Journal
EARTH AND PLANETARY SCIENCE LETTERS
Volume 522, Issue -, Pages 107-117Publisher
ELSEVIER
DOI: 10.1016/j.epsl.2019.06.030
Keywords
subduction interface; porosity; permeability; seismic cycle; fluid overpressure
Categories
Funding
- INSU through the national Raman facility in Lyon
- INSU through the Programme national de Planetologie
- PNP-INSU program of the Universite de Lyon within the program Investissements d'Avenir of the French government [ANR-11-IDEX-0007]
- LABEX Lyon Institute of Origins of the Universite de Lyon within the program Investissements d'Avenir of the French government [ANR-11-IDEX-0007, ANR-10-LABX-0066]
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Large earthquakes break the subduction interface to depths of 60 to 80 km. Current models hold that seismic rupture occurs when fluid overpressure builds in link with porosity cycles, an assumption still to be experimentally validated at high pressures. Porosities of subduction zone rocks are experimentally determined under pressures equivalent to depths of up to 90 km with a novel experimental approach that uses Raman deuterium-hydrogen mapping. Natural rocks (blueschists, antigorite serpentinites, and chlorite-schists) representing a typical cross-section of the subduction interface corresponding to the deep seismogenic zone are investigated. In serpentinite, and to a smaller extent blueschist, porosity increases with deformation, whereas chlorite-rich schists remain impermeable regardless of their deformation history. Such a contrasting behavior explains the observation of over-pressurized oceanic crust and the limited hydration of the forearc mantle wedge. These results provide quantitative evidence that serpentinite, and likely blueschist, may undergo porosity cycles making possible the downdip propagation of large seismic rupture to great depths. (C) 2019 Elsevier B.V. All rights reserved.
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