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Variations in platinum group element concentrations in the Alexo mine komatiite, Abitibi greenstone belt, northern Ontario

Published online by Cambridge University Press:  01 May 2009

Sarah-Jane Barnes
Affiliation:
Geological Survey of Norway, P. O. Box 3006, Trondheim N-7001, Norway
A. J. Naldrett
Affiliation:
Department of Geology, University of Toronto, Toronto M5S 1A1, Canada

Abstract

The noble element (Os, Ir, Ru, Rh, Pt, Pd, Au) patterns from sulphides associated with the komatiites at the Alexo mine show variable degrees of fractionation. Massive sulphides at the contact between underlying intermediate volcanics and overlying komatiites have the least fractionated patterns (Pd/Ir = 44). Net-textured sulphides which immediately overlie the massive sulphides have extremely fractionated noble element patterns (Pd/Ir = 171). The disseminated sulphides in the overlying komatiite exhibit an intermediate degree of fractionation (Pd/Ir = 110). The variations in noble element patterns are complemented by variations in the Ni, Cu and Co concentrations. The massive sulphides are depleted in all three of these elements relative to the net-textured sulphide ore. The disseminated sulphides have intermediate values of Ni and Co, but are enriched in Cu relative to the other two sulphides.

Processes that could have affected the composition of the sulphides include: (a) fractionation of monosulphide solid solution (Mss) from a sulphide liquid during initial cooling of the komatiite, and (b) mobilization of Pt, Pd, Au, Cu, Ni and Co from the massive sulphide into footwall veins. A mass balance calculation indicates that the sum of the massive and net-textured sulphide agrees with the disseminated sulphide for all elements except Au. Thus the massive sulphide cannot have lost significant amounts of Pt, Pd, Ni and Co to footwall veins and significant mobilization of these elements does not appear to have occurred. The crystallization of Mss from a sulphide liquid will account for the enrichment of Ir, Os, Ru and Rh in the massive sulphide relative to the net-textured sulphide, and enrichment of Pd, Pt, Au, Co and Ni in the net-textured sulphide relative to the disseminated sulphide.

Type
Articles
Copyright
Copyright © Cambridge University Press 1986

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References

Baker, H. B. 1917. Alexo nickel mine; Timiskaming District. Ontario Bureau of Mines Report no. 26, 258–72.Google Scholar
Barnes, S.-J. 1985. The petrology and geochemistry of komatiite flows from the Abitibi Greenstone Belt, Canada, and a model for their formation. Lithos 18, 241–70.CrossRefGoogle Scholar
Barnes, S.-J. & Naldrett, A. J. (in press). The fractionation of the platinum group elements in some komatiites, of the Abitibi Greenstone Belt, Northern Ontario: Economic Geology.Google Scholar
Barnes, S.-J., Naldrett, A. J. & Gorton, M. P. 1985. The origin of the fractionation of platinum-group elements in terrestrial magmas. Chemical Geology 53, 303–23.CrossRefGoogle Scholar
Cowden, A., Donaldson, M. J., Naldrett, A. J. & Campbell, I. H. 1985. Platinum-group elements in the komatiite-hosted Fe–Ni–Cu sulfide deposits at Kambalda, Western Australia. Canadian Mineralogist 23, 300.Google Scholar
Coad, P. R. 1979. Nickel sulphide deposits associated with ultramafic rocks of the Abitibi Belt and economic potential of mafic–ultramafic intrusions. Ontario Geological Survey Study no. 20, 84 pp.Google Scholar
Distler, V. V., Malevskiy, A. YU. & Laputina, I. P. 1977. Distribution of platinoids between pyrrohotite and pentlandite in crystallization of a sulphide melt. Geochem International 11, 3040.Google Scholar
Ewers, W. E. & Hudson, D. R. 1972. An interpretive study of a nickel iron sulphide ore intersection, Lunnon Shoot, Kambalda, Western Australia. Economic Geology 67, 1075–92.CrossRefGoogle Scholar
Hoffman, E. L., Naldrett, A. J., Van Loon, J. C., Hancock, R. G. V. & Mason, A. 1978. The determination of all the platinum group elements and gold in rocks ores, etc. Analytica Chimica Acta 102, 157–66.CrossRefGoogle Scholar
Jolly, W. T. 1982. Progressive metamorphism of komatiites and related Archaean lavas of the Abitibi area, Canada. In Komatiites (eds. Arndt, N. T. Nisbet, E. G.), pp. 247–66. London: Allen and Unwin.Google Scholar
Keays, R. R. & Davidson, R. M. 1976. Palladium, iridium and gold in the ores and host rocks of nickel sulfide deposits in Western Australia. Economic Geologist 71, 1214–28.CrossRefGoogle Scholar
Keays, R. R., Ross, J. R. & Woolrich, P. 1981. Precious metals in volcanic peridotite-associated nickel sulfide deposits in Western Australia. Economic Geology 71, the ores and host rocks at Kambalda. Economic Geology 76, 1645–74.CrossRefGoogle Scholar
Keays, R. R., Nickel, E. H., Groves, D. I. & Mcgoldrick, P. J. 1982. Iridium and palladium as discriminants of volcanic-exhalative, hydrothermal, and magmatic nickel sulphide mineralization. Economic Geology 77, 1535–47.CrossRefGoogle Scholar
Kilburn, L. C., Wilson, H. D. B., Graham, A. R., Oguro, Y., Coats, C. J. A. & Scoates, R. F. J. 1969. Nickel sulphide ores related to ultrabasic intrusions in Canada. Economic Geology Monograph no. 4, 276–93.Google Scholar
Lightfoot, P. C., Naldrett, A. J. & Hawkesworth, C. J. 1984. The geology and geochemistry of the Waterfall Gorge section of the Insizwa Complex with particular reference to the origin of the nickel-sulfide deposits. Economic Geology 79, 1857–79.CrossRefGoogle Scholar
Luck, J.-M. & Arndt, N. T. 1985. Re/Os isochron for Archean komatiite from Alexo, Ontario. Terra Cognita 5, 323.Google Scholar
Naldrett, A. J. 1966. The role of sulphurization in the genesis of iron-nickel sulphide deposits of the Porcupine district, Ontario. Canadian Institute of Mining and Metallurgy Transactions 69, 147–55.Google Scholar
Naldrett, A. J. 1981. Nickel sulfide deposits. Classification, composition and genesis. Economic Geology 75, 628–85.Google Scholar
Naldrett, A. J., Hoffman, E. L., Green, A. H., Chou, C.-L. & Naldrett, S. R. 1979. The composition of Ni-sulphide ores, with particular reference to their content of PGE and Au. Canadian Mineralogist 17, 403–15.Google Scholar
Naldrett, A. J., Innes, D., Gorton, M. P. & Sowa, J. 1982. Compositional variations within and between five Sudbury ore deposits. Economic Geology 77, 1519–34.CrossRefGoogle Scholar
Pyke, D. R. & Middleton, R. S. 1970. Distribution and characteristics of the sulphide ores of the Timmins Area. Ontario Department of Mines, Miscellaneous Paper no. 42, 24 pp.Google Scholar
Steele, T. W., Levin, J. & Copelowitz, I. 1975. The preparation and certification of a reference sample for a precious metal ore. National Institute of Metallurgy Report no. 1969.Google Scholar
Usselman, T. M., Hodge, D. S., Naldrett, A. J. & Campbell, I. H. 1979. Physical constraints on the characteristics of nickel-sulphide ore in ultramafic lavas. Canadian Mineralogist 17, 361–72.Google Scholar