Studying ancient iron-rich sediments in Western Australia and South Africa, Dr Andrew Glikson and colleague Mr John Vickers, from the Department of Earth and Marine Sciences at ANU discovered that the formation of banded iron formations, jasper and iron-rich shale coincided closely with asteroid and comet impacts.
The impacts of the asteroids and comets caused volcanic and hydrothermal activity including eruption of iron-rich basalt, according to Dr Glickson. This created an environment which suited primitive bacteria that lived on the floor of the early oceans, and which derived their energy by oxidising water-soluble (ferrous) iron into insoluble (ferric) iron.
This bacterial activity is thought to have precipitated iron and silica-rich sediments, known as banded iron formations, in areas such as the Pilbara in Western Australia. These banded iron formations host the huge Hamersley and Yarrie iron ore deposits of the Pilbara region.
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