Identification Of As-bearing Minerals Associated With Mine Wastes From Former Metalliferous Mines In France Using Laboratory Reflectance Spectra
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Arsenopyrite-rich wastes from former metalliferous mines in the Massif Central Region, France, contribute, through intensive leaching, to the formation of thin layers of As-Fe crusts on the tailing surfaces acting as a cement. When subject to rainfall, acid mine drainage develops, As is remobilized and trapped secondarily by oxyhydroxides or sulphates such as goethite, hematite, jarosite, etc., depending on water pH. The aim of this study is to assess the potential of hyperspectral remote sensing in this particular environment (small outcrops, important leaching process, vegetated environment). Samples were collected in the field from tailings and stream bottoms in various sites. Reflectance spectra of the samples were acquired in the laboratory using a field spectrometer under artificial illumination (0.4–2.5 µm spectral range). Mineral composition was estimated by comparing reflectance spectra to reference spectral libraries. This was done after continuum removal, using two different techniques, in order to minimize the influence of factors such as grain size or moisture content. Geochemical and SEM-EDS analyses were performed to gather information on the mineralogy. Preliminary results from spectral analyses show clear evidence of jarosite, goethite or limonite, schwertmannite and scheelite in various proportions, depending on crust types, confirmed by SEM-EDS analyses. Keywords: surface spectral reflectance, mine wastes, continuum removal, iron oxyhydroxides.
surface spectral reflectance, mine wastes, continuum removal, iron oxyhydroxides.