PETROGRAFICKÁ VARIABILITA TĚŠÍNITOVÉHO TĚLESA V BLUDOVICÍCH U NOVÉHO JIČÍNA (SLEZSKÁ JEDNOTKA, VNĚJŠÍ ZÁPADNÍ KARPATY)
Roč.23,č.1-2(2016)
A petrographically complex teschenite sill occurs 800 m south-eastern from the village of Bludovice near Nový Jičín. The rocks are composed mainly of chemically zonal clinopyroxene (diopside core – Fe-rich diopside or Mg-rich hedenbergite rim) and clinoamphibole (kaersutite or ferrokaersutite core – hastingsite or ferropargasite rim) phenocrysts which range up to few cm in size, apatite, biotite, opaque minerals and bright gray to pinkish matrix. Main constituents of the matrix are alkali feldspars and analcime which are accompanied by secondary minerals (titanite, chlorite, prehnite, carbonates, epidote, and hydrated iron oxide-hydroxides). In this paper, we characterize various rock types of analcime-rich teschenites and thus try to elucidate petrographic variability of the teschenite body from Bludovice. Based on the mineral composition, texture, and geological position, four types of teschenites were distinguished: (I) leucocratic (M´ = 28–35) medium- to coarse-grained teschenites with pyroxene and amphibole phenocrysts; (II) mesocratic to melanocratic (M´ = 46–66) fine- to medium-grained pyroxene-amphibole to amphibole-pyroxene teschenites; (III) nests of leucocratic (M´ = 20–21) fine-grained pyroxene teschenite; and (IV) dykes of leucocratic to mesocratic amphibole-pyroxene to amphibole (M´ = 22–38) teschenite. Large petrographic variability resulted from processes of magmatic differentiation (fractional crystallisation, gravitational differentiation, and irregular distribution of volatile components) and subsequent hydrothermal alteration. Leucocratic nests and dykes represent most differentiated parts of the teschenite body.
teschenite; Silesian Unit; Flysch Belt; Outer Western Carpathians
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