Eclogite facies rocks of the Monotonous unit, clue to Variscan suture in the Moldanubian Zone (Bohemian Massif)

Abstract The formation and exhumation of Variscan high- to ultrahigh-pressure metamorphic rocks from the Moldanubian Zone in the Bohemian Massif are the subject of controversy regarding their unclear relationship to possible subduction zones. In this paper we present the results of a petrological study of eclogites that occur together with serpentinites within amphibolite facies gneisses in the Moldanubian Zone, east of the Teplá–Barrandian Block. More than 100 bodies of retrogressed eclogite and serpentinite follow an approximately 250 km long SW–NE trending zone in the central part of the Bohemian Massif. Together with surrounding gneisses, the eclogites share a medium to low-pressure amphibolite facies metamorphism. P–T conditions estimated for the eclogite facies stage indicate a relatively low-temperature geothermal gradient similar to those observed in the Saxothuringian Zone, which occurs north and northwest of the Teplá–Barrandian Block. The presence and distribution of eclogites and comparison of their P–T and age data with HP–UHPM rocks in other units in the Bohemian Massif allow us to constrain the Variscan suture, which straddles the SE of the Teplá–Barrandian Block. The existence of this suture in relation to available geotectonic models and its possible continuation through other allochthonous units along the European Variscan Belt are discussed.