Author/Authors :
Sara Yousefifar Department of Geology - Science and Research branch, Islamic Azad University, Tehran , Alireza Gharagozlu Geometrics College of NCC, Tehran , Hooshang Asadi Haroni Department of Mining Engineering - Isfahan University of Technology
كليدواژه :
Iran , Dali , porphyry , ASTER , Alteration , SAM , MNF
چكيده لاتين :
Dali Cu-Au porphyry deposit is situated in UrumiehDokhtar Magmatic Arc (UDMA), central Iran. Application of satellite images for mineral explorations has been very successful especially for determination the presence of minerals which are significant in the recognition of hydrothermal alterations. Shortwave infrared (SWIR) bands from Advanced Space borne Thermal Emission and Reflection Radiometer (ASTER) have appropriate potential for mapping hydrothermal alteration minerals. Moreover, visible near infrared (VNIR) bands is suitable for recognition FeOX minerals which have been produced by hydrothermal alteration and thermal infrared (TIR) bands are appropriate for identification silisified zone. In this research, atmospheric and topographic effects have been removed from ASTER data by dark subtract, log-residual for SWIR and VNIR bands, also calculation emissivity for TIR bands separately. Minimum noise fraction (MNF) transformation method has been used to separate alteration zones from back ground. Spectral analyses of the hydrothermal minerals of studied area were obtained by matching and resampling the unknown spectra of the purest pixels to the U.S. Geological Survey (USGS) mineral library. Spectral angle mapping (SAM) has been applied for identification of certain various mineral classes, including hematite, limonite, goethite, jarosite, epidote, chlorite, pyrophyllite, alunite, muscovite, illite, montmorillonite, dickite, haloyssite, kaolinite and silica ,however several spectra of these minerals are the same. After processing, propyllitic and phyllic, argillic, advanced argillic alteration, FeOX minerals and silisified zones have been determined and separated by using their compositions of these minerals. These alteration zones are significant for recognition of porphyry Cu-Au deposits. Identified alteration zones have been verified by field geology observations, thin section studies X-ray florescence (XRF) and X-ray diffraction (XRD) analyses. All evidences have confirmed that SAM is a sufficient and commodious method for extraction various minerals of hydrothermal alterations.
