Application of Spectral Analysis and Image Processing Methods to Discriminate Hydrothermal Alteration Minerals Around the Tutakdağı (Şebinkarahisar-Giresun) Lead–Zinc Deposits, Northeastern Turkey

The Tutakdağı (Şebinkarahisar-Giresun) area is located in the southern part of the Eastern Pontides, northeastern Turkey. It contains numerous types of mineralization, examples include massive sulfide, porphyry, skarn, and vein. The Tutakdağı area contains vein-type Pb–Zn deposits hosted by Upper Cretaceous volcanic rocks. Hydrothermal alteration and oxidized weathering products are well exposed in this mineralization area. Due to the inaccessible points, steep slopes, and rugged topography of the area, it is difficult to apply traditional geological field studies. This research addresses the applicability of remote sensing methods to identify and map alteration mineralogy within the area and presents the results of a set of remote sensing investigations, including spectral measurements, band ratios, relative absorption band depth, principal component analysis, and matched filtering techniques on the Landsat-8 OLI and the ASTER data sets. The spectral investigations were performed on the representative altered rock samples and the powder samples obtained during the clay separation processes. The spectra of hydrothermal alteration minerals like kaolinite, halloysite, illite, montmorillonite, kaolin/smectite, illite + smectite, illite + montmorillonite, montmorillonite + smectite, muscovite, chlorite, and calcite and the iron oxide/hydroxide minerals like jarosite, limonite and goethite were identified. A mineral distribution map has been prepared, and all the outputs on these maps contain useful information to track the distributions of hydrothermal alteration minerals, weathering-related iron oxide/hydroxide occurrences surrounding mineralization zones, and the lineament/lineament density. These maps are prepared in a shorter time and with lower costs compared to classical field geological methods and can make a valuable contribution to the exploration of new lead–zinc deposits in the region.