Abstract: The Gan-Hang tectonic belt (GHB) is an important uranium polymetallic ore belt, which is located at the junction of the Yangtze plate and the Cathaysia plate. A series of intermediate-felsic volcano-intrusive rocks are developed in the belt. There are still many controversies about the geodynamic backgrounds of magmatic eruption and intrusion in the belt. Therefore, the magnetotelluric (MT) data collected in the middle part of the Gan-Hang Belt (Shengyuan Basin) and its adjacent areas are processed and inverted by MT phase tensor decomposition technique, two-dimensional nonlinear conjugate gradient method (NLCG), and other technical means to obtain reliable lithospheric electrical structures in the area. The analysis reveals that the shallow volcano-intrusive hybrid rocks in the middle part of the GHB is connected with the southeast downdipping highconductivity band and the deep asthenosphere area, suggesting that the felsic magmatism in the region was controlled by the regional Jiang-Shao deep fracture. In the late Mesozoic lithospheric stretching led to magma rise along the regional deep fracture under the action of intrusion and eruption, forming the volcano-intrusive complexes; The magmatism in the extensional tectonic regime was related to the coeval retreat of the subducting Pacific plate.

Key words: magnetotelluric sounding (MT), Gan-Hang belt, 2D inversion, electrical structure, lithosphere