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TitreGeochemistry and petrogenesis of the Black Thor intrusive complex and associated chromite mineralization, McFaulds Lake greenstone belt, Ontario
TéléchargerTéléchargement (publication entière)
AuteurCarson, H J E; Lesher, C M; Houlé, M G
SourceTargeted Geoscience Initiative 4: Canadian nickel-copper-platinum group elements-chromium ore systems -- fertility, pathfinders, new and revised models; par Ames, D E (éd.); Houlé, M G (éd.); Commission géologique du Canada, Dossier public 7856, 2015 p. 87-102, https://doi.org/10.4095/296681
Année2015
ÉditeurRessources naturelles Canada
Documentdossier public
Lang.anglais
DOIhttps://doi.org/10.4095/296681
Mediaen ligne; numérique
Référence reliéeCette publication est contenue dans Ames, D E; Houlé, M G; (2015). Targeted Geoscience Initiative 4: Canadian nickel-copper-platinum group elements-chromium ore systems -- fertility, pathfinders, new and revised models, Commission géologique du Canada, Dossier public 7856
Formatspdf
ProvinceOntario
SNRC43D/16
Lat/Long OENS -86.2278 -86.1783 52.7969 52.7722
Sujetspétrogenèse; nickel; platine; chrome; genèse des minerais; métallogénie; chromite; minéralisation; établissement de modèles; géochimie des éléments en trace; géochimie des roches totales; analyses stratigraphiques; Province de Superior ; minéraux métalliques; pétrologie ignée et métamorphique; Précambrien
ProgrammeÉtude des gîtes magmatiques de Ni-Cu-EPG, Initiative géoscientifique ciblée (IGC-4)
Diffusé2015 06 22
Résumé(disponible en anglais seulement)
The Black Thor intrusive complex (BTIC) contains a conduit-hosted, stratiform Cr-Ni-Cu-(PGE) deposit with a very large amount of chromite for an intrusion of its size. Most conduit-hosted stratiform deposits are Archean, formed from komatiitic magmas containing approximately 3000 ppm Cr2O3, and are typically saturated in chromite. The fundamental problem in understanding the genesis of the BTIC deposit and other deposits of this type is explaining how such large quantities of chromite crystalized from a magma that normally crystallizes only small amounts chromite and normally have a chromite:olivine abundance ratio of ~1:60. Current genetic models, such as in situ crystallization (by oxidation, pressure increase, magma mixing, and/or wholesale assimilation of felsic rocks or iron formation) or physical transportation of chromite slurries do not provide a wholly satisfactory explanation for the high abundance of chromite in this type of deposit. We are testing an alternative model: partial assimilation (as opposed to wholesale assimilation) of local oxide-silicate-facies iron formation by a Cr-rich magma. As low-Mg komatiite is saturated in chromite, the magma may dissolve the silicate component (quartz/chert and Fe-silicate minerals) of the iron formation, but would be unable to dissolve the oxide component (magnetite). Through interaction with the hightemperature (1400°C) Cr-rich magma, the fine-grained magnetite could be upgraded via diffusion to chromite during transportation within the conduit. This upgrading is similar to the upgrading of barren sulphide xenomelts that has been proposed for Ni-Cu-(PGE) deposits.
GEOSCAN ID296681