A workflow for exploration sampling in regolith-dominated terranes using portable X-ray fluorescence: comparison with laboratory data and a case study

The Influence of Spectral Interferences on Critical Element Determination with Portable X-Ray Fluorescence (pXRF)

“…The false positives may be due to spectral interferences from As K-lines, Pb L-lines, and Th L-lines, which are close to the Bi L-lines. Although generally not observed in our spectral data (possible exception: RTS-3a, 20.49 % Fe), Fe sum peaks may also result in an overestimation of Bi concentrations [10].…”

“…Hence, in order to correct inaccurate data, users have to establish their own calibrations based on matrix-matched standards and well-characterised samples containing the elements of interest at different concentration levels. Commonly, the data is corrected and re-calibrated by post-processing using correction factors based on simple linear regression (e.g., [7,10,15,25,26]). This may work for elements that show only minor to moderate inaccuracy, i.e., bias, however, this method may not be appropriate for elements yielding highly erroneous results, like false positives (e.g., Bi, W, Co in our dataset; Zr, Ce in carbonatites).…”

“…The potential of quick in situ analysis coupled with the instant display of results makes this technology particularly appealing for the mining industry. Most of the mineral resources-related pXRF projects have focussed on base and precious metals and have shown that this technology, when appropriately used, may yield data of sufficient quality for exploration and geochemical comparison [7][8][9][10][11][12][13][14][15].…”

“…Moreover, variable concentrations of interfering elements result in matrix effects, which show as peak overlaps or as X-ray absorption and enhancement phenomena [17]. Gazley et al [10] have demonstrated that high Fe and Pb contents of a sample may lead to the pile up of Fe sum peaks that interfere with Pb and Bi L-lines and ultimately yield erroneous Pb and Bi values.…”

“…Consequently, critical elements can be detected and reliably quantified in geological materials devoid of interfering elements or when enriched. Generally, pXRF data need to be corrected or re-calibrated to yield accurate results, which is mostly achieved through linear correlation (e.g., [3,5,10,[25][26][27][28]. This is frequently done without checking the energy spectra corresponding to pXRF measurements for spectral interferences and, in particular, for false positives.…”