NEW INSIGHTS IN GEOLOGY OF THE ALBANIDES (ALBANIA)

The Albanides and especially the Albanian ophiolites (Pindos-Mirdita basin) represent the remnants of Mesozoic (Jurassic) oceanic crust within the Dinaride-Hellenide segment of the Alpine orogenic system. These ophiolites and the reconstruction of their geodynamic history form therefore a critical transition from the Alpine Jurassic ophiolites in the northwest to the Jurassic-Cretaceous ophiolites in the eastern Mediterranean area to the southeast. The beginning of the closure of these ocean was estimated as Tithonian. Our new biostratigraphic data on the Melangé deposits show, that subduction starts in Middle Jurassic times and that the first nappe thrusting was sealed by a Kimmeridgian/Tithonian shallow water carbonate platform. In the Kurbnesch area in central Albania (Perlat-Kurbnesh ophiolitic melange), we evidenced the existence of an unknown Late Jurassic shallow water carbonate platform by component analysis of mass-flow deposits in pelagic sediments. The hemipelagic and pelagic Triassic sediments were dated by conodonts. These sediments, in many cases, form huge slides embedded in a matrix of Jurassic radiolarian chert - dated as Middle to early Late Jurassic by means of radiolarians. Using the CAI to determine the diagenetic or metamorphic overprint of the carbonates we find: A) slides with a high diagenetic overprint within a low diagenetic overprinted matrix. This leads to the important conclusion that the thermal overprint of the Triassic carbonates predates the emplacement of the slides and is therefore transported. B) a decrease of the thermal overprint from east to west. This thermal overprint is younger than early nappe stacking but older as nappe reactivation and final emplacement in ?Early Tertiary times, because we partly found inverted thermal overprint in the nappe stack. These first results show a polyphase tectonic and thermal history of Albanides, not exactly dated at the moment. Our data show also that the previous tectonic interpretations have to be modified. Our new data of the sealing of these ophiolites, dating their emplacement bring them in a greater geodynamic scenario of the Tethyan region.