Mineral composition of laminated basalt metapyroclastics and marbles at the localities near Ochtiná (Slovak Republic)Article PDF
Mineral composition of laminated basalt metapyroclastics and marbles at the localities near Ochtiná (Slovak Republic)
Basalt metapyroclastics at the localities Ochtina – Pod Vapnom and Ochtina – Hradok form laminated intercalations in marbles of the Borka nappe (Meliatic Unit), Western Carpathians. The mineral association consists of amphiboles (actinolite – tremolite), chlorites (clinochlore – chamosite), epidote and albite which occurs in the stripes. Accessory minerals are represented by titanite and fluorapatite, in the marbles hydrothermal pyrite was also identified. The amphiboles reveal dominant Mg (2.50–4.48 apfu) in C position. The content of Mg in clinochlore varies between 2.40–2.69 apfu and the content of Fe2+ in chamosite is up to 2.62 apfu. Epidote shows two slightly pronounced substitutions in the M positions and one in the T position. The most significant substitution is in M3 position between Fe3+ (0.52–0.95 apfu), Al (0.03–0.45 apfu), negligible Fe2+ (up to 0.08 apfu), Cr (up to 0.01 apfu) and V (up to 0.02 apfu). Albite reaches a nearly pure end-member composition (Ab99–100Or0.2An0.7). Titanite shows contents of Ca and Si close to the ideal composition, Ti content is slightly reduced (0.87–0.92 apfu) by (Al, Fe)3+ + (OH, F)–↔ Ti4+ + O2- substitution and the F content is increased up to 0.6 wt. % and (OH)– up to 0,08 apfu. Fluorapatite represents the end-member with a content of 0.83–1.00 apfu F without an increased concentration of REE elements. In pyrites, the Co content slightly increases from the center to the edge of some grains (up to 0.05 apfu). Marbles formed during the regional metamorphism of sedimentary limestones, which were locally enriched in pyroclastic material of basaltic composition. The recrystallized pyroclastic material was transformed into a laminar arrangement in the marbles. The calcu lated temperature interval for chlorites is in the range of 303–343 ± 9.5 °C.
Peter Ružička, Department of Mineralogy, Petrology and Economic Geology, Faculty of Natural Sciences, Comenius University, Ilkovičova 6, 842 15 Bratislava, Slovak Republic; e-mail: firstname.lastname@example.org
Pavol Myšľan, Earth Science Institute, Slovak Academy of Sciences, Dubravska cesta 9, 840 05 Bratislava, Slovak Republic. Department of Mineralogy, Petrology and Economic Geology, Faculty of Natural Sciences, Comenius University, Ilkovičova 6, 842 15 Bratislava, Slovak Republic