Textural and compositional evidence for a polyphase saturation of tourmaline in granitic rocks from the Třebíč Pluton (Bohemian Massif)

Abstract

Crystallization of granite melts produced several textural types of granites and pegmatites in the Třebic Pluton: dykes of volumetrically dominant muscovite–biotite granite, minor tourmaline granite and veins of tourmaline pegmatite. Evidence for polyphase saturation of tourmaline was observed including the following textural and compositional types of tourmaline: (i) nodules surrounded by leucocratic halos; (ii) euhedral to subhedral grains randomly distributed within tourmaline granite and tourmaline–quartz accumulations with leucocratic halos in the marginal part of granite dykes; (iii) rare columnar crystals of black tourmaline occurring locally in central parts of pegmatite; (iv) dravite-rich rims and late dravite veinlets in tourmaline grains from nodules, suggesting crystallization from hydrothermal fluids.