Filippo Schenker

From Mesoproterozoic magmatism to collisional Cretaceous anatexis: Tectonomagmatic history of the Pelagonian Zone, Greece

The magmatic history of the Pelagonian Zone, in northern Greece, is constrained with secondary ion mass spectrometer (SIMS) U-Pb dating on zircons of various granitoids whose structural positions were defined with respect to the regional main foliation. Ages pertain to four groups: (i) Mesoproterozoic (circa 1430u2009Ma) crystallization of granites inferred from inherited magmatic zircon cores that have been partially molten during the (ii) Neoproterozoic at circa 685u2009Ma (metamorphic zircon rims) and subsequently intruded by a Neoproterozoic leucogranite (circa 600u2009Ma). (iii) Late- or post-Variscan calc-alkaline granitoids (315–301u2009Ma) were in turn intruded by a subvolcanic dike at about 280u2009Ma. In the Early Permian the eNd(t) in magmas decreased from −7.3 to −1.3, hinting to mantle-derived melts produced during extension. Rifting is further heralded by two acidic and one mafic dike containing Lower-Middle Triassic zircons (246–242u2009Ma). (iv) Early Cretaceous anatectic melts at 117u2009±u20098u2009Ma formed during regional metamorphism. This age is the first report of in situ anatexis in the Pelagonian Zone. Cretaceous anatexis developed during the Mesozoic collision of Pelagonia with the Eurasian margin. Major- and trace-element geochemistry of amphibolites further attests for the complex pre-Alpine tectonic history with Neoproterozoic calc-alkaline and back-arc geochemical signature and Triassic alkali-magmatism.

Metamorphic conditions and structural evolution of the Kesebir-Kardamos dome: Rhodope metamorphic complex (Greece-Bulgaria)

The synmetamorphic nappe system of the Rhodope Metamorphic Complex has been deformed into dome-and-basin structures attributed to syn- to post-convergent exhumation. We document the deformation style and present new thermobarometric and geochronological constraints for the Kesebir–Kardamos dome in southern Bulgaria and northern Greece. The dome consists of a migmatitic core overlain by high-grade thrust sheets. Kinematic indicators indicate a continuum from ductile to brittle conditions during exhumation. Thermodynamic modeling applied to the high-grade, intermediate thrust sheets yielded peak conditions of 1.2xa0GPa and ca 730u2009°C. New U–Pb SHRIMP-II dating of zircons from rocks of the same unit revealed Late Jurassic–Early Cretaceous (145xa0Ma) as the time of metamorphic crystallization; some zircon rims yielded Eocene ages (53 and 44xa0Ma) interpreted as having been thermally reset owing to coeval granitoid magmatism. The high-grade rocks were covered by Lutetian–Priabonian marine sediments after exhumation. Slumps suggest that sedimentation took place in a tectonically active environment. Our new structural, petrological and geochronological results suggest that the major shear zone in the core of the Kesebir-Kardamos dome is equivalent to the Late Jurassic–Early Cretaceous Nestos Shear Zone. Post-Jurassic metamorphic ages recorded in the Rhodope most likely represent crustal rather than deep subduction geodynamic processes.