Impact of regional mantle flow on subducting plate geometry and interplate stress: insights from physical modelling

Abstract

SUMMARY Physical models of subduction investigate the impact of regional mantle flow on the structure of the subducted slab and deformation of the downgoing and overriding plates. The initial mantle flow direction beneath the overriding plate can be horizontal or vertical, depending on its location with respect to the asthenospheric flow field. Imposed mantle flow produces either over or underpressure on the lower surface of the slab depending on the initial mantle flow pattern (horizontal or vertical, respectively). Overpressure promotes shallow dip subduction while underpressure tends to steepen the slab. Horizontal mantle flow with rates of 1–10 cm yr−1 provides sufficient overpressure on a dense subducting lithosphere to obtain a subduction angle of ∼60°, while the same lithospheric slab sinks vertically when no flow is imposed. Vertical drag force (due to downward mantle flow) exerted on a slab can result in steep subduction if the slab is neutrally buoyant but fails to produce steep subduction of buoyant oceanic lithosphere. The strain regime in the overriding plate due to the asthenospheric drag force depends largely on slab geometry. When the slab dip is steeper than the interplate zone, the drag force produces negative additional normal stress on the interplate zone and tensile horizontal stress in the overriding plate. When the slab dip is shallower than the interplate zone, an additional positive normal stress is produced on the interplate zone and the overriding plate experiences additional horizontal compressive stress. However, the impact of the mantle drag force on interplate pressure is small compared to the influence of the slab pull force since these stress variations can only be observed when the slab is dense and interplate pressure is low.

Modeling Slab‐Slab Interactions: Dynamics of Outward Dipping Double‐Sided Subduction Systems

“…Presently, the distance between the Hellenic and Calabrian arc is increasing toward the south. We speculate that this geometric configuration induces a slightly different escape flow pattern with more divergent outflow at the Southern end of the slab, which may actively deform and curve the smaller Calabrian slab (e.g., Boutelier & Cruden, ).…”

“…The material properties and scaling factors are summarized in Table . These materials fulfill the standard scaling procedure for stresses to density, viscosity and length under the natural gravity field (see in Table ; Boutelier & Cruden, ; Davy & Cobbold, ; Funiciello et al, ; Hubbert, ; Weijermars & Schmeling, ).…”

The surface tectonics of mantle lithosphere delamination following ocean lithosphere subduction: Insights from physical‐scaled analogue experiments

“…P wave tomography in the Mediterranean shows similar structures of subducting slabs folding over themselves [ Piromallo and Morelli , 2003]. However, we recognize that the morphology of such features in the model is controlled by the assumed reference frame within an active mantle circulation [ Boutelier and Cruden , 2008]. Further dedicated work is required to understand the lithospheric dynamics within the “wedge” of the delamination zone (i.e., between the delaminating and overlying/remaining lithosphere).…”

Role of the plate margin curvature in the plateau buildup: Consequences for the central Andes

“…This threshold limit of the slab pull force has not been investigated in this study. Finally, flow in the asthenospheric mantle around the subducting slab can also produce an additional pressure on the upper or lower surfaces of the slab, which would increase or decrease, respectively, the nonhydrostatic normal stress on the interplate zone [ Shemenda , 1993; Boutelier and Cruden , 2008]. A decrease of the nonhydrostatic normal stress with other parameters being constant is presented in Figure 10a with a series of experiments in which decreases from 25 to 10 MPa while is kept constant at 10 MPa.…”