High-resolution 3-D lithospheric structure beneath the Qinling-Dabie orogenic belt from joint inversion of receiver functions and ambient noise

Abstract

Resulting from the convergence of the Yangtze and North China Cratons, the Qinling-Dabie orogenic zone (QD) represents an important element in the central China orogenic system. To fully comprehend the craton evolution and lower crustal flow from the Tibetan Plateau, it is important to understand the crust and mantle structure of the QD. We reconstructed the three-dimensional lithospheric structure beneath the QD with high resolution using the joint inversion of receiver functions and ambient noise. Observations reveal that a high-velocity anomaly in the middle to lower crust beneath the western Qinling (WQL) orogen obstructs the eastward extension of a crustal low-velocity anomaly originating from the Tibetan Plateau. This finding provides unambiguous evidence that the WQL orogen is not crossed by eastward lower crustal flow from the Tibetan Plateau. The lithospheric mantle beneath the Weihe Rift and East Qinling orogen exhibits low-velocity characteristics, indicating that eastward asthenospheric flow from the Tibetan Plateau has caused substantial thermal-chemical erosion in the uppermost mantle beneath these regions. The results additionally indicate that the uppermost mantle high-velocity anomalies beneath the Dabie orogen is confined in a limited area and extends only to a depth of 70 km. We propose that during the Triassic, deeply subducted continental lithosphere returned into the uppermost mantle, forming the high-velocity anomalies beneath the Dabie orogen.