Surface Mineralogy in Areas Affected by Acid ? Saline Seeps, Southwestern Australia

   Abstract:
      The study of morphological and mineralogical changes within an acid saline seeps affected landscape revealed seasonal differences in surface mineralogy, reflecting the operation of sulfidization and oxidative sulfide weathering processes. During the wet season, the surface and near surface of the waterlogged seep and marsh areas is dominated by black sulfidic materials (pyrite) with negligible iron oxides and oxyhydroxides. During the dry season, the surface mineralogy of the seepage zone is dominated by sulfates (gypsum and barite) and importantly, iron oxyhydroxides gel precipitates and crusts (ferrihydrite, goethite, schwertmannite). The gradual drying of previously waterlogged zones during summer facilitates oxidative weathering of the sulfides, which together with rapid oxidation of Fe2+ emerging from the still persisting minor seeps, results in the formation of iron oxyhydroxides and acid generation. The visible near infra-red (VNIR) reflectance spectra of the surface minerals from unaffected, salt crusted and acid seep areas, showed spectral differences expressed in the VNIR region due to absorption bands of iron oxides and hydroxides. The spectral difference can be utilized for regional scale mapping of acid seeps, acid sulfate soils and mine acid soils as well.
  
   Keywords: Acid-Saline Seeps. Iron oxyhydroxide, Reflectance spectra(VNIR), Southwestern Australia