Abstract

The Dinaride and Vardar zone ophiolite belts extend from the south-eastern margins of the Alps to the Albanian and Greek ophiolites. Detailed sampling of the Krivaja–Konjuh massif, one of the largest massifs in the Dinaride belt (> 600 km2), reveals fertile compositions and an extensive record of deformation at spinel peridotite facies conditions. High Na2O clinopyroxene and spinel–orthopyroxene symplectites after garnet, as well as cpx trace element patterns indicate a garnet facies (subcontinental) origin of the southern and western parts, similar to orogenic massifs such as Lherz, Ronda and the Eastern Central Alpine peridotites. In contrast to those massifs the peridotites from Krivaja are not refertilised. Clinopyroxene and spinel compositions from the eastern parts show similarities with fertile abyssal peridotite. In the central parts of the massif the spinel lherzolites contain locally abundant patches of plagioclase. The pyroxene abundances of the plagioclase peridotites range from similar to the fertile spinel peridotites to massive olivine-rich troctolites with no primary pyroxene. We infer that the olivine-rich troctolites are due to migrating melt dissolving pyroxene and then freezing, with interstitial plagioclase and cpx geometries similar to experimentally produced partial melts.

Overall we infer that the massif represents the onset of continental rifting and early stages of formation of a new ocean basin. Combining our data with previously published analyses of other Balkan massifs we create a compositional map that suggests a simple tectonic setting for the Balkan massifs.