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TitreProtracted Paleoproterozoic gold history at the Archean BIF-hosted Meliadine Gold District, Nunavut
TéléchargerTéléchargements
AuteurLawley, C J M; Creaser, R A; Jackson, S; Yang, Z; Davis, B; Dubé, B; Mercier-Langevin, P; Pehrsson, S; Vaillancourt, D
SourceCommission géologique du Canada, Dossier public 7743, 2015, 23 pages, https://doi.org/10.4095/295629
Année2015
ÉditeurRessources naturelles Canada
Documentdossier public
Lang.anglais
DOIhttps://doi.org/10.4095/295629
Mediaen ligne; numérique
Formatspdf
ProvinceNunavut
SNRC55J/13; 55K/16; 55N/01; 55O/04
Lat/Long OENS-92.5833 -91.4167 63.7500 63.1250
Sujetsparagenèse; sulfures; gîtes sulfureux; arsénopyrite; formations ferrifères; or; gisements minéraux; gîtes minéralogiques; Archéen; datations au uranium-plomb; datation au uranium-plomb; rapports uranium-plomb; osmium; failles; Province de Churchill ; Orogenèse de Trans-hudson ; géochronologie; géologie économique; Précambrien
Illustrationslocation maps; photographs; plots; photomicrographs
Consultation
Endroit
 
Bibliothèque de Ressources naturelles Canada - Ottawa (Sciences de la Terre)
 
ProgrammeÉtude des gîtes d'or, Initiative géoscientifique ciblée (IGC-4)
Diffusé2015 03 12
Résumé(disponible en anglais seulement)
The Meliadine Gold District, Nunavut, represents one of Canada's largest emerging greenstone- and BIF-hosted gold districts (reserves of 2.8 Moz Au, plus indicated and inferred resources of 5.8 Moz Au). Most known gold deposits are co-spatial with the Pyke Break, which cuts Meso to Neoarchean (ca. 2.66 Ga) supracrustal and igneous rocks and represents an E-W trending fault associated with a NE-SW trending trans-cratonic fault network. The latter cuts the Western Churchill Province and records a complex and protracted reactivation history that spans at least four Paleoproterozoic orogenic episodes. Gold occurs as inclusions within idioblastic arsenopyrite crystals, at sulfide crystal boundaries and/or as sulfide fracture fills. Arsenopyrite crystal boundaries and domains adjacent to late fractures are variably recrystallized and relatively enriched in precious- and base-metals. In contrast, inclusion-free arsenopyrite crystals and overgrowths along with arsenopyrite domains devoid of fractures are relatively gold-poor. Clusters of gold and galena that correspond with recrystallized arsenopyrite domains and at contacts between disparate arsenopyrite generations suggest that sulfide recrystallization liberated gold and was remobilized, at least locally, into low-strain micro-textural sites along with precious- and base-metals during late fluid-assisted and deformation/metamorphic-driven remobilization. New U-Pb xenotime ages at ca. 1.86 Ga, coupled with previously reported U-Pb hydrothermal monazite ages, post-date arsenopyrite recrystallization, which suggests that gold remobilization was concomitant with the Trans-Hudson orogeny (1.9¬-1.8 Ga). New Re-Os arsenopyrite model ages range from 2.3-1.8 Ga and document a hitherto unrecognized and complex pre-1.86 Ga hydrothermal and sulfide history. The range of Re-Os model ages tends to support partial open-system behaviour and/or mixing of disparate arsenopyrite generations that are evident from micro-textures and in situ element mapping. Replicate analyses of the two most Re-rich and homogeneous arsenopyrite samples yield Re-Os model ages at ca. 2.27 and 1.90 Ga, which are broadly concurrent with the Arrowsmith (2.4-2.3 Ga) orogeny and the earliest phase of the Trans-Hudson orogeny (known locally as the Snowbird orogeny; ca. 1.9 Ga), respectively. These Re-rich samples also tend to be gold-poor and likely yield ages that pre-date gold remobilization and subsequent enrichment along arsenopyrite crystal boundaries and fractures at 1.86 Ga. We speculate that the bulk of the gold was initially introduced at 2.27 Ga and/or 1.90 Ga along with idioblastic arsenopyrite crystals and was subsequently re-mobilized, coupled with arsenopyrite recrystallization, during the Trans-Hudson orogeny.
Résumé(Résumé en langage clair et simple, non publié)
L'Initiative géoscientifique ciblée (IGC-4) est un programme géoscientifique fédéral de collaboration qui fournit à l'industrie les connaissances géoscientifiques et les techniques novatrices de prochaine génération dont elle a besoin pour mieux détecter les gîtes minéraux enfouis, réduisant ainsi certains risques liés à l'exploration. Une présentation donnée lors du Forum de géoscience de Yellowknife (du 25 au 27 novembre). La présentation résume la datation du district aurifère Meliadine dans le cadre de l'IGC-4. Les nouvelles dates obtenues suggèrent que l'or est apparu plus tôt qu'on ne le croyait. La formation de failles ultérieure expliquerait la géométrie actuelle de zones minéralisées à haute teneur.
GEOSCAN ID295629