Plume-Induced Rifting of Thickened Crust: 2D Numerical Model and Implications for N–S Rifts in Southern Tibet

Abstract

N–S rifting is one of the most typical tectonics in southern Tibet, but its formation mechanism remains controversial. Geophysical observations indicated spatial correlations between rifts and lithospheric mantle anomalies, presumably caused by asthenospheric upwelling. Here, we investigate possible plume-induced rifting via a series of 2-D thermomechanical models of plume interactions with a heterogeneous lithosphere. The numerical results indicate that a small-scale mantle plume could promote the formation of a single giant rift throughout the whole thickened crust. In addition, presence of a weak mid-crustal zone facilitates the rifting development in the upper crust while inhibiting the formation of a giant crustal rift. Instead, multiple rifts develop in the upper crust and thickened crust, jointly controlled by a heterogeneous weak crustal zone and mantle plume. Our numerical results thus emphasize the distinct roles of the weak mid-crustal zone and small-scale mantle plume in promoting N‒S rifting in southern Tibet.