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<p>In southwestern Mali, the Bougouni region yields significant pegmatite occurrences. These pegmatites are related to igneous rocks that intruded the Birrimian metasediments. This study is the first attempt at structural, lithological, and alteration mapping, as well as pegmatite identification, using a combination of field data, laboratory analyses, and Landsat 9 OLI coupled with ASTER data in the country. Several processing techniques were employed, such as Color Composite (CC), Band Ratioing (BR), Principal Component Analysis (PCA), Minimum Noise Fraction (MNF), Maximum Likelihood Classification (MLC), and Linear Spectral Unmixing (LSU), after radiometric and atmospheric correction. CC, PCA, and MNF facilitated the differentiation of lithological units, while MLC effectively generated a remote sensing-based geological map highlighting distinct lithologies such as granite, granodiorite, diorite, gabbro, and metasediments across the region. The results were then compared with the geological map and the ground truth sample locations for accuracy assessment and were 97.29% correct quantitatively. Specific OLI band ratios (4/2, 1/4, 6/7) were effective for identifying alteration minerals, while ASTER band ratios (1/3, 1/4, 2/5) helped identify pegmatites. LSU also facilitated the identification of mineral groups, such as iron oxides, ferrous minerals and hydroxyl-bearing minerals. Significant lineaments were mapped, following ENE-WSW, NNW-SSE, and EES-WWN trends, and these results were validated through field investigations. The results from this research proved the importance of remote sensing techniques applied to Landsat 9 OLI and the ASTER data in structural, lithological and alteration minerals mapping. The integration of this approach in pegmatite exploration could enhance and complement conventional methodologies in southwestern Mali.</p>

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Discriminating Lithological Units and Alteration Zones of Bougouni Area Using Remote Technology: Implication for Pegmatite Mapping

  • 期刊论文

  • 发表日期：

    2025年3月4日

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  • Elhadji Mory Traore,
  • Akinade S. Olatunji,
  • Mory Sidibe,
  • Umaru Aliyu Ohiani,
  • Sory I. M. Konate,
  • N’Tcha Daniel Kouagou N’dah

摘要

In southwestern Mali, the Bougouni region yields significant pegmatite occurrences. These pegmatites are related to igneous rocks that intruded the Birrimian metasediments. This study is the first attempt at structural, lithological, and alteration mapping, as well as pegmatite identification, using a combination of field data, laboratory analyses, and Landsat 9 OLI coupled with ASTER data in the country. Several processing techniques were employed, such as Color Composite (CC), Band Ratioing (BR), Principal Component Analysis (PCA), Minimum Noise Fraction (MNF), Maximum Likelihood Classification (MLC), and Linear Spectral Unmixing (LSU), after radiometric and atmospheric correction. CC, PCA, and MNF facilitated the differentiation of lithological units, while MLC effectively generated a remote sensing-based geological map highlighting distinct lithologies such as granite, granodiorite, diorite, gabbro, and metasediments across the region. The results were then compared with the geological map and the ground truth sample locations for accuracy assessment and were 97.29% correct quantitatively. Specific OLI band ratios (4/2, 1/4, 6/7) were effective for identifying alteration minerals, while ASTER band ratios (1/3, 1/4, 2/5) helped identify pegmatites. LSU also facilitated the identification of mineral groups, such as iron oxides, ferrous minerals and hydroxyl-bearing minerals. Significant lineaments were mapped, following ENE-WSW, NNW-SSE, and EES-WWN trends, and these results were validated through field investigations. The results from this research proved the importance of remote sensing techniques applied to Landsat 9 OLI and the ASTER data in structural, lithological and alteration minerals mapping. The integration of this approach in pegmatite exploration could enhance and complement conventional methodologies in southwestern Mali.