Publication details

Milarite-group minerals from the NYF pegmatite Velká skála, Písek district, Czech Republic: sole carriers of Be from the magmatic to hydrothermal stage

Authors

NOVÁK Milan JAROSLAV Cícha ČOPJAKOVÁ Renata ŠKODA Radek VAŠINOVÁ GALIOVÁ Michaela

Year of publication 2017
Type Article in Periodical
Magazine / Source European Journal of Mineralogy
MU Faculty or unit

Faculty of Science

Citation
Web https://www.schweizerbart.de/papers/ejm/detail/29/88113/Milarite_group_minerals_from_the_NYF_pegmatite_Velka_skala_Pisek_district_Czech_Republic_sole_carriers_of_Be_from_the_magmatic_to_hydrothermal_stage
Doi http://dx.doi.org/10.1127/ejm/2017/0029-2652
Keywords milarite; agakhanovite-(Y); EPMA; LA–ICP-MS; CL; compositional trends; beryllium; NYF pegmatite
Description Four distinct paragenetic, morphological and compositional types of milarite-group minerals were distinguished in the NYF pegmatite Velka skala, Pisek district, Czech Republic (Moldanubian Zone). The simply zoned (Kfs, Plg, Ab, Qz> Bt> Ap> Tur) pegmatite dike, similar to 60 cm thick, is enclosed in durbachite (K, Mg-rich melasyenite). The milarite-group minerals include: yellowish, subhedral, prismatic grains of homogeneous milarite I (milarite s. s.); prismatic subparallel aggregates of white to grayish milarite II (zoned milarite s. s. to Sc-rich milarite, up to similar to 20 mol% of the oftedalite component) from small pockets; colorless hexagonal prismatic crystals of milarite III (milarite s. s.) lining open fractures and microscopic fillings in recrystallized K-feldspar locally associated with REE-bearing minerals (allanite, aeschynite, titanite); very rare milarite IV (milarite s. s. to agakhanovite) as prismatic crystals and thin overgrowths with complex oscillatory zoning, <= 200mm in size, on crystals of milarite II and milarite III. Their mineral assemblages, textures and compositions suggest primary (magmatic) for milarite I and hydrothermal origin for milarite II, III, and IV. The simplified compositional evolution in these milarites is: Al+Ca -> Be+Sc -> Be+Y, HREE -> Be+LREE. Milaritegroup minerals are the sole carriers of Be in the pegmatite, no relics or pseudomorphs after other Be-rich minerals were found; thus milarite is now established as an additional primary Be-rich mineral in granitic pegmatites. Mineral assemblages, chemical composition of minerals and close relation to the host durbachite suggest an NYF affinity of the Velka skala pegmatite as well as a close relation to euxenite-type pegmatites of the Trebic Pluton. Milarite-group minerals from Velka Skala exhibit very similar compositional evolution to those found in the Heftetjern pegmatite, Tordal, Norway.
Related projects:

You are running an old browser version. We recommend updating your browser to its latest version.

More info