The Role of History-Dependent Rheology in Plate Boundary Lubrication for Generating One-Sided Subduction

Abstract

We have developed a two-dimensional dynamical model of asymmetric subduction integrated into the mantle convection without imposed plate velocities. In this model we consider that weak oceanic crust behaves as a lubricator on the thrust fault at the plate boundary. We introduce a rheological layer that depends on the history of the past fracture to simulate the effect of the oceanic crust. The thickness of this layer is set to be as thin as the Earth's oceanic crust. To treat 1-kilometer scale structure at the plate boundary in the 1000-kilometer scale mantle convection calculation, we introduce a new numerical method to solve the hydrodynamic equations using a couple of uniform and nonuniform grids of control volumes. Using our developed models, we have systematically investigated effects of basic rheological parameters that determine the deformation strength of the lithosphere and the oceanic crust on the development of the subducted slab, with a focus on the plate motion controlling mechanism. In our model the plate subduction is produced when the friction coefficient (0.004 -0.008) of the modeled oceanic crust and the maximum strength (400 MPa) of the lithosphere are in plausible range inferred from the observations on the plate driving forces and the plate deformation, and the rheology experiments. In this range of the plate strength, yielding induces the plate bending. In this case the speed of plate motion is controlled more by viscosity layering of the underlying mantle than by the plate strength. To examine the setting of the overriding plate, we also consider the two end-member cases in which the overriding plate is fixed or freely-movable. In the case of the freely-movable overriding plate, the trench motion considerably changes the dip angle of the deep slab. Especially in the case with a shallow-angle plate boundary, retrograde slab motion occurs to generate a shallow-angle deep slab.

Breakup Without Borders: How Continents Speed Up and Slow Down During Rifting

“…We also prescribe weak oceanic crust that decouples to a certain degree the sinking slab from the overriding plate causing subduction asymmetry (Crameri et al, 2012;Gerya et al, 2008;Tagawa et al, 2007). The crust is neutrally buoyant, and it follows the same viscosity law as ambient mantle while being 10 times less viscous and more easily deformable.…”

A free plate surface and weak oceanic crust produce single‐sided subduction on Earth

“…Previous studies showed that weak hydrated crust (sediments, hydrothermally altered basalts, serpentinites) present on top of the terrestrial oceanic plates have an important effect on the style of subduction by acting as a lubricating layer between two converging plates [Lenardic and Kaula, 1994;Gerya et al, 2008;Tagawa et al, 2007]. A common explanation of the weakness of deep faults (up to 200 km depth) is the presence of fluids (CO 2 , H 2 O) released by dehydration or decarbonatization reactions [Peacock, 1990;Schmidt and Poli, 1998].…”

Dynamics of interplate domain in subduction zones: influence of rheological parameters and subducting plate age

“…Moreover, numerical models of dynamic subduction simulating realistic viscoplastic rheology (including sometimes elasticity) reveal that a low strength interplate plane (γ c < 0.1) is required to model realistic convergence of strong lithospheres (Hassani et al, 1997;Hall and Gurnis, 2003;Sobolev and Babeyko, 2005;Tagawa et al, 2007;Gorczyk et al, 2007). Gerya et al (2008) show that a very high strength contrast between converging plates and the sheared interplate material, favoured by an interplate friction coefficient close to zero, is necessary to model one-sided subduction over a wide range of subducting lithosphere age.…”