Simulation of mass fluxes and accretion processes in the Torlesse accretionary wedge

This project aims to understand accretion processes at subduction zones. Therefore, we will model the growth and dynamics of accretionary wedges using DEM and the critical taper approach. One major goal is to expand the capabilities of DE models applied to accretionary wedges. This includes taking into account additional effects like tectonic erosion, lithification, changing subduction velocities, and pore fluid pressure.

We want to use the Torlesse wedge in New Zealand as a case study for the numerical simulation of accretionary wedges. The broad database on the Torlesse wedge makes it a perfect example to investigate the interplay between processes occurring at the wedge front and those taking place at its base and in the internal part of the wedge that are not accessible in modern accretionary prisms.

In detail, we are going to address the following general questions by numerical modelling:

  • How important are progressive changes in rock properties (i.e. how do they influence strain hardening/weakening)?
  • Which process evoked the long depositional hiatus of 40 to 60 Ma along the Esk Head Mélange in New Zealand and the coeval high pressure metamorphism? Was it subduction erosion that excised already accreted material from a former continuous sediment succession at the toe of the wedge or was it a change in accretion mode, i.e. underthrusting of newly incoming sediments instead of frontal accretion?
  • If subduction erosion was the cause for underplating, than what triggered this process? Is it possible that tectonic erosion was forced by incoming seamounts or plateaus that dragged frontal parts of the wedge to depth and would these be efficient enough to create such a long hiatus?

Aktuelle Veröffentlichungen zu diesem Thema:

Rahl, J., Brandon, M.T., Deckert, H., Ring, U. and Mortimer, N. 2011.Tectonic significance of ductile deformation in low-grade sandstones in the Mesozoic Otago subduction wedge, New Zealand. American Journal of Sciences, in press.