| Titre | Reactive gossans in permafrost: case studies from the Canadian Arctic Islands |
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| Auteur | Williamson, M -C |
| Source | GSA 2020: Geological Society of America Annual Meeting 2020; Geological Society of America, Abstracts With Programs vol. 52, no. 6, 2020 p. 1, https://doi.org/10.1130/abs/2020AM-357919 |
| Image |  |
| Année | 2020 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20200487 |
| Éditeur | Geological Society of America |
| Réunion | GSA 2020: Geological Society of America Annual Meeting 2020; Octobre 26-30, 2020 |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1130/abs/2020AM-357919 |
| Media | en ligne; numérique |
| Formats | html; pdf |
| Province | Nunavut |
| SNRC | 67C; 67F; 67G; 77; 78A; 78B; 78C; 78D; 87; 88A; 88B; 88C; 88D |
| Région | Canadian Arctic Islands; Axel Heiberg Island; Victoria Island |
| Lat/Long OENS | -120.0000 -100.0000 74.0000 68.0000 |
| Lat/Long OENS | -97.0000 -84.0000 81.5000 78.0000 |
| Sujets | chapeaux ferrugineux; pergélisol; glace fossile; géochimie du pergélisol; sulfures; oxydes; minéralisation secondaire; roches hôtes; géologie du substratum rocheux; lithologie; roches sédimentaires;
évaporites; géochimie des sédiments de cours d'eau; gisements minéraux; prospection minière; méthodes d'exploration; méthodes de prospection; méthodes analytiques; télédétection; imagerie par satellite; analyses spectrales; analyses minéralogiques;
analyses géochimiques; couleur; analyses stratigraphiques; mécanismes de transport; fluage; Méthodologie; géologie des dépôts meubles/géomorphologie; minéralogie; géologie économique; géophysique; géochimie; stratigraphie; hydrogéologie; Sciences et
technologie; Nature et environnement |
| Diffusé | 2020 10 01 |
| Résumé | (disponible en anglais seulement)
Gossans are surficial deposits that form through the chemical and physical weathering of the host bedrock. Gossans may produce secondary minerals that reflect
the composition of their primary mineral sources, including buried ore deposits. The mineralogy of gossans (e.g. silica, jarosite and goethite) results from the oxidation of sulphides by acidic and oxidizing fluids. Research carried out by the
Geological Survey of Canada (GSC) over the past decade has led to new insights on the mapping, morphology, stratigraphy, mineralogy and geochemistry of gossans that form in a permafrost environment. Gossans located on Victoria Island and Axel Heiberg
Island were the focus of GSC field and laboratory studies carried out from 2011 to 2015. Study protocols included (1) the identification of gossans using satellite imagery; (2) field mapping, sampling and in situ spectral analyses; (3) mineralogical
and geochemical studies; and (4) comparative studies of bedrock and stream sediments located in proximity to gossans. The distinctive colours of the oxide cap allow for the identification of gossans using multispectral and hyperspectral optical
remotely sensed imagery especially in the visible-near-infrared (VNIR) portion of the electromagnetic spectrum. The small size of most gossans (a few tens of meters to less than 1 to 2 km in length) requires access to high spatial resolution images
such as those provided by the WorldView multispectral sensor. Field observations and sampling of gossans at seven localities suggest that their morphology is complex. For example, the observed stratigraphy does not always match the classic gossan
profile of sulphide-depleted and silica-enriched cap underlain by Fe-oxides and other secondary minerals. Gossans were grouped into three categories based on stratigraphy, presence or absence of evaporitic rocks and reactivity with permafrost. In all
cases, cryogenic and oxidation processes were clearly ongoing and sulphide oxidation led to acidic conditions and the formation of relatively uniform mineralogical and textural characteristics. We propose that the pumping action of fluids in a
permafrost environment, similar to a solifluction process, acts as a concentration mechanism over time and contributes to the transport of materials down slope. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Les chapeaux de fer sont des sols très altérés, riches en fer, qui recouvrent le socle rocheux. La minéralogie des gossans résulte de
l'oxydation des sulfures par des fluides acides et oxydants. Ces gisements se forment dans des contextes géologiques très variés, mais les affleurements ont généralement une taille de quelques mètres à kilomètres. Les recherches menées par la
Commission géologique du Canada (CGC) au cours de la dernière décennie ont permis d'acquérir de nouvelles connaissances sur la cartographie, la morphologie, la stratigraphie, la minéralogie et la géochimie des chapeaux de fer qui se forment dans les
grandes provinces ignées. Cette présentation est un aperçu des résultats importants et des façons dont ils pourraient être utilisés dans le cadre de la recherche sur les minéraux essentiels dans le Nord du Canada. |
| GEOSCAN ID | 327401 |
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