Acta Musei Moraviae

Lepidolite pegmatite from Dobrá Voda near Velké Meziřící, western Moravia

Lepidolite pegmatite from Dobrá Voda is located in the southeastern part of the Strážek Moldanubicum, close to the contact with the Třebíč Durbachite Massif. Pegmatite forms a symmetrically zoned, steeply dipping dike, up to 6 m in width and about 100 m in length, emplaced in amphibolite and gneiss. The pegmatite dike consists of a dominant, marginal fine- to medium-grained granitic unit (I) with locally abundant aplitic subunit (I a), a graphic unit (2), abundanr coarse-grained albite unit consisting of muscovite-albite subunit (3a), outer lepidolite-albite subunit (3b), and inner lepidolite-albite subunit (3c) adjacent to a lepidolite unit (4) in center of the dike. Blocky K-feldspar, amblygonite-montebrasite and pseudomorphs consisting of spodumene + quartz intergrowths after petalite occur in albite unit (3), particularly in lepidolite-albite subunits (3b, 3c). Three types of pockets were rocognized – rubelite-bearing pockets (5), verdelite-bearing pockets (6) and late cookeite-bearing pockets (7).

The most abundant minerals include quartz, K-feldspars and albite. Micas (biotite, muscovite, trilithionite, polylithionite) and tourmaline (schorl, foitite, elbaite, rossmanite) are typical subordinate minerals present in almost all textural-paragenetic units. Amblygonite-montebrasite and spodumene + quartz intergrowths are typical mi nor minerals. Cassiterite, apatite, manganocolumbite, stibiotantalite, zircon and topaz are typical accessory minerals. Hydrothermal minerals include cookeite, microlite, stibiomicrolite, cesstibtantite, manganotantalite, tapiolite mineral, clay minerals (montmorillonite, halloysite, kaolinite), chalcedony and opal.

Internal structure, mineralogy, chemistry of minerals and their compositional trends indicate that the Dobrá Voda lepidolite pegmatite is a typical lepidolite subtype pegmatite similar to other lepidolite pegmatites in the Bory region (Dolní Bory, Laštovičky) and to the pegmatites Nová Ves near Český Krumlov and Jeclov near Jihlava.