Along the geotraverse wich runs from Albania to eastern Greece, all the elements necessary to a complete reconstruction of the Triassic to Tertiary tectonic history of the Dinaric-Hellenic belt can be found. This belt can be subdivided in four main zones, each consisting of a pile of tectonic units of both oceanic and continental origin. These zones, from west to east, are: 1- the Deformed Adria Zone, 2- the External Ophiolite Belt (EOB), 3- the Pelagonian-Korab Zone, considered the easternmost part of the Adria Plate, 4- the Vardar Zone. These zones are bounded to the west by the Undeformed Adria Zone and to the east by the Serbo-Macedonian-Rhodope Massif, considered the deformed margin of the Eurasia Plate. The history started in the Early Triassic with a rifting stage followed by the Middle to Upper Triassic oceanic opening (Vardar Ocean) between the Pelagonian-Korab Zone and the Eurasia continental margin. Subsequently, in the Early Jurassic, the oceanic basin was affected by convergence resulting into the development of an intraoceanic east-dipping (present-day coordinates) subduction zone, where the role of the lower and upper plates were played, respectively by Adria and Eurasia Plates. This subduction zone was associated in the Middle Jurassic with a supra-subduction zone consisting of MOR trapped crust bounded to the west by an accretionary wedge, whose remnants are represented by the Middle to Upper Triassic MOR ophiolites, today found in the mélange from EOB. In the Middle Jurassic, the subduction of oceanic lithosphere was still active with a progressive retreat of the slab. A fore-arc oceanic basin opened into the trapped MOR oceanic crust, whose remnants are y the MOR- and SSZ-related magmatic sequences found in EOB, found from the Mirdita area to the western Vardar zone. Later on (Late Jurassic), a marginal oceanic basin opened inside the easternmost area of the continental margin of the Eurasia Plate, east of an extensional volcanic arc. The remnants of this marginal oceanic basin can be identified in the Guevgueli ophiolites, belonging to central and eastern Vardar zone, It is still debatable if the Guevgueli ophiolites constitute a back arc or a leaky-transform basin. At the boundary between Middle and Late Jurassic, the continuous convergence resulted in the involvement of the Pelagonian continental crust (Adria) in the subduction. This event produced a sharp shifting from extension to compression in the supra-subduction zone. This event lead to the obduction of the oceanic lithosphere, in two different stages, respectively the intraoceanic and continental phases. The intraoceanic stage (Middle Jurassic) was characterized by the westward thrusting of young and still hot section of the oceanic lithosphere leading to development of metamorphic soles. The continental stage (uppermost Upper Jurassic) was characterized by the emplacement of the ophiolitic nappe onto the continental margin. The root of the fore-arc-derived ophiolite nappe (EOB and eastern Vardar ophiolites) can be today identified in the Vardar zone. In the same time span, the compression, that affected also the volcanic arc and the neighbouringh marginal oceanic basin (Guevgueli), resulted along the Albania-Greece geotraverse into a continental collision during the Late Jurassic-Early Cretaceous boundary. Starting from the lowermost Early Cretaceous (or Late Jurassic?), the relationships between the oceanic and continental units are sealed by the unconformable sedimentation of the platform carbonate. From Late Cretaceous to Late Miocene the progressive migration of the deformation front toward the Adria Plate developed. In the Middle to Late Miocene, an extensional tectonics occurred in the internal zones of the Dinaric-Hellenic belt, while the compression was still active in the westernmost areas of the Adria Plate. In this frame, the Pelagonian-Korab zone, that represent a core of continental crust cropping below the ophiolites from EOB and Vardar zone, can be interpreted as the result of extensional tectonics of Tertiary age.
The ophiolites of Albania: geodynamic History
MARRONI, MICHELE;PANDOLFI, LUCA;
2011-01-01
Abstract
Along the geotraverse wich runs from Albania to eastern Greece, all the elements necessary to a complete reconstruction of the Triassic to Tertiary tectonic history of the Dinaric-Hellenic belt can be found. This belt can be subdivided in four main zones, each consisting of a pile of tectonic units of both oceanic and continental origin. These zones, from west to east, are: 1- the Deformed Adria Zone, 2- the External Ophiolite Belt (EOB), 3- the Pelagonian-Korab Zone, considered the easternmost part of the Adria Plate, 4- the Vardar Zone. These zones are bounded to the west by the Undeformed Adria Zone and to the east by the Serbo-Macedonian-Rhodope Massif, considered the deformed margin of the Eurasia Plate. The history started in the Early Triassic with a rifting stage followed by the Middle to Upper Triassic oceanic opening (Vardar Ocean) between the Pelagonian-Korab Zone and the Eurasia continental margin. Subsequently, in the Early Jurassic, the oceanic basin was affected by convergence resulting into the development of an intraoceanic east-dipping (present-day coordinates) subduction zone, where the role of the lower and upper plates were played, respectively by Adria and Eurasia Plates. This subduction zone was associated in the Middle Jurassic with a supra-subduction zone consisting of MOR trapped crust bounded to the west by an accretionary wedge, whose remnants are represented by the Middle to Upper Triassic MOR ophiolites, today found in the mélange from EOB. In the Middle Jurassic, the subduction of oceanic lithosphere was still active with a progressive retreat of the slab. A fore-arc oceanic basin opened into the trapped MOR oceanic crust, whose remnants are y the MOR- and SSZ-related magmatic sequences found in EOB, found from the Mirdita area to the western Vardar zone. Later on (Late Jurassic), a marginal oceanic basin opened inside the easternmost area of the continental margin of the Eurasia Plate, east of an extensional volcanic arc. The remnants of this marginal oceanic basin can be identified in the Guevgueli ophiolites, belonging to central and eastern Vardar zone, It is still debatable if the Guevgueli ophiolites constitute a back arc or a leaky-transform basin. At the boundary between Middle and Late Jurassic, the continuous convergence resulted in the involvement of the Pelagonian continental crust (Adria) in the subduction. This event produced a sharp shifting from extension to compression in the supra-subduction zone. This event lead to the obduction of the oceanic lithosphere, in two different stages, respectively the intraoceanic and continental phases. The intraoceanic stage (Middle Jurassic) was characterized by the westward thrusting of young and still hot section of the oceanic lithosphere leading to development of metamorphic soles. The continental stage (uppermost Upper Jurassic) was characterized by the emplacement of the ophiolitic nappe onto the continental margin. The root of the fore-arc-derived ophiolite nappe (EOB and eastern Vardar ophiolites) can be today identified in the Vardar zone. In the same time span, the compression, that affected also the volcanic arc and the neighbouringh marginal oceanic basin (Guevgueli), resulted along the Albania-Greece geotraverse into a continental collision during the Late Jurassic-Early Cretaceous boundary. Starting from the lowermost Early Cretaceous (or Late Jurassic?), the relationships between the oceanic and continental units are sealed by the unconformable sedimentation of the platform carbonate. From Late Cretaceous to Late Miocene the progressive migration of the deformation front toward the Adria Plate developed. In the Middle to Late Miocene, an extensional tectonics occurred in the internal zones of the Dinaric-Hellenic belt, while the compression was still active in the westernmost areas of the Adria Plate. In this frame, the Pelagonian-Korab zone, that represent a core of continental crust cropping below the ophiolites from EOB and Vardar zone, can be interpreted as the result of extensional tectonics of Tertiary age.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
