Jeweller - November 2021

in catastrophic explosions known as kimberlitic eruptions.
Those familiar with diamond formation will recognise the term
‘kimberlite’, which refers to the diamond-rich channels made by
these eruptions.
Dazzling diamonds
Intriguingly, the rarest and largest diamonds are believed to be
of super-deep origin.
These diamonds are often described as ‘Cullinan-like’, named
after the largest diamond ever discovered – the Cullinan diamond,
which weighed 3,106 carats. It was discovered by Thomas Evan
Powell on 26 January 1905 at the Premier Mine in South Africa.
Cullinan-like diamonds have metallic inclusions with
compositions that support the processes involved in the
formation of super-deep diamonds.
So far, mines containing super-deep diamonds have been
identified as the most productive globally, with South Africa
and Brazil the main producers of super-deep diamonds.
Other locations might bear super-deep diamonds, but they
have not been discovered yet.
Unlocking Earth’s secrets
An even rarer type of diamonds is the oceanic type. These
diamonds share similarities with super-deep diamonds and
formed when the oceanic crust crashed into the continental
lithosphere.
The comparative study of both super-deep and oceanic diamonds
indicates that carbon from dead organisms seems to be the
primary source of carbon, suggesting that the deep carbon
cycles are closely linked to the surface carbon cycles.
The super-deep and oceanic diamonds are the sole samples we
have from deep within the Earth and give us invaluable information
on what is happening hundreds to thousands of kilometres below
our feet. So far, studies on these diamonds demonstrate that
Earth’s interior is wetter than expected and that surface material,
including organic matter, has been recycled deep in the mantle.
The fundamental question that remains to be answered is, when
does it start? This question will keep scientists busy for the years
to come.
While recycling is becoming a modern-day necessity for our
sustainable survival, we were particularly surprised to learn,
through this research, that Mother Nature has been showing
us how to recycle with style for billions of years.
This research helps us to understand Earth’s carbon cycle and
could provide the key to even more secrets of the Earth’s history;
by mapping the distribution of continental and oceanic diamonds,
we can potentially identify the past locations of mantle plumes and
superplumes.
The Curtin University Earth Dynamics Research Group's study
of super-deep diamonds, 'Oceanic and super-deep continental
diamonds share a transition zone origin and mantle plume
transportation', was published in the journal Nature Scientific
Report in August 2021. Visit: geodynamics.curtin.edu.au/research/
research-highlights
18ct Diamond & Precious Coloured Gemstone Jewellery
DJDIAMONDDESIGNS.COM.AU
DR LUC DOUCET is a research fellow at the Earth Dynamics
Research Group of Curtin University in Perth, Western Australia. He
and his team reconstruct the geodynamic processes that made the
Earth the way it is today. Visit: geodynamics.curtin.edu.au
Daniel Jacuk - 0412 071 103
sales@djdiamonddesigns.com.au