Micronutrient availability in Precambrian oceans controlled by greenalite formation
In: Nature Geoscience. Nature Publishing Group: London. ISSN 1752-0894; e-ISSN 1752-0908, more
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| Authors | | Top |
- Tostevin, R.
- Ahmed, I.A.M.
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| Abstract |
Metabolisms that evolved in the Archaean era (4.0–2.5 billion years ago) preferentially selected iron, manganese and molybdenum to form metalloproteins, whereas the majority of zinc-, copper- and vanadium-binding proteins emerged much later. The initial preference for these elements is commonly interpreted to reflect their availability in anoxic seawater, with free sulfide proposed as a key influence. While sulfidic waters reduce the availability of zinc and copper, they also remove molybdenum and leave behind vanadium. Furthermore, current geochemical data reflect predominantly ferruginous (Fe2+-rich), rather than sulfidic, conditions. Consistent with this, recent sedimentological work has uncovered abundant iron silicate minerals in Archaean rocks. Here we quantify metal partitioning during the formation and subsequent diagenesis of an Fe(II) silicate mineral, a precursor to crystalline greenalite, in both seawater and hot hydrothermal fluids. Our data show that Fe(II) silicates could have precipitated rapidly in Archaean hydrothermal plumes, severely attenuating hydrothermal delivery of key nutrients, in particular copper, zinc and vanadium. These results provide a mechanistic explanation for metal availability patterns in Archaean oceans that is consistent with temporal patterns of metal utilization predicted from protein structures and comparative genomics. Further, our data suggest natural greenalite may provide an archive of metal availability in deep time. |
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