A remote sensing method for mapping sillimanite mineralization

Abstract

This study aims to analyze the spectral profiles of the sillimanite mineral to identify sillimanite mineralization in the Migif-Hafafit area in the southern Eastern Desert of Egypt. ASTER imagery and reference spectra of sillimanite from the USGS and Jet Propulsion Laboratory (JPL) spectral libraries were used to map the zones mineralized with sillimanite. The spectra of sillimanite in the JPL spectral library is presented at three different particle sizes coarse, medium, and fine (125–500, 45–125, and <45 μm), respectively. The spectrum of sillimanite is presented at one particle size in the USGS spectral library. Results of sample purity analysis using petrography indicated that there are no significant changes in composition of the USGS and JPL samples, and the sillimanite samples collected from the study area. The position, depth, and full-width-half-maximum (FWHM) of the absorption features were calculated for all of the continuum-removed spectra. Results demonstrated that the absorption features attributes are affected by varying particle sizes. The occurrence of a prominent absorption feature in the SWIR spectra at 1.72 μm associated with absorption features at ∼1.40, ∼1.91 and 2.20–2.40 μm can be used to distinguish sillimanite mineral mixtures from the other hydroxylated and hydrated silicate minerals. This study suggests that spectral libraries should include spectra of different particle sizes and mineral mixtures.