|TAIGER (TAiwan Integrated GEodynamics Research) project for testing models of Taiwan orogeny.|
Geodynamical modeling of Taiwan Orogeny
The numerical experiment shown below is intended to describe the evolution of an arc-continent setting similar to Taiwan from incipient subduction through collision. The numerical code is an extended version of the model PARAVOZ (Lavier and Manatschal, 2006) that contains Eulerian-Lagragian particles to track phase boundaries and the temperature-pressure-strain history of the material transported during the brittle and ductile processes simulated in the model. The model box size is 300 km deep and 1200 km wide. The grid size is 4x4 km. The initial geometry of the model (Fig. A) is that of a low-resolution passive margin (to the left) and an oceanic plate (to the right). The continent (equivalent to Eurasia) is 400 km wide with a 30 km thick crust. The transition from continent to ocean is defined as a zone of thin continental crust (200 km x 8 km thick). Next to the margin the ocean lithosphere is covered by an 8 km thick crust. A 100 km wide and 20 km thick zone of oceanic crust representing a thickened arc (i.e. Luzon arc) is initially set on the extreme right side of the model box. A 400 m thick layer of sediments is covering the oceanic crust and a 4 km thick layer of sediments covers the margin. A zone of pre-deformed and pre-weakened oceanic crust and mantle is set to the left of the arc to initiate subduction there. Also included in the model is a simple erosion law (e.g., Beaumont et al., 2001), where the erosion rate is proportional to the topographic slope that is calibrated to describe rapid erosion in Taiwan (~3 mm yr-1). Eclogite transformation of the oceanic crust and lower continental crust as a function of pressure and temperature is included in the model. The collision is imposed kinematically by allowing flux of oceanic lithosphere at 5 cm yr-1 on the right side of the box.
Wu, F. T.,Lavier, L. UT, and US and Taiwan TAIGER TEAMS (2007) Collision Tectonics of Taiwan and TAIGER Experiments, Eos Trans. AGU, 88(52), Fall Meet. Suppl., Abstract T51A-0321.
For each phase the density fields, zoomed areas with the velocity field and topography are shown. The rates of deformation are indicated by black arrows. The rheology of the model material is temperature dependent elastoplastic/ viscoelastic. The elastoplastic rheology (brittle) allows for the spontaneous localization of the deformation in a cohesional/frictional material by decreasing as a function of the plastic strain both the frictional and cohesional strength. The viscoelastic rheology (ductile) is temperature and strain rate sensitive and is defined by creep laws (dry olivine for the mantle, wet quartz for the sediments, dunite for the oceanic crust and anorthosite for the crust (Shelton and Tullis,1981)).
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