engleski

The ophiolite complex of the Mt. Medvednica (NR Croatia)

The Mt. Medvednica ophiolite complex, which crops out in the junction area of the southwestern Alps, north-western Dinarides and southwest Pannonian Basin, is included in the Zagreb-Mid-Transdanubian tectonic unit wedged between the Pelso and Tisia megaunits. The ophiolite complex is thrust by the Paleozoic-Triassic formation which were affected by Early Cretaceous (122-110 Ma) low-pressure metamorphism (Belak et al., 1995) Based on geological characteristics two main mappable units can be distinguished: 1) The ophiolite melange is a chaotic unit composed of pervasively sheared shale-silty matrix in which fragments of native greywackes predominate over the fragments of peridotites, gabbros, diabases, basalts, cherts, tuffs and exotic blocks of dolomites and limestones of different environments. It is believed that sedimentary age of graywackes and shale is Jurassic to Early Cretaceous. 2) The radiolarite formation is characterized by interlayering of basalts, ribbon radiolarites and siliceous shales that grade into layered micrites with nodular and intercalated cherts. The Mt. Medvednica ophiolite complex shows positive correlation with the ophiolite complexes of the surrounding Mts. Ivanščica, Kalnik and Samoborska gora as well as with the ophiolite complexes of the Dinaride ophiolite zone. Emplacement of ophiolites and native sedimentary formations might have been related to subduction processes which took place in Late Jurrasic-Early Cretaceous time. Allochtonous Paleozoic-Triassic formations must have been also emplaced in somewhat younger phase.

Dinarides; ophiolite melange; radiolarite; emplacement of ophiolites

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