Spectral reflectance of carbonate mineral mixtures and bidirectional reflectance theory: Quantitative analysis techniques for application in remote sensing

Abstract High‐spectral resolution imaging spectrometers, which acquire remotely sensed data in many contiguous spectral bands, allow for the direct identification of surface mineralogy by comparing pixel and laboratory spectra. The advent of such technology requires a better understanding of reflectance spectroscopy, therefore visible and near‐infrared (0.4–2.5 μm) reflectance spectra of carbonates are discussed in this paper. Electronic processes in cations and vibrational processes involving the crystal lattice produce the main spectral absorption features. Subsequently, mineral impurities are reflected in the reflectance spectra. A simple semi‐empirical model is presented for determination of artificial spectral reflectance of mineral mixtures based on their single‐component reflectivity. The model is used to explain the effect of particle size and distribution, iron, water bounded by clay minerals, and organic material on the reflectivity of carbonate minerals. Similarly, reflectance spectra of calcite‐dolomite mixtures are modelled and compared with spectra measured from well mixed samples. The theoretical results from modelling are compared with reflectance spectra measured for 44 rock samples.