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Lehrstuhl für Geologie und Lagerstättenlehre

Peter Onuk

In the beginning of the 1990ies, both the long-lasting experience and tradition of Austrian companies in base metal mining from domestic sources was terminated by the closure of the zinc-lead mine at Bleiberg-Kreuth. Zinc, copper, lead and silver were the major commodities mined in base metal deposits within Austria; time was not ripe for the extraction of high-technology metals (germanium, gallium, indium, cobalt), most of which are on the list of critical raw materials nowadays, and the world demand was low. It was only in the smelter located at Arnoldstein that trace metals such as cadmium and germanium had been recovered in the 1980ies as by-products of zinc and lead ores from Bleiberg. Trace metals usually do not form discrete minerals that are susceptible to pre-concentration methods, but are frequently substituted into the lattices of common zinc-copper-lead sulphides (such as sphalerite, galena, chalcopyrite, pyrite) and fahlores, complex copper-arsenic-antimony sulphide minerals. In this case, the trace elements can only be liberated by hydro- or pyro-metallurgical methods. Only small amounts may be present as discrete minerals such as cobalt arsenide or cobalt sulpharsenide. Generally, complex and fine intergrowth textures require the use of complex processing methods that need to be developed based on a sound knowledge of process mineralogical parameters such as grain size, liberation and associated minerals.

Austria is known as a “country rich in poor ore deposits” (Friedrich, 1953). However, there are numerous occurrences of ore deposits that are potentially enriched in high-technology metals. Starting in the 1950ies, the late Erich Schroll was the first to analyse trace metals in ores. However, investigations on the concentration and especially on the mineralogical siting of trace metals in ores have been carried out in a limited manner only; modern, systematic research using state-of-the-art analytical methods is almost completely missing. Such methods have only recently been used to analyse ore samples from Bleiberg and a few surrounding deposits (Henjes-Kunst, 2014).

The Austrian Mineral Resources Plan, developed by the former Federal Ministry for Economy, Family and Youth (now Federal Ministry of Science, Research and Economy, bmwfw) and edited by the Geologische Bundesanstalt (Weber, 2012) has identified former mining areas that, based on the data available, deserve to be protected and secured for future generations. Five areas potentially endowed with critical metals will be selected from a list of protectable base metal deposits and investigated in this project. This includes (1) systematic research of literature and archives, (2) a search for sample material available in mineral and ore collections, (3) geological mapping, (4) sampling of accessible mines and waste dumps, as well as (5) analyses of the critical elements using modern analytical methods (XRF, EPMA, MLA, LA-ICP-MS). The major goals are to investigate the mineralogical and chemical siting of critical high-technology metals in the ores using high spatial resolution techniques, to analyse their distribution, and to calculate possible resources. The results will provide specific parameters for mineral processing, including a process-mineralogical characterization of the ores.

Main Pb-Zn-(Cu)-deposits of the Eastern Alps. Red arrow: carbonate-hosted Pb-Zn deposit; green arrow: SEDEX-Type; yellow arrow: vein deposit; black arrow: VMS-type deposit. Blue circles mark the Pb-Zn-deposit covered by IRIS; modified from Geologische Bundesanstalt (2014).