Abstract
Abstract. Geothermal systems are essentially associated with hydrothermal alteration mineral assemblages such as iron oxide/hydroxide, clay, sulfate, carbonate and silicate groups. Blind and fossilized geothermal systems are not characterized by obvious surface manifestations like hot springs, geysers and fumaroles, therefore, they could not be easily identifiable using conventional techniques. In this investigation, the applicability of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) were evaluated in discriminating hydrothermal alteration minerals associated with geothermal systems as a proxy in identifying subtle Geothermal systems at Yankari Park in northeastern Nigeria. The area is characterized by a number of thermal springs such as Wikki and Mawulgo. Feature-oriented Principal Component selection (FPCS) was applied to ASTER data based on spectral characteristics of hydrothermal alteration minerals for a systematic and selective extraction of the information of interest. Application of FPCS analysis to bands 5, 6 and 8 and bands 1, 2, 3 and 4 datasets of ASTER was used for mapping clay and iron oxide/hydroxide minerals in the zones of Wikki and Mawulgo thermal springs in Yankari Park area. Field survey using GPS and laboratory analysis, including X-ray Diffractometer (XRD) and Analytical Spectral Devices (ASD) were carried out to verify the image processing results. The results indicate that ASTER dataset reliably and complementarily be used for reconnaissance stage of targeting subtle alteration mineral assemblages associated with geothermal systems.
Highlights
Remote sensing satellite sensors have been used for detection of prospective geothermal sites by capability of mapping hydrothermal alteration mineral assemblages and thermal anomaly in the visible and near-infrared (VNIR), shortwave infrared (SWIR) and thermal infrared (TIR) portions of the electromagnetic spectrum (Littlefield and Calvin, 2015)
Geothermal systems are essentially associated with hydrothermal alteration mineral assemblages such as iron oxide/hydroxide, clay, sulfate, carbonate and silicate groups, which are produced by surface alteration of primary minerals as a result of metasomatism or contact of the hot fluids derived from magmatic intrusions (Pournamdari et al, 2014a,b; Calvin and Pace, 2016)
ASTER subset scene (1515 × 1515 pixels) covering the zones of Wikki and Mawulgo thermal springs in Yankari Park area was used for Feature-oriented Principal Component selection (FPCS) analysis
Summary
Remote sensing satellite sensors have been used for detection of prospective geothermal sites by capability of mapping hydrothermal alteration mineral assemblages and thermal anomaly in the visible and near-infrared (VNIR), shortwave infrared (SWIR) and thermal infrared (TIR) portions of the electromagnetic spectrum (Littlefield and Calvin, 2015). Availability and significant improvement in spectral resolution of satellite remote sensors such as the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) in the VNIR and SWIR bands increases the capability of mapping subtle alteration mineral features associated with concealed and fossilized geothermal systems (Pour and Hashim, 2014). Depending on the spatial and spectral resolution of the satellite remote sensor, hydrothermal alteration mineral groups associated with the geothermal system could be identified using spectral bands in the VNIR and SWIR regions
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