GEOLOGICA CARPATHICA, APRIL 2022, 73, 2, 97–122 https://doi.org/10.31577/GeolCarp.73.2.1 www.geologicacarpathica.com Variscan metamorphism and partial melting of sillimanite-bearing metapelites in the High Tatra Mts. constrained by Th–U–Pb dating of monazite MARIAN JANÁK 1,  , IGOR PETRÍK 1 , PATRIK KONEČNÝ 2 , SERGII KURYLO 3 , MILAN KOHÚT 1 and JÁN MADARÁS 1 1 Earth Science Institute, Slovak Academy of Sciences, Dúbravská cesta 9, P.O. Box 106, 840 05 Bratislava, Slovakia;  marian.janak@savba.sk 2 Dionýz Štúr State Geological Institute, Mlynská dolina 1, 817 04 Bratislava, Slovakia 3 Earth Science Institute, Slovak Academy of Sciences, Ďumbierska 1, 974 11 Banská Bystrica, Slovakia (Manuscript received December 3, 2021; accepted in revised form February 8, 2022; Associate Editor: Igor Broska) Abstract: The Tatra Mountains of the Western Carpathians are a key area for the study of the eastern continuation of the Variscan basement within the Alpine–Carpathian orogenic belt in Central Europe. Metamorphic zonation in the Tatra Mts. displays an inverted metamorphic sequence related to Variscan thrusting and emplacement of gneisses, migmatites and granites over micaschists. Here we present new results of Th–U–Pb dating of monazite in sillimanite-bearing metapelitic gneisses, migmatite and granodiorite from the High Tatra along with petrological interpretation based on thermodynamic modelling. The metapelitic gneisses show the peak metamorphic assemblage garnet + sillimanite + plagioclase + biotite + muscovite + ilmenite + quartz; inclusions of rutile, phengitic muscovite and paragonite in the garnet core indicate an earlier metamorphic stage. Thermodynamic modelling suggests a clockwise, prograde P–T path via staurolite-to-sillimanite sequence reactions from above 6 kbar to ca. 5–6 kbar and 650–700 °C, at mid-crustal levels. Migmatites, with dominant K-feldspar, plagioclase (An 12–35 ) and quartz in the leucosome, underwent partial melting involving biotite dehydration reactions and formation of peritectic, Mn-rich garnet and/or Ti-magnetite at ca. 7–8 kbar and 760–770 °C, during decom- pression from lower-crustal levels. Monazite composition in metapelitic gneisses differs from that in leucosome of migmatite. The latter shows pronounced Eu-negative anomalies interpreted as the result of co-crystallization with feldspars and higher Y contents indicating higher temperature of crystallization. Monazite ages are identical within 2σ errors and indicate that both metamorphic and melting events occurred in Early Carboniferous, between 350–345 Ma as a consequence of continental collision and crustal thickening in the course of the Variscan orogeny. Keywords: Th–U–Pb dating of monazite, metapelites, partial melting, Variscan orogeny, Tatra Mts., Western Carpathians. Introduction This paper deals with high-grade metapelites from the Tatra Mountains in the Western Carpathians (Slovakia), a key area for the study of the eastern continuation of the Variscan base- ment within the Alpine–Carpathian orogenic belt in Central Europe (Fig. 1). Metamorphic zonation in the Tatra Mts. displays an inverted metamorphic sequence with high-grade rocks (gneiss, migmatite, amphibolite, eclogite) of kyanite and sillimanite zone in the hangingwall and lower-grade rocks (micaschist) of staurolite–kyanite and kyanite–fibrolite zone in the footwall (Fig. 2a), related to Variscan thrusting (Janák 1994; Janák et al. 1999). Most details on Variscan metamor- phic evolution of the Tatra Mts. are known from the Western Tatra (e.g. Janák 1994; Janák et al. 1996, 1999; Poller et al. 2000; Moussallam et al. 2012; Burda et al. 2021). In the High Tatra, metamorphic rocks are less abundant and belong to the sillimanite zone (Fig. 2a). Age data on the High Tatra are known mostly from zircon dating of granitoids (Poller & Todt 2000; Poller et al. 2001; Burda et al. 2013a, b; Gawęda et al. 2016; Kohút & Larionov 2021; Broska et al. 2022). Most of the data record metamorphism and magmatism in Late Devo- nian and Carboniferous time (ca. 365–330 Ma). Monazite is one of the most important accessory minerals in metapelitic lithologies, stable at various P–T conditions of metamorphism and partial melting (e.g. Zhu & O’Nions 1999; Terry et al. 2000; Catlos et al. 2002; Spear & Pyle 2002; Hermann & Rubatto 2003; Kohn et al. 2005; Janots et al. 2008; Krenn et al. 2009; Gieré et al. 2011; Majka et al. 2012; Engi 2017; Skrzypek et al. 2017; Hacker et al. 2019; Petrík et al. 2019). Monazite typically contains large amounts of radio- active elements and can be dated using various methods (isotope dilution, LA-ICPMS, ion microprobe, electron micro- probe). Electron microprobe chemical dating method (Parrish 1990; Suzuki & Adachi 1991; Montel et al. 1996; Finger et al. 1998; Cocherie & Albarede 2001; Suzuki & Kato 2008; Konečný et al. 2018) produces typically an error of 5–8 % (2 σ) for individual dates (caused mostly by analytical error of Pb determination) and 1.5–2 % for weighted averages and iso chrons, which is sufficient for the distinction of main mag- matic and metamorphic events. U–Th–Pb chemical dating of monazite was also applied to granitic and metamorphic rocks in the Western Carpathians (e.g. Finger et al. 2003; Petrík & Konečný 2009; Broska & Petrík 2015; Petrík et al. 2020). The composition of metamorphic monazite commonly occur- ring in metapelites and migmatites, either in the matrix or