Abstract:

With the advent of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), a 14-band multispectral sensor operating onboard the Earth Observation System (EOS). Terra satellite, the availability of spectral features in the shortwave infrared (SWIR) portion of the electromagnetic spectrum has been greatly increased.This allows us to reveal the detailed spectral characterization of surface targets, particularly of minerals with diagnostic spectral features in this wavelength range, such as clay minerals.In this study, Landsat ETM+ and ASTER remote sensing data were used to map the alteration of rocks and minerals in Fenghuangshan Orefield based on the spectral feature analysis. Principal component analysis (PCA) was done using four ETM+bands as input bands to extract clay-alteration information, based on the relationship between the wavelengths of the ETM+ bands and absorption features of the clay minerals. PCA was also applied to the subsets of four and six ASTER bands to discriminate two kinds of clay minerals in the study area: kaolinite+sericite and chlorite, using the Crosta technique proposed by Loughlin.The subsets were selected according to the bands with characteristic spectral features of key alteration mineral end-members in the VNIR and SWIR of the spectrum. The information of clay mineral distribution was extracted by each data set. Comparison between ETM+ and ASTER data for extraction of alteration information in this study shows that ASTER data has better capability for recognition of alteration minerals.

Key words: alteration, spectral feature, ETM+, ASTER, principal component analysis, Fenghuangshan , Orefield, Tongling