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Influence of cratonic lithosphere on the formation and evolution of flat slabs: Insights from 3-D time-dependent modeling.

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Taramón, Jorge M. and Rodríguez González, Juan and Negredo Moreno, Ana María and Billen, Magali I. (2015) Influence of cratonic lithosphere on the formation and evolution of flat slabs: Insights from 3-D time-dependent modeling. Geochemistry, geophysics, geosystems, 16 (9). pp. 2933-2948. ISSN 1525-2027

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Official URL: http://dx.doi.org/10.1002/2015GC005940




Abstract

Several mechanisms have been suggested for the formation of flat slabs including buoyant features on the subducting plate, trenchward motion and thermal or cratonic structure of the overriding plate. Analysis of episodes of flat subduction indicate that not all flat slabs can be attributed to only one of these mechanisms and it is likely that multiple mechanisms work together to create the necessary conditions for flat slab subduction. In this study we examine the role of localized regions of cratonic lithosphere in the overriding plate in the formation and evolution of flat slabs. We explicitly build on previous models, by using time-dependent simulations with three-dimensional variation in overriding plate structure. We find that there are two modes of flat subduction: permanent underplating occurs when the slab is more buoyant (shorter or younger), while transient flattening occurs when there is more negative buoyancy (longer or older slabs). Our models show how regions of the slab adjacent to the subcratonic flat portion continue to pull the slab into the mantle leading to highly contorted slab shapes with apparent slab gaps beneath the craton. These results show how the interpretation of seismic images of subduction zones can be complicated by the occurrence of either permanent or transient flattening of the slab, and how the signature of a recent flat slab episode may persist as the slab resumes normal subduction. Our models suggest that permanent underplating of slabs may preferentially occur below thick and cold lithosphere providing a built-in mechanism for regeneration of cratons.


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© John Wiley & Sons, Inc.
The data displayed in this paper were computed with the free software CitcomS (http://www.geodynamics. org/cig/software/citcoms). Model results were postprocessed and represented (Figures 2, 3, 5–9, S1–S6, and Movies S2, S3, S5, and S6) using commercial code Matlab (www. mathworks.com/products/matlab/). Figure 4 and Movies S1 and S4 were produced using public domain software ParaView (http://www. paraview.org). This work was supported by Spanish Ministry of Economy and Competitiveness projects CGL2012-37222 and CGL2014- 58821-C2-1-R. M.I. Billen acknowledges support from NSF grants 6877321 and 0748818. We thank the Editor and Leland O’Driscoll, Maxim Ballmer and an anonymous reviewer for their thoughtful and constructive comments.

Uncontrolled Keywords:Oceanic plateau subduction; Western North-America; Overriding plate; Mantle convection; Trench migration; Laramide orogeny; Transition-zone; Thermal-model; Farallon slab.
Subjects:Sciences > Physics > Geophysics
Sciences > Physics > Meteorology
ID Code:37276
Deposited On:21 Apr 2016 17:23
Last Modified:21 Apr 2016 17:23

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