Protolithic age and time of metamorphism of amphibolites from Slasten lithotectonic unit (Southern Pirin Mountains).

The investigated amphibolites from the Slasten lithotectonic unit are found as a strongly elongated body trending north-south at the eastern slope of the Pirin Mountain, near the village of Ilinden. These rocks are hosted by biotite and biotite-amphibole gneisses, some partially migmatized and containing thin intercalations of marble. The mineral composition is amphibole, plagioclase, epidote, quartz, garnet, pyroxene, titanite, and calcite. P-T conditions of metamorphism are in the range 691-724 °C and 0.74-0.86 GPa. LA-ICP-MS analyses of zircons yield a Middle Triassic (246.4±3.2 Ma) age of formation of these amphibolites. [ABSTRACT FROM AUTHOR]