PRESSURE-TEMPERATURE-TIME EVOLUTION OF THE HIGH-PRESSURE METAMORPHIC COMPLEX OF SIFNOS, GREECE

Model studies of continental collision tectonics and pressure-temperature-time (P-T-t) predictions quantitatively demonstrate the key role of synsubduction uplift in the preservation of blueschist- and eclogite-facies metamorphic rocks. Rheological stratification of the subducting lithosphere allows development of detachment faults at the compositional boundary between the upper and lower crust. Material of supracrustal continental affinity is subducted to depths in excess of 50 km and then delaminated from the downgoing slab. Subduction continues while the detached domain is uplifted independently from the newly active hanging walls and footwalls. Two-dimensional thermal calculations indicate that the nearby active subduction provides the cooling mechanism required to preserve blueschists and eclogites, whereas the differential motions of the independently uplifted domains can explain the observed heterogeneity in P-T-t pathways, with some domains displaying a greenschist overprint.