Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original paper

Stefan Kiefer, Martin Števko, Rastislav Vojtko, Daniel Ozdín, Axel Gerdes, Robert A. Creaser, Marek Szczerba, Juraj Majzlan

Geochronological constraints on the carbonate-sulfarsenide veins in Dobšiná, Slovakia: U/Pb ages of hydrothermal carbonates, Re/Os age of gersdorffite, and K/Ar ages of fuchsite

Journal of Geosciences, volume 65 (2020), issue 4, 229 - 247

DOI: http://doi.org/10.3190/jgeosci.314

The abandoned deposit Dobšiná in eastern Slovakia used to be exploited for Ni-Fe-Co sulfarsenides in siderite-ankerite hydrothermal veins. These veins are locally accompanied by alteration zones of fuchsite-quartz-carbonate rocks. The Ni-Fe-Co sulfarsenides are postdated by chalcopyrite and tetrahedrite. This work aims to determine the age of these mineralizations utilizing U/Pb, Re/Os, and K/Ar dating of selected minerals. U/Pb dating of hydrothermal siderite and ankerite gave ages from 145 ± 5 Ma to 114 ± 24 Ma. They broadly coincide with the metamorphic peak in the Gemeric Unit and the formation of the Gemeric cleavage fan (CGF) during partial exhumation of this unit. Hydrothermal gersdorffite was dated (Re/Os) to 93.6 ± 0.9 Ma, the time of exhumation of the Gemeric unit. No data were extracted for the younger Cu sulfides. By correlation with other units in the Western Carpathians, they could be assigned Late Cretaceous age, corresponding to welding of the Gemeric and Veporic units and the formation of the Trans-Gemeric shear zone. The fuchsite rocks were dated (K/Ar) to 110 Ma, but this datum conflicts with textural evidence, which shows that these rocks are older than the hydrothermal carbonates. The age of 110 Ma is therefore considered to be cooling age after the reset of the geochronometer by the Alpine metamorphism, in agreement with earlier data. The geochronological results are supported by structural measurements and field observations. The main mineralized zone, investigated in one of the accessible adits, conforms with the Variscan - ?Alpine metamorphic foliation. There are also younger, less significant structures whose relevance to the ore mineralization is not yet clear.