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Platinum-group element remobilization and concentration in the Cliff chromitites of the Shetland Ophiolite Complex, Scotland

  • Brian O'Driscoll (a1), Russell Garwood (a1) (a2), James M. D. Day (a3) and Roy Wogelius (a1)
Abstract

The ~492 Ma Shetland Ophiolite Complex contains an extensive mantle section, within which numerous podiform chromitite bodies formed during melt percolation in a supra-subduction zone setting. One of the Shetland ophiolite chromitite localities has an unusual style of platinum-group element (PGE) mineralization. Specifically, the Cliff chromitite suite has relatively high (>250 ppm) Pt plus Pd, compared to other chromitites in the Shetland Ophiolite Complex. In this study, we apply petrographic observation, mineral chemistry and novel X-ray microtomography data to elucidate the petrogenesis of PGE-bearing phases at Cliff. The combined datasets reveal that the PGE at Cliff have probably been fractionated by an As-rich fluid, concentrating Pt and Ir into visible (0.1–1 µm) platinum-group minerals (PGM) such as sperrylite and irarsite, respectively. The high (>1 ppm) bulk-rock concentrations of the other PGE (e.g. Os) in the Cliff chromitites suggests the presence of abundant fine-grained unidentified PGM in the serpentinized groundmass. The spatial association of arsenide phases and PGM with alteration rims on Cr-spinel grains suggests that the high Pt and Pd abundances at Cliff result from a late-stage low-temperature (e.g. 200–300°C) hydrothermal event. This conclusion highlights the potential effects that secondary alteration processes can have on modifying and upgrading the tenor of PGE deposits.

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This paper is published as part of a thematic set in memory of Professor Hazel M. Prichard

Associate Editor: John Bowles

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References
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Ahmed, A.H. and Arai, S. (2002) Unexpectedly high-PGE chromitite from the deeper mantle section of the northern Oman ophiolite and its tectonic implications. Contributions to Mineralogy and Petrology, 143, 263278.
Ahmed, A.H., Arai, S., Abdel-Aziz, Y.M., Ikenne, M. and Rahimi, A. (2009 a) Platinum-group elements distribution and spinel composition in podiform chromitites and associated rocks from the upper mantle section of the Neoproterozoic Bou Azzer ophiolite, Anti-Atlas, Morocco. Journal of African Earth Sciences, 55, 92104.
Ahmed, A.H., Arai, S. and Ikenne, M. (2009 b) Mineralogy and Paragenesis of the Co-Ni arsenide ores of Bou Azzer, Anti-Atlas, Morocco. Economic Geology, 104, 249266.
Barnes, S.J. (2000) Chromite in Komatiites II. Modification during greenschist to mid-amphibolite facies metamorphism. Journal of Petrology, 41, 387409.
Barnes, S.J. and Roeder, P.L. (2001) The range of spinel compositions in terrestrial mafic and ultramafic rocks. Journal of Petrology, 42, 22792302.
Brenan, J.M. and Rose, L.A. (2002) Experimental constraints on the wetting of chromite by sulfide liquid. The Canadian Mineralogist, 40, 11131126.
Büchl, A., Brügmann, G.E. and Batanova, V.G (2004) Formation of podiform chromitite deposits: implications from PGE abundances and Os isotopic compositions of chromites from the Troodos complex, Cyprus. Chemical Geology, 208, 217232.
Chew, D.M., Daly, J.S., Magna, T., Pagé, L.M., Kirkland, C.L., Whitehouse, M.J. and Lam, R. (2010) Timing of ophiolite obduction in the Grampian orogen. Geological Society of America Bulletin, 122, 17871799.
Coggon, J.A., Nowell, G.M., Pearson, D.G., Lorand, J.-P., Oberthür, T. and Parman, S.W. (2011) The 190Pt-186Os decay system applied to dating platinum-group element mineralization of the Bushveld Complex, South Africa. Chemical Geology, 302–303, 4860.
Crowley, Q.G. and Strachan, R.A. (2015) U-Pb constraints on obduction initiation of the Unst Ophiolite: an oceanic core complex in the Scottish Caledonides? Journal of the Geological Society, London, 172, 279282.
Cutts, K.A., Hand, M., Kelsey, D.E. and Strachan, R.A. (2011) P-T constraints and timing of Barrovian metamorphism in the Shetland Islands, Scottish Caledonides: implications for the structural setting of the Unst ophiolite. Journal of the Geological Society, London, 168, 12651284.
Dare, S.A.S., Barnes, S.-J., Prichard, H.M. and Fisher, P.C. (2010) The timing and formation of platinum-group minerals from the Creighton Ni-Cu-platinum-group element sulfide deposit, Sudbury, Canada: Early crystallization of PGE-rich sulfarsenides. Economic Geology, 105, 10711096.
