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Titre	Magmatic and structural controls on hypogene mineralization at the Carmacks copper deposit
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Auteur	Kovacs, N; Allan, M; Zagorevski, A; Milton, J; Hart, C J R
Source	Margins through time: GAC-MAC 2016; Association géologique du Canada-Association minéralogique du Canada, Réunion annuelle, Programme et résumés vol. 39, 2016 p. 48 Accès ouvert
Liens	Online - En ligne (complete volume - volume complet, PDF, 1.3 MB)
Année	2016
Séries alt.	Ressources naturelles Canada, Contribution externe 20190383
Éditeur	Association géologique du Canada
Réunion	GAC-MAC 2016; Whitehorse, YK; CA; juin 1-3, 2016
Document	publication en série
Lang.	anglais
Media	en ligne; numérique
Formats	pdf
Province	Colombie-Britannique
Sujets	gisements minéraux; cuivre; or; genèse des minerais; contrôles des minerais; géologie économique; tectonique; géologie structurale; Sciences et technologie; Nature et environnement; Phanérozoïque; Mésozoïque; Jurassique; Trias
Programme	GEM2 : La géocartographie de l'énergie et des minéraux Transitions de porphyres régionaux de l'ouest de la Cordillère
Diffusé	2016 06 01
Résumé	(disponible en anglais seulement) Late Triassic to Early Jurassic magmatism is responsible for many of the porphyry deposits in British Columbia. Same age intrusive rocks in west-central Yukon host several Cu-Au deposits such as Minto and Carmacks Copper. Both of these examples of mineralization are overprinted by deformation and metamorphism that obscure the genesis of the deposits. Copper sulphide mineralization at the Carmacks Copper Cu-Au-Ag oxide deposit is located within a 3 km-long, ~20 to 100 m-wide northwest trending corridor of deformed amphibolite-facies metavolcanic rocks. These rocks occur as enclaves within arc granitoids of the Late Triassic to Early Jurassic Minto plutonic suite (204-195 Ma). The Carmacks deposit has a complex history of polyphase deformation that is punctuated by discrete intrusive events. An early metamorphic fabric in the metavolcanic rocks comprises NNW-trending, steeply dipping foliation. This early fabric envelops boudined diorite dykes that represent the earliest intrusive phase. Tightly folded diorite dykes commonly cross-cut earlier boudined dykes and are interpreted as a result of a second deformation event. Finally, granodioritic magma engulfs the amphibolitic rocks and cross-cuts all metamorphic fabrics and pre-existing magmatic units. Previous studies on this intrusive phase reported zircon dates of 197.3±1.5 Ma with a pressure during crystallization of at least 6 kbar. Most of the hypogene mineralization occurs as stringers of chalcopyrite parallel to the dominant metamorphic fabric within the amphibolites. This sulphide texture is interpreted to represent a pre- Early Jurassic mineralizing system that occurred prior to or during ductile deformation and metamorphism of the volcanic host rock. Close to the contact with the batholith, foliated amphibolitic rocks change gradationally into granoblastic microdiorite and migmatite. Field relationships suggest that heat from the intrusion of the batholith may have been sufficient to generate partial melts of the amphibolitic rocks to modify their texture and perhaps remobilize some of the hypogene mineralization. Where these rocks have undergone recrystallization and partial melting to form microdiorite and migmatite, mineralization characteristically forms discordant veinlets and net-textured chalcopyrite and bornite. This distinct ore facies is likely associated with the generation of partial melt which has led to the remobilization of sulphides. Most porphyry deposits in British Columbia formed during a ~15 M.y. time period, with ~90 % of known copper resources generated between 202 and 208 Ma. However, foliation-parallel chalcopyrite veinlets in the amphibolitic rocks suggest that hypogene mineralization is pre-Early Jurassic and that post mineralization modification of hypogene mineralization likely explains its seemingly enigmatic origin.
GEOSCAN ID	321658