Hyperspectral remote sensing of potential mineral resources at Elephant Mountain, Interior Alaska

Abstract

This study explores the application of hyperspectral remote sensing for mineral mapping purposes at Elephant Mountain, Interior Alaska, focusing on airborne and laboratory-based spectroscopic techniques. Hyperspectral imaging (HSI) was conducted using the HySpex imaging system, acquiring airborne hyperspectral imagery over an area of proven mineral resources. The research aimed to evaluate the effectiveness of HSI in identifying alteration minerals, considering the impact of spatial resolution, sensor altitude, and spatial resampling on mineral detection accuracy. A spectral feature-fitting algorithm within the USGS-developed PRISM software was employed to compare airborne-derived spectra with USGS spectral library standards. Laboratorybased spectrometric analyses of rock samples collected from the field area were conducted to validate airborne results. Detailed maps of iron-bearing minerals were made from the visible-near infrared (VNIR) part of the spectrum. Preliminary data analysis indicated widespread lichen coverage in the study area, leading to a detailed analysis of how lichen spectral features overlap and interfere with the spectral features of key alteration minerals in the shortwave infrared (SWIR) part of the spectrum. Synthetic spectral mixtures of lichen and minerals were generated to quantify these effects, demonstrating how lichen presence alters the position of absorption feature of SWIR minerals, leading to misclassification of minerals as lichens. The results emphasize the need to correct lichen interference in hyperspectral mineral exploration, particularly in high-latitude terrains where biological cover is prevalent. This study also presents an analysis of choices leading to optimal spatial resolution in hyperspectral mineral mapping, by analyzing HSI at varying resolutions and sensor altitudes. Findings indicate that while finer spatial resolutions improve mineral classification accuracy, increased sensor altitude and resampling can degrade mapping results. Mineral exploration in remote regions of Alaska will benefit from understanding how lichen can interfere with mapping key alteration minerals, what information can be derived in such a circumstance, and what options to choose when deciding on flight altitudes and processing steps.