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摘要:
西太平洋板内玄武岩主要是南太平洋中生代板内岩浆作用的产物。对西太平洋板内玄武岩和南太平洋板内玄武岩的对比研究有助于进一步揭示南太平洋超级地幔柱的性质及其时空演化规律。本文收集整理了西太平洋板内玄武岩的Sr，Nd，Pb同位素数据，并与南太平洋板内玄武岩对比。得到如下认识：(1)西太平洋板内玄武岩同位素组成极不均一，覆盖了所有的富集地幔端元，但主要表现为HIMU和EM-1两端元的混合特征；(2)与南太平洋板内玄武岩相比，西太平洋板内玄武岩的同位素组成的极端程度相对偏低，可能是其地幔源区各组分间混合更均匀的结果；(3)自约120 Ma以来，由于HIMU组分在西太平洋板内玄武岩中持续存在，而EM-1和EM-2型组分表现为断续出现，这可能暗示HIMU端元与两种富集端元在深部地幔中所处的空间不同。
Abstract:Most of the West Pacific intraplate basalts are the products of Mesozoic intraplate volcanisms in the South Pacific. The comparison made for the intraplate basalts in the West and South Pacific may reveal the characteristics and the evolution of the super plume in the South Pacific. Based on the previous data published on basalts in the West and South Pacific, we made a study of Sr-Nd-Pb isotopic geochemistry and compared the results from the two regions. The results show that: 1) The isotopic composition of the West Pacific intraplate basalts shows a great heterogeneity, almost covering all the enriched mantle end members, while most of the West Pacific intraplate basalts are the mixture of HIMU and EM-1; 2) Compared to the South Pacific, the isotopic composition of the West Pacific intraplate basalts is less extreme, which indicates a more thorough mixing between mantle end members; 3) Since ~120 Ma, the HIMU-type of basalts are continuous, while EM1-type and EM2-type basalts are intermittent, which may imply that the spatial distribution of HIMU is different from other enriched end members in the deep mantle.
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Key words:
- intraplate basalts /
- isotope /
- deep mantle /
- West Pacific
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