Provenance of detrital zircons in the Late Triassic Sichuan foreland basin: constraints on the evolution of the Qinling Orogen and Longmen Shan thrust-fold belt in central China

Abstract

In this article, we present in situ U–Pb and Lu–Hf isotope data for Upper Triassic detritus in the Sichuan region of northwestern South China, which was a foreland basin during the Late Triassic. The aim is to determine the provenance of sediments in the foreland basin and to constrain the evolution of the surrounding mountain belts. U–Pb age data for the Late Triassic detrital zircons generally show populations at 2.4–2.6 Ga, 1.7–1.9 Ga, 710–860 Ma, 410–460 Ma, and 210–300 Ma. By fitting the zircon data into the tectonic, sedimentologic, and palaeographic framework, we propose that the north Yangtze Block and South Qinling–Dabie Orogen were the important source areas of sediments in the northern part of the foreland basin, whereas the Longmen Shan thrust-fold belt was the main source region for detritus in other parts of the foreland basin. The South Qinling–Dabie Orogen could also have served as a physical barrier to block most detritus shed from the southern North China Block into the foreland basin during the sedimentation of the Xujiahe Formation. Our results also reveal that part of the flysch from the eastern margin of the Songpan–Ganzi region had been displaced into the Longmen Shan thrust-fold belt before the deposition of the foreland basin sediments. In addition, the Lu-Hf data indicate that Phanerozoic igneous rocks in central China show insignificant formation of the juvenile crust.

Keywords:

• detrital zircon
• Late Triassic Sichuan foreland basin
• provenance study
• North and South China blocks
• South Qinling-Dabie Orogen

Acknowledgements

We would like to express our gratitude to Xiaolei Wang, Xiumian Hu, Jinhai Yu, Joseph Stockmeyer, Yiquan Li, Hailin Wu, Maomao Wang, Meng Zhang, Kai Wang, and Tianbao Wang for their field and analytical assistance, R.J. Stern for kind editorial handling, and two reviewers for helpful suggestions.

Additional information

Funding

This work was supported by the 973 Programme of China [grant number 2012CB214703]; National S&T Major Project of China [grant number 2011ZX05009-001], [grant number 2011ZX05003-002].