最新發表的研究指出許久以前的構造活動在海洋板塊內部造成的岩石成分異常，會影響其沉入地函時的速度與軌跡。
本研究區域的構造背景與用到的地震站。圖片來源:
Nature (2025). DOI: 10.1038/s41586-025-08754-0
地函過渡帶(mantle
transition zone, MTZ)位於地下410到660公里處，這個重要區域是物質進入地函深處的必經通道。地函過渡帶分佈著一些成分為玄武岩質的大型區域，它們會造成隱沒板塊(滑到另一個板塊下方的板塊)經過這裡時減速或停止下來，而不是直接沉到下部地函。雖然之前已經在地函過渡帶看到玄武岩質的儲集區域，但它們的起源卻還是不太清楚。
由南安普敦大學的研究人員(現在任職於伍茲霍爾海洋研究所)主持的國際地震學家團隊，提出了證據顯示他們找到一塊非常厚的地函過渡帶，其只能以該區域含有許多玄武岩質的成分來解釋。這項發現意謂在某些區域，整個海洋隱沒板塊(約100公里厚)都帶有大量玄武岩質的材料。
這篇發表於期刊《自然》(Nature)的發現讓我們對於板塊的隱沒作用有更多理解。此作用能把地表的物質和揮發性元素回收到地球內部深處，使得地球數十億年來可以維持氣候的長期穩定性、大氣成分的平衡以及生命的適居性。
這項突破性的研究是VoiLA(Volatiles
in the Lesser Antilles，小安地列斯群島的揮發性元素)計畫的一部分，執行此計畫的團隊在小安地列斯群島的海床裝設了34具地震儀。
「這是首次在大西洋的隱沒帶進行的大規模海底地震實驗，」Catherine
Rychert博士表示。她之前是南安普敦大學的副教授，現在則任職於伍茲霍爾海洋研究所。「我們並沒有預料到會在安地列斯群島下方發現厚度異常、約有330公里的地函過渡帶，這讓我們感到相當驚訝。在全世界觀察過的過渡帶中，這種厚度也是名列前茅。雖然加勒比海本來就因為陽光與沙灘而富有盛名，但它在板塊構造學的領域現在又有了新的名號。」
「板塊具有某種『記憶』並影響到它驅動地函對流以及把物質攪回地球內部的方式，這種想法實在是很瘋狂，」Nick Harmon博士表示。他之前是南安普敦大學的副教授，現在任職於伍茲霍爾海洋研究所。
主要作者Xusong
Yang之前是南安普敦大學的訪問學者，現在任職於邁阿密大學。他強調：「我們不能忽視傳承在隱沒海洋板塊內部的組成不均，這種性質可能對它進入地球內部之後最終的命運會是如何有相當大的影響。」
主持這項實驗的為之前任職於南安普敦大學的Kate
Rychert博士Nick
Harmon博士、倫敦帝國學院的Saskia
Goes教授、卡爾斯魯爾理工學院的Andreas
Reitbrock教授。經費來自NERC(英國自然環境研究委員會)與ERC(歐洲研究院)。
Sink or Swim: the
fate of sinking tectonic plates depends on their ancient tectonic histories
Newly published research has revealed
that compositional rock anomalies within oceanic plates caused by ancient
tectonics influence the trajectory and speed of the plates as they plunge deep
into Earth’s mantle.
Between depths of 410 and 660 kilometers lies the
mantle transition zone (MTZ), a critical region acting as a gateway for
materials entering Earth's deeper mantle. Large distributions of basalt rock
compositions within the MTZ can cause subducting plates—ones that slide beneath
other—to slow and/or stagnate within this zone, instead of descending directly
into the lower mantle. Although basalt reservoirs have previously been
discovered in the MTZ, their origins have remained unclear.
An international team of seismologists led by the
University of Southampton (and now at the Woods Hole Oceanographic Institution)
has provided evidence of an extremely thick MTZ, which can only be explained by
a large basaltic rock composition, suggesting that, in certain regions, entire
oceanic slabs—approximately 100 kilometers thick—can possess significant
basaltic material.
The findings, published in the journal Nature, provide a greater understanding
of plate subduction, which recycles surface materials and volatile elements
deep into the Earth's interior, sustaining long-term climate stability,
atmospheric balance, and the habitability of our planet over billions of years.
This groundbreaking research is part of the VoiLA
(Volatiles in the Lesser Antilles) project, in which the team deployed 34
seismometers on the ocean floor beneath the Lesser Antilles.
"This is the first large scale ocean bottom
seismic experiment conducted at an Atlantic subduction zone," said Dr.
Catherine Rychert, formerly an Associate Professor at the University of
Southampton and currently at the Woods Hole Oceanographic Institution. "We
were very surprised to find an unexpected and exceptionally thick—approximately
330 kilometers—mantle transition zone beneath the Antilles, which makes it one
of the thickest transition zones observed worldwide. Although the Caribbean is
well-known for its sunshine and beaches, it now has a new claim to fame in the
world of plate tectonics."
“It’s wild to think that in some ways tectonic plates
have a ‘memory’ and that affects the way the plates drive mantle convection and
mix material back into the Earth,” said Dr. Nick Harmon, formerly an Associate
Professor at the University of Southampton and currently at the Woods Hole
Oceanographic Institution.
Lead author, Dr. Xusong Yang, a former visiting
scholar at the University of Southampton and currently at University of Miami,
emphasized, "We cannot overlook the inherited compositional heterogeneity
of subducting oceanic slabs. It may greatly influence their ultimate fate in Earth's
deep interior.”
Dr. Kate Rychert and Dr. Nick Harmon, formerly of the
University of Southampton, Professor Saskia Goes from Imperial College London,
and Professor Andreas Reitbrock from Karlsruhe Institute of Technology, led the
experiment. The experiment was funded by NERC (Natural Environment Research
Council, UK) and the ERC (European Research Council).
原始論文：Xusong Yang,
Yujiang Xie, Catherine A. Rychert, Nicholas Harmon, Saskia Goes, Andreas
Rietbrock, Lloyd Lynch, Colin G. Macpherson, Jeroen Van Hunen, Jon Davidson,
Marjorie Wilson, Robert Allen, Jenny Collier, Jamie J. Wilkinson, Timothy J.
Henstock, John-Michael Kendall, Jonathan D. Blundy, Joan Latchman, Richard
Robertson. Seismic imaging of a basaltic Lesser Antilles slab from
ancient tectonics. Nature, 2025; DOI: 10.1038/s41586-025-08754-0
引用自：Woods Hole Oceanographic Institution.
"Sink or Swim: The fate of sinking tectonic plates depends on their
ancient tectonic histories."
