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Magmatic and post-magmatic phenomena in the Karkonosze granite and its metamorphic envelope (West Sudetes, SW Poland)

Kozłowski A., Ilnicki S., Matyszczak W., Marcinowska A.

Acta Geologica Polonica

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2016

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Vol. 66, no. 3

451--471

EN

Mineralogical studies of the Karkonosze granite (ca. 322–312 Ma) and its surroundings in West Sudetes (SW Poland) have provided data on Nb-Ta-REE minerals from pegmatites in the NE part of the pluton and several new finds of Ag minerals and 15 oxygenic Bi phases, hitherto not reported from the massif. The Karkonosze pegmatites are enriched in HREE as fergusonite-(Y) or xenotime-(Y) appear in almost every studied pegmatite, together with a subordinate assemblage of the aeschynite, euxenite or columbite group. The abundance of LREE minerals such as allanite-(Ce) and the monazite group, correlates inversely with the Nb-Ta-Ti minerals, whilst an early generation of monazite-(Ce) revealed an exceptionally high amount of Nd (up to 22 wt.% of Nd2O3). The physical and chemical conditions during the magmatic and post-magmatic processes were reconstructed and the effects of contact metamorphism in amphibolites from hornfelsed zones examined. Changes in solution composition and concentration at the early magmatic stage (825–920ºC), pegmatitic stage overlapping with hydrothermal (560°C which ended at 160–90°C) and clearly hydrothermal stage (400 to 110°C) were studied in detail by means of melt and fluid inclusions in quartz. Furthermore, post-magmatic fluids, including some enriched in Li and B, were identified in rock-forming quartz from the whole pluton. In turn, study of the amphibolites indicates that the pair cummingtonite + anorthite or the presence of Ca-rich plagioclase with actinolite seem to be reliable mineral proxies of the thermal impact of the granitoid body on amphibolites in its envelope. The inferred conditions of the contact processes (450–550°C, 2.5–4.8 kbar) point to an elevated geothermal gradient (ca. 32–45°C/km) probably reflecting the heat flow induced by the Karkonosze intrusion. Moreover, despite the textural and mineral changes imposed by regional and contact metamorphism, the amphibolites have their pre-metamorphic (magmatic) geochemical features undisturbed.

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Vestiges of Cadomian back-arc environments in the Nové Mesto belt and the western part of the Orlica-Snieżnik Dome

Ilnicki S., Szczepański J., Pin C.

Geologia Sudetica

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2014

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Vol. 42

31--32

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The CETeG 2014 excursion to crystalline basement of the Orlica–Śnieżnik Dome, the Sudetes

Żelaźniewicz A., Budzyń B, Ilnicki S., Jastrzębski M., Murtezi M, Redlińska-Marczyńska A., Stawikowski W., Szczepański J.

Geologia Sudetica

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2014

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Vol. 42

125--136

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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

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2013

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Vol. 57, No. 3

467–-484

EN

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.