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

Model studies of continental collision tectonics and pressure-temperat ure-time (P-T-t) predictions quantitatively demonstrate the key role o f synsubduction uplift in the preservation of blueschist- and eclogite -facies metamorphic rocks. Rheological stratification of the subductin g lithosphere allows development of detachment faults at the compositi onal boundary between the upper and lower crust. Material of supracrus tal 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 ha nging walls and footwalls. Two-dimensional thermal calculations indica te that the nearby active subduction provides the cooling mechanism re quired to preserve blueschists and eclogites, whereas the differential motions of the independently uplifted domains can explain the observe d heterogeneity in P-T-t pathways, with some domains displaying a gree nschist overprint.