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Native silver in the eastern part of the Karkonosze granitoid pluton, Lower Silesia, Poland

Kozłowski Andrzej, Matyszczak Witold

Acta Geologica Polonica

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2023

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Vol. 73, no. 2

223--245

EN

This article describes silver specimens of the size of tenths to a few millimetres, found in small pegmatites and quartz veinlets of the porphyritic granitoid area in 22 sites in the eastern part of the Variscan granitoid Karkonosze pluton, from 20 of which native silver occurrences were previously not known. The sites are scattered on the whole surface of the granitoid. The native silver occurred in wire, rod, platy, dendritic, anhedral granular and euhedral cubic and octahedral habits; in some specimens twins and fenster faces were also found. Associated with native silver small amounts of acanthite crystallized commonly, sometimes apparently formed by sulphur diffusion into silver. Inclusions of native gold, electrum, galena, chalcopyrite and pyrite occurred in the native silver. The parent fluids of the specimens were epithermal, because the homogenization temperature (Th) of inclusions in quartz, calcite and cleavelandite that were the host minerals of the native silver was generally 91–165ºC and for individual samples the Th range was 4–11ºC. The total salinity of the fluid was 2.4–7.2 wt. % with Na and Ca (hydro)carbonates as the main dissolved components and admixtures of K, Mg, Fe, Al, S, Cl and F. The parent granitoid contains Ag in trace amounts (0.034–0.056 ppm) and was probably the source of this element for the crystals of native silver. Migration of Ag was made easier by the presence of fluoride ions in fluids.

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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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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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Nowe kierunki naukowo-badawcze w polskiej części obszaru sudeckiego w aspekcie zastosowania technologii HDR i EGS

Bujakowski W., Barbacki A., Skrzypczak R.

Przegląd Geologiczny

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2013

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Vol. 61, nr 11-2

706–-711

EN

The fast-growing discipline in the field of geothermal research is the prospecting for geological structures useful for HDR (Hot Dry Rock) or EGS (Enhanced Geothermal Systems) technologies. In Poland, an interesting area for such research is the Sudetes, particularly the Karkonosze Mts. pluton and Fore-Sudetic Block. The article presents issues of scientific projects prepared in the Division of Renewable Energy of Mineral and Energy Economy Research, Institute of the Polish Academy of Sciences in Kraków, related to the recognition of geothermal conditions of the Sudetic region. On the background of global research, these projects demonstrate an innovative character mainly by targeting research on the analysis of tectonics and volcanism of the Sudetes as important factors of the presence of local positive thermal anomalies. Implementation of the afore-mentioned projects would create the possibility of extending still modest knowledge of the deep geological structure of the Sudetic area.

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Mantled alkali-feldspar megacrysts from the marginal part of the Karkonosze granitoid massif (SW Poland)

Słaby E., Galbarczyk-Gąsiorowska L., Baszkiewicz A.

Acta Geologica Polonica

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2002

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Vol. 52, nr 4

501-519

EN

Mantled alkali feldspar megacrysts from the porphyritic granite variety of the Karkonosze Variscan pluton (SW Poland) have been studied. The feldspars contain numerous inclusions of minerals (mainly plagioclases), which form inner rims, marking successive zones of megacryst growth, and they are surroundet by a plagioclase mantle (rapakivi texture). Although, due to maturation and coarsening, the feldspars display a heterogeneous exsolutions pattern, in the core part some homogeneous sectors (without visible decomposition) are also preserved. Chemical composition of alkali feldspar megacrysts (including barium concentration) and of plagioclases (inner inclusions and mantle) has been determined and used for evaluation of thermal conditions of melt crystallization. The highest calculated temperature for single equilibrium and close-to-equilibrium pairs of un-decomposed domains in alkali feldspar + plagioclase inclusion ranges 809-750 stopni C. The differences in crystallization temperature calculated for the pairs alkali feldspar domains (megacryst) and plagioclase inclusions from successive inner rims or for the pairs alkali feldspar domains (megacryst) - plagioclase mantle varied within 100 stopni C. Common lack of equilibrium for neighbouring pairs of plagioclase inclusion - alkali feldspar is noticeable. Growth morphologies of plagioclases (inclusions and mantle) and alkali feldspar have been proved by means of CL. Mostly the feldspars display sings of resorption and re-growth at many stages of their formation. The barium concentration in the feldspars also points to discontinuous growth. The crystallization path of the megacrysts and the formation of rapakivi texture were influenced by magma mixing, not by decompression processes.