Abstract
The Bou-Azzer ophiolite complex, of Upper Proterozoic age, is located in the central Anti-Atlas. The corresponding mantle peridotites, including chromitites pods, were fully serpentinized during a multistage history resulting in serpentinite minerals and accessory magnetites. Locally, chromite was altered to stichtite (Cr carbonate) during post-obduction weathering. The Bou-Azzer district is well known for its cobalt-arsenide mineralization in quartz—carbonate lenses located along the borders of serpentinite massifs and grading laterally, through a talc-carbonate zone, into serpentinites. These carbonate rocks (listwaenites) result from an hydrothermal metasomatic transformation of the ultramafic rocks. Listwaenites and cobalt arsenides may contain very high gold contents (>10 ppm).
The aim of this paper is to investigate the PGE distribution in some minerals derived from ultramafic rocks. The samples have been analysed by electrothermal atomic absorption spectrophotometry after extraction and enrichment by coprecipitation with selenium and tellurium.
To allow comparison between samples, analytical data have been normalized against C1 chondritic oncentrations.
PGE distributions can be related to the main formation steps of the Bou-Azzer ophiolite and its cobalt mineralization. It is proposed that the very different PGE patterns in chromitites and magnetites result from PGE distributions in the primary magmatic assemblages.
Chromitite patterns, with a negative slope, are characteristic of ophiolitic podiform deposits, and ascribed to PGE minerals like laurite or Ir-Ru alloys. On the other hand, magnetite patterns exhibit a positive slope and may represent the primary PGE distribution in magmatic Fe-Ni sulphide or arsenide in mantle peridotites.
During late hydrothermal processes, carbonatization and cobalt ore formation, it appears that PGE were less mobile than gold in the hydrothermal fluids. PGE contents in arsenides do not correlate with gold contents, and may have been deposited as discrete PGE minerals. PGE minerals have not yet been observed.
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References
Amossé, J., Fischer, W., Allibert, M. & Piboule, M. (1986). Méthode de dosage d’ultra- traces de platine, palladium, rhodium et or dans les roches silicatées par spectro- photométrie d’absorption atomique électrothermique. Analysis , 14(1), 26–31.
Amossé, J., Allibert, M., Fischer, W. & Piboule, M. (1987). Etude de l’influence des fugacités d’oxygène et de sourfes sur la différenciation des platinoïdes dans les magmas ultramafiques. Résultats préliminaires. C.r. Acad. Sci. Paris, 304, Série 2(19), 1883–5.
Augé, T. (1986). Platinum-group-mineral inclusions in chromitites from the Oman Ophiolites. Bull. Mineral., 109, 301–4.
Barnes, S.-J., Naldrett, A. J. & Gorton, M. P. (1985). The origin of the fractionation of platinum group elements in terrestrial magmas. Chem. Geol., 53, 303–23.
Bischoff, J. L. & Seyfried, W. E. (1978). Hydrothermal chemistry of seawater from 25° to 350°C. Am. J. Sci., 278, 838–60.
Bonatti, E., Simmons, E. C., Breger, D., Hamlyn, P. R. & Lawrence, J. (1983). Ultramafic rock/seawater interaction in the oceanic crust. Earth Planet. Sci. Lett., 62, 229–38.
Buisson, G. & Leblanc, M. (1986). Gold bearing listwaenites (carbonatized ultramafic rocks) in ophiolite complexes. In Metallogeny of Basic and Ultramafic Rocks, ed. M. J. Gallagher, R. A. Ixer, C. R. Neary & H. M. Prichard. The Institution of Mining and Metallurgy, London, pp. 121–32.
Buisson, G. & Leblanc, M. (1987). Gold in mantle peridotites from Upper Proterozoic ophiolites in Arabia, Mali and Morocco. Econ. Geol., 82, 2091–7.
Dillon-Leitch, H. C. H. & Watkinson, D. H. (1986). Distribution of platinum-group elements in the Donaldson West Deposit, Cape Smith Belt, Quebec. Econ. Geol., 81, 1147–58.
Foose, M. P., Economou, M. & Panayiotou, A. (1985). Compositional and mineralogic constraints on the genesis of ophiolite hosted nickel mineralization in the Pevkos Area, Limassol Forest, Cyprus. Mineral. Deposita, 20, 234–40.
Hudson, D. R. & Donaldson, M. J. (1984). Mineralogy of platinum-group elements in the Kambalda nickel deposits, Western Australia. In Sulphide Deposits in Mafic and Ultramafic Rocks, eds D. L. Buchanan & M. J. Jones. The Institution of Mining and Metallurgy, London, pp. 55–61.
Jagoutz, E., Palme, H., Baddenhausen, M., Blum, K., Dreibus, G., Spettel, B., Lorenz, V. & Wanke, H. (1979). The abundance of major, minor and trace elements in the earth’s mantle as derived from primitive ultramafic nodules. Proceedings 10th Lunar Planet. Sci. Conf., Pergamon Press, New York, pp. 2031–50.
Keays, R. R. & Davidson, R. M. (1976). Palladium, iridium and gold in the ores and host rocks of nickel sulfide deposits in Western Australia. Econ. Geol., 71, 1214–28.
Lago, B. L., Rabinowicz, M. & Nicolas, A. (1982). Podiform chromite orebodies: a genetic model. J. Petrol., 23, 103–23.
