Acta Musei Moraviae

Metamorphic evolution of Upper Moravian Nappe in the South part of the Svratka Dome

The southern part of the Svratka Dome is built two crystalline napes overlying Cadomian basement (Brunovistulicum) and its Devonian cover. The Upper Moravian Nappe consists of orthogneisses, muscovite to muscovite-biotite mica schists and gneisses with layers or boudins of amphibolites, quartzites, calc-silicate rocks and marbles. Textural observation and study of mineral chemistry in these rocks resulted in distinguishing three metamorphic stages of the P-T evolution of the Upper Moravian Nappe. First syntectonic metamorphic assemblage M1 is preserved only as relicts in central parts of some garnet or amphibole porphyroblasts and is considered to have occurred at T 520–620 °C and P ~ 9 kbar. The following metamorphic event (M2) indicates peak conditions of T = 600–670 °C and P = 8–10 kbar. The mineral assemblages in marbles (Tr + Cal ± Dol) indicate X_CO2 in fluid between 0.1 and 0.6, while calcsilicate rocks (Qtz + Pl + Di ± Cal) reflect X_CO2 < 0.2. The temperature of a low-grade metamorphic event (M3) was established at ~450 °C for pressure 2 kbar.