Mapping of Ni-Cu-PGE ore hosting ultramafic rocks using airborne and simulated EnMap hyperspectral data

Abstract

Hyperspectral imaging is a promising avenue to facilitate detailed continuous regional mapping in sub-Arctic regions. This study investigates the use of AISA optical airborne hyperspectral and simulated EnMAP satellite imagery (2m and 30m spatial resolution, respectively) to demonstrate the capability of producing detailed maps to highlight ultramafic rock units associated with Ni-Cu-(PGE) mineralization in the presence of lichen coatings. A total of 20 AISA flight-lines were flown over part of the Proterozoic fold and thrust Cape Smith Belt (Nunavik, Canada) in 2008. These lines have been radiometrically leveled and merged to form a single mosaic approximately 10x20 km in size. This mosaic was subsequently used to generate a simulated EnMAP scene using the EnMAP End-to-End Simulation Tool (EeteS). The Spatial Spectral Endmember Extraction tool (SSEE) was used on both the AISA and EnMAP simulation data to derive spectral endmembers for the complete study area. Image endmember spectra were compared and contrasted with spectral measurements taken from field samples to determine if spectral features associated with index minerals that discriminate between rock types and lichen were well represented. Results show that the 2m AISA imagery allowed for a better representation of specific rock types compared with the 30m EnMAP simulated data. The derived endmembers were also used to map the distribution of various geological materials for both scenes using the Iterative Spectral Mixture Analysis tool. Results indicate that the airborne data, as expected, allow for better detailed regional mapping compared with the EnMAP simulated data. However, results also showed that even at the 30m spatial resolution of the EnMAP data, broad scale lithological units could be discriminated and mapped. This work is a collaboration between the German Remote Sensing Data Center and the University of Alberta, Canada.