Rheologic controls on slab dynamics

Abstract

[1] Several models have been proposed to relate slab geometry to parameters such as plate velocity or plate age. However, studies on the observed relationships between slab geometry and a wide range of subduction parameters show that there is not a simple global relationship between slab geometry and any one of these other subduction parameters for all subduction zones. Numerical and laboratory models of subduction provide a method to explore the relative importance of different physical processes in determining subduction dynamics. Employing 2-D numerical models with a viscosity structure constrained by laboratory experiments for the deformation of olivine, we show that the observed range in slab dip and the observed trends between slab dip and convergence velocity, subducting plate age, and subduction duration can be reproduced without trench motion (i.e., slab roll-back) for locations away from slab edges. Successful models include a stiff slab that is 100-1000 times more viscous than previous estimates from models of plate bending, the geoid, and global plate motions. We find that slab dip in the upper mantle depends primarily on slab strength and plate boundary coupling, with a small dependence on subducting plate age. Once the slab sinks into the lower mantle the primary processes controlling slab evolution are (1) the ability of the stiff slab to transmit stresses up dip, (2) resistance to slab descent into the higherviscosity lower mantle, and (3) subduction-induced flow in the mantle-wedge corner.

An Evaluation of Proposed Mechanisms of Slab Flattening in Central Mexico

“…One of the predictions of plate tectonics is that the angle of subduction is a function of the age of the subducting plate, because as a plate ages it cools and increases in density (BILLEN and HIRTH, 2007;PARSONS and SCLATER, 1977). The relationship between age and density is clearly seen in the half space cooling models of Fig.…”

“…The major driving force of plate motion is slab buoyancy and the pull of subducting slabs descending into the mantle (BILLEN and HIRTH, 2007;CHAPPLE and TULLIS, 1977;FORSYTH and UYEDA, 1975). However, the current understanding of the initiation of subduction zones and the balance of forces controlling the 3D geometry and evolution of a subducting slab is not well understood (BILLEN, 2008).…”

Using the level set method in geodynamical modeling of multi-material flows and Earth's free surface

“…For instance multiple materials are important to investigate the influence of an oceanic crust on the decoupling of subducting and overriding plates as well as on the buoyancy of the subducting slab (Běhounková andČižková, 2008;van Hunen and van den Berg, 2008;Androvičová et al, 2013); they are also important for research involving subduction termination by continental collision (e.g., Baumann et al, 2010;Magni et al, 2012). Other studies focus on the influence of complex rheologies on slab dynamics (Billen and Hirth, 2007;Andrews and Billen, 2009); finally, the aim of many recent studies has been to investigate the influence and response of a free surface in subduction modeling (e.g., Schmeling et al, 2008;Gerya et al, 2009;Quinquis et al, 2011;Duretz et al, 2011).…”

A community benchmark for subduction zone modeling

“…While fully dynamic models are needed to develop an understanding of the dynamics of subduction zones and the selfconsistent generation of plate tectonics in mantle convection (Gurnis and Hager, 1988;King and Hager, 1994;King and Ita, 1995;Kincaid and Sacks, 1997;Chen and King, 1998;Zhong et al, 1998;Van Hunen et al, 2002;Billen and Hirth, 2007), models that prescribe the kinematics of the slab are simpler and better suited in some cases. Such models are particularly appropriate for the study of the Earth's subduction zones where the slab geometry is well described by Benioff zone seismicity and local seismic studies and those where the relative plate motion can be extracted from global tectonic models (e.g.…”

“…Furukawa, 1993;Van Keken et al, 2002) or to use fully dynamic models of subduction zones (e.g. Billen and Hirth, 2007).…”