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New Insights on Oceanic Plates and the Mantle Transition Zone
Recent research has unveiled the impact of ancient tectonic activities on the composition of oceanic plates, which in turn affects their movement and velocity as they descend into the Earth’s mantle.
The mantle transition zone (MTZ), located between 410 and 660 kilometers deep, serves as a crucial passage for materials moving into the deeper mantle. Within this zone, the presence of large basaltic rock formations can lead to a slowdown or stagnation of subducting plates, which are those that slip beneath others, rather than allowing a seamless transition into the lower mantle. While previous studies have identified basalt reservoirs in the MTZ, their origins had largely remained a mystery until now.
An international team of seismologists, spearheaded by researchers from the University of Southampton, has uncovered evidence of a remarkably thick MTZ that can only be attributed to substantial basaltic material. This discovery indicates that in certain areas, entire oceanic slabs could contain notable amounts of basalt, with thicknesses reaching approximately 100 kilometers.
The research findings, which are detailed in the journal Nature, enhance our comprehension of the subduction process, which plays a vital role in recycling materials and volatile components deep within Earth’s structure. This process is essential for the long-term stability of climate, maintenance of atmospheric balance, and overall habitability of our planet over billions of years.
This significant study is part of the VoiLA (Volatiles in the Lesser Antilles) project, where the research team installed 34 seismometers on the ocean floor in the region of the Lesser Antilles.
Dr. Catherine Rychert, a key member of the research team now affiliated with the Woods Hole Oceanographic Institution, remarked, “This marks the first large-scale seismic experiment conducted on the ocean floor in an Atlantic subduction zone. Our findings revealed an unexpectedly thick mantle transition zone, measuring around 330 kilometers beneath the Antilles, making it one of the thickest transition zones documented globally. While the Caribbean is renowned for its pleasant climate and scenic beaches, it now holds an important position in the field of plate tectonics.”
Dr. Nick Harmon, also formerly associated with the University of Southampton and currently at Woods Hole Oceanographic Institution, elaborated on the implications of their discoveries: “It’s fascinating to consider that tectonic plates exhibit a form of ‘memory’, influencing how they facilitate mantle convection and the recycling of material back into the Earth.”
Lead author Dr. Xusong Yang, who has transitioned from a visiting scholar at the University of Southampton to a position at the University of Miami, emphasized the importance of understanding the inherited compositional diversity of oceanic slabs. “This heterogeneity is crucial as it could significantly impact their ultimate outcomes within Earth’s deep interior,” he stated.
In addition to Dr. Rychert, Dr. Harmon, and Dr. Yang, the research team included Professor Saskia Goes from Imperial College London and Professor Andreas Reitbrock from Karlsruhe Institute of Technology. The experiment received funding from the Natural Environment Research Council (NERC) in the UK and the European Research Council (ERC).
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