Mapping Hydrothermal Mineral groups and Geological Structures in the Kirk range - Lisungwe Valley Area in Malawi using ASTER imagery data

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Remote sensing studies have recently been used to aid early stages of mineral exploration and lineament mapping. A multispectral remote sensing sensor known as Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) was used in this research as a main remote sensing data source. ASTER sensor measures reflected radiation in VNIR, SWIR and TIR of the electromagnetic spectrum, which allow identification of various alteration mineral groups. In this paper, 9 bands of ASTER (VNIR-SWIR) data were used to detect alteration mineral groups and geological structures. ASTER band ratio operations were applied to delineate hydrothermal alteration mineral groups and LINE Module algorithm was used to detect geological lineaments on principal component enhanced images. The findings indicate that the band ratio method successfully mapped various alteration mineral zones including FeO minerals (hematite, goethite), Al-OH clay minerals (muscovite, illite, montmorillonite, kaolinite, dickite) and Mg-OH mineral (calcite, dolomite, magnesite, chlorite, epidote, serpentine). The automated lineament extraction method was found suitable for extraction of lineaments from ASTER data as it delineated geological lineaments that are comparable to the existing published lineaments and help in updating the old structural map of the study area. The study suggests that hydrothermal mineralization in the study area is structurally controlled and that further mineral exploration in the Kirk range – Lisungwe area should target the NE-SW geological structures since they represent areas of fluid flow conduits and hydrothermal mineral concentration. This research has presented the potential zones of mineralization within the Kirk-range Lisungwe Valley area and demonstrated that spectral remote sensing techniques have excellent potential for mineral alteration and structural mapping.