Some of the world's oldest rubies linked to early life

Date:
October 21, 2021
Source:
University of Waterloo
Summary:
While analyzing some of the world's oldest colored gemstones,
researchers discovered carbon residue that was once ancient life,
encased in a 2.5 billion-year-old ruby.



FULL STORY ========================================================================== While analyzing some of the world's oldest coloured gemstones, researchers
from the University of Waterloo discovered carbon residue that was once
ancient life, encased in a 2.5 billion-year-old ruby.


==========================================================================
The research team, led by Chris Yakymchuk, professor of Earth and
Environmental Sciences at Waterloo, set out to study the geology of rubies
to better understand the conditions necessary for ruby formation. During
this research in Greenland, which contains the oldest known deposits of
rubies in the world, the team found a ruby sample that contained graphite,
a mineral made of pure carbon. Analysis of this carbon indicates that
it is a remnant of early life.

"The graphite inside this ruby is really unique. It's the first time we've
seen evidence of ancient life in ruby-bearing rocks," says Yakymchuk. "The presence of graphite also gives us more clues to determine how rubies
formed at this location, something that is impossible to do directly
based on a ruby's colour and chemical composition." The presence of the graphite allowed the researchers to analyze a property called isotopic composition of the carbon atoms, which measures the relative amounts of different carbon atoms. More than 98 per cent of all carbon atoms have
a mass of 12 atomic mass units, but a few carbon atoms are heavier,
with a mass of 13 or 14 atomic mass units.

"Living matter preferentially consists of the lighter carbon atoms because
they take less energy to incorporate into cells," said Yakymchuk. "Based
on the increased amount of carbon-12 in this graphite, we concluded that
the carbon atoms were once ancient life, most likely dead microorganisms
such as cyanobacteria." The graphite is found in rocks older than 2.5
billion years ago, a time on the planet when oxygen was not abundant in
the atmosphere, and life existed only in microorganisms and algae films.

During this study, Yakymchuk's team discovered that this graphite not
only links the gemstone to ancient life but was also likely necessary
for this ruby to exist at all. The graphite changed the chemistry of the surrounding rocks to create favourable conditions for ruby growth. Without
it, the team's models showed that it would not have been possible to
form rubies in this location.

========================================================================== Story Source: Materials provided by University_of_Waterloo. Note:
Content may be edited for style and length.


========================================================================== Journal References:
1. Chris Yakymchuk, Vincent van Hinsberg, Christopher L. Kirkland,
Kristoffer Szilas, Carson Kinney, Jillian Kendrick, Julie A. Hollis.

Corundum (ruby) growth during the final assembly of the Archean
North Atlantic Craton, southern West Greenland. Ore Geology Reviews,
2021; 138: 104417 DOI: 10.1016/j.oregeorev.2021.104417
2. Vincent van Hinsberg, Chris Yakymchuk, Angunguak Thomas Kleist
Jepsen,
Christopher L. Kirkland, Kristoffer Szilas. The corundum conundrum:
Constraining the compositions of fluids involved in ruby formation
in metamorphic melanges of ultramafic and aluminous rocks. Chemical
Geology, 2021; 571: 120180 DOI: 10.1016/j.chemgeo.2021.120180 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211021084608.htm

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