Focusing of upward fluid migration beneath volcanic arcs: Effect of mineral grain size variation in the mantle wedge

Ikuko Wada, Mark D. Behn

    Research output: Contribution to journalArticlepeer-review

    22 Citations (Scopus)


    We use numerical models to investigate the effects of mineral grain size variation on fluid migration in the mantle wedge at subduction zones and on the location of the volcanic arc. Previous coupled thermal-grain size evolution (T-GSE) models predict small grain size (<1 mm) in the corner flow of the mantle wedge, a downdip grain size increase by ∼2 orders of magnitude along the base of the mantle wedge, and finer grain size in the mantle wedge for colder-slab subduction zones. We integrate these T-GSE modeling results with a fluid migration model, in which permeability depends on grain size, and fluid flow through a moving mantle matrix is driven by fluid buoyancy and dynamic pressure gradients induced by mantle flow. Our modeling results indicate that fluids introduced along the base of the mantle wedge beneath the fore arc are initially dragged downdip by corner flow due to the small grain size and low permeability immediately above the slab. As grain size increases with depth, permeability increases, resulting in upward fluid migration. Fluids released beneath the arc and the back arc are also initially dragged downdip, but typically are not transported as far laterally before they begin to travel upward. As the fluids rise through the back-arc mantle wedge, they become deflected toward the trench due to the effect of mantle inflow. The combination of downdip migration in the fore arc and trench-ward migration in the back arc results in pathways that focus fluids beneath the arc.

    Original languageEnglish
    Pages (from-to)3905-3923
    Number of pages19
    JournalGeochemistry, Geophysics, Geosystems
    Issue number11
    Publication statusPublished - 2015 Nov 1


    • fluid migration
    • grain size variation
    • mantle wedge
    • subduction zone
    • volcanic arc

    ASJC Scopus subject areas

    • Geophysics
    • Geochemistry and Petrology


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