International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

Permian single crystal U-Pb zircon age of the Roznava Formation volcanites (Southern Gemeric Unit, Western Carpathians, Slovakia)

Pages: 439 - 448


Abstract: Zircon populations from the Roznava Formation volcanic rock complex have been analysed. Euhedral zircons from the 1st volcanogenic horizon with fine oscillatory growth zoning, typical of magmatic origin, gave the average concordia age of 273.3±2.8 Ma, with Th/U ratios in the range of 0.44–0.73. The Permian ages ranging from 266 to 284 Ma were identified in the wider, zoned or unzoned, central zircon parts, as well as in their fine-zoned oscillatory rims. The average concordia age of 275.3±2.9 was obtained from the euhedral zircon population of the 2nd volcanogenic horizon of the Roznava Formation. The analyses were performed on zoned magmatic zircons in the age interval from 267 to 287 Ma, with Th/U ratios in the range of 0.39–0.75. In the later zircon population two inherited zircon grains were dated giving the age of 842±12 Ma (Neoproterozoic) and 456±7 Ma (Late Ordovician). The magmatic zircon ages document the Kungurian age of Permian volcanic activity and contemporaneous establishment of the south-Gemeric basin. The time span of volcanic activity corresponds to the collapse of the Western Carpathian Variscan foreland which expanded southward.

Keywords: Permian, Kungurian, post-Variscan rifting, synsedimentary volcanism, U-Pb magmatic zircon ages, inherited grains

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