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Oblique subduction and mantle flow control on upper plate deformation: 3D geodynamic modeling.

Authors :
Balázs, Attila
Faccenna, Claudio
Ueda, Kosuke
Funiciello, Francesca
Boutoux, Alexandre
Blanc, Eric J.-P.
Gerya, Taras
Source :
Earth & Planetary Science Letters. Sep2021, Vol. 569, pN.PAG-N.PAG. 1p.
Publication Year :
2021

Abstract

• Most of the recent and probably fossil subduction zones on Earth are oblique. • Oblique subduction results in asymmetric mantle flow pattern leading to plate rotation. • Transition to continental subduction facilitates coeval trench advance and retreat. • Back-arc extension is led by toroidal mantle flow. • Sediments are transported in the trench and along the subduction interface. Most subduction zones on Earth are oblique, i.e., the angle between the plate convergence vector and the trench notably differs from 90°. Therefore, modeling and understanding the strain partitioning in the forearc, the development of extensional basins in the back-arc region and the diachronous transition from subduction to collision require a 3D approach. Here, we assess how oblique oceanic subduction and subsequent collision and associated mantle flow around the subducted lithosphere control the thermo-mechanical evolution of active margins. We conducted a series of 3D thermo-mechanical subduction models and discuss the influence of different subduction obliquity angles, the role of mantle flow variations and their connection with sediment transport and back-arc deformation. Numerical models are complemented by scaled analogue models to visualize the mantle flow evolution. Oceanic subduction along an oblique trench results in asymmetric mantle return flow leading to the gradual decrease of the subduction obliquity angle driven by the gradual rotation of the lower plate and the along-trench variation of slab retreat. This creates laterally variable subduction velocities and slab geometries. Back-arc extension is governed by both the toroidal mantle flow along the slab edges and by the oblique subduction induced lateral mantle flow gradient. The diachronous transition from oceanic to continental subduction and collision facilitates the laterally variable trench advance and retreat and back-arc deformation. Tectonically induced lateral sediment transport in the trench and along the subduction interface decreases its strength and viscosity and can alter subduction velocities. Our model results provide critical insights into the evolution of oblique subduction and collisional systems, such as the Arabia-Eurasia convergence zone. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
0012821X
Volume :
569
Database :
Academic Search Index
Journal :
Earth & Planetary Science Letters
Publication Type :
Academic Journal
Accession number :
151307202
Full Text :
https://doi.org/10.1016/j.epsl.2021.117056