Geologic Mapping of The Changgo Dome in Southern Tibet Using ASTER Imagery

by Folfas, Andrew Paul

Within the thick TSS, south of the Indus-Tsangpo Suture, a series of granitic intrusions and gneissic domes crop out along the NHA. These culminations are common features that are seen in orogenic belts; therefore, understanding the nature and development of these features is an integral part of this study and other collisional orogenic studies. Changgo Dome is a granitic dominated feature that is characterized by the presence of two spectrally similar Tertiary granites. This zone is nearly inaccessible for ground mapping, thus it is an ideal setting for the use of satellite imagery as a cartographic medium. In a previous study of this area, the EOS satellite used ASTER sensor™s SWIR bands to map the aforementioned granite and gneiss metamorphic core complexes. Working with a regional ASTER image and spectral data from ten samples collected across the northern boundary of the complex, a series of six lithologies return examinable spectra. Band ratios and the RBD method are used in tandem with the ASTER imagery to constrain the locations the two differing Tertiary granites (defined by their concentrations of muscovite), a metamorphic carapace, and surrounding calcite rich sandstones and shales. The resulting map shows that a carapace of marble overlies the two granites and that two calcitic sedimentary units surround the dome. These results constrain interpretations of the origin of Changgo Dome and are viewed from a top-down perspective and three-dimensionally.