HR: 0800h
AN: V21A-0593    [Abstracts]
TI: Rheology of fine-grained siliciclastic rocks deforming in the middle crust
AU: * Kenis, I
EM: Ilse.Kenis@geo.kuleuven.ac.be
AF: Structural Geology and Tectonics Group, K.U.Leuven, Redingenstraat 16, Leuven, B-3000 Belgium
AU: Urai, J L
EM: j.urai@ged.rwth-aachen.de
AF: Geologie-Endogene Dynamik, RWTH, Lochnerstrasse 4-20, Aachen, D-52056 Germany
AU: van der Zee, W
EM: zee@geomi.com
AF: Geologie-Endogene Dynamik, RWTH, Lochnerstrasse 4-20, Aachen, D-52056 Germany
AU: van der Zee, W
EM: zee@geomi.com
AF: GeoMechanics International, Emmerich Josefstrasse 5, Mainz, D-55116 Germany
AU: Hilgers, C
EM: c.hilgers@ged.rwth-achen.de
AF: Geologie-Endogene Dynamik, RWTH, Lochnerstrasse 4-20, Aachen, D-52056 Germany
AU: Sintubin, M
EM: Manuel.Sintubin@geo.kuleuven.ac.be
AF: Structural Geology and Tectonics Group, K.U.Leuven, Redingenstraat 16, Leuven, B-3000 Belgium
AB: Geomechanical models form an essential basis part our quantitative understanding of tectonic processes. In these models, a long-standing problem involves the quantification of the constitutive equations that describe the rheology of the middle crust (7-12 km). A combination of indirect methods has yielded first order descriptions of the rheology of these rocks, but much is still unknown and controversial. Constraints on rock rheology are needed from careful field and observational studies and mechanical modelling. Here we present a new method to quantify the rheology of fine-grained siliciclastic rocks, which are common in the middle crust at around 400 degrees C and deform by solution-precipitation processes. We use a combined structural and numerical analysis of the mullion structures developed in these rocks, to quantify the rheological parameters during flow at geologic strain rates. The method is based on a parameter estimation scheme developed in structural mechanics. Results consistently converge towards a set of rheological properties which are in agreement with observed microstructures and indicate that fine grained siliciclastic rocks in the middle crust have a Newtonian viscous rheology, approximately ten times weaker than wet quartz. Because siliciclastic rocks control the rheology of the middle crust in many sedimentary basins, our results provide new parameters for geodynamic modelling.
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8159 Rheology--crust and lithosphere
DE: 5120 Plasticity, diffusion, and creep
DE: 3902 Creep and deformation
DE: 3924 High-pressure behavior
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting