Petrology, geochemistry and tectono-magmatic affinity of gabbroic olistoliths from the ophiolite mélange in the NW Dinaric-Vardar ophiolite zone (Mts. Kalnik and Ivanščica, North Croatia)

Previous study of mafic extrusive sequences suggested an 80 Ma period of tectono-magmatic evolution of the ROD from intra-continental rifting during the Anisian, to the formation of proto-arc crust during the Callovian-Oxfordian. Representative gabbro samples of each geochemical group were dated by the Ar-Ar and/or the K-Ar dating method. The Early Jurassic N-MORB-type gabbros, ∼185 Ma old, signifies a peculiar stage of Palaeo-Tethyan slab break-off. The Late Jurassic IAT-type gabbros (geochemical group B), ∼147 Ma old, is the vestige of a nascent intra-oceanic arc, whilst the Early Cretaceous BABB-type gabbros, ∼100 Ma old, provides evidence of magmatism in the back-arc marginal basin. The analyzed gabbroic rocks enable refinement and completion of the geodynamic evolution of the ROD, from the opening of an ensialic back-arc basin during the Ladinian and a continuous spreading event until the Bajocian. There are many lines of evidence that correlate the geodynamic evolution of the ROD with the Albanide-Hellenide Neo-Tethyan oceanic segment.