| The Qinghai-Tibet Plateau is Asia's most eye-catching geomorphic unit, which is the product of the collision between the Indian continent and the Asian continent. The Indian lithosphere is wedged northward into the Asian continent due to the continuous expansion of the midline of the Indian Ocean. The thickening of the Tibetan Plateau, It has a complex and unique thick crust and lithosphere structure. The western part of the Qinghai-Tibet Plateau is one of the typical areas of the continental-continental collision orogenic belt,which has a very complicated geological structure and material composition. The detailed study on this area plays a key role in understanding the Qinghai-Tibet Plateau as a whole.Therefore, the western part of the Qinghai-Tibet Plateau has become a hot spot for geoscience researchers in recent years.In this paper, the magnetotulluric (MT) data collected from the experimental study of"deep exploration technology and experimental research (SinoProbe, 2008-2012)" special subject "Continental Electromagnetic Parameters Standard Network Experimental Research (SinoProbe-01) " is taken as the original data. A total of 148 magnetotulluric points from 14 "standard points" at along the 80°E, 81° E, 82 ° E warp directions were used as data support. The data are processed, analyzed and inversed. Finally, the two-dimensional and three-dimensional electrical structure models of the study area are obtained.The two - dimensional inversion model and the three - dimensional inversion slice correspond well, indicating that the obtained electrical structure model has high reliability.The electrical structure model shows that the upper crust is dominated by high resistance in the study area. In the suture zone and fault zone, there is a low resistance zone with high resistance. Medium and lower crust with large-scale high-conductivity layer, Yarlung Zangbojiang suture at the high conductivity layer thickness, buried depth. The thickness of the high-conductivity layer and the depth of the bottom interface in the Lhasa-Gangdise Formation increase northward. In the Bangong Lake - Nujiang suture near the bottom of the high conductivity layer thickness, the bottom interface has reached the upper mantle depth. The thickness of the high-conductivity layer in the Qiangtang area is large. The high conductivity layer is a high resistance layer, but is limited by the effective depth of the profile and does not determine the thickness of the layer.It is concluded that the thermal effect of the subduction of the Indian plate lithosphere to the lower part of the Qinghai - Tibet Plateau has resulted in partial melting of the rock on the subduction contact surface and reduced the resistivity of the molten rock. In addition, the molten rock will precipitate water, the water will move under pressure to the top; so in some of the melting and water under the action of the fluid led to the Himalayan terrane and Lhasa - Gangdisi underground body under the high conductivity layer. The cause of the high-conductivity layer in the Qiangtang body is mainly due to the upwelling of the mantle-derived material, which leads to the partial melting of the rock in the shell,forming a high conductivity layer. The study shows that the Indian lithosphere has subducted into the Qinghai-Tibet Plateau, and in the western part of the Qinghai-Tibet Plateau, its subduction front does not cross the Bangong-Nujiang suture zone. The subduction of the Indian lithosphere is below the Bangong-Nujiang suture Into the upper mantle. |
PDF Full Text Request