THERMOCHRONOLOGY OF THE HIGH-PRESSURE METAMORPHIC ROCKS OF CRETE, GREECE - IMPLICATIONS FOR THE SPEED OF TECTONIC PROCESSES

New fission-track thermochronologic data from the high-pressure (P)-lo w-tenaperature (T) rocks of Crete, Greece, combined with pressure, tem perature, and stratigraphic constraints reveal that their subduction b egan between 36 and 29 Ma. Metamorphism took place in western Crete at peak conditions of 10 +/- 2 kbar and 400 +/- 50 degrees C between 24 and 19 Ma, and rapid exhumation to <10 km and <300 degrees C at a mini mum rate of 4 km/m.y. was completed before 19 Ma, Constraints from the thermal history of the plate above the inferred extensional detachmen t reveal that tectonic unroofing contributed 85% to 90% of the overall exhumation of the high-P-low-T rocks of Crete. We propose that the He llenic subduction zone has acted as a retreating plate boundary since at least the early Oligocene, and collision and extension during this time were driven by roll-back associated with slab-pull rather than by gravitational collapse as a consequence of crustal thickening. The sp eed of subduction and exhumation of the high-P-low-T rocks of Crete wi thin similar to 10 m.y. has important implications for other orogenic belts, showing that rocks can be subducted, metamorphosed at high pres sure, and exhumed, despite slow overall plate convergence, within the uncertainties of many paleontologic and isotopic age data.