XRD and XRF investigation of Martian analog basalt from terrestrial craters

Significance of the Topic

The combined use of X-ray diffraction (XRD) and X-ray fluorescence (XRF) provides comprehensive mineralogical and compositional data essential for geologic research, including studies of Mars analog materials. Rapid and accurate analysis of basaltic samples supports both fundamental scientific investigations and applied mission planning in planetary science.

Study Objectives and Overview

This application note details the analysis of a terrestrial basalt sample from Craters of the Moon National Monument, Idaho, USA, serving as an analog for Martian basalt. The study aims to quantify the mineral phases and elemental composition using Thermo Scientific ARL EQUINOX 100 XRD and ARL QUANT’X EDXRF instruments, demonstrating their synergistic capabilities in geologic analysis.

Methodology and Instrumentation

The bulk basalt sample was ground and prepared for reflection-mode XRD analysis employing a rotating sample holder to minimize preferred orientation. A Co Kα micro-focus source (1.78897 Å) and a curved position sensitive detector (CPS) enabled simultaneous real-time acquisition over 0–115° 2θ in 30 minutes.

Energy-dispersive XRF used a 50 W Rh source and eight primary filters to optimize excitation across elements from Na to U. Measurements were conducted on an electronically cooled SDD with 140 eV resolution and quantification applied via a fundamental parameters software package (UniQuant).

Main Findings and Discussion

XRF analysis revealed a high-phosphorous basalt composition, with major oxides: SiO2 (43.25 ± 0.24 wt %), Fe2O3 (19.30 ± 0.44 wt %), Al2O3 (15.75 ± 0.19 wt %), CaO (7.16 ± 0.13 wt %), TiO2 (3.00 ± 0.17 wt %), MgO (3.00 ± 0.09 wt %), P2O5 (2.21 ± 0.10 wt %). Minor components included Na2O, K2O, and trace elements such as ZrO2, MnO, and SrO.

XRD Rietveld refinement achieved Rwp = 6.21 and GooF = 1.25, identifying plagioclase (anorthite + albite, 40.9 wt %) and potassic feldspars (orthoclase, microcline, sanidine, 17.1 wt %), along with hematite (21.9 wt %), pyroxenes (10.7 wt %), olivine (1.4 wt %), and apatite (~7.9 wt %). The phase distribution correlated closely with bulk elemental data, confirming the sample’s high P and Fe content.

Benefits and Practical Applications

• Synergistic XRD–XRF approach delivers both structural and compositional insights in a single workflow.
• Portable, low-wattage XRD instrumentation allows flexible laboratory deployment without specialized infrastructure.
• Rapid data acquisition accelerates sample throughput in geologic, mining, and planetary analog research.

Future Trends and Potential Applications

• Advancements in detector technologies (e.g., faster CPS, larger SDD arrays) will further reduce analysis times.
• Integration of portable XRD and XRF into field-deployable systems may enable in situ planetary measurements on future missions.
• Machine learning algorithms applied to diffraction and fluorescence data could enhance phase identification and quantification.

Conclusion

The Thermo Scientific ARL EQUINOX 100 diffractometer combined with the ARL QUANT’X EDXRF spectrometer provides a robust, rapid, and portable solution for comprehensive analysis of basaltic materials. The study demonstrates accurate phase quantification and elemental determination, underscoring the value of this dual-technology approach for geologic and planetary analog investigations.

Reference

1. Adcock C.T., Rogers L.C., Beaty D.W., 2018. Craters of the Moon National Monument Basalts as Unshocked Compositional and Weathering Analogs for Martian Rocks and Meteorites. American Mineralogist.