Abstract

Reactivation of structures inherited from previous collisional or rifting events, especially lithospheric-scale faults, is a major feature of plate tectonics. Its expression ranges from continental break-up along ancient collisional belts1,2 to linear arrays of intraplate magmatism and seismicity3,4. Here we use multiscale numerical models to show that this reactivation can result from an anisotropic mechanical behaviour of the lithospheric mantle due to an inherited preferred orientation of olivine crystals. In our models, we explicitly consider an evolving anisotropic viscosity controlled by the orientation of olivine crystals in the mantle. We find that strain is localized in domains where shear stresses on the inherited mantle fabric are high, and that shearing is parallel to the inherited fabric. During rifting, structural reactivation induced by anisotropy results in oblique extension, followed by either extension or failure. Our results suggest that anisotropic viscosity in the lithospheric mantle controls the location and 18 orientation of intraplate deformation zones that may evolve into new plate boundaries.