Geoscientists from the US and Canada have discovered that ancient sulfur-rich mineral deposits, trapped inside diamonds, can offer new insights into how the Earth’s continents were formed.
The research group from the Carnegie Institution of Washington, the Gemological Institute of America (GIA) and the University of Alberta demonstrated diamonds held details about historic geological events that led to long-term land stability, a key factor in supporting life.
Lead study author Karen Smit of the GIA said that while mineral diamond inclusions may lack appeal in the gem trade, for geoscientists they have helped solve mysteries about the foundations of Earth.
“We’ve found a way to use traces of sulfur from ancient volcanoes that made its way into the mantle and eventually into diamonds to provide evidence for one particular process of continent building,” Smit said following the study, recently published in the journal Science.
The group’s analysis of Sierra Leonean diamonds indicated the West African continent experienced two ‘subduction events’, where oceanic plates sink from the Earth’s surface into its depths when one tectonic plate slides beneath another.
The sulfur-rich inclusions only exist in diamond samples from more than 2.5 billion years ago – before atmospheric oxygen became as abundant as it is today.
“This means that the sulfur in these mineral inclusions must have once existed on the Earth’s surface and was then drawn down into the mantle by subduction,” the researchers wrote.
The team’s comparison to diamonds from Botswana showed similar results, however diamonds mined from northern Canada did not show the same sulfur chemistry, meaning that the North American continent was formed differently.