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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Anomalous strontium and lead isotope signatures in the off-rift Orfajokull central volcano in south-east Iceland Evidence for enriched endmember(s) of the Iceland mantle plume?
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Anomalous strontium and lead isotope signatures in the off-rift Orfajokull central volcano in south-east Iceland Evidence for enriched endmember(s) of the Iceland mantle plume?

机译：冰岛东南部裂谷Orfajokull中央火山中的锶和铅同位素异常特征冰岛地幔柱末端成员丰富的证据？

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摘要

The currently active off-rift central volcano Orfajokull in south-east Iceland sits unconformably on much older (～10-12 Ma) and eroded crust. The composition of recent volcanics ranges from basalt to rhyolite, but the series is more sodic alkaline than the common rift zone tholeiitic suites. In this study we present Sr, Nd, Pb and O isotopic data for a suite of Orfajokull samples. The complete suite shows typical mantle values for oxygen isotopes. The ~(87)Sr/~(86)Sr ratios (average of 15 samples = 0.703702) of the modern Orfajokull rocks (basalts as well as rhyolites) are much higher than observed so far for any other Icelandic rocks. The ~(143)Nd/~(144)Nd ratios (average = 0.512947; n = 14) are lower than for rift rocks, but similar to rocks of the off-rift Snfellsnes volcanic zone. Furthermore, the Orfajokull rocks are enriched in the ~(207)Pb/~(204)Pb and ~(208)Pb/~(204)Pb isotope ratios compared to Icelandic rift basalts. The enriched nature of the suite indicates that Orfajokull samples a source component that has characteristics common with EM2 type mantle. Furthermore, it is concluded that the silicic rocks of Orfajokull formed by fractional crystallization from mafic melts rather than by partial melting of older crust.
机译：冰岛东南部目前活跃的离线中央火山Orfajokull位置不合时宜地位于年龄较大（约10-12 Ma）且地壳受到侵蚀的地方。最近的火山岩的成分从玄武岩到流纹岩，但该系列比普通的裂谷带变质岩组更具苏打碱性。在这项研究中，我们提供了一组Orfajokull样品的Sr，Nd，Pb和O同位素数据。完整的套件显示了氧同位素的典型地幔值。现代Orfajokull岩石（玄武岩和流纹岩）的〜（87）Sr /〜（86）Sr比（15个样品的平均值= 0.703702）比迄今为止任何其他冰岛岩石的观测值都高得多。 〜（143）Nd /〜（144）Nd的比率（平均值= 0.512947; n = 14）比裂谷岩石低，但与裂谷Snfellsnes火山带的岩石相似。此外，与冰岛裂谷玄武岩相比，Orfajokull岩石富含〜（207）Pb /〜（204）Pb和〜（208）Pb /〜（204）Pb同位素比。该套件的丰富特性表明Orfajokull对具有EM2型地幔共同特征的源组件进行了采样。此外，可以得出结论，奥法约库尔硅质岩是由镁铁质熔体的分步结晶而不是较旧地壳的部分熔融形成的。

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