Tectonometamorphic evolution of the Rhodope orogen

Abstract

This study combines new data on tectonostratigraphy, macrostructures and microstructures, petrology, and geochronology to propose a comprehensive model for the tectonometamorphic evolution of the Rhodope orogen from the Jurassic to the early Paleogene. Rocks from two study areas in the central and eastern Greek Rhodope represent a continental suture zone (Rhodope Suture Zone), with the included material most likely forming an extensional allochthon south of the European continent during Permo/Triassic times that was subsequently subducted beneath Europe in the Early Jurassic (≥180 Ma). On the basis of comparable metamorphic ages and coherent structures but differences in metamorphic conditions and lithologies, the rocks of the Rhodope Suture Zone are subdivided into an upper and a lower part. The prograde history is linked with subduction‐related structures in the lower part (uniaxial stretching, deformation stage D1). In metapelites, the earliest stage of metamorphism recorded at circa 180 Ma occurred at least under ultrahigh‐pressure metamorphic conditions. The rocks of the upper part experienced isothermal decompression with partial anatexis. Exhumation paths of both parts differ in temperature because of the relative tectonic position within the exhuming wedge. Exhumation was forced by the Nestos Shear Zone that controlled the early phase of normal displacement by SW shearing at the base (lower part) and NE shearing on top (upper part) from the Late Jurassic to the Late Cretaceous (deformation stage D2). An intervening stage of mineral recrystallization and thermal reequilibration in the upper part was followed by a common exhumation history of both parts at pressures lower than about 12 kbar (35–40 km depth). During this stage, exhumation was controlled by southwest directed shearing and folding (deformation stage D3). Slab retreat to the south led to subsequent extension (deformation stage D4) and final exhumation coeval with the formation of basement domes, thus making the Rhodope a classic core complex juxtaposed with former structurally higher units.

Polycyclic alpine orogeny in the Rhodope metamorphic complex: the record in migmatites from the Nestos shear zone (N. Greece)

“…17). Consequently, the picture of the NSZ representing a Mesozoic or Mesozoic-Paleocene thrust (Ricou et al, 1998;Papanikolaou and Kranis, 2004;Krenn et al, 2010;Burg, 2011;Schenker et al, 2014;Brun et al, 2016) must be abandoned, an inference also supported by the complete lack of Mesozoic-Paleocene ages in the geochronological record of the PU and the UPU.…”

“…These pegmatites also contain inherited zircon grains with features documenting their growth during medium-to high-grade metamorphism and UPb ages between ∼120 and ∼160 Ma (Bosse et al, 2009). The garnet-kyanite metapelites of the Xanthi section have yielded one U-Pb zircon age of 149 ± 2 Ma, interpreted as dating conditions close to the peak of UHP metamorphism (Liati, 2005), and another U-Pb zircon age of 144 ± 2 Ma, interpreted as dating post-UHP high-temperature metamorphism (Krenn et al, 2010). Two samples of garnet-kyanite micaschist from the mélange south of Sidironero have yielded U-Th-Pb monazite ages spread between ∼120 and ∼170 Ma and a mean age of 142 ± 11 Ma interpreted as dating upper amphibolitegranulite facies conditions (Didier et al, 2014).…”

“…As for the age of the shear zone, the inference that is was active during the Eocene (Barr et al, 1999) and as late as 37 Ma (Dinter, 1998;Krohe and Mposkos, 2002) relies mainly on a set of K-Ar hornblende ages between 37 and 47 Ma (Liati, 1986). Many authors implicitly consider that these K-Ar data yield only a minimum possible age of shearing, so that the NSZ can be accepted as a major SW-vergent thrust of much older age (Mesozoic or Mesozoic-Paleocene; Ricou et al, 1998;Papanikolaou and Kranis, 2004;Krenn et al, 2010;Burg, 2011;Schenker et al, 2014;Kydonakis et al, 2016;Brun et al, 2016). With regard to the age and tectonic significance of the NSZ, three studies should be considered more closely.…”

“…Since the late 1990s, numerous scenarios have been proposed for the tectonic evolution of the RMC during Alpine times. A primary difference between these scenarios is whether there has been a single protracted orogenic cycle since around the midMesozoic (Ricou et al, 1998;Barr et al, 1999;Papanikolaou and Kranis, 2004;Turpaud and Reischmann, 2010;Krenn et al, 2010;Burg, 2011;Kydonakis et al, 2016) or whether Alpine orogeny involved distinct episodes of subduction and crustal accretion (Liati, 2005;Mposkos et al, 2010;Liati et al, 2011Liati et al, , 2016Nagel et al, 2011;Kirchenbaur et al, 2012;Froitzheim et al, 2014;Wawrzenitz et al, 2015). The difference between the two views mainly stems from different interpretations of the available geochronological data (e.g., Burg, 2011;Liati et al, 2011).…”

Tourmalinite Veins and Breccias From the Symvolon-Kavala Pluton, Northern Greece: Petrogenetic Preliminary Results

“…The Rhodope Metamorphic Province (RMP) is a polymetamorphic geological complex located in northeast Greece to southwest Bulgaria, in the hinterland of the Hellenic Subduction System (Burg et al, 1990;Bonev et al, 2006;Krenn et al, 2010;Jahn-Awe et al, 2010;Nagel et al, 2011). RMP consists of three allochthon tectonic units (Lower, Middle and Upper) and is bordered by Servomacedonian Massif in the west and Circum-Rhodope Belt in the east (e.g.…”