HR: 0830h
AN: T31D-0865    [PDF]
TI: Time-Dependent Crustal Response to Linear and Point Mantle Lithosphere Instabilities: Analogue and Numerical Modeling
AU: * Cruden, A R
EM: cruden@geology.utoronto.ca
AF: Department of Geology, University of Toronto, 22 Russel Street, Toronto, ON M5S 3B1 Canada
AU: Pysklywec, R N
EM: russ@geology.utoronto.ca
AF: Department of Geology, University of Toronto, 22 Russel Street, Toronto, ON M5S 3B1 Canada
AU: Hacat, K
EM: kevrok64@hotmail.com
AF: Department of Geology, University of Toronto, 22 Russel Street, Toronto, ON M5S 3B1 Canada
AB: Tectonic deformation of some intraplate regions may be caused by the Rayleigh-Taylor (RT) instability of dense sub-crustal lithosphere (mantle lithosphere) as it descends into the mantle. Here we report on a series of 3D analogue and 2D numerical experiments of coupled crust-mantle dynamics. In particular, the topographic evolution of a stratified model crust is investigated in response to RT instability of the underlying mantle lithosphere. We compare the time series of topography and rates of drip descent between the laboratory and numerical experiments and test the sensitivity of these measurable quantities to variations in crustal rheology and the geometry of the mantle instability (linear vs. axisymmetric point instabilities). Evolving surface topography is tracked on the free-surface of the numerical models and a high precision laser scanning system measures the surface of the analogue models. The models demonstrate simple subsidence for a strong crust end-member, but significant internal deformation and topographic variation for certain weaker crustal configurations. Topographic evolution and drip descent rates are consistent between numerical and analogue experiments for the case of the linear 2D instability. In general, the variation of topography in the laboratory experiments displays more complexity due to 3D effects (i.e., out-of-plane relaxation) and the development of second-order instabilities, which are absent in the numerical runs. Internal crustal deformation tends to be more pronounced in the analogue experiments with point instabilities, due to the focused convergence of mantle flow and the generation of greater in-plane stresses in the overlying crust.
DE: 3210 Modeling
DE: 8015 Local crustal structure
DE: 8020 Mechanics
DE: 8110 Continental tectonics--general (0905)
DE: 8120 Dynamics of lithosphere and mantle--general
SC: Tectonophysics [T]
MN: 2003 Fall Meeting