Mapping hydrothermal alteration zone through aster data in Gadag Schist Belt of Western Dharwar Craton of Karnataka, India

Abstract

Alteration zones are developed in a wide range of geological milieus such as volcano-plutonic rocks. Hydrothermal alteration zones are considered an important guide for mineral exploration and can act as a potential zone of mineralization. The minerals in alteration zones have very diagnostic absorption features in visible–near infrared (VNIR) and shortwave infrared (SWIR) regions of the electromagnetic spectrum. The Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) data have the potential to identify mineral assemblages in different hydrothermal alteration zones because of its 14 spectral bands which cover a wide spectral range. In the present article, FCC, band ratio, and SPCA techniques were applied to map the hydrothermal alteration zones in Gadag Schist Belt (GSB) of Western Dharwar Craton (WDC) of Karnataka. FCC has highlighted lithology, alteration zones, and given a fair idea about the lithological control and alteration occurrences in the area. Band ratio technique for muscovite, kaolinite, chlorite, iron oxide gossan, and silica alteration have yielded promising results. SPCA analysis successfully mapped hydrothermal alteration and delineated phyllic, argillic, and propylitic zones in the area. These results were verified through the existing geological map and by geological fieldwork in the area and these results are satisfactory. The total area, altered by different alteration process, was also calculated. In the GSB, iron alteration zone, phyllic, argillic, propylitic, and silica alteration zones were effectively mapped with the help of ASTER data.