Strontium isotopic evidence for the origin of siderite,ankerite and magnesite mineralizations in the Eastern Alps

Metasomatic magnesite, siderite and ankerite mineralizations within Paleozoic sediments of the Northern Greywacke zone and its metamorphic counterpart in the crystalline basement (Upper Austroalpine unit) were investigated with respect to their strontium isotopic composition. The results support a sedimentary (s.l.) model for the magnesites within Viséan platform carbonates of the Veitsch nappe and an epigenetic hydrothermal model for the siderites and ankerites in Devonian platform carbonates of the Noric nappe and from Hüttenberg. The Fe transporting fluids can be characterized either as magmatogene or, more probably, as metamorphogene. By increasing the stage of recrystallization and/or remobilization due to at least two later metamorphic overprints, Sr in the various ore minerals beame ± enriched in radiogenic ⁸⁷Sr.