Using geochemical background to accentuate areas of interest in geochemical mapping

Why is this useful?

Understanding how to determine and use a background geochemical signature in a region, a stratigraphic interval, or within a set of outcrops is helpful to unravel whether any particular geochemical excursion is of geological and economic significance in mineral exploration. We recently presented this workflow in a poster at SEG 2024. ‍

The process:

This simple workflow can be used to remove a ‘background’ sediment, rock, or stream geochemical signal in order to better highlight the relevant geochemical signature for exploration. In this example, we have plotted all the sediment geochem data in the area of interest, comparing U to Th (Fig. 1), where you can see the U data strongly clustered to the lower part of the plot, with a median value of 2 ppm, which we take as a simple measure of the ‘background signal’.

‍

In Figure 2, the U values 2 ppm and below are shown on a heatmap, and you can see how consistent the signal is across the field area (supporting the conclusion that this approximates a ‘background’ signal).

‍

‍

Figure 3 shows all the U geochem values on a heatmap, whereas Figure 4 shows the U values minus the background.

‍

‍

Contrasting Figure 4 with Figure 3, you can clearly see more geographically distinct ‘hot zones’ in Figure 4 versus Figure 3. Figure 4, therefore is more useful for focusing work toward distinct areas of interest. This workflow could also be done in a set of drainage catchments to help focus on specific areas of interest.