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TitreTrace elements in Fe-oxide minerals from fertile and barren igneous complexes: investigating their use as a vectoring tool for Ni-Cu-PGE sulphide mineralization
TéléchargerTéléchargement (publication entière)
AuteurDare, S A S; Ames, D E; Lightfoot, P C; Barnes, S-J; Beaudoin, 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. 175-185, (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
ProvinceOntario; Terre-Neuve-et-Labrador
SNRC14C; 14D; 41I
Lat/Long OENS -82.0000 -80.0000 47.0000 46.0000
Lat/Long OENS -64.0000 -60.0000 57.0000 56.0000
Sujetsétablissement de modèles; nickel; platine; chrome; genèse des minerais; métallogénie; oxydes de fer; magnetite; ilménite; cuivre; sulfures; géochimie des éléments en trace; éléments en trace; roches intrusives; cuivre; Province de Nain ; Province de Superior ; Complexe de Sudbury Igneous ; minéraux métalliques; 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)
The aim of this study was to develop a new technique to determine the fertility of mafic intrusions for Ni-Cu-PGE sulphide mineralization using the mineral chemistry of Fe oxides in the silicate host rocks. A suite of 25 trace elements was determined in magnetite and ilmenite, by laser ablation ICP-MS at LabMaTer (UQAC), from a variety of barren and fertile igneous complexes. Two of Canada’s largest Ni deposits, the 1.85 Ga Sudbury Igneous Complex and its vast Ni-Cu-PGE mineral district (Ontario) and the 1.34 Ga Eastern Deeps Intrusion-hosting Ni-Cu-Co sulphide mineralization at Voisey’s Bay (Newfoundland), were selected for study. Samples chosen from igneous complexes that are barren of significant Ni sulphide mineralization comprise layered mafic intrusions (Bushveld Complex, South Africa and Sept Iles, Quebec) and anorthosite suites (Saguenay-Lac-St.-Jean, Quebec) that host Fe-Ti-V-P oxide deposits, some of which contain trace amounts of Ni-Cu-PGE sulphides. Mafic rocks of the 1.33 Ga Newark Island layered intrusion (Labrador) were also studied as they are similar in composition and setting to Voisey's Bay but devoid of significant Ni sulphide mineralization.
In sulphide-undersaturated magmas, Cu, Sn, Mo, and Zn are incompatible during fractionation and thus increase in concentration in late-crystallizing magnetite and ilmenite. Upon sulphide saturation and the formation of a trace amount of sulphide, only Cu is depleted in the silicate magma relative to the incompatible elements. Copper depletion, as recorded by Fe oxides, is a sensitive indicator of sulphide saturation and can be diagnostic of whether a Ni-bearing sulphide deposit will have formed if the Cu depletion occurred early during fractionation. In contrast, Ni and Co are compatible during fractionation, partitioning into olivine, orthopyroxene, and, where present, sulphide, and their concentrations steadily decrease in the Fe oxides, together with Cr, as crystallization proceeds. Iron oxides from barren igneous complexes plot on a single Ni-Cr trend but Fe oxides from fertile complexes (those hosting Ni sulphide deposits) plot on a parallel Ni-Cr trend displaced to lower Ni concentration. Nickel depletion is therefore recorded in Fe oxides and has the potential to identify intrusions with buried Ni-sulphide mineralization. The advantages of using Fe oxides as an exploration tool include their resistance to post-magmatic processes, such as alteration, and their preservation and easy recovery from glacial till and heavy mineral separates.