3D Thermo-mechanical modelling of a stretched continental lithosphere containing localized low-viscosity anomalies (the soft-point theory of plate break-up)

Abstract

We present numerical models of extensional visco-elasto-plastic 3D continental lithosphere containing weaker areas within its mantle section. We aim at understanding the 3D crustal structure of volcanic passive margins that is characterized by both across-strike and along-strike finite strain gradients, with maxima around central igneous complex or their feeding magma reservoirs. It is suggested that localized hot melting zones within the lithosphere act as mechanical soft points and result in the local focusing of extension. To test this hypothesis 3D thermo-mechanical models of extensional continental lithosphere containing thermally induced soft points are implemented. Results show that crustal extension initiates and is focused over soft points in the mantle, reproducing the tectonic segmentation and zig-zag pattern of VPMs (volcanic passive margins).