Petrology, Geochemistry and Mineralogy of Greisens Associated with Tin-Tungsten Mineralisation: Hub Stock Deposit at Krásno–Horní Slavkov Ore District, Czech Republic (original) (raw)
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Acta Geodynamica et Geomaterialia, 2014
Argillized granites from the Hub stock contain a clay mineral assemblage formed by dickite, illite, tosudite and smectite. These granites occur in the upper part of the topaz granite stock, immediately beneath topaz-mica greisens consisting of quartz, clay minerals, lithium mica (protolithionite) and topaz. Argillized granites are enriched in Si (up to 78 wt.% SiO 2), Fe (0.5-3 wt.% FeO tot.), F (up to 1.6 wt.%), Rb (830-1380 ppm), Li (515-2317 ppm), Nb (25-435 ppm) and Ta (21-64 ppm), but poor in Th (2-9 ppm), Zr (7-35 ppm) and bulk of REE (3-7 ppm). Newly recognized tosudite was identified on the basis of d (001) 29.4 Å XRD reflection on natural, oriented sample and 31.6 Å reflection after ethylene glycol treatment. The d (060) reflection appeared at 1.493 Å. The tosudite originated, according to fluid inclusion study of quartz from quartz veins at temperatures of 374-393 ºC. The hydrothermal activity of Li-enriched solutions, originated by muscovitization of Li-micas from greisenized topaz-albite granites and greisens was satisfactory for the formation of tosudite. The clay mineral assemblage (dickite, illite and smectite) originated, according to fluid inclusion study of fluorite, at temperatures ranging between 90 ºC and 185 ºC.
Mineralium Deposita, 1999
Integration of geochemical, mineralogical, isotopic, and geochronological data with geodynamic considerations suggests that the Variscan granites in the Erzgebirge-Slavkovský les domain originated from repeated melting events and were emplaced over a period of about 40 Ma (330–290 Ma). Several lines of evidence exist supporting the idea that Erzgebirge granites assigned to different types (biotite granites, two-mica granites, strongly peraluminous P-rich Li-mica granites, and slightly peraluminous P-poor granites) are in most cases not genetically related via continuous fractional crystallization from a common magmatic reservoir. The genesis of the Slavkovsky les granites, however, might be discussed in terms of an uninterrupted fractionation series. Geological models of Sn-W deposits based upon geochemical and structural results imply that the main ore depositional events followed immediately the emplacement and solidification processes of melt via fluid-melt immiscibility, breccia-pipe formation and/or pervasive rock-fluid interactions.
Geologica Carpathica, 2018
The S-type accessory mineral assemblage of zircon, monazite-(Ce), fluorapatite and tourmaline in the cupolas of Permian granites of the Gemeric Unit underwent compositional changes and increased variability and volume due to intensive volatile flux. The extended S-type accessory mineral assemblage in the apical parts of the granite resulted in the formation of rare-metal granites from in-situ differentiation and includes abundant tourmaline, zircon, fluorapatite, monazite-(Ce), Nb-Ta-W minerals (Nb-Ta rutile, ferrocolumbite, manganocolumbite, ixiolite, Nb-Ta ferberite, hübnerite), cassiterite, topaz, molybdenite, arsenopyrite and aluminophosphates. The rare-metal granites from cupolas in the western segment of the Gemeric Unit represent the topaz-zinnwaldite granites, albitites and greisens. Zircon in these evolved rare-metal Li-F granite cupolas shows a larger xenotime-(Y) component and heterogeneous morphology compared to zircons from deeper porphyritic biotite granites. The zircon Zr/Hf wt ratio in deeper rooted porphyritic granite varies from 29 to 45, where in the differentiated upper granites an increase in Hf content results in a Zr/Hf wt ratio of 5. The cheralite component in monazite from porphyritic granites usually does not exceed 12 mol. %, however, highly evolved upper rare-metal granites have monazites with 14 to 20 mol. % and sometimes > 40 mol. % of cheralite. In granite cupolas , pure secondary fluorapatite is generated by exsolution of P from P-rich alkali feldspar and high P and F contents may stabilize aluminophosphates. The biotite granites contain scattered schorlitic tourmaline, while textural late-magmatic tourmaline is more alkali deficient with lower Ca content. The differentiated granites contain also nodular and dendritic tourmaline aggregations. The product of crystallization of volatile-enriched granite cupolas are not only variable in their accessory mineral assemblage that captures high field strength elements, but also in numerous veins in country rocks that often contain cassiterite and tourmaline. Volatile flux is documented by the tetrad effect via patterns of chondrite normalized REEs (T1,3 value 1.46). In situ differentiation and tectonic activity caused multiple intrusive events of fluid-rich magmas rich in incompatible elements, resulting in the formation of rare-metal phases in granite roofs. The emplacement of volatile-enriched magmas into upper crustal conditions was followed by deeper rooted porphyritic magma portion undergoing second boiling and re-melting to form porphyritic granite or granite-porphyry during its ascent.
