Provenance and Variscan low-grade regional metamorphism recorded in slates from the basement of the (SW Hungary)

A metapelitic sequence with Silurian protolith from the Horváthertelend Unit (Tisza Mega-unit, Hungary) has a K-white mica + chlorite + quartz + albite + anatase ± tourmaline mineral assemblage. Moderately developed disjunctive and well-developed continuous foliations are present. Geochemical results reflect a dominantly felsic source of the protoliths, suggesting an intermediate to acidic volcanic arc in the provenance area. Metasandstone pebbles in the metaconglomerate indicate a recycled sedimentary source. Raman spectroscopy of carbonaceous material indicates a ~ 350‒370 °C peak metamorphic temperature. The Kübler Index (KI Basel ) values of the phengitic K-white mica indicate epizonal metamorphism (0.22 ± 0.04 Δ°2 θ ). The Chlorite ‘Crystallinity’ Index (ChC CIS ) suggests metamorphic alteration near to the anchizone‒epizone boundary (0.31 ± 0.06 Δ°2 θ ). K–Ar ages of K-white mica are interpreted as a result of Variscan metamorphism ( c. > 310 Ma) and post-Variscan uplift ( c. 290 Ma). The predominance of lydite and slate of Llandoverian age and the overlying coarse-grained metagreywacke and metaconglomerate beds of the Szalatnak Slate Formation show strong lithological similarities with the proximal Silurian sequences in the Małopolska Massif (Kielce Region, Holy Cross Mountains, Poland). The original position of the Horváthertelend Unit is presumably to the northeast from the Bohemian Massif, next to the Upper Silesian Block (Moravo-Silesian Zone) and the Małopolska Terrane.