Complex deformation mechanisms of the Qinling orogenic belt lithosphere and clockwise rotation of the Yangtze craton crust: Insights from Rayleigh wave azimuthally anisotropic tomography

The collision and convergence between the Yangtze Craton (YZC) and North China Craton (NCC) beneath the Qinling orogenic belt (QOB) have resulted in complex lithospheric deformation, the mechanisms of which remain unclear. In this study, we extracted 10–60 s Rayleigh-wave dispersion curves using the two-station method from vertical-component waveform data of 1087 teleseismic events, recorded at 110 seismic stations across the QOB and adjacent regions. Subsequently, anisotropic tomography was employed to reconstruct high-resolution isotropic and anisotropic phase velocity models of the crust and upper mantle beneath the QOB and surrounding regions. We focused on analyzing deformation patterns in four key subregions of the QOB. Our results demonstrated that crustal deformation is affected by multiple geological factors. Major tectonic activities, such as island arc collisions, oceanic basin closure, and orogenic events, have fundamentally shaped the regional structural framework. Building on this, crustal lithological features, thrust tectonic movements, and the strike of fault systems, which together control present-day deformation. Furthermore, our anisotropic model, in combination with previous geodetic and seismological observations, suggests that the clockwise rotation of the YZC during its convergence with the NCC plays a significant role in influencing crustal deformation. Upper mantle deformation is primarily driven by absolute plate motion, with additional influences from the northeastward escape of material in the Tibetan Plateau and mantle flow. Notably, our anisotropic model provides new seismological evidence supporting the clockwise rotation of the YZC crust, which is closely related to the tectonic development of the Sichuan basin and the formation of the Dabashan arcuate structure. Integrating with previous studies, we propose a conceptual model to explain the formation mechanism of the Dabashan arcuate structure, which we attribute to the combined effects of the clockwise rotation of the YZC crust during the Middle to Late Triassic and the ongoing convergence between the YZC and the NCC. These findings provide new insights into the lithospheric dynamic processes of the QOB.