Seismic Evidence for Stepwise Lithospheric Delamination Beneath the Tibetan Plateau

Abstract

AbstractSeveral models were proposed to account for the tectonic evolution of Tibetan Plateau, among which delamination of the Tibetan lithosphere is suggested to be a leading process. However, direct evidence for the removed Tibetan lithosphere in the deep mantle remains highly lacking. Here we image the mantle transition zone (MTZ) structure beneath western Tibet and Himalaya by common conversion point stacking of 25254 receiver functions (RFs) with unprecedented clarity. One striking feature is the significant depression (15–20 km) of 660‐km discontinuity beneath Himalaya, which indicates the presence of the detached Lhasa lithospheric mantle (∼26 Ma) at the bottom of the MTZ. Our results also show ∼15 km uplift of 410‐km discontinuity (d410) and small d410 amplitude beneath western Tibet, which we ascribe to the more recently delaminated Qiangtang lithosphere (∼15 Ma). Furthermore, the small dependence of d410 amplitude on frequency indicates that the MTZ is anhydrous in the study area.