Subscribe free to our newsletters via your
. 24/7 Space News .




CARBON WORLDS
Journey to the lower mantle and back
by Staff Writers
Bristol UK (SPX) Sep 19, 2011


File image.

The theory of plate tectonics is at the centre of our understanding of how the 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 the Earth's mantle. What is not so well known is the fate of these subducted plates.

In this week's edition of 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 the 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 Debora 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."

'Deep Mantle Cycling of Oceanic Crust: Evidence from Diamonds and their Mineral Inclusions' by M.J. Walter, S.C. Kohn, D. Araujo, G.P. Bulanova, C.B. Smith, E. Gaillou, J. Wang, A. Steele and S.B. Shirey in Science.

.


Related Links
University of Bristol
Carbon Worlds - where graphite, diamond, amorphous, fullerenes meet






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle








CARBON WORLDS
Carbon cycle reaches Earth's lower mantle
Washington DC (SPX) Sep 19, 2011
The carbon cycle, upon which most living things depend, reaches much deeper into the Earth than generally supposed-all the way to the lower mantle, researchers report. The findings, which are based on the chemistry of an unusual set of Brazilian diamonds, will be published online by the journal Science, at the Science Express Web site, on 15 September. Science is published by AAAS, the non ... read more


CARBON WORLDS
United Launch Alliance Launches GRAIL Spacecrafts To Moon

NASA launches twin spacecraft to study Moon's core

Second bid to launch NASA's Moon-bound spacecraft

NASA to launch Moon-bound twin spacecraft

CARBON WORLDS
Opportunity on verge of new discovery

Opportunity Studies Chester Lake Rock Outcrop

Opportunity Inspects Next Rock at Endeavour

Opportunity Continues Early Exploration Of Endeavour Crater Rim

CARBON WORLDS
Astronauts dive deep in practice for asteroid visit

Virgin aims for first space launch within 12 months

Statement on Importance of Supporting Planetary Exploration

NASA Offers Shuttle Tiles And Space Food To Schools And Universities

CARBON WORLDS
Tiangong: Better Late Than Lost

Tiangong 1 might be launched in late September

Chang'e-2 moon orbiter travels around L2 in outer space

China State media says Tiangong 1 to launch in early Sept

CARBON WORLDS
Private US capsule not to dock with ISS

Crew safely returns to Earth after crash

Russia postpones next manned launch to ISS

Russia announces launch of 2 spacecraft in Oct-Nov

CARBON WORLDS
Arianespace to launch up to four satellites for DIRECTV

Build-up is underway for the no. 1 Soyuz to be launched from French Guiana

Space Systems/Loral Delivers ViaSat-1 Broadband Satellite to Launch Base

Arianespace to launch BepiColombo spacecraft

CARBON WORLDS
Astronomers confirm first planet orbiting two stars

Astronomers find extreme weather on an alien world

Latest Exoplanet Haul Includes Super Earth At Habitat Zone Edge

Invisible World Discovered

CARBON WORLDS
Vesta an asteroid full of surprises

Latest Tumbling Satellite Fails to Warrant Space Intercept

Google opening smartphone wallets

US satellite may crash back to Earth Sept 23: NASA




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement