Mapping of Hydrothermally Altered Rocks for Mineral Targeting in Jos Plateau and Its Environs North Central Nigeria Using Aster Image

Abstract

ASTER short wave infrared (SWIR) bands have been known to be suitable for mapping hydrous silicates and carbonates. The occurrence of certain mineral groups and specific minerals which include; kaolinite, alunite, illite, muscovite, montmorillonite, chlorite, calcite, dolomite, serpentine, and others, have been predicted using the SWIR bands. The aim of this research is to investigate the presence of hydrothermal alteration minerals and their relationship with the tin mineralisation in the study area using ASTER satellite imagery and other data sets. The study area falls within parts of Naraguta Sheet 188, which is part of the younger granite province of Jos Plateau in north central Nigeria. False-color composite (FCC), band ratios, principal component analysis (PCA), methods, were used to process the ASTER data. The (SWIR468) image of the Jos plateau and environs, shows a general sight of alteration, a compound band ratio of RGB (2/1, 4/9, 3/2) was applied, where the bright yellow color represents the presence of hydrothermal alteration in the study area. A colour composite of (-PC4 (1234), PC4 (1346), 3/2) was also used where green and yellow color show hydrothermal alteration in the study area. The following band compositions were transformed using PCA to discriminate phyllosilicates which are the main features of alteration. For Alunite, (bands 1, 3, 5, and 7), Ilit (bands 1, 3, 5, and 6), Kaolinte and Smectit (bands 1, 4, 6, and 9), Kaolinte (bands 1, 4, 6, and 7). The results of the study shows the relationship of the Tin rich younger granite complexes of parts of Jos Plateau and their association with the hydrothermally altered rocks, where Kaolinite, Alunite Biotite Muscovite and Illite where identified using ASTER data.