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TitreGeochemical signatures of uraninite from iron-oxide-copper-gold (IOCG) systems of the Great Bear Magmatic Zone, Canada
AuteurPotter, E G; Corriveau, L; Montreuil, J -F; Yang, Z; Comeau, J-S
SourceGeological Society of America, Abstracts With Programs vol. 45, no. 7, 2013 p. 537
Séries alt.Secteur des sciences de la Terre, Contribution externe 20140158
ÉditeurGeological Society of America
RéunionGeological Society of America; Denver; US; Octobre 27-30, 2013
Documentpublication en série
Référence reliéeCette publication est reliée à Potter, E G; Corriveau, L; Montreuil, J -F; Yang, Z; Comeau, J-S; (2013). Preliminary geochemical signatures of uraninite from iron-oxide-copper-gold (IOCG) systems of the Great Bear Magmatic Zone, Canada, Geological Society of America annual meeting, posters, Geological Society of America, Abstracts With Programs vol. 45 no. 7
ProvinceTerritoires du Nord-Ouest
SNRC85N; 86C; 86D; 86E; 86F; 86K; 86L
Lat/Long OENS-119.0000 -116.0000 67.0000 63.0000
Sujetsgîtes minéralogiques; minéralisation; minerais de fer; oxydes de fer; or; cuivre; uranium; uraninite; Zone de Great Bear Magmatic ; géologie économique; Précambrien
ProgrammeUranium, GEM : La géocartographie de l'énergie et des minéraux
LiensOnline - En ligne
Résumé(disponible en anglais seulement)
Although the Olympic Dam deposit contains the world’s largest recoverable U resources, little is known regarding the processes and timing of U enrichment in iron oxide-copper-gold (IOCG) systems. The Great Bear magmatic zone in the Northwest Territories of Canada is an ideal natural laboratory to study U in iron oxide-alkali-altered (IOAA) systems. Re-examination of the excellent glaciated 3D exposures of the weakly to un-deformed/metamorphosed IOAA systems has shown these systems to encompass iron oxide-apatite (IOA or Kiruna-type), magnetite-, magnetite-hematite and hematite-group IOCG, skarns, and albitite-hosted U prospects to deposits.

Trace-element concentrations in uraninite from IOCG and affiliated occurrences were determined by LA-ICP-MS. Preliminary results indicate that the chondrite-normalized REE patterns are remarkably consistent and are inferred to reflect precipitation from higher temperature fluid(s). The patterns are characterized by minor fractionation amongst the REE, resulting in relatively flat patterns with negative Eu anomalies, La depletion and mild HREE depletion. In some of the occurrences, mild LREE depletion may relate to co-precipitation of LREE-bearing allanite. The negative Eu anomalies are interpreted to reflect scavenging of metals during reduced sodic alteration and subsequent precipitation from fluids that evolved and equilibrated through progressive sodic (albite), calcic-iron (amphibole+magnetite) and ultimately potassic-iron (K-feldspar/biotite + iron oxides) alteration. In most systems, mineral parageneses indicate precipitation of U minerals during potassic-iron alteration wherein the alteration assemblages record input of oxidizing fluids. During this stage of IOCG development, magnetite-dominant (reduced) alteration is overprinted by hematite-bearing (oxidized) potassic-iron alteration. Secondary or re-mobilized uraninite is characterized by chondrite-normalized REE patterns similar to the altered host rocks. These LREE-enriched patterns are also typical of lower temperature, vein-type U mineralization. The presence of abundant hematite in the remobilized veins points to the involvement of more strongly oxidized fluids than previous alteration stages.