Minerálne zloženie laminovaných vápnitých fylitov z Črmeľskej doliny pri Košiciach (severné gemerikum, Slovenská republika)

Abstract

Studied calcareous phyllites represent a part of Carboniferous Črmeľ Formation of the Northern Gemericum Unit (Western Carpathians, Slovak Republic). The mineral association of calcareous phyllites is composed of quartz, calcite, muscovite, Mg-Fe chlorites, albite and accessory minerals (fluorapatite, titanite, zircon and tourmalines). Chemical composition of analyzed muscovites has higher contents of Si (3.38 - 3.40 apfu) with K (up to 0.94 apfu), Fe2+ (up to 0.18 apfu) and Mg (up to 0.33 apfu). Chlorites contain Mg in range 2.12 - 2.36 apfu and Fe2+ in range 2.12 - 2.36 apfu with Fe/(Fe+Mg) ratio between 0.49 and 0.54. Chemical composition of albites is Ab97.9-99.7 An1.9Or0.5. Content of F- (up to 0.07 apfu) and OH- (up to 0.07 apfu) in titanite is slightly increased with lower amount Ti (0.89 - 0.92 apfu). In titanites not very significant (Al, Fe3+) + (OH, F) ↔ Ti + O substitution was also identified. Zircon consists of Si (up to 1.04 apfu), Zr (up to 0.96 apfu) and very low content of Hf (up to 0.02 apfu). Two types of tourmalines in calcareous phyllites are also present. Zonal tourmalines with central parts composed of schorl (1.95 - 2.47 apfu Fe; 0.93 - 0.97 apfu Mg; 0.45 apfu Na) and peripheral parts composed of dravite (1.09 - 1.19 apfu Fe; 1.66 - 1.93 apfu Mg; Na up to 0.79 apfu) and indistinctly zoned to non-zoned tourmalines were identified as magnesio-foitite (1.01 - 1.34 apfu Fe; 1.23 - 1.70 apfu Mg; 0.52 - 0.67 pfu vacancy). Studies of calcareous phyllites indicated metamorphic pressure-temperature conditions of 8 - 9 kbar at 330 - 340 °C using chlorite geothermometer and phengite geobarometer.