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Geochemical dispersion patterns of As, Sb, Bi and Se associated with sulfide mineralization at Avoca, Eire

Journal of Geochemical Exploration
Publication Date
DOI: 10.1016/0375-6742(83)90054-7
  • Chemistry
  • Earth Science


Abstract At Avoca, Eire, Kuroko-like sulfide mineralization comprising massive stratiform cupriferous pyrite, accompanied by hanging-wall galena-sphalerite mineralization and footwall stringer pyrite, is hosted by Ordovician sediments, calc-alkaline lavas and pyroclastics. The sequence has been subjected to low-grade regional metamorphism, isoclinal folding and thrusting. The surficial cover comprises nonexotic glacial drift some 2 m thick. Previous work has demonstrated that major-element lithogeochemistry reflects the wall-rock alteration associated with the mineralization, but these signatures are absent from the overlying till. There is a poor heavy metal-expression at surface of the concealed mineralization. Analysis of wall rock, basal till and surface till samples for the chalcophile pathfinder elements As, Sb, Bi and Se (by rapid techniques which involve the introduction of their volatile hydrides into an inductively coupled plasma emission spectrometer) shows that a primary zonation of these elements around the mineralization can, in part, be traced to surface. In wall rocks, Bi enrichment is associated with the massive pyrite and footwall mineralization, Sb and Se anomalies occur in the hanging wall, and an As halo extends across all three types of mineralization. At surface, Bi and As anomalies are found over the massive pyrite and footwall zones, and an Sb anomaly occurs above the hanging-wall mineralization. The development of these patterns is attributed to mainly hydromorphic dispersion. The primary and surficial dispersion patterns of the chalcophile pathfinders should prove useful in exploration for other examples of Kuroko-type mineralization. The determination of these elements in geochemical exploration can be carried out quickly and cost-effectively.

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