地学前缘 ›› 2020, Vol. 27 ›› Issue (1): 194-203.DOI: 10.13745/j.esf.sf.2019.11.29

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藏南地区新生代多阶段构造演化及其动力学的探讨

刘德民,杨巍然,郭铁鹰   

  1. 中国地质大学(武汉) 地球科学学院, 湖北 武汉 430074
  • 收稿日期:2019-10-10 修回日期:2019-10-30 出版日期:2020-01-20 发布日期:2020-01-20
  • 作者简介:刘德民(1975—),男,博士,副教授,主要从事构造地质学与地热地质学方面的教学和研究。 E-mail:5guc@163.com
  • 基金资助:

    国家自然科学基金项目(41172087);广西壮族自治区企事业单位委托项目(2019016110,2019016207)

Discussion on Cenozoic tectonic development and dynamics in South Tibet

LIU Demin,YANG Weiran,GUO Tieying   

  1. School of Earth Sciences, China University of Geosciences (Wuhan), Wuhan 430074, China
  • Received:2019-10-10 Revised:2019-10-30 Online:2020-01-20 Published:2020-01-20

摘要:

开合构造是一种全球构造假说,该假说基础为地球上的一切物质和地质体都存在开合表现;可以用开合构造观解释一些板块构造理论登陆后不能合理解释的地质现象。文章在结合前人基础地质资料基础上,分析藏南地区基本的构造单元划分;强调动态构造单元划分,提出了被重力拆离断层改造叠加的逆断层区以及被拆离断层改造的正断层区。在主流观点提出碰撞挤压造山形成青藏高原时,野外科学考察发现了绒布寺伸展正断层的存在。文章认为绒布寺伸展正断层与主中央逆冲断层形成时间比藏南拆离系要早,两者构成了藏南挤出构造的两个边界;而藏南拆离系是晚期形成的,局部叠加在主中央逆冲断层之上,并且珠峰北追踪了早期绒布寺正断层呈相对高角度产出。3条断裂构造系统是不同时期、不同构造背景下的产物。藏南由前人所划分的飞来峰、构造窗等逆冲推覆构造系统中的构造单元,往往挤压逆冲特征表现不明显,却表现出由新的地层覆盖在老地层之上而显示地层柱缺失的特征。文章认为这些是滑覆构造的表现,是藏南地区晚期重力滑覆作用的产物。用开合构造理论将该地区新生代构造演化划分为由开转换为合;然后由合转换为开,构成一个完整开合演化历史,在这多阶段构造演化过程中,地球深部的热能、地球内部的重力势能以及构造引起的附加应力能起到关键作用。

关键词: 藏南, 地质结构, 新生代构造演化, 开合构造

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

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