Identification of hydrothermal alteration zones for porphyry copper and gold exploration using satellite remote sensing data

摘要

This study developed a new approach to extract geologic information for porphyry copper and epithermal gold exploration in the arid and semi-arid regions using combined satellite remotely sensed data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Advanced Land Imager (ALI) and Hyperion sensors. Two copper mining districts have been selected in southeastern segment of the NW-SE trending Urumieh-Dokhtar Volcanic Belt that is located in the Tethyan Copper Belt of Iran. The performance of the principal component analysis, band ratio and minimum noise fraction methods was evaluated for ASTER and ALI data to enhance vegetation, iron oxide/hydroxide, clay minerals and lithological units. Spectral angle mapper (SAM), linear spectral unmixing (LSU), matched-filtering (MF) and mixture-tuned matched-filtering (MTMF) methods were tested on shortwave infrared (SWIR) bands of ASTER and ALI to distinguish the phyllic, argillic and propylitic alteration zones associated with porphyry copper mineralization. Analytical Imaging and Geophysics (AIG)-Developed hyperspectral analysis processing methods were used for spectral bands covering the SWIR spectral range (2.0 to 2.4 µm) of the Hyperion data for mapping predominant mineral assemblages in hydrothermal alteration zones. A field reconnaissance, X-ray diffraction (XRD) analysis and spectral reflectance measurements were performed to verify the results of the study. It is concluded that the integration of spectral information derived from ASTER, ALI and Hyperion data can produce comprehensive and accurate information for copper and gold resource investigations. This approach has a strictly regional interest to Middle Eastern economic geologists for the reconnaissance stages of exploring high economic-potential copper and gold mineralization zones in the arid and semi-arid regions.