Underplating altered oceanic crust: Insights from numerical modelling

Abstract

Observations of several active shallow subduction megathrusts suggest that they are localized as décollements within sedimentary sequences or at the contact between sedimentary layers and the underlying mafic oceanic crust. Exhumed accretionary complexes from a range of subduction depths, however, preserve underplated mafic slivers, which indicate that megathrust faults can occasionally develop within the mafic oceanic crustal column. The incorporation of mafic rocks into the subduction interface shear zone has the potential to influence both long-term subduction dynamics and short-term seismic and transient slip behaviour, but the processes and conditions that favour localisation of the megathrust into deeper oceanic crustal levels are poorly understood.