Mapping hydrothermal alteration minerals using highresolution AVIRIS-NG hyperspectral data in the Hutti-Maski gold deposit area, India

The present study exploits high-resolution hyperspectral imagery
acquired by the Airborne Visible/Infrared Imaging Spectrometer-Next
Generation (AVIRIS-NG) sensor from the Hutti-Maski gold deposit area,
India, to map hydrothermal alteration minerals. The study area is a
volcanic-dominated late Archean greenstone belt that hosts major
gold mineralization in the Eastern Dharwar Craton of southern India.
The study encompasses pre-processing, spectral and spatial image
reduction using Minimum Noise Fraction (MNF) and Fast Pixel Purity
Index (FPPI), followed by endmember extraction using n-dimensional
visualizer and the United States Geological Survey (USGS) mineral
spectral library. Image derived endmembers such as goethite, chlorite,
chloriteat themine site (chloritemixedwithminedmaterials), kaolinite,
and muscovite were subsequently used in spectral mapping methods
such as Spectral AngleMapper (SAM), Spectral Information Divergence
(SID) and its hybrid, i.e. SIDSAMtan. Spectral similarity matrix of the
target and non-target-based method has been proposed to find the
possible optimum threshold needed to obtain mineral map using
spectral mapping methods. Relative Spectral Discrimination Power
(RSDPW) and Confusion Matrix (CM) have been used to evaluate the
performance of SAM, SID, and SIDSAMtan. The RSDPW and CM illustrate
that the SIDSAMtan benefits from the unique characteristics of SAM and
SID to achieve better discrimination capability. The Overall Accuracy
(OA) and kappa coefficient (ҡ) of SAM, SID, and SIDSAMtan were computed
using 900 random validation points and obtained 90% (OA) and
0.88 (ҡ), 91.4% and 0.90, and 94.4% and 0.93, respectively. Obtained
mineralmap demonstrates that the northern portion of the areamainly
consists of muscovite whereas the southern part ismarked by chlorite,
goethite, muscovite and kaolinite, indicating the propylitic alteration.
Most of these minerals are associated with altered metavolcanic rocks
and migmatite.