Hydrothermal Alteration Mapping Using Multispectral Satellite Images in Cenozoic Volcanic Rocks of Tafresh Area, Markazi province, Central Iran

چکیده مقاله

The relation between hydrothermally altered rocks and mineral deposits has been recognized and applied as an exploration tool. In this research, hydrothermal alteration zones in Cenozoic volcanic rocks of Tafresh in the Urmia- Dokhtar zone of Iran was investigated using ETM+, OLI and Aster data. The false color composite (FCC), band ratio (BR) and selective principal components analysis (SPCA) methods were performed on ETM+ and OLI images. The color composite method on OLI was carried out using optimum index factor (OIF) technique. This method and band ratio showed very clearly the hydrothermal altered deposits of clay minerals and iron oxides in the study area. The selective principal component analysis using the Crosta technique also enabled for the representation of the altered hydroxyl and iron-oxide mineral deposits in the region. Three types of algorithms used to extract spectral information from ASTER data are Relative absorption-Band Depth (RBD), the Minimum Noise Fraction (MNF) and the Least Square Fit (LS-Fit) of which iron oxide, argillic, phyllic and propylitic zones have been separated by them. Field observations in the study approved the results.

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