Detrital pyroxenes in the Eocene flysch of the Istrian basin (Slovenia, Croatia)

For the first time, few detrital augite and pigeonite crystals have been found in the Eocene flysch basins of Istria (Trieste-Koper basin; Italy, Slovenia, Croatia) and Krk Island (Croatia). Their chemistry suggests that they are related to subalkaline rocks (within-plate tholeiites) crystallized at a pressure between 0 and 5 kbar. As a possible source, the nearby basaltic andesites of Ljuba¡c have been taken into consideration. The argument for a ?Late Tertiary age of the Ljuba¡c volcanics is that no detrital pyroxenes have been found in the Eocene flysch and Oligo- Miocene molasse deposits of the area (Lugovi´c et al., 1998). Radiometric data are not available until now. The detection of detrital pyroxene could be an indication of an older age of the Ljuba¡c volcanics. The presence of similar pyroxenes in the Trieste-Koper and the Krk Island flysch and their absence in Brkini flysch suggest that the basin of Krk was linked with the Istrian basin rather than the Brkini basin.