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The Shetland Ophiolite: Evidence for a Supra-Subduction Zone Origin and Implications for Platinum-Group Element Mineralization

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Book cover Mineral Deposits within the European Community

Part of the book series: Special Publication No. 6 of the Society for Geology Applied to Mineral Deposits ((MINERAL DEPOS.,volume 6))

Abstract

Chromite-rich samples from the ultrabasic and basic igneous complex in the Shetland Islands contain exceptionally rich PGE concentrations previously unrecorded in other ophiolite complexes and geochemically similar to those in stratiform complexes. This chapter re-assesses the Shetland complex, with particular emphasis on the chrome spinels and dykes, confirming that it forms the lower part of a Penrose ophiolite assembly. The podiform chromite is shown to have ophiolitic compositions and new electron microprobe analyses from chromite-rich samples indicate that there is nothing unusual about the compositions of the chrome spinels in PGM-rich samples, which have similar compositions to barren samples. The uppermost part of the ophiolite complex consists of a swarm of dykes in gabbro and their geochemistry has boninitic affinities possibly indicating an origin for the complex from a hydrous magma source in a supra-subduction zone (SSZ). The relative roles of primary and secondary fluids in the concentration of the PGE in Shetland are difficult to determine because the chromite-rich lithologies characteristically lie in altered, highly serpentinized zones. Dunites associated with some of the PGE-rich chromite in lenses in the mantle harzburgite have been found to be PGE-rich and significantly these are some of the least altered of the ultramafic rocks. This suggests that the PGE concentrations are not solely related to alteration zones or secondary processes.

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Authors and Affiliations

  1. Department of Earth Sciences, The Open University, Walton Hall, Milton Keynes, Buckinghamshire, MK7 6AA, UK

    R. A. Lord

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  1. H. M. Prichard
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  2. R. A. Lord
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Editors and Affiliations

  1. Directorate-general for Science, Research and Development, Commission of the European Communities, Rue de la Loi 200, 1049, Brussels, Belgium

    Jean Boissonnas

  2. Istituto di Mineralogia e Petrologia, Corso Garibaldi 37, 35100, Padova, Italy

    Paolo Omenetto

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© 1988 Springer-Verlag Berlin Heidelberg

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Prichard, H.M., Lord, R.A. (1988). The Shetland Ophiolite: Evidence for a Supra-Subduction Zone Origin and Implications for Platinum-Group Element Mineralization. In: Boissonnas, J., Omenetto, P. (eds) Mineral Deposits within the European Community. Special Publication No. 6 of the Society for Geology Applied to Mineral Deposits, vol 6. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-51858-4_16

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  • DOI: https://doi.org/10.1007/978-3-642-51858-4_16

  • Publisher Name: Springer, Berlin, Heidelberg

  • Print ISBN: 978-3-642-51860-7

  • Online ISBN: 978-3-642-51858-4

  • eBook Packages: Springer Book Archive

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