Leblanc, M. (1981). The late Proterozoic ophiolites of Bou-Azzer (Morocco): evidence for Pan-African plate tectonics. In Precambrian Plate Tectonics, ed. A. Kroner. Elsevier, Amsterdam, pp. 435–51.
Leblanc, M. & Billaud, P. (1982). Cobalt arsenide orebodies related to an Upper Proterozoic ophiolite: Bou-Azzer (Morocco). Econ. Geol., 77, 162–75.
Leblanc, M. & Gervilla-Linares, F. (1987). PGE and Au distribution in Ni arsenide-chromite veins from the Rifo-Betic lherzolite massifs (Morocco-Spain). In Geo-platinum 87, eds H. M. Prichard, P. J. Potts, J. F. W. Bowles & S. J. Cribb. Elsevier Applied Science Publishers, London, pp. 181–98.
Leblanc, M., Dupuy, C. & Merlet, C. (1984). Nickel content of olivine as discriminatory factor between tectonic and cumulate peridotite in ophiolites. Sciences Terra, Strasbourg, 37, 131–5.
Legendre, O. (1982). Minéralogie et géochimie des platinoïdes dans les chromitites ophiolitiques. Comparaison avec d’autres types de concentrations en platinoïdes. These Doct. 3° cycle, Université Sciences, Paris VII, 157 pp.
Lesher, C. M. & Keays, R. R. (1984). Metamorphically and hydrothermally mobilized Fe-Ni-Cu sulphides at Kambalda, Western Australia. In Sulphide Deposits in Mafic and Ultramafic Rocks, eds D. L. Buchanan & M. J. Jones. The Institution of Mining and Metallurgy, London, pp. 62–9.
Lorand, J. P. & Pinet, M. (1984). L’orcelite des péridotites de Ronda (Espagne), Beni- Boussera (Maroc). Table Mountain et Blow-Me-Down (Terre Neuve) et du Pinde septentrional (Grèce). Can. Min., 22, 553–60.
Lydon, J. W. (1987). The potential for hydrothermal platinum deposits. In Geo-platinum 87, eds H. M. Prichard, P. J. Potts, J. F. W. Bowles & S. J. Cribb. Elsevier Applied Science Publishers, London, pp. 111–2.
Mitchell, R. H. & Keays, R. R. (1981). Abundance and distribution of gold, palladium and iridium in some spinel and garnet lherzolites. Implications for the nature and origin of precious metal-rich intergranular components in the upper mantle. Geochim. Cosmochim. Acta, 45, 2425–42.
Mountain, B. W. & Wood, S. A. (1987). Solubility and transport of PGE in hydrothermal solutions: Thermodynamic and physical chemical constraints. In Geo-platinum 87, eds H. M. Prichard, P. J. Potts, J. F. W. Bowles & S. J. Cribb. Elsevier Applied Science Publishers, London, pp. 57–82.
Naldrett, A. J., Hoffman, E. L., Green, A. H., Chou, C. L., Naldrett, S. R. & Alcock, R. A. (1979). The composition of nickel-sulfide ores, with particular reference to their content of platinum-group elements and gold. Can. Mineral., 17, 403–15.
Naldrett, A. J. & Duke, J. M. (1980). Platinum metals in magmatic sulfide ores. Science, 208 (4451), 1417–24.
Oshin, I. O. & Crocket, J. H. (1982). Noble metals in Thetford Mines Ophiolites, Quebec, Canada. Part I: Distribution of gold, iridium, platinum and palladium in the ultramafic and gabbroic rocks. Econ. Geol., 77, 1556–70.
Parry, S. (1984). Abundance and distribution of palladium, platinum, iridium and gold in some oxide minerals. Chem. Geol., 43, 115–25.
Rosenblum, S., Carlson, R. R., Nishi, J. M. & Overstreet, W. C. (1986). Platinum-group elements in magnetic concentrates from the Goodnews Bay District, Alaska, US Geol. Survey Bulletin A 1660.
Ross, J. S. & Keays, R. R. (1979). Precious metals in volcanic-type nickel sulfide deposits in Western Australia. I: Relationship with the composition of the ores and their host rocks. Can. Mineral 17, 417–35.
Rowell, W. F. & Edgar, A. D. (1986). Platinum-group element mineralization in a hydrothermal Cu-Ni sulfide occurrence, Rathbun Lake, Northeastern Ontario. Econ. Geol., 81, 1272–7.
Stumpfl, E. F. (1986). Distribution, transport and concentration of platinum group elements. In Metallogeny of Basic and Ultramafic Rocks, eds M. J. Gallagher, R. A. Ixer, C. R. Neary & H. M. Prichard. Institution of Mining and Metallurgy, London, p. 379–94.
Talkington, R. W. & Watkinson, D. H. (1986). Whole rock platinum-group element trends in chromite-rich rocks in ophiolitic and stratiform igneous complexes. In Metallogeny of Basic and Ultramafic Rocks, eds M. J. Gallagher, R. A. Ixer, C. R. Neary & H. M. Prichard. Institution of Mining and Metallurgy, London, pp. 427–40.
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Fischer, W., Amossé, J., Leblanc, M. (1988). PGE Distribution in some Ultramafic Rocks and Minerals from the Bou-Azzer Ophiolite Complex (Morocco). In: Prichard, H.M., Potts, P.J., Bowles, J.F.W., Cribb, S.J. (eds) Geo-Platinum 87. Springer, Dordrecht. https://doi.org/10.1007/978-94-009-1353-0_20
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DOI: https://doi.org/10.1007/978-94-009-1353-0_20
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