A diamond that formed deep in the earth’s mantle contains a mineral never seen before in nature. The discovery is a rare glimpse into the deep mantle and may help reveal new information about the structure of the planet at depths of more than 660 kilometres. This, in turn, can help geologists better understand how the mantle controls the earth’s plate tectonics.
In a study published in Science, researchers said that the mineral, calcium silicate perovskite, only forms under the incredibly high pressures that occur deep in the earth. However, the newly identified sample likely formed between 660 and 900 km below the planet’s surface, says mineralogist Oliver Tschauner of the University of Nevada, Las Vegas.
The mineral, calcium silicate perovskite is also known as davemaoite, after geophysicist Ho-Kwang (Dave) Mao for his studies on high-pressure elements
Chemical analysis of the mineral showed the presence of radioactive isotopes of uranium, thorium and potassium inside it. "Davemaoite can thus host three of the major heat-producing elements (uranium and thorium were previously shown experimentally) affecting heat generation in Earth’s lower mantle," the paper said.
"The discovery of davemaoite came as a surprise," lead author Oliver Tschauner, a mineralogist at the University of Nevada, Las Vegas, told Live Science.
In the 2014 study, researchers described another theoretical high-pressure mineral from the mantle, known as bridgmanite. However, the sample of bridgmanite did not originate from the mantle but rather inside a meteorite. The discovery of davemaoite shows that diamonds can form farther down in the mantle than previously thought, and it suggests that they might be the best place to look for more new minerals from the mantle, Tschauner said.