TECTONOSTRATIGRAPHY OF THE OPHIOLITES OF SE ALBANIA IN CONNECTION WITH THE OPHIOLITES IN NW GREECE

The Albanian ophiolites are part of a large ophiolitic belt ranging from Croatia, Bosnia, Montenegro and Albania to Greece. In Albania, the ophiolites are divided in a western and an eastern belt, where the former shows MORB affinity and the latter a SSZ signature. Both types of ophiolites formed during the Middle to Late Jurassic and have comparable radiolarian cherts on their top. Their tectonic relations are still unclear and there are no clearcut tectonic boundaries between the two belts.

The ophiolite massifs in SE Albania (part of the western belt) link the Mirdita ophiolites with the Pindos ophiolites in Greece, and were considered in the past to have MORB features. However, detailed petrological and geochemical observations have shown the presence of SSZ basalts closely associated with MOR-basalts. Unlike in the neighbouring Pindos ophiolites, volcanic differentiation products (andesites, dacites, rhyolites) and high-Mg andesites (boninites) are absent and the mantle sequence consists mainly of lherzolites with an subordinate amount of harzburgites.

The neritic limestones of Late Triassic to Early Jurassic age are the oldest rocks of the region. During the Early Jurassic (Lias) the rifting and opening of an ocean basin started, which led to the formation of the ophiolite assemblages. Pelagic limestones of Dogger to Malm were normally emplaced on the Upper Triassic to Lower Jurassic carbonate periphery. Both, the carbonate periphery and the ophiolite rocks are covered by the same radiolarian cherts of Kimmeridgian age, thus closing the magmatic activity in the region.

During the Tithonian to the Early Cretaceous the ophiolite displacement,fragmentation and uplift led to the formation of an ophiolite melange and flyschoidal sediments. In some parts of the region the ophiolites were thrusted westward onto the J3t-Cr1 flysch and the Upper Triassic to Lower Jurassic limestones. Conglomerates and shallow water carbonates were transgressively emplaced onto the ophiolites during the Early Cretaceous, continuing with pelagic carbonates of Late Cretaceous age as the sea deepened. The ophiolites and the carbonate periphery together with the younger overlaying deposits were finally thrusted westward onto the Eocene flysch of the Krasta Zone, the analogue of the Olonos-Pindos zone in Greece.