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TitreDeveloping indicator mineral methods: application of iron oxides in discovery of VMS deposits
AuteurMakvandi, S; Beaudoin, G; Ghasemzadeh-Barvarz, M; McClenaghan, B
SourceAssociation géologique du Canada-Association minéralogique du Canada, Réunion annuelle, Programme et résumés vol. 36, 2013 p. 136
LiensOnline - En ligne
Séries alt.Secteur des sciences de la Terre, Contribution externe 20130525
Réunion GAC-MAC 2013; Joint annual meeting of Geological Association of Canada and Mineralogical Association of Canada; Winnipeg; CA; mai 22-24, 2013
Documentpublication en série
Mediapapier; en ligne; numérique
Lat/Long OENS-112.5000 -112.0000 65.7500 65.5000
Sujetsmagnetite; éléments d'indice; exploration de dépôts glaciaires; dépôts glaciaires; directions du transport de la glace; directions des mouvements de la glace; tills; géochimie du till; analyses de till; dépôts de till; gîtes volcanogènes; gîtes sulfureux; sulfures; dépôts glaciaires; minéralisation; zinc; cuivre; plomb; argent; géologie des dépôts meubles/géomorphologie; géologie économique; Cénozoïque; Quaternaire
ProgrammeÉtude des gîtes de sulfures massifs volcaniques, Initiative géoscientifique ciblée (IGC-4)
Résumé(disponible en anglais seulement)
Magnetite is a useful indicator mineral for provenance discrimination studies because it can incorporate a large number of minor or trace cations in its crystalline structure, and it is resistant to both chemical and physical weathering. Magnetite is known to be present at the base of a massive sulphide (MS) lens and the top of the alteration pipes where it replaces sulfide minerals such as pyrite, pyrrhotite, and/or chalcopyrite. Magnetite from two VMS deposits, the Izok Lake Zn-Cu- Pb-Ag (Nunavut) and Halfmile Lake Zn-Pb-Cu (Bathurst Camp) have been examined. The MS mineralization, related alteration zones, host rocks, and till, both up- and down- ice flow, were sampled in each area. Major, minor and trace element concentrations in magnetite were determined by Electron Probe Micro-Analysis (EPMA) and Laser Ablation- Inductively Coupled Plasma- Mass Spectrometry (LA-ICPMS). The results show high concentrations of P, Ge, W, Sn, Mn, Mg, Cu, Co and Zn in the Izok Lake MS Magnetite (ILMSM) and elevated contents of P, Pb, Sn, Ge, Ga, Mn, Mo, Ti and Zn in the Halfmile Lake MS Magnetite (HLMSM). Multivariate Principal Component Analysis (PCA) was used to discriminate different lithologies based on the chemistry of magnetite. The results show that the ILMSM and the HLMSM form different clusters because of their different contents of Mg, Cu, Al and Ti. These variations in composition relate to different geological settings and grades of metamorphism that have affected these deposits. In the Izok Lake area, the statistical results demonstrate that detrital magnetite grains are mainly clustered with the ILMSM or magnetite from the gahnite-rich dacite because of their Mg, Cu and Mn contents. The gahnite rich zone is located at the margins of, or within the sulphide stringer zone. Magnetite from hostrock dacite has high Ge, Sn, Ga, Mn, Zn and Ni contents. In the Halfmile Lake area, the chemical signature of the HLMSM is found in detrital magnetite more than 2 km far away from the ore zone, though, a high proportion of magnetite grains show signatures similar to those derived from local andesitic rocks. In conclusion, applying magnetite chemistry to trace VMS deposits is a reliable exploration technique because 1) magnetite carries the chemical signature of its host lithology, 2) magnetite persists for a long distance of glacial transport, and 3) it is relatively abundant in till samples. These characteristics provide the ability to track a VMS deposits eroded by glaciers for a distance of several kilometers.