Mineralogy of titanite-rich nodules from biotite granite of Tábor Pluton (Moldanubicum, Dražičky near Tábor quarry, Central Bohemia)Article PDF
Mineralogy of titanite-rich nodules from biotite granite of Tábor Pluton (Moldanubicum, Dražičky near Tábor quarry, Central Bohemia)
The elongated body of biotite granite with titanite-rich nodules is situated on the contact of amphibole-biotite and amphibole-pyroxene melasyenites of the Tábor pluton. Titanite-rich nodules are spherical, 1 to 3 cm in diameter and consists of a dark core (titanite + quartz + K-feldspar + plagioclase) surrounded by a leucocratic rim (quartz + K-feldspar + plagioclase ± phlogopite). Titanite, with an elevated Al (~ 0.07–0.11 apfu) and low F (0.039–0.069 apfu), forms subhedral poikilitic grains with abundant inclusions of euhedral to subhedral crystals of K-feldspar, plagioclase (An5–25) and anhedral quartz. The presence of titanite-rich nodules indicates intrusion of the felsic melt into the mafic system. This process led to the destabilization of biotite (amphibole) and the formation of titanium-rich melt, which was in corporated by the incoming felsic melt. The occurrence of isolated patches of poikilitic titanite rimmed by leucocratic rim indicates that Ti-rich melt flowed along with the felsic melt as a separate immiscible phase.
David Buriánek, Czech Geological Survey, Leitnerova 22, 659 37 Brno, Czech Republic, e-mail: email@example.com
Stanislav Houzar, Department of Mineralogy and Petrography, Moravian Museum, Zelný trh 6, 659 37 Brno, Czech Republic