Coupled trace element and isotope enrichment in the Cook-Austral-Samoa Islands, Southwest Pacific

Coupled trace element and isotope enrichment in the Cook-Austral-Samoa Islands, Southwest Pacific
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DOI：
10.1016/0012-821x(86)90185-8
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发表时间：
1986-09
期刊：
--
影响因子：
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通讯作者：
Z. Palacz;Andrew D. Saunder
Z. Palacz;Andrew D. Saunder
中科院分区：
其他
文献类型：
--
作者：
Z. Palacz;Andrew D. Saunder

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提供了西南太平洋库克-澳大利亚-萨摩亚群岛内八个岛屿的 Pb-Sr-Nd 同位素和微量元素组合数据。这些数据揭示了 OIB 地幔内存在两种地球化学上不同的成分。以 Mangaia 岛和 Tubuai 岛为代表的 Mangaia 部分具有极高放射性的 Pb 同位素，但 87Sr/86Sr 含量较低。以萨摩亚为代表的Dupal组分，87Sr/86Sr较高，Pb比较低，富集207Pb和208Pb。 Dupal 成分的 Nd 同位素比略低于 Mangaia。 Dupal 同位素富集与相对于 Mangaia 的高 LIL/HFS 元素比率相结合。 Mangaia 同位素富集与与 MORB 相当或低于 MORB 的低 LIL/HFS 元素比率相关，并表明源中 LIL 元素的时间积分消耗。然而，推断的低 ThU 和 PbNb 比率表明，相对于 MORB，Mangaia 富含 U，但缺乏 Pb。有人认为 Mangaia 可能源自热液蚀变、俯冲的 MORB。 Dupal 成分可能包括再循环的次大陆岩石圈。
Combined Pb-Sr-Nd isotope and trace element data are presented for eight islands within the Cook-Austral-Samoa island archipelago, southwest Pacific. These data reveal the presence of two geochemically distinct components within the OIB mantle. The Mangaia component represented by the islands of Mangaia and Tubuai has extremely radiogenic Pb isotopes but low87Sr/86Sr . A Dupal component represented by Samoa has high87Sr/86Sr , with low Pb ratios which are enriched in207Pb and208Pb. Nd isotope ratios of the Dupal component are slightly lower than for Mangaia. The Dupal isotope enrichment is coupled with high LIL/HFS element ratios relative to Mangaia. The Mangaia isotope enrichment is associated with low LIL/HFS element ratios comparable with or lower than MORB and indicates a time-integrated depletion in LIL elements in the source. However, inferred lowThU, and PbNb ratios indicate that Mangaia has been enriched in U but depleted in Pb relative to MORB. It is suggested that Mangaia could be derived from hydrothermally altered, subducted MORB. The Dupal component may include recycled subcontinental lithosphere.