The Research On Three Dimensional Electrical Structure Of West Qinling Belt

Based on “ the magnetotellurics array observation of the intersection zone of central orogenic belt and the north-south seismic belt”and “Deep Exploration Technology and Experimentation”,Three dimensional electrical structure of west Qinling belt and its adjacent area has been acquired by using magnetotellurics method.The scope of study area is E104°? E108°,N30°? N38°,including the Sichuan Basin,Songpan-Ganzi block,west Qinling,Qilian block,Alashan block and Ordos Basin.In order to improve SNR(Signal-Noise Ratio),the remote reference,Robust method and power spectrum editing are used during date processing.After that,we analyse the skewness and magnetic vectors of all dates.Finally,we got high confidence 3D electrical structure by 2D inversion and 3D inversion.As we can see from the 2D/3D electrical structure model,the electrical structure of crust and beneath the Sichuan Basin is relatively simple.the resistivity from shallow to deep shows an electrical characteristic of low-high,the shallow layer of low resistivity may be terrigenous detrital mineral.the substratum of High resistivity body in the deep crust and mantle may be widely crystalline basement of Yangtze craton,including granite.The electrical structure between Songpan-Ganzi block and Sichuan basin is quite different.We can infer that,under the north-west pressing of Sichaun basin and the north-east pressing of Qinghai-Tibet plateau,while the upper and middle curst decoupling,the upper crust overthust along the surface of high conductivity body,and above to the Sichuan basin.In the boundary of west Qinling belt,there exists thrust nappe structure.The whole electrical structure model shows,tht crust and mantle of Yangtze block and North china block thrust toward to the Qinling belt which uplifts as asymmetric sector?conbined with heat flow value and crust temperature,we can infer,as Tibetan Plateau is under the east or north-east pressing of the Indian Plate,part of material escape to the east during crustal thickening of Tibetan Plateau.Because of the block of Sichuan basin and ordos basin,the material of the Tibetan Plateau cross the fault into west Qinling?This movement mainly occurred in the middle and lower crust of 20?50km,in the form of material melting.