Evaluating the Influence of Plate Boundary Friction and Mantle Viscosity on Plate Velocities

Abstract

Lithospheric plates move over the low‐viscosity asthenosphere balancing several forces, which generate plate motions. We use a global 3‐D lithosphere‐asthenosphere model (SLIM3D) with visco‐elasto‐plastic rheology coupled to a spectral model of mantle flow at 300 km depth to quantify the influence of intra‐plate friction and asthenospheric viscosity on plate velocities. We account for the brittle‐ductile deformation at plate boundaries (yield stress) using a plate boundary friction coefficient to predict the present‐day plate motion and net rotation of the lithospheric plates. Previous modeling studies have suggested that small friction coefficients ( μ<0.1, yield stress ∼ 100 MPa) can lead to plate tectonics in models of mantle convection. Here we show that in order to match the observed present‐day plate motion and net rotation, the frictional parameter must be less than 0.05. We obtain a good fit with the magnitude and orientation of the observed plate velocities (NUVEL‐1A) in a no‐net‐rotation (NNR) reference frame with μ<0.05 and a minimum asthenosphere viscosity of ∼ 5·1019 Pas to 1020 Pas. Our estimates of net rotation (NR) of the lithosphere suggest that amplitudes ∼ 0.1−0.2 ( °/Ma), similar to most observation‐based estimates, can be obtained with asthenosphere viscosity cutoff values of ∼ 1019 Pas to 5·1019 Pas and friction coefficients μ<0.05.

Effects of upper mantle heterogeneities on the lithospheric stress field and dynamic topography

“…This study complements our previous study (Osei Tutu et al, 2018) about the influence of plastic yielding at plate boundaries on plate velocities in a no-net-rotation reference frame and on lithospheric net rotation. A forward model is run for half a million years with a time step of 50 kyr, and at each time step tractions in the lower mantle due to density heterogeneities are computed using the spectral mantle code and then passed across the coupling dynamic boundary to the top component SLIM3D.…”

“…1a), which are only considered below the depth of 300 km. The top thermo-mechanical component (SLIM3D) has been used in a wide range of 2-D and 3-D regional numerical studies of crustal and lithospheric deformations (Popov and Sobolev, 2008;Brune et al, 2012Brune et al, , 2014Brune et al, , 2016Quinteros and Sobolev, 2013) with different spatial and temporal resolutions, but the coupled code is used here and in Osei Tutu et al (2018) for the first time. In this 3-D global study, we distinguish three material layers (phases) within the top component (SLIM3D), the crustal layer, the lithosphere and the sub-lithospheric mantle layers, in order to account for the stress and temperature-dependent rheology in the presence of major continental keels and the uppermost part of the subducted lithospheric plates.…”

“…In this 3-D global study, we distinguish three material layers (phases) within the top component (SLIM3D), the crustal layer, the lithosphere and the sub-lithospheric mantle layers, in order to account for the stress and temperature-dependent rheology in the presence of major continental keels and the uppermost part of the subducted lithospheric plates. The visco-elastoplastic rheology is described in detail by Popov and Sobolev (2008), with specific modeling parameters given in Osei Tutu et al (2018) and in the Appendix of this paper.…”

“…Within the upper mantle, our crustal rheology is taken from Wilks (1990) and below the crust we have considered dry and wet olivine parameters in the lithosphere and sub-lithospheric mantle layers, respectively, modified after the axial compression experiments of Hirth and Kohlstedt (2004) (shown in the Appendix, Table A1. Adopted from Osei Tutu et al (2018) for studying the influence of both the driving and resisting forces that generate global plate velocities and lithospheric plate net rotation).…”

“…In regions of continental shelf, where there is neither age grid nor heat flow data, we interpolated the resulting thermal structures surrounding these regions while in Iceland where both age grid and heat flow data exist, the TC1 model was assigned. We explicitly include slabs in TM1 as described in Osei Tutu et al (2018). The second model of the upper mantle thermal structure (TM2) is inferred from the seismic tomography model SL2013sv (Schaeffer and Lebedev, 2013).…”