VNITŘNÍ ZONÁLNOST TĚLES HORNIN TĚŠÍNITOVÉ ASOCIACE VE SLEZSKÉ JEDNOTCE: KORELACE PETROGRAFICKÝCH A PETROFYZIKÁLNÍCH PARAMETRŮ

Abstract

This article is focused on petrography of igneous rocks of the teschenite association and its correlation with selected petrophysical parameters. These igneous rocks were studied at three localities in the Silesian unit (Outer Western Carpathians) – Hodslavice, Žilina near Nový Jičín and Tichá. We conducted petrographic study (including modal composition based on planimetry) and then we compared results with previously published data on magnetic susceptibility and density of the same rock samples. The primary magmatic phases (clinopyroxenes, amphibole, biotite, opaque phases, feldspars and analcime) show in all cases less or more signs of post-magmatic alteration, giving rise mainly to secondary chlorite, carbonate and “limonite”. The amount of chlorite ranges from 21 to 23, 3 to 9, and 16 to 35 mod. % and those of carbonate vary from 5 to 15, 3 to 4, and 16 to 24 mod. % in Hodslavice, Žilina near Nový Jičín, and Tichá, respectively. The values of magnetic susceptibility range from 5.56 × 10-8 to 7.66 × 10-5, 5.07 × 10-7 to 1.61 × 10-5, and 2.46 × 10-7 to 2.93 × 10-5 SI and those of density are between 2.50 and 2.77, 2.66 to 3.88, and 2.65 to 2.86 g/cm3 in Hodslavice, Žilina near Nový Jičín, and Tichá, respectively. Correlation of petrographic and petrophysical parameters suggests that various postmagmatic alterations (including chloritization, carbonatization and weathering associated with formation of limonite) can influence the values of magnetic susceptibility and density. The intensity of these alterations varies significantly among samples and sites.