The Vardar zone as a suture for the Mirdita ophiolites, Albania: Constraints from the structural analysis of the Korabi-Pelagonia zone

Abstract

The Dinarides-Hellenides result from underthrusting of the Adriatic margin during Africa-Europe convergence. In Albania, they consist of (1) a western zone of nappes derived from Adria; (2) a central belt made up of the Mirdita ophiolites; and (3) an eastern zone, the Korabi-Pelagonia zone, of Variscan basement overlain by Permian to Mesozoic rift deposits and carbonates. Some authors interpret the Korabi-Pelagonia zone as a microcontinent between the Mirdita-Pindos oceanic basin to the west and the eastern Vardar oceanic basin to the east; other regard the Korabi-Pelagonia zone as a tectonic window below a single ophiolitic nappe. This contribution argues for a far-traveled thrust sheet. The Mirdita ophiolites are 165-160 Ma. The metamorphic sole yielded 40 Ar/ 39 Ar ages of 171 to 162 Ma. The Korabi-Pelagonia zone is subdivided into the Korabi and Gjegjan subzones. The structural analysis of these rocks supports the rooting of the Mirdita ophiolites in the Western Vardar zone. The post-Variscan cover sequence of the Korabi subzone records two phases of deformation: D 1 is associated with a SE dipping to flat-lying schistosity axial planar to NW verging folds and thrust faults, related to ophiolite obduction; D 2 is a postobduction NNE trending crenulation cleavage. Published zircon fission track analyses yielded 150-125 Ma, suggesting that regional metamorphism is Early Cretaceous or older. K-Ar mica ages from correlative rocks of Macedonia cluster between 148 and 130 Ma, indicating that D 1 is Late Jurassic. A west directed obduction is favored, as is a rooting east of the Mirdita ophiolites because of the top-to-the-west structural polarity of obduction-related deformation.

Tectono‐magmatic and Stratigraphic Evolution of the Cycladic Basement, Ios Island, Greece

“…The sedimentary protolith of the CBU was deposited in the Pindos Basin (e.g., Aubuin, 1959;Bonneau, 1984;Papanikolaou, 1987), starting in the earliest Mesozoic until subduction in the Paleocene-Eocene~60-40 Ma (Jolivet & Brun, 2010;Ring et al, 2010;Seman et al, 2017). However, the exact tectonic setting for the deposition of CBU protoliths remains contentious and centers around the nature of the Pindos Basin (e.g., Bortolotti et al, 2009;Menant, Jolivet, & Vrielynck, 2016;Papanikolaou, 2009Papanikolaou, , 2013Stampfli et al, 2003;Tremblay et al, 2015;van Hinsbergen, Hafkenscheid, et al, 2005;van Hinsbergen, Zachariasse, et al, 2005;van Hinsbergen & Schmid, 2012). The ages of intercalated volcanic rocks and DZ studies in the western and northern Cyclades demonstrated that CBU deposition spanned from Triassic to Paleogene Henjes-Kunst & Kreuzer, 1982;Hinsken et al, 2016;Keay, 1998;Löwen et al, 2015;Seman et al, 2017) and was likely initially accumulated along a rifted continental margin (Seman et al, 2017).…”

Zircon in amphibolites from Naxos, Aegean Sea, Greece: origin, significance and tectonic setting

“…The Pelagonian was also overthrust by Jurassic ophiolites of the Vardar-_ Izmir-Ankara zone in the early Cretaceous (e.g. Tremblay et al, 2015). The Cycladic zone consists of continental fragments of the Adriatic plate and can be further subdivided into three tectonic units (Ring et al, 1999), which are from top to bottom: (i) the non-to weakly metamorphosed ophiolitic Upper unit, (ii) the high-P rocks of the CBU, which is subdivided into three separate members: (a) an ophiolitic m elange, (b) a Permo-Carboniferous to uppermost Cretaceous passive-margin sequence and (c) a Carboniferous basement nappe, which also occurs as slices in the passive-margin sequence.…”

“…The different zones represent, at least in part, distinct palaeogeographic entities that formed during Triassic rifting and Jurassic drifting within Tethys (Robertson, 2002;Tremblay et al, 2015) and created ribbon-like zones of thinned continental and oceanic crust with intervening ridges on which carbonate platforms developed in the Mesozoic. Reischmann (1998) provided evidence for a period of mid-Triassic granitic magmatism prior to late-Triassic to Jurassic ocean formation.…”

The Age, Origin, and Emplacement of the Tsiknias Ophiolite, Tinos, Greece

“…They either formed in a back‐arc basin setting (e.g., Guevgeili Ophiolite), above a NE dipping subduction zone between the Paikon Arc and the Eurasian Margin (Ricou & Godfriaux, ; Robertson, ) or above a westward dipping subduction zone at ~160 Ma, responsible for SSZ signatures and eastward emplacement of ophiolites onto the Eurasian Margin (Maffione & van Hinsbergen, and references therein). The latter suggestion is the most likely, as continued westward dipping subduction on the eastern side of the Vardar Ocean resulted in high‐pressure metamorphism as the Eurasian Margin attempted to subduct at ~150 Ma (Tremblay et al, ). Despite the Jurassic‐aged deformation, it remains debated when the Eastern Vardar Ophiolites were emplaced either onto the Eurasian margin and whether they were emplaced onto the Adriatic–Apulian (Pelagonian) margin, associated with the closure of the Vardar Ocean as there are no identified metamorphic soles.…”

“…The location of the MOR ophiolites derived from the Vardar Ocean is shown in stage (a), while these plus the SSZ and BAB ophiolites produced after subduction initiation are shown in stage (b). (c) Approximately 150 Ma, obduction of the West Vardar Ophioites onto Adria‐Apulia and eastward obduction of East Vardar Ophiolites on to Eurasia, subsequent HP metamorphism of Eurasian margin (Tremblay et al, ). Position of Tsiknias to the SE of the East Vardar Ophiolites to the east of the zone of active subduction.…”