Acta Musei Moraviae

Large almandine porphyroblasts from Senorady, western Moravia

Large garnet crystals (porphyroblasts) occur in migmatized biotite paragneiss near Senorady (Moldanubian Zone, Western Moravia). In their chemical composition prevails almandine komponent (Alm_68–72 Sps_3–10 Prp_16–22 Grs_0–6 Adr_1–6). Only weak diffuse zonation (Mn-rich core and Mg-rich rim) and inclusions of quartz, ilmenite, apatite and rutile is noticeable in almandine porphyroblasts. The mineral assemblage includes plagioclase An_34–35, quartz, biotite (phlogopite-annite) and sillimanite. Almandine garnet formed during exhumation of this part of Moldanubian Zone including partial melting at T ~ 650 °C and pressure of ~ 5–6 kbar. Almandine-bearing biotite gneisses with amphibolites, dolomite marbles and calc-silicate rocks between Senorady and Oslavany studied are part of separate varied rock sequence. According to the lithologies, mineral assemblages and metamorphic development are these rocks ether equivalent to the Varied (Drosendorf?) Unit than the Gföhl Unit, where is usually assigned.