Like an insect in amber, mineral inclusions trapped in diamonds can reveal much about the Earth’s deep interior. The study by Walter et al. reveals mineral inclusions that originated in oceanic crust subducted into the lower mantle.

DTM's Steven Shirey, Eloise Gaillou, and Jianhua Wang teamed up with Geophysical Laboratory staff scientist Andrew Steele and others to document the first direct evidence that slabs of subducted oceanic crust cycle carbon deep into Earth’s mantle. Their research is published in today’s online Science Express.

The team, led by former Carnegie postdoctoral fellow Michael Walter, now at the University of Bristol, England, analyzed diamonds that originated from Earth’s lower mantle at depths greater than 700 km. Those diamonds were later carried to the surface in volcanic eruptions that formed kimberlites. Analysis of inclusions in six diamonds from the Juina region in Brazil shows mineralogical compositions consistent with high-pressure equivalents of oceanic crust.  Shirey, Wang, and colleagues showed that the carbon isotopes of the host diamonds preserve a signature consistent with surface-derived carbon.

For more information on this new research, please see Carnegie Institution for Science’s News Release.