Late Triassic Dabie–Sulu Orocline: New exhumation model of the HP–UHP rocks

Abstract

The Dabie–Sulu orogen is located in the eastern segment of the Central China Orogen between the North China Block (NCB) and the South China Block (SCB). The complex processes of break‐up and assemblage among the continental blocks of East Asia caused them to undergo multiple‐stage continental collisions. It is extremely important for the final kinematics and dynamics of convergence and collision among continental blocks to explore the exhumation mechanism of the HP (high pressure)‐UHP (ultra‐high pressure) metamorphic rocks. Therefore, this paper focuses on the final collisional process and tries to find a reasonable exhumation mechanism of the HP–UHP rocks. On the basis of the structural geology, petrology, seismic tomography, palaeomagnetism, and mathematical calculation, we propose a south‐eastward subduction of the NCB under the SCB in the Indosinian, and the Sulu Orogen actually became an orocline. This was caused by continuous south‐eastward subduction and the subsequent westward‐retreating delamination of the NCB slab. Coevally, it produced a two‐stage exhumation process, a vertical extrusion during the first stage (240–220 Ma) and an eastward extrusion controlled by an oroclinal contraction at the second stage (220–200 Ma).