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TitleAlteration mapping as vectors towards iron oxide Cu-Au (Ag-U-Co-Bi) mineralization in green-field exploration settings: case examples from the Great Bear Magmatic Zone, NWT
AuthorCorriveau, L; Mumin, H; Ootes, L; Landry, J -Y
SourceMontreal 2006 - Planet Earth in Montreal/Montréal 2006 - Planète Terre à Montréal; Geological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Abstracts Volume vol. 31, 2006 p. 30
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20060395
MeetingMontreal 2006 - Planet Earth in Montreal - Geological Association of Canada-Mineralogical Association of Canada Joint Annual Meeting / Planète Terre à Montréal: Réunion annuelle conjointe de l'Association géologique du Canada et l'Association minéralogique du Canada; Montreal, QC; CA; May 14-17, 2006
Mediapaper; on-line; digital
File formathtml; pdf
ProvinceNorthwest Territories
NTS85N; 86C; 86F; 86K
AreaPort Radium-Echo Bay; Contact Lake; DeVries Lake; Faber Lake
Subjectseconomic geology; mineral deposits; polymetallic ores; mineral exploration; exploration guidelines; mapping techniques; metamorphism; deformation; alteration; mineralization; iron oxides; copper; gold; silver; uranium; cobalt; bismuth; igneous rocks; volcanic rocks; plutonic rocks; felsic rocks; metamorphic rocks; metasedimentary rocks; potassium; iron; tourmaline; silica; stockworks; calcium; sodium; magnetite; actinolite; apatite; hydrothermal deposits; breccias; diatremes; recrystallization; andesites; feldspar; pegmatites; textural analyses; host rocks; ironstone; structural features; faults; Great Bear Magmatic Zone; Wopmay Orogen; iron-oxide-copper-gold (IOCG) deposits; overprinting; calc-alkaline volcanic rocks; Precambrian; Proterozoic
AbstractIn Canada, the two known IOCG deposits, NICO and Sue-Dianne, occur in the better studied southern region of the Great Bear Magmatic Zone (GBMZ), Wopmay Orogen, NWT. In contrast, the historic Port Radium - Echo Bay U-Ag (Cu, Ni, Co, Bi) mining district to the north has only recently been recognized as an important IOCG district. Exploring for IOCGs in Canada requires targeting felsic to intermediate volcano-plutonic complexes and metamorphic terranes where modern geoscience knowledge may be rare or only at reconnaissance scale. In many of these environments, mapping was commonly conducted prior to the recognition of the deposit type, hence vectors to mineralization as significant as widespread hematite, K-feldspar, magnetite and albite alteration are missing in available records. In economic polymetallic IOCG deposits, tracers of mineralization have significant lateral extent and include diagnostic alteration zones and overprinting relationships. Consequently, alteration mapping provides a key vector towards mineralization. For this study, three lesser known areas of the GBMZ with disparate Cu, Au, Ag and U mineralization in Andean-type calc-alkaline volcanic rocks and older
metasedimentary rocks were selected to gain a better understanding of the potential of Canadian Proterozoic felsic volcano-plutonic terranes and to test the suitability of available geological knowledge to support emerging exploration plays. At Contact Lake, documentation that Cu-Au-Ag-Co mineralization overprints focussed potassic-iron-tourmaline-silica alteration in some areas, and laterally extensive Kiruna-type calcic-sodic and magnetite-actinolite-apatite stockwork in others, combined with the discovery of hydrothermal breccias and diatremes indicate a high potential for bulk-mineable polymetallic resources.
Recrystallization of andesite to a feldspar-magnetite-actinolite-apatite pegmatoidal rock highlights potential problems in mapping stemming from grain-coarsening processes that lead to igneous-looking textures. With its extensive exposures of intensely altered rocks that permit characterization of overprinting relationships, the Contact Lake area provides classic and well exposed examples of polymetallic IOCG alteration superimposed on host rocks initially devoid of significant iron oxides. In contrast, DeVries Lake mineralizing systems are a distinct IOCG sub-type that overprints ironstones in older metasedimentary rocks, and comprises pre-, syn- and post-deformation alteration near a major fault. At Fab Lake, a unit formerly mapped as conglomerate is best interpreted as hydrothermal breccia. This new data along with previous work in the southern GBMZ underscores the potential of the entire zone to host several types of polymetallic IOCG deposits. While geophysics and remote studies help define regionally prospective areas, targeted mapping remains the single most effective discovery tool for IOCGs in the GBMZ.