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TitreAge constraints and geochemical evolution of the Neoarchean mafic-ultramafic Wabassi Intrusive Complex in the Miminiska-Fort Hope greenstone belt, Superior Province, Canada
AuteurSappin, A -A; Houlé, M G; Lesher, C M; McNicoll, V; Vaillancourt, C; Kamber, B S
SourcePrecambrian Research vol. 286, 2016 p. 101-125,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20160026
Documentpublication en série
Mediapapier; en ligne; numérique
Formatspdf; html; xls
SNRC42M; 42N/04; 42N/05; 42N/12; 42N/13; 43C/04; 43D/01; 43D/02; 43D/03; 43D/04; 52P/01; 52P/02; 52P/03; 52P/06; 52P/07; 52P/08; 52P/09; 52P/10; 52P/11; 52P/14; 52P/15; 52P/16; 53A/01; 53A/02; 53A/03
Lat/Long OENS -89.4833 -85.7833 52.1833 51.0167
Sujetsintrusions; géologie du substratum rocheux; lithologie; roches ignées; roches intrusives; roches volcaniques; roches mafiques; roches ultramafiques; roches métamorphiques; roches sédimentaires métamorphosées; zonation minéralogique; gisements minéraux; sulfures; fer; nickel; cuivre; thorium; niobium; tantale; titane; magmatisme; mise en place; magmas; olivine; pyroxene; plagioclase; amphibole; analyses des éléments en trace; analyses des éléments majeurs; géochimie des éléments en trace; filons de diabase; datation radiométrique; zircon; datation au uranium-plomb; analyse par spectromètre de masse; métamorphisme; altération; analyses minéralogiques; interprétations tectoniques; analyses de carottes de sondage; Province de Superior ; Domaine d'Uchi ; géochronologie; géochimie; géologie économique; pétrologie ignée et métamorphique; Précambrien
Illustrationsgeological sketch maps; stratigraphic columns; photographs; photomicrographs; tables; geochemical plots; profiles; models
ProgrammeÉtude des gîtes magmatiques de Ni-Cu-EPG, Initiative géoscientifique ciblée (IGC-4)
ProgrammeCRSNG Conseil de recherches en sciences naturelles et en génie du Canada
Résumé(disponible en anglais seulement)
The ca. 2.75-2.71 Ga Miminiska-Fort Hope greenstone belt (MFHGB) of the eastern Uchi domain of the Superior Province (northern Ontario) contains numerous mafic and ultramafic intrusions hosting Ni-Cu-(PGE) occurrences. The most significant, the mafic-ultramafic Wabassi Intrusive Complex and the nearby mafic Oxtoby Lake intrusion, formed between 2728 and 2727 Ma and at ca. 2717 Ma, respectively. The Max, Wabassi Main, and Wabassi South parts of the Wabassi Intrusive Complex and the Oxtoby Lake intrusion have been studied to establish their petrogenesis and metallogenesis, and to compare them to the highly prospective 2734 Ma mafic-ultramafic intrusions in the McFaulds Lake greenstone belt ~120 km to the north that host world-class Cr-(PGE), significant Ni-Cu-(PGE), and potentially significant Fe-Ti-V mineralization.
