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TitreGeochemical composition of chromite from Alexo komatiite in the western Abitibi greenstone belt: Implications for mineral exploration
TéléchargerTéléchargement (publication entière)
AuteurPagé, P; Barnes, S-J; Méric, J; 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. 187-195,
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 -81.0000 -80.7333 48.7500 48.5833
Sujetschromite; prospection minière; géochimie des roches totales; basaltes; roches volcaniques; komatiites; géochimie du chrome; osmium; iridium; ruthénium; rhodium; Ceinture d'Abitibi Greenstone ; Province de Superior ; géochimie; pétrologie ignée et métamorphique
ProgrammeÉtude des gîtes magmatiques de Ni-Cu-EPG, Initiative géoscientifique ciblée (IGC-4)
Diffusé2015 06 22
Résumé(disponible en anglais seulement)
This study, which focuses on the composition of chromite from mineralized and unmineralized komatiitic flows and sills from the Alexo Mine area in Dundonald Township, within the western Abitibi greenstone belt, aims to develop new exploration tools for poorly exposed mineralized komatiitic systems. It is possible to clearly identify chromite derived from massive sulphide (having very high Cr# and depleted Ru content) from chromite derived from barren and poorly mineralized samples based on its composition. LA-ICPMS analyses show that chromite from massive sulphide are depleted in Al, Ni, and Mg, and are enriched in Ti, Zn, Mn, Fe and V compared to chromite from barren samples; however, alteration can also modify chromite chemistry. Samples from the Hart deposit are pervasively altered and their chromite compositions are enriched in Fe, Zn, Co, and Mn, and are depleted in Mg. We propose a binary diagram of Ni/Mn versus Ni/Cr ratios which can be used to clearly discriminate between sulphide segregation prior to chromite crystallization and later superimposed alteration. Mass balance calculations show that chromite does fractionate and concentrate Ir-group platinum-group elements (IPGE: Os, Ir, Ru) and Rh but that chromite contribution to the whole-rock IPGE and Rh budget is rather limited, and for mineralized samples, this contribution is even smaller. From these results, it is clear that IPGE+Rh-rich phases (nano- to micro- platinum-group minerals) are needed to account for the IPGE and Rh contents in whole-rock geochemistry.