Abstract:

The availability of spectral information in the shortwave infrared (SWIR) and thermal infrared (TIR) channels of the advanced spaceborne thermal emission and reflection radiometer (ASTER) is much better than that from Landsat ETM. It allows a detailed spectral characterization of land covers, particularly of those rocks and minerals with diagnostic spectra falling into the wavelength range of SWIR and TIR. The authors present a technical approach based on spectral angle mapper (SAM) for hydrothermal alternation information extraction from ASTER images. The method is applied to northern Dong Ujimqin in Inner Mongolia as a case study. The results shows that the ASTER images, through appropriate band combination and image enhancement, are preferable for retrieval of the following three kinds of hydrothermal alteration which contains Fe-OH (jarosite,iron dolomite),Al-OH (clay mineral, alunite, chlorite, sericite) and Fe³⁺(limonite, hematite). Comparatively, ASTER images indicate a greater ability of depictin.

Key words: hydrothermal alteration, advanced spaceborne thermal emission and reflection radiometer (ASTER), spectral angle mapper(SAM), Dong Ujimqin