Featured Research

from universities, journals, and other organizations

Journey to the lower mantle and back: Minerals from ocean-floor rocks are found in ultra-deep diamonds

Date:
September 15, 2011
Source:
University of Bristol
Summary:
Mineral inclusions discovered in diamonds prove that surface rocks can be subducted into the deep part of the Earth's mantle. The isotopic composition of the diamonds confirms that recycling of crustal materials, including carbon, extends into the lower mantle.

This figure shows the location of the Juina-5 kimberlite in Brazil, where the raw diamonds come from. Thousands of diamonds are examined in order to identify stones that might contain an inclusion.
Credit: Image © Science/AAAS

The theory of plate tectonics is at the centre of our understanding of how Earth works. It has been known for decades that new crust is formed at mid-ocean ridges and that this crust is subducted as plates dive underneath other plates in regions such as the Pacific Ring of Fire and descend into Earth's mantle. What is not so well known is the fate of these subducted plates.

In a new paper in the journal Science, scientists from the University of Bristol (Prof. M. Walter, Dr. S. Kohn, Dr. G. Bulanova, Mr. C. Smith), Universidade de Brasilia (Prof. D. Araujo), and the Carnegie Institution of Washington (Dr. E. Gaillou, Dr. J. Wang, Dr. A. Steele, Dr. S. Shirey), show that oceanic crust can make its way right down to the lower mantle (deeper than 660km) and then be transported back to the surface.

The samples studied are tiny inclusions of minerals trapped in diamonds from the Juina region of Brazil. Diamonds are extremely durable, and so they make excellent hosts for the trapped minerals they contain. However, the original minerals can change as the pressure and temperature conditions of the diamond change, and the inclusions record that history.

Walter and coworkers discovered, for the first time, a set of mineral inclusions with compositions matching the entire mineral assemblage characteristic of oceanic crust subducted into the lower mantle (depth > ~ 700 km). Trapped originally as single mineral phases, the inclusions become multi-mineral assemblages upon uplift. The authors suggest that the diamonds were transported from the lower to upper mantle via large-scale upwelling beneath Brazil during the Cretaceous Era, possibly in a mantle plume. The diamonds were ultimately exhumed rapidly to the surface in kimberlite magmas (kimberlites are the main volcanic rock to transport diamonds to the surface).

The authors also observe that four of the six diamonds studied have extremely low amounts of 13C, a feature never previously seen in diamonds from the lower mantle. Low 13C is consistent with an origin of the carbon in oceanic crust at Earth's surface. These and future results from investigations of diamonds and their inclusions could transform our understanding of the oxidation state, volatile content, and geological history of the lower mantle. They certainly mean that recycling of crustal materials, including carbon, is not limited to the upper mantle but extends deeper into the lower mantle.

Dr. Simon Kohn said: "The amazing thing about the diamonds from Juina is that each new batch we study provides something unexpected. As we investigate them in more detail with new techniques they continue to give up more of their remarkable secrets."

Prof. Michael Walter said: "Inclusions in diamonds are fantastically useful for studying the inaccessible part of the deep Earth. It's a bit like studying extinct insects in amber. Although we can't extract DNA and grow dinosaurs, we can extract their chemical compositions and tell where they formed by growing minerals in the lab at extreme conditions!"

Prof Dιbora Araujo said: "It is really exciting to see Brazilian diamonds playing such an important role in this scientific breakthrough. Samples from this region have been investigated for several years and yet we are not running out of exciting new discoveries. We are all very pleased to be involved in such a successful international collaboration"

Dr Steven Shirey said: "I find it astonishing that we can use the tiniest of mineral grains to show some of the largest scale motions of the Earth's mantle."


Story Source:

The above story is based on materials provided by University of Bristol. Note: Materials may be edited for content and length.


Journal Reference:

  1. M. J. Walter, S. C. Kohn, D. Araujo, G. P. Bulanova, C. B. Smith, E. Gaillou, J. Wang, A. Steele, S. B. Shirey. Deep Mantle Cycling of Oceanic Crust: Evidence from Diamonds and their Mineral Inclusions. Science, 2011; DOI: 10.1126/science.1209300

Cite This Page:

University of Bristol. "Journey to the lower mantle and back: Minerals from ocean-floor rocks are found in ultra-deep diamonds." ScienceDaily. ScienceDaily, 15 September 2011. <www.sciencedaily.com/releases/2011/09/110915141224.htm>.
University of Bristol. (2011, September 15). Journey to the lower mantle and back: Minerals from ocean-floor rocks are found in ultra-deep diamonds. ScienceDaily. Retrieved September 22, 2014 from www.sciencedaily.com/releases/2011/09/110915141224.htm
University of Bristol. "Journey to the lower mantle and back: Minerals from ocean-floor rocks are found in ultra-deep diamonds." ScienceDaily. www.sciencedaily.com/releases/2011/09/110915141224.htm (accessed September 22, 2014).

Share This



More Earth & Climate News

Monday, September 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Will Climate Rallies Spur Change?

Will Climate Rallies Spur Change?

Newsy (Sep. 21, 2014) — Organizers of the People's Climate March and other rallies taking place in 166 countries hope to move U.N. officials to action ahead of their summit. Video provided by Newsy
Powered by NewsLook.com
Thousands March in NYC Over Climate Change

Thousands March in NYC Over Climate Change

AP (Sep. 21, 2014) — Accompanied by drumbeats, wearing costumes and carrying signs, thousands of demonstrators filled the streets of Manhattan and other cities around the world on Sunday to urge policy makers to take action on climate change. (Sept. 21) Video provided by AP
Powered by NewsLook.com
Climate Change Rally Held in India Ahead of UN Summit

Climate Change Rally Held in India Ahead of UN Summit

AFP (Sep. 20, 2014) — Some 125 world leaders are expected to commit to action on climate change at a UN summit Tuesday called to inject momentum in struggling efforts to tackle global warming. Duration: 00:41 Video provided by AFP
Powered by NewsLook.com
New Music With Recycled Instruments at Colombia Fest

New Music With Recycled Instruments at Colombia Fest

AFP (Sep. 19, 2014) — Jars, bottles, caps and even a pizza box, recovered from the trash, were the elements used by four musical groups at the "RSFEST2014 Sonorities Recycling Festival", in Colombian city of Cali. Duration: 00:49 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

More Coverage


Carbon Cycle Reaches Earth's Lower Mantle: Evidence of Carbon Cycle Found in 'superdeep' Diamonds From Brazil

Sep. 15, 2011 — The carbon cycle, upon which most living things depend, reaches much deeper into Earth than generally supposed -- all the way to the lower mantle, researchers ... read more
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins