Cr-spinel supply in the Brkini, Istrian and Krk Island flysch basins (Slovenia, Italy and Croatia)

In Late Cretaceous times, subduction of oceanic crust occurred to the north of the Adria plate and was followed by the formation of ophiolitic complexes. Continental collision in Alpine orogenic belts lasted from Late Cretaceous to Early Tertiary times. The progressive contraction of oceanic crust caused the uplift of previously rifted continental margin and platforms and the formation of foredeep flysch basins. Detrital Cr-spinels are widespread in Eocene sandstones of the Brkini, Istrian and Krk Island foredeep flysch basins. On the basis of their TiO2 content and FeO/Fe2O3 ratio, spinels derived from peridotites and mantle-derived magmatic rocks were distinguished. The first are statistically more abundant and are considered to have been derived from type I and II peridotites. The second appear to be mainly related to backarc basin products. These results suggest that Cr-spinels were derived from the erosion of the Internal Dinarides, where type II and III peridotites are present, and also from the Outer Dinarides, where type I peridotites crop out.