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Geology, petrography, geochemistry, and genesis of sulfide-rich pods in the Lac des Iles palladium deposits, western Ontario, Canada

Duran Charley J., Barnes Sarah-Jane et Corkery John T.. (2016). Geology, petrography, geochemistry, and genesis of sulfide-rich pods in the Lac des Iles palladium deposits, western Ontario, Canada. Mineralium Deposita, 51, (4), p. 509-532.

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URL officielle: http://dx.doi.org/doi:10.1007/s00126-015-0622-z

Résumé

The Lac des Iles Pd deposits are known for their Pd-rich sulfide-poor mineralization. However, previously undocumented sulfide-rich pods also occur within the intrusion that hosts the deposits. Given the complex magmatic and hydrothermal history of the mineralization at Lac des Iles, the sulfide-rich pods could have crystallized from magmatic sulfide liquids or precipitated from hydrothermal fluids. Sulfide-rich pods occur throughout the stratigraphy, in all rock types, and along comagmatic shear zones, and contain net-textured to massive sulfides. They can be divided into four main groups based on the variation in mineral assemblages: (1) pyrrhotite–pentlandite ± pyrite–chalcopyrite–magnetite–ilmenite; (2) chalcopyrite ± pyrrhotite–pentlandite–pyrite–magnetite–ilmenite; (3) pyrite ± pentlandite–chalcopyrite–pyrrhotite–magnetite–ilmenite; and (4) magnetite ± ilmenite–pyrrhotite–pentlandite–pyrite–chalcopyrite. Whole rock metal contents and S isotopic compositions do not change with the amount of pyrite present, except for slight enrichments in As and Bi. The presence of an essentially magmatic sulfide mineral assemblage (pyrrhotite–pentlandite ± chalcopyrite) with pentlandite exsolution flames in pyrrhotite in some pods suggests that the pods crystallized from magmatic sulfide liquids. The very low Cu contents of the pods suggests that they are mainly cumulates of monosulfide solid solution (MSS). We propose a model whereby sulfide liquids were concentrated into dilation zones prior to crystallizing cumulus MSS. Intermediate solid solution crystallized from the fractionated liquids at the edges of some pods leaving residual liquids enriched in Pt, Pd, Au, As, Bi, Sb, and Te. These residual liquids are no longer associated with the pods. During subsequent alteration, pyrite replaced MSS/pyrrhotite, but this did not affect the platinum-group element contents of the pods.

Type de document:Article publié dans une revue avec comité d'évaluation
ISSN:0026-4598
Volume:51
Numéro:4
Pages:p. 509-532
Version évaluée par les pairs:Oui
Date:2016
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:Lac des Iles Pd deposits, sulfide-rich pods, platinum-group elements, Dilation zones, MSS fractionation
Déposé le:09 juin 2016 19:30
Dernière modification:09 déc. 2016 14:48
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