Mapping of hydrothermal alteration in the upper mantle-lower crust transition zone of the Tayin Massif, Sultanate of Oman using remote sensing technique

Abstract

This study maps hydrothermal alteration of Wadi Tayin Massif of the Sultanate of Oman using the spectral bands of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the image processing methods namely band ratios, false color composite (FCC), spectral angle mapper (SAM), mixture tuned matched filtering (MTMF) and linear spectral unmixing (LSU) to understand alteration of the upper mantle-lower crust transition zone. The study of FCC image of the spectral bands 8, 4, and 1 in Red (R), Green (G), and Blue (B), respectively, showed the presence of the hydrothermal alteration in shades of purple and brown over the mantle peridotites, dunites, and crustal gabbros. The ASTER band ratios R:9/8, G:4/3, B:2/1 used in this study able to show the occurrence and distribution of alteration in orange distinctly. The SAM, LSU and MTMF image processing methods applied over the region confirmed the presence of alteration and altered minerals in the rocks. The assessment of accuracy for the methods provided the high accuracy of 91.86% and Kappa Coefficient = 0.89 in the LSU method. The image interpretations are studied in the field and the occurrence of alterations are validated by presence of strong serpentinization in the peridotites and dunites, and secondary veins in the micro cracks of gabbros. Laboratory studies showed presence of the serpentinization, iddingsitization, chloritization and development of pargasite in the altered rocks. This study shows application of the ASTER sensor to map hydrothermal alteration found near the fast-spreading oceanic ridge.