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

Előd Mészáros,Béla Raucsik,Adrián Heincz,Christoph A Hauzenberger,Andrea Varga,Zsolt Benkó

doi:10.1007/s00531-019-01720-y

Abstract

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 (KIBasel) values of the phengitic K-white mica indicate epizonal metamorphism (0.22 ± 0.04 Δ°2θ). The Chlorite ‘Crystallinity’ Index (ChCCIS) suggests metamorphic alteration near to the anchizone‒epizone boundary (0.31 ± 0.06 Δ°2θ). 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.

Highlights

The European Variscan and Alpine mountain chains are collisional orogens and are built up of pre-Variscan basement blocks originated at the Gondwana Palaeo-tethyan marginElectronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.1 ‘Vulcano’ Petrology and Geochemistry Research Group, Department of Mineralogy, Geochemistry and Petrology, University of Szeged, Egyetem utca 2, 6722 Szeged, Hungary
The major aim of this study is to evaluate the metamorphic conditions and provenance of the Palaeozoic organicrich metasedimentary Szalatnak Slate Formation from southern Transdanubia, Tisza Mega-unit (Horváthertelend Unit), Hungary (Fig. 2)
K-white mica composition analysis was made with an energy-dispersive and a wavelength-dispersive equipped JEOL JSM-6310 microprobe

Summary

Introduction

The European Variscan and Alpine mountain chains are collisional orogens and are built up of pre-Variscan basement blocks originated at the Gondwana Palaeo-tethyan margin. 1 ‘Vulcano’ Petrology and Geochemistry Research Group, Department of Mineralogy, Geochemistry and Petrology, University of Szeged, Egyetem utca 2, 6722 Szeged, Hungary (von Raumer et al 2003; Novo-Fernández et al 2016). PreVariscan domains, such as the Iberian Massif, Bohemian Massif and French Massif Central, are essential components in the Variscan basement areas in Western and Central Europe (von Raumer et al 2003; Kroner et al 2008). The Variscan orogenic phase resulted in superimposed structures and juxtaposition of pre-Variscan and Variscan blocks (von Raumer et al 2003; Kroner et al 2008; Kříbek et al 2009). The Bohemian Massif represents the eastern termination of the European Variscan Orogen. Further Variscan continental crust fragments to the southeast are, partly hidden and/or moderately to strongly overprinted by the subsequent Alpine Orogeny (Fig. 1a)

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