Conductivity key to mapping water inside Earth

July 26, 2017
A mantle nodule collected from San Carlos, Arizona, brought to the surface during a deep volcanic eruption about 1 million years ago. Olivine, which is the focus of the LLNL study, is the predominant light green-colored mineral that is present in this rock. Credit: Wyatt Du Frane/LLNL

Hydrogen at elevated temperature creates high electrical conductivity in the Earth's mantle.

New work by Lawrence Livermore National Laboratory (LLNL) scientists shows the dispersal of (incorporated as hydrogen in olivine, the most abundant mineral in the ), could account for seen in the asthenosphere (part of the upper mantle just below the lithosphere that is involved in plate tectonic movement). The research appears in Scientific Reports .

The work could lead to a better understanding of present day water distribution in the mantle, which has strong implications for planetary dynamics and evolution. Researchers said such information might provide key evidence as to why Earth is the only known planetary body in our solar system to develop plate tectonics and to retain liquid water oceans on its surface.

"We approached the problem from a different perspective, using new hydrogen diffusion measurements to infer what the contribution of hydrogen would be to electrical conductivity," said LLNL's Wyatt Du Frane, the principal investigator on the project. "Our experiments on olivine indicated a larger temperature dependence than previously thought to occur for this phenomenon. The contribution of hydrogen to electrical conductivity, while modest at lower temperatures, becomes quite large at the temperatures expected to occur in the mantle."

Minerals formed deep in the mantle and transported to the Earth's surface contain tens to hundreds of parts per million in weight (ppm wt) of water, providing evidence for the presence of dissolved water in the Earth's interior. Even at these low concentrations, water greatly affects the physico-chemical properties of mantle materials. The diffusion of hydrogen controls the transport of water in the Earth's upper , but until now was not fully understood for olivine.

Earth's hydrosphere is a distinctive feature of our planet where massive oceans affect its climate and support its ecosystem. The distribution of water on Earth is not limited to its outermost shell (hydrosphere and hydrated minerals), but extends to great depths within the planet. Downwelling oceanic lithosphere (at subduction zones) and upwelling magmas (at , volcanoes and hotspots) are vehicles for transport of H2O between the surface and the Earth's deep interior.

"The amount of hydrogen required to match geophysical measurements of electrical conductivity inside Earth are in line with the concentrations that are observed in oceanic basalts. This demonstrates that of are a promising tool for mapping out water distributions deep inside the Earth," Du Frane said.

Explore further: Study suggests mid-mantle holds as much water as Earth's oceans

More information: Davide Novella et al. Hydrogen self-diffusion in single crystal olivine and electrical conductivity of the Earth's mantle, Scientific Reports (2017). DOI: 10.1038/s41598-017-05113-6

Related Stories

Is there an ocean beneath our feet?

January 27, 2014

(Phys.org) —Scientists at the University of Liverpool have shown that deep sea fault zones could transport much larger amounts of water from the Earth's oceans to the upper mantle than previously thought.

New timeline proposed for plate tectonics

May 11, 2017

Earth's history should include 'pre-plate tectonic' and 'plate tectonic' phases beginning less than a billion years ago, according to a team of geoscientists in the journal Geology.

Recommended for you

The world needs to rethink the value of water

November 23, 2017

Research led by Oxford University highlights the accelerating pressure on measuring, monitoring and managing water locally and globally. A new four-part framework is proposed to value water for sustainable development to ...

'Lost' 99% of ocean microplastics to be identified with dye?

November 23, 2017

The smallest microplastics in our oceans – which go largely undetected and are potentially harmful – could be more effectively identified using an innovative and inexpensive new method, developed by researchers at the ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.