Carbon, oxygen and sulfur isotope composition of minerals from the Variscan lead-zinc-fluorite veins of southeast Skåne, southern Sweden

Abstract

Abstract Vein deposits containing fluorite, quartz, calcite, galena, pyrite, marcasite, sphalerite and chalcopyrite occur in steep, N-S or NW-trending faults in Cambrian sandstones in southeast Skåne, southern Sweden. They are of late Variscan (probably late Carboniferous) age, related to the transcurrent faulting of the Tornquist-Teisseyre lineament and the subsidence of the Danish-Polish Trough. A relation to intracontinental holspot magmatism and incipient rifting in the Oslo Graben may also be suggested. Carbon isotopes in eight calcite samples from the Scanian veins show a δ13C-range of −3 to −5 per mil versus PDB, while oxygen isotope values fall in two groups, one with δ18O around + 11 to + 12 per mil versus SMOW in the calcite and another with δ18O around + 16 per mil. Sulfur isotope data on sulfides in the veins show a large spread towards rather light values. δ34S of eleven sulfide samples from the veins thus ranges between −2 and −19 per mil versus CDT. Heavier sulfur (+ 5.2 and + 25.5 per mil, respectively) is found in two samples of marcasite occurring in fragments of alum shale. No linear relation between lead and sulfur isotopes in galena exists for the Scanian veins. In their carbon and sulfur isotope geochemistry, the Scanian veins differ markedly from the sandstone-hosted Pb-Zn impregnation deposits of Laisvall and Vassbo. The geological setting and mineralogy of the Scanian veins instead suggest a relationship to the fluoritic ‘Rosiclare-Pennine’ subtype of Mississippi Valley-type deposits.