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TitleThe Archean Côté Gold intrusion-related Au (-Cu) deposit, Ontario, Canada: A largetonnage, low-grade deposit centred on a magmatic-hydrothermal breccia
AuthorKatz, L R; Kontak, D J; Dubé, B
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Abstracts Volume vol. 37, 2014 p. 133-134
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20130598
MeetingGeological Association of Canada - Mineralogical Association of Canada (GAC-MAC) annual joint meeting; Fredericton; CA; May 21-23, 2014
File formatpdf
AreaKirkland Lake; Côté Lake
Lat/Long WENS-80.5000 -80.0000 48.0000 47.7500
Subjectseconomic geology; Archean; gold; mineralization; hydrothermal alteration; hydrothermal deposits; Upper Beaver gold system; Côté Lake gold system; Côté Gold deposit; Precambrian
ProgramGold Ore Systems, Targeted Geoscience Initiative (TGI-4)
AbstractThe recently discovered (2009/2010) Côté Gold deposit, located in the Archean Swayze greenstone belt, Abitibi Subprovince is a large-tonnage, low-grade Au (-Cu) deposit with an indicated resource of 269 Mt averaging 0.88 g/t Au (7.61 M oz) and an inferred resource of 44 Mt averaging 0.74 g/t Au (1.04 M oz) at a 0.3 g/t Au cut-off grade. The deposit is hosted by the Chester intrusive complex, a high-level, multi-stage composite intrusion consisting of gabbro, diorite and tonalite; these phases are constrained to 2741 ± 1 Ma based on U-Pb high-precision zircon dating. Field relationships indicate that two leucotonalites occur; tonalite I is cut by diorite whereas tonalite II contains <1% - 40% dioritic enclaves. Tonalite II locally displays autobrecciation and UST textures, chilled contacts and miarolitic cavities. Gold mineralisation is associated with disseminated sulphide and quartz-sulphide ± carbonate vein arrays. A maximum age for this mineralisation, provided from Re-Os dating of molybdenite, including an auriferous sample, is 2739 ± 8 Ma which overlaps with the age of magmatism. Mineralisation is hosted by a multi-phase magmatic-hydrothermal breccia that intrudes tonalite and diorite. The breccia is a largely continuous, discrete body containing variably sized (<1 cm to rarely 1 m) and shaped (angular to rounded), biotite-altered tonalite clasts within a dark, fine-grained hydrothermal matrix (biotite ± amphibole-chlorite-quartz-carbonate ± apatite ± sulphides) or magmatic matrix (plagioclase-quartz-biotite-chlorite ± sulphides). Biotite alteration (biotite ± magnetite ± epidote ± pyrite), the earliest type, occurs as dissemination or veins. Silica-sodic alteration (quartz-albite), a texturally destructive alteration, occurs as vein- and fracturecontrolled alteration that coalesces to form a pervasive replacement with rare, localised episyenites due to silica leaching. Sericite alteration (sericite ± quartz ± carbonate ± pyrite) occurs as haloes surrounding veins and fractures and also coalesces into pervasive alteration. Rare, vein- and fracture-controlled propylitic alteration is also documented. This apparent ca. 2741 Ma mineralisation age is significant for several reasons: (1) it establishes a new, pre-main stage deformation, metallogenic event in the Abitibi Subprovince; (2) globally represents a rare example of an intrusion-related, Archean-age large-tonnage, low-grade Au deposit; and (3) the nature and style of mineralisation and alteration, and the overlap of magmatic and hydrothermal events suggests possible affinities to younger porphyry-style Au (-Cu) mineralisation, although the paleo-tectonic settings may differ.