【作者】 唐熊；

【导师】 陶晓风；

【作者基本信息】 成都理工大学 ， 构造地质学， 2009， 硕士

【摘要】 措勤盆地位于青藏高原腹地,南北宽约130km,东西长约700km,近东西向展布。其北边以班公错-怒江缝合带为界线,南边以冈底斯岩浆弧为界线,东边与比如盆地相接,西边延出国境。盆地在班公错-怒江带和雅鲁藏布江缝合带所挟持的近东西向狭长地带中,其形成和演化过程与这两个缝合带息息相关。本文主要从措勤盆地的沉积充填特征和其构造特征着手,通过野外露头的考察、实测剖面和柱状图的资料来分析盆地中沉积岩的岩性特征、沉积相及空间展布;通过大地构造位置、大地构造环境及盆地内褶皱和断裂构造等综合分析反演措勤盆地的构造演化过程。三叠纪以来,到始新世,措勤地区表现为盆地特征,因此,措勤盆地实际是指中-新生代时期的盆地,其充填地层包括上三叠统、中上侏罗统、白垩系和古近系古新统和始新统;而在晚古生代时期,措勤地区以大陆边缘及近岸沉积为主,此时措勤盆地还未形成,主要出露地层有上古生界的泥盆系、石炭系和二叠系,它们组成措勤盆地的褶皱基底;渐新世以来,盆地折返逐渐消亡,措勤地区沉积了新近系和第四系。措勤盆地普遍缺失下-中三叠统和下侏罗统。措勤盆地总体上为东西向狭长带状坳隆相间排列,由北向南,可大致划分出三个坳陷带和三个隆起带,坳陷和隆起内部构造也多呈长条状近东西向展布。因此,本文将盆地划分为6个单元,由北至南依次为洞错-阿苏坳陷带、拉果错-当雄隆起带、川巴-它日错坳陷带、夏东-雅弄隆起带、措勤-色陇拉坳陷带和隆格尔-江让断隆带。根据地层接触关系、构造背景及变形特征可以将盆地大致划分为海西期构造层、燕山期构造层和喜马拉雅期构造层三个构造层。措勤盆地褶皱特征:褶皱多发育于早白垩世地层中,在北部川巴-它日错坳陷和塔若错-措勤坳陷带最为集中,轴迹多以北西西向为主,且平行排列构成线状褶皱组合。纵向看,盆地基底褶皱多为斜歪紧闭褶皱,盖层以中常褶皱为主,向上为开阔褶皱,地层由老到新,变形渐弱。褶皱形成的力学机制,以纵弯褶皱为主,主应力是近南北向水平挤压力。措勤盆地断层特征:断层方向以北西西-南东东为主,数量最多,另外有少数北西向、北东向和近南北向断层。北西西-南东东向断层断面多略向北或向南倾,且倾角较陡,反映区域上南北挤压的主应力状态,且此类断层具有多期活动的特征。北东向和北西向断层以平移走滑为主,形成小型拉分盆地。南北向断层基本为正断层,形成南北向展布的地堑或地垒。盆地北部断裂数量多,密度大,主要切割侏罗系及白垩系多尼组、郎山组地层,构成多个北西西向断裂带;而盆地南部达瓦错-昂孜错坳陷内,断层数量相对较少。盆地所处的冈底斯地块,在古生代时期处于南半球冈瓦纳大陆北缘,随后羌南地块、冈底斯地块、喜马拉雅地块以及印度板块与冈瓦纳大陆分离,依次拼贴于欧亚板块南部,在此过程中,盆地地区经历了海西运动、印支运动、燕山运动和喜山运动,其演化过程受特提斯洋演化的影响制约。本文将盆地演化过程分为三个阶段:盆地基底形成;盆地充填演化;盆地折返消亡。盆地基底形成阶段:晚古生代时期,冈底斯地块和羌南地块联合在一起处于古特提斯洋以南,其演化过程受古特提斯影响较大,从古特提斯的扩张到闭合,盆地地区构造背景从拉张断陷转变为南北挤压,使得盆地地区褶皱抬升,海陆交替,形成了古生界基底。盆地充填演化阶段:中特提斯在晚三叠世扩张,中晚侏罗世开始向南俯冲,盆地构造背景也从拉张转变为挤压,此时盆地演化受中特提斯影响较大,此时期盆地沉积了接奴群。早白垩世,新特提斯洋壳开始向北俯冲,盆地处于两个俯冲带之间,其演化受两个俯冲带的共同影响,盆地沉积了则弄群、多尼组和郎山组。晚白垩世,中特提斯完全闭合,发生陆陆碰撞造山,盆地整体抬升,发育竟柱山组磨拉石沉积,盆地结束了中生代时期大面积沉积的历史。古新世至始新世时期,新特提斯洋闭合造山,盆地受其影响,火山及岩浆活动强烈,发育林子宗群火山岩。盆地折返消亡阶段:渐新世以来,盆地逐渐消亡。中新世时期,盆地经历长期的夷平作用,地势变的非常平坦,随后盆地区随青藏高原一起快速隆升,在差异隆升的过程中,地壳表层表现出强烈伸展作用,一系列近南北向的地堑(断陷盆地)和地垒开始形成。此后高原持续隆升,原有的东西向和北西西向逆冲断层转变多为右行走滑正断层,形成许多小型的断陷盆地和走滑拉分盆地。更新世至全新世时期,南北向正断层持续活动,断陷盆地继承性明显,边界断裂仍以张性正断为主。从古生代至今,盆地地区几度离合,几度沉浮,终于演变成了今天我们所看到的样子。更多还原

