Unraveling Mantle Heterogeneity through Advanced Plate Tectonic Reconstructions

Published in Commun. Earth Environ., Qian et al. study isotopic heterogeneity in Earth's mantle by isotopic composition of basalts reconstructed to their original location, highlighting how the Philippine Sea Plate's northward movement across different mantle domains influences its composition.
Unraveling Mantle Heterogeneity through Advanced Plate Tectonic Reconstructions
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This is an English-Chinese bilingual summary for the paper. 此文為以上期刊文章的中英雙語簡介。

Geologists have long recognized the heterogeneity of the Earth's mantle. Basalts, whether formed at mid-ocean ridges or other magmatic contexts, carry distinct geochemical signatures that reflect their mantle origins. By analyzing isotopes such as lead, neodymium, and hafnium in these rocks, distinct geochemical characteristics emerge, delineating various mantle regions. Notably, the isotopic ratio of 208Pb/204Pb in basalts from the Indian Ocean's mid-ocean ridge differs markedly from those of the East Pacific Rise, indicating the existence of distinct mantle domains—specifically, the Pacific and Indian domains. Recent research in 2019 introduced another domain: the Zealandia-Antarctic domain, located between the Indian and Pacific domains, identified through basalts sourced from the Southern Ocean, Tonga, New Zealand, and nearby southern hemisphere regions.

Traditionally, studies have focused on zero-age or Quaternary basalts to investigate mantle heterogeneity, primarily because these samples are minimally affected by plate tectonic complexities. However, over geological timescales, the extensive movement of tectonic plates necessitates the adjustment of older basalts to their original locations.

Qian et al. leverages digital plate tectonic reconstructions to address the challenges posed by the movement of older basalts. This approach allows them to more comprehensively reconstruct the spatial distribution of the Zealandia-Antarctic domain. Furthermore, their findings reveal the dynamic history of the Philippine Sea Plate, which initially traversed the Zealandia-Antarctic domain before moving into the Indian Domain. This tectonic journey resulted in the older western side of the Philippine Sea Plate predominantly comprising basalts from the Zealandia-Antarctic domain, whereas the younger eastern side features basalts from the Indian Domain.

For a longer summary, please see the link below:

https://communities.springernature.com/posts/secrets-of-the-mantle-underworld-revealed-by-magmatic-rocks-on-the-philippine-sea-earth-s-fastest-tectonic-plate

地球的地函並非均質是地質學界長久以來的共識。以中洋脊玄武岩為主、由上部地函源區產生的玄武岩繼承了岩漿源區地質化學特徵,彷彿直接從地函取樣帶至地殼上。前人對這些玄武岩中的鉛、釹、鉿等同位素進行研究,揭示了地函不同地區的獨特化學特性。例如,印度洋中洋脊的208Pb/204Pb比值高於東太平洋洋脊,加上其他相異的同位素化學特徵,顯示了太平洋和印度兩大異質性區域的存在。2019年,科學家們在南半球印度洋與太平洋之間的區域,包括南極冰洋、東加群島及紐西蘭,發現了名為Zealandia-Antarctic domain的新地函異質性區。
過去研究者通常選擇地質時代近期形成的玄武岩來研究地函異質性,因是板塊運動在地質時間尺度下會造成顯著的物質遷移,玄武岩形成後也將隨著板塊遷移,離開原本的地函源區。因此,若要使用較古老的玄武岩,則必須將它們重建至對應其地函源區的原始位置;否則就如同「刻舟求劍」的古諺所示:在疾駛的船上劃下刻痕無法協助找尋掉入水中的劍。
Qian et al.利用數位板塊重建技術解決了這一問題,從而能夠利用更多老玄武岩的同位素數據,更完整地重建Zealandia-Antarctic domain的空間分布。此外,該研究發現菲律賓海板塊在向北移動的過程中,先經過Zealandia-Antarctic domain,再進入Indian Domain,這一過程導致其西半部主要由Zealandia-Antarctic domain的玄武岩組成,東半部則主要是Indian Domain的玄武岩。
更詳盡的介紹請見以下連結:

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Earth Sciences
Physical Sciences > Earth and Environmental Sciences > Earth Sciences
Geology
Physical Sciences > Earth and Environmental Sciences > Earth Sciences > Geology
Geochemistry
Life Sciences > Biological Sciences > Ecology > Environmental Chemistry > Geochemistry

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