| TANG Limei,DONG Yanhui,CHU Fengyou,CHEN Ling,MA Weilin,LIU Yonggang. 2019. Geochemistry and age of seamounts in the West Pacific: mantle processes and petrogenetic implications. Acta Oceanologica Sinica, 38(1):71－77 |
| Geochemistry and age of seamounts in the West Pacific: mantle processes and petrogenetic implications |
| 西太平洋海山年龄及地球化学:地幔过程及岩石成因 |
| Received:May 03, 2017 |
| DOI：10.1007/s13131-019-1371-0 |
| Key words:40Ar/39Ar ages geochemistry magmatic evolution basalts West Pacific |
| 中文关键词: 40Ar/39Ar年龄 地球化学 岩浆演化 玄武岩 西太平洋 |
| 基金项目:The National Basic Research Program (973 Program) of China under contract No. 2015CB755905; the National Natural Science Foundation of China under contract No. 41506070; the Scientific Research Fund of the Second Institute of Oceanography, SOA under contract Nos JG1803, JG1603 and JG1403; the Natural Science Foundation of Zhejiang Province of China under contract No. LQY18D060002. |
| Author Name | Affiliation | E-mail | | TANG Limei | Key Laboratory of Submarine Geosciences, Ministry of Natural Resources, Hangzhou 310012, China
Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China | | | DONG Yanhui | Key Laboratory of Submarine Geosciences, Ministry of Natural Resources, Hangzhou 310012, China
Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China | luster15991@163.com | | CHU Fengyou | Key Laboratory of Submarine Geosciences, Ministry of Natural Resources, Hangzhou 310012, China
Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China | | | CHEN Ling | Key Laboratory of Submarine Geosciences, Ministry of Natural Resources, Hangzhou 310012, China
Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China | | | MA Weilin | Key Laboratory of Submarine Geosciences, Ministry of Natural Resources, Hangzhou 310012, China
Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China | | | LIU Yonggang | Guangzhou Marine Geological Survey, Ministry of Natural Resources, Guangzhou 510760, China | |
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| Abstract: |
| Research on seamounts provides some of the best constraints for understanding intraplate volcanism, and samples from seamounts reveal crucial evidence about the geochemical makeup of the oceanic mantle. There are still many seamounts in the West Pacific Seamount Province (WPSP) that have not been studied, meaning their ages and geochemistry remain unknown. A better understanding of these seamount trails and their evolutionary history, investigated with age and geochemistry data, will enable better understanding of the geological processes operating underneath the Pacific Ocean Plate. Here, new 40Ar/39Ar ages and trace element and Sr-Nd-Pb isotopic data for seven basalt rocks from four seamounts in the WPSP are provided. Chemically, these rocks are all Oceanic Island Alkali basalt (OIA type); analysis of olivine phenocrysts shows that the magmas experienced strong olivine fractionation and changed from olivine + plagioclase to olivine + plagioclase + clinopyroxene cotectic during their evolution. Rare earth element (REE) patterns and a spider diagram of the samples in this study show OIB (Ocean Island Basalt) like behavior. The range of 87Sr/86Sr values is from 0.704 60 to 0.706 24, the range of 206Pb/204Pb values is from 18.241 to 18.599, and the range of 143Nd/144Nd values is from 0.512 646 to 0.512 826; together, these values indicate magma sources ranging from EMI to EMⅡ. Finally, new 40Ar/39Ar age data show that these seamounts formed at ~97 and ~106 Ma, indicating that some may have undergone the same formation processes as seamounts in the eastern part of the Magellan Seamount Trail, but other seamounts likely have different origins. |
| 中文摘要: |
| 海山样品为海底深部地幔地球化学组成提供了重要证据，对海山的研究可以更好的揭示板内火山活动。西太平洋海山省（WPSP）仍有许多尚未研究的海山，它们的年龄和地球化学组成仍然未知。对它们的研究可以了解其运动轨迹及演化历史，有助于更好地理解下覆太平洋板块运行的地质过程。本研究提供了WPSP中4座海山的7个玄武岩样品的40Ar/39Ar年龄和微量元素以及Sr-Nd-Pb同位素数据。数据表明，这些岩石都属于洋岛碱性玄武岩（OIA型）。对其中橄榄石斑晶的分析表明，岩浆经历了强烈的橄榄石分馏，并且在其演化过程中经历了从橄榄石+斜长石到橄榄石+斜长石+单斜辉石的岩浆演化过程。样品的REE模式和蜘蛛图显示了OIB（洋岛玄武岩）的特征。87Sr/86Sr范围为0.70460±23~0.70624±15，206Pb/204Pb范围为18.241±16~18.599±15，143Nd/144Nd范围为0.512646±8~0.512826±7，暗示源区为EMI和EMⅡ。40Ar/39Ar年龄数据显示，这些海山形成于~97Ma和~106Ma，一部分海山的形成可能经历了与麦哲伦海山链的东侧海山相同的形成过程，但是其他海山可能具有不同的岩浆起源。 |
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