Nav: Home

There and back again: Mantle xenon has a story to tell

August 08, 2018

The Earth has been through a lot of changes in its 4.5 billion year history, including a shift to start incorporating and retaining volatile compounds from the atmosphere in the mantle before spewing them out again through volcanic eruptions.

This transport could not have begun much before 2.5 billion years ago, according to new research by Washington University in St. Louis, published in the August 9 issue of the journal Nature.

"Life on Earth cares about changes in the volatile budget of the surface," said Rita Parai, assistant professor of geochemistry in Earth and Planetary Sciences in Arts & Sciences and first author of the study. "And there's an interplay between what the deep Earth was doing and how the surface environment changed over billion-year timescales."

Volatiles -- such as water, carbon dioxide and the noble gases -- come out of the mantle through volcanism and may be injected into the Earth's interior from the atmosphere, a pair of processes called mantle degassing and regassing. The exchange controls the habitability of the planet, as it determines the surface availability of compounds that are critical to life -- such as carbon, nitrogen and water.

The new model presented by Parai and collaborator Sujoy Mukhopadhyay, of the University of California, Davis, also establishes a range of dates during which the Earth shifted from a net degassing regime -- again, think about those oozy volcanoes -- to one that tilted the balance to net regassing potentially enabled by subduction, the conveyor-belt action of tectonic plates.

Mechanical properties change as water is added or removed from the mantle, so the onset of regassing had an important effect on the internal churning of the mantle, known as convection, which controls plate motions at the surface, Parai said.

Parai uses noble gases to address questions about how planetary bodies form and evolve over time. In this new research, she modeled the fate and transport of volatile compounds into the Earth's mantle using xenon isotopes as tracers.

"Xenon is an excellent volatile tracer, because all minerals that carry water also carry xenon," Parai said. "So if xenon regassing was negligible, water regassing must also have been negligible during the Archean (4 billion-2.5 billion years ago)."

Substantial regassing began sometime between a few hundred million to 2.5 billion years ago, the researchers found.

If plate tectonics and subduction began earlier than 2.5 billion years ago, then perhaps by then the Earth's interior had cooled sufficiently for volatiles to remain in subducting plates, rather than getting released and percolating back to the surface through magmatism, Parai suggests.

"Most people rarely have an occasion to think about volatiles trapped in the Earth's interior," Parai said. "They're present at low concentrations, but the mantle is huge in terms of mass. So for the Earth's total volatile budget, the mantle is an important reservoir."

She plans to focus her future research on pushing the limits of precision in xenon isotopic measurements in a variety of geological samples.

"The more observational constraints we have, the better," she said.
-end-


Washington University in St. Louis

Related Plate Tectonics Articles:

Plate tectonics goes global
A research team led by Dr. WAN Bo from the Institute of Geology and Geophysics (IGG) of the Chinese Academy of Sciences has revealed that plate tectonics went global 2 billion years ago.
Remixed mantle suggests early start of plate tectonics
New Curtin University research on the remixing of Earth's stratified deep interior suggests that global plate tectonic processes, which played a pivotal role in the existence of life on Earth, started to operate at least 3.2 billion years ago.
Why the Victoria Plate in Africa rotates
The East African Rift System is a newly forming plate tectonic boundary at which the African continent is being separated into several plates.
Evidence for plate tectonics on earth prior to 3.2 billion years ago
New research indicates that plate tectonics may have been well underway on Earth more than 3.2 billion years ago, adding a new dimension to an ongoing debate about exactly when plate tectonics began influencing the early evolution of the planet.
Upper-plate earthquakes caused uplift along New Zealand's Northern Hikurangi Margin
Earthquakes along a complex series of faults in the upper plate of New Zealand's northern Hikurangi Subduction Margin were responsible for coastal uplift in the region, according to a new evaluation of local marine terraces.
Breathing? Thank volcanoes, tectonics and bacteria
A Rice University study in Nature Geoscience suggests Earth's first burst of oxygen was added by a spate of volcanic eruptions brought about by tectonics.
What drives plate tectonics?
Scientists found ''switches'' between continental rupture, continental collision, and oceanic subduction initiation in the Tethyan evolution after a reappraisal of geological records from the surface and new global-scale geophysical images at depth.
Plate tectonics may have driven 'Cambrian Explosion, study shows
The quest to discover what drove one of the most important evolutionary events in the history of life on Earth has taken a new, fascinating twist.
Zipingpu Reservoir reveals climate-tectonics interplay around 2008 Wenchuan earthquake
A new study led by Prof. JIN Zhangdong from the Institute of Earth Environment (IEE) of the Chinese Academy of Sciences provided a new insight on the interplay between climate and tectonics from a sediment record in the Zipingpu Reservoir around the 2008 Wenchuan earthquake.
How to keep fish in the sea and on the plate
Temporary bans on fishing can be better than permanent ones as a way of allowing fish stocks in an area to recover, while still providing enough to eat, a research team has found.
More Plate Tectonics News and Plate Tectonics Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Debbie Millman: Designing Our Lives
From prehistoric cave art to today's social media feeds, to design is to be human. This hour, designer Debbie Millman guides us through a world made and remade–and helps us design our own paths.
Now Playing: Science for the People

#574 State of the Heart
This week we focus on heart disease, heart failure, what blood pressure is and why it's bad when it's high. Host Rachelle Saunders talks with physician, clinical researcher, and writer Haider Warraich about his book "State of the Heart: Exploring the History, Science, and Future of Cardiac Disease" and the ails of our hearts.
Now Playing: Radiolab

Insomnia Line
Coronasomnia is a not-so-surprising side-effect of the global pandemic. More and more of us are having trouble falling asleep. We wanted to find a way to get inside that nighttime world, to see why people are awake and what they are thinking about. So what'd Radiolab decide to do?  Open up the phone lines and talk to you. We created an insomnia hotline and on this week's experimental episode, we stayed up all night, taking hundreds of calls, spilling secrets, and at long last, watching the sunrise peek through.   This episode was produced by Lulu Miller with Rachael Cusick, Tracie Hunte, Tobin Low, Sarah Qari, Molly Webster, Pat Walters, Shima Oliaee, and Jonny Moens. Want more Radiolab in your life? Sign up for our newsletter! We share our latest favorites: articles, tv shows, funny Youtube videos, chocolate chip cookie recipes, and more. Support Radiolab by becoming a member today at Radiolab.org/donate.