Re-Os isotope systematics of Ni-Cu sulfide ores, Sudbury Igneous Complex, Ontario: evidence for a major crustal component

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Abstract

Sudbury Igneous Complex sublayer ores from the Levack West, Falconbridge and Strathcona mines were analyzed for their Re and Os concentrations and Os isotopic compositions. The Re-Os isotope systematics of three ores from the different mines give isochron ages of1 840 ± 60 Ma, 1770 ± 60 Ma and 1780 ± 110 Ma, suggesting that the Re-Os system became closed at the time of, or soon after the 1850 ± 1 Ma crystallization age of the complex. The Os isotopic compositions of different portions of the complex at the time of crystallization varied considerably, with initial187Os/186Os1850 ranging from 4.64 at Levack West to 7.55 at Strathcona. These heterogeneities require that the Os, and probably also the other platinum-group elements contained in the ores, were derived from at least two sources. In addition, the high initial187Os/186Os ratios indicate that the Os was derived predominantly from ancient crust. Previous studies have suggested that the complex either crystallized from a mixture of mantle-derived basaltic melt and ancient continental crust, or was derived exclusively from the fusion of ancient continental crust resulting from a meteorite impact. Results of modelling suggest that if a contemporaneous mantle-derived basaltic melt was involved in the origin of the SIC, it likely contributed < 50% of the Os to all three ores. The large percentage of ancient crust involved in the production of the ores is most consistent with an interpretation of substantial crustal fusion resulting from meteorite impact.

Reference (44)

  • GuptaV.K. et al.

    Gravity and magnetic characteristics of the Sudbury structure

  • B.T. Scribbins, D.R. Rae and A.J. Naldrett, Mafic and ultramafic inclusions in the Sublayer of the Sudbury Igneous...
  • FrenchB.M.

    Sudbury structure Ontario: Some petrographic evidence for origin by meteorite impact

    Science

    (1967)
  • MorrisonG.G.

    Morphological features of the Sudbury structure in relation to an impact origin

  • FaggartB.E. et al.

    Origin of the Sudbury Complex by meteotite impact: Neodymium isotopic evidence

    Science

    (1985)
  • ThompsonJ.E.

    Geology of the Sudbury basin

    Ont. Dep. Mines, Annu. Rep. 1956

    (1957)
  • MuirT.L.

    The Sudbury structure: Considerations and models for an endogenetic origin

  • NaldrettA.J. et al.

    Contamination at Sudbury and its role in ore formation

  • MuirT.L.

    Geology of the Morgan Lake-Nelson Lake Area, District of Sudbury

    Ont. Geol. Surv., Open File Rep. 5426

    (1982)
  • NaldrettA.J. et al.

    A study of the Strathcona Mine and its bearing on the origin of the nickel-copper ores of the Sudbury District, Ontario

    J. Petrol.

    (1967)
  • NaldrettA.J.

    Mineralogy and composition of the Sudbury ores

  • SouchB.E. et al.

    The sulfide ores of Sudbury: Their particular relationship to a distinctive inclusion-bearing species of the nickel irruptive

  • Cited by (0)

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