Simulations Predict New Manganese-Rich Oxide Stable at Extreme Mantle Pressures
Computer models found a manganese oxide with four manganese atoms per oxygen atom that remains stable at pressures up to 1.5 million times surface levels. Researchers link the compound to seismic anomalies and the ancient manganese cycle.
sciencenews.orgComputer simulations identified a previously unknown manganese oxide containing four manganese atoms for every oxygen atom that remains stable across a wide pressure range. 5 million times atmospheric pressure, conditions comparable to those about 2900 kilometres beneath Earth’s surface. Jingming Shi at Jiangsu Normal University in China led the work.
“We did not necessarily expect such a manganese-rich oxide to be stable over such a wide pressure range. That was the most interesting and unexpected finding,” he said. 1103/85kd-vnbt, also found several other new manganese oxide compounds.
Researchers noted that high pressure can stabilise compounds that would not normally exist near Earth’s surface. Manganese oxides began accumulating in Earth’s crust around the time of the Great Oxygenation Event roughly 2 billion years ago, when oxygen produced by photosynthesising microbes started to accumulate in the atmosphere.
Manganese is thought to have played a role in an early version of photosynthesis.
Shi said the new compound’s properties could partly explain why seismic waves travel unusually slowly through some regions where the mantle and core meet. He added that the findings raise the possibility that very manganese-rich patches in Earth’s interior have gone unrecognised.
Timothy Lyons at the University of California, Riverside, said the compound could have moved from Earth’s interior to the floor of ancient oceans.
“[It’s] a potentially important piece of the manganese cycle, an element with far reaching importance from the early evolution of life to modern production of steel and batteries and human health,” he said. Caroline Peacock at the University of Leeds in the UK said the links to seismic data and the Great Oxygenation Event remain fairly speculative.
She noted that more evidence is required before firm conclusions can be drawn about manganese oxides within Earth.
Shi and his colleagues plan to study the new manganese oxide in experiments that use diamond instruments to compress samples to very high pressures, emulating deep Earth conditions.
