A NEW METHOD FOR LITHOLOGICAL DSCRIMINATION AND MAPPING BY USING ASTER DATA IN DONG CO AREA, NORTHERN TIBET

A new method is proposed to discriminate various lithological units, including dunites, harzburgites, cumulate gabbros, serpentinites and basalts of the Dong Co ophiolites and sedimentary rocks and volcanic rocks, in Dong Co area by using Advanced Space borne Thermal Emission and Reflection Radiometer (ASTER) data. In this paper, firstly, based on the ASTER image spectra of the known lithological units, a subset of bands are selected to enhance the differences between each unit and eliminate interference information by principle component analysis (PCA). Then, the RGB image of PC1, PC2 and PC3 effectively discriminates various rock units and also contains the texture information of sedimentary rocks, which is key evidence for lithological discrimination. At last, a new lithological map of Dong Co area was proposed, which is consistent with the geological map. It is concluded that this method is rapid and cost effective to map ophiolites in exposed areas in Tibet where it is difficult to do conventional fieldwork