Provenance and Tectonic Implications of Upper Neoproterozoic-Lower Paleozoic Sedimentary Rocks in the Yidun Terrane, Eastern Tibetan Plateau

The Yidun Terrane, sandwiched between the Qiangtang and Songpan-Ganze terranes, hosts important information in the tectonic evolution of the eastern Tibetan Plateau. However, its tectonic link with adjacent terranes and East Gondwana remains equivocal. Here, we present detrital zircon U-Pb-Hf isotope data from the upper Neoproterozoic-lower Paleozoic clastic rocks in the Yidun Terrane. The results show that detrital zircons from the Neoproterozoic rocks are mainly of ca. 821 – 890 Ma, 1714 – 1977 Ma, and 2317 – 2520 Ma, with ε_Hf(t) values of each group comparable to coeval magmatic rocks in the nearby South China Block. This suggests that the Yidun Terrane and South China were possibly connected at that time, with the latter being the main detrital provenance. In contrast, the five Paleozoic samples have markedly different detrital zircon age spectra at ca. 2600 – 2300 Ma, 1100 – 900 Ma, 900 – 740 Ma, and 690 – 480 Ma, which were interpreted to have derived from Pan-African and Grenville-age provinces in the East Gondwana, as well as the South China Block and Songpan-Ganze Terrane. Such major provenance change suggests that after prolonged isolation in the Proto-Tethys, the Yidun Terrane began to collide with the East Gondwana in the early Paleozoic. Integrated with published works, we consider that the Yidun Terrane has close tectonic link with the Yangtze Block, and that it was located on the northeastern margin of the India Plate during the early Paleozoic.