The ca. 2728 Ma ultramafic-dominated Max intrusion is relatively homogeneous in composition, comprising mainly harzburgite, lherzolite, and wherlite with minor olivine orthopyroxenite, orthopyroxenite, websterite, and mesocratic gabbroic rocks. It also contains disseminated to patchy net-textured Fe-Ni-Cu-(PGE) sulfides. In contrast, the ca. 2727 Ma Wabassi Main intrusion is a layered mafic-dominated intrusion that consists of: (1) a basal zone containing leucocratic to mesocratic olivine gabbronorite and olivine norite, troctolite, lherzolite, and harzburgite with high Cr contents, olivine with Mg#78-72, orthopyroxene with Mg#84-67, clinopyroxene with Mg#95-91, and plagioclase with An96-37, (2) a lower zone containing mesocratic olivine gabbronorite-gabbro-norite and up to 10% Fe-Ti oxides, olivine with Mg#64-19, orthopyroxene with Mg#67-58, clinopyroxene with Mg#80-56, and plagioclase with An79-46, (3) a middle zone containing leuco- to mesocratic gabbronorite with up to 8% Fe-Ti oxides, orthopyroxene with Mg#57-56, clinopyroxene with Mg#73-66, and plagioclase with An71-63, and (4) an upper zone containing mesocratic gabbronorite, gabbro, and ferrogabbroic rocks with up to 50% Fe-Ti oxides, up to 8% apatite, low Cr and high P contents, orthopyroxene with Mg#44, clinopyroxene with Mg#60, and plagioclase with An63-52. The ultramafic-dominated Wabassi South intrusion is homogeneous in composition and is composed of peridotite. All three intrusions are enriched in Th > LREE > MREE relative to Nb-Ta and Ti, suggesting that they incorporated significant amounts of upper crustal material. This, together with their overlapping petrographic, geochemical, and mineralogical characteristics, suggests that they are co-genetic. Their formation appears to have begun with the accumulation of olivine, pyroxene, and minor chromite from a contaminated high-Mg basaltic parental magma (~12% MgO) in the Max and Wabassi South magmatic conduits. Later, this magma crystallized cumulates in the Wabassi Main magma chamber with the following order of appearance of cumulus phases: olivine + chromite->orthopyroxene/clinopyroxene->plagioclase->magnetite + ilmenite->apatite. The parental magma composition is more evolved than magmas responsible for the generation of the Cr-(PGE) and Ni-Cu-(PGE) mineralization in the McFaulds Lake greenstone belt, but they may be more contaminated equivalents. The ca. 2717 Ma mafic Oxtoby Lake intrusion is more mesocratic with significantly different trace element signatures, suggesting that it is unrelated or only indirectly related to the Wabassi Intrusive Complex.
The Max, Wabassi Main, Wabassi South, and Oxtoby Lake intrusions are coeval with different volcanic assemblages of the MFHGB. Together with the mafic-ultramafic intrusions of the McFaulds Lake greenstone belt, they probably represent the remnants of an Archean large igneous complex that was emplaced within the northern Superior Province between ca. 2.88 and 2.70 Ga. Among these four intrusions, Max may be the most prospective for Ni-Cu-(PGE) mineralization. The high abundance of primitive ultramafic rocks suggests that it was an open, dynamic system that accumulated olivine and pyroxene, and the trace element signature is consistent with incorporation of significant amounts of upper crustal material, permissive to the formation of Ni-Cu-(PGE) mineralization.
Résumé(Résumé en langage clair et simple, non publié)
Le complexe intrusif Wabassi (intrusions de Max, Wabassi Main, Wabassi South) situé en Ontario a été étudié afin de comprendre leur mise en place. Plus au nord, une intrusion plus jeune, l'intrusion Oxtoby Lake, a également été étudiée et comparée au complexe intrusif Wabassi. L'intrusion Max, datée à 2736 Ma, est relativement homogène en composition. Elle comprend des péridotites, des pyroxénites à olivine et des roches gabbroïques. Au contraire, l'intrusion Wabassi Main, datée à 2727 Ma, est une intrusion litée composée d'une variété de péridotites, gabbros à olivine et de gabbros pouvant contenir jusqu'à 50% d'oxydes de Fe-Ti et 8% d'apatite. L'intrusion Wabassi South est également homogène en terme de composition et comprend des roches riches en olivine. Les trois intrusions sont co-génétiques et présentent des caractéristiques pétrographiques, chimiques et minéralogiques similaires. L'intrusion Oxtoby Lake, datée à 2717 Ma, est composée de roches gabbroïques et présente des signatures chimiques distinctes, suggérant que sa mise en place a été indépendante de la formation du complexe intrusif Wabassi.