Thermo-mechanically coupled subductionmodelling with ASPECT.
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Subduction is one of the major processes driving the Earth's plate tectonics and is still actively researched in many different fields within the Earth sciences. This report presents a 2D fully thermo-mechanically coupled subduction model with a free surface, using the finite element code ASPECT (short for Advanced Solver for Problem in Earth's ConvecTion). ASPECT is a new finite element code which was originally designed for thermally driven (mantle) convection. It is built on state of the art numerical methods and includes adaptive mesh refinement, linear and non-linear solvers, stabilisation of transport dominated processes and a high scalability on multiple processors. The presented thermo-mechanically coupled subduction model contains four different materials: a crust for the subducting plate, a crust for the overriding plate, a mantle and a sticky air layer. The sticky air layer allows for topography buildup. The extend of the lithosphere into the mantle is mainly defined by the temperature. The initial temperature within our model assumes an adiabatic temperature profile for the mantle, a linear temperature for the lithosphere, and a slab with a linear temperature which has been heated when it descended into the mantle. The viscosity of the materials is defined by visco-plastic rheology using power-law creep and a Mohr-Coulomb criterion. The model contains a free-slip boundary condition at the bottom, an open boundary at the top and an inflow/outflow velocity boundaries at the sides. The presented model is applied to an investigation of the Western Mediterranean subduction and rollback. During the rollback of the subducting slab beneath Iberia, Corsica and Sardinia were pulled of the northern part of Iberia. To simulate this geological process has proved to be numerically challenging. In this case study the Western Mediterranean setting is in investigated. Also an attempt is made to investigate the influence of a weak-zone in the lithosphere.