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TitreGossan Hill, Victoria Island, Northwest Territories: An analogue for mine waste reactions within permafrost and implication for the subsurface mineralogy of Mars
AuteurPeterson, 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
Année2014
Séries alt.Secteur des sciences de la Terre, Contribution externe 20120292
ÉditeurElsevier
Documentpublication en série
Lang.anglais
DOIhttps://doi.org/10.1016/j.epsl.2014.05.010
Mediapapier; numérique; en ligne
Formatspdf
ProvinceTerritoires du Nord-Ouest
SNRC87H/06
Lat/Long OENS-114.9667 -114.9500 71.3667 71.3500
Sujetsrésidus miniers; gestion des déchets; élimination des déchets; pergélisol; congélation du sol; glace fossile; géologie extraterrestre; géologie de l'environnement; géologie des dépôts meubles/géomorphologie; minéralogie; Cénozoïque; Quaternaire
Illustrationslocation maps; photographs; photomicrographs; schematic representations
Programmeadaptation et impacts sur l'environnement, environnement du nord, Géosciences environnementales
Résumé(disponible en anglais seulement)
Gossan 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