The significance of deformation associated with blueschist facies metamorphism on the Aegean island of Syros

Summary A thorough examination of the syn-metamorphic minor structures in the blueschists of the Aegean island of Syros allows a determination of the kinetics and nature of the deformation. The deformation is essentially related to ductile thrusting at up to 45 km depth. The change in fold geometry with orientation, and the presence of a locally developed mineral lineation at a high-angle to the fold axes give two independent determinations of the direction of thrusting. The direction, 130 ± 10°, suggests a link between the tectonism here and that in the Izmir-Ankara zone of mainland Turkey. The nature of the small-scale asymmetrical folding indicates shortening of the pile parallel to this thrust displacement. This, together with the suggestion from the metamorphic textures of increasing pressure and temperature during deformation suggest that the deformation is related to burial and is compressional, and hence is presumably related to a major collision event.