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Greece; exhumation; high-pressure; metamorphism; tectonic wedges; extension
Abstract:
Low-angle normal faults (detachments) are only efficient agents for bringing rocks from 40->100 km depth back to the Earth's surface if they operate with extreme slip rates exceeding 20 km Ma(-1). Here we propose a slip rate of greater than or equal to 20-30 km Ma(-1) for the Cretan detachment in the Aegean, Greece. The Cretan detachment and the subjacent subduction thrust bounded an extruding wedge above the Miocene Hellenic subduction zone. During exhumation the high-pressure rocks in the wedge were not significantly deformed. Very low shear coupling at the bounding faults (which are therefore weak) is needed to prevent significant deformation in the extruding wedge. The proposed slip rate of greater than or equal to20-30 km Ma(-1) is similar to the subduction rate of 35-45 km Ma(-1) at the Hellenic subduction zone. We argue that extruding wedges can only slip at rates similar to subduction rates if there is very low shear coupling at the bounding faults, which may also explain the paradox of almost non-deformed but very rapidly exhumed rocks.
