Monazite geochronology in melt-percolated UHP meta-granitoids: An example from the Erzgebirge continental subduction wedge, Bohemian Massif

Trans-lithospheric diapirism explains the presence of ultra-high pressure rocks in the European Variscides

“…For the orogenic root association (red), high temperatures at~15-20 kbar are typical showing a significant deviation from the cold subduction environment. b Metamorphic ages show a similar pattern for all domains: ages of~360-355 Ma for the prograde path or early UHP metamorphism 28,30-32~3 40 Ma for the main HT metamorphic event 14,29,32 and~340-335 Ma for retrogression in the middle crust 28,29,31 . An exception is the age of~340 Ma reported for all the three phases in granulites near the plate interface 73 .…”

“…In both regions, modern U-Pb petro-chronological studies on zircon and monazite dated the prograde PT path to~360-350 Ma and peak temperature conditions followed by retrogression in the middle crust to 345-338 Ma [29][30][31][32] .…”

New constraints on the tectonometamorphic evolution of the Erzgebirge orogenic wedge (Saxothuringian Domain, Bohemian Massif)

“…The Erzgebirge/Krušné hory region is a part of the Saxothuringian Domain in the northwest of the Variscan Bohemian Massif (Figure 1a). The Saxothuringian Domain represents the lower plate subducted underneath the hanging wall Teplá‐Barrandian Domain along the major Variscan suture (Franke, 1989; Kroner et al, 2007; Schulmann et al, 2014; Willner et al, 1997, 2000) marked by occurrences of HP ‐ UHP rocks: eclogites, blueschists, and coesite‐ or diamond‐bearing paragneisses and granulites (Collett et al, 2017; Faryad & Kachlík, 2013; Klápová et al, 1998; Konopásek & Schulmann, 2005; Kotková et al, 2011; Kotková & Janák, 2015; Massonne, 2005; Massonne et al, 2007; Nasdala & Massonne, 2000; Schmädicke et al, 1992, 1995; Závada et al, 2018, 2021). The studied area comprises metasedimentary and metavolcanic rocks, intruded by younger Variscan granitoids (Figure 1b) at 314–325 Ma (Förster et al, 1999; Romer et al, 2007; Tichomirowa et al, 2019).…”

“…Based on the lithostratigraphy and metamorphic grade, Schmädicke et al (1992) subdivided the Erzgebirge complex into several tectonometamorphic units (Figure 1b). From the structurally lower to the upper units (i.e., from the core to the mantle of the Erzgebirge dome), these are (i) the Cadomian basement parautochton also called Red‐and‐Grey Gneiss Unit metamorphosed at 7–11 kbar and ~600–720°C (Kröner et al, 1995; Mingram, 1998; Roetzler et al, 1998; Willner et al, 1997); (ii) the Gneiss/Eclogite Unit (lower allochthon) metamorphosed at UHP conditions as shown by presence of coesite and diamond (Kotková et al, 2011; Massonne & Nasdala, 2003; Nasdala & Massonne, 2000; Rötzler et al, 2008; Schmädicke et al, 1992; Závada et al, 2021); (iii) the Micaschist/Eclogite Unit (middle allochthon) metamorphosed up to 26 kbar and 615–700°C (Collett et al, 2017; Gross et al, 2008; Klápová et al, 1998; Konopásek, 2001; Rahimi & Massonne, 2018, 2020; Roetzler et al, 1998; Schmädicke et al, 1992); (iv) the Garnet‐Phyllite Unit (upper allochthon) and (v) the Phyllite Unit (upper allochthon), both metamorphosed at 2–15 kbar and 300–470°C (Faryad & Kachlík, 2013; Roetzler et al, 1998); and (vi) the crystalline complexes of Münchberg or Wildenfels massifs (uppermost allochthon).…”

“…Based on the existing geochronological data, this phase occurred between ca. 350–340 Ma (Kotková et al, 2016; Závada et al, 2021). The E‐W convergence has been reported from numerous places in the Bohemian Massif and is restricted to the period 390–340 Ma (Edel et al, 2018; Jeřábek et al, 2016; Konopásek et al, 2019; Peřestý et al, 2017; Racek et al, 2017).…”