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Epithermal Cu mineralization in the Stary Lesieniec rhyodacite quarry, Lower Silesia : primary and secondary mineral paragenesis

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Mederski S. , Kruszewski Ł. , Pršek J.

Geological Quarterly

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2021

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tom Vol. 65, No. 3

art. no. 43

EN

Primary epithermal and secondary Cu mineralization in the Stary Lesieniec rhyodacite quarry, located within the Intra-Sudetic Depression, was studied using reflected light microscopy, powder X-ray diffraction, and electron microprobe. Samples containing copper sulphides, baryte, and secondary weathering minerals were collected from mineralized veinlets in the Upper Carboniferous rhyodacite. Copper sulphides (chalcocite Cu2S, djurleite Cu31S16, anilite Cu7S4 / digenite Cu9S5, and covellite CuS) are the major ore minerals and are associated with quartz, hematite, and very minor uraninite. The samples studied indicate phase transformation from chalcocite to anilite, which indicates that Cu sulphides began to crystallize at ~100°C. Then, during the epithermal stage of precipitation, the temperature of the solutions dropped <72°C, based on the Cu-S ternary diagram and anilite stability. Admixtures of Ag, Fe, Bi, and Se in the sulphides are very minor. Supergene paragenesis is represented by chrysocolla with minor brochantite and very scarce malachite. These only bear trace impurities at the anionic sites. The supergene oxidation process began with the formation of abundant chrysocolla, at a relatively neutral pH. After dropping of the pH to ~4-6, brochantite was deposited.

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Geochemistry of tetrahedrite group minerals and associated silver paragenesis in the Boguszów baryte deposit, Poland

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Mederski S. , Pršek J. , Niemasz Ż.

Geological Quarterly

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2020

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tom Vol. 64, No. 4

958--968

EN

Primary ore mineralization in the abandoned Boguszów baryte-polymetallic deposit, located in the Intra-Sudetic Depression, was studied by reflected light microscopy and electron microprobe. Ore minerals, occurring as veinlets, irregular aggregates and lenses in baryte veins are hosted by the Upper Carboniferous Chełmiec rhyodacite laccolith. They are dominated by galena, sphalerite (with Cd up to 0.04 apfu) and tetrahedrite group minerals (TGM). Four generations of the TGM were distinguished according to textural features and Ag content: (1) low-Ag tetrahedrite-(Zn) (Ag: 0.22-0.6 apfu), (2) Ag-enriched tetrahedrite-(Zn) and Ag-enriched tetrahedrite-(Fe) (Ag: 0.71-1.45 apfu), (3) members of the freibergite series: “freibergite-(Fe)” and “freibergite-(Zn)” (Ag: 3.21-3.48 apfu; Hg: up to 0.75 apfu), (4) member of the “freibergite-(Fe)” series (Ag: 5.32-5.78 apfu). Several elongated inclusions of Ag-bearing sulphosalts within galena crystals were observed (members of the series “freibergite-(Fe)” and “freibergite-(Zn)”, pyrargyrite and polybasite). These polymetallic silver-bearing ores were mined in Boguszów from the 15th to the 19th century. Additionally, small grains of cobalt-enriched löllingite and gersdorffite were observed, which were formed from fluids sourced from the ultramafic basement. The textural characteristics of the ore, the mineral paragenesis and the chemical composition of individual ore minerals indicate low-temperature crystallization conditions.

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Mineralogy and geochemistry of Cu-Ni±Co±Ag±Bi polymetallic ores from the Hintermühlergang vein in the Chełmiec deposit, Sudetes Mountains, Poland

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Muszyński K. , Pršek J. , Mederski S. , Drzymała A.

Geological Quarterly

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2023

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tom Vol. 67, No. 3

art. no. 38

EN

Chełmiec is a hydrothermal vein-type carbonate-sulphide deposit in the Kaczawa Mountains, where polymetallic Cu-Ni±Co±Ag±Bi mineralization occurs. Samples, collected from an old dump of the Hintermühlergang vein, were studied by reflected light microscopy and electron microprobe. Two mineral parageneses, Ni-Co±Bi and Cu-Zn-Pb±Sb±Ag, associated with two stages of precipitation, were discovered in samples from the Chełmiec deposit. The first stage is associated with quartz, and is represented by pyrite, arsenopyrite, gersdorffite, cobaltite, bismuth minerals (native Bi, bismuthinite, and matildite), pyrrhotite, marcasite and chalcopyrite. The second stage associated with siderite and quartz is represented by sulphides (sphalerite, chalcopyrite, galena, pyrite), tetrahedrite group minerals [tetrahedrite-(Fe), tetrahedrite-(Zn), tennantite-(Zn), and argentotetrahedrite-(Fe)], gersdorffite and bournonite. Two generations of sulpharsenides were discovered in the samples studied. The first is represented by massive gersdorffite-cobaltite aggregates, the second generation occurs as tiny zoned gersdorffite crystals. Sulpharsenides are characterized locally by presence of high amounts of As (up to 1.55 apfu). Silver in the Chełmiec ores is hosted mainly in tetrahedrite group minerals [from 0.07 to 2.07 apfu in tetrahedrite – (Zn) and -(Fe), and from 4.37 to 4.90 apfu in argentotetrahedrite-(Fe)], less in matildite. In the Sudetes, the presence of massive sulpharsenides is rare, whereas freibergite is much more common.