Majzlan J., Mikuš T. & Milovský R., 2022: Small occurrences of Middle Triassic ore mineralizations in the Western Carpathians. Acta Geologica Slovaca, 14, 2, 103–114.

Small occurrences of Middle Triassic ore mineralizations in the Western Carpathians

Juraj Majzlan¹, Tomáš Mikuš² & Rastislav Milovský²

¹Institute of Geosciences, Friedrich-Schiller University, Burgweg 11, D-07749 Jena, Germany
²Earth Science Institute of the Slovak Academy of Sciences, Ďumbierska 1, Banská Bystrica, Slovakia

Abstract

Two small occurrences Ľubietová-Kolba (Veporic Superunit) and Čierna Lehota (Tatric Superunit) are characterized by an earlier assemblage of Ni-Co-Fe arsenides and a later assemblage of chalcopyrite, tennantite, and Bi sulfosalts. The earlier assemblage was previously dated (Re-Os) to Ladinian (Middle Triassic, 238 Ma) and linked to the opening of the Meliata Ocean. Ore textures at Kolba are interpreted in this work as diffusion, not replacement textures. Quantitative diffusion modeling shows that the observed profiles could be produced at ≈ 350 °C over ≈ 6 million years, compatible with the Alpine metamorphic conditions determined for the host rocks. The results thus support the radiometric dating. The stable isotopic composition of sulfur (δ³⁴S) in the Ni-Co minerals is + 12 to + 17 ‰ at Kolba and 0 to – 1 ‰ at Čierna Lehota.The most likely sulfur source is the Permian and Triassic sedimentary cover of the Tatric and Veporic superunits. At Čierna Lehota, there is a distinct contribution of the syngenetic pyrite-pyrrhotite ores to the sulfur budget. There is a cluster of previously published model Pb-Pb Middle Triassic ages for the small ore occurrences Nižné Matejkovo, Čavoj, Častá, and perhaps also Trangoška. They could represent small hydrothermal cells with fluids that leached the local host rocks during a Middle Triassic thermal event. The ore veins have small extent and their content corresponds well to the chemical and mineralogical composition of the leached local rocks.

Key words: ore mineralizations, Western Carpathians, Ľubietová-Kolba, Čierna Lehota, diffusion modeling, sulfur isotopes, Triassic hydrothermal events

Manuscript received: 2022-01-01

Revised version accepted: 2022-06-27