Application of spectral signature study and geochemical analysis in the characterization of Bhavani Mettupalayam Ultramafic Complex in the Southern Granulite Terrane, India

Abstract

The Bhavani Suture Zone, a region in the Southern Granulite Terrane (SGT), is where the Neoarchean Madurai Block and the Southern Madurai Block in western Tamil Nadu have been joined. The Mettupalayam Mafic-Ultramafic Complex, located in the eastern section of the BSZ, is made up of metagabbros, metadiorites, amphibolites and mafic granulites. The mafic-ultramafic outcrops are viewed and mafic-ultramafic rocks collected from Nellimalai, Togamalai, Sakkitiyan Karadu, Karudamalai, Karattur, Odhimalai, Tenkalmalai, Ramakavundanur hills. This study methodology is composed of three perspectives such as remote sensing study, laboratory spectral signature study and geochemical study. Firstly this study applied on Advanced Spaceborne Thermal Emission Reflection Radiometer (ASTER) and Sentinel-2A used as a tool for mapping mafic-ultramafic rocks and applied the remote sensing techniques like color composites, BR (band ratio), PCA (Principal Component Analysis), MNF (Minimum Noise Fraction), SAM (Spectral Angle Mapper) and SVM (Support Vector Machine). Secondly laboratory spectral signature study is conducted for the 19 samples with ASD FieldSpec Pro® spectroradiometer was used to get the reflectance spectra in the 350–2500 nm spectral region. For different host rocks, the continuum-removed reflectance spectra offer diagnostic absorption features. Critical analysis was done on how the rock samples' elemental composition and related important minerals affected the absorption bands. The major and minor elements geochemical compositions of the BMUC rock samples identified by XRF method. The aim of this research is to characterize the BMUC using remote sensing studies, spectral signature study and geochemical analysis. The Sentinel-2A showing discriminating the lithology well than ASTER data and the spectral signatures absorptions are indicating presence of Fe and Mg contents. The rock samples are falling the series of tholeiitic to calc alkaline characteristics in geochemistry.