Extended Data Figure 2 : Fe3+/ΣFe versus total Fe for Precambrian ophiolite basalts.

From: A record of deep-ocean dissolved O2 from the oxidation state of iron in submarine basalts

Extended Data Figure 2

The regression line (dotted grey line) is a linear regression through Precambrian ophiolite basalts with a 95% confidence interval shaded in grey. The slope is not distinguishable from 0 at the 2σ level. If secondary metamorphic reduction occurred in these samples, we would expect samples with less Fe to be consistently lower in Fe3+/ΣFe ratios than samples with more Fe. This is not observed, indicating that such metamorphic reduction has not obviously affected the Fe3+/ΣFe ratios of samples.