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

Re-Os and U-Th-Pb dating of the Rochovce granite and its mineralization (Western Carpathians, Slovakia)

Pages: 71 - 79

Authors: MILAN KOHUT, HOLLY STEIN, PAVEL UHER, AARON ZIMMERMAN, LUBOMIR HRASKO

Abstract: The subsurface Rochovce granite intrusion was emplaced into the contact zone between two principal tectonic units (the Veporic Unit and the Gemeric Unit) of the Central Western Carpathians (CWC), Slovakia. The Cretaceous age of this granite and its Mo-W mineralization is shown using two independent methods: U-Pb on zircon and Re-Os on molybdenite. The studied zircons have a typical homogeneous character with oscillatory zoning and scarce restite cores. SHRIMP U-Pb data provide an age of 81.5±0.7 Ma, whereas restite cores suggest a latest Neoproterozoic–Ediacaran age (~565 Ma) source. Zircon εHf(81) values –5.2 to +0.2 suggest a lower crustal source, whereas one from the Neoproterozoic core εHf(565)=+7.4 call for the mantle influenced old precursor. Two molybdenite-bearing samples of very different character affirm a genetic relation between W-Mo mineralization and the Rochovce granite. One sample, a quartz-molybdenite vein from the exocontact (altered quartz-sericite schist of the Ochtina Formation), provides a Re-Os age of 81.4±0.3 Ma. The second molybdenite occurs as 1–2 mm disseminations in fine-grained granite, and provides an age of 81.6±0.3 Ma. Both Re-Os ages are identical within their 2-sigma analytical uncertainty and suggest rapid exhumation as a consequence of post-collisional, orogen-parallel extension and unroofing. The Rochovce granite represents the northernmost occurrence of Cretaceous calc-alkaline magmatism with Mo-W mineralization associated with the Alpine-Balkan-Carpathian-Dinaride metallogenic belt.

Keywords: Western Carpathians, Cretaceous granitic rocks, SHRIMP zircon dating, Re-Os molybdenite dating, Mo-W mineralization

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