Investigating The 3-D Numerical Simulation Of Subduction Initiation Processes At Passive Margins And Transform Faults

Studying the processes of subduction initiation is a key for understanding the Wilson cycle and improving the theory of plate tectonics.Previous studies investigated subduction initiation with geological synthesis and geodynamic modeling methods,discovering that subduction intends to initiate at the continental plate passive margins or transform faults close to oceanic arcs,and that its evolutionary processes which are controlled by plate strength and rheology usually accompanied by surface volcanic expressions and earthquakes.However,early geodynamic numerical simulation studies are mainly conducted with 2-D models,which cannot deal with lateral heterogeneities of crustal thickness and strength along the plate interface geometry.Here we first summarized 2-D model methods,then we extend the 2-D model to a semi 2-D parallel subduction model and discussed the feasibility of model extension.Then we use 3-D model to study the geodynamic mechanism and rheology parameters which may have influence on the subduction initiation,we also study the geometry style and plate interface expression of slab along passive margins and transform faults.After analyzing those 3-D model results,we find that the existence of mid-low crust of arcs in overriding plate lithosphere may cause lateral lithospheric heterogeneities which would control the starting point of the subduction initiation along the newly formed trenches and the propagation speed for the trench formation.Also,our 3-D model results proposed that new subduction tends to firstly initiate at the property changing point along the transform faults or passive margins.Such finds may be applied to explain the formation process of the Izu-Bonin-Mariana subduction zone in the western Pacific and the Scotia subduction zone at the south end of the South America.Other part of our 3-D model results also reveals that if the overriding plate interface has heterogeneous geometry,the slab may tear itself during its subduction processing,this may be a possible explanation for the existence of slab windows in Cenozoic.Our results enhance our understanding for the formation of new trenches and help to provide a possible geodynamic modeling explanations for the observed remnant slabs in the upper mantle and the surface volcanic expressions.