印度与欧亚板块碰撞以来东喜马拉雅构造结的演化

在野外填图,构造观察及前人研究的基础上,本文识别并描述了东喜马拉雅构造结中的推覆断裂、正断裂及走滑断裂、背斜(形)和向斜(形)等构造类型,讨论了这些构造位置及与印度板块挤入,印支地块旋转的关系,还探讨了东喜马拉雅构造结对印度板块持续向北推挤下的特殊应变调节方式。在印度大陆部分,东喜马拉雅构造结由3个向外逐渐变新的构造结组成,即北东向的南迦巴瓦峰复式背斜、北西向的桑复式向斜及北东向的阿萨母复式向斜。上述3个构造结是协调印度板块的挤入、喜马拉雅弧的扩展及印支地块的旋转的构造。在欧亚大陆内部的冈底斯岛弧,在派区及阿尼桥走滑断裂协调下,高喜马拉雅结晶岩的基底挤入冈底斯岛弧内部,在大拐弯顶端形成向上的挤出构造。在南迦巴瓦峰构造结的北西侧,由于掀斜式抬升及重力滑动,使得冈底斯盖层与结晶基底脱耦,上盘盖层沿东久向北西方向滑动。在南迦巴瓦峰构造结北东侧,由于印支地块的挤出和旋转,形成一系列的北西向走滑断裂,如实皆断裂、嘉黎-高黎贡断裂、澜沧江断裂及红河断裂等。

The tectonic evolution of the eastern Himalaya syntaxis since the collision of the Indian and Eurasian plates

Based on the field mapping,structures measuring and pre-studies reviewing in these areas,this paper identify and describe the major thrust faults,normal faults and strike-slip faults,anticlines(antiforms) and synclines(synforms),then discuss the relationship of their structural positions with the dentation of the Indian plate and rotation of the Indochina block,and how these structures accommodated for the Indian plate,which continued to push northward into the eastern Himalayan syntaxis.The eastern Himalayan syntaxis is composed of three syntaxises which gradually changed younger from north to south,such as the NE direction Namjag-Barwa anticline,the NW trending Siang syntaxis in the middle and the NE Asam syncline.These three tectonics result from the dentation of the NE Indian plate,the extension of the Himalayan arc and the rotation of the Indochina block.The Namjag-Barwa pop-up structure was formed in the center of the Namja-Barwa syntaxis with the dentation of the High Himalayan crystalline rock basement into the Gangdes Arc under the coordination of the Pai and Aniqiao strike-slip faults.In the NW side of Namjag-Barwa within Gangdese Arc,because of the tilting uplift and gravity sliding,the Gangdese cover was decoupled with the crystalline basement along Dongjiu detachment fault,and the hingwall of the fault slide to the NW direction.In the NE side of the Namjag-Barwa syntaxis within the Eurasian continent,due to the extrusion and rotation of the Indochina block,a series of NW trending strike-slip faults was formatted,such as Sagaing fault,Jiali-Gaoligpng fault,Lanchang river fault and Red river fault.