Robert Gauthier, Paul Budkewitsch, H. Peter White, Canada Centre for Remote Sensing, Natural Resources Canada.
Figure 1: CCRS Arctic Hyperspectral Geology Project, Borden Rift Basin, Baffin Island.
Development of the mineral and energy resources in Canada's north requires the detection and mapping of surface lithology and geochemistry to provide the key indicators used by exploration companies for natural resource evaluation and exploitation. The remote nature and environmental challenges posed by the arctic environment reduces the capacity to economically explore and locate mineral resources by traditional techniques. Hyperspectral remote sensing is providing the mineral exploration community a new tool to explore larger areas and focus on key lithological detections to reduce exploration costs and increase development.
A large proportion of Canada's land mass north of the tree-line remains unexplored and poorly understood from a remote sensing perspective. Hyperspectral remote sensing investigations have been carried out in temperate and tropical regions, but few have occurred in Arctic environments. The Canada Centre for Remote Sensing pursues arctic geology hyperspectral study support in collaboration with the Canadian mineral exploration community.
Foundation
Imaging Spectrometry Science at the Canada Centre for Remote Sensing (CCRS) pursues research necessary to develop information products from hyperspectral remote sensing data. Within this framework, exploration and mineral mapping applications are prime candidates to exploit imaging spectrometry data. These efforts will help the geoscience community evaluate hyperspectral data and will allow industry to develop confidence and expertise in using these data sets.
Advances
A key contribution of hyperspectral remote sensing to exploration geology is the mapping of indicator minerals. New improved techniques have to be developed to increase the accuracy of the retrieved information from hyperspectral imagery, including more accurate derivation of at-surface spectral reflectance, extraction of key spectral signatures, and surface material delineation and unmixing. It is important to bring these techniques and the development of data products to an operational level for use in the exploration industry and for mapping programs.
Figure 2: Field spectrometer in operation over a bedrock target in the High Arctic
For this reason, CCRS engages in projects on Arctic Hyperspectral Geology. An example field site includes Cape Smith Belt in northern Quebec, which hosts economic occurrences of Ni-Cu-PGE and represents a Low Arctic environment with the challenge of abundant tundra vegetation. The Borden Basin on Baffin Island was chosen for study as a High Arctic environment with relatively little vegetation where geology is fairly well understood and there exists an economic Zn-Pb deposit.
Field work data acquisition for the development of a representative spectral data base of arctic materials is an important contribution to the successful application of this technology. In these projects, the spectral reflectance characteristics of different lithologies, vegetation types and alteration zones near mineral occurrences are measured using a GER3700TM portable field spectrometer, covering a wavelength range of 400 to 2400 nm. Overflights with sensors such as the Probe-1, an airborne visible near-infrared and short-wave infrared hyperspectral sensor provides the imagery for localized case studies. Additional ground-based spectral measurements and validation of the airborne and satellite hyperspectral data round out project campaign planning. Preliminary results to-date indicates successful results can be obtained from hyperspectral data at high latitudes for mapping and mineral exploration endeavours.
References
Budkewitsch, P.; Peshko, M. The maturing of hyperspectral imaging technology and its benefits for exploration programs. In PDAC 2005 International Convention, trade show and investors exchange. 2005
Neville, R. A.; Lévesque, J.; Staenz, K.; Nadeau, C.; Hauff, P.; Borstad, G A. Spectral Unmixing of Hyperspectral Imagery for Mineral Exploration: Comparison of Results from SFSI and AVIRIS. Canadian Journal of Remote Sensing 29(1), 2003
Budkewitsch, P.; Wong, P.-Y.; Staenz, K.; Hitchcock, R.; Gauthier, E. Spectral Reflectance Characteristics of Arctic Vegetation for Mapping Ecozones with Hyperspectral Imaging Systems. Canadian Journal of Remote Sensing, 2002
Staenz, K.; Budkewitsch, P.; Neville, R. A.; Hitchcock, R.; Nadeau, C. Spectral Unmixing of Rock/Mineral Targets Based on Different Spatial Resolution Hyperspectral Data. Proceedings of ISSSR'01, Québec City, Canada, 10-15 June; 2001.