Deep Earth Microdiamonds Formed by Acidic Water and Silicate Rocks

Summary: A study Nov. 3, 2015, in Nature Communication models Deep Earth microdiamonds formed as chemical process end-products of acidic water and silicate rocks.

"Caption This is the rare Udachnaya diamondiferous peridotite"; unique diamondiferous garnet-peridotite golf-sized rock found in Udachnaya pipe, Sakha (Yakutia) Republic, Far Eastern Russia, contains more than 30,000 microdiamonds; credit Larry Taylor: No usage restrictions, via EurekAlert!

Diamonds are not at all rare in deep Earth, according to a study published Nov. 3, 2015, by the journal Nature Communications.

Dimitri A. Sverjensky, lead author and Morton K. Blaustein Department of Earth and Planetary Sciences Professor at Johns Hopkins University in Baltimore, Maryland, believe that “Diamond formation in the deep Earth, the very deep Earth, may be a more common process than we thought.” He and Fang Huang, doctoral student and study co-author, consider a theoretical explanation of diamond formation that may suit deep-earth conditions 90 to 120 miles (144.84 to 193.12 kilometers) below the surface and temperatures of 1,650 to 2,000 degrees Fahrenheit (898.89 to 1093.33 degrees Celsius).

Geochemists describe diamond formation from the surface to 8 or 9 miles (12.87 to 14.48 kilometers) down in terms of fluid mixtures of dissolved neutral gas molecules of carbon dioxide, hydrogen, methane and water. Movement entails either the chemical reduction of carbon dioxide and the loss of electrons or the oxidation of methane and the gain of electrons.

The study’s Deep Earth Water (DEW) chemical model examines a third possibility of diamonds forming as chemical process end-products of water’s pH levels falling into acidic ranges while moving through upper mantle silicate rocks.

Microdiamonds form during deep earth fluid interaction with eclogite (mantle rock); eclogite rock from Kola Peninsula, far northwestern Russia: James St. John, CC BY 2.0 Generic, via Wikimedia Commons

Diamonds form when fluids react with the mantle rock eclogite at high pressures and temperatures of 5.0 gigapascals and 1652 degrees Fahrenheit (900 degrees Celsius).

Gemologists give the terms blemishes and inclusions to a diamond’s respectively external and internal flaws since flawlessness is rare in the world’s hardest gem and material. Exterior chips and scratches that indicate the conditions under which diamonds are shaped head the list of blemishes. Inclusive bubbles, cracks and crystals indicate the conditions under which diamonds are formed.

The study judges secondary minerals as possibly generated by the theorized upper mantle interactions between acidic water and silicate rocks. The study’s two co-authors know of secondary clinopyroxene, coesite and garnet whose intrusions in natural diamonds are accounted for by the study’s reacting magnesium-rich carbonate with a fluid-, heat-, pressure-altered sedimentary rock model, eclogite, consisting of clinopyroxene, coesite and pyroxene.

The research lacks testing with actual materials despite the results remaining important for natural diamonds as carbon cycle participants and as pricey gems. Dr. Sverjensky mentions the singular significance of fluid movement studies regarding mysterious deep Earth components of the life-enabling carbon cycle since “Fluids are the key link between the shallow and the deep Earth. That’s why it’s important.”

Gemologists need not ponder imminent disruptions to supply and demand curves by Dr. Sverjensky’s observation that “The more people look, the more they’re finding diamonds in different rock types now. I think everybody would agree there’s more and more environments of diamond formation being discovered.”

Deep Earth micro-diamonds offer micron-sized, not carat-sized, priciness visible only through microscopes.

Figure 3 Predicted versus measured fluid during diamond formation evaluates measured fluid compositions from worldwide diamonds, include diamonds from Yakutia, the source of rare garnet-peridotite rock with over 30,000 microdiamonds; Dmitri A. Sverjensky and Fang Huang, "Diamond formation due to a pH drop during fluid–rock interactions," Nature Communications, : vol. 6, article number 8702 (published Nov. 3, 2015), Figure 3: CC BY 4.0 International, via Nature Communications

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

"Caption This is the rare Udachnaya diamondiferous peridotite"; unique diamondiferous garnet-peridotite golf-sized rock found in Udachnaya pipe, Sakha (Yakutia) Republic, Far Eastern Russia, contains more than 30,000 microdiamonds; credit Larry Taylor: No usage restrictions, via EurekAlert! @ https://www.eurekalert.org/multimedia/614943; (EurekAlert! news release URL @ https://www.eurekalert.org/news-releases/619133); (former URL @ http://www.eurekalert.org/multimedia/pub/84659.php)

Microdiamonds form during deep earth fluid interaction with eclogite (mantle rock); eclogite rock from Kola Peninsula, far northwestern Russia: James St. John, CC BY 2.0 Generic, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Eclogite_from_the_Kola_Peninsula_of_Russia.jpg

Figure 3 Predicted versus measured fluid during diamond formation evaluates measured fluid compositions from worldwide diamonds, include diamonds from Yakutia, the source of rare garnet-peridotite rock with over 30,000 microdiamonds; Dmitri A. Sverjensky and Fang Huang, "Diamond formation due to a pH drop during fluid–rock interactions," Nature Communications, : vol. 6, article number 8702 (published Nov. 3, 2015), Figure 3: CC BY 4.0 International, via Nature Communications @ http://www.nature.com/ncomms/2015/151103/ncomms9702/full/ncomms9702.html#affil-auth

For further information:

Hays, Brooks. 4 November 2015. "Deep Earth is likely filled with diamonds, scientists say." Science News.
Available @ http://www.upi.com/Science_News/2015/11/03/Deep-Earth-is-likely-filled-with-diamonds-scientists-say/2241446610966/

Hirsch, Arthur. 3 November 2015. "Diamonds May Not Be So Rare As Once Thought." The Johns Hopkins University > Office of Communications > News Releases.
Available @ http://releases.jhu.edu/2015/11/03/diamonds-may-not-be-so-rare-as-once-thought/

Sci-News Staff. 17 January 2015. "Geologists Find Rock with 30,000 Diamonds." Sci-News > Geology.
Available @ http://www.sci-news.com/geology/science-rock-30000-diamonds-udachnaya-mine-02411.html

Sverjensky, Dmitri A., and Fang Huang. 3 November 2015. "Diamond formation due to a pH drop during fluid-rock interactions." Nature Communications 6 (Nov. 3, 2015): 8702. DOI: 10.1038/ncomms9702
Available @ http://www.nature.com/ncomms/2015/151103/ncomms9702/full/ncomms9702.html