Provenance and tectonic setting of the Neoproterozoic meta-sedimentary rocks at southeastern Tibetan Plateau: Implications for the tectonic affinity of Yidun terrane

Abstract

The Yidun terrane is located between the Qiangtang terrane and Songpan-Ganzi Fold Belt and its tectonic affinity with other adjacent terrane is of significance to understand the tectonic evolution of southeastern Tibetan Plateau. In this study, we present integrated bulk geochemical data, detrital zircon U-Pb ages and Hf isotopes of meta-sedimentary rocks from the Qiasi Group, which represents the oldest Precambrian basement of the Yidun terrane, to constrain the depositional age and provenance of the meta-sedimentary rocks as well as the tectonic affinity of the terrane. Zircon U-Pb dating results show that detrital zircons from three samples have almost identical age spectra with two major age clusters of 800–780 Ma and 850–820 Ma at age peaks of ca. 790 Ma and ca. 827 Ma, and one minor age cluster of 910–860 Ma. The youngest group of detrital zircons reveals that the maximum depositional age of the Qiasi Group was 779–777 Ma. Low SiO2/Al2O3 (2.9–4.1), CIA (59–47), and PIA (63–47) values indicate that the sediments could be derived mainly from the low mature sources that had undergone weak to mildly moderate degree of chemical weathering. Bulk geochemical and zircon U-Pb-Hf isotopic data suggest that the provenance was composed mainly of Neoproterozoic intermediate to felsic igneous rocks. In combination with the published geological data and detrital zircon U-Pb age spectra on the western Yangtze Block, and the Kunlun-Qilian-Qaidam Block, we propose that the Neoproterozoic basement of the Yidun terrane has a close tectonic affinity with the former one.