Discriminating lithological diversity within the Nidar Ophiolite Complex, Ladakh, NW Himalaya using multispectral, hyperspectral and thermal remote sensing satellite data.

Abstract

Multi-sensor satellite data such as ASTER, Sentinel-2, and Hyperion images help to gain an excellent perspective of the lithological variations in the Nidar Ophiolite Complex exposed in the high-altitude region of the Trans-Himalayan terrain. Field mapping results and petrographic analysis further strengthen the remote sensing data analysis. Rocks samples are spectrally characterized and incorporated into image classification. The spectral angle mapping classification algorithm helps to detect Dunite, Peridotite, and Gabbro systematically across the Nidar Ophiolite Complex. Spectral emissivity helps to distinguish the ultramafic rocks clearly. The image-based serpentinization index is useful in determining the extent of serpentinization. Peridotite and Dunite are mostly affected by serpentinization, which is validated by image analysis. Field maps and petrographic analysis of the rock samples help to verify the frequently occurring mixture of classes, such as gabbroic intrusions in peridotites. Image analysis used in this study also reveals that peridotites contain gabbroic intrusions. The Hyperion image analysis reveals the presence of peridotite and gabbro in the rocks near Hanle further east of Nidar Valley. The ASTER image is most effective in regional lithological classification of the Nidar Ophiolite Complex because of its wider swath and short-wave infrared bands. The minimum distance supervised classification algorithm is very useful in classifying the ASTER image as the errors associated with misclassification is minimal based on visual matching with available field maps. Robust error analysis on the classification product can be conducted based on future field validations. The spectral and multisensor satellite images show great potential to map the ophiolite suite in the inaccessible Trans-Himalayan terrain remotely