Abstract

We constrain the slip and cooling history of the Mykonos detachment footwall using thermochronometry. A U–Pb zircon age of 13.5 ± 0.3 Ma dates intrusion of the Mykonos monzogranite. ⁴⁰Ar/³⁹Ar hornblende and biotite ages from the monzogranite are 12.7 ± 0.6 Ma and 10.9 ± 0.6 Ma, whereas zircon and apatite fission-track ages range from 13 ± 0.8 Ma to 10.7 ± 0.8 Ma and 12.5 ± 2.2 Ma to 10.5 ± 1.8 Ma. (U–Th)/He ages range from 13.6 ± 0.6 Ma to 9.0 ± 0.7 Ma for zircon and 11.1 ± 0.5 Ma to 8.9 ± 0.4 Ma for apatite. The ages in part overlap within 2σ errors and together with the long apatite fission-track lengths (>14 μm) support rapid cooling at rates >100 °C Ma⁻¹. The low-temperature thermochronometric ages decrease east-northeastwards in the direction of hanging-wall transport on the Mykonos detachment. Age–distance relationships show that the Mykonos detachment slipped at an average rate of 6.0 +9.2/−2.4 km Ma⁻¹ causing c. 30 km of offset and c. 12 km of exhumation. This result indicates that Miocene low-angle normal faulting was not important for the exhumation of the Cycladic blueschist unit. The opening of the Aegean Sea basin in the Miocene was controlled by a few large-magnitude low-angle normal faults.