Formation of iron oxides – Københavns Universitet

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Formation of iron oxides

The figure is a simplified illustration of the main pathways for the formation of selected iron oxides. The pathways start with Fe2+ from primary minerals such as olivine and pyroxene.


Roughly speaking the left side of the diagram leading to magnetite, maghemite and lepidocrocite, is the pathway typical of a non-aqueous environment, and the right half of the diagram, leading to hematite and goethite, is typical for an aqueous environment. All the end products in the diagram, except for lepidocrocite, have been found on Mars but in different locations: Magnetite and indications of maghemite have been found in dust and surface rocks along with the primary minerals olivine and pyroxene. Hematite has been found on the surface at Meridiani Planum and both hematite and goethite in outcrops accessible to the Spirit rover in Columbia Hills.

It has been proposed that Columbia Hills is the remnants of a central uplift formed by the impact that created Gusev Crater. The findings described above suggest that water has played different roles in the formation of the minerals in the different locations.