A team of researchers from James Cook University and the University of Adelaide discovered metamorphic diamonds in rocks near Australia’s northeast coast. Alexander Edgar, IoanSanislav, Paul Dirks, and Carl Spandler describe how they discovered the tiny diamonds and why they believe the discovery will help reveal more about Australia’s early history and formation in a paper published in the journal Science Advances.
Metamorphic diamonds are extremely rare and only occur in a few locations. They are also extremely small, ranging from microscopic to nanoscale. The rare diamonds form in subduction zones, where the pressure of opposing plates grinding against one another over millions of years results in the formation of diamonds so small that they cannot be seen with the naked eye. They have only ever been discovered in six other locations on Earth. The researchers discovered a slew of them inside rocks along the Clarke River Fault, which formed around 500 million years ago when crustal blocks were pushed together.
The researchers began looking into the rocks along the fault line after one of their students told them about some rock formations they had seen that appeared to have been revealed when one of the tectonic plates pushed them above the surface of the ground around them.
The researchers went to the site and collected some of the rocks, which they then brought back to their lab to study. They cut them into very thin slabs and used Raman spectroscopy to identify the minerals contained within. They discovered silica, amphibole, apatite, rutile lamella, coesite, quartz, and, most importantly, metamorphic diamonds.
The diamonds discovered were the first to be discovered in the Gondwana-Pacific region of the Terra Australis Orogen, according to the researchers. They also believe that because metamorphic diamonds can only be formed under very specific conditions, studying them and the locations where they are found could provide more information about how Australia formed.