Desilicated pegmatite with OH-rich fluorapatite and niobian rutile from Utín near Havlíčkův Brod

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Acta Mus. Moraviae, Sci. Geol. 93 (2008), issue 1–2, pages 81–89
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Abstract:

Desilicated pegmatite with OH-rich fluorapatite and niobian rutile from Utín near Havlíčkův Brod

Mineral assemblages of strongly desilicated granitic pegmatite at Utín near Havlíčkův Brod were examined. The pegmatite crosscuts a small serpentinite body. Prevailing mineral of the pegmatite is a massive chlorite; it encloses relics of plagioclase, fresh phlogopite and accumulations of phlogopite with macroscopically red apatite, colored by thin veinlets of Fe-oxides. Hyalophane (K, Ba-feldspar), scheelite, Nb-rutile, uraninite and zircon were found in microscopic grains. Chlorite occurs in at least three generations, chlorite I and II replaces plagioclase, chlorite III fills fissures in older minerals. Plagioclase is preferentially replaced along twinning lamellae. Phlogopite is a primary mineral; it remained stable during replacement processes. Apatite is a member of fluorapatite-hydroxylapatite (FAp0.6–0.7HAp0.3–0.4) solid solution with slightly elevated content of Fe, Mn and Mg, and low content of Y+REE. Nb-rutile contains 7.33 wt. % of Nb2O5, 2.03 wt. % Ta2O5 and 1.49 wt. % SnO2. Desilication of the pegmatite is most probably related to the hydrothermal alteration processes in the host serpentinite.

Contact:

Jan Cempírek, Moravian Museum, Dept. of Mineralogy and Petrography, Zelný trh 6, 659 37 Brno; e-mail: jcempirek@mzm.cz
Vladimír Strunga, Institute of Geological Sciences, Masaryk University, Kotlářská 2, 61137 Brno
Radek Škoda, Institute of Geological Sciences, Masaryk University, Kotlářská 2, 61137 Brno

Citation:
Cempírek, J., Strunga, V., Škoda, R., 2008: Desilikovaný pegmatit s OH-bohatým fluorapatitem a niobovým rutilem z Utína u Havlíčkova Brodu. – Acta Mus. Morav., Sci. Geol., 93, 1–2, 81–89 (with English summary)
ISSN: 1211–8796