UNIVERZITA KOMENSKÉHO V BRATISLAVE VZÁCNOPRVKOVÁ ...

Summary
Exploration of the granitic pegmatites, as well as study of granites in the Western
Carpathians area, yielded a discovery of a new granitic pegmatite with the rare-element
mineralization in the Bratislava granitic massif, Malé Karpaty Mts. (locality Bratislava –
Jezuitské lesy) and also a discovery of the Nb-Ta mineralization in pegmatitic
leucogranite from the Považský Inovec Mts. (locality Prašice - Duchonka). Attention was
aimed also to previously identified Nb-Ta mineralization in the leucogranite from Dlhá
dolina near Gemerská Poloma (gemeric unit).
The Jezuitské Lesy granitic pegmatite is located in the Malé Karpaty Mountains,
about 6 km NW of Bratislava town centre, at the locality Jezuitské lesy. The pegmatite is
hosted by muscovite-biotite granodiorite to granites of the Bratislava Granitic Massif
(BMG). The Jezuitské Lesy pegmatite represents a relatively small pegmatite dike,
approx. only 1 to 2 m thick, poorly outcropped in flat hill around the forest path. The
contact between the granodiorite and pegmatite dike is sharp, intrusive. On the basis of
excavated pegmatite blocks and rock fragments, the dike show internal zoning comprises
a coarse-grained quartz-microcline-muscovite zone, locally with gradual transition into
blocky K-feldspar and quartz zone (probably in the central part of the dike). Common
aplitic, fine-grained saccharoidal albite unit (albite >> quartz + muscovite + garnet), rarely
fan-shaped platy albite (cleavelandite) extensively replace the older pegmatite zones. The
accessory minerals include beryl (locally Na,Cs-rich), phenakite, bertrandite, garnet
(almandine-spessartine), Mn-rich fluorapatite, monazite-(Ce), cheralite, Hf-rich zircon,
gahnite, uraninite, pyrite, galena and the Nb-Ta oxide minerals.
Besides the most widespread columbite-tantalite group minerals, ferrotapiolite,
ferrowodginite and microlite were identified in the Jezuitské Lesy pegmatite. The
occurrences of the all above mentioned minerals are restricted to the coarse-grained
quartz-microcline-muscovite and fine-grained late saccharoidal albite unit. On the basis of
compositions and textural relationships, the columbite-tantalite, ferrotapiolite and
ferrowodginite form three generations with distinct textural and compositional features.
The first generation of the Nb-Ta minerals comprises ferrotantalite (Ct I), ferrotapiolite (Ft
I) and ferrowodginite (Fw I), in the coarse-grained quartz-microcline-muscovite zone.
They show Ta,Fe-rich compositions with Ta/(Ta+Nb) = 0.52-0.70 (Ct I), 0.88-0.90 (Ft I)
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