Mapping of Ophiolitic Complex in Logar and Surrounding Areas (SE Afghanistan) With ASTER Data

Abstract

Ophiolites are the distinctive assemblage of mafic to ultramafic rocks and represent the abducted remnant of oceanic crust that was overthrust onto continental crust. Such types of rocks are rare around the world. One of the largest mafic–ultramafic complexes with an apparent area of about 2000 km2 is in the southeast of Afghanistan between two active sinistral strike-slip faults within Logar and surrounding provinces. This study aims to discriminate, characterize, and separate the ophiolitic complex within Logar and adjacent regions in Afghanistan using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data. In this study, four different methods; Mineral Spectral Indices (SI), Band Ratios (BR), Relative Absorption Band Depth (RBD), and Spectral Angle Mapper (SAM), are applied to discriminate and separate the ophiolitic complex. SAM classifier is an efficient way to distinguish the selected surface mineral assemblage using USGS spectral library. The combination of SAM and refined MI yields efficient discrimination of mafic–ultramafic rocks with their alteration minerals around. Detailed mapping of the ophiolitic complex and associated rocks was achieved using refined MI, Band Ration 4/8, and relative absorption band depth (RBD). The field works verified the results from ASTER data.