New Find in Tungsten Iron Ore Contradicts Theory of Earth Lost Oxygen

The new finding in ancient tungsten iron ore contradicts the theory of the mysteriously lost oxygen of the Earth 2 billion years ago. The Earth didn't always have this much oxygen. About 2.4 billion years ago, the rise of cyanobacteria and shifting of tectonic plates breathed new life into our planet, triggering a Great Oxidation Event (GOE).

The ensuing surge in oxygen-hungry life did not last long. Many scientists now believe that the evolution of life "overshot" the amount of oxygen available in the atmosphere. Evidence found last year suggests that this triggered a sudden and catastrophic mass extinction of microorganisms about 2 billion years ago that was even direr than the dinosaur die-off.

Nevertheless, although the oxygen overshoot theory has become more popular in recent years, new research suggests that it might be wrong.

In Russia, analysis of ancient sedimentary rocks shows that for millions of years after GOE, conditions on our planet were more appropriate than the continuous evolution of complex organisms.

Kaarel Mänd, a palaeogeographer at the University of Alberta, said: "What we found contradicts the prevailing view - essentially we have clear evidence that atmospheric oxygen levels rose even further after the carbon isotope anomaly ended. This will force the science community to rethink what drove the carbon and oxygen cycles on the early Earth."

The evidence comes from new drill cores in the Lake Onega region in the northwestern corner of Russia, Europe. Here, researchers have discovered ancient tungsten iron ore, a black lustrous mineral, from 2 billion years ago.

This shiny shale is composed almost entirely of carbon and is one of the best archives of the state of the environment that we had to figure out long ago.

At present, it is generally understood that carbon isotope in sedimentary rocks has changed due to the increase of oxygen more than 2 billion years ago, which is called the Lomagundi–Jatuli Event (LJE). This indicates that a large amount of organic matter was being buried in ocean sediments, resulting in the release of excess oxygen. But then, our planet mysteriously lost oxygen.

However, in these tungsten iron cores deposited after the end of LJE, researchers found strikingly high traces of molybdenum, uranium, and rhenium, and these metals are often associated with abundant oxygen.

The concentrations they found were unmatched by any other known point in Earth's history, and can be compared with the most "organic-rich modern marine sediments" or the most uranium- enriched "Precambrian shale measurement that has been reported to date".

If shungite was deposited, there must have been enough oxygen around. The authors argue that the discovery of ancient tungsten iron ore contradicts the theory of the mysteriously lost oxygen of our planet 2 billion years ago, this conclusion undoubtedly forces a "re-evaluation of our basic view of this turbulent interval of Earth's history".

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