Tectonic evolution of the Qinling orogen, China: Review and synthesis

Abstract

This contribution reviews the tectonic structure and evolution of the Qinling orogenic belt, which extends east–west nearly 2500 km across Central China and is a giant orogenic belt formed by the convergence and collision between North China and South China Blocks. The principal tectonic elements including metamorphic basement and its Neoproterozoic to Triassic cover, ophiolitic sutures, nature and ages of granitoid belts, provenance studies and tectonometamorphic studies of metamorphic belts allow tracing the polarity of two stages of plate convergence and collision and the further tectonic history. In this review, we present new distribution maps of the Early Paleozoic ophiolites and associated volcanics in the Shangdan suture zone and the Middle Devonian–Middle Triassic ophiolitic melange in the Mianlue suture zone, as well as the maps of granitoid and metamorphic belts displaying various ages (Silurian–Devonian, Triassic, Late Jurassic–Early Cretaceous). These maps allow better constrain the polarity of subduction and collision. We also discuss the significance of the Early Cretaceous Yanshanian events, which represent a linkage between tectonic events in the Tethyan and East China/Pacific realms. Two ophiolitic sutures, the Shangdan suture zone in the north and the Mianlue suture in the south, have been intensively studied during the past two decades. The Qinling Orogen is divided into the North Qinling and the South Qinling Belts by the Shangdan suture zone, and this suture zone is thought to represent the major suture separating the North China and South China Blocks. However, the timing and processes of convergence between these two blocks have been disputed for many years, and Silurian–Devonian or Late Triassic collision has been proposed as well. Based on the recent results, a detailed convergent evolutionary history between the North China and South China Blocks along the Shangdan suture is here proposed. The Mianlue suture zone is well documented and represents the Mianlue ocean which separates the South Qinling from the South China Block in Devonian to Mid Triassic times. After the closure of the Mianlue ocean, the South Qinling Belt was emplaced onto the Yangtze Block along the Middle Triassic Mianlue suture zone in Late Triassic–Jurassic times. This suture was overprinted by the south-directed overthrust of the Mianlue–Bashan–Xiangguang thrust fault operative in Late Jurassic-Cretaceous times. Furthermore, we note that the Yanshanian tectonic events play a major role for rapid Early Cretaceous exhumation of significant portions of the Qinling orogenic belt. In contrast, although high topographic gradients, the Cenozoic tectonism related to lateral extrusion of the Tibet plateau resulted in minor and continuous exhumation and erosion along major transtensional and strike-slip faults were activated.