Analog and Numerical Experiments of Double Subduction Systems With Opposite Polarity in Adjacent Segments

Abstract

In this work we study the dynamics of double subduction systems with opposite polarity in adjacent segments. A combined approach of numerical and analog experiments allows us to compare results and exploit the strengths of both methodologies. High-resolution numerical experiments complement laboratory results by providing quantities difficult to measure in the laboratory such as stress state, flow patterns and energy dissipation. Results show strong asymmetries in the mantle flow that produce in turn asymmetries in the trench and in the downgoing slab deformation. The mantle flow pattern varies with time; the toroidal cells between the plates evolve until merging into one unique cell when the trenches align. In that moment the maximum upward flow is observed close to the trenches. The interaction between the mantle flow produced by each subducting plate makes the rollback processes slower than in a single subduction case. This is consistent with the observed energy dissipation rate that is smaller in the double subduction system than in two single subductions. Moreover, we provide a detailed analysis on the setup and boundary conditions required to numerically reproduce the analog experiments. Boundary conditions at the bottom of the domain are crucial to reproduce their analog counterparts. Numerical results are compared to natural examples of multi-slab subduction systems in terms of upper mantle seismic anisotropy, relative trench-retreat velocities and composition of subduction-related magmatism. Keypoints• Numerical models of double subduction have been developed to reproduce laboratory experiments and to understand the dynamics of the system.• The interaction between the induced mantle flows slows down the evolution of the system and generates additional deformation of plates.• In the horizontal plane mantle flow forms four toroidal cells with symmetry axes that rotate during trench retreat.

Tomographic Image Interpretation and Central-Western Mediterranean-Like Upper Mantle Dynamics From Coupled Seismological and Geodynamic Modeling Approach

“…Similarly to previous studies (Luth et al, 2013;Jagoutz et al, 2015;Holt et al, 2017Holt et al, , 2018Király et al, 2018;Peral et al, 2020), here we notice that the presence of multiple subducting slabs influences the overall force balance, the geometry and kinematics of the subduction systems, as well as the mantle flow patterns. The inclusion of additional subduction zones has partly improved the prediction of the mantle dynamics leading to a better correspondence between the modeled and observed surface and deep isotropic structures, and seismic anisotropy patterns when compared to Model CM of Lo Bue et al (2021).…”

The Role of Adria Plate Lithospheric Structures on the Recent Dynamics of the Central Mediterranean Region

“…The Central Mediterranean dynamics has been likely affected by the presence of multiple subducting slabs rather than a single one as in our models. Numerical and analog models with multiple subductions demonstrated that the number and geometry of interacting slabs strongly affect the overall force balance, and that interactions through the mantle can exert a primary control on the geometry and kinematics of subduction (Holt et al, 2017(Holt et al, , 2018Jagoutz et al, 2015;Luth et al, 2013;Peral et al, 2020). In addition, it remains difficult if not impossible to evaluate the role of other structural heterogeneities (i.e., oceanic transform faults) and geometrical complexities that might have been potentially present within the subducted Ionian plate and eastern Adria margin and that have not been considered here.…”

Opposite Symmetry in the Lithospheric Structure of the Alboran and Algerian Basins and Their Margins (Western Mediterranean): Geodynamic Implications

“…The dynamics of such subduction system has been studied using analogue and numerical experiments by Peral et al. (2018, 2020). The observed lithospheric scale thickening beneath the HP/LT metamorphic rocks of the Betics followed by extension driven thinning and abundant volcanism in the Alboran Basin is consistent with the NNW retreat of the Alboran slab.…”

“…The margin segmentation exerted a strong control on the further evolution of the Ligurian-Tethys realm allowing for opposed subduction polarities in adjacent segments. The dynamics of such subduction system has been studied using analogue and numerical experiments by Peral et al (2018Peral et al ( , 2020. The observed lithospheric scale thickening beneath the HP/LT metamorphic rocks of the Betics followed by extension driven thinning and abundant volcanism in the Alboran Basin is consistent with the NNW retreat of the Alboran slab.…”