Study reveals deep-Earth silicate melts can store significant oxygen
Researchers found that magma under high pressure can hold excess oxygen, offering a potential explanation for Earth's atmospheric oxygen increase billions of years ago.
A research team led by the Beijing High Pressure Science Research Center has discovered that silicate melts can store significantly more oxygen under high pressure than previously estimated. The findings, published in the National Science Review, suggest that the Earth’s mantle may have acted as an unexpected oxygen reservoir throughout geological history.
Through high-pressure experiments simulating conditions in the upper mantle—up to 7 gigapascals—the team observed that molten rock can contain over 5 percent of its weight in "extra" oxygen. Unlike traditional models where oxygen is strictly fixed by chemical stoichiometry, this study shows it can be incorporated into the silicate network at high pressures.
This mechanism offers a new perspective on the Great Oxidation Event (GOE) that occurred between 2.5 and 2 billion years ago. As magma rises and pressure drops, its capacity to hold oxygen decreases, releasing the gas into the mantle and eventually the atmosphere. The authors note that the timing of massive volcanic events during that era correlates with the observed increase in atmospheric oxygen, suggesting a causal link.