Studying Subduction using a 2D coupled Thermomechanical Petrological Model

Abstract

Subduction is a prominent geological process that occurs at convergent margins and it is closely linked to natural disasters like volcanic eruptions, earthquakes and tsunamis. Over the past several years numerical modelling have been used by scientists to study several aspects of subduction ranging from its underlying causes to morphological changes in the region where it occurs. In this thesis, a 2D coupled thermomechanical petrological model was used to primarily study subduction by varying several control parameters like rheological weakening by pore fluid pressure and melt pressure factors, geothermal gradient, velocities of oceanic and continental plates. The experiments described in this thesis also explored the impact of control parameters on the structural changes in the region above the subduction zone. It is known that at times subduction may result in back-arc extension, which is interesting considering that it occurs near convergent margins. Another broad goal of this thesis was to explore the possibility of finding out a set of control parameters responsible for creating back-arc extension by modifying the model parameters appropriately at the end of each experiment. Our results suggest that the occurrence of subduction is favoured at a particular range of temperature elevation close to the interface between the mantle lithosphere and the asthenosphere. The nature or style of subduction is sensitive to the geothermal gradient, pore fluid and melt pressure factors while the kinetics of subduction are mainly dependent upon the velocities of the oceanic and continental plates.