Reconciling strong slab pull and weak plate bending: The plate motion constraint on the strength of mantle slabs

Wu, Buyun; Conrad, Clinton P.; Heuret, Arnauld; Lithgow‐Bertelloni, Carolina; Lallemand, Serge

doi:10.1016/j.epsl.2008.05.009

Cited by 105 publications

(137 citation statements)

References 36 publications

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“…68 Ma, for averaged effective viscosity ratios of 500 and 200, respectively). This idea of a relatively weak slab is consistent with studies on plate strength and fl exural rigidity by using topographygravity admittance (Billen and Gurnis, 2005) and arguments about subductability of purely viscous slabs (Conrad and Hager, 1999;Becker et al, 1999;Funiciello et al, 2008) and global plate mobility (Wu et al, 2008) as constrained by numerical and laboratory modeling results integrated with natural data. However, there is a discrepancy with respect to the lower value and the extremely weak slab viscosity (less than 10 22 ) predicted by geopotential, dynamic topography and in-slab force transmission (Hager, 1984;Zhong and Davies, 1999;Billen et al, 2003).…”

Section: Discussionsupporting

confidence: 83%

On the relation between trench migration, seafloor age, and the strength of the subducting lithosphere

Giuseppe¹,

Faccenna

Funiciello

et al. 2009

Lithosphere

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Oceanic lithosphere thickens and strengthens as it grows older. Worldwide databases reveal that the age of the slab to a certain extent controls the subduction style. Old and thick (and consequently strong) slabs show a trench "advance, " while younger, thin (weak) slabs are migrating in retreating style (trench "rollback"). We performed numerical models to show that this confi guration could be the result of the dynamic equilibrium between gravity and resisting forces. In particular we show that energy dissipation caused by bending and unbending of the slab, although less important than other resisting forces, could be a primary control on trench migration. Our results fi t well with global compilations of kinematic data from modern subduction zones in two reference frames with different amounts of net rotations. Based on the age at which the transition from retreating to advancing style occurs, we propose an effective lithosphere/mantle viscosity of ~200 during bending of the lithosphere into the subduction zone.

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Section: Discussionsupporting

confidence: 83%

On the relation between trench migration, seafloor age, and the strength of the subducting lithosphere

Giuseppe¹,

Faccenna

Funiciello

et al. 2009

Lithosphere

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“…Viscosity of the overriding lithosphere, when present, is 2.9 × 10 4 Pa s and the viscosity of the mantle ranges between 30 and 40 Pa s. The obtained viscosity ratio between the slab and the upper mantle varies between 7.75×10 2 and 25×10 2 (Table 1), which is in the high range of proposed values (e.g. Billen et al, 2003;Faccenna et al, 2007;Funiciello et al, 2008;Wu et al, 2008;Loiselet et al, 2009Loiselet et al, , 2010. In the following, we directly express the quantities with their corresponding scaled values for a better relevance to real Earth.…”

Section: Setupmentioning

confidence: 71%

The dynamics of laterally variable subductions: laboratory models applied to the Hellenides

et al. 2013

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Abstract. We designed three-dimensional dynamically selfconsistent laboratory models of subduction to analyse the relationships between overriding plate deformation and subduction dynamics in the upper mantle. We investigated the effects of the subduction of a lithosphere of laterally variable buoyancy on the temporal evolution of trench kinematics and shape, horizontal flow at the top of the asthenosphere, dynamic topography and deformation of the overriding plate. Two subducting units, which correspond to a negatively buoyant oceanic plate and positively buoyant continental one, are juxtaposed via a trench-perpendicular interface (analogue to a tear fault) that is either fully-coupled or shear-stress free. Differential rates of trench retreat, in excess of 6 cm yr −1 between the two units, trigger a more vigorous mantle flow above the oceanic slab unit than above the continental slab unit. The resulting asymmetrical sublithospheric flow shears the overriding plate in front of the tear fault, and deformation gradually switches from extension to transtension through time. The consistency between our models results and geological observations suggests that the Late Cenozoic deformation of the Aegean domain, including the formation of the North Aegean Trough and Central Hellenic Shear zone, results from the spatial variations in the buoyancy of the subducting lithosphere. In particular, the lateral changes of the subduction regime caused by the Early Pliocene subduction of the old oceanic Ionian plate redesigned mantle flow and excited an increasingly vigorous dextral shear underneath the overriding plate. The models suggest that it is the inception of the Kefalonia Fault that caused the transition between an extension dominated tectonic regime to transtension, in the North Aegean, Mainland Greece and Peloponnese. The subduction of the tear fault may also have helped the propagation of the North Anatolian Fault into the Aegean domain.

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“…Previous work has argued that the upper mantle is dominantly non-Newtonian and strain rate softening [Billen, 2008;Cizkova and Bina, 2013], which implies that the effective viscosity ratio between a slab and the ambient upper mantle should be relatively high. Nevertheless, the effective viscosity ratio that we use in our experiments (~160) is well within the previous estimates of approximately 50-500 [e.g., Schellart, 2008;Funiciello et al, 2008;Ribe, 2010;Wu et al, 2008;Loiselet et al, 2009;Li and Ribe, 2012]. For the density difference we consider a natural upper limit of Δρ = 80 kg m 3 , which would correspond to an old lithospheric slab in which all the oceanic crust has been altered to eclogite and with no heat diffusion into the slab.…”

Section: 1002/2014gl062876mentioning

confidence: 80%

How weak is the subduction zone interface?

Duarte

Schellart

Cruden

2015

Geophysical Research Letters

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Several lines of evidence suggest that subduction zones are weak and that the unique availability of water on Earth is a critical factor in the weakening process. We have evaluated the strength of subduction zone interfaces using two approaches: (i) from empirical relationships between shear stress at the interface and subduction velocity, deduced from laboratory experiments; and (ii) from a parametric study of natural subduction zones that provides new insights on subduction zone interface strength. Our results suggest that subduction is only mechanically feasible when shear stresses along the plate interface are relatively low (less than~35 MPa). To account for this requirement, we propose that there is a feedback mechanism between subduction velocity, water released from the subducting plate, and weakening of the fore-arc mantle that may explain how relatively low shear stresses are maintained at subduction interfaces globally.

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Reconciling strong slab pull and weak plate bending: The plate motion constraint on the strength of mantle slabs

Cited by 105 publications

References 36 publications

On the relation between trench migration, seafloor age, and the strength of the subducting lithosphere

On the relation between trench migration, seafloor age, and the strength of the subducting lithosphere

The dynamics of laterally variable subductions: laboratory models applied to the Hellenides

How weak is the subduction zone interface?

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