Relative flat topography and lower elevation of the Qiangtang Terrane before 25 Ma, central Tibetan Plateau

Collision between the India and Asia continents during Cenozoic is generally considered as the main driver forming the high Tibetan Plateau (TP). But, when and how the relative flat and high elevated central TP formed that is still debated. Here, our new and collected thermochronology data from Qiangtang Terrane (QT), central TP, indicate that timing of crustal shortening and thickening is no later than ~40 Ma. Together with sedimentary records, we confirm that low relief and relative flat topography was already formed before ~40 Ma in the QT. Due to there were small amount of crustal shortening/thickening occurred in the QT after ~40 Ma, therefore QT crust was probably already thickened >60 km. Nonetheless, timing of the QT uplift to similar modern elevation is later than ~25 Ma which was also constrained by palaeogeography evidences. According to elevation is controlled both by crustal and lithospheric mantle thickness, therefore the Cenozoic lithospheric mantle evolution was critical to reveal variation of palaeoelevation of the QT. Based on summering magmatic records, which show lithospheric mantle delamination during ~30-25 Ma beneath the QT. Thus, we proposed that this lithospheric mantle delamination lead to the QT elevation raise from ~2 km to >4.5 km. And, this conclusion was supported by semi-quantitatively isostatic estimating on QT elevation evolution. In brief, geological constraints reveal a two-stage development of the QT elevation during Cenozoic, central TP.