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

TRIASSIC AGE OF THE HRONCOK PRE-OROGENIC A-TYPE GRANITE RELATED TO CONTINENTAL RIFTING: A NEW RESULT OF U-Pb ISOTOPE DATING (WESTERN CARPATHIANS)

Pages: 59 - 66

Authors: MARIAN PUTIS, ALEXANDER B. KOTOV, PAVEL UHER, EKATHERINA B. SALNIKOVA, SERGEI P. KORIKOVSKY

Abstract: The Hroncok leucocratic biotite granite represents a small intrusion located in the basement rocks of northern part of the Veporic Superunit (Central Western Carpathians, the Vepor Mts., Slovakia). The rock geochemistry, zircon typology and zircon Zr/Hf ratios reveal their A-type geochemical features and the higher degree of fractionation. Isotope U-Pb data yielded a discordia line with a lower intercept age of 238.6 ± 1.4 Ma (MSWD=1.2), which is interpreted as the crystallization age of the granite. This result shows a younger magmatic event than has often been ascribed to the post-Variscan plutonic activity in the pre-Alpine basement of the Western Carpathians up to now. However, it is synchronous and geochemically analogous with the acid volcanism, products of which occur in the Veporic basement and its Permian-Lower Triassic cover rocks as well as within Triassic sequences of the Silica Superunit. All previously given examples of magmatic/volcanic activity are considered to be indicators of early Alpine continental rifting.

Keywords: Triassic, Western Carpathians, Veporic Superunit, Hroncok A-type Granite, U-Pb isotope dating, zircon

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