Fluid migration in the mantle wedge: Influence of mineral grain size and mantle compaction

Mineral grain size in the mantle affects fluid migration by controlling mantle permeability; the smaller the grain size, the less permeable the mantle is. Mantle shear viscosity also affects fluid migration by controlling compaction pressure; high mantle shear viscosity can act as a barrier to fluid flow. Here we investigate for the first time their combined effects on fluid migration in the mantle wedge of subduction zones over ranges of subduction parameters and patterns of fluid influx using a 2‐D numerical fluid migration model. Our results show that fluids introduced into the mantle wedge beneath the forearc are first dragged downdip by the mantle flow due to small grain size (