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TitleDevelopment of albitite-hosted uranium systems within iron oxide-copper-gold (IOCG) systems: the Southern Breccia, Great Bear magmatic zone, Canada
AuthorPotter, E G; Montreuil, J -F; Corriveau, L; Davis, W J
SourceIAEA technical meeting on metasomatite uranium occurences and deposits, abstracts; by IAEA; 2013.
Alt SeriesEarth Sciences Sector, Contribution Series 20130005
MeetingIAEA Technical Meeting on Metasomatite Uranium Occurences and Deposits; Vienna; AT; June 17-19, 2013
ProvinceNorthwest Territories
AreaLou Lake; Cole Lake; Fab Lake
Lat/Long WENS-117.0000 -116.5000 63.7500 63.5000
Subjectseconomic geology; alteration; mineral occurrences; mineral deposits; iron oxides; copper; gold; uranium; Great Bear Magmatic Zone
ProgramTargeted Geoscience Initiative (TGI-4), Uranium Ore Systems
AbstractThe Southern Breccia albitite-hosted uranium system is a 3 km long corridor of uranium-rich, polymetallic showings located 1 km south of the NICO magnetite-group, iron oxide-copper-gold (IOCG) deposit located in the Great Bear magmatic zone (GBmz), Northwest Territories. The southeast-trending, 500 m wide albitite corridor is bound by local-scale faults and is hosted within intensely altered metasedimentary rocks of the Treasure Lake Group. The corridor is bordered to the south by an albitized granitic intrusion, which as a member of the oldest intrusive suite in the southern GBmz provides a maximum age of the system. Systematic field and petrographic studies record multiple episodes of (early to late): sodic (albite), calcic-iron (amphibole + magnetite), potassic-iron (K-feldspar/biotite + magnetite-ilmenite), potassic (K-feldspar + phyllosilicates) and hematite + chlorite alteration associated with development of the NICO IOCG deposit. Primary uranium oxides and silicates are associated with magnetite-bearing potassic-iron alteration with ± pyrite ± chalcopyrite ± molybdenite ± bismuthinite ± galena within magnetite + ilmenite + K-feldspar ± biotite-cemented breccias developed in early albitite. Late, northeast-trending brittle faults, which offset and truncate the corridor to the northwest, remobilized uranium into earthy hematite-chlorite veins.

Field relationships, mineral parageneses, geochemistry and geochronological data indicate that formation of the Southern Breccia was coeval with the NICO deposit, circa 1873 to 1869 Ma. This time period corresponds to a major iron-oxide alkali-alteration (IOAA) event in the Great Bear magmatic zone, during which formation of metasomatic IOAA systems linked to high-level intrusive activity generated iron oxide-apatite (IOA), specialized metal, magnetite- to hematite-group IOCG, albitite-hosted uranium and epithermal mineralization. The results of the study illustrate that albitite-hosted uranium systems can form in pre-IOCG ore, sodic alteration zones during development of IOCG deposits.
Summary(Plain Language Summary, not published)
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 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.