|Title||Mineralogy and economic potential of oxide-sulphide gossans, Canadian Arctic Islands|
|Author||Percival, J B; Williamson, M C|
|Source||XV International Clay Conference, abstracts; by Sociedade Brasileira de Geoquimica; 2013.|
|Alt Series||Earth Sciences Sector, Contribution Series 20130155|
|Meeting||XV International Clay Conference; Rio de Janeiro; BR; July 7-11, 2013|
|Media||paper; on-line; digital|
|Province||Northwest Territories; Nunavut|
|NTS||97G; 97H; 59G; 59H|
|Area||Victoria Island; Axel Heiberg Island|
|Lat/Long WENS|| -96.0000 -92.0000 80.0000 79.0000|
|Lat/Long WENS||-120.0000 -112.0000 72.0000 71.0000|
|Subjects||metallic minerals; geochemistry; gossans; evaporites; permafrost; nickel; copper; oxides; sulphides; analytical methods; alteration; sills; dykes; geochemical analyses; platinum group elements;
|Program||environmental impacts and adaptation in the northern environment, Environmental Geoscience|
|Links||XV International Clay Conference (XV ICC)|
|Abstract||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.
|Summary||(Plain Language Summary, not published)|
This presentation discusses the potential for using weathered Fe-oxide rich surficial materials, known as gossans, as analogues for mine wastes that
could be generated from a mine in a permafrost environment and as potential indicators for mineral deposits as well. The paper presents results from detailed analyses of the composition (mineralogical and geochemical) of soils collected from gossans
at three sites on Victoria Island, Northwest Territories, and Axel Heiberg Island, Nunavut. The genesis of the gossans and their economic/environmental potential is explored.