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The skarn alteration is poorly preserved at the Elatsite, restricted to the hornfelses from the East, Southeast and Southern part of the deposit. The rocks are defined as exoskarns, with a mineral composition including garnets, epidote, pyroxene, amphiboles, carbonates, prehnite, quartz, sulphides. The newly formed minerals occur in poorly preserved layers. The garnet grains are subhedral with inclusions of epidote and quartz, while some of them are corrode with carbonate and zeolites formed in the fractures. The garnets are grossular-andradite type, with higher values for HREE over LREE, and low values for Rb, Sr, Ba, Pb and U. The skarn formation is related with the intrusion of the magma which causes the heating of the metamorphic rocks (rich in carbonate material -- chlorite-sericite-carbonite, sericite-carbonate schists, etc.) from the low-grade metamorphic rocks. The Fe+3--Al+3 exchanges in the cores of the garnets indicate their formation from fluids with high oxygen fugacity. [ABSTRACT FROM AUTHOR]

The short lasting compressional to transpressional tectonic event between the latest Oligocene and Middle Miocene is an important element of the Late Alpine evolution of the Balkan peninsula and the Aegean area. It is well recorded by the termination of the sedimentation in a relatively short period of 6-7 Ma (between 20.5 Ma and ~13 Ma). This crustal shortening represents a stage of the Late Alpine tectonic evolution of the area separating the late Paleogene extensional regime from the Aegean extension that took place from ~13 Ma on and finally shaped this branch of the orogen. [ABSTRACT FROM AUTHOR]

The crustal thickness in the area of the Rhodope Metamorphic Complex decreases from west to east from ~50 km to ~30 km. This regional-scale feature is mostly due to the different rates of extension that the basement rocks experienced in different parts of the complex. In our model, we postulate that the crustal thickness in the area is an effect of the late Eocene zipper-like or hinge-like extensional tectonics that caused a larger amount exhumation of high-grade metamorphic rocks in the eastern parts of the area and lesser one in the west. This zipper-like orogen parallel extension caused a vast tectonic erosion and progressive thinning of the crust from west to east. [ABSTRACT FROM AUTHOR]

The Rhodope Metamorphic Complex (RMC) in Bulgaria has been established as a Mesozoic ultra‐high‐pressure metamorphic province by findings of microdiamond in gneisses. Additionally, Variscan ultra‐high‐pressure metamorphism has been proposed for the Ograzhden/Vertiskos Unit in the Upper Allochthon of the RMC, based on findings of coesite, graphite pseudomorphs after diamond and indirect age constraints. We confirm ultra‐high‐pressure metamorphism of eclogites in this unit using thermobarometry, phase‐equilibrium modelling and the Variscan age of metamorphism using Lu–Hf garnet–whole‐rock dating. In Belica (southern Rila Mountains), kyanite‐ and phengite‐bearing eclogite enclosed in high‐grade gneisses records P‐T conditions of 3.0–3.5 GPa and 700–750°C. Lu–Hf dating of eclogite samples from Belica and Gega (Ograzhden Mountain), where coesite was found, yielded ages of 334.1 ± 1.8 and 334.0 ± 2.2 Ma, respectively, interpreted as the age of garnet growth during post‐collisional subduction of continental crust after closure of the Rheic Ocean. [ABSTRACT FROM AUTHOR]

The Rhodope Metamorphic Province in the area around the Mesta Graben (SW Bulgaria) exposes a structurally lower complex, the Pangaion-Pirin Complex of Variscan continental crust and its cover (mostly orthogneiss and marble), and a higher complex, the Rhodope Terrane of mixed oceanic and continental origin with metamorphosed Jurassic arc magmatites. The boundary between the two is the top-to-the-southwest Nestos Shear Zone. The regional top-to-the-southwest shearing of the two basement complexes is related to the emplacement of the Rhodope Terrane over the Pangaion-Pirin Complex along this shear zone. Syntectonic and posttectonic Alpine intrusions within the basement can provide age limits for the thrusting. Zircons from the posttectonic Teshovo (south Pirin) Granitoid Pluton in the Pangaion-Pirin Complex yielded crystallization ages of 32 [+ or -] 0.2 Ma (LA-SFICP-MS U-Pb method). Zircons from two syntectonic granite plutons in the Rhodope Terrane (Dolno Dryanovo and Spanchevo) have circa 143 to 145 Ma old inherited magmatic cores and circa 55 to 56 Ma old magmatic rims. These ages, especially the presence of the Upper Jurassic/Lower Cretaceous cores in the plutons from the Rhodope Terrane, and the structural relations indicate that the southwestward thrusting of the Rhodope Terrane over the Pangaion-Pirin Complex took place in the Paleogene. A model is proposed in which the Pangaion-Pirin Complex represents the margin of Apulia and the structure of the Rhodopes is explained by a switch of subduction polarity from SW dipping in the Jurassic and Early Cretaceous to NE dipping in the Late Cretaceous and Paleogene. Citation: Jahn-Awe, S., N. Froitzheim, T. J. Nagel, D. Frei, N. Georgiev, and J. Pleuger (2010), Structural and geochronological evidence for Paleogene thrusting in the western Rhodopes, SW Bulgaria: Elements for a new tectonic model of the Rhodope Metamorphic Province, Tectonics, 29, TC3008, doi: 10.1029/2009TC002558.