Polykras-(Y), uranpolykras a Ti-Nb-Ta-Fe minerál v kremenných žilách a exokontaktných zónách gemerika, Slovenské rudohorie
Peter Chudík, Peter Bačík, Pavol Malachovský, Pavel Uher, Martin Števko
Accessory polycrase-(Y), uranopolycrase and rutile-like Ti,Nb,Ta,Fe-mineral have been identified in quartz and quartz albitite veins, and silicified phyllites in exocontact zones of tin-bearing granites of the Spiš-Gemer region, Slovak Ore Mountains, eastern Slovakia. Polycrase-(Y) is partly replaced by uranopolycrase and locally also by the Ti,Nb,Ta,Fephase. XRD investigation indicates partly metamict state of the polycrase-(Y) to uranopolycrase. EMPA compositions show wide variations in Y+REE, U+Th, Ca, Ti and Nb+Ta concents and a possible presence of Ca(U,Th)(Y,REE)-2, (U,Th)Ti(Y,REE)-1(Nb,Ta)-1, Ca(Nb,Ta)(Y,REE)-1Ti-1, and Ca(Nb,Ta)2(U,Th)-1Ti-2 substitution mechanisms. The minerals originated probably during post-magmatic to hydrothermal stage of the granite evolution in F-rich fluid regime.