Permeability of subducted oceanic crust revealed by eclogite-facies vugs

Abstract We report the finding of rare eclogite-facies vugs forming millimeter- to centimeter-sized pockets in meta-ophiolites from western European Alps. Euhedral garnet crystals covering vug walls display oscillatory chemical zoning for a wide range major and trace elements, including Cr, Mn, earth elements. Thermodynamic modeling revealed that closed-system fluid production through breakdown prograde glaucophane, lawsonite, chlorite between 505 °C 525 can successfully explain porosity creation ~4% mineralogical properties vugs. Available geologic geochronologic constraints indicate eclogitization downgoing mafic crust spanned window at least 1 m.y. These observations only be explained by presence extremely low permeability values (<10−22 m2) keep confined meter scale within on such time scales. Our field-based eclogite provides first situ confirmation previous experimental data geophysical estimates active margins. A substantial amount trapped this may carried deeper than expected into Earth's mantle, with implications volatile recycling budgets.