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.
