Study On The Electrical Structure Of The Crust And Upper Mantle Of Yanshan Area

The thesis is based on the national program of "Sinoprobe-O1-02",aiming to process the 2-D inversion of "NLCG" with the data of 5 MT profiles in the area of YanShan,in order to prove that the electrical structure model is reliable.The basic understanding of the area of YanShan can be concluded,after the studies of the 5 electrical structure models.The electrical spindle direction of the area is two-dimensionally applicable of NE 45°?80°.With the complicated geological structure of area and the destructive magmatic activity,the electrical stratification results of the model are under expectations.The area of YanShan was divided into two part by the Shangyi-Chicheng fault,the north of which is Innermongolia Earth's Axis and the south is Yanshan Plaform Fold Belt.With increasing depth,the resistance of the north decreased first and then increased.From the west to the east in the profile,the high resistant block in the earth crust thickenned first and then thinned,and the high resistant block in the upper mantle slowly lifted.With increasing depth,the resistance of the south decreased first and then increased.From the west to east in the profile,the high resistant block in earth crust thickenned first and then thinned,and the low resistant block in the upper mantle slowly lifted and thinned.The existence of the belts of low electrical resistance in the lower crust and the upper mantle of YanShan area are very likely to be caused by the salty fluids.The faults of different developed levels in the YanShan area are presented by showing whether the electrical gradient belts or the low resistant belts.The belts with low resistance in the faults connecting with the low resistant upper mantle may provide the rotation and uplift strength and influenced the mantle structure of YanShan area.Shangyi-Chicheng fault is the lithospheric fault,providing clear electrical boundary in the deep area.The low resistant block in the south and the high resistant block in the north lifted slowly and thinned from the west to the east in the area,which may prove the thinning of lithosphere to the east in Northern China.