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

[摘要] The abandoned deposit Dobšiná in eastern Slovakia used to be exploited for Ni–Fe–Co sulfarsenides in siderite-ankeritehydrothermal veins. These veins are locally accompanied by alteration zones of fuchsite-quartz-carbonate rocks. TheNi–Fe–Co sulfarsenides are postdated by chalcopyrite and tetrahedrite. This work aims to determine the age of thesemineralizations utilizing U/Pb, Re/Os, and K/Ar dating of selected minerals. U/Pb dating of hydrothermal siderite andankerite gave ages from 145±5 Ma to 114±24 Ma. They broadly coincide with the metamorphic peak in the GemericUnit 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 theyounger Cu sulfides. By correlation with other units in the Western Carpathians, they could be assigned Late Cretaceousage, 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 theserocks are older than the hydrothermal carbonates. The age of 110 Ma is therefore considered to be cooling age after thereset of the geochronometer by the Alpine metamorphism, in agreement with earlier data. The geochronological resultsare supported by structural measurements and field observations. The main mineralized zone, investigated in one of theaccessible adits, conforms with the Variscan – ?Alpine metamorphic foliation. There are also younger, less significantstructures whose relevance to the ore mineralization is not yet clear.

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[关键词] hydrothermal mineralization;geochronology;ore mineralogy;isotopic dating