<title>Mapping quartz, carbonate minerals, and mafic-ultramafic rocks using remotely sensed multispectral thermal infrared ASTER data</title>

Abstract

ASTER sensor aboard Terra satellite has a capability of spectral measurement in the thermal infrared (TIR) region with a spatial resolution adequate for geological applications. This paper attempts mapping quarts, carbonate minerals and bulk SiO<SUB>2</SUB> content in silicate rocks with the indices defined for ASTER TIR multispectral data. Silica minerals represented by the commonest mineral on earth, quartz, have a unique spectral property in TIR. They have lower emissivity in ASTER band 10 and band 12 spectral regions than in band 11. All the common carbonate minerals represented by calcite and dolomite have another unique spectral feature. They have low emissivity in ASTER band 14 spectral region, and high emissivity in ASTER band 10 to 13 spectral region. In silicate rocks, the wavelength at trough in TIR emissivity spectra systematically moves to longer wavelength as the rock type changes from felsic to ultramafic. The emissivity in band 12 is lower than in band 13 for felsic rocks, and higher for ultramafic rocks. Using the spectral features described above, several indices are defined. They are applied to ASTER Level 1B data in the study areas. The results are compared with the information from the field and the laboratory geological investigations including the TIR spectra of the rocks collected at the site and published geological maps. Potential ability of the indices in mapping quarts, carbonate minerals and silicate rocks is suggested.