Subduction zones are characterized by significant geological activities including arc volcanism and earthquakes. At subduction zone settings, hydrated crusts are subducted into the mantle. This releases fluids and rehydrates mantle wedges. It also provides an additional source of aqueous fluid above the slab causing melting and eventually arc volcanism. Often, mantle wedge regions are characterized by anomalously high electrical conductivity signals. Geophysicists have been invoking aqueous fluids with enhanced salinity to explain such observations.