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TitreThe Lonnie niobium deposit and its relationship to metamorphism
AuteurReid, H M; Simandl, G J; Ferri, F; Veltheer, J
SourceBritish Columbia Geological Survey, Geofile 2013-02, 2013, 1 feuille (Accès ouvert)
LiensOnline - En ligne
Séries alt.Secteur des sciences de la Terre, Contribution externe 20120515
Documentpublication en série
Lat/Long OENS-124.4333 -124.3833 55.7167 55.6667
Sujetsniobium; fénitisation; pyrochlore; minéralisation; columbite; géologie structurale
Illustrationsgraphs; photographs; magnetic maps; diagrams; tables
ProgrammeÉtude des gîtes des métaux rares, Initiative géoscientifique ciblée (IGC-4)
Résumé(disponible en anglais seulement)
The Lonnie Nb deposit is spatially associated with the Wolverine Fault, which is in turn related to the Manson Creek Fault system. The Lonnie deposit is the thirdmost developed Nb prospect in British Columbia. In the larger Aley Carbonatite and Upper Fir deposits, the Nb and Nb±Ta zones are carbonatite-hosted. Historical work done on the Lonnie deposit suggests that the highest Nb grades are associated with quartz-free feldspathic rocks; nevertheless, carbonatite (metacarbonatite) zones also contain significant concentrations of Nb. Limited sampling, carried out in 2012, agrees with historical findings in these respects. It also indicates that metacarbonatites have similar chondrite-normalized REE patterns to quartz-free feldspathic rocks, fenites, and nearby outcropping limestone; however, they have the highest REE concentrations. Fenitization extends for more than 30 metres from the complex southwestward into the host rock, perpendicularly to the strike of the Lonnie mineralization and the projection of the Wolverine fault. Carbonatite emplacement predates 4 periods of tectonic activity and the upper-amphibolite grade metamorphic climax. Pyrochlore is the main Nb-bearing mineral within aegirine-bearing metacarbonatite; however, it is absent, or a trace constituent in quartz-free feldspathic rocks - suggesting that Nb mineralization is present as columbite-series minerals or fersmite. Microprobe analysis is needed to confirm the presence and nature of these ore minerals. The adjusted Wolverine Fault Zone, as shown here, is probably the main Nb metalotect in the area; it aligns with a recently-available magnetic survey. Geochemical anomalies identified by Rara Terra Minerals Corp. at the Vergil carbonatite complex also appear to be located on the re-interpreted projection of the Wolverine fault.