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首页> 外文期刊>Geochemistry, geophysics, geosystems >Geochemical evidence in the northeast Lau Basin for subduction of the Cook-Austral volcanic chain in the Tonga Trench
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Geochemical evidence in the northeast Lau Basin for subduction of the Cook-Austral volcanic chain in the Tonga Trench

机译：汤加海沟劳克盆地东北部俯冲库克-澳大利亚火山链的地球化学证据

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摘要

Lau Basin basalts host an array of geochemical signatures that suggest incorporation of enriched mantle source material often associated with intraplate hotspots, but the origin of these signatures remain uncertain. Geochemical signatures associated with mantle material entrained from the nearby Samoan hotspot are present in northwest Lau Basin lavas, and subducted seamounts from the Louisville hotspot track may contribute geochemical signatures to the Tonga Arc. However, lavas in the northeast Lau Basin (NELB) have unique enriched geochemical signatures that cannot be related to these hotspots, but can be attributed to the subduction of seamounts associated with the Cook-Austral volcanic lineament. Here we present geochemical data on a new suite of NELB lavasranging in Ar-40/Ar-39 age from 1.3 Ma to 0.365 kathat have extreme signatures of geochemical enrichment, including lavas with the highest Pb-206/Pb-204 (19.580) and among the lowest Nd-143/Nd-144 (0.512697) encountered in the Lau Basin to date. These signatures are linked to the canonical EM1 (enriched mantle 1) and HIMU (high-=U-238/Pb-204) mantle end-members, respectively. Using a plate reconstruction model, we show that older portions of the traces of two of the Cook-Austral hotspots that contributed volcanism to the Cook-Austral volcanic lineamentthe Rarotonga and Rurutu hotspotswere potentially subducted in the Tonga Trench beneath the NELB. The geochemical signatures of the Rarotonga, Rurutu, and Samoan hotspots provide a compelling match to the extreme geochemical components observed in the new NELB lavas.
机译：劳盆地的玄武岩具有一系列地球化学特征，这些特征暗示了通常与板内热点有关的富集地幔源物质的结合，但这些特征的起源仍不确定。 Lau盆地西北部的熔岩中存在与附近萨摩亚热点夹带的地幔物质相关的地球化学特征，路易斯维尔热点轨道的俯冲海山可能为汤加弧形成了地球化学特征。但是，东北Lau盆地（NELB）的熔岩具有独特的丰富的地球化学特征，这些特征与这些热点无关，但是可以归因于与库克-澳大利亚火山岩系相关的海山俯冲。在这里，我们介绍了Ar-40 / Ar-39年龄从1.3 Ma至0.365 ka的一组新的NELB熔岩的地球化学数据，这些熔岩具有地球化学富集的极端特征，包括Pb-206 / Pb-204（19.580）最高的熔岩和是迄今为止在Lau盆地中遇到的最低Nd-143 / Nd-144（0.512697）之中。这些签名分别与规范的EM1（富集地幔1）和HIMU（高= U-238 / Pb-204）地幔末端成员相关。使用板块重建模型，我们显示了在库克-澳大利亚火山岩系中造成火山作用的两个库克-澳大利亚热点的痕迹的较旧部分可能在NELB下方的汤加海沟中被俯冲了。拉罗汤加，鲁鲁图和萨摩亚热点地区的地球化学特征与新NELB熔岩中观察到的极端地球化学成分极具吸引力。

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