Application of spectral signature to analyze quality of magnesite ore mineral deposits and altered rocks of Salem, India

Abstract

The developers of remote sensing and an advancement of imaging spectroscopy have provided an opportunity to extract compositional information of mineral mixtures. The geochemistry and mineralogical studies support ethical hold on spectral compositional studies of the ultramafic complex. The Salem ultramafic complex region covered by peridotite, dunite, and magnesite ore and surrounded by country rocks like hornblende biotite gneiss and charnockite. The rock samples include peridotite, dunites, metagabbro, and different kinds of magnesite ore minerals collected from the magnesite mines sections and outcrops exposure of reflectance spectral studies, geochemical analysis, and petrographical studies. Spectral measurements were carried out under 350–2500 nm spectral range from whole rock as well as powdered samples of different grain sizes using ASD Spectroradiometer. In the spectral analysis, the intensity of the carbonate bands assumed as fewer than three spectral ranges at 1900 nm, 2300 nm, and 2450 nm bandwidth and band depth based on absorbing characters and quality. The common absorption bands for dunites are 640 nm, 1050 nm, 1392 nm, 1910 nm, 2325 nm, and 2388 nm. In the shorter wavelength region, OH/Mn3+, OH/Fe2+, Mg-OH vibration and carbonate absorptions indicate the presence of ferric iron, olivine, and pyroxene overlapping spectra. Assessing the proportions of composition of rocks and ore minerals based on the spectral signature is a challenging task due to the minerals that exist in the form of intimate mixtures and variations. A thin section study reveals the presence of the major minerals in the rocks and the characteristics of ore minerals. The XRF geochemistry exposes major oxides and determines correlation of the geochemical elements using cluster and PCA analysis.