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TitleInsights on the geology of the world-class Roberto Gold Deposit, Eleonore Property, James Bay, Quebec
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorRavenelle, J -F; Dubé, B; Malo, M; McNicoll, V; Nadeau, L; Simoneau, J
SourceGeological Survey of Canada, Current Research (Online) no. 2010-1, 2010, 29 pages, Open Access logo Open Access
PublisherNatural Resources Canada
Mediaon-line; digital; paper
File formatpdf (Adobe Acrobat Reader)
AreaJames Bay
Lat/Long WENS -78.2500 -71.6667 54.3333 51.0000
Subjectseconomic geology; structural geology; igneous and metamorphic petrology; geochronology; tectonics; geochemistry; mineral occurrences; mineral deposits; mineralization; gold; copper; silver; bedrock geology; deformation; structural features; folds; folding; metamorphic rocks; metagreywackes; paragneisses; metamorphism; metasomatism; alteration; hydrothermal alteration; lithology; tectonic environments; tectonic setting; Archean; Opinaca Subprovince; La Grande Subprovince; Superior Province; Ell Lake Diorite; Precambrian
Illustrationslocation maps; photographs; photomicrographs; drawings; tables
ProgramNorthern Resources Development Program
Released2010 06 25
AbstractThe world-class Roberto gold deposit is an atypical gold deposit located in an underexplored part of the Superior Province. The purpose of this paper is to present a preliminary geological description of deposit and provide insights on geological features that may have played a role in its formation and can be used to help exploration programs. The deposit is located within a km-scale F2 fold hinge that affects upper-greenschist to amphibolite-facies turbiditic metagreywacke and paragneiss. Gold mineralization is primarily confined to a series of sub-parallel decameter-scale-wide mineralized zones and is associated with an hydrothermal system characterized by calc-silicate veins and metasomatic replacement zones, potassic alteration, and tourmaline. The principal mineralized zone (Roberto) consists of a stockwork of quartz ± actinolite ± diopside ± biotite-arsenopyrite-pyrrhotite veins and quartz-dravite-arsenopyrite veinlets, contained within microcline (potassic alteration) and dravite replacement zones. While most of the alteration and mineralized zones are deformed by structures attributed to D2, some occurrences appear to be controlled by D2 structures; gold mineralization is thus interpreted as being pre- or early-D2. Although geochronological data allow to refute the hypothesis that Roberto (<2675 ± 6 Ma) is associated with the nearby Ell Lake diorite (2705 ± 1.9 Ma), the potential input from magmatic fluids should not be blindly discarded, as indicated by the presence of potentially younger porphyritic intrusions and multiple generations of pegmatites, some of which potentially being contemporaneous with a part of the mineralization or its remobilization.

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