Arzenic-rich mineral assemblage in granite from Hora Svaté Kateřiny Škoda
Abstract
Small stock of late-Variscan tin-specialised granite intruded lower Palaeozoic crystalline basement at Hora Svaté Kateřiny, Krušné Hory/Erzgebirge, NW Bohemia. The granite is geochemically specialised: enriched in F, Rb, Li, Sn, Nb, Ta, Th, Y, HREE, Be, As, and poor in P. Some textural features (magmatic brecciation and layering) reveal its subvolcanic character. Low content of phosphorus (<0.1 % P2O5 WR) in intruded silicic melt suppressed crystallisation of common accessory phosphates: monazite and xenotime are rare, apatite is completely absent. Major primary host of Y, HREE and Th are As-enriched zircon and zircon-thorite transitional phases containing 5-12 wt. % Y2O3, up to 32 wt. % of ThO2 and 1-2 wt. % As2O5. As-dominant minerals černovite and zircon-černovite transitional phases crystallized later during the hydrothermal stage.