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Grain-size distribution in the mantle wedge of subduction zones

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dc.contributor.author Wada, Ikuko
dc.contributor.author Behn, Mark D.
dc.contributor.author He, Jiangheng
dc.date.accessioned 2011-11-21T20:24:00Z
dc.date.available 2012-04-20T08:33:14Z
dc.date.issued 2011-10-20
dc.identifier.citation Journal of Geophysical Research 116 (2011): B10203 en_US
dc.identifier.uri http://hdl.handle.net/1912/4893
dc.description Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 116 (2011): B10203, doi:10.1029/2011JB008294. en_US
dc.description.abstract Mineral grain size plays an important role in controlling many processes in the mantle wedge of subduction zones, including mantle flow and fluid migration. To investigate the grain-size distribution in the mantle wedge, we coupled a two-dimensional (2-D) steady state finite element thermal and mantle-flow model with a laboratory-derived grain-size evolution model. In our coupled model, the mantle wedge has a composite olivine rheology that incorporates grain-size-dependent diffusion creep and grain-size-independent dislocation creep. Our results show that all subduction settings lead to a characteristic grain-size distribution, in which grain size increases from 10 to 100 μm at the most trenchward part of the creeping region to a few centimeters in the subarc mantle. Despite the large variation in grain size, its effect on the mantle rheology and flow is very small, as >90% of the deformation in the flowing part of the creeping region is accommodated by grain-size-independent dislocation creep. The predicted grain-size distribution leads to a downdip increase in permeability by ∼5 orders of magnitude. This increase is likely to promote greater upward migration of aqueous fluids and melts where the slab reaches ∼100 km depth compared with shallower depths, potentially providing an explanation for the relatively uniform subarc slab depth. Seismic attenuation derived from the predicted grain-size distribution and thermal field is consistent with the observed seismic structure in the mantle wedge at many subduction zones, without requiring a significant contribution by the presence of melt. en_US
dc.description.sponsorship Funding for this research was provided by the National Science Foundation through a MARGINS Postdoctoral Fellowship (NSF OCE‐0840800) and NSF grant EAR‐0854673. en_US
dc.format.mimetype application/pdf
dc.language.iso en_US en_US
dc.publisher American Geophysical Union en_US
dc.relation.uri http://dx.doi.org/10.1029/2011JB008294
dc.subject Grain-scale permeability en_US
dc.subject Mantle wedge flow en_US
dc.subject Mineral grain size en_US
dc.subject Seismic attenuation en_US
dc.subject Subduction zone thermal structure en_US
dc.title Grain-size distribution in the mantle wedge of subduction zones en_US
dc.type Article en_US
dc.identifier.doi 10.1029/2011JB008294


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