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Interaction of subducted slabs with the mantle transition-zone: A regime diagram from 2-D thermo-mechanical models with a mobile trench and an overriding plate

Garel, F, Goes, S, Davies, R, Davies, J. H., Kramer, S. and Wilson, C. 2014. Interaction of subducted slabs with the mantle transition-zone: A regime diagram from 2-D thermo-mechanical models with a mobile trench and an overriding plate. Geochemistry, Geophysics, Geosystems 15 (5) 10.1002/2014GC005257

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Abstract

Transition zone slab deformation influences Earth's thermal, chemical and tectonic evolution. However, the mechanisms responsible for the wide-range of imaged slab morphologies remain debated. Here, we use 2-D thermo-mechanical models with a mobile trench, an overriding plate, a temperature- and stress-dependent rheology, and a 10, 30 or 100-fold increase in lower mantle viscosity, to investigate the effect of initial subducting- and overriding-plate ages on slab transition-zone interaction. Four subduction styles emerge: (i) a “vertical folding” mode, with a quasi-stationary trench, near-vertical subduction and buckling/folding at depth (VF); (ii) slabs that induce mild trench retreat, which are flattened/“horizontally deflected” and stagnate at the upper-lower mantle interface (HD); (iii) inclined slabs, which result from rapid sinking and strong trench retreat (ISR); (iv) a two-stage mode, displaying backward-bent and subsequently inclined slabs, with late trench retreat (BIR). Transitions from regime (i) to (iii) occur with increasing subducting-plate age (i.e. buoyancy and strength). Regime (iv) develops for old (strong) subducting and overriding plates. We find that the interplay between trench motion and slab deformation at depth dictate the subduction style, both being controlled by slab strength, which is consistent with predictions from previous compositional subduction models. However, due to feedbacks between deformation, sinking rate, temperature and slab strength, the subducting-plate buoyancy, overriding-plate strength and upper-lower mantle viscosity jump are also important controls in thermo-mechanical subduction. For intermediate upper-lower mantle viscosity jumps (×30), our regimes reproduce the diverse range of seismically imaged slab morphologies.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Subjects: Q Science > QE Geology
Uncontrolled Keywords: subduction dynamics; slab morphology; overriding plate; transition zone; trench retreat; slab rheology
Additional Information: Online publication date: 10 April 2014. This is an open access article under the terms of the Creative Commons Attribution License,
Publisher: American Geophysical Union (AGU)
ISSN: 1525-2027
Funders: NERC . Grant Number: NE/I024429/1, HPC Wales - Project 40, HECTOR - National Supercomputing
Date of First Compliant Deposit: 30 March 2016
Date of Acceptance: 4 April 2014
Last Modified: 23 May 2020 11:24
URI: http://orca.cf.ac.uk/id/eprint/59109

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