The Geophysical Detection Of The Deep Structures Of Altyn Tagh Fault

This thesis is based on the Youth Science Foundation:lithospheric electrical structure of the eastern section of the Altyn Tagh Fault(Project No.40904025),using 5000 line MT field measured data,which across the eastern section of the Altyn Tagh fault,complete magnetotelluric data fine processing by the international leading processing technology;design a series of two-dimensional forward and inverse model to obtain reasonable and reliable electrical structure model of the profile;combination of the geological imformation and other geophysical results around the survey area,explained the lithospheric electrical structure of the eastern Altyn Tagh fault,fault structure and the meaning of tectonic.Along the eastern section of the Altyn profile,the impedance tensor decomposition is more complex,in the northern section of the regional electricity spindle azimuth is 60° or 150°,the southern section of the region is 20° or 110°,According to the regional geological structure information,determine structural trend is N60E.Underground electric media dimension of the discriminant that can be approximated by a two-dimensional structure to be studied along the profile.Done a lot of two-dimensional inversion model by the combination of different inversion mode and parameters,than select the most reliable and reasonable model for the final interpretation.The results of 2D inversion show the resistivity distribution with the depth,and along the profile the characteristics of the resistivity distribution is vertical stratification and horizontal partition:there is a great difference in resistivity between the different tectonic units,in the eastern edge of Tarim Basin,Dunhuang block has higher resistivity values,and the Qilian block has lower resistivity values,with the performance of electrical segmentation.according to the differences of the electrical components divided the fault structure's location and occurrence,Altyn Tagh fault perform as vertical resistivity boundary,cut vertically,and the cutting depth is about 40 km,deep structure slightly southward tilting,positive flower structures are apparent,the other fracture and fault structure delineated by the geological are basically the same.Dunhuang block high impedance characteristics reveal a relatively cold,rigid Tarim lithosphere,which is consistent with the geodynamic model of oblique subduction of the Tarim Basin below Altyn Tagh fault.The inversion results show the existence of the crust and upper mantle high-conductivity layer in the study areas,based on the difference formation mechanism of the high-conductivity layer,intracrustal high conductivity layer has rock shear thermogenesis,prompting the raphitization of the rock,resulting the resistivity decreases,while the upper mantle high conductivity layer beneath the Qinghai-Tibet subcontinent,its formation is likely related to partial melting of rocks at high temperature and high pressure environment.Basically the MT probe result is conform with other geophysical results,which provides a reliable electrical constraints to study the geophysical characteristics of this region,and provides a relevant evidence for the geodynamic model.