Objective geological logging using portable XRF geochemical multi-element data at Plutonic Gold Mine, Marymia Inlier, Western Australia

• Subjectivity in geological logging results in inconsistent datasets through time
• Portable XRF allows large geochemical datasets to be collected rapidly
• A schema that allows objective logging utilising geochemical data was developed
• K/V is used to determine alteration; As + 12Cu to determine sulphide abundance
• Far from replacing geologists a schema is complementary and adds significant value

Geological logging by mine and exploration geologists involves the application of a classification code that requires a geologist to make a subjective decision to classify a particular rock unit (e.g. rock type, alteration intensity, mineralisation content). Where multiple geologists carry out logging this approach will most likely result in inconsistencies that are difficult to monitor or assess over time. A potential solution to this problem is to have a method to determine the nature of a given sample based on a set of fixed and quantifiable parameters. Plutonic Gold Mine (Plutonic), in Western Australia, has a growing dataset of more than 150 000 portable X-ray fluorescence (pXRF) multi-element analyses from core and underground face samples, reconciled to Au fire-assay concentration, and logging codes. This study analyses and validates the consistency with which Plutonic's logging codes have been applied from 2009 to 2013. In doing so, we have developed a schema that allows objective logging by utilising elemental data from pXRF analyses to allocate a mineralisation code. A K/V ratio is used to determine the degree of alteration, while As + 12Cu concentrations are used to determine how sulphide-rich a sample is. Thresholds were defined to maintain consistency with pre-existing logged dataset. While far from replacing the geologist, this method is complementary that adds significant value to a dataset.

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