Detection of hydrothermally alteration rocks in the east Gandise, Tibet (China) using aster imagery

Evaluation of an Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image of the east Gandise, Tibet in China indicates that several important mineralization altered classes can be mapped with good exposure by using ratio image and spectral-angle mapper methods. The resampled ASTER nine-band image data set VNIR+SWIR in 15m spatial resolution was calibrated by using in situ measurements of spectral reflectance. Subsequently, four ASTER ratio images were employed for Al-OH, Fe, Mg-OH, Fe2+, Fe3+ and CO3 alteration extractions. For comparison purpose, in situ surface reflectance data were used to map alteration minerals using spectral angle mapper method for phyllic, propylitic, silicic, argillic, and carbonatic. The result shows that the distribution of the alteration rocks from the spectral angle mapper agrees very well with the alteration zones extracted from the mineralogic ratio images for hydrothermally altered rocks zone associated with copper polymetallic mineralization using ASTER data. The result shows that ASTER data may provide independent parameters useful for regional geological surveys.