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TitleUranium enrichment processes in metasomatic iron oxide and alkali-calcic systems as revealed by uraninite trace element chemistry
AuthorPotter, E GORCID logo; Acosta-Góngora, P; Corriveau, LORCID logo; Montreuil, J -F; Yang, Z
SourceMineral systems with iron oxide copper-gold (IOCG) and affiliated deposits; by Corriveau, LORCID logo (ed.); Potter, E GORCID logo (ed.); Mumin, A H (ed.); Geological Association of Canada, Special Paper 42, 2022 p. 325-345
Alt SeriesNatural Resources Canada, Contribution Series 20210044
PublisherGeological Association of Canada
Mediadigital; on-line
RelatedThis publication is related to Uranium enrichment processes in metasomatic iron oxide and alkali-calcic systems as revealed by uraninite trace element chemistry - supplementary data
File formatpdf
ProvinceNorthwest Territories
NTS85M; 85N; 85O; 86A; 86B; 86C; 86D; 86E; 86F; 86G; 86J; 86K; 86L
AreaLou Lake; Cole Lake; Fab Lake; Hottah Lake; Great Bear Lake; Gameti
Lat/Long WENS-120.0000 -114.0000 67.0000 63.0000
Subjectseconomic geology; geochemistry; Science and Technology; Nature and Environment; mineral deposits; metasomatic deposits; uranium; iron oxides; copper; gold; ore mineral genesis; mineralization; mineral enrichment; uraninite; provenance; geochemical analyses; trace element geochemistry; electron probe analyses; mass spectrometer analysis; Great Bear Magmatic Zone
Illustrationslocation maps; tables; diagrams; photographs; charts
ProgramTargeted Geoscience Initiative (TGI-5) Uranium ore systems - deep metasomatic processes
Released2022 07 01
AbstractUranium enrichment is relatively common in metasomatic iron oxide and alkali-calcic systems that can host iron oxide- apatite (IOA), magnetite-, magnetite-hematite and hematite-group iron oxide-copper-gold (IOCG) and albitite-hosted uranium and Au-Co-U deposits. In Canada, the best exposed and studied IOCG and affiliated occurrences are those of the Great Bear magmatic zone in the Northwest Territories. Trace element concentrations in uraninite from these occurrences produce relatively flat chondrite-normalized rare earth element (REE) patterns with negative europium anomalies, lanthanum depletion and mild heavy-REE depletion. In one of the occurrences, mild light-REE (LREE) depletion is linked to co-precipitation of LREE-bearing allanite (Nori showing). The high REE and thorium concentrations and negative europium anomalies are interpreted to reflect precipitation from high-temperature, reduced fluids that evolved and equilibrated through extensive Na alteration (albite), then Ca-Fe (amphibole+magnetite±apatite) and ultimately K-Fe (K-feldspar/biotite+iron-oxides) metasomatic facies. In most systems, field observations, petrography, and geochemistry indicate precipitation of primary uraninite during the transition from high temperature Ca-Fe to K-Fe facies in magnetite-dominant (reduced) assemblages. Unlike models proposed for hematite-group deposits, primary uranium enrichment in magnetite-dominant systems was likely sourced and transported as chloride complexes in high-temperature, reducing fluids rather than oxidized brines. Uranium precipitation was likely triggered by cooling of the fluids and/or changes in fluid chemistry induced by extensive fluid-rock interactions. Alteration of primary uraninite caused significant changes in major element chemistry (e.g. Pb, Ca, Fe, Si, etc.) but the chondrite-normalized REE patterns only deviate slightly, primarily through changes to LREE abundances. As observed in both magnetite- and hematite-group deposits globally, the remobilization of uranium indicates that although IOCG systems may have primary magmatic-hydrothermal origins, multiple generations of uranium mineralization occur through alteration, dissolution and re-precipitation as the hydrothermal cells collapse and surface-derived waters interact with the ores.
Summary(Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI) is a collaborative federal geoscience program that provides industry with the next generation of geoscience knowledge and innovative techniques to better detect buried mineral deposits, thereby reducing some of the risks of exploration. This contribution uses the trace element composition of an ore mineral (uraninite) to unravel the metal sourcing, transport and precipitation in uranium-bearing iron oxide-copper-gold (IOCG) deposits. The results support a revised genetic model that can be applied to exploration programs.

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