- 1Dept. of Applied Geosciences and Geophysics, Montanuniversität Leoben, Peter-Tunner Straβe, 8700, Leoben, AT
- 2Dept. of Materials, Imperial College London, Royal School of Mines: Exhibition Road, SW7 2AZ, London, UK
- 3Dept. of Materials, University of Oxford, Parks Road, OX1 3PH, Oxford, UK
- 4Earth Institute, Columbia University, 2910 Broadway, 10025, New York, USA
- 5Dept. of Earth Sciences, University of Oxford, S. Parks Road, OX1 3AN, Oxford, UK
Although metallic iron (Fe0) is a ubiquitous product of space weathering, its formation mechanisms are still poorly understood. On the lunar surface, Fe0 particles ranges in size from a few nm to several mm and are widely believed to have formed by a variety of mechanisms. These include the in-situ reduction of FeO during cosmic ray bombardment, localized heating by micrometeorites and the subsequent reduction of FeO, as well as the addition of Fe0 from iron-nickel meteorites during micrometeorite bombardment (Hapke, 2001; Kuhlman et al., 2015; Gopon et al., 2017; Day, 2020). The exact formation mechanism has wide ranging implications for remote spectral analysis of airless planetary bodies, the cosmic ray and micrometeorite flux to the Moon, correction of bulk-geochemical data on the moon, and the potential of the lunar surface to be a source of critical metals.
We present the results of a combined Electron Probe Micro-Analyses (EPMA) and Atom Probe Tomographic (APT) study to characterize the composition of Fe0 from Apollo 16 Regolith (sample #61500). Combining these techniques allowed us to explore the wide range of textural occurrences and size fractions of Fe0 and constrain the origin and emplacement mechanisms of these metallic regolith components. We focused on the germanium, iron, and nickel concentrations of the Fe0, as these three elements are key tracers that enable differentiation of in-situ vs extra-lunar processes. Our work shows that all Fe0 analysed in sample 61500 exhibit a meteoritic geochemical signature, which is most closely linked to the IIAB group of iron meteorites (Gopon et al., 2024). This rare meteorite group is notable for its low nickel but high germanium concentrations. The lunar regolith’s significant inventory of meteoritic metals implies that it is a potentially valuable resource for a range of critical metals (EU Report, 2023), not least the Pt group metals and germanium. Furthermore, the host phase – npFe –contained within powdered regolith implies extraction and refining of these elements might be significantly more energy and cost effective than terrestrial deposits.
References:
Day, J.M.D., 2020, Metal grains in lunar rocks as indicators of igneous and impact processes: Meteoritics and Planetary Science, v. 15, doi:10.1111/maps.13544.
EU Report, 2023, Study on the Critical Raw Materials for the EU 2023 – Final Report:
Gopon, P., Douglas, J.O., Gardner, H., Moody, M.P., Wood, B., Halliday, A.N., and Wade, J., 2024, Metal impact and vaporization on the Moon’s surface: Nano-geochemical insights into the source of lunar metals: Meteoritics & Planetary Science, v. 59, p. 1775–1789, doi:10.1111/maps.14184.
Gopon, P., Spicuzza, M.J., Kelly, T.F., Reinhard, D., Prosa, T.J., and Fournelle, J., 2017, Ultra-reduced phases in Apollo 16 regolith: Combined field emission electron probe microanalysis and atom probe tomography of submicron Fe-Si grains in Apollo 16 sample 61500: Meteoritics & Planetary Science, v. 22, p. 1–22, doi:10.1111/maps.12899.
Hapke, B., 2001, Space Weathering from Mercury to the asteroid belt: Journal of Geophysical Research, v. 106, p. 39–73.
Kuhlman, K.R., Sridharan, K., and Kvit, A., 2015, Simulation of solar wind space weathering in orthopyroxene: Planetary and Space Science, p. 1–5, doi:10.1016/j.pss.2015.04.003.
How to cite: Gopon, P., Douglas, J., Moody, M., Halliday, A., Wood, B., and Wade, J.: Nano-geochemical insights into the source of lunar metals, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4338, https://doi.org/10.5194/egusphere-egu25-4338, 2025.
