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TitleGossan Hill, Victoria Island, Northwest Territories: An analogue for mine waste reactions within permafrost and implication for the subsurface mineralogy of Mars
AuthorPeterson, R C; Williamson, M -C; Rainbird, R H
SourceEarth and Planetary Science Letters vol. 400, 2014 p. 88-93, https://doi.org/10.1016/j.epsl.2014.05.010
Year2014
Alt SeriesEarth Sciences Sector, Contribution Series 20120292
PublisherElsevier
Documentserial
Lang.English
Mediapaper; digital; on-line
File formatpdf
ProvinceNorthwest Territories
NTS87H/06
AreaGossan Hill; Minto Inlier; Victoria Island
Lat/Long WENS-114.9667 -114.9500 71.3667 71.3500
Subjectsextraterrestrial geology; environmental geology; surficial geology/geomorphology; mineralogy; mine waste products; waste management; waste disposal; permafrost; freezing ground; ground ice; Mars; Cenozoic; Quaternary
Illustrationslocation maps; photographs; photomicrographs; schematic representations
Programenvironmental impacts and adaptation in the northern environment, Environmental Geoscience
AbstractGossan Hill is located within the Minto Inlier in central Victoria Island, Northwest Territories (N 9 71.36697° W 114.95155°). A study of the mineralogical associations and geological setting of this deposit indicates that it is an arrested hydrothermal system frozen in permafrost. From above, the hill stands out because of the topographic relief of 75m and the orange-brown colour of the surficial material. The surface of the hill is marked by areas of concentric colour zonation up to 3 meters across, with light grey centers surrounded by a yellow-orange ring that is surrounded by an orange-brown colour that covers the rest of the surface of the hill. Trenches dug into these areas reveal that the central zone contains quartz and pyrite +/- native sulfur in a loose aggregate of sand-sized grains. This central area is surrounded by a zone dominated by gypsum and quartz with some jarosite. Beyond this, the surrounding surface consists of quartz, hematite, and amorphous iron oxides. The radial arrangement of the mineral assemblage indicates an increase in oxidation of sulfur from the center outward. Analysis of isotopic composition of the sulfur indicates the source of sulfur could be the underlying strata. The hill is underlain by inter-bedded carbonate and sulfate-evaporite sedimentary rocks of the Kilian formation in the upper part of the Neoproterozoic Shaler Super group. The sedimentary rocks were intruded by diabase sills of the 720 Ma Franklin igneous event, which crop out 2 km to the south of Gossan Hill. The soft friable nature of the deposit and the topographic relief of the hill indicate a post-glacial (Pleistocene) age of formation. Permafrost has maintained the disequilibrium mineral assemblage since the cessation of fluid flow. Extraction of the permafrost ice from the central zone yields a liquid with a pH of 2.3. The observed long-term persistence of pyrite encased within the acidic permafrost indicates that oxidation and dissolution reactions common in mine waste are slowed, if not stopped, in such an environment. The predicted rise of Arctic temperatures will cause the active layer to move deeper and result in the release of the acidic solutions frozen in the permafrost. Water ice or frozen CO2 just below the Martian surface would also preserve such mineral disequilibrium for very long periods of time. No region exists on Earth where ice has existed continuously for millions of years, but on Mars, some sub-surface ice may be very old. These frozen mineral-ice mixtures could be a repository of ancient fluids. These reactive mineral assemblages and the fluids associated with them have the potential to indicate that life existed on Mars in the past.
GEOSCAN ID291996