A New Band Ratio Approach for Discriminating Calcite and Dolomite by ASTER Imagery in Arid and Semiarid Regions
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Original Paper
A New Band Ratio Approach for Discriminating Calcite and Dolomite by ASTER Imagery in Arid and Semiarid Regions Meisam Rasouli Beirami1 and Majid H. Tangestani1,2 Received 17 October 2019; accepted 24 February 2020
In this article, a new approach is developed for discrimination of calcite (limestone) and dolomite (dolostone) by utilizing data of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). The study area is located at the Zagros Mountains, SW Iran, in which outcrops of sedimentary carbonate rocks are abundant. The approach exploits short-wave infrared spectral features of dolomite and calcite and is based on the spectral variations of these minerals in bands 7 and 8 of ASTER imagery. In order to evaluate the efficacy of the method, spectral analysis was carried out on the spectra of dolomite, dolostone, calcite, and limestone, available in ASTER spectral library. The statistical analysis of the spectra showed that dolomite and calcite have distinguishable b8/b7 band ratios. Spectral measurements of rock samples and knowledge of the mineral composition of rock samples attained by staining carbonate rocks in Alizarin red-S solution were used to evaluate the method used in this study. The applied imagery was normalized by the internal average relative reflectance (IARR) method due to the arid and semiarid climate of the region. The results showed that combined with spectral measurements of rock samples, the ((b5 + b9)/ b7)/((b6 + b9)/b8), and b8/b7 band ratios can be used to effectively discriminate limestone and dolostone. This approach is completely independent of variations in illumination conditions of image pixels; therefore, topographic correction of the image is not needed. The approach performs better in areas where weathering of rock surfaces and vegetation cover are minimal. KEY WORDS: Dolomite, Calcite, Carbonate rocks, Band ratioing, Lithological mapping, ASTER.
INTRODUCTION Good-quality dolomite and limestone are used in the manufacturing process of a variety of products such as steel and cement (Harrison 1993), and dolomitized carbonate rocks are of importance to geologists because of their association with carbonate-hosted lead–zinc ore deposits (Leach et al. 1
Department of Earth Sciences, Shiraz University, Shiraz, Iran. 2 To whom correspondence should be addressed; e-mail: [email protected]
2005). Discerning dolomites in the field by rock sampling can be a tedious and time-consuming task not feasible to carry out in extensive areas. Therefore, satellite imagery like Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) can offer a fast tool for identifying dolostone and limestone. The ASTER sensor onboard the Earth Observing Terra satellite launched in 1999 (Abrams 2000; Ninomiya 2004) is a multispectral scanner which collected data in 14 spectral bands up until April 2008 when its SWIR sensor failed (Abrams 2000). The six SWIR spectral bands of
Ó 2020 International Association for Mathematical Geosciences
Beirami and Tangestani A
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