Subducting and overriding plates were separated by a weak zone and decoupled from neighboring plates by weak transform faults to permit toroidal mantle flow ( van Hunen and Allen, 2011 Magni et al., 2014). We did not apply external forcing all dynamics were driven by internal buoyancy forces. We used a visco-plastic rheology including diffusion and dislocation creep, lithospheric yielding, and an upper-limit viscosity ( Magni et al., 2014 van Hunen and Allen, 2011).
After effects 2014 serial mac code#
The finite element code Citcom ( Moresi et al., 1996 Zhong et al., 2000 Magni et al., 2014) solves the conservation equations for momentum, energy, mass, and composition. 2) in a model space of 3300 by 3960 by 660 km in size. We investigated the stress regime evolution during continental collision with an irregular margin ( Fig. It is unclear in these examples how the geologic evolution is linked to the highly arcuate geometry and irregular shape of the subducting continental margin, if at all. The world's largest subcontinental mantle exposures, the Ronda and Beni peridotites in the Alboran arc ( Gueydan et al., 2019), have been suggested to have been exhumed by gravitational collapse after slab break-off ( Platt and Vissers, 1989 Van der Wal and Vissers, 1993), by thrusting of an older Jurassic rifted margin ( Tubia et al., 2009), or by hyperextension of the overriding plate before, and thrusting during, continental collision ( Frasca et al., 2017 Gueydan et al., 2019 see Fig. The Banda system involves ophiolite obduction ( Ishikawa et al., 2007), but this has not been identified in the Alboran arc. With this mechanism, obduction of back-arc oceanic lithosphere naturally evolves from a given initial margin geometry during continental collision.īoth regions share puzzling geological features, such as extensional basins in the upper plate ( Pownall et al., 2016 Watts et al., 1993), and exhumed subcrustal continental lithosphere ( Frasca et al., 2017 Gueydan et al., 2019 Pownall et al., 2014). The models show how subduction of an irregular continental margin can form a highly curved orogenic belt. Collision along the entire trench follows rapidly, with inversion of this spreading center, ophiolite obduction, and compression in the overriding plate. These stresses thin the overriding plate and may open a back-arc spreading center. Results show how tensional stresses are localized in the overriding plate during the diachronous onset of collision. Here, we modeled collision with an irregular subducting continental margin in three-dimensional (3-D) thermo-mechanical models and used the generated stress field evolution to understand resulting geologic processes. While external forces or preexisting weaknesses are often invoked, we suggest that ophiolite obduction can equally be caused by internal stress buildup during collision. Ancient systems include the Newfoundland and Norwegian Caledonides. Modern examples include the Alboran and Banda arcs. Such systems may feature back-arc extension and ophiolite obduction postdating initial collision. Continental collisions commonly involve highly curved passive plate margins, leading to diachronous continental subduction during trench rollback.
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