Day, J.M.D., O'Driscoll, B., Strachan, R.A., Daly, J.S. and Walker, R.J. (2017) Identification of mantle peridotite as a possible Iapetan ophiolite sliver in south Shetland, Scottish Caledonides. Journal of the Geological Society, London, 174(1), 8892.
Derbyshire, E.J., O'Driscoll, B., Lenaz, D., Gertisser, R. and Kronz, A. (2013) Compositionally heterogeneous podiform chromitite in the Shetland Ophiolite Complex (Scotland): implications for chromitite petrogenesis and late-stage alteration in the upper mantle portion of a supra-subduction zone ophiolite. Lithos, 162–163, 279300.
Fleet, M.E., Chryssoulis, S.L., Stone, W.E. and Weisener, G. (1993) Partitioning of platinum-group elements and Au in the Fe-Ni-Cu-S system: Experiments on the fractional crystallization of sulfide melt. Contributions to Mineralogy and Petrology, 115, 3644.
Flinn, D. (2001) The basic rocks of the Shetland Ophiolite Complex and their bearing on its genesis. Scottish Journal of Geology, 37, 7996.
Flinn, D., Miller, J.A. and Roddom, D. (1991) The age of the Norwick hornblendic schists of Unst and Fetlar and the obduction of the Shetland ophiolite. Scottish Journal of Geology, 27, 1119.
Garwood, R.J. and Dunlop, J.A. (2014) The walking dead: Blender as a tool for palaeontologists with a case study on extinct arachnids. Journal of Palaeontology, 88(4), 735746.
Garwood, R.J. and Sutton, M.D. (2010) X-ray micro-tomography of Carboniferous stem-Dictyoptera: New insights into early insects. Biology Letters, 6, 699702.
Gauthier, M., Corrivaux, L., Trottier, L.J., Cabri, J., Gilles Laflamme, J.H. and Bergeron, M. (1990) Mineralium Deposita, 25, 169178.
Godel, B. (2013) High resolution X-ray computed tomography and its application to ore deposits: case studies from Ni-Cu-PGE deposits. Economic Geology, 108, 20052019.
Godel, B. (2015) Platinum-group element deposits in layered intrusions: recent advances in the understanding of the ore forming processes. Pp. 379432 in: Layered Intrusions (Charlier, B., Namur, O., Latypov, R. and Tegner, C., editors). Springer, The Netherlands.
Godel, B. and Barnes, S.-J. (2008) Image analysis and composition of platinum-group minerals in the J-M Reef, Stillwater Complex. Economic Geology, 103, 637651.
Godel, B., Barnes, S.J., Barnes, S.-J. and Maier, W.D. (2010) Platinum ore in 3D: Insights from high-resolution X-ray computed tomography. Geology, 38(12), 11271130.
Godel, B., Gonzalez-Alvarez, I., Barnes, S.J., Barnes, S.-J., Parker, P. and Day, J. (2012) Sulfides and sulfarsenides from the Rosie Nickel Prospect, Duketon Greenstone Belt, Western Australia. Economic Geology, 107, 275294.
González-Jiménez, J.M., Kerestedjian, T., Proenza, J.A. and Gervilla, F. (2009) Metamorphism of chromite ores from the Dobromirtsi Ultramafic Massif, Rhodope Mountains (SE Bulgaria). Geologica Acta, 7, 413429.
González-Jiménez, J.M., Griffin, W.L., Gervilla, F., Proenza, J.A., O'Reilly, S.Y. and Pearson, N.J. (2014 a) Chromitites in ophiolites: how, where, when, why? Part I. Origin and significance of platinum-group minerals. Lithos, 189, 127139.
González-Jiménez, J.M., Griffin, W.L., Proenza, J.A., Gervilla, F., O'Reilly, S.Y., Akbulut, M., Pearson, N.J. and Arai, S. (2014 b) Chromitites in ophiolites: how, where, when, why? Part II. The crystallisation of chromitites. Lithos, 189, 140158.
Hanley, J.J. (2005) The aqueous geochemistry of the platinum-group elements (PGE) in surficial, low-T hydrothermal and high-T magmatic hydrothermal environments. Pp. 3556 in: Exploration for Platinum-Group Element Deposits (Mungall, J.E., editor). Mineral Association of Canada, Quebec, Canada.
Hanley, J.J. (2007) The role of arsenic-rich melts and mineral phases in the development of high grade Pt-Pd mineralization within komatiite-associated magmatic Ni–Cu sulfide horizons at Dundonald Beach South, Abitibi Subprovince, Ontario, Canada. Economic Geology, 102, 305317.
