Recovering Record-Breaking Mantle Rocks Could Redefine Earth’s History

Scientists’ groundbreaking discovery of mantle rocks is providing new insights into Earth’s volcanic activity, early cycles, and possibly the origins of life, marking a major advance in Earth science.

An international team has begun investigating the mantle’s role in supporting life on Earth, driving volcanic activity, and influencing global cycles.

Scientists have recovered the first long fragment of rock that originated in Earth’s mantle, the layer beneath the crust and the planet’s largest component. The rocks are expected to shed light on the mantle’s role in the origin of life on Earth, the volcanic activity that occurs when it melts, and its influence on global cycles of vital elements like carbon and hydrogen, according to the research team.

1,268 metres (4,160 ft) of nearly continuous mantle rock was extracted from a “tectonic window,” a section of the seafloor where mantle rocks are exposed along the Mid-Atlantic Ridge, during Expedition 399 of the “Building Blocks of Life, Block Atlantis” drilling vessel in the ocean. Guedes decision In spring 2023.

With attempts dating back to the early 1960s, the extraction was a record-breaking achievement led by the International Ocean Discovery Program, an international marine research consortium of more than two dozen nations that retrieves cylindrical samples of sediment and rock from the ocean floor to study Earth’s history.

The rocks extracted from the mantle are more similar to those found on early Earth than the more common rocks that make up our continents today, researchers say. Image credit: Professor Johan Lissenberg

Analysis of recovered rocks

Since then, the mission team has compiled an inventory of rocks extracted from the mantle to understand their composition, structure and context.

Their results were presented in the journal. sciencesThis study reveals a longer history of melting in the recovered rocks than expected.

Lead author Professor Johan Lissenberg from Cardiff University’s School of Earth and Environmental Sciences said: “When we recovered the rocks last year, it was a major achievement in the history of Earth science, but more importantly, their value lies in what mantle cores can tell us about the formation and evolution of our planet. Our study begins by looking at the composition of the mantle by documenting the minerals in the recovered rocks, as well as their chemical composition. Our results are different from what we expected. There is much less pyroxene in the rocks, and the rocks have very high concentrations of magnesium, both of which are the result of much higher amounts of melt than we expected.”

Professor Johan Lissenberg (left) and colleagues analyze cores retrieved from a “tectonic window” on the Mid-Atlantic Ridge. Image credit: Leslie Anderson, Exp. 399, JRSO_IODP

This melting occurred when the mantle rose from the deep parts of the Earth towards the surface.

The researchers say the results of further analysis of this process could have major implications for understanding how magma forms and how it leads to volcanic activity.

“We also found channels through which magma was transported through the mantle, so we can trace the fate of magma after it forms and travels to the surface. This is important because it tells us how the mantle melts and feeds volcanoes, especially those at the bottom of the oceans, which account for most of the volcanic activity on Earth. Access to these mantle rocks will allow us to establish the connection between volcanoes and the ultimate source of magma.”

Possible link to the origin of life

The study also provides preliminary results on how peridot, a mineral abundant in mantle rocks, interacts with seawater, triggering a series of chemical reactions that produce hydrogen and other molecules that could fuel life.

Scientists believe this may have been one of the fundamental processes in the origin of life on Earth.

“The rocks that were on the early Earth are much more similar to those we recovered during this mission than to the more common rocks that make up our continents today,” said Dr. Susan Q. Lang, an associate scientist in geology and geophysics at Woods Hole Oceanographic Institution, who was a co-scientist on the expedition and is part of a team that continues to analyze rock and fluid samples.

Expedition 399 “Building Blocks of Life, Atlantis Block” of the ocean drilling vessel JOIDES Resolution recovered 1,268 meters of nearly continuous mantle rock in spring 2023. Copyright: Thomas Runge (Expedition 399, JRSO_IODP)

“Analysis of these data gives us critical insight into the chemical and physical environments that existed early in Earth’s history, which may have provided a steady source of fuel and favorable conditions over long geological time periods to host the earliest forms of life.”

The international team of more than 30 scientists from the JOIDES Resolution mission will continue their research on the recovered drill samples to address a wide range of problems.

Dr Andrew McCaig, Associate Professor in the School of Earth and Environment at the University of Leeds, who was the lead proponent of Expedition 399 and the mission’s co-chief scientist, added: “Everyone involved in Expedition 399, from the first proposal in 2018, can be proud of the achievements documented in this paper. Our new deep hole will be a department of sorts for decades to come in disciplines as diverse as mantle melting processes, rock-ocean chemical exchange, organic geochemistry and microbiology. All data from the mission will be fully available, setting a model for how international science should be conducted.”

Reference: “A Long Section of Depleted Serpentine Peridotite” by C. Johan Lissenberg, Andrew M. McCaig, Susan Q. Lang, Peter Bloom, Natsuo Abe, William J. Brazelton, Remi Coltat, Jeremy R. Deans, Kristen L. Dickerson, Margaret Godard, Barbara E. John, Frieder Klein, Rebecca Cohn, Kuan Yu Lin, Haiyang Liu, Ethan L. Lopez, Toshio Nozaka, Andrew J. Parsons, Vamdev Pathak, Mark K. Regan, Jordyn A. Robari, Evan B. Savov, Esther M. Schwarzenbach, Olivier J. Sisman, Gordon Southam, Feng Ping Wang, C. Jeffrey Witt, Leslie Anderson and Sarah Treadwell, August 8, 2024, sciences.
DOI: 10.1126/science.adp1058