Paleobasinal to band-scale REE + Y distribution in iron formations from Carajás, Amazon Craton, Brazil

Anoxygenic photosynthesis linked to Neoarchean iron formations in Carajás (Brazil)

“…Most pre-GOE IFs that were not altered by secondary processes (e.g., Bonnand et al, 2020) Sampaio et al, 2018;Wang et al, 2016;Warchola et al, 2018). This suggests that the Carajás IFs are formed under anoxic conditions, also suggested by previous studies in the basin (Justo et al, 2020), possibly due to limited generation and accumulation of O 2 produced by oxygenic photosynthetic organisms (if present) that were not likely abundant during the Late Archean (Ossa et al, 2019).…”

Chemical extraction of iron from carbonate in banded iron formations for isotope analysis

“…The studied samples consisting of IF, Fe-rich and Fe-poor carbonates from Carajás basin have been previously described in Rego et al (2021) and the mineralogical assemblages were similar to those shown by Justo et al (2020). Carbonates in IF facies in Carajás occur commonly as ankerite [Ca(Fe 2+ ,Mg,Mn)CO 3 ] disseminated in a microcrystalline quartz (chert) matrix (Fig.…”

“…This implies that most of the Fe-carbonates, pre- dominantly ankerite as shown by petrographic work (Figs. 5 and 6) (Justo et al, 2020;Rego et al, 2021), were dissolved. The average mass loss of 14.95 ± 2.5 wt% (n = 6) after HAc treatments was slightly higher when compared to the carbonate content and Fe-carbonate ankerite dissolution estimates.…”