Mineralium Deposita, 1999
Integration of geochemical, mineralogical, isotopic, and geochronological data with geodynamic considerations suggests that the Variscan granites in the Erzgebirge-Slavkovsky les domain originated from repeated melting events and were emplaced over a period of about 40 Ma (330±290 Ma). Several lines of evidence exist supporting the idea that Erzgebirge granites assigned to dierent types (biotite granites, two-mica granites, strongly peraluminous P-rich Li-mica granites, and slightly peraluminous P-poor granites) are in most cases not genetically related via continuous fractional crystallization from a common magmatic reservoir. The genesis of the Slavkovsky les granites, however, might be discussed in terms of an uninterrupted fractionation series. Geological models of Sn-W deposits based upon geochemical and structural results imply that the main ore depositional events followed immediately the emplacement and solidi®cation processes of melt viā uid-melt immiscibility, breccia-pipe formation and/or pervasive rock-¯uid interactions.
Mineralogy and Petrology, 2011
Nb-Ta-Ti-bearing oxide minerals (Nb-Ta-bearing rutile, columbite-group minerals) represent the most common Nb-Ta host in topaz-albite granites and related rocks from the Krásno-Horní Slavkov ore district. Tungsten-bearing columbite-(Fe), W-bearing ixiolite, wodginite and tapiolite-(Fe) are extremely rare in these rocks. Rutile contains significant levels of Ta (up to 37 wt.% Ta 2 O 5) and Nb (up to 24 wt.% Nb 2 O 5), with Ta/ (Ta+Nb) ratio ranging from 0.04 to 0.61. Columbitegroup minerals are represented mostly by columbite-(Fe) and rarely by columbite-(Mn), with Mn/(Mn+Fe) ratio ranging from 0.23 to 0.94. The exceptionally rare Fe-rich, W-bearing ixiolite occurs only as inclusions in Nb-Tabearing rutile from quartz-free alkali-feldspar syenites (Vysoký Kámen stock). Wodginite was found only in the topaz-albite microgranite of gneissic breccia matrix that occurs in the upper most part of the Hub topaz-albite granite stock. In wodginite, the Mn/(Mn+Fe) ratio is 0.42-0.51, whereas the coexisting tapiolite-(Fe) has a distinctly lower Mn/(Mn+Fe) ratio close to 0.06.
Bulletin of Geosciences, 2005
A wolframite-bearing greisen at Vykmanov, near Ostrov (Czech Republic) occurs at the contact of a small granite stock belonging to the Late Variscan Younger Intrusive Complex (YIC) of the Western Krušné hory/Erzgebirge pluton. The stock emerges as an outcrop of 0.8 × 0.3 km size from a hidden granite body in the eastern continuation of the Nejdek-Eibenstock granite massif. The lens-like greisen body consists mainly of quartz, topaz, protolithionite, and muscovite; it also contains wolframite (ferberite) and native bismuth mineralization. It was formed by replacement of a medium-grained, equigranular, slightly porphyritic Li-F granite of the Karlovy Vary pluton characterized by weak postmagmatic albitization and pervasive muscovitization. The greisen is geologically and compositionally transitional between the Li-rich greisens in albite granites (e.g. with zinnwaldite such as at Krásno) and the Li-poor greisens (e.g. phengite greisens at Gottesberg and Přebuz) associated with weakly albitized granites of the Younger Intrusive Complex. The Vykmanov greisen formed in a subsolidus stage of granite evolution by progressive alkali loss and fluorine metasomatism, leading to the formation of Li-mica quartz greisen subsequently replaced by topaz-quartz greisen at the granite/crystalline contact. These greisens were affected by late-stage muscovitization and argillitization (sericitization, the formation of clay minerals). The LiFe mica composition of the greisens corresponds to protolithionite (lithian siderophyllite) and is similar to the composition of micas in the enclosing granite. The tungsten-bearing greisenization represents a postmagmatic episode in the development of the Krušné hory/Erzgebirge batholith, and is located at the eastern contact of highly evolved YIC granites of the Western Krušné hory pluton. The greisen formed from CO 2-poor hydrothermal solutions, at about 400°C, which evolved from highly saline brines as evidenced by fluid inclusion studies. The geological situation suggests that the mineralizing fluids were mostly magmatic and were responsible for the tungsten-bismuth specialization of the greisens, whereas meteoric waters participated in mineralization during later stages.
