Lateral variation in seismic velocities and rheology beneath the Qinling-Dabie orogen

The Qinling-Dabie orogen is an important tectonic belt that trends east-west and divides continental China into northern and southern parts. Due to its strong deformation, complicated structure, multiphase structural superposition and the massive exposed high and ultrahigh metamorphic rocks, its tectonic formation and geodynamical evolution are hot research topics worldwide. Previous studies mainly focused on the regional geological or geochemical aspects, whereas the geophysical constraints are few and isolated, in particular on the orogenic scale. Here, we integrate the available P- and S-wave seismic and seismicity data, and construct the rheological structures along the Qinling-Dabie orogen. The results demonstrate that: (1) there are strong lateral variations in the crustal velocity between the western and eastern sections of the Qinling-Dabie orogen, indicating the different origin and tectonic evolution between these two parts; (2) the lateral variations are also manifested in the rheological structure. The rigid blocks, such as South China and Ordos basin (North China Craton), resist deformation and show low seismicity. The weak regions, such as the margin of Tibet and western Qinling-Dabie experience strong deformation and accumulated stress, thus show active seismicity; (3) in the lower crust of most of the HP/UHP terranes the values of P-wave velocity are higher than the global average ones; nally (4) low P- and S-wave velocities and low strength in the lower crust and lithospheric mantle beneath Dabie indicate lithospheric delamination, and/or high temperature, and partial melting condition.