羌塘盆地额斯玛地区构造变形特征及演化

发布时间：2018-01-25 16:25

本文关键词： 南羌塘盆地额斯玛地区平衡剖面恢复缩短率两期构造运动　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】：羌塘盆地,位于青藏高原中部可可西里-金沙江构造带与班公错-怒江构造带之间,经历了自古生代以来古特提斯洋的闭合、拉萨-羌塘地体碰撞以及印度-欧亚大陆碰撞等多期构造事件。羌塘盆地结构和变形特征复杂,并且盆地构造变形记录了青藏高原中生代晚期以来演化过程和动力学信息。然而,目前对羌塘盆地构造变形和地壳缩短过程还存在不同认识,这不仅是羌塘地块存在的重大地质问题,而且直接影响到对整个高原隆升历史和机制的准确认识。本论文通过对南羌塘盆地额斯玛地区野外构造调查并结合二维地震研究,对该地区构造变形特征进行深入分析,其研究目的在于查明南羌塘盆地额斯玛地区的构造格架与变形特征基础上,探讨不同构造事件对南羌塘盆地形成演化的影响,以及变形过程与高原早期隆升的关系。通过地表构造及二维地震研究,对南羌塘盆地额斯玛进行了精细的构造单元解析,额斯玛地区深部以薄皮构造为主,盖层构造多未卷入基底,并且基底顶面作为主要拆离面,地表断层多向下汇聚于基底拆离面上。在二维地震剖面中,盆地基底特征在地震剖面中具有清晰反映。在南羌塘盆地之中可以识别明显的双层基底结构,内部构造复杂。但由于地震剖面品质相对较差,盆地深部构造的厘定,仍有待相关资料的进一步完善。本研究通过对额斯玛地区进行平衡剖面恢复,得到了南羌塘盆地的构造缩短率,南羌塘盆地侏罗纪构造层的缩短率在65-70%左右,白垩纪构造层缩短率在50-60%左右。第一期构造运动与晚白垩世拉萨-羌塘地体之间的碰撞相关,导致南羌塘盆地中挤压构造吸收了100km缩短量,而第二期构造运动与印度-欧亚大陆的碰撞相关,发生于新生代初期(约40Ma之前),南羌塘盆地地表构造吸收约150km缩短量;两次构造事件决定了原青藏高原的形成,拉萨-羌塘地体碰撞及印度-欧亚大陆碰撞对于原青藏高原早期隆起均起到决定性作用。
[Abstract]:The Qiangtang basin, located between the Hehexili-Jinshajiang tectonic belt and the Bangongcao-Nujiang tectonic belt in the central part of the Qinghai-Tibet Plateau, has experienced the closure of the PaleoTethys ocean since the Paleozoic. Lhasa-Qiangtang terrane collision and Indo-Eurasian collision, etc. The structure and deformation characteristics of Qiangtang basin are complex. And the tectonic deformation of the basin records the evolution process and dynamic information of the Qinghai-Tibet Plateau since the late Mesozoic. However, there are still different understandings on the tectonic deformation and crustal shortening of the Qiangtang basin. This is not only a major geological problem in Qiangtang massif. And it has a direct impact on the accurate understanding of the history and mechanism of uplift of the whole plateau. In this paper, through the investigation of the field structure in Esma area of the southern Qiangtang basin and combined with the two-dimensional seismic research. The purpose of this study is to find out the tectonic framework and deformation characteristics of Esma area in the southern Qiangtang Basin. The influence of different tectonic events on the formation and evolution of the southern Qiangtang basin and the relationship between the deformation process and the early uplift of the plateau are discussed. The detailed structural unit analysis of Esma in the southern Qiangtang basin shows that the deep part of the Eisma area is dominated by thin crust structure and the caprock structure is not involved in the basement and the basement top surface is the main detachment surface. Most of the surface faults converge on the basement detachment surface. In the two-dimensional seismic profile, the basement features of the basin are clearly reflected in the seismic profile, and in the southern Qiangtang basin, the obvious double-layer basement structure can be identified. The internal structure is complex, but because the quality of seismic profile is relatively poor, the determination of deep structure in the basin still needs to be further improved. The structural shortening rate of the southern Qiangtang basin is obtained, and the shortening rate of Jurassic tectonic layer in the southern Qiangtang basin is about 65-70%. The shortening rate of the Cretaceous tectonic layer is about 50-60%. The first stage of tectonic movement is related to the collision between Lhasa and Qiangtang terrane in late Cretaceous, which leads to the absorption of 100 km shortening by the compressional structure in the Qiangtang basin. The second tectonic movement is related to the collision between India and Eurasia, which occurred in the early Cenozoic (about 40 Ma ago) and absorbed about 150 km shortening of the surface structure in the southern Qiangtang basin. The formation of the original Qinghai-Xizang Plateau was determined by two tectonic events. Lhasa-Qiangtang collision and India-Eurasia collision played a decisive role in the early uplift of the original Qinghai-Xizang Plateau.
【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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