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TitleGeology of the banded iron formation-hosted Meadowbank gold deposit, Nunavut, Canada
AuthorJanvier, V; Castonguay, S; Mercier-Langevin, P; Dubé, B; Malo, M; McNicoll, V; Pehrsson, S; De Chavigny, B; Côté-Mantha, O
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Abstracts Volume vol. 37, 2014 p. 127
Year2014
Alt SeriesEarth Sciences Sector, Contribution Series 20130597
Publishergac
MeetingGAC-MAC Joint annual meeting; Fredericton; CA; May 21-23, 2014
Documentserial
Lang.English
Mediapaper
File formatpdf
ProvinceNunavut
NTS56D/13NW; 56E/04SW; 66A/16NE; 66H/01SE
AreaKavallik; Goose Island; Third Portage Lake; Second Portage Lake
Lat/Long WENS-96.2500 -95.7500 65.0833 64.9167
Subjectsstructural geology; economic geology; 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; Meadowbank mine; Woodburn Lake Group; Precambrian; Proterozoic
ProgramGold Ore Systems, Targeted Geoscience Initiative (TGI-4)
LinksOnline - En Ligne
AbstractThe Meadowbank banded iron formation (BIF)-hosted world-class gold deposit is hosted in the polydeformed and metamorphosed ca. 2711 Ma Pipedream-Third Portage volcanic sequence of the Woodburn Lake Group that comprises several similar BIFs, of the most significant of which being the East BIF, the Central-BIF and the West-BIF. Despite their similarity, only the Central BIF contains economical gold mineralization. The deposit host succession consists of greenschist to amphibolite grade intermediate volcaniclastic rocks, BIFs, intermediate to felsic volcaniclastic rocks, mafic and ultramafic rocks, and quartzite. The pronounced negative Nb, Ta and Ti anomalies of the intermediate and intermediate to felsic units indicate an arc-like affinity. Notwithstanding cryptic and strongly overprinted Archean tectonism, four phases of Trans- Hudsonian (Proterozoic) deformation, have been recognized in the Meadowbank deposit area: isoclinal F1 folds and early shear zones, strongly overprinted by coplanar N-trending isoclinal F2 folds and associated D2 shear zones that cut the stratigraphy and mineralized zones. Shallowly to moderately-inclined, open to tight, chevron-style F3 folds and open to closed SW-plunging F4 folds further affect the deposit, resulting in a complex polyphase geometry. The bulk of the gold at Meadowbank is hosted in iron-formation occurring at or near the contact with sheared ultramafic rocks and 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 intercalated with BIFs. The ore-associated mineral assemblages include grunerite/cummingtonite and chlorite in BIF layers, whereas sericite ± chlorite and carbonates dominate in altered volcaniclastic rocks. The metamorphic grade increases southward along the deposit, where biotite, Fe-Mg amphibole and garnet occur in variable proportion. Crosscutting relationships suggest that the bulk of the gold was introduced prior to D2, preferentially along the sheared contact between BIFs and ultramafic rocks, and was later locally remobilized during D2. Deposit- and regional-scale lithogeochemistry and new U-Pb zircon ages indicate that the Meadowbank deposit is located at the boundary between two distinct lithological assemblages (2711 Ma and 2717 Ma) separated by long-lived shear zones that potentially have controlled gold deposition and distribution. The study demonstrates that integrated structural analysis, lithogeochemistry and geochronology are essential aspects to understand BIF-hosted gold deposits in order to develop better genetic and exploration models.
GEOSCAN ID296198