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Kozłowski Andrzej, Matyszczak Witold

Acta Geologica Polonica

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2022

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Vol. 72, no. 1

9--31

EN

Fluorite mineralization was studied in the Variscan granitoid Karkonosze pluton in the northern part of the Bohemian massif (Lower Silesia, Poland). Fluid inclusions in fluorite and quartz were investigated by the following methods: heating and freezing on an immersion microscope stage, spectrophotometric and electron probe analysis, calcination and water leachate. The parent fluids of fluorite were of the Na-Ca-Cl type with a low CO₂ content. The fluoride ions had sources in the pluton and in its host rocks. Fluid inclusion observations provide evidence of various post-formation alteration. such as refilling, partition, cracking, migration, expulsion or vacuole modification from irregular to cubic habit. A final model of fluorite origin and parent fluid evolution is presented.

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Oxygenic bismuth minerals in the NE part of the Karkonosze pluton (West Sudetes, SW Poland)

Kozłowski A., Matyszczak W.

Acta Geologica Polonica

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2018

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Vol. 68, no. 4

537--554

EN

The study presents fifteen oxygen-bearing secondary minerals of bismuth from the north-eastern part of the Variscan Karkonosze granitoid pluton in the northern zone of the Bohemian massif. The minerals were investigated by optical, electron microprobe, classic chemical, XRD, IR absorption and fluid inclusion methods. The late, very low temperature epithermal solutions most probably caused formation of sillénite, kusachiite, bismoclite, bismutite, beyerite, kettnerite, pucherite, schumacherite, namibite and eulytite. Solutions dominated by supergene (meteoric) waters were the parents for bismite, russellite, koechlinite, ximengite and walpurgite. The paper also contains information on early research on the investigated minerals.

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Graftonite-sarcopside intergrowths in phosphate nodulas from pegmatite at Michałkowa, Sowie Mountains Block, SW Poland

Grochowina A., Gołębiowska B., Pieczka A.

Geology, Geophysics and Environment

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2012

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Vol. 38, no. 4

477--478

EN

Sareopside (Fe,Mn,Mg)3(PO4)2 and graftonite (Fe,Mn,Ca)3(PO4)2 are the dominant minerals found in the phosphate nodules from the Michalkowa pegmatite in the Sowie Mountains block. The nodules are rather small with mainly varying brown coloration and with lamellar texture visible in hand specimen. Both minerals occur with other primary and secondary phosphates in the form of nodules like triphylite or ferrisicklerite, stanekite or wolfeite, members of the arrojadite and wyllieite groups, kryzhanovskite, fluorapatite and others. Apart of typical pegmatite minerals like quartz, microcline, albite, muscovite and biotite, only black tourmaline can be found. Pyrrhotite, pyrite and chalcopyrite, occurring in the form of tiny grains or veinlets, penetrating also the phosphate nodules are common. Standard mineralogical investigations (light and reflected microscopy, XRD), combined with SEM-EDS analyses and WDS method were carried out to characterize these phases. Graftonite and sareopside form massive aggregates of euhedral crystals or lamellar intergrowths. Euhedral crystals of sareopside are typically enriched in Mn and Mg. Ca is commonly absent or present in negligible amounts. MnO usually ranges between 10.0-11.0 wt. %; only locally reaches a higher content up to 13.3 wt. %, MgO content commonly reaching 4.0-5.0 wt. %, or only about 2.0 wt. % in Mn-rich compositions. The lamellar sareopside shows compositional characteristics similar to the variety forming the euhedral crystals. In consequence, the Mn/(Mn+Fe) ratio that informs about a degree of Mn-Fe fractionation in the parental, pegmatite forming melt, attains in both morphological varieties of sareopside rather low values, usually 0.18-0.20. In graftonite the CaO content is higher in crystals co-occurring with euhedral sareopside, reaching in this variety up to 11.0 wt. %, whereas the lamellar graftonite has only 6-7 wt. % of the component. In both types of graftonite the contents of MgO are less than in sarcopsi-de and they do not exceed 2.0 wt. %. Graftonite richer in Ca is simultaneously poorer in Mg. FeO content is higher in graftonite forming lammelar intergrowths with sarcopside (31.0-32.0 wt. %), and slightly lower in euhedral crystals (27.0-28.0 wt. %). Manganese is close similar in both varieties, whereas Zn is undetectable or present in a small content distinctly below 1 wt. % ZnO. The lower Mn/(Mn+Fe) values (0.36-0.39) are characteristic of lamellar graftonite; only slightly higher values (0.40-0.41) attains graftonite in association with euhedral sarcopside. Both minerals show weakly varying compositions resulted from homovalent substitutions (Fe, Mn)2+ <-> Mg2+ and Ca2+ <-> (Fe, Mn)2+ marked in varying values of Mn/(Mn+Fe) ratio. The minerals crystallized from the parental P-bearing melt exsolved from pegmatite-forming silica melt during temperature decreasing. The formation of the massive or lamellar forms depends on a relationship between amounts of the exsolved Ca-and P-bearing melt and its Ca-negligible counterpart.

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Cadomian versus younger deformations in the basement of the Moravo-Silesian Variscides, East Sudetes, SW Poland: U-Pb SHRIMP and Rb-Sr age data

Żelaźniewicz A., Nowak I., Bachliński R., Larionov A.N., Sergeev S.A.

Geologia Sudetica

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2005

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Vol. 37

35-51

EN

U-Pb SHRIMP dating of zircons from a metapegmatite vein which cross-cuts amphibolite facies paragneisses confirms ~580 Ma magmatism in the basement of the northern part of the Moravo-Silesian Zone (Jeseníky Mts.). Structures older than the felsic vein set are interpreted as a record of the Cadomian orogeny. This has been represented by N-trending, W-vergent folds followed by a top-to-the east shearing that occurred at T = 600°C and P = 5 kbar in the Neoproterozoic. The subsequent tectonic overprint led to folding and shearing of the pegmatite, which took place at similar P-T conditions but was associated with top-to-the west kinematics and shortening at a high angle to the foliation. This event likely developed during early stages of Variscan convergence when the Moravo-Silesian crust (Brunovistulia) was subducted and forced down below the approaching upper plate composed of terranes of the Bohemian Massif. Alternatively, it may have occurred around 500 Ma, related to crustal extensional (break-up of Gondwana margins in Cambrian times). Although the first option is favoured, presumably the two may have actually happened. The last ductile deformation was a top-to-the-east younger shearing localized in zones of various widths, assigned to the Variscan collision and reverse movement of the basement rocks. The latter two events occurred at temperatures that allowed in the metapegmatite for the crystal plastic deformation of quartz grains from which the strain was removed by subsequent static recrystallization, and that were high enough to reset the Rb-Sr system in this rock. Consequently, the obtained Rb-Sr isochron age of 290 Ma is considered to reflect the time of uplift. Such late regional uplift is characteristic of the northern part of the Moravo-Silesian Zone, which is the footwall to the Moldanubian Thrust, which separates the Bohemian Massif terranes from the Brunovistulia terrane. It follows from this study that in the East Sudetes basement rocks, structures which are often classified as Variscan may in fact be Cadomian and that the Cadomian record in these rocks is richer than previously assumed.

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A rare mineral-bearing pegmatite from the Szklary serpentinite massif, the Fore-Sudetic Block, SW Poland

Pieczka A.

Geologia Sudetica

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2000

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Vol. 33, nr 1

23-31

EN

In the Szklary serpentinite massif, besides serpentinites, amphibolites, rare rodingites and altered gabbros, rather common light-coloured aplites occur. Occurrences of pegmatites are very rare. A small fragment of a pegmatite, basically composed of feldspars, quartz, micas and tourmaline, is exposed only on Mt. Szklana. During detailed mineralogical investigations on it, numerous and sometimes rare or very rare minerals have been identified: chrysoberyl, spessartine, manganocolumbite and manganotantalite, stibiocolumbite, holtite, pyrochlore, beusite, paradocrasite and stibarsen, manganoan apatite and others, occurring in small or very small grains. The pegmatite from Szklary probably represents a product of the crystallization of silicic magma generated from the partial melting of older sediments during high-grade metamorphism. Its structural and textural development (graphic intergrowths), and to some extent its mineral composition make it comparable to some anatectic pegmatites of the gneissic block of the Góry Sowie Mts.