滇西哀牢山缝合带中、南段古特提斯演化：构造变形特征

发布时间：2018-05-19 14:27

本文选题：构造变形特征 + 古特提斯　；参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：滇西哀牢山构造带是多期构造叠加的复合造山带,特提斯演化、印度-欧亚碰撞是最主要的两期构造活动。作为特提斯构造域的重要组成部分,新生代以来由于该带处于印度-欧亚板块碰撞带的前缘位置,遭受了强烈的叠加变形改造,对于前新生代时期(尤其是特提斯演化阶段)的构造格局和面貌难以恢复,对于特提斯洋的闭合、俯冲及消减过程缺少足够的证据。本文针对哀牢山缝合带中、南段各单元开展详细野外地质调查,重点观察各构造形迹,进行期次划分,区分晚三叠世前后岩石不同变形表现,剥离出新生代叠加构造,厘清古特提斯变形构造组合。此外,利用变形及未变形的花岗质侵入岩体进行LA-ICP-MS锆石U-Pb年代学测试和分析,限定相关构造变形时间;同时结合与构造变形相关的地层所属时代,按照时间主线建立构造期次,进行区域对比建立变形事件演化序列。哀牢山缝合带是古特提斯哀牢山洋盆由东向西俯冲-消减-增生-碰撞形成的一条近南北向的构造混杂岩带,将北东侧扬子地块和南西侧印支地块隔开,其主要组成包括:志留系-泥盆系深海扇复理石沉积、蛇绿岩、石炭系-下二叠统海相碳酸盐岩、岛弧岩浆岩、二叠系弧后盆地浊积岩。哀牢山古特提斯构造变形主要可分为两个阶段:(1)俯冲期变形(D1),在北东向逆冲剪切作用下,中-深部层次形成透入性劈理(S1),平行于横卧褶皱-斜歪水平剪切褶皱(f1)轴面方向,叶理面上北东-南西向拉伸线理发育(L1),并有数条千糜岩带发育;浅部层次发育顺层剪切带、逆冲断层及相关褶皱,增生过程中受阻发生反冲作用形成轴面倾向东的平卧-斜歪水平褶皱(f1),不发育轴面劈理。(2)碰撞期挤压收缩变形(D2),在近东西向挤压作用下,在浅部层次形成近南北向紧闭斜歪褶皱及陡倾伏-倾竖褶皱(f2)、皱纹线理(f2)、褶劈理(S2)。新生代以来,由于印度-欧亚大陆碰撞作用,受到逆冲推覆构造、走滑剪切带、地堑-半地堑盆地等叠加构造影响,发育北北西向开阔褶皱及断层。
[Abstract]:The Ailaoshan tectonic belt in western Yunnan is a composite orogenic belt with multiple tectonic superpositions. The Tethys evolution and the India-Eurasian collision are the two main tectonic activities. As an important part of the Tethys tectonic domain, the belt has been subjected to a strong superimposed deformation since the Cenozoic because it is in the leading position of the India-Eurasian plate collision zone. It is difficult to restore the tectonic framework and features of the pre-Cenozoic period (especially the Tethys evolution stage), and lack sufficient evidence for the closure, subduction and subduction of the Tethys ocean. In this paper, detailed field geological survey is carried out for the units in the southern segment of the Ailaoshan suture zone, with emphasis on observing the structural features, dividing the stages, distinguishing the different deformation of rocks before and after the late Triassic, and stripping off the Cenozoic superimposed structures. To clarify the paleoTethys deformed structural assemblage. In addition, the LA-ICP-MS zircon U-Pb chronology test and analysis are carried out by using the deformed and undeformed granitic intrusive rocks to limit the relevant tectonic deformation time, and the tectonic periods are established according to the main line of time combined with the age of the strata associated with the tectonic deformation. The evolution sequence of deformation events was established by regional comparison. The Ailaoshan suture zone is a tectonic melange belt formed by subduction, accretion and collision from east to west of the ancient Tethys Ailao ocean basin, which separates the Yangtze block in the east and the Indosinian block in the west. Its main composition includes Silurian Devonian deep-sea fan cladding deposit ophiolite Carboniferous Lower Permian marine carbonate rock island arc magmatic rock and Permian back-arc basin turbidite. The tectonic deformation of the ancient Tethys in Ailao Mountain can be divided into two stages: 1) the deformation of D _ (1) during the subduction period. Under the action of NE thrust shear, the permeable cleavage is formed in the mid-deep layer, which is parallel to the axial direction of horizontal shear fold (f _ 1) of horizontal shear fold in horizontal shear fold, horizontal shear fold and horizontal shear fold. On the foliation plane, the NSE-NW extensional lineage developed L1, and several thousand chymoliths developed, and the shallow-layer shearing zones, thrust faults and related folds were developed in the shallow layer. In the process of proliferation, the recoil action occurs to form the horizontal fold f _ (1), which inclines eastward to the east, and does not develop axial plane cleavage. (2) during the collision period, the compression shrinkage deformation (D _ 2N) is formed, and under the action of near-east-west extrusion, In the shallow layer, the close tilted fold and steep dip vertical fold are formed in the shallow layer, and the lines of wrinkle and cleavage are formed. Since the Cenozoic, due to the collision between India and Eurasia, the thrust nappe structure, strike-slip shear zone, graben-half graben basin and other superimposed structures have formed the NNW open fold and fault.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P548

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