In the Aegean back-arc domain, some 30–35 Ma ago, an increase of the rate of slab retreat led to the initiation of post-orogenic extension, largely accommodated by large-scale structures such as the North Cycladic Detachment System (NCDS). Although this extension is still active nowadays, an E–W compressional regime developed in the Late Miocene with the propagation of the North Anatolian Fault. On Mykonos island (Cyclades), the NE–SW back-arc extension is particularly well expressed with the Livada and Mykonos detachments that belong to the NCDS and that are associated with NW–SE barite veins emplaced during the synkinematic cooling of the Mykonos intrusion. This study shows that the formation of the mineralization occurred when the pluton crossed the ductile-to-brittle transition during its exhumation below the NCDS at ~11–10 Ma. In addition, the kinematics of mineralized structures evolved with time: (1) most of the displacement was accommodated by the top-to-the-NE Livada and Mykonos detachments accompanied by the formation of mineralized normal faults that were (2) reworked in a strike-slip regime with an E–W direction of shortening and a persistent NE–SW stretching and (3) a late post-mineralization E–W compressional stage with a minor reworking of shallow-dipping faults (locally including the detachments themselves). We interpret this increase of the E–W shortening component recorded during the mineral deposition as a consequence of the initiation of the westward motion of Anatolia from 10 Ma, thus 4 Ma before the propagation of the North Anatolian Fault in the Dardanelles Strait and the localization of the strain on the Aegean Sea margins.