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

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

Preliminary results of sulphur isotope studies on sulfides from selected ore deposits and occurrences in the Karkonosze–Izera Massif (the Sudety Mts., Poland)

Preliminary sulphur isotope data are presented for selected ore deposits and occurrences in the Karkonosze-Izera Massif, namely, polymetallic mineralization sites at Budniki, Ciechanowice, Izerskie Garby and Sowia Dolina, and the pyrite deposit at Wieściszowice. The data reveal two populations of δ34S values: from 2.74 to 3.95‰ (pyrrhotites and pyrites in Sowia Dolina, and some pyrites in Wieściszowice) and from 0.79 to 1.8‰ (pyrites in Budniki, Ciechanowice and Izerskie Garby, and some pyrites from Wieściszowice). All of the data are indicative of endogenic sulphur typical of hydrothermal mineralization despite the genetic differences between the sites

Chemical abrasion applied to SHRIMP zircon geochronology: An example from the Variscan Karkonosze Granite (Sudetes, SW Poland)

International audienceThermal annealing followed by acid etching of zircon (chemical abrasion or CA) can be successfully utilised to minimize or eliminate the effects of major and cryptic Pb-loss for SIMS U-Pb zircon dating. The procedure is demonstrated by applying the U-Pb SIMS technique to both untreated and chemically abraded zircons from the Karkonosze Granite, Sudetes, SW Poland. Conventional U-Pb SIMS dating of untreated zircons yields an apparently coherent age population (n = 9) with a weighted mean 206Pb/238U age of 306 ± 4 Ma. Some untreated zircons display anomalously young 206Pb/238U ages (c. 225 and 238 Ma) and are likely to have suffered substantial Pb-loss. A sub-set of zircons from the same sample was chemically abraded. Physically, zircons treated in this manner display a range in the degree of etching and partial dissolution. Extreme examples developed a 3D network of sub-μm channels which follow high-U (dark CL) zones or linear defects, such as micro fractures or indistinct cleavage planes. U-Pb SIMS dating of treated zircons (n = 11) yields a mean 206Pb/238U age of 322 ± 3 Ma. Two analyses of treated zircons still display younger 206Pb/238U ages (c. 297 and 301 Ma) ascribed to the effects of Pb-loss. For the analysed sample, U-Pb ages determined from chemically abraded zircons are c. 5% older than those from untreated zircons. This is attributed to effective removal of metamict domains susceptible to Pb-loss. The CA technique also removes micro-inclusions thus lowering common Pb and reducing matrix effects. A cryptic Pb-loss in untreated zircons is only recognised when compared with chemically abraded counterparts or ages determined using other isotope techniques. This clearly demonstrates the utility of CA to high-spatial resolution methods and stresses that Pb-loss is detectable at a range of scales, regardless of the analytical technique used