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TitleDifferential exhumation and concurrent fluid flow at the NICO Au-Co-Bi-Cu deposit, Great Bear magmatic zone, NWT - A paleomagnetic and structural record
AuthorEnkin, R J; Montreuil, J -F; Corriveau, L
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Programs with Abstracts vol. 35, 2012 p. 41-42
LinksOnline - En ligne
Year2012
Alt SeriesEarth Sciences Sector, Contribution Series 20120259
PublisherGeological Association of Canada, Mineralogical Association of Canada
MeetingGeological Association of Canada, Mineralogical Association of Canada, Joint Annual Meeting; St. John's; CA; May 27-29, 2012
Documentserial
Lang.English
Mediapaper
ProvinceNorthwest Territories
NTS85N; 86C; 86D; 86E; 86F; 86K; 86L
AreaGreat Bear Lake; Lac la Martre; Hottah Lake
Lat/Long WENS-119.0000 -116.0000 67.0000 63.0000
Subjectseconomic geology; structural geology; magnetite; glacial deposits; iron oxides; copper; gold; mineralization; fluid flow; paleomagnetic interpretations; paleomagnetism; structural analyses; structural interpretations; Great Bear magmatic zone
ProgramIron-oxide Copper-gold (IOCG) / Multiple Metals - Great Bear Lake (NWT), GEM: Geo-mapping for Energy and Minerals
AbstractThe 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.
GEOSCAN ID291958