Calcium silicate perovskite (CaSiO3)

Calcium silicate perovskite (CaSiO3)

Calcium silicate perovskite is among the most geochemically important minerals in the lower mantle, largely because it concentrates elements that are incompatible in the upper mantle, including rare-earth elements and radioactive isotopes that make an important contribution to the heat of Earth’s mantle,” said lead author Dr. Oliver Tschauner from the Department of Geoscience at the University of Nevada, Las Vegas, and his colleagues.

No one has ever successfully retrieved this high-pressure compound from the lower mantle before. This is because CaSiO3-perovskite is ‘unquenchable,’ meaning that it cannot retain its structure after being removed from its high-pressure environment.

In a new study, U.S. geologists have finally found the first calcium silicate perovskite from Earth’s lower mantle in a diamond from the Orapa kimberlite pipe in Botswana. the world’s largest diamond mine by area — in the 1980s. A gem dealer sold the diamond in 1987 to a mineralogist at the California Institute of Technology.

The crystalline compound the researchers found was named davemaoite in honor of the prominent experimental high-pressure geophysicist Ho-kwang (Dave) Mao and confirmed as a new mineral by the Commission of New Minerals.

The structural and chemical analysis of davemaoite showed that it is able to host a wide variety of elements in its structure, including potassium, thorium and uranium — three of the major heat-producing elements. The findings support the existence of compositional heterogeneity within the lower mantle and, given the mineral’s overall abundance, suggest that davemaoite likely influences heat generation in the deep mantle.