Fig. 1.
Variations of bulk Fe2O3 and P2O5 measured in (A) Neoarchean (∼2.74 Ga old) iron formations, Fe-rich and Fe-poor carbonates from Carajás Brazil, and compared in (B) with Archean IF literature data (3.8–2.6 Ga; 2, 5, 16–22) and modern hydrothermal sediments (23).