The electrical structure beneath the Yarlung Zangbo suture zone in southern Tibet

In order to study the tectonic relationship between the shallow and deep active faults as well as deep seismogenic machanism around Xigaze city in South Tibet, totally 48 wide-band magnetotelluric sounding points were deployed on a 108 km long line across the Xietongmen-Xigaze section of the Yarlung Zangbo suture zone （YZSZ） , hence 2D inversion technique was employed to reveal the deep electrical structure whose depth range is less than 200 km. This south-north trending profile passes through the Himalayan block, YZSZ and Lhasa-Gangdise block in turn. Most of the crust beneath the Himalayan block is of high resistance, and at the north side of the Zhongba-Langjie xue continental margin displaced mixed terrane, it develops a huge north-dipping high conductive body that stretches downward into the upper mantle. There exists a 10 km wide trumpet-shaped low resistance tunnel and two typical high conductive bodies beneath the YZSZ, of which the shallow one is south-dipping whereas the deep one is north-dipping. Besides, in the crust and upper mantle beneath the YZSZ, there also develops two high resistance bodies, the southern one is nearly vertical or south-dipping ophiolite, and the northern one is upright Gangdise granite. Hence it expresses like a low-resistance channel clamped by those two bodies stretching downward into the upper mantle. Lhasa-Gangdise block is dominated by high resistance and the high conductive bodies are generally developed within the middle and lower crust. The subduction of Indian plate leads to the local thicken and thinning of the crust and mantle, therefore there exhibits an obvious gradient change nearby themajor suture belt （MSB） , and the YZSZ control the migration channel of crust-mantle material.