Potential ore deposits on Mars based on studies of selected terrestrial concretions

Potential ore deposits on Mars based on studies of selected terrestrial concretions

The terrestrial concretions may be analogous to the “blueberry” concretions found on Mars by the Opportunity rover Fig.1A. We selected three types of terrestrial concretions for study:

1.Utah concretions from the Dakota Formation (Cretaceous period ), 2. Utah Navajo Formation concretions (Jurassic), 3. Romanian „Trovants”- gigantic concretions up to 4.5 meters in diameter (Miocene- Neogene) Fig.1.

These analogs were examined using X-ray (Microprobe and EDS) and microscopic techniques to determine their mineralogical composition. One of the key findings was the presence of elements such as copper, as well as iron oxides and sulfides, in the terrestrial analogues, indicating a high degree of mineralization. Correspondingly, MiniTES data revealed spectral signatures consistent with ore-related minerals such as e.g. pyrite, ilmenite, hematite, and jarosite. These minerals are known indicators of metal ores, including copper, gold, and silver, i.e. elements important for future exploitation. The analyzed Martian APXS data indicate the dominance of iron sulfate (jarosite), iron oxides (hematite) and magnesium sulfates (epsomite, kiezerite), as well as the presence of chlorides (halite, sylvite, bischofite).

Fig.1 A. Martian spherules. Microscopic Imager (MI) camera. Visible spherules on the surface - sol 319. B. Utah spherules from the Dakota Formation, with leached iron oxides. Visible spherules fused due to mineralization and single ones. Spherule diameter about 1 cm. C. Moqui marbles spherules from the Navajo covered with iron oxides. Spherule diameter about 4-5 cm. D. Fragment of the Romanian Trovant concretion. E. Deposited Romanian gigantic Trovant concretions in Costesti, Trovanti Museum Natural Reserve. Photos B, C, D - Natalia Zalewska. E- picture from Geologyin (https://www.geologyin.com/2018/04/the-mysterious)

Metodology

Measurements were made using X-ray spectroscopy with energy dispersion -EDS on a Bruker spectrometer. The samples were analyzed in their entirety without fragmentation. As a result of the analysis, we obtained a spectrum of elements that make up the concretion minerals. Magnification pictures of the internal structure of the concretions were taken on a Sigma UP Zeiss microscope. For the microprobe analyses at University of Warsaw, thin sections were prepared from selected concretions. Each measurement point was identified using the Zeiss Auriga scanning electron microscope Fig.2

Results

A chemical and process comparison indicates significant differences between the Martian sulfate system and its terrestrial analogues, but also shares many common features. Data from Meridiani Planum correlate best with the Navajo Formation concretions, where iron occurs as oxides in a siliceous-clay matrix, and diagenetic processes lead to the formation of concretion structures.

Concretions from the Navajo Sandstone, which are considered terrestrial analogs of similar concretions observed on Mars, were found to contain high concentrations of copper and tin. Energy-dispersive spectroscopy (EDS) analyses revealed copper (Cu) contents of 44.78 and 53.15 wt.%, with corresponding tin (Sn) contents of 8.49 and 11.13 wt.%. In addition, six electron microprobe analyses of these concretions showed even higher concentrations, ranging from 78 to 85 wt.% Cu and 13 to 16 wt.% Sn, Fig.2.

These results indicate the presence of Cu–Sn-rich mineral phases within the concretions and demonstrate that the Utah occurrences provide an important geochemical analog for Martian concretions. If similar mineralized concretions occur on Mars, they may represent indicators of hydrothermal and ore-forming processes and could serve as pathfinders for other economically significant metal deposits, including gold and silver, in the Martian subsurface.

Fig 2. A.„Moqui Marbles”, hematite, goethite concretions, from the Navajo Sandstone of southeast Utah. Tightly packed, consolidated quartz grains with mineralization in addition to iron oxides, copper and tin minerals. Microscope Sigma VP Zeiss. Top square- A cut Moqui Marble. A spot measurement was taken on a white mineral. The result indicates high Cu and Sn content. B. Data from detector EDS Bruker, X Flash 6I10. C. Scanning electron microscope images (ZEISS AURIGA 60, Faculty of Geology, University of Warsaw) of thin plates from terrestrial spherules.. Navajo Formation concretion, A spot measurement was taken on a white mineral. The result indicates high Cu and Sn content.

Conclusion

Our results suggest that both the Martian environment and its Earth analogues may harbor conditions favorable for ore mineral formation. This has significant implications for the planning of future missions to Mars, particularly in the context of identifying potential sites for resource extraction. The results suggest that at least some of the concretions in Meridiani Planum may have formed through low-temperature ore-related processes, analogous to those observed in terrestrial settings. This supports the hypothesis that ancient Martian environments may have hosted localized hydrothermal systems or prolonged groundwater circulation favorable to increase metal concentration. As such, these findings strengthen the case that the Martian subsurface could have supported formation of complex mineral structures and also geochemical processes conducive to the accumulation of potentially economically valuable resources.

Acknowledgments: This work was supported by grant no: 852-3-17-12 FBW N. Zalewska TT/407 by statutory project of Space Research Center PAS. The authors would like to thank the Space Research Centre PAS for the support during research.

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