Did diamonds begin on the ancient ocean floor?

April 18, 2013 by Mark Witten
Did diamonds begin on the ancient ocean floor?

(Phys.org) —Geology professor Dan Schulze calls this singular gem from the remote Guaniamo region of Venezuela the "Picasso" diamond. The blue luminescent, high-resolution image of a diamond formed over a billion years ago reminds him of some paintings from Picasso's Blue Period. Like a cubist masterpiece, its striking irregular and anomalous features carry timeless secrets and yield new perspectives on life and the Earth's early history.

"A diamond is a time capsule. Anomalies in the are the key to understanding the unusual conditions under which some diamonds were formed," says Schulze, an professor in the Department of Chemical and Physical Sciences at U of T Mississauga.

Led by Schulze, an international team of scientists from Australia, Scotland, the United States and Venezuela discovered persuasive new evidence to support the idea that some diamonds, like Picasso, were formed from bacteria or algae on the floor. Their findings suggest these diamonds, known as eclogitic diamonds, originated as organic matter on the floor, which was thrust down into the Earth's mantle by a geological process known as subduction. Attached to ocean floor rock deep beneath the surface, the remnants were then transformed by and pressure into diamonds.

The research is published in the April 2 issue of Geology.

Unlike the more common peridotitic diamonds, formed from found deep in the Earth's mantle, the origins of eclogitic diamonds have been puzzling and controversial due to differences in their carbon signature. "Because diamonds are impermeable, they preserve inside themselves a record of the chemical and physical conditions that existed as they were formed," says Schulze, noting that tiny minerals trapped within the diamonds contain telltale clues to help solve the puzzle.

In their Geology study, Schulze and his colleagues deciphered this record by analyzing the oxygen composition of tiny garnet and silica grains encapsulated in eclogitic diamonds from mines in Venezuela, Australia and Botswana, and the carbon composition of the diamonds themselves. They observed a pattern of striking anomalies in the chemical signatures of both the mineral grains and diamonds that appear to explain how eclogite diamonds were formed.

The silica grains in the Picasso diamond, for example, have a high oxygen composition that matches volcanic rock hydrothermally altered at low temperatures on the ancient , but is different from typical mantle material. "There is no other place on Earth where you get these values except on the ," says Schultze. The diamond itself has a low carbon composition similar to the remains of living organisms.

The same pattern of anomalies was consistently found in over 20 diamonds from three continents. "The simplest hypothesis is that the diamonds were formed from subducted organic materials. It's not just a local phenomenon. This is a that was repeated worldwide in diamonds of different ages from three different locations," explains Schulze.

His research also sheds new light on the origins of two famous diamonds in the British Crown Jewels, the Cullinan I and Cullinan II. "There is a high probability that the Cullinan diamond, the largest gem-quality diamond ever found, is an eclogitic diamond made of biogenic material," he says. "But we'll never know for sure, as we can't get the diamonds for study!"

Life may have begun on the ancient sea floor and Schulze's research suggests many of the world's diamonds originated there too. "There are some people who will never believe this. But these findings will convert more skeptics to a hypothesis that's getting harder and harder to refute," he says.

Explore further: Meteorite yields carbon crystals harder than diamond

Related Stories

Meteorite yields carbon crystals harder than diamond

February 3, 2010

(PhysOrg.com) -- Two new types of ultra-hard carbon crystals have been found by researchers investigating the ureilite class Haverö meteorite that crashed to Earth in Finland in 1971. Ureilite meteorites are carbon-rich ...

New scientific research reveals diamonds aren't forever

July 18, 2011

(PhysOrg.com) -- In a paper published in the US journal Optical Materials Express this week, Macquarie University researchers show that even the earth's hardest naturally occurring material, the diamond, is not forever.

Diamonds pinpoint start of colliding continents

July 21, 2011

Jewelers abhor diamond impurities, but they are a bonanza for scientists. Safely encased in the super-hard diamond, impurities are unaltered, ancient minerals that can tell the story of Earth's distant past. Researchers analyzed ...

Diamonds show depth extent of Earth's carbon cycle

September 15, 2011

Scientists have speculated for some time that the Earth's carbon cycle extends deep into the planet's interior, but until now there has been no direct evidence. The mantle–Earth's thickest layer –is largely inaccessible. ...

Geologists explore clues to Earth's formation in diamonds

November 8, 2011

(PhysOrg.com) -- When jewelers inspect diamonds, they look for cut, clarity, color, and carat. When University of Tennessee, Knoxville, geologists Larry Taylor and Yang Liu inspect diamonds, they look for minerals, inclusions ...

Russia boasts of huge diamond field

September 17, 2012

(AP)—Russian scientists are claiming that a gigantic deposit of industrial diamonds found in a huge Siberian meteorite crater during Soviet times could revolutionize industry.

Recommended for you

Could 'The Day After Tomorrow' happen?

October 9, 2015

A researcher from the University of Southampton has produced a scientific study of the climate scenario featured in the disaster movie 'The Day After Tomorrow'.

Horn of Africa drying ever faster as climate warms

October 9, 2015

The Horn of Africa has become increasingly arid in sync with the global and regional warming of the last century and at a rate unprecedented in the last 2,000 years, according to new research led by a University of Arizona ...

Image: Sentinel-1A captures Azore islands

October 9, 2015

This Sentinel-1A radar image was processed to depict water in blue and land in earthen colours. It features some of the Azore islands about 1600 km west of Lisbon, including the turtle-shaped Faial, the dagger-like Sao Jorge ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

5 / 5 (2) Apr 19, 2013
Nice! Perhaps then the anomalous early Jack Hill diamonds with their light carbon (low delta13) are at least examples of chemical evolution homologous to first autotroph life before the Late bombardment.

Paper here: http://www.geolog...2013.pdf

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.