Lithological and mineralogical survey of the Oyu Tolgoi region, Southeastern Gobi, Mongolia using ASTER reflectance and emissivity data

The Oyu Tolgoi porphyry Cu-Au deposits, Southeastern Gobi, Mongolia, are estimated to be among the world's largest reserves. Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) reflectance and emissivity data were used to map distribution patterns of hydrothermal alteration and igneous rocks, and to locate areas with potential mineral deposit in the Oyu Tolgoi region. To obtain more accurate information for the detection and classification of minerals, pre-processing such as crosstalk correction and additional radiometric correction was performed. The shortwave infrared band ratio logical operator (SWIR-BRLO) models and matched filtering were used to map alteration zone and minerals in the Oyu Tolgoi region. These results were fairly consistent with mineralogical information of previous researches. In addition, we identified mineral potential areas with characteristics similar to the Oyu Tolgoi Cu-Au deposits. In particular, in the northwestern part of the OT North Pluton, an extensive area predicted to be an argillic zone was newly detected. ASTER Level 2B surface emissivity data was effectively used for lithological mapping of the Oyu Tolgoi region. The new thermal infrared band ratio logical operator (TIR-BRLO) models could detect areas showing emissivity features of quartzose and alkalic rocks. These results indicate that despite some limitations, ASTER data can provide basic information in the initial steps of ore deposit exploration, or when mapping the distribution of altered, quartzose and igneous rocks, especially in areas where direct field survey is difficult.