An episode of extreme volcanic activity may have generated large iron formations long after a rise in atmospheric oxygen should have prevented iron from forming.
The so-called Great Oxidation Event 2.4 billion years ago mostly ended the geological production of iron, so scientists have long been puzzled by evidence of iron formations less than 2 billion years old. The new study compares volcanic ash beds and concludes that a “superplume” volcanic event could explain the relatively recent formations.
Read more at The University of Western Australia