Mylonitic gneisses of the Bulgarian and Greek Rhodope were deformed under medium pressure‐type metamorphism. The kinematic information contained in these gneisses shows that shear‐deformation occurred during development of a nappe complex. Lithologies and metamorphic histories allow a lower (footwall) and an upper (hanging wall) terrane to be distinguished that define a crustal‐scale duplex. As oceanic crust is involved, collision between two continental units with subsequent crustal thickening is inferred. The blocks would be Moesia to the north, and the Lower‐Rhodope promontory to the south, which collided in the Mesozoic to early Cenozoic. The nappe complex is characterized by south to southwestward (foreland directed) piling‐up and is associated with both coeval and subsequent extension. The late extension is associated with the establishment of a high temperature‐low pressure metamorphic gradient and plutonism that predates, but makes a transition to, the lithospheric extension of the Aegean Arc.
Several plutons located in the southwestern part of the Sredna Gora Zone -Bulgaria are examples of the Apuseni-Banat-Timok-Sredna Gora type of granites emplaced during Late Cretaceous (86-75 Ma) times. The studied intrusive bodies are spatially related to and deformed by the dextral Iskar-Yavoritsa shear zone. The deformation along the shear zone ceased at the time of emplacement of the undeformed Upper Cretaceous Gutsal pluton, which has intruded the Iskar-Yavoritsa mylonites. A clear transition from magmatic foliation to high-, moderate-and low-temperature superimposed foliation and lineation in the vicinity of the Iskar-Yavoritsa and related shear zones gives evidence for simultaneous tectonics and plutonism. Away from the shear zones, the granitoids appear macroscopically isotropic and were investigated using measurements of anisotropy of magnetic susceptibility at 113 stations. The studied samples show magnetic lineation and foliation, in agreement with the magmatic structures observed at a few sites. Typical features of the internal structure of the plutons are several sheet-like mafic bodies accompanied by swarms of mafic microgranular enclaves. Field observations indicate spatial relationships between mafic bodies and shear zones as well as mingling processes in the magma chamber which suggest simultaneous shearing and magma emplacement. Structural investigations as well as anisotropy of magnetic susceptibility (AMS) data attest to the controlling role of the NW-SE trending Iskar-Yavoritsa shear zone and to the syntectonic emplacement of the plutons with deformation in both igneous rocks and their hosts. The tectonic situation may be explained by partitioning of oblique plate convergence into plate-boundary-normal thrusting in the Rhodopes and plate-boundary-parallel transcurrent shearing in the hinterland (Sredna Gora).
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