Thermochronometric constraints on the tectonic evolution of the Serifos detachment, Aegean Sea, Greece

We constrain the timing and kinematics of the Serifos detachment in the southwestern Cyclades, Greece, using low-temperature thermochronometry. Fission-track dating shows that the Serifos detachment was active between similar to 13 and 6 Ma and that the Serifos granodiorite in its footwall intruded at or before similar to 12-11 Ma into the extensional shear zone and initially cooled very rapidly at rates > 180A degrees C per million year. The mylonite zone at the top of the granodiorite and mylonitic structures in its country rocks record a consistent top-SSW shear sense in the ductile crust. In the brittle regime top-NNE shear-sense indicators occur as well. Conjugate top-SSW and top-NNE high-angle normal faults are the youngest deformational features and cut across the detachment. Age-distance relationships for the fission-track data display a relatively flat pattern. We discuss a model advocating initial top-SSW movement on the Serifos detachment before and during emplacement of the granodiorite. Updoming of the detachment during exhumation and cooling caused subsequent bivergent extension in the brittle crust.