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TitleGossan Hill, Victoria Island, Northwest Territories: an analogue for mine waste reactions within permafrost and mineral persistence in the sub-surface of Mars
AuthorPeterson, R C; Williamson, M -C
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Programs with Abstracts vol. 35, 2012 p. 105
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20120031
PublisherGeological Association of Canada
MeetingThe Geological Association of Canada (GAC) and the Mineralogical Association of Canada (MAC)Joint Annual Meeting; St. John's, NL; CA; May 27-29, 2012
Mediapaper; on-line; digital
File formatpdf
ProvinceNorthwest Territories
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
ProgramEnvironmental Geoscience, Program management and Transition Activities
AbstractGossan Hill is located within the Minto Inlier on northwestern Victoria Island, Northwest Territories (N 71.36697° W 114.95155°). From above, the hill stands out because of the topographic relief of 75m and the orange-brown colour of the surficial rocks. 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 Supergroup. The sedimentary rocks were intruded by diabase sills of the 723 My Franklin igneous event which crop out ~1km to the south of Gossan Hill. 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 which is, in turn, surrounded by a red-orange 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 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 is underway to assess the involvement of bacteria in the formation of the Gossan Hill deposit. The soft friable nature of these deposits and the topographic relief of the hill indicate a post-glacial (Pleistocene) age of formation. Crustal flexure, as the result of isostatic rebound after the loss of the ice sheet, could have created fluid migration pathways from the sulfate-evaporite deposits in the lower part of the Kilian Formation. Permafrost has maintained this 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 2.0. 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. Water ice 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 and could be a repository of ancient fluid compositions and reactive mineral assemblages.