PORTABLE XRF INSTRUMENTS: A MINERAL EXPLORATION PROSPECTIVE (Invited Presentation)

The advancement over the past decade in portable XRF instruments (pXRF) using advanced Silicon Drift Detector, higher kV settings marked a step change in “off-the-shelf” handheld XRF technology allowing for real time “fit for purpose” data to be collected. On-going hardware and software developments have prompted an increasing number of manufacturers to introduce pXRF instruments with mining and exploration applications into the market.

Within the mining and exploration industry the ability to make an objective assessment and decision on the significance of a sample’s chemistry can take days to months through a commercial laboratory by the time a sample is transported, prepared, analysed and results reported. This advancement in pXRF instrumentation allows for real time data to be collected allowing for real time assessments and decisions to be made assuming the instruments are used correctly and their limitations understood by the user.

Under standardized test conditions, the analytical performance of portable XRF instruments varies significantly between individual instruments from the same manufacturer, and between manufacturers using similar instruments. The precision of the instruments to repeat a constant element concentration from a single sample is typically very good (<5% RSD); however, the accuracy is generally poor to very poor with large concentration differences in some elements.

Thus each pXRF instrument provides uniquely individual data that should not be combined with data from any other units without appropriate post-processing or recalibration. To significantly improve the quality and value of the pXRF data, a calibration procedure appropriate to the material(s) being evaluated should be implemented with regular baseline data collected to ensure instrument and data stability. Over time, matrix calibrations need to be verified with the instrument undergoing a manufacturer’s recalibration when control limits deteriorate significantly.

Using case study examples it will be demonstrated that if correctly used, portable XRFs can result in the discovery of significant mineral systems.