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TitreGeological, petrological and geochemical observations of an Archean syenite-associated Cu-Au deposit, Kirkland Lake, Ontario: A temporal or genetic relationship
AuteurKontak, D J; Dubé, B; Kyser, T K
SourceAssociation géologique du Canada-Association minéralogique du Canada, Réunion annuelle, Programme et résumés vol. 34, 2011 p. 111
LiensOnline - En ligne
Séries alt.Secteur des sciences de la Terre, Contribution externe 20130570
RéunionGAC-MAC-SEG-SGA Joint Annual Meeting 2011; Ottawa; CA; mai 25-27, 2011
Documentpublication en série
Lat/Long OENS-80.1000 -80.0000 48.0667 48.0000
Sujetsgîtes minéralogiques; gisements minéraux; potentiel minier; minéralisation; or; gîtes volcanogènes; sulfures; gîtes sulfureux; syenites; cuivre; Archéen; géologie économique; pétrologie ignée et métamorphique; géochimie; Précambrien; Protérozoïque
ProgrammeÉtude des gîtes d'or, Initiative géoscientifique ciblée (IGC-4)
Résumé(disponible en anglais seulement)
The Upper Beaver Au-Cu deposit of the Kirkland Lake gold camp, northern Ontario, produced 136,650 oz Au from 0.5 Mt grading 7.9 g/t and 1% Cu (1912-1972). Recent work has delineated a resource of over 0.64 M oz Au, which is increasing with continued exploration. The region is underlain by mafic to felsic volcanic rock sequences with intercalated sedimentary rocks of the Tisdale and Blake River groups with younger sedimentary rocks of the Timiskaming Group; all units are cut by syenitic intrusions. At Upper Beaver, located on a splay off the main, regional E-W trending and metallogenetically significant Kirkland-Larder Lake break, mineralization is spatially related to a 2679 Ma multi-phase syenite complex, which includes magmatic and hydrothermal breccias. The Cu-Au mineralization, which is structurally controlled, is centred on the syenite complex, but also occurs in adjacent metavolcanic rocks. Unusual compared to the stockwork ore of the Kirkland Lake gold domain is the association of mineralization with abundant hydrothermal Fe oxide (Mt>>Hmt) and variably pervasive epidote-albite ± sericite ± actinolite ± tourmaline alteration; rare anhydrite also occurs. Petrological and geochemical studies indicate (1) fractionation of the syenite from an Amph-bearing phase to Qtz-Kfs dykes associated with ore zones. The absence of a Eu anomaly suggests an oxidized magma; (2) Fenrichment in both magmatic (i.e. Amph) and hydrothermal (i.e. Apt) stages; (3) Au shows an association with potassic enrichment; and (4) although free Au dominates, silver, bismuth telluride phases (Bi-Hg-Te-Se-Pb-Ag) occur and d30 ppm Au occur in chalcopyrite. Stable isotopic analysis indicate: (1) d34SH2S = 0 ± 2perthousand and that vein formation occurred at 450-400°C; (2) d18OH2O = +10 ± 2perthousand based on Qtz and Mt and ?18OH2O = +8 ± 2perthousand for carbonate; and (3) d13CCO2 = 0perthousand. Limited fluid inclusion studies have identified both aqueous and aqueous-carbonic fluids, the latter being typical of fluids in Archean vein systems. The data are permissible with a model for the Upper Beaver Cu-Au deposit that involves focusing of mineralizing fluids of mixed parentage involving both that magmatic and metamorphic reservoirs, as supported by a Re-Os age of 2685 Ma for moly from a mineralized zone.