High Resolution 3-D Lithosphere Structure Underneath the Qinling-Dabie Orogenic Belt from Combined 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) stands as a pivotal element in the central China orogenic system. To fully comprehend the craton evolution and lower crustal flow from Tibetan Plateau (LCFFTP), it is important to understand the crust and mantle structure of QD. We constructed a three-dimensional lithosphere structure with excellent resolution underneath the QD using an inversion of receiver functions and ambient noise combined. The results indicate that the middle to lower crust underneath the western Qinling (WQL) orogen has a significant high-speed component that can obstruct the LCFFTP in an easterly direction. This provides unambiguous confirmation that the WQL orogen is not traversed by the eastward LCFFTP. The lithospheric mantle underneath the Weihe rift and East Qinling (EQL) orogen shows low-speed characteristics, which suggests that the asthenospheric flow from Tibetan Plateau (AFFTP) in an easterly direction led to significant thermal-chemical erosion in the uppermost mantle underneath the Weihe rift and EQL orogen. The results additionally indicate that the uppermost mantle high-speed component underneath the Dabie orogen is only confined to a limited area and extends only to a depth of 70 km. We propose that during the Triassic, the deeply subducted continental crust exhumed into the uppermost mantle, forming the high-speed component underneath the Dabie orogen.

Keywords: high resolution 3-D lithosphere structure, Qinling-Dabie orogenic belt, crustal flow, asthenospheric flow, Northeastern Tibetan plateau