Discovery of the Late Cretaceous detrital zircon in Renbu tectonic melange, South Tibet, and its tectonic significance

The existence and distribution of the peripheral foreland basins in the Yarlung-Tsangpo suture zone and Gandese zone remains controversial. Here we report the in-situ detrital zircon U-Pb and Hf isotopic analysis of sedimentary rock from a sedimentary relict, paraconformably covering the Triassic ophiolite relicts in the Renbu melange belt, Dejilin Town, Renbu County. Nine detrital zircon grains out of 54 grains have ages from 83 to 121Ma and three grains have ages of 197 +/- 3Ma, 203 +/- 5Ma and 208 +/- 5Ma. The majority of these young zircons are characterized by high Hf-176/Hf-177 isotopic ratios and positive epsilon(Hf) values that are similar to magmatic zircons from the Gangdese batholith, indicating the latter has been a predominant source provenance of the sedimentary relict. It may be a part of the foreland basin systems in the Gandese-Himalayan collisional orogen belt, which plays a significant indicator of the initial collision between India and Eurasian plates.