Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Rust under pressure could explain deep Earth anomalies

09.06.2016

Using laboratory techniques to mimic the conditions found deep inside the Earth, a team of Carnegie scientists led by Ho-Kwang "Dave" Mao has identified a form of iron oxide that they believe could explain seismic and geothermal signatures in the deep mantle. Their work is published in Nature.

Iron and oxygen are two of the most geochemically important elements on Earth. The core is rich in iron and the atmosphere is rich in oxygen, and between them is the entire range of pressures and temperatures on the planet.


An artwork depicting the decomposition of FeOOH in lower mantle conditions. The cycle starts from α-FeOOH (blue dot on the top) to its high-pressure form (brown dot), to FeO2 (center crystal) and hydrogen (cyan bubbles), and finally produce other minerals (bubbles on the left side).

Courtesy of Ms. Xiaoya

"Interactions between oxygen and iron dictate Earth's formation, differentiation--or the separation of the core and mantle--and the evolution of our atmosphere, so naturally we were curious to probe how such reactions would change under the high-pressure conditions of the deep Earth," said Mao.

The research team--Qingyang Hu, Duck Young Kim, Wenge Yang, Liuxiang Yang, Yue Meng, Li Zhang, & Ho-Kwang Mao--put ordinary rust, or FeOOH, under about 900,000 times normal atmospheric pressure and at about 3200 degrees Fahrenheit and were able to synthesize a form of iron oxide, FeO2, that structurally resembles pyrite, also known as fool's gold. The reaction gave off hydrogen in the form of H2.

FeOOH is found in iron ore deposits that exist in bogs, so it could easily move into the deep Earth at plate tectonic boundaries, as could samples of ferric oxide, Fe2O3, which along with water will also form the pyrite-like iron oxide under deep lower mantle conditions.

Why does this interest the researchers? For one thing, this type of reaction could have started in Earth's infancy, and understanding it could inform theories of our own planet's evolution, as well as its current geochemistry.

Furthermore, the H2 released in this reaction would work its way upward, possibly reacting with other materials on its way. Meanwhile, the iron oxide would settle planet's depths and form reservoirs of oxygen there, particularly if one of these patches of iron oxide moved upward along the pressure gradient to the middle part of the mantle and separated into iron and O2.

"Pools of free oxygen under these conditions could create many reactions and chemical phases, which might be responsible for seismic and geochemical signatures of the deep Earth," Mao explained.

"Our experiments mimicking mantle conditions demonstrate that more research is needed on this pyrite-like phase of iron oxide." Hu added.

The research team believes their findings could even offer an alternate explanation for the Great Oxygenation Event that changed Earth's atmosphere between 2 and 2.5 billion years ago. The rise of bacteria performing photosynthesis, which releases oxygen as a byproduct, is often considered the source of the rapid increase in atmospheric oxygen, which had previously been scarce. But releases of oxygen from upwelling of deep mantle FeO2 patches could provide an abiotic explanation for the phenomenon, they say.

###

Researchers were supported by the NSF and the National Natural Science Foundation of China.

Measurements were performed at the High Pressure Collaborative Access Team, Advanced Photon Source, Argonne National Laboratory, and the BL15U1 beamline, Shanghai Synchrotron Radiation Facility in China. Parts of the experiments were performed at the 13BM-C experimental station of the GeoSoilEnviroCARS facility at the APS. HPCAT operations are supported by the DOE-NNSA and by the DOE-BES, with partial instrumentation funding by the NSF. 13BM-C operation is supported by COMPRES through the Partnership for Extreme Crystallography (PX2) project, under an NSF Cooperative Agreement. APS is supported by the DOE-BES.

The Carnegie Institution for Science is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.

Media Contact

Ho-Kwang "Dave" Mao
hmao@carnegiescience.edu

 @carnegiescience

https://carnegiescience.edu/ 

Ho-Kwang "Dave" Mao | EurekAlert!

Further reports about: Atmosphere Earth's mantle Oxygen atmospheric pressure ferric oxide iron oxide

More articles from Earth Sciences:

nachricht Wintertime Arctic sea ice growth slows long-term decline: NASA
07.12.2018 | NASA/Goddard Space Flight Center

nachricht Why Tehran Is Sinking Dangerously
06.12.2018 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Topological material switched off and on for the first time

Key advance for future topological transistors

Over the last decade, there has been much excitement about the discovery, recognised by the Nobel Prize in Physics only two years ago, that there are two types...

Im Focus: Researchers develop method to transfer entire 2D circuits to any smooth surface

What if a sensor sensing a thing could be part of the thing itself? Rice University engineers believe they have a two-dimensional solution to do just that.

Rice engineers led by materials scientists Pulickel Ajayan and Jun Lou have developed a method to make atom-flat sensors that seamlessly integrate with devices...

Im Focus: Three components on one chip

Scientists at the University of Stuttgart and the Karlsruhe Institute of Technology (KIT) succeed in important further development on the way to quantum Computers.

Quantum computers one day should be able to solve certain computing problems much faster than a classical computer. One of the most promising approaches is...

Im Focus: Substitute for rare earth metal oxides

New Project SNAPSTER: Novel luminescent materials by encapsulating phosphorescent metal clusters with organic liquid crystals

Nowadays energy conversion in lighting and optoelectronic devices requires the use of rare earth oxides.

Im Focus: A bit of a stretch... material that thickens as it's pulled

Scientists have discovered the first synthetic material that becomes thicker - at the molecular level - as it is stretched.

Researchers led by Dr Devesh Mistry from the University of Leeds discovered a new non-porous material that has unique and inherent "auxetic" stretching...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

Expert Panel on the Future of HPC in Engineering

03.12.2018 | Event News

 
Latest News

Electronic evidence of non-Fermi liquid behaviors in an iron-based superconductor

11.12.2018 | Physics and Astronomy

Topological material switched off and on for the first time

11.12.2018 | Materials Sciences

NIST's antenna evaluation method could help boost 5G network capacity and cut costs

11.12.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>