Discussion on Cenozoic tectonic development and dynamics in South Tibet

doi:10.13745/j.esf.sf.2019.11.29

Abstract

Abstract:

Opening-closing tectonics is a hypothesis about the whole earth based on the theory that every tectonic movement on earth is opening-closing movement. It can explain some geological phenomena developing on the continents which can not be explained by plate theory. In this paper, using opening-closing theory, we analyzed the characteristics of tectonic units in South Tibet, and proposed that South Tibet can be divided into the gravitational detachment fault reformed thrust and normal faults. The field scientific investigation team found the Rongbusi normal fault when the mainstream opinion believed that the Tibetan plateau was formed by collision-compression orogenesis in 1970s. We consider that the Rongbusi normal fault and the Main Central Thrust developed before the South Tibet detachment fault, and that the former two faults are the two boundaries of the South Tibet extrusion structure. The South Tibet detachment fault partially superimposes on the Main Central Thrust and manifests high angle following the Rongbusi normal fault in the north of Chomolangma. We believe that the three fault systems developed in different tectonic backgrounds and periods. The structural units such as klippes and windows, which were identified by previous researchers in southern Tibet, belong to thrust fault system but usually have no obvious features of extrusion or thrust; however, they have the characteristics of missing strata column as younger strata overlaying on the older ones. We consider the klippes and windows the results of later gravitational decollement and having clear characteristics of extension and slippery. Based on opening-closing theory, we believe that since Cenozoic, the study area had undergone multiple developmental stages such as oceanic crust expansion (opening) and subduction (closing), continental collision (closing) and intra-continental extension (opening). Geothermal energy from deep earth, gravitational potential energy from Earth's interior, and stress energy from tectonic movements, played a key role in the multi-stage development.

Key words: South Tibet, geological structure, cenozoic tectonic evolution, opening-closing tectonics

CLC Number:

P541

LIU Demin, YANG Weiran, GUO Tieying. Discussion on Cenozoic tectonic development and dynamics in South Tibet[J]. Earth Science Frontiers, 2020, 27(1): 194-203.

Figures/Tables 8

References 42

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对比特征		推覆构造(飞来峰)	滑覆构造(滑来峰)
对比特征		推覆构造(飞来峰)	伸展滑覆	重力滑动
构造体制		挤压体制	伸展体制	隆起背景下的重力作用
构造体的变形	断层组合	逆断层	正断层	兼而有之,其前缘更似推覆构造,根部则具伸展构造特征
	褶皱特点	倒转-平卧背斜为主, 倒转翼变薄拉断	下翼成倒转翼保存完好
	杏仁等变形	长轴直立,短轴水平, 常成直立椭球状	与之相反,常为平躺的椭球状
	变形序列	老地层推覆于新地层之上, 常地层重复	与之相反,常地层缺失
	变形结构	水平缩短,垂向相厚	水平拉长,垂向变薄
构造面之下变形		多经受挤压缩短	伸展变形微弱	有时有明显伸展变形

对比特征		推覆构造(飞来峰)	滑覆构造(滑来峰)
对比特征		推覆构造(飞来峰)	伸展滑覆	重力滑动
构造体制		挤压体制	伸展体制	隆起背景下的重力作用
构造体的变形	断层组合	逆断层	正断层	兼而有之,其前缘更似推覆构造,根部则具伸展构造特征
	褶皱特点	倒转-平卧背斜为主, 倒转翼变薄拉断	下翼成倒转翼保存完好
	杏仁等变形	长轴直立,短轴水平, 常成直立椭球状	与之相反,常为平躺的椭球状
	变形序列	老地层推覆于新地层之上, 常地层重复	与之相反,常地层缺失
	变形结构	水平缩短,垂向相厚	水平拉长,垂向变薄
构造面之下变形		多经受挤压缩短	伸展变形微弱	有时有明显伸展变形