Identification and characterization of hydrothermally altered minerals using surface and space‑based reflectance spectroscopy, in parts of south‑eastern Rajasthan, India

摘要

Imaging spectroscopy has evolved as one of the most significant advancements due to contiguous spectral coverageand higher spectral resolution which enable mineral identification and mineral exploration. Many phyllosilicate andcarbonate minerals show specific spectral absorption feature in the wavelength range of visible-to-near-infra-red regionof electromagnetic spectrum. These spectral features enable delineation of different mineral assemblages which in turnhelp in mineral prospecting using hyperspectral imaging spectra. The present study is focussed on evaluation and applicationof EO-1 Hyperion (hyperspectral) data as an Earth Observation tool for mineral detection and mapping in partsof Udaipur district in south-eastern Rajasthan. Hyperion reflectance imagery of this area was analysed using spectralangle mapper after pre-processing, atmospheric correction and geometric correction. Five endmembers, viz. dolomite,montmorillonite, chlorite, phlogopite and serpentine, were derived from both atmospherically corrected image and fromrock samples in the laboratory using ASD field spectroradiometer covering spectral range of 0.4–2.5 μm. The reflectancespectra of endmembers derived from satellite image were initially compared with USGS mineral spectral library, and thenafter comparing with laboratory-based spectra with respect to absorption features, target minerals were identified whichshows more than 70% match with the USGS and laboratory spectra. These minerals were also cross-checked with thereported litho-sequence of the area. Minerals derived from laboratory and image spectra are indicative of hydrothermallyaltered outer thermal aureole which is also corroborated by litho-structural association of the area.