A sulphur isotopic study of the Bleikvassli Zn-Pb-Cu deposit, Nordland, northern Norway

Skauli, H., Boyce, A.J. and Fallick, A.E. (1992) A sulphur isotopic study of the Bleikvassli Zn-Pb-Cu deposit, Nordland, northern Norway. Mineralium Deposita, 27(4), pp. 284-292. (doi: 10.1007/BF00193399)

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The Bleikvassli Zn-Pb-Cu deposit occurs in the Uppermost Allochthon in the Caledonides of northern Norway. The orebody is enclosed in amphibolite-facies schists and gneisses, underlain by amphibolites, and it has been classified as a sediment-hosted massive sulphide (SEDEX) deposit. The stratiform ore is dominantly pyritic, with a basal layer of pyrrhotitic ore. Sulphide veins occur in the footwall. The orebody generally has a limited range of δ34S, from 0.3 to 4.5% (x = 2.4 ± 1.2‰, 1 σ, n = 26). The lowest δ34S values (0.3–2.3‰) were found in sulphide veins in the footwall and vent proximal stratiform ore. More distal pyritic Zn-Pb ore has heavier average δ34S values (up to 4.5‰). The ore sulphides were deposited from a hydrothermal solution with δ34S about 2‰ perhaps with the incorporation of a minor portion of sulphide from the ambient seawater. The hydrothermal solution probably acquired most of its sulphide from the underlying mixed lithology; notably basaltic rocks. Sulphide produced by thermochemical reduction of seawater in the deep conduit system may also have been incorporated. Bacteriogenic sulphide is not likely as a major source of ore sulphur in the massive ore. Sulphide incorporated in distal pyrite, which have δ34S from -12 to-10‰, could have formed either by oxidation of the hydrothermal sulphide, or by bacterial reduction of seawater sulphate in the depositional environment. Exchange of sulphur isotopes probably took place only on a localized scale during Caledonian metamorphism, the bulk sulphur isotopic composition of the ore being preserved in a hand specimen scale.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Boyce, Professor Adrian and Fallick, Professor Anthony
Authors: Skauli, H., Boyce, A.J., and Fallick, A.E.
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Mineralium Deposita
ISSN (Online):1432-1866

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