Remote sensing techniques using Landsat ETM+ applied to the detection of iron ore deposits in Western Africa
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ORIGINAL PAPER
Remote sensing techniques using Landsat ETM+ applied to the detection of iron ore deposits in Western Africa Andrea Ciampalini & Francesca Garfagnoli & Benedetta Antonielli & Sandro Moretti & Gaia Righini
Received: 27 February 2012 / Accepted: 16 October 2012 # Saudi Society for Geosciences 2012
Abstract Remote sensing methods enable the rapid and inexpensive mapping of surface geological and mineralogical features. This capability proves highly useful when working on isolated or inaccessible areas. In this study, several enhancements of Landsat Enhanced Thematic Mapper plus (i.e. band ratios, false colour composites and principal component analysis) were used and evaluated to obtain the best possible visualisation of iron deposits hosted in the Devonian sedimentary rocks of northwestern Africa. In particular, two test sites were chosen: southern Algeria (Djebilet area), where the literature mineralogical and geological data on iron mine fields were already available, and the Western Sahara (the southern flank of Tindouf Basin), which was investigated during a field campaign and was where the occurrence of an analogous sedimentary succession led us to hypothesise the possible presence of exploitable iron deposits. This work demonstrates the usefulness of multispectral imagery in the detection of iron-rich areas and establishes a full remote sensing procedure, which can be profitably applied to a wider region of Western Sahara and can provide interesting perspectives on the possibility of detecting new exploitable iron ore deposits in arid environments. Keywords Iron . Western Sahara . Landsat 7 ETM+ . Mineral detection . PCA . OIF A. Ciampalini (*) : F. Garfagnoli : B. Antonielli : S. Moretti Department of Earth Sciences, University of Firenze, Via La Pira 4, 50121 Firenze, Italy e-mail: [email protected] G. Righini ENEA (Italian National Agency for New Technologies, Energy and Sustainable Economic Development), Via Martiri di Monte Sole 4, 40129 Bologna, Italy
Introduction The extraction of metallic minerals (e.g. hematite, limonite, goethite and magnetite) derived from iron ores is important for the product industries utilising iron and steel and for the infrastructure requirements of agriculture, where the ores can be used as fertilisers. The determination of the spatial distribution of iron oxyhydroxides becomes crucial in planning for the exploration of mineral resources. In remote sensing, satellite and airborne multispectral or hyperspectral sensors are used to measure the properties of the land, sea and atmosphere. Compared to the most traditional methods, this technique offers the possibility of covering large areas quickly and often at a relatively low cost. This method is generally used to monitor the state of the environment, to observe and study Earth surface processes and to map lithologies and natural resources, such as iron ore deposits. The multispectral sensors carried by the Thematic Mapper (TM) and the Enhanced Thematic Mapper plus (ETM+) mounted on the Landsat satell
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