The Julianna peg ma tite vein sys tem at the Pi 3 awa Górna Mine
The newly dis cov ered Julianna peg ma titic sys tem from the Pi3awa Górna Quarry (the Góry Sowie Block, Sudetes, NE mar gin of the Bo he mian Mas sif) is de scribed in terms of geo log i cal set ting, pe trog ra phy and de scrip tive min er al ogy. The sys tem rep re sents the larg est peg ma titic oc cur rence in the Pol ish Sudetes and con sists of a com plex net work of cogenetic rare-el e ment gra nitic pegmatites that in truded into tectonized am phi bo lite as dis cor dant dikes. The pegmatites range from bar ren and weakly zoned to tex tur ally well-dif fer en ti ated ones that are com posed of a fine-grained bor der zone, coarse-grained wall zone, graphic and blocky feld spar in ter me di ate zones and a quartz core. Uni di rec tional and skel e tal so lid i fi ca tion tex tures are well-de vel oped. The Julianna pegmatites con sist of rock-form ing plagioclase (£An39), microcline, quartz and bi o tite ac com pa nied mostly by ac ces sory to mi nor mus co vite, tour ma line, gar net and beryl. They crys tal lised from anatectic melt of hy brid NYF (ni o bium-yt trium-flu o rine) + LCT (lith ium-ce sium-tan ta lum) geo chem i cal char ac ter is tics. Pegmatites with a low to mod er ate de gree of frac tion ation, that dom i nate in the Julianna sys tem, bear NYF-sig na ture ac ces sory min er als, such as al la nite-(Ce), colum bite-, euxeniteand samarskite-group min er als, fergusonite-(Y) and gadolinite-(Y). How ever, rare dikes that at tained a very high de gree of frac tion ation con tain typ i cal min er als of LCT-sig na ture in clud ing tour ma lines of the elbaite-olenite-rossmanite se ries, le pido lite, lithiophilite, spodumene, Cs-rich beryl and pollucite.
Granulitic inliers amidst a gneissic/migmatitic complex of the Owl Mts, Sudetes
In NW part of the Owl Mts, Sudetes, the granulites are characteristically accompanied by serpentinized ultramafic and pyriboIitic rocks, including gametiferous peridotite and websterite of an upper mantle provenance. The ultrabasites display irregular intrusive contacts against the granuIites which pass diaphtoretica1ly into their migmatitic surroundings through a zone of transitional gneissic rock in which the retrogressive replacement of Gr + Ksp by Bio + PIg has been extensively accomplishing. Along the granulite/gneiss contact a belt of strongly recrystallized blastomylonite developed. Both the granulites and serpentinites are foliated and lineated, having received a distinct imprint from the F 2 + M 2 tectonometamorphic episode that affected the gneissic/migmatiti complex. Hence interpretation that the upper mantle ultrabasites had intruded a deep-seated granulitic domain, localized outside the actual Moldanubian Sowie Mts complex, in another level or portion ()f the earth's crust. Then, during the pre- F 2 movements, some indetermined slices were tectonically cut from the parent granulitic domain and after undefined vertical or lateral transport (or both) became upthrust along the ductile shear zones, or otherwise inlaid, into the gneisses just undergoing intense regional folding, metamorphism, and migmatization. Since F 2 + M 2 episode the granulites and accompanying ultramafites have had their further tectonothermal history in common with the Owl Mts gneisses and migmatites.
Trace element and Sm-Nd `age' zoning in garnets from peridotites of the Caledonian and Variscan Mountains and tectonic implications
Ion probe traverses across garnets from peridotites of the Caledonides of Norway and the Variscides of Poland show zoning patterns for Y, V, Zr, Cr, Ti and the REE. The complexly zoned patterns of garnets from the Bystrzyca Gorna peridotite, Poland, are interpreted in terms of a changing P–T history (isobaric cooling followed by decompression and cooling). Weak rimward gradients in REE concentrations in garnets from the Almklovdalen and Sandvika peridotites, Norway, may be relicts of the original growth history of the garnets, but the nearly flat Y, V, Zr, Cr and Ti profiles from the same garnets imply a later period of near-homogenization at uniform P–T. Crushed garnet separates from each body were separated into three or more fractions on the assumption that density and magnetic susceptibility vary with Fe/Mg ratio, and Fe/Mg ratios change from garnet core to rim. Sm-Nd garnet–clinopyroxene ‘ages’ were determined for each fraction to determine whether they are also zoned. Four garnet fractions from the Gory Sowie peridotite give nearly the same ages (397–412 Ma) that are believed to span the interval of garnet growth. Garnet fractions from the Norwegian peridotites define scattered ages (816–1350 Ma) that are suspect, but hint at a Sveconorwegian equilibration event. The data indicate the Variscan and Norwegian peridotites had different histories, despite superficial mineralogical and tectonic similarities. Norwegian garnet peridotites had a long pre-Caledonian history and were extracted from a relatively cold mantle whereas the Variscan garnet peridotites had a comparatively short pre- or Eo-Variscan history and were extracted from a hot mantle.