African diamonds show billions of years of evolution deep in the earth

Scientists call diamonds “messengers from deep within the Earth,” and a study published May 11 in Nature Communications not only makes a technical breakthrough in the study of diamonds, but also shows how the Earth has evolved in part over billions of years through the impurities inside. The situation.

Gem-quality diamonds require a high degree of purity, but this provides little information to researchers. The study’s lead author, Yaakov Weiss of Columbia University, said the 10 diamonds they studied came from several sites in South Africa owned by diamond maker De Beers.

“We like diamonds that nobody wants.” Weiss said the diamonds with many inclusions and a “dirty” look have an endless treasure of information for them.

Scientists used to study the solid inclusions inside diamonds to determine the age of their formation. But these solid impurities are not necessarily the same period as the diamond was created. This study has dated diamonds by using small droplets of impurities inside them. The researchers concluded that the droplets must have come from the same time period as the diamonds were formed.

The team dated the formation of diamonds by identifying the ratio of the radioactive elements thorium and uranium inside the droplets to their decay product helium 4. The results revealed that the diamonds in the South African subsurface come from three main historical periods.

The oldest diamonds come from the period between 2.6 billion and 700 million years ago. The fluids from this period are rich in carbonate minerals. This period, however, coincides with the formation of a large number of mountains on Earth’s land masses, as known to geologists. The study speculates that this is a clear indication of the large amount of subsurface rock that underwent the process of impact and extrusion.

The next period is from 550 million years ago to 300 million years ago. The topography of the African continent underwent a phase of adjustment during this period. Droplets from this period are rich in silica minerals. Researchers believe that this indicates that the condition of the subsurface rocks changed at that time. Many mountains on land were also formed during this period.

The most recent period is 130 million years ago to 85 million years ago. The composition of the droplets from this period is different again: they are rich in potassium and sodium salt compounds. This suggests that the carbon elements that formed these diamonds did not come directly from the depths of the Earth, but from the bottom of the oceans, and that they would have been sunk to the land plates at the bottom of the sea during crustal movements. In other words, the carbon that formed some of the diamonds may have come from the Earth’s surface, which scientists previously thought was not possible. This study proves the possibility of such a process.

Interestingly, this study found at least one diamond with fluid inside that came from both the earliest and the latest age of diamond formation. The study believes this illustrates the process of diamond development: a new layer can be wrapped around the original crystal.

Weiss said this approach could also be used to study diamonds from other regions, such as those in Australia, Brazil, northern Canada and Russia, to try to understand the secrets that lie deep underground in these regions.