GEOSCAN, résultats de la recherche


TitreMineralogy and economic potential of oxide-sulphide gossans, Canadian Arctic Islands
AuteurPercival, J B; Williamson, M C
SourceXV International Clay Conference, abstracts; par Sociedade Brasileira de Geoquimica; 2013.
LiensXV International Clay Conference (XV ICC)
Séries alt.Secteur des sciences de la Terre, Contribution externe 20130155
RéunionXV International Clay Conference; Rio de Janeiro; BR; juillet 7-11, 2013
Mediapapier; en ligne; numérique
ProvinceTerritoires du Nord-Ouest; Nunavut
SNRC97G; 97H; 59G; 59H
Lat/Long OENS -96.0000 -92.0000 80.0000 79.0000
Lat/Long OENS-120.0000 -112.0000 72.0000 71.0000
Sujetschapeaux ferrugineux; évaporites; pergélisol; nickel; cuivre; oxydes; sulfures; méthodes analytiques; altération; filons-couches; filons rocheux; analyses géochimiques; Éléments du groupe de platine; minéraux métalliques; géochimie; Crétacé; Protérozoïque
Programmeadaptation et impacts sur l'environnement, environnement du nord, Géosciences environnementales
Résumé(disponible en anglais seulement)
Gossans result from the oxidation of sulphide-rich bedrock and their trace metal contents are used as indicators of potential mineral deposits. In the Canadian Arctic Islands, some gossans display reactive zones in permafrost characterized by specific textures and mineralogical facies. These gossans were mapped in two arctic large igneous provinces (LIPs) to determine their potential as analogues for mine waste in a permafrost environment. The mineralogy and geochemistry of the gossans were also examined in support of bedrock mapping and the identification of Ni-Cu-PGE targets because in both volcanic provinces, the plumbing system is dominated by sills and dykes that locally interact with evaporite beds or diapirs (Bédard et al., 2012). This integrated, multidisciplinary approach to the study of arctic gossans ultimately reduces the gap between the exploration cycle and environmental impact assessment studies in Canada's North.
Three sites in the early Neoproterozoic Minto Inlier of Victoria Island, Northwest Territories, which hosts the ~720 Ma Franklin LIP were visited during the 2011 field season. Samples from gossans that were identified on high-resolution satellite imagery were collected for detailed mineralogical and geochemical analysis. In addition, mineralogy was determined in situ using a portable spectroradiometer (FieldSpec Pro® ASD, Inc.) with follow-up laboratory measurements for two stations. Station 1, Gossan Hill, is a 400-m topographic high capped by a poorly consolidated, rust-coloured layer overlying pyrite-rich sands. Station 2, Gossan Sill, underlies a mineralized Franklin diabase sill consisting of sulphide-rich veins and pods. Visible ' Near Infrared ' Short Wave Infrared spectral analyses of surficial materials at Station 1 indicate gypsum, goethite and jarosite, and X-ray diffraction (XRD) confirms their presence as well as quartz, illite and feldspar. At Station 2, spectral analyses show gypsum and jarosite and XRD indicates variable amounts of goethite, hematite, pyrite, chlorite, calcite and feldspar.
Similar alteration zones were previously identified during field work at the North Agate Fiord diapir on western Axel Heiberg Island, Nunavut. At this site, basaltic lava flows of Cretaceous age form rafts in evaporite structures and result in chaotic terrain at the periphery of diapirs. The altered basaltic rocks contain copper and iron sulphides in association with secondary sulphates copiapite, fibroferrite and jarosite. Alteration zones contain irregularly shaped, structures (2-5 m across) composed of a sulphide-rich breccia enclosed by whitish-yellow to ochre material consisting of thin layers of goethite, hematite, illite and jarosite. In some cases, layered oxide deposits in poorly-consolidated sandstone beds appear to be the result of intermittent spring activity within the active layer of permafrost (Williamson et al., 2011).
In this paper, we present mineralogical, whole rock trace element, and assay geochemical data for protolith and soils collected from the gossan localities. We discuss models that could explain the genesis of the alteration zones in permafrost and implications for Ni-Cu-PGE exploration strategies applied to large igneous provinces.
Résumé(Résumé en langage clair et simple, non publié)
Cette présentation porte sur la possibilité d'utiliser des matériaux de surface riches en oxydes de fer, appelés « chapeaux de fer », comme analogues des résidus miniers qui pourraient être générés par une mine dans un milieu pergélisolé et aussi comme indicateurs potentiels de gîtes minéraux. Le document présente les résultats d'analyses détaillées de la composition (minéralogique et géochimique) de sols prélevés dans des chapeaux de fer à trois endroits dans l'île Victoria (Territoires du Nord-Ouest) et dans l'île Axel Heiberg (Nunavut). La genèse des chapeaux de fer et leur potentiel économique et environnemental y sont étudiés.