Cu-(U) mineralisation in the copper sandstones at Šafárka occurrence near Novoveská Huta (Spišská Nová Ves), Spišsko-gemerské Rudohorie Mts., Western Carpathians, Gemeric Unit, eastern Slovakia

Ferenc, Štefan, 1977-

Cu-(U) mineralisation in the copper sandstones at Šafárka occurrence near Novoveská Huta (Spišská Nová Ves), Spišsko-gemerské Rudohorie Mts., Western Carpathians, Gemeric Unit, eastern Slovakia / Štefan Ferenc ... [et al.]. -- Several occurrences of copper sandstone mineralisation type occur in the Permian volcano-sedimentary sequences of the Northern Gemeric Unit (Spišsko-gemerské Rudohorie Mts.). The object of presented mineralogical research was Cu-(U) mineralisation in the copper sandstones at the Šafárka occurrence, located about 4 km SE of Novoveská Huta (part of Spišská Nová Ves district town). Cu-(U) mineralisation occurs in fine-grained psammites of greenish-grey colour. The surface of the samples is limonitized, with coatings of green Cu and U supergene minerals. The main rock-forming mineral is quartz. Carbonate (probably authigenic), muscovite and fragments of sericite shales or highly altered volcanics are present to a lesser extent. Accessories represent K-feldspar, tourmaline and leucoxenized Fe-Ti oxides. Rock matrix is formed mainly by sericite, and fine-grained quartz. Ore minerals (chalcopyrite, pyrite - also var. bravoite, tennantite-(Fe), uranium-bearing leucoxene) form disseminations and veinlets in sandstones. Supergene minerals of Fe, Cu and U (chalcocite, yarrowite, uranophane-α, goethite, malachite, baryte, anglesite and cinnabar) fill microscopic cavities and cracks in the rock. Based on the chemical composition, the studied pyrite can be divided into several groups: a) pyrite with a minimum content of admixtures (composition almost corresponding to the formula FeS2; b) As-bearing pyrite; and c) Ni- and Co-bearing bravoite. Arsenic most likely enters the anionic position of pyrite by the substitution As1-→S1-, and is probably present in solid solution. Zonality of bravoites is caused by ranging in Ni content and the corresponding fluctuations in Fe content (negative correlation), at a relatively constant Co content. Studied bravoites represent a nice example of the preferred concentration of Ni at the edges of the crystals and growth zones. Formation of uranophane-α documents the neutralisation of the environment during weathering of sandstones. Precipitation of baryte and anglesite caused an increase in the pH of the environment (from acid to the slightly basic), which allowed the precipitation of uranophane-α and malachite.

In Acta Geologica Slovaca. -- Bratislava : Univerzita Komenského, 2022. -- ISSN 1338-0044. -- ISSN 1338-5674. -- Roč. 14, č. 2 (2022), s. 87-101