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TitreIdentifying and tracing crustal contamination in the Hart komatiite-associated Ni-Cu-(PGE) deposit using multiple S and Fe isotopes: Abitibi greenstone belt, Ontario
TéléchargerTéléchargement (publication entière)
AuteurHiebert, R S; Bekker, A; Houlé, M G; Rouxel, O J; Wing, B A
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. 197-207, (Accès ouvert)
ÉditeurRessources naturelles Canada
Documentdossier public
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
Lat/Long OENS -81.5000 -81.0000 48.5000 48.2500
Sujetsisotopes; soufre; fer; gîtes sulfureux; Archéen; minéralisation; komatiites; roches volcaniques; prospection minière; lithologie; établissement de modèles; Ceinture d'Abitibi Greenstone ; 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)
Assimilation by mafic/ultramafic magmas of sulphur-bearing country rocks, typically of sedimentary origin, is commonly considered a critical factor for the genesis of magmatic sulphide deposits. Mass-independent fractionation of sulphur isotopes in the Archean atmosphere produced isotopically distinct pools of S that are recorded in Archean sediments, and can be differentiated easily from mantle sulphur. Likewise, low-temperature processing of iron, potentially including biological and abiotic redox cycling, is also expected to produce Fe isotope values in sediments distinct from the mantle.
The Hart deposit is composed of two mineralized zones; the main zone, a type-I komatiite-associated Ni-Cu-(PGE) sulphide deposit at the base of the basal flow, and the eastern extension, a zone of semi-massive sulphides 12 to 25 m above the base of the second flow within the komatiite sequence. Isotopic characterization, using multiple S and Fe isotopes, of exhalite and graphitic argillite present in the footwall of the mineralization allows tracing the extent of contamination and the degree of mixing within, and adjacent to, the deposit with these potential S sources. This method identifies the exhalite and graphitic argillite as the dominant contaminants for the main zone and the eastern extension mineralization of the Hart deposit, respectively. Additionally, the contamination signature is greatest within the deposit and decreases away from it in the komatiite flow and could potentially be used as a vector towards mineralization. This pattern points also to a local source for crustal contamination of the mantle-derived komatiitic melt and a low degree of homogenization between the mineralization and the surrounding lava flow.