Hydrothermal alteration mapping from Landsat-8 data, Sar Cheshmeh copper mining district, south-eastern Islamic Republic of Iran

We studied the applicability of data from the recently launched Landsat-8 for mapping hydrothermal alteration areas and lithological units associated with porphyry copper exploration in arid and semi-arid regions. Sar Cheshmeh copper mining district in the Urumieh-Dokhtar volcanic belt in south-eastern Iran was selected for a case study. Several red–green–blue colour combination images and specialized band ratios were prepared from Landsat-8 bands. Band ratios derived from image spectra (4/2, 6/7, 5 and 10 in red–green–blue) allow identification of altered rocks, lithological units and vegetation at regional scale. Analytical imaging and geophysical hyperspectral analysis processing methods and mixture tuned matched filtering were applied to Landsat-8 bands to identify alteration zones associated with known porphyry copper deposits. Fieldwork, previous remote sensing studies and laboratory analysis were used to verify the image processing results. We conclude that Landsat-8 bands, especially bands 2 and 4 in the visible and near-infrared, 6 and 7 in the shortwave infrared and 10 in the thermal infrared spectra, contain useful information for porphyry copper exploration. The thermal infrared bands of Landsat-8 significantly improved the quality and availability of remote-sensing data for lithological mapping. The results of this investigation should encourage geologists to use Landsat-8 operational land imager and thermal infrared sensor data for porphyry copper exploration and geological purposes.