• February 28, 2017

A new approach to defining geochemical exploration targets

Published on February 28th, 2017

CSA Global congratulates Managing Director-Vancouver, Dennis Arne and Principal Consultant, Rob Mackie on their recently accepted poster paper on “A new simplified multivariate approach to defining geochemical exploration targets from regional stream sediment data”.

The paper will be presented later in the year at the upcoming Exploration 2017 mining conference between October 22-25, 2017 in Canada.  The theme of this year’s conference; “Integrating the Geosciences: The Challenge of Discovery” will feature a multinational, multi-disciplinary technical programme that examines the future mineral exploration challenges and the next wave of discoveries as commodities rebound to fulfill their long term potential.

The conference will present the achievements and ongoing progress of the geosciences over the last ten years and seeks to showcase the integration of geology, geophysics and geochemistry which is critical to the improvement of data acquisition, processing, interpretation and targeting.


The interpretation of stream sediment data for mineral exploration is complicated by the influence of bedrock lithology, the effects of scavenging by secondary Fe and Mn hydroxides, clays and organic matter, and by dilution dependent on the size of the catchment area draining through the sample site. A number of ways have been proposed in the literature to correct for the effects of background variations in lithology, but most are driven by a knowledge of the bedrock geology that may not always be available in reconnaissance exploration programs.

We present a new approach for correcting for lithological and scavenging influences that is data-driven. Lithological controls on stream sediment geochemical data are identified by interpreting the results of principal component analysis. Values for elements strongly controlled by lithology are corrected by regression against the relevant component(s). Positive residuals represent elevated geochemical concentrations above what is defined by background bedrock geology. These positive residuals represent samples worthy of further investigation and allow regional data sets to be gridded to reveal trends in elevated metal concentrations above background.

The residuals are incorporated in weighted sums models which define geochemical indices using element associations typical for a given mineral deposit type. These models are refined through validation against known mineral occurrences and then weighted by catchment area to define anomalous catchments for follow-up investigation. The selected catchments include not only those that have anomalous raw element values, but also highlight areas with more subtle raw data responses that may have been overlooked by previous exploration campaigns. Use of the approach is illustrated through selected examples of high quality geochemical analyses from British Columbia and Yukon, and the results compared to other methods, including levelling of stream sediment data based on dominant catchment lithology, an estimated background value for catchments based on proportions of different lithologies within the catchment, and the presence or absence of particular lithologies in each catchment.

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