Geological and metal sample surface mapping with WDXRF spectrometer

Importance of the topic

The ability to map elemental distributions on sample surfaces using wavelength-dispersive X-ray fluorescence (WDXRF) provides critical insights in fields from geology to metallurgy. Surface mapping reveals heterogeneities, impurities and zonation that bulk analysis cannot resolve, enabling deeper understanding of material genesis, process control and quality assessment.

Objectives and study overview

This application note demonstrates how the Thermo Scientific ARL PERFORM’X WDXRF spectrometer can produce high-resolution elemental maps of geological and metal samples. Key goals include:

• Illustrating mapping of pseudotachylite and feldspar to visualize grain boundaries and chemical zoning.
• Identifying inclusions and contamination in metallic assemblies.
• Highlighting benefits of standard-less quantitative analysis for unknown matrices.

Methodology and instrumentation

Samples were prepared as polished or pressed surfaces to ensure homogeneity at the macro scale. Mapping scans were acquired in step sizes down to 0.1 mm across selected areas. The spectrometer configuration featured:

• Thermo Scientific ARL PERFORM’X WDXRF Sequential Spectrometer (4200 W).
• Five primary beam filters, four collimators, up to nine analyzing crystals.
• Dual detectors under helium purge for light-element sensitivity.
• 5 GN+ Rh X-ray tube with 50 µm Be window and low-current filament for long-term stability.
• LoadSafe sample handling with liquid cassette recognition and vacuum-safety shutters.

Mapping control and data processing were performed using the Thermo Scientific OXSAS software, with optional UniQuant standard-less package enabling quantification of up to 79 elements without dedicated calibration standards.

Main results and discussion

Geological mapping
The pseudotachylite sample revealed sharp compositional gradients of Al, Si, K, Ca and Fe corresponding to microfracture boundaries. Na, Mg, Ti and Sr were more uniformly distributed, highlighting primary versus secondary alteration zones. In a heterogeneous feldspar, alkali and plagioclase domains were clearly distinguished by element contrast, demonstrating sequential crystallization processes.

Metallic mapping
Mapping of a copper rod embedded in steel identified localized Cr and Fe enrichments around the interface, as well as traces of Cu inclusions. This enabled rapid assessment of contamination pathways and phase segregation in metallurgical assemblies.

Standard-less quantification
The UniQuant package successfully provided quantitative concentration maps for unknown samples without matrix-matched standards. Complex algorithms corrected for matrix and inter-element effects, producing accurate elemental distributions across diverse matrices.

Benefits and practical applications

Surface mapping with the ARL PERFORM’X WDXRF system offers:

• Non-destructive high-resolution analysis bridging bulk and micro-analysis techniques.
• Rapid detection of heterogeneities, inclusions and gradients in research and QC laboratories.
• Enhanced process troubleshooting in mining, cement, glass, ceramics and metal production.
• Flexibility to analyze light and heavy elements under helium purge with minimal spectral interferences.

Future trends and possibilities

Advances in X-ray optics, detector technology and data analytics are expected to further improve spatial resolution below 0.1 mm and reduce analysis times. Integration with machine-learning algorithms may enable automated phase identification and predictive modelling of material behaviour. Portable WDXRF systems could expand in-field mapping for environmental monitoring and resource exploration.

Conclusion

The Thermo Scientific ARL PERFORM’X WDXRF spectrometer demonstrates robust surface mapping capabilities for both geological and metallic samples. High spatial resolution, comprehensive instrument safety features and standard-less analysis tools make it an indispensable asset for detailed elemental characterization and quality control across diverse material science applications.

Reference

Thermo Fisher Scientific. Application Note AN41652: Geological and metal sample surface mapping with WDXRF spectrometer, 2024.