| Title | Reactive gossans in permafrost: case studies from the Canadian Arctic Islands |
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| Author | 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 |
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| Year | 2020 |
| Alt Series | Natural Resources Canada, Contribution Series 20200487 |
| Publisher | Geological Society of America |
| Meeting | GSA 2020: Geological Society of America Annual Meeting 2020; October 26-30, 2020 |
| Document | serial |
| Lang. | English |
| Media | on-line; digital |
| File format | html; pdf |
| Province | Nunavut |
| NTS | 67C; 67F; 67G; 77; 78A; 78B; 78C; 78D; 87; 88A; 88B; 88C; 88D |
| Area | Canadian Arctic Islands; Axel Heiberg Island; Victoria Island |
| Lat/Long WENS | -120.0000 -100.0000 74.0000 68.0000 |
| Lat/Long WENS | -97.0000 -84.0000 81.5000 78.0000 |
| Subjects | surficial geology/geomorphology; mineralogy; economic geology; geophysics; geochemistry; stratigraphy; hydrogeology; Science and Technology; Nature and Environment; gossans; permafrost; ground ice;
permafrost geochemistry; sulphides; oxides; mineralization, secondary; host rocks; bedrock geology; lithology; sedimentary rocks; evaporites; stream sediment geochemistry; mineral deposits; mineral exploration; exploration methods; field methods;
analytical methods; remote sensing; satellite imagery; spectral analyses; mineralogical analyses; geochemical analyses; colour; stratigraphic analyses; transport mechanisms; fluid flow; Methodology |
| Released | 2020 10 01 |
| Abstract | 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. |
| Summary | (Plain Language Summary, not published)
Gossans are highly weathered, iron-rich soils overlying bedrock. The mineralogy of gossans results from the oxidation of sulfides by acidic and oxidizing
fluids. These deposits form in a wide range of geologic settings but outcrops are generally a few meters to kilometers in size. 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 Large Igneous Provinces. This presentation is an overview of important findings and how they could be used in critical minerals research in Canada's North. |
| GEOSCAN ID | 327401 |
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