【Abstract】 Coqen basin is located in the hinterland of the Qinghai-Tibet Plateau, from north to south, it’s approximately 130 kilometers wide, and approximately 700 kilometers long from east to west, nearly east-west distribution. Its north takes Bangong-Nujiang suture zone as boundary line, the south takes Gangdese magmatic arc as boundary line, the east connect with Biru basin, the west extension out of the country. The basin is in the nearly east-west strip and between BanGong-nujiang suture zone and Brahmaputra suture zone. Its formation and evolution closely related to the two suture zone.In this paper, analyse Coqen basin’s sedimentary characteristics and structural characteristics at first, through the field outcrop of the inspection, the measured profile and the histogram of the data to analyze the Sedimentary rock’s lithologic characteristic, sedimentary facies and the space distribution. Through tectonic position, tectonic setting, basin fold and fault structure as a comprehensive analysis of inversion Coqen basin evolution of the structure.Since the Triassic until the Eocene, the Coqen areas performance characteristics of the basin, Its filling stratigraphy including late Triassic, Middle-Late Jurassic, Cretaceous and Paleogene, Paleocene and Eocene; In the Late Paleozoic Period, Coqen region is made up of continental margin and littoral sediment mainly, Coqen Basin at this time has not yet formed, the main exposed strata are late Paleozoic Devonian, Carboniferous and Permian, which formed the fold basement of Coqen basin; since the Oligocene, The basin disappeared gradually, then Coqen areas deposited the Neogene and the quaternary. Coqen basin in a general lack of early-middle Triassic and early Jurassic.On the whole, the concave and convex strips in East-west direction of Coqen basin are often alternate with arrangement. From north to south, it can be broadly classified into three sag zone and three uplifted uone, the internal structure of the sag zone and uplifted zone also arranged nearly east-west strip distribution.Therefore, the basin were be divided into six unit in this article, from north to south there were the Dongcuo-Asu sag zone, Laguocuo-Dangxiong uplifted zone,Chuanba-Taricuo sag zone, Xiadong-Yanong uplifted zone, Coqen-SeLongla sag zone and Longgeer- Jiangrang fault-uplift zone. According to the contact relationship of strata and the tectonic setting and the deformation characteristics , the basin can be broadly divided into three tectonic epochs , Including Hercynian tectonic period, Yanshan tectonic period and the Himalayas tectonic period.Fold characteristics of Coqen basin: the folds growth in the Early Cretaceous strata, They were most concentrate in the northern part of Chuanba- Taricuo sag zone and Taruocuo-Coqen sag zone, the axial trace north-west-west mainly,and parallel arrangement constitute to combination of linear fold. Vertical view, the fundus of basin most are closeness folds, closed fold covered the cap rock mainly, up is the broad fold, The stratum from the old to the new, and deformation diminuendo.The formation mechanism of the folds main longitudinal bend fold, the main stress is the level of squeezing pressure on nearly north-south.The fault characteristics of Cuoqin basin : the largest number of the fault trend in the north-west-west to south-east-east direction, while a small number of the fault in north-west or north-east and north-south direction. The fault in north-west-west to south-east-east direction have high dip angle in north or south tendency, it reflect the main north-south stress state, and such a fault with characteristics of multiple activities. General, the fault in north-west or north-east direction were strike-slip faults, came into being pull-apart basins. Usually the fault in north-south direction were normal fault, came into being grabens or horsts. Faults have the high number and high density in the north of basin, these faults cut jurassic and cretaceous Duoni, Langshan formation, make up of fault zone in north-west-west direction; Less faults were distrbuted Dawacuo-Angzhicuo sag zone in the south of basin.Paleozoic era, Gangdese Terrane of the basin area was located in the north verge of the Gondwanaland. Qiangnan Terrane, Gangdese Terrane, Himalaya Terrane and India Terrane apart from Gondwanaland subsequently, piece together the southof the Eurasia in turn. In these period, the basin area come through Varisian movement , Indosinian movement and Himalaya movement. The evolvement of the Coqen basin was restricted by the evolution of the Tethys. The evolvement of the Coqen basin was divide into three moment in this article, the form of basin fundus;the evolvement of basin; back-turning and destruction of basin.The form of basin fundus: late Paleozoic era, Gangdese Terrane and Qiangnan Terrane located the south of the ancient Tethys, The evolvement is restricted by the evolution of the ancient Tethys, from open to close of the ancient Tethys, the backdrop of Coqen basin from fault depression to extrusion. The basin area fold and uplift, so came into being fundus of Paleozoic. The evolvement of basin: Meso-Tethys opend at late Triassic and southward subduction at mid-late Jurassic. The backdrop of Coqen basin from fault depression to extrusion again. At this point, basin was deposited Jienu Group. Early Cretaceous, Neo-Tethys northward subduction, the evolution of basin area was restricted by the two subduction zone. At this period, Coqen basin was deposited Zenong Group, Duoni Formation and Langshan Formation. Late Cretaceous, Meso-Tethys closed and continent-continent collisional, whole basin area uplift. It was deposited molasses of the Jingzhushan Formation.The history that large area deposition at Mesozoic was over.During Paleocene and Eocene, Neo-Tethys closed and continent-continent collisional, basin area volcanic and magmatic activity strongly, developed Linzizong Group lava. Back-turning and destruction of basin: after Oligocene, basin wither gradually. Miocene period, basin area was leveled, later it uplift along with Tibetan Plateau. Differences in the course of the uplift, it developed a series of rift basins and pull-apart basins. Pleistocene to Holocene period, in the transmeridional tensile stress, basin area developed a series of grabens (rift basins) and horsts. From Paleozoic to this day, Coqen basin area after several Separation and combination, several ups and downs, finally evolved into what we see now.更多还原