Using ASTER imagery for massive sulphide deposits exploration

Abstract

This study aims at exploiting multi-spectral data, acquired from ASTER, satellite to explore areas of hydrothermal alteration and Gossan including massive Sulphide deposits. Auger sulphide is a good source of raw materials such as economic copper, silver, gold and zinc. Major steps involved in the analysis of ASTER satellite data have been discussed using ERDAS Imagine Software. The extent of interdependence among spectral regions, hydrothermal alteration and Gossan has been studied through digital image analysis and classification. The visual interpretation techniques have been employed to identify and earmark hydrothermal alteration and Gossan zones on the satellite image for carrying out subsequent supervised image classification. Imagery Analysis was supported by the color composite, developed by exposing bands 4, 6 & 9 with Red, Green and Blue radiations respectively, to make iron-rich cap or Gossan and hydrothermal alteration zones prominent. The Gossan-laden regions appeared in Red color while the hydrothermal alteration zones took color range from reddish green to light green. Image enhancement has also been achieved through the application of image ratioing techniques and an improved color composite was developed by exposing results of band ratios of band 5 & band 7, band 5 & band 4, and band 2 & band 1 with Red, Green and Blue radiations respectively. Resultantly, the combination of visual interpretation, previous knowledge of the landcover and digital image processing techniques applied on the ASTER Satellite imagery in multi-spectral mode, has proved beneficial in studying hydrothermal alteration zones and Gossan in the Nuqrah area.