Geochemistry of the Krivoy Rog Banded Iron Formation, Ukraine, and the impact of peak episodes of increased global magmatic activity on the trace element composition of Precambrian seawater

The magnitude of positive Eu anomalies steadily decreases from the Eoarchaean, reflecting both high hydrothermal input and low dissolved oxygen required to stabilise Eu2+ for transport before the deep oceans became oxygenated.

“The magnitude of positive Eu anomalies steadily decreases from the Eoarchaean, which reflects both high hydrothermal input and low dissolved oxygen required to stabilise Eu 2+ for transport before the deep oceans became oxygenated (Viehmann et al., 2015).”

Deposition of large, economically important IF coincided in time with mantle plume breakout events.

“It is now widely accepted that the deposition of large, economically important IF coincided in time with mantle plume breakout events”

La anomalies are strongly expressed in pure iron formations (LaSN/LaSN* ratios between 1.32 and 1.80), whereas they are small or absent in impure iron formations (between 0.85 and 1.52).

“Similarly, Viehmann et al. (2015) noted the depression of the La anomaly in IF with increased detrital contamination; La anomalies are strongly expressed in pure IF (LaSN/LaSN * ratios between 1.32 and 1.80), whereas they are small or absent in impure IF (between 0.85 and 1.52).”

Most Archaean to Palaeoproterozoic IFs have εNd(t) values intermediate between those of the depleted mantle and ancient continental crust.

“Compilations of Nd isotope data from Archaean to Palaeoproterozoic IFs highlight the fact that most IFs have ε Nd(t) values that are intermediate between those of the depleted mantle and ancient continental crust”