Helmy, H.M. and Bragagini, A. (2017) Platinum-group elements fractionation by selective complexing, the Os, Ir, Ru, Rh-arsenide-sulfide systems above 1020°C. Geochimica et Cosmochimica Acta, 216, 169183.
Helmy, H.M., Ballhaus, C., Fonseca, R.O.C. and Nagel, T.J. (2013) Fractionation of platinum, palladium, nickel, and copper in sulfide-arsenide systems at magmatic temperature. Contributions to Mineralogy and Petrology, 166, 17251737.
Holwell, D.A. and McDonald, I. (2010) A review of the behaviour of platinum group elements within natural magmatic sulfide ore systems. Platinum Metals Review, 54, 2636.
Irvine, T.N. (1977) Origin of chromitite layers in the Muskox intrusion and other stratiform intrusions: A new interpretation. Geology, 5, 273277.
Karup-Møller, S., Mackovicky, E. and Barnes, S.-J. (2008) The metal-rich portions of the phase system Cu–Fe–Pd–S at 1000°C, 900°C and 725°C: implications for mineralization in the Skaergaard intrusion. Mineralogical Magazine, 72, 941951.
Ketcham, R.A. and Carlson, W.D. (2001) Acquisition, optimization and interpretation of X-ray computed tomographic imagery: applications to the geosciences. Computers and Geosciences, 27, 381400.
Kiefer, S., Majzlan, J., Chovan, M. and Števko, M. (2017) Mineral compositions and phase relations of the complex sulfarsenides and arsenides from Dobšiná (Western Carpathians, Slovakia). Ore Geology Reviews, 89, 894908.
Kimball, K. (1990) Effects of hydrothermal alteration on the composition of chromian spinels. Contributions to Mineral Petrology, 105, 337346.
Latypov, R., O'Driscoll, B. and Lavrenchuk, A. (2013) Towards a model for an in situ origin for PGE reefs in layered intrusions: insights from the chromitite seams of the Rum Eastern Layered Intrusion, Scotland. Contributions to Mineral Petrology, 166, 309327.
Le Vaillant, M., Barnes, S.J., Fiorentini, M.L., Miller, J., McCuaig, T.C. and Muccilli, P. (2015) A hydrothermal Ni-As-PGE geochemical halo around the Miitel komatiite-hosted nickel sulfide deposit, Yilgarn Craton, Western Australia. Economic Geology, 110, 505530.
Limaye, A. (2012) Drishti: a volume exploration and presentation tool. Developments in X-Ray Tomography VIII, SPIE Proceedings, 8506. International Society for Optics and Photonics, pp. 85060X–85060X.
Melcher, F., Grum, W., Simon, G., Thalhammer, T.V. and Stumpfl, E.F. (1997) Petrogenesis of the ophiolitic giant chromite deposits of Kempirsai, Kazakhstan: a study of solid and fluid inclusions in chromite. Journal of Petrology, 38, 14191458.
Mellini, M., Rumori, C. and Viti, C. (2005) Hydrothermally reset magmatic spinels in retrograde serpentinites: formation of ‘ferritchromit’ rims and chlorite aureoles. Contributions to Mineralogy and Petrology, 149, 266275.
Merlini, A., Grieco, G. and Diella, V. (2009) Ferritchromit and chromium-chlorite formation in melange-hosted Kalkan chromitite (Southern Urals, Russia). American Mineralogist, 94, 14591467.
Mungall, J.E. and Brenan, J.M. (2014) Partitioning of platinum-group elements and Au between sulfide liquid and basalt and the origins of mantle–crust fractionation of the chalcophile elements. Geochimica et Cosmochimica Acta, 125, 265289.
Naldrett, A.J. and Duke, J.M. (1980) Platinum metals in magmatic sulfide ores. Science, 208, 14171424.
O'Driscoll, B. and González-Jiménez, J.M. (2016) Petrogenesis of the platinum-group minerals. Pp. 489578 in: Highly Siderophile and Strongly Chalcophile Elements in High-Temperature Geochemistry and Cosmochemistry, (Harvey, J. and Day, J.M.D., editors). Reviews in Mineralogy & Geochemistry, 81. Mineralogical Society of America and the Geochemical Society, Chantilly, Virginia, USA.
O'Driscoll, B., Day, J.M.D., Daly, J.S., Walker, R.J. and McDonough, W.F. (2009) Rhenium-osmium isotope and platinum-group elements in the Rum Layered Suite, Scotland: Implications for Cr-spinel seam formation and the composition of the Iceland mantle anomaly. Earth and Planetary Science Letters, 286, 4151.
O'Driscoll, B., Day, J.M.D., Walker, R.J., Daly, J.S., McDonough, W.F. and Piccoli, P.M. (2012) Chemical heterogeneity in the upper mantle recorded by peridotites and chromitites from the Shetland Ophiolite Complex, Scotland. Earth and Planetary Science Letters, 333–334, 226237.
