LA-ICP-MS U-Pb geochronology of detrital zircons from the Liuling Group in the South Qinling tectonic belt and its tectonic significance

The tectonic evolution of the Qinling orogen is the key to understanding the assembly of the North China and South China blocks. The Liuling Group in the south of the Shangdan fault can provide an important window for detecting the Late Paleozoic evolutionary process of the Qinling orogen. The LA-ICP-MS U-Pb ages of detrital zircons from three metasandstone samples from the Liuling Group show a age spectrum with major populations at ca. 442Ma and in the range of 780~850Ma and 900~970Ma, with the youngest population being ca. 377~395Ma. These data suggest that the deposition of the Liuling Group might have lasted to the Late Devonian, and sediments were probably derived from the North Qinling tectonic belt. In combination with the recent investigation of the Wuguan complex in the north of the Liuling Group, the authors infer that a Middle to Late Devonian turbidite sequence might have formed in a fore-arc basin on the southern margin of the North China block, and the closure of the Paleo-Qinling ocean might have occurred after Devonian. Hence, the collisional boundary of the North and South China blocks should be located in the south of the Liuling Group.