Middle-Late Alpine thermotectonic evolution of the southern Rhodope Massif, Greece

The transition from the Alpine tectonic assembly to the exhumation of the u nits in the Rhodope metamorphic province in northernmost Greece has been re fined by Ar-40/Ar-39 laserprobe mica analyses. Preservation of pre-Alpine ( similar to 280 Ma and 145 Ma) muscovite cooling ages at the western margin of the Rhodope indicate that subsequent events failed to reset the argon sy stem thermally in white mice in the outcropping basement of this region. Th e central and eastern Rhodope are characterized by white mica cooling ages of 40-35 Ma with ages gradually decreasing to ca. 15 Ma near the eastern ma rgin of the Strymon Valley. The Eo-Oligocene ages reflect the regional exhu mation of the metamorphosed units to shallow crustal levels, with correspon ding temperatures below ca. 350 DC, by 40-35 Ma. The younger cooling ages a re attributed to the initiation and subsequent operation of the Strymon-Tha sos detachment system since ca. 30 Ma. This study provides a crucial contri bution to future regional tectonic models for the Rhodope region as it reco gnizes an early stage of development of the Strymon-Thasos detachment syste m, and has constrained the regional exhumation of the Rhodope metamorphic p rovince since 40 Ma indicating that the regionally observed amphibolite fac ies metamorphism had terminated by this time. (C) 2000 Editions scientifiqu es et medicales Elsevier SAS.