Interrelations between intermediate-depth earthquakes and fluid flow within subducting oceanic plates: Constraints from eclogite facies pseudotachylytes

Field evidence preserved in ancient subducted oceanic crust documents that eclogite facies frictional failure with melting (pseudotachylyte formation during intermediate-depth earthquakes) was accompanied and followed, not preceded, by infiltration of external fluids and progressive vein formation in the eclogites. Eclogitization began during seismic failure and fluid passage through the shear zone. Subsequent fluid flow produced hydraulic fracturing and continuous vein formation during ongoing burial. We suggest that this kind of shear zone may allow channellized fluid flow within and out of slabs.