The effect of clay minerals on Li in martian groundwater simulant

The high mobility of Li allows it to be used as a tracer for groundwater processes, recording past aqueous conditions. On Earth, a relationship has been noted in multiple field sites between clay mineral abundance and elevated Li in bedrock. Observations from the Curiosity MSL mission at Gale crater on Mars showed a high-clay mineral and high-Li area near the Vera Rubin ridge (VRR) and Glen Torridon region, suggesting Li was perhaps substituting into clay minerals (Frydenvang et al., 2020) as was seen in these terrestrial field settings. However, the possibility of this substitution has not been examined in the laboratory, especially not with Mars-relevant mineralogy. To investigate this open question in the laboratory using Mars-relevant regolith and clay minerals, we conducted continuous flow packed-bed reactor experiments to test which clay minerals affect the Li concentration of Mars regolith simulant MGS-1 during aqueous alteration. We tested four dioctahedral clay minerals (kaolinite, illite, nontronite, mixed layer illite/smectite) and two trioctahedral clay minerals (talc, saponite) and found that talc is capable of increasing in Li content when exposed to Li-bearing groundwater. This has implications for ongoing Mars missions as well as astrobiology.