From subduction to collision: Control of deep processes on the evolution of convergent plate boundary

Abstract

[1] Using laboratory experiments, we investigate the dynamics of the collisional process that follows the closure of an oceanic basin. The evolution of these experiments systematically shows four successive episodes of deformation, which correspond to (1) the initiation of oceanic subduction, (2) a mature period of oceanic subduction, (3) an episode of continental subduction, during which the trench absorbs all the convergence and the superficial tectonic regime does not change significantly within the continental plates, and (4) continental collision that starts when the trench locks and convergence is absorbed by a system of thrust faults and folds. We observe that the amount of continental material that subducts before the onset of collision depends on the slab pull exerted by the subducted oceanic lithosphere. The slab-pull force, in turn, depends on the amount of subducted oceanic material, on the thickness of the convective mantle, and also on the rheology of the slab. Our experiments, indeed, suggest that parts of the oceanic slab may separate from the superficial slab to sink rapidly in the mantle, decreasing the slab-pull level and triggering the rapid onset of collision. We observe two possible modes of slab deformation: slab break-off and development of viscous instabilities. We define two dimensionless rheological numbers to characterize the possible occurrence of these modes of deformation. In all cases, oceanic closure is followed by episode of continental subduction during which the continental lithosphere may reach depths varying between 50 and 450 km, prior to the onset of continental collision.

Cenozoic geodynamic evolution of the Aegean

“…It is usually considered that continental subduction leads almost inevitably to slab break-off (Davies and von Blanckenburg 1995; see also the experiments of Regard et al 2003Regard et al , 2005. Gravitational forces tend to stretch the oceanic slab and separate it from the continental lithosphere that resists subduction.…”

A review of analogue modelling of geodynamic processes: Approaches, scaling, materials and quantification, with an application to subduction experiments

“…Examples of mantle-scale experiments include a variety of subduction experiments with negatively buoyant slabs in which the rate of plate motion is externally controlled by one or more pistons (e.g. Shemenda, 1992Shemenda, , 1993Faccenna et al, 1999;Regard et al, 2003;Boutelier et al, 2003;Schellart, 2005;Heuret et al, 2007;Guillaume et al, 2009;Gögüş et al, 2011;Martinod et al, 2013;Bajolet et al, 2013;Agard et al, 2014), experiments that include buoyancy-driven subduction and externally-controlled plume injection (e.g. Mériaux et al, 2015aMériaux et al, , 2015b, and thermochemical convection and plume formation experiments, where motions in the system are driven by temperature gradients applied externally and by internal density heterogeneities of chemical origin (Davaille et al, 2002;Le Bars and Davaille, 2004;Kumagai et al, 2007).…”

“…Shemenda (1992) investigated subduction initiation and progressive subduction evolution using undeformed lithosphere, either laterally homogeneous or heterogeneous, or pre-cut lithosphere. Faccenna et al (1999) and Regard et al (2003) investigated subduction initiation and progressive subduction evolution using undeformed, laterally heterogeneous, lithosphere. More recently subduction models were developed that used a geometric set-up comparable to that of Kincaid and Olson (1987), thus including an overriding plate and starting with a short subduction perturbation, but that used a combined approach with one or two external pistons to drive plate motion (e.g.…”

“…Other modellers followed suite, also using a combined approach (e.g. Faccenna et al, 1999;Regard et al, 2003;Boutelier et al, 2003). Shemenda (1992) investigated subduction initiation and progressive subduction evolution using undeformed lithosphere, either laterally homogeneous or heterogeneous, or pre-cut lithosphere.…”

Numerical models of slab migration in continental collision zones

“…After continental collision, different scenarios may occur: (1) continental crustal material arrives at the trench and subducts together with the lithospheric mantle (e.g. Ranalli et al, 2000;Regard et al, 2003;Toussaint et al, 2004); (2) part of the continental buoyant crust is delaminated from the lithospheric mantle and accreted onto the overriding plate, allowing continuation of plate convergence (delamination) (e.g. Cloos, 1993;Chemenda et al, 1996;Kerr and Tarney, 2005;Vos et al, 2007) or (3) the slab breaks off as a consequence of tensile stress from the pull of the sinking oceanic lithosphere in the mantle connected to the continental part of the plate (e.g.…”