O'Driscoll, B., Walker, R.J., Day, J.M.D., Ash, R.D. and Daly, J.S. (2015) Generations of melt extraction, melt-rock interaction and high-temperature metasomatism preserved in peridotites of the ~497 Ma Leka Ophiolite Complex, Norway. Journal of Petrology, 56(9), 17971828.
Oshin, I.O. and Crocket, J.H. (1986) Noble metals in the Thetford Mines ophiolites, Quebec, Canada. II. Distribution of gold, silver, iridium, platinum and palladium in the Lac de l'Est volcano-sedimentary section. Economic Geology, 81, 931945.
Page, N.J. and Talkington, R.W. (1984) Palladium, platinum, rhodium, ruthenium, and iridium in peridotites and chromites from ophiolite complexes in Newfoundland. Canadian Mineralogist, 22, 137149.
Pina, R., Gervilla, F., Barnes, S.-J., Ortega, L. and Lunar, R. (2013) Partition coefficients of platinum group and chalcophile elements between arsenide and sulfide phases as determined in the Beni Bousera Cr-Ni mineralization (North Morocco). Economic Geology, 108, 935951.
Prichard, H.M. (1985) The Shetland Ophiolite. Pp. 11731184 in: The Caledonide Orogen – Scandinavia and Related Areas (Gee, D.G. and Sturt, B.A., editors). Wiley, New York.
Prichard, H.M. and Lord, R. (1993) An overview of the PGE concentrations in the Shetland Ophiolite Complex. Pp. 273294 in: Magmatic Processes and Plate Tectonics (Prichard, H.M., Alabaster, T., Harris, N.B.W. and Neary, C.R., editors). Geological Society of London Special Publications, 76.
Prichard, H. and Tarkian, M. (1988) Platinum and palladium minerals from two PGE-rich localities in the Shetland Ophiolite Complex. The Canadian Mineralogist, 26, 979990.
Prichard, H.M., Ixer, R., Lord, R.A., Maynard, J. and Williams, N. (1994) Assemblages of platinum-group minerals and sulfides in silicate lithologies and chromite-rich rocks within the Shetland Ophiolite. The Canadian Mineralogist, 32, 271294.
Prichard, H.M., Fisher, P.C., McDonald, I., Knight, R.D., Sharp, D.R. and Williams, J.P. (2013) The distribution of PGE and the role of Arsenic as a collector of PGE in the Spotted Quoll nickel ore deposit in the Forrestania Greenstone Belt, Western Australia. Economic Geology, 108, 19031921.
Prichard, H.M., Barnes, S.J., Godel, B., Halfpenny, A., Neary, C.R. and Fisher, P.C. (2015) The structure of and origin of nodular chromite from the Troodos ophiolite, Cyprus, revealed using high-resolution X-ray computed tomography and electron backscatter diffraction. Lithos, 218–219, 8798.
Prichard, H.M., Barnes, S.J., Dale, C.W., Godel, B., Fisher, P.C. and Nowell, G.M. (2017) Paragenesis of multiple platinum-group mineral populations in Shetland ophiolite chromitite: 3D X-ray tomography and in situ Os isotopes. Geochimica et Cosmochimica Acta, 216, 314334.
Schouwstra, R.P., Kinloch, E.D. and Lee, C.A. (2000) A short geological review of the Bushveld Complex. Platinum Metals Review, 44, 3339.
Spray, J.G. and Dunning, G.R. (1991) A U/Pb age for the Shetland Islands oceanic fragment, Scottish Caledonides: evidence from anatectic plagiogranites in ‘layer 3’ shear zones. Geological Magazine, 128, 667671.
Sutton, M.D., Garwood, R.J., Siveter, D.J. and Siveter, D.J. (2012) Spiers and VAXML; A software toolkit for tomographic visualisation, and a format for virtual specimen interchange. Palaeontologia Electronica, 15(2), T4, 14 pp.
Tarkian, M. and Prichard, H.M. (1987) Irarsite-hollingworthite solid-solution series and other associated Ru-, Os-, Ir- and Rh-bearing PGM's from the Shetland ophiolite complex. Mineralium Deposita, 22, 178184.
Titarenko, V., Bradley, R., Martin, C., Withers, P.J. and Titarenko, S. (2010) Regularization methods for inverse problems in x-ray tomography. Developments in X-Ray Tomography VII, Proceedings, 7804, 40Z.
Wood, M. (2003) Arsenic in Igneous Systems: An Experimental Investigation. Unpublished BASc thesis, University of Toronto, Ontario, Canada.
Yund, R.A. (1961) Phase relations in the system Ni-As. Economic Geology, 56, 12731296.
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