Discovery of native aluminum on Variscan metagranitoids in Upper Carinthia, Austria: natural or anthropogenic origin?
Abstract
Native aluminum was discovered in 2004 at Hochwurten, Goldberg mountain group, Upper Carinthia, Austria. The discovery site is close to the Wurtenkees (glacier), where the dominant rock (Central gneiss) was exposed during the retreat of the glacier. Here, also veins with gold-bearing ores associated with tellurides (tetradymite, tsumoite, joséite-A) and Ag–Pb–Bi-sulfosalts are exposed and were mined intermittently during the last centuries. Native aluminum occurs at some distance (several 100 m laterally and vertically) to the veins as an isolated crystalline aggregate measuring 10 × 3 mm, and a closely associated flake (200 µm length), which was used for most of the studies. Both occur on gneiss and are intensely intergrown with it. Two groups of inclusions in the aluminum were observed and studied by SEM and EPMA. Group one consists of Bi–Te–(S)–(O) minerals, such as tetradymite, Bi2Te2S, tsumoite, BiTe, tellurobismuthite, Bi_2Te_3, bismuth and a montanite-type secondary mineral. The other group contains a new phase with composition (Al,Si)_(19)Fe_4, rare grains of hollisterite (Al_3Fe), and abundant Zn,Mg-bearing metallic nano-phases. A transition zone is developed between native aluminum and albite, a constituent of the gneiss, and is characterized by strongly changing concentrations of aluminum, silicon, iron and sulfur. Micro-computed tomography studies reveal that the Al metal is clearly intermixed with the host rock and not just juxtaposed over it. To shed further light on the origin of the Al metal, SIMS Mg isotopic measurements were carried out on the Austrian aluminum and on selected synthetic alloys with similar composition. A thorough discussion about the possible naturalness of this native aluminum and its possible formation is presented. The paper aims at augmenting the rare, assured knowledge of native metal formation/alteration under crustal and subcrustal conditions.
Additional Information
© 2019 Accademia Nazionale dei Lincei. Received: 23 August 2018; Accepted: 10 January 2019; First Online: 21 January 2019. Our special thanks go to Prof. Vesselin M. Dekov, University of Sofia, Bulgaria, for his motivating comments and pioneering work on the find of native aluminum. We acknowledge the expert help of Dr. Wolfgang Greibl, Federal Ministry of the Interior, Vienna, for the first results from GADDS/XRF/EDS total sample analyses; nanotomographic measurements and interpretation of data was kindly done by Mag.a Jördis Rosc, Materials Center Leoben Forschung GmbH (MCL). The authors thank Ing. Walter Eisler, Doppelmayr (Korneuburg) and Mr. Adolf Gugganig, BL Moelltaler Gletscherbahnen (Flattach) for detail information on materials and technological processes in the Hochwurten ski lifts' construction phase. Help in the local map and ortho-photo context by Dr. Michael Marketz and DI. Harald Felsberger, KNG-Kärnten Netz GmbH (Klagenfurt a.W.), as well as support by Mrs Theresia Culetto (Obervellach) in connection with the Moell Valley 1944 meteor(?) observation, and by Prof. Christian Köberl (NHM Vienna) in excluding meteorite falls/finds in the Wurten region are gratefully acknowledged. We further thank Ing. Werner Tobisch/EMD, BMLV (Vienna) for his help concerning WW2-time aircraft parts/load-jettisoning as potential source of aluminum alloys in the Hochwurten area, and Ing. Roman Vala, MBA (Research and Development Manager) as well as Mr. Pavel Kubenka (Area Sales Manager), Austin Detonator (Vsetin, Czech Republic) for their valuable expert comments on commercial detonator shell materials. Last but not least, we thank Dr. Gerhard Diendorfer, OVE (Vienna) for communication and valuable help in interpretation of his ALDIS database special query's results, and Mr. Matthias Reinhardt for his excellent quality photo of the aluminum aggregate. Finally, we thank two reviewers for their very constructive reviews. Compliance with ethical standards. The authors declare that they have no conflict of interest.Additional details
- Eprint ID
- 92418
- DOI
- 10.1007/s12210-019-00760-5
- Resolver ID
- CaltechAUTHORS:20190123-094132030
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2019-01-23Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field