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TitleGeological, petrological and geochemical observations of an Archean syenite-associated Cu-Au deposit, Kirkland Lake, Ontario: A temporal or genetic relationship
AuthorKontak, D J; Dubé, B; Kyser, T K
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Programs with Abstracts vol. 34, 2011 p. 111
LinksOnline - En ligne
Year2011
Alt SeriesEarth Sciences Sector, Contribution Series 20130570
Publishergac
MeetingGAC-MAC-SEG-SGA Joint Annual Meeting 2011; Ottawa; CA; May 25-27, 2011
Documentserial
Lang.English
Mediapaper
File formatpdf
ProvinceOntario
NTS42A/01
AreaKirkland Lake
Lat/Long WENS-80.1000 -80.0000 48.0667 48.0000
Subjectseconomic geology; igneous and metamorphic petrology; geochemistry; mineral occurrences; mineral deposits; mineral potential; mineralization; gold; volcanogenic deposits; sulphides; sulphide deposits; syenites; copper; Archean; Kirkland Lake gold camp; Precambrian; Proterozoic
ProgramGold Ore Systems, Targeted Geoscience Initiative (TGI-4)
AbstractThe 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.
GEOSCAN ID296044