HIGH-TECH METAL CONTENT OF SPHALERITE FROM EASTERN ALPINE PALEOZOIC SEDIMENT-HOSTED LEAD-ZINC DEPOSITS Onuk P., Melcher F. Department of Applied Geological Sciences and Geophysics, University of Leoben, A-8700 Austria LA-ICP-MS, Pb-Zn deposits, critical metals Silver-bearing Pb-Zn mineralization hosted within Paleozoic units of the Eastern Alps is known since Medieval times. Mining stopped due to the small size and the economic situation after the Second World War. The renewed interest in Pb-Zn deposits is driven by the incorporation of critical metals like Ge, Ga and In into the sphalerite lattice. Because these metals are extensively used in the electronics industry, some of the deposits may become economically interesting in the future. In the Austroalpine nappe system, SEDEX-type deposits are known from the Graz Paleozoic and the Gurktal nappe. The Pb-Zn-Ba ores located in the Graz Paleozoic (Styria) formed in the Lower Devonian in an euxinic basin structure associated with submarine alkaline volcanism (Weber 1990). In a sphalerite concentrate from the deposit Arzberg-Haufenreith, 10 ppm Ge, 11 ppm Ga, 1800 ppm Cd, 29 ppm In, and 5 ppm Tl have been reported (Cerny and Schroll, 1995). In-situ LA-ICP-MS measurements of sphalerite grains collected from five ancient mining sites and one exploration adit reveal a large variation of trace element concentrations with median values of 4.67 wt% Fe, 1832 ppm Cd, 138 ppm Co, 18 ppm Ag, 9 ppm Ga, 0.36 ppm Ge, 1 ppm In, 1 ppm Sn and 5 ppm Sb. Maximum values reach 220 ppm for Ge, 399 ppm for Ag and 83 ppm for In. Pb-Zn-mineralization at Meiselding located in the Gurktal Nappe (Carinthia) is classified as a metamorphically overprinted SEDEX-type deposit. The Pb-Zn mineralisation of Vellach-Metnitz in the same tectonic unit shows vein-like NW-SE striking tectonic structures (Weber 1997). At Meiselding, sphalerite carries up to 1900 ppm In, 250 ppm Ge, 65ppm Ga, 282 ppm Co and 2.9 wt% Cd. From Metnitz, sphalerite carries up to 65 ppm In, 924 ppm Ge, 381ppm Ga, 679 ppm Co and 4380 ppm Cd. The Zn-Cu-Pb veins next to Koprein (Paleozoic of the Karawanken Range, Carinthia), showing high indium concentrations according to Cerny and Schroll (1995), may also represent a vein-type deposit of unknown age. LA-ICP-MS analyses of sphalerite from Koprein show up to 373 ppm In, 2 ppm Ge, 177 ppm Ga and 457 ppm Co; Cd ranges from 1495-3180 ppm, and Fe from 1.1-7.7 wt%. The Eastern Alps host a variety of small to medium-sized copper and “Kies” (pyrite) mineralizations, which are located in both, the Penninic and Austroalpine nappe systems. Major deposits have been mined in the Subpenninic Habach Group, the Penninic Bündnerschiefer Group, the Austroalpine Ennstal quartz phyllite zone and the Austroalpine Greywacke Zone. Literature and recent LA-ICP-MS data indicate elevated concentrations of In, Sn and Cu in sphalerite. Literature: Cerny I. & Schroll E. (1995): Heimische Vorräte an Spezialmetallen (Ga, In, Tl, Ge, Se, Te und Cd) in Blei-Zink- und anderen Erzen. - Archiv für Lagerstättenforschung der Geologische Bundesanstalt, 18, 5-33p. Weber L. (1990): Die Blei-Zinkerzlagerstätten des Grazer Paläozoikums und ihr geologischer Rahmen. Archiv für Lagerstättenforschung der Geologischen Bundesanstalt, 12, 289 p.