COMPARISON OF EVOLUTION AND TECTONIC SIGNIFICANCE OF THE PINDOS AND VUORINOS OPHIOLITE SUITES, NORTHERN GREECE

The Pindos ophiolite, located on the western edge of the Sub-Pelagonia n (Othris) zone, comprises a complex series of westward-verging thrust sheets dominantly composed of peridotite tectonite, phaneritic mafic and leucocratic rocks, and pillow lavas. Harzburgite tectonites from p art of the east-central thrust sheet (Dramala Complex) show three well developed foliations. The oldest, compositional layering (S-0), has b een isoclinally folded, and preferred orientations of elongate grains and aggregates of olivine and orthopyroxene parallel to the axial surf aces of the isoclines define the second foliation (S-1). Spinel lineat ions parallel fold axes of the isoclinal folds. Thermometric calculati ons from mineral compositions and grain sizes of olivines and pyroxene s associated with the oldest preserved foliations (compositional layer ing, S-0 = S-1) indicate that rocks of the tectonite suite equilibrate d at depths of between 45 and 60 km, at temperatures between 1210 degr ees C and 925 degrees C and at differential stresses from 5 to 10 MPa. In general, rocks indicative of higher temperatures of equilibration formed at lower values of differential stress. The third, and youngest , foliation is defined by bands of fine-grained olivine and pyroxene m ylonite that cut across older structural elements. Mylonites equilibra ted at temperatures between 650 degrees C and 710 degrees C, presumabl y indicative of shallower depths (30-20 km) than the older foliations, accompanied by differential stresses ranging from 200 to 300 MPa, and probably formed during obduction of the complex. The sense and orient ation of shear determined from kinematic indicators within the mylonit ic zones indicate an updip displacement vector inclined at an angle of 20 degrees to 40 degrees toward 016 degrees, suggesting obduction to the east-northeast relative to the present position of the Pindos ophi olite. There is no direct evidence for the amount of rotation about a vertical axis that may have occurred during obduction or later tectoni c transport. The composition, internal structure, environments of equi libration, stress history, and inferred direction of obduction of the Pindos ultramafites are strikingly similar to those of the Vourinos Co mplex located 40 km to the northeast on the eastern margin of the Sub- Pelagonian zone. It is probable that the two ophiolites shared a commo n origin and an identical early obduction history. During Late Jurassi c times, the Vourinos and its metamorphic sole were thrust over a thic k sequence of shelf carbonates and a thin, diamictitic melange, both u nits being metamorphosed to lower greenschist facies. Comparable units beneath the Pindos thrust sheet (the Loumnitsa Unit and the Avdella M elange) are thicker, somewhat more lithologically diverse, and compris e amphibolite, greenschist, radiolarite, pillow lava, garnetite, exoti c marble, flysch, and poorly metamorphosed, fossiliferous limestone, t ypically occurring in tightly folded, thin thrust slices. Differences in the timing and direction of post-emplacement thrust transport of th e two complexes are marked and may have begun late in the obduction ph ase.