Crust and uppermost mantle electrical structure beneath the middle Qinling Orogen and adjacent regions

Abstract:

The Qinling Orogen is located at the central part of the China Central Orogenic Belt and links the Qilian and Kunlun Orogens to the west with the Dabie-Sulu Orogen to the east, which is sandwiched between the South China Block and North China Block. Its formation evolution processes are affected by the subduction of oceanic plate and subsequent continental collision. The Lithospheric structure records the deep processes, and the magnetotelluric (MT) method can probe the sub-surface electrical conductivity. A broadband and long period MT profile across the middle Qinling Orogen has been completed, which starts from the Sichuan Basin, crosses the Dabashan and the Qinling, and finally reaches the Weihe basin. Based on data analysis results, a two-dimensional (2-D) resistivity model of crust and upper mantle is finally obtained from inversion of the transverse magnetic mode and transverse electric mode. The MT results show that a relatively low resistivity zone exists at the bottom of the upper crust of the Qinling Orogen, features as an intracrustal decollement, which indicates the decoupling deformation between the upper and lower crust. The South China Block lithospheric mantle may have underthrust northward the South Qinling.