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TitleNew insights on the geological setting of the world-class Musselwhite gold deposit, Superior Province, northwestern Ontario
AuthorOswald, W; Dubé, B; Castonguay, S; McNicoll, V; Biczok, J; Mercier-Langevin, P; Malo, M; Skulski, T
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Abstracts Volume vol. 37, 2014 p. 207-208
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20130599
PublisherGeological Association of Canada
Meeting GAC-MAC 2014; Joint annual meeting of Geological Association of Canada and Mineralogical Association of Canada; Fredericton; CA; May 21-23, 2014
Mediaon-line; digital
File formatpdf
NTS53B/09; 53B/10; 53B/15; 53B/16
AreaNorth Caribou Lake; Opapimiskan Lake; Schade Lake
Lat/Long WENS -92.0000 -79.5000 53.0000 48.0000
Subjectsmetallic minerals; structural geology; economic geology; Archean; gold; mineral deposits; iron formations; exploration; metallogeny; ore mineral genesis; fault zones; Algoma type iron formations; Algoma type deposits; mineralization; Musselwhite mine; North Caribou greenstone belt; Northern Iron Formation; Precambrian
ProgramTargeted Geoscience Initiative (TGI-4), Gold Ore Systems
AbstractThe Musselwhite mine is a world-class syn-deformation gold deposit hosted by amphibolite facies Algoma-type banded iron formation (BIF) and comprised in the Mesoarchean North Caribou Lake greenstone belt, Superior Province. The deposit is located 2km west of a major fault zone that defines the tectonic boundary with the ca. 2857 Ma Schade Lake gneissic complex of the Island Lake Domain. Detailed surface mapping provides new data on D1 and D2 structures and their influences on the regional and deposit scales setting of the gold mineralisation. Multiple occurrences of decimeter to meter scale refolded F1 folds, along with S0 and S1 geometries, indicate the presence of megascopic F1 folds. Reappraisal of stratigraphic relationships supported by ongoing U-Pb geochronological results indicates that the mine stratigraphy is overturned. These datasets suggest the mine is located along the overturned limb of an early map-scale F1 syncline, which axis lies to the South of Opapimiskan Lake. F1 folds, evidence of which are strongly overprinted by D2 in the immediate mine area, influence the distribution and geometry of the BIF units hosting the bulk of gold mineralisation and could generate new regional exploration target areas. The bulk of the ore is hosted by the Northern BIF and occurs as stratabound pyrrhotiterich replacements and associated silica flooding of the silicate BIF with local discordant syntectonic grey quartz±pyrrhotite veins. The ore zones are associated with D2-related to high strain zones concentrated along hinges (T Antiform and PQ Deeps) and strongly attenuated fold limbs (e.g. Lynx Zone) of shallow northwest-plunging F2 folds. The layered anisotropy induced by competent BIF horizons embedded in strongly deformed and less competent mafic and ultramafic volcanic rocks strongly influenced rheological response to deformation, both at macro and microscopic scales, and hence played an important role in gold-bearing fluids flow and ore formation and distribution. Volcanic rocks proximal to the ore zones display a strong biotite alteration. Preliminary petrographic observations of the ore, such as iron carbonate content, Ca-bearing amphiboles and locally hedenbergite suggest calcium-rich alteration. Initial geochemistry results indicate traces elements such as Cu, Se, Te, Zn ±As are associated with gold. Typically, the high-grade ore zones display metasomatic/metamorphic layering with ~50% coarse red almandine garnet porphyroblasts, intergrown with fine to medium grained, bladed grunerite-cummingtonite (5- 10%) and red brown biotite (&le10%) aligned sub-parallel to the S2 foliation. Such mineral assemblages can be found regionally as well as closely associated with gold mineralisation so that its characterization is most probably instrumental in uncovering the hydrothermal footprint of the deposit.