Information extraction of red clay and siliceous limestone in red clay-type gold deposit in southwestern Guizhou, China, using short-wave infrared reflectance data of ASTER

In this paper, short-wave infrared reflectance(SWIR) standard data of Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) was utilized to extract information of red clay and siliceous limestone in Hongqipo gold fields, southwest of Guizhou, China. Based on the field-measured reflectance data of red clay and siliceous limestone in the mining areas, we calculated the coefficients of 5-D spectral indices. That is a kind of orthogonal transformation in the five SWIR spectral spaces of ASTER data, expressed as a linear combination of reflectance of the five SWIR bands. The two indices were used to substitute the V and S in the HSV color transform, and subsequently a useful image was created for visual interpretation of red clay and siliceous limestone. Taking into account there are still large areas of irrelevant information in the image, such as vegetation and water body, we applied masks to the SWIR reflectance image. The two masks were built with band ratio thresholds for vegetation and water body using the dark target corrected ASTER L1B data. In this masked SWIR image, red clay index and siliceous limestone index were also used to substitute the V and S in the HSV color transform, also a result image obtained. A comparative analysis on the two resultant imagines show that vegetation and water body in the image does have an influence on the ore-bearing information extraction.