Fig. 2.

Measurements of a Mg²⁺ and b Fe²⁺ concentrations in solutions after experiments were concluded. Linear best fit lines are shown for clarity although weathering rates were only calculated using longest duration experiments (> 3 days). The R ² for the linear fits are 0.98 for the experiments at −40 °C. The R ² values for linear fit of the −60 °C are not as good 0.53 for Mg²⁺ and 0.22 for Fe²⁺ as these experiments were closer to the blank values. Atomic absorption measurements were performed in triplicate with analytical uncertainties (s.e.m.) < 1% (< 0.05 p.p.m.) so that error bars are smaller than the data points. However the experimental procedure is not perfectly consistent, therefore we expect some natural variance in the results that would exceed the analytical uncertainties due to differences in how the materials interact during each experiment