Dating of detrital zircons from the Dabure clastic rocks: the discovery of Neoproterozoic strata in southern Qiangtang, Tibet

ABSTRACT

This article reports the results of field mapping and the petrology of clastic rocks in the Dabure area, southern Qiangtang, Tibet, together with the results of U–Pb dating of detrital zircons from these rocks. The Dabure clastic rocks are characterized by low compositional and textural maturity, and they have been affected by lower greenschist facies metamorphism. The deposits exhibit the typical features of turbidites. Altogether, 279 detrital zircons were selected for U–Pb dating, and the ages fall into five groups: 550–650, ~800, 900–1100, 1600–1800, and 2300–2500 Ma. In general, the ages of the detrital zircons that are older than ~550 Ma are similar to those found elsewhere in the southern Qiangtang and Himalayan terranes. The most reliable youngest age of a detrital zircon from the Dabure clastic rocks is ~550 Ma. In the southern part of the Tibet Plateau, strata with the same ages and lithologies as the Dabure clastic rocks are widespread, especially in the Himalayan terrane. Combining our data with previous work on the basalts in the Dabure area (the Dabure basalts), we tentatively suggest that the Dabure clastic rocks represent the late Ediacaran (~550 Ma) sedimentary record for the Qiangtang terrane, and that before the late Neoproterozoic the southern Qiangtang terrane was possibly connected to the Himalayan terrane.

Keywords:

• Tibet
• southern Qiangtang
• detrital zircon
• clastic rocks
• Gondwana

Acknowledgements

We thank the staff of the Geological Laboratory Centre of China, University of Geosciences (Beijing), for help with the LA-ICP-MS zircon U–Pb dating, and staff of the Institute of Physics, Peking University, for help with the CL image analysis. We also thank Dr Wu Yanwang, Dr Hu Peiyuan, and Dr Zhang Xiuzheng for help in the field.

Additional information

Funding

This research was funded by the National Science Foundation of China [grant numbers 41272240 and 41072166] and the China Geological Survey [grant numbers 1212011221093 and 12120113036700].