Journal
EARTH AND PLANETARY SCIENCE LETTERS
Volume 451, Issue -, Pages 208-220Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.epsl.2016.06.054
Keywords
subduction; metamorphic sole; rheology; plate interface; slab dehydration; mechanical coupling
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Funding
- Agence nationale de la recherche [ANR-10-BLAN-0615]
- Institut Universitaire de France
- ZIP project (REA) from People Programme (Marie Curie Actions) of the European Union [604713]
- Agence Nationale de la Recherche (ANR) [ANR-10-BLAN-0615] Funding Source: Agence Nationale de la Recherche (ANR)
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Subduction infancy corresponds to the first few million years following subduction initiation, when slabs start their descent into the mantle. It coincides with the transient (yet systematic) transfer of material from the top of the slab to the upper plate, as witnessed by metamorphic soles welded beneath obducted ophiolites. Combining structure-lithology-pressure-temperature-time data from metamorphic soles with flow laws derived from experimental rock mechanics, this study highlights two main successive rheological switches across the subduction interface (mantle wedge vs. basalts, then mantle wedge vs. sediments; at similar to 800 degrees C and similar to 600 degrees C, respectively), during which interplate mechanical coupling is maximized by the existence of transiently similar rheologies across the plate contact. We propose that these rheological switches hinder slab penetration and are responsible for slicing the top of the slab and welding crustal pieces (high- then low-temperature metamorphic soles) to the base of the mantle wedge during subduction infancy. This mechanism has implications for the rheological properties of the crust and mantle (and for transient episodes of accretion/exhumation of HP-LT rocks in mature subduction systems) and highlights the role of fluids in enabling subduction to overcome the early resistance to slab penetration. (C) 2016 Elsevier B.V. All rights reserved.
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