Map images at these scales are typically produced to support major regional studies and “big-science” projects. However, as they are usually compiled from many detailed airborne surveys1 flown with close line-spacings, the underlying data also supports application at smaller, exploration property and deposit scales.
There are eight radioactive element layers produced from an airborne survey. In this striking compilation from northern Saskatchewan, Canada, the Ternary (K-eU-eTh) image displays sharp, fundamental geochemical contrasts between major geological domains. Although relatively low radioactive element concentrations occur within the large central Helikian Athabasca Sandstone Basin, patterns have been shown to reflect bedrock variations2 even though extensive exotic glacial deposits blanket the area3, dominating the gamma ray signatures. North and east of the Basin intense colour contrasts correlate with known Precambrian lithotectonic domains. Effects of glacial dispersion are evident, within and south of, the Basin.
The Ternary mapping process is data dependent, such that resulting Ternary maps are influenced by the full range of values processed. Therefore, images can be enhanced through “data windowing” to focus on relative contrasts within a given geological unit or area of interest.
For example, variations over Basin rocks within the outlined square (Fig.A and enlarged in Fig.B) are enhanced by restricting the Ternary data-set to the area within the square only (see result in Fig.C), eliminating much of the overall data-set. This is improved still further when the data are restricted to areas underlain by Athabasca Basin rocks ONLY, eliminating the very strong influence of the neighboring crystalline basement rocks (Fig.D). This approach has been commonly used to improve geological understanding at all scales.
1. Shives, R.B.K., et.al., 2000: Airborne multisensor (gamma ray spectrometric/magnetic/VLF-EM) surveys in Northern Saskatchewan: A status report; in Summary of Investigations 2000, Volume 2. Saskatchewan Geological Survey, Sask. Energy and Mines, Misc. Rep. 2000-4.2
2. Shives, R.B.K., et.al., 2000a: Detection of K-enrichment (illite) chimneys using ground gamma ray spectrometry, McArthur River area, northern Saskatchewan; in Summary of Investigations 2000, Volume 2. Saskatchewan Geological Survey, Sask. Energy and Mines, Misc. Rep. 2000-4.2
3. Campbell, J.E., Shives, R.B.K and Klassen, R.A. (2002): Integrated Field Investigations of Airborne Radiometric Spectral Domains, NEA-IAEA Test Area, eastern Athabasca Basin: A preliminary report ; in Summary of Investigations 2002, Volume 2, Saskatchewan Geological Survey, Sask. Energy and Mines, Misc Rep. 2002-4.2, CD