Zircon U-Pb geochronology and Hf isotopes of granitic rocks and river sands in the Nyingchi region, Tibet: Constraints on evolution of the deep crust beneath the southeast Lhasa terrane

•The Nyingchi region developed two main stages of magmatism (67–44 and 28–23Ma).•The Late Oligocene magmatism is dominant in the Nyingchi region.•The Late Oligocene magmatic rocks exhibit homogenous and depleted source composition.•The Late Oligocene magmatism was attributed to lithospheric delamination.