EGU25-13284, updated on 15 Mar 2025
https://doi.org/10.5194/egusphere-egu25-13284
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Geochemical and Mineralogical Signatures of Alluvial Fans in Iceland and their Implications for Late Stage Aqueous Activity on Mars
Amanda Rudolph1, James Haber2, Sharon Wilson2, Rossman Irwin2, Alexander Morgan3, Briony Horgan4, Timothy Rose5, and Rob Wardell5
Amanda Rudolph et al.
  • 1Smithsonian Institution, National Air and Space Museum, Center for Earth and Planetary Studies, United States of America (rudolpha@si.edu)
  • 2Smithsonian Institution, National Air and Space Museum, Center for Earth and Planetary Studies, United States of America
  • 3Planetary Science Institute, United States of America
  • 4Purdue University, United States of America
  • 5Smithsonian Institution, National Museum of Natural History, Department of Mineral Sciences, United States of America

Extensive physical and chemical evidence from orbiter, lander, and rover data show that surface water was widespread on Mars into the Amazonian. Alluvial fans are geologic landforms on Mars that preserve evidence of this late-stage aqueous activity in the geologic record. The composition and distribution materials in an alluvial fan, either in the catchment (source) and/or the fan (sink), help inform our understanding of the origin and extent of aqueous alteration, either in the source rocks prior to deposition or after, in the fan itself. However, the geochemical and mineralogical properties of martian alluvial fans, and how these properties vary from the catchment to the fan, are not well constrained. 

The work presented here characterizes the geochemistry and mineralogy of two alluvial fans and their associated catchments at sites in Iceland—Fjallabak and near Hoffellsjökull—which serve as close compositional analogs for Mars. These results can help us to understand the aqueous alteration that formed similar deposits on Mars while placing constraints on martian geologic history and paleoclimate.

We utilize a suite of complementary laboratory techniques: Raman spectroscopy, scanning electron microscopy with an energy dispersive X-ray detector (SEM/EDS), and X-ray diffraction (XRD). Raman spectroscopy qualitatively maps spectral properties to confirm existing mineral identification and spectra are processed to determine the relative abundance materials; this technique is of particular use to identify amorphous glass. SEM/EDS is used to quantitatively map elemental compositions, and XRD with Rietveld refinement can identify the type and abundance of crystalline minerals. Raman and XRD both have in situ instrument analogs on the surface of Mars: the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) on the Perseverance rover, and Chemistry and Mineralogy (CheMin) instrument on the Curiosity rover, respectively. SEM/EDS techniques are also likely to be applied to samples returned from Mars.

At Fjallabak, source rocks are primarily a combination of hyaloclastite (a product of subglacial volcanism) and rhyolite. At Hoffellsjökull, the rocks are mostly basalt with evidence of minor hydrothermal alteration. Rocks and sediments do not appear to be heavily altered upon deposition into the alluvial fan, although some authigenic alteration may have occurred in the catchment itself.

Preliminary Raman spectral analyses support our initial field interpretations of the rocks and minerals observed at both field sites. To date, we have analyzed hyaloclastite source rocks and confirmed the presence of obsidian and/or albite glass, along with signs of aqueous alteration indicated by Fe-oxides (i.e., goethite) at Fjallabak. We have also identified diopside (Ca-Mg clinopyroxene) and actinolite (a low-grade metamorphic mineral) in inferred hydrothermally altered basalt, along possible Fe-oxide-hydroxides (i.e., lepidocrocite) that indicate aqueous alteration in the Hoffellsjökull fan. Initial results suggest aqueous alteration of materials at both field sites but the distribution of primary versus secondary materials has yet to be constrained. 

Our results will include the laboratory analysis that characterize these Iceland fans that will help determine the extent and distribution of alteration products in alluvial fans at Mars compositional analog sites.

How to cite: Rudolph, A., Haber, J., Wilson, S., Irwin, R., Morgan, A., Horgan, B., Rose, T., and Wardell, R.: Geochemical and Mineralogical Signatures of Alluvial Fans in Iceland and their Implications for Late Stage Aqueous Activity on Mars, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13284, https://doi.org/10.5194/egusphere-egu25-13284, 2025.