Fluids Found on African Diamonds Brings Clues on Earth's Evolution From 1 Billion Years Ago

A team of researchers recently came up with a way to solve a pair of long-lasting puzzles, including the ages of individual fluid-bearing African diamonds and their parent material's chemistry.

A SciTechDaily report specified that diamonds are at times described as "messengers" from the deep earth and scientists examine them closely for understandings into the otherwise inaccessible depths from which they originate. However, messages are frequently difficult to read and decipher.

This study has enabled the authors to sketch out geologic occurrences going back more than one billion years, a possible breakthrough, not just in the study of diamonds, but of Earth's evolution as well.

Essentially, gem-quality diamonds are described as almost pure structures of carbon. This essential pureness provides them their luster; although it means too, that they are carrying very little information about both their origins and ages.

Nonetheless, some lower-grade samples are harboring imperfections in the form of small pockets of liquid, residues of the more compound fluids from which there was an evolution of crystals.

Diamond Formation, Chemical Conditions Shift Analyzed

In their new study, the scientists by analyzing the said fluids, worked out the times when there was formation of different diamond, as well as the shifting chemical conditions surrounding them.

According to the study's lead author, adjunct scientists Yaakov Weiss from the Columbia University's Lamont-Doherty Earth Observatory, the new finding has opened a window, even a door, to a number of really big questions.

Weiss, who's also a lecturer at the Hebrew University of Jerusalem added, this is the first time they can get reliable ages for such fluids.

The study entitled "Helium in diamonds unravels over a billion years of craton metasomatism," was published in the Nature Communications journal.

African Diamonds

The 10 diamonds the research team examined came from the mines of De Beers company in and around Kimberly, South Africa.

Weiss explained, they like the ones no one else definitely wants, dirty-looking, fibrous samples which have solid or liquid impurities that exclude them as jewelry, although carry possibly valuable chemical information.

Until now, most scientists have focused on solid inclusions, like small bits of garnet, tiny garnet bits to identify the ages of diamonds.

However, the ages indicated by solid inclusions can be arguable since the inclusions may or may not have shaped at a similar time as the diamond itself did.

Meanwhile, encapsulated fluids are said to be the real thing, the object from which the diamond itself shaped or formed.

Figuring Out Way to Date the Fluids

What Weis and his team did was figure out a way to date the fluids. The group did this by gauging traces of radioactive thorium and uranium, as well as their ratios to helium-4, an unusual isotope resulting from their decay.

The researchers also figured out the highest rate at which the nimble tiny helium molecules can escape out of the diamond, minus which data, conclusions on ages according to the large quantity of the isotope could be thrown far off. And, it was found out that diamonds are excellent at containing helium.

The scientists were able to identify three distinct periods of formation of the African diamonds. These all occurred within separate rock masses that ultimately merged into present-day Africa. The oldest occurred between 2.6 billion to 700 million years back.

Fluid inclusions from that time exhibited a distinct composition, highly rich in carbonate minerals. The period coincided with the accumulation of abundant mountain ranges on the surface, seemingly from the collisions and squashing of rocks together.

Such collisions may be connected with the carbonate-rich fluids' production below, although exactly how remains unclear, said the study authors.

The succeeding diamond-formation phase spanned a possible time frame from 550 million to 300 million years back, as the proto-African continued rearranging itself.

At this time, the liquid inclusions demonstrate, the fluids were abundant in silica minerals, specifying a shift in subterranean circumstances. The time frame also coincided with one more major mountain-building incident.

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