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TitleGeology and hydrothermal alteration of the Fab lake region, Northwest Territories
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorPotter, E GORCID logo; Montreuil, J -F; Corriveau, LORCID logo; DeToni, A
SourceGeological Survey of Canada, Open File 7339, 2013, 26 pages (1 sheet), Open Access logo Open Access
PublisherNatural Resources Canada
Documentopen file
MapsPublication contains 1 map
Map Info.geological, bedrock geology, hydrothermal alteration, 1:7,500
Mediaon-line; digital
File formatpdf
ProvinceNorthwest Territories
AreaFab Lake
Lat/Long WENS-117.2000 -117.0000 64.2000 64.0833
Subjectsmetallic minerals; hydrothermal alteration; alteration; mineralization; lithology; granites; iron oxides; copper; gold; mineral assemblages; modelling; brecciation; uranium; magnetite; calcium; iron; potassium; chloritization; epidotization; Great Bear Magmatic Zone; Precambrian
ProgramGEM: Geo-mapping for Energy and Minerals Iron-oxide Copper-gold (IOCG) / Multiple Metals - Great Bear Lake (NWT)
Released2013 05 15
AbstractDetailed mapping of the Fab Lake magnetite-group iron oxide-copper-gold (IOCG) system has defined an alteration footprint extending almost 10 by 5 km, with the long axis trending in a southeastnorthwest direction. Within this area, field mapping identified seven alteration assemblages: 1) high temperature albite and albite + amphibole ± magnetite [HT Na and HT Na-Ca-Fe]; 2) amphibole + magnetite ± apatite and amphibole + magnetite + K-feldspar [HT Ca-Fe and HT Ca-Fe-K]; 3) high temperature K-feldspar + magnetite ± hematite [HT K-Fe]; 4) K-feldspar; 5) chlorite; 6) hematite; and 7) low temperature epidote + K-feldspar + quartz [LT Ca-Fe]. These alteration assemblages are expressed as incipient to pervasive alteration in the form of veins, hydrothermal breccias and replacement fronts in the host rocks exhibiting multiple crosscutting and overprinting relationships. All of the historic Fab U-Cu-Fe mineral showings occur within zones characterized by intense, texture-destructive alteration comprising multiple episodes of high temperature albite/albite + amphibole + magnetite (Na and Na-Ca-Fe) and amphibole + magnetite ± apatite/amphibole + magnetite + K-feldspar (Ca-Fe and Ca-Fe-K) overprinted by K-feldspar + magnetite ± biotite (K-Fe) assemblages.
The conceptual alteration to brecciation and mineralization model is key to understanding the alteration assemblages documented in the Fab IOCG system. These assemblages record the build-up of a magnetite-group IOCG system: early high-temperature Na/Na-Ca-Fe and Ca-Fe/Ca-Fe-K alteration, overprinted by high temperature K-Fe alterations and incipient to well-developed hydrothermal breccias. The alteration assemblages themselves and the zoning observed in outcrop provide true vectors towards mineralization, which based on the nature of the hydrothermal system, can be applied elsewhere in the Great Bear magmatic zone and other prospective terranes. As field observations indicate that lower-temperature K-Fe alteration associated with hematite-group IOCG systems is only weakly developed, the Fab Lake region is most prospective for magnetite-group types of IOCG mineralization.
Summary(Plain Language Summary, not published)
Prospective settings for iron oxide-copper-gold (IOCG) deposits in Canada have largely remained underexplored and inadequately mapped. Consequently, costly field-based geological mapping and research, high-resolution geophysical surveys, and multidisciplinary tools and teams with IOCG-targeted expertise are required to advance exploration for this newly defined ore system. Targeting these issues, this report documents geological mapping of an IOCG system located in the Great Bear magmatic zone. Despite a lengthy heritage of mineral exploration and production of vein-type uranium and silver deposits, the Great Bear magmatic zone is the most prospective region for IOCG and affiliated mineralization in Canada. The geological and hydrothermal alteration map produced in this study highlights the predictability of the alteration footprint in IOCG systems and documents the successful application of the conceptual IOCG alteration to brecciation and mineralization model developed under the GEM program.

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