Integrating Data of ASTER and Landsat-8 OLI (AO) for Hydrothermal Alteration Mineral Mapping in Duolong Porphyry Cu-Au Deposit, Tibetan Plateau, China
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Abstract:
One of the most important characteristics of porphyry copper deposits (PCDs) is the type and distribution pattern of alteration zones which can be used for screening and recognizing these deposits. Hydrothermal alteration minerals with diagnostic spectral absorption properties in the visible and near-infrared (VNIR) through the shortwave infrared (SWIR) regions can be identified by multispectral and hyperspectral remote sensing data. Six Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) bands in SWIR have been shown to be effective in the mapping of Al-OH, Fe-OH, Mg-OH group minerals. The five VNIR bands of Landsat-8 (L8) Operational Land Imager (OLI) are useful for discriminating ferric iron alteration minerals. In the absence of complete hyperspectral coverage area, an opportunity, however, exists to integrate ASTER and L8-OLI (AO) to compensate each other’s shortcomings in covering area for mineral mapping. This study examines the potential of AO data in mineral mapping in an arid area of the Duolong porphyry Cu-Au deposit(Tibetan Plateau in China) by using spectral analysis techniques. Results show the following conclusions: (1) Combination of ASTER and L8-OLI data (AO) has more mineral information content than either alone; (2) The Duolong PCD alteration zones of phyllic, argillic and propylitic zones are mapped using ASTER SWIR bands and the iron-bearing mineral information is best mapped using AO VNIR bands; (3) The multispectral integration data of AO can provide a compensatory data of ASTER VNIR bands for iron-bearing mineral mapping in the arid and semi-arid areas.Keywords:
VNIR
The reflectance-based vicarious calibration approach has been applied to the Advanced spaceborne Thermal emission and reflection radiometer (ASTER) that is on the Terra platform. The results from three separate groups operating at the same sites at the same time are presented. The three groups show good agreement between each other, with differences between the groups being smaller than 4% in all bands ranging from 0.6 to 2.2 mum and with larger differences being seen at shorter wavelengths and beyond 2.2 mum. comparisons between the groups and to the ASTER sensor are best at 1.66 mum (band 4), with differences between each group being less than 0.5% and all of the groups agreeing with ASTER to better than 5%. Differences in the visible and near infrared (VNIR) are larger, particularly prior to August 2002 when an update to the calibration processing was performed. These differences exceed 10% in some bands. In addition, the vicarious results appear to show a different trend than the onboard calibration for the VNIR indicating a possible problem with the onboard calibrator for bands 1-3.
VNIR
Ranging
Radiometry
Reflection
Radiometric Calibration
Spectral bands
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