Electrical structure of crust and upper mantle beneath Gangdise belt in Tibet

Abstract:

Broadband Magnetotelluric (MT) data were collected in southern Tibet. The MT profile extended 400 km roughly north-south across the northern Himalayan terrane, the Yarlung-Zangbo suture (YZS) and the Lhasa-Gangdise terrane (LGT). The electrical model (Figure 1.) obtained from MT two-dimensional nonlinear conjugate gradient (NLCG) inversion using TM-mode data alone. On the southern of profile two steeply north dipping electrical gradient belts (F1, F2) which extended to a depth of about 20 km were imaged. This might represent the faults belonged to YZS. Positive flower structures (F3, f1, f2, f3) were apparent on the central of profile and the main fault extended about 60 km. The model indicated that the upper crust of LGT was covered with a thick high resistivity overlay which extended to depths from 10 – 30km. The huge low resistivity bodies in middle and lower crust indicated the possibility of partial melt.

*This research was supported by China Geological Survey (Grant No. 1212011120185), the Fundamental Research Funds for the Central Universities (Grant No. 2652014018) and SinoProbe-01-02.