Study confirms that ringed iron formations come from oxidized iron

A new study by scientists at the University of Alberta has shown that iron-banded iron is from oxidized iron, confirming the relevance and accuracy of existing models – a finding of great importance to the community. geological.

Ringed iron formations are a distinct type of sedimentary rock with layers of iron deposited as horizontal bands. The majority of these formations have been formed over the last 2.5 billion years and are now a major source of iron. "We are successfully using band iron formations to monitor the evolution of seawater and biosphere chemistry," said Kurt Konhauser, professor in the Department of Earth Sciences and Earth Sciences. the atmosphere and co-author of the document. "But these experiments are based on the assumption that we understand the primary minerals that make up these rocks."

Over the past decade, a new model has been proposed, suggesting that the formations initially had a ferrous iron that was oxidized by oxygen in the environment – a model that, if it were correct, would require a change. major paradigm in this field of study.

To examine this possibility, a group of researchers led by Konhauser student doctoral student Leslie Robbins, tested the theory with the help of a hydrogeological model, designed to determine the time it would take to oxygen to oxidize such formation. The research team included Professor Ben Roston, Assistant Professor Daniel Alessi and Professor Larry Heaman.

"Essentially, we found that this would only be possible in 1% of cases within the suggested time frame of 250 million years," Konhauser said. "In addition, we had to create unrealistic conditions to run the proposed new model – for example, an extremely steep slope, or a rock that was actually sand, or a large amount of oxygen."

These results confirmed the inaccuracy of the proposed new model, indicating that existing models and our current understanding remain the most effective method for studying ringed iron formations.

"This is a powerful result that stems from the simple question of whether the recently proposed models for ringed iron formations are plausible when they are extrapolated to the size of a sedimentation basin", said Robbins, currently a postdoctoral fellow at Yale University in New Haven, United States. . "This result has fundamental implications for the formation of these deposits, and this work has greatly benefited from strong collaborations within the Earth and Atmospheric Sciences and with our external collaborators."

The document "Hydrogeological constraints for the formation of Paleoproterozoic banded iron formations" was published in Nature Geoscience.