Detection and Quantification of Extraterrestrial Platinum Group Element Alloy Micronuggets from Archean Impactite Deposits by Low-Voltage Scanning Electron Microscopy/Energy-Dispersive X-ray Spectrometry
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2023-08-02
Submitted Date
2023-03-24
Subject Terms
automated feature analysis
electron probe X-ray microanalysis
energy-dispersive X-ray spectrometry
hyperspectral imaging
low-voltage quantification
scanning electron microscopy
spatial resolution
electron probe X-ray microanalysis
energy-dispersive X-ray spectrometry
hyperspectral imaging
low-voltage quantification
scanning electron microscopy
spatial resolution
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Abstract
Rare, heterogeneously composed platinum group element alloy micronuggets (PGNs) occur in primitive meteorites, micrometeorites, and terrestrial impactite deposits. To gain insight into the nature of these phases, we developed a workflow for the characterization of PGNs using modern scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry at a low accelerating voltage of 6 kV. Automated feature analysis—a combination of morphological image analysis and elemental analysis with stage control—allowed us to detect PGNs down to 200 nm over a relatively large analysis area of 53 mm2 with a conventional silicon drift detector (SDD). Hyperspectral imaging with a high-sensitivity, annular SDD can be performed at low beam current (∼100 pA) which improves the SEM image resolution and minimizes hydrocarbon contamination. The severe overlapping peaks of the platinum group element L and M line families at 2–3 keV and the Fe and Ni L line families at <1 keV can be resolved by peak deconvolution. Quantitative elemental analysis can be performed at a spatial resolution of <80 nm; however, the results are affected by background subtraction errors for the Fe L line family. Furthermore, the inaccuracy of the matrix correction coefficients may influence standards-based quantification with pure element reference samples.
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Tobias Salge, Tanja Mohr-Westheide, Detection and Quantification of Extraterrestrial Platinum Group Element Alloy Micronuggets from Archean Impactite Deposits by Low-Voltage Scanning Electron Microscopy/Energy-Dispersive X-ray Spectrometry, Microscopy and Microanalysis, Volume 29, Issue 6, December 2023, Pages 1837–1846, https://doi.org/10.1093/micmic/ozad088
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Copyright © The Author(s) 2023. Published by Oxford University Press on behalf of the Microscopy Society of America. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
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1431-9276
EISSN
1435-8115