With super-wide band magnetotelluric sounding data of Jilong-Cuoqin profile (named line 800) and Dingri-Cuomai profile (named line 900), obtained the strike direction of each MT station by strike analysis, then traced profiles which were perpendicular to main strike direction, finally got resistivity model of each profile by Nonlinear Conjugate Gradients(NLCG) Inversion. With these two models,described resistivity structure features of crust and upper mantle beneath the southern-central Tibetan plateau and its relationship with Yaluzangbo Suture: upper crust of research area is a resistive layer with resistivity value from 200~3000 Ohm-meter, the depth of its bottom surface is about 15~20km generally, but the bottom surface of this resistive layer is deeper at the middle of these two profile, at line 900 it is about 30km deep and even at line 800 it is about 38km deep. There is a gradient belt of resistivity at the depth of 15~45km,and a conductive layer is beneath it whose resistivity is even little than 5 Ohm-meter, this conductive layer is composed by individual conductive bodies, and at the south of Yaluzangbo suture the conductive bodies is smaller and its thickness is about 10km and leans to north slightly, but at the north of Yaluzangbo suture the conductive bodies is bigger and its thickness is about 30km and leans to north slightly too, relatively, the conductive bodies of line 900 is thinner than its of line 800, the depth of bottom surface of line 900 is also shallower. At last after analyzing effect factors to the resistivity of rocks, concluded that the very conductive layer was caused by partial melt or connective water in rocks, it suggests that middle and lower crust of the center-southern Tibetan plateau which is very thick is hot,flabby and waxy.
展开▼
