Controls of subducting slab dip and age on the extensional versus compressional deformation in the overriding plate

Abstract

Oceanic plate subduction can exert extensional, compressional or both types of deformations simultaneously in overriding plates. In this study, we explore the factors controlling these two competing modes of deformation in response to contrasting stress fields. Two-dimensional computational fluid dynamics models are presented to show that the dip and age of subducting slabs are crucial parameters to modulate the extensional versus compressional deformations. Shallow-dipping (< 30°) and/or young (< 60 Myr) subducting slabs favor compressional tectonics to form an orogenic wedge (accretionary type), whereas steeply dipping (> 45°) and/or old (> 60 Myr) slabs facilitate extensional tectonics, expressed as a back-arc basin (non-accretionary type). We validate the parametric analysis by comparing our model results with the observed modes of overriding plate deformation in natural subduction zones.