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Nagaya T, Walker AM, Wookey J, et al. Seismic evidence for flow in the hydrated mantle wedge of the Ryukyu subduction zone. Sci Rep. 2016;6:29981doi: 10.1038/srep29981.
Nagaya, T., Walker, A. M., Wookey, J., Wallis, S. R., Ishii, K., & Kendall, J. M. (2016). Seismic evidence for flow in the hydrated mantle wedge of the Ryukyu subduction zone. Scientific reports, 629981. https://doi.org/10.1038/srep29981
Nagaya, Takayoshi, et al. "Seismic evidence for flow in the hydrated mantle wedge of the Ryukyu subduction zone." Scientific reports vol. 6 (2016): 29981. doi: https://doi.org/10.1038/srep29981
Nagaya T, Walker AM, Wookey J, Wallis SR, Ishii K, Kendall JM. Seismic evidence for flow in the hydrated mantle wedge of the Ryukyu subduction zone. Sci Rep. 2016 Jul 20;6:29981. doi: 10.1038/srep29981. PMID: 27436676; PMCID: PMC4951697.
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Sci Rep. 2016 Jul 20;6:29981. doi: 10.1038/srep29981.

Seismic evidence for flow in the hydrated mantle wedge of the Ryukyu subduction zone.

Scientific reports

Takayoshi Nagaya, Andrew M Walker, James Wookey, Simon R Wallis, Kazuhiko Ishii, J-Michael Kendall

Affiliations

  1. Graduate School of Environmental Studies, Nagoya University, Nagoya 464-8601, Japan.
  2. School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK.
  3. Graduate School of Environmental Studies, Tohoku University, Sendai 980-8579, Japan.
  4. School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK.
  5. Graduate School of Science, Osaka Prefecture University, Sakai 599-8531, Japan.

PMID: 27436676 PMCID: PMC4951697 DOI: 10.1038/srep29981

Abstract

It is widely accepted that water-rich serpentinite domains are commonly present in the mantle above shallow subducting slabs and play key roles in controlling the geochemical cycling and physical properties of subduction zones. Thermal and petrological models show the dominant serpentine mineral is antigorite. However, there is no good consensus on the amount, distribution and alignment of this mineral. Seismic velocities are commonly used to identify antigorite-rich domains, but antigorite is highly-anisotropic and depending on the seismic ray path, its properties can be very difficult to distinguish from non-hydrated olivine-rich mantle. Here, we utilize this anisotropy and show how an analysis of seismic anisotropy that incorporates measured ray path geometries in the Ryukyu arc can constrain the distribution, orientation and amount of antigorite. We find more than 54% of the wedge must consist of antigorite and the alignment must change from vertically aligned to parallel to the slab. This orientation change suggests convective flow in the hydrated forearc mantle. Shear wave splitting analysis in other subduction zones indicates large-scale serpentinization and forearc mantle convection are likely to be more widespread than generally recognized. The view that the forearc mantle of cold subduction zones is dry needs to be reassessed.

References

  1. Nature. 2002 May 30;417(6888):536-8 - PubMed
  2. Science. 2007 Dec 21;318(5858):1910-3 - PubMed
  3. Nature. 2009 Oct 22;461(7267):1114-7 - PubMed

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