Low-Fe(III) Greenalite Was a Primary Mineral From Neoarchean Oceans

Jena E. Johnson, Janet R. Muhling, Julie Cosmidis, Birger Rasmussen, Alexis S. Templeton

Research output: Contribution to journalArticlepeer-review

50 Scopus citations


Banded iron formations (BIFs) represent chemical precipitation from Earth's early oceans and therefore contain insights into ancient marine biogeochemistry. However, BIFs have undergone multiple episodes of alteration, making it difficult to assess the primary mineral assemblage. Nanoscale mineral inclusions from 2.5 billion year old BIFs and ferruginous cherts provide new evidence that iron silicates were primary minerals deposited from the Neoarchean ocean, contrasting sharply with current models for BIF inception. Here we used multiscale imaging and spectroscopic techniques to characterize the best preserved examples of these inclusions. Our integrated results demonstrate that these early minerals were low-Fe(III) greenalite. We present potential pathways in which low-Fe(III) greenalite could have formed through changes in saturation state and/or iron oxidation and reduction. Future constraints for ancient ocean chemistry and early life's activities should include low-Fe(III) greenalite as a primary mineral in the Neoarchean ocean.

Original languageEnglish (US)
Pages (from-to)3182-3192
Number of pages11
JournalGeophysical Research Letters
Issue number7
StatePublished - Apr 16 2018

All Science Journal Classification (ASJC) codes

  • Geophysics
  • General Earth and Planetary Sciences


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