Abstract
The lead-zinc-barium deposits of the southern Benue Trough, Nigeria belong to a suite of clastic dominated fracture filling hydrothermal vein deposits. The alteration types and spread are poorly known yet required to aid exploration. Band ratio composites (BRC), Principal Component Analysis (PCA), and Minimum Noise Fraction (MNF) were applied to a full scene Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery covering the study area. Spectral analysis of sulphide minerals known in the area led to the development of the (B1+B3)/2 ratio, which provided a highly effective sulphide discriminant. PCA and MNF bands with high eigenvectors in the absorption features of target minerals qualified as colour composite candidates for alteration mapping. This study demonstrated the effectiveness of combining the BRC, PCA and MNF techniques in the discrimination of ferric-ferrous/sulphide and silica alteration zones in the Southern Benue Trough.
Highlights
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) consists of a multispectral imaging system made up of 14 bands
ASTER system having three bands in the visible – near-infrared (VNIR) and six bands in the Shortwave Infrared (SWIR) channels adds to its strength for mapping ferric and sulphide mineral groups since their absorption feature lies within the bands of VNIR-SWIR channels
This study employed a combination of band ratio composites (BRC), minimum noise fraction (MNF) and principal component analysis (PCA) over a full aster scene covering areas around the Abakaliki-Enyigba-Ameri lead-zinc deposits and the Iyamitet-Obubra-Ekukunela baryte deposits
Summary
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) consists of a multispectral imaging system made up of 14 bands. Band Ratio on ASTER multispectral data has been utilized to identify alteration associated with ferric iron oxides mineral group like hematite and goethite as well as silicification (Cudahy and Ramanaidou 1996; Rowan and Mars 2003; Rowan et al 2005; Heswon et al 2005; Cudahy et al 2008; Cudahy 2012; Haest et al 2012). This study employed a combination of band ratio composites (BRC), minimum noise fraction (MNF) and principal component analysis (PCA) over a full aster scene covering areas around the Abakaliki-Enyigba-Ameri lead-zinc deposits and the Iyamitet-Obubra-Ekukunela baryte deposits. The goal is to map areas of ferric/ferrous, silica and sulphide alteration and to explore its usability in developing an exploration model for the area
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