Ore lead isotopical composition of Lower Proterozoic volcanogenic sulfide ores at Garpenberg, south central Sweden

The isotopic composition of ore lead in galena from the volcanogenic sulfide ores at Garpenberg district is presented. Despite of textural, compositional, and mineralogical differences, as well as the variable extent of deformation of the various sulfide ore types, the ores are characterized by a narrow range in lead isotopic composition. Dolomite-hosted ores are commonly more radiogenic than those hosted by skarn or altered volcanic rocks. Compared with the average growth curve of Stacey & Kramers, the ore lead at Garpenberg is slightly enriched in radiogenic lead. The influence of metamorphism on the ore lead composition of galena samples is negligible. The observed trend in the standard diagrams may be explained in terms of a mixing line, where the ore lead was derived from two different crustal sources originally enriched in radiogenic lead (e.g. volcanic and sedimentary rocks). Alternatively, it could represent sulfide ores of slightly different ages derived from a common rock source. The co...