Crustal structure underneath central China across the Tibetan Plateau, the North China Craton, the South China Block and the Qinling-Dabie Orogen constrained by multifrequency receiver function and surface wave data

摘要

Investigating the crustal structure at the juncture region of the Tibetan Plateau, the North China Craton, the South China Block and the Qinling-Dabie Orogen is important to understand processes of uplift of the Tibetan Plateau and the craton destruction and preservation. In this study, we dropped the H-k stacking of receiver functions (RFs), RF nonlinear inversion, and joint inversion of RF and surface wave dispersion with multiple Gaussian factors successively to invert the crustal thickness (H), average Vp/Vs ratio (k) and S-wave velocity in the juncture region. The imaging results and the synthetic tests of multifrequency H-k stacking were further used to study the crustal structure and related tectonic evolution. Our results show that the H and k values generally increase and decrease, respectively, as the Gaussian factor increases in the study region, which is consistent with synthetic tests of H-k stacking. The cores of the Ordos Block and the Sichuan Basin exhibit a typical cratonic crust, whereas the Zhongtiao Mountains and adjacent Qinling-Dabie Orogen to the south may have undergone delamination of the lower crust. Local low-velocity anomalies in the middle-lower crust were observed in the Western Qinling Orogen and Qilian Orogen, whereas high S-wave velocities in the middle-lower crust were observed at the juncture region between the Western Qinling Orogen and the Qinling-Dabie Orogen. Our results suggest that the lower crustal flow is probably restricted to the central area in the Western Qinling Orogen and does not flow into the Qilian Orogen or the Qinling-Dabie Orogen.