Delineating compositionally different dykes in the Uluksla basin (Central Anatolia, Turkey) using computer-enhanced multi-spectral remote sensing data

Abstract

In the Uluksla basin (Central Anatolia, Turkey) several geological mapping campaigns were carried out using conventional field methods to delineate compositionally different Middle-Upper Eocene dykes. However, complete and correct mapping of these dykes was hampered by rugged terrain, lack of road access, wide spatial dyke distributions with small exposures and diverse weathering of these dykes. For these reasons, Landsat-5 Thematic Mapper (TM) satellite image of the study area was used to facilitate delineation of the exact boundaries of gabbroic, dioritic and trachytic dykes found in the area. Remotely sensed data were analysed using several image enhancement procedures, including colour composites, band ratios, principal components analysis (PCA), and Crosta technique. Results obtained from all the processes were examined, and it was found that dyke boundaries are best visible in the PCA123 image; RGB 731 colour composite; TM band ratio 5/7, 5/1, 4 combination; and 1457-PC4 image obtained by Crosta technique. The alteration differences of three dyke groups are enhanced much better in the 1457-PC4 image obtained by Crosta technique, which highlights the hydroxyl-bearing minerals as white-coloured pixels. Using computer-enhanced multi-spectral remote sensing data, we were able to map the boundaries and spatial distributions of compositionally different dykes, which otherwise is an overwhelmingly difficult task to achieve using conventional field methods. In similar settings, remote sensing techniques applied in this study may provide an efficient and low-cost alternative to time-consuming and physically demanding field-mapping campaigns.