Gems shine light on ancient Earth
Diamonds are not only a girl’s best friend; scientists are fond of them too.
Three of these gemstones, dug up in Johannesburg between 1890 and 1930, have revealed secrets of how the Earth worked more than 3.5 billion years ago.
These green diamonds – extracted from the 3 billion-year-old Witwatersrand Supergroup, the rock formation that is host to the famous Johannesburg gold mines – were investigated by scientists including Dr Katie Smart and professors Susan Webb and Lewis Ashwal from Wits University. Their research was published in the journal Nature Geoscience this month.
The diamonds were found in the Witwatersrand conglomerate, where the gold that led to the establishment of the city of Johannesburg was found.
“Because diamonds are some of the hardest, most robust materials on Earth, they are perfect little time capsules and have the capacity to tell us what processes were occurring extremely early in Earth’s history,” said Smart.
“We are not the first research group to study diamonds in order to tell when plate tectonics [the theory dealing with the plates that make up the Earth’s outer shell] began, but our study of confirmed Archaean [the aeon from 4 billion to 2.5 billion years ago] diamonds suggests that plate tectonics was in operation by as early as 3.5 billion years ago.”
The research team say the plate tectonic process is vital for shaping the Earth as we know it, because it is the activity of plate tectonics that causes earthquakes and volcanic eruptions, and that is responsible for constructing Earth’s landscapes, such as deep-sea trenches and the development of mountains on the continents.