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Tectonic evolution of the East Qinling Mountains, China, in the Palaeozoic: A review and new tectonic model

Abstract:

East Asia is a composite assemblage built up from various plates, and the Qinling Mountains are prominent among the orogenic belts dividing these plates. Because of its complex and prolonged history, interpretation of the geology of the Qinling Mountains has led to a variety of tectonic models. We review and summarize recently published data and previous work and develop a new tectonic model for the eastern part of this mountain range. Four tectonic zones are recognized from north to south: the Lesser Qinling, the North Qinling, the Central Qinling and the South Qinling zones. The Lesser and North Qinling zones are interpreted as a late Proterozoic to early Palaeozoic passive continental margin bordering the North China Block. The Central Qinling, separated from the Lesser/North Qinling zone by a suture zone, mainly consists of volcanic arcs and a high-grade metamorphic complex. The South Qinling zone forms part of the northern margin of the Yangtze Block and has a long (latest Proterozoic to Middle Triassic) depositional history as revealed by its sedimentary cover. Available data do not support the hypothesized existence of a major suture divide between the Central and the South Qinling zones. These two zones seem to have collectively formed an early Palaeozoic destructive continental margin on the northern edge of the Yangtze Block, with the Central Qinling as an island-arc system and the South Qinling as a wide, highly attentuated marginal basin. Late Ordovician to Early Silurian collision between the North China and the Yangtze Block built up the Palaeozoic orogenic belt in the northern part of the Qinling and gave rise to the embryonic East Asian continent. Yet the South Qinling was transformed to a remnant basin and remained undeformed until the Late Triassic when the palaeo-Tethys collision to the south of the Yangtze Block drove the Yangtze Block to move northeastwards. Deformation in a transpressive regime during this late event largely reconstructed the Qinling belt and hence further complicated its tectonics.