The mapping of hydrothermal alteration zones on the island of Lesvos, Greece using an integrated remote sensing dataset

The mapping of hydrothermal alteration zones associated with epithermal gold deposits on the island of Lesvos in Greece has been carried out using Landsat Thematic Mapper (TM) satellite and ground remote sensing data. The initial analysis of the satellite data using the minimum noise fraction, matched filter and spectral unmixing techniques identified the altered rock outcrops clearly. The identified pixels were almost completely contained within the highest grade alteration zones mapped by the field geologists. The analysis of the field spectroscopy data using two quantitative techniques, spectral angle mapper and crosscorrelogram spectral matching, identified clearly the presence of high grade kaolinite and alunite outcrops. The further application of the matched filter and spectral unmixing techniques using the additional information from the field spectroscopy survey identified the outcrop of alunite and kaolinite quite clearly. This study indicates the ability of existing satellite data combined with atmospheric correction and novel image processing techniques to locate the regions of highest mineral prospectivity. The addition of a limited amount of field spectroscopy data into the processing of the satellite data suggests that two of the most diagnostic clay minerals can be differentiated.