Massive lithospheric delamination in southeastern Tibet facilitating continental extrusion

Abstract

Significant left-lateral movement along the Ailao Shan-Red River fault accommodated a substantial amount of the late Eocene to early Miocene India-Asia convergence. However, the activation of this critical strike-slip fault remains poorly understood. Here, we show key seismic evidence for the occurrence of massive lithospheric delamination in southeastern Tibet. Our novel observation of reflected body waves (e.g. P410P and P660P) retrieved from ambient noise interferometry sheds new light on the massive foundered lithosphere currently near the bottom of the mantle transition zone beneath southeastern Tibet. By integrating the novel seismic and pre-existing geochemical observations, we highlight a linkage between massive lithospheric delamination shortly after the onset of hard collision and activation of continental extrusion along the Ailao Shan-Red River fault. This information provides critical insights into the early-stage evolution of the India-Asia collision in southeastern Tibet, which has significant implications for continental collision and its intracontinental response.

Indian plate paleogeography, subduction and horizontal underthrusting below Tibet: paradoxes, controversies and opportunities

“…Horizontally underthrusting Indian continental lithosphere directly underlies Tibetan crust and Tibetan lithospheric mantle must thus have delaminated prior to the 25-Ma onset of horizontal underthrusting in western and eastern Tibet. In addition, not only the source area below the Tibetan Plateau, but also the ‘sink’ of Middle Miocene and younger crustal motion in the Yunnan region has undergone lithospheric delamination [ 47 ]. This suggests that the onset of E–W extension 15–10 Ma was likely not triggered by delamination.…”

“…In addition, seismic tomographic evidence for bodies of high-velocity material that may represent delaminated Tibetan lithosphere have been identified in the upper mantle below the horizontally underthrust Indian lithosphere, suggesting delamination prior to underthrusting [ 46 ]. Moreover, recent seismological analysis has shown that delamination is not restricted to Tibet, but also affected the Yunnan region to the southeast of the eastern Himalayan syntaxis, where a conspicuous, circular-shaped hole in the continental lithosphere is underlain by a body of high-velocity material at the base of the upper mantle [ 47 ].…”

3-D azimuthal anisotropy structure reveals different deformation modes of the crust and upper mantle in the southeastern Tibetan Plateau

“…Receiver function results (Hu et al, 2012;Yang et al, 2017) suggest that the lithospheric thickness has significantly thinned (<100 km) in the Indochina Block and Cathaysia Block. Lithospheric thinning may be caused by lithospheric delamination (Chung et al, 1997;Feng et al, 2022) and rollback of the Indian Plate (Li et al, 2008;Lei and Zhao, 2016;Huang et al, 2019). Then, asthenospheric upwelling and dehydration of the subducting plate caused the large-scale lowvelocity anomaly in this area.…”

Leucogranite Records Multiple Collisional Orogenies

“…The heating source of partial melting is from asthenospheric upwelling linked to breakoff and roll back of the subducting Neo‐Tethys oceanic lithosphere (Hou et al., 2012; Ji et al., 2016; Kapp & DeCelles, 2019). Geochronology, topographic modeling, and seismic data have been used to argue for massive lithospheric delamination in southeastern Tibet from 40 to 30 Ma (Feng et al., 2022; Xiong et al., 2022). Geochronology from the Mabja dome constrains the timing of peak metamorphism, and onset of mid‐crustal ductile extension to ca.…”