Catchment Analysis of Re-analyzed Regional Stream Sediment Geochemical Data from the Yukon

The June Explore Newsletter, Number 179 for the Association of Applied Geochemists features “Catchment Analysis of Re-analyzed Regional Stream Sediment Geochemical Data from the Yukon” from CSA Global authors Dennis Arne, Rob Mackie and Chris Pennimpede who were contracted in 2015 and 2016 to generate a series of maps products targeting different mineral deposit styles using catchment analysis following the completion of an extensive re-analysis program by the Yukon Geological Survey (YGS) (Mackie et al. 2015).

The re-analysis program resulted in new ICP-MS data for the <0.177 mm fraction of 24,279 archived regional stream sediment samples collected by the YGS and the Geological Survey of Canada (GSC) for the southern two-thirds of the Yukon (Fig. 1). Interpretation of the new geochemical data investigated two approaches to correct for the influence of variable bedrock lithology and metal scavenging on commodity and pathfinder elements of interest for mineral exploration. One was Z-score levelling of specific commodity and pathfinder elements by dominant bedrock lithology, and the second was a new approach – regression analysis of commodity and pathfinder elements against principal components that can be related to regional lithological variations and/or metal scavenging.

Digital copies of deposit-specific geochemical prospectivity maps and data packages are available for all maps sheets from the YGS web site (; see listing in Mackie et al. 2017). The results of both approaches are presented in the form of weighted sums models for specific mineral deposit types that were visually tested against known mineral deposits and occurrences on each map sheet. A subsequent review of data quality, including an assessment of geochemical data quality, sample locations, and geomorphological controls on dilution was provided by Mackie et al. (2017). A previous contribution to EXPLORE No. 176 demonstrated the wide variability of Au data from the re-analyses of archived stream sediment samples by modified aqua regia/ICP-MS using a small (0.5 g) sample aliquot (Arne 2017).

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DATE: 28 JUNE, 2018

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