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本研究通过东喜马拉雅构造结及周围地区连续6年的大地电磁观测,获得了青藏高原东部岩石圈电性结构的初步认识。结果发现,在青藏高原东部存在两条巨大的中下地壳低阻异常带,理论计算显示这是两条中下地壳的弱物质流:一条从拉萨地块沿雅鲁藏布缝合带向东延伸,环绕东喜马拉雅构造结向南转折,最后通过腾冲火山;另一条从羌塘地体沿金沙江-鲜水河断裂带向东延伸,在四川盆地西缘向南转折,最后通过小江断裂和红河断裂之间的川滇菱形块体。本项研究认为,青藏高原深部以两个地壳弱物质流的快速塑性变形为主,上地壳则以块体的走滑变形为主。该模型将有助于对青藏高原动力学的定量研究以及对高原东部和滇川西部地区地震活动机制的分析。
In this study, we first obtained the lithospheric electrical structure of the eastern Qinghai-Tibet Plateau through the 6-year geomagnetic observation of the East Himalayan tectonic knot and the surrounding area. The results show that there are two huge low-resistivity anomalous belts in the eastern part of the Qinghai-Tibet Plateau. Theoretical calculations show that this is the weak material flow of the two middle and lower crusts. One extends from the Lhasa block to the east along the Yarlung Zangbo suture , Turning around the eastern Himalayan tectonism to the south and finally passing through the Tengchong volcano. The other extends eastward from the Qiangtang terrain along the Jinsha-Xianshuihe fault zone, turning southwards on the western margin of the Sichuan Basin. Finally, it passes through the Xiaojiang fault and the Red River Sichuan-Yunnan diamond between the fracture block. In this study, the rapid plastic deformation of two weak crustal flows in the deep Qinghai-Tibet Plateau is dominant, while the upper crust is dominated by the block-based strike-slip deformation. The model will be helpful for the quantitative study of the dynamics of the Tibetan Plateau and the analysis of the seismic activity mechanisms in the eastern plateau and western Yunnan.