A Study Of The Characteristics And Tectonic Implications Of Electrical Structure In The Crust And Mantle Across The East Part Of Central Asian Orogenic Belt,Central And Eastern Inner Monglia,China

Under the auspices of the comprehensive geophysical survey in eastern part of the China and Mongolia border project,three magnetotelluric profiles were acquired from central and northeast part of Inner Mongolia.Lots of methods were used during the magnetotelluric data processing,such as the robust estimation,the remote reference method and the editing of the power spectrum in order to acquire the high quality magnetotelluric data.The qualitative analyses of electrical structure along the profile have been done by analyzing many parameters such as Swift and Bahr skewness,phase tensor,magnetic induction vector,and the direction of strike.Dimensionality analysis has shown a good two-dimensional character along the three profiles.Subsurface electrical structure has been obtained through nonlinear conjugate gradients algorithm for two-dimensional magnetotelluric inversion.The electrical resistivity model along the profile indicates that the electrical structure in central and northeast part of Inner Mongolia is different.The electrical resistivity model along the linel profile indicates that the electrical structure in North China Craton is characterized by four distinct layers in vertical direction,and the electrical structure in the northern margin of North China Craton is characterized by block division in horizontal direction.The electrical resistivity model along the line3 profile indicates that the electrical structure in central part of Inner Mongolia is characterized by block division in horizontal direction.The electrical resistivity model along the line4 profile indicates that the electrical structure in northeast part of Inner Mongolia is characterized by block division in horizontal direction.There are high-conductivity layers in the middle and lower crust in central and northeast part of Inner Mongolia,the distribution of the high-conductivity layers in different blocks is based on different formation processes.The high-conductivity regions in the crust under the line3 and line4 profiles are likely due to the converging continents of North China Craton and Siberian Craton during the closure of the Paleo-Asian Ocean.The high-conductivity layers in the crust under the linel profile is likely due to mafic and ultrabasic rock which derived from earth mantle.The igneous rocks are the main components of the continental crust in central and northeast part of Inner Mongolia,these igneous rocks are the product of igneous activity.Ernhot-Hegenshan fault,Xar Moron fault,Chifeng-Bayan Obo fault are showed significantly low resistance electrical anomaly band in electrical structure model.Electrical structure models show that these faults are lithospheric-scale which comply with the electrical characteristics of the subduction zone.The tectonic and crustal evolution of the east part of central Asian orogenic belt is more likely to be interpreted as a continuous accretion model.The electrical structure of solonker suture is complex,lithospheric-scale electrical differences were found in this area.The suture of North China Craton and Siberian Craton should be in solonker suture.