Multiple generations of extensional detachments in the Rhodope Mountains (northern Greece): evidence of episodic exhumation of high-pressure rocks

Abstract

AbstractAn integrated structural and petrological study shows that exhumation of high-P rocks of the Rhodope occurred in several pulses. The structurally uppermost Kimi Complex recording an Early Cretaceous high-P metamorphism was exhumed between about 65 and >42 Ma. The Sidironero, Kardamos and Kechros Complexes that record Early Tertiary high-P metamorphism (at least 19 kbar at 700 °C) were exhumed at >42–30 Ma. Exhumation occurred with isothermal decompression. Strain episodes depict thrusting of medium/high grade above lower grade high-P rocks, syn-thrusting extension and post-thrusting extension. Polyphase extension created several generations of detachment zones, which, in sum, excise about 20 km of material within the crustal profile. This reduction in crustal thickness is consistent with a reduction of the present crustal thickness from more than 40 km to less than 30 km in the eastern Rhodope. We mapped the post-thrusting Xanthi low-angle detachment system over 100 km, from its break up zone above the Sidironero Complex (Central Rhodope) into the eastern Rhodope. This detachment shows an overall ESE-dip with a ramp and flat geometry cutting across the earlier thrust structures. The Kimi Complex is the hanging wall of all syn- and post-thrusting extensional systems. On top of the Kimi Complex, marine basins were formed from the Lutetian (c. 48–43 Ma) through the Oligocene, during extension. Successively, at c. 26 to 8 Ma, the Thasos/Pangeon metamorphic core complexes were exhumed. In these times representing the early stages of Aegean back-arc extension, the Strymon and Thasos detachment systems caused crustal thinning in the western Rhodope. Renewed heating of the lithosphere associated with magmatism and exhumation of hot middle crust from beneath the Sidironero Complex occurred. We focus on the geometry, timing and kinematics of extension and contraction structures related to the >42–30 Ma interval and how these exhumed high-P rocks. We interpret high-P rocks exhumed in this interval as a window of the Apulian plate beneath the earlier (in the Cretaceous) accreted Kimi Complex.