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Ore mineralization in the Miedzianka area (Karkonosze-Izera Massif, the Sudetes, Poland): new information

Mochnacka K., Oberc-Dziedzic T., Mayer W., Pieczka A.

Mineralogia

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2012

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Vol. 43, iss. 3/4

155--178

EN

The Miedzianka mining district has been known for ages as a site of polymetallic ore deposits with copper and, later, uranium as the main commodities. Although recently uneconomic and hardly accessible, the Miedzianka ores attract Earth scientists due to the interesting and still controversial details of their ore structure, mineralogy and origin. Our examination of the ore mineralization from the Miedzianka district was based exclusively on samples collected from old mining dumps located in the vicinity of Miedzianka and Ciechanowice, and on samples from the only available outcrop in Przybkowice. In samples from the Miedzianka field, chalcopyrite, pyrite, galena, bornite, chalcocite, digenite, arsenopyrite, magnetite, sphalerite, tetrahedrite-tennantite, bornite, hematite, martite, pyrrhotite, ilmenite, cassiterite and covellite are hosted in quartz-mica schists and in coarse-grained quartz with chlorite. In the Ciechanowice field, the ore mineralization occurs mainly in strongly chloritized amphibolites occasionally intergrown with quartz and, rarely, with carbonates. Other host-rocks are quartz-chlorite schist and quartzites. Microscopic examination revealed the presence of chalcopyrite, pyrite, sphalerite, galena, tetrahedrite-tennantite, bismuthinite, native Bi, arsenopyrite, löllingite, cassiterite, cobaltite, gersdorffite, chalcocite, cassiterite, bornite, covellite, marcasite and pyrrhotite. Moreover, mawsonite and wittichenite were identified for the first time in the district. In barite veins cross-cutting the greenstones and greenschists in Przybkowice, we found previously-known chalcopyrite, chalcocite and galena. The composition of the hydrothermal fluids is suggested to evolved through a series of consecutive systems characterized, in turn, by Ti-Fe-Sn, Fe- As-S, Fe-Co-As-S, Cu-Zn-S and, finally, Cu-Pb-Sb-As-Bi compositions.

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Charakterystyka i geneza złotonośnej mineralizacji arsenowo-polimetalicznej w złożu Czarnów (Sudety Zachodnie)

Mikulski S. Z.

Biuletyn Państwowego Instytutu Geologicznego

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2010

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nr 439 (2)

303--320

PL

Szczegółowe badania geochemiczno-mineralogiczne okruszcowanych skał ze złoża w Czarnowie wykazały obecność kilku różniących się składem i teksturą złotonośnych typów rud siarczkowo-polimetalicznych, występujących w żyle kwarcowej, jak również w skałach ją otaczających (łupki, amfibolity i skały węglanowo-krzemianowe). Średnia zawartość złota w zbadanych próbkach wynosi ok. 1,1 ppm arsenu i miedzi, odpowiednio 5,6 i 0,75% (n = 47). Zakres koncentracji złota w próbkach rud siarczkowych jest od ok. 1 do 2,5 ppm (maks. 12,6 ppm), przy zawartości As 3–15% i Cu 1–4%. W masywnych rudach arsenopirytowych koncentracje As mogą osiągać ok. 20–30%. W rudach polimetalicznych udokumentowano pojedyncze wysokie koncentracje Ag (380 ppm), Bi (0,55%) i Sn (0,4%). Krystalizacja złota przebiegała w co najmniej dwóch etapach. Pierwszy związany był z precypitacją złota submikroskopowego (1 µm śred.), w paragenezie z siarczkami metali podstawowych, minerałów Bi, Au, Ag i Te oraz krystalizacją kwarcu mleczno-białego w temperaturze 250–320°C. Następny etap okruszcowania zaznaczył się precypitacją przezroczystego kwarcu, młodszej generacji kalcytu, galeny oraz różnych siarkosoli, w temperaturach od 210 do 130°C. Najmłodszy etap mineralizacji związany był z procesami hipergenicznymi, co przejawia się zastępowaniem siarczków przez minerały wtórne. Geneza okruszcowania złotonośnego w złożu związana była z co najmniej dwoma oddzielnymi procesami precypitacji kruszców z roztworów hydrotermalnych pochodnych procesom magmowo-tektonicznym w strefie kontaktu granitoidów Karkonoszy ze skałami jej wschodniej osłony metamorficznej. Źródłem arsenu, miedzi, siarki (δ S34 CDT w siarczkach w zakresie od 0,07 do 4,33‰) i innych metali były oprócz waryscyjskich granitoidów również skały związane z dolnopaleozoiczną aktywnością magmowo-wulkaniczną w jednostce Kowar-Czarnowa. Po raz pierwszy w złożu rozpoznano następujące minerały: argentyt, joseit, matyldyt, treasuryt, stannin oraz najprawdopodobniej hessyt i protojoseit.

