Researchers help define Southern Ocean's geological features

February 08, 2019

New data collected by University of Wyoming researchers and others point to a newly defined mantle domain in a remote part of the Southern Ocean.

UW Department of Geology and Geophysics Professor Ken Sims and recent Ph.D. graduate Sean Scott are co-authors of an article, "An isotopically distinct Zealandia-Antarctic mantle domain in the Southern Ocean," published by the scientific journal Nature Geoscience in January.

"The Australian-Antarctic Ridge is the remotest mid-ocean ridge in the world's oceans and one of the last explored ridge segments, and, lo and behold, our isotope measurements of the samples we collected provided us with quite a surprise -- an entirely new domain in the Earth's mantle," Sims says.

The two were part of a group investigating the Australian-Antarctic Ridge (AAR) that included researchers from the United States, South Korea and France. Known as the last gap in the mapping and sampling of seafloor spreading centers, AAR is a 1,200-mile expanse in the most remote parts of the ocean ridge system. Specifically, the team was looking to resolve questions surrounding the boundaries of Earth's mantle domains as seen in ocean basalt formations created during mantle melting.

Those basalt formations are pushed up from the Earth's mantle beneath the Indian and Pacific oceans through the ridges and have distinct isotopic compositions. That has created a long-accepted boundary at the Australian-Antarctic Discordance along the Southeast Indian Ridge. This boundary has been widely used to place constraints on large-scale patterns of the mantle flow and composition in the Earth's upper mantle. However, sampling between the Indian and Pacific ridges was lacking, because of difficulty in obtaining samples.

Now, Sims, Scott and company present data from the region that show the ridge has isotopic compositions distinct from both the Pacific and Indian mantle domains. The data define a separate Zealandia-Antarctic domain that appears to have formed in response to the deep mantle upwelling and ensuing volcanism that led to the breakup of ancient supercontinent Gondwana around 90 million years ago. The Zealandia-Antarctic domain currently persists at the margins of the Antarctic continent.

The group surmises that the relatively shallow depths of the AAR may be the result of this deep mantle upwelling, and large offset transformations to the east may be its boundary with the Pacific domain.

University of Wyoming

Related Mantle Articles from Brightsurf:

Distinct slab interfaces found within mantle transition zone
Prof. CHEN Qifu's group from the Institute of Geology and Geophysics, Chinese Academy of Sciences (IGGCAS) and their collaborators observed two distinct seismic discontinuities within the mantle transition zone (~410 km to 660 km) beneath the western Pacific.

FSU geologists publish new findings on carbonate melts in Earth's mantle
Geologists from Florida State University's Department of Earth, Ocean and Atmospheric Science have discovered how carbon-rich molten rock in the Earth's upper mantle might affect the movement of seismic waves.

Is the Earth's transition zone deforming like the upper mantle?
In a recently published paper in Earth and Planetary Science Letters, researchers from the Geodynamics Research Center, Ehime University and the University of Lille combine numerical modeling of dislocation glide and results from diffusion experiments to revisit the rheology of wadsleyite, ringwoodite and majorite garnet under geological strain rates across the transition zone of the Earth's mantle based on theoretical plasticity modeling.

Simulations reveal how saltwater behaves in Earth's mantle
Giulia Galli's complex computer simulations reveal how saltwater behaves in the Earth's mantle, affecting everything from magma production to the carbon cycle.

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.

Volcanic activity and changes in Earth's mantle were key to rise of atmospheric oxygen
Evidence from rocks billions of years old suggest that volcanoes played a key role in the rise of oxygen in the atmosphere of the early Earth.

The lower mantle can be oxidized in the presence of water
In regions at depths greater than 1900 kilometers, scientists found active interactions between water and mantle rocks, which are oxidizing Earth's mantle.

Quantum mechanical simulations of Earth's lower mantle minerals
The theoretical mineral physics group of Ehime University led by Dr.

Heat transport property at the lowermost part of the Earth's mantle
Lattice thermal conductivities of MgSiO3 bridgmanite and postperovskite (PPv) phases under the Earth's deepest mantle conditions were determined by quantum mechanical computer simulations.

Viscosity measurements offer new insights into the earth's mantle
An international research group with Dr. Longjian Xie from the Bavarian Research Institute of Experimental Geochemistry & Geophysics (BGI) of the University of Bayreuth has succeeded for the first time in measuring the viscosity that molten solids exhibit under the pressure and temperature conditions found in the lower earth mantle.

Read More: Mantle News and Mantle Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to