Devonian–Triassic tectonic evolution of the Western Qinling Orogenic Belt of central China: Insights from detrital zircon UPb chronology and rock geochemistry

Analysis of the Palaeozoic tectonic evolution of the Western Qinling Orogenic Belt (WQOB) is important for understanding the development of the eastern segment of the Paleo-Tethys domain. In this paper, UPb zircon chronology and rock geochemistry of Devonian-Triassic strata in the WQOB are analyzed to shed light on the tectonic evolution of this region. Comparison of age spectra reveals that the WQOB had a significant detrital source from the northwest margin of the Yangtze Block in Early Devonian times. However, during Middle Devonian-Carboniferous times, the Middle Qilian and North Qinling orogens became the dominant source areas. A further transition occurred in Permian to Middle Triassic times when detrital sources originated from the southwest margin of the North China Block, and in late Triassic times, mixed sourcelands prevailed including the northern margin of the North China Block and the east of Middle Qilian Orogen. Based on our geochemical analysis, we identify a Devonian-Carboniferous tectonic context characterized by a stable passive continental margin, and a Permian-Triassic tectonic period involving evolution towards an unstable active continental margin. The detrital zircon age spectrum characteristics and geochemical results support the view that the Shangdan Ocean had closed before the Early Devonian and the Mianlue Ocean closed during the Late Triassic.