The Northeastern Emplacement of the Pindos Basin Ophiolites and Their Response to Pelagonian Exhumation Tectonics (Northern Greece)

The Pindos Basin ophiolites in the Western Hellenides are a single nappe, emplaced onto the Pelagonian ribbon-continent in the mid-Jurassic. The nappe is rooted within the Tertiary Mesohellenic Trough to a depth of ~25 km along the Africa-Europe suture zone. Structural evidence documents an original NE ophiolite emplacement. The ophiolitic slab was transported over an upper Jurassic sedimentary accretionary complex (Avdella Mélange) in the west, and created a sedimentary-tectonic mélange (Ayios Nikolas Melange, ANM) beneath as it overrode the Pelagonian margin in the Vourinos area. Ophiolitic outliers to the east are remnants of the same oceanic slab preserved on the now exhumed Pelagonia. The Pelagonian massif represents a metamorphic core complex tectonically overridden by the Pindos ophiolite nappe.

Pelagonian exhumation, beginning by ~ the late Jurassic and continuing into mid-Cretaceous, affected this slab in the following ways: i) The metamorphic facies of the ANM grades from phyllitic to schist and amphibolite-schist over the exhumed Pelagonia. ii) Ophiolites are metasomatized where in contact with the exhumed Pelagonian rocks. iii) Outcrops of remnant ophiolitic fragments are largely disassociated from their original relative positions in their parent slab. iv) No emplacement soles are preserved directly above Pelagonia. East of Vourinos, remnants of the slab were tectonically entrapped between the exhuming Pelagonian core and its sedimentary overburden undergoing extensional, largely gravitational displacements. Deformation of the slab during this entrapment caused rotation of original emplacement vectors (e.g. towards the north, Rodiani near Vourinos). Farther east, primary emplacement features are obscured in serpentinite fragments that show a general westerly topping constriction. In the exhumation model, this "SW topping" direction cannot be interpreted as indicative of an eastern origin of the Pindos Basin ophiolites from the Vardar Zone, but rather as a local response to the uplift of Pelagonia and active deformation of the sedimentary overburden.