Mineralogical and Chemical Characteristics of Clay Areas, Gümüşhane Region (NE Turkey), and Their Detection Using the Crósta Technique with Landsat 7 and 8 Images

The clay areas in Gümüşhane (NE Turkey) were examined in mineralogical and geochemical terms, and by remote sensing methods. X-ray diffraction, scanning electron microscope and chemical analysis were completed on samples from 11 selected clay areas in the region. Within the scope of remote sensing, Landsat 7 and 8 satellite images of the region were processed with the Crósta technique to assess the clay areas. The Kale and Tamzı clays are contained within a Late Cretaceous turbiditic series. The clays in Canca, Refene and Çamlıca occur in intensively hydrothermally altered volcanic rocks of the Eocene Alibaba Formation. The other clay areas are in the Liassic Şenköy Formation consisting of a volcano-sedimentary series. The clays in the Şenköy Formation are generally below the coal levels. While mainly illite and lesser kaolinite were determined in Dörtkonak, Alemdar, Yukarı Kov and Çamlıca, the clays in Tahnis and Kabantaşı are smectite. Tekke, Canca and Refene clays are kaolinite with smaller amounts of illite, whereas Kale and Tamzı clays are mainly chlorite with lower content of illite–smectite interlayers. Illites in Dörtkonak, Alemdar, Yukarı Kov and Çamlıca are poor in iron and magnesium and formed by hydrothermal alteration of feldspars in the host rocks. Findings of the remote sensing studies using Landsat 7 and 8 datasets were compatible with the results obtained from field observations and general geological studies, and so it is concluded that the Crósta technique provided good results for exploration of clay occurrences and their determination in the region.