HR: 16:45h
AN: T14A-04 INVITED     [Abstracts]
TI: Effects of the metamorphic changes on the subducting processes
AU: * Bousquet, R
EM: romain@geo.uni-potsdam.de
AF: Inst. für Geowissenschaften, Univ. Potsdam, Karl-Liebknecht-Str. 24, Potsdam, 14469 Germany
AU: De Capitani, C
EM: Christian.Decapitani@unibas.ch
AF: Earth Sciences, Univ. Basel, Bernoullistr. 30, Basel, 4056 Switzerland
AU: Arcay, D
EM: arcay@geoazur.unice.fr
AF: Géosciences Azur, 250 rue A. Einstein, Valbonne, 06560 France
AB: During the subduction-collision processes, the Earth's crust is squeezed, thickened and uplifted. Therefore rocks will be exposed to changing temperature, pressures and stress regimes and they may undergo metamorphism or partial melting. Meanwhile less attention has been paid to other important aspects of the metamorphic processes. The formation of different kind of rocks (amphibolites, eclogites, granulites) can lead to dramatic changes in petrophysical properties. When reacting rocks expand and contract, the volume changes will set up in the surrounding material. Modeling several cases of subduction for different types of rocks (granites, sediments, mafic and ultramafic rocks), we explore implications 1) on the dynamic of the subduction. Hence computing changes of physical properties of rocks as well quantity of released fluids by dynamic modeling of metamorphic reactions, we will show that some subductions are more propitious to exhume (U)HP rocks and thus to obstruct the subduction dynamic the while others are more propitious to produce heavier rocks and self-sustained subduction. 2) on the localization of earthquakes into the subducting slab. As shown by several authors, intermediate-depth earthquakes mainly occur where hydrous minerals are predicted to be present, implying a causal link between dehydration reactions and seismicity. We investigate petrophysical changes related to dehydration and their implications for generating an earthquake? 3) on the dynamic of the mantle wedge. In many subductions, the upper plate thinning seems to be controlled by the dehydration reactions. We test influence of bulk composition of the lithosphere to estimate the back-arc dynamic. Preliminary results suggest that the appearance of amphiboles within the lithosphere favors local convection and formation of back-arc basin. We conclude that changes associated with metamorphism as an alternative to changes attributed solely to compositional differences.
DE: 1012 Reactions and phase equilibria (3612, 8412)
DE: 1031 Subduction zone processes (3060, 3613, 8170, 8413)
DE: 1038 Mantle processes (3621)
DE: 1744 Tectonophysics
SC: Tectonophysics [T]
MN: Fall Meeting 2005