Extraction mechanism of alteration zones using ASTER imagery

Remote sensing plays an important role in the mineral exploration. One of the common applications is to locate alteration zones related to gold deposits. Many studies based on landsat thematic mapper (TM) imagery have been carried out and several methods have been developed. However, the advanced spaceborne thermal emission and reflection radiometer (ASTER) imagery, which has better spectral resolution (14 bands) and spatial resolution (15 m in VNIR bands), was not widely used in this application field. This article indicates the ASTER imagery application in locating alteration zones in Laizhou area of Shandong Province. First, we studied the geological information and main alteration minerals' spectral features of the study area. Based on the above work, we calculated some band ratios (b4/bl, b4/b6, b3/b2) to enhance spectral response of some mineral materials and vegetations. Then, a principal component analysis was applied to these band ratios. After applying PCA, the eigenvector matrix was analyzed to identify which PC (principal component) contained more useful information of alteration minerals. We chose the PC that enhanced the response of alteration minerals and reduced the response of vegetations, from which we could discriminate the alteration rocks. The satisfactory result shows that ASTER imagery works well in the exploration of alteration zones