Differential deformation mechanisms in the northeastern Tibetan plateau modulated by lithospheric heterogeneities

Determining the driving mechanisms for distributed intracontinental deformation is an important topic in continental tectonics. The ~2000-km-wide Cenozoic Himalayan-Tibetan orogen and the related thickened Tibetan plateau represent an archetypical continent-continent collision to study intra-plate deformation. There are two debated paradigms for how this orogen accommodates plate convergence. The first highlights the motion and translation of rigid blocks, whereas the second quantifies lithospheric deformation as a flowing continuum. Both models have been used to quantify deformation at the northeastern margin of the Tibetan plateau, which deforms far from any plate-boundary interactions. To interrogate this issue, here we use seismic profiling data collected in northeastern Tibet to conduct new S-wave receiver functions, joint inversion imaging, and regional synthesis to develop a comprehensive lithosphere-scale structural model of the differential deformation mechanisms operating along the northern and eastern margins of the Tibetan plateau. The northern plateau margin is dominated by a complex lithospheric thrust-wedge system with multiple detachment zones that accommodate intracontinental oblique underthrusting/subduction. Conversely, the eastern plateau margin does not exhibit discrete fault structures and appears to deform via the vertical inflation of a hot and weak mid-lower crust induced by mantle melting. We attribute these different styles of deformation to significant vertical and lateral lithospheric heterogeneities, governed primarily by temperature variations reflecting the recency of Cenozoic volcanism and pre-Cenozoic terrane accretion. Our results provide comprehensive insights into the intraplate processes and geodynamics that shape the development of a continental collisional zone.