HR: 0800h
AN: T11C-0730    [Abstracts]
TI: Dynamics of Continental Plate Delamination: a Numerical Study Applied to the Northern Apenninic Belt.
AU: Minelli, G
EM: gminelli@unipg.it
AF: GSG, Universita' degli studi di Perugia, Piazza dell'Universita', Perugia, 06100, Italy
AU: * Faccenda, M
EM: faccenda@erdw.ethz.ch
AF: Institute of Geophysics, ETH Zurich, HPP, ETH Hoenggerberg, Zurich, 8093, Switzerland
AU: Gerya, T
EM: taras.gerya@erdw.ethz.ch
AF: Institute of Geophysics, ETH Zurich, HPP, ETH Hoenggerberg, Zurich, 8093, Switzerland
AB: Suduction zone are sites on the earth surface where a gravitationally unstable lithosphere sinks into the mantle. Normally, cold oceanic plates are good candidates for such behaviour, thought subduction of young slabs is sometimes observed (i.e., Cascadia and Nankai subduction zones). However, other ¢®¡Æanomalous¢®¡¾ subduction zones exist where the subducting plate is a gravitationally stable continent. How is it possible, hence, to subduct continets (or at least part of them)? What are the dynamical processes that occur when weak and buoyant material as the continental crust enter the trench? To answer to these intriguing questions we perform 2D numerical models of an oceanic plate with the attached continental passive margin subducting at 2 cm/yr under a fix continent. As collision occurs, weak (Wet Quartzite flow law) upper crust is deeply subducted and hydrated mantle wedges between the plates through deformation of the low viscosity material. The plates have now lost completely coupling and the lower plate, pulled by the oceanic slab, starts to retreat. The buoyant and weak upper crust is scraped off by the passively advancing astenospheric wedge so that the lower plate increases its negative buoyancy. The upper crust undergoes two deformational phases with early compressional structures being later dissected by extension. The compressional front is characterized by thick crust and low heat flux, while the extensional domain has shallow mantle and high heat flux. Results of the model are on good agreement with the geological and geophysical data collected in the Northern Apennnines, supporting, hence, the retreating and delaminating continental plate model for the last 20 Ma evolution of this belt.
DE: 7218 Lithosphere (1236)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
DE: 8180 Tomography (6982, 7270)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting