Deformation of the Circum-Rhodope Belt Mesozoic (Middle Triassic to
earliest Lower Cretaceous) low-grade schists underneath an arc-related
ophiolitic magmatic suite and associated sedimentary successions in the
eastern Rhodope-Thrace region occurred as a two-episode tectonic
process: (i) Late Jurassic deformation of arc to margin units resulting
from the eastern Rhodope-Evros arc-Rhodope terrane continental margin
collision and accretion to that margin, and (ii) Middle Eocene
deformation related to the Tertiary crustal extension and final
collision resulting in the closure of the Vardar ocean south of the
Rhodope terrane. The first deformational event D-1 is expressed by Late
Jurassic NW-N vergent fold generations and the main and subsidiary
planar-linear structures. Although overprinting, these structural
elements depict uniform bulk north-directed thrust kinematics and are
geometrically compatible with the increments of progressive deformation
that develops in same greenschist-facies metamorphic grade. It followed
the Early-Middle Jurassic magmatic evolution of the eastern
Rhodope-Evros arc established on the upper plate of the southward
subducting Maliac-Meliata oceanic lithosphere that established the
Vardar Ocean in a supra-subduction back-arc setting. This first event
resulted in the thrust-related tectonic emplacement of the Mesozoic
schists in a supra-crustal level onto the Rhodope continental margin.
This Late Jurassic-Early Cretaceous tectonic event related to N-vergent
Balkan orogeny is well-constrained by geochronological data and traced
at a regional-scale within distinct units of the Carpatho-Balkan Belt.
Following subduction reversal towards the north whereby the Vardar Ocean
was subducted beneath the Rhodope margin by latest Cretaceous times, the
low-grade schists aquired a new position in the upper plate, and hence,
the Mesozoic schists are lacking the Cretaceous S-directed
tectono-metamorphic episode whose effects are widespread in the
underlying high-grade basement. The subduction of the remnant Vardar
Ocean located behind the colliding arc since the middle Cretaceous was
responsible for its ultimate closure, Early Tertiary collision with the
Pelagonian block and extension in the region caused the extensional
collapse related to the second deformational event D-2. This extensional
episode was experienced passively by the Mesozoic schists located in the
hanging wall of the extensional detachments in Eocene times. It resulted
in NE-SW oriented open folds representing corrugation antiforms of the
extensional detachment surfaces, brittle faulting and burial history
beneath thick Eocene sediments as indicated by 42.1-39.7 Ma Ar-40/Ar-39
mica plateau ages obtained in the study. The results provide structural
constraints for the involvement components of Jurassic paleo-subduction
zone in a Late Jurassic arc-continental margin collisional history that
contributed to accretion-related crustal growth of the Rhodope terrane.
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