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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Temporal source evolution and crustal contamination at Lopevi Volcano, Vanuatu Island Arc
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Temporal source evolution and crustal contamination at Lopevi Volcano, Vanuatu Island Arc

机译：瓦努阿图岛弧形洛佩维火山的时间来源演变和地壳污染

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摘要

Here we present a new geochemical study of Lopevi volcano, one the most active volcanoes in the Vanuatu island arc. We focus on the temporally well-defined sequence of lava flows emitted since 1960, and for the first time, on pre-1960 volcanic products, including high-MgO basalts and felsic andesites, the most evolved lavas sampled so far on this island. This work reports the first Pb and Hf isotopic study of lavas from Lopevi island. These lavas display correlations between differentiation indexes such as SiO_2 content and isotopic ratios. The felsic andesites extend the known correlations with both the least (Sr-Pb) and the most (Nd-Hf) radiogenic isotopic compositions on the island. Our results confirm that the rising magma interacted with the sub-arc crust. Assimilation-Fractional Crystallization (AFC) quantitative modeling of trace element ratios and isotopic compositions requires 1% and 10% of assimilated partial melts of a mafic oceanic crust to account for the pre- and post-1960 lavas, respectively. The post-1960 lavas differ from the former lavas emitted -20 years earlier by enrichments in fluid mobile elements (K, Ba, Rb...), Th, and Light Rare Earth Elements (LREE). We ascribe these features to slight variations in the meta-somatic agent added to the sub-arc mantle and ultimately derived from the subducted lithosphere. However, the contrasting time scales involved in subducted lithosphere dehydration and magma genesis, relative to the time elapsed between eruptions of the two lava series, suggest that two different portions of mantle which have undergone slightly different metasomatism, gave birth to the Lopevi lavas. These distinct magmas are still present beneath the volcano.
机译：在这里，我们介绍了Lopevi火山的新地球化学研究，该火山是瓦努阿图岛弧线上最活跃的火山之一。我们关注的是自1960年以来散发出来的熔岩流在时间上定义明确的序列，并且首次关注了1960年前的火山产物，包括高MgO玄武岩和长英质安山岩，这是迄今为止在该岛上采样最迅速的熔岩。这项工作报告了洛佩维岛熔岩的第一个Pb和Hf同位素研究。这些熔岩显示出诸如SiO_2含量和同位素比率之类的分化指数之间的相关性。长英质安山岩与岛上最少的（Sr-Pb）和最多的（Nd-Hf）放射性同位素组成扩展了已知的相关性。我们的结果证实上升的岩浆与弧下地壳相互作用。微量元素比率和同位素组成的同化-破碎结晶（AFC）定量建模需要1％和10％的镁铁质洋壳的同化部分熔体来分别解释1960年前和之后的熔岩。 1960年后的熔岩与20年前排放的前熔岩的不同之处在于，它们富含流体可移动元素（K，Ba，Rb ...），Th和轻稀土元素（LREE）。我们将这些特征归因于添加到弧下地幔中并最终源自俯冲岩石圈的超体细胞因子的细微变化。然而，相对于两个熔岩系列喷发之间所经历的时间，俯冲的岩石圈脱水和岩浆成因所涉及的相对时间尺度表明，经历了些微交代作用的地幔的两个不同部分催生了洛佩维熔岩。这些独特的岩浆仍存在于火山下面。

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    Aurelien Beaumais; Gilles Chazot; Laure Dosso; Herve Bertrand;

  • 作者单位

    Universite de Brest (UBO), UMR 6538, Domaines Oceaniques, Institut Universitaire Europeen de la Mer, place Copernic, 29280 Plouzane, France;

    Universite de Brest (UBO), UMR 6538, Domaines Oceaniques, Institut Universitaire Europeen de la Mer, place Copernic, 29280 Plouzane, France;

    CNRS-UMR6538, Ifremer, Departement Geosdences Marines, 29280 Plouzane, France;

    UMR-CNRS 5570, Laboratoire de Geologie de Lyon, Ecole Normale Superieure de Lyon et Universite Lyon 1, 69364 Lyon, France;

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  • 关键词

    Lopevi; Vanuatu; Geochemistry; Isotopes; Subduction; Mantle source;

    机译：洛佩维;瓦努阿图地球化学;同位素;俯冲地幔源;

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