[1] Comenius Univ, Fac Nat Sci, Dept Mineral & Petrol, Ilkovicova 6, Bratislava 84215, Slovakia
[2] AP Karpinsky Russian Geol Res Inst FGBU VSEGEI, Ctr Isotop Res, Sredny Prospekt 74, St Petersburg 199106, Russia
[3] Slovak Acad Sci, Earth Sci Inst, Dubravska Cesta 9, Bratislava 84005, Slovakia