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TitreDifferential exhumation and concurrent fluid flow at the NICO Au-Co-Bi-Cu deposit, Great Bear magmatic zone, NWT - A paleomagnetic and structural record
AuteurEnkin, R J; Montreuil, J -F; Corriveau, L
SourceAssociation géologique du Canada-Association minéralogique du Canada, Réunion annuelle, Programme et résumés vol. 35, 2012 p. 41-42
LiensOnline - En ligne
Séries alt.Secteur des sciences de la Terre, Contribution externe 20120259
ÉditeurGeological Association of Canada, Mineralogical Association of Canada
RéunionGeological Association of Canada, Mineralogical Association of Canada, Joint Annual Meeting; St. John's; CA; mai 27-29, 2012
Documentpublication en série
ProvinceTerritoires du Nord-Ouest
SNRC85N; 86C; 86D; 86E; 86F; 86K; 86L
Lat/Long OENS-119.0000 -116.0000 67.0000 63.0000
Sujetsmagnetite; dépôts glaciaires; oxydes de fer; cuivre; or; minéralisation; fluage; interprétations paléomagnétiques; paléomagnétisme; analyses structurales; interpretations structurelles; Zone de Great Bear Magmatic ; géologie économique; géologie structurale
ProgrammeGisements polymétalliques - Zone magmatique du Grand lac de l'Ours (T.N-O.), GEM : La géocartographie de l'énergie et des minéraux
Résumé(disponible en anglais seulement)
The iron oxide copper-gold (IOCG) mineralization model is offering new exploration possibilities, especially in the Proterozoic Great Bear magmatic zone, NWT. The NICO Au-Co-Bi-Cu deposit, the numerous U-Th-REE±Cu-Mo showings of the Southern Breccia and the nearby Cu- Ag-(Au) Sue Dianne deposit provide well-exposed examples of IOCG-type and IOCG-affiliated mineralization. A paleomagnetism study (39 sites, 318 oriented specimens) was undertaken in this region with the goal of determining the interplay of hydrothermal fluids, deformation and iron-oxide mineralization. Because of the high concentrations of large magnetite grains in these altered rocks, hybrid alternating field and thermal demagnetization was done to clean a large unstable magnetic component from the useful paleomagnetic components. Strong stable magnetic remanence was observed throughout the collection, almost fully carried by magnetite even in dominantly hematite-bearing rocks. The rich range of lithologies, alteration levels and contact relationships in this small area provided the whole range of paleomagnetic stability tests. Negative conglomerate and tilt tests reveal pervasive remagnetization. The collection almost completely holds downward polarity (but not in the present field direction), as do the reference directions observed in stable Paleoproterozoic formations northwest of the Trans-Hudson Orogeny. While 4 sites retain an untilted Paleoproterozoic direction, most sites hold steeper remanence directions interpreted as variable tilting after remanence was acquired, dominantly down to the south-east. Rare 3-component magnetizations reveal magnetization acquisition during tilting. Five contact tests offer the exotic result that dykes were magnetized at different times than their contact zones, interpreted to be the result of subsequent hydrothermal pathways exploiting the differential permeability pathways. Combined with detailed analysis of polyphase structural evidence, the paleomagnetic remanence may indicate a form of bookcase normal faulting active during late deformation. Along with the complex results revealed from many complementary methods used to examine IOCG deposits, paleomagnetism provides quantitative proof of differential exhumation and concurrent fluid flow in this mineralization setting.