Mantle flows driving tectonic escape around eastern Himalaya syntaxis.

Plate subduction exerts a strong influence over the tectonic evolution of the eastern Himalayan syntaxis (EHS) due to the substantial heterogeneity of plate contacts over space and time. The variability in tectonic escapes around EHS presents challenges for understanding the primary drivers. Here we use 3D models to mimic the ≥ 40 Myr subduction of India based on different leading edges and quantitatively analyze the associated viscous flows at various depths across the eastern Tibet. We find that the continuous, northeastward indentation of India enhances clockwise rotation and that the difference between shallow subduction in the north and steep subduction in the south of the EHS is critical to tectonic extrusion. The dynamic mechanism of this bottom-up process leads to significant lateral mantle flow and contributes to > 1000 km of material escaping southward.