MAPPING Ni-Cu (PGE) BEARING ULTRAMAFIC ROCKS WITH HYPERSPECTRAL IMAGERY, NUNAVIK, CANADA D. Rogge 1 , B. Rivard 1 , B. Grant 2 , and J. Pardy 2 1 Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada 2 Goldbrook Ventures Inc., Vancouver, B.C., Canada ABSTRACT Hyperspectral imaging is a promising avenue to facilitate detailed continuous regional mapping in the Arctic, if issues such as low illumination and lichen cover on bedrock can be addressed. This study investigates the use of AISA optical airborne hyperspectral imagery 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. Spectral and mineralogical analysis of field samples was completed to determine spectral features associated with key index minerals that could be used to discriminate between rock types and lichen. From these spectral features a set of normalized band ratios were developed to map pixels comprising peridotite or pyroxenite rocks associated with mineralization. In addition, an algorithm was developed to effectively minimize calibration issues between flight lines, which impedes the simultaneous analysis of multiple lines. Index Terms— Hyperspectral mapping, ultramafic, lichen 1. INTRODUCTION Regional geologic mapping in the Arctic is time intensive and costly, primarily owing to poor accessibility, but it is essential for subsequent geologic investigations and to guide mineral exploration activities. Along with established geophysical exploration technologies (e.g. magnetic and radiometric surveys), hyperspectral imaging is a promising avenue to facilitate detailed continuous regional mapping in the Arctic, if issues such as low illumination and lichen cover on bedrock can be addressed [1]. This study investigates AISA optical airborne hyperspectral imagery acquired over the 1.9 Ga Cape Smith greenstone belt of northern Quebec (Nunavik), Canada (62 lat, -75 long) (Figure 1). Mineral exploration in the belt began as early as 1898 and has resulted in the Katinniq mine currently in operation [2]. The belt is host to Nickel-Cu- (PGE) mineralization occurring within a series of thick (50- 200 m) mafic-ultramafic complexes that outcrop discontinuously [3]. Vegetation is minimal, but rock encrusting lichens are predominant on bedrock surfaces, adding to the challenge of remotely mapping packages of rocks (mafic to ultramafic) with similar mineralogy. The ores, host rocks, and country rocks have been regionally metamorphosed to lower greenschist facies, but igneous and volcanic fabrics and textures are well preserved. The objective of this paper is to demonstrate the capability of producing detailed maps from such imagery to highlight ultramafic rock units associated with mineralization in the presence of lichen coatings. The size of the data set (~2500 km 2 ) also presents numerous challenges beyond the computational intensity of data analysis. These include within flight line, and line to line calibration issues, particularly in the shortwave infrared, that result in inconsistent signals between lines for the same locations. These inconsistencies impede the simultaneous analysis of multiple lines, and thus, the continuous mapping of spectrally significant lithologic units across lines. To effectively minimize these inconsistencies a leveling algorithm was developed. The collaboration between the University of Alberta and Goldbrook Ventures was initiated in 2009. Thus, the work presented here represents early results that will be used to guide subsequent analysis of the data. 2. HYPERSPECTRAL DATA The AISA airborne data were acquired for Goldbrook Ventures Inc. in 2008. Radiance data was atmospherically corrected using ATCOR4 with the resulting reflectance data comprising 178 bands (400 to 2500 nm) at a spectral resolution of 10 nm and spatial resolution of 2 metres. The total survey comprises 478 flight lines with adjacent lines having an average overlap of 30%. This study focused on 10 flight lines, each approximately 30 km long and 650 m in width, that coincide with an active exploration and drilling program along the Belanger trend, which comprises a number of known Nickel-Cu-(PGE) occurrences. Field work was also conducted to collect representative samples of the various rock types for subsequent laboratory spectral and X- Ray Diffraction (XRD) analysis. 978-1-4244-8907-7/10/$26.00 ©2010 IEEE