Geochemical studies on the Boda Pb-Zn deposit in the Siljan astrobleme, central Sweden
1984; Taylor & Francis; Volume: 106; Issue: 1 Linguagem: Inglês
10.1080/11035898409454598
ISSN0016-786X
Autores Tópico(s)Geology and Paleoclimatology Research
ResumoAbstract Abstract The Boda Pb-Zn deposit is located in the eastern part of the Siljan impact structure in central Sweden. It consists of calcite, baritc, sphalerite, galena, pyrite and marcasite, mainly as fracture and breccia fillings along a thrust zone in Ordovician limestones. Boda, and the smaller but similar Sollerön deposit, probably formed in close connection with the tectonic disturbance following the Devonian meteorite impact considered to have created the Siljan Ring structure. A geochemical profile through the ore-hosting limestone at Boda shows that wall rock alteration is not very marked. Lead isotope data point to the Proterozoic basement as the direct or indirect source of the ore lead, and to a large contribution of redeposited Proterozoic lead in the Ordovician limestone, presumably contained in the clastic silicate fraction. The extreme radiogenicity of the Boda ore lead may be explained by selective leaching of the more radiogenic lead fraction from the source rocks, rather than leaching of average rock lead. Relatively heavy sulfur isotope values in the galena may point to a sulfate source in the Paleozoic sediments for the sulfur. The schalenblende texture of the sphalerite ore suggests repeated pulses of rapid precipitation from supersaturated ore solutions. Key Words: BodaAgnmyrgruvanSollerönSiljan astroblemecentral Swedenmeteorite impact structurelead-zinc orelead isotopesradiogenic leadsulfur isotopesN6101N6056E1513E1437
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