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Geochemistry and origin of “platinum-nuggets” in lateritic covers from ultrabasic rocks and birbirites of W. Ethiopia

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Abstract

Pt-nuggets consisting of “ferroplatin” and containing little gold are found in lateritic covers of ultrabasic rocks and in birbirites in Yubdo/Birbir, W. Ethiopia. These nuggets have angular protuberances, a limonitic coating, and contain osmiridium and other minerals containing elements of the Pt-group. Microprobe analysis has determined the existence of (Os,Ir)S, for which the name “roseite” is proposed. Other new minerals are tentatively recognised; however, with the small amount of material available at present, only qualitative microprobe analyses were possible.

Zusammenfassung

Platin-Nuggets, die aus Ferroplatin mit etwas Gold bestehen, finden sich in Lateritdecken auf ultrabasischen Gesteinen und Birbiriten in Yubdo am Birbir/Westäthiopien. Diese Nuggets besitzen eine höckerige, limonitische Oberfläche und enthalten als Einschlüsse Osmiridium sowie andere Mineralien mit Elementen der Platin-Gruppe. Mit der Elektronen-Mikrosonde wurde das neue Mineral, Roseit (Os,Ir)S, gefunden. Auch andere neue Mineralien wurden erkannt, deren Zusammensetzung sich infolge geringer Menge bisher nur mit Hilfe von Scanning-Aufnahmen feststellen ließ.

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Authors and Affiliations

  1. Mineralogisch-Petrographisches Institut der Universität Heidelberg, Germany

    J. Ottemann & S. S. Augustithis

  2. Ministry of Mines, Addis-Abeba

    J. Ottemann & S. S. Augustithis

Authors
  1. J. Ottemann
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  2. S. S. Augustithis
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Ottemann, J., Augustithis, S.S. Geochemistry and origin of “platinum-nuggets” in lateritic covers from ultrabasic rocks and birbirites of W. Ethiopia. Mineral. Deposita 1, 269–277 (1967). https://doi.org/10.1007/BF00205201

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  • DOI: https://doi.org/10.1007/BF00205201

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