Mapping mantle flow during retreating subduction: Laboratory models analyzed by feature tracking

Abstract

[1] Three-dimensional dynamically consistent laboratory models are carried out to model the large-scale mantle circulation induced by subduction of a laterally migrating slab. A laboratory analogue of a slab-upper mantle system is set up with two linearly viscous layers of silicone putty and glucose syrup in a tank. The circulation pattern is continuously monitored and quantitatively estimated using a feature tracking image analysis technique. The effects of plate width and mantle viscosity/density on mantle circulation are systematically considered. The experiments show that rollback subduction generates a complex three-dimensional time-dependent mantle circulation pattern characterized by the presence of two distinct components: the poloidal and the toroidal circulation. The poloidal component is the answer to the viscous coupling between the slab motion and the mantle, while the toroidal one is produced by lateral slab migration. Spatial and temporal features of mantle circulation are carefully analyzed. These models show that (1) poloidal and toroidal mantle circulation are both active since the beginning of the subduction process, (2) mantle circulation is intermittent, (3) plate width affects the velocity and the dimension of subduction induced mantle circulation area, and (4) mantle flow in subduction zones cannot be correctly described by models assuming a two-dimensional steady state process. We show that the intermittent toroidal component of mantle circulation, missed in those models, plays a crucial role in modifying the geometry and the efficiency of the poloidal component.

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

“…Thus, besides promoting single-sided subduction, a free surface results in a more characteristic curvature of the subduction trenches along the surface [Schellart et al, 2007]. This feature is formed due to toroidal mantle flow from the region of high pressure below the inclined sinking slab around its edges towards the region of low pressure above the slab, as has been shown by, e.g., analogue modeling [Funiciello et al, 2006] and as found in nature [Zandt and Humphreys, 2008].…”

Subduction-transition zone interaction: A review

“…In 3-D, additional variations in trench motion occur because of along-strike plate bending in response to flow around the plate edges (Funiciello et al, 2006;Schellart et al, 2007;Loiselet et al, 2009;Stegman et al, 2010a;Li and Ribe, 2012), leading to lower retreat of the plate edges and, for very wide plates, a trench stagnation point can develop in the center. Lateral changes in slab buoyancy can also lead to variations in trench motions, which depend on the scale of the features of different buoyancy and their relative contribution to overall slab pull (Martinod et al, 2005;Goes et al, 2008;Mason et al, 2010;Magni et al, 2014;Goes et al, 2014).…”

Tectonics and seismicity of the Tindari Fault System, southern Italy: Crustal deformations at the transition between ongoing contractional and extensional domains located above the edge of a subducting slab

“…the extensional tectonics of the southeastern Tyrrhenian region; however, the back-arc extension model and the model for a transform boundary (i.e., more properly a transfer zone linking two destructive margins) across the northeastern Sicily may better fit some of the data presented in this paper. Fore instance, the location of the Tindari Fault System right above the western edge of the Ionian narrow slab, where a complex pattern of mantle return flow is expected [Gvirtzman and Nur, 1999;Marani and Trua, 2002;Faccenna et al, 2004Faccenna et al, , 2005, may well explain its ongoing transtensional kinematics by a combination of pure extension induced by the back-arc processes and of strikeslip movements induced by the mantle flows around the narrow slab [Funiciello et al, 2006]. Moreover, the ongoing transtensional displacements along the Tindari Fault System may support the model of a transfer zone across the northeastern Sicily; however, the evidence that the present activity of the Tindari Fault System is restricted to its northern portion suggests that if such transfer zone is truly developing, this should be in its inception stage.…”