Journal of Geosciences, 2015
At Vítkov, sparse molybdenite occurs within tungsten mineralization hosted by topaz greisen in orthogneiss in the envelope of the Variscan Krkonoše-Jizera granite Pluton (northern Bohemian Massif). Mineralogical study showed that sulfide mineralization started with precipitation of arsenopyrite followed by molybdenite, tungstenite, transitional Mo-and W-dominated disulfides and concluded by pyrite. Textural relationships between molybdenite and tungstenite imply that tungstenite was formed during several stages related to molybdenite bending and fracturing. Laser Ablation Inductively Coupled Mass Spectrometry (LA-ICP-MS) analyses of Re-poor (< 0.3 ppm) molybdenite showed extreme concentrations of W (up to 26 558 ppm) accompanied by Ag, As, Bi, Pb, Se, Te and other metals. Electron microprobe analyses of inclusions-free molybdenite confirmed the abundance of W (~0.5 wt. %) and tungstenite showed ~4 wt. % Mo, indicating a substitution of Mo 4+ for W 4+. Stability and phase relationships between molybdenite and tungstenite and locally identified transitional Mo-and W-dominated disulfidic phases suggest that tungstenite crystallization was triggered by a decrease in fO 2 below WO 2-WO 3 buffer that followed after molybdenite precipitation. Tungstenite zoning and sharp tungstenite-molybdenite contacts indicate disequilibrium during their formation.
Mineralogy and Petrology, 2003
Igneous quartz of the late-Variscan topaz-bearing granites from the Hub Stock (Slavkovsk y y Les, Czech Republic) was investigated by cathodoluminescence (CL) and electron probe micro-analysis (EPMA) to demonstrate the intra-granular heterogeneity of growth patterns and trace element distribution in quartz. We show that EPMA is well suited for the in situ study of Al and Ti in zoned quartz, because of its high spatial resolution down to 5 mm in conjunction with the ability to combine spot analyses with CL imaging. In the quartz phenocrysts of the topaz granites high Ti is associated with blue luminescent growth zones. High Ti (>40 ppm) in quartz indicates a high crystallisation temperature and pressure. The groundmass quartz of the granites which is almost free of Ti, has higher Al than the phenocrysts which may reflect an increase of lithophile elements and water content in melt during the late magmatic stage. The occurrence of similar quartz phenocrysts in most of the late-Variscan granites and rhyolites of the Kru s sn e e Hory=Erzgebirge which intruded over a period of about 40 Ma points to a similar crystallisation environment and origin of the quartz phenocrysts in the lower to middle crust.
Bulletin of Geosciences
A wolframite-bearing greisen at Vykmanov, near Ostrov (Czech Republic) occurs at the contact of a small granite stock belonging to the Late Variscan Younger Intrusive Complex (YIC) of the Western Krušné hory/Erzgebirge pluton. The stock emerges as an outcrop of 0.8 × 0.3 km size from a hidden granite body in the eastern continuation of the Nejdek-Eibenstock granite massif. The lens-like greisen body consists mainly of quartz, topaz, protolithionite, and muscovite; it also contains wolframite (ferberite) and native bismuth mineralization. It was formed by replacement of a me-dium-grained, equigranular, slightly porphyritic Li-F granite of the Karlovy Vary pluton characterized by weak postmagmatic albitization and pervasive muscovitization. The greisen is geologically and compositionally transitional between the Li-rich greisens in albite granites (e.g. with zinnwaldite such as at Krásno) and the Li-poor greisens (e.g. phengite greisens at Gottesberg and Přebuz) associated with weakly...