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Chalcophile and platinum-group element distribution in pyrites from the sulfide-rich pods of the Lac des Iles Pd deposits, Western Ontario, Canada : implications for post-cumulus re-equilibration of the ore and the use of pyrite compositions in exploration

Duran Charley J., Barnes Sarah-Jane et Corkery John T.. (2015). Chalcophile and platinum-group element distribution in pyrites from the sulfide-rich pods of the Lac des Iles Pd deposits, Western Ontario, Canada : implications for post-cumulus re-equilibration of the ore and the use of pyrite compositions in exploration. Journal of Geochemical Exploration, 158, p. 223-242.

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URL officielle: http://dx.doi.org/doi:10.1016/j.gexplo.2015.08.002

Résumé

The Lac des Iles Pd-deposits are atypical within the scope of platinum-group element (PGE) deposits. This is because the deposits do not resemble a classical PGE deposit in a number of ways: the intrusion is small and concentrically zoned; most of the host rocks to the deposits no longer have a primary mineralogy and equilibrated under greenschist conditions; the textures of the rocks from the ore zones are extremely variable; and the ores have very high Pd/Ir and Pd/Pt ratios. In addition to the disseminated sulfides, there are sulfide-rich pods present throughout the stratigraphy. The sulfide mineral textures and proportions within the pods vary from those which are essentially magmatic to those which consist predominantly of pyrite. The pyrite could have been deposited from hydrothermal fluids or it could have formed by alteration of magmatic sulfides. In order to distinguish between these two origins, the PGE and chalcophile element contents of the pyrite were investigated. It was found that the pyrite contains Os, Ir, Ru and Rh. These elements also concentrate in the magmatic sulfides pyrrhotite and pentlandite. Their presence in the pyrite could be explained by redistribution of Fe from pyrrhotite to silicate minerals that are present within and around the sulfide pods, possibly during cooling. Maps of the distribution of the elements show that there is zoning of the elements. The IPGE–Rh are present towards the cores of pyrite along with As whereas Co and Se are present towards the rims. Mobile elements such as Pb, Bi and Ag are present in thin overgrowths at the edges of pyrite and in a few cases, Pt, Te and Sn are also present in the overgrowths. Comparison of the composition and element distribution with pyrites from other igneous settings (Sudbury and Aguablanca) shows similarities, suggesting a common ore-modifying process. In contrast, pyrites from low-temperature hydrothermal deposits have different compositions. A plot of Co/Se vs Sb/As appears to be effective at separating the igneous pyrites from pyrites found in other settings and could possibly be used in exploration.

Type de document:Article publié dans une revue avec comité d'évaluation
ISSN:0375-6742
Volume:158
Pages:p. 223-242
Version évaluée par les pairs:Oui
Date:2015
Sujets:Sciences naturelles et génie > Sciences naturelles > Sciences de la terre (géologie, géographie)
Département, module, service et unité de recherche:Départements et modules > Département des sciences appliquées > Unité d'enseignement en sciences de la Terre
Mots-clés:Pyrite, LA-ICP-MS, Lac des Iles Pd deposits, sulfide-rich pods, post-cumulus re-equilibration of monosulfide solid solution, discriminants of use in exploration
Déposé le:10 juin 2016 13:39
Dernière modification:09 déc. 2016 14:49
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