The water content of davemaoite, a major mineral in the Earth's deep interior, was found to be extremely low, revealing a new destination for water in the deep Earth. The announcement was made by a research team from Okayama University and other institutions.
The mantle transition zone at depths of 410–660 km has been thought to contain high-pressure forms of olivine, such as wadsleyite and ringwoodite, which may retain 2–3 wt% water. By contrast, bridgmanite and ferropericlase in the lower mantle below 660 km were known to contain almost no water.
For davemaoite (CaSiO3 perovskite), however, the water content had remained unknown for many years, and some reports suggested that it could contain 1 wt% or more water. The new study conducted an analysis aimed at resolving this uncertainty.
The analysis found that davemaoite contains almost no water in the Earth's deep interior. This places new constraints on models of deep-Earth water circulation and suggests that pathways involving water derived from other minerals may account for most of the water in the deep Earth.
The study was announced by a joint research group including Okayama University and other institutions. It is regarded as an important step toward advancing understanding of water circulation within the Earth.