西藏吉普地区上古生界构造变形特征研究

发布时间：2018-03-20 16:45

本文选题：南羌塘　切入点：日土县　出处：《中国地质大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：南羌塘地块上古生界在阿里地区日土县北部、改则县北部冈玛错地区以及荣玛县温泉沟一带均有发育。本文以增生造山理论为指导,以构造解析为主要构造方法,通过野外大比例尺构造—岩性填图,构造—岩性实测剖面测量,结合室内显微构造、应变测量及碎屑锆石同位素年代学,对研究区上古生界构造变形进行了系统研究,研究成果对于羌塘构造属性的厘定及班公湖—怒江缝合带演化具有重要意义。通过碎屑锆石年代学研究,认为碎屑岩碎屑锆石年龄特征曲线与区域上的上古生界碎屑锆石年龄曲线一致,确定该套地层为上古生界并分析其物源特征。在系统构造解析基础上,发现南羌塘日土县北部吉普地区上古生界虽发育透入性劈理(S1),建立了透入性劈理面理及相关置换构造的构造样式,认为在泥质岩与砂岩互层的褶皱中,泥质岩为转折端为尖棱顶厚褶皱、发育正扇形连续劈理,砂岩层为转折圆滑的等厚褶皱,发育反扇形间隔劈理。通过野外系统观察和研究基础,将研究区构造变形期次划分为三期:早期变形为纵弯褶皱变形,形成区域性透入劈理S1,并认为该期变形与古特提斯洋俯冲削刮作用有关,形成近东西向走向的褶皱,早期褶皱形成的劈理S1走向也近东西向;中期变形同样为纵弯褶皱变形,与早期变形的方向相近,呈共轴叠加在早期构造变形之上,在局部使S1形成的劈理再褶皱,并形成非透入性劈理S2,该期变形与古特提斯洋闭合碰撞挤压作用有关;晚期变形为逆冲推覆构造,发育大量大规模的逆冲断层及其相关的膝折构造(劈理S3),发现距离逆冲断层面越近膝折变形越强烈,膝折的幅度越大,该期变形区域上与新生代的逆冲推覆构造一致,与印度板块和亚洲板块的碰撞作用有关。通过对研究区膝折构造的大量观测以及显微构造研究,将研究区所出现的膝折模式分为4类,并确定其在露头尺度及镜下的构造特征。并通过对地层中褶皱转折端强变形砾石与褶皱翼部未变形砾石的应变状态测量计算了该套地层的变形缩短量为31.3%。
[Abstract]:The Upper Paleozoic of the South Qiangtang block is developed in the northern part of Yitu County in Ali area, the Gangmaoco area in the northern part of Reze County, and the hot spring ditch area in Rongma County. This paper is guided by the theory of accretive orogeny and takes structural analysis as the main tectonic method. The structural deformation of the Upper Paleozoic in the study area has been systematically studied by large scale tectonic-lithologic mapping in the field and the measured profile of tectonic-lithology, combined with indoor microstructures, strain measurements and clastic zircon isotopic chronology. The results of the study are of great significance for the determination of tectonic attributes and evolution of Bangonghu-Nujiang suture zone in Qiangtang. It is considered that the age characteristic curve of clastic zircon in clastic rocks is consistent with that of the upper Paleozoic clastic zircon in the region. The strata are determined to be Upper Paleozoic and their provenance characteristics are analyzed. It is found that although the Upper Paleozoic developed permeable cleavage S1, the structural patterns of permeable cleavage and related replacement structures have been established in the Gyibug area of northern Qiangtang County, South Qiangtang. It is considered that in the folding of the interbedded mudstone and sandstone, The mudstone is a turning point with a sharp ridge thick fold, a normal sector continuous cleavage, a sandstone layer with a smooth turn and an equal thickness fold, and an inverse fan-shaped interval cleavage. Based on the systematic observation and research in the field, The tectonic deformation period in the study area is divided into three stages: the early deformation is longitudinal bend fold deformation, forming regional penetration cleavage S _ 1, and the deformation is related to the subduction and scraping of the paleoTethys ocean, forming a fold with a near-east-west strike. The cleavage S1 strike formed by early fold is also near east-west direction, and the middle deformation is also longitudinal bend fold deformation, which is close to the direction of early deformation, and is coaxial superimposed on the early tectonic deformation. And formed non-permeable cleavage S _ 2, which was related to the close collision and extrusion of the PaleoTethys Ocean, and the late deformation was a thrusting nappe structure. A large number of large-scale thrust faults and their associated knee fracture structures (cleavage S3N) have been developed. It is found that the closer to the thrust plane, the stronger the deformation of the knee fracture is, and the greater the amplitude of the knee fracture is, which is consistent with the Cenozoic thrust nappe tectonics in the deformation area of this period. Related to the collision between the Indian plate and the Asian plate. Based on a large number of observations of the knee fracture structures in the study area and the study of microtectonics, the genu fracture patterns in the study area are classified into four categories. The deformation shortening of the stratum is 31.3 by measuring the strain state of the strong deformed gravel and the undeformed gravel in the fold and wing of the fold in the outcrop scale and under the mirror. The deformation shortening of the stratum is calculated by measuring the strain state of the deformed gravel and the undeformed gravel in the wing of the fold.
【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】：P542

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