EN

Detailed geochemical-mineralogical studies of ore samples from the Czarnów deposit revealed the presence of ores with different composition and texture of gold-bearing sulphide polymetallic ores. They are hosting by quartz vein and its country rocks (schists, amphibolites and calc-silicate rocks). An average content of Au is 1.06 ppm, of As – 5.6% and of Cu – 0.75% (n = 47). The range of gold contents in sulphide ores is from 1 to 2.5 ppm (max. 12.6 ppm) at As contents 3 to 15% and Cu 1 to 4%. In massive arsenopyrite ore As concentration reaches up to 20–30%. In polymetallic ores a single high contents of Ag (max. 380 ppm), Bi (max. 0.55%) and Sn (max. 0.4%) were documented. Gold precipitation underwent at least in 2 separate stages. The first one was connected with submicroscopic gold (<1 μm in size) mostly bound in arsenopyrite and minor in pyrrhotite in the range of a high temperature (380– 490°C) determined by application of the arsenopyrite geothermometer and of fluid inclusions study of grey and/or grey-white quartz (330– 420°C). The second stage was related to gold redistribution from arsenopyrite and precipitation of microscopic gold (>1μmin size) in paragenetic association with base metal sulphides, and Bi, Au, Ag and Te minerals and crystallization of milky-white quartz in the temperature range 250–320°C. Next stage of ore precipitation was connected with crystallization of transparent quartz and younger generation of calcite, associated by galena and variable composition sulphosalts, in temperature range 130–210°C. The youngest stage is connected with weathering processes and is marked by replacement of primary sulphides by secondary minerals. Genesis of auriferous mineralization in the Czarnów deposit was related to at least two separate stages of ore minerals precipitation from hydrothermal fluids connected with post-magmatic-tectonic evolution of the Karkonosze granite along its contact with the Eastern metamorphic cover. Source of gold, arsenic, copper, sulphur (δ S34 CDT in sulphides range from 0.07 to 4.33‰), and other metals, beside Variscan granites, were credibly rocks related to Lower Paleozoic magmatic-volcanic processes in the Kowary–Czarnów unit. For the first time the following minerals have been recognized in the deposit: argentite, joseite, matildite, treasurite, stannite and most probably hessite and protojoseite.

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New insights into the mineralization of the Czarnów ore deposit (West Sudetes, Poland)

Mochnacka K., Oberc-Dziedzic T., Mayer W., Pieczka A., Góralski M.

Geologia Sudetica

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2009

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Vol. 41

43-56

EN

This paper provides new data on the mineralogy and mineral chemistry of the Czarnów ore deposit, a polymetallic vein that occurs within the eastern envelope of the Karkonosze Pluton (West Sudetes). New data are also provided on the deposits' geothermometry, mineral succession, and origins. The Czarnów ore vein is about 500 m long, strikes SW-NE, dips 80° SE and continues to a depth of 200 m. It is hosted within the albite-mica schists, quartzofeldspathic rocks and striped amphibolites that comprise the Czarnów Schist Formation (CSF); its western part is composed of almost monomineral arsenopyrite, whereas the southwestern part locally contains a pyrrhotite lens that extends downwards. Although many types of sulphides, sulphoarsenides, sulphosalts and native phases accompanied by oxides and arsenates have been previously reported, this paper describes four minerals that have not been previously identified from the Czarnów deposit: ferrokësterite, ikunolite, bismite and pentlandite. Geothermometry data suggest formation temperatures of arsenopyrite between 551 °C and 420 °C and that of sphalerite between about 400 °C to about 200 °C. Fluid inclusion data from vein quartz gave homogenization temperatures between 430 °C and 150 °C. Integrat on of textural and other data suggests the following primary mineral succession: early arsenopyrite and cassiterite as the high-temperature phases; then combinations of pyrrhotite, pyrite, chalcopyrite and sphalerite, all of which formed over a wide temperature range; finally, low temperature galena and Bi phases. Secondary weathering products overprint the primary sequences. Cataclasis of the first-formed arsenopyrite imply that mineralization was related to at least one tectonic event in the region. The Czarnów ore deposit probably resulted from hydrothermal activity associated with the near Karkonosze granite.

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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.