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TitlePreliminary results of the geology of the Portage deposit, Meadowbank gold mine, Churchill Province, Nunavut
AuthorJanvier, V; Castonguay, S; Mercier-Langevin, P; Dubé, B; McNicoll, V; Pehrsson, S; Malo, M; De Chavigny, B; Côté-Mantha, O
SourceGeological Survey of Canada, Current Research (Online) 2015-2, 2015, 21 pages, (Open Access)
PublisherNatural Resources Canada
Mediadigital; on-line
RelatedNRCan photo(s) in this publication
File formatpdf
NTS66A/16; 66H/01
AreaKavallik; Goose Island; Third Portage Lake; Second Portage Lake
Lat/Long WENS-96.1667 -96.0000 65.0833 64.9167
Subjectsstructural geology; economic geology; geochemistry; Archean; iron formations; mineral occurrences; mineral assemblages; mineralization; gold; bedrock geology; structural interpretations; structural features; faults; folds; lithology; volcanic rocks; plutonic rocks; igneous rocks; quartzites; felsic volcanic rocks; ultramafic rocks; deformation; geochemical surveys; geochemical interpretations; Meadowbank mine; Woodburn Lake Group; Precambrian; Proterozoic
Illustrationslocation maps; cross-sections; plots; ternary diagrams; photographs
ProgramTargeted Geoscience Initiative (TGI-4), Gold Ore Systems
Released2015 04 02
AbstractThe Meadowbank banded iron-formation-hosted world-class gold deposit is comprised in the polydeformed and metamorphosed 2711 Ma Pipedream-Third Portage sequence of the Woodburn Lake Group, which also comprises mafic and ultramafic rocks, and quartzite. At least four phases of regional Trans- Hudsonian (Proterozoic) deformation are documented in the Meadowbank deposit area: 1) isoclinal FP1 folds and DP1 fault zones, strongly overprinted by younger deformation; 2) north-trending isoclinal FP2 folds and associated DP2 fault zones cutting the stratigraphy and mineralization; and two set of younger folds, 3) open to closed southwest-plunging FP3 folds, and 4) shallowly to moderately inclined, open to tight, chevron-style mesoscopic FP4 folds. The bulk of the gold at Meadowbank is hosted in banded iron-formation and occurs at or near the contact with sheared ultramafic rocks where it is associated with pyrrhotite±pyrite and traces of chalcopyrite and arsenopyrite. Gold-rich quartz-pyrrhotite±pyrite veins are locally present in intermediate to felsic volcaniclastic rocks interlayered with banded iron-formation units. The ore-associated mineral assemblages include grunerite and/or cummingtonite and chlorite in banded iron-formation layers, whereas sericite±chlorite dominate in altered volcaniclastic rocks. Geochemical analyses of the major rock types are essential to further discriminate the host units, thus increasing the knowledge of the stratigraphic and structural setting of the deposit. Crosscutting relationships indicate that the bulk of the gold was introduced prior to DP2, preferentially near or along fault zones developed at contacts between banded iron-formation units and ultramafic rocks.
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. Agnico-Eagle Mines¿ Meadowbank mine is located in the Kivallik region of Nunavut. Research to date has mostly been concentrated on the geological mapping of the Portage ore body with an emphasis on the chemical signature of host rocks, the geometry of the deposit and its structural controls, and on the ore and associated mineral assemblages. The lithological sequence of the deposit consists of Neoarchean metamorphosed volcaniclastic rocks, banded iron formation (BIF), ultramafic rocks and quartzite. The predominant gold mineralization is hosted in BIF and is associated with pyrrhotite and pyrite, which have replaced magnetite. Gold also is found in high-grade quartz veins in volcaniclastic rocks. Four deformation events affect the host rocks, including two generations of faults and several folding phases.