshan and Bayingou and Tianshan-cohering fully stage;D3-C3, collision and orogenesis stage;Pi, extending after orogenesis stage.更多还原