Abstract

An electron microprobe study of Y-REE-Th phosphate, silicate and Nb-Ta-Y-REE accessory-mineral assemblages revealed the compositional variations and evolution in post-orogenic, hypersolvus Permian A-type metagranite from Turčok, in the Gemeric Unit, of the Western Carpathians, eastern Slovakia. Prismatic zircon I and allanite-(Ce) are primary magmatic phases. However, the late-magmatic to earlysubsolidus processes led to the formation of a more complex younger assemblage: bipyramidal zircon II, xenotime-(Y), thorite, gadolinite-hingganite-(Y), Nb-Ta-Y-REE oxide phases [fergusonite-(beta)/samarskite-(Y), aeschynite/polycrase-(Y), and Nb-rich rutile?] and possibly monazite-(Ce). However, monazite-(Ce) and the partial alteration of allanite-(Ce), xenotime-(Y) and the Nb-Ta-Y-REE minerals are probably connected with a younger Alpine metamorphic overprint of the granite. Thorite appears as a solid solution in the thorite-xenotime-zircon series; it is also enriched in Al. Fergusonite-(beta)/samarskite-(Y) and especially aeschynite/polycrase-(Y) show increased P, Si and Al contents.

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