U-Pb detrital zircon geochronology and Hf isotopic composition of Permian clastic rocks, Zhen'an basin, South Qinling belt: implications for the Paleozoic tectonic evolution of the Qinling orogenic belt

摘要

Detrital zircon U-Pb geochronology, and Hf isotope compositional data for Permian strata near Xikou, Zhen'an in the South Qinling belt help constrain the tectonic evolutionary history of the Qinling Orogenic Belt. Results show that detrital zircons recovered from three sandstone samples share similar age-probabilities, including four age groups comprising 2100-1760 Ma (55.8%), 2750-2300 Ma (16.1%), 1200-770 Ma (12.3%), and 512-256 Ma (10.1%). By comparison with potential source areas, we conclude that Permian detrital zircons mainly originated from the southern margin of the North China Block, and probably the North Qinling belt as well, while the northern margin of the Yangtze Block did not supply detrital sediment. This distribution implies the South Qinling belt lay adjacent to the North Qinling belt and the North China Block by the Permian, but was separated from the Yangtze Block by the Mianlue Ocean, and support the Late Triassic collision between the Yangtze and North China Blocks.