Diamonds in Earth's oldest zircons are nothing but laboratory contamination

Dec 18, 2013
This image explains how synthetic diamond can be distinguished from natural diamond. Credit: Dobrzhinetskaya Lab, UC Riverside.

As is well known, the Earth is about 4.6 billion years old. No rocks exist, however, that are older than about 3.8 billion years. A sedimentary rock section in the Jack Hills of western Australia, more than 3 billion years old, contains within it zircons that were eroded from rocks as old as about 4.3 billion years, making these zircons, called Jack Hills zircons, the oldest recorded geological material on the planet.

In 2007 and 2008, two research papers reported in the journal Nature that a suite of zircons from the Jack Hills included diamonds, requiring a radical revision of early Earth history. The papers posited that the diamonds formed, somehow, before the oldest zircons—that is, before 4.3 billion years ago—and then were recycled repeatedly over a period of 1.2 billion years during which they were periodically incorporated into the zircons by an unidentified process.

Now a team of three researchers, two of whom are at the University of California, Riverside, has discovered using electron microscopy that the diamonds in question are not diamonds at all but broken fragments of a diamond-polishing compound that got embedded when the zircon specimen was prepared for analysis by the authors of the Nature papers.

"The diamonds are not indigenous to the zircons," said Harry Green, a research geophysicist and a distinguished professor of the Graduate Division at UC Riverside, who was involved in the research. "They are contamination. This, combined with the lack of diamonds in any other samples of Jack Hills zircons, strongly suggests that there are no indigenous diamonds in the Jack Hills zircons."

Study results appear online this week in the journal Earth and Planetary Science Letters.

"It occurred to us that a long-term history of diamond recycling with intermittent trapping into zircons would likely leave some sort of microstructural record at the interface between the diamonds and zircon," said Larissa Dobrzhinetskaya, a professional researcher in the Department of Earth Sciences at UCR and the first author of the research paper. "We reasoned that high-resolution electron microscopy of the material should be able to distinguish whether the diamonds are indeed what they have been believed to be."

Using an intensive search with high-resolution secondary-electron imaging and , the research team confirmed the presence of in the Jack Hills zircon samples they examined but could readily identify them as broken fragments of diamond paste that the original authors had used to polish the zircons for examination. They also observed quartz, graphite, apatite, rutile, iron oxides, feldspars and other low-pressure minerals commonly included into in granitic rocks.

"In other words, they are contamination from polishing with diamond paste that was mechanically injected into silicate inclusions during polishing" Green said.

The research was supported by a grant from the National Science Foundation.

Green and Dobrzhinetskaya were joined in the research by Richard Wirth at the Helmholtz Centre Potsdam, Germany.

Dobrzhinetskaya and Green planned the research project; Dobrzhinetskaya led the project; she and Wirth did the .

Explore further: Keep a lid on it: The controversy over Earth's oldest rocks

Related Stories

Diamonds grow like trees, but over millions of years

Sep 16, 2013

Diamonds consist of highly compressed carbon atoms and develop deep underground at relatively high pressures and temperatures of over 1000 degrees Celsius. Earth scientists from VU University Amsterdam show ...

Did diamonds begin on the ancient ocean floor?

Apr 18, 2013

(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 ...

Indirect study of Earth's core

Nov 27, 2013

The center of the Earth is about 6,371 kilometers or 4, 000 miles away, roughly the distance between Phoenix and the North Pole.

Recommended for you

Kiribati leader visits Arctic on climate mission

Sep 20, 2014

Fearing that his Pacific island nation could be swallowed by a rising ocean, the president of Kiribati says a visit to the melting Arctic has helped him appreciate the scale of the threat.

NASA catches a weaker Edouard, headed toward Azores

Sep 19, 2014

NASA's Aqua satellite passed over the Atlantic Ocean and captured a picture of Tropical Storm Edouard as it continues to weaken. The National Hurricane Center expects Edouard to affect the western Azores ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

foxpup
5 / 5 (4) Dec 18, 2013
One of the best aspects of science is that it is self-correcting.
HannesAlfven
1 / 5 (1) Dec 19, 2013
There is clearly a reputational bounty waiting to be collected on this hot issue for anybody who can come up with such results. I would advise caution, for we saw the same exact "contamination" pattern with the polywater debate. But, more modern investigations -- like Gerald Pollack's at the University of Washington -- reveal that neither side of the polywater debate were right, and there remains widespread confusion on the topic of water's highly ordered exclusion zone to this day. The inferential step is far more dangerous (and oftentimes far more politicized and biased) than idealized views of the scientific process suggest. I would go so far as to suggest that the most likely outcome is that both the creationists and the modern scientists will turn out to be wrong on the zircons.
Torbjorn_Larsson_OM
not rated yet Dec 19, 2013
Yes, foxpup. A bummer though, since the diamonds were indicative of carbon cycling. But the results that shows early water and crust (crustal erosion) are from the zircons themselves IIRC.

*********
As always, the antiscience creationism trolling suggesting it, or pseudoscience such as "polywater" and "inferential step[s]", has anything to do with this, is hilarious. #LOL"science"