Saline aqueous fluid circulation in mantle wedge inferred from olivine wetting properties.

ABSTRACT: Recently, high electrical conductors have been detected beneath some fore-arcs and are believed to store voluminous slab-derived fluids. This implies that the for-arc mantle wedge is permeable for aqueous fluids. Here, we precisely determine the dihedral (wetting) angle in an olivine-NaCl-H₂O system at fore-arc mantle conditions to assess the effect of salinity of subduction-zone fluids on the fluid connectivity. We find that NaCl significantly decreases the dihedral angle to below 60° in all investigated conditions at concentrations above 5?wt% and, importantly, even at 1?wt% at 2?GPa. Our results show that slab-released fluid forms an interconnected network at relatively shallow depths of ~80?km and can partly reach the fore-arc crust without causing wet-melting and serpentinization of the mantle. Fluid transport through this permeable window of mantle wedge accounts for the location of the high electrical conductivity anomalies detected in fore-arc regions.

SUBMITTER: Huang Y 

PROVIDER: S-EPMC6895192 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature