W-, Nb-, Ta-, and Fe-rich brookite from pegmatite near Bobrůvka, Strážek Moldanubicum (Bohemian Massif, Czech Republic)

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Acta Mus. Moraviae, Sci. Geol. 100 (2015), issue 1, pages 3–16
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Abstract:

W-, Nb-, Ta-, and Fe-rich brookite from pegmatite near Bobrůvka, Strážek Moldanubicum (Bohemian Massif, Czech Republic)

Anatase, brookite, and rutile have been identified in small cavities along with albite, muscovite, tourmaline (Mg-rich schorl) and fluorapatite in pegmatitic material stored in the depositories of the Moravian Museum in Brno and originating from Houperk-hillock near Bobrůvka (Strážek Moldanubicum, Czech Republic). Primitive mineral compositions and simple structure of pegmatites show characteristics of anatectic pegmatites. Brookite shows a significantly complex zonation caused by variation in contents of W (up to 5.7 wt.% WO3), Nb (up to 10.8 wt.% Nb2O5), Ta (up to 2.7 wt.% Ta2O5), Fe (up to 3.8 wt:% FeO) and Al (up to 0.5 wt.% Al2O3). X-ray elemental maps of the selected brookite crystal showed preferential incorporation into different structural levels corresponding to matching crystal faces via three different substitutions. Brookite from Bobrůvka represents the first occurrence of W-rich brookite worldwide. Mineral assemblage in pockets show transitional character from late pegmatitic to alpine-type fissures.

Contact:

Petr Gadas, Department of Geological Sciences, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic. e-mail: pgadas@centrum.cz
Milan Novák, Department of Geological Sciences, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic. e-mail: mnovak@sci.muni.cz
Vladimír Hrazdil, Department of Mineralogy and Petrography, Moravian Museum, Zelný trh 6, 659 37 Brno, Czech Republic. e-mail: vhrazdil@mzm.cz
Juraj Mozola, Department of Geological Sciences, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic. e-mail: 382423@mail.muni.cz
Radek Kummer, Tomečkova 887/3, 638 00 Brno. e-mail: radek.kummer@seznam.cz

Citation:
Gadas, P., Novák, M., Hrazdil, V., Mozola, J., Kummer, R., 2015: W, Nb, Ta a Fe bohatý brookit z pegmatitu u Bobrůvky, strážecké moldanubikum, Česká republika. – Acta Mus. Morav., Sci. Geol., 100, 1, 3–16 (with English summary)
ISSN: 1211–8796