2013) The Julianna pegmatite vein system at the Piława Górna mine, Góry Sowie Block, SW Poland -preliminary data on geology and descriptive mineralogy. Geological Quarterly, 57 (3): The newly discovered Julianna pegmatitic system from the Piława Górna quarry (the Góry Sowie Block, Sudetes, 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

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... 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 the texturally well-differentiated ones that are composed of a fine-grained border zone, coarse-grained wall zone, graphic and blocky feldspar intermediate zones and quartz core. Unidirectional and skeletal solidification textures are well developed. The Julianna pegmatites consist of rock-forming plagioclase (≤An 39 ), microcline, quartz and biotite accompanied mostly by accessory to minor muscovite, tourmaline, garnet and beryl. They crystallized from anatectic melt of hybrid NYF+LCT geochemical characteristics. Pegmatites with 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 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. INTRODUCTION Until the beginning of the 1900s pegmatites of the Góry Sowie Block (GSB) were locally mined for feldspar and quartz for use in the ceramics and glass industry. The mining activity included even underground exploitation and was especially intensive in the area between Piława, Różana, Owiesno and Bielawa (Meister, 1932 fide Lis and Sylwestrzak, 1986). Since the end of the exploitation, no new large-scale outcrops have been uncovered. Thus contemporary studies of GSB pegmatites have been limited to old quarries, mine dumps, and small-sized natural exposures along the shoreline of Lake Bystrzyckie, road and railroad cuts. As a consequence, the amount of available research material was insufficient for studying rare minerals and the lack of in situ exposures of larger pegmatitic bodies precluded systematic research on their textural and geochemical internal zoning. In 2001 the Dolnośląskie Surowce Skalne mining company initiated a project to open a quarry for amphibolite and migmatite at Piława Górna. At the end of 2007, the preparatory works uncovered the first portion of a system of pegmatitic veins, which was later named "Julianna" (Szełęg et al., 2010). Various sections of Julianna were exposed between 2008 and 2010. The whole pegmatitic system consisted of numerous anastomosing and sometimes cross-cutting veins hosted by tectonized amphibolites. In 2009, when the most complete exposure was achieved, the system extended over 60-80 metres in plan view and was defined by three main dikes oriented NNE-SSW and dipping WNW at moderate-to-steep angles. Some pegmatitic dikes could be traced up to 50 metres in vertical section. The dimensions of this exposure, unprecedented on the scale of the whole GSB massif, and the possibility of sampling various sections of the veins systematically uncovered during the on-going exploitation offered a unique opportunity for comprehensive petrological and mineralogical studies. This paper aims at providing the first coherent report on the results of field studies of the Julianna system, supported by identification of selected minerals by means of X-ray powder diffraction, semi-quantitative SEM-EDS or quantitative WDS electron microprobe analyses. The present study focused on the low-to moderately-evolved pegmatites, which largely dominate in the Julianna system. However fragments of the pegmatites that display very high degree of geochemical fractionation, as evidenced by the presence of Cs-and Li-rich minerals, were also found (Pieczka, 2010c). GEOLOGICAL SETTING The Sudetes form the NE margin of the Bohemian massif and represent the NE termination of the European Variscan orogenic belt. The region extends between the WNW-ESE trending regional tectonic zones of the Upper Elbe and the Middle Odra. Sudetic rocks subcrop under Permo-Mesosoic and Miocene sediments in the NE and SE, respectively, and merge with the Neoproterozoic Lusatian massif towards NW (Mazur et al., 2007 and references therein). The Sudetes are generally built of: (i) basement units that include fragments of Cadomian crust with Lower Paleozoic metasediments and metaigneous rocks, injected by Variscan granitoids and (ii) late-to post-Variscan cover of Lower Carboniferous-Cenozoic age. Based on major differences in lithology, structural characteristics and geological evolution, the Sudetes are divided into western, central and eastern parts, each consisting of a number of smaller, mostly tectonically bounded, units (Mazur et al., 2007). Thus the whole region represents a complex mosaic of distinct tectono-stratigraphic units, whose mutual relations are blurred by blocky type tectonics related to the Alpine orogeny. The Sudetic Boundary Fault, a NE-SW trending Late Variscan structure rejuvenated during the Alpine orogeny (Aleksandrowski et al., 1997; Badura et al., 2003), separates the Sudetes into a topographically distinctive mountainous part in the SW and strongly peneplained lowlands of the Fore-Sudetic Block in the NE, now mostly under thick Cenozoic cover. The triangular-shaped GSB is one of the main geological units of the Central Sudetes (Fig. 1) . It extends over ~600 km 2 between Szczawno Zdrój, Srebrna Góra and Oleszna, SW from Wrocław (SW Poland). GSB is divided by the Sudetic Boundary Fault and about two-thirds of the area is located in the Fore-Sudetic Block, whilst the remaining one-third is in the elevated mountainous part of the Sowie Mts. The foreland domain is considered to represent an intersection level about 5 km deeper than the mountainous part (Żelaźniewicz, 1995). GSB (Fig. 1) is composed predominantly of metasedimentary and felsic metaigneous gneisses and migmatites, with minor intercalations of amphibolites, granulites, recently discovered eclogites (Ilnicki et al., 2010 (Ilnicki et al., , 2011, hyperites, highly serpentinized mantle rocks, marbles and calc-silicate rocks (e.g., Polański). The metamorphic suite is cut by granites, aplites, pegmatites, rhyolitic and lamprophyric dikes as well as barite and quartz hydrothermal veins. The late Proterozoic -early Cambrian protolith (Gunia, 1985; Kröner and Hegner, 1998; Kryza and Fanning, 2007) has undergone polymetamorphic evolution (Kryza, 1981; Żelaźniewicz, 1987 , 1990 . Early HP-HT episode at ∼400 Ma was overprinted by the event under high amphibolite facies conditions ca. 385-370 Ma (van Breemen et al., 1988; Brueckner et al., 1996; O'Brien et al., 1997; Bröcker et al., 1998; Aftalion and Bowes, 2002; Gordon et al., 2005; Kryza and Fanning, 2007). Decompression led to local partial melting and formation of anatectic granodiorites and pegmatites (Kryza, 1981; Timmermann et al., 2000) . Piława Górna is located in the east of the GSB foreland, about 10 km SE of Dzierżoniów and over 50 km SW of Wrocław (Lower Silesia, SW Poland). The "Piława Górna" open pit quarry, situated on the Rybak hill 1.5 km north of the town (Fig. 2) , exploits the migmatite-amphibolite rock deposit with over 323 million tons of measured resources. Migmatite accounts for about 72% of the raw rock and the rest is mainly amphibolite, with minor bodies of granitic pegmatite. Rock processing takes place in a plant located nearby (Fig. 3) . Final products are used as construction and concrete rock aggregates. THE GÓRY SOWIE PEGMATITES In GSB pegmatites occur as pods, lenses and dikes in amphibolites, migmatites, gneisses and granulites, rarely in other rock types (Smulikowski). At most occurrences the pegmatites are from centimetres to 1 m thick, reaching several metres only exceptionally. Textural and mineral zonation is well pronounced only in the thickest pegmatitic bodies. Field relationships allow the distinction of an older generation of pegmatites, concordant with the host rocks, mainly migmatites, and a younger one crosscutting the surrounding rocks discordantly. Syntectonic older pegmatites are clearly related to the Late Devonian migmatitization event. According to Żelaźniewicz (1990), sub-vertical pegmatitic veins of the younger generation were emplaced along generally N-trending extensional fractures in the D 4 tectonometamorphic event. Crystallisation ages of GSB pegmatites were established at 370±4 Ma using muscovite from Lutomia (van Breemen et al., 1988; Rb-Sr method) and 383-370 Ma using xenotime from Zagórze Śląskie (Timmermann et al., 2000; U-Pb method). Pegmatites of GSB have been well known for large, well-developed crystals of K-feldspar, beryl, garnet and tourmaline since at least the early 1800s (Sachanbiński, 1972(Sachanbiński, , 1973 Lis and Sylwestrzak, 1986 and references therein). The most spectacular specimens were encountered during mining of the pegmatitic bodies near Piława Górna, Kamionki, Bielawa, Różana, Owiesno and Grodziszcze in the Fore-Sudetic Block. Most of the pegmatitic bodies have a simple mineral composition, limited to rock-forming quartz, albite-oligoclase, K-feldspar and micas. Common accessory minerals include tourmaline, garnet and apatite and sometimes also beryl whilst hornblende, andalusite, sillimanite, kyanite, cordierite, zircon, titanite and others are rare (Sachanbiński, 1972; Kryza, 1977). Hybridization of pegmatitic melt emplaced in metabasites resulted in enrichment in biotite, epidote, hornblende, apatite and tourmaline at the expense of quartz, plagioclase and muscovite and sometimes led to the formation of cordierite-bearing bodies (Kryza, 1977). The garnet belongs to the almandine-spessartine series and the tourmaline is mostly Al-and