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TitleThe Southern Breccia metasomatic uranium system of the Great Bear Magmatic Zone, Canada: iron oxide-copper-gold (IOCG) and albitite-hosted uranium linkages
AuthorPotter, E GORCID logo; Montreuil, J -F; Corriveau, LORCID logo; Davis, W JORCID logo
SourceOre deposits: origin, exploration, and exploitation; by Decrée, S (ed.); Robb, L (ed.); Geophysical Monograph Series 242, 2019 p. 109-130
Alt SeriesEarth Sciences Sector, Contribution Series 20130267
PublisherJohn Wiley & Sons, Inc.
PublisherAmerican Geophysical Union
Mediapaper; digital
File formatpdf (Adobe® Reader®)
ProvinceNorthwest Territories
AreaLou Lake
Lat/Long WENS-116.8189 -116.7183 63.5603 63.5328
Subjectseconomic geology; geochemistry; igneous and metamorphic petrology; geochronology; mineral deposits; mineral exploration; exploration guidelines; metasomatic deposits; uranium; iron oxides; copper; gold; polymetallic ores; ore mineral genesis; mineralization; host rocks; bedrock geology; lithology; metamorphic rocks; albitites; breccias; igneous rocks; intrusive rocks; rhyodacites; rhyodacite porphyries; leucogranites; monzonites; monzodiorites; tectonic history; magmatism; intrusions; dykes; metasomatism; alteration; albitization; hydrothermal systems; fluid dynamics; precipitation; mineral assemblages; mineral occurrences; field relations; petrographic analyses; whole rock geochemistry; models; thin section microscopy; scanning electron microscope analyses; trace element analyses; major element analyses; electron probe analyses; mass spectrometer analysis; uraninite; radiometric dating; uranium lead dating; Paleoproterozoic; Southern Breccia Showing; Great Bear Magmatic Zone; NICO Deposit; Wopmay Fault Zone; McTavish Supergroup; Faber Group; Mazenod Lake Formation; Cole Lake Formation; Lou Lake Formation; Hottah Terrane; Treasure Lake Formation; Precambrian; Proterozoic
Illustrationslocation maps; geoscientific sketch maps; models; geochronological charts; photographs; photomicrographs; tables; geochemical plots
ProgramTargeted Geoscience Initiative (TGI-4) Uranium Ore Systems
Released2019 04 01
AbstractThe Southern Breccia metasomatic uranium (U) showings are located 1 km south of the NICO deposit, an iron oxide-copper-gold (IOCG) deposit, in the Great Bear magmatic zone of Canada. The timing of both occurrences is tightly constrained to 1873-1868 Ma, linking formation of the albitite-hosted U to development of IOCG mineralization. During this period, regional iron oxide and alkali-calcic metasomatism formed: Na (albite), high-temperature Ca-Fe (amphibole + magnetite), high-temperature Ca-K-Fe (amphibole + magnetite + biotite ± K-feldspar), high-temperature K-Fe (K-feldspar/biotite + magnetite), K (K-feldspar ± biotite), and low-temperature K-Fe-Mg (K-feldspar + hematite + chlorite) assemblages. Primary uraninite and brannerite occur within high-temperature K-Fe alteration composed of magnetite + K-feldspar ± biotite-cemented breccias developed in earlier albitite. The chemistry of primary uraninite supports precipitation from high-temperature, magmatic-derived fluids, as previously proposed for the NICO deposit. Field relationships, petrography, whole-rock geochemistry, and geochronology indicate that alteration of the Southern Breccia corridor host rocks was coeval with early alteration at NICO, whereas U mineralization postdated Au-Co-Bi at NICO. The linkage of the Southern Breccia to the regional iron-oxide and alkali-calcic alteration system that generated the NICO deposit presents a new driver for formation of albitite-hosted U deposits and highlights an exploration target in IOCG districts globally.
Summary(Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI-4) is a collaborative federal geoscience program that provides industry with the next generation of geoscience knowledge and innovative techniques to better detect buried mineral deposits, thereby reducing some of the risks of exploration. Iron oxide-copper-gold (IOCG) deposits are characterized by regionally extensive alteration patterns which systematically remove, transport and precipitate elements during their development. Recent studies of Canadian IOCG systems have shown that the evolving nature of these alteration assemblages can used to predict potential ore deposit types. One such deposit type is metasomatic uranium, also known as albitite-hosted uranium, which as shown in this study, can form in the pre-IOCG ore, sodic alteration zones of these systems. Although this relationship has long been conjectured, this study documents the first example of an albite-hosted uranium system associated with an IOCG deposit that is located in the Northwest Territories.

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