Kinematics and flow patterns in deep mantle and upper mantle subduction models: Influence of the mantle depth and slab to mantle viscosity ratio

Abstract

[1] Three-dimensional fluid dynamic laboratory simulations are presented that investigate the subduction process in two mantle models, an upper mantle model and a deep mantle model, and for various subducting plate/mantle viscosity ratios (h SP /h M = 59-1375). The models investigate the mantle flow field, geometrical evolution of the slab, sinking kinematics, and relative contributions of subducting plate motion and trench migration to the total rate of subduction. All models show that the subducting plate is always moving trenchward resulting from slab pull. Furthermore, all deep mantle models show trench retreat, as do upper mantle models in the initial stage of subduction before slab tip-transition zone interaction. Upper mantle models with a low h SP /h M (66, 217) continue to show trench retreat after interaction. Upper mantle models with a high h SP /h M (378, 709) show a period of trench advance after interaction followed by trench retreat. Upper mantle models with a very high h SP /h M (1375) show continued trench advance after interaction. The difference in trench migration behavior and associated slab geometries is attributed to both h SP /h M and the mantle depth to plate thickness ratio T M /T SP , which both affect the slab bending radius to mantle thickness ratio r B /T M . Four subduction regimes can be defined: Regime I with r B /T M $0.3, trench retreat, slab draping, and a concave trench; Regime II with $0.3 < r B /T M < $0.5, episodic trench migration, slab folding, and a concave trench; Regime III with r B /T M % 0.5, trench advance, slab rollover geometries, and minor trench curvature; and Regime IV with r B /T M ! $0.8, trench retreat, slab draping, and a rectilinear trench. In all models, slab-parallel downdip motion induces poloidal mantle flow structures. In addition, trench retreat and rollback motion of the slab induce quasi-toroidal return flow around the lateral slab edges toward the mantle wedge. Rollback-induced poloidal flow around the slab tip is not observed in any of the experiments. Finally, comparison between the slab geometries observed in the upper mantle models and slab geometries observed in nature imply that the effective viscosity ratio between slab and ambient upper mantle in nature is less than 10 3 and of the order 1-7 Â 10 2 , with a best estimate of 1-3 Â 10 2 .

Subduction-transition zone interaction: A review

“…Such retro-Goes et al | Subduction-transition zone review GEOSPHERE | Volume 13 | Number 3 grade motion is the consequence of vertical sinking of the plate, as expected for the most basic form of free subduction, driven by the slab's negative buoyancy and not significantly hampered by the upper plate or mantle convective forcing (Kincaid and Olson, 1987;Zhong and Gurnis, 1995;Becker et al, 1999;Funiciello et al, 2003a;Funiciello et al, 2003b;Schellart, 2008). Motivated by the free-subduction models of Kincaid and Olson (1987), Van der Hilst and Seno (1993) proposed that trench retreat could be responsible for the slab flattening as tomographically observed in the transition zone below the western Pacific.…”

“…The advance occurs when plates are able to (i.e., have sufficient sinking time to) fully bend over but do not have a chance to unbend before reaching the base of the upper mantle (Ribe, 2010). Interaction of an overturned plate (dip >90°) with a resisting upper-to lower-mantle interface triggers trench advance (Bellahsen et al, 2005;Funiciello et al, 2008;Schellart, 2008;Ribe, 2010). Weaker plates will unbend in response to the viscous mantle flow driven by the sinking and moving plate and thus arrive at the base of the upper mantle at an angle less than 90°.…”

“…The speed of trench retreat is controlled by subducting-plate strength and buoyancy (Bellahsen et al, 2005;Capitanio et al, 2007;Di Giuseppe et al, 2008;Schellart, 2008;Ribe, 2010;Stegman et al, 2010b;Capitanio and Morra, 2012;Fourel et al, 2014) (Fig. 7).…”

Slab detachment of subducted Indo-Australian plate beneath Sunda arc, Indonesia

“…However, necking, tearing and subsequent break-off of subducting slabs make slab architecture much more complex, which are well documented worldwide using geophysical observations (e.g., Barazangi et al 1973;Protti et al 1994;Gvirtzman and Nur 1999;Wortel and Spakman 2000;Bautista et al 2001;Levin et al 2002;Ferrari 2004;Miller et al 2006;Richards et al 2007;Rosenbaum et al 2008;Lister et al 2008;Obayashi et al 2009;Schellart et al 2009;Kundu and Gahalaut 2010). Slab tearing produces physical gaps in subducted slabs that enhances asthenospheric inflow around the lateral edges of the tear (Kincaid and Griffiths 2003;Schellart 2004Schellart , 2008Stegman et al 2006) and reflects on geochemistry of subduction-related arc magmatism (Maury et al 2000;Yogodzinski et al 2001;Guivel et al 2006). In case of sub-horizontal slab tear, it can affect the seismicity by creating gaps in seismic clusters, and may lead to a slowdown in subduction velocity because of the sudden loss of slab pull force at the detached segment of the subduction zone.…”

New analogue materials for nonlinear lithosphere rheology, with an application to slab break-off

“…Davy and Cobbold (1988);Faccenna et al (1999); Guillaume et al (2009);Duarte et al (2013)). By adding fine iron powder (Funiciello et al, 2004;Schellart, 2008; sample h R σ r Newtonian Power-law rs Figure 3: Schematic rheometer setup, with gap height h and disk radius R, including a schematic depiction of shear stress σ variation as function of radial distance r for Newtonian and power-law materials, rs is the radial distance where the shear stress curves of Newtonian as well as power-law materials intersect (Carvalho et al, 1994). Guillaume et al, 2013) we adjust the mixture density to be able to create both buoyant and negatively buoyant materials.…”