Cenozoic Vertically-tearing of Indian Slab Modified the Asian Lithosphere beneath the Eastern Tibetan Plateau

Abstract

A subducted continental slab is sometimes torn during collision, yet the exact impact of slab-tearing on the overlying lithosphere remains unclear. Here, we image the structure and architecture of the Asian lithosphere above the Indian slab in the eastern Tibetan Plateau using multiscale seismic tomography models and zircon Hf isotopic mapping, respectively. Our mantle V_p model shows that a large low-velocity anomaly extends laterally beneath the thinned Asian lithosphere above the tear zone roughly along the 26°N. The V_s images, magmatic records and Hf isotopic mapping indicate that this low-velocity anomaly recorded an asthenosphere flow eastward along the tear zone, which thermally eroded and refertilized the overlying Asian lithosphere, leading to the lithospheric melting, thinning and root delaminating. The vertical tear also generated a tectonic weak zone with associated Cenozoic potassic and carbonatitic magma suites. We argue that such a hot lithosphere discontinuity provided a reasonable mechanism for the abrupt change of crust thickness and the transformation of crust-mantle deformation from coupling to decoupling across the tear zone.