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The Julianna pegmatite vein system at the Piława Górna Mine, Góry Sowie Block, SW Poland – preliminary data on geology and descriptive mineralogy

Szuszkiewicz A., Szełęg E., Pieczka A., Ilnicki S., Nejbert K., Turniak K., Banach M., Łodziński M., Różniak R., Michałowski P.

Geological Quarterly

2013

Vol. 57, No. 3

467–-484

The newly discovered Julianna pegmatitic system from the Piława Górna Quarry (the Góry Sowie Block, Sudetes Mts., NE margin of the Bohemian Massif) is described in terms of geological setting, petrography and descriptive mineralogy. The system represents the largest pegmatitic occurrence in the Polish Sudetes and consists of a complex network of cogenetic rare-element granitic pegmatites that intruded into tectonized amphibolite as discordant dikes. The pegmatites range from barren and weakly zoned to texturally well-differentiated ones that are composed of a fine-grained border zone, coarse-grained wall zone, graphic and blocky feldspar intermediate zones and a quartz core. Unidirectional and skeletal solidification textures are well-developed. The Julianna pegmatites consist of rock-forming plagioclase (ŁAn39), microcline, quartz and biotite accompanied mostly by accessory to minor muscovite, tourmaline, garnet and beryl. They crystallized from anatectic melt of hybrid NYF (niobium-yttrium-fluorine) + LCT (lithium-cesium-tantalum) geochemical characteristics. Pegmatites with a low to moderate degree of fractionation, that dominate in the Julianna system, bear NYF-signature accessory minerals, such as allanite-(Ce), columbite-, euxenite- and samarskite-group minerals, fergusonite-(Y) and gadolinite-(Y). However rare dikes that attained a very high degree of fractionation contain typical minerals of LCT-signature including tourmalines of the elbaite-olenite-rossmanite series, lepidolite, lithiophilite, spodumene, Cs-rich beryl and pollucite.

New K-Ar cooling ages of granitoids from the Strzegom Sobótka Massif, SW Poland

Turniak K., Halas S., Wójtowicz A.

Geochronometria

2007

Vol. 27

5-9

The Strzegom-Sobótka Variscan Massif (Fore-Sudetic Block, NE Bohemian Massif) consists of various post-kinematic Variscan granitoids emplaced into Palaeozoic low grade metamorphic rocks. Biotite from five samples representing the hornblende-biotite monzogranite, biotite monzogranite and biotite granodiorite has been dated using the K-Ar method for two size-fractions (0.25-0.35 and 0.35-0.5 mm). Finer fractions show more intense chloritization and therefore the results for them were rejected in further discussion. Coarser fractions with higher potassium content were accepted as yielding a maximum estimate approaching the true K-Ar biotite cooling ages. The results are clustered in two groups. The older age group (308.8 ±4.6 Ma and 305.5 ±4.3 Ma) comprises results obtained from the biotite granodiorites. They are generally consistent with the zircon crystallization age of 308.4 ±1.7 Ma reported by Turniak et al. (2005) and imply rapid cooling of the biotite granodiorite from magmatic temperatures down to the closure temperature of K-Ar isotopic system in biotite. The younger group is defined by 291.0 ±4.4 Ma and 298.7 ±5.2 Ma ages for the hornblende-biotite monzogranite and 294.2 ±4.3 Ma age for the biotite monzogranite. In the absence of precise U-Pb or Pb-Pb zircon data further geochronological studies are needed to decipher precisely the cooling history of the monzogranites.