Integration of multispectral and hyperspectral remote sensing data for lithological mapping in Zhob Ophiolite, Western Pakistan

This work integrates processed satellite-based remote sensing products and the laboratory data for the geological studies of the Naweoba block of Zhob ophiolite. This ophiolite is one of the north–south trending chain of ophiolite bodies obducted onto the Indian Plate during the collision of the Indian and Eurasian Plates. Lack of a complete accessibility to this area due to the prevailing law and order situation and economic mineral resources usually associated with ophiolite bodies gave a motivation to study the area using remote sensing techniques. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Sentinel-2B reflectance data are processed using decorrelation stretch (DS), band indices (BI), principal component analysis (PCA), and minimum noise fraction (MNF). Each of these algorithms generated the products of varying accuracy for both the datasets because they have a different spatial resolution, 30 m for ASTER and 10–20 m for Sentinel 2B, and a varying number of spectral bands, ASTER have six shortwave infrared (SWIR) bands while Sentinel 2B have only two SWIR bands. Therefore, these remote sensing products are integrated for better discrimination of the lithological units of the Naweoba block. Six rock samples collected during brief fieldwork are analyzed in the laboratory for the spectral signatures using analytical spectral device (ASD) FieldSpec Pro FR spectroradiometer and SPECIMS Hyperspectral SWIR camera. Diagnostic spectral absorption features of different minerals are used for lithological mapping of satellite images. A petrographic study of the field samples is also conducted to confirm the lithologies identified through the spectral signatures. The lithological map prepared in this study correlates well with the recently published geological map of the Naweoba block that had been prepared through conventional fieldwork methods. Based on the spectral signatures, corrections in the extension of some of the previously mapped ultramafic bodies are also made, along with the identification of some new peridotite exposures in the ophiolite that had not been mapped previously by the conventional field methods. Chert and basalt units identified in this block may have the potential for economic deposits of manganese. Additionally, chromite can be found in the peridotite and Rare Earth Elements (REEs) in the gabbro and plagiogranite of the Naweoba block of Zhob ophiolite.