Spectral pathways for effective delineation of high-grade bauxites: a case study from the Savitri River Basin, Maharashtra, India, using EO-1 Hyperion data

• Published in: International journal of remote sensing Vol. 33; no. 22; pp. 7273 - 7290
• Main Authors: Kusuma, K. N, Ramakrishnan, D, Pandalai, H. S
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 01-01-2012
• Subjects: aluminum; Animal, plant and microbial ecology; Applied geophysics; Biological and medical sciences; case studies; chemistry; Earth sciences; Earth, ocean, space; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General aspects. Techniques; gibbsite; goethite; hematite; hydroxides; industry; Internal geophysics; metamorphic rocks; remote sensing; silica; spectral analysis; Teledetection and vegetation maps; watersheds; Asia; Maharashtra India; India; data; oxides; Parent; springs; impurities; silica; Delineation; mineralogy; industry; aluminum; case studies; aggregate; goethite; Field; soils; geochemistry; sampling; bauxite; hematite; River basins; metamorphic rocks; quality; laterites; hydroxides; sedimentary rocks; techniques; alteration; iron
• ISSN: 1366-5901; 0143-1161; 1366-5901
• DOI: 10.1080/01431161.2012.700131

Bauxite, the only source of aluminium, is an aggregate of minerals, most of which are oxides and hydroxides of aluminium and iron such as gibbsite, bohemite, goethite and haematite. Bauxite is used in the chemical and refractory industries and its quality is controlled by the presence of impurities such as iron and silica. Bauxite commonly occurs together with iron-rich laterites as alteration products of parental igneous and metamorphic rocks. Aluminium-rich bauxites grade towards highly ferruginous laterites with a transitional Al-rich laterites or ferruginous bauxite, herein described as Al-laterites. In the Savitri River Basin, bauxite contains 58–75% gibbsite, 6–11% goethite and 19–26% haematite, whereas the mineralogy of Al-laterites and Fe-laterites are dominated by haematite (29–68%) and goethite (6–25%) with subordinate amounts of gibbsite. Conventional techniques to demarcate the high-grade pockets of bauxites rich in gibbsite are tedious, time consuming and involve detailed field sampling and geochemical analyses. Our work illustrates how spectral properties of these three litho-units can be effectively utilized in mapping of high-grade bauxites occurring over wide areas using hyperspectral remote sensing (HRS). The methodology adopted herein involves generation of noise-free field spectral database of target materials, linear unmixing of field spectra for constituent minerals, classification of preprocessed Hyperion images using field spectra and finally accuracy assessment for ore grade estimation. It is observed that bauxite mapping using Hyperion data and noise-free field spectra yielded results that correlate well with the chemistry and mineralogy of representative samples. By adopting the above procedure, we achieved classification accuracies of 100%, 71% and 89% for bauxite, Al-laterite and Fe-laterite classes, respectively.