Application of ASTER Satellite Imagery to Delineate Hydrothermal Alteration Zones Associated with Geothermal Resource: A Case Study of Olkaria and Eburru Geothermal Systems, Kenya Rift

Abstract

Olkaria and Eburru geothermal prospects are within the central region of the Kenyan rift. Exploration for geothermal resources in these prospects has conventionally been done using geophysical, geochemical and geological exploration techniques. However, advance in remote sensing technology and digital image processing techniques, has provided significant tools for mapping surface distribution of important hydrothermal minerals and alteration zones associated with geothermal resource. Subsequently, information derived from remote sensing data can be used in early stages of geothermal exploration thus reducing time and cost required for exploration. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) optical and thermal satellite sensor is one of the remote sensing instruments that has been used to optimize geothermal exploration techniques by providing free data for mapping hydrothermal alteration minerals and alteration zones associated with geothermal resource. It has a total of 14 bands measuring reflected radiation in Visible Near Infrared (VNIR) with 3 bands, Short Wave Infrared (SWIR) 6 bands and Thermal Infrared (TIR). This study uses VNIR-SWIR ASTER data to map hydrothermal alteration minerals and dominant alteration zones in the study areas. Image processing techniques used for this study includes; color composite, logical algorithms, band ratios and Relative Band Depth (RBD). Results shows successful mapping of alteration zones with argillic-phyllic alteration dominating in the area of study.