Granitic pegmatites of the beryl-columbite subtype in the Tatric Superunit, Western Carpathians, Slovakia: Variscan age determination by in-situ LA-ICP-MS U-Pb dating of columbite-group minerals

Accessory columbite-(Fe) to tantalite-(Fe) from three granitic pegmatites of the Tatric Superunit (Bratislava Massif of the Male Karpaty Mts., Bojna Massif of the Povazsky Inovec Mts. and Suchy Massif of the Strazovske Mts.) was used for dating by the in-situ LA-ICP-MS U-Pb method. The columbite-tantalite crystals were sampled from the most fractionated pegmatite dykes of the beryl-columbite subtype situated in the pre-Alpine, Paleozoic crystalline basement of the Tatric Superunit, Western Carpathians (western and central Slovakia). The obtained columbite-tantalite Concordia ages are as follows: 354.5 +/- 4.5 Ma (Jezuitske Lesy pegmatite, the Bratislava granite Massif), 360 +/- 5.0 Ma (Moravany nad Vahom, Striebornica Ridge pegmatite, the Bojna Massif), and 352 +/- 8.5 Ma (Liestany, Bystry Hill pegmatite, the Suchy Massif). The columbite-tantalite ages show Mid-Variscan formation of rare-element pegmatites from the Devonian/Carboniferous boundary to Tournaisian stage, which is coeval with the emplacement of cogenetic granites during the main phase of Variscan intracontinental subduction and collision. The obtained columbite-tantalite age interval of rare-element granitic pegmatites of the Tatric Superunit (similar to 360 to 350 Ma) is generally older than the ages of Be- and Li-rich rare-element pegmatites of the Moldanubian Superunit in the Bohemian Massif (similar to 340 to 320 Ma). The rare-element granitic pegmatites of the Austroalpine Superunit (Eastern Alps) are significantly younger (similar to 290 to 240 Ma) because they were formed in an extension regime during the Permian to Early Triassic post-Variscan orogenic collapse.