Weak and vanishing upper mantle discontinuities generated by large-scale lithospheric delamination in the Longmenshan area, China

A large amount of high-quality teleseismic data is used for common conversion point (CCP) stacking of receiver functions in the Longmenshan area and near-by region. The results show that a large-scale high-velocity anomaly (LHVA) or lithospheric delamination can modify the structure of upper mantle discontinuities or weaken the phase boundary of olivine, which is a very important finding and can be used to assess stagnant slabs in the mantle transition zone globally. The deepening region of the 660 km discontinuity beneath the Songpan-Ganzi terrane identified in this study might be generated by the LHVA.