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TitreApplied reflectance spectroscopy and mineralogical studies of Gossan Hill, Victoria Island, Northwest Territories, Canada
AuteurFroome, J; Williamson, M -C; Peterson, R C
SourceAssociation géologique du Canada-Association minéralogique du Canada, Réunion annuelle, Programme et résumés vol. 35, 2012 p. 46
LiensOnline - En ligne
Séries alt.Secteur des sciences de la Terre, Contribution externe 20120028
ÉditeurAssociation géologique du Canada
RéunionGeological Association of Canada - Mineralogical Association of Canada (GAC-MAC) Joint Annual Meeting; St.John's, Nfld; CA; mai 27-29, 2012
Documentpublication en série
ProvinceTerritoires du Nord-Ouest
Lat/Long OENS-114.9667 -114.9500 71.3667 71.3500
Sujetsméthodes analytiques; réflectance; analyses spectroscopiques; diffraction des rayons x; analyses par diffraction des rayons x; minéralogie
ProgrammeGestionnaire de programme, Géoscience de l'environnement
Résumé(disponible en anglais seulement)
Iron-oxide and sulfate-rich alteration halos were discovered surrounding exposed and sub-surface pyrite deposits in an area of positive relief known as 'Gossan Hill' on Victoria Island, Northwest Territories. This site provides an excellent example of iron-sulfide and native sulfur deposit alteration processes in an arctic environment where the permafrost exists at shallow depth. Samples of surficial material were sieved into coarse (500u µm-1410 µm, >1410 µm) and fine (<500 µm) fractions for spectral reflectance and X-ray diffraction analysis at varying grain-sizes. Finer grain sizes typically yielded greater absolute reflectance and enabled a more direct comparison of samples with different initial grain size. Sieved samples were analyzed with an ASD Inc. Terraspec Examiner VNIR/SWIR spectrometer to characterize the spectral reflectance of each zone of mineral alteration. X-ray Diffraction analysis was used to identify minerals within the surficial alteration halo and the underlying source material. Mineral assemblages were characterized by comparison with a library of mineral spectral reflectance using The Spectral Geologist (TSG) software. The spectral reflectance data was then smoothed and processed with TSG and ENVI EX applications. Hull quotient, derivative and other spectral profile correction techniques have been considered; however, care was taken in order to avoid destruction of the faint SWIR spectral characteristics produced by cations such as ferrous iron present in the structure of pyrite and some ferrous iron oxides. Over-processing of laboratory data was avoided to allow for direct comparison with remote sensing imagery. Laboratory reflectance of each sample was averaged into a weighted linear mix, with weighting placed on greater surficial volume, finer grain sizes and greater absolute reflectance. The mixed spectral profile was tuned to LANDSAT-7 and SPOT-5 multispectral images of the study site by creating a limited profile of specific bands at 500-590nm, 610-680nm, 780 -890nm and 1580-1750nm. The results of the study provide a test of remote predictive mapping techniques for gossans related to ore bodies based on remote multispectral data.