Discriminating Qiangtang, Lhasa, and Himalayan sediment sources in the Tibetan Plateau by detrital-zircon U-Pb age and Hf isotope facies

The detrital zircon has been most widely used in sediment provenance studies and basin analysis over the past 20 years. With the accumulation of a bounty of detrital zircon ages, however, the traditional method of data treatment and visualization easily ignores the internal differences of potential source regions. In this study, 49,111 U-Pb ages (533 samples) and 8532 Hf isotope data (156 samples) of detrital zircons from six major geological domains across the Tibetan Plateau were compiled and a new method of data treatment (detrital-zircon age facies) was established. Multidimensional scaling (MDS) statistical analysis allowed a rigorous discrimination among detrital-zircon U-Pb age spectra in numerous pre-collisional units from South Qiangtang, North Lhasa, South Lhasa and Tethys Himalayan domains, and to establish the detrital-zircon age facies (DZF) characteristic of each. Several distinct DZF were identified: two for South Qiangtang (DZF SQ-1, SQ-2), and three each for North Lhasa (DZF NL-1, NL-2, NL-3), South Lhasa (DZF SL-1, SL-2, SL-3) and the Tethys Himalaya (DZF TH-1, TH-2, TH-3). These 11 DZF effectively identify sandstone provenance for 19 stratigraphic units exposed along the Bangong Nujiang and Yarlung Zangbo suture zones and of the Tethys Himalaya, thus proving the validity of the DZF approach to effectively discriminate among the detrital sources of sedimentary units in diverse geological terranes. We also shed new light on the palaeogeography of the Triassic to Cretaceous Bangong Nujiang Ocean and the Cretaceous to Paleocene Yarlung Zangbo Ocean based on the provenance result of the DZF approach. This study demonstrates that the DZF method provides a more accurate image of the time structure of source rocks than the conventional approach and documents the usefulness of combining DZF and MDS methods in provenance analysis based on large detrital-zircon datasets.