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New insights on the geological and structural settings of the Musselwhite banded iron-formation–hosted gold deposit, North Caribou greenstone belt, Superior Province, Ontario.

Oswald, William; Castonguay, Sébastien; Dubé, Benoît; Malo, Michel; Mercier-Langevin, Patrick; Biczok, John (2015). New insights on the geological and structural settings of the Musselwhite banded iron-formation–hosted gold deposit, North Caribou greenstone belt, Superior Province, Ontario. Comptes rendus de Projets. Geological Survey of Canada / Commission géologique du Canada, Ottawa, Ontario.

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Résumé

The Musselwhite mine is a world-class gold deposit hosted in polydeformed amphibolite-facies banded iron-formation of the Mesoarchean North Caribou greenstone belt, northwestern Superior Province. The deposit is located about 2 km west of the tectonic boundary with the gneissic Island Lake domain. Detailed underground and surface mapping, core logging, and structural analyses have been undertaken to better characterize the various controls on gold mineralization. The west antiform trench 1 and esker docks exposures show the dominant northwest-trending structural pattern related to the main (D2) deformation phase. Multiple metre-scale type 3 F1-F2 and F2-F3 fold interference patterns are documented in the banded iron-formation. Coupled with regional-scale geological and U-Pb geochronological data, structural observations by the authors suggest that the mine area is located along the overturned limb of a kilometric-scale F1 syncline that influenced the regional distribution and geometry of the prospective banded iron-formation units, preceding the main D2 deformation. Underground mapping of the 1045 main ramp and 770 level 11780N crosscut sections indicates that the ore, in the northern iron-formation, mainly occurs as stratabound pyrrhotite-rich replacements and associated quartz-flooding of the garnet-rich silicate banded iron-formation facies, and locally as discordant syndeformation quartz±pyrrhotite veins. The ore zones are associated with D2-related high-strain zones, and are concentrated in hinges and along strongly attenuated limbs of F2 folds. The composition of the garnet-rich silicate facies and layered mechanical anisotropy induced by competent banded iron-formation horizons embedded in less competent mafic and ultramafic volcanic rocks strongly influenced the deformation style and played an important role in controlling flow of gold-bearing fluids and formation and distribution of the ore.

Type de document: (Comptes rendus de Projets)
Mots-clés libres: structural geology; economic geology; structural analyses; structural features; antiforms; deformation; cherts; iron; iron formations; Archean; gold; mineral deposits; exploration; metallogeny; ore mineral genesis; fault zones; Algoma type iron formations; Algoma type deposits; mineralization; bedrock geology; Musselwhite mine; North Caribou greenstone belt; Northern Iron Formation; Musselwhite deposit
Centre: Centre Eau Terre Environnement
Date de dépôt: 13 déc. 2016 21:21
Dernière modification: 13 déc. 2016 21:21
URI: http://espace.inrs.ca/id